diff --git a/weight/_dep/abseil-cpp/absl/container/internal/common_policy_traits_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/common_policy_traits_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..faee3e7a92ff8703b35a076e1975d7a76b39f00b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/common_policy_traits_test.cc
@@ -0,0 +1,134 @@
+// Copyright 2022 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/common_policy_traits.h"
+
+#include <functional>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using ::testing::MockFunction;
+using ::testing::AnyNumber;
+using ::testing::ReturnRef;
+
+using Slot = int;
+
+struct PolicyWithoutOptionalOps {
+  using slot_type = Slot;
+  using key_type = Slot;
+  using init_type = Slot;
+
+  static std::function<void(void*, Slot*, Slot)> construct;
+  static std::function<void(void*, Slot*)> destroy;
+
+  static std::function<Slot&(Slot*)> element;
+};
+
+std::function<void(void*, Slot*, Slot)> PolicyWithoutOptionalOps::construct;
+std::function<void(void*, Slot*)> PolicyWithoutOptionalOps::destroy;
+
+std::function<Slot&(Slot*)> PolicyWithoutOptionalOps::element;
+
+struct PolicyWithOptionalOps : PolicyWithoutOptionalOps {
+  static std::function<void(void*, Slot*, Slot*)> transfer;
+};
+std::function<void(void*, Slot*, Slot*)> PolicyWithOptionalOps::transfer;
+
+struct PolicyWithMemcpyTransfer : PolicyWithoutOptionalOps {
+  static std::function<std::true_type(void*, Slot*, Slot*)> transfer;
+};
+std::function<std::true_type(void*, Slot*, Slot*)>
+    PolicyWithMemcpyTransfer::transfer;
+
+struct Test : ::testing::Test {
+  Test() {
+    PolicyWithoutOptionalOps::construct = [&](void* a1, Slot* a2, Slot a3) {
+      construct.Call(a1, a2, std::move(a3));
+    };
+    PolicyWithoutOptionalOps::destroy = [&](void* a1, Slot* a2) {
+      destroy.Call(a1, a2);
+    };
+
+    PolicyWithoutOptionalOps::element = [&](Slot* a1) -> Slot& {
+      return element.Call(a1);
+    };
+
+    PolicyWithOptionalOps::transfer = [&](void* a1, Slot* a2, Slot* a3) {
+      return transfer.Call(a1, a2, a3);
+    };
+  }
+
+  std::allocator<Slot> alloc;
+  int a = 53;
+
+  MockFunction<void(void*, Slot*, Slot)> construct;
+  MockFunction<void(void*, Slot*)> destroy;
+
+  MockFunction<Slot&(Slot*)> element;
+
+  MockFunction<void(void*, Slot*, Slot*)> transfer;
+};
+
+TEST_F(Test, construct) {
+  EXPECT_CALL(construct, Call(&alloc, &a, 53));
+  common_policy_traits<PolicyWithoutOptionalOps>::construct(&alloc, &a, 53);
+}
+
+TEST_F(Test, destroy) {
+  EXPECT_CALL(destroy, Call(&alloc, &a));
+  common_policy_traits<PolicyWithoutOptionalOps>::destroy(&alloc, &a);
+}
+
+TEST_F(Test, element) {
+  int b = 0;
+  EXPECT_CALL(element, Call(&a)).WillOnce(ReturnRef(b));
+  EXPECT_EQ(&b, &common_policy_traits<PolicyWithoutOptionalOps>::element(&a));
+}
+
+TEST_F(Test, without_transfer) {
+  int b = 42;
+  EXPECT_CALL(element, Call(&a)).Times(AnyNumber()).WillOnce(ReturnRef(a));
+  EXPECT_CALL(element, Call(&b)).WillOnce(ReturnRef(b));
+  EXPECT_CALL(construct, Call(&alloc, &a, b)).Times(AnyNumber());
+  EXPECT_CALL(destroy, Call(&alloc, &b)).Times(AnyNumber());
+  common_policy_traits<PolicyWithoutOptionalOps>::transfer(&alloc, &a, &b);
+}
+
+TEST_F(Test, with_transfer) {
+  int b = 42;
+  EXPECT_CALL(transfer, Call(&alloc, &a, &b));
+  common_policy_traits<PolicyWithOptionalOps>::transfer(&alloc, &a, &b);
+}
+
+TEST(TransferUsesMemcpy, Basic) {
+  EXPECT_FALSE(
+      common_policy_traits<PolicyWithOptionalOps>::transfer_uses_memcpy());
+  EXPECT_TRUE(
+      common_policy_traits<PolicyWithMemcpyTransfer>::transfer_uses_memcpy());
+}
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/compressed_tuple_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/compressed_tuple_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..74111f975e9ec045ac87f5633b124b66c52fb1ce
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/compressed_tuple_test.cc
@@ -0,0 +1,419 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/compressed_tuple.h"
+
+#include <memory>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/test_instance_tracker.h"
+#include "absl/memory/memory.h"
+#include "absl/types/any.h"
+#include "absl/types/optional.h"
+#include "absl/utility/utility.h"
+
+// These are declared at global scope purely so that error messages
+// are smaller and easier to understand.
+enum class CallType { kConstRef, kConstMove };
+
+template <int>
+struct Empty {
+  constexpr CallType value() const& { return CallType::kConstRef; }
+  constexpr CallType value() const&& { return CallType::kConstMove; }
+};
+
+template <typename T>
+struct NotEmpty {
+  T value;
+};
+
+template <typename T, typename U>
+struct TwoValues {
+  T value1;
+  U value2;
+};
+
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using absl::test_internal::CopyableMovableInstance;
+using absl::test_internal::InstanceTracker;
+
+TEST(CompressedTupleTest, Sizeof) {
+  EXPECT_EQ(sizeof(int), sizeof(CompressedTuple<int>));
+  EXPECT_EQ(sizeof(int), sizeof(CompressedTuple<int, Empty<0>>));
+  EXPECT_EQ(sizeof(int), sizeof(CompressedTuple<int, Empty<0>, Empty<1>>));
+  EXPECT_EQ(sizeof(int),
+            sizeof(CompressedTuple<int, Empty<0>, Empty<1>, Empty<2>>));
+
+  EXPECT_EQ(sizeof(TwoValues<int, double>),
+            sizeof(CompressedTuple<int, NotEmpty<double>>));
+  EXPECT_EQ(sizeof(TwoValues<int, double>),
+            sizeof(CompressedTuple<int, Empty<0>, NotEmpty<double>>));
+  EXPECT_EQ(sizeof(TwoValues<int, double>),
+            sizeof(CompressedTuple<int, Empty<0>, NotEmpty<double>, Empty<1>>));
+}
+
+TEST(CompressedTupleTest, OneMoveOnRValueConstructionTemp) {
+  InstanceTracker tracker;
+  CompressedTuple<CopyableMovableInstance> x1(CopyableMovableInstance(1));
+  EXPECT_EQ(tracker.instances(), 1);
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_LE(tracker.moves(), 1);
+  EXPECT_EQ(x1.get<0>().value(), 1);
+}
+
+TEST(CompressedTupleTest, OneMoveOnRValueConstructionMove) {
+  InstanceTracker tracker;
+
+  CopyableMovableInstance i1(1);
+  CompressedTuple<CopyableMovableInstance> x1(std::move(i1));
+  EXPECT_EQ(tracker.instances(), 2);
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_LE(tracker.moves(), 1);
+  EXPECT_EQ(x1.get<0>().value(), 1);
+}
+
+TEST(CompressedTupleTest, OneMoveOnRValueConstructionMixedTypes) {
+  InstanceTracker tracker;
+  CopyableMovableInstance i1(1);
+  CopyableMovableInstance i2(2);
+  Empty<0> empty;
+  CompressedTuple<CopyableMovableInstance, CopyableMovableInstance&, Empty<0>>
+      x1(std::move(i1), i2, empty);
+  EXPECT_EQ(x1.get<0>().value(), 1);
+  EXPECT_EQ(x1.get<1>().value(), 2);
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 1);
+}
+
+struct IncompleteType;
+CompressedTuple<CopyableMovableInstance, IncompleteType&, Empty<0>>
+MakeWithIncomplete(CopyableMovableInstance i1,
+                   IncompleteType& t,  // NOLINT
+                   Empty<0> empty) {
+  return CompressedTuple<CopyableMovableInstance, IncompleteType&, Empty<0>>{
+      std::move(i1), t, empty};
+}
+
+struct IncompleteType {};
+TEST(CompressedTupleTest, OneMoveOnRValueConstructionWithIncompleteType) {
+  InstanceTracker tracker;
+  CopyableMovableInstance i1(1);
+  Empty<0> empty;
+  struct DerivedType : IncompleteType {int value = 0;};
+  DerivedType fd;
+  fd.value = 7;
+
+  CompressedTuple<CopyableMovableInstance, IncompleteType&, Empty<0>> x1 =
+      MakeWithIncomplete(std::move(i1), fd, empty);
+
+  EXPECT_EQ(x1.get<0>().value(), 1);
+  EXPECT_EQ(static_cast<DerivedType&>(x1.get<1>()).value, 7);
+
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 2);
+}
+
+TEST(CompressedTupleTest,
+     OneMoveOnRValueConstructionMixedTypes_BraceInitPoisonPillExpected) {
+  InstanceTracker tracker;
+  CopyableMovableInstance i1(1);
+  CopyableMovableInstance i2(2);
+  CompressedTuple<CopyableMovableInstance, CopyableMovableInstance&, Empty<0>>
+      x1(std::move(i1), i2, {});  // NOLINT
+  EXPECT_EQ(x1.get<0>().value(), 1);
+  EXPECT_EQ(x1.get<1>().value(), 2);
+  EXPECT_EQ(tracker.instances(), 3);
+  // We are forced into the `const Ts&...` constructor (invoking copies)
+  // because we need it to deduce the type of `{}`.
+  // std::tuple also has this behavior.
+  // Note, this test is proof that this is expected behavior, but it is not
+  // _desired_ behavior.
+  EXPECT_EQ(tracker.copies(), 1);
+  EXPECT_EQ(tracker.moves(), 0);
+}
+
+TEST(CompressedTupleTest, OneCopyOnLValueConstruction) {
+  InstanceTracker tracker;
+  CopyableMovableInstance i1(1);
+
+  CompressedTuple<CopyableMovableInstance> x1(i1);
+  EXPECT_EQ(tracker.copies(), 1);
+  EXPECT_EQ(tracker.moves(), 0);
+
+  tracker.ResetCopiesMovesSwaps();
+
+  CopyableMovableInstance i2(2);
+  const CopyableMovableInstance& i2_ref = i2;
+  CompressedTuple<CopyableMovableInstance> x2(i2_ref);
+  EXPECT_EQ(tracker.copies(), 1);
+  EXPECT_EQ(tracker.moves(), 0);
+}
+
+TEST(CompressedTupleTest, OneMoveOnRValueAccess) {
+  InstanceTracker tracker;
+  CopyableMovableInstance i1(1);
+  CompressedTuple<CopyableMovableInstance> x(std::move(i1));
+  tracker.ResetCopiesMovesSwaps();
+
+  CopyableMovableInstance i2 = std::move(x).get<0>();
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 1);
+}
+
+TEST(CompressedTupleTest, OneCopyOnLValueAccess) {
+  InstanceTracker tracker;
+
+  CompressedTuple<CopyableMovableInstance> x(CopyableMovableInstance(0));
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 1);
+
+  CopyableMovableInstance t = x.get<0>();
+  EXPECT_EQ(tracker.copies(), 1);
+  EXPECT_EQ(tracker.moves(), 1);
+}
+
+TEST(CompressedTupleTest, ZeroCopyOnRefAccess) {
+  InstanceTracker tracker;
+
+  CompressedTuple<CopyableMovableInstance> x(CopyableMovableInstance(0));
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 1);
+
+  CopyableMovableInstance& t1 = x.get<0>();
+  const CopyableMovableInstance& t2 = x.get<0>();
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 1);
+  EXPECT_EQ(t1.value(), 0);
+  EXPECT_EQ(t2.value(), 0);
+}
+
+TEST(CompressedTupleTest, Access) {
+  struct S {
+    std::string x;
+  };
+  CompressedTuple<int, Empty<0>, S> x(7, {}, S{"ABC"});
+  EXPECT_EQ(sizeof(x), sizeof(TwoValues<int, S>));
+  EXPECT_EQ(7, x.get<0>());
+  EXPECT_EQ("ABC", x.get<2>().x);
+}
+
+TEST(CompressedTupleTest, NonClasses) {
+  CompressedTuple<int, const char*> x(7, "ABC");
+  EXPECT_EQ(7, x.get<0>());
+  EXPECT_STREQ("ABC", x.get<1>());
+}
+
+TEST(CompressedTupleTest, MixClassAndNonClass) {
+  CompressedTuple<int, const char*, Empty<0>, NotEmpty<double>> x(7, "ABC", {},
+                                                                  {1.25});
+  struct Mock {
+    int v;
+    const char* p;
+    double d;
+  };
+  EXPECT_EQ(sizeof(x), sizeof(Mock));
+  EXPECT_EQ(7, x.get<0>());
+  EXPECT_STREQ("ABC", x.get<1>());
+  EXPECT_EQ(1.25, x.get<3>().value);
+}
+
+TEST(CompressedTupleTest, Nested) {
+  CompressedTuple<int, CompressedTuple<int>,
+                  CompressedTuple<int, CompressedTuple<int>>>
+      x(1, CompressedTuple<int>(2),
+        CompressedTuple<int, CompressedTuple<int>>(3, CompressedTuple<int>(4)));
+  EXPECT_EQ(1, x.get<0>());
+  EXPECT_EQ(2, x.get<1>().get<0>());
+  EXPECT_EQ(3, x.get<2>().get<0>());
+  EXPECT_EQ(4, x.get<2>().get<1>().get<0>());
+
+  CompressedTuple<Empty<0>, Empty<0>,
+                  CompressedTuple<Empty<0>, CompressedTuple<Empty<0>>>>
+      y;
+  std::set<Empty<0>*> empties{&y.get<0>(), &y.get<1>(), &y.get<2>().get<0>(),
+                              &y.get<2>().get<1>().get<0>()};
+#ifdef _MSC_VER
+  // MSVC has a bug where many instances of the same base class are layed out in
+  // the same address when using __declspec(empty_bases).
+  // This will be fixed in a future version of MSVC.
+  int expected = 1;
+#else
+  int expected = 4;
+#endif
+  EXPECT_EQ(expected, sizeof(y));
+  EXPECT_EQ(expected, empties.size());
+  EXPECT_EQ(sizeof(y), sizeof(Empty<0>) * empties.size());
+
+  EXPECT_EQ(4 * sizeof(char),
+            sizeof(CompressedTuple<CompressedTuple<char, char>,
+                                   CompressedTuple<char, char>>));
+  EXPECT_TRUE((std::is_empty<CompressedTuple<Empty<0>, Empty<1>>>::value));
+
+  // Make sure everything still works when things are nested.
+  struct CT_Empty : CompressedTuple<Empty<0>> {};
+  CompressedTuple<Empty<0>, CT_Empty> nested_empty;
+  auto contained = nested_empty.get<0>();
+  auto nested = nested_empty.get<1>().get<0>();
+  EXPECT_TRUE((std::is_same<decltype(contained), decltype(nested)>::value));
+}
+
+TEST(CompressedTupleTest, Reference) {
+  int i = 7;
+  std::string s = "Very long string that goes in the heap";
+  CompressedTuple<int, int&, std::string, std::string&> x(i, i, s, s);
+
+  // Sanity check. We should have not moved from `s`
+  EXPECT_EQ(s, "Very long string that goes in the heap");
+
+  EXPECT_EQ(x.get<0>(), x.get<1>());
+  EXPECT_NE(&x.get<0>(), &x.get<1>());
+  EXPECT_EQ(&x.get<1>(), &i);
+
+  EXPECT_EQ(x.get<2>(), x.get<3>());
+  EXPECT_NE(&x.get<2>(), &x.get<3>());
+  EXPECT_EQ(&x.get<3>(), &s);
+}
+
+TEST(CompressedTupleTest, NoElements) {
+  CompressedTuple<> x;
+  static_cast<void>(x);  // Silence -Wunused-variable.
+  EXPECT_TRUE(std::is_empty<CompressedTuple<>>::value);
+}
+
+TEST(CompressedTupleTest, MoveOnlyElements) {
+  CompressedTuple<std::unique_ptr<std::string>> str_tup(
+      absl::make_unique<std::string>("str"));
+
+  CompressedTuple<CompressedTuple<std::unique_ptr<std::string>>,
+                  std::unique_ptr<int>>
+  x(std::move(str_tup), absl::make_unique<int>(5));
+
+  EXPECT_EQ(*x.get<0>().get<0>(), "str");
+  EXPECT_EQ(*x.get<1>(), 5);
+
+  std::unique_ptr<std::string> x0 = std::move(x.get<0>()).get<0>();
+  std::unique_ptr<int> x1 = std::move(x).get<1>();
+
+  EXPECT_EQ(*x0, "str");
+  EXPECT_EQ(*x1, 5);
+}
+
+TEST(CompressedTupleTest, MoveConstructionMoveOnlyElements) {
+  CompressedTuple<std::unique_ptr<std::string>> base(
+      absl::make_unique<std::string>("str"));
+  EXPECT_EQ(*base.get<0>(), "str");
+
+  CompressedTuple<std::unique_ptr<std::string>> copy(std::move(base));
+  EXPECT_EQ(*copy.get<0>(), "str");
+}
+
+TEST(CompressedTupleTest, AnyElements) {
+  any a(std::string("str"));
+  CompressedTuple<any, any&> x(any(5), a);
+  EXPECT_EQ(absl::any_cast<int>(x.get<0>()), 5);
+  EXPECT_EQ(absl::any_cast<std::string>(x.get<1>()), "str");
+
+  a = 0.5f;
+  EXPECT_EQ(absl::any_cast<float>(x.get<1>()), 0.5);
+}
+
+TEST(CompressedTupleTest, Constexpr) {
+  struct NonTrivialStruct {
+    constexpr NonTrivialStruct() = default;
+    constexpr int value() const { return v; }
+    int v = 5;
+  };
+  struct TrivialStruct {
+    TrivialStruct() = default;
+    constexpr int value() const { return v; }
+    int v;
+  };
+  constexpr CompressedTuple<int, double, CompressedTuple<int>, Empty<0>> x(
+      7, 1.25, CompressedTuple<int>(5), {});
+  constexpr int x0 = x.get<0>();
+  constexpr double x1 = x.get<1>();
+  constexpr int x2 = x.get<2>().get<0>();
+  constexpr CallType x3 = x.get<3>().value();
+
+  EXPECT_EQ(x0, 7);
+  EXPECT_EQ(x1, 1.25);
+  EXPECT_EQ(x2, 5);
+  EXPECT_EQ(x3, CallType::kConstRef);
+
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4
+  constexpr CompressedTuple<Empty<0>, TrivialStruct, int> trivial = {};
+  constexpr CallType trivial0 = trivial.get<0>().value();
+  constexpr int trivial1 = trivial.get<1>().value();
+  constexpr int trivial2 = trivial.get<2>();
+
+  EXPECT_EQ(trivial0, CallType::kConstRef);
+  EXPECT_EQ(trivial1, 0);
+  EXPECT_EQ(trivial2, 0);
+#endif
+
+  constexpr CompressedTuple<Empty<0>, NonTrivialStruct, absl::optional<int>>
+      non_trivial = {};
+  constexpr CallType non_trivial0 = non_trivial.get<0>().value();
+  constexpr int non_trivial1 = non_trivial.get<1>().value();
+  constexpr absl::optional<int> non_trivial2 = non_trivial.get<2>();
+
+  EXPECT_EQ(non_trivial0, CallType::kConstRef);
+  EXPECT_EQ(non_trivial1, 5);
+  EXPECT_EQ(non_trivial2, absl::nullopt);
+
+  static constexpr char data[] = "DEF";
+  constexpr CompressedTuple<const char*> z(data);
+  constexpr const char* z1 = z.get<0>();
+  EXPECT_EQ(std::string(z1), std::string(data));
+
+#if defined(__clang__)
+  // An apparent bug in earlier versions of gcc claims these are ambiguous.
+  constexpr int x2m = absl::move(x.get<2>()).get<0>();
+  constexpr CallType x3m = absl::move(x).get<3>().value();
+  EXPECT_EQ(x2m, 5);
+  EXPECT_EQ(x3m, CallType::kConstMove);
+#endif
+}
+
+#if defined(__clang__) || defined(__GNUC__)
+TEST(CompressedTupleTest, EmptyFinalClass) {
+  struct S final {
+    int f() const { return 5; }
+  };
+  CompressedTuple<S> x;
+  EXPECT_EQ(x.get<0>().f(), 5);
+}
+#endif
+
+// TODO(b/214288561): enable this test.
+TEST(CompressedTupleTest, DISABLED_NestedEbo) {
+  struct Empty1 {};
+  struct Empty2 {};
+  CompressedTuple<Empty1, CompressedTuple<Empty2>, int> x;
+  CompressedTuple<Empty1, Empty2, int> y;
+  // Currently fails with sizeof(x) == 8, sizeof(y) == 4.
+  EXPECT_EQ(sizeof(x), sizeof(y));
+}
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hash_function_defaults.h b/weight/_dep/abseil-cpp/absl/container/internal/hash_function_defaults.h
new file mode 100644
index 0000000000000000000000000000000000000000..a3613b4bc514a69ab88c2fe0d0c2446817e43235
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hash_function_defaults.h
@@ -0,0 +1,209 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Define the default Hash and Eq functions for SwissTable containers.
+//
+// std::hash<T> and std::equal_to<T> are not appropriate hash and equal
+// functions for SwissTable containers. There are two reasons for this.
+//
+// SwissTable containers are power of 2 sized containers:
+//
+// This means they use the lower bits of the hash value to find the slot for
+// each entry. The typical hash function for integral types is the identity.
+// This is a very weak hash function for SwissTable and any power of 2 sized
+// hashtable implementation which will lead to excessive collisions. For
+// SwissTable we use murmur3 style mixing to reduce collisions to a minimum.
+//
+// SwissTable containers support heterogeneous lookup:
+//
+// In order to make heterogeneous lookup work, hash and equal functions must be
+// polymorphic. At the same time they have to satisfy the same requirements the
+// C++ standard imposes on hash functions and equality operators. That is:
+//
+//   if hash_default_eq<T>(a, b) returns true for any a and b of type T, then
+//   hash_default_hash<T>(a) must equal hash_default_hash<T>(b)
+//
+// For SwissTable containers this requirement is relaxed to allow a and b of
+// any and possibly different types. Note that like the standard the hash and
+// equal functions are still bound to T. This is important because some type U
+// can be hashed by/tested for equality differently depending on T. A notable
+// example is `const char*`. `const char*` is treated as a c-style string when
+// the hash function is hash<std::string> but as a pointer when the hash
+// function is hash<void*>.
+//
+#ifndef ABSL_CONTAINER_INTERNAL_HASH_FUNCTION_DEFAULTS_H_
+#define ABSL_CONTAINER_INTERNAL_HASH_FUNCTION_DEFAULTS_H_
+
+#include <stdint.h>
+#include <cstddef>
+#include <memory>
+#include <string>
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/hash/hash.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/string_view.h"
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+// The hash of an object of type T is computed by using absl::Hash.
+template <class T, class E = void>
+struct HashEq {
+  using Hash = absl::Hash<T>;
+  using Eq = std::equal_to<T>;
+};
+
+struct StringHash {
+  using is_transparent = void;
+
+  size_t operator()(absl::string_view v) const {
+    return absl::Hash<absl::string_view>{}(v);
+  }
+  size_t operator()(const absl::Cord& v) const {
+    return absl::Hash<absl::Cord>{}(v);
+  }
+};
+
+struct StringEq {
+  using is_transparent = void;
+  bool operator()(absl::string_view lhs, absl::string_view rhs) const {
+    return lhs == rhs;
+  }
+  bool operator()(const absl::Cord& lhs, const absl::Cord& rhs) const {
+    return lhs == rhs;
+  }
+  bool operator()(const absl::Cord& lhs, absl::string_view rhs) const {
+    return lhs == rhs;
+  }
+  bool operator()(absl::string_view lhs, const absl::Cord& rhs) const {
+    return lhs == rhs;
+  }
+};
+
+// Supports heterogeneous lookup for string-like elements.
+struct StringHashEq {
+  using Hash = StringHash;
+  using Eq = StringEq;
+};
+
+template <>
+struct HashEq<std::string> : StringHashEq {};
+template <>
+struct HashEq<absl::string_view> : StringHashEq {};
+template <>
+struct HashEq<absl::Cord> : StringHashEq {};
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+
+template <typename TChar>
+struct BasicStringHash {
+  using is_transparent = void;
+
+  size_t operator()(std::basic_string_view<TChar> v) const {
+    return absl::Hash<std::basic_string_view<TChar>>{}(v);
+  }
+};
+
+template <typename TChar>
+struct BasicStringEq {
+  using is_transparent = void;
+  bool operator()(std::basic_string_view<TChar> lhs,
+                  std::basic_string_view<TChar> rhs) const {
+    return lhs == rhs;
+  }
+};
+
+// Supports heterogeneous lookup for w/u16/u32 string + string_view + char*.
+template <typename TChar>
+struct BasicStringHashEq {
+  using Hash = BasicStringHash<TChar>;
+  using Eq = BasicStringEq<TChar>;
+};
+
+template <>
+struct HashEq<std::wstring> : BasicStringHashEq<wchar_t> {};
+template <>
+struct HashEq<std::wstring_view> : BasicStringHashEq<wchar_t> {};
+template <>
+struct HashEq<std::u16string> : BasicStringHashEq<char16_t> {};
+template <>
+struct HashEq<std::u16string_view> : BasicStringHashEq<char16_t> {};
+template <>
+struct HashEq<std::u32string> : BasicStringHashEq<char32_t> {};
+template <>
+struct HashEq<std::u32string_view> : BasicStringHashEq<char32_t> {};
+
+#endif  // ABSL_HAVE_STD_STRING_VIEW
+
+// Supports heterogeneous lookup for pointers and smart pointers.
+template <class T>
+struct HashEq<T*> {
+  struct Hash {
+    using is_transparent = void;
+    template <class U>
+    size_t operator()(const U& ptr) const {
+      return absl::Hash<const T*>{}(HashEq::ToPtr(ptr));
+    }
+  };
+  struct Eq {
+    using is_transparent = void;
+    template <class A, class B>
+    bool operator()(const A& a, const B& b) const {
+      return HashEq::ToPtr(a) == HashEq::ToPtr(b);
+    }
+  };
+
+ private:
+  static const T* ToPtr(const T* ptr) { return ptr; }
+  template <class U, class D>
+  static const T* ToPtr(const std::unique_ptr<U, D>& ptr) {
+    return ptr.get();
+  }
+  template <class U>
+  static const T* ToPtr(const std::shared_ptr<U>& ptr) {
+    return ptr.get();
+  }
+};
+
+template <class T, class D>
+struct HashEq<std::unique_ptr<T, D>> : HashEq<T*> {};
+template <class T>
+struct HashEq<std::shared_ptr<T>> : HashEq<T*> {};
+
+// This header's visibility is restricted.  If you need to access the default
+// hasher please use the container's ::hasher alias instead.
+//
+// Example: typename Hash = typename absl::flat_hash_map<K, V>::hasher
+template <class T>
+using hash_default_hash = typename container_internal::HashEq<T>::Hash;
+
+// This header's visibility is restricted.  If you need to access the default
+// key equal please use the container's ::key_equal alias instead.
+//
+// Example: typename Eq = typename absl::flat_hash_map<K, V, Hash>::key_equal
+template <class T>
+using hash_default_eq = typename container_internal::HashEq<T>::Eq;
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_HASH_FUNCTION_DEFAULTS_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hash_function_defaults_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/hash_function_defaults_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c31af3be9027ebd1c0809594d98780ab017599be
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hash_function_defaults_test.cc
@@ -0,0 +1,549 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hash_function_defaults.h"
+
+#include <functional>
+#include <type_traits>
+#include <utility>
+
+#include "gtest/gtest.h"
+#include "absl/random/random.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/cord_test_helpers.h"
+#include "absl/strings/string_view.h"
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using ::testing::Types;
+
+TEST(Eq, Int32) {
+  hash_default_eq<int32_t> eq;
+  EXPECT_TRUE(eq(1, 1u));
+  EXPECT_TRUE(eq(1, char{1}));
+  EXPECT_TRUE(eq(1, true));
+  EXPECT_TRUE(eq(1, double{1.1}));
+  EXPECT_FALSE(eq(1, char{2}));
+  EXPECT_FALSE(eq(1, 2u));
+  EXPECT_FALSE(eq(1, false));
+  EXPECT_FALSE(eq(1, 2.));
+}
+
+TEST(Hash, Int32) {
+  hash_default_hash<int32_t> hash;
+  auto h = hash(1);
+  EXPECT_EQ(h, hash(1u));
+  EXPECT_EQ(h, hash(char{1}));
+  EXPECT_EQ(h, hash(true));
+  EXPECT_EQ(h, hash(double{1.1}));
+  EXPECT_NE(h, hash(2u));
+  EXPECT_NE(h, hash(char{2}));
+  EXPECT_NE(h, hash(false));
+  EXPECT_NE(h, hash(2.));
+}
+
+enum class MyEnum { A, B, C, D };
+
+TEST(Eq, Enum) {
+  hash_default_eq<MyEnum> eq;
+  EXPECT_TRUE(eq(MyEnum::A, MyEnum::A));
+  EXPECT_FALSE(eq(MyEnum::A, MyEnum::B));
+}
+
+TEST(Hash, Enum) {
+  hash_default_hash<MyEnum> hash;
+
+  for (MyEnum e : {MyEnum::A, MyEnum::B, MyEnum::C}) {
+    auto h = hash(e);
+    EXPECT_EQ(h, hash_default_hash<int>{}(static_cast<int>(e)));
+    EXPECT_NE(h, hash(MyEnum::D));
+  }
+}
+
+using StringTypes = ::testing::Types<std::string, absl::string_view>;
+
+template <class T>
+struct EqString : ::testing::Test {
+  hash_default_eq<T> key_eq;
+};
+
+TYPED_TEST_SUITE(EqString, StringTypes);
+
+template <class T>
+struct HashString : ::testing::Test {
+  hash_default_hash<T> hasher;
+};
+
+TYPED_TEST_SUITE(HashString, StringTypes);
+
+TYPED_TEST(EqString, Works) {
+  auto eq = this->key_eq;
+  EXPECT_TRUE(eq("a", "a"));
+  EXPECT_TRUE(eq("a", absl::string_view("a")));
+  EXPECT_TRUE(eq("a", std::string("a")));
+  EXPECT_FALSE(eq("a", "b"));
+  EXPECT_FALSE(eq("a", absl::string_view("b")));
+  EXPECT_FALSE(eq("a", std::string("b")));
+}
+
+TYPED_TEST(HashString, Works) {
+  auto hash = this->hasher;
+  auto h = hash("a");
+  EXPECT_EQ(h, hash(absl::string_view("a")));
+  EXPECT_EQ(h, hash(std::string("a")));
+  EXPECT_NE(h, hash(absl::string_view("b")));
+  EXPECT_NE(h, hash(std::string("b")));
+}
+
+TEST(BasicStringViewTest, WStringEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::wstring> eq;
+  EXPECT_TRUE(eq(L"a", L"a"));
+  EXPECT_TRUE(eq(L"a", std::wstring_view(L"a")));
+  EXPECT_TRUE(eq(L"a", std::wstring(L"a")));
+  EXPECT_FALSE(eq(L"a", L"b"));
+  EXPECT_FALSE(eq(L"a", std::wstring_view(L"b")));
+  EXPECT_FALSE(eq(L"a", std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, WStringViewEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::wstring_view> eq;
+  EXPECT_TRUE(eq(L"a", L"a"));
+  EXPECT_TRUE(eq(L"a", std::wstring_view(L"a")));
+  EXPECT_TRUE(eq(L"a", std::wstring(L"a")));
+  EXPECT_FALSE(eq(L"a", L"b"));
+  EXPECT_FALSE(eq(L"a", std::wstring_view(L"b")));
+  EXPECT_FALSE(eq(L"a", std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u16string> eq;
+  EXPECT_TRUE(eq(u"a", u"a"));
+  EXPECT_TRUE(eq(u"a", std::u16string_view(u"a")));
+  EXPECT_TRUE(eq(u"a", std::u16string(u"a")));
+  EXPECT_FALSE(eq(u"a", u"b"));
+  EXPECT_FALSE(eq(u"a", std::u16string_view(u"b")));
+  EXPECT_FALSE(eq(u"a", std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringViewEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u16string_view> eq;
+  EXPECT_TRUE(eq(u"a", u"a"));
+  EXPECT_TRUE(eq(u"a", std::u16string_view(u"a")));
+  EXPECT_TRUE(eq(u"a", std::u16string(u"a")));
+  EXPECT_FALSE(eq(u"a", u"b"));
+  EXPECT_FALSE(eq(u"a", std::u16string_view(u"b")));
+  EXPECT_FALSE(eq(u"a", std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u32string> eq;
+  EXPECT_TRUE(eq(U"a", U"a"));
+  EXPECT_TRUE(eq(U"a", std::u32string_view(U"a")));
+  EXPECT_TRUE(eq(U"a", std::u32string(U"a")));
+  EXPECT_FALSE(eq(U"a", U"b"));
+  EXPECT_FALSE(eq(U"a", std::u32string_view(U"b")));
+  EXPECT_FALSE(eq(U"a", std::u32string(U"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringViewEqWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_eq<std::u32string_view> eq;
+  EXPECT_TRUE(eq(U"a", U"a"));
+  EXPECT_TRUE(eq(U"a", std::u32string_view(U"a")));
+  EXPECT_TRUE(eq(U"a", std::u32string(U"a")));
+  EXPECT_FALSE(eq(U"a", U"b"));
+  EXPECT_FALSE(eq(U"a", std::u32string_view(U"b")));
+  EXPECT_FALSE(eq(U"a", std::u32string(U"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, WStringHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::wstring> hash;
+  auto h = hash(L"a");
+  EXPECT_EQ(h, hash(std::wstring_view(L"a")));
+  EXPECT_EQ(h, hash(std::wstring(L"a")));
+  EXPECT_NE(h, hash(std::wstring_view(L"b")));
+  EXPECT_NE(h, hash(std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, WStringViewHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::wstring_view> hash;
+  auto h = hash(L"a");
+  EXPECT_EQ(h, hash(std::wstring_view(L"a")));
+  EXPECT_EQ(h, hash(std::wstring(L"a")));
+  EXPECT_NE(h, hash(std::wstring_view(L"b")));
+  EXPECT_NE(h, hash(std::wstring(L"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u16string> hash;
+  auto h = hash(u"a");
+  EXPECT_EQ(h, hash(std::u16string_view(u"a")));
+  EXPECT_EQ(h, hash(std::u16string(u"a")));
+  EXPECT_NE(h, hash(std::u16string_view(u"b")));
+  EXPECT_NE(h, hash(std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U16StringViewHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u16string_view> hash;
+  auto h = hash(u"a");
+  EXPECT_EQ(h, hash(std::u16string_view(u"a")));
+  EXPECT_EQ(h, hash(std::u16string(u"a")));
+  EXPECT_NE(h, hash(std::u16string_view(u"b")));
+  EXPECT_NE(h, hash(std::u16string(u"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u32string> hash;
+  auto h = hash(U"a");
+  EXPECT_EQ(h, hash(std::u32string_view(U"a")));
+  EXPECT_EQ(h, hash(std::u32string(U"a")));
+  EXPECT_NE(h, hash(std::u32string_view(U"b")));
+  EXPECT_NE(h, hash(std::u32string(U"b")));
+#endif
+}
+
+TEST(BasicStringViewTest, U32StringViewHashWorks) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  hash_default_hash<std::u32string_view> hash;
+  auto h = hash(U"a");
+  EXPECT_EQ(h, hash(std::u32string_view(U"a")));
+  EXPECT_EQ(h, hash(std::u32string(U"a")));
+  EXPECT_NE(h, hash(std::u32string_view(U"b")));
+  EXPECT_NE(h, hash(std::u32string(U"b")));
+#endif
+}
+
+struct NoDeleter {
+  template <class T>
+  void operator()(const T* ptr) const {}
+};
+
+using PointerTypes =
+    ::testing::Types<const int*, int*, std::unique_ptr<const int>,
+                     std::unique_ptr<const int, NoDeleter>,
+                     std::unique_ptr<int>, std::unique_ptr<int, NoDeleter>,
+                     std::shared_ptr<const int>, std::shared_ptr<int>>;
+
+template <class T>
+struct EqPointer : ::testing::Test {
+  hash_default_eq<T> key_eq;
+};
+
+TYPED_TEST_SUITE(EqPointer, PointerTypes);
+
+template <class T>
+struct HashPointer : ::testing::Test {
+  hash_default_hash<T> hasher;
+};
+
+TYPED_TEST_SUITE(HashPointer, PointerTypes);
+
+TYPED_TEST(EqPointer, Works) {
+  int dummy;
+  auto eq = this->key_eq;
+  auto sptr = std::make_shared<int>();
+  std::shared_ptr<const int> csptr = sptr;
+  int* ptr = sptr.get();
+  const int* cptr = ptr;
+  std::unique_ptr<int, NoDeleter> uptr(ptr);
+  std::unique_ptr<const int, NoDeleter> cuptr(ptr);
+
+  EXPECT_TRUE(eq(ptr, cptr));
+  EXPECT_TRUE(eq(ptr, sptr));
+  EXPECT_TRUE(eq(ptr, uptr));
+  EXPECT_TRUE(eq(ptr, csptr));
+  EXPECT_TRUE(eq(ptr, cuptr));
+  EXPECT_FALSE(eq(&dummy, cptr));
+  EXPECT_FALSE(eq(&dummy, sptr));
+  EXPECT_FALSE(eq(&dummy, uptr));
+  EXPECT_FALSE(eq(&dummy, csptr));
+  EXPECT_FALSE(eq(&dummy, cuptr));
+}
+
+TEST(Hash, DerivedAndBase) {
+  struct Base {};
+  struct Derived : Base {};
+
+  hash_default_hash<Base*> hasher;
+
+  Base base;
+  Derived derived;
+  EXPECT_NE(hasher(&base), hasher(&derived));
+  EXPECT_EQ(hasher(static_cast<Base*>(&derived)), hasher(&derived));
+
+  auto dp = std::make_shared<Derived>();
+  EXPECT_EQ(hasher(static_cast<Base*>(dp.get())), hasher(dp));
+}
+
+TEST(Hash, FunctionPointer) {
+  using Func = int (*)();
+  hash_default_hash<Func> hasher;
+  hash_default_eq<Func> eq;
+
+  Func p1 = [] { return 1; }, p2 = [] { return 2; };
+  EXPECT_EQ(hasher(p1), hasher(p1));
+  EXPECT_TRUE(eq(p1, p1));
+
+  EXPECT_NE(hasher(p1), hasher(p2));
+  EXPECT_FALSE(eq(p1, p2));
+}
+
+TYPED_TEST(HashPointer, Works) {
+  int dummy;
+  auto hash = this->hasher;
+  auto sptr = std::make_shared<int>();
+  std::shared_ptr<const int> csptr = sptr;
+  int* ptr = sptr.get();
+  const int* cptr = ptr;
+  std::unique_ptr<int, NoDeleter> uptr(ptr);
+  std::unique_ptr<const int, NoDeleter> cuptr(ptr);
+
+  EXPECT_EQ(hash(ptr), hash(cptr));
+  EXPECT_EQ(hash(ptr), hash(sptr));
+  EXPECT_EQ(hash(ptr), hash(uptr));
+  EXPECT_EQ(hash(ptr), hash(csptr));
+  EXPECT_EQ(hash(ptr), hash(cuptr));
+  EXPECT_NE(hash(&dummy), hash(cptr));
+  EXPECT_NE(hash(&dummy), hash(sptr));
+  EXPECT_NE(hash(&dummy), hash(uptr));
+  EXPECT_NE(hash(&dummy), hash(csptr));
+  EXPECT_NE(hash(&dummy), hash(cuptr));
+}
+
+TEST(EqCord, Works) {
+  hash_default_eq<absl::Cord> eq;
+  const absl::string_view a_string_view = "a";
+  const absl::Cord a_cord(a_string_view);
+  const absl::string_view b_string_view = "b";
+  const absl::Cord b_cord(b_string_view);
+
+  EXPECT_TRUE(eq(a_cord, a_cord));
+  EXPECT_TRUE(eq(a_cord, a_string_view));
+  EXPECT_TRUE(eq(a_string_view, a_cord));
+  EXPECT_FALSE(eq(a_cord, b_cord));
+  EXPECT_FALSE(eq(a_cord, b_string_view));
+  EXPECT_FALSE(eq(b_string_view, a_cord));
+}
+
+TEST(HashCord, Works) {
+  hash_default_hash<absl::Cord> hash;
+  const absl::string_view a_string_view = "a";
+  const absl::Cord a_cord(a_string_view);
+  const absl::string_view b_string_view = "b";
+  const absl::Cord b_cord(b_string_view);
+
+  EXPECT_EQ(hash(a_cord), hash(a_cord));
+  EXPECT_EQ(hash(b_cord), hash(b_cord));
+  EXPECT_EQ(hash(a_string_view), hash(a_cord));
+  EXPECT_EQ(hash(b_string_view), hash(b_cord));
+  EXPECT_EQ(hash(absl::Cord("")), hash(""));
+  EXPECT_EQ(hash(absl::Cord()), hash(absl::string_view()));
+
+  EXPECT_NE(hash(a_cord), hash(b_cord));
+  EXPECT_NE(hash(a_cord), hash(b_string_view));
+  EXPECT_NE(hash(a_string_view), hash(b_cord));
+  EXPECT_NE(hash(a_string_view), hash(b_string_view));
+}
+
+void NoOpReleaser(absl::string_view data, void* arg) {}
+
+TEST(HashCord, FragmentedCordWorks) {
+  hash_default_hash<absl::Cord> hash;
+  absl::Cord c = absl::MakeFragmentedCord({"a", "b", "c"});
+  EXPECT_FALSE(c.TryFlat().has_value());
+  EXPECT_EQ(hash(c), hash("abc"));
+}
+
+TEST(HashCord, FragmentedLongCordWorks) {
+  hash_default_hash<absl::Cord> hash;
+  // Crete some large strings which do not fit on the stack.
+  std::string a(65536, 'a');
+  std::string b(65536, 'b');
+  absl::Cord c = absl::MakeFragmentedCord({a, b});
+  EXPECT_FALSE(c.TryFlat().has_value());
+  EXPECT_EQ(hash(c), hash(a + b));
+}
+
+TEST(HashCord, RandomCord) {
+  hash_default_hash<absl::Cord> hash;
+  auto bitgen = absl::BitGen();
+  for (int i = 0; i < 1000; ++i) {
+    const int number_of_segments = absl::Uniform(bitgen, 0, 10);
+    std::vector<std::string> pieces;
+    for (size_t s = 0; s < number_of_segments; ++s) {
+      std::string str;
+      str.resize(absl::Uniform(bitgen, 0, 4096));
+      // MSVC needed the explicit return type in the lambda.
+      std::generate(str.begin(), str.end(), [&]() -> char {
+        return static_cast<char>(absl::Uniform<unsigned char>(bitgen));
+      });
+      pieces.push_back(str);
+    }
+    absl::Cord c = absl::MakeFragmentedCord(pieces);
+    EXPECT_EQ(hash(c), hash(std::string(c)));
+  }
+}
+
+// Cartesian product of (std::string, absl::string_view)
+// with (std::string, absl::string_view, const char*, absl::Cord).
+using StringTypesCartesianProduct = Types<
+    // clang-format off
+    std::pair<absl::Cord, std::string>,
+    std::pair<absl::Cord, absl::string_view>,
+    std::pair<absl::Cord, absl::Cord>,
+    std::pair<absl::Cord, const char*>,
+
+    std::pair<std::string, absl::Cord>,
+    std::pair<absl::string_view, absl::Cord>,
+
+    std::pair<absl::string_view, std::string>,
+    std::pair<absl::string_view, absl::string_view>,
+    std::pair<absl::string_view, const char*>>;
+// clang-format on
+
+constexpr char kFirstString[] = "abc123";
+constexpr char kSecondString[] = "ijk456";
+
+template <typename T>
+struct StringLikeTest : public ::testing::Test {
+  typename T::first_type a1{kFirstString};
+  typename T::second_type b1{kFirstString};
+  typename T::first_type a2{kSecondString};
+  typename T::second_type b2{kSecondString};
+  hash_default_eq<typename T::first_type> eq;
+  hash_default_hash<typename T::first_type> hash;
+};
+
+TYPED_TEST_SUITE_P(StringLikeTest);
+
+TYPED_TEST_P(StringLikeTest, Eq) {
+  EXPECT_TRUE(this->eq(this->a1, this->b1));
+  EXPECT_TRUE(this->eq(this->b1, this->a1));
+}
+
+TYPED_TEST_P(StringLikeTest, NotEq) {
+  EXPECT_FALSE(this->eq(this->a1, this->b2));
+  EXPECT_FALSE(this->eq(this->b2, this->a1));
+}
+
+TYPED_TEST_P(StringLikeTest, HashEq) {
+  EXPECT_EQ(this->hash(this->a1), this->hash(this->b1));
+  EXPECT_EQ(this->hash(this->a2), this->hash(this->b2));
+  // It would be a poor hash function which collides on these strings.
+  EXPECT_NE(this->hash(this->a1), this->hash(this->b2));
+}
+
+TYPED_TEST_SUITE(StringLikeTest, StringTypesCartesianProduct);
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+enum Hash : size_t {
+  kStd = 0x1,       // std::hash
+#ifdef _MSC_VER
+  kExtension = kStd,  // In MSVC, std::hash == ::hash
+#else                 // _MSC_VER
+  kExtension = 0x2,  // ::hash (GCC extension)
+#endif                // _MSC_VER
+};
+
+// H is a bitmask of Hash enumerations.
+// Hashable<H> is hashable via all means specified in H.
+template <int H>
+struct Hashable {
+  static constexpr bool HashableBy(Hash h) { return h & H; }
+};
+
+namespace std {
+template <int H>
+struct hash<Hashable<H>> {
+  template <class E = Hashable<H>,
+            class = typename std::enable_if<E::HashableBy(kStd)>::type>
+  size_t operator()(E) const {
+    return kStd;
+  }
+};
+}  // namespace std
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+template <class T>
+size_t Hash(const T& v) {
+  return hash_default_hash<T>()(v);
+}
+
+TEST(Delegate, HashDispatch) {
+  EXPECT_EQ(Hash(kStd), Hash(Hashable<kStd>()));
+}
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hash_generator_testing.cc b/weight/_dep/abseil-cpp/absl/container/internal/hash_generator_testing.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e89dfdb5ba7abe22baaf99973061caa4910719b7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hash_generator_testing.cc
@@ -0,0 +1,78 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hash_generator_testing.h"
+
+#include <deque>
+
+#include "absl/base/no_destructor.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace hash_internal {
+namespace {
+
+class RandomDeviceSeedSeq {
+ public:
+  using result_type = typename std::random_device::result_type;
+
+  template <class Iterator>
+  void generate(Iterator start, Iterator end) {
+    while (start != end) {
+      *start = gen_();
+      ++start;
+    }
+  }
+
+ private:
+  std::random_device gen_;
+};
+
+}  // namespace
+
+std::mt19937_64* GetSharedRng() {
+  static absl::NoDestructor<std::mt19937_64> rng([] {
+    RandomDeviceSeedSeq seed_seq;
+    return std::mt19937_64(seed_seq);
+  }());
+  return rng.get();
+}
+
+std::string Generator<std::string>::operator()() const {
+  // NOLINTNEXTLINE(runtime/int)
+  std::uniform_int_distribution<short> chars(0x20, 0x7E);
+  std::string res;
+  res.resize(32);
+  std::generate(res.begin(), res.end(),
+                [&]() { return chars(*GetSharedRng()); });
+  return res;
+}
+
+absl::string_view Generator<absl::string_view>::operator()() const {
+  static absl::NoDestructor<std::deque<std::string>> arena;
+  // NOLINTNEXTLINE(runtime/int)
+  std::uniform_int_distribution<short> chars(0x20, 0x7E);
+  arena->emplace_back();
+  auto& res = arena->back();
+  res.resize(32);
+  std::generate(res.begin(), res.end(),
+                [&]() { return chars(*GetSharedRng()); });
+  return res;
+}
+
+}  // namespace hash_internal
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hash_generator_testing.h b/weight/_dep/abseil-cpp/absl/container/internal/hash_generator_testing.h
new file mode 100644
index 0000000000000000000000000000000000000000..f1f555a5c148cbf52ca6eab78e101d8a9dc6f884
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hash_generator_testing.h
@@ -0,0 +1,182 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Generates random values for testing. Specialized only for the few types we
+// care about.
+
+#ifndef ABSL_CONTAINER_INTERNAL_HASH_GENERATOR_TESTING_H_
+#define ABSL_CONTAINER_INTERNAL_HASH_GENERATOR_TESTING_H_
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <cassert>
+#include <iosfwd>
+#include <random>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "absl/container/internal/hash_policy_testing.h"
+#include "absl/memory/memory.h"
+#include "absl/meta/type_traits.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace hash_internal {
+namespace generator_internal {
+
+template <class Container, class = void>
+struct IsMap : std::false_type {};
+
+template <class Map>
+struct IsMap<Map, absl::void_t<typename Map::mapped_type>> : std::true_type {};
+
+}  // namespace generator_internal
+
+std::mt19937_64* GetSharedRng();
+
+enum Enum {
+  kEnumEmpty,
+  kEnumDeleted,
+};
+
+enum class EnumClass : uint64_t {
+  kEmpty,
+  kDeleted,
+};
+
+inline std::ostream& operator<<(std::ostream& o, const EnumClass& ec) {
+  return o << static_cast<uint64_t>(ec);
+}
+
+template <class T, class E = void>
+struct Generator;
+
+template <class T>
+struct Generator<T, typename std::enable_if<std::is_integral<T>::value>::type> {
+  T operator()() const {
+    std::uniform_int_distribution<T> dist;
+    return dist(*GetSharedRng());
+  }
+};
+
+template <>
+struct Generator<Enum> {
+  Enum operator()() const {
+    std::uniform_int_distribution<typename std::underlying_type<Enum>::type>
+        dist;
+    while (true) {
+      auto variate = dist(*GetSharedRng());
+      if (variate != kEnumEmpty && variate != kEnumDeleted)
+        return static_cast<Enum>(variate);
+    }
+  }
+};
+
+template <>
+struct Generator<EnumClass> {
+  EnumClass operator()() const {
+    std::uniform_int_distribution<
+        typename std::underlying_type<EnumClass>::type>
+        dist;
+    while (true) {
+      EnumClass variate = static_cast<EnumClass>(dist(*GetSharedRng()));
+      if (variate != EnumClass::kEmpty && variate != EnumClass::kDeleted)
+        return static_cast<EnumClass>(variate);
+    }
+  }
+};
+
+template <>
+struct Generator<std::string> {
+  std::string operator()() const;
+};
+
+template <>
+struct Generator<absl::string_view> {
+  absl::string_view operator()() const;
+};
+
+template <>
+struct Generator<NonStandardLayout> {
+  NonStandardLayout operator()() const {
+    return NonStandardLayout(Generator<std::string>()());
+  }
+};
+
+template <class K, class V>
+struct Generator<std::pair<K, V>> {
+  std::pair<K, V> operator()() const {
+    return std::pair<K, V>(Generator<typename std::decay<K>::type>()(),
+                           Generator<typename std::decay<V>::type>()());
+  }
+};
+
+template <class... Ts>
+struct Generator<std::tuple<Ts...>> {
+  std::tuple<Ts...> operator()() const {
+    return std::tuple<Ts...>(Generator<typename std::decay<Ts>::type>()()...);
+  }
+};
+
+template <class T>
+struct Generator<std::unique_ptr<T>> {
+  std::unique_ptr<T> operator()() const {
+    return absl::make_unique<T>(Generator<T>()());
+  }
+};
+
+template <class U>
+struct Generator<U, absl::void_t<decltype(std::declval<U&>().key()),
+                                decltype(std::declval<U&>().value())>>
+    : Generator<std::pair<
+          typename std::decay<decltype(std::declval<U&>().key())>::type,
+          typename std::decay<decltype(std::declval<U&>().value())>::type>> {};
+
+template <class Container>
+using GeneratedType = decltype(
+    std::declval<const Generator<
+        typename std::conditional<generator_internal::IsMap<Container>::value,
+                                  typename Container::value_type,
+                                  typename Container::key_type>::type>&>()());
+
+// Naive wrapper that performs a linear search of previous values.
+// Beware this is O(SQR), which is reasonable for smaller kMaxValues.
+template <class T, size_t kMaxValues = 64, class E = void>
+struct UniqueGenerator {
+  Generator<T, E> gen;
+  std::vector<T> values;
+
+  T operator()() {
+    assert(values.size() < kMaxValues);
+    for (;;) {
+      T value = gen();
+      if (std::find(values.begin(), values.end(), value) == values.end()) {
+        values.push_back(value);
+        return value;
+      }
+    }
+  }
+};
+
+}  // namespace hash_internal
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_HASH_GENERATOR_TESTING_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hash_policy_testing.h b/weight/_dep/abseil-cpp/absl/container/internal/hash_policy_testing.h
new file mode 100644
index 0000000000000000000000000000000000000000..01c40d2e5cff126f06db66d3b8f4088c598e7b91
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hash_policy_testing.h
@@ -0,0 +1,184 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Utilities to help tests verify that hash tables properly handle stateful
+// allocators and hash functions.
+
+#ifndef ABSL_CONTAINER_INTERNAL_HASH_POLICY_TESTING_H_
+#define ABSL_CONTAINER_INTERNAL_HASH_POLICY_TESTING_H_
+
+#include <cstdlib>
+#include <limits>
+#include <memory>
+#include <ostream>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "absl/hash/hash.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace hash_testing_internal {
+
+template <class Derived>
+struct WithId {
+  WithId() : id_(next_id<Derived>()) {}
+  WithId(const WithId& that) : id_(that.id_) {}
+  WithId(WithId&& that) : id_(that.id_) { that.id_ = 0; }
+  WithId& operator=(const WithId& that) {
+    id_ = that.id_;
+    return *this;
+  }
+  WithId& operator=(WithId&& that) {
+    id_ = that.id_;
+    that.id_ = 0;
+    return *this;
+  }
+
+  size_t id() const { return id_; }
+
+  friend bool operator==(const WithId& a, const WithId& b) {
+    return a.id_ == b.id_;
+  }
+  friend bool operator!=(const WithId& a, const WithId& b) { return !(a == b); }
+
+ protected:
+  explicit WithId(size_t id) : id_(id) {}
+
+ private:
+  size_t id_;
+
+  template <class T>
+  static size_t next_id() {
+    // 0 is reserved for moved from state.
+    static size_t gId = 1;
+    return gId++;
+  }
+};
+
+}  // namespace hash_testing_internal
+
+struct NonStandardLayout {
+  NonStandardLayout() {}
+  explicit NonStandardLayout(std::string s) : value(std::move(s)) {}
+  virtual ~NonStandardLayout() {}
+
+  friend bool operator==(const NonStandardLayout& a,
+                         const NonStandardLayout& b) {
+    return a.value == b.value;
+  }
+  friend bool operator!=(const NonStandardLayout& a,
+                         const NonStandardLayout& b) {
+    return a.value != b.value;
+  }
+
+  template <typename H>
+  friend H AbslHashValue(H h, const NonStandardLayout& v) {
+    return H::combine(std::move(h), v.value);
+  }
+
+  std::string value;
+};
+
+struct StatefulTestingHash
+    : absl::container_internal::hash_testing_internal::WithId<
+          StatefulTestingHash> {
+  template <class T>
+  size_t operator()(const T& t) const {
+    return absl::Hash<T>{}(t);
+  }
+};
+
+struct StatefulTestingEqual
+    : absl::container_internal::hash_testing_internal::WithId<
+          StatefulTestingEqual> {
+  template <class T, class U>
+  bool operator()(const T& t, const U& u) const {
+    return t == u;
+  }
+};
+
+// It is expected that Alloc() == Alloc() for all allocators so we cannot use
+// WithId base. We need to explicitly assign ids.
+template <class T = int>
+struct Alloc : std::allocator<T> {
+  using propagate_on_container_swap = std::true_type;
+
+  // Using old paradigm for this to ensure compatibility.
+  explicit Alloc(size_t id = 0) : id_(id) {}
+
+  Alloc(const Alloc&) = default;
+  Alloc& operator=(const Alloc&) = default;
+
+  template <class U>
+  Alloc(const Alloc<U>& that) : std::allocator<T>(that), id_(that.id()) {}
+
+  template <class U>
+  struct rebind {
+    using other = Alloc<U>;
+  };
+
+  size_t id() const { return id_; }
+
+  friend bool operator==(const Alloc& a, const Alloc& b) {
+    return a.id_ == b.id_;
+  }
+  friend bool operator!=(const Alloc& a, const Alloc& b) { return !(a == b); }
+
+ private:
+  size_t id_ = (std::numeric_limits<size_t>::max)();
+};
+
+template <class Map>
+auto items(const Map& m) -> std::vector<
+    std::pair<typename Map::key_type, typename Map::mapped_type>> {
+  using std::get;
+  std::vector<std::pair<typename Map::key_type, typename Map::mapped_type>> res;
+  res.reserve(m.size());
+  for (const auto& v : m) res.emplace_back(get<0>(v), get<1>(v));
+  return res;
+}
+
+template <class Set>
+auto keys(const Set& s)
+    -> std::vector<typename std::decay<typename Set::key_type>::type> {
+  std::vector<typename std::decay<typename Set::key_type>::type> res;
+  res.reserve(s.size());
+  for (const auto& v : s) res.emplace_back(v);
+  return res;
+}
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// ABSL_UNORDERED_SUPPORTS_ALLOC_CTORS is false for glibcxx versions
+// where the unordered containers are missing certain constructors that
+// take allocator arguments. This test is defined ad-hoc for the platforms
+// we care about (notably Crosstool 17) because libstdcxx's useless
+// versioning scheme precludes a more principled solution.
+// From GCC-4.9 Changelog: (src: https://gcc.gnu.org/gcc-4.9/changes.html)
+// "the unordered associative containers in <unordered_map> and <unordered_set>
+// meet the allocator-aware container requirements;"
+#if (defined(__GLIBCXX__) && __GLIBCXX__ <= 20140425 ) || \
+( __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 9 ))
+#define ABSL_UNORDERED_SUPPORTS_ALLOC_CTORS 0
+#else
+#define ABSL_UNORDERED_SUPPORTS_ALLOC_CTORS 1
+#endif
+
+#endif  // ABSL_CONTAINER_INTERNAL_HASH_POLICY_TESTING_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hash_policy_traits_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/hash_policy_traits_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..82d7cc3a70b0524617750a9070302a1c70e00c0a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hash_policy_traits_test.cc
@@ -0,0 +1,80 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hash_policy_traits.h"
+
+#include <functional>
+#include <memory>
+#include <new>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using ::testing::MockFunction;
+using ::testing::Return;
+using ::testing::ReturnRef;
+
+using Alloc = std::allocator<int>;
+using Slot = int;
+
+struct PolicyWithoutOptionalOps {
+  using slot_type = Slot;
+  using key_type = Slot;
+  using init_type = Slot;
+
+  static std::function<Slot&(Slot*)> element;
+  static int apply(int v) { return apply_impl(v); }
+  static std::function<int(int)> apply_impl;
+  static std::function<Slot&(Slot*)> value;
+};
+
+std::function<int(int)> PolicyWithoutOptionalOps::apply_impl;
+std::function<Slot&(Slot*)> PolicyWithoutOptionalOps::value;
+
+struct Test : ::testing::Test {
+  Test() {
+    PolicyWithoutOptionalOps::apply_impl = [&](int a1) -> int {
+      return apply.Call(a1);
+    };
+    PolicyWithoutOptionalOps::value = [&](Slot* a1) -> Slot& {
+      return value.Call(a1);
+    };
+  }
+
+  std::allocator<int> alloc;
+  int a = 53;
+  MockFunction<int(int)> apply;
+  MockFunction<Slot&(Slot*)> value;
+};
+
+TEST_F(Test, apply) {
+  EXPECT_CALL(apply, Call(42)).WillOnce(Return(1337));
+  EXPECT_EQ(1337, (hash_policy_traits<PolicyWithoutOptionalOps>::apply(42)));
+}
+
+TEST_F(Test, value) {
+  int b = 0;
+  EXPECT_CALL(value, Call(&a)).WillOnce(ReturnRef(b));
+  EXPECT_EQ(&b, &hash_policy_traits<PolicyWithoutOptionalOps>::value(&a));
+}
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler.cc b/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..79a0973a6d464c308bcc1bc96b01d508307ce915
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler.cc
@@ -0,0 +1,285 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hashtablez_sampler.h"
+
+#include <algorithm>
+#include <atomic>
+#include <cassert>
+#include <cmath>
+#include <functional>
+#include <limits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/memory/memory.h"
+#include "absl/profiling/internal/exponential_biased.h"
+#include "absl/profiling/internal/sample_recorder.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/time/clock.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr int HashtablezInfo::kMaxStackDepth;
+#endif
+
+namespace {
+ABSL_CONST_INIT std::atomic<bool> g_hashtablez_enabled{
+    false
+};
+ABSL_CONST_INIT std::atomic<int32_t> g_hashtablez_sample_parameter{1 << 10};
+std::atomic<HashtablezConfigListener> g_hashtablez_config_listener{nullptr};
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+ABSL_PER_THREAD_TLS_KEYWORD absl::profiling_internal::ExponentialBiased
+    g_exponential_biased_generator;
+#endif
+
+void TriggerHashtablezConfigListener() {
+  auto* listener = g_hashtablez_config_listener.load(std::memory_order_acquire);
+  if (listener != nullptr) listener();
+}
+
+}  // namespace
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+ABSL_PER_THREAD_TLS_KEYWORD SamplingState global_next_sample = {0, 0};
+#endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+
+HashtablezSampler& GlobalHashtablezSampler() {
+  static auto* sampler = new HashtablezSampler();
+  return *sampler;
+}
+
+HashtablezInfo::HashtablezInfo() = default;
+HashtablezInfo::~HashtablezInfo() = default;
+
+void HashtablezInfo::PrepareForSampling(int64_t stride,
+                                        size_t inline_element_size_value) {
+  capacity.store(0, std::memory_order_relaxed);
+  size.store(0, std::memory_order_relaxed);
+  num_erases.store(0, std::memory_order_relaxed);
+  num_rehashes.store(0, std::memory_order_relaxed);
+  max_probe_length.store(0, std::memory_order_relaxed);
+  total_probe_length.store(0, std::memory_order_relaxed);
+  hashes_bitwise_or.store(0, std::memory_order_relaxed);
+  hashes_bitwise_and.store(~size_t{}, std::memory_order_relaxed);
+  hashes_bitwise_xor.store(0, std::memory_order_relaxed);
+  max_reserve.store(0, std::memory_order_relaxed);
+
+  create_time = absl::Now();
+  weight = stride;
+  // The inliner makes hardcoded skip_count difficult (especially when combined
+  // with LTO).  We use the ability to exclude stacks by regex when encoding
+  // instead.
+  depth = absl::GetStackTrace(stack, HashtablezInfo::kMaxStackDepth,
+                              /* skip_count= */ 0);
+  inline_element_size = inline_element_size_value;
+}
+
+static bool ShouldForceSampling() {
+  enum ForceState {
+    kDontForce,
+    kForce,
+    kUninitialized
+  };
+  ABSL_CONST_INIT static std::atomic<ForceState> global_state{
+      kUninitialized};
+  ForceState state = global_state.load(std::memory_order_relaxed);
+  if (ABSL_PREDICT_TRUE(state == kDontForce)) return false;
+
+  if (state == kUninitialized) {
+    state = ABSL_INTERNAL_C_SYMBOL(AbslContainerInternalSampleEverything)()
+                ? kForce
+                : kDontForce;
+    global_state.store(state, std::memory_order_relaxed);
+  }
+  return state == kForce;
+}
+
+HashtablezInfo* SampleSlow(SamplingState& next_sample,
+                           size_t inline_element_size) {
+  if (ABSL_PREDICT_FALSE(ShouldForceSampling())) {
+    next_sample.next_sample = 1;
+    const int64_t old_stride = exchange(next_sample.sample_stride, 1);
+    HashtablezInfo* result =
+        GlobalHashtablezSampler().Register(old_stride, inline_element_size);
+    return result;
+  }
+
+#if !defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+  next_sample = {
+      std::numeric_limits<int64_t>::max(),
+      std::numeric_limits<int64_t>::max(),
+  };
+  return nullptr;
+#else
+  bool first = next_sample.next_sample < 0;
+
+  const int64_t next_stride = g_exponential_biased_generator.GetStride(
+      g_hashtablez_sample_parameter.load(std::memory_order_relaxed));
+
+  next_sample.next_sample = next_stride;
+  const int64_t old_stride = exchange(next_sample.sample_stride, next_stride);
+  // Small values of interval are equivalent to just sampling next time.
+  ABSL_ASSERT(next_stride >= 1);
+
+  // g_hashtablez_enabled can be dynamically flipped, we need to set a threshold
+  // low enough that we will start sampling in a reasonable time, so we just use
+  // the default sampling rate.
+  if (!g_hashtablez_enabled.load(std::memory_order_relaxed)) return nullptr;
+
+  // We will only be negative on our first count, so we should just retry in
+  // that case.
+  if (first) {
+    if (ABSL_PREDICT_TRUE(--next_sample.next_sample > 0)) return nullptr;
+    return SampleSlow(next_sample, inline_element_size);
+  }
+
+  return GlobalHashtablezSampler().Register(old_stride, inline_element_size);
+#endif
+}
+
+void UnsampleSlow(HashtablezInfo* info) {
+  GlobalHashtablezSampler().Unregister(info);
+}
+
+void RecordRehashSlow(HashtablezInfo* info, size_t total_probe_length) {
+#ifdef ABSL_INTERNAL_HAVE_SSE2
+  total_probe_length /= 16;
+#else
+  total_probe_length /= 8;
+#endif
+  info->total_probe_length.store(total_probe_length, std::memory_order_relaxed);
+  info->num_erases.store(0, std::memory_order_relaxed);
+  // There is only one concurrent writer, so `load` then `store` is sufficient
+  // instead of using `fetch_add`.
+  info->num_rehashes.store(
+      1 + info->num_rehashes.load(std::memory_order_relaxed),
+      std::memory_order_relaxed);
+}
+
+void RecordReservationSlow(HashtablezInfo* info, size_t target_capacity) {
+  info->max_reserve.store(
+      (std::max)(info->max_reserve.load(std::memory_order_relaxed),
+                 target_capacity),
+      std::memory_order_relaxed);
+}
+
+void RecordClearedReservationSlow(HashtablezInfo* info) {
+  info->max_reserve.store(0, std::memory_order_relaxed);
+}
+
+void RecordStorageChangedSlow(HashtablezInfo* info, size_t size,
+                              size_t capacity) {
+  info->size.store(size, std::memory_order_relaxed);
+  info->capacity.store(capacity, std::memory_order_relaxed);
+  if (size == 0) {
+    // This is a clear, reset the total/num_erases too.
+    info->total_probe_length.store(0, std::memory_order_relaxed);
+    info->num_erases.store(0, std::memory_order_relaxed);
+  }
+}
+
+void RecordInsertSlow(HashtablezInfo* info, size_t hash,
+                      size_t distance_from_desired) {
+  // SwissTables probe in groups of 16, so scale this to count items probes and
+  // not offset from desired.
+  size_t probe_length = distance_from_desired;
+#ifdef ABSL_INTERNAL_HAVE_SSE2
+  probe_length /= 16;
+#else
+  probe_length /= 8;
+#endif
+
+  info->hashes_bitwise_and.fetch_and(hash, std::memory_order_relaxed);
+  info->hashes_bitwise_or.fetch_or(hash, std::memory_order_relaxed);
+  info->hashes_bitwise_xor.fetch_xor(hash, std::memory_order_relaxed);
+  info->max_probe_length.store(
+      std::max(info->max_probe_length.load(std::memory_order_relaxed),
+               probe_length),
+      std::memory_order_relaxed);
+  info->total_probe_length.fetch_add(probe_length, std::memory_order_relaxed);
+  info->size.fetch_add(1, std::memory_order_relaxed);
+}
+
+void RecordEraseSlow(HashtablezInfo* info) {
+  info->size.fetch_sub(1, std::memory_order_relaxed);
+  // There is only one concurrent writer, so `load` then `store` is sufficient
+  // instead of using `fetch_add`.
+  info->num_erases.store(1 + info->num_erases.load(std::memory_order_relaxed),
+                         std::memory_order_relaxed);
+}
+
+void SetHashtablezConfigListener(HashtablezConfigListener l) {
+  g_hashtablez_config_listener.store(l, std::memory_order_release);
+}
+
+bool IsHashtablezEnabled() {
+  return g_hashtablez_enabled.load(std::memory_order_acquire);
+}
+
+void SetHashtablezEnabled(bool enabled) {
+  SetHashtablezEnabledInternal(enabled);
+  TriggerHashtablezConfigListener();
+}
+
+void SetHashtablezEnabledInternal(bool enabled) {
+  g_hashtablez_enabled.store(enabled, std::memory_order_release);
+}
+
+int32_t GetHashtablezSampleParameter() {
+  return g_hashtablez_sample_parameter.load(std::memory_order_acquire);
+}
+
+void SetHashtablezSampleParameter(int32_t rate) {
+  SetHashtablezSampleParameterInternal(rate);
+  TriggerHashtablezConfigListener();
+}
+
+void SetHashtablezSampleParameterInternal(int32_t rate) {
+  if (rate > 0) {
+    g_hashtablez_sample_parameter.store(rate, std::memory_order_release);
+  } else {
+    ABSL_RAW_LOG(ERROR, "Invalid hashtablez sample rate: %lld",
+                 static_cast<long long>(rate));  // NOLINT(runtime/int)
+  }
+}
+
+size_t GetHashtablezMaxSamples() {
+  return GlobalHashtablezSampler().GetMaxSamples();
+}
+
+void SetHashtablezMaxSamples(size_t max) {
+  SetHashtablezMaxSamplesInternal(max);
+  TriggerHashtablezConfigListener();
+}
+
+void SetHashtablezMaxSamplesInternal(size_t max) {
+  if (max > 0) {
+    GlobalHashtablezSampler().SetMaxSamples(max);
+  } else {
+    ABSL_RAW_LOG(ERROR, "Invalid hashtablez max samples: 0");
+  }
+}
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler.h b/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler.h
new file mode 100644
index 0000000000000000000000000000000000000000..e41ee2d747aeac40f2aca4a09854598832ede2c7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler.h
@@ -0,0 +1,257 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: hashtablez_sampler.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the API for a low level library to sample hashtables
+// and collect runtime statistics about them.
+//
+// `HashtablezSampler` controls the lifecycle of `HashtablezInfo` objects which
+// store information about a single sample.
+//
+// `Record*` methods store information into samples.
+// `Sample()` and `Unsample()` make use of a single global sampler with
+// properties controlled by the flags hashtablez_enabled,
+// hashtablez_sample_rate, and hashtablez_max_samples.
+//
+// WARNING
+//
+// Using this sampling API may cause sampled Swiss tables to use the global
+// allocator (operator `new`) in addition to any custom allocator.  If you
+// are using a table in an unusual circumstance where allocation or calling a
+// linux syscall is unacceptable, this could interfere.
+//
+// This utility is internal-only. Use at your own risk.
+
+#ifndef ABSL_CONTAINER_INTERNAL_HASHTABLEZ_SAMPLER_H_
+#define ABSL_CONTAINER_INTERNAL_HASHTABLEZ_SAMPLER_H_
+
+#include <atomic>
+#include <functional>
+#include <memory>
+#include <vector>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/per_thread_tls.h"
+#include "absl/base/optimization.h"
+#include "absl/profiling/internal/sample_recorder.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+// Stores information about a sampled hashtable.  All mutations to this *must*
+// be made through `Record*` functions below.  All reads from this *must* only
+// occur in the callback to `HashtablezSampler::Iterate`.
+struct HashtablezInfo : public profiling_internal::Sample<HashtablezInfo> {
+  // Constructs the object but does not fill in any fields.
+  HashtablezInfo();
+  ~HashtablezInfo();
+  HashtablezInfo(const HashtablezInfo&) = delete;
+  HashtablezInfo& operator=(const HashtablezInfo&) = delete;
+
+  // Puts the object into a clean state, fills in the logically `const` members,
+  // blocking for any readers that are currently sampling the object.
+  void PrepareForSampling(int64_t stride, size_t inline_element_size_value)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(init_mu);
+
+  // These fields are mutated by the various Record* APIs and need to be
+  // thread-safe.
+  std::atomic<size_t> capacity;
+  std::atomic<size_t> size;
+  std::atomic<size_t> num_erases;
+  std::atomic<size_t> num_rehashes;
+  std::atomic<size_t> max_probe_length;
+  std::atomic<size_t> total_probe_length;
+  std::atomic<size_t> hashes_bitwise_or;
+  std::atomic<size_t> hashes_bitwise_and;
+  std::atomic<size_t> hashes_bitwise_xor;
+  std::atomic<size_t> max_reserve;
+
+  // All of the fields below are set by `PrepareForSampling`, they must not be
+  // mutated in `Record*` functions.  They are logically `const` in that sense.
+  // These are guarded by init_mu, but that is not externalized to clients,
+  // which can read them only during `SampleRecorder::Iterate` which will hold
+  // the lock.
+  static constexpr int kMaxStackDepth = 64;
+  absl::Time create_time;
+  int32_t depth;
+  void* stack[kMaxStackDepth];
+  size_t inline_element_size;  // How big is the slot?
+};
+
+void RecordRehashSlow(HashtablezInfo* info, size_t total_probe_length);
+
+void RecordReservationSlow(HashtablezInfo* info, size_t target_capacity);
+
+void RecordClearedReservationSlow(HashtablezInfo* info);
+
+void RecordStorageChangedSlow(HashtablezInfo* info, size_t size,
+                              size_t capacity);
+
+void RecordInsertSlow(HashtablezInfo* info, size_t hash,
+                      size_t distance_from_desired);
+
+void RecordEraseSlow(HashtablezInfo* info);
+
+struct SamplingState {
+  int64_t next_sample;
+  // When we make a sampling decision, we record that distance so we can weight
+  // each sample.
+  int64_t sample_stride;
+};
+
+HashtablezInfo* SampleSlow(SamplingState& next_sample,
+                           size_t inline_element_size);
+void UnsampleSlow(HashtablezInfo* info);
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+#error ABSL_INTERNAL_HASHTABLEZ_SAMPLE cannot be directly set
+#endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+class HashtablezInfoHandle {
+ public:
+  explicit HashtablezInfoHandle() : info_(nullptr) {}
+  explicit HashtablezInfoHandle(HashtablezInfo* info) : info_(info) {}
+
+  // We do not have a destructor. Caller is responsible for calling Unregister
+  // before destroying the handle.
+  void Unregister() {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    UnsampleSlow(info_);
+  }
+
+  inline bool IsSampled() const { return ABSL_PREDICT_FALSE(info_ != nullptr); }
+
+  inline void RecordStorageChanged(size_t size, size_t capacity) {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordStorageChangedSlow(info_, size, capacity);
+  }
+
+  inline void RecordRehash(size_t total_probe_length) {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordRehashSlow(info_, total_probe_length);
+  }
+
+  inline void RecordReservation(size_t target_capacity) {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordReservationSlow(info_, target_capacity);
+  }
+
+  inline void RecordClearedReservation() {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordClearedReservationSlow(info_);
+  }
+
+  inline void RecordInsert(size_t hash, size_t distance_from_desired) {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordInsertSlow(info_, hash, distance_from_desired);
+  }
+
+  inline void RecordErase() {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordEraseSlow(info_);
+  }
+
+  friend inline void swap(HashtablezInfoHandle& lhs,
+                          HashtablezInfoHandle& rhs) {
+    std::swap(lhs.info_, rhs.info_);
+  }
+
+ private:
+  friend class HashtablezInfoHandlePeer;
+  HashtablezInfo* info_;
+};
+#else
+// Ensure that when Hashtablez is turned off at compile time, HashtablezInfo can
+// be removed by the linker, in order to reduce the binary size.
+class HashtablezInfoHandle {
+ public:
+  explicit HashtablezInfoHandle() = default;
+  explicit HashtablezInfoHandle(std::nullptr_t) {}
+
+  inline void Unregister() {}
+  inline bool IsSampled() const { return false; }
+  inline void RecordStorageChanged(size_t /*size*/, size_t /*capacity*/) {}
+  inline void RecordRehash(size_t /*total_probe_length*/) {}
+  inline void RecordReservation(size_t /*target_capacity*/) {}
+  inline void RecordClearedReservation() {}
+  inline void RecordInsert(size_t /*hash*/, size_t /*distance_from_desired*/) {}
+  inline void RecordErase() {}
+
+  friend inline void swap(HashtablezInfoHandle& /*lhs*/,
+                          HashtablezInfoHandle& /*rhs*/) {}
+};
+#endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+extern ABSL_PER_THREAD_TLS_KEYWORD SamplingState global_next_sample;
+#endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+
+// Returns an RAII sampling handle that manages registration and unregistation
+// with the global sampler.
+inline HashtablezInfoHandle Sample(
+    size_t inline_element_size ABSL_ATTRIBUTE_UNUSED) {
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+  if (ABSL_PREDICT_TRUE(--global_next_sample.next_sample > 0)) {
+    return HashtablezInfoHandle(nullptr);
+  }
+  return HashtablezInfoHandle(
+      SampleSlow(global_next_sample, inline_element_size));
+#else
+  return HashtablezInfoHandle(nullptr);
+#endif  // !ABSL_PER_THREAD_TLS
+}
+
+using HashtablezSampler =
+    ::absl::profiling_internal::SampleRecorder<HashtablezInfo>;
+
+// Returns a global Sampler.
+HashtablezSampler& GlobalHashtablezSampler();
+
+using HashtablezConfigListener = void (*)();
+void SetHashtablezConfigListener(HashtablezConfigListener l);
+
+// Enables or disables sampling for Swiss tables.
+bool IsHashtablezEnabled();
+void SetHashtablezEnabled(bool enabled);
+void SetHashtablezEnabledInternal(bool enabled);
+
+// Sets the rate at which Swiss tables will be sampled.
+int32_t GetHashtablezSampleParameter();
+void SetHashtablezSampleParameter(int32_t rate);
+void SetHashtablezSampleParameterInternal(int32_t rate);
+
+// Sets a soft max for the number of samples that will be kept.
+size_t GetHashtablezMaxSamples();
+void SetHashtablezMaxSamples(size_t max);
+void SetHashtablezMaxSamplesInternal(size_t max);
+
+// Configuration override.
+// This allows process-wide sampling without depending on order of
+// initialization of static storage duration objects.
+// The definition of this constant is weak, which allows us to inject a
+// different value for it at link time.
+extern "C" bool ABSL_INTERNAL_C_SYMBOL(AbslContainerInternalSampleEverything)();
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_HASHTABLEZ_SAMPLER_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8ebb08da4a383c03f8e03f59fa8448d4c15944a7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/hashtablez_sampler_test.cc
@@ -0,0 +1,424 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hashtablez_sampler.h"
+
+#include <atomic>
+#include <limits>
+#include <random>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/profiling/internal/sample_recorder.h"
+#include "absl/synchronization/blocking_counter.h"
+#include "absl/synchronization/internal/thread_pool.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/synchronization/notification.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+
+#ifdef ABSL_INTERNAL_HAVE_SSE2
+constexpr int kProbeLength = 16;
+#else
+constexpr int kProbeLength = 8;
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+class HashtablezInfoHandlePeer {
+ public:
+  static HashtablezInfo* GetInfo(HashtablezInfoHandle* h) { return h->info_; }
+};
+#else
+class HashtablezInfoHandlePeer {
+ public:
+  static HashtablezInfo* GetInfo(HashtablezInfoHandle*) { return nullptr; }
+};
+#endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+
+namespace {
+using ::absl::synchronization_internal::ThreadPool;
+using ::testing::IsEmpty;
+using ::testing::UnorderedElementsAre;
+
+std::vector<size_t> GetSizes(HashtablezSampler* s) {
+  std::vector<size_t> res;
+  s->Iterate([&](const HashtablezInfo& info) {
+    res.push_back(info.size.load(std::memory_order_acquire));
+  });
+  return res;
+}
+
+HashtablezInfo* Register(HashtablezSampler* s, size_t size) {
+  const int64_t test_stride = 123;
+  const size_t test_element_size = 17;
+  auto* info = s->Register(test_stride, test_element_size);
+  assert(info != nullptr);
+  info->size.store(size);
+  return info;
+}
+
+TEST(HashtablezInfoTest, PrepareForSampling) {
+  absl::Time test_start = absl::Now();
+  const int64_t test_stride = 123;
+  const size_t test_element_size = 17;
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  info.PrepareForSampling(test_stride, test_element_size);
+
+  EXPECT_EQ(info.capacity.load(), 0);
+  EXPECT_EQ(info.size.load(), 0);
+  EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.num_rehashes.load(), 0);
+  EXPECT_EQ(info.max_probe_length.load(), 0);
+  EXPECT_EQ(info.total_probe_length.load(), 0);
+  EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
+  EXPECT_EQ(info.hashes_bitwise_and.load(), ~size_t{});
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0);
+  EXPECT_EQ(info.max_reserve.load(), 0);
+  EXPECT_GE(info.create_time, test_start);
+  EXPECT_EQ(info.weight, test_stride);
+  EXPECT_EQ(info.inline_element_size, test_element_size);
+
+  info.capacity.store(1, std::memory_order_relaxed);
+  info.size.store(1, std::memory_order_relaxed);
+  info.num_erases.store(1, std::memory_order_relaxed);
+  info.max_probe_length.store(1, std::memory_order_relaxed);
+  info.total_probe_length.store(1, std::memory_order_relaxed);
+  info.hashes_bitwise_or.store(1, std::memory_order_relaxed);
+  info.hashes_bitwise_and.store(1, std::memory_order_relaxed);
+  info.hashes_bitwise_xor.store(1, std::memory_order_relaxed);
+  info.max_reserve.store(1, std::memory_order_relaxed);
+  info.create_time = test_start - absl::Hours(20);
+
+  info.PrepareForSampling(test_stride * 2, test_element_size);
+  EXPECT_EQ(info.capacity.load(), 0);
+  EXPECT_EQ(info.size.load(), 0);
+  EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.num_rehashes.load(), 0);
+  EXPECT_EQ(info.max_probe_length.load(), 0);
+  EXPECT_EQ(info.total_probe_length.load(), 0);
+  EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
+  EXPECT_EQ(info.hashes_bitwise_and.load(), ~size_t{});
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0);
+  EXPECT_EQ(info.max_reserve.load(), 0);
+  EXPECT_EQ(info.weight, 2 * test_stride);
+  EXPECT_EQ(info.inline_element_size, test_element_size);
+  EXPECT_GE(info.create_time, test_start);
+}
+
+TEST(HashtablezInfoTest, RecordStorageChanged) {
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  const int64_t test_stride = 21;
+  const size_t test_element_size = 19;
+  info.PrepareForSampling(test_stride, test_element_size);
+  RecordStorageChangedSlow(&info, 17, 47);
+  EXPECT_EQ(info.size.load(), 17);
+  EXPECT_EQ(info.capacity.load(), 47);
+  RecordStorageChangedSlow(&info, 20, 20);
+  EXPECT_EQ(info.size.load(), 20);
+  EXPECT_EQ(info.capacity.load(), 20);
+}
+
+TEST(HashtablezInfoTest, RecordInsert) {
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  const int64_t test_stride = 25;
+  const size_t test_element_size = 23;
+  info.PrepareForSampling(test_stride, test_element_size);
+  EXPECT_EQ(info.max_probe_length.load(), 0);
+  RecordInsertSlow(&info, 0x0000FF00, 6 * kProbeLength);
+  EXPECT_EQ(info.max_probe_length.load(), 6);
+  EXPECT_EQ(info.hashes_bitwise_and.load(), 0x0000FF00);
+  EXPECT_EQ(info.hashes_bitwise_or.load(), 0x0000FF00);
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0x0000FF00);
+  RecordInsertSlow(&info, 0x000FF000, 4 * kProbeLength);
+  EXPECT_EQ(info.max_probe_length.load(), 6);
+  EXPECT_EQ(info.hashes_bitwise_and.load(), 0x0000F000);
+  EXPECT_EQ(info.hashes_bitwise_or.load(), 0x000FFF00);
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0x000F0F00);
+  RecordInsertSlow(&info, 0x00FF0000, 12 * kProbeLength);
+  EXPECT_EQ(info.max_probe_length.load(), 12);
+  EXPECT_EQ(info.hashes_bitwise_and.load(), 0x00000000);
+  EXPECT_EQ(info.hashes_bitwise_or.load(), 0x00FFFF00);
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0x00F00F00);
+}
+
+TEST(HashtablezInfoTest, RecordErase) {
+  const int64_t test_stride = 31;
+  const size_t test_element_size = 29;
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  info.PrepareForSampling(test_stride, test_element_size);
+  EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.size.load(), 0);
+  RecordInsertSlow(&info, 0x0000FF00, 6 * kProbeLength);
+  EXPECT_EQ(info.size.load(), 1);
+  RecordEraseSlow(&info);
+  EXPECT_EQ(info.size.load(), 0);
+  EXPECT_EQ(info.num_erases.load(), 1);
+  EXPECT_EQ(info.inline_element_size, test_element_size);
+}
+
+TEST(HashtablezInfoTest, RecordRehash) {
+  const int64_t test_stride = 33;
+  const size_t test_element_size = 31;
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  info.PrepareForSampling(test_stride, test_element_size);
+  RecordInsertSlow(&info, 0x1, 0);
+  RecordInsertSlow(&info, 0x2, kProbeLength);
+  RecordInsertSlow(&info, 0x4, kProbeLength);
+  RecordInsertSlow(&info, 0x8, 2 * kProbeLength);
+  EXPECT_EQ(info.size.load(), 4);
+  EXPECT_EQ(info.total_probe_length.load(), 4);
+
+  RecordEraseSlow(&info);
+  RecordEraseSlow(&info);
+  EXPECT_EQ(info.size.load(), 2);
+  EXPECT_EQ(info.total_probe_length.load(), 4);
+  EXPECT_EQ(info.num_erases.load(), 2);
+
+  RecordRehashSlow(&info, 3 * kProbeLength);
+  EXPECT_EQ(info.size.load(), 2);
+  EXPECT_EQ(info.total_probe_length.load(), 3);
+  EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.num_rehashes.load(), 1);
+  EXPECT_EQ(info.inline_element_size, test_element_size);
+}
+
+TEST(HashtablezInfoTest, RecordReservation) {
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  const int64_t test_stride = 35;
+  const size_t test_element_size = 33;
+  info.PrepareForSampling(test_stride, test_element_size);
+  RecordReservationSlow(&info, 3);
+  EXPECT_EQ(info.max_reserve.load(), 3);
+
+  RecordReservationSlow(&info, 2);
+  // High watermark does not change
+  EXPECT_EQ(info.max_reserve.load(), 3);
+
+  RecordReservationSlow(&info, 10);
+  // High watermark does change
+  EXPECT_EQ(info.max_reserve.load(), 10);
+}
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+TEST(HashtablezSamplerTest, SmallSampleParameter) {
+  const size_t test_element_size = 31;
+  SetHashtablezEnabled(true);
+  SetHashtablezSampleParameter(100);
+
+  for (int i = 0; i < 1000; ++i) {
+    SamplingState next_sample = {0, 0};
+    HashtablezInfo* sample = SampleSlow(next_sample, test_element_size);
+    EXPECT_GT(next_sample.next_sample, 0);
+    EXPECT_EQ(next_sample.next_sample, next_sample.sample_stride);
+    EXPECT_NE(sample, nullptr);
+    UnsampleSlow(sample);
+  }
+}
+
+TEST(HashtablezSamplerTest, LargeSampleParameter) {
+  const size_t test_element_size = 31;
+  SetHashtablezEnabled(true);
+  SetHashtablezSampleParameter(std::numeric_limits<int32_t>::max());
+
+  for (int i = 0; i < 1000; ++i) {
+    SamplingState next_sample = {0, 0};
+    HashtablezInfo* sample = SampleSlow(next_sample, test_element_size);
+    EXPECT_GT(next_sample.next_sample, 0);
+    EXPECT_EQ(next_sample.next_sample, next_sample.sample_stride);
+    EXPECT_NE(sample, nullptr);
+    UnsampleSlow(sample);
+  }
+}
+
+TEST(HashtablezSamplerTest, Sample) {
+  const size_t test_element_size = 31;
+  SetHashtablezEnabled(true);
+  SetHashtablezSampleParameter(100);
+  int64_t num_sampled = 0;
+  int64_t total = 0;
+  double sample_rate = 0.0;
+  for (int i = 0; i < 1000000; ++i) {
+    HashtablezInfoHandle h = Sample(test_element_size);
+    ++total;
+    if (h.IsSampled()) {
+      ++num_sampled;
+    }
+    sample_rate = static_cast<double>(num_sampled) / total;
+    if (0.005 < sample_rate && sample_rate < 0.015) break;
+  }
+  EXPECT_NEAR(sample_rate, 0.01, 0.005);
+}
+
+TEST(HashtablezSamplerTest, Handle) {
+  auto& sampler = GlobalHashtablezSampler();
+  const int64_t test_stride = 41;
+  const size_t test_element_size = 39;
+  HashtablezInfoHandle h(sampler.Register(test_stride, test_element_size));
+  auto* info = HashtablezInfoHandlePeer::GetInfo(&h);
+  info->hashes_bitwise_and.store(0x12345678, std::memory_order_relaxed);
+
+  bool found = false;
+  sampler.Iterate([&](const HashtablezInfo& h) {
+    if (&h == info) {
+      EXPECT_EQ(h.weight, test_stride);
+      EXPECT_EQ(h.hashes_bitwise_and.load(), 0x12345678);
+      found = true;
+    }
+  });
+  EXPECT_TRUE(found);
+
+  h.Unregister();
+  h = HashtablezInfoHandle();
+  found = false;
+  sampler.Iterate([&](const HashtablezInfo& h) {
+    if (&h == info) {
+      // this will only happen if some other thread has resurrected the info
+      // the old handle was using.
+      if (h.hashes_bitwise_and.load() == 0x12345678) {
+        found = true;
+      }
+    }
+  });
+  EXPECT_FALSE(found);
+}
+#endif
+
+
+TEST(HashtablezSamplerTest, Registration) {
+  HashtablezSampler sampler;
+  auto* info1 = Register(&sampler, 1);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(1));
+
+  auto* info2 = Register(&sampler, 2);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(1, 2));
+  info1->size.store(3);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(3, 2));
+
+  sampler.Unregister(info1);
+  sampler.Unregister(info2);
+}
+
+TEST(HashtablezSamplerTest, Unregistration) {
+  HashtablezSampler sampler;
+  std::vector<HashtablezInfo*> infos;
+  for (size_t i = 0; i < 3; ++i) {
+    infos.push_back(Register(&sampler, i));
+  }
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 1, 2));
+
+  sampler.Unregister(infos[1]);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 2));
+
+  infos.push_back(Register(&sampler, 3));
+  infos.push_back(Register(&sampler, 4));
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 2, 3, 4));
+  sampler.Unregister(infos[3]);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 2, 4));
+
+  sampler.Unregister(infos[0]);
+  sampler.Unregister(infos[2]);
+  sampler.Unregister(infos[4]);
+  EXPECT_THAT(GetSizes(&sampler), IsEmpty());
+}
+
+TEST(HashtablezSamplerTest, MultiThreaded) {
+  HashtablezSampler sampler;
+  Notification stop;
+  ThreadPool pool(10);
+
+  for (int i = 0; i < 10; ++i) {
+    const int64_t sampling_stride = 11 + i % 3;
+    const size_t elt_size = 10 + i % 2;
+    pool.Schedule([&sampler, &stop, sampling_stride, elt_size]() {
+      std::random_device rd;
+      std::mt19937 gen(rd());
+
+      std::vector<HashtablezInfo*> infoz;
+      while (!stop.HasBeenNotified()) {
+        if (infoz.empty()) {
+          infoz.push_back(sampler.Register(sampling_stride, elt_size));
+        }
+        switch (std::uniform_int_distribution<>(0, 2)(gen)) {
+          case 0: {
+            infoz.push_back(sampler.Register(sampling_stride, elt_size));
+            break;
+          }
+          case 1: {
+            size_t p =
+                std::uniform_int_distribution<>(0, infoz.size() - 1)(gen);
+            HashtablezInfo* info = infoz[p];
+            infoz[p] = infoz.back();
+            infoz.pop_back();
+            EXPECT_EQ(info->weight, sampling_stride);
+            sampler.Unregister(info);
+            break;
+          }
+          case 2: {
+            absl::Duration oldest = absl::ZeroDuration();
+            sampler.Iterate([&](const HashtablezInfo& info) {
+              oldest = std::max(oldest, absl::Now() - info.create_time);
+            });
+            ASSERT_GE(oldest, absl::ZeroDuration());
+            break;
+          }
+        }
+      }
+    });
+  }
+  // The threads will hammer away.  Give it a little bit of time for tsan to
+  // spot errors.
+  absl::SleepFor(absl::Seconds(3));
+  stop.Notify();
+}
+
+TEST(HashtablezSamplerTest, Callback) {
+  HashtablezSampler sampler;
+
+  auto* info1 = Register(&sampler, 1);
+  auto* info2 = Register(&sampler, 2);
+
+  static const HashtablezInfo* expected;
+
+  auto callback = [](const HashtablezInfo& info) {
+    // We can't use `info` outside of this callback because the object will be
+    // disposed as soon as we return from here.
+    EXPECT_EQ(&info, expected);
+  };
+
+  // Set the callback.
+  EXPECT_EQ(sampler.SetDisposeCallback(callback), nullptr);
+  expected = info1;
+  sampler.Unregister(info1);
+
+  // Unset the callback.
+  EXPECT_EQ(callback, sampler.SetDisposeCallback(nullptr));
+  expected = nullptr;  // no more calls.
+  sampler.Unregister(info2);
+}
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/layout_benchmark.cc b/weight/_dep/abseil-cpp/absl/container/internal/layout_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3af35e33ed014ba8a8df9b243410ad60b165c13b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/layout_benchmark.cc
@@ -0,0 +1,122 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Every benchmark should have the same performance as the corresponding
+// headroom benchmark.
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/container/internal/layout.h"
+#include "benchmark/benchmark.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using ::benchmark::DoNotOptimize;
+
+using Int128 = int64_t[2];
+
+// This benchmark provides the upper bound on performance for BM_OffsetConstant.
+template <size_t Offset, class... Ts>
+void BM_OffsetConstantHeadroom(benchmark::State& state) {
+  for (auto _ : state) {
+    DoNotOptimize(Offset);
+  }
+}
+
+template <size_t Offset, class... Ts>
+void BM_OffsetConstant(benchmark::State& state) {
+  using L = Layout<Ts...>;
+  ABSL_RAW_CHECK(L::Partial(3, 5, 7).template Offset<3>() == Offset,
+                 "Invalid offset");
+  for (auto _ : state) {
+    DoNotOptimize(L::Partial(3, 5, 7).template Offset<3>());
+  }
+}
+
+template <class... Ts>
+size_t VariableOffset(size_t n, size_t m, size_t k);
+
+template <>
+size_t VariableOffset<int8_t, int16_t, int32_t, Int128>(size_t n, size_t m,
+                                                        size_t k) {
+  auto Align = [](size_t n, size_t m) { return (n + m - 1) & ~(m - 1); };
+  return Align(Align(Align(n * 1, 2) + m * 2, 4) + k * 4, 8);
+}
+
+template <>
+size_t VariableOffset<Int128, int32_t, int16_t, int8_t>(size_t n, size_t m,
+                                                        size_t k) {
+  // No alignment is necessary.
+  return n * 16 + m * 4 + k * 2;
+}
+
+// This benchmark provides the upper bound on performance for BM_OffsetVariable.
+template <size_t Offset, class... Ts>
+void BM_OffsetVariableHeadroom(benchmark::State& state) {
+  size_t n = 3;
+  size_t m = 5;
+  size_t k = 7;
+  ABSL_RAW_CHECK(VariableOffset<Ts...>(n, m, k) == Offset, "Invalid offset");
+  for (auto _ : state) {
+    DoNotOptimize(n);
+    DoNotOptimize(m);
+    DoNotOptimize(k);
+    DoNotOptimize(VariableOffset<Ts...>(n, m, k));
+  }
+}
+
+template <size_t Offset, class... Ts>
+void BM_OffsetVariable(benchmark::State& state) {
+  using L = Layout<Ts...>;
+  size_t n = 3;
+  size_t m = 5;
+  size_t k = 7;
+  ABSL_RAW_CHECK(L::Partial(n, m, k).template Offset<3>() == Offset,
+                 "Invalid offset");
+  for (auto _ : state) {
+    DoNotOptimize(n);
+    DoNotOptimize(m);
+    DoNotOptimize(k);
+    DoNotOptimize(L::Partial(n, m, k).template Offset<3>());
+  }
+}
+
+// Run all benchmarks in two modes:
+//
+//   Layout with padding: int8_t[3], int16_t[5], int32_t[7], Int128[?].
+//   Layout without padding: Int128[3], int32_t[5], int16_t[7], int8_t[?].
+
+#define OFFSET_BENCHMARK(NAME, OFFSET, T1, T2, T3, T4) \
+  auto& NAME##_##OFFSET##_##T1##_##T2##_##T3##_##T4 =  \
+      NAME<OFFSET, T1, T2, T3, T4>;                    \
+  BENCHMARK(NAME##_##OFFSET##_##T1##_##T2##_##T3##_##T4)
+
+OFFSET_BENCHMARK(BM_OffsetConstantHeadroom, 48, int8_t, int16_t, int32_t,
+                 Int128);
+OFFSET_BENCHMARK(BM_OffsetConstant, 48, int8_t, int16_t, int32_t, Int128);
+OFFSET_BENCHMARK(BM_OffsetConstantHeadroom, 82, Int128, int32_t, int16_t,
+                 int8_t);
+OFFSET_BENCHMARK(BM_OffsetConstant, 82, Int128, int32_t, int16_t, int8_t);
+OFFSET_BENCHMARK(BM_OffsetVariableHeadroom, 48, int8_t, int16_t, int32_t,
+                 Int128);
+OFFSET_BENCHMARK(BM_OffsetVariable, 48, int8_t, int16_t, int32_t, Int128);
+OFFSET_BENCHMARK(BM_OffsetVariableHeadroom, 82, Int128, int32_t, int16_t,
+                 int8_t);
+OFFSET_BENCHMARK(BM_OffsetVariable, 82, Int128, int32_t, int16_t, int8_t);
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/layout_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/layout_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ae55cf7e51c1a4c3c949306ecc6ebbd1fd5b0536
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/layout_test.cc
@@ -0,0 +1,1646 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/layout.h"
+
+// We need ::max_align_t because some libstdc++ versions don't provide
+// std::max_align_t
+#include <stddef.h>
+
+#include <cstdint>
+#include <cstring>
+#include <initializer_list>
+#include <memory>
+#include <ostream>
+#include <string>
+#include <tuple>
+#include <type_traits>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/log/check.h"
+#include "absl/types/span.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using ::absl::Span;
+using ::testing::ElementsAre;
+
+size_t Distance(const void* from, const void* to) {
+  CHECK_LE(from, to) << "Distance must be non-negative";
+  return static_cast<const char*>(to) - static_cast<const char*>(from);
+}
+
+template <class Expected, class Actual>
+Expected Type(Actual val) {
+  static_assert(std::is_same<Expected, Actual>(), "");
+  return val;
+}
+
+// Helper classes to test different size and alignments.
+struct alignas(8) Int128 {
+  uint64_t a, b;
+  friend bool operator==(Int128 lhs, Int128 rhs) {
+    return std::tie(lhs.a, lhs.b) == std::tie(rhs.a, rhs.b);
+  }
+
+  static std::string Name() {
+    return internal_layout::adl_barrier::TypeName<Int128>();
+  }
+};
+
+// int64_t is *not* 8-byte aligned on all platforms!
+struct alignas(8) Int64 {
+  int64_t a;
+  friend bool operator==(Int64 lhs, Int64 rhs) {
+    return lhs.a == rhs.a;
+  }
+};
+
+// Properties of types that this test relies on.
+static_assert(sizeof(int8_t) == 1, "");
+static_assert(alignof(int8_t) == 1, "");
+static_assert(sizeof(int16_t) == 2, "");
+static_assert(alignof(int16_t) == 2, "");
+static_assert(sizeof(int32_t) == 4, "");
+static_assert(alignof(int32_t) == 4, "");
+static_assert(sizeof(Int64) == 8, "");
+static_assert(alignof(Int64) == 8, "");
+static_assert(sizeof(Int128) == 16, "");
+static_assert(alignof(Int128) == 8, "");
+
+template <class Expected, class Actual>
+void SameType() {
+  static_assert(std::is_same<Expected, Actual>(), "");
+}
+
+TEST(Layout, ElementType) {
+  {
+    using L = Layout<int32_t>;
+    SameType<int32_t, L::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial())::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<0>>();
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    SameType<int32_t, L::ElementType<0>>();
+    SameType<int32_t, L::ElementType<1>>();
+    SameType<int32_t, decltype(L::Partial())::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial())::ElementType<1>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<1>>();
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    SameType<int8_t, L::ElementType<0>>();
+    SameType<int32_t, L::ElementType<1>>();
+    SameType<Int128, L::ElementType<2>>();
+    SameType<int8_t, decltype(L::Partial())::ElementType<0>>();
+    SameType<int8_t, decltype(L::Partial(0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0))::ElementType<1>>();
+    SameType<int8_t, decltype(L::Partial(0, 0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0, 0))::ElementType<1>>();
+    SameType<Int128, decltype(L::Partial(0, 0))::ElementType<2>>();
+    SameType<int8_t, decltype(L::Partial(0, 0, 0))::ElementType<0>>();
+    SameType<int32_t, decltype(L::Partial(0, 0, 0))::ElementType<1>>();
+    SameType<Int128, decltype(L::Partial(0, 0, 0))::ElementType<2>>();
+  }
+}
+
+TEST(Layout, ElementTypes) {
+  {
+    using L = Layout<int32_t>;
+    SameType<std::tuple<int32_t>, L::ElementTypes>();
+    SameType<std::tuple<int32_t>, decltype(L::Partial())::ElementTypes>();
+    SameType<std::tuple<int32_t>, decltype(L::Partial(0))::ElementTypes>();
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    SameType<std::tuple<int32_t, int32_t>, L::ElementTypes>();
+    SameType<std::tuple<int32_t, int32_t>,
+             decltype(L::Partial())::ElementTypes>();
+    SameType<std::tuple<int32_t, int32_t>,
+             decltype(L::Partial(0))::ElementTypes>();
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    SameType<std::tuple<int8_t, int32_t, Int128>, L::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial())::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial(0))::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial(0, 0))::ElementTypes>();
+    SameType<std::tuple<int8_t, int32_t, Int128>,
+             decltype(L::Partial(0, 0, 0))::ElementTypes>();
+  }
+}
+
+TEST(Layout, OffsetByIndex) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial().Offset<0>());
+    EXPECT_EQ(0, L::Partial(3).Offset<0>());
+    EXPECT_EQ(0, L(3).Offset<0>());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, L::Partial().Offset<0>());
+    EXPECT_EQ(0, L::Partial(3).Offset<0>());
+    EXPECT_EQ(12, L::Partial(3).Offset<1>());
+    EXPECT_EQ(0, L::Partial(3, 5).Offset<0>());
+    EXPECT_EQ(12, L::Partial(3, 5).Offset<1>());
+    EXPECT_EQ(0, L(3, 5).Offset<0>());
+    EXPECT_EQ(12, L(3, 5).Offset<1>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, L::Partial().Offset<0>());
+    EXPECT_EQ(0, L::Partial(0).Offset<0>());
+    EXPECT_EQ(0, L::Partial(0).Offset<1>());
+    EXPECT_EQ(0, L::Partial(1).Offset<0>());
+    EXPECT_EQ(4, L::Partial(1).Offset<1>());
+    EXPECT_EQ(0, L::Partial(5).Offset<0>());
+    EXPECT_EQ(8, L::Partial(5).Offset<1>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<0>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<1>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(1, 0).Offset<0>());
+    EXPECT_EQ(4, L::Partial(1, 0).Offset<1>());
+    EXPECT_EQ(8, L::Partial(1, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(5, 3).Offset<0>());
+    EXPECT_EQ(8, L::Partial(5, 3).Offset<1>());
+    EXPECT_EQ(24, L::Partial(5, 3).Offset<2>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<0>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<1>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(1, 0, 0).Offset<0>());
+    EXPECT_EQ(4, L::Partial(1, 0, 0).Offset<1>());
+    EXPECT_EQ(8, L::Partial(1, 0, 0).Offset<2>());
+    EXPECT_EQ(0, L::Partial(5, 3, 1).Offset<0>());
+    EXPECT_EQ(24, L::Partial(5, 3, 1).Offset<2>());
+    EXPECT_EQ(8, L::Partial(5, 3, 1).Offset<1>());
+    EXPECT_EQ(0, L(5, 3, 1).Offset<0>());
+    EXPECT_EQ(24, L(5, 3, 1).Offset<2>());
+    EXPECT_EQ(8, L(5, 3, 1).Offset<1>());
+  }
+}
+
+TEST(Layout, OffsetByType) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial().Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(3).Offset<int32_t>());
+    EXPECT_EQ(0, L(3).Offset<int32_t>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, L::Partial().Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0).Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(1).Offset<int8_t>());
+    EXPECT_EQ(4, L::Partial(1).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(5).Offset<int8_t>());
+    EXPECT_EQ(8, L::Partial(5).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(0, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(1, 0).Offset<int8_t>());
+    EXPECT_EQ(4, L::Partial(1, 0).Offset<int32_t>());
+    EXPECT_EQ(8, L::Partial(1, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(5, 3).Offset<int8_t>());
+    EXPECT_EQ(8, L::Partial(5, 3).Offset<int32_t>());
+    EXPECT_EQ(24, L::Partial(5, 3).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<int8_t>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<int32_t>());
+    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(1, 0, 0).Offset<int8_t>());
+    EXPECT_EQ(4, L::Partial(1, 0, 0).Offset<int32_t>());
+    EXPECT_EQ(8, L::Partial(1, 0, 0).Offset<Int128>());
+    EXPECT_EQ(0, L::Partial(5, 3, 1).Offset<int8_t>());
+    EXPECT_EQ(24, L::Partial(5, 3, 1).Offset<Int128>());
+    EXPECT_EQ(8, L::Partial(5, 3, 1).Offset<int32_t>());
+    EXPECT_EQ(0, L(5, 3, 1).Offset<int8_t>());
+    EXPECT_EQ(24, L(5, 3, 1).Offset<Int128>());
+    EXPECT_EQ(8, L(5, 3, 1).Offset<int32_t>());
+  }
+}
+
+TEST(Layout, Offsets) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
+    EXPECT_THAT(L::Partial(3).Offsets(), ElementsAre(0));
+    EXPECT_THAT(L(3).Offsets(), ElementsAre(0));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
+    EXPECT_THAT(L::Partial(3).Offsets(), ElementsAre(0, 12));
+    EXPECT_THAT(L::Partial(3, 5).Offsets(), ElementsAre(0, 12));
+    EXPECT_THAT(L(3, 5).Offsets(), ElementsAre(0, 12));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
+    EXPECT_THAT(L::Partial(1).Offsets(), ElementsAre(0, 4));
+    EXPECT_THAT(L::Partial(5).Offsets(), ElementsAre(0, 8));
+    EXPECT_THAT(L::Partial(0, 0).Offsets(), ElementsAre(0, 0, 0));
+    EXPECT_THAT(L::Partial(1, 0).Offsets(), ElementsAre(0, 4, 8));
+    EXPECT_THAT(L::Partial(5, 3).Offsets(), ElementsAre(0, 8, 24));
+    EXPECT_THAT(L::Partial(0, 0, 0).Offsets(), ElementsAre(0, 0, 0));
+    EXPECT_THAT(L::Partial(1, 0, 0).Offsets(), ElementsAre(0, 4, 8));
+    EXPECT_THAT(L::Partial(5, 3, 1).Offsets(), ElementsAre(0, 8, 24));
+    EXPECT_THAT(L(5, 3, 1).Offsets(), ElementsAre(0, 8, 24));
+  }
+}
+
+TEST(Layout, AllocSize) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).AllocSize());
+    EXPECT_EQ(12, L::Partial(3).AllocSize());
+    EXPECT_EQ(12, L(3).AllocSize());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(32, L::Partial(3, 5).AllocSize());
+    EXPECT_EQ(32, L(3, 5).AllocSize());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, L::Partial(0, 0, 0).AllocSize());
+    EXPECT_EQ(8, L::Partial(1, 0, 0).AllocSize());
+    EXPECT_EQ(8, L::Partial(0, 1, 0).AllocSize());
+    EXPECT_EQ(16, L::Partial(0, 0, 1).AllocSize());
+    EXPECT_EQ(24, L::Partial(1, 1, 1).AllocSize());
+    EXPECT_EQ(136, L::Partial(3, 5, 7).AllocSize());
+    EXPECT_EQ(136, L(3, 5, 7).AllocSize());
+  }
+}
+
+TEST(Layout, SizeByIndex) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Size<0>());
+    EXPECT_EQ(3, L::Partial(3).Size<0>());
+    EXPECT_EQ(3, L(3).Size<0>());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Size<0>());
+    EXPECT_EQ(3, L::Partial(3).Size<0>());
+    EXPECT_EQ(3, L::Partial(3, 5).Size<0>());
+    EXPECT_EQ(5, L::Partial(3, 5).Size<1>());
+    EXPECT_EQ(3, L(3, 5).Size<0>());
+    EXPECT_EQ(5, L(3, 5).Size<1>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Size<0>());
+    EXPECT_EQ(3, L::Partial(3, 5).Size<0>());
+    EXPECT_EQ(5, L::Partial(3, 5).Size<1>());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Size<0>());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Size<1>());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Size<2>());
+    EXPECT_EQ(3, L(3, 5, 7).Size<0>());
+    EXPECT_EQ(5, L(3, 5, 7).Size<1>());
+    EXPECT_EQ(7, L(3, 5, 7).Size<2>());
+  }
+}
+
+TEST(Layout, SizeByType) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Size<int32_t>());
+    EXPECT_EQ(3, L::Partial(3).Size<int32_t>());
+    EXPECT_EQ(3, L(3).Size<int32_t>());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Size<int8_t>());
+    EXPECT_EQ(3, L::Partial(3, 5).Size<int8_t>());
+    EXPECT_EQ(5, L::Partial(3, 5).Size<int32_t>());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Size<int8_t>());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Size<int32_t>());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Size<Int128>());
+    EXPECT_EQ(3, L(3, 5, 7).Size<int8_t>());
+    EXPECT_EQ(5, L(3, 5, 7).Size<int32_t>());
+    EXPECT_EQ(7, L(3, 5, 7).Size<Int128>());
+  }
+}
+
+TEST(Layout, Sizes) {
+  {
+    using L = Layout<int32_t>;
+    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
+    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
+    EXPECT_THAT(L(3).Sizes(), ElementsAre(3));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
+    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
+    EXPECT_THAT(L::Partial(3, 5).Sizes(), ElementsAre(3, 5));
+    EXPECT_THAT(L(3, 5).Sizes(), ElementsAre(3, 5));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
+    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
+    EXPECT_THAT(L::Partial(3, 5).Sizes(), ElementsAre(3, 5));
+    EXPECT_THAT(L::Partial(3, 5, 7).Sizes(), ElementsAre(3, 5, 7));
+    EXPECT_THAT(L(3, 5, 7).Sizes(), ElementsAre(3, 5, 7));
+  }
+}
+
+TEST(Layout, PointerByIndex) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L(3).Pointer<0>(p))));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(12,
+              Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<1>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int32_t*>(L::Partial(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(
+        12, Distance(p, Type<const int32_t*>(L::Partial(3, 5).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<const int32_t*>(L(3, 5).Pointer<1>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial(0).Pointer<0>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int32_t*>(L::Partial(0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial(1).Pointer<0>(p))));
+    EXPECT_EQ(4,
+              Distance(p, Type<const int32_t*>(L::Partial(1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L::Partial(5).Pointer<0>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<const int32_t*>(L::Partial(5).Pointer<1>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(0, 0).Pointer<0>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int32_t*>(L::Partial(0, 0).Pointer<1>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const Int128*>(L::Partial(0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(1, 0).Pointer<0>(p))));
+    EXPECT_EQ(
+        4, Distance(p, Type<const int32_t*>(L::Partial(1, 0).Pointer<1>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<const Int128*>(L::Partial(1, 0).Pointer<2>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<const int8_t*>(L::Partial(5, 3).Pointer<0>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<const int32_t*>(L::Partial(5, 3).Pointer<1>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<const Int128*>(L::Partial(5, 3).Pointer<2>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(0, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int32_t*>(L::Partial(0, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const Int128*>(L::Partial(0, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(1, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<const int32_t*>(L::Partial(1, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<const Int128*>(L::Partial(1, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<const Int128*>(L::Partial(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<const int32_t*>(L::Partial(5, 3, 1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(L(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(24, Distance(p, Type<const Int128*>(L(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const int32_t*>(L(5, 3, 1).Pointer<1>(p))));
+  }
+}
+
+TEST(Layout, PointerByType) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0, Distance(p, Type<const int32_t*>(L::Partial().Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int32_t*>(L::Partial(3).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(L(3).Pointer<int32_t>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial().Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int32_t*>(L::Partial(0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(1).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<const int32_t*>(L::Partial(1).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<const int8_t*>(L::Partial(5).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<const int32_t*>(L::Partial(5).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int8_t*>(L::Partial(0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(
+                                 L::Partial(0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const Int128*>(L::Partial(0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int8_t*>(L::Partial(1, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(4, Distance(p, Type<const int32_t*>(
+                                 L::Partial(1, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<const Int128*>(L::Partial(1, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<const int8_t*>(L::Partial(5, 3).Pointer<int8_t>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const int32_t*>(
+                                 L::Partial(5, 3).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<const Int128*>(L::Partial(5, 3).Pointer<Int128>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(
+                                 L::Partial(0, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int32_t*>(
+                                 L::Partial(0, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const Int128*>(
+                                 L::Partial(0, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(
+                                 L::Partial(1, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(4, Distance(p, Type<const int32_t*>(
+                                 L::Partial(1, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const Int128*>(
+                                 L::Partial(1, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0, Distance(p, Type<const int8_t*>(
+                                 L::Partial(5, 3, 1).Pointer<int8_t>(p))));
+    EXPECT_EQ(24, Distance(p, Type<const Int128*>(
+                                  L::Partial(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(8, Distance(p, Type<const int32_t*>(
+                                 L::Partial(5, 3, 1).Pointer<int32_t>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<const Int128*>(L(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<const int32_t*>(L(5, 3, 1).Pointer<int32_t>(p))));
+  }
+}
+
+TEST(Layout, MutablePointerByIndex) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L(3).Pointer<0>(p))));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<int32_t*>(L::Partial(3).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<int32_t*>(L::Partial(3, 5).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L(3, 5).Pointer<0>(p))));
+    EXPECT_EQ(12, Distance(p, Type<int32_t*>(L(3, 5).Pointer<1>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial().Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1).Pointer<0>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5).Pointer<0>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0, 0).Pointer<0>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial(0, 0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<Int128*>(L::Partial(0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1, 0).Pointer<0>(p))));
+    EXPECT_EQ(4, Distance(p, Type<int32_t*>(L::Partial(1, 0).Pointer<1>(p))));
+    EXPECT_EQ(8, Distance(p, Type<Int128*>(L::Partial(1, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5, 3).Pointer<0>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L::Partial(5, 3).Pointer<1>(p))));
+    EXPECT_EQ(24, Distance(p, Type<Int128*>(L::Partial(5, 3).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int32_t*>(L::Partial(0, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<Int128*>(L::Partial(0, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1, 0, 0).Pointer<0>(p))));
+    EXPECT_EQ(4,
+              Distance(p, Type<int32_t*>(L::Partial(1, 0, 0).Pointer<1>(p))));
+    EXPECT_EQ(8, Distance(p, Type<Int128*>(L::Partial(1, 0, 0).Pointer<2>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<Int128*>(L::Partial(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<int32_t*>(L::Partial(5, 3, 1).Pointer<1>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L(5, 3, 1).Pointer<0>(p))));
+    EXPECT_EQ(24, Distance(p, Type<Int128*>(L(5, 3, 1).Pointer<2>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L(5, 3, 1).Pointer<1>(p))));
+  }
+}
+
+TEST(Layout, MutablePointerByType) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L::Partial().Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int32_t*>(L::Partial(3).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int32_t*>(L(3).Pointer<int32_t>(p))));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial().Pointer<int8_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(0).Pointer<int8_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int32_t*>(L::Partial(0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(1).Pointer<int8_t>(p))));
+    EXPECT_EQ(4,
+              Distance(p, Type<int32_t*>(L::Partial(1).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L::Partial(5).Pointer<int8_t>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<int32_t*>(L::Partial(5).Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int8_t*>(L::Partial(0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<int32_t*>(L::Partial(0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<Int128*>(L::Partial(0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int8_t*>(L::Partial(1, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        4, Distance(p, Type<int32_t*>(L::Partial(1, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(8,
+              Distance(p, Type<Int128*>(L::Partial(1, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(0,
+              Distance(p, Type<int8_t*>(L::Partial(5, 3).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<int32_t*>(L::Partial(5, 3).Pointer<int32_t>(p))));
+    EXPECT_EQ(24,
+              Distance(p, Type<Int128*>(L::Partial(5, 3).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<int8_t*>(L::Partial(0, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<int32_t*>(L::Partial(0, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<Int128*>(L::Partial(0, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<int8_t*>(L::Partial(1, 0, 0).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<int32_t*>(L::Partial(1, 0, 0).Pointer<int32_t>(p))));
+    EXPECT_EQ(
+        8, Distance(p, Type<Int128*>(L::Partial(1, 0, 0).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        0, Distance(p, Type<int8_t*>(L::Partial(5, 3, 1).Pointer<int8_t>(p))));
+    EXPECT_EQ(
+        24, Distance(p, Type<Int128*>(L::Partial(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<int32_t*>(L::Partial(5, 3, 1).Pointer<int32_t>(p))));
+    EXPECT_EQ(0, Distance(p, Type<int8_t*>(L(5, 3, 1).Pointer<int8_t>(p))));
+    EXPECT_EQ(24, Distance(p, Type<Int128*>(L(5, 3, 1).Pointer<Int128>(p))));
+    EXPECT_EQ(8, Distance(p, Type<int32_t*>(L(5, 3, 1).Pointer<int32_t>(p))));
+  }
+}
+
+TEST(Layout, Pointers) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p)),
+              Type<std::tuple<const int8_t*>>(x.Pointers(p)));
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p)),
+              (Type<std::tuple<const int8_t*, const int8_t*>>(x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<const int8_t*, const int8_t*, const Int128*>>(
+            x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<const int8_t*, const int8_t*, const Int128*>>(
+            x.Pointers(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<const int8_t*, const int8_t*, const Int128*>>(
+            x.Pointers(p))));
+  }
+}
+
+TEST(Layout, MutablePointers) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p)),
+              Type<std::tuple<int8_t*>>(x.Pointers(p)));
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p)),
+              (Type<std::tuple<int8_t*, int8_t*>>(x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<int8_t*, int8_t*, Int128*>>(x.Pointers(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<int8_t*, int8_t*, Int128*>>(x.Pointers(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_EQ(
+        std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
+        (Type<std::tuple<int8_t*, int8_t*, Int128*>>(x.Pointers(p))));
+  }
+}
+
+TEST(Layout, SliceByIndexSize) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L(3).Slice<0>(p).size());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(5, L(3, 5).Slice<1>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<2>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<2>(p).size());
+  }
+}
+
+TEST(Layout, SliceByTypeSize) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L(3).Slice<int32_t>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<int8_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<Int128>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<Int128>(p).size());
+  }
+}
+
+TEST(Layout, MutableSliceByIndexSize) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L(3).Slice<0>(p).size());
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(5, L(3, 5).Slice<1>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<2>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<0>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<1>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<2>(p).size());
+  }
+}
+
+TEST(Layout, MutableSliceByTypeSize) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L(3).Slice<int32_t>(p).size());
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(3, L::Partial(3).Slice<int8_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5).Slice<int32_t>(p).size());
+    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<Int128>(p).size());
+    EXPECT_EQ(3, L(3, 5, 7).Slice<int8_t>(p).size());
+    EXPECT_EQ(5, L(3, 5, 7).Slice<int32_t>(p).size());
+    EXPECT_EQ(7, L(3, 5, 7).Slice<Int128>(p).size());
+  }
+}
+
+TEST(Layout, SliceByIndexData) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int32_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<const int32_t>>(L(3).Slice<0>(p)).data()));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        12,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(3, 5).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<const int32_t>>(L(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        12, Distance(p, Type<Span<const int32_t>>(L(3, 5).Slice<1>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<const int8_t>>(L::Partial(5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(1, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(1, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<const int8_t>>(L::Partial(5, 3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p, Type<Span<const int32_t>>(L::Partial(5, 3).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(0, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(0, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const Int128>>(L::Partial(0, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(1, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(1, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<const Int128>>(L::Partial(1, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(
+            p,
+            Type<Span<const Int128>>(L::Partial(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(5, 3, 1).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<Span<const Int128>>(L(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<Span<const int32_t>>(L(5, 3, 1).Slice<1>(p)).data()));
+  }
+}
+
+TEST(Layout, SliceByTypeData) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int32_t>>(L::Partial(3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int32_t>>(L(3).Slice<int32_t>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<const int8_t>>(L::Partial(5).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L::Partial(0, 0).Slice<int8_t>(p))
+                        .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const int32_t>>(
+                                 L::Partial(0, 0).Slice<int32_t>(p))
+                                 .data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L::Partial(1, 0).Slice<int8_t>(p))
+                        .data()));
+    EXPECT_EQ(4, Distance(p, Type<Span<const int32_t>>(
+                                 L::Partial(1, 0).Slice<int32_t>(p))
+                                 .data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<const int8_t>>(L::Partial(5, 3).Slice<int8_t>(p))
+                        .data()));
+    EXPECT_EQ(8, Distance(p, Type<Span<const int32_t>>(
+                                 L::Partial(5, 3).Slice<int32_t>(p))
+                                 .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const int8_t>>(
+                                 L::Partial(0, 0, 0).Slice<int8_t>(p))
+                                 .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const int32_t>>(
+                                 L::Partial(0, 0, 0).Slice<int32_t>(p))
+                                 .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const Int128>>(
+                                 L::Partial(0, 0, 0).Slice<Int128>(p))
+                                 .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const int8_t>>(
+                                 L::Partial(1, 0, 0).Slice<int8_t>(p))
+                                 .data()));
+    EXPECT_EQ(4, Distance(p, Type<Span<const int32_t>>(
+                                 L::Partial(1, 0, 0).Slice<int32_t>(p))
+                                 .data()));
+    EXPECT_EQ(8, Distance(p, Type<Span<const Int128>>(
+                                 L::Partial(1, 0, 0).Slice<Int128>(p))
+                                 .data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<const int8_t>>(
+                                 L::Partial(5, 3, 1).Slice<int8_t>(p))
+                                 .data()));
+    EXPECT_EQ(24, Distance(p, Type<Span<const Int128>>(
+                                  L::Partial(5, 3, 1).Slice<Int128>(p))
+                                  .data()));
+    EXPECT_EQ(8, Distance(p, Type<Span<const int32_t>>(
+                                 L::Partial(5, 3, 1).Slice<int32_t>(p))
+                                 .data()));
+    EXPECT_EQ(
+        0,
+        Distance(p,
+                 Type<Span<const int8_t>>(L(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(p,
+                 Type<Span<const Int128>>(L(5, 3, 1).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p, Type<Span<const int32_t>>(L(5, 3, 1).Slice<int32_t>(p)).data()));
+  }
+}
+
+TEST(Layout, MutableSliceByIndexData) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int32_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<int32_t>>(L(3).Slice<0>(p)).data()));
+  }
+  {
+    using L = Layout<int32_t, int32_t>;
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int32_t>>(L::Partial(3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int32_t>>(L::Partial(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        12,
+        Distance(p, Type<Span<int32_t>>(L::Partial(3, 5).Slice<1>(p)).data()));
+    EXPECT_EQ(0, Distance(p, Type<Span<int32_t>>(L(3, 5).Slice<0>(p)).data()));
+    EXPECT_EQ(12, Distance(p, Type<Span<int32_t>>(L(3, 5).Slice<1>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L::Partial(5).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int32_t>>(L::Partial(0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(1, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(p, Type<Span<int32_t>>(L::Partial(1, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(5, 3).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<Span<int32_t>>(L::Partial(5, 3).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int8_t>>(L::Partial(0, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int32_t>>(L::Partial(0, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<Int128>>(L::Partial(0, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int8_t>>(L::Partial(1, 0, 0).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        4, Distance(
+               p, Type<Span<int32_t>>(L::Partial(1, 0, 0).Slice<1>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(
+               p, Type<Span<Int128>>(L::Partial(1, 0, 0).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int8_t>>(L::Partial(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(
+        24, Distance(
+                p, Type<Span<Int128>>(L::Partial(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(
+        8, Distance(
+               p, Type<Span<int32_t>>(L::Partial(5, 3, 1).Slice<1>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int8_t>>(L(5, 3, 1).Slice<0>(p)).data()));
+    EXPECT_EQ(24,
+              Distance(p, Type<Span<Int128>>(L(5, 3, 1).Slice<2>(p)).data()));
+    EXPECT_EQ(8,
+              Distance(p, Type<Span<int32_t>>(L(5, 3, 1).Slice<1>(p)).data()));
+  }
+}
+
+TEST(Layout, MutableSliceByTypeData) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  {
+    using L = Layout<int32_t>;
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int32_t>>(L::Partial(0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(
+               p, Type<Span<int32_t>>(L::Partial(3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(0,
+              Distance(p, Type<Span<int32_t>>(L(3).Slice<int32_t>(p)).data()));
+  }
+  {
+    using L = Layout<int8_t, int32_t, Int128>;
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p, Type<Span<int8_t>>(L::Partial(5).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p,
+                 Type<Span<int8_t>>(L::Partial(0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p, Type<Span<int32_t>>(L::Partial(0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p,
+                 Type<Span<int8_t>>(L::Partial(1, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p, Type<Span<int32_t>>(L::Partial(1, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(p,
+                 Type<Span<int8_t>>(L::Partial(5, 3).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p, Type<Span<int32_t>>(L::Partial(5, 3).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<int8_t>>(L::Partial(0, 0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<int32_t>>(L::Partial(0, 0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<Int128>>(L::Partial(0, 0, 0).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<int8_t>>(L::Partial(1, 0, 0).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        4,
+        Distance(
+            p,
+            Type<Span<int32_t>>(L::Partial(1, 0, 0).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<Int128>>(L::Partial(1, 0, 0).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        0,
+        Distance(
+            p,
+            Type<Span<int8_t>>(L::Partial(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(
+            p,
+            Type<Span<Int128>>(L::Partial(5, 3, 1).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(
+            p,
+            Type<Span<int32_t>>(L::Partial(5, 3, 1).Slice<int32_t>(p)).data()));
+    EXPECT_EQ(
+        0, Distance(p, Type<Span<int8_t>>(L(5, 3, 1).Slice<int8_t>(p)).data()));
+    EXPECT_EQ(
+        24,
+        Distance(p, Type<Span<Int128>>(L(5, 3, 1).Slice<Int128>(p)).data()));
+    EXPECT_EQ(
+        8,
+        Distance(p, Type<Span<int32_t>>(L(5, 3, 1).Slice<int32_t>(p)).data()));
+  }
+}
+
+MATCHER_P(IsSameSlice, slice, "") {
+  return arg.size() == slice.size() && arg.data() == slice.data();
+}
+
+template <typename... M>
+class TupleMatcher {
+ public:
+  explicit TupleMatcher(M... matchers) : matchers_(std::move(matchers)...) {}
+
+  template <typename Tuple>
+  bool MatchAndExplain(const Tuple& p,
+                       testing::MatchResultListener* /* listener */) const {
+    static_assert(std::tuple_size<Tuple>::value == sizeof...(M), "");
+    return MatchAndExplainImpl(
+        p, absl::make_index_sequence<std::tuple_size<Tuple>::value>{});
+  }
+
+  // For the matcher concept. Left empty as we don't really need the diagnostics
+  // right now.
+  void DescribeTo(::std::ostream* os) const {}
+  void DescribeNegationTo(::std::ostream* os) const {}
+
+ private:
+  template <typename Tuple, size_t... Is>
+  bool MatchAndExplainImpl(const Tuple& p, absl::index_sequence<Is...>) const {
+    // Using std::min as a simple variadic "and".
+    return std::min(
+        {true, testing::SafeMatcherCast<
+                   const typename std::tuple_element<Is, Tuple>::type&>(
+                   std::get<Is>(matchers_))
+                   .Matches(std::get<Is>(p))...});
+  }
+
+  std::tuple<M...> matchers_;
+};
+
+template <typename... M>
+testing::PolymorphicMatcher<TupleMatcher<M...>> Tuple(M... matchers) {
+  return testing::MakePolymorphicMatcher(
+      TupleMatcher<M...>(std::move(matchers)...));
+}
+
+TEST(Layout, Slices) {
+  alignas(max_align_t) const unsigned char p[100] = {0};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_THAT(Type<std::tuple<>>(x.Slices(p)), Tuple());
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_THAT(Type<std::tuple<Span<const int8_t>>>(x.Slices(p)),
+                Tuple(IsSameSlice(x.Slice<0>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_THAT(
+        (Type<std::tuple<Span<const int8_t>, Span<const int8_t>>>(x.Slices(p))),
+        Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_THAT((Type<std::tuple<Span<const int8_t>, Span<const int8_t>,
+                                 Span<const Int128>>>(x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+                      IsSameSlice(x.Slice<2>(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_THAT((Type<std::tuple<Span<const int8_t>, Span<const int8_t>,
+                                 Span<const Int128>>>(x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+                      IsSameSlice(x.Slice<2>(p))));
+  }
+}
+
+TEST(Layout, MutableSlices) {
+  alignas(max_align_t) unsigned char p[100] = {0};
+  using L = Layout<int8_t, int8_t, Int128>;
+  {
+    const auto x = L::Partial();
+    EXPECT_THAT(Type<std::tuple<>>(x.Slices(p)), Tuple());
+  }
+  {
+    const auto x = L::Partial(1);
+    EXPECT_THAT(Type<std::tuple<Span<int8_t>>>(x.Slices(p)),
+                Tuple(IsSameSlice(x.Slice<0>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2);
+    EXPECT_THAT((Type<std::tuple<Span<int8_t>, Span<int8_t>>>(x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p))));
+  }
+  {
+    const auto x = L::Partial(1, 2, 3);
+    EXPECT_THAT((Type<std::tuple<Span<int8_t>, Span<int8_t>, Span<Int128>>>(
+                    x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+                      IsSameSlice(x.Slice<2>(p))));
+  }
+  {
+    const L x(1, 2, 3);
+    EXPECT_THAT((Type<std::tuple<Span<int8_t>, Span<int8_t>, Span<Int128>>>(
+                    x.Slices(p))),
+                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
+                      IsSameSlice(x.Slice<2>(p))));
+  }
+}
+
+TEST(Layout, UnalignedTypes) {
+  constexpr Layout<unsigned char, unsigned char, unsigned char> x(1, 2, 3);
+  alignas(max_align_t) unsigned char p[x.AllocSize() + 1];
+  EXPECT_THAT(x.Pointers(p + 1), Tuple(p + 1, p + 2, p + 4));
+}
+
+TEST(Layout, CustomAlignment) {
+  constexpr Layout<unsigned char, Aligned<unsigned char, 8>> x(1, 2);
+  alignas(max_align_t) unsigned char p[x.AllocSize()];
+  EXPECT_EQ(10, x.AllocSize());
+  EXPECT_THAT(x.Pointers(p), Tuple(p + 0, p + 8));
+}
+
+TEST(Layout, OverAligned) {
+  constexpr size_t M = alignof(max_align_t);
+  constexpr Layout<unsigned char, Aligned<unsigned char, 2 * M>> x(1, 3);
+#ifdef __GNUC__
+  // Using __attribute__ ((aligned ())) instead of alignas to bypass a gcc bug:
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89357
+  __attribute__((aligned(2 * M))) unsigned char p[x.AllocSize()];
+#else
+  alignas(2 * M) unsigned char p[x.AllocSize()];
+#endif
+  EXPECT_EQ(2 * M + 3, x.AllocSize());
+  EXPECT_THAT(x.Pointers(p), Tuple(p + 0, p + 2 * M));
+}
+
+TEST(Layout, Alignment) {
+  static_assert(Layout<int8_t>::Alignment() == 1, "");
+  static_assert(Layout<int32_t>::Alignment() == 4, "");
+  static_assert(Layout<Int64>::Alignment() == 8, "");
+  static_assert(Layout<Aligned<int8_t, 64>>::Alignment() == 64, "");
+  static_assert(Layout<int8_t, int32_t, Int64>::Alignment() == 8, "");
+  static_assert(Layout<int8_t, Int64, int32_t>::Alignment() == 8, "");
+  static_assert(Layout<int32_t, int8_t, Int64>::Alignment() == 8, "");
+  static_assert(Layout<int32_t, Int64, int8_t>::Alignment() == 8, "");
+  static_assert(Layout<Int64, int8_t, int32_t>::Alignment() == 8, "");
+  static_assert(Layout<Int64, int32_t, int8_t>::Alignment() == 8, "");
+}
+
+TEST(Layout, ConstexprPartial) {
+  constexpr size_t M = alignof(max_align_t);
+  constexpr Layout<unsigned char, Aligned<unsigned char, 2 * M>> x(1, 3);
+  static_assert(x.Partial(1).template Offset<1>() == 2 * M, "");
+}
+// [from, to)
+struct Region {
+  size_t from;
+  size_t to;
+};
+
+void ExpectRegionPoisoned(const unsigned char* p, size_t n, bool poisoned) {
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+  for (size_t i = 0; i != n; ++i) {
+    EXPECT_EQ(poisoned, __asan_address_is_poisoned(p + i));
+  }
+#endif
+}
+
+template <size_t N>
+void ExpectPoisoned(const unsigned char (&buf)[N],
+                    std::initializer_list<Region> reg) {
+  size_t prev = 0;
+  for (const Region& r : reg) {
+    ExpectRegionPoisoned(buf + prev, r.from - prev, false);
+    ExpectRegionPoisoned(buf + r.from, r.to - r.from, true);
+    prev = r.to;
+  }
+  ExpectRegionPoisoned(buf + prev, N - prev, false);
+}
+
+TEST(Layout, PoisonPadding) {
+  using L = Layout<int8_t, Int64, int32_t, Int128>;
+
+  constexpr size_t n = L::Partial(1, 2, 3, 4).AllocSize();
+  {
+    constexpr auto x = L::Partial();
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {});
+  }
+  {
+    constexpr auto x = L::Partial(1);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}});
+  }
+  {
+    constexpr auto x = L::Partial(1, 2);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}});
+  }
+  {
+    constexpr auto x = L::Partial(1, 2, 3);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}, {36, 40}});
+  }
+  {
+    constexpr auto x = L::Partial(1, 2, 3, 4);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}, {36, 40}});
+  }
+  {
+    constexpr L x(1, 2, 3, 4);
+    alignas(max_align_t) const unsigned char c[n] = {};
+    x.PoisonPadding(c);
+    EXPECT_EQ(x.Slices(c), x.Slices(c));
+    ExpectPoisoned(c, {{1, 8}, {36, 40}});
+  }
+}
+
+TEST(Layout, DebugString) {
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial();
+    EXPECT_EQ("@0<signed char>(1)", x.DebugString());
+  }
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1);
+    EXPECT_EQ("@0<signed char>(1)[1]; @4<int>(4)", x.DebugString());
+  }
+  {
+    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2);
+    EXPECT_EQ("@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)",
+              x.DebugString());
+  }
+  {
+    constexpr auto x =
+        Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2, 3);
+    EXPECT_EQ(
+        "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
+        "@16" +
+            Int128::Name() + "(16)",
+        x.DebugString());
+  }
+  {
+    constexpr auto x =
+        Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2, 3, 4);
+    EXPECT_EQ(
+        "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
+        "@16" +
+            Int128::Name() + "(16)[4]",
+        x.DebugString());
+  }
+  {
+    constexpr Layout<int8_t, int32_t, int8_t, Int128> x(1, 2, 3, 4);
+    EXPECT_EQ(
+        "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
+        "@16" +
+            Int128::Name() + "(16)[4]",
+        x.DebugString());
+  }
+}
+
+TEST(Layout, CharTypes) {
+  constexpr Layout<int32_t> x(1);
+  alignas(max_align_t) char c[x.AllocSize()] = {};
+  alignas(max_align_t) unsigned char uc[x.AllocSize()] = {};
+  alignas(max_align_t) signed char sc[x.AllocSize()] = {};
+  alignas(max_align_t) const char cc[x.AllocSize()] = {};
+  alignas(max_align_t) const unsigned char cuc[x.AllocSize()] = {};
+  alignas(max_align_t) const signed char csc[x.AllocSize()] = {};
+
+  Type<int32_t*>(x.Pointer<0>(c));
+  Type<int32_t*>(x.Pointer<0>(uc));
+  Type<int32_t*>(x.Pointer<0>(sc));
+  Type<const int32_t*>(x.Pointer<0>(cc));
+  Type<const int32_t*>(x.Pointer<0>(cuc));
+  Type<const int32_t*>(x.Pointer<0>(csc));
+
+  Type<int32_t*>(x.Pointer<int32_t>(c));
+  Type<int32_t*>(x.Pointer<int32_t>(uc));
+  Type<int32_t*>(x.Pointer<int32_t>(sc));
+  Type<const int32_t*>(x.Pointer<int32_t>(cc));
+  Type<const int32_t*>(x.Pointer<int32_t>(cuc));
+  Type<const int32_t*>(x.Pointer<int32_t>(csc));
+
+  Type<std::tuple<int32_t*>>(x.Pointers(c));
+  Type<std::tuple<int32_t*>>(x.Pointers(uc));
+  Type<std::tuple<int32_t*>>(x.Pointers(sc));
+  Type<std::tuple<const int32_t*>>(x.Pointers(cc));
+  Type<std::tuple<const int32_t*>>(x.Pointers(cuc));
+  Type<std::tuple<const int32_t*>>(x.Pointers(csc));
+
+  Type<Span<int32_t>>(x.Slice<0>(c));
+  Type<Span<int32_t>>(x.Slice<0>(uc));
+  Type<Span<int32_t>>(x.Slice<0>(sc));
+  Type<Span<const int32_t>>(x.Slice<0>(cc));
+  Type<Span<const int32_t>>(x.Slice<0>(cuc));
+  Type<Span<const int32_t>>(x.Slice<0>(csc));
+
+  Type<std::tuple<Span<int32_t>>>(x.Slices(c));
+  Type<std::tuple<Span<int32_t>>>(x.Slices(uc));
+  Type<std::tuple<Span<int32_t>>>(x.Slices(sc));
+  Type<std::tuple<Span<const int32_t>>>(x.Slices(cc));
+  Type<std::tuple<Span<const int32_t>>>(x.Slices(cuc));
+  Type<std::tuple<Span<const int32_t>>>(x.Slices(csc));
+}
+
+TEST(Layout, ConstElementType) {
+  constexpr Layout<const int32_t> x(1);
+  alignas(int32_t) char c[x.AllocSize()] = {};
+  const char* cc = c;
+  const int32_t* p = reinterpret_cast<const int32_t*>(cc);
+
+  EXPECT_EQ(alignof(int32_t), x.Alignment());
+
+  EXPECT_EQ(0, x.Offset<0>());
+  EXPECT_EQ(0, x.Offset<const int32_t>());
+
+  EXPECT_THAT(x.Offsets(), ElementsAre(0));
+
+  EXPECT_EQ(1, x.Size<0>());
+  EXPECT_EQ(1, x.Size<const int32_t>());
+
+  EXPECT_THAT(x.Sizes(), ElementsAre(1));
+
+  EXPECT_EQ(sizeof(int32_t), x.AllocSize());
+
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<0>(c)));
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<0>(cc)));
+
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<const int32_t>(c)));
+  EXPECT_EQ(p, Type<const int32_t*>(x.Pointer<const int32_t>(cc)));
+
+  EXPECT_THAT(Type<std::tuple<const int32_t*>>(x.Pointers(c)), Tuple(p));
+  EXPECT_THAT(Type<std::tuple<const int32_t*>>(x.Pointers(cc)), Tuple(p));
+
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<0>(c)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<0>(cc)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<const int32_t>(c)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+  EXPECT_THAT(Type<Span<const int32_t>>(x.Slice<const int32_t>(cc)),
+              IsSameSlice(Span<const int32_t>(p, 1)));
+
+  EXPECT_THAT(Type<std::tuple<Span<const int32_t>>>(x.Slices(c)),
+              Tuple(IsSameSlice(Span<const int32_t>(p, 1))));
+  EXPECT_THAT(Type<std::tuple<Span<const int32_t>>>(x.Slices(cc)),
+              Tuple(IsSameSlice(Span<const int32_t>(p, 1))));
+}
+
+namespace example {
+
+// Immutable move-only string with sizeof equal to sizeof(void*). The string
+// size and the characters are kept in the same heap allocation.
+class CompactString {
+ public:
+  CompactString(const char* s = "") {  // NOLINT
+    const size_t size = strlen(s);
+    // size_t[1], followed by char[size + 1].
+    // This statement doesn't allocate memory.
+    const L layout(1, size + 1);
+    // AllocSize() tells us how much memory we need to allocate for all our
+    // data.
+    p_.reset(new unsigned char[layout.AllocSize()]);
+    // If running under ASAN, mark the padding bytes, if any, to catch memory
+    // errors.
+    layout.PoisonPadding(p_.get());
+    // Store the size in the allocation.
+    // Pointer<size_t>() is a synonym for Pointer<0>().
+    *layout.Pointer<size_t>(p_.get()) = size;
+    // Store the characters in the allocation.
+    memcpy(layout.Pointer<char>(p_.get()), s, size + 1);
+  }
+
+  size_t size() const {
+    // Equivalent to reinterpret_cast<size_t&>(*p).
+    return *L::Partial().Pointer<size_t>(p_.get());
+  }
+
+  const char* c_str() const {
+    // Equivalent to reinterpret_cast<char*>(p.get() + sizeof(size_t)).
+    // The argument in Partial(1) specifies that we have size_t[1] in front of
+    // the characters.
+    return L::Partial(1).Pointer<char>(p_.get());
+  }
+
+ private:
+  // Our heap allocation contains a size_t followed by an array of chars.
+  using L = Layout<size_t, char>;
+  std::unique_ptr<unsigned char[]> p_;
+};
+
+TEST(CompactString, Works) {
+  CompactString s = "hello";
+  EXPECT_EQ(5, s.size());
+  EXPECT_STREQ("hello", s.c_str());
+}
+
+}  // namespace example
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_map.h b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_map.h
new file mode 100644
index 0000000000000000000000000000000000000000..97182bc7bdb49a88ddd0ff2d7aa21659d7c4b3b4
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_map.h
@@ -0,0 +1,224 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CONTAINER_INTERNAL_RAW_HASH_MAP_H_
+#define ABSL_CONTAINER_INTERNAL_RAW_HASH_MAP_H_
+
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/throw_delegate.h"
+#include "absl/container/internal/container_memory.h"
+#include "absl/container/internal/raw_hash_set.h"  // IWYU pragma: export
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+template <class Policy, class Hash, class Eq, class Alloc>
+class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
+  // P is Policy. It's passed as a template argument to support maps that have
+  // incomplete types as values, as in unordered_map<K, IncompleteType>.
+  // MappedReference<> may be a non-reference type.
+  template <class P>
+  using MappedReference = decltype(P::value(
+      std::addressof(std::declval<typename raw_hash_map::reference>())));
+
+  // MappedConstReference<> may be a non-reference type.
+  template <class P>
+  using MappedConstReference = decltype(P::value(
+      std::addressof(std::declval<typename raw_hash_map::const_reference>())));
+
+  using KeyArgImpl =
+      KeyArg<IsTransparent<Eq>::value && IsTransparent<Hash>::value>;
+
+ public:
+  using key_type = typename Policy::key_type;
+  using mapped_type = typename Policy::mapped_type;
+  template <class K>
+  using key_arg = typename KeyArgImpl::template type<K, key_type>;
+
+  static_assert(!std::is_reference<key_type>::value, "");
+
+  // TODO(b/187807849): Evaluate whether to support reference mapped_type and
+  // remove this assertion if/when it is supported.
+  static_assert(!std::is_reference<mapped_type>::value, "");
+
+  using iterator = typename raw_hash_map::raw_hash_set::iterator;
+  using const_iterator = typename raw_hash_map::raw_hash_set::const_iterator;
+
+  raw_hash_map() {}
+  using raw_hash_map::raw_hash_set::raw_hash_set;
+
+  // The last two template parameters ensure that both arguments are rvalues
+  // (lvalue arguments are handled by the overloads below). This is necessary
+  // for supporting bitfield arguments.
+  //
+  //   union { int n : 1; };
+  //   flat_hash_map<int, int> m;
+  //   m.insert_or_assign(n, n);
+  template <class K = key_type, class V = mapped_type, K* = nullptr,
+            V* = nullptr>
+  std::pair<iterator, bool> insert_or_assign(key_arg<K>&& k, V&& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign_impl(std::forward<K>(k), std::forward<V>(v));
+  }
+
+  template <class K = key_type, class V = mapped_type, K* = nullptr>
+  std::pair<iterator, bool> insert_or_assign(key_arg<K>&& k, const V& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign_impl(std::forward<K>(k), v);
+  }
+
+  template <class K = key_type, class V = mapped_type, V* = nullptr>
+  std::pair<iterator, bool> insert_or_assign(const key_arg<K>& k, V&& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign_impl(k, std::forward<V>(v));
+  }
+
+  template <class K = key_type, class V = mapped_type>
+  std::pair<iterator, bool> insert_or_assign(const key_arg<K>& k, const V& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign_impl(k, v);
+  }
+
+  template <class K = key_type, class V = mapped_type, K* = nullptr,
+            V* = nullptr>
+  iterator insert_or_assign(const_iterator, key_arg<K>&& k,
+                            V&& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign(std::forward<K>(k), std::forward<V>(v)).first;
+  }
+
+  template <class K = key_type, class V = mapped_type, K* = nullptr>
+  iterator insert_or_assign(const_iterator, key_arg<K>&& k,
+                            const V& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign(std::forward<K>(k), v).first;
+  }
+
+  template <class K = key_type, class V = mapped_type, V* = nullptr>
+  iterator insert_or_assign(const_iterator, const key_arg<K>& k,
+                            V&& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign(k, std::forward<V>(v)).first;
+  }
+
+  template <class K = key_type, class V = mapped_type>
+  iterator insert_or_assign(const_iterator, const key_arg<K>& k,
+                            const V& v) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert_or_assign(k, v).first;
+  }
+
+  // All `try_emplace()` overloads make the same guarantees regarding rvalue
+  // arguments as `std::unordered_map::try_emplace()`, namely that these
+  // functions will not move from rvalue arguments if insertions do not happen.
+  template <class K = key_type, class... Args,
+            typename std::enable_if<
+                !std::is_convertible<K, const_iterator>::value, int>::type = 0,
+            K* = nullptr>
+  std::pair<iterator, bool> try_emplace(key_arg<K>&& k, Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return try_emplace_impl(std::forward<K>(k), std::forward<Args>(args)...);
+  }
+
+  template <class K = key_type, class... Args,
+            typename std::enable_if<
+                !std::is_convertible<K, const_iterator>::value, int>::type = 0>
+  std::pair<iterator, bool> try_emplace(const key_arg<K>& k, Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return try_emplace_impl(k, std::forward<Args>(args)...);
+  }
+
+  template <class K = key_type, class... Args, K* = nullptr>
+  iterator try_emplace(const_iterator, key_arg<K>&& k,
+                       Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return try_emplace(std::forward<K>(k), std::forward<Args>(args)...).first;
+  }
+
+  template <class K = key_type, class... Args>
+  iterator try_emplace(const_iterator, const key_arg<K>& k,
+                       Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return try_emplace(k, std::forward<Args>(args)...).first;
+  }
+
+  template <class K = key_type, class P = Policy>
+  MappedReference<P> at(const key_arg<K>& key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto it = this->find(key);
+    if (it == this->end()) {
+      base_internal::ThrowStdOutOfRange(
+          "absl::container_internal::raw_hash_map<>::at");
+    }
+    return Policy::value(&*it);
+  }
+
+  template <class K = key_type, class P = Policy>
+  MappedConstReference<P> at(const key_arg<K>& key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto it = this->find(key);
+    if (it == this->end()) {
+      base_internal::ThrowStdOutOfRange(
+          "absl::container_internal::raw_hash_map<>::at");
+    }
+    return Policy::value(&*it);
+  }
+
+  template <class K = key_type, class P = Policy, K* = nullptr>
+  MappedReference<P> operator[](key_arg<K>&& key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    // It is safe to use unchecked_deref here because try_emplace
+    // will always return an iterator pointing to a valid item in the table,
+    // since it inserts if nothing is found for the given key.
+    return Policy::value(
+        &this->unchecked_deref(try_emplace(std::forward<K>(key)).first));
+  }
+
+  template <class K = key_type, class P = Policy>
+  MappedReference<P> operator[](const key_arg<K>& key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    // It is safe to use unchecked_deref here because try_emplace
+    // will always return an iterator pointing to a valid item in the table,
+    // since it inserts if nothing is found for the given key.
+    return Policy::value(&this->unchecked_deref(try_emplace(key).first));
+  }
+
+ private:
+  template <class K, class V>
+  std::pair<iterator, bool> insert_or_assign_impl(K&& k, V&& v)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto res = this->find_or_prepare_insert(k);
+    if (res.second)
+      this->emplace_at(res.first, std::forward<K>(k), std::forward<V>(v));
+    else
+      Policy::value(&*this->iterator_at(res.first)) = std::forward<V>(v);
+    return {this->iterator_at(res.first), res.second};
+  }
+
+  template <class K = key_type, class... Args>
+  std::pair<iterator, bool> try_emplace_impl(K&& k, Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto res = this->find_or_prepare_insert(k);
+    if (res.second)
+      this->emplace_at(res.first, std::piecewise_construct,
+                       std::forward_as_tuple(std::forward<K>(k)),
+                       std::forward_as_tuple(std::forward<Args>(args)...));
+    return {this->iterator_at(res.first), res.second};
+  }
+};
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_RAW_HASH_MAP_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set.cc b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9f8ea51987681b3d7bbc282ebf3d03464319dcf2
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set.cc
@@ -0,0 +1,380 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/raw_hash_set.h"
+
+#include <atomic>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/dynamic_annotations.h"
+#include "absl/container/internal/container_memory.h"
+#include "absl/hash/hash.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+// We have space for `growth_left` before a single block of control bytes. A
+// single block of empty control bytes for tables without any slots allocated.
+// This enables removing a branch in the hot path of find(). In order to ensure
+// that the control bytes are aligned to 16, we have 16 bytes before the control
+// bytes even though growth_left only needs 8.
+constexpr ctrl_t ZeroCtrlT() { return static_cast<ctrl_t>(0); }
+alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[32] = {
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
+    ctrl_t::kSentinel, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
+    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
+    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
+    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty};
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr size_t Group::kWidth;
+#endif
+
+namespace {
+
+// Returns "random" seed.
+inline size_t RandomSeed() {
+#ifdef ABSL_HAVE_THREAD_LOCAL
+  static thread_local size_t counter = 0;
+  // On Linux kernels >= 5.4 the MSAN runtime has a false-positive when
+  // accessing thread local storage data from loaded libraries
+  // (https://github.com/google/sanitizers/issues/1265), for this reason counter
+  // needs to be annotated as initialized.
+  ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(&counter, sizeof(size_t));
+  size_t value = ++counter;
+#else   // ABSL_HAVE_THREAD_LOCAL
+  static std::atomic<size_t> counter(0);
+  size_t value = counter.fetch_add(1, std::memory_order_relaxed);
+#endif  // ABSL_HAVE_THREAD_LOCAL
+  return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter));
+}
+
+bool ShouldRehashForBugDetection(const ctrl_t* ctrl, size_t capacity) {
+  // Note: we can't use the abseil-random library because abseil-random
+  // depends on swisstable. We want to return true with probability
+  // `min(1, RehashProbabilityConstant() / capacity())`. In order to do this,
+  // we probe based on a random hash and see if the offset is less than
+  // RehashProbabilityConstant().
+  return probe(ctrl, capacity, absl::HashOf(RandomSeed())).offset() <
+         RehashProbabilityConstant();
+}
+
+}  // namespace
+
+GenerationType* EmptyGeneration() {
+  if (SwisstableGenerationsEnabled()) {
+    constexpr size_t kNumEmptyGenerations = 1024;
+    static constexpr GenerationType kEmptyGenerations[kNumEmptyGenerations]{};
+    return const_cast<GenerationType*>(
+        &kEmptyGenerations[RandomSeed() % kNumEmptyGenerations]);
+  }
+  return nullptr;
+}
+
+bool CommonFieldsGenerationInfoEnabled::
+    should_rehash_for_bug_detection_on_insert(const ctrl_t* ctrl,
+                                              size_t capacity) const {
+  if (reserved_growth_ == kReservedGrowthJustRanOut) return true;
+  if (reserved_growth_ > 0) return false;
+  return ShouldRehashForBugDetection(ctrl, capacity);
+}
+
+bool CommonFieldsGenerationInfoEnabled::should_rehash_for_bug_detection_on_move(
+    const ctrl_t* ctrl, size_t capacity) const {
+  return ShouldRehashForBugDetection(ctrl, capacity);
+}
+
+bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl) {
+  // To avoid problems with weak hashes and single bit tests, we use % 13.
+  // TODO(kfm,sbenza): revisit after we do unconditional mixing
+  return (H1(hash, ctrl) ^ RandomSeed()) % 13 > 6;
+}
+
+void ConvertDeletedToEmptyAndFullToDeleted(ctrl_t* ctrl, size_t capacity) {
+  assert(ctrl[capacity] == ctrl_t::kSentinel);
+  assert(IsValidCapacity(capacity));
+  for (ctrl_t* pos = ctrl; pos < ctrl + capacity; pos += Group::kWidth) {
+    Group{pos}.ConvertSpecialToEmptyAndFullToDeleted(pos);
+  }
+  // Copy the cloned ctrl bytes.
+  std::memcpy(ctrl + capacity + 1, ctrl, NumClonedBytes());
+  ctrl[capacity] = ctrl_t::kSentinel;
+}
+// Extern template instantiation for inline function.
+template FindInfo find_first_non_full(const CommonFields&, size_t);
+
+FindInfo find_first_non_full_outofline(const CommonFields& common,
+                                       size_t hash) {
+  return find_first_non_full(common, hash);
+}
+
+// Returns the address of the slot just after slot assuming each slot has the
+// specified size.
+static inline void* NextSlot(void* slot, size_t slot_size) {
+  return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) + slot_size);
+}
+
+// Returns the address of the slot just before slot assuming each slot has the
+// specified size.
+static inline void* PrevSlot(void* slot, size_t slot_size) {
+  return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) - slot_size);
+}
+
+void DropDeletesWithoutResize(CommonFields& common,
+                              const PolicyFunctions& policy, void* tmp_space) {
+  void* set = &common;
+  void* slot_array = common.slot_array();
+  const size_t capacity = common.capacity();
+  assert(IsValidCapacity(capacity));
+  assert(!is_small(capacity));
+  // Algorithm:
+  // - mark all DELETED slots as EMPTY
+  // - mark all FULL slots as DELETED
+  // - for each slot marked as DELETED
+  //     hash = Hash(element)
+  //     target = find_first_non_full(hash)
+  //     if target is in the same group
+  //       mark slot as FULL
+  //     else if target is EMPTY
+  //       transfer element to target
+  //       mark slot as EMPTY
+  //       mark target as FULL
+  //     else if target is DELETED
+  //       swap current element with target element
+  //       mark target as FULL
+  //       repeat procedure for current slot with moved from element (target)
+  ctrl_t* ctrl = common.control();
+  ConvertDeletedToEmptyAndFullToDeleted(ctrl, capacity);
+  auto hasher = policy.hash_slot;
+  auto transfer = policy.transfer;
+  const size_t slot_size = policy.slot_size;
+
+  size_t total_probe_length = 0;
+  void* slot_ptr = SlotAddress(slot_array, 0, slot_size);
+  for (size_t i = 0; i != capacity;
+       ++i, slot_ptr = NextSlot(slot_ptr, slot_size)) {
+    assert(slot_ptr == SlotAddress(slot_array, i, slot_size));
+    if (!IsDeleted(ctrl[i])) continue;
+    const size_t hash = (*hasher)(set, slot_ptr);
+    const FindInfo target = find_first_non_full(common, hash);
+    const size_t new_i = target.offset;
+    total_probe_length += target.probe_length;
+
+    // Verify if the old and new i fall within the same group wrt the hash.
+    // If they do, we don't need to move the object as it falls already in the
+    // best probe we can.
+    const size_t probe_offset = probe(common, hash).offset();
+    const auto probe_index = [probe_offset, capacity](size_t pos) {
+      return ((pos - probe_offset) & capacity) / Group::kWidth;
+    };
+
+    // Element doesn't move.
+    if (ABSL_PREDICT_TRUE(probe_index(new_i) == probe_index(i))) {
+      SetCtrl(common, i, H2(hash), slot_size);
+      continue;
+    }
+
+    void* new_slot_ptr = SlotAddress(slot_array, new_i, slot_size);
+    if (IsEmpty(ctrl[new_i])) {
+      // Transfer element to the empty spot.
+      // SetCtrl poisons/unpoisons the slots so we have to call it at the
+      // right time.
+      SetCtrl(common, new_i, H2(hash), slot_size);
+      (*transfer)(set, new_slot_ptr, slot_ptr);
+      SetCtrl(common, i, ctrl_t::kEmpty, slot_size);
+    } else {
+      assert(IsDeleted(ctrl[new_i]));
+      SetCtrl(common, new_i, H2(hash), slot_size);
+      // Until we are done rehashing, DELETED marks previously FULL slots.
+
+      // Swap i and new_i elements.
+      (*transfer)(set, tmp_space, new_slot_ptr);
+      (*transfer)(set, new_slot_ptr, slot_ptr);
+      (*transfer)(set, slot_ptr, tmp_space);
+
+      // repeat the processing of the ith slot
+      --i;
+      slot_ptr = PrevSlot(slot_ptr, slot_size);
+    }
+  }
+  ResetGrowthLeft(common);
+  common.infoz().RecordRehash(total_probe_length);
+}
+
+static bool WasNeverFull(CommonFields& c, size_t index) {
+  if (is_single_group(c.capacity())) {
+    return true;
+  }
+  const size_t index_before = (index - Group::kWidth) & c.capacity();
+  const auto empty_after = Group(c.control() + index).MaskEmpty();
+  const auto empty_before = Group(c.control() + index_before).MaskEmpty();
+
+  // We count how many consecutive non empties we have to the right and to the
+  // left of `it`. If the sum is >= kWidth then there is at least one probe
+  // window that might have seen a full group.
+  return empty_before && empty_after &&
+         static_cast<size_t>(empty_after.TrailingZeros()) +
+                 empty_before.LeadingZeros() <
+             Group::kWidth;
+}
+
+void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size) {
+  assert(IsFull(c.control()[index]) && "erasing a dangling iterator");
+  c.decrement_size();
+  c.infoz().RecordErase();
+
+  if (WasNeverFull(c, index)) {
+    SetCtrl(c, index, ctrl_t::kEmpty, slot_size);
+    c.set_growth_left(c.growth_left() + 1);
+    return;
+  }
+
+  SetCtrl(c, index, ctrl_t::kDeleted, slot_size);
+}
+
+void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
+                       bool reuse) {
+  c.set_size(0);
+  if (reuse) {
+    ResetCtrl(c, policy.slot_size);
+    ResetGrowthLeft(c);
+    c.infoz().RecordStorageChanged(0, c.capacity());
+  } else {
+    // We need to record infoz before calling dealloc, which will unregister
+    // infoz.
+    c.infoz().RecordClearedReservation();
+    c.infoz().RecordStorageChanged(0, 0);
+    (*policy.dealloc)(c, policy);
+    c.set_control(EmptyGroup());
+    c.set_generation_ptr(EmptyGeneration());
+    c.set_slots(nullptr);
+    c.set_capacity(0);
+  }
+}
+
+void HashSetResizeHelper::GrowIntoSingleGroupShuffleControlBytes(
+    ctrl_t* new_ctrl, size_t new_capacity) const {
+  assert(is_single_group(new_capacity));
+  constexpr size_t kHalfWidth = Group::kWidth / 2;
+  assert(old_capacity_ < kHalfWidth);
+
+  const size_t half_old_capacity = old_capacity_ / 2;
+
+  // NOTE: operations are done with compile time known size = kHalfWidth.
+  // Compiler optimizes that into single ASM operation.
+
+  // Copy second half of bytes to the beginning.
+  // We potentially copy more bytes in order to have compile time known size.
+  // Mirrored bytes from the old_ctrl_ will also be copied.
+  // In case of old_capacity_ == 3, we will copy 1st element twice.
+  // Examples:
+  // old_ctrl = 0S0EEEEEEE...
+  // new_ctrl = S0EEEEEEEE...
+  //
+  // old_ctrl = 01S01EEEEE...
+  // new_ctrl = 1S01EEEEEE...
+  //
+  // old_ctrl = 0123456S0123456EE...
+  // new_ctrl = 456S0123?????????...
+  std::memcpy(new_ctrl, old_ctrl_ + half_old_capacity + 1, kHalfWidth);
+  // Clean up copied kSentinel from old_ctrl.
+  new_ctrl[half_old_capacity] = ctrl_t::kEmpty;
+
+  // Clean up damaged or uninitialized bytes.
+
+  // Clean bytes after the intended size of the copy.
+  // Example:
+  // new_ctrl = 1E01EEEEEEE????
+  // *new_ctrl= 1E0EEEEEEEE????
+  // position      /
+  std::memset(new_ctrl + old_capacity_ + 1, static_cast<int8_t>(ctrl_t::kEmpty),
+              kHalfWidth);
+  // Clean non-mirrored bytes that are not initialized.
+  // For small old_capacity that may be inside of mirrored bytes zone.
+  // Examples:
+  // new_ctrl = 1E0EEEEEEEE??????????....
+  // *new_ctrl= 1E0EEEEEEEEEEEEE?????....
+  // position           /
+  //
+  // new_ctrl = 456E0123???????????...
+  // *new_ctrl= 456E0123EEEEEEEE???...
+  // position           /
+  std::memset(new_ctrl + kHalfWidth, static_cast<int8_t>(ctrl_t::kEmpty),
+              kHalfWidth);
+  // Clean last mirrored bytes that are not initialized
+  // and will not be overwritten by mirroring.
+  // Examples:
+  // new_ctrl = 1E0EEEEEEEEEEEEE????????
+  // *new_ctrl= 1E0EEEEEEEEEEEEEEEEEEEEE
+  // position           S       /
+  //
+  // new_ctrl = 456E0123EEEEEEEE???????????????
+  // *new_ctrl= 456E0123EEEEEEEE???????EEEEEEEE
+  // position                  S       /
+  std::memset(new_ctrl + new_capacity + kHalfWidth,
+              static_cast<int8_t>(ctrl_t::kEmpty), kHalfWidth);
+
+  // Create mirrored bytes. old_capacity_ < kHalfWidth
+  // Example:
+  // new_ctrl = 456E0123EEEEEEEE???????EEEEEEEE
+  // *new_ctrl= 456E0123EEEEEEEE456E0123EEEEEEE
+  // position                  S/
+  ctrl_t g[kHalfWidth];
+  std::memcpy(g, new_ctrl, kHalfWidth);
+  std::memcpy(new_ctrl + new_capacity + 1, g, kHalfWidth);
+
+  // Finally set sentinel to its place.
+  new_ctrl[new_capacity] = ctrl_t::kSentinel;
+}
+
+void HashSetResizeHelper::GrowIntoSingleGroupShuffleTransferableSlots(
+    void* old_slots, void* new_slots, size_t slot_size) const {
+  assert(old_capacity_ > 0);
+  const size_t half_old_capacity = old_capacity_ / 2;
+
+  SanitizerUnpoisonMemoryRegion(old_slots, slot_size * old_capacity_);
+  std::memcpy(new_slots,
+              SlotAddress(old_slots, half_old_capacity + 1, slot_size),
+              slot_size * half_old_capacity);
+  std::memcpy(SlotAddress(new_slots, half_old_capacity + 1, slot_size),
+              old_slots, slot_size * (half_old_capacity + 1));
+}
+
+void HashSetResizeHelper::GrowSizeIntoSingleGroupTransferable(
+    CommonFields& c, void* old_slots, size_t slot_size) {
+  assert(old_capacity_ < Group::kWidth / 2);
+  assert(is_single_group(c.capacity()));
+  assert(IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity()));
+
+  GrowIntoSingleGroupShuffleControlBytes(c.control(), c.capacity());
+  GrowIntoSingleGroupShuffleTransferableSlots(old_slots, c.slot_array(),
+                                              slot_size);
+
+  // We poison since GrowIntoSingleGroupShuffleTransferableSlots
+  // may leave empty slots unpoisoned.
+  PoisonSingleGroupEmptySlots(c, slot_size);
+}
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set.h b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set.h
new file mode 100644
index 0000000000000000000000000000000000000000..3518bc34040df3a5d8d231a3dbd6a0146f6a1174
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set.h
@@ -0,0 +1,3325 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// An open-addressing
+// hashtable with quadratic probing.
+//
+// This is a low level hashtable on top of which different interfaces can be
+// implemented, like flat_hash_set, node_hash_set, string_hash_set, etc.
+//
+// The table interface is similar to that of std::unordered_set. Notable
+// differences are that most member functions support heterogeneous keys when
+// BOTH the hash and eq functions are marked as transparent. They do so by
+// providing a typedef called `is_transparent`.
+//
+// When heterogeneous lookup is enabled, functions that take key_type act as if
+// they have an overload set like:
+//
+//   iterator find(const key_type& key);
+//   template <class K>
+//   iterator find(const K& key);
+//
+//   size_type erase(const key_type& key);
+//   template <class K>
+//   size_type erase(const K& key);
+//
+//   std::pair<iterator, iterator> equal_range(const key_type& key);
+//   template <class K>
+//   std::pair<iterator, iterator> equal_range(const K& key);
+//
+// When heterogeneous lookup is disabled, only the explicit `key_type` overloads
+// exist.
+//
+// find() also supports passing the hash explicitly:
+//
+//   iterator find(const key_type& key, size_t hash);
+//   template <class U>
+//   iterator find(const U& key, size_t hash);
+//
+// In addition the pointer to element and iterator stability guarantees are
+// weaker: all iterators and pointers are invalidated after a new element is
+// inserted.
+//
+// IMPLEMENTATION DETAILS
+//
+// # Table Layout
+//
+// A raw_hash_set's backing array consists of control bytes followed by slots
+// that may or may not contain objects.
+//
+// The layout of the backing array, for `capacity` slots, is thus, as a
+// pseudo-struct:
+//
+//   struct BackingArray {
+//     // Sampling handler. This field isn't present when the sampling is
+//     // disabled or this allocation hasn't been selected for sampling.
+//     HashtablezInfoHandle infoz_;
+//     // The number of elements we can insert before growing the capacity.
+//     size_t growth_left;
+//     // Control bytes for the "real" slots.
+//     ctrl_t ctrl[capacity];
+//     // Always `ctrl_t::kSentinel`. This is used by iterators to find when to
+//     // stop and serves no other purpose.
+//     ctrl_t sentinel;
+//     // A copy of the first `kWidth - 1` elements of `ctrl`. This is used so
+//     // that if a probe sequence picks a value near the end of `ctrl`,
+//     // `Group` will have valid control bytes to look at.
+//     ctrl_t clones[kWidth - 1];
+//     // The actual slot data.
+//     slot_type slots[capacity];
+//   };
+//
+// The length of this array is computed by `AllocSize()` below.
+//
+// Control bytes (`ctrl_t`) are bytes (collected into groups of a
+// platform-specific size) that define the state of the corresponding slot in
+// the slot array. Group manipulation is tightly optimized to be as efficient
+// as possible: SSE and friends on x86, clever bit operations on other arches.
+//
+//      Group 1         Group 2        Group 3
+// +---------------+---------------+---------------+
+// | | | | | | | | | | | | | | | | | | | | | | | | |
+// +---------------+---------------+---------------+
+//
+// Each control byte is either a special value for empty slots, deleted slots
+// (sometimes called *tombstones*), and a special end-of-table marker used by
+// iterators, or, if occupied, seven bits (H2) from the hash of the value in the
+// corresponding slot.
+//
+// Storing control bytes in a separate array also has beneficial cache effects,
+// since more logical slots will fit into a cache line.
+//
+// # Hashing
+//
+// We compute two separate hashes, `H1` and `H2`, from the hash of an object.
+// `H1(hash(x))` is an index into `slots`, and essentially the starting point
+// for the probe sequence. `H2(hash(x))` is a 7-bit value used to filter out
+// objects that cannot possibly be the one we are looking for.
+//
+// # Table operations.
+//
+// The key operations are `insert`, `find`, and `erase`.
+//
+// Since `insert` and `erase` are implemented in terms of `find`, we describe
+// `find` first. To `find` a value `x`, we compute `hash(x)`. From
+// `H1(hash(x))` and the capacity, we construct a `probe_seq` that visits every
+// group of slots in some interesting order.
+//
+// We now walk through these indices. At each index, we select the entire group
+// starting with that index and extract potential candidates: occupied slots
+// with a control byte equal to `H2(hash(x))`. If we find an empty slot in the
+// group, we stop and return an error. Each candidate slot `y` is compared with
+// `x`; if `x == y`, we are done and return `&y`; otherwise we continue to the
+// next probe index. Tombstones effectively behave like full slots that never
+// match the value we're looking for.
+//
+// The `H2` bits ensure when we compare a slot to an object with `==`, we are
+// likely to have actually found the object.  That is, the chance is low that
+// `==` is called and returns `false`.  Thus, when we search for an object, we
+// are unlikely to call `==` many times.  This likelyhood can be analyzed as
+// follows (assuming that H2 is a random enough hash function).
+//
+// Let's assume that there are `k` "wrong" objects that must be examined in a
+// probe sequence.  For example, when doing a `find` on an object that is in the
+// table, `k` is the number of objects between the start of the probe sequence
+// and the final found object (not including the final found object).  The
+// expected number of objects with an H2 match is then `k/128`.  Measurements
+// and analysis indicate that even at high load factors, `k` is less than 32,
+// meaning that the number of "false positive" comparisons we must perform is
+// less than 1/8 per `find`.
+
+// `insert` is implemented in terms of `unchecked_insert`, which inserts a
+// value presumed to not be in the table (violating this requirement will cause
+// the table to behave erratically). Given `x` and its hash `hash(x)`, to insert
+// it, we construct a `probe_seq` once again, and use it to find the first
+// group with an unoccupied (empty *or* deleted) slot. We place `x` into the
+// first such slot in the group and mark it as full with `x`'s H2.
+//
+// To `insert`, we compose `unchecked_insert` with `find`. We compute `h(x)` and
+// perform a `find` to see if it's already present; if it is, we're done. If
+// it's not, we may decide the table is getting overcrowded (i.e. the load
+// factor is greater than 7/8 for big tables; `is_small()` tables use a max load
+// factor of 1); in this case, we allocate a bigger array, `unchecked_insert`
+// each element of the table into the new array (we know that no insertion here
+// will insert an already-present value), and discard the old backing array. At
+// this point, we may `unchecked_insert` the value `x`.
+//
+// Below, `unchecked_insert` is partly implemented by `prepare_insert`, which
+// presents a viable, initialized slot pointee to the caller.
+//
+// `erase` is implemented in terms of `erase_at`, which takes an index to a
+// slot. Given an offset, we simply create a tombstone and destroy its contents.
+// If we can prove that the slot would not appear in a probe sequence, we can
+// make the slot as empty, instead. We can prove this by observing that if a
+// group has any empty slots, it has never been full (assuming we never create
+// an empty slot in a group with no empties, which this heuristic guarantees we
+// never do) and find would stop at this group anyways (since it does not probe
+// beyond groups with empties).
+//
+// `erase` is `erase_at` composed with `find`: if we
+// have a value `x`, we can perform a `find`, and then `erase_at` the resulting
+// slot.
+//
+// To iterate, we simply traverse the array, skipping empty and deleted slots
+// and stopping when we hit a `kSentinel`.
+
+#ifndef ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
+#define ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
+
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <initializer_list>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/macros.h"
+#include "absl/base/optimization.h"
+#include "absl/base/options.h"
+#include "absl/base/port.h"
+#include "absl/base/prefetch.h"
+#include "absl/container/internal/common.h"  // IWYU pragma: export // for node_handle
+#include "absl/container/internal/compressed_tuple.h"
+#include "absl/container/internal/container_memory.h"
+#include "absl/container/internal/hash_policy_traits.h"
+#include "absl/container/internal/hashtable_debug_hooks.h"
+#include "absl/container/internal/hashtablez_sampler.h"
+#include "absl/memory/memory.h"
+#include "absl/meta/type_traits.h"
+#include "absl/numeric/bits.h"
+#include "absl/utility/utility.h"
+
+#ifdef ABSL_INTERNAL_HAVE_SSE2
+#include <emmintrin.h>
+#endif
+
+#ifdef ABSL_INTERNAL_HAVE_SSSE3
+#include <tmmintrin.h>
+#endif
+
+#ifdef _MSC_VER
+#include <intrin.h>
+#endif
+
+#ifdef ABSL_INTERNAL_HAVE_ARM_NEON
+#include <arm_neon.h>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+#ifdef ABSL_SWISSTABLE_ENABLE_GENERATIONS
+#error ABSL_SWISSTABLE_ENABLE_GENERATIONS cannot be directly set
+#elif defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
+    defined(ABSL_HAVE_HWADDRESS_SANITIZER) || \
+    defined(ABSL_HAVE_MEMORY_SANITIZER)
+// When compiled in sanitizer mode, we add generation integers to the backing
+// array and iterators. In the backing array, we store the generation between
+// the control bytes and the slots. When iterators are dereferenced, we assert
+// that the container has not been mutated in a way that could cause iterator
+// invalidation since the iterator was initialized.
+#define ABSL_SWISSTABLE_ENABLE_GENERATIONS
+#endif
+
+// We use uint8_t so we don't need to worry about padding.
+using GenerationType = uint8_t;
+
+// A sentinel value for empty generations. Using 0 makes it easy to constexpr
+// initialize an array of this value.
+constexpr GenerationType SentinelEmptyGeneration() { return 0; }
+
+constexpr GenerationType NextGeneration(GenerationType generation) {
+  return ++generation == SentinelEmptyGeneration() ? ++generation : generation;
+}
+
+#ifdef ABSL_SWISSTABLE_ENABLE_GENERATIONS
+constexpr bool SwisstableGenerationsEnabled() { return true; }
+constexpr size_t NumGenerationBytes() { return sizeof(GenerationType); }
+#else
+constexpr bool SwisstableGenerationsEnabled() { return false; }
+constexpr size_t NumGenerationBytes() { return 0; }
+#endif
+
+template <typename AllocType>
+void SwapAlloc(AllocType& lhs, AllocType& rhs,
+               std::true_type /* propagate_on_container_swap */) {
+  using std::swap;
+  swap(lhs, rhs);
+}
+template <typename AllocType>
+void SwapAlloc(AllocType& lhs, AllocType& rhs,
+               std::false_type /* propagate_on_container_swap */) {
+  (void)lhs;
+  (void)rhs;
+  assert(lhs == rhs &&
+         "It's UB to call swap with unequal non-propagating allocators.");
+}
+
+template <typename AllocType>
+void CopyAlloc(AllocType& lhs, AllocType& rhs,
+               std::true_type /* propagate_alloc */) {
+  lhs = rhs;
+}
+template <typename AllocType>
+void CopyAlloc(AllocType&, AllocType&, std::false_type /* propagate_alloc */) {}
+
+// The state for a probe sequence.
+//
+// Currently, the sequence is a triangular progression of the form
+//
+//   p(i) := Width * (i^2 + i)/2 + hash (mod mask + 1)
+//
+// The use of `Width` ensures that each probe step does not overlap groups;
+// the sequence effectively outputs the addresses of *groups* (although not
+// necessarily aligned to any boundary). The `Group` machinery allows us
+// to check an entire group with minimal branching.
+//
+// Wrapping around at `mask + 1` is important, but not for the obvious reason.
+// As described above, the first few entries of the control byte array
+// are mirrored at the end of the array, which `Group` will find and use
+// for selecting candidates. However, when those candidates' slots are
+// actually inspected, there are no corresponding slots for the cloned bytes,
+// so we need to make sure we've treated those offsets as "wrapping around".
+//
+// It turns out that this probe sequence visits every group exactly once if the
+// number of groups is a power of two, since (i^2+i)/2 is a bijection in
+// Z/(2^m). See https://en.wikipedia.org/wiki/Quadratic_probing
+template <size_t Width>
+class probe_seq {
+ public:
+  // Creates a new probe sequence using `hash` as the initial value of the
+  // sequence and `mask` (usually the capacity of the table) as the mask to
+  // apply to each value in the progression.
+  probe_seq(size_t hash, size_t mask) {
+    assert(((mask + 1) & mask) == 0 && "not a mask");
+    mask_ = mask;
+    offset_ = hash & mask_;
+  }
+
+  // The offset within the table, i.e., the value `p(i)` above.
+  size_t offset() const { return offset_; }
+  size_t offset(size_t i) const { return (offset_ + i) & mask_; }
+
+  void next() {
+    index_ += Width;
+    offset_ += index_;
+    offset_ &= mask_;
+  }
+  // 0-based probe index, a multiple of `Width`.
+  size_t index() const { return index_; }
+
+ private:
+  size_t mask_;
+  size_t offset_;
+  size_t index_ = 0;
+};
+
+template <class ContainerKey, class Hash, class Eq>
+struct RequireUsableKey {
+  template <class PassedKey, class... Args>
+  std::pair<
+      decltype(std::declval<const Hash&>()(std::declval<const PassedKey&>())),
+      decltype(std::declval<const Eq&>()(std::declval<const ContainerKey&>(),
+                                         std::declval<const PassedKey&>()))>*
+  operator()(const PassedKey&, const Args&...) const;
+};
+
+template <class E, class Policy, class Hash, class Eq, class... Ts>
+struct IsDecomposable : std::false_type {};
+
+template <class Policy, class Hash, class Eq, class... Ts>
+struct IsDecomposable<
+    absl::void_t<decltype(Policy::apply(
+        RequireUsableKey<typename Policy::key_type, Hash, Eq>(),
+        std::declval<Ts>()...))>,
+    Policy, Hash, Eq, Ts...> : std::true_type {};
+
+// TODO(alkis): Switch to std::is_nothrow_swappable when gcc/clang supports it.
+template <class T>
+constexpr bool IsNoThrowSwappable(std::true_type = {} /* is_swappable */) {
+  using std::swap;
+  return noexcept(swap(std::declval<T&>(), std::declval<T&>()));
+}
+template <class T>
+constexpr bool IsNoThrowSwappable(std::false_type /* is_swappable */) {
+  return false;
+}
+
+template <typename T>
+uint32_t TrailingZeros(T x) {
+  ABSL_ASSUME(x != 0);
+  return static_cast<uint32_t>(countr_zero(x));
+}
+
+// An abstract bitmask, such as that emitted by a SIMD instruction.
+//
+// Specifically, this type implements a simple bitset whose representation is
+// controlled by `SignificantBits` and `Shift`. `SignificantBits` is the number
+// of abstract bits in the bitset, while `Shift` is the log-base-two of the
+// width of an abstract bit in the representation.
+// This mask provides operations for any number of real bits set in an abstract
+// bit. To add iteration on top of that, implementation must guarantee no more
+// than the most significant real bit is set in a set abstract bit.
+template <class T, int SignificantBits, int Shift = 0>
+class NonIterableBitMask {
+ public:
+  explicit NonIterableBitMask(T mask) : mask_(mask) {}
+
+  explicit operator bool() const { return this->mask_ != 0; }
+
+  // Returns the index of the lowest *abstract* bit set in `self`.
+  uint32_t LowestBitSet() const {
+    return container_internal::TrailingZeros(mask_) >> Shift;
+  }
+
+  // Returns the index of the highest *abstract* bit set in `self`.
+  uint32_t HighestBitSet() const {
+    return static_cast<uint32_t>((bit_width(mask_) - 1) >> Shift);
+  }
+
+  // Returns the number of trailing zero *abstract* bits.
+  uint32_t TrailingZeros() const {
+    return container_internal::TrailingZeros(mask_) >> Shift;
+  }
+
+  // Returns the number of leading zero *abstract* bits.
+  uint32_t LeadingZeros() const {
+    constexpr int total_significant_bits = SignificantBits << Shift;
+    constexpr int extra_bits = sizeof(T) * 8 - total_significant_bits;
+    return static_cast<uint32_t>(
+               countl_zero(static_cast<T>(mask_ << extra_bits))) >>
+           Shift;
+  }
+
+  T mask_;
+};
+
+// Mask that can be iterable
+//
+// For example, when `SignificantBits` is 16 and `Shift` is zero, this is just
+// an ordinary 16-bit bitset occupying the low 16 bits of `mask`. When
+// `SignificantBits` is 8 and `Shift` is 3, abstract bits are represented as
+// the bytes `0x00` and `0x80`, and it occupies all 64 bits of the bitmask.
+//
+// For example:
+//   for (int i : BitMask<uint32_t, 16>(0b101)) -> yields 0, 2
+//   for (int i : BitMask<uint64_t, 8, 3>(0x0000000080800000)) -> yields 2, 3
+template <class T, int SignificantBits, int Shift = 0>
+class BitMask : public NonIterableBitMask<T, SignificantBits, Shift> {
+  using Base = NonIterableBitMask<T, SignificantBits, Shift>;
+  static_assert(std::is_unsigned<T>::value, "");
+  static_assert(Shift == 0 || Shift == 3, "");
+
+ public:
+  explicit BitMask(T mask) : Base(mask) {}
+  // BitMask is an iterator over the indices of its abstract bits.
+  using value_type = int;
+  using iterator = BitMask;
+  using const_iterator = BitMask;
+
+  BitMask& operator++() {
+    if (Shift == 3) {
+      constexpr uint64_t msbs = 0x8080808080808080ULL;
+      this->mask_ &= msbs;
+    }
+    this->mask_ &= (this->mask_ - 1);
+    return *this;
+  }
+
+  uint32_t operator*() const { return Base::LowestBitSet(); }
+
+  BitMask begin() const { return *this; }
+  BitMask end() const { return BitMask(0); }
+
+ private:
+  friend bool operator==(const BitMask& a, const BitMask& b) {
+    return a.mask_ == b.mask_;
+  }
+  friend bool operator!=(const BitMask& a, const BitMask& b) {
+    return a.mask_ != b.mask_;
+  }
+};
+
+using h2_t = uint8_t;
+
+// The values here are selected for maximum performance. See the static asserts
+// below for details.
+
+// A `ctrl_t` is a single control byte, which can have one of four
+// states: empty, deleted, full (which has an associated seven-bit h2_t value)
+// and the sentinel. They have the following bit patterns:
+//
+//      empty: 1 0 0 0 0 0 0 0
+//    deleted: 1 1 1 1 1 1 1 0
+//       full: 0 h h h h h h h  // h represents the hash bits.
+//   sentinel: 1 1 1 1 1 1 1 1
+//
+// These values are specifically tuned for SSE-flavored SIMD.
+// The static_asserts below detail the source of these choices.
+//
+// We use an enum class so that when strict aliasing is enabled, the compiler
+// knows ctrl_t doesn't alias other types.
+enum class ctrl_t : int8_t {
+  kEmpty = -128,   // 0b10000000
+  kDeleted = -2,   // 0b11111110
+  kSentinel = -1,  // 0b11111111
+};
+static_assert(
+    (static_cast<int8_t>(ctrl_t::kEmpty) &
+     static_cast<int8_t>(ctrl_t::kDeleted) &
+     static_cast<int8_t>(ctrl_t::kSentinel) & 0x80) != 0,
+    "Special markers need to have the MSB to make checking for them efficient");
+static_assert(
+    ctrl_t::kEmpty < ctrl_t::kSentinel && ctrl_t::kDeleted < ctrl_t::kSentinel,
+    "ctrl_t::kEmpty and ctrl_t::kDeleted must be smaller than "
+    "ctrl_t::kSentinel to make the SIMD test of IsEmptyOrDeleted() efficient");
+static_assert(
+    ctrl_t::kSentinel == static_cast<ctrl_t>(-1),
+    "ctrl_t::kSentinel must be -1 to elide loading it from memory into SIMD "
+    "registers (pcmpeqd xmm, xmm)");
+static_assert(ctrl_t::kEmpty == static_cast<ctrl_t>(-128),
+              "ctrl_t::kEmpty must be -128 to make the SIMD check for its "
+              "existence efficient (psignb xmm, xmm)");
+static_assert(
+    (~static_cast<int8_t>(ctrl_t::kEmpty) &
+     ~static_cast<int8_t>(ctrl_t::kDeleted) &
+     static_cast<int8_t>(ctrl_t::kSentinel) & 0x7F) != 0,
+    "ctrl_t::kEmpty and ctrl_t::kDeleted must share an unset bit that is not "
+    "shared by ctrl_t::kSentinel to make the scalar test for "
+    "MaskEmptyOrDeleted() efficient");
+static_assert(ctrl_t::kDeleted == static_cast<ctrl_t>(-2),
+              "ctrl_t::kDeleted must be -2 to make the implementation of "
+              "ConvertSpecialToEmptyAndFullToDeleted efficient");
+
+// See definition comment for why this is size 32.
+ABSL_DLL extern const ctrl_t kEmptyGroup[32];
+
+// Returns a pointer to a control byte group that can be used by empty tables.
+inline ctrl_t* EmptyGroup() {
+  // Const must be cast away here; no uses of this function will actually write
+  // to it, because it is only used for empty tables.
+  return const_cast<ctrl_t*>(kEmptyGroup + 16);
+}
+
+// Returns a pointer to a generation to use for an empty hashtable.
+GenerationType* EmptyGeneration();
+
+// Returns whether `generation` is a generation for an empty hashtable that
+// could be returned by EmptyGeneration().
+inline bool IsEmptyGeneration(const GenerationType* generation) {
+  return *generation == SentinelEmptyGeneration();
+}
+
+// Mixes a randomly generated per-process seed with `hash` and `ctrl` to
+// randomize insertion order within groups.
+bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl);
+
+// Returns a per-table, hash salt, which changes on resize. This gets mixed into
+// H1 to randomize iteration order per-table.
+//
+// The seed consists of the ctrl_ pointer, which adds enough entropy to ensure
+// non-determinism of iteration order in most cases.
+inline size_t PerTableSalt(const ctrl_t* ctrl) {
+  // The low bits of the pointer have little or no entropy because of
+  // alignment. We shift the pointer to try to use higher entropy bits. A
+  // good number seems to be 12 bits, because that aligns with page size.
+  return reinterpret_cast<uintptr_t>(ctrl) >> 12;
+}
+// Extracts the H1 portion of a hash: 57 bits mixed with a per-table salt.
+inline size_t H1(size_t hash, const ctrl_t* ctrl) {
+  return (hash >> 7) ^ PerTableSalt(ctrl);
+}
+
+// Extracts the H2 portion of a hash: the 7 bits not used for H1.
+//
+// These are used as an occupied control byte.
+inline h2_t H2(size_t hash) { return hash & 0x7F; }
+
+// Helpers for checking the state of a control byte.
+inline bool IsEmpty(ctrl_t c) { return c == ctrl_t::kEmpty; }
+inline bool IsFull(ctrl_t c) { return c >= static_cast<ctrl_t>(0); }
+inline bool IsDeleted(ctrl_t c) { return c == ctrl_t::kDeleted; }
+inline bool IsEmptyOrDeleted(ctrl_t c) { return c < ctrl_t::kSentinel; }
+
+#ifdef ABSL_INTERNAL_HAVE_SSE2
+// Quick reference guide for intrinsics used below:
+//
+// * __m128i: An XMM (128-bit) word.
+//
+// * _mm_setzero_si128: Returns a zero vector.
+// * _mm_set1_epi8:     Returns a vector with the same i8 in each lane.
+//
+// * _mm_subs_epi8:    Saturating-subtracts two i8 vectors.
+// * _mm_and_si128:    Ands two i128s together.
+// * _mm_or_si128:     Ors two i128s together.
+// * _mm_andnot_si128: And-nots two i128s together.
+//
+// * _mm_cmpeq_epi8: Component-wise compares two i8 vectors for equality,
+//                   filling each lane with 0x00 or 0xff.
+// * _mm_cmpgt_epi8: Same as above, but using > rather than ==.
+//
+// * _mm_loadu_si128:  Performs an unaligned load of an i128.
+// * _mm_storeu_si128: Performs an unaligned store of an i128.
+//
+// * _mm_sign_epi8:     Retains, negates, or zeroes each i8 lane of the first
+//                      argument if the corresponding lane of the second
+//                      argument is positive, negative, or zero, respectively.
+// * _mm_movemask_epi8: Selects the sign bit out of each i8 lane and produces a
+//                      bitmask consisting of those bits.
+// * _mm_shuffle_epi8:  Selects i8s from the first argument, using the low
+//                      four bits of each i8 lane in the second argument as
+//                      indices.
+
+// https://github.com/abseil/abseil-cpp/issues/209
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87853
+// _mm_cmpgt_epi8 is broken under GCC with -funsigned-char
+// Work around this by using the portable implementation of Group
+// when using -funsigned-char under GCC.
+inline __m128i _mm_cmpgt_epi8_fixed(__m128i a, __m128i b) {
+#if defined(__GNUC__) && !defined(__clang__)
+  if (std::is_unsigned<char>::value) {
+    const __m128i mask = _mm_set1_epi8(0x80);
+    const __m128i diff = _mm_subs_epi8(b, a);
+    return _mm_cmpeq_epi8(_mm_and_si128(diff, mask), mask);
+  }
+#endif
+  return _mm_cmpgt_epi8(a, b);
+}
+
+struct GroupSse2Impl {
+  static constexpr size_t kWidth = 16;  // the number of slots per group
+
+  explicit GroupSse2Impl(const ctrl_t* pos) {
+    ctrl = _mm_loadu_si128(reinterpret_cast<const __m128i*>(pos));
+  }
+
+  // Returns a bitmask representing the positions of slots that match hash.
+  BitMask<uint16_t, kWidth> Match(h2_t hash) const {
+    auto match = _mm_set1_epi8(static_cast<char>(hash));
+    BitMask<uint16_t, kWidth> result = BitMask<uint16_t, kWidth>(0);
+    result = BitMask<uint16_t, kWidth>(
+        static_cast<uint16_t>(_mm_movemask_epi8(_mm_cmpeq_epi8(match, ctrl))));
+    return result;
+  }
+
+  // Returns a bitmask representing the positions of empty slots.
+  NonIterableBitMask<uint16_t, kWidth> MaskEmpty() const {
+#ifdef ABSL_INTERNAL_HAVE_SSSE3
+    // This only works because ctrl_t::kEmpty is -128.
+    return NonIterableBitMask<uint16_t, kWidth>(
+        static_cast<uint16_t>(_mm_movemask_epi8(_mm_sign_epi8(ctrl, ctrl))));
+#else
+    auto match = _mm_set1_epi8(static_cast<char>(ctrl_t::kEmpty));
+    return NonIterableBitMask<uint16_t, kWidth>(
+        static_cast<uint16_t>(_mm_movemask_epi8(_mm_cmpeq_epi8(match, ctrl))));
+#endif
+  }
+
+  // Returns a bitmask representing the positions of full slots.
+  // Note: for `is_small()` tables group may contain the "same" slot twice:
+  // original and mirrored.
+  BitMask<uint16_t, kWidth> MaskFull() const {
+    return BitMask<uint16_t, kWidth>(
+        static_cast<uint16_t>(_mm_movemask_epi8(ctrl) ^ 0xffff));
+  }
+
+  // Returns a bitmask representing the positions of empty or deleted slots.
+  NonIterableBitMask<uint16_t, kWidth> MaskEmptyOrDeleted() const {
+    auto special = _mm_set1_epi8(static_cast<char>(ctrl_t::kSentinel));
+    return NonIterableBitMask<uint16_t, kWidth>(static_cast<uint16_t>(
+        _mm_movemask_epi8(_mm_cmpgt_epi8_fixed(special, ctrl))));
+  }
+
+  // Returns the number of trailing empty or deleted elements in the group.
+  uint32_t CountLeadingEmptyOrDeleted() const {
+    auto special = _mm_set1_epi8(static_cast<char>(ctrl_t::kSentinel));
+    return TrailingZeros(static_cast<uint32_t>(
+        _mm_movemask_epi8(_mm_cmpgt_epi8_fixed(special, ctrl)) + 1));
+  }
+
+  void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
+    auto msbs = _mm_set1_epi8(static_cast<char>(-128));
+    auto x126 = _mm_set1_epi8(126);
+#ifdef ABSL_INTERNAL_HAVE_SSSE3
+    auto res = _mm_or_si128(_mm_shuffle_epi8(x126, ctrl), msbs);
+#else
+    auto zero = _mm_setzero_si128();
+    auto special_mask = _mm_cmpgt_epi8_fixed(zero, ctrl);
+    auto res = _mm_or_si128(msbs, _mm_andnot_si128(special_mask, x126));
+#endif
+    _mm_storeu_si128(reinterpret_cast<__m128i*>(dst), res);
+  }
+
+  __m128i ctrl;
+};
+#endif  // ABSL_INTERNAL_RAW_HASH_SET_HAVE_SSE2
+
+#if defined(ABSL_INTERNAL_HAVE_ARM_NEON) && defined(ABSL_IS_LITTLE_ENDIAN)
+struct GroupAArch64Impl {
+  static constexpr size_t kWidth = 8;
+
+  explicit GroupAArch64Impl(const ctrl_t* pos) {
+    ctrl = vld1_u8(reinterpret_cast<const uint8_t*>(pos));
+  }
+
+  BitMask<uint64_t, kWidth, 3> Match(h2_t hash) const {
+    uint8x8_t dup = vdup_n_u8(hash);
+    auto mask = vceq_u8(ctrl, dup);
+    return BitMask<uint64_t, kWidth, 3>(
+        vget_lane_u64(vreinterpret_u64_u8(mask), 0));
+  }
+
+  NonIterableBitMask<uint64_t, kWidth, 3> MaskEmpty() const {
+    uint64_t mask =
+        vget_lane_u64(vreinterpret_u64_u8(vceq_s8(
+                          vdup_n_s8(static_cast<int8_t>(ctrl_t::kEmpty)),
+                          vreinterpret_s8_u8(ctrl))),
+                      0);
+    return NonIterableBitMask<uint64_t, kWidth, 3>(mask);
+  }
+
+  // Returns a bitmask representing the positions of full slots.
+  // Note: for `is_small()` tables group may contain the "same" slot twice:
+  // original and mirrored.
+  BitMask<uint64_t, kWidth, 3> MaskFull() const {
+    uint64_t mask = vget_lane_u64(
+        vreinterpret_u64_u8(vcge_s8(vreinterpret_s8_u8(ctrl),
+                                    vdup_n_s8(static_cast<int8_t>(0)))),
+        0);
+    return BitMask<uint64_t, kWidth, 3>(mask);
+  }
+
+  NonIterableBitMask<uint64_t, kWidth, 3> MaskEmptyOrDeleted() const {
+    uint64_t mask =
+        vget_lane_u64(vreinterpret_u64_u8(vcgt_s8(
+                          vdup_n_s8(static_cast<int8_t>(ctrl_t::kSentinel)),
+                          vreinterpret_s8_u8(ctrl))),
+                      0);
+    return NonIterableBitMask<uint64_t, kWidth, 3>(mask);
+  }
+
+  uint32_t CountLeadingEmptyOrDeleted() const {
+    uint64_t mask =
+        vget_lane_u64(vreinterpret_u64_u8(vcle_s8(
+                          vdup_n_s8(static_cast<int8_t>(ctrl_t::kSentinel)),
+                          vreinterpret_s8_u8(ctrl))),
+                      0);
+    // Similar to MaskEmptyorDeleted() but we invert the logic to invert the
+    // produced bitfield. We then count number of trailing zeros.
+    // Clang and GCC optimize countr_zero to rbit+clz without any check for 0,
+    // so we should be fine.
+    return static_cast<uint32_t>(countr_zero(mask)) >> 3;
+  }
+
+  void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
+    uint64_t mask = vget_lane_u64(vreinterpret_u64_u8(ctrl), 0);
+    constexpr uint64_t msbs = 0x8080808080808080ULL;
+    constexpr uint64_t slsbs = 0x0202020202020202ULL;
+    constexpr uint64_t midbs = 0x7e7e7e7e7e7e7e7eULL;
+    auto x = slsbs & (mask >> 6);
+    auto res = (x + midbs) | msbs;
+    little_endian::Store64(dst, res);
+  }
+
+  uint8x8_t ctrl;
+};
+#endif  // ABSL_INTERNAL_HAVE_ARM_NEON && ABSL_IS_LITTLE_ENDIAN
+
+struct GroupPortableImpl {
+  static constexpr size_t kWidth = 8;
+
+  explicit GroupPortableImpl(const ctrl_t* pos)
+      : ctrl(little_endian::Load64(pos)) {}
+
+  BitMask<uint64_t, kWidth, 3> Match(h2_t hash) const {
+    // For the technique, see:
+    // http://graphics.stanford.edu/~seander/bithacks.html##ValueInWord
+    // (Determine if a word has a byte equal to n).
+    //
+    // Caveat: there are false positives but:
+    // - they only occur if there is a real match
+    // - they never occur on ctrl_t::kEmpty, ctrl_t::kDeleted, ctrl_t::kSentinel
+    // - they will be handled gracefully by subsequent checks in code
+    //
+    // Example:
+    //   v = 0x1716151413121110
+    //   hash = 0x12
+    //   retval = (v - lsbs) & ~v & msbs = 0x0000000080800000
+    constexpr uint64_t msbs = 0x8080808080808080ULL;
+    constexpr uint64_t lsbs = 0x0101010101010101ULL;
+    auto x = ctrl ^ (lsbs * hash);
+    return BitMask<uint64_t, kWidth, 3>((x - lsbs) & ~x & msbs);
+  }
+
+  NonIterableBitMask<uint64_t, kWidth, 3> MaskEmpty() const {
+    constexpr uint64_t msbs = 0x8080808080808080ULL;
+    return NonIterableBitMask<uint64_t, kWidth, 3>((ctrl & ~(ctrl << 6)) &
+                                                   msbs);
+  }
+
+  // Returns a bitmask representing the positions of full slots.
+  // Note: for `is_small()` tables group may contain the "same" slot twice:
+  // original and mirrored.
+  BitMask<uint64_t, kWidth, 3> MaskFull() const {
+    constexpr uint64_t msbs = 0x8080808080808080ULL;
+    return BitMask<uint64_t, kWidth, 3>((ctrl ^ msbs) & msbs);
+  }
+
+  NonIterableBitMask<uint64_t, kWidth, 3> MaskEmptyOrDeleted() const {
+    constexpr uint64_t msbs = 0x8080808080808080ULL;
+    return NonIterableBitMask<uint64_t, kWidth, 3>((ctrl & ~(ctrl << 7)) &
+                                                   msbs);
+  }
+
+  uint32_t CountLeadingEmptyOrDeleted() const {
+    // ctrl | ~(ctrl >> 7) will have the lowest bit set to zero for kEmpty and
+    // kDeleted. We lower all other bits and count number of trailing zeros.
+    constexpr uint64_t bits = 0x0101010101010101ULL;
+    return static_cast<uint32_t>(countr_zero((ctrl | ~(ctrl >> 7)) & bits) >>
+                                 3);
+  }
+
+  void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
+    constexpr uint64_t msbs = 0x8080808080808080ULL;
+    constexpr uint64_t lsbs = 0x0101010101010101ULL;
+    auto x = ctrl & msbs;
+    auto res = (~x + (x >> 7)) & ~lsbs;
+    little_endian::Store64(dst, res);
+  }
+
+  uint64_t ctrl;
+};
+
+#ifdef ABSL_INTERNAL_HAVE_SSE2
+using Group = GroupSse2Impl;
+using GroupEmptyOrDeleted = GroupSse2Impl;
+#elif defined(ABSL_INTERNAL_HAVE_ARM_NEON) && defined(ABSL_IS_LITTLE_ENDIAN)
+using Group = GroupAArch64Impl;
+// For Aarch64, we use the portable implementation for counting and masking
+// empty or deleted group elements. This is to avoid the latency of moving
+// between data GPRs and Neon registers when it does not provide a benefit.
+// Using Neon is profitable when we call Match(), but is not when we don't,
+// which is the case when we do *EmptyOrDeleted operations. It is difficult to
+// make a similar approach beneficial on other architectures such as x86 since
+// they have much lower GPR <-> vector register transfer latency and 16-wide
+// Groups.
+using GroupEmptyOrDeleted = GroupPortableImpl;
+#else
+using Group = GroupPortableImpl;
+using GroupEmptyOrDeleted = GroupPortableImpl;
+#endif
+
+// When there is an insertion with no reserved growth, we rehash with
+// probability `min(1, RehashProbabilityConstant() / capacity())`. Using a
+// constant divided by capacity ensures that inserting N elements is still O(N)
+// in the average case. Using the constant 16 means that we expect to rehash ~8
+// times more often than when generations are disabled. We are adding expected
+// rehash_probability * #insertions/capacity_growth = 16/capacity * ((7/8 -
+// 7/16) * capacity)/capacity_growth = ~7 extra rehashes per capacity growth.
+inline size_t RehashProbabilityConstant() { return 16; }
+
+class CommonFieldsGenerationInfoEnabled {
+  // A sentinel value for reserved_growth_ indicating that we just ran out of
+  // reserved growth on the last insertion. When reserve is called and then
+  // insertions take place, reserved_growth_'s state machine is N, ..., 1,
+  // kReservedGrowthJustRanOut, 0.
+  static constexpr size_t kReservedGrowthJustRanOut =
+      (std::numeric_limits<size_t>::max)();
+
+ public:
+  CommonFieldsGenerationInfoEnabled() = default;
+  CommonFieldsGenerationInfoEnabled(CommonFieldsGenerationInfoEnabled&& that)
+      : reserved_growth_(that.reserved_growth_),
+        reservation_size_(that.reservation_size_),
+        generation_(that.generation_) {
+    that.reserved_growth_ = 0;
+    that.reservation_size_ = 0;
+    that.generation_ = EmptyGeneration();
+  }
+  CommonFieldsGenerationInfoEnabled& operator=(
+      CommonFieldsGenerationInfoEnabled&&) = default;
+
+  // Whether we should rehash on insert in order to detect bugs of using invalid
+  // references. We rehash on the first insertion after reserved_growth_ reaches
+  // 0 after a call to reserve. We also do a rehash with low probability
+  // whenever reserved_growth_ is zero.
+  bool should_rehash_for_bug_detection_on_insert(const ctrl_t* ctrl,
+                                                 size_t capacity) const;
+  // Similar to above, except that we don't depend on reserved_growth_.
+  bool should_rehash_for_bug_detection_on_move(const ctrl_t* ctrl,
+                                               size_t capacity) const;
+  void maybe_increment_generation_on_insert() {
+    if (reserved_growth_ == kReservedGrowthJustRanOut) reserved_growth_ = 0;
+
+    if (reserved_growth_ > 0) {
+      if (--reserved_growth_ == 0) reserved_growth_ = kReservedGrowthJustRanOut;
+    } else {
+      increment_generation();
+    }
+  }
+  void increment_generation() { *generation_ = NextGeneration(*generation_); }
+  void reset_reserved_growth(size_t reservation, size_t size) {
+    reserved_growth_ = reservation - size;
+  }
+  size_t reserved_growth() const { return reserved_growth_; }
+  void set_reserved_growth(size_t r) { reserved_growth_ = r; }
+  size_t reservation_size() const { return reservation_size_; }
+  void set_reservation_size(size_t r) { reservation_size_ = r; }
+  GenerationType generation() const { return *generation_; }
+  void set_generation(GenerationType g) { *generation_ = g; }
+  GenerationType* generation_ptr() const { return generation_; }
+  void set_generation_ptr(GenerationType* g) { generation_ = g; }
+
+ private:
+  // The number of insertions remaining that are guaranteed to not rehash due to
+  // a prior call to reserve. Note: we store reserved growth in addition to
+  // reservation size because calls to erase() decrease size_ but don't decrease
+  // reserved growth.
+  size_t reserved_growth_ = 0;
+  // The maximum argument to reserve() since the container was cleared. We need
+  // to keep track of this, in addition to reserved growth, because we reset
+  // reserved growth to this when erase(begin(), end()) is called.
+  size_t reservation_size_ = 0;
+  // Pointer to the generation counter, which is used to validate iterators and
+  // is stored in the backing array between the control bytes and the slots.
+  // Note that we can't store the generation inside the container itself and
+  // keep a pointer to the container in the iterators because iterators must
+  // remain valid when the container is moved.
+  // Note: we could derive this pointer from the control pointer, but it makes
+  // the code more complicated, and there's a benefit in having the sizes of
+  // raw_hash_set in sanitizer mode and non-sanitizer mode a bit more different,
+  // which is that tests are less likely to rely on the size remaining the same.
+  GenerationType* generation_ = EmptyGeneration();
+};
+
+class CommonFieldsGenerationInfoDisabled {
+ public:
+  CommonFieldsGenerationInfoDisabled() = default;
+  CommonFieldsGenerationInfoDisabled(CommonFieldsGenerationInfoDisabled&&) =
+      default;
+  CommonFieldsGenerationInfoDisabled& operator=(
+      CommonFieldsGenerationInfoDisabled&&) = default;
+
+  bool should_rehash_for_bug_detection_on_insert(const ctrl_t*, size_t) const {
+    return false;
+  }
+  bool should_rehash_for_bug_detection_on_move(const ctrl_t*, size_t) const {
+    return false;
+  }
+  void maybe_increment_generation_on_insert() {}
+  void increment_generation() {}
+  void reset_reserved_growth(size_t, size_t) {}
+  size_t reserved_growth() const { return 0; }
+  void set_reserved_growth(size_t) {}
+  size_t reservation_size() const { return 0; }
+  void set_reservation_size(size_t) {}
+  GenerationType generation() const { return 0; }
+  void set_generation(GenerationType) {}
+  GenerationType* generation_ptr() const { return nullptr; }
+  void set_generation_ptr(GenerationType*) {}
+};
+
+class HashSetIteratorGenerationInfoEnabled {
+ public:
+  HashSetIteratorGenerationInfoEnabled() = default;
+  explicit HashSetIteratorGenerationInfoEnabled(
+      const GenerationType* generation_ptr)
+      : generation_ptr_(generation_ptr), generation_(*generation_ptr) {}
+
+  GenerationType generation() const { return generation_; }
+  void reset_generation() { generation_ = *generation_ptr_; }
+  const GenerationType* generation_ptr() const { return generation_ptr_; }
+  void set_generation_ptr(const GenerationType* ptr) { generation_ptr_ = ptr; }
+
+ private:
+  const GenerationType* generation_ptr_ = EmptyGeneration();
+  GenerationType generation_ = *generation_ptr_;
+};
+
+class HashSetIteratorGenerationInfoDisabled {
+ public:
+  HashSetIteratorGenerationInfoDisabled() = default;
+  explicit HashSetIteratorGenerationInfoDisabled(const GenerationType*) {}
+
+  GenerationType generation() const { return 0; }
+  void reset_generation() {}
+  const GenerationType* generation_ptr() const { return nullptr; }
+  void set_generation_ptr(const GenerationType*) {}
+};
+
+#ifdef ABSL_SWISSTABLE_ENABLE_GENERATIONS
+using CommonFieldsGenerationInfo = CommonFieldsGenerationInfoEnabled;
+using HashSetIteratorGenerationInfo = HashSetIteratorGenerationInfoEnabled;
+#else
+using CommonFieldsGenerationInfo = CommonFieldsGenerationInfoDisabled;
+using HashSetIteratorGenerationInfo = HashSetIteratorGenerationInfoDisabled;
+#endif
+
+// Returns whether `n` is a valid capacity (i.e., number of slots).
+//
+// A valid capacity is a non-zero integer `2^m - 1`.
+inline bool IsValidCapacity(size_t n) { return ((n + 1) & n) == 0 && n > 0; }
+
+// Computes the offset from the start of the backing allocation of control.
+// infoz and growth_left are stored at the beginning of the backing array.
+inline size_t ControlOffset(bool has_infoz) {
+  return (has_infoz ? sizeof(HashtablezInfoHandle) : 0) + sizeof(size_t);
+}
+
+// Returns the number of "cloned control bytes".
+//
+// This is the number of control bytes that are present both at the beginning
+// of the control byte array and at the end, such that we can create a
+// `Group::kWidth`-width probe window starting from any control byte.
+constexpr size_t NumClonedBytes() { return Group::kWidth - 1; }
+
+// Given the capacity of a table, computes the offset (from the start of the
+// backing allocation) of the generation counter (if it exists).
+inline size_t GenerationOffset(size_t capacity, bool has_infoz) {
+  assert(IsValidCapacity(capacity));
+  const size_t num_control_bytes = capacity + 1 + NumClonedBytes();
+  return ControlOffset(has_infoz) + num_control_bytes;
+}
+
+// Given the capacity of a table, computes the offset (from the start of the
+// backing allocation) at which the slots begin.
+inline size_t SlotOffset(size_t capacity, size_t slot_align, bool has_infoz) {
+  assert(IsValidCapacity(capacity));
+  return (GenerationOffset(capacity, has_infoz) + NumGenerationBytes() +
+          slot_align - 1) &
+         (~slot_align + 1);
+}
+
+// Given the capacity of a table, computes the total size of the backing
+// array.
+inline size_t AllocSize(size_t capacity, size_t slot_size, size_t slot_align,
+                        bool has_infoz) {
+  return SlotOffset(capacity, slot_align, has_infoz) + capacity * slot_size;
+}
+
+// CommonFields hold the fields in raw_hash_set that do not depend
+// on template parameters. This allows us to conveniently pass all
+// of this state to helper functions as a single argument.
+class CommonFields : public CommonFieldsGenerationInfo {
+ public:
+  CommonFields() = default;
+
+  // Not copyable
+  CommonFields(const CommonFields&) = delete;
+  CommonFields& operator=(const CommonFields&) = delete;
+
+  // Movable
+  CommonFields(CommonFields&& that) = default;
+  CommonFields& operator=(CommonFields&&) = default;
+
+  ctrl_t* control() const { return control_; }
+  void set_control(ctrl_t* c) { control_ = c; }
+  void* backing_array_start() const {
+    // growth_left (and maybe infoz) is stored before control bytes.
+    assert(reinterpret_cast<uintptr_t>(control()) % alignof(size_t) == 0);
+    return control() - ControlOffset(has_infoz());
+  }
+
+  // Note: we can't use slots() because Qt defines "slots" as a macro.
+  void* slot_array() const { return slots_; }
+  void set_slots(void* s) { slots_ = s; }
+
+  // The number of filled slots.
+  size_t size() const { return size_ >> HasInfozShift(); }
+  void set_size(size_t s) {
+    size_ = (s << HasInfozShift()) | (size_ & HasInfozMask());
+  }
+  void increment_size() {
+    assert(size() < capacity());
+    size_ += size_t{1} << HasInfozShift();
+  }
+  void decrement_size() {
+    assert(size() > 0);
+    size_ -= size_t{1} << HasInfozShift();
+  }
+
+  // The total number of available slots.
+  size_t capacity() const { return capacity_; }
+  void set_capacity(size_t c) {
+    assert(c == 0 || IsValidCapacity(c));
+    capacity_ = c;
+  }
+
+  // The number of slots we can still fill without needing to rehash.
+  // This is stored in the heap allocation before the control bytes.
+  size_t growth_left() const {
+    const size_t* gl_ptr = reinterpret_cast<size_t*>(control()) - 1;
+    assert(reinterpret_cast<uintptr_t>(gl_ptr) % alignof(size_t) == 0);
+    return *gl_ptr;
+  }
+  void set_growth_left(size_t gl) {
+    size_t* gl_ptr = reinterpret_cast<size_t*>(control()) - 1;
+    assert(reinterpret_cast<uintptr_t>(gl_ptr) % alignof(size_t) == 0);
+    *gl_ptr = gl;
+  }
+
+  bool has_infoz() const {
+    return ABSL_PREDICT_FALSE((size_ & HasInfozMask()) != 0);
+  }
+  void set_has_infoz(bool has_infoz) {
+    size_ = (size() << HasInfozShift()) | static_cast<size_t>(has_infoz);
+  }
+
+  HashtablezInfoHandle infoz() {
+    return has_infoz()
+               ? *reinterpret_cast<HashtablezInfoHandle*>(backing_array_start())
+               : HashtablezInfoHandle();
+  }
+  void set_infoz(HashtablezInfoHandle infoz) {
+    assert(has_infoz());
+    *reinterpret_cast<HashtablezInfoHandle*>(backing_array_start()) = infoz;
+  }
+
+  bool should_rehash_for_bug_detection_on_insert() const {
+    return CommonFieldsGenerationInfo::
+        should_rehash_for_bug_detection_on_insert(control(), capacity());
+  }
+  bool should_rehash_for_bug_detection_on_move() const {
+    return CommonFieldsGenerationInfo::
+        should_rehash_for_bug_detection_on_move(control(), capacity());
+  }
+  void maybe_increment_generation_on_move() {
+    if (capacity() == 0) return;
+    increment_generation();
+  }
+  void reset_reserved_growth(size_t reservation) {
+    CommonFieldsGenerationInfo::reset_reserved_growth(reservation, size());
+  }
+
+  // The size of the backing array allocation.
+  size_t alloc_size(size_t slot_size, size_t slot_align) const {
+    return AllocSize(capacity(), slot_size, slot_align, has_infoz());
+  }
+
+  // Returns the number of control bytes set to kDeleted. For testing only.
+  size_t TombstonesCount() const {
+    return static_cast<size_t>(
+        std::count(control(), control() + capacity(), ctrl_t::kDeleted));
+  }
+
+ private:
+  // We store the has_infoz bit in the lowest bit of size_.
+  static constexpr size_t HasInfozShift() { return 1; }
+  static constexpr size_t HasInfozMask() {
+    return (size_t{1} << HasInfozShift()) - 1;
+  }
+
+  // TODO(b/182800944): Investigate removing some of these fields:
+  // - control/slots can be derived from each other
+
+  // The control bytes (and, also, a pointer near to the base of the backing
+  // array).
+  //
+  // This contains `capacity + 1 + NumClonedBytes()` entries, even
+  // when the table is empty (hence EmptyGroup).
+  //
+  // Note that growth_left is stored immediately before this pointer.
+  ctrl_t* control_ = EmptyGroup();
+
+  // The beginning of the slots, located at `SlotOffset()` bytes after
+  // `control`. May be null for empty tables.
+  void* slots_ = nullptr;
+
+  // The number of slots in the backing array. This is always 2^N-1 for an
+  // integer N. NOTE: we tried experimenting with compressing the capacity and
+  // storing it together with size_: (a) using 6 bits to store the corresponding
+  // power (N in 2^N-1), and (b) storing 2^N as the most significant bit of
+  // size_ and storing size in the low bits. Both of these experiments were
+  // regressions, presumably because we need capacity to do find operations.
+  size_t capacity_ = 0;
+
+  // The size and also has one bit that stores whether we have infoz.
+  size_t size_ = 0;
+};
+
+template <class Policy, class Hash, class Eq, class Alloc>
+class raw_hash_set;
+
+// Returns the next valid capacity after `n`.
+inline size_t NextCapacity(size_t n) {
+  assert(IsValidCapacity(n) || n == 0);
+  return n * 2 + 1;
+}
+
+// Applies the following mapping to every byte in the control array:
+//   * kDeleted -> kEmpty
+//   * kEmpty -> kEmpty
+//   * _ -> kDeleted
+// PRECONDITION:
+//   IsValidCapacity(capacity)
+//   ctrl[capacity] == ctrl_t::kSentinel
+//   ctrl[i] != ctrl_t::kSentinel for all i < capacity
+void ConvertDeletedToEmptyAndFullToDeleted(ctrl_t* ctrl, size_t capacity);
+
+// Converts `n` into the next valid capacity, per `IsValidCapacity`.
+inline size_t NormalizeCapacity(size_t n) {
+  return n ? ~size_t{} >> countl_zero(n) : 1;
+}
+
+// General notes on capacity/growth methods below:
+// - We use 7/8th as maximum load factor. For 16-wide groups, that gives an
+//   average of two empty slots per group.
+// - For (capacity+1) >= Group::kWidth, growth is 7/8*capacity.
+// - For (capacity+1) < Group::kWidth, growth == capacity. In this case, we
+//   never need to probe (the whole table fits in one group) so we don't need a
+//   load factor less than 1.
+
+// Given `capacity`, applies the load factor; i.e., it returns the maximum
+// number of values we should put into the table before a resizing rehash.
+inline size_t CapacityToGrowth(size_t capacity) {
+  assert(IsValidCapacity(capacity));
+  // `capacity*7/8`
+  if (Group::kWidth == 8 && capacity == 7) {
+    // x-x/8 does not work when x==7.
+    return 6;
+  }
+  return capacity - capacity / 8;
+}
+
+// Given `growth`, "unapplies" the load factor to find how large the capacity
+// should be to stay within the load factor.
+//
+// This might not be a valid capacity and `NormalizeCapacity()` should be
+// called on this.
+inline size_t GrowthToLowerboundCapacity(size_t growth) {
+  // `growth*8/7`
+  if (Group::kWidth == 8 && growth == 7) {
+    // x+(x-1)/7 does not work when x==7.
+    return 8;
+  }
+  return growth + static_cast<size_t>((static_cast<int64_t>(growth) - 1) / 7);
+}
+
+template <class InputIter>
+size_t SelectBucketCountForIterRange(InputIter first, InputIter last,
+                                     size_t bucket_count) {
+  if (bucket_count != 0) {
+    return bucket_count;
+  }
+  using InputIterCategory =
+      typename std::iterator_traits<InputIter>::iterator_category;
+  if (std::is_base_of<std::random_access_iterator_tag,
+                      InputIterCategory>::value) {
+    return GrowthToLowerboundCapacity(
+        static_cast<size_t>(std::distance(first, last)));
+  }
+  return 0;
+}
+
+constexpr bool SwisstableDebugEnabled() {
+#if defined(ABSL_SWISSTABLE_ENABLE_GENERATIONS) || \
+    ABSL_OPTION_HARDENED == 1 || !defined(NDEBUG)
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline void AssertIsFull(const ctrl_t* ctrl, GenerationType generation,
+                         const GenerationType* generation_ptr,
+                         const char* operation) {
+  if (!SwisstableDebugEnabled()) return;
+  // `SwisstableDebugEnabled()` is also true for release builds with hardening
+  // enabled. To minimize their impact in those builds:
+  // - use `ABSL_PREDICT_FALSE()` to provide a compiler hint for code layout
+  // - use `ABSL_RAW_LOG()` with a format string to reduce code size and improve
+  //   the chances that the hot paths will be inlined.
+  if (ABSL_PREDICT_FALSE(ctrl == nullptr)) {
+    ABSL_RAW_LOG(FATAL, "%s called on end() iterator.", operation);
+  }
+  if (ABSL_PREDICT_FALSE(ctrl == EmptyGroup())) {
+    ABSL_RAW_LOG(FATAL, "%s called on default-constructed iterator.",
+                 operation);
+  }
+  if (SwisstableGenerationsEnabled()) {
+    if (ABSL_PREDICT_FALSE(generation != *generation_ptr)) {
+      ABSL_RAW_LOG(FATAL,
+                   "%s called on invalid iterator. The table could have "
+                   "rehashed or moved since this iterator was initialized.",
+                   operation);
+    }
+    if (ABSL_PREDICT_FALSE(!IsFull(*ctrl))) {
+      ABSL_RAW_LOG(
+          FATAL,
+          "%s called on invalid iterator. The element was likely erased.",
+          operation);
+    }
+  } else {
+    if (ABSL_PREDICT_FALSE(!IsFull(*ctrl))) {
+      ABSL_RAW_LOG(
+          FATAL,
+          "%s called on invalid iterator. The element might have been erased "
+          "or the table might have rehashed. Consider running with "
+          "--config=asan to diagnose rehashing issues.",
+          operation);
+    }
+  }
+}
+
+// Note that for comparisons, null/end iterators are valid.
+inline void AssertIsValidForComparison(const ctrl_t* ctrl,
+                                       GenerationType generation,
+                                       const GenerationType* generation_ptr) {
+  if (!SwisstableDebugEnabled()) return;
+  const bool ctrl_is_valid_for_comparison =
+      ctrl == nullptr || ctrl == EmptyGroup() || IsFull(*ctrl);
+  if (SwisstableGenerationsEnabled()) {
+    if (ABSL_PREDICT_FALSE(generation != *generation_ptr)) {
+      ABSL_RAW_LOG(FATAL,
+                   "Invalid iterator comparison. The table could have rehashed "
+                   "or moved since this iterator was initialized.");
+    }
+    if (ABSL_PREDICT_FALSE(!ctrl_is_valid_for_comparison)) {
+      ABSL_RAW_LOG(
+          FATAL, "Invalid iterator comparison. The element was likely erased.");
+    }
+  } else {
+    ABSL_HARDENING_ASSERT(
+        ctrl_is_valid_for_comparison &&
+        "Invalid iterator comparison. The element might have been erased or "
+        "the table might have rehashed. Consider running with --config=asan to "
+        "diagnose rehashing issues.");
+  }
+}
+
+// If the two iterators come from the same container, then their pointers will
+// interleave such that ctrl_a <= ctrl_b < slot_a <= slot_b or vice/versa.
+// Note: we take slots by reference so that it's not UB if they're uninitialized
+// as long as we don't read them (when ctrl is null).
+inline bool AreItersFromSameContainer(const ctrl_t* ctrl_a,
+                                      const ctrl_t* ctrl_b,
+                                      const void* const& slot_a,
+                                      const void* const& slot_b) {
+  // If either control byte is null, then we can't tell.
+  if (ctrl_a == nullptr || ctrl_b == nullptr) return true;
+  const void* low_slot = slot_a;
+  const void* hi_slot = slot_b;
+  if (ctrl_a > ctrl_b) {
+    std::swap(ctrl_a, ctrl_b);
+    std::swap(low_slot, hi_slot);
+  }
+  return ctrl_b < low_slot && low_slot <= hi_slot;
+}
+
+// Asserts that two iterators come from the same container.
+// Note: we take slots by reference so that it's not UB if they're uninitialized
+// as long as we don't read them (when ctrl is null).
+inline void AssertSameContainer(const ctrl_t* ctrl_a, const ctrl_t* ctrl_b,
+                                const void* const& slot_a,
+                                const void* const& slot_b,
+                                const GenerationType* generation_ptr_a,
+                                const GenerationType* generation_ptr_b) {
+  if (!SwisstableDebugEnabled()) return;
+  // `SwisstableDebugEnabled()` is also true for release builds with hardening
+  // enabled. To minimize their impact in those builds:
+  // - use `ABSL_PREDICT_FALSE()` to provide a compiler hint for code layout
+  // - use `ABSL_RAW_LOG()` with a format string to reduce code size and improve
+  //   the chances that the hot paths will be inlined.
+  const bool a_is_default = ctrl_a == EmptyGroup();
+  const bool b_is_default = ctrl_b == EmptyGroup();
+  if (ABSL_PREDICT_FALSE(a_is_default != b_is_default)) {
+    ABSL_RAW_LOG(
+        FATAL,
+        "Invalid iterator comparison. Comparing default-constructed iterator "
+        "with non-default-constructed iterator.");
+  }
+  if (a_is_default && b_is_default) return;
+
+  if (SwisstableGenerationsEnabled()) {
+    if (ABSL_PREDICT_TRUE(generation_ptr_a == generation_ptr_b)) return;
+    const bool a_is_empty = IsEmptyGeneration(generation_ptr_a);
+    const bool b_is_empty = IsEmptyGeneration(generation_ptr_b);
+    if (a_is_empty != b_is_empty) {
+      ABSL_RAW_LOG(FATAL,
+                   "Invalid iterator comparison. Comparing iterator from a "
+                   "non-empty hashtable with an iterator from an empty "
+                   "hashtable.");
+    }
+    if (a_is_empty && b_is_empty) {
+      ABSL_RAW_LOG(FATAL,
+                   "Invalid iterator comparison. Comparing iterators from "
+                   "different empty hashtables.");
+    }
+    const bool a_is_end = ctrl_a == nullptr;
+    const bool b_is_end = ctrl_b == nullptr;
+    if (a_is_end || b_is_end) {
+      ABSL_RAW_LOG(FATAL,
+                   "Invalid iterator comparison. Comparing iterator with an "
+                   "end() iterator from a different hashtable.");
+    }
+    ABSL_RAW_LOG(FATAL,
+                 "Invalid iterator comparison. Comparing non-end() iterators "
+                 "from different hashtables.");
+  } else {
+    ABSL_HARDENING_ASSERT(
+        AreItersFromSameContainer(ctrl_a, ctrl_b, slot_a, slot_b) &&
+        "Invalid iterator comparison. The iterators may be from different "
+        "containers or the container might have rehashed or moved. Consider "
+        "running with --config=asan to diagnose issues.");
+  }
+}
+
+struct FindInfo {
+  size_t offset;
+  size_t probe_length;
+};
+
+// Whether a table is "small". A small table fits entirely into a probing
+// group, i.e., has a capacity < `Group::kWidth`.
+//
+// In small mode we are able to use the whole capacity. The extra control
+// bytes give us at least one "empty" control byte to stop the iteration.
+// This is important to make 1 a valid capacity.
+//
+// In small mode only the first `capacity` control bytes after the sentinel
+// are valid. The rest contain dummy ctrl_t::kEmpty values that do not
+// represent a real slot. This is important to take into account on
+// `find_first_non_full()`, where we never try
+// `ShouldInsertBackwards()` for small tables.
+inline bool is_small(size_t capacity) { return capacity < Group::kWidth - 1; }
+
+// Whether a table fits entirely into a probing group.
+// Arbitrary order of elements in such tables is correct.
+inline bool is_single_group(size_t capacity) {
+  return capacity <= Group::kWidth;
+}
+
+// Begins a probing operation on `common.control`, using `hash`.
+inline probe_seq<Group::kWidth> probe(const ctrl_t* ctrl, const size_t capacity,
+                                      size_t hash) {
+  return probe_seq<Group::kWidth>(H1(hash, ctrl), capacity);
+}
+inline probe_seq<Group::kWidth> probe(const CommonFields& common, size_t hash) {
+  return probe(common.control(), common.capacity(), hash);
+}
+
+// Probes an array of control bits using a probe sequence derived from `hash`,
+// and returns the offset corresponding to the first deleted or empty slot.
+//
+// Behavior when the entire table is full is undefined.
+//
+// NOTE: this function must work with tables having both empty and deleted
+// slots in the same group. Such tables appear during `erase()`.
+template <typename = void>
+inline FindInfo find_first_non_full(const CommonFields& common, size_t hash) {
+  auto seq = probe(common, hash);
+  const ctrl_t* ctrl = common.control();
+  while (true) {
+    GroupEmptyOrDeleted g{ctrl + seq.offset()};
+    auto mask = g.MaskEmptyOrDeleted();
+    if (mask) {
+#if !defined(NDEBUG)
+      // We want to add entropy even when ASLR is not enabled.
+      // In debug build we will randomly insert in either the front or back of
+      // the group.
+      // TODO(kfm,sbenza): revisit after we do unconditional mixing
+      if (!is_small(common.capacity()) && ShouldInsertBackwards(hash, ctrl)) {
+        return {seq.offset(mask.HighestBitSet()), seq.index()};
+      }
+#endif
+      return {seq.offset(mask.LowestBitSet()), seq.index()};
+    }
+    seq.next();
+    assert(seq.index() <= common.capacity() && "full table!");
+  }
+}
+
+// Extern template for inline function keep possibility of inlining.
+// When compiler decided to not inline, no symbols will be added to the
+// corresponding translation unit.
+extern template FindInfo find_first_non_full(const CommonFields&, size_t);
+
+// Non-inlined version of find_first_non_full for use in less
+// performance critical routines.
+FindInfo find_first_non_full_outofline(const CommonFields&, size_t);
+
+inline void ResetGrowthLeft(CommonFields& common) {
+  common.set_growth_left(CapacityToGrowth(common.capacity()) - common.size());
+}
+
+// Sets `ctrl` to `{kEmpty, kSentinel, ..., kEmpty}`, marking the entire
+// array as marked as empty.
+inline void ResetCtrl(CommonFields& common, size_t slot_size) {
+  const size_t capacity = common.capacity();
+  ctrl_t* ctrl = common.control();
+  std::memset(ctrl, static_cast<int8_t>(ctrl_t::kEmpty),
+              capacity + 1 + NumClonedBytes());
+  ctrl[capacity] = ctrl_t::kSentinel;
+  SanitizerPoisonMemoryRegion(common.slot_array(), slot_size * capacity);
+}
+
+// Sets `ctrl[i]` to `h`.
+//
+// Unlike setting it directly, this function will perform bounds checks and
+// mirror the value to the cloned tail if necessary.
+inline void SetCtrl(const CommonFields& common, size_t i, ctrl_t h,
+                    size_t slot_size) {
+  const size_t capacity = common.capacity();
+  assert(i < capacity);
+
+  auto* slot_i = static_cast<const char*>(common.slot_array()) + i * slot_size;
+  if (IsFull(h)) {
+    SanitizerUnpoisonMemoryRegion(slot_i, slot_size);
+  } else {
+    SanitizerPoisonMemoryRegion(slot_i, slot_size);
+  }
+
+  ctrl_t* ctrl = common.control();
+  ctrl[i] = h;
+  ctrl[((i - NumClonedBytes()) & capacity) + (NumClonedBytes() & capacity)] = h;
+}
+
+// Overload for setting to an occupied `h2_t` rather than a special `ctrl_t`.
+inline void SetCtrl(const CommonFields& common, size_t i, h2_t h,
+                    size_t slot_size) {
+  SetCtrl(common, i, static_cast<ctrl_t>(h), slot_size);
+}
+
+// growth_left (which is a size_t) is stored with the backing array.
+constexpr size_t BackingArrayAlignment(size_t align_of_slot) {
+  return (std::max)(align_of_slot, alignof(size_t));
+}
+
+// Returns the address of the ith slot in slots where each slot occupies
+// slot_size.
+inline void* SlotAddress(void* slot_array, size_t slot, size_t slot_size) {
+  return reinterpret_cast<void*>(reinterpret_cast<char*>(slot_array) +
+                                 (slot * slot_size));
+}
+
+// Helper class to perform resize of the hash set.
+//
+// It contains special optimizations for small group resizes.
+// See GrowIntoSingleGroupShuffleControlBytes for details.
+class HashSetResizeHelper {
+ public:
+  explicit HashSetResizeHelper(CommonFields& c)
+      : old_ctrl_(c.control()),
+        old_capacity_(c.capacity()),
+        had_infoz_(c.has_infoz()) {}
+
+  // Optimized for small groups version of `find_first_non_full` applicable
+  // only right after calling `raw_hash_set::resize`.
+  // It has implicit assumption that `resize` will call
+  // `GrowSizeIntoSingleGroup*` in case `IsGrowingIntoSingleGroupApplicable`.
+  // Falls back to `find_first_non_full` in case of big groups, so it is
+  // safe to use after `rehash_and_grow_if_necessary`.
+  static FindInfo FindFirstNonFullAfterResize(const CommonFields& c,
+                                              size_t old_capacity,
+                                              size_t hash) {
+    if (!IsGrowingIntoSingleGroupApplicable(old_capacity, c.capacity())) {
+      return find_first_non_full(c, hash);
+    }
+    // Find a location for the new element non-deterministically.
+    // Note that any position is correct.
+    // It will located at `half_old_capacity` or one of the other
+    // empty slots with approximately 50% probability each.
+    size_t offset = probe(c, hash).offset();
+
+    // Note that we intentionally use unsigned int underflow.
+    if (offset - (old_capacity + 1) >= old_capacity) {
+      // Offset fall on kSentinel or into the mostly occupied first half.
+      offset = old_capacity / 2;
+    }
+    assert(IsEmpty(c.control()[offset]));
+    return FindInfo{offset, 0};
+  }
+
+  ctrl_t* old_ctrl() const { return old_ctrl_; }
+  size_t old_capacity() const { return old_capacity_; }
+
+  // Allocates a backing array for the hashtable.
+  // Reads `capacity` and updates all other fields based on the result of
+  // the allocation.
+  //
+  // It also may do the folowing actions:
+  // 1. initialize control bytes
+  // 2. initialize slots
+  // 3. deallocate old slots.
+  //
+  // We are bundling a lot of functionality
+  // in one ABSL_ATTRIBUTE_NOINLINE function in order to minimize binary code
+  // duplication in raw_hash_set<>::resize.
+  //
+  // `c.capacity()` must be nonzero.
+  // POSTCONDITIONS:
+  //  1. CommonFields is initialized.
+  //
+  //  if IsGrowingIntoSingleGroupApplicable && TransferUsesMemcpy
+  //    Both control bytes and slots are fully initialized.
+  //    old_slots are deallocated.
+  //    infoz.RecordRehash is called.
+  //
+  //  if IsGrowingIntoSingleGroupApplicable && !TransferUsesMemcpy
+  //    Control bytes are fully initialized.
+  //    infoz.RecordRehash is called.
+  //    GrowSizeIntoSingleGroup must be called to finish slots initialization.
+  //
+  //  if !IsGrowingIntoSingleGroupApplicable
+  //    Control bytes are initialized to empty table via ResetCtrl.
+  //    raw_hash_set<>::resize must insert elements regularly.
+  //    infoz.RecordRehash is called if old_capacity == 0.
+  //
+  //  Returns IsGrowingIntoSingleGroupApplicable result to avoid recomputation.
+  template <typename Alloc, size_t SizeOfSlot, bool TransferUsesMemcpy,
+            size_t AlignOfSlot>
+  ABSL_ATTRIBUTE_NOINLINE bool InitializeSlots(CommonFields& c, void* old_slots,
+                                               Alloc alloc) {
+    assert(c.capacity());
+    // Folks with custom allocators often make unwarranted assumptions about the
+    // behavior of their classes vis-a-vis trivial destructability and what
+    // calls they will or won't make.  Avoid sampling for people with custom
+    // allocators to get us out of this mess.  This is not a hard guarantee but
+    // a workaround while we plan the exact guarantee we want to provide.
+    const size_t sample_size =
+        (std::is_same<Alloc, std::allocator<char>>::value &&
+         c.slot_array() == nullptr)
+            ? SizeOfSlot
+            : 0;
+    HashtablezInfoHandle infoz =
+        sample_size > 0 ? Sample(sample_size) : c.infoz();
+
+    const bool has_infoz = infoz.IsSampled();
+    const size_t cap = c.capacity();
+    const size_t alloc_size =
+        AllocSize(cap, SizeOfSlot, AlignOfSlot, has_infoz);
+    char* mem = static_cast<char*>(
+        Allocate<BackingArrayAlignment(AlignOfSlot)>(&alloc, alloc_size));
+    const GenerationType old_generation = c.generation();
+    c.set_generation_ptr(reinterpret_cast<GenerationType*>(
+        mem + GenerationOffset(cap, has_infoz)));
+    c.set_generation(NextGeneration(old_generation));
+    c.set_control(reinterpret_cast<ctrl_t*>(mem + ControlOffset(has_infoz)));
+    c.set_slots(mem + SlotOffset(cap, AlignOfSlot, has_infoz));
+    ResetGrowthLeft(c);
+
+    const bool grow_single_group =
+        IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity());
+    if (old_capacity_ != 0 && grow_single_group) {
+      if (TransferUsesMemcpy) {
+        GrowSizeIntoSingleGroupTransferable(c, old_slots, SizeOfSlot);
+        DeallocateOld<AlignOfSlot>(alloc, SizeOfSlot, old_slots);
+      } else {
+        GrowIntoSingleGroupShuffleControlBytes(c.control(), c.capacity());
+      }
+    } else {
+      ResetCtrl(c, SizeOfSlot);
+    }
+
+    c.set_has_infoz(has_infoz);
+    if (has_infoz) {
+      infoz.RecordStorageChanged(c.size(), cap);
+      if (grow_single_group || old_capacity_ == 0) {
+        infoz.RecordRehash(0);
+      }
+      c.set_infoz(infoz);
+    }
+    return grow_single_group;
+  }
+
+  // Relocates slots into new single group consistent with
+  // GrowIntoSingleGroupShuffleControlBytes.
+  //
+  // PRECONDITIONS:
+  // 1. GrowIntoSingleGroupShuffleControlBytes was already called.
+  template <class PolicyTraits, class Alloc>
+  void GrowSizeIntoSingleGroup(CommonFields& c, Alloc& alloc_ref,
+                               typename PolicyTraits::slot_type* old_slots) {
+    assert(old_capacity_ < Group::kWidth / 2);
+    assert(IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity()));
+    using slot_type = typename PolicyTraits::slot_type;
+    assert(is_single_group(c.capacity()));
+
+    auto* new_slots = reinterpret_cast<slot_type*>(c.slot_array());
+
+    size_t shuffle_bit = old_capacity_ / 2 + 1;
+    for (size_t i = 0; i < old_capacity_; ++i) {
+      if (IsFull(old_ctrl_[i])) {
+        size_t new_i = i ^ shuffle_bit;
+        SanitizerUnpoisonMemoryRegion(new_slots + new_i, sizeof(slot_type));
+        PolicyTraits::transfer(&alloc_ref, new_slots + new_i, old_slots + i);
+      }
+    }
+    PoisonSingleGroupEmptySlots(c, sizeof(slot_type));
+  }
+
+  // Deallocates old backing array.
+  template <size_t AlignOfSlot, class CharAlloc>
+  void DeallocateOld(CharAlloc alloc_ref, size_t slot_size, void* old_slots) {
+    SanitizerUnpoisonMemoryRegion(old_slots, slot_size * old_capacity_);
+    Deallocate<BackingArrayAlignment(AlignOfSlot)>(
+        &alloc_ref, old_ctrl_ - ControlOffset(had_infoz_),
+        AllocSize(old_capacity_, slot_size, AlignOfSlot, had_infoz_));
+  }
+
+ private:
+  // Returns true if `GrowSizeIntoSingleGroup` can be used for resizing.
+  static bool IsGrowingIntoSingleGroupApplicable(size_t old_capacity,
+                                                 size_t new_capacity) {
+    // NOTE that `old_capacity < new_capacity` in order to have
+    // `old_capacity < Group::kWidth / 2` to make faster copies of 8 bytes.
+    return is_single_group(new_capacity) && old_capacity < new_capacity;
+  }
+
+  // Relocates control bytes and slots into new single group for
+  // transferable objects.
+  // Must be called only if IsGrowingIntoSingleGroupApplicable returned true.
+  void GrowSizeIntoSingleGroupTransferable(CommonFields& c, void* old_slots,
+                                           size_t slot_size);
+
+  // Shuffle control bits deterministically to the next capacity.
+  // Returns offset for newly added element with given hash.
+  //
+  // PRECONDITIONs:
+  // 1. new_ctrl is allocated for new_capacity,
+  //    but not initialized.
+  // 2. new_capacity is a single group.
+  //
+  // All elements are transferred into the first `old_capacity + 1` positions
+  // of the new_ctrl. Elements are rotated by `old_capacity_ / 2 + 1` positions
+  // in order to change an order and keep it non deterministic.
+  // Although rotation itself deterministic, position of the new added element
+  // will be based on `H1` and is not deterministic.
+  //
+  // Examples:
+  // S = kSentinel, E = kEmpty
+  //
+  // old_ctrl = SEEEEEEEE...
+  // new_ctrl = ESEEEEEEE...
+  //
+  // old_ctrl = 0SEEEEEEE...
+  // new_ctrl = E0ESE0EEE...
+  //
+  // old_ctrl = 012S012EEEEEEEEE...
+  // new_ctrl = 2E01EEES2E01EEE...
+  //
+  // old_ctrl = 0123456S0123456EEEEEEEEEEE...
+  // new_ctrl = 456E0123EEEEEES456E0123EEE...
+  void GrowIntoSingleGroupShuffleControlBytes(ctrl_t* new_ctrl,
+                                              size_t new_capacity) const;
+
+  // Shuffle trivially transferable slots in the way consistent with
+  // GrowIntoSingleGroupShuffleControlBytes.
+  //
+  // PRECONDITIONs:
+  // 1. old_capacity must be non-zero.
+  // 2. new_ctrl is fully initialized using
+  //    GrowIntoSingleGroupShuffleControlBytes.
+  // 3. new_slots is allocated and *not* poisoned.
+  //
+  // POSTCONDITIONS:
+  // 1. new_slots are transferred from old_slots_ consistent with
+  //    GrowIntoSingleGroupShuffleControlBytes.
+  // 2. Empty new_slots are *not* poisoned.
+  void GrowIntoSingleGroupShuffleTransferableSlots(void* old_slots,
+                                                   void* new_slots,
+                                                   size_t slot_size) const;
+
+  // Poison empty slots that were transferred using the deterministic algorithm
+  // described above.
+  // PRECONDITIONs:
+  // 1. new_ctrl is fully initialized using
+  //    GrowIntoSingleGroupShuffleControlBytes.
+  // 2. new_slots is fully initialized consistent with
+  //    GrowIntoSingleGroupShuffleControlBytes.
+  void PoisonSingleGroupEmptySlots(CommonFields& c, size_t slot_size) const {
+    // poison non full items
+    for (size_t i = 0; i < c.capacity(); ++i) {
+      if (!IsFull(c.control()[i])) {
+        SanitizerPoisonMemoryRegion(SlotAddress(c.slot_array(), i, slot_size),
+                                    slot_size);
+      }
+    }
+  }
+
+  ctrl_t* old_ctrl_;
+  size_t old_capacity_;
+  bool had_infoz_;
+};
+
+// PolicyFunctions bundles together some information for a particular
+// raw_hash_set<T, ...> instantiation. This information is passed to
+// type-erased functions that want to do small amounts of type-specific
+// work.
+struct PolicyFunctions {
+  size_t slot_size;
+
+  // Returns the hash of the pointed-to slot.
+  size_t (*hash_slot)(void* set, void* slot);
+
+  // Transfer the contents of src_slot to dst_slot.
+  void (*transfer)(void* set, void* dst_slot, void* src_slot);
+
+  // Deallocate the backing store from common.
+  void (*dealloc)(CommonFields& common, const PolicyFunctions& policy);
+};
+
+// ClearBackingArray clears the backing array, either modifying it in place,
+// or creating a new one based on the value of "reuse".
+// REQUIRES: c.capacity > 0
+void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
+                       bool reuse);
+
+// Type-erased version of raw_hash_set::erase_meta_only.
+void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size);
+
+// Function to place in PolicyFunctions::dealloc for raw_hash_sets
+// that are using std::allocator. This allows us to share the same
+// function body for raw_hash_set instantiations that have the
+// same slot alignment.
+template <size_t AlignOfSlot>
+ABSL_ATTRIBUTE_NOINLINE void DeallocateStandard(CommonFields& common,
+                                                const PolicyFunctions& policy) {
+  // Unpoison before returning the memory to the allocator.
+  SanitizerUnpoisonMemoryRegion(common.slot_array(),
+                                policy.slot_size * common.capacity());
+
+  std::allocator<char> alloc;
+  common.infoz().Unregister();
+  Deallocate<BackingArrayAlignment(AlignOfSlot)>(
+      &alloc, common.backing_array_start(),
+      common.alloc_size(policy.slot_size, AlignOfSlot));
+}
+
+// For trivially relocatable types we use memcpy directly. This allows us to
+// share the same function body for raw_hash_set instantiations that have the
+// same slot size as long as they are relocatable.
+template <size_t SizeOfSlot>
+ABSL_ATTRIBUTE_NOINLINE void TransferRelocatable(void*, void* dst, void* src) {
+  memcpy(dst, src, SizeOfSlot);
+}
+
+// Type-erased version of raw_hash_set::drop_deletes_without_resize.
+void DropDeletesWithoutResize(CommonFields& common,
+                              const PolicyFunctions& policy, void* tmp_space);
+
+// A SwissTable.
+//
+// Policy: a policy defines how to perform different operations on
+// the slots of the hashtable (see hash_policy_traits.h for the full interface
+// of policy).
+//
+// Hash: a (possibly polymorphic) functor that hashes keys of the hashtable. The
+// functor should accept a key and return size_t as hash. For best performance
+// it is important that the hash function provides high entropy across all bits
+// of the hash.
+//
+// Eq: a (possibly polymorphic) functor that compares two keys for equality. It
+// should accept two (of possibly different type) keys and return a bool: true
+// if they are equal, false if they are not. If two keys compare equal, then
+// their hash values as defined by Hash MUST be equal.
+//
+// Allocator: an Allocator
+// [https://en.cppreference.com/w/cpp/named_req/Allocator] with which
+// the storage of the hashtable will be allocated and the elements will be
+// constructed and destroyed.
+template <class Policy, class Hash, class Eq, class Alloc>
+class raw_hash_set {
+  using PolicyTraits = hash_policy_traits<Policy>;
+  using KeyArgImpl =
+      KeyArg<IsTransparent<Eq>::value && IsTransparent<Hash>::value>;
+
+ public:
+  using init_type = typename PolicyTraits::init_type;
+  using key_type = typename PolicyTraits::key_type;
+  // TODO(sbenza): Hide slot_type as it is an implementation detail. Needs user
+  // code fixes!
+  using slot_type = typename PolicyTraits::slot_type;
+  using allocator_type = Alloc;
+  using size_type = size_t;
+  using difference_type = ptrdiff_t;
+  using hasher = Hash;
+  using key_equal = Eq;
+  using policy_type = Policy;
+  using value_type = typename PolicyTraits::value_type;
+  using reference = value_type&;
+  using const_reference = const value_type&;
+  using pointer = typename absl::allocator_traits<
+      allocator_type>::template rebind_traits<value_type>::pointer;
+  using const_pointer = typename absl::allocator_traits<
+      allocator_type>::template rebind_traits<value_type>::const_pointer;
+
+  // Alias used for heterogeneous lookup functions.
+  // `key_arg<K>` evaluates to `K` when the functors are transparent and to
+  // `key_type` otherwise. It permits template argument deduction on `K` for the
+  // transparent case.
+  template <class K>
+  using key_arg = typename KeyArgImpl::template type<K, key_type>;
+
+ private:
+  // Give an early error when key_type is not hashable/eq.
+  auto KeyTypeCanBeHashed(const Hash& h, const key_type& k) -> decltype(h(k));
+  auto KeyTypeCanBeEq(const Eq& eq, const key_type& k) -> decltype(eq(k, k));
+
+  using AllocTraits = absl::allocator_traits<allocator_type>;
+  using SlotAlloc = typename absl::allocator_traits<
+      allocator_type>::template rebind_alloc<slot_type>;
+  // People are often sloppy with the exact type of their allocator (sometimes
+  // it has an extra const or is missing the pair, but rebinds made it work
+  // anyway).
+  using CharAlloc =
+      typename absl::allocator_traits<Alloc>::template rebind_alloc<char>;
+  using SlotAllocTraits = typename absl::allocator_traits<
+      allocator_type>::template rebind_traits<slot_type>;
+
+  static_assert(std::is_lvalue_reference<reference>::value,
+                "Policy::element() must return a reference");
+
+  template <typename T>
+  struct SameAsElementReference
+      : std::is_same<typename std::remove_cv<
+                         typename std::remove_reference<reference>::type>::type,
+                     typename std::remove_cv<
+                         typename std::remove_reference<T>::type>::type> {};
+
+  // An enabler for insert(T&&): T must be convertible to init_type or be the
+  // same as [cv] value_type [ref].
+  // Note: we separate SameAsElementReference into its own type to avoid using
+  // reference unless we need to. MSVC doesn't seem to like it in some
+  // cases.
+  template <class T>
+  using RequiresInsertable = typename std::enable_if<
+      absl::disjunction<std::is_convertible<T, init_type>,
+                        SameAsElementReference<T>>::value,
+      int>::type;
+
+  // RequiresNotInit is a workaround for gcc prior to 7.1.
+  // See https://godbolt.org/g/Y4xsUh.
+  template <class T>
+  using RequiresNotInit =
+      typename std::enable_if<!std::is_same<T, init_type>::value, int>::type;
+
+  template <class... Ts>
+  using IsDecomposable = IsDecomposable<void, PolicyTraits, Hash, Eq, Ts...>;
+
+ public:
+  static_assert(std::is_same<pointer, value_type*>::value,
+                "Allocators with custom pointer types are not supported");
+  static_assert(std::is_same<const_pointer, const value_type*>::value,
+                "Allocators with custom pointer types are not supported");
+
+  class iterator : private HashSetIteratorGenerationInfo {
+    friend class raw_hash_set;
+
+   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = typename raw_hash_set::value_type;
+    using reference =
+        absl::conditional_t<PolicyTraits::constant_iterators::value,
+                            const value_type&, value_type&>;
+    using pointer = absl::remove_reference_t<reference>*;
+    using difference_type = typename raw_hash_set::difference_type;
+
+    iterator() {}
+
+    // PRECONDITION: not an end() iterator.
+    reference operator*() const {
+      AssertIsFull(ctrl_, generation(), generation_ptr(), "operator*()");
+      return unchecked_deref();
+    }
+
+    // PRECONDITION: not an end() iterator.
+    pointer operator->() const {
+      AssertIsFull(ctrl_, generation(), generation_ptr(), "operator->");
+      return &operator*();
+    }
+
+    // PRECONDITION: not an end() iterator.
+    iterator& operator++() {
+      AssertIsFull(ctrl_, generation(), generation_ptr(), "operator++");
+      ++ctrl_;
+      ++slot_;
+      skip_empty_or_deleted();
+      return *this;
+    }
+    // PRECONDITION: not an end() iterator.
+    iterator operator++(int) {
+      auto tmp = *this;
+      ++*this;
+      return tmp;
+    }
+
+    friend bool operator==(const iterator& a, const iterator& b) {
+      AssertIsValidForComparison(a.ctrl_, a.generation(), a.generation_ptr());
+      AssertIsValidForComparison(b.ctrl_, b.generation(), b.generation_ptr());
+      AssertSameContainer(a.ctrl_, b.ctrl_, a.slot_, b.slot_,
+                          a.generation_ptr(), b.generation_ptr());
+      return a.ctrl_ == b.ctrl_;
+    }
+    friend bool operator!=(const iterator& a, const iterator& b) {
+      return !(a == b);
+    }
+
+   private:
+    iterator(ctrl_t* ctrl, slot_type* slot,
+             const GenerationType* generation_ptr)
+        : HashSetIteratorGenerationInfo(generation_ptr),
+          ctrl_(ctrl),
+          slot_(slot) {
+      // This assumption helps the compiler know that any non-end iterator is
+      // not equal to any end iterator.
+      ABSL_ASSUME(ctrl != nullptr);
+    }
+    // For end() iterators.
+    explicit iterator(const GenerationType* generation_ptr)
+        : HashSetIteratorGenerationInfo(generation_ptr), ctrl_(nullptr) {}
+
+    // Fixes up `ctrl_` to point to a full by advancing it and `slot_` until
+    // they reach one.
+    //
+    // If a sentinel is reached, we null `ctrl_` out instead.
+    void skip_empty_or_deleted() {
+      while (IsEmptyOrDeleted(*ctrl_)) {
+        uint32_t shift =
+            GroupEmptyOrDeleted{ctrl_}.CountLeadingEmptyOrDeleted();
+        ctrl_ += shift;
+        slot_ += shift;
+      }
+      if (ABSL_PREDICT_FALSE(*ctrl_ == ctrl_t::kSentinel)) ctrl_ = nullptr;
+    }
+
+    ctrl_t* control() const { return ctrl_; }
+    slot_type* slot() const { return slot_; }
+
+    // We use EmptyGroup() for default-constructed iterators so that they can
+    // be distinguished from end iterators, which have nullptr ctrl_.
+    ctrl_t* ctrl_ = EmptyGroup();
+    // To avoid uninitialized member warnings, put slot_ in an anonymous union.
+    // The member is not initialized on singleton and end iterators.
+    union {
+      slot_type* slot_;
+    };
+
+    // An equality check which skips ABSL Hardening iterator invalidation
+    // checks.
+    // Should be used when the lifetimes of the iterators are well-enough
+    // understood to prove that they cannot be invalid.
+    bool unchecked_equals(const iterator& b) { return ctrl_ == b.control(); }
+
+    // Dereferences the iterator without ABSL Hardening iterator invalidation
+    // checks.
+    reference unchecked_deref() const { return PolicyTraits::element(slot_); }
+  };
+
+  class const_iterator {
+    friend class raw_hash_set;
+    template <class Container, typename Enabler>
+    friend struct absl::container_internal::hashtable_debug_internal::
+        HashtableDebugAccess;
+
+   public:
+    using iterator_category = typename iterator::iterator_category;
+    using value_type = typename raw_hash_set::value_type;
+    using reference = typename raw_hash_set::const_reference;
+    using pointer = typename raw_hash_set::const_pointer;
+    using difference_type = typename raw_hash_set::difference_type;
+
+    const_iterator() = default;
+    // Implicit construction from iterator.
+    const_iterator(iterator i) : inner_(std::move(i)) {}  // NOLINT
+
+    reference operator*() const { return *inner_; }
+    pointer operator->() const { return inner_.operator->(); }
+
+    const_iterator& operator++() {
+      ++inner_;
+      return *this;
+    }
+    const_iterator operator++(int) { return inner_++; }
+
+    friend bool operator==(const const_iterator& a, const const_iterator& b) {
+      return a.inner_ == b.inner_;
+    }
+    friend bool operator!=(const const_iterator& a, const const_iterator& b) {
+      return !(a == b);
+    }
+
+   private:
+    const_iterator(const ctrl_t* ctrl, const slot_type* slot,
+                   const GenerationType* gen)
+        : inner_(const_cast<ctrl_t*>(ctrl), const_cast<slot_type*>(slot), gen) {
+    }
+    ctrl_t* control() const { return inner_.control(); }
+    slot_type* slot() const { return inner_.slot(); }
+
+    iterator inner_;
+
+    bool unchecked_equals(const const_iterator& b) {
+      return inner_.unchecked_equals(b.inner_);
+    }
+  };
+
+  using node_type = node_handle<Policy, hash_policy_traits<Policy>, Alloc>;
+  using insert_return_type = InsertReturnType<iterator, node_type>;
+
+  // Note: can't use `= default` due to non-default noexcept (causes
+  // problems for some compilers). NOLINTNEXTLINE
+  raw_hash_set() noexcept(
+      std::is_nothrow_default_constructible<hasher>::value &&
+      std::is_nothrow_default_constructible<key_equal>::value &&
+      std::is_nothrow_default_constructible<allocator_type>::value) {}
+
+  ABSL_ATTRIBUTE_NOINLINE explicit raw_hash_set(
+      size_t bucket_count, const hasher& hash = hasher(),
+      const key_equal& eq = key_equal(),
+      const allocator_type& alloc = allocator_type())
+      : settings_(CommonFields{}, hash, eq, alloc) {
+    if (bucket_count) {
+      resize(NormalizeCapacity(bucket_count));
+    }
+  }
+
+  raw_hash_set(size_t bucket_count, const hasher& hash,
+               const allocator_type& alloc)
+      : raw_hash_set(bucket_count, hash, key_equal(), alloc) {}
+
+  raw_hash_set(size_t bucket_count, const allocator_type& alloc)
+      : raw_hash_set(bucket_count, hasher(), key_equal(), alloc) {}
+
+  explicit raw_hash_set(const allocator_type& alloc)
+      : raw_hash_set(0, hasher(), key_equal(), alloc) {}
+
+  template <class InputIter>
+  raw_hash_set(InputIter first, InputIter last, size_t bucket_count = 0,
+               const hasher& hash = hasher(), const key_equal& eq = key_equal(),
+               const allocator_type& alloc = allocator_type())
+      : raw_hash_set(SelectBucketCountForIterRange(first, last, bucket_count),
+                     hash, eq, alloc) {
+    insert(first, last);
+  }
+
+  template <class InputIter>
+  raw_hash_set(InputIter first, InputIter last, size_t bucket_count,
+               const hasher& hash, const allocator_type& alloc)
+      : raw_hash_set(first, last, bucket_count, hash, key_equal(), alloc) {}
+
+  template <class InputIter>
+  raw_hash_set(InputIter first, InputIter last, size_t bucket_count,
+               const allocator_type& alloc)
+      : raw_hash_set(first, last, bucket_count, hasher(), key_equal(), alloc) {}
+
+  template <class InputIter>
+  raw_hash_set(InputIter first, InputIter last, const allocator_type& alloc)
+      : raw_hash_set(first, last, 0, hasher(), key_equal(), alloc) {}
+
+  // Instead of accepting std::initializer_list<value_type> as the first
+  // argument like std::unordered_set<value_type> does, we have two overloads
+  // that accept std::initializer_list<T> and std::initializer_list<init_type>.
+  // This is advantageous for performance.
+  //
+  //   // Turns {"abc", "def"} into std::initializer_list<std::string>, then
+  //   // copies the strings into the set.
+  //   std::unordered_set<std::string> s = {"abc", "def"};
+  //
+  //   // Turns {"abc", "def"} into std::initializer_list<const char*>, then
+  //   // copies the strings into the set.
+  //   absl::flat_hash_set<std::string> s = {"abc", "def"};
+  //
+  // The same trick is used in insert().
+  //
+  // The enabler is necessary to prevent this constructor from triggering where
+  // the copy constructor is meant to be called.
+  //
+  //   absl::flat_hash_set<int> a, b{a};
+  //
+  // RequiresNotInit<T> is a workaround for gcc prior to 7.1.
+  template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
+  raw_hash_set(std::initializer_list<T> init, size_t bucket_count = 0,
+               const hasher& hash = hasher(), const key_equal& eq = key_equal(),
+               const allocator_type& alloc = allocator_type())
+      : raw_hash_set(init.begin(), init.end(), bucket_count, hash, eq, alloc) {}
+
+  raw_hash_set(std::initializer_list<init_type> init, size_t bucket_count = 0,
+               const hasher& hash = hasher(), const key_equal& eq = key_equal(),
+               const allocator_type& alloc = allocator_type())
+      : raw_hash_set(init.begin(), init.end(), bucket_count, hash, eq, alloc) {}
+
+  template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
+  raw_hash_set(std::initializer_list<T> init, size_t bucket_count,
+               const hasher& hash, const allocator_type& alloc)
+      : raw_hash_set(init, bucket_count, hash, key_equal(), alloc) {}
+
+  raw_hash_set(std::initializer_list<init_type> init, size_t bucket_count,
+               const hasher& hash, const allocator_type& alloc)
+      : raw_hash_set(init, bucket_count, hash, key_equal(), alloc) {}
+
+  template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
+  raw_hash_set(std::initializer_list<T> init, size_t bucket_count,
+               const allocator_type& alloc)
+      : raw_hash_set(init, bucket_count, hasher(), key_equal(), alloc) {}
+
+  raw_hash_set(std::initializer_list<init_type> init, size_t bucket_count,
+               const allocator_type& alloc)
+      : raw_hash_set(init, bucket_count, hasher(), key_equal(), alloc) {}
+
+  template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
+  raw_hash_set(std::initializer_list<T> init, const allocator_type& alloc)
+      : raw_hash_set(init, 0, hasher(), key_equal(), alloc) {}
+
+  raw_hash_set(std::initializer_list<init_type> init,
+               const allocator_type& alloc)
+      : raw_hash_set(init, 0, hasher(), key_equal(), alloc) {}
+
+  raw_hash_set(const raw_hash_set& that)
+      : raw_hash_set(that, AllocTraits::select_on_container_copy_construction(
+                               that.alloc_ref())) {}
+
+  raw_hash_set(const raw_hash_set& that, const allocator_type& a)
+      : raw_hash_set(0, that.hash_ref(), that.eq_ref(), a) {
+    const size_t size = that.size();
+    if (size == 0) return;
+    reserve(size);
+    // Because the table is guaranteed to be empty, we can do something faster
+    // than a full `insert`.
+    for (const auto& v : that) {
+      const size_t hash = PolicyTraits::apply(HashElement{hash_ref()}, v);
+      auto target = find_first_non_full_outofline(common(), hash);
+      SetCtrl(common(), target.offset, H2(hash), sizeof(slot_type));
+      emplace_at(target.offset, v);
+      common().maybe_increment_generation_on_insert();
+      infoz().RecordInsert(hash, target.probe_length);
+    }
+    common().set_size(size);
+    set_growth_left(growth_left() - size);
+  }
+
+  ABSL_ATTRIBUTE_NOINLINE raw_hash_set(raw_hash_set&& that) noexcept(
+      std::is_nothrow_copy_constructible<hasher>::value &&
+      std::is_nothrow_copy_constructible<key_equal>::value &&
+      std::is_nothrow_copy_constructible<allocator_type>::value)
+      :  // Hash, equality and allocator are copied instead of moved because
+         // `that` must be left valid. If Hash is std::function<Key>, moving it
+         // would create a nullptr functor that cannot be called.
+         // TODO(b/296061262): move instead of copying hash/eq/alloc.
+         // Note: we avoid using exchange for better generated code.
+        settings_(std::move(that.common()), that.hash_ref(), that.eq_ref(),
+                  that.alloc_ref()) {
+    that.common() = CommonFields{};
+    maybe_increment_generation_or_rehash_on_move();
+  }
+
+  raw_hash_set(raw_hash_set&& that, const allocator_type& a)
+      : settings_(CommonFields{}, that.hash_ref(), that.eq_ref(), a) {
+    if (a == that.alloc_ref()) {
+      std::swap(common(), that.common());
+      maybe_increment_generation_or_rehash_on_move();
+    } else {
+      move_elements_allocs_unequal(std::move(that));
+    }
+  }
+
+  raw_hash_set& operator=(const raw_hash_set& that) {
+    if (ABSL_PREDICT_FALSE(this == &that)) return *this;
+    constexpr bool propagate_alloc =
+        AllocTraits::propagate_on_container_copy_assignment::value;
+    // TODO(ezb): maybe avoid allocating a new backing array if this->capacity()
+    // is an exact match for that.size(). If this->capacity() is too big, then
+    // it would make iteration very slow to reuse the allocation. Maybe we can
+    // do the same heuristic as clear() and reuse if it's small enough.
+    raw_hash_set tmp(that, propagate_alloc ? that.alloc_ref() : alloc_ref());
+    // NOLINTNEXTLINE: not returning *this for performance.
+    return assign_impl<propagate_alloc>(std::move(tmp));
+  }
+
+  raw_hash_set& operator=(raw_hash_set&& that) noexcept(
+      absl::allocator_traits<allocator_type>::is_always_equal::value &&
+      std::is_nothrow_move_assignable<hasher>::value &&
+      std::is_nothrow_move_assignable<key_equal>::value) {
+    // TODO(sbenza): We should only use the operations from the noexcept clause
+    // to make sure we actually adhere to that contract.
+    // NOLINTNEXTLINE: not returning *this for performance.
+    return move_assign(
+        std::move(that),
+        typename AllocTraits::propagate_on_container_move_assignment());
+  }
+
+  ~raw_hash_set() { destructor_impl(); }
+
+  iterator begin() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto it = iterator_at(0);
+    it.skip_empty_or_deleted();
+    return it;
+  }
+  iterator end() ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return iterator(common().generation_ptr());
+  }
+
+  const_iterator begin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return const_cast<raw_hash_set*>(this)->begin();
+  }
+  const_iterator end() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return iterator(common().generation_ptr());
+  }
+  const_iterator cbegin() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return begin();
+  }
+  const_iterator cend() const ABSL_ATTRIBUTE_LIFETIME_BOUND { return end(); }
+
+  bool empty() const { return !size(); }
+  size_t size() const { return common().size(); }
+  size_t capacity() const { return common().capacity(); }
+  size_t max_size() const { return (std::numeric_limits<size_t>::max)(); }
+
+  ABSL_ATTRIBUTE_REINITIALIZES void clear() {
+    // Iterating over this container is O(bucket_count()). When bucket_count()
+    // is much greater than size(), iteration becomes prohibitively expensive.
+    // For clear() it is more important to reuse the allocated array when the
+    // container is small because allocation takes comparatively long time
+    // compared to destruction of the elements of the container. So we pick the
+    // largest bucket_count() threshold for which iteration is still fast and
+    // past that we simply deallocate the array.
+    const size_t cap = capacity();
+    if (cap == 0) {
+      // Already guaranteed to be empty; so nothing to do.
+    } else {
+      destroy_slots();
+      ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/cap < 128);
+    }
+    common().set_reserved_growth(0);
+    common().set_reservation_size(0);
+  }
+
+  // This overload kicks in when the argument is an rvalue of insertable and
+  // decomposable type other than init_type.
+  //
+  //   flat_hash_map<std::string, int> m;
+  //   m.insert(std::make_pair("abc", 42));
+  // TODO(cheshire): A type alias T2 is introduced as a workaround for the nvcc
+  // bug.
+  template <class T, RequiresInsertable<T> = 0, class T2 = T,
+            typename std::enable_if<IsDecomposable<T2>::value, int>::type = 0,
+            T* = nullptr>
+  std::pair<iterator, bool> insert(T&& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return emplace(std::forward<T>(value));
+  }
+
+  // This overload kicks in when the argument is a bitfield or an lvalue of
+  // insertable and decomposable type.
+  //
+  //   union { int n : 1; };
+  //   flat_hash_set<int> s;
+  //   s.insert(n);
+  //
+  //   flat_hash_set<std::string> s;
+  //   const char* p = "hello";
+  //   s.insert(p);
+  //
+  template <
+      class T, RequiresInsertable<const T&> = 0,
+      typename std::enable_if<IsDecomposable<const T&>::value, int>::type = 0>
+  std::pair<iterator, bool> insert(const T& value)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return emplace(value);
+  }
+
+  // This overload kicks in when the argument is an rvalue of init_type. Its
+  // purpose is to handle brace-init-list arguments.
+  //
+  //   flat_hash_map<std::string, int> s;
+  //   s.insert({"abc", 42});
+  std::pair<iterator, bool> insert(init_type&& value)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return emplace(std::move(value));
+  }
+
+  // TODO(cheshire): A type alias T2 is introduced as a workaround for the nvcc
+  // bug.
+  template <class T, RequiresInsertable<T> = 0, class T2 = T,
+            typename std::enable_if<IsDecomposable<T2>::value, int>::type = 0,
+            T* = nullptr>
+  iterator insert(const_iterator, T&& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert(std::forward<T>(value)).first;
+  }
+
+  template <
+      class T, RequiresInsertable<const T&> = 0,
+      typename std::enable_if<IsDecomposable<const T&>::value, int>::type = 0>
+  iterator insert(const_iterator,
+                  const T& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert(value).first;
+  }
+
+  iterator insert(const_iterator,
+                  init_type&& value) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return insert(std::move(value)).first;
+  }
+
+  template <class InputIt>
+  void insert(InputIt first, InputIt last) {
+    for (; first != last; ++first) emplace(*first);
+  }
+
+  template <class T, RequiresNotInit<T> = 0, RequiresInsertable<const T&> = 0>
+  void insert(std::initializer_list<T> ilist) {
+    insert(ilist.begin(), ilist.end());
+  }
+
+  void insert(std::initializer_list<init_type> ilist) {
+    insert(ilist.begin(), ilist.end());
+  }
+
+  insert_return_type insert(node_type&& node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    if (!node) return {end(), false, node_type()};
+    const auto& elem = PolicyTraits::element(CommonAccess::GetSlot(node));
+    auto res = PolicyTraits::apply(
+        InsertSlot<false>{*this, std::move(*CommonAccess::GetSlot(node))},
+        elem);
+    if (res.second) {
+      CommonAccess::Reset(&node);
+      return {res.first, true, node_type()};
+    } else {
+      return {res.first, false, std::move(node)};
+    }
+  }
+
+  iterator insert(const_iterator,
+                  node_type&& node) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto res = insert(std::move(node));
+    node = std::move(res.node);
+    return res.position;
+  }
+
+  // This overload kicks in if we can deduce the key from args. This enables us
+  // to avoid constructing value_type if an entry with the same key already
+  // exists.
+  //
+  // For example:
+  //
+  //   flat_hash_map<std::string, std::string> m = {{"abc", "def"}};
+  //   // Creates no std::string copies and makes no heap allocations.
+  //   m.emplace("abc", "xyz");
+  template <class... Args, typename std::enable_if<
+                               IsDecomposable<Args...>::value, int>::type = 0>
+  std::pair<iterator, bool> emplace(Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return PolicyTraits::apply(EmplaceDecomposable{*this},
+                               std::forward<Args>(args)...);
+  }
+
+  // This overload kicks in if we cannot deduce the key from args. It constructs
+  // value_type unconditionally and then either moves it into the table or
+  // destroys.
+  template <class... Args, typename std::enable_if<
+                               !IsDecomposable<Args...>::value, int>::type = 0>
+  std::pair<iterator, bool> emplace(Args&&... args)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    alignas(slot_type) unsigned char raw[sizeof(slot_type)];
+    slot_type* slot = reinterpret_cast<slot_type*>(&raw);
+
+    construct(slot, std::forward<Args>(args)...);
+    const auto& elem = PolicyTraits::element(slot);
+    return PolicyTraits::apply(InsertSlot<true>{*this, std::move(*slot)}, elem);
+  }
+
+  template <class... Args>
+  iterator emplace_hint(const_iterator,
+                        Args&&... args) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return emplace(std::forward<Args>(args)...).first;
+  }
+
+  // Extension API: support for lazy emplace.
+  //
+  // Looks up key in the table. If found, returns the iterator to the element.
+  // Otherwise calls `f` with one argument of type `raw_hash_set::constructor`,
+  // and returns an iterator to the new element.
+  //
+  // `f` must abide by several restrictions:
+  //  - it MUST call `raw_hash_set::constructor` with arguments as if a
+  //    `raw_hash_set::value_type` is constructed,
+  //  - it MUST NOT access the container before the call to
+  //    `raw_hash_set::constructor`, and
+  //  - it MUST NOT erase the lazily emplaced element.
+  // Doing any of these is undefined behavior.
+  //
+  // For example:
+  //
+  //   std::unordered_set<ArenaString> s;
+  //   // Makes ArenaStr even if "abc" is in the map.
+  //   s.insert(ArenaString(&arena, "abc"));
+  //
+  //   flat_hash_set<ArenaStr> s;
+  //   // Makes ArenaStr only if "abc" is not in the map.
+  //   s.lazy_emplace("abc", [&](const constructor& ctor) {
+  //     ctor(&arena, "abc");
+  //   });
+  //
+  // WARNING: This API is currently experimental. If there is a way to implement
+  // the same thing with the rest of the API, prefer that.
+  class constructor {
+    friend class raw_hash_set;
+
+   public:
+    template <class... Args>
+    void operator()(Args&&... args) const {
+      assert(*slot_);
+      PolicyTraits::construct(alloc_, *slot_, std::forward<Args>(args)...);
+      *slot_ = nullptr;
+    }
+
+   private:
+    constructor(allocator_type* a, slot_type** slot) : alloc_(a), slot_(slot) {}
+
+    allocator_type* alloc_;
+    slot_type** slot_;
+  };
+
+  template <class K = key_type, class F>
+  iterator lazy_emplace(const key_arg<K>& key,
+                        F&& f) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto res = find_or_prepare_insert(key);
+    if (res.second) {
+      slot_type* slot = slot_array() + res.first;
+      std::forward<F>(f)(constructor(&alloc_ref(), &slot));
+      assert(!slot);
+    }
+    return iterator_at(res.first);
+  }
+
+  // Extension API: support for heterogeneous keys.
+  //
+  //   std::unordered_set<std::string> s;
+  //   // Turns "abc" into std::string.
+  //   s.erase("abc");
+  //
+  //   flat_hash_set<std::string> s;
+  //   // Uses "abc" directly without copying it into std::string.
+  //   s.erase("abc");
+  template <class K = key_type>
+  size_type erase(const key_arg<K>& key) {
+    auto it = find(key);
+    if (it == end()) return 0;
+    erase(it);
+    return 1;
+  }
+
+  // Erases the element pointed to by `it`.  Unlike `std::unordered_set::erase`,
+  // this method returns void to reduce algorithmic complexity to O(1).  The
+  // iterator is invalidated, so any increment should be done before calling
+  // erase.  In order to erase while iterating across a map, use the following
+  // idiom (which also works for standard containers):
+  //
+  // for (auto it = m.begin(), end = m.end(); it != end;) {
+  //   // `erase()` will invalidate `it`, so advance `it` first.
+  //   auto copy_it = it++;
+  //   if (<pred>) {
+  //     m.erase(copy_it);
+  //   }
+  // }
+  void erase(const_iterator cit) { erase(cit.inner_); }
+
+  // This overload is necessary because otherwise erase<K>(const K&) would be
+  // a better match if non-const iterator is passed as an argument.
+  void erase(iterator it) {
+    AssertIsFull(it.control(), it.generation(), it.generation_ptr(), "erase()");
+    destroy(it.slot());
+    erase_meta_only(it);
+  }
+
+  iterator erase(const_iterator first,
+                 const_iterator last) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    // We check for empty first because ClearBackingArray requires that
+    // capacity() > 0 as a precondition.
+    if (empty()) return end();
+    if (first == begin() && last == end()) {
+      // TODO(ezb): we access control bytes in destroy_slots so it could make
+      // sense to combine destroy_slots and ClearBackingArray to avoid cache
+      // misses when the table is large. Note that we also do this in clear().
+      destroy_slots();
+      ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/true);
+      common().set_reserved_growth(common().reservation_size());
+      return end();
+    }
+    while (first != last) {
+      erase(first++);
+    }
+    return last.inner_;
+  }
+
+  // Moves elements from `src` into `this`.
+  // If the element already exists in `this`, it is left unmodified in `src`.
+  template <typename H, typename E>
+  void merge(raw_hash_set<Policy, H, E, Alloc>& src) {  // NOLINT
+    assert(this != &src);
+    for (auto it = src.begin(), e = src.end(); it != e;) {
+      auto next = std::next(it);
+      if (PolicyTraits::apply(InsertSlot<false>{*this, std::move(*it.slot())},
+                              PolicyTraits::element(it.slot()))
+              .second) {
+        src.erase_meta_only(it);
+      }
+      it = next;
+    }
+  }
+
+  template <typename H, typename E>
+  void merge(raw_hash_set<Policy, H, E, Alloc>&& src) {
+    merge(src);
+  }
+
+  node_type extract(const_iterator position) {
+    AssertIsFull(position.control(), position.inner_.generation(),
+                 position.inner_.generation_ptr(), "extract()");
+    auto node = CommonAccess::Transfer<node_type>(alloc_ref(), position.slot());
+    erase_meta_only(position);
+    return node;
+  }
+
+  template <
+      class K = key_type,
+      typename std::enable_if<!std::is_same<K, iterator>::value, int>::type = 0>
+  node_type extract(const key_arg<K>& key) {
+    auto it = find(key);
+    return it == end() ? node_type() : extract(const_iterator{it});
+  }
+
+  void swap(raw_hash_set& that) noexcept(
+      IsNoThrowSwappable<hasher>() && IsNoThrowSwappable<key_equal>() &&
+      IsNoThrowSwappable<allocator_type>(
+          typename AllocTraits::propagate_on_container_swap{})) {
+    using std::swap;
+    swap(common(), that.common());
+    swap(hash_ref(), that.hash_ref());
+    swap(eq_ref(), that.eq_ref());
+    SwapAlloc(alloc_ref(), that.alloc_ref(),
+              typename AllocTraits::propagate_on_container_swap{});
+  }
+
+  void rehash(size_t n) {
+    if (n == 0 && capacity() == 0) return;
+    if (n == 0 && size() == 0) {
+      ClearBackingArray(common(), GetPolicyFunctions(), /*reuse=*/false);
+      return;
+    }
+
+    // bitor is a faster way of doing `max` here. We will round up to the next
+    // power-of-2-minus-1, so bitor is good enough.
+    auto m = NormalizeCapacity(n | GrowthToLowerboundCapacity(size()));
+    // n == 0 unconditionally rehashes as per the standard.
+    if (n == 0 || m > capacity()) {
+      resize(m);
+
+      // This is after resize, to ensure that we have completed the allocation
+      // and have potentially sampled the hashtable.
+      infoz().RecordReservation(n);
+    }
+  }
+
+  void reserve(size_t n) {
+    if (n > size() + growth_left()) {
+      size_t m = GrowthToLowerboundCapacity(n);
+      resize(NormalizeCapacity(m));
+
+      // This is after resize, to ensure that we have completed the allocation
+      // and have potentially sampled the hashtable.
+      infoz().RecordReservation(n);
+    }
+    common().reset_reserved_growth(n);
+    common().set_reservation_size(n);
+  }
+
+  // Extension API: support for heterogeneous keys.
+  //
+  //   std::unordered_set<std::string> s;
+  //   // Turns "abc" into std::string.
+  //   s.count("abc");
+  //
+  //   ch_set<std::string> s;
+  //   // Uses "abc" directly without copying it into std::string.
+  //   s.count("abc");
+  template <class K = key_type>
+  size_t count(const key_arg<K>& key) const {
+    return find(key) == end() ? 0 : 1;
+  }
+
+  // Issues CPU prefetch instructions for the memory needed to find or insert
+  // a key.  Like all lookup functions, this support heterogeneous keys.
+  //
+  // NOTE: This is a very low level operation and should not be used without
+  // specific benchmarks indicating its importance.
+  template <class K = key_type>
+  void prefetch(const key_arg<K>& key) const {
+    (void)key;
+    // Avoid probing if we won't be able to prefetch the addresses received.
+#ifdef ABSL_HAVE_PREFETCH
+    prefetch_heap_block();
+    auto seq = probe(common(), hash_ref()(key));
+    PrefetchToLocalCache(control() + seq.offset());
+    PrefetchToLocalCache(slot_array() + seq.offset());
+#endif  // ABSL_HAVE_PREFETCH
+  }
+
+  // The API of find() has two extensions.
+  //
+  // 1. The hash can be passed by the user. It must be equal to the hash of the
+  // key.
+  //
+  // 2. The type of the key argument doesn't have to be key_type. This is so
+  // called heterogeneous key support.
+  template <class K = key_type>
+  iterator find(const key_arg<K>& key,
+                size_t hash) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto seq = probe(common(), hash);
+    slot_type* slot_ptr = slot_array();
+    const ctrl_t* ctrl = control();
+    while (true) {
+      Group g{ctrl + seq.offset()};
+      for (uint32_t i : g.Match(H2(hash))) {
+        if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
+                EqualElement<K>{key, eq_ref()},
+                PolicyTraits::element(slot_ptr + seq.offset(i)))))
+          return iterator_at(seq.offset(i));
+      }
+      if (ABSL_PREDICT_TRUE(g.MaskEmpty())) return end();
+      seq.next();
+      assert(seq.index() <= capacity() && "full table!");
+    }
+  }
+  template <class K = key_type>
+  iterator find(const key_arg<K>& key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    prefetch_heap_block();
+    return find(key, hash_ref()(key));
+  }
+
+  template <class K = key_type>
+  const_iterator find(const key_arg<K>& key,
+                      size_t hash) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return const_cast<raw_hash_set*>(this)->find(key, hash);
+  }
+  template <class K = key_type>
+  const_iterator find(const key_arg<K>& key) const
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    prefetch_heap_block();
+    return find(key, hash_ref()(key));
+  }
+
+  template <class K = key_type>
+  bool contains(const key_arg<K>& key) const {
+    // Here neither the iterator returned by `find()` nor `end()` can be invalid
+    // outside of potential thread-safety issues.
+    // `find()`'s return value is constructed, used, and then destructed
+    // all in this context.
+    return !find(key).unchecked_equals(end());
+  }
+
+  template <class K = key_type>
+  std::pair<iterator, iterator> equal_range(const key_arg<K>& key)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto it = find(key);
+    if (it != end()) return {it, std::next(it)};
+    return {it, it};
+  }
+  template <class K = key_type>
+  std::pair<const_iterator, const_iterator> equal_range(
+      const key_arg<K>& key) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    auto it = find(key);
+    if (it != end()) return {it, std::next(it)};
+    return {it, it};
+  }
+
+  size_t bucket_count() const { return capacity(); }
+  float load_factor() const {
+    return capacity() ? static_cast<double>(size()) / capacity() : 0.0;
+  }
+  float max_load_factor() const { return 1.0f; }
+  void max_load_factor(float) {
+    // Does nothing.
+  }
+
+  hasher hash_function() const { return hash_ref(); }
+  key_equal key_eq() const { return eq_ref(); }
+  allocator_type get_allocator() const { return alloc_ref(); }
+
+  friend bool operator==(const raw_hash_set& a, const raw_hash_set& b) {
+    if (a.size() != b.size()) return false;
+    const raw_hash_set* outer = &a;
+    const raw_hash_set* inner = &b;
+    if (outer->capacity() > inner->capacity()) std::swap(outer, inner);
+    for (const value_type& elem : *outer) {
+      auto it = PolicyTraits::apply(FindElement{*inner}, elem);
+      if (it == inner->end() || !(*it == elem)) return false;
+    }
+    return true;
+  }
+
+  friend bool operator!=(const raw_hash_set& a, const raw_hash_set& b) {
+    return !(a == b);
+  }
+
+  template <typename H>
+  friend typename std::enable_if<H::template is_hashable<value_type>::value,
+                                 H>::type
+  AbslHashValue(H h, const raw_hash_set& s) {
+    return H::combine(H::combine_unordered(std::move(h), s.begin(), s.end()),
+                      s.size());
+  }
+
+  friend void swap(raw_hash_set& a,
+                   raw_hash_set& b) noexcept(noexcept(a.swap(b))) {
+    a.swap(b);
+  }
+
+ private:
+  template <class Container, typename Enabler>
+  friend struct absl::container_internal::hashtable_debug_internal::
+      HashtableDebugAccess;
+
+  struct FindElement {
+    template <class K, class... Args>
+    const_iterator operator()(const K& key, Args&&...) const {
+      return s.find(key);
+    }
+    const raw_hash_set& s;
+  };
+
+  struct HashElement {
+    template <class K, class... Args>
+    size_t operator()(const K& key, Args&&...) const {
+      return h(key);
+    }
+    const hasher& h;
+  };
+
+  template <class K1>
+  struct EqualElement {
+    template <class K2, class... Args>
+    bool operator()(const K2& lhs, Args&&...) const {
+      return eq(lhs, rhs);
+    }
+    const K1& rhs;
+    const key_equal& eq;
+  };
+
+  struct EmplaceDecomposable {
+    template <class K, class... Args>
+    std::pair<iterator, bool> operator()(const K& key, Args&&... args) const {
+      auto res = s.find_or_prepare_insert(key);
+      if (res.second) {
+        s.emplace_at(res.first, std::forward<Args>(args)...);
+      }
+      return {s.iterator_at(res.first), res.second};
+    }
+    raw_hash_set& s;
+  };
+
+  template <bool do_destroy>
+  struct InsertSlot {
+    template <class K, class... Args>
+    std::pair<iterator, bool> operator()(const K& key, Args&&...) && {
+      auto res = s.find_or_prepare_insert(key);
+      if (res.second) {
+        s.transfer(s.slot_array() + res.first, &slot);
+      } else if (do_destroy) {
+        s.destroy(&slot);
+      }
+      return {s.iterator_at(res.first), res.second};
+    }
+    raw_hash_set& s;
+    // Constructed slot. Either moved into place or destroyed.
+    slot_type&& slot;
+  };
+
+  // TODO(b/303305702): re-enable reentrant validation.
+  template <typename... Args>
+  inline void construct(slot_type* slot, Args&&... args) {
+    PolicyTraits::construct(&alloc_ref(), slot, std::forward<Args>(args)...);
+  }
+  inline void destroy(slot_type* slot) {
+    PolicyTraits::destroy(&alloc_ref(), slot);
+  }
+  inline void transfer(slot_type* to, slot_type* from) {
+    PolicyTraits::transfer(&alloc_ref(), to, from);
+  }
+
+  inline void destroy_slots() {
+    const size_t cap = capacity();
+    const ctrl_t* ctrl = control();
+    slot_type* slot = slot_array();
+    for (size_t i = 0; i != cap; ++i) {
+      if (IsFull(ctrl[i])) {
+        destroy(slot + i);
+      }
+    }
+  }
+
+  inline void dealloc() {
+    assert(capacity() != 0);
+    // Unpoison before returning the memory to the allocator.
+    SanitizerUnpoisonMemoryRegion(slot_array(), sizeof(slot_type) * capacity());
+    infoz().Unregister();
+    Deallocate<BackingArrayAlignment(alignof(slot_type))>(
+        &alloc_ref(), common().backing_array_start(),
+        common().alloc_size(sizeof(slot_type), alignof(slot_type)));
+  }
+
+  inline void destructor_impl() {
+    if (capacity() == 0) return;
+    destroy_slots();
+    dealloc();
+  }
+
+  // Erases, but does not destroy, the value pointed to by `it`.
+  //
+  // This merely updates the pertinent control byte. This can be used in
+  // conjunction with Policy::transfer to move the object to another place.
+  void erase_meta_only(const_iterator it) {
+    EraseMetaOnly(common(), static_cast<size_t>(it.control() - control()),
+                  sizeof(slot_type));
+  }
+
+  // Resizes table to the new capacity and move all elements to the new
+  // positions accordingly.
+  //
+  // Note that for better performance instead of
+  // find_first_non_full(common(), hash),
+  // HashSetResizeHelper::FindFirstNonFullAfterResize(
+  //    common(), old_capacity, hash)
+  // can be called right after `resize`.
+  ABSL_ATTRIBUTE_NOINLINE void resize(size_t new_capacity) {
+    assert(IsValidCapacity(new_capacity));
+    HashSetResizeHelper resize_helper(common());
+    auto* old_slots = slot_array();
+    common().set_capacity(new_capacity);
+    // Note that `InitializeSlots` does different number initialization steps
+    // depending on the values of `transfer_uses_memcpy` and capacities.
+    // Refer to the comment in `InitializeSlots` for more details.
+    const bool grow_single_group =
+        resize_helper.InitializeSlots<CharAlloc, sizeof(slot_type),
+                                      PolicyTraits::transfer_uses_memcpy(),
+                                      alignof(slot_type)>(
+            common(), const_cast<std::remove_const_t<slot_type>*>(old_slots),
+            CharAlloc(alloc_ref()));
+
+    if (resize_helper.old_capacity() == 0) {
+      // InitializeSlots did all the work including infoz().RecordRehash().
+      return;
+    }
+
+    if (grow_single_group) {
+      if (PolicyTraits::transfer_uses_memcpy()) {
+        // InitializeSlots did all the work.
+        return;
+      }
+      // We want GrowSizeIntoSingleGroup to be called here in order to make
+      // InitializeSlots not depend on PolicyTraits.
+      resize_helper.GrowSizeIntoSingleGroup<PolicyTraits>(common(), alloc_ref(),
+                                                          old_slots);
+    } else {
+      // InitializeSlots prepares control bytes to correspond to empty table.
+      auto* new_slots = slot_array();
+      size_t total_probe_length = 0;
+      for (size_t i = 0; i != resize_helper.old_capacity(); ++i) {
+        if (IsFull(resize_helper.old_ctrl()[i])) {
+          size_t hash = PolicyTraits::apply(
+              HashElement{hash_ref()}, PolicyTraits::element(old_slots + i));
+          auto target = find_first_non_full(common(), hash);
+          size_t new_i = target.offset;
+          total_probe_length += target.probe_length;
+          SetCtrl(common(), new_i, H2(hash), sizeof(slot_type));
+          transfer(new_slots + new_i, old_slots + i);
+        }
+      }
+      infoz().RecordRehash(total_probe_length);
+    }
+    resize_helper.DeallocateOld<alignof(slot_type)>(
+        CharAlloc(alloc_ref()), sizeof(slot_type),
+        const_cast<std::remove_const_t<slot_type>*>(old_slots));
+  }
+
+  // Prunes control bytes to remove as many tombstones as possible.
+  //
+  // See the comment on `rehash_and_grow_if_necessary()`.
+  inline void drop_deletes_without_resize() {
+    // Stack-allocate space for swapping elements.
+    alignas(slot_type) unsigned char tmp[sizeof(slot_type)];
+    DropDeletesWithoutResize(common(), GetPolicyFunctions(), tmp);
+  }
+
+  // Called whenever the table *might* need to conditionally grow.
+  //
+  // This function is an optimization opportunity to perform a rehash even when
+  // growth is unnecessary, because vacating tombstones is beneficial for
+  // performance in the long-run.
+  void rehash_and_grow_if_necessary() {
+    const size_t cap = capacity();
+    if (cap > Group::kWidth &&
+        // Do these calculations in 64-bit to avoid overflow.
+        size() * uint64_t{32} <= cap * uint64_t{25}) {
+      // Squash DELETED without growing if there is enough capacity.
+      //
+      // Rehash in place if the current size is <= 25/32 of capacity.
+      // Rationale for such a high factor: 1) drop_deletes_without_resize() is
+      // faster than resize, and 2) it takes quite a bit of work to add
+      // tombstones.  In the worst case, seems to take approximately 4
+      // insert/erase pairs to create a single tombstone and so if we are
+      // rehashing because of tombstones, we can afford to rehash-in-place as
+      // long as we are reclaiming at least 1/8 the capacity without doing more
+      // than 2X the work.  (Where "work" is defined to be size() for rehashing
+      // or rehashing in place, and 1 for an insert or erase.)  But rehashing in
+      // place is faster per operation than inserting or even doubling the size
+      // of the table, so we actually afford to reclaim even less space from a
+      // resize-in-place.  The decision is to rehash in place if we can reclaim
+      // at about 1/8th of the usable capacity (specifically 3/28 of the
+      // capacity) which means that the total cost of rehashing will be a small
+      // fraction of the total work.
+      //
+      // Here is output of an experiment using the BM_CacheInSteadyState
+      // benchmark running the old case (where we rehash-in-place only if we can
+      // reclaim at least 7/16*capacity) vs. this code (which rehashes in place
+      // if we can recover 3/32*capacity).
+      //
+      // Note that although in the worst-case number of rehashes jumped up from
+      // 15 to 190, but the number of operations per second is almost the same.
+      //
+      // Abridged output of running BM_CacheInSteadyState benchmark from
+      // raw_hash_set_benchmark.   N is the number of insert/erase operations.
+      //
+      //      | OLD (recover >= 7/16        | NEW (recover >= 3/32)
+      // size |    N/s LoadFactor NRehashes |    N/s LoadFactor NRehashes
+      //  448 | 145284       0.44        18 | 140118       0.44        19
+      //  493 | 152546       0.24        11 | 151417       0.48        28
+      //  538 | 151439       0.26        11 | 151152       0.53        38
+      //  583 | 151765       0.28        11 | 150572       0.57        50
+      //  628 | 150241       0.31        11 | 150853       0.61        66
+      //  672 | 149602       0.33        12 | 150110       0.66        90
+      //  717 | 149998       0.35        12 | 149531       0.70       129
+      //  762 | 149836       0.37        13 | 148559       0.74       190
+      //  807 | 149736       0.39        14 | 151107       0.39        14
+      //  852 | 150204       0.42        15 | 151019       0.42        15
+      drop_deletes_without_resize();
+    } else {
+      // Otherwise grow the container.
+      resize(NextCapacity(cap));
+    }
+  }
+
+  void maybe_increment_generation_or_rehash_on_move() {
+    common().maybe_increment_generation_on_move();
+    if (!empty() && common().should_rehash_for_bug_detection_on_move()) {
+      resize(capacity());
+    }
+  }
+
+  template<bool propagate_alloc>
+  raw_hash_set& assign_impl(raw_hash_set&& that) {
+    // We don't bother checking for this/that aliasing. We just need to avoid
+    // breaking the invariants in that case.
+    destructor_impl();
+    common() = std::move(that.common());
+    // TODO(b/296061262): move instead of copying hash/eq/alloc.
+    hash_ref() = that.hash_ref();
+    eq_ref() = that.eq_ref();
+    CopyAlloc(alloc_ref(), that.alloc_ref(),
+              std::integral_constant<bool, propagate_alloc>());
+    that.common() = CommonFields{};
+    maybe_increment_generation_or_rehash_on_move();
+    return *this;
+  }
+
+  raw_hash_set& move_elements_allocs_unequal(raw_hash_set&& that) {
+    const size_t size = that.size();
+    if (size == 0) return *this;
+    reserve(size);
+    for (iterator it = that.begin(); it != that.end(); ++it) {
+      insert(std::move(PolicyTraits::element(it.slot())));
+      that.destroy(it.slot());
+    }
+    that.dealloc();
+    that.common() = CommonFields{};
+    maybe_increment_generation_or_rehash_on_move();
+    return *this;
+  }
+
+  raw_hash_set& move_assign(raw_hash_set&& that,
+                            std::true_type /*propagate_alloc*/) {
+    return assign_impl<true>(std::move(that));
+  }
+  raw_hash_set& move_assign(raw_hash_set&& that,
+                            std::false_type /*propagate_alloc*/) {
+    if (alloc_ref() == that.alloc_ref()) {
+      return assign_impl<false>(std::move(that));
+    }
+    // Aliasing can't happen here because allocs would compare equal above.
+    assert(this != &that);
+    destructor_impl();
+    // We can't take over that's memory so we need to move each element.
+    // While moving elements, this should have that's hash/eq so copy hash/eq
+    // before moving elements.
+    // TODO(b/296061262): move instead of copying hash/eq.
+    hash_ref() = that.hash_ref();
+    eq_ref() = that.eq_ref();
+    return move_elements_allocs_unequal(std::move(that));
+  }
+
+ protected:
+  // Attempts to find `key` in the table; if it isn't found, returns a slot that
+  // the value can be inserted into, with the control byte already set to
+  // `key`'s H2.
+  template <class K>
+  std::pair<size_t, bool> find_or_prepare_insert(const K& key) {
+    prefetch_heap_block();
+    auto hash = hash_ref()(key);
+    auto seq = probe(common(), hash);
+    const ctrl_t* ctrl = control();
+    while (true) {
+      Group g{ctrl + seq.offset()};
+      for (uint32_t i : g.Match(H2(hash))) {
+        if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
+                EqualElement<K>{key, eq_ref()},
+                PolicyTraits::element(slot_array() + seq.offset(i)))))
+          return {seq.offset(i), false};
+      }
+      if (ABSL_PREDICT_TRUE(g.MaskEmpty())) break;
+      seq.next();
+      assert(seq.index() <= capacity() && "full table!");
+    }
+    return {prepare_insert(hash), true};
+  }
+
+  // Given the hash of a value not currently in the table, finds the next
+  // viable slot index to insert it at.
+  //
+  // REQUIRES: At least one non-full slot available.
+  size_t prepare_insert(size_t hash) ABSL_ATTRIBUTE_NOINLINE {
+    const bool rehash_for_bug_detection =
+        common().should_rehash_for_bug_detection_on_insert();
+    if (rehash_for_bug_detection) {
+      // Move to a different heap allocation in order to detect bugs.
+      const size_t cap = capacity();
+      resize(growth_left() > 0 ? cap : NextCapacity(cap));
+    }
+    auto target = find_first_non_full(common(), hash);
+    if (!rehash_for_bug_detection &&
+        ABSL_PREDICT_FALSE(growth_left() == 0 &&
+                           !IsDeleted(control()[target.offset]))) {
+      size_t old_capacity = capacity();
+      rehash_and_grow_if_necessary();
+      // NOTE: It is safe to use `FindFirstNonFullAfterResize`.
+      // `FindFirstNonFullAfterResize` must be called right after resize.
+      // `rehash_and_grow_if_necessary` may *not* call `resize`
+      // and perform `drop_deletes_without_resize` instead. But this
+      // could happen only on big tables.
+      // For big tables `FindFirstNonFullAfterResize` will always
+      // fallback to normal `find_first_non_full`, so it is safe to use it.
+      target = HashSetResizeHelper::FindFirstNonFullAfterResize(
+          common(), old_capacity, hash);
+    }
+    common().increment_size();
+    set_growth_left(growth_left() - IsEmpty(control()[target.offset]));
+    SetCtrl(common(), target.offset, H2(hash), sizeof(slot_type));
+    common().maybe_increment_generation_on_insert();
+    infoz().RecordInsert(hash, target.probe_length);
+    return target.offset;
+  }
+
+  // Constructs the value in the space pointed by the iterator. This only works
+  // after an unsuccessful find_or_prepare_insert() and before any other
+  // modifications happen in the raw_hash_set.
+  //
+  // PRECONDITION: i is an index returned from find_or_prepare_insert(k), where
+  // k is the key decomposed from `forward<Args>(args)...`, and the bool
+  // returned by find_or_prepare_insert(k) was true.
+  // POSTCONDITION: *m.iterator_at(i) == value_type(forward<Args>(args)...).
+  template <class... Args>
+  void emplace_at(size_t i, Args&&... args) {
+    construct(slot_array() + i, std::forward<Args>(args)...);
+
+    assert(PolicyTraits::apply(FindElement{*this}, *iterator_at(i)) ==
+               iterator_at(i) &&
+           "constructed value does not match the lookup key");
+  }
+
+  iterator iterator_at(size_t i) ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return {control() + i, slot_array() + i, common().generation_ptr()};
+  }
+  const_iterator iterator_at(size_t i) const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return {control() + i, slot_array() + i, common().generation_ptr()};
+  }
+
+  reference unchecked_deref(iterator it) { return it.unchecked_deref(); }
+
+ private:
+  friend struct RawHashSetTestOnlyAccess;
+
+  // The number of slots we can still fill without needing to rehash.
+  //
+  // This is stored separately due to tombstones: we do not include tombstones
+  // in the growth capacity, because we'd like to rehash when the table is
+  // otherwise filled with tombstones: otherwise, probe sequences might get
+  // unacceptably long without triggering a rehash. Callers can also force a
+  // rehash via the standard `rehash(0)`, which will recompute this value as a
+  // side-effect.
+  //
+  // See `CapacityToGrowth()`.
+  size_t growth_left() const { return common().growth_left(); }
+  void set_growth_left(size_t gl) { return common().set_growth_left(gl); }
+
+  // Prefetch the heap-allocated memory region to resolve potential TLB and
+  // cache misses. This is intended to overlap with execution of calculating the
+  // hash for a key.
+  void prefetch_heap_block() const {
+#if ABSL_HAVE_BUILTIN(__builtin_prefetch) || defined(__GNUC__)
+    __builtin_prefetch(control(), 0, 1);
+#endif
+  }
+
+  CommonFields& common() { return settings_.template get<0>(); }
+  const CommonFields& common() const { return settings_.template get<0>(); }
+
+  ctrl_t* control() const { return common().control(); }
+  slot_type* slot_array() const {
+    return static_cast<slot_type*>(common().slot_array());
+  }
+  HashtablezInfoHandle infoz() { return common().infoz(); }
+
+  hasher& hash_ref() { return settings_.template get<1>(); }
+  const hasher& hash_ref() const { return settings_.template get<1>(); }
+  key_equal& eq_ref() { return settings_.template get<2>(); }
+  const key_equal& eq_ref() const { return settings_.template get<2>(); }
+  allocator_type& alloc_ref() { return settings_.template get<3>(); }
+  const allocator_type& alloc_ref() const {
+    return settings_.template get<3>();
+  }
+
+  // Make type-specific functions for this type's PolicyFunctions struct.
+  static size_t hash_slot_fn(void* set, void* slot) {
+    auto* h = static_cast<raw_hash_set*>(set);
+    return PolicyTraits::apply(
+        HashElement{h->hash_ref()},
+        PolicyTraits::element(static_cast<slot_type*>(slot)));
+  }
+  static void transfer_slot_fn(void* set, void* dst, void* src) {
+    auto* h = static_cast<raw_hash_set*>(set);
+    h->transfer(static_cast<slot_type*>(dst), static_cast<slot_type*>(src));
+  }
+  // Note: dealloc_fn will only be used if we have a non-standard allocator.
+  static void dealloc_fn(CommonFields& common, const PolicyFunctions&) {
+    auto* set = reinterpret_cast<raw_hash_set*>(&common);
+
+    // Unpoison before returning the memory to the allocator.
+    SanitizerUnpoisonMemoryRegion(common.slot_array(),
+                                  sizeof(slot_type) * common.capacity());
+
+    common.infoz().Unregister();
+    Deallocate<BackingArrayAlignment(alignof(slot_type))>(
+        &set->alloc_ref(), common.backing_array_start(),
+        common.alloc_size(sizeof(slot_type), alignof(slot_type)));
+  }
+
+  static const PolicyFunctions& GetPolicyFunctions() {
+    static constexpr PolicyFunctions value = {
+        sizeof(slot_type),
+        &raw_hash_set::hash_slot_fn,
+        PolicyTraits::transfer_uses_memcpy()
+            ? TransferRelocatable<sizeof(slot_type)>
+            : &raw_hash_set::transfer_slot_fn,
+        (std::is_same<SlotAlloc, std::allocator<slot_type>>::value
+             ? &DeallocateStandard<alignof(slot_type)>
+             : &raw_hash_set::dealloc_fn),
+    };
+    return value;
+  }
+
+  // Bundle together CommonFields plus other objects which might be empty.
+  // CompressedTuple will ensure that sizeof is not affected by any of the empty
+  // fields that occur after CommonFields.
+  absl::container_internal::CompressedTuple<CommonFields, hasher, key_equal,
+                                            allocator_type>
+      settings_{CommonFields{}, hasher{}, key_equal{}, allocator_type{}};
+};
+
+// Erases all elements that satisfy the predicate `pred` from the container `c`.
+template <typename P, typename H, typename E, typename A, typename Predicate>
+typename raw_hash_set<P, H, E, A>::size_type EraseIf(
+    Predicate& pred, raw_hash_set<P, H, E, A>* c) {
+  const auto initial_size = c->size();
+  for (auto it = c->begin(), last = c->end(); it != last;) {
+    if (pred(*it)) {
+      c->erase(it++);
+    } else {
+      ++it;
+    }
+  }
+  return initial_size - c->size();
+}
+
+namespace hashtable_debug_internal {
+template <typename Set>
+struct HashtableDebugAccess<Set, absl::void_t<typename Set::raw_hash_set>> {
+  using Traits = typename Set::PolicyTraits;
+  using Slot = typename Traits::slot_type;
+
+  static size_t GetNumProbes(const Set& set,
+                             const typename Set::key_type& key) {
+    size_t num_probes = 0;
+    size_t hash = set.hash_ref()(key);
+    auto seq = probe(set.common(), hash);
+    const ctrl_t* ctrl = set.control();
+    while (true) {
+      container_internal::Group g{ctrl + seq.offset()};
+      for (uint32_t i : g.Match(container_internal::H2(hash))) {
+        if (Traits::apply(
+                typename Set::template EqualElement<typename Set::key_type>{
+                    key, set.eq_ref()},
+                Traits::element(set.slot_array() + seq.offset(i))))
+          return num_probes;
+        ++num_probes;
+      }
+      if (g.MaskEmpty()) return num_probes;
+      seq.next();
+      ++num_probes;
+    }
+  }
+
+  static size_t AllocatedByteSize(const Set& c) {
+    size_t capacity = c.capacity();
+    if (capacity == 0) return 0;
+    size_t m = c.common().alloc_size(sizeof(Slot), alignof(Slot));
+
+    size_t per_slot = Traits::space_used(static_cast<const Slot*>(nullptr));
+    if (per_slot != ~size_t{}) {
+      m += per_slot * c.size();
+    } else {
+      for (auto it = c.begin(); it != c.end(); ++it) {
+        m += Traits::space_used(it.slot());
+      }
+    }
+    return m;
+  }
+};
+
+}  // namespace hashtable_debug_internal
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#undef ABSL_SWISSTABLE_ENABLE_GENERATIONS
+
+#endif  // ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f9797f565f4735a1db3c5fb49b67bb5128c4f859
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/raw_hash_set_test.cc
@@ -0,0 +1,2684 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/raw_hash_set.h"
+
+#include <algorithm>
+#include <atomic>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <deque>
+#include <functional>
+#include <iostream>
+#include <iterator>
+#include <list>
+#include <map>
+#include <memory>
+#include <numeric>
+#include <ostream>
+#include <random>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/cycleclock.h"
+#include "absl/base/prefetch.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/container/internal/container_memory.h"
+#include "absl/container/internal/hash_function_defaults.h"
+#include "absl/container/internal/hash_policy_testing.h"
+#include "absl/container/internal/hashtable_debug.h"
+#include "absl/container/internal/hashtablez_sampler.h"
+#include "absl/container/internal/test_allocator.h"
+#include "absl/hash/hash.h"
+#include "absl/log/log.h"
+#include "absl/memory/memory.h"
+#include "absl/meta/type_traits.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+struct RawHashSetTestOnlyAccess {
+  template <typename C>
+  static auto GetSlots(const C& c) -> decltype(c.slot_array()) {
+    return c.slot_array();
+  }
+  template <typename C>
+  static size_t CountTombstones(const C& c) {
+    return c.common().TombstonesCount();
+  }
+};
+
+namespace {
+
+using ::testing::ElementsAre;
+using ::testing::Eq;
+using ::testing::Ge;
+using ::testing::Lt;
+using ::testing::Pair;
+using ::testing::UnorderedElementsAre;
+
+// Convenience function to static cast to ctrl_t.
+ctrl_t CtrlT(int i) { return static_cast<ctrl_t>(i); }
+
+TEST(Util, NormalizeCapacity) {
+  EXPECT_EQ(1, NormalizeCapacity(0));
+  EXPECT_EQ(1, NormalizeCapacity(1));
+  EXPECT_EQ(3, NormalizeCapacity(2));
+  EXPECT_EQ(3, NormalizeCapacity(3));
+  EXPECT_EQ(7, NormalizeCapacity(4));
+  EXPECT_EQ(7, NormalizeCapacity(7));
+  EXPECT_EQ(15, NormalizeCapacity(8));
+  EXPECT_EQ(15, NormalizeCapacity(15));
+  EXPECT_EQ(15 * 2 + 1, NormalizeCapacity(15 + 1));
+  EXPECT_EQ(15 * 2 + 1, NormalizeCapacity(15 + 2));
+}
+
+TEST(Util, GrowthAndCapacity) {
+  // Verify that GrowthToCapacity gives the minimum capacity that has enough
+  // growth.
+  for (size_t growth = 0; growth < 10000; ++growth) {
+    SCOPED_TRACE(growth);
+    size_t capacity = NormalizeCapacity(GrowthToLowerboundCapacity(growth));
+    // The capacity is large enough for `growth`.
+    EXPECT_THAT(CapacityToGrowth(capacity), Ge(growth));
+    // For (capacity+1) < kWidth, growth should equal capacity.
+    if (capacity + 1 < Group::kWidth) {
+      EXPECT_THAT(CapacityToGrowth(capacity), Eq(capacity));
+    } else {
+      EXPECT_THAT(CapacityToGrowth(capacity), Lt(capacity));
+    }
+    if (growth != 0 && capacity > 1) {
+      // There is no smaller capacity that works.
+      EXPECT_THAT(CapacityToGrowth(capacity / 2), Lt(growth));
+    }
+  }
+
+  for (size_t capacity = Group::kWidth - 1; capacity < 10000;
+       capacity = 2 * capacity + 1) {
+    SCOPED_TRACE(capacity);
+    size_t growth = CapacityToGrowth(capacity);
+    EXPECT_THAT(growth, Lt(capacity));
+    EXPECT_LE(GrowthToLowerboundCapacity(growth), capacity);
+    EXPECT_EQ(NormalizeCapacity(GrowthToLowerboundCapacity(growth)), capacity);
+  }
+}
+
+TEST(Util, probe_seq) {
+  probe_seq<16> seq(0, 127);
+  auto gen = [&]() {
+    size_t res = seq.offset();
+    seq.next();
+    return res;
+  };
+  std::vector<size_t> offsets(8);
+  std::generate_n(offsets.begin(), 8, gen);
+  EXPECT_THAT(offsets, ElementsAre(0, 16, 48, 96, 32, 112, 80, 64));
+  seq = probe_seq<16>(128, 127);
+  std::generate_n(offsets.begin(), 8, gen);
+  EXPECT_THAT(offsets, ElementsAre(0, 16, 48, 96, 32, 112, 80, 64));
+}
+
+TEST(BitMask, Smoke) {
+  EXPECT_FALSE((BitMask<uint8_t, 8>(0)));
+  EXPECT_TRUE((BitMask<uint8_t, 8>(5)));
+
+  EXPECT_THAT((BitMask<uint8_t, 8>(0)), ElementsAre());
+  EXPECT_THAT((BitMask<uint8_t, 8>(0x1)), ElementsAre(0));
+  EXPECT_THAT((BitMask<uint8_t, 8>(0x2)), ElementsAre(1));
+  EXPECT_THAT((BitMask<uint8_t, 8>(0x3)), ElementsAre(0, 1));
+  EXPECT_THAT((BitMask<uint8_t, 8>(0x4)), ElementsAre(2));
+  EXPECT_THAT((BitMask<uint8_t, 8>(0x5)), ElementsAre(0, 2));
+  EXPECT_THAT((BitMask<uint8_t, 8>(0x55)), ElementsAre(0, 2, 4, 6));
+  EXPECT_THAT((BitMask<uint8_t, 8>(0xAA)), ElementsAre(1, 3, 5, 7));
+}
+
+TEST(BitMask, WithShift) {
+  // See the non-SSE version of Group for details on what this math is for.
+  uint64_t ctrl = 0x1716151413121110;
+  uint64_t hash = 0x12;
+  constexpr uint64_t msbs = 0x8080808080808080ULL;
+  constexpr uint64_t lsbs = 0x0101010101010101ULL;
+  auto x = ctrl ^ (lsbs * hash);
+  uint64_t mask = (x - lsbs) & ~x & msbs;
+  EXPECT_EQ(0x0000000080800000, mask);
+
+  BitMask<uint64_t, 8, 3> b(mask);
+  EXPECT_EQ(*b, 2);
+}
+
+TEST(BitMask, LeadingTrailing) {
+  EXPECT_EQ((BitMask<uint32_t, 16>(0x00001a40).LeadingZeros()), 3);
+  EXPECT_EQ((BitMask<uint32_t, 16>(0x00001a40).TrailingZeros()), 6);
+
+  EXPECT_EQ((BitMask<uint32_t, 16>(0x00000001).LeadingZeros()), 15);
+  EXPECT_EQ((BitMask<uint32_t, 16>(0x00000001).TrailingZeros()), 0);
+
+  EXPECT_EQ((BitMask<uint32_t, 16>(0x00008000).LeadingZeros()), 0);
+  EXPECT_EQ((BitMask<uint32_t, 16>(0x00008000).TrailingZeros()), 15);
+
+  EXPECT_EQ((BitMask<uint64_t, 8, 3>(0x0000008080808000).LeadingZeros()), 3);
+  EXPECT_EQ((BitMask<uint64_t, 8, 3>(0x0000008080808000).TrailingZeros()), 1);
+
+  EXPECT_EQ((BitMask<uint64_t, 8, 3>(0x0000000000000080).LeadingZeros()), 7);
+  EXPECT_EQ((BitMask<uint64_t, 8, 3>(0x0000000000000080).TrailingZeros()), 0);
+
+  EXPECT_EQ((BitMask<uint64_t, 8, 3>(0x8000000000000000).LeadingZeros()), 0);
+  EXPECT_EQ((BitMask<uint64_t, 8, 3>(0x8000000000000000).TrailingZeros()), 7);
+}
+
+TEST(Group, EmptyGroup) {
+  for (h2_t h = 0; h != 128; ++h) EXPECT_FALSE(Group{EmptyGroup()}.Match(h));
+}
+
+TEST(Group, Match) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {ctrl_t::kEmpty, CtrlT(1), ctrl_t::kDeleted,  CtrlT(3),
+                      ctrl_t::kEmpty, CtrlT(5), ctrl_t::kSentinel, CtrlT(7),
+                      CtrlT(7),       CtrlT(5), CtrlT(3),          CtrlT(1),
+                      CtrlT(1),       CtrlT(1), CtrlT(1),          CtrlT(1)};
+    EXPECT_THAT(Group{group}.Match(0), ElementsAre());
+    EXPECT_THAT(Group{group}.Match(1), ElementsAre(1, 11, 12, 13, 14, 15));
+    EXPECT_THAT(Group{group}.Match(3), ElementsAre(3, 10));
+    EXPECT_THAT(Group{group}.Match(5), ElementsAre(5, 9));
+    EXPECT_THAT(Group{group}.Match(7), ElementsAre(7, 8));
+  } else if (Group::kWidth == 8) {
+    ctrl_t group[] = {ctrl_t::kEmpty,    CtrlT(1), CtrlT(2),
+                      ctrl_t::kDeleted,  CtrlT(2), CtrlT(1),
+                      ctrl_t::kSentinel, CtrlT(1)};
+    EXPECT_THAT(Group{group}.Match(0), ElementsAre());
+    EXPECT_THAT(Group{group}.Match(1), ElementsAre(1, 5, 7));
+    EXPECT_THAT(Group{group}.Match(2), ElementsAre(2, 4));
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
+}
+
+TEST(Group, MaskEmpty) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {ctrl_t::kEmpty, CtrlT(1), ctrl_t::kDeleted,  CtrlT(3),
+                      ctrl_t::kEmpty, CtrlT(5), ctrl_t::kSentinel, CtrlT(7),
+                      CtrlT(7),       CtrlT(5), CtrlT(3),          CtrlT(1),
+                      CtrlT(1),       CtrlT(1), CtrlT(1),          CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskEmpty().LowestBitSet(), 0);
+    EXPECT_THAT(Group{group}.MaskEmpty().HighestBitSet(), 4);
+  } else if (Group::kWidth == 8) {
+    ctrl_t group[] = {ctrl_t::kEmpty,    CtrlT(1), CtrlT(2),
+                      ctrl_t::kDeleted,  CtrlT(2), CtrlT(1),
+                      ctrl_t::kSentinel, CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskEmpty().LowestBitSet(), 0);
+    EXPECT_THAT(Group{group}.MaskEmpty().HighestBitSet(), 0);
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
+}
+
+TEST(Group, MaskFull) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {
+        ctrl_t::kEmpty, CtrlT(1),          ctrl_t::kDeleted,  CtrlT(3),
+        ctrl_t::kEmpty, CtrlT(5),          ctrl_t::kSentinel, CtrlT(7),
+        CtrlT(7),       CtrlT(5),          ctrl_t::kDeleted,  CtrlT(1),
+        CtrlT(1),       ctrl_t::kSentinel, ctrl_t::kEmpty,    CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskFull(),
+                ElementsAre(1, 3, 5, 7, 8, 9, 11, 12, 15));
+  } else if (Group::kWidth == 8) {
+    ctrl_t group[] = {ctrl_t::kEmpty,    CtrlT(1), ctrl_t::kEmpty,
+                      ctrl_t::kDeleted,  CtrlT(2), ctrl_t::kSentinel,
+                      ctrl_t::kSentinel, CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskFull(), ElementsAre(1, 4, 7));
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
+}
+
+TEST(Group, MaskEmptyOrDeleted) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {ctrl_t::kEmpty,   CtrlT(1), ctrl_t::kEmpty,    CtrlT(3),
+                      ctrl_t::kDeleted, CtrlT(5), ctrl_t::kSentinel, CtrlT(7),
+                      CtrlT(7),         CtrlT(5), CtrlT(3),          CtrlT(1),
+                      CtrlT(1),         CtrlT(1), CtrlT(1),          CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskEmptyOrDeleted().LowestBitSet(), 0);
+    EXPECT_THAT(Group{group}.MaskEmptyOrDeleted().HighestBitSet(), 4);
+  } else if (Group::kWidth == 8) {
+    ctrl_t group[] = {ctrl_t::kEmpty,    CtrlT(1), CtrlT(2),
+                      ctrl_t::kDeleted,  CtrlT(2), CtrlT(1),
+                      ctrl_t::kSentinel, CtrlT(1)};
+    EXPECT_THAT(Group{group}.MaskEmptyOrDeleted().LowestBitSet(), 0);
+    EXPECT_THAT(Group{group}.MaskEmptyOrDeleted().HighestBitSet(), 3);
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
+}
+
+TEST(Batch, DropDeletes) {
+  constexpr size_t kCapacity = 63;
+  constexpr size_t kGroupWidth = container_internal::Group::kWidth;
+  std::vector<ctrl_t> ctrl(kCapacity + 1 + kGroupWidth);
+  ctrl[kCapacity] = ctrl_t::kSentinel;
+  std::vector<ctrl_t> pattern = {
+      ctrl_t::kEmpty, CtrlT(2), ctrl_t::kDeleted, CtrlT(2),
+      ctrl_t::kEmpty, CtrlT(1), ctrl_t::kDeleted};
+  for (size_t i = 0; i != kCapacity; ++i) {
+    ctrl[i] = pattern[i % pattern.size()];
+    if (i < kGroupWidth - 1)
+      ctrl[i + kCapacity + 1] = pattern[i % pattern.size()];
+  }
+  ConvertDeletedToEmptyAndFullToDeleted(ctrl.data(), kCapacity);
+  ASSERT_EQ(ctrl[kCapacity], ctrl_t::kSentinel);
+  for (size_t i = 0; i < kCapacity + kGroupWidth; ++i) {
+    ctrl_t expected = pattern[i % (kCapacity + 1) % pattern.size()];
+    if (i == kCapacity) expected = ctrl_t::kSentinel;
+    if (expected == ctrl_t::kDeleted) expected = ctrl_t::kEmpty;
+    if (IsFull(expected)) expected = ctrl_t::kDeleted;
+    EXPECT_EQ(ctrl[i], expected)
+        << i << " " << static_cast<int>(pattern[i % pattern.size()]);
+  }
+}
+
+TEST(Group, CountLeadingEmptyOrDeleted) {
+  const std::vector<ctrl_t> empty_examples = {ctrl_t::kEmpty, ctrl_t::kDeleted};
+  const std::vector<ctrl_t> full_examples = {
+      CtrlT(0), CtrlT(1), CtrlT(2),   CtrlT(3),
+      CtrlT(5), CtrlT(9), CtrlT(127), ctrl_t::kSentinel};
+
+  for (ctrl_t empty : empty_examples) {
+    std::vector<ctrl_t> e(Group::kWidth, empty);
+    EXPECT_EQ(Group::kWidth, Group{e.data()}.CountLeadingEmptyOrDeleted());
+    for (ctrl_t full : full_examples) {
+      for (size_t i = 0; i != Group::kWidth; ++i) {
+        std::vector<ctrl_t> f(Group::kWidth, empty);
+        f[i] = full;
+        EXPECT_EQ(i, Group{f.data()}.CountLeadingEmptyOrDeleted());
+      }
+      std::vector<ctrl_t> f(Group::kWidth, empty);
+      f[Group::kWidth * 2 / 3] = full;
+      f[Group::kWidth / 2] = full;
+      EXPECT_EQ(Group::kWidth / 2,
+                Group{f.data()}.CountLeadingEmptyOrDeleted());
+    }
+  }
+}
+
+template <class T, bool kTransferable = false>
+struct ValuePolicy {
+  using slot_type = T;
+  using key_type = T;
+  using init_type = T;
+
+  template <class Allocator, class... Args>
+  static void construct(Allocator* alloc, slot_type* slot, Args&&... args) {
+    absl::allocator_traits<Allocator>::construct(*alloc, slot,
+                                                 std::forward<Args>(args)...);
+  }
+
+  template <class Allocator>
+  static void destroy(Allocator* alloc, slot_type* slot) {
+    absl::allocator_traits<Allocator>::destroy(*alloc, slot);
+  }
+
+  template <class Allocator>
+  static std::integral_constant<bool, kTransferable> transfer(
+      Allocator* alloc, slot_type* new_slot, slot_type* old_slot) {
+    construct(alloc, new_slot, std::move(*old_slot));
+    destroy(alloc, old_slot);
+    return {};
+  }
+
+  static T& element(slot_type* slot) { return *slot; }
+
+  template <class F, class... Args>
+  static decltype(absl::container_internal::DecomposeValue(
+      std::declval<F>(), std::declval<Args>()...))
+  apply(F&& f, Args&&... args) {
+    return absl::container_internal::DecomposeValue(
+        std::forward<F>(f), std::forward<Args>(args)...);
+  }
+};
+
+using IntPolicy = ValuePolicy<int64_t>;
+using Uint8Policy = ValuePolicy<uint8_t>;
+
+using TranferableIntPolicy = ValuePolicy<int64_t, /*kTransferable=*/true>;
+
+class StringPolicy {
+  template <class F, class K, class V,
+            class = typename std::enable_if<
+                std::is_convertible<const K&, absl::string_view>::value>::type>
+  decltype(std::declval<F>()(
+      std::declval<const absl::string_view&>(), std::piecewise_construct,
+      std::declval<std::tuple<K>>(),
+      std::declval<V>())) static apply_impl(F&& f,
+                                            std::pair<std::tuple<K>, V> p) {
+    const absl::string_view& key = std::get<0>(p.first);
+    return std::forward<F>(f)(key, std::piecewise_construct, std::move(p.first),
+                              std::move(p.second));
+  }
+
+ public:
+  struct slot_type {
+    struct ctor {};
+
+    template <class... Ts>
+    explicit slot_type(ctor, Ts&&... ts) : pair(std::forward<Ts>(ts)...) {}
+
+    std::pair<std::string, std::string> pair;
+  };
+
+  using key_type = std::string;
+  using init_type = std::pair<std::string, std::string>;
+
+  template <class allocator_type, class... Args>
+  static void construct(allocator_type* alloc, slot_type* slot, Args... args) {
+    std::allocator_traits<allocator_type>::construct(
+        *alloc, slot, typename slot_type::ctor(), std::forward<Args>(args)...);
+  }
+
+  template <class allocator_type>
+  static void destroy(allocator_type* alloc, slot_type* slot) {
+    std::allocator_traits<allocator_type>::destroy(*alloc, slot);
+  }
+
+  template <class allocator_type>
+  static void transfer(allocator_type* alloc, slot_type* new_slot,
+                       slot_type* old_slot) {
+    construct(alloc, new_slot, std::move(old_slot->pair));
+    destroy(alloc, old_slot);
+  }
+
+  static std::pair<std::string, std::string>& element(slot_type* slot) {
+    return slot->pair;
+  }
+
+  template <class F, class... Args>
+  static auto apply(F&& f, Args&&... args)
+      -> decltype(apply_impl(std::forward<F>(f),
+                             PairArgs(std::forward<Args>(args)...))) {
+    return apply_impl(std::forward<F>(f),
+                      PairArgs(std::forward<Args>(args)...));
+  }
+};
+
+struct StringHash : absl::Hash<absl::string_view> {
+  using is_transparent = void;
+};
+struct StringEq : std::equal_to<absl::string_view> {
+  using is_transparent = void;
+};
+
+struct StringTable
+    : raw_hash_set<StringPolicy, StringHash, StringEq, std::allocator<int>> {
+  using Base = typename StringTable::raw_hash_set;
+  StringTable() = default;
+  using Base::Base;
+};
+
+template <typename T, bool kTransferable = false>
+struct ValueTable
+    : raw_hash_set<ValuePolicy<T, kTransferable>, hash_default_hash<T>,
+                   std::equal_to<T>, std::allocator<T>> {
+  using Base = typename ValueTable::raw_hash_set;
+  using Base::Base;
+};
+
+using IntTable = ValueTable<int64_t>;
+using Uint8Table = ValueTable<uint8_t>;
+
+using TransferableIntTable = ValueTable<int64_t, /*kTransferable=*/true>;
+
+template <typename T>
+struct CustomAlloc : std::allocator<T> {
+  CustomAlloc() = default;
+
+  template <typename U>
+  explicit CustomAlloc(const CustomAlloc<U>& /*other*/) {}
+
+  template <class U>
+  struct rebind {
+    using other = CustomAlloc<U>;
+  };
+};
+
+struct CustomAllocIntTable
+    : raw_hash_set<IntPolicy, hash_default_hash<int64_t>,
+                   std::equal_to<int64_t>, CustomAlloc<int64_t>> {
+  using Base = typename CustomAllocIntTable::raw_hash_set;
+  using Base::Base;
+};
+
+struct MinimumAlignmentUint8Table
+    : raw_hash_set<Uint8Policy, hash_default_hash<uint8_t>,
+                   std::equal_to<uint8_t>, MinimumAlignmentAlloc<uint8_t>> {
+  using Base = typename MinimumAlignmentUint8Table::raw_hash_set;
+  using Base::Base;
+};
+
+// Allows for freezing the allocator to expect no further allocations.
+template <typename T>
+struct FreezableAlloc : std::allocator<T> {
+  explicit FreezableAlloc(bool* f) : frozen(f) {}
+
+  template <typename U>
+  explicit FreezableAlloc(const FreezableAlloc<U>& other)
+      : frozen(other.frozen) {}
+
+  template <class U>
+  struct rebind {
+    using other = FreezableAlloc<U>;
+  };
+
+  T* allocate(size_t n) {
+    EXPECT_FALSE(*frozen);
+    return std::allocator<T>::allocate(n);
+  }
+
+  bool* frozen;
+};
+
+struct BadFastHash {
+  template <class T>
+  size_t operator()(const T&) const {
+    return 0;
+  }
+};
+
+struct BadHashFreezableIntTable
+    : raw_hash_set<IntPolicy, BadFastHash, std::equal_to<int64_t>,
+                   FreezableAlloc<int64_t>> {
+  using Base = typename BadHashFreezableIntTable::raw_hash_set;
+  using Base::Base;
+};
+
+struct BadTable : raw_hash_set<IntPolicy, BadFastHash, std::equal_to<int>,
+                               std::allocator<int>> {
+  using Base = typename BadTable::raw_hash_set;
+  BadTable() = default;
+  using Base::Base;
+};
+
+TEST(Table, EmptyFunctorOptimization) {
+  static_assert(std::is_empty<std::equal_to<absl::string_view>>::value, "");
+  static_assert(std::is_empty<std::allocator<int>>::value, "");
+
+  struct MockTable {
+    void* ctrl;
+    void* slots;
+    size_t size;
+    size_t capacity;
+  };
+  struct StatelessHash {
+    size_t operator()(absl::string_view) const { return 0; }
+  };
+  struct StatefulHash : StatelessHash {
+    size_t dummy;
+  };
+
+  struct GenerationData {
+    size_t reserved_growth;
+    size_t reservation_size;
+    GenerationType* generation;
+  };
+
+// Ignore unreachable-code warning. Compiler thinks one branch of each ternary
+// conditional is unreachable.
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunreachable-code"
+#endif
+  constexpr size_t mock_size = sizeof(MockTable);
+  constexpr size_t generation_size =
+      SwisstableGenerationsEnabled() ? sizeof(GenerationData) : 0;
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
+  EXPECT_EQ(
+      mock_size + generation_size,
+      sizeof(
+          raw_hash_set<StringPolicy, StatelessHash,
+                       std::equal_to<absl::string_view>, std::allocator<int>>));
+
+  EXPECT_EQ(
+      mock_size + sizeof(StatefulHash) + generation_size,
+      sizeof(
+          raw_hash_set<StringPolicy, StatefulHash,
+                       std::equal_to<absl::string_view>, std::allocator<int>>));
+}
+
+TEST(Table, Empty) {
+  IntTable t;
+  EXPECT_EQ(0, t.size());
+  EXPECT_TRUE(t.empty());
+}
+
+TEST(Table, LookupEmpty) {
+  IntTable t;
+  auto it = t.find(0);
+  EXPECT_TRUE(it == t.end());
+}
+
+TEST(Table, Insert1) {
+  IntTable t;
+  EXPECT_TRUE(t.find(0) == t.end());
+  auto res = t.emplace(0);
+  EXPECT_TRUE(res.second);
+  EXPECT_THAT(*res.first, 0);
+  EXPECT_EQ(1, t.size());
+  EXPECT_THAT(*t.find(0), 0);
+}
+
+TEST(Table, Insert2) {
+  IntTable t;
+  EXPECT_TRUE(t.find(0) == t.end());
+  auto res = t.emplace(0);
+  EXPECT_TRUE(res.second);
+  EXPECT_THAT(*res.first, 0);
+  EXPECT_EQ(1, t.size());
+  EXPECT_TRUE(t.find(1) == t.end());
+  res = t.emplace(1);
+  EXPECT_TRUE(res.second);
+  EXPECT_THAT(*res.first, 1);
+  EXPECT_EQ(2, t.size());
+  EXPECT_THAT(*t.find(0), 0);
+  EXPECT_THAT(*t.find(1), 1);
+}
+
+TEST(Table, InsertCollision) {
+  BadTable t;
+  EXPECT_TRUE(t.find(1) == t.end());
+  auto res = t.emplace(1);
+  EXPECT_TRUE(res.second);
+  EXPECT_THAT(*res.first, 1);
+  EXPECT_EQ(1, t.size());
+
+  EXPECT_TRUE(t.find(2) == t.end());
+  res = t.emplace(2);
+  EXPECT_THAT(*res.first, 2);
+  EXPECT_TRUE(res.second);
+  EXPECT_EQ(2, t.size());
+
+  EXPECT_THAT(*t.find(1), 1);
+  EXPECT_THAT(*t.find(2), 2);
+}
+
+// Test that we do not add existent element in case we need to search through
+// many groups with deleted elements
+TEST(Table, InsertCollisionAndFindAfterDelete) {
+  BadTable t;  // all elements go to the same group.
+  // Have at least 2 groups with Group::kWidth collisions
+  // plus some extra collisions in the last group.
+  constexpr size_t kNumInserts = Group::kWidth * 2 + 5;
+  for (size_t i = 0; i < kNumInserts; ++i) {
+    auto res = t.emplace(i);
+    EXPECT_TRUE(res.second);
+    EXPECT_THAT(*res.first, i);
+    EXPECT_EQ(i + 1, t.size());
+  }
+
+  // Remove elements one by one and check
+  // that we still can find all other elements.
+  for (size_t i = 0; i < kNumInserts; ++i) {
+    EXPECT_EQ(1, t.erase(i)) << i;
+    for (size_t j = i + 1; j < kNumInserts; ++j) {
+      EXPECT_THAT(*t.find(j), j);
+      auto res = t.emplace(j);
+      EXPECT_FALSE(res.second) << i << " " << j;
+      EXPECT_THAT(*res.first, j);
+      EXPECT_EQ(kNumInserts - i - 1, t.size());
+    }
+  }
+  EXPECT_TRUE(t.empty());
+}
+
+TEST(Table, EraseInSmallTables) {
+  for (int64_t size = 0; size < 64; ++size) {
+    IntTable t;
+    for (int64_t i = 0; i < size; ++i) {
+      t.insert(i);
+    }
+    for (int64_t i = 0; i < size; ++i) {
+      t.erase(i);
+      EXPECT_EQ(t.size(), size - i - 1);
+      for (int64_t j = i + 1; j < size; ++j) {
+        EXPECT_THAT(*t.find(j), j);
+      }
+    }
+    EXPECT_TRUE(t.empty());
+  }
+}
+
+TEST(Table, InsertWithinCapacity) {
+  IntTable t;
+  t.reserve(10);
+  const size_t original_capacity = t.capacity();
+  const auto addr = [&](int i) {
+    return reinterpret_cast<uintptr_t>(&*t.find(i));
+  };
+  // Inserting an element does not change capacity.
+  t.insert(0);
+  EXPECT_THAT(t.capacity(), original_capacity);
+  const uintptr_t original_addr_0 = addr(0);
+  // Inserting another element does not rehash.
+  t.insert(1);
+  EXPECT_THAT(t.capacity(), original_capacity);
+  EXPECT_THAT(addr(0), original_addr_0);
+  // Inserting lots of duplicate elements does not rehash.
+  for (int i = 0; i < 100; ++i) {
+    t.insert(i % 10);
+  }
+  EXPECT_THAT(t.capacity(), original_capacity);
+  EXPECT_THAT(addr(0), original_addr_0);
+  // Inserting a range of duplicate elements does not rehash.
+  std::vector<int> dup_range;
+  for (int i = 0; i < 100; ++i) {
+    dup_range.push_back(i % 10);
+  }
+  t.insert(dup_range.begin(), dup_range.end());
+  EXPECT_THAT(t.capacity(), original_capacity);
+  EXPECT_THAT(addr(0), original_addr_0);
+}
+
+template <class TableType>
+class SmallTableResizeTest : public testing::Test {};
+
+TYPED_TEST_SUITE_P(SmallTableResizeTest);
+
+TYPED_TEST_P(SmallTableResizeTest, InsertIntoSmallTable) {
+  TypeParam t;
+  for (int i = 0; i < 32; ++i) {
+    t.insert(i);
+    ASSERT_EQ(t.size(), i + 1);
+    for (int j = 0; j < i + 1; ++j) {
+      EXPECT_TRUE(t.find(j) != t.end());
+      EXPECT_EQ(*t.find(j), j);
+    }
+  }
+}
+
+TYPED_TEST_P(SmallTableResizeTest, ResizeGrowSmallTables) {
+  TypeParam t;
+  for (size_t source_size = 0; source_size < 32; ++source_size) {
+    for (size_t target_size = source_size; target_size < 32; ++target_size) {
+      for (bool rehash : {false, true}) {
+        for (size_t i = 0; i < source_size; ++i) {
+          t.insert(static_cast<int>(i));
+        }
+        if (rehash) {
+          t.rehash(target_size);
+        } else {
+          t.reserve(target_size);
+        }
+        for (size_t i = 0; i < source_size; ++i) {
+          EXPECT_TRUE(t.find(static_cast<int>(i)) != t.end());
+          EXPECT_EQ(*t.find(static_cast<int>(i)), static_cast<int>(i));
+        }
+      }
+    }
+  }
+}
+
+TYPED_TEST_P(SmallTableResizeTest, ResizeReduceSmallTables) {
+  TypeParam t;
+  for (size_t source_size = 0; source_size < 32; ++source_size) {
+    for (size_t target_size = 0; target_size <= source_size; ++target_size) {
+      size_t inserted_count = std::min<size_t>(source_size, 5);
+      for (size_t i = 0; i < inserted_count; ++i) {
+        t.insert(static_cast<int>(i));
+      }
+      t.rehash(target_size);
+      for (size_t i = 0; i < inserted_count; ++i) {
+        EXPECT_TRUE(t.find(static_cast<int>(i)) != t.end());
+        EXPECT_EQ(*t.find(static_cast<int>(i)), static_cast<int>(i));
+      }
+    }
+  }
+}
+
+REGISTER_TYPED_TEST_SUITE_P(SmallTableResizeTest, InsertIntoSmallTable,
+                            ResizeGrowSmallTables, ResizeReduceSmallTables);
+using SmallTableTypes = ::testing::Types<IntTable, TransferableIntTable>;
+INSTANTIATE_TYPED_TEST_SUITE_P(InstanceSmallTableResizeTest,
+                               SmallTableResizeTest, SmallTableTypes);
+
+TEST(Table, LazyEmplace) {
+  StringTable t;
+  bool called = false;
+  auto it = t.lazy_emplace("abc", [&](const StringTable::constructor& f) {
+    called = true;
+    f("abc", "ABC");
+  });
+  EXPECT_TRUE(called);
+  EXPECT_THAT(*it, Pair("abc", "ABC"));
+  called = false;
+  it = t.lazy_emplace("abc", [&](const StringTable::constructor& f) {
+    called = true;
+    f("abc", "DEF");
+  });
+  EXPECT_FALSE(called);
+  EXPECT_THAT(*it, Pair("abc", "ABC"));
+}
+
+TEST(Table, ContainsEmpty) {
+  IntTable t;
+
+  EXPECT_FALSE(t.contains(0));
+}
+
+TEST(Table, Contains1) {
+  IntTable t;
+
+  EXPECT_TRUE(t.insert(0).second);
+  EXPECT_TRUE(t.contains(0));
+  EXPECT_FALSE(t.contains(1));
+
+  EXPECT_EQ(1, t.erase(0));
+  EXPECT_FALSE(t.contains(0));
+}
+
+TEST(Table, Contains2) {
+  IntTable t;
+
+  EXPECT_TRUE(t.insert(0).second);
+  EXPECT_TRUE(t.contains(0));
+  EXPECT_FALSE(t.contains(1));
+
+  t.clear();
+  EXPECT_FALSE(t.contains(0));
+}
+
+int decompose_constructed;
+int decompose_copy_constructed;
+int decompose_copy_assigned;
+int decompose_move_constructed;
+int decompose_move_assigned;
+struct DecomposeType {
+  DecomposeType(int i = 0) : i(i) {  // NOLINT
+    ++decompose_constructed;
+  }
+
+  explicit DecomposeType(const char* d) : DecomposeType(*d) {}
+
+  DecomposeType(const DecomposeType& other) : i(other.i) {
+    ++decompose_copy_constructed;
+  }
+  DecomposeType& operator=(const DecomposeType& other) {
+    ++decompose_copy_assigned;
+    i = other.i;
+    return *this;
+  }
+  DecomposeType(DecomposeType&& other) : i(other.i) {
+    ++decompose_move_constructed;
+  }
+  DecomposeType& operator=(DecomposeType&& other) {
+    ++decompose_move_assigned;
+    i = other.i;
+    return *this;
+  }
+
+  int i;
+};
+
+struct DecomposeHash {
+  using is_transparent = void;
+  size_t operator()(const DecomposeType& a) const { return a.i; }
+  size_t operator()(int a) const { return a; }
+  size_t operator()(const char* a) const { return *a; }
+};
+
+struct DecomposeEq {
+  using is_transparent = void;
+  bool operator()(const DecomposeType& a, const DecomposeType& b) const {
+    return a.i == b.i;
+  }
+  bool operator()(const DecomposeType& a, int b) const { return a.i == b; }
+  bool operator()(const DecomposeType& a, const char* b) const {
+    return a.i == *b;
+  }
+};
+
+struct DecomposePolicy {
+  using slot_type = DecomposeType;
+  using key_type = DecomposeType;
+  using init_type = DecomposeType;
+
+  template <typename T>
+  static void construct(void*, DecomposeType* slot, T&& v) {
+    ::new (slot) DecomposeType(std::forward<T>(v));
+  }
+  static void destroy(void*, DecomposeType* slot) { slot->~DecomposeType(); }
+  static DecomposeType& element(slot_type* slot) { return *slot; }
+
+  template <class F, class T>
+  static auto apply(F&& f, const T& x) -> decltype(std::forward<F>(f)(x, x)) {
+    return std::forward<F>(f)(x, x);
+  }
+};
+
+template <typename Hash, typename Eq>
+void TestDecompose(bool construct_three) {
+  DecomposeType elem{0};
+  const int one = 1;
+  const char* three_p = "3";
+  const auto& three = three_p;
+  const int elem_vector_count = 256;
+  std::vector<DecomposeType> elem_vector(elem_vector_count, DecomposeType{0});
+  std::iota(elem_vector.begin(), elem_vector.end(), 0);
+
+  using DecomposeSet =
+      raw_hash_set<DecomposePolicy, Hash, Eq, std::allocator<int>>;
+  DecomposeSet set1;
+
+  decompose_constructed = 0;
+  int expected_constructed = 0;
+  EXPECT_EQ(expected_constructed, decompose_constructed);
+  set1.insert(elem);
+  EXPECT_EQ(expected_constructed, decompose_constructed);
+  set1.insert(1);
+  EXPECT_EQ(++expected_constructed, decompose_constructed);
+  set1.emplace("3");
+  EXPECT_EQ(++expected_constructed, decompose_constructed);
+  EXPECT_EQ(expected_constructed, decompose_constructed);
+
+  {  // insert(T&&)
+    set1.insert(1);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+  }
+
+  {  // insert(const T&)
+    set1.insert(one);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+  }
+
+  {  // insert(hint, T&&)
+    set1.insert(set1.begin(), 1);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+  }
+
+  {  // insert(hint, const T&)
+    set1.insert(set1.begin(), one);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+  }
+
+  {  // emplace(...)
+    set1.emplace(1);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+    set1.emplace("3");
+    expected_constructed += construct_three;
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+    set1.emplace(one);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+    set1.emplace(three);
+    expected_constructed += construct_three;
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+  }
+
+  {  // emplace_hint(...)
+    set1.emplace_hint(set1.begin(), 1);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+    set1.emplace_hint(set1.begin(), "3");
+    expected_constructed += construct_three;
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+    set1.emplace_hint(set1.begin(), one);
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+    set1.emplace_hint(set1.begin(), three);
+    expected_constructed += construct_three;
+    EXPECT_EQ(expected_constructed, decompose_constructed);
+  }
+
+  decompose_copy_constructed = 0;
+  decompose_copy_assigned = 0;
+  decompose_move_constructed = 0;
+  decompose_move_assigned = 0;
+  int expected_copy_constructed = 0;
+  int expected_move_constructed = 0;
+  {  // raw_hash_set(first, last) with random-access iterators
+    DecomposeSet set2(elem_vector.begin(), elem_vector.end());
+    // Expect exactly one copy-constructor call for each element if no
+    // rehashing is done.
+    expected_copy_constructed += elem_vector_count;
+    EXPECT_EQ(expected_copy_constructed, decompose_copy_constructed);
+    EXPECT_EQ(expected_move_constructed, decompose_move_constructed);
+    EXPECT_EQ(0, decompose_move_assigned);
+    EXPECT_EQ(0, decompose_copy_assigned);
+  }
+
+  {  // raw_hash_set(first, last) with forward iterators
+    std::list<DecomposeType> elem_list(elem_vector.begin(), elem_vector.end());
+    expected_copy_constructed = decompose_copy_constructed;
+    DecomposeSet set2(elem_list.begin(), elem_list.end());
+    // Expect exactly N elements copied into set, expect at most 2*N elements
+    // moving internally for all resizing needed (for a growth factor of 2).
+    expected_copy_constructed += elem_vector_count;
+    EXPECT_EQ(expected_copy_constructed, decompose_copy_constructed);
+    expected_move_constructed += elem_vector_count;
+    EXPECT_LT(expected_move_constructed, decompose_move_constructed);
+    expected_move_constructed += elem_vector_count;
+    EXPECT_GE(expected_move_constructed, decompose_move_constructed);
+    EXPECT_EQ(0, decompose_move_assigned);
+    EXPECT_EQ(0, decompose_copy_assigned);
+    expected_copy_constructed = decompose_copy_constructed;
+    expected_move_constructed = decompose_move_constructed;
+  }
+
+  {  // insert(first, last)
+    DecomposeSet set2;
+    set2.insert(elem_vector.begin(), elem_vector.end());
+    // Expect exactly N elements copied into set, expect at most 2*N elements
+    // moving internally for all resizing needed (for a growth factor of 2).
+    const int expected_new_elements = elem_vector_count;
+    const int expected_max_element_moves = 2 * elem_vector_count;
+    expected_copy_constructed += expected_new_elements;
+    EXPECT_EQ(expected_copy_constructed, decompose_copy_constructed);
+    expected_move_constructed += expected_max_element_moves;
+    EXPECT_GE(expected_move_constructed, decompose_move_constructed);
+    EXPECT_EQ(0, decompose_move_assigned);
+    EXPECT_EQ(0, decompose_copy_assigned);
+    expected_copy_constructed = decompose_copy_constructed;
+    expected_move_constructed = decompose_move_constructed;
+  }
+}
+
+TEST(Table, Decompose) {
+  if (SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Generations being enabled causes extra rehashes.";
+  }
+
+  TestDecompose<DecomposeHash, DecomposeEq>(false);
+
+  struct TransparentHashIntOverload {
+    size_t operator()(const DecomposeType& a) const { return a.i; }
+    size_t operator()(int a) const { return a; }
+  };
+  struct TransparentEqIntOverload {
+    bool operator()(const DecomposeType& a, const DecomposeType& b) const {
+      return a.i == b.i;
+    }
+    bool operator()(const DecomposeType& a, int b) const { return a.i == b; }
+  };
+  TestDecompose<TransparentHashIntOverload, DecomposeEq>(true);
+  TestDecompose<TransparentHashIntOverload, TransparentEqIntOverload>(true);
+  TestDecompose<DecomposeHash, TransparentEqIntOverload>(true);
+}
+
+// Returns the largest m such that a table with m elements has the same number
+// of buckets as a table with n elements.
+size_t MaxDensitySize(size_t n) {
+  IntTable t;
+  t.reserve(n);
+  for (size_t i = 0; i != n; ++i) t.emplace(i);
+  const size_t c = t.bucket_count();
+  while (c == t.bucket_count()) t.emplace(n++);
+  return t.size() - 1;
+}
+
+struct Modulo1000Hash {
+  size_t operator()(int x) const { return x % 1000; }
+};
+
+struct Modulo1000HashTable
+    : public raw_hash_set<IntPolicy, Modulo1000Hash, std::equal_to<int>,
+                          std::allocator<int>> {};
+
+// Test that rehash with no resize happen in case of many deleted slots.
+TEST(Table, RehashWithNoResize) {
+  if (SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Generations being enabled causes extra rehashes.";
+  }
+
+  Modulo1000HashTable t;
+  // Adding the same length (and the same hash) strings
+  // to have at least kMinFullGroups groups
+  // with Group::kWidth collisions. Then fill up to MaxDensitySize;
+  const size_t kMinFullGroups = 7;
+  std::vector<int> keys;
+  for (size_t i = 0; i < MaxDensitySize(Group::kWidth * kMinFullGroups); ++i) {
+    int k = i * 1000;
+    t.emplace(k);
+    keys.push_back(k);
+  }
+  const size_t capacity = t.capacity();
+
+  // Remove elements from all groups except the first and the last one.
+  // All elements removed from full groups will be marked as ctrl_t::kDeleted.
+  const size_t erase_begin = Group::kWidth / 2;
+  const size_t erase_end = (t.size() / Group::kWidth - 1) * Group::kWidth;
+  for (size_t i = erase_begin; i < erase_end; ++i) {
+    EXPECT_EQ(1, t.erase(keys[i])) << i;
+  }
+  keys.erase(keys.begin() + erase_begin, keys.begin() + erase_end);
+
+  auto last_key = keys.back();
+  size_t last_key_num_probes = GetHashtableDebugNumProbes(t, last_key);
+
+  // Make sure that we have to make a lot of probes for last key.
+  ASSERT_GT(last_key_num_probes, kMinFullGroups);
+
+  int x = 1;
+  // Insert and erase one element, before inplace rehash happen.
+  while (last_key_num_probes == GetHashtableDebugNumProbes(t, last_key)) {
+    t.emplace(x);
+    ASSERT_EQ(capacity, t.capacity());
+    // All elements should be there.
+    ASSERT_TRUE(t.find(x) != t.end()) << x;
+    for (const auto& k : keys) {
+      ASSERT_TRUE(t.find(k) != t.end()) << k;
+    }
+    t.erase(x);
+    ++x;
+  }
+}
+
+TEST(Table, InsertEraseStressTest) {
+  IntTable t;
+  const size_t kMinElementCount = 250;
+  std::deque<int> keys;
+  size_t i = 0;
+  for (; i < MaxDensitySize(kMinElementCount); ++i) {
+    t.emplace(i);
+    keys.push_back(i);
+  }
+  const size_t kNumIterations = 1000000;
+  for (; i < kNumIterations; ++i) {
+    ASSERT_EQ(1, t.erase(keys.front()));
+    keys.pop_front();
+    t.emplace(i);
+    keys.push_back(i);
+  }
+}
+
+TEST(Table, InsertOverloads) {
+  StringTable t;
+  // These should all trigger the insert(init_type) overload.
+  t.insert({{}, {}});
+  t.insert({"ABC", {}});
+  t.insert({"DEF", "!!!"});
+
+  EXPECT_THAT(t, UnorderedElementsAre(Pair("", ""), Pair("ABC", ""),
+                                      Pair("DEF", "!!!")));
+}
+
+TEST(Table, LargeTable) {
+  IntTable t;
+  for (int64_t i = 0; i != 100000; ++i) t.emplace(i << 40);
+  for (int64_t i = 0; i != 100000; ++i) ASSERT_EQ(i << 40, *t.find(i << 40));
+}
+
+// Timeout if copy is quadratic as it was in Rust.
+TEST(Table, EnsureNonQuadraticAsInRust) {
+  static const size_t kLargeSize = 1 << 15;
+
+  IntTable t;
+  for (size_t i = 0; i != kLargeSize; ++i) {
+    t.insert(i);
+  }
+
+  // If this is quadratic, the test will timeout.
+  IntTable t2;
+  for (const auto& entry : t) t2.insert(entry);
+}
+
+TEST(Table, ClearBug) {
+  if (SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Generations being enabled causes extra rehashes.";
+  }
+
+  IntTable t;
+  constexpr size_t capacity = container_internal::Group::kWidth - 1;
+  constexpr size_t max_size = capacity / 2 + 1;
+  for (size_t i = 0; i < max_size; ++i) {
+    t.insert(i);
+  }
+  ASSERT_EQ(capacity, t.capacity());
+  intptr_t original = reinterpret_cast<intptr_t>(&*t.find(2));
+  t.clear();
+  ASSERT_EQ(capacity, t.capacity());
+  for (size_t i = 0; i < max_size; ++i) {
+    t.insert(i);
+  }
+  ASSERT_EQ(capacity, t.capacity());
+  intptr_t second = reinterpret_cast<intptr_t>(&*t.find(2));
+  // We are checking that original and second are close enough to each other
+  // that they are probably still in the same group.  This is not strictly
+  // guaranteed.
+  EXPECT_LT(static_cast<size_t>(std::abs(original - second)),
+            capacity * sizeof(IntTable::value_type));
+}
+
+TEST(Table, Erase) {
+  IntTable t;
+  EXPECT_TRUE(t.find(0) == t.end());
+  auto res = t.emplace(0);
+  EXPECT_TRUE(res.second);
+  EXPECT_EQ(1, t.size());
+  t.erase(res.first);
+  EXPECT_EQ(0, t.size());
+  EXPECT_TRUE(t.find(0) == t.end());
+}
+
+TEST(Table, EraseMaintainsValidIterator) {
+  IntTable t;
+  const int kNumElements = 100;
+  for (int i = 0; i < kNumElements; i++) {
+    EXPECT_TRUE(t.emplace(i).second);
+  }
+  EXPECT_EQ(t.size(), kNumElements);
+
+  int num_erase_calls = 0;
+  auto it = t.begin();
+  while (it != t.end()) {
+    t.erase(it++);
+    num_erase_calls++;
+  }
+
+  EXPECT_TRUE(t.empty());
+  EXPECT_EQ(num_erase_calls, kNumElements);
+}
+
+TEST(Table, EraseBeginEnd) {
+  IntTable t;
+  for (int i = 0; i < 10; ++i) t.insert(i);
+  EXPECT_EQ(t.size(), 10);
+  t.erase(t.begin(), t.end());
+  EXPECT_EQ(t.size(), 0);
+}
+
+// Collect N bad keys by following algorithm:
+// 1. Create an empty table and reserve it to 2 * N.
+// 2. Insert N random elements.
+// 3. Take first Group::kWidth - 1 to bad_keys array.
+// 4. Clear the table without resize.
+// 5. Go to point 2 while N keys not collected
+std::vector<int64_t> CollectBadMergeKeys(size_t N) {
+  static constexpr int kGroupSize = Group::kWidth - 1;
+
+  auto topk_range = [](size_t b, size_t e,
+                       IntTable* t) -> std::vector<int64_t> {
+    for (size_t i = b; i != e; ++i) {
+      t->emplace(i);
+    }
+    std::vector<int64_t> res;
+    res.reserve(kGroupSize);
+    auto it = t->begin();
+    for (size_t i = b; i != e && i != b + kGroupSize; ++i, ++it) {
+      res.push_back(*it);
+    }
+    return res;
+  };
+
+  std::vector<int64_t> bad_keys;
+  bad_keys.reserve(N);
+  IntTable t;
+  t.reserve(N * 2);
+
+  for (size_t b = 0; bad_keys.size() < N; b += N) {
+    auto keys = topk_range(b, b + N, &t);
+    bad_keys.insert(bad_keys.end(), keys.begin(), keys.end());
+    t.erase(t.begin(), t.end());
+    EXPECT_TRUE(t.empty());
+  }
+  return bad_keys;
+}
+
+struct ProbeStats {
+  // Number of elements with specific probe length over all tested tables.
+  std::vector<size_t> all_probes_histogram;
+  // Ratios total_probe_length/size for every tested table.
+  std::vector<double> single_table_ratios;
+
+  // Average ratio total_probe_length/size over tables.
+  double AvgRatio() const {
+    return std::accumulate(single_table_ratios.begin(),
+                           single_table_ratios.end(), 0.0) /
+           single_table_ratios.size();
+  }
+
+  // Maximum ratio total_probe_length/size over tables.
+  double MaxRatio() const {
+    return *std::max_element(single_table_ratios.begin(),
+                             single_table_ratios.end());
+  }
+
+  // Percentile ratio total_probe_length/size over tables.
+  double PercentileRatio(double Percentile = 0.95) const {
+    auto r = single_table_ratios;
+    auto mid = r.begin() + static_cast<size_t>(r.size() * Percentile);
+    if (mid != r.end()) {
+      std::nth_element(r.begin(), mid, r.end());
+      return *mid;
+    } else {
+      return MaxRatio();
+    }
+  }
+
+  // Maximum probe length over all elements and all tables.
+  size_t MaxProbe() const { return all_probes_histogram.size(); }
+
+  // Fraction of elements with specified probe length.
+  std::vector<double> ProbeNormalizedHistogram() const {
+    double total_elements = std::accumulate(all_probes_histogram.begin(),
+                                            all_probes_histogram.end(), 0ull);
+    std::vector<double> res;
+    for (size_t p : all_probes_histogram) {
+      res.push_back(p / total_elements);
+    }
+    return res;
+  }
+
+  size_t PercentileProbe(double Percentile = 0.99) const {
+    size_t idx = 0;
+    for (double p : ProbeNormalizedHistogram()) {
+      if (Percentile > p) {
+        Percentile -= p;
+        ++idx;
+      } else {
+        return idx;
+      }
+    }
+    return idx;
+  }
+
+  friend std::ostream& operator<<(std::ostream& out, const ProbeStats& s) {
+    out << "{AvgRatio:" << s.AvgRatio() << ", MaxRatio:" << s.MaxRatio()
+        << ", PercentileRatio:" << s.PercentileRatio()
+        << ", MaxProbe:" << s.MaxProbe() << ", Probes=[";
+    for (double p : s.ProbeNormalizedHistogram()) {
+      out << p << ",";
+    }
+    out << "]}";
+
+    return out;
+  }
+};
+
+struct ExpectedStats {
+  double avg_ratio;
+  double max_ratio;
+  std::vector<std::pair<double, double>> pecentile_ratios;
+  std::vector<std::pair<double, double>> pecentile_probes;
+
+  friend std::ostream& operator<<(std::ostream& out, const ExpectedStats& s) {
+    out << "{AvgRatio:" << s.avg_ratio << ", MaxRatio:" << s.max_ratio
+        << ", PercentileRatios: [";
+    for (auto el : s.pecentile_ratios) {
+      out << el.first << ":" << el.second << ", ";
+    }
+    out << "], PercentileProbes: [";
+    for (auto el : s.pecentile_probes) {
+      out << el.first << ":" << el.second << ", ";
+    }
+    out << "]}";
+
+    return out;
+  }
+};
+
+void VerifyStats(size_t size, const ExpectedStats& exp,
+                 const ProbeStats& stats) {
+  EXPECT_LT(stats.AvgRatio(), exp.avg_ratio) << size << " " << stats;
+  EXPECT_LT(stats.MaxRatio(), exp.max_ratio) << size << " " << stats;
+  for (auto pr : exp.pecentile_ratios) {
+    EXPECT_LE(stats.PercentileRatio(pr.first), pr.second)
+        << size << " " << pr.first << " " << stats;
+  }
+
+  for (auto pr : exp.pecentile_probes) {
+    EXPECT_LE(stats.PercentileProbe(pr.first), pr.second)
+        << size << " " << pr.first << " " << stats;
+  }
+}
+
+using ProbeStatsPerSize = std::map<size_t, ProbeStats>;
+
+// Collect total ProbeStats on num_iters iterations of the following algorithm:
+// 1. Create new table and reserve it to keys.size() * 2
+// 2. Insert all keys xored with seed
+// 3. Collect ProbeStats from final table.
+ProbeStats CollectProbeStatsOnKeysXoredWithSeed(
+    const std::vector<int64_t>& keys, size_t num_iters) {
+  const size_t reserve_size = keys.size() * 2;
+
+  ProbeStats stats;
+
+  int64_t seed = 0x71b1a19b907d6e33;
+  while (num_iters--) {
+    seed = static_cast<int64_t>(static_cast<uint64_t>(seed) * 17 + 13);
+    IntTable t1;
+    t1.reserve(reserve_size);
+    for (const auto& key : keys) {
+      t1.emplace(key ^ seed);
+    }
+
+    auto probe_histogram = GetHashtableDebugNumProbesHistogram(t1);
+    stats.all_probes_histogram.resize(
+        std::max(stats.all_probes_histogram.size(), probe_histogram.size()));
+    std::transform(probe_histogram.begin(), probe_histogram.end(),
+                   stats.all_probes_histogram.begin(),
+                   stats.all_probes_histogram.begin(), std::plus<size_t>());
+
+    size_t total_probe_seq_length = 0;
+    for (size_t i = 0; i < probe_histogram.size(); ++i) {
+      total_probe_seq_length += i * probe_histogram[i];
+    }
+    stats.single_table_ratios.push_back(total_probe_seq_length * 1.0 /
+                                        keys.size());
+    t1.erase(t1.begin(), t1.end());
+  }
+  return stats;
+}
+
+ExpectedStats XorSeedExpectedStats() {
+  constexpr bool kRandomizesInserts =
+#ifdef NDEBUG
+      false;
+#else   // NDEBUG
+      true;
+#endif  // NDEBUG
+
+  // The effective load factor is larger in non-opt mode because we insert
+  // elements out of order.
+  switch (container_internal::Group::kWidth) {
+    case 8:
+      if (kRandomizesInserts) {
+        return {0.05,
+                1.0,
+                {{0.95, 0.5}},
+                {{0.95, 0}, {0.99, 2}, {0.999, 4}, {0.9999, 10}}};
+      } else {
+        return {0.05,
+                2.0,
+                {{0.95, 0.1}},
+                {{0.95, 0}, {0.99, 2}, {0.999, 4}, {0.9999, 10}}};
+      }
+    case 16:
+      if (kRandomizesInserts) {
+        return {0.1,
+                2.0,
+                {{0.95, 0.1}},
+                {{0.95, 0}, {0.99, 1}, {0.999, 8}, {0.9999, 15}}};
+      } else {
+        return {0.05,
+                1.0,
+                {{0.95, 0.05}},
+                {{0.95, 0}, {0.99, 1}, {0.999, 4}, {0.9999, 10}}};
+      }
+  }
+  LOG(FATAL) << "Unknown Group width";
+  return {};
+}
+
+// TODO(b/80415403): Figure out why this test is so flaky, esp. on MSVC
+TEST(Table, DISABLED_EnsureNonQuadraticTopNXorSeedByProbeSeqLength) {
+  ProbeStatsPerSize stats;
+  std::vector<size_t> sizes = {Group::kWidth << 5, Group::kWidth << 10};
+  for (size_t size : sizes) {
+    stats[size] =
+        CollectProbeStatsOnKeysXoredWithSeed(CollectBadMergeKeys(size), 200);
+  }
+  auto expected = XorSeedExpectedStats();
+  for (size_t size : sizes) {
+    auto& stat = stats[size];
+    VerifyStats(size, expected, stat);
+    LOG(INFO) << size << " " << stat;
+  }
+}
+
+// Collect total ProbeStats on num_iters iterations of the following algorithm:
+// 1. Create new table
+// 2. Select 10% of keys and insert 10 elements key * 17 + j * 13
+// 3. Collect ProbeStats from final table
+ProbeStats CollectProbeStatsOnLinearlyTransformedKeys(
+    const std::vector<int64_t>& keys, size_t num_iters) {
+  ProbeStats stats;
+
+  std::random_device rd;
+  std::mt19937 rng(rd());
+  auto linear_transform = [](size_t x, size_t y) { return x * 17 + y * 13; };
+  std::uniform_int_distribution<size_t> dist(0, keys.size() - 1);
+  while (num_iters--) {
+    IntTable t1;
+    size_t num_keys = keys.size() / 10;
+    size_t start = dist(rng);
+    for (size_t i = 0; i != num_keys; ++i) {
+      for (size_t j = 0; j != 10; ++j) {
+        t1.emplace(linear_transform(keys[(i + start) % keys.size()], j));
+      }
+    }
+
+    auto probe_histogram = GetHashtableDebugNumProbesHistogram(t1);
+    stats.all_probes_histogram.resize(
+        std::max(stats.all_probes_histogram.size(), probe_histogram.size()));
+    std::transform(probe_histogram.begin(), probe_histogram.end(),
+                   stats.all_probes_histogram.begin(),
+                   stats.all_probes_histogram.begin(), std::plus<size_t>());
+
+    size_t total_probe_seq_length = 0;
+    for (size_t i = 0; i < probe_histogram.size(); ++i) {
+      total_probe_seq_length += i * probe_histogram[i];
+    }
+    stats.single_table_ratios.push_back(total_probe_seq_length * 1.0 /
+                                        t1.size());
+    t1.erase(t1.begin(), t1.end());
+  }
+  return stats;
+}
+
+ExpectedStats LinearTransformExpectedStats() {
+  constexpr bool kRandomizesInserts =
+#ifdef NDEBUG
+      false;
+#else   // NDEBUG
+      true;
+#endif  // NDEBUG
+
+  // The effective load factor is larger in non-opt mode because we insert
+  // elements out of order.
+  switch (container_internal::Group::kWidth) {
+    case 8:
+      if (kRandomizesInserts) {
+        return {0.1,
+                0.5,
+                {{0.95, 0.3}},
+                {{0.95, 0}, {0.99, 1}, {0.999, 8}, {0.9999, 15}}};
+      } else {
+        return {0.4,
+                0.6,
+                {{0.95, 0.5}},
+                {{0.95, 1}, {0.99, 14}, {0.999, 23}, {0.9999, 26}}};
+      }
+    case 16:
+      if (kRandomizesInserts) {
+        return {0.1,
+                0.4,
+                {{0.95, 0.3}},
+                {{0.95, 1}, {0.99, 2}, {0.999, 9}, {0.9999, 15}}};
+      } else {
+        return {0.05,
+                0.2,
+                {{0.95, 0.1}},
+                {{0.95, 0}, {0.99, 1}, {0.999, 6}, {0.9999, 10}}};
+      }
+  }
+  LOG(FATAL) << "Unknown Group width";
+  return {};
+}
+
+// TODO(b/80415403): Figure out why this test is so flaky.
+TEST(Table, DISABLED_EnsureNonQuadraticTopNLinearTransformByProbeSeqLength) {
+  ProbeStatsPerSize stats;
+  std::vector<size_t> sizes = {Group::kWidth << 5, Group::kWidth << 10};
+  for (size_t size : sizes) {
+    stats[size] = CollectProbeStatsOnLinearlyTransformedKeys(
+        CollectBadMergeKeys(size), 300);
+  }
+  auto expected = LinearTransformExpectedStats();
+  for (size_t size : sizes) {
+    auto& stat = stats[size];
+    VerifyStats(size, expected, stat);
+    LOG(INFO) << size << " " << stat;
+  }
+}
+
+TEST(Table, EraseCollision) {
+  BadTable t;
+
+  // 1 2 3
+  t.emplace(1);
+  t.emplace(2);
+  t.emplace(3);
+  EXPECT_THAT(*t.find(1), 1);
+  EXPECT_THAT(*t.find(2), 2);
+  EXPECT_THAT(*t.find(3), 3);
+  EXPECT_EQ(3, t.size());
+
+  // 1 DELETED 3
+  t.erase(t.find(2));
+  EXPECT_THAT(*t.find(1), 1);
+  EXPECT_TRUE(t.find(2) == t.end());
+  EXPECT_THAT(*t.find(3), 3);
+  EXPECT_EQ(2, t.size());
+
+  // DELETED DELETED 3
+  t.erase(t.find(1));
+  EXPECT_TRUE(t.find(1) == t.end());
+  EXPECT_TRUE(t.find(2) == t.end());
+  EXPECT_THAT(*t.find(3), 3);
+  EXPECT_EQ(1, t.size());
+
+  // DELETED DELETED DELETED
+  t.erase(t.find(3));
+  EXPECT_TRUE(t.find(1) == t.end());
+  EXPECT_TRUE(t.find(2) == t.end());
+  EXPECT_TRUE(t.find(3) == t.end());
+  EXPECT_EQ(0, t.size());
+}
+
+TEST(Table, EraseInsertProbing) {
+  BadTable t(100);
+
+  // 1 2 3 4
+  t.emplace(1);
+  t.emplace(2);
+  t.emplace(3);
+  t.emplace(4);
+
+  // 1 DELETED 3 DELETED
+  t.erase(t.find(2));
+  t.erase(t.find(4));
+
+  // 1 10 3 11 12
+  t.emplace(10);
+  t.emplace(11);
+  t.emplace(12);
+
+  EXPECT_EQ(5, t.size());
+  EXPECT_THAT(t, UnorderedElementsAre(1, 10, 3, 11, 12));
+}
+
+TEST(Table, Clear) {
+  IntTable t;
+  EXPECT_TRUE(t.find(0) == t.end());
+  t.clear();
+  EXPECT_TRUE(t.find(0) == t.end());
+  auto res = t.emplace(0);
+  EXPECT_TRUE(res.second);
+  EXPECT_EQ(1, t.size());
+  t.clear();
+  EXPECT_EQ(0, t.size());
+  EXPECT_TRUE(t.find(0) == t.end());
+}
+
+TEST(Table, Swap) {
+  IntTable t;
+  EXPECT_TRUE(t.find(0) == t.end());
+  auto res = t.emplace(0);
+  EXPECT_TRUE(res.second);
+  EXPECT_EQ(1, t.size());
+  IntTable u;
+  t.swap(u);
+  EXPECT_EQ(0, t.size());
+  EXPECT_EQ(1, u.size());
+  EXPECT_TRUE(t.find(0) == t.end());
+  EXPECT_THAT(*u.find(0), 0);
+}
+
+TEST(Table, Rehash) {
+  IntTable t;
+  EXPECT_TRUE(t.find(0) == t.end());
+  t.emplace(0);
+  t.emplace(1);
+  EXPECT_EQ(2, t.size());
+  t.rehash(128);
+  EXPECT_EQ(2, t.size());
+  EXPECT_THAT(*t.find(0), 0);
+  EXPECT_THAT(*t.find(1), 1);
+}
+
+TEST(Table, RehashDoesNotRehashWhenNotNecessary) {
+  IntTable t;
+  t.emplace(0);
+  t.emplace(1);
+  auto* p = &*t.find(0);
+  t.rehash(1);
+  EXPECT_EQ(p, &*t.find(0));
+}
+
+TEST(Table, RehashZeroDoesNotAllocateOnEmptyTable) {
+  IntTable t;
+  t.rehash(0);
+  EXPECT_EQ(0, t.bucket_count());
+}
+
+TEST(Table, RehashZeroDeallocatesEmptyTable) {
+  IntTable t;
+  t.emplace(0);
+  t.clear();
+  EXPECT_NE(0, t.bucket_count());
+  t.rehash(0);
+  EXPECT_EQ(0, t.bucket_count());
+}
+
+TEST(Table, RehashZeroForcesRehash) {
+  IntTable t;
+  t.emplace(0);
+  t.emplace(1);
+  auto* p = &*t.find(0);
+  t.rehash(0);
+  EXPECT_NE(p, &*t.find(0));
+}
+
+TEST(Table, ConstructFromInitList) {
+  using P = std::pair<std::string, std::string>;
+  struct Q {
+    operator P() const { return {}; }  // NOLINT
+  };
+  StringTable t = {P(), Q(), {}, {{}, {}}};
+}
+
+TEST(Table, CopyConstruct) {
+  IntTable t;
+  t.emplace(0);
+  EXPECT_EQ(1, t.size());
+  {
+    IntTable u(t);
+    EXPECT_EQ(1, u.size());
+    EXPECT_THAT(*u.find(0), 0);
+  }
+  {
+    IntTable u{t};
+    EXPECT_EQ(1, u.size());
+    EXPECT_THAT(*u.find(0), 0);
+  }
+  {
+    IntTable u = t;
+    EXPECT_EQ(1, u.size());
+    EXPECT_THAT(*u.find(0), 0);
+  }
+}
+
+TEST(Table, CopyConstructWithAlloc) {
+  StringTable t;
+  t.emplace("a", "b");
+  EXPECT_EQ(1, t.size());
+  StringTable u(t, Alloc<std::pair<std::string, std::string>>());
+  EXPECT_EQ(1, u.size());
+  EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+}
+
+struct ExplicitAllocIntTable
+    : raw_hash_set<IntPolicy, hash_default_hash<int64_t>,
+                   std::equal_to<int64_t>, Alloc<int64_t>> {
+  ExplicitAllocIntTable() = default;
+};
+
+TEST(Table, AllocWithExplicitCtor) {
+  ExplicitAllocIntTable t;
+  EXPECT_EQ(0, t.size());
+}
+
+TEST(Table, MoveConstruct) {
+  {
+    StringTable t;
+    t.emplace("a", "b");
+    EXPECT_EQ(1, t.size());
+
+    StringTable u(std::move(t));
+    EXPECT_EQ(1, u.size());
+    EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+  }
+  {
+    StringTable t;
+    t.emplace("a", "b");
+    EXPECT_EQ(1, t.size());
+
+    StringTable u{std::move(t)};
+    EXPECT_EQ(1, u.size());
+    EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+  }
+  {
+    StringTable t;
+    t.emplace("a", "b");
+    EXPECT_EQ(1, t.size());
+
+    StringTable u = std::move(t);
+    EXPECT_EQ(1, u.size());
+    EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+  }
+}
+
+TEST(Table, MoveConstructWithAlloc) {
+  StringTable t;
+  t.emplace("a", "b");
+  EXPECT_EQ(1, t.size());
+  StringTable u(std::move(t), Alloc<std::pair<std::string, std::string>>());
+  EXPECT_EQ(1, u.size());
+  EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+}
+
+TEST(Table, CopyAssign) {
+  StringTable t;
+  t.emplace("a", "b");
+  EXPECT_EQ(1, t.size());
+  StringTable u;
+  u = t;
+  EXPECT_EQ(1, u.size());
+  EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+}
+
+TEST(Table, CopySelfAssign) {
+  StringTable t;
+  t.emplace("a", "b");
+  EXPECT_EQ(1, t.size());
+  t = *&t;
+  EXPECT_EQ(1, t.size());
+  EXPECT_THAT(*t.find("a"), Pair("a", "b"));
+}
+
+TEST(Table, MoveAssign) {
+  StringTable t;
+  t.emplace("a", "b");
+  EXPECT_EQ(1, t.size());
+  StringTable u;
+  u = std::move(t);
+  EXPECT_EQ(1, u.size());
+  EXPECT_THAT(*u.find("a"), Pair("a", "b"));
+}
+
+TEST(Table, MoveSelfAssign) {
+  StringTable t;
+  t.emplace("a", "b");
+  EXPECT_EQ(1, t.size());
+  t = std::move(*&t);
+  // As long as we don't crash, it's fine.
+}
+
+TEST(Table, Equality) {
+  StringTable t;
+  std::vector<std::pair<std::string, std::string>> v = {{"a", "b"},
+                                                        {"aa", "bb"}};
+  t.insert(std::begin(v), std::end(v));
+  StringTable u = t;
+  EXPECT_EQ(u, t);
+}
+
+TEST(Table, Equality2) {
+  StringTable t;
+  std::vector<std::pair<std::string, std::string>> v1 = {{"a", "b"},
+                                                         {"aa", "bb"}};
+  t.insert(std::begin(v1), std::end(v1));
+  StringTable u;
+  std::vector<std::pair<std::string, std::string>> v2 = {{"a", "a"},
+                                                         {"aa", "aa"}};
+  u.insert(std::begin(v2), std::end(v2));
+  EXPECT_NE(u, t);
+}
+
+TEST(Table, Equality3) {
+  StringTable t;
+  std::vector<std::pair<std::string, std::string>> v1 = {{"b", "b"},
+                                                         {"bb", "bb"}};
+  t.insert(std::begin(v1), std::end(v1));
+  StringTable u;
+  std::vector<std::pair<std::string, std::string>> v2 = {{"a", "a"},
+                                                         {"aa", "aa"}};
+  u.insert(std::begin(v2), std::end(v2));
+  EXPECT_NE(u, t);
+}
+
+TEST(Table, NumDeletedRegression) {
+  IntTable t;
+  t.emplace(0);
+  t.erase(t.find(0));
+  // construct over a deleted slot.
+  t.emplace(0);
+  t.clear();
+}
+
+TEST(Table, FindFullDeletedRegression) {
+  IntTable t;
+  for (int i = 0; i < 1000; ++i) {
+    t.emplace(i);
+    t.erase(t.find(i));
+  }
+  EXPECT_EQ(0, t.size());
+}
+
+TEST(Table, ReplacingDeletedSlotDoesNotRehash) {
+  size_t n;
+  {
+    // Compute n such that n is the maximum number of elements before rehash.
+    IntTable t;
+    t.emplace(0);
+    size_t c = t.bucket_count();
+    for (n = 1; c == t.bucket_count(); ++n) t.emplace(n);
+    --n;
+  }
+  IntTable t;
+  t.rehash(n);
+  const size_t c = t.bucket_count();
+  for (size_t i = 0; i != n; ++i) t.emplace(i);
+  EXPECT_EQ(c, t.bucket_count()) << "rehashing threshold = " << n;
+  t.erase(0);
+  t.emplace(0);
+  EXPECT_EQ(c, t.bucket_count()) << "rehashing threshold = " << n;
+}
+
+TEST(Table, NoThrowMoveConstruct) {
+  ASSERT_TRUE(
+      std::is_nothrow_copy_constructible<absl::Hash<absl::string_view>>::value);
+  ASSERT_TRUE(std::is_nothrow_copy_constructible<
+              std::equal_to<absl::string_view>>::value);
+  ASSERT_TRUE(std::is_nothrow_copy_constructible<std::allocator<int>>::value);
+  EXPECT_TRUE(std::is_nothrow_move_constructible<StringTable>::value);
+}
+
+TEST(Table, NoThrowMoveAssign) {
+  ASSERT_TRUE(
+      std::is_nothrow_move_assignable<absl::Hash<absl::string_view>>::value);
+  ASSERT_TRUE(
+      std::is_nothrow_move_assignable<std::equal_to<absl::string_view>>::value);
+  ASSERT_TRUE(std::is_nothrow_move_assignable<std::allocator<int>>::value);
+  ASSERT_TRUE(
+      absl::allocator_traits<std::allocator<int>>::is_always_equal::value);
+  EXPECT_TRUE(std::is_nothrow_move_assignable<StringTable>::value);
+}
+
+TEST(Table, NoThrowSwappable) {
+  ASSERT_TRUE(
+      container_internal::IsNoThrowSwappable<absl::Hash<absl::string_view>>());
+  ASSERT_TRUE(container_internal::IsNoThrowSwappable<
+              std::equal_to<absl::string_view>>());
+  ASSERT_TRUE(container_internal::IsNoThrowSwappable<std::allocator<int>>());
+  EXPECT_TRUE(container_internal::IsNoThrowSwappable<StringTable>());
+}
+
+TEST(Table, HeterogeneousLookup) {
+  struct Hash {
+    size_t operator()(int64_t i) const { return i; }
+    size_t operator()(double i) const {
+      ADD_FAILURE();
+      return i;
+    }
+  };
+  struct Eq {
+    bool operator()(int64_t a, int64_t b) const { return a == b; }
+    bool operator()(double a, int64_t b) const {
+      ADD_FAILURE();
+      return a == b;
+    }
+    bool operator()(int64_t a, double b) const {
+      ADD_FAILURE();
+      return a == b;
+    }
+    bool operator()(double a, double b) const {
+      ADD_FAILURE();
+      return a == b;
+    }
+  };
+
+  struct THash {
+    using is_transparent = void;
+    size_t operator()(int64_t i) const { return i; }
+    size_t operator()(double i) const { return i; }
+  };
+  struct TEq {
+    using is_transparent = void;
+    bool operator()(int64_t a, int64_t b) const { return a == b; }
+    bool operator()(double a, int64_t b) const { return a == b; }
+    bool operator()(int64_t a, double b) const { return a == b; }
+    bool operator()(double a, double b) const { return a == b; }
+  };
+
+  raw_hash_set<IntPolicy, Hash, Eq, Alloc<int64_t>> s{0, 1, 2};
+  // It will convert to int64_t before the query.
+  EXPECT_EQ(1, *s.find(double{1.1}));
+
+  raw_hash_set<IntPolicy, THash, TEq, Alloc<int64_t>> ts{0, 1, 2};
+  // It will try to use the double, and fail to find the object.
+  EXPECT_TRUE(ts.find(1.1) == ts.end());
+}
+
+template <class Table>
+using CallFind = decltype(std::declval<Table&>().find(17));
+
+template <class Table>
+using CallErase = decltype(std::declval<Table&>().erase(17));
+
+template <class Table>
+using CallExtract = decltype(std::declval<Table&>().extract(17));
+
+template <class Table>
+using CallPrefetch = decltype(std::declval<Table&>().prefetch(17));
+
+template <class Table>
+using CallCount = decltype(std::declval<Table&>().count(17));
+
+template <template <typename> class C, class Table, class = void>
+struct VerifyResultOf : std::false_type {};
+
+template <template <typename> class C, class Table>
+struct VerifyResultOf<C, Table, absl::void_t<C<Table>>> : std::true_type {};
+
+TEST(Table, HeterogeneousLookupOverloads) {
+  using NonTransparentTable =
+      raw_hash_set<StringPolicy, absl::Hash<absl::string_view>,
+                   std::equal_to<absl::string_view>, std::allocator<int>>;
+
+  EXPECT_FALSE((VerifyResultOf<CallFind, NonTransparentTable>()));
+  EXPECT_FALSE((VerifyResultOf<CallErase, NonTransparentTable>()));
+  EXPECT_FALSE((VerifyResultOf<CallExtract, NonTransparentTable>()));
+  EXPECT_FALSE((VerifyResultOf<CallPrefetch, NonTransparentTable>()));
+  EXPECT_FALSE((VerifyResultOf<CallCount, NonTransparentTable>()));
+
+  using TransparentTable =
+      raw_hash_set<StringPolicy, hash_default_hash<absl::string_view>,
+                   hash_default_eq<absl::string_view>, std::allocator<int>>;
+
+  EXPECT_TRUE((VerifyResultOf<CallFind, TransparentTable>()));
+  EXPECT_TRUE((VerifyResultOf<CallErase, TransparentTable>()));
+  EXPECT_TRUE((VerifyResultOf<CallExtract, TransparentTable>()));
+  EXPECT_TRUE((VerifyResultOf<CallPrefetch, TransparentTable>()));
+  EXPECT_TRUE((VerifyResultOf<CallCount, TransparentTable>()));
+}
+
+TEST(Iterator, IsDefaultConstructible) {
+  StringTable::iterator i;
+  EXPECT_TRUE(i == StringTable::iterator());
+}
+
+TEST(ConstIterator, IsDefaultConstructible) {
+  StringTable::const_iterator i;
+  EXPECT_TRUE(i == StringTable::const_iterator());
+}
+
+TEST(Iterator, ConvertsToConstIterator) {
+  StringTable::iterator i;
+  EXPECT_TRUE(i == StringTable::const_iterator());
+}
+
+TEST(Iterator, Iterates) {
+  IntTable t;
+  for (size_t i = 3; i != 6; ++i) EXPECT_TRUE(t.emplace(i).second);
+  EXPECT_THAT(t, UnorderedElementsAre(3, 4, 5));
+}
+
+TEST(Table, Merge) {
+  StringTable t1, t2;
+  t1.emplace("0", "-0");
+  t1.emplace("1", "-1");
+  t2.emplace("0", "~0");
+  t2.emplace("2", "~2");
+
+  EXPECT_THAT(t1, UnorderedElementsAre(Pair("0", "-0"), Pair("1", "-1")));
+  EXPECT_THAT(t2, UnorderedElementsAre(Pair("0", "~0"), Pair("2", "~2")));
+
+  t1.merge(t2);
+  EXPECT_THAT(t1, UnorderedElementsAre(Pair("0", "-0"), Pair("1", "-1"),
+                                       Pair("2", "~2")));
+  EXPECT_THAT(t2, UnorderedElementsAre(Pair("0", "~0")));
+}
+
+TEST(Table, IteratorEmplaceConstructibleRequirement) {
+  struct Value {
+    explicit Value(absl::string_view view) : value(view) {}
+    std::string value;
+
+    bool operator==(const Value& other) const { return value == other.value; }
+  };
+  struct H {
+    size_t operator()(const Value& v) const {
+      return absl::Hash<std::string>{}(v.value);
+    }
+  };
+
+  struct Table : raw_hash_set<ValuePolicy<Value>, H, std::equal_to<Value>,
+                              std::allocator<Value>> {
+    using Base = typename Table::raw_hash_set;
+    using Base::Base;
+  };
+
+  std::string input[3]{"A", "B", "C"};
+
+  Table t(std::begin(input), std::end(input));
+  EXPECT_THAT(t, UnorderedElementsAre(Value{"A"}, Value{"B"}, Value{"C"}));
+
+  input[0] = "D";
+  input[1] = "E";
+  input[2] = "F";
+  t.insert(std::begin(input), std::end(input));
+  EXPECT_THAT(t, UnorderedElementsAre(Value{"A"}, Value{"B"}, Value{"C"},
+                                      Value{"D"}, Value{"E"}, Value{"F"}));
+}
+
+TEST(Nodes, EmptyNodeType) {
+  using node_type = StringTable::node_type;
+  node_type n;
+  EXPECT_FALSE(n);
+  EXPECT_TRUE(n.empty());
+
+  EXPECT_TRUE((std::is_same<node_type::allocator_type,
+                            StringTable::allocator_type>::value));
+}
+
+TEST(Nodes, ExtractInsert) {
+  constexpr char k0[] = "Very long string zero.";
+  constexpr char k1[] = "Very long string one.";
+  constexpr char k2[] = "Very long string two.";
+  StringTable t = {{k0, ""}, {k1, ""}, {k2, ""}};
+  EXPECT_THAT(t,
+              UnorderedElementsAre(Pair(k0, ""), Pair(k1, ""), Pair(k2, "")));
+
+  auto node = t.extract(k0);
+  EXPECT_THAT(t, UnorderedElementsAre(Pair(k1, ""), Pair(k2, "")));
+  EXPECT_TRUE(node);
+  EXPECT_FALSE(node.empty());
+
+  StringTable t2;
+  StringTable::insert_return_type res = t2.insert(std::move(node));
+  EXPECT_TRUE(res.inserted);
+  EXPECT_THAT(*res.position, Pair(k0, ""));
+  EXPECT_FALSE(res.node);
+  EXPECT_THAT(t2, UnorderedElementsAre(Pair(k0, "")));
+
+  // Not there.
+  EXPECT_THAT(t, UnorderedElementsAre(Pair(k1, ""), Pair(k2, "")));
+  node = t.extract("Not there!");
+  EXPECT_THAT(t, UnorderedElementsAre(Pair(k1, ""), Pair(k2, "")));
+  EXPECT_FALSE(node);
+
+  // Inserting nothing.
+  res = t2.insert(std::move(node));
+  EXPECT_FALSE(res.inserted);
+  EXPECT_EQ(res.position, t2.end());
+  EXPECT_FALSE(res.node);
+  EXPECT_THAT(t2, UnorderedElementsAre(Pair(k0, "")));
+
+  t.emplace(k0, "1");
+  node = t.extract(k0);
+
+  // Insert duplicate.
+  res = t2.insert(std::move(node));
+  EXPECT_FALSE(res.inserted);
+  EXPECT_THAT(*res.position, Pair(k0, ""));
+  EXPECT_TRUE(res.node);
+  EXPECT_FALSE(node);  // NOLINT(bugprone-use-after-move)
+}
+
+TEST(Nodes, HintInsert) {
+  IntTable t = {1, 2, 3};
+  auto node = t.extract(1);
+  EXPECT_THAT(t, UnorderedElementsAre(2, 3));
+  auto it = t.insert(t.begin(), std::move(node));
+  EXPECT_THAT(t, UnorderedElementsAre(1, 2, 3));
+  EXPECT_EQ(*it, 1);
+  EXPECT_FALSE(node);  // NOLINT(bugprone-use-after-move)
+
+  node = t.extract(2);
+  EXPECT_THAT(t, UnorderedElementsAre(1, 3));
+  // reinsert 2 to make the next insert fail.
+  t.insert(2);
+  EXPECT_THAT(t, UnorderedElementsAre(1, 2, 3));
+  it = t.insert(t.begin(), std::move(node));
+  EXPECT_EQ(*it, 2);
+  // The node was not emptied by the insert call.
+  EXPECT_TRUE(node);  // NOLINT(bugprone-use-after-move)
+}
+
+IntTable MakeSimpleTable(size_t size) {
+  IntTable t;
+  while (t.size() < size) t.insert(t.size());
+  return t;
+}
+
+std::vector<int> OrderOfIteration(const IntTable& t) {
+  return {t.begin(), t.end()};
+}
+
+// These IterationOrderChanges tests depend on non-deterministic behavior.
+// We are injecting non-determinism from the pointer of the table, but do so in
+// a way that only the page matters. We have to retry enough times to make sure
+// we are touching different memory pages to cause the ordering to change.
+// We also need to keep the old tables around to avoid getting the same memory
+// blocks over and over.
+TEST(Table, IterationOrderChangesByInstance) {
+  for (size_t size : {2, 6, 12, 20}) {
+    const auto reference_table = MakeSimpleTable(size);
+    const auto reference = OrderOfIteration(reference_table);
+
+    std::vector<IntTable> tables;
+    bool found_difference = false;
+    for (int i = 0; !found_difference && i < 5000; ++i) {
+      tables.push_back(MakeSimpleTable(size));
+      found_difference = OrderOfIteration(tables.back()) != reference;
+    }
+    if (!found_difference) {
+      FAIL()
+          << "Iteration order remained the same across many attempts with size "
+          << size;
+    }
+  }
+}
+
+TEST(Table, IterationOrderChangesOnRehash) {
+  std::vector<IntTable> garbage;
+  for (int i = 0; i < 5000; ++i) {
+    auto t = MakeSimpleTable(20);
+    const auto reference = OrderOfIteration(t);
+    // Force rehash to the same size.
+    t.rehash(0);
+    auto trial = OrderOfIteration(t);
+    if (trial != reference) {
+      // We are done.
+      return;
+    }
+    garbage.push_back(std::move(t));
+  }
+  FAIL() << "Iteration order remained the same across many attempts.";
+}
+
+// Verify that pointers are invalidated as soon as a second element is inserted.
+// This prevents dependency on pointer stability on small tables.
+TEST(Table, UnstablePointers) {
+  IntTable table;
+
+  const auto addr = [&](int i) {
+    return reinterpret_cast<uintptr_t>(&*table.find(i));
+  };
+
+  table.insert(0);
+  const uintptr_t old_ptr = addr(0);
+
+  // This causes a rehash.
+  table.insert(1);
+
+  EXPECT_NE(old_ptr, addr(0));
+}
+
+TEST(TableDeathTest, InvalidIteratorAsserts) {
+  if (!IsAssertEnabled() && !SwisstableGenerationsEnabled())
+    GTEST_SKIP() << "Assertions not enabled.";
+
+  IntTable t;
+  // Extra simple "regexp" as regexp support is highly varied across platforms.
+  EXPECT_DEATH_IF_SUPPORTED(t.erase(t.end()),
+                            "erase.* called on end.. iterator.");
+  typename IntTable::iterator iter;
+  EXPECT_DEATH_IF_SUPPORTED(
+      ++iter, "operator.* called on default-constructed iterator.");
+  t.insert(0);
+  iter = t.begin();
+  t.erase(iter);
+  const char* const kErasedDeathMessage =
+      SwisstableGenerationsEnabled()
+          ? "operator.* called on invalid iterator.*was likely erased"
+          : "operator.* called on invalid iterator.*might have been "
+            "erased.*config=asan";
+  EXPECT_DEATH_IF_SUPPORTED(++iter, kErasedDeathMessage);
+}
+
+// Invalid iterator use can trigger use-after-free in asan/hwasan,
+// use-of-uninitialized-value in msan, or invalidated iterator assertions.
+constexpr const char* kInvalidIteratorDeathMessage =
+    "use-after-free|use-of-uninitialized-value|invalidated "
+    "iterator|Invalid iterator|invalid iterator";
+
+// MSVC doesn't support | in regex.
+#if defined(_MSC_VER)
+constexpr bool kMsvc = true;
+#else
+constexpr bool kMsvc = false;
+#endif
+
+TEST(TableDeathTest, IteratorInvalidAssertsEqualityOperator) {
+  if (!IsAssertEnabled() && !SwisstableGenerationsEnabled())
+    GTEST_SKIP() << "Assertions not enabled.";
+
+  IntTable t;
+  t.insert(1);
+  t.insert(2);
+  t.insert(3);
+  auto iter1 = t.begin();
+  auto iter2 = std::next(iter1);
+  ASSERT_NE(iter1, t.end());
+  ASSERT_NE(iter2, t.end());
+  t.erase(iter1);
+  // Extra simple "regexp" as regexp support is highly varied across platforms.
+  const char* const kErasedDeathMessage =
+      SwisstableGenerationsEnabled()
+          ? "Invalid iterator comparison.*was likely erased"
+          : "Invalid iterator comparison.*might have been erased.*config=asan";
+  EXPECT_DEATH_IF_SUPPORTED(void(iter1 == iter2), kErasedDeathMessage);
+  EXPECT_DEATH_IF_SUPPORTED(void(iter2 != iter1), kErasedDeathMessage);
+  t.erase(iter2);
+  EXPECT_DEATH_IF_SUPPORTED(void(iter1 == iter2), kErasedDeathMessage);
+
+  IntTable t1, t2;
+  t1.insert(0);
+  t2.insert(0);
+  iter1 = t1.begin();
+  iter2 = t2.begin();
+  const char* const kContainerDiffDeathMessage =
+      SwisstableGenerationsEnabled()
+          ? "Invalid iterator comparison.*iterators from different hashtables"
+          : "Invalid iterator comparison.*may be from different "
+            ".*containers.*config=asan";
+  EXPECT_DEATH_IF_SUPPORTED(void(iter1 == iter2), kContainerDiffDeathMessage);
+  EXPECT_DEATH_IF_SUPPORTED(void(iter2 == iter1), kContainerDiffDeathMessage);
+
+  for (int i = 0; i < 10; ++i) t1.insert(i);
+  // There should have been a rehash in t1.
+  if (kMsvc) return;  // MSVC doesn't support | in regex.
+
+  // NOTE(b/293887834): After rehashing, iterators will contain pointers to
+  // freed memory, which may be detected by ThreadSanitizer.
+  const char* const kRehashedDeathMessage =
+      SwisstableGenerationsEnabled()
+          ? kInvalidIteratorDeathMessage
+          : "Invalid iterator comparison.*might have rehashed.*config=asan"
+            "|ThreadSanitizer: heap-use-after-free";
+  EXPECT_DEATH_IF_SUPPORTED(void(iter1 == t1.begin()), kRehashedDeathMessage);
+}
+
+#if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
+TEST(RawHashSamplerTest, Sample) {
+  // Enable the feature even if the prod default is off.
+  SetHashtablezEnabled(true);
+  SetHashtablezSampleParameter(100);
+
+  auto& sampler = GlobalHashtablezSampler();
+  size_t start_size = 0;
+  absl::flat_hash_set<const HashtablezInfo*> preexisting_info;
+  start_size += sampler.Iterate([&](const HashtablezInfo& info) {
+    preexisting_info.insert(&info);
+    ++start_size;
+  });
+
+  std::vector<IntTable> tables;
+  for (int i = 0; i < 1000000; ++i) {
+    tables.emplace_back();
+
+    const bool do_reserve = (i % 10 > 5);
+    const bool do_rehash = !do_reserve && (i % 10 > 0);
+
+    if (do_reserve) {
+      // Don't reserve on all tables.
+      tables.back().reserve(10 * (i % 10));
+    }
+
+    tables.back().insert(1);
+    tables.back().insert(i % 5);
+
+    if (do_rehash) {
+      // Rehash some other tables.
+      tables.back().rehash(10 * (i % 10));
+    }
+  }
+  size_t end_size = 0;
+  absl::flat_hash_map<size_t, int> observed_checksums;
+  absl::flat_hash_map<ssize_t, int> reservations;
+  end_size += sampler.Iterate([&](const HashtablezInfo& info) {
+    if (preexisting_info.count(&info) == 0) {
+      observed_checksums[info.hashes_bitwise_xor.load(
+          std::memory_order_relaxed)]++;
+      reservations[info.max_reserve.load(std::memory_order_relaxed)]++;
+    }
+    EXPECT_EQ(info.inline_element_size, sizeof(int64_t));
+    ++end_size;
+  });
+
+  EXPECT_NEAR((end_size - start_size) / static_cast<double>(tables.size()),
+              0.01, 0.005);
+  EXPECT_EQ(observed_checksums.size(), 5);
+  for (const auto& [_, count] : observed_checksums) {
+    EXPECT_NEAR((100 * count) / static_cast<double>(tables.size()), 0.2, 0.05);
+  }
+
+  EXPECT_EQ(reservations.size(), 10);
+  for (const auto& [reservation, count] : reservations) {
+    EXPECT_GE(reservation, 0);
+    EXPECT_LT(reservation, 100);
+
+    EXPECT_NEAR((100 * count) / static_cast<double>(tables.size()), 0.1, 0.05)
+        << reservation;
+  }
+}
+#endif  // ABSL_INTERNAL_HASHTABLEZ_SAMPLE
+
+TEST(RawHashSamplerTest, DoNotSampleCustomAllocators) {
+  // Enable the feature even if the prod default is off.
+  SetHashtablezEnabled(true);
+  SetHashtablezSampleParameter(100);
+
+  auto& sampler = GlobalHashtablezSampler();
+  size_t start_size = 0;
+  start_size += sampler.Iterate([&](const HashtablezInfo&) { ++start_size; });
+
+  std::vector<CustomAllocIntTable> tables;
+  for (int i = 0; i < 1000000; ++i) {
+    tables.emplace_back();
+    tables.back().insert(1);
+  }
+  size_t end_size = 0;
+  end_size += sampler.Iterate([&](const HashtablezInfo&) { ++end_size; });
+
+  EXPECT_NEAR((end_size - start_size) / static_cast<double>(tables.size()),
+              0.00, 0.001);
+}
+
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+template <class TableType>
+class SanitizerTest : public testing::Test {};
+
+TYPED_TEST_SUITE_P(SanitizerTest);
+
+TYPED_TEST_P(SanitizerTest, PoisoningUnused) {
+  TypeParam t;
+  for (size_t reserve_size = 2; reserve_size < 1024;
+       reserve_size = reserve_size * 3 / 2) {
+    t.reserve(reserve_size);
+    // Insert something to force an allocation.
+    int64_t& v = *t.insert(0).first;
+
+    // Make sure there is something to test.
+    ASSERT_GT(t.capacity(), 1);
+
+    int64_t* slots = RawHashSetTestOnlyAccess::GetSlots(t);
+    for (size_t i = 0; i < t.capacity(); ++i) {
+      EXPECT_EQ(slots + i != &v, __asan_address_is_poisoned(slots + i)) << i;
+    }
+  }
+}
+
+REGISTER_TYPED_TEST_SUITE_P(SanitizerTest, PoisoningUnused);
+using SanitizerTableTypes = ::testing::Types<IntTable, TransferableIntTable>;
+INSTANTIATE_TYPED_TEST_SUITE_P(InstanceSanitizerTest, SanitizerTest,
+                               SanitizerTableTypes);
+
+TEST(Sanitizer, PoisoningOnErase) {
+  IntTable t;
+  int64_t& v = *t.insert(0).first;
+
+  EXPECT_FALSE(__asan_address_is_poisoned(&v));
+  t.erase(0);
+  EXPECT_TRUE(__asan_address_is_poisoned(&v));
+}
+#endif  // ABSL_HAVE_ADDRESS_SANITIZER
+
+template <typename T>
+class AlignOneTest : public ::testing::Test {};
+using AlignOneTestTypes =
+    ::testing::Types<Uint8Table, MinimumAlignmentUint8Table>;
+TYPED_TEST_SUITE(AlignOneTest, AlignOneTestTypes);
+
+TYPED_TEST(AlignOneTest, AlignOne) {
+  // We previously had a bug in which we were copying a control byte over the
+  // first slot when alignof(value_type) is 1. We test repeated
+  // insertions/erases and verify that the behavior is correct.
+  TypeParam t;
+  std::unordered_set<uint8_t> verifier;  // NOLINT
+
+  // Do repeated insertions/erases from the table.
+  for (int64_t i = 0; i < 100000; ++i) {
+    SCOPED_TRACE(i);
+    const uint8_t u = (i * -i) & 0xFF;
+    auto it = t.find(u);
+    auto verifier_it = verifier.find(u);
+    if (it == t.end()) {
+      ASSERT_EQ(verifier_it, verifier.end());
+      t.insert(u);
+      verifier.insert(u);
+    } else {
+      ASSERT_NE(verifier_it, verifier.end());
+      t.erase(it);
+      verifier.erase(verifier_it);
+    }
+  }
+
+  EXPECT_EQ(t.size(), verifier.size());
+  for (uint8_t u : t) {
+    EXPECT_EQ(verifier.count(u), 1);
+  }
+}
+
+TEST(Iterator, InvalidUseCrashesWithSanitizers) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
+
+  IntTable t;
+  // Start with 1 element so that `it` is never an end iterator.
+  t.insert(-1);
+  for (int i = 0; i < 10; ++i) {
+    auto it = t.begin();
+    t.insert(i);
+    EXPECT_DEATH_IF_SUPPORTED(*it, kInvalidIteratorDeathMessage);
+    EXPECT_DEATH_IF_SUPPORTED(void(it == t.begin()),
+                              kInvalidIteratorDeathMessage);
+  }
+}
+
+TEST(Iterator, InvalidUseWithReserveCrashesWithSanitizers) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
+
+  IntTable t;
+  t.reserve(10);
+  t.insert(0);
+  auto it = t.begin();
+  // Reserved growth can't rehash.
+  for (int i = 1; i < 10; ++i) {
+    t.insert(i);
+    EXPECT_EQ(*it, 0);
+  }
+  // ptr will become invalidated on rehash.
+  const int64_t* ptr = &*it;
+  (void)ptr;
+
+  // erase decreases size but does not decrease reserved growth so the next
+  // insertion still invalidates iterators.
+  t.erase(0);
+  // The first insert after reserved growth is 0 is guaranteed to rehash when
+  // generations are enabled.
+  t.insert(10);
+  EXPECT_DEATH_IF_SUPPORTED(*it, kInvalidIteratorDeathMessage);
+  EXPECT_DEATH_IF_SUPPORTED(void(it == t.begin()),
+                            kInvalidIteratorDeathMessage);
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+  EXPECT_DEATH_IF_SUPPORTED(std::cout << *ptr, "heap-use-after-free");
+#endif
+}
+
+TEST(Iterator, InvalidUseWithMoveCrashesWithSanitizers) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
+
+  IntTable t1, t2;
+  t1.insert(1);
+  auto it = t1.begin();
+  // ptr will become invalidated on rehash.
+  const int64_t* ptr = &*it;
+  (void)ptr;
+
+  t2 = std::move(t1);
+  EXPECT_DEATH_IF_SUPPORTED(*it, kInvalidIteratorDeathMessage);
+  EXPECT_DEATH_IF_SUPPORTED(void(it == t2.begin()),
+                            kInvalidIteratorDeathMessage);
+#ifdef ABSL_HAVE_ADDRESS_SANITIZER
+  EXPECT_DEATH_IF_SUPPORTED(std::cout << *ptr, "heap-use-after-free");
+#endif
+}
+
+TEST(Table, ReservedGrowthUpdatesWhenTableDoesntGrow) {
+  IntTable t;
+  for (int i = 0; i < 8; ++i) t.insert(i);
+  // Want to insert twice without invalidating iterators so reserve.
+  const size_t cap = t.capacity();
+  t.reserve(t.size() + 2);
+  // We want to be testing the case in which the reserve doesn't grow the table.
+  ASSERT_EQ(cap, t.capacity());
+  auto it = t.find(0);
+  t.insert(100);
+  t.insert(200);
+  // `it` shouldn't have been invalidated.
+  EXPECT_EQ(*it, 0);
+}
+
+TEST(Table, EraseBeginEndResetsReservedGrowth) {
+  bool frozen = false;
+  BadHashFreezableIntTable t{FreezableAlloc<int64_t>(&frozen)};
+  t.reserve(100);
+  const size_t cap = t.capacity();
+  frozen = true;  // no further allocs allowed
+
+  for (int i = 0; i < 10; ++i) {
+    // Create a long run (hash function returns constant).
+    for (int j = 0; j < 100; ++j) t.insert(j);
+    // Erase elements from the middle of the long run, which creates tombstones.
+    for (int j = 30; j < 60; ++j) t.erase(j);
+    EXPECT_EQ(t.size(), 70);
+    EXPECT_EQ(t.capacity(), cap);
+    ASSERT_EQ(RawHashSetTestOnlyAccess::CountTombstones(t), 30);
+
+    t.erase(t.begin(), t.end());
+
+    EXPECT_EQ(t.size(), 0);
+    EXPECT_EQ(t.capacity(), cap);
+    ASSERT_EQ(RawHashSetTestOnlyAccess::CountTombstones(t), 0);
+  }
+}
+
+TEST(Table, GenerationInfoResetsOnClear) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+  if (kMsvc) GTEST_SKIP() << "MSVC doesn't support | in regexp.";
+
+  IntTable t;
+  for (int i = 0; i < 1000; ++i) t.insert(i);
+  t.reserve(t.size() + 100);
+
+  t.clear();
+
+  t.insert(0);
+  auto it = t.begin();
+  t.insert(1);
+  EXPECT_DEATH_IF_SUPPORTED(*it, kInvalidIteratorDeathMessage);
+}
+
+TEST(Table, InvalidReferenceUseCrashesWithSanitizers) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+#ifdef ABSL_HAVE_MEMORY_SANITIZER
+  GTEST_SKIP() << "MSan fails to detect some of these rehashes.";
+#endif
+
+  IntTable t;
+  t.insert(0);
+  // Rehashing is guaranteed on every insertion while capacity is less than
+  // RehashProbabilityConstant().
+  int64_t i = 0;
+  while (t.capacity() <= RehashProbabilityConstant()) {
+    // ptr will become invalidated on rehash.
+    const int64_t* ptr = &*t.begin();
+    t.insert(++i);
+    EXPECT_DEATH_IF_SUPPORTED(std::cout << *ptr, "use-after-free") << i;
+  }
+}
+
+TEST(Iterator, InvalidComparisonDifferentTables) {
+  if (!SwisstableGenerationsEnabled()) GTEST_SKIP() << "Generations disabled.";
+
+  IntTable t1, t2;
+  IntTable::iterator default_constructed_iter;
+  // We randomly use one of N empty generations for generations from empty
+  // hashtables. In general, we won't always detect when iterators from
+  // different empty hashtables are compared, but in this test case, we
+  // should deterministically detect the error due to our randomness yielding
+  // consecutive random generations.
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.end() == t2.end()),
+                            "Invalid iterator comparison.*empty hashtables");
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.end() == default_constructed_iter),
+                            "Invalid iterator comparison.*default-constructed");
+  t1.insert(0);
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == t2.end()),
+                            "Invalid iterator comparison.*empty hashtable");
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == default_constructed_iter),
+                            "Invalid iterator comparison.*default-constructed");
+  t2.insert(0);
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == t2.end()),
+                            "Invalid iterator comparison.*end.. iterator");
+  EXPECT_DEATH_IF_SUPPORTED(void(t1.begin() == t2.begin()),
+                            "Invalid iterator comparison.*non-end");
+}
+
+template <typename Alloc>
+using RawHashSetAlloc = raw_hash_set<IntPolicy, hash_default_hash<int64_t>,
+                                     std::equal_to<int64_t>, Alloc>;
+
+TEST(Table, AllocatorPropagation) { TestAllocPropagation<RawHashSetAlloc>(); }
+
+struct CountedHash {
+  size_t operator()(int value) const {
+    ++count;
+    return static_cast<size_t>(value);
+  }
+  mutable int count = 0;
+};
+
+struct CountedHashIntTable
+    : raw_hash_set<IntPolicy, CountedHash, std::equal_to<int>,
+                   std::allocator<int>> {
+  using Base = typename CountedHashIntTable::raw_hash_set;
+  using Base::Base;
+};
+
+TEST(Table, CountedHash) {
+  // Verify that raw_hash_set does not compute redundant hashes.
+#ifdef NDEBUG
+  constexpr bool kExpectMinimumHashes = true;
+#else
+  constexpr bool kExpectMinimumHashes = false;
+#endif
+  if (!kExpectMinimumHashes) {
+    GTEST_SKIP() << "Only run under NDEBUG: `assert` statements may cause "
+                    "redundant hashing.";
+  }
+
+  using Table = CountedHashIntTable;
+  auto HashCount = [](const Table& t) { return t.hash_function().count; };
+  {
+    Table t;
+    EXPECT_EQ(HashCount(t), 0);
+  }
+  {
+    Table t;
+    t.insert(1);
+    EXPECT_EQ(HashCount(t), 1);
+    t.erase(1);
+    EXPECT_EQ(HashCount(t), 2);
+  }
+  {
+    Table t;
+    t.insert(3);
+    EXPECT_EQ(HashCount(t), 1);
+    auto node = t.extract(3);
+    EXPECT_EQ(HashCount(t), 2);
+    t.insert(std::move(node));
+    EXPECT_EQ(HashCount(t), 3);
+  }
+  {
+    Table t;
+    t.emplace(5);
+    EXPECT_EQ(HashCount(t), 1);
+  }
+  {
+    Table src;
+    src.insert(7);
+    Table dst;
+    dst.merge(src);
+    EXPECT_EQ(HashCount(dst), 1);
+  }
+}
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_constructor_test.h b/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_constructor_test.h
new file mode 100644
index 0000000000000000000000000000000000000000..7e84dc2554d4e7af5021f500095cba86c0b74904
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_constructor_test.h
@@ -0,0 +1,494 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_CONSTRUCTOR_TEST_H_
+#define ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_CONSTRUCTOR_TEST_H_
+
+#include <algorithm>
+#include <unordered_map>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/hash_generator_testing.h"
+#include "absl/container/internal/hash_policy_testing.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+template <class UnordMap>
+class ConstructorTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE_P(ConstructorTest);
+
+TYPED_TEST_P(ConstructorTest, NoArgs) {
+  TypeParam m;
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCount) {
+  TypeParam m(123);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHash) {
+  using H = typename TypeParam::hasher;
+  H hasher;
+  TypeParam m(123, hasher);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHashEqual) {
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  H hasher;
+  E equal;
+  TypeParam m(123, hasher, equal);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHashEqualAlloc) {
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(123, hasher, equal, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+template <typename T>
+struct is_std_unordered_map : std::false_type {};
+
+template <typename... T>
+struct is_std_unordered_map<std::unordered_map<T...>> : std::true_type {};
+
+#if defined(UNORDERED_MAP_CXX14) || defined(UNORDERED_MAP_CXX17)
+using has_cxx14_std_apis = std::true_type;
+#else
+using has_cxx14_std_apis = std::false_type;
+#endif
+
+template <typename T>
+using expect_cxx14_apis =
+    absl::disjunction<absl::negation<is_std_unordered_map<T>>,
+                      has_cxx14_std_apis>;
+
+template <typename TypeParam>
+void BucketCountAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void BucketCountAllocTest(std::true_type) {
+  using A = typename TypeParam::allocator_type;
+  A alloc(0);
+  TypeParam m(123, alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountAlloc) {
+  BucketCountAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+template <typename TypeParam>
+void BucketCountHashAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void BucketCountHashAllocTest(std::true_type) {
+  using H = typename TypeParam::hasher;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  A alloc(0);
+  TypeParam m(123, hasher, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHashAlloc) {
+  BucketCountHashAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+#if ABSL_UNORDERED_SUPPORTS_ALLOC_CTORS
+using has_alloc_std_constructors = std::true_type;
+#else
+using has_alloc_std_constructors = std::false_type;
+#endif
+
+template <typename T>
+using expect_alloc_constructors =
+    absl::disjunction<absl::negation<is_std_unordered_map<T>>,
+                      has_alloc_std_constructors>;
+
+template <typename TypeParam>
+void AllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void AllocTest(std::true_type) {
+  using A = typename TypeParam::allocator_type;
+  A alloc(0);
+  TypeParam m(alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(m, ::testing::UnorderedElementsAre());
+}
+
+TYPED_TEST_P(ConstructorTest, Alloc) {
+  AllocTest<TypeParam>(expect_alloc_constructors<TypeParam>());
+}
+
+TYPED_TEST_P(ConstructorTest, InputIteratorBucketHashEqualAlloc) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::UniqueGenerator<T>());
+  TypeParam m(values.begin(), values.end(), 123, hasher, equal, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+template <typename TypeParam>
+void InputIteratorBucketAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InputIteratorBucketAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using A = typename TypeParam::allocator_type;
+  A alloc(0);
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::UniqueGenerator<T>());
+  TypeParam m(values.begin(), values.end(), 123, alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InputIteratorBucketAlloc) {
+  InputIteratorBucketAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+template <typename TypeParam>
+void InputIteratorBucketHashAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InputIteratorBucketHashAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  A alloc(0);
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::UniqueGenerator<T>());
+  TypeParam m(values.begin(), values.end(), 123, hasher, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InputIteratorBucketHashAlloc) {
+  InputIteratorBucketHashAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+TYPED_TEST_P(ConstructorTest, CopyConstructor) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(gen());
+  TypeParam n(m);
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+template <typename TypeParam>
+void CopyConstructorAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void CopyConstructorAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(gen());
+  TypeParam n(m, A(11));
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_NE(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, CopyConstructorAlloc) {
+  CopyConstructorAllocTest<TypeParam>(expect_alloc_constructors<TypeParam>());
+}
+
+// TODO(alkis): Test non-propagating allocators on copy constructors.
+
+TYPED_TEST_P(ConstructorTest, MoveConstructor) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(gen());
+  TypeParam t(m);
+  TypeParam n(std::move(t));
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+template <typename TypeParam>
+void MoveConstructorAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void MoveConstructorAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(gen());
+  TypeParam t(m);
+  TypeParam n(std::move(t), A(1));
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_NE(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, MoveConstructorAlloc) {
+  MoveConstructorAllocTest<TypeParam>(expect_alloc_constructors<TypeParam>());
+}
+
+// TODO(alkis): Test non-propagating allocators on move constructors.
+
+TYPED_TEST_P(ConstructorTest, InitializerListBucketHashEqualAlloc) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::UniqueGenerator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(values, 123, hasher, equal, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+template <typename TypeParam>
+void InitializerListBucketAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InitializerListBucketAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using A = typename TypeParam::allocator_type;
+  hash_internal::UniqueGenerator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  A alloc(0);
+  TypeParam m(values, 123, alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InitializerListBucketAlloc) {
+  InitializerListBucketAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+template <typename TypeParam>
+void InitializerListBucketHashAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InitializerListBucketHashAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m(values, 123, hasher, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InitializerListBucketHashAlloc) {
+  InitializerListBucketHashAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+TYPED_TEST_P(ConstructorTest, Assignment) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m({gen(), gen(), gen()}, 123, hasher, equal, alloc);
+  TypeParam n;
+  n = m;
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m, n);
+}
+
+// TODO(alkis): Test [non-]propagating allocators on move/copy assignments
+// (it depends on traits).
+
+TYPED_TEST_P(ConstructorTest, MoveAssignment) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m({gen(), gen(), gen()}, 123, hasher, equal, alloc);
+  TypeParam t(m);
+  TypeParam n;
+  n = std::move(t);
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentFromInitializerList) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::UniqueGenerator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m;
+  m = values;
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentOverwritesExisting) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m({gen(), gen(), gen()});
+  TypeParam n({gen()});
+  n = m;
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, MoveAssignmentOverwritesExisting) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::UniqueGenerator<T> gen;
+  TypeParam m({gen(), gen(), gen()});
+  TypeParam t(m);
+  TypeParam n({gen()});
+  n = std::move(t);
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentFromInitializerListOverwritesExisting) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::UniqueGenerator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m;
+  m = values;
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentOnSelf) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::UniqueGenerator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m(values);
+  m = *&m;  // Avoid -Wself-assign
+  EXPECT_THAT(items(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+// We cannot test self move as standard states that it leaves standard
+// containers in unspecified state (and in practice in causes memory-leak
+// according to heap-checker!).
+
+REGISTER_TYPED_TEST_SUITE_P(
+    ConstructorTest, NoArgs, BucketCount, BucketCountHash, BucketCountHashEqual,
+    BucketCountHashEqualAlloc, BucketCountAlloc, BucketCountHashAlloc, Alloc,
+    InputIteratorBucketHashEqualAlloc, InputIteratorBucketAlloc,
+    InputIteratorBucketHashAlloc, CopyConstructor, CopyConstructorAlloc,
+    MoveConstructor, MoveConstructorAlloc, InitializerListBucketHashEqualAlloc,
+    InitializerListBucketAlloc, InitializerListBucketHashAlloc, Assignment,
+    MoveAssignment, AssignmentFromInitializerList, AssignmentOverwritesExisting,
+    MoveAssignmentOverwritesExisting,
+    AssignmentFromInitializerListOverwritesExisting, AssignmentOnSelf);
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_CONSTRUCTOR_TEST_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_members_test.h b/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_members_test.h
new file mode 100644
index 0000000000000000000000000000000000000000..7d48cdb890bba6f853a01501d1e1368631e400c5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_members_test.h
@@ -0,0 +1,87 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MEMBERS_TEST_H_
+#define ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MEMBERS_TEST_H_
+
+#include <type_traits>
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+template <class UnordMap>
+class MembersTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE_P(MembersTest);
+
+template <typename T>
+void UseType() {}
+
+TYPED_TEST_P(MembersTest, Typedefs) {
+  EXPECT_TRUE((std::is_same<std::pair<const typename TypeParam::key_type,
+                                      typename TypeParam::mapped_type>,
+                            typename TypeParam::value_type>()));
+  EXPECT_TRUE((absl::conjunction<
+               absl::negation<std::is_signed<typename TypeParam::size_type>>,
+               std::is_integral<typename TypeParam::size_type>>()));
+  EXPECT_TRUE((absl::conjunction<
+               std::is_signed<typename TypeParam::difference_type>,
+               std::is_integral<typename TypeParam::difference_type>>()));
+  EXPECT_TRUE((std::is_convertible<
+               decltype(std::declval<const typename TypeParam::hasher&>()(
+                   std::declval<const typename TypeParam::key_type&>())),
+               size_t>()));
+  EXPECT_TRUE((std::is_convertible<
+               decltype(std::declval<const typename TypeParam::key_equal&>()(
+                   std::declval<const typename TypeParam::key_type&>(),
+                   std::declval<const typename TypeParam::key_type&>())),
+               bool>()));
+  EXPECT_TRUE((std::is_same<typename TypeParam::allocator_type::value_type,
+                            typename TypeParam::value_type>()));
+  EXPECT_TRUE((std::is_same<typename TypeParam::value_type&,
+                            typename TypeParam::reference>()));
+  EXPECT_TRUE((std::is_same<const typename TypeParam::value_type&,
+                            typename TypeParam::const_reference>()));
+  EXPECT_TRUE((std::is_same<typename std::allocator_traits<
+                                typename TypeParam::allocator_type>::pointer,
+                            typename TypeParam::pointer>()));
+  EXPECT_TRUE(
+      (std::is_same<typename std::allocator_traits<
+                        typename TypeParam::allocator_type>::const_pointer,
+                    typename TypeParam::const_pointer>()));
+}
+
+TYPED_TEST_P(MembersTest, SimpleFunctions) {
+  EXPECT_GT(TypeParam().max_size(), 0);
+}
+
+TYPED_TEST_P(MembersTest, BeginEnd) {
+  TypeParam t = {typename TypeParam::value_type{}};
+  EXPECT_EQ(t.begin(), t.cbegin());
+  EXPECT_EQ(t.end(), t.cend());
+  EXPECT_NE(t.begin(), t.end());
+  EXPECT_NE(t.cbegin(), t.cend());
+}
+
+REGISTER_TYPED_TEST_SUITE_P(MembersTest, Typedefs, SimpleFunctions, BeginEnd);
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MEMBERS_TEST_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9cbf512f32b20c757def90048f44d162a7476d6f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_map_test.cc
@@ -0,0 +1,50 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <memory>
+#include <unordered_map>
+
+#include "absl/container/internal/unordered_map_constructor_test.h"
+#include "absl/container/internal/unordered_map_lookup_test.h"
+#include "absl/container/internal/unordered_map_members_test.h"
+#include "absl/container/internal/unordered_map_modifiers_test.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using MapTypes = ::testing::Types<
+    std::unordered_map<int, int, StatefulTestingHash, StatefulTestingEqual,
+                       Alloc<std::pair<const int, int>>>,
+    std::unordered_map<std::string, std::string, StatefulTestingHash,
+                       StatefulTestingEqual,
+                       Alloc<std::pair<const std::string, std::string>>>>;
+
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, ConstructorTest, MapTypes);
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, LookupTest, MapTypes);
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, MembersTest, MapTypes);
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, ModifiersTest, MapTypes);
+
+using UniquePtrMapTypes = ::testing::Types<std::unordered_map<
+    int, std::unique_ptr<int>, StatefulTestingHash, StatefulTestingEqual,
+    Alloc<std::pair<const int, std::unique_ptr<int>>>>>;
+
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, UniquePtrModifiersTest,
+                               UniquePtrMapTypes);
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_constructor_test.h b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_constructor_test.h
new file mode 100644
index 0000000000000000000000000000000000000000..af1116e6c3ef1f1174024415c74d695adf6e4783
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_constructor_test.h
@@ -0,0 +1,496 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CONTAINER_INTERNAL_UNORDERED_SET_CONSTRUCTOR_TEST_H_
+#define ABSL_CONTAINER_INTERNAL_UNORDERED_SET_CONSTRUCTOR_TEST_H_
+
+#include <algorithm>
+#include <unordered_set>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/hash_generator_testing.h"
+#include "absl/container/internal/hash_policy_testing.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+template <class UnordMap>
+class ConstructorTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE_P(ConstructorTest);
+
+TYPED_TEST_P(ConstructorTest, NoArgs) {
+  TypeParam m;
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCount) {
+  TypeParam m(123);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHash) {
+  using H = typename TypeParam::hasher;
+  H hasher;
+  TypeParam m(123, hasher);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHashEqual) {
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  H hasher;
+  E equal;
+  TypeParam m(123, hasher, equal);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHashEqualAlloc) {
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(123, hasher, equal, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+
+  const auto& cm = m;
+  EXPECT_EQ(cm.hash_function(), hasher);
+  EXPECT_EQ(cm.key_eq(), equal);
+  EXPECT_EQ(cm.get_allocator(), alloc);
+  EXPECT_TRUE(cm.empty());
+  EXPECT_THAT(keys(cm), ::testing::UnorderedElementsAre());
+  EXPECT_GE(cm.bucket_count(), 123);
+}
+
+template <typename T>
+struct is_std_unordered_set : std::false_type {};
+
+template <typename... T>
+struct is_std_unordered_set<std::unordered_set<T...>> : std::true_type {};
+
+#if defined(UNORDERED_SET_CXX14) || defined(UNORDERED_SET_CXX17)
+using has_cxx14_std_apis = std::true_type;
+#else
+using has_cxx14_std_apis = std::false_type;
+#endif
+
+template <typename T>
+using expect_cxx14_apis =
+    absl::disjunction<absl::negation<is_std_unordered_set<T>>,
+                      has_cxx14_std_apis>;
+
+template <typename TypeParam>
+void BucketCountAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void BucketCountAllocTest(std::true_type) {
+  using A = typename TypeParam::allocator_type;
+  A alloc(0);
+  TypeParam m(123, alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountAlloc) {
+  BucketCountAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+template <typename TypeParam>
+void BucketCountHashAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void BucketCountHashAllocTest(std::true_type) {
+  using H = typename TypeParam::hasher;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  A alloc(0);
+  TypeParam m(123, hasher, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, BucketCountHashAlloc) {
+  BucketCountHashAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+#if ABSL_UNORDERED_SUPPORTS_ALLOC_CTORS
+using has_alloc_std_constructors = std::true_type;
+#else
+using has_alloc_std_constructors = std::false_type;
+#endif
+
+template <typename T>
+using expect_alloc_constructors =
+    absl::disjunction<absl::negation<is_std_unordered_set<T>>,
+                      has_alloc_std_constructors>;
+
+template <typename TypeParam>
+void AllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void AllocTest(std::true_type) {
+  using A = typename TypeParam::allocator_type;
+  A alloc(0);
+  TypeParam m(alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_TRUE(m.empty());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+}
+
+TYPED_TEST_P(ConstructorTest, Alloc) {
+  AllocTest<TypeParam>(expect_alloc_constructors<TypeParam>());
+}
+
+TYPED_TEST_P(ConstructorTest, InputIteratorBucketHashEqualAlloc) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  std::vector<T> values;
+  for (size_t i = 0; i != 10; ++i)
+    values.push_back(hash_internal::Generator<T>()());
+  TypeParam m(values.begin(), values.end(), 123, hasher, equal, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+template <typename TypeParam>
+void InputIteratorBucketAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InputIteratorBucketAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using A = typename TypeParam::allocator_type;
+  A alloc(0);
+  std::vector<T> values;
+  for (size_t i = 0; i != 10; ++i)
+    values.push_back(hash_internal::Generator<T>()());
+  TypeParam m(values.begin(), values.end(), 123, alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InputIteratorBucketAlloc) {
+  InputIteratorBucketAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+template <typename TypeParam>
+void InputIteratorBucketHashAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InputIteratorBucketHashAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  A alloc(0);
+  std::vector<T> values;
+  for (size_t i = 0; i != 10; ++i)
+    values.push_back(hash_internal::Generator<T>()());
+  TypeParam m(values.begin(), values.end(), 123, hasher, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InputIteratorBucketHashAlloc) {
+  InputIteratorBucketHashAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+TYPED_TEST_P(ConstructorTest, CopyConstructor) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(hash_internal::Generator<T>()());
+  TypeParam n(m);
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+  EXPECT_NE(TypeParam(0, hasher, equal, alloc), n);
+}
+
+template <typename TypeParam>
+void CopyConstructorAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void CopyConstructorAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(hash_internal::Generator<T>()());
+  TypeParam n(m, A(11));
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_NE(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, CopyConstructorAlloc) {
+  CopyConstructorAllocTest<TypeParam>(expect_alloc_constructors<TypeParam>());
+}
+
+// TODO(alkis): Test non-propagating allocators on copy constructors.
+
+TYPED_TEST_P(ConstructorTest, MoveConstructor) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(hash_internal::Generator<T>()());
+  TypeParam t(m);
+  TypeParam n(std::move(t));
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+template <typename TypeParam>
+void MoveConstructorAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void MoveConstructorAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(123, hasher, equal, alloc);
+  for (size_t i = 0; i != 10; ++i) m.insert(hash_internal::Generator<T>()());
+  TypeParam t(m);
+  TypeParam n(std::move(t), A(1));
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_NE(m.get_allocator(), n.get_allocator());
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, MoveConstructorAlloc) {
+  MoveConstructorAllocTest<TypeParam>(expect_alloc_constructors<TypeParam>());
+}
+
+// TODO(alkis): Test non-propagating allocators on move constructors.
+
+TYPED_TEST_P(ConstructorTest, InitializerListBucketHashEqualAlloc) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::Generator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  TypeParam m(values, 123, hasher, equal, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.key_eq(), equal);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+template <typename TypeParam>
+void InitializerListBucketAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InitializerListBucketAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using A = typename TypeParam::allocator_type;
+  hash_internal::Generator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  A alloc(0);
+  TypeParam m(values, 123, alloc);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InitializerListBucketAlloc) {
+  InitializerListBucketAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+template <typename TypeParam>
+void InitializerListBucketHashAllocTest(std::false_type) {}
+
+template <typename TypeParam>
+void InitializerListBucketHashAllocTest(std::true_type) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  A alloc(0);
+  hash_internal::Generator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m(values, 123, hasher, alloc);
+  EXPECT_EQ(m.hash_function(), hasher);
+  EXPECT_EQ(m.get_allocator(), alloc);
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_GE(m.bucket_count(), 123);
+}
+
+TYPED_TEST_P(ConstructorTest, InitializerListBucketHashAlloc) {
+  InitializerListBucketHashAllocTest<TypeParam>(expect_cxx14_apis<TypeParam>());
+}
+
+TYPED_TEST_P(ConstructorTest, CopyAssignment) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::Generator<T> gen;
+  TypeParam m({gen(), gen(), gen()}, 123, hasher, equal, alloc);
+  TypeParam n;
+  n = m;
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m, n);
+}
+
+// TODO(alkis): Test [non-]propagating allocators on move/copy assignments
+// (it depends on traits).
+
+TYPED_TEST_P(ConstructorTest, MoveAssignment) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using H = typename TypeParam::hasher;
+  using E = typename TypeParam::key_equal;
+  using A = typename TypeParam::allocator_type;
+  H hasher;
+  E equal;
+  A alloc(0);
+  hash_internal::Generator<T> gen;
+  TypeParam m({gen(), gen(), gen()}, 123, hasher, equal, alloc);
+  TypeParam t(m);
+  TypeParam n;
+  n = std::move(t);
+  EXPECT_EQ(m.hash_function(), n.hash_function());
+  EXPECT_EQ(m.key_eq(), n.key_eq());
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentFromInitializerList) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::Generator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m;
+  m = values;
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentOverwritesExisting) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::Generator<T> gen;
+  TypeParam m({gen(), gen(), gen()});
+  TypeParam n({gen()});
+  n = m;
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, MoveAssignmentOverwritesExisting) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::Generator<T> gen;
+  TypeParam m({gen(), gen(), gen()});
+  TypeParam t(m);
+  TypeParam n({gen()});
+  n = std::move(t);
+  EXPECT_EQ(m, n);
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentFromInitializerListOverwritesExisting) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::Generator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m;
+  m = values;
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+TYPED_TEST_P(ConstructorTest, AssignmentOnSelf) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  hash_internal::Generator<T> gen;
+  std::initializer_list<T> values = {gen(), gen(), gen(), gen(), gen()};
+  TypeParam m(values);
+  m = *&m;  // Avoid -Wself-assign.
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(
+    ConstructorTest, NoArgs, BucketCount, BucketCountHash, BucketCountHashEqual,
+    BucketCountHashEqualAlloc, BucketCountAlloc, BucketCountHashAlloc, Alloc,
+    InputIteratorBucketHashEqualAlloc, InputIteratorBucketAlloc,
+    InputIteratorBucketHashAlloc, CopyConstructor, CopyConstructorAlloc,
+    MoveConstructor, MoveConstructorAlloc, InitializerListBucketHashEqualAlloc,
+    InitializerListBucketAlloc, InitializerListBucketHashAlloc, CopyAssignment,
+    MoveAssignment, AssignmentFromInitializerList, AssignmentOverwritesExisting,
+    MoveAssignmentOverwritesExisting,
+    AssignmentFromInitializerListOverwritesExisting, AssignmentOnSelf);
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_CONSTRUCTOR_TEST_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_lookup_test.h b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_lookup_test.h
new file mode 100644
index 0000000000000000000000000000000000000000..b35f766e794831a19eec05e5f0fb764fea50c40f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_lookup_test.h
@@ -0,0 +1,91 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CONTAINER_INTERNAL_UNORDERED_SET_LOOKUP_TEST_H_
+#define ABSL_CONTAINER_INTERNAL_UNORDERED_SET_LOOKUP_TEST_H_
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/hash_generator_testing.h"
+#include "absl/container/internal/hash_policy_testing.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+template <class UnordSet>
+class LookupTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE_P(LookupTest);
+
+TYPED_TEST_P(LookupTest, Count) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m;
+  for (const auto& v : values)
+    EXPECT_EQ(0, m.count(v)) << ::testing::PrintToString(v);
+  m.insert(values.begin(), values.end());
+  for (const auto& v : values)
+    EXPECT_EQ(1, m.count(v)) << ::testing::PrintToString(v);
+}
+
+TYPED_TEST_P(LookupTest, Find) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m;
+  for (const auto& v : values)
+    EXPECT_TRUE(m.end() == m.find(v)) << ::testing::PrintToString(v);
+  m.insert(values.begin(), values.end());
+  for (const auto& v : values) {
+    typename TypeParam::iterator it = m.find(v);
+    static_assert(std::is_same<const typename TypeParam::value_type&,
+                               decltype(*it)>::value,
+                  "");
+    static_assert(std::is_same<const typename TypeParam::value_type*,
+                               decltype(it.operator->())>::value,
+                  "");
+    EXPECT_TRUE(m.end() != it) << ::testing::PrintToString(v);
+    EXPECT_EQ(v, *it) << ::testing::PrintToString(v);
+  }
+}
+
+TYPED_TEST_P(LookupTest, EqualRange) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m;
+  for (const auto& v : values) {
+    auto r = m.equal_range(v);
+    ASSERT_EQ(0, std::distance(r.first, r.second));
+  }
+  m.insert(values.begin(), values.end());
+  for (const auto& v : values) {
+    auto r = m.equal_range(v);
+    ASSERT_EQ(1, std::distance(r.first, r.second));
+    EXPECT_EQ(v, *r.first);
+  }
+}
+
+REGISTER_TYPED_TEST_SUITE_P(LookupTest, Count, Find, EqualRange);
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_LOOKUP_TEST_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_modifiers_test.h b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_modifiers_test.h
new file mode 100644
index 0000000000000000000000000000000000000000..d8864bb28e067cdf8f147046a69466a7d8fcd9c8
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_modifiers_test.h
@@ -0,0 +1,221 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CONTAINER_INTERNAL_UNORDERED_SET_MODIFIERS_TEST_H_
+#define ABSL_CONTAINER_INTERNAL_UNORDERED_SET_MODIFIERS_TEST_H_
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/hash_generator_testing.h"
+#include "absl/container/internal/hash_policy_testing.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+
+template <class UnordSet>
+class ModifiersTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE_P(ModifiersTest);
+
+TYPED_TEST_P(ModifiersTest, Clear) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m(values.begin(), values.end());
+  ASSERT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  m.clear();
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_TRUE(m.empty());
+}
+
+TYPED_TEST_P(ModifiersTest, Insert) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  T val = hash_internal::Generator<T>()();
+  TypeParam m;
+  auto p = m.insert(val);
+  EXPECT_TRUE(p.second);
+  EXPECT_EQ(val, *p.first);
+  p = m.insert(val);
+  EXPECT_FALSE(p.second);
+}
+
+TYPED_TEST_P(ModifiersTest, InsertHint) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  T val = hash_internal::Generator<T>()();
+  TypeParam m;
+  auto it = m.insert(m.end(), val);
+  EXPECT_TRUE(it != m.end());
+  EXPECT_EQ(val, *it);
+  it = m.insert(it, val);
+  EXPECT_TRUE(it != m.end());
+  EXPECT_EQ(val, *it);
+}
+
+TYPED_TEST_P(ModifiersTest, InsertRange) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m;
+  m.insert(values.begin(), values.end());
+  ASSERT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+}
+
+TYPED_TEST_P(ModifiersTest, InsertWithinCapacity) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  T val = hash_internal::Generator<T>()();
+  TypeParam m;
+  m.reserve(10);
+  const size_t original_capacity = m.bucket_count();
+  m.insert(val);
+  EXPECT_EQ(m.bucket_count(), original_capacity);
+  m.insert(val);
+  EXPECT_EQ(m.bucket_count(), original_capacity);
+}
+
+TYPED_TEST_P(ModifiersTest, InsertRangeWithinCapacity) {
+#if !defined(__GLIBCXX__)
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> base_values;
+  std::generate_n(std::back_inserter(base_values), 10,
+                  hash_internal::Generator<T>());
+  std::vector<T> values;
+  while (values.size() != 100) {
+    values.insert(values.end(), base_values.begin(), base_values.end());
+  }
+  TypeParam m;
+  m.reserve(10);
+  const size_t original_capacity = m.bucket_count();
+  m.insert(values.begin(), values.end());
+  EXPECT_EQ(m.bucket_count(), original_capacity);
+#endif
+}
+
+TYPED_TEST_P(ModifiersTest, Emplace) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  T val = hash_internal::Generator<T>()();
+  TypeParam m;
+  // TODO(alkis): We need a way to run emplace in a more meaningful way. Perhaps
+  // with test traits/policy.
+  auto p = m.emplace(val);
+  EXPECT_TRUE(p.second);
+  EXPECT_EQ(val, *p.first);
+  p = m.emplace(val);
+  EXPECT_FALSE(p.second);
+  EXPECT_EQ(val, *p.first);
+}
+
+TYPED_TEST_P(ModifiersTest, EmplaceHint) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  T val = hash_internal::Generator<T>()();
+  TypeParam m;
+  // TODO(alkis): We need a way to run emplace in a more meaningful way. Perhaps
+  // with test traits/policy.
+  auto it = m.emplace_hint(m.end(), val);
+  EXPECT_EQ(val, *it);
+  it = m.emplace_hint(it, val);
+  EXPECT_EQ(val, *it);
+}
+
+template <class V>
+using IfNotVoid = typename std::enable_if<!std::is_void<V>::value, V>::type;
+
+// In openmap we chose not to return the iterator from erase because that's
+// more expensive. As such we adapt erase to return an iterator here.
+struct EraseFirst {
+  template <class Map>
+  auto operator()(Map* m, int) const
+      -> IfNotVoid<decltype(m->erase(m->begin()))> {
+    return m->erase(m->begin());
+  }
+  template <class Map>
+  typename Map::iterator operator()(Map* m, ...) const {
+    auto it = m->begin();
+    m->erase(it++);
+    return it;
+  }
+};
+
+TYPED_TEST_P(ModifiersTest, Erase) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m(values.begin(), values.end());
+  ASSERT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  std::vector<T> values2;
+  for (const auto& val : values)
+    if (val != *m.begin()) values2.push_back(val);
+  auto it = EraseFirst()(&m, 0);
+  ASSERT_TRUE(it != m.end());
+  EXPECT_EQ(1, std::count(values2.begin(), values2.end(), *it));
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values2.begin(),
+                                                            values2.end()));
+}
+
+TYPED_TEST_P(ModifiersTest, EraseRange) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m(values.begin(), values.end());
+  ASSERT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  auto it = m.erase(m.begin(), m.end());
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAre());
+  EXPECT_TRUE(it == m.end());
+}
+
+TYPED_TEST_P(ModifiersTest, EraseKey) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> values;
+  std::generate_n(std::back_inserter(values), 10,
+                  hash_internal::Generator<T>());
+  TypeParam m(values.begin(), values.end());
+  ASSERT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values));
+  EXPECT_EQ(1, m.erase(values[0]));
+  EXPECT_EQ(0, std::count(m.begin(), m.end(), values[0]));
+  EXPECT_THAT(keys(m), ::testing::UnorderedElementsAreArray(values.begin() + 1,
+                                                            values.end()));
+}
+
+TYPED_TEST_P(ModifiersTest, Swap) {
+  using T = hash_internal::GeneratedType<TypeParam>;
+  std::vector<T> v1;
+  std::vector<T> v2;
+  std::generate_n(std::back_inserter(v1), 5, hash_internal::Generator<T>());
+  std::generate_n(std::back_inserter(v2), 5, hash_internal::Generator<T>());
+  TypeParam m1(v1.begin(), v1.end());
+  TypeParam m2(v2.begin(), v2.end());
+  EXPECT_THAT(keys(m1), ::testing::UnorderedElementsAreArray(v1));
+  EXPECT_THAT(keys(m2), ::testing::UnorderedElementsAreArray(v2));
+  m1.swap(m2);
+  EXPECT_THAT(keys(m1), ::testing::UnorderedElementsAreArray(v2));
+  EXPECT_THAT(keys(m2), ::testing::UnorderedElementsAreArray(v1));
+}
+
+// TODO(alkis): Write tests for extract.
+// TODO(alkis): Write tests for merge.
+
+REGISTER_TYPED_TEST_SUITE_P(ModifiersTest, Clear, Insert, InsertHint,
+                            InsertRange, InsertWithinCapacity,
+                            InsertRangeWithinCapacity, Emplace, EmplaceHint,
+                            Erase, EraseRange, EraseKey, Swap);
+
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CONTAINER_INTERNAL_UNORDERED_SET_MODIFIERS_TEST_H_
diff --git a/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_test.cc b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a134b53984bce94e385391f6e04ec8c977736a15
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/container/internal/unordered_set_test.cc
@@ -0,0 +1,41 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <unordered_set>
+
+#include "absl/container/internal/unordered_set_constructor_test.h"
+#include "absl/container/internal/unordered_set_lookup_test.h"
+#include "absl/container/internal/unordered_set_members_test.h"
+#include "absl/container/internal/unordered_set_modifiers_test.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace container_internal {
+namespace {
+
+using SetTypes = ::testing::Types<
+    std::unordered_set<int, StatefulTestingHash, StatefulTestingEqual,
+                       Alloc<int>>,
+    std::unordered_set<std::string, StatefulTestingHash, StatefulTestingEqual,
+                       Alloc<std::string>>>;
+
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedSet, ConstructorTest, SetTypes);
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedSet, LookupTest, SetTypes);
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedSet, MembersTest, SetTypes);
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedSet, ModifiersTest, SetTypes);
+
+}  // namespace
+}  // namespace container_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/crc/crc32c.h b/weight/_dep/abseil-cpp/absl/crc/crc32c.h
new file mode 100644
index 0000000000000000000000000000000000000000..362861e4a6dab925080d125dd9c42861bd7c3ca4
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/crc32c.h
@@ -0,0 +1,190 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: crc32c.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the API for computing CRC32C values as checksums
+// for arbitrary sequences of bytes provided as a string buffer.
+//
+// The API includes the basic functions for computing such CRC32C values and
+// some utility functions for performing more efficient mathematical
+// computations using an existing checksum.
+#ifndef ABSL_CRC_CRC32C_H_
+#define ABSL_CRC_CRC32C_H_
+
+#include <cstdint>
+#include <ostream>
+
+#include "absl/crc/internal/crc32c_inline.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+//-----------------------------------------------------------------------------
+// crc32c_t
+//-----------------------------------------------------------------------------
+
+// `crc32c_t` defines a strongly-typed integer for holding a CRC32C value.
+//
+// Some operators are intentionally omitted. Only equality operators are defined
+// so that `crc32c_t` can be directly compared. Methods for putting `crc32c_t`
+// directly into a set are omitted because this is bug-prone due to checksum
+// collisions. Use an explicit conversion to the `uint32_t` space for operations
+// that treat `crc32c_t` as an integer.
+class crc32c_t final {
+ public:
+  crc32c_t() = default;
+  constexpr explicit crc32c_t(uint32_t crc) : crc_(crc) {}
+
+  crc32c_t(const crc32c_t&) = default;
+  crc32c_t& operator=(const crc32c_t&) = default;
+
+  explicit operator uint32_t() const { return crc_; }
+
+  friend bool operator==(crc32c_t lhs, crc32c_t rhs) {
+    return static_cast<uint32_t>(lhs) == static_cast<uint32_t>(rhs);
+  }
+
+  friend bool operator!=(crc32c_t lhs, crc32c_t rhs) { return !(lhs == rhs); }
+
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, crc32c_t crc) {
+    absl::Format(&sink, "%08x", static_cast<uint32_t>(crc));
+  }
+
+ private:
+  uint32_t crc_;
+};
+
+
+namespace crc_internal {
+// Non-inline code path for `absl::ExtendCrc32c()`. Do not call directly.
+// Call `absl::ExtendCrc32c()` (defined below) instead.
+crc32c_t ExtendCrc32cInternal(crc32c_t initial_crc,
+                              absl::string_view buf_to_add);
+}  // namespace crc_internal
+
+// -----------------------------------------------------------------------------
+// CRC32C Computation Functions
+// -----------------------------------------------------------------------------
+
+// ComputeCrc32c()
+//
+// Returns the CRC32C value of the provided string.
+crc32c_t ComputeCrc32c(absl::string_view buf);
+
+// ExtendCrc32c()
+//
+// Computes a CRC32C value from an `initial_crc` CRC32C value including the
+// `buf_to_add` bytes of an additional buffer. Using this function is more
+// efficient than computing a CRC32C value for the combined buffer from
+// scratch.
+//
+// Note: `ExtendCrc32c` with an initial_crc of 0 is equivalent to
+// `ComputeCrc32c`.
+//
+// This operation has a runtime cost of O(`buf_to_add.size()`)
+inline crc32c_t ExtendCrc32c(crc32c_t initial_crc,
+                             absl::string_view buf_to_add) {
+  // Approximately 75% of calls have size <= 64.
+  if (buf_to_add.size() <= 64) {
+    uint32_t crc = static_cast<uint32_t>(initial_crc);
+    if (crc_internal::ExtendCrc32cInline(&crc, buf_to_add.data(),
+                                         buf_to_add.size())) {
+      return crc32c_t{crc};
+    }
+  }
+  return crc_internal::ExtendCrc32cInternal(initial_crc, buf_to_add);
+}
+
+// ExtendCrc32cByZeroes()
+//
+// Computes a CRC32C value for a buffer with an `initial_crc` CRC32C value,
+// where `length` bytes with a value of 0 are appended to the buffer. Using this
+// function is more efficient than computing a CRC32C value for the combined
+// buffer from scratch.
+//
+// This operation has a runtime cost of O(log(`length`))
+crc32c_t ExtendCrc32cByZeroes(crc32c_t initial_crc, size_t length);
+
+// MemcpyCrc32c()
+//
+// Copies `src` to `dest` using `memcpy()` semantics, returning the CRC32C
+// value of the copied buffer.
+//
+// Using `MemcpyCrc32c()` is potentially faster than performing the `memcpy()`
+// and `ComputeCrc32c()` operations separately.
+crc32c_t MemcpyCrc32c(void* dest, const void* src, size_t count,
+                      crc32c_t initial_crc = crc32c_t{0});
+
+// -----------------------------------------------------------------------------
+// CRC32C Arithmetic Functions
+// -----------------------------------------------------------------------------
+
+// The following functions perform arithmetic on CRC32C values, which are
+// generally more efficient than recalculating any given result's CRC32C value.
+
+// ConcatCrc32c()
+//
+// Calculates the CRC32C value of two buffers with known CRC32C values
+// concatenated together.
+//
+// Given a buffer with CRC32C value `crc1` and a buffer with
+// CRC32C value `crc2` and length, `crc2_length`, returns the CRC32C value of
+// the concatenation of these two buffers.
+//
+// This operation has a runtime cost of O(log(`crc2_length`)).
+crc32c_t ConcatCrc32c(crc32c_t crc1, crc32c_t crc2, size_t crc2_length);
+
+// RemoveCrc32cPrefix()
+//
+// Calculates the CRC32C value of an existing buffer with a series of bytes
+// (the prefix) removed from the beginning of that buffer.
+//
+// Given the CRC32C value of an existing buffer, `full_string_crc`; The CRC32C
+// value of a prefix of that buffer, `prefix_crc`; and the length of the buffer
+// with the prefix removed, `remaining_string_length` , return the CRC32C
+// value of the buffer with the prefix removed.
+//
+// This operation has a runtime cost of O(log(`remaining_string_length`)).
+crc32c_t RemoveCrc32cPrefix(crc32c_t prefix_crc, crc32c_t full_string_crc,
+                            size_t remaining_string_length);
+// RemoveCrc32cSuffix()
+//
+// Calculates the CRC32C value of an existing buffer with a series of bytes
+// (the suffix) removed from the end of that buffer.
+//
+// Given a CRC32C value of an existing buffer `full_string_crc`, the CRC32C
+// value of the suffix to remove `suffix_crc`, and the length of that suffix
+// `suffix_len`, returns the CRC32C value of the buffer with suffix removed.
+//
+// This operation has a runtime cost of O(log(`suffix_len`))
+crc32c_t RemoveCrc32cSuffix(crc32c_t full_string_crc, crc32c_t suffix_crc,
+                            size_t suffix_length);
+
+// operator<<
+//
+// Streams the CRC32C value `crc` to the stream `os`.
+inline std::ostream& operator<<(std::ostream& os, crc32c_t crc) {
+  return os << absl::StreamFormat("%08x", static_cast<uint32_t>(crc));
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CRC_CRC32C_H_
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc32c.h b/weight/_dep/abseil-cpp/absl/crc/internal/crc32c.h
new file mode 100644
index 0000000000000000000000000000000000000000..34027c55e42bfbdf7b619fae8ed6bde44ff7c7c1
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc32c.h
@@ -0,0 +1,39 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CRC_INTERNAL_CRC32C_H_
+#define ABSL_CRC_INTERNAL_CRC32C_H_
+
+#include "absl/base/config.h"
+#include "absl/crc/crc32c.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+// Modifies a CRC32 value by removing `length` bytes with a value of 0 from
+// the end of the string.
+//
+// This is the inverse operation of ExtendCrc32cByZeroes().
+//
+// This operation has a runtime cost of O(log(`length`))
+//
+// Internal implementation detail, exposed for testing only.
+crc32c_t UnextendCrc32cByZeroes(crc32c_t initial_crc, size_t length);
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CRC_INTERNAL_CRC32C_H_
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_cord_state.h b/weight/_dep/abseil-cpp/absl/crc/internal/crc_cord_state.h
new file mode 100644
index 0000000000000000000000000000000000000000..fbbb8c004c859cce70a026eaf06c2ff6cadef5fc
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_cord_state.h
@@ -0,0 +1,159 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CRC_INTERNAL_CRC_CORD_STATE_H_
+#define ABSL_CRC_INTERNAL_CRC_CORD_STATE_H_
+
+#include <atomic>
+#include <cstddef>
+#include <deque>
+
+#include "absl/base/config.h"
+#include "absl/crc/crc32c.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+// CrcCordState is a copy-on-write class that holds the chunked CRC32C data
+// that allows CrcCord to perform efficient substring operations. CrcCordState
+// is used as a member variable in CrcCord. When a CrcCord is converted to a
+// Cord, the CrcCordState is shallow-copied into the root node of the Cord. If
+// the converted Cord is modified outside of CrcCord, the CrcCordState is
+// discarded from the Cord. If the Cord is converted back to a CrcCord, and the
+// Cord is still carrying the CrcCordState in its root node, the CrcCord can
+// re-use the CrcCordState, making the construction of the CrcCord cheap.
+//
+// CrcCordState does not try to encapsulate the CRC32C state (CrcCord requires
+// knowledge of how CrcCordState represents the CRC32C state). It does
+// encapsulate the copy-on-write nature of the state.
+class CrcCordState {
+ public:
+  // Constructors.
+  CrcCordState();
+  CrcCordState(const CrcCordState&);
+  CrcCordState(CrcCordState&&);
+
+  // Destructor. Atomically unreferences the data.
+  ~CrcCordState();
+
+  // Copy and move operators.
+  CrcCordState& operator=(const CrcCordState&);
+  CrcCordState& operator=(CrcCordState&&);
+
+  // A (length, crc) pair.
+  struct PrefixCrc {
+    PrefixCrc() = default;
+    PrefixCrc(size_t length_arg, absl::crc32c_t crc_arg)
+        : length(length_arg), crc(crc_arg) {}
+
+    size_t length = 0;
+
+    // TODO(absl-team): Memory stomping often zeros out memory. If this struct
+    // gets overwritten, we could end up with {0, 0}, which is the correct CRC
+    // for a string of length 0. Consider storing a scrambled value and
+    // unscrambling it before verifying it.
+    absl::crc32c_t crc = absl::crc32c_t{0};
+  };
+
+  // The representation of the chunked CRC32C data.
+  struct Rep {
+    // `removed_prefix` is the crc and length of any prefix that has been
+    // removed from the Cord (for example, by calling
+    // `CrcCord::RemovePrefix()`). To get the checksum of any prefix of the
+    // cord, this value must be subtracted from `prefix_crc`. See `Checksum()`
+    // for an example.
+    //
+    // CrcCordState is said to be "normalized" if removed_prefix.length == 0.
+    PrefixCrc removed_prefix;
+
+    // A deque of (length, crc) pairs, representing length and crc of a prefix
+    // of the Cord, before removed_prefix has been subtracted. The lengths of
+    // the prefixes are stored in increasing order. If the Cord is not empty,
+    // the last value in deque is the contains the CRC32C of the entire Cord
+    // when removed_prefix is subtracted from it.
+    std::deque<PrefixCrc> prefix_crc;
+  };
+
+  // Returns a reference to the representation of the chunked CRC32C data.
+  const Rep& rep() const { return refcounted_rep_->rep; }
+
+  // Returns a mutable reference to the representation of the chunked CRC32C
+  // data. Calling this function will copy the data if another instance also
+  // holds a reference to the data, so it is important to call rep() instead if
+  // the data may not be mutated.
+  Rep* mutable_rep() {
+    if (refcounted_rep_->count.load(std::memory_order_acquire) != 1) {
+      RefcountedRep* copy = new RefcountedRep;
+      copy->rep = refcounted_rep_->rep;
+      Unref(refcounted_rep_);
+      refcounted_rep_ = copy;
+    }
+    return &refcounted_rep_->rep;
+  }
+
+  // Returns the CRC32C of the entire Cord.
+  absl::crc32c_t Checksum() const;
+
+  // Returns true if the chunked CRC32C cached is normalized.
+  bool IsNormalized() const { return rep().removed_prefix.length == 0; }
+
+  // Normalizes the chunked CRC32C checksum cache by subtracting any removed
+  // prefix from the chunks.
+  void Normalize();
+
+  // Returns the number of cached chunks.
+  size_t NumChunks() const { return rep().prefix_crc.size(); }
+
+  // Helper that returns the (length, crc) of the `n`-th cached chunked.
+  PrefixCrc NormalizedPrefixCrcAtNthChunk(size_t n) const;
+
+  // Poisons all chunks to so that Checksum() will likely be incorrect with high
+  // probability.
+  void Poison();
+
+ private:
+  struct RefcountedRep {
+    std::atomic<int32_t> count{1};
+    Rep rep;
+  };
+
+  // Adds a reference to the shared global empty `RefcountedRep`, and returns a
+  // pointer to the `RefcountedRep`. This is an optimization to avoid unneeded
+  // allocations when the allocation is unlikely to ever be used. The returned
+  // pointer can be `Unref()`ed when it is no longer needed.  Since the returned
+  // instance will always have a reference counter greater than 1, attempts to
+  // modify it (by calling `mutable_rep()`) will create a new unshared copy.
+  static RefcountedRep* RefSharedEmptyRep();
+
+  static void Ref(RefcountedRep* r) {
+    assert(r != nullptr);
+    r->count.fetch_add(1, std::memory_order_relaxed);
+  }
+
+  static void Unref(RefcountedRep* r) {
+    assert(r != nullptr);
+    if (r->count.fetch_sub(1, std::memory_order_acq_rel) == 1) {
+      delete r;
+    }
+  }
+
+  RefcountedRep* refcounted_rep_;
+};
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CRC_INTERNAL_CRC_CORD_STATE_H_
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_cord_state_test.cc b/weight/_dep/abseil-cpp/absl/crc/internal/crc_cord_state_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e2c8e3cda131f975d6c514218d142d9ccc7ae457
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_cord_state_test.cc
@@ -0,0 +1,124 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/crc/internal/crc_cord_state.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <string>
+#include <utility>
+
+#include "gtest/gtest.h"
+#include "absl/crc/crc32c.h"
+
+namespace {
+
+TEST(CrcCordState, Default) {
+  absl::crc_internal::CrcCordState state;
+  EXPECT_TRUE(state.IsNormalized());
+  EXPECT_EQ(state.Checksum(), absl::crc32c_t{0});
+  state.Normalize();
+  EXPECT_EQ(state.Checksum(), absl::crc32c_t{0});
+}
+
+TEST(CrcCordState, Normalize) {
+  absl::crc_internal::CrcCordState state;
+  auto* rep = state.mutable_rep();
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(1000, absl::crc32c_t{1000}));
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(2000, absl::crc32c_t{2000}));
+  rep->removed_prefix =
+      absl::crc_internal::CrcCordState::PrefixCrc(500, absl::crc32c_t{500});
+
+  // The removed_prefix means state is not normalized.
+  EXPECT_FALSE(state.IsNormalized());
+
+  absl::crc32c_t crc = state.Checksum();
+  state.Normalize();
+  EXPECT_TRUE(state.IsNormalized());
+
+  // The checksum should not change as a result of calling Normalize().
+  EXPECT_EQ(state.Checksum(), crc);
+  EXPECT_EQ(rep->removed_prefix.length, 0);
+}
+
+TEST(CrcCordState, Copy) {
+  absl::crc_internal::CrcCordState state;
+  auto* rep = state.mutable_rep();
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(1000, absl::crc32c_t{1000}));
+
+  absl::crc_internal::CrcCordState copy = state;
+
+  EXPECT_EQ(state.Checksum(), absl::crc32c_t{1000});
+  EXPECT_EQ(copy.Checksum(), absl::crc32c_t{1000});
+}
+
+TEST(CrcCordState, UnsharedSelfCopy) {
+  absl::crc_internal::CrcCordState state;
+  auto* rep = state.mutable_rep();
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(1000, absl::crc32c_t{1000}));
+
+  const absl::crc_internal::CrcCordState& ref = state;
+  state = ref;
+
+  EXPECT_EQ(state.Checksum(), absl::crc32c_t{1000});
+}
+
+TEST(CrcCordState, Move) {
+  absl::crc_internal::CrcCordState state;
+  auto* rep = state.mutable_rep();
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(1000, absl::crc32c_t{1000}));
+
+  absl::crc_internal::CrcCordState moved = std::move(state);
+  EXPECT_EQ(moved.Checksum(), absl::crc32c_t{1000});
+}
+
+TEST(CrcCordState, UnsharedSelfMove) {
+  absl::crc_internal::CrcCordState state;
+  auto* rep = state.mutable_rep();
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(1000, absl::crc32c_t{1000}));
+
+  absl::crc_internal::CrcCordState& ref = state;
+  state = std::move(ref);
+
+  EXPECT_EQ(state.Checksum(), absl::crc32c_t{1000});
+}
+
+TEST(CrcCordState, PoisonDefault) {
+  absl::crc_internal::CrcCordState state;
+  state.Poison();
+  EXPECT_NE(state.Checksum(), absl::crc32c_t{0});
+}
+
+TEST(CrcCordState, PoisonData) {
+  absl::crc_internal::CrcCordState state;
+  auto* rep = state.mutable_rep();
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(1000, absl::crc32c_t{1000}));
+  rep->prefix_crc.push_back(
+      absl::crc_internal::CrcCordState::PrefixCrc(2000, absl::crc32c_t{2000}));
+  rep->removed_prefix =
+      absl::crc_internal::CrcCordState::PrefixCrc(500, absl::crc32c_t{500});
+
+  absl::crc32c_t crc = state.Checksum();
+  state.Poison();
+  EXPECT_NE(state.Checksum(), crc);
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy.h b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy.h
new file mode 100644
index 0000000000000000000000000000000000000000..a0fed65afa2c2c29c57b0c6a76d34355d2aa8b86
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy.h
@@ -0,0 +1,122 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CRC_INTERNAL_CRC_MEMCPY_H_
+#define ABSL_CRC_INTERNAL_CRC_MEMCPY_H_
+
+#include <cstddef>
+#include <memory>
+
+#include "absl/base/config.h"
+#include "absl/crc/crc32c.h"
+#include "absl/crc/internal/crc32_x86_arm_combined_simd.h"
+
+// Defined if the class AcceleratedCrcMemcpyEngine exists.
+// TODO(b/299127771): Consider relaxing the pclmul requirement once the other
+// intrinsics are conditionally compiled without it.
+#if defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD)
+#define ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE 1
+#elif defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD)
+#define ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE 1
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+class CrcMemcpyEngine {
+ public:
+  virtual ~CrcMemcpyEngine() = default;
+
+  virtual crc32c_t Compute(void* __restrict dst, const void* __restrict src,
+                           std::size_t length, crc32c_t initial_crc) const = 0;
+
+ protected:
+  CrcMemcpyEngine() = default;
+};
+
+class CrcMemcpy {
+ public:
+  static crc32c_t CrcAndCopy(void* __restrict dst, const void* __restrict src,
+                             std::size_t length,
+                             crc32c_t initial_crc = crc32c_t{0},
+                             bool non_temporal = false) {
+    static const ArchSpecificEngines engines = GetArchSpecificEngines();
+    auto* engine = non_temporal ? engines.non_temporal : engines.temporal;
+    return engine->Compute(dst, src, length, initial_crc);
+  }
+
+  // For testing only: get an architecture-specific engine for tests.
+  static std::unique_ptr<CrcMemcpyEngine> GetTestEngine(int vector,
+                                                        int integer);
+
+ private:
+  struct ArchSpecificEngines {
+    CrcMemcpyEngine* temporal;
+    CrcMemcpyEngine* non_temporal;
+  };
+
+  static ArchSpecificEngines GetArchSpecificEngines();
+};
+
+// Fallback CRC-memcpy engine.
+class FallbackCrcMemcpyEngine : public CrcMemcpyEngine {
+ public:
+  FallbackCrcMemcpyEngine() = default;
+  FallbackCrcMemcpyEngine(const FallbackCrcMemcpyEngine&) = delete;
+  FallbackCrcMemcpyEngine operator=(const FallbackCrcMemcpyEngine&) = delete;
+
+  crc32c_t Compute(void* __restrict dst, const void* __restrict src,
+                   std::size_t length, crc32c_t initial_crc) const override;
+};
+
+// CRC Non-Temporal-Memcpy engine.
+class CrcNonTemporalMemcpyEngine : public CrcMemcpyEngine {
+ public:
+  CrcNonTemporalMemcpyEngine() = default;
+  CrcNonTemporalMemcpyEngine(const CrcNonTemporalMemcpyEngine&) = delete;
+  CrcNonTemporalMemcpyEngine operator=(const CrcNonTemporalMemcpyEngine&) =
+      delete;
+
+  crc32c_t Compute(void* __restrict dst, const void* __restrict src,
+                   std::size_t length, crc32c_t initial_crc) const override;
+};
+
+// CRC Non-Temporal-Memcpy AVX engine.
+class CrcNonTemporalMemcpyAVXEngine : public CrcMemcpyEngine {
+ public:
+  CrcNonTemporalMemcpyAVXEngine() = default;
+  CrcNonTemporalMemcpyAVXEngine(const CrcNonTemporalMemcpyAVXEngine&) = delete;
+  CrcNonTemporalMemcpyAVXEngine operator=(
+      const CrcNonTemporalMemcpyAVXEngine&) = delete;
+
+  crc32c_t Compute(void* __restrict dst, const void* __restrict src,
+                   std::size_t length, crc32c_t initial_crc) const override;
+};
+
+// Copy source to destination and return the CRC32C of the data copied.  If an
+// accelerated version is available, use the accelerated version, otherwise use
+// the generic fallback version.
+inline crc32c_t Crc32CAndCopy(void* __restrict dst, const void* __restrict src,
+                              std::size_t length,
+                              crc32c_t initial_crc = crc32c_t{0},
+                              bool non_temporal = false) {
+  return CrcMemcpy::CrcAndCopy(dst, src, length, initial_crc, non_temporal);
+}
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CRC_INTERNAL_CRC_MEMCPY_H_
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_fallback.cc b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_fallback.cc
new file mode 100644
index 0000000000000000000000000000000000000000..07795504e398a3966925fccd38ccceaa406844d1
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_fallback.cc
@@ -0,0 +1,77 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdint>
+#include <memory>
+
+#include "absl/base/config.h"
+#include "absl/crc/crc32c.h"
+#include "absl/crc/internal/crc_memcpy.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+absl::crc32c_t FallbackCrcMemcpyEngine::Compute(void* __restrict dst,
+                                                const void* __restrict src,
+                                                std::size_t length,
+                                                crc32c_t initial_crc) const {
+  constexpr size_t kBlockSize = 8192;
+  absl::crc32c_t crc = initial_crc;
+
+  const char* src_bytes = reinterpret_cast<const char*>(src);
+  char* dst_bytes = reinterpret_cast<char*>(dst);
+
+  // Copy + CRC loop - run 8k chunks until we are out of full chunks.  CRC
+  // then copy was found to be slightly more efficient in our test cases.
+  std::size_t offset = 0;
+  for (; offset + kBlockSize < length; offset += kBlockSize) {
+    crc = absl::ExtendCrc32c(crc,
+                             absl::string_view(src_bytes + offset, kBlockSize));
+    memcpy(dst_bytes + offset, src_bytes + offset, kBlockSize);
+  }
+
+  // Save some work if length is 0.
+  if (offset < length) {
+    std::size_t final_copy_size = length - offset;
+    crc = absl::ExtendCrc32c(
+        crc, absl::string_view(src_bytes + offset, final_copy_size));
+    memcpy(dst_bytes + offset, src_bytes + offset, final_copy_size);
+  }
+
+  return crc;
+}
+
+// Compile the following only if we don't have
+#if !defined(ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE) && \
+    !defined(ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE)
+
+CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
+  CrcMemcpy::ArchSpecificEngines engines;
+  engines.temporal = new FallbackCrcMemcpyEngine();
+  engines.non_temporal = new FallbackCrcMemcpyEngine();
+  return engines;
+}
+
+std::unique_ptr<CrcMemcpyEngine> CrcMemcpy::GetTestEngine(int /*vector*/,
+                                                          int /*integer*/) {
+  return std::make_unique<FallbackCrcMemcpyEngine>();
+}
+
+#endif  // !ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE &&
+        // !ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_test.cc b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..045a1e5e189bc66a935a96e75d5526b27ec397f1
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_test.cc
@@ -0,0 +1,177 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/crc/internal/crc_memcpy.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <limits>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "gtest/gtest.h"
+#include "absl/crc/crc32c.h"
+#include "absl/memory/memory.h"
+#include "absl/random/distributions.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+namespace {
+
+enum CrcEngine {
+  ACCELERATED = 0,
+  NONTEMPORAL = 1,
+  FALLBACK = 2,
+};
+
+// Correctness tests:
+// - Every source/destination byte alignment 0-15, every size 0-511 bytes
+// - Arbitrarily aligned source, large size
+template <size_t max_size>
+class CrcMemcpyTest : public testing::Test {
+ protected:
+  CrcMemcpyTest() {
+    source_ = std::make_unique<char[]>(kSize);
+    destination_ = std::make_unique<char[]>(kSize);
+  }
+  static constexpr size_t kAlignment = 16;
+  static constexpr size_t kMaxCopySize = max_size;
+  static constexpr size_t kSize = kAlignment + kMaxCopySize;
+  std::unique_ptr<char[]> source_;
+  std::unique_ptr<char[]> destination_;
+
+  absl::BitGen gen_;
+};
+
+// Small test is slightly larger 4096 bytes to allow coverage of the "large"
+// copy function.  The minimum size to exercise all code paths in that function
+// would be around 256 consecutive tests (getting every possible tail value
+// and 0-2 small copy loops after the main block), so testing from 4096-4500
+// will cover all of those code paths multiple times.
+typedef CrcMemcpyTest<4500> CrcSmallTest;
+typedef CrcMemcpyTest<(1 << 24)> CrcLargeTest;
+// Parametrize the small test so that it can be done with all configurations.
+template <typename ParamsT>
+class EngineParamTestTemplate : public CrcSmallTest,
+                                public ::testing::WithParamInterface<ParamsT> {
+ protected:
+  EngineParamTestTemplate() {
+    if (GetParam().crc_engine_selector == FALLBACK) {
+      engine_ = std::make_unique<absl::crc_internal::FallbackCrcMemcpyEngine>();
+    } else if (GetParam().crc_engine_selector == NONTEMPORAL) {
+      engine_ =
+          std::make_unique<absl::crc_internal::CrcNonTemporalMemcpyEngine>();
+    } else {
+      engine_ = absl::crc_internal::CrcMemcpy::GetTestEngine(
+          GetParam().vector_lanes, GetParam().integer_lanes);
+    }
+  }
+
+  // Convenience method.
+  ParamsT GetParam() const {
+    return ::testing::WithParamInterface<ParamsT>::GetParam();
+  }
+
+  std::unique_ptr<absl::crc_internal::CrcMemcpyEngine> engine_;
+};
+struct TestParams {
+  CrcEngine crc_engine_selector = ACCELERATED;
+  int vector_lanes = 0;
+  int integer_lanes = 0;
+};
+using EngineParamTest = EngineParamTestTemplate<TestParams>;
+// SmallCorrectness is designed to exercise every possible set of code paths
+// in the memcpy code, not including the loop.
+TEST_P(EngineParamTest, SmallCorrectnessCheckSourceAlignment) {
+  constexpr size_t kTestSizes[] = {0, 100, 255, 512, 1024, 4000, kMaxCopySize};
+
+  for (size_t source_alignment = 0; source_alignment < kAlignment;
+       source_alignment++) {
+    for (auto size : kTestSizes) {
+      char* base_data = static_cast<char*>(source_.get()) + source_alignment;
+      for (size_t i = 0; i < size; i++) {
+        *(base_data + i) =
+            static_cast<char>(absl::Uniform<unsigned char>(gen_));
+      }
+      SCOPED_TRACE(absl::StrCat("engine=<", GetParam().vector_lanes, ",",
+                                GetParam().integer_lanes, ">, ", "size=", size,
+                                ", source_alignment=", source_alignment));
+      absl::crc32c_t initial_crc =
+          absl::crc32c_t{absl::Uniform<uint32_t>(gen_)};
+      absl::crc32c_t experiment_crc =
+          engine_->Compute(destination_.get(), source_.get() + source_alignment,
+                           size, initial_crc);
+      // Check the memory region to make sure it is the same
+      int mem_comparison =
+          memcmp(destination_.get(), source_.get() + source_alignment, size);
+      SCOPED_TRACE(absl::StrCat("Error in memcpy of size: ", size,
+                                " with source alignment: ", source_alignment));
+      ASSERT_EQ(mem_comparison, 0);
+      absl::crc32c_t baseline_crc = absl::ExtendCrc32c(
+          initial_crc,
+          absl::string_view(
+              static_cast<char*>(source_.get()) + source_alignment, size));
+      ASSERT_EQ(baseline_crc, experiment_crc);
+    }
+  }
+}
+
+TEST_P(EngineParamTest, SmallCorrectnessCheckDestAlignment) {
+  constexpr size_t kTestSizes[] = {0, 100, 255, 512, 1024, 4000, kMaxCopySize};
+
+  for (size_t dest_alignment = 0; dest_alignment < kAlignment;
+       dest_alignment++) {
+    for (auto size : kTestSizes) {
+      char* base_data = static_cast<char*>(source_.get());
+      for (size_t i = 0; i < size; i++) {
+        *(base_data + i) =
+            static_cast<char>(absl::Uniform<unsigned char>(gen_));
+      }
+      SCOPED_TRACE(absl::StrCat("engine=<", GetParam().vector_lanes, ",",
+                                GetParam().integer_lanes, ">, ", "size=", size,
+                                ", destination_alignment=", dest_alignment));
+      absl::crc32c_t initial_crc =
+          absl::crc32c_t{absl::Uniform<uint32_t>(gen_)};
+      absl::crc32c_t experiment_crc =
+          engine_->Compute(destination_.get() + dest_alignment, source_.get(),
+                           size, initial_crc);
+      // Check the memory region to make sure it is the same
+      int mem_comparison =
+          memcmp(destination_.get() + dest_alignment, source_.get(), size);
+      SCOPED_TRACE(absl::StrCat("Error in memcpy of size: ", size,
+                                " with dest alignment: ", dest_alignment));
+      ASSERT_EQ(mem_comparison, 0);
+      absl::crc32c_t baseline_crc = absl::ExtendCrc32c(
+          initial_crc,
+          absl::string_view(static_cast<char*>(source_.get()), size));
+      ASSERT_EQ(baseline_crc, experiment_crc);
+    }
+  }
+}
+
+INSTANTIATE_TEST_SUITE_P(EngineParamTest, EngineParamTest,
+                         ::testing::Values(
+                             // Tests for configurations that may occur in prod.
+                             TestParams{ACCELERATED, 3, 0},
+                             TestParams{ACCELERATED, 1, 2},
+                             TestParams{ACCELERATED, 1, 0},
+                             // Fallback test.
+                             TestParams{FALLBACK, 0, 0},
+                             // Non Temporal
+                             TestParams{NONTEMPORAL, 0, 0}));
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_x86_arm_combined.cc b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_x86_arm_combined.cc
new file mode 100644
index 0000000000000000000000000000000000000000..968e9ae359fe640ca5c504659a680d1ee3860b61
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_memcpy_x86_arm_combined.cc
@@ -0,0 +1,450 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Simultaneous memcopy and CRC-32C for x86-64 and ARM 64. Uses integer
+// registers because XMM registers do not support the CRC instruction (yet).
+// While copying, compute the running CRC of the data being copied.
+//
+// It is assumed that any CPU running this code has SSE4.2 instructions
+// available (for CRC32C).  This file will do nothing if that is not true.
+//
+// The CRC instruction has a 3-byte latency, and we are stressing the ALU ports
+// here (unlike a traditional memcopy, which has almost no ALU use), so we will
+// need to copy in such a way that the CRC unit is used efficiently. We have two
+// regimes in this code:
+//  1. For operations of size < kCrcSmallSize, do the CRC then the memcpy
+//  2. For operations of size > kCrcSmallSize:
+//      a) compute an initial CRC + copy on a small amount of data to align the
+//         destination pointer on a 16-byte boundary.
+//      b) Split the data into 3 main regions and a tail (smaller than 48 bytes)
+//      c) Do the copy and CRC of the 3 main regions, interleaving (start with
+//         full cache line copies for each region, then move to single 16 byte
+//         pieces per region).
+//      d) Combine the CRCs with CRC32C::Concat.
+//      e) Copy the tail and extend the CRC with the CRC of the tail.
+// This method is not ideal for op sizes between ~1k and ~8k because CRC::Concat
+// takes a significant amount of time.  A medium-sized approach could be added
+// using 3 CRCs over fixed-size blocks where the zero-extensions required for
+// CRC32C::Concat can be precomputed.
+
+#ifdef __SSE4_2__
+#include <immintrin.h>
+#endif
+
+#ifdef _MSC_VER
+#include <intrin.h>
+#endif
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <memory>
+
+#include "absl/base/config.h"
+#include "absl/base/optimization.h"
+#include "absl/base/prefetch.h"
+#include "absl/crc/crc32c.h"
+#include "absl/crc/internal/cpu_detect.h"
+#include "absl/crc/internal/crc32_x86_arm_combined_simd.h"
+#include "absl/crc/internal/crc_memcpy.h"
+#include "absl/strings/string_view.h"
+
+#if defined(ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE) || \
+    defined(ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+namespace {
+
+inline crc32c_t ShortCrcCopy(char* dst, const char* src, std::size_t length,
+                             crc32c_t crc) {
+  // Small copy: just go 1 byte at a time: being nice to the branch predictor
+  // is more important here than anything else
+  uint32_t crc_uint32 = static_cast<uint32_t>(crc);
+  for (std::size_t i = 0; i < length; i++) {
+    uint8_t data = *reinterpret_cast<const uint8_t*>(src);
+    crc_uint32 = CRC32_u8(crc_uint32, data);
+    *reinterpret_cast<uint8_t*>(dst) = data;
+    ++src;
+    ++dst;
+  }
+  return crc32c_t{crc_uint32};
+}
+
+constexpr size_t kIntLoadsPerVec = sizeof(V128) / sizeof(uint64_t);
+
+// Common function for copying the tails of multiple large regions.
+template <size_t vec_regions, size_t int_regions>
+inline void LargeTailCopy(crc32c_t* crcs, char** dst, const char** src,
+                          size_t region_size, size_t copy_rounds) {
+  std::array<V128, vec_regions> data;
+  std::array<uint64_t, kIntLoadsPerVec * int_regions> int_data;
+
+  while (copy_rounds > 0) {
+    for (size_t i = 0; i < vec_regions; i++) {
+      size_t region = i;
+
+      auto* vsrc = reinterpret_cast<const V128*>(*src + region_size * region);
+      auto* vdst = reinterpret_cast<V128*>(*dst + region_size * region);
+
+      // Load the blocks, unaligned
+      data[i] = V128_LoadU(vsrc);
+
+      // Store the blocks, aligned
+      V128_Store(vdst, data[i]);
+
+      // Compute the running CRC
+      crcs[region] = crc32c_t{static_cast<uint32_t>(
+          CRC32_u64(static_cast<uint32_t>(crcs[region]),
+                    static_cast<uint64_t>(V128_Extract64<0>(data[i]))))};
+      crcs[region] = crc32c_t{static_cast<uint32_t>(
+          CRC32_u64(static_cast<uint32_t>(crcs[region]),
+                    static_cast<uint64_t>(V128_Extract64<1>(data[i]))))};
+    }
+
+    for (size_t i = 0; i < int_regions; i++) {
+      size_t region = vec_regions + i;
+
+      auto* usrc =
+          reinterpret_cast<const uint64_t*>(*src + region_size * region);
+      auto* udst = reinterpret_cast<uint64_t*>(*dst + region_size * region);
+
+      for (size_t j = 0; j < kIntLoadsPerVec; j++) {
+        size_t data_index = i * kIntLoadsPerVec + j;
+
+        int_data[data_index] = *(usrc + j);
+        crcs[region] = crc32c_t{static_cast<uint32_t>(CRC32_u64(
+            static_cast<uint32_t>(crcs[region]), int_data[data_index]))};
+
+        *(udst + j) = int_data[data_index];
+      }
+    }
+
+    // Increment pointers
+    *src += sizeof(V128);
+    *dst += sizeof(V128);
+    --copy_rounds;
+  }
+}
+
+}  // namespace
+
+template <size_t vec_regions, size_t int_regions>
+class AcceleratedCrcMemcpyEngine : public CrcMemcpyEngine {
+ public:
+  AcceleratedCrcMemcpyEngine() = default;
+  AcceleratedCrcMemcpyEngine(const AcceleratedCrcMemcpyEngine&) = delete;
+  AcceleratedCrcMemcpyEngine operator=(const AcceleratedCrcMemcpyEngine&) =
+      delete;
+
+  crc32c_t Compute(void* __restrict dst, const void* __restrict src,
+                   std::size_t length, crc32c_t initial_crc) const override;
+};
+
+template <size_t vec_regions, size_t int_regions>
+crc32c_t AcceleratedCrcMemcpyEngine<vec_regions, int_regions>::Compute(
+    void* __restrict dst, const void* __restrict src, std::size_t length,
+    crc32c_t initial_crc) const {
+  constexpr std::size_t kRegions = vec_regions + int_regions;
+  static_assert(kRegions > 0, "Must specify at least one region.");
+  constexpr uint32_t kCrcDataXor = uint32_t{0xffffffff};
+  constexpr std::size_t kBlockSize = sizeof(V128);
+  constexpr std::size_t kCopyRoundSize = kRegions * kBlockSize;
+
+  // Number of blocks per cacheline.
+  constexpr std::size_t kBlocksPerCacheLine = ABSL_CACHELINE_SIZE / kBlockSize;
+
+  char* dst_bytes = static_cast<char*>(dst);
+  const char* src_bytes = static_cast<const char*>(src);
+
+  // Make sure that one prefetch per big block is enough to cover the whole
+  // dataset, and we don't prefetch too much.
+  static_assert(ABSL_CACHELINE_SIZE % kBlockSize == 0,
+                "Cache lines are not divided evenly into blocks, may have "
+                "unintended behavior!");
+
+  // Experimentally-determined boundary between a small and large copy.
+  // Below this number, spin-up and concatenation of CRCs takes enough time that
+  // it kills the throughput gains of using 3 regions and wide vectors.
+  constexpr size_t kCrcSmallSize = 256;
+
+  // Experimentally-determined prefetch distance.  Main loop copies will
+  // prefeth data 2 cache lines ahead.
+  constexpr std::size_t kPrefetchAhead = 2 * ABSL_CACHELINE_SIZE;
+
+  // Small-size CRC-memcpy : just do CRC + memcpy
+  if (length < kCrcSmallSize) {
+    crc32c_t crc =
+        ExtendCrc32c(initial_crc, absl::string_view(src_bytes, length));
+    memcpy(dst, src, length);
+    return crc;
+  }
+
+  // Start work on the CRC: undo the XOR from the previous calculation or set up
+  // the initial value of the CRC.
+  // initial_crc ^= kCrcDataXor;
+  initial_crc = crc32c_t{static_cast<uint32_t>(initial_crc) ^ kCrcDataXor};
+
+  // Do an initial alignment copy, so we can use aligned store instructions to
+  // the destination pointer.  We align the destination pointer because the
+  // penalty for an unaligned load is small compared to the penalty of an
+  // unaligned store on modern CPUs.
+  std::size_t bytes_from_last_aligned =
+      reinterpret_cast<uintptr_t>(dst) & (kBlockSize - 1);
+  if (bytes_from_last_aligned != 0) {
+    std::size_t bytes_for_alignment = kBlockSize - bytes_from_last_aligned;
+
+    // Do the short-sized copy and CRC.
+    initial_crc =
+        ShortCrcCopy(dst_bytes, src_bytes, bytes_for_alignment, initial_crc);
+    src_bytes += bytes_for_alignment;
+    dst_bytes += bytes_for_alignment;
+    length -= bytes_for_alignment;
+  }
+
+  // We are going to do the copy and CRC in kRegions regions to make sure that
+  // we can saturate the CRC unit.  The CRCs will be combined at the end of the
+  // run.  Copying will use the SSE registers, and we will extract words from
+  // the SSE registers to add to the CRC.  Initially, we run the loop one full
+  // cache line per region at a time, in order to insert prefetches.
+
+  // Initialize CRCs for kRegions regions.
+  crc32c_t crcs[kRegions];
+  crcs[0] = initial_crc;
+  for (size_t i = 1; i < kRegions; i++) {
+    crcs[i] = crc32c_t{kCrcDataXor};
+  }
+
+  // Find the number of rounds to copy and the region size.  Also compute the
+  // tail size here.
+  size_t copy_rounds = length / kCopyRoundSize;
+
+  // Find the size of each region and the size of the tail.
+  const std::size_t region_size = copy_rounds * kBlockSize;
+  const std::size_t tail_size = length - (kRegions * region_size);
+
+  // Holding registers for data in each region.
+  std::array<V128, vec_regions> vec_data;
+  std::array<uint64_t, int_regions * kIntLoadsPerVec> int_data;
+
+  // Main loop.
+  while (copy_rounds > kBlocksPerCacheLine) {
+    // Prefetch kPrefetchAhead bytes ahead of each pointer.
+    for (size_t i = 0; i < kRegions; i++) {
+      absl::PrefetchToLocalCache(src_bytes + kPrefetchAhead + region_size * i);
+#ifdef ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE
+      // TODO(b/297082454): investigate dropping prefetch on x86.
+      absl::PrefetchToLocalCache(dst_bytes + kPrefetchAhead + region_size * i);
+#endif
+    }
+
+    // Load and store data, computing CRC on the way.
+    for (size_t i = 0; i < kBlocksPerCacheLine; i++) {
+      // Copy and CRC the data for the CRC regions.
+      for (size_t j = 0; j < vec_regions; j++) {
+        // Cycle which regions get vector load/store and integer load/store, to
+        // engage prefetching logic around vector load/stores and save issue
+        // slots by using the integer registers.
+        size_t region = (j + i) % kRegions;
+
+        auto* vsrc =
+            reinterpret_cast<const V128*>(src_bytes + region_size * region);
+        auto* vdst = reinterpret_cast<V128*>(dst_bytes + region_size * region);
+
+        // Load and CRC data.
+        vec_data[j] = V128_LoadU(vsrc + i);
+        crcs[region] = crc32c_t{static_cast<uint32_t>(
+            CRC32_u64(static_cast<uint32_t>(crcs[region]),
+                      static_cast<uint64_t>(V128_Extract64<0>(vec_data[j]))))};
+        crcs[region] = crc32c_t{static_cast<uint32_t>(
+            CRC32_u64(static_cast<uint32_t>(crcs[region]),
+                      static_cast<uint64_t>(V128_Extract64<1>(vec_data[j]))))};
+
+        // Store the data.
+        V128_Store(vdst + i, vec_data[j]);
+      }
+
+      // Preload the partial CRCs for the CLMUL subregions.
+      for (size_t j = 0; j < int_regions; j++) {
+        // Cycle which regions get vector load/store and integer load/store, to
+        // engage prefetching logic around vector load/stores and save issue
+        // slots by using the integer registers.
+        size_t region = (j + vec_regions + i) % kRegions;
+
+        auto* usrc =
+            reinterpret_cast<const uint64_t*>(src_bytes + region_size * region);
+        auto* udst =
+            reinterpret_cast<uint64_t*>(dst_bytes + region_size * region);
+
+        for (size_t k = 0; k < kIntLoadsPerVec; k++) {
+          size_t data_index = j * kIntLoadsPerVec + k;
+
+          // Load and CRC the data.
+          int_data[data_index] = *(usrc + i * kIntLoadsPerVec + k);
+          crcs[region] = crc32c_t{static_cast<uint32_t>(CRC32_u64(
+              static_cast<uint32_t>(crcs[region]), int_data[data_index]))};
+
+          // Store the data.
+          *(udst + i * kIntLoadsPerVec + k) = int_data[data_index];
+        }
+      }
+    }
+
+    // Increment pointers
+    src_bytes += kBlockSize * kBlocksPerCacheLine;
+    dst_bytes += kBlockSize * kBlocksPerCacheLine;
+    copy_rounds -= kBlocksPerCacheLine;
+  }
+
+  // Copy and CRC the tails of each region.
+  LargeTailCopy<vec_regions, int_regions>(crcs, &dst_bytes, &src_bytes,
+                                          region_size, copy_rounds);
+
+  // Move the source and destination pointers to the end of the region
+  src_bytes += region_size * (kRegions - 1);
+  dst_bytes += region_size * (kRegions - 1);
+
+  // Copy and CRC the tail through the XMM registers.
+  std::size_t tail_blocks = tail_size / kBlockSize;
+  LargeTailCopy<0, 1>(&crcs[kRegions - 1], &dst_bytes, &src_bytes, 0,
+                      tail_blocks);
+
+  // Final tail copy for under 16 bytes.
+  crcs[kRegions - 1] =
+      ShortCrcCopy(dst_bytes, src_bytes, tail_size - tail_blocks * kBlockSize,
+                   crcs[kRegions - 1]);
+
+  if (kRegions == 1) {
+    // If there is only one region, finalize and return its CRC.
+    return crc32c_t{static_cast<uint32_t>(crcs[0]) ^ kCrcDataXor};
+  }
+
+  // Finalize the first CRCs: XOR the internal CRCs by the XOR mask to undo the
+  // XOR done before doing block copy + CRCs.
+  for (size_t i = 0; i + 1 < kRegions; i++) {
+    crcs[i] = crc32c_t{static_cast<uint32_t>(crcs[i]) ^ kCrcDataXor};
+  }
+
+  // Build a CRC of the first kRegions - 1 regions.
+  crc32c_t full_crc = crcs[0];
+  for (size_t i = 1; i + 1 < kRegions; i++) {
+    full_crc = ConcatCrc32c(full_crc, crcs[i], region_size);
+  }
+
+  // Finalize and concatenate the final CRC, then return.
+  crcs[kRegions - 1] =
+      crc32c_t{static_cast<uint32_t>(crcs[kRegions - 1]) ^ kCrcDataXor};
+  return ConcatCrc32c(full_crc, crcs[kRegions - 1], region_size + tail_size);
+}
+
+CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
+#ifdef UNDEFINED_BEHAVIOR_SANITIZER
+  // UBSAN does not play nicely with unaligned loads (which we use a lot).
+  // Get the underlying architecture.
+  CpuType cpu_type = GetCpuType();
+  switch (cpu_type) {
+    case CpuType::kAmdRome:
+    case CpuType::kAmdNaples:
+    case CpuType::kAmdMilan:
+    case CpuType::kAmdGenoa:
+    case CpuType::kAmdRyzenV3000:
+    case CpuType::kIntelCascadelakeXeon:
+    case CpuType::kIntelSkylakeXeon:
+    case CpuType::kIntelSkylake:
+    case CpuType::kIntelBroadwell:
+    case CpuType::kIntelHaswell:
+    case CpuType::kIntelIvybridge:
+      return {
+          /*.temporal=*/new FallbackCrcMemcpyEngine(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyAVXEngine(),
+      };
+    // INTEL_SANDYBRIDGE performs better with SSE than AVX.
+    case CpuType::kIntelSandybridge:
+      return {
+          /*.temporal=*/new FallbackCrcMemcpyEngine(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyEngine(),
+      };
+    default:
+      return {/*.temporal=*/new FallbackCrcMemcpyEngine(),
+              /*.non_temporal=*/new FallbackCrcMemcpyEngine()};
+  }
+#else
+  // Get the underlying architecture.
+  CpuType cpu_type = GetCpuType();
+  switch (cpu_type) {
+    // On Zen 2, PEXTRQ uses 2 micro-ops, including one on the vector store port
+    // which data movement from the vector registers to the integer registers
+    // (where CRC32C happens) to crowd the same units as vector stores.  As a
+    // result, using that path exclusively causes bottlenecking on this port.
+    // We can avoid this bottleneck by using the integer side of the CPU for
+    // most operations rather than the vector side.  We keep a vector region to
+    // engage some of the prefetching logic in the cache hierarchy which seems
+    // to give vector instructions special treatment.  These prefetch units see
+    // strided access to each region, and do the right thing.
+    case CpuType::kAmdRome:
+    case CpuType::kAmdNaples:
+    case CpuType::kAmdMilan:
+    case CpuType::kAmdGenoa:
+    case CpuType::kAmdRyzenV3000:
+      return {
+          /*.temporal=*/new AcceleratedCrcMemcpyEngine<1, 2>(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyAVXEngine(),
+      };
+    // PCLMULQDQ is slow and we don't have wide enough issue width to take
+    // advantage of it.  For an unknown architecture, don't risk using CLMULs.
+    case CpuType::kIntelCascadelakeXeon:
+    case CpuType::kIntelSkylakeXeon:
+    case CpuType::kIntelSkylake:
+    case CpuType::kIntelBroadwell:
+    case CpuType::kIntelHaswell:
+    case CpuType::kIntelIvybridge:
+      return {
+          /*.temporal=*/new AcceleratedCrcMemcpyEngine<3, 0>(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyAVXEngine(),
+      };
+    // INTEL_SANDYBRIDGE performs better with SSE than AVX.
+    case CpuType::kIntelSandybridge:
+      return {
+          /*.temporal=*/new AcceleratedCrcMemcpyEngine<3, 0>(),
+          /*.non_temporal=*/new CrcNonTemporalMemcpyEngine(),
+      };
+    default:
+      return {/*.temporal=*/new FallbackCrcMemcpyEngine(),
+              /*.non_temporal=*/new FallbackCrcMemcpyEngine()};
+  }
+#endif  // UNDEFINED_BEHAVIOR_SANITIZER
+}
+
+// For testing, allow the user to specify which engine they want.
+std::unique_ptr<CrcMemcpyEngine> CrcMemcpy::GetTestEngine(int vector,
+                                                          int integer) {
+  if (vector == 3 && integer == 0) {
+    return std::make_unique<AcceleratedCrcMemcpyEngine<3, 0>>();
+  } else if (vector == 1 && integer == 2) {
+    return std::make_unique<AcceleratedCrcMemcpyEngine<1, 2>>();
+  } else if (vector == 1 && integer == 0) {
+    return std::make_unique<AcceleratedCrcMemcpyEngine<1, 0>>();
+  }
+  return nullptr;
+}
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE ||
+        // ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_non_temporal_memcpy.cc b/weight/_dep/abseil-cpp/absl/crc/internal/crc_non_temporal_memcpy.cc
new file mode 100644
index 0000000000000000000000000000000000000000..adc867f6b7d2b14ffa216c09e8664a720012ffc0
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_non_temporal_memcpy.cc
@@ -0,0 +1,93 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdint>
+
+#include "absl/base/config.h"
+#include "absl/crc/crc32c.h"
+#include "absl/crc/internal/crc_memcpy.h"
+#include "absl/crc/internal/non_temporal_memcpy.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+crc32c_t CrcNonTemporalMemcpyEngine::Compute(void* __restrict dst,
+                                             const void* __restrict src,
+                                             std::size_t length,
+                                             crc32c_t initial_crc) const {
+  constexpr size_t kBlockSize = 8192;
+  crc32c_t crc = initial_crc;
+
+  const char* src_bytes = reinterpret_cast<const char*>(src);
+  char* dst_bytes = reinterpret_cast<char*>(dst);
+
+  // Copy + CRC loop - run 8k chunks until we are out of full chunks.
+  std::size_t offset = 0;
+  for (; offset + kBlockSize < length; offset += kBlockSize) {
+    crc = absl::ExtendCrc32c(crc,
+                             absl::string_view(src_bytes + offset, kBlockSize));
+    non_temporal_store_memcpy(dst_bytes + offset, src_bytes + offset,
+                              kBlockSize);
+  }
+
+  // Save some work if length is 0.
+  if (offset < length) {
+    std::size_t final_copy_size = length - offset;
+    crc = ExtendCrc32c(crc,
+                       absl::string_view(src_bytes + offset, final_copy_size));
+
+    non_temporal_store_memcpy(dst_bytes + offset, src_bytes + offset,
+                              final_copy_size);
+  }
+
+  return crc;
+}
+
+crc32c_t CrcNonTemporalMemcpyAVXEngine::Compute(void* __restrict dst,
+                                                const void* __restrict src,
+                                                std::size_t length,
+                                                crc32c_t initial_crc) const {
+  constexpr size_t kBlockSize = 8192;
+  crc32c_t crc = initial_crc;
+
+  const char* src_bytes = reinterpret_cast<const char*>(src);
+  char* dst_bytes = reinterpret_cast<char*>(dst);
+
+  // Copy + CRC loop - run 8k chunks until we are out of full chunks.
+  std::size_t offset = 0;
+  for (; offset + kBlockSize < length; offset += kBlockSize) {
+    crc = ExtendCrc32c(crc, absl::string_view(src_bytes + offset, kBlockSize));
+
+    non_temporal_store_memcpy_avx(dst_bytes + offset, src_bytes + offset,
+                                  kBlockSize);
+  }
+
+  // Save some work if length is 0.
+  if (offset < length) {
+    std::size_t final_copy_size = length - offset;
+    crc = ExtendCrc32c(crc,
+                       absl::string_view(src_bytes + offset, final_copy_size));
+
+    non_temporal_store_memcpy_avx(dst_bytes + offset, src_bytes + offset,
+                                  final_copy_size);
+  }
+
+  return crc;
+}
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/crc_x86_arm_combined.cc b/weight/_dep/abseil-cpp/absl/crc/internal/crc_x86_arm_combined.cc
new file mode 100644
index 0000000000000000000000000000000000000000..51eff4eddcb3376932569b61e693ca68bc570d91
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/crc_x86_arm_combined.cc
@@ -0,0 +1,733 @@
+// Copyright 2022 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Hardware accelerated CRC32 computation on Intel and ARM architecture.
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <vector>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/prefetch.h"
+#include "absl/crc/internal/cpu_detect.h"
+#include "absl/crc/internal/crc32_x86_arm_combined_simd.h"
+#include "absl/crc/internal/crc_internal.h"
+#include "absl/memory/memory.h"
+#include "absl/numeric/bits.h"
+
+#if defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD) || \
+    defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD)
+#define ABSL_INTERNAL_CAN_USE_SIMD_CRC32C
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+#if defined(ABSL_INTERNAL_CAN_USE_SIMD_CRC32C)
+
+// Implementation details not exported outside of file
+namespace {
+
+// Some machines have CRC acceleration hardware.
+// We can do a faster version of Extend() on such machines.
+class CRC32AcceleratedX86ARMCombined : public CRC32 {
+ public:
+  CRC32AcceleratedX86ARMCombined() {}
+  ~CRC32AcceleratedX86ARMCombined() override {}
+  void ExtendByZeroes(uint32_t* crc, size_t length) const override;
+  uint32_t ComputeZeroConstant(size_t length) const;
+
+ private:
+  CRC32AcceleratedX86ARMCombined(const CRC32AcceleratedX86ARMCombined&) =
+      delete;
+  CRC32AcceleratedX86ARMCombined& operator=(
+      const CRC32AcceleratedX86ARMCombined&) = delete;
+};
+
+// Constants for switching between algorithms.
+// Chosen by comparing speed at different powers of 2.
+constexpr size_t kSmallCutoff = 256;
+constexpr size_t kMediumCutoff = 2048;
+
+#define ABSL_INTERNAL_STEP1(crc)                      \
+  do {                                                \
+    crc = CRC32_u8(static_cast<uint32_t>(crc), *p++); \
+  } while (0)
+#define ABSL_INTERNAL_STEP2(crc)                                               \
+  do {                                                                         \
+    crc =                                                                      \
+        CRC32_u16(static_cast<uint32_t>(crc), absl::little_endian::Load16(p)); \
+    p += 2;                                                                    \
+  } while (0)
+#define ABSL_INTERNAL_STEP4(crc)                                               \
+  do {                                                                         \
+    crc =                                                                      \
+        CRC32_u32(static_cast<uint32_t>(crc), absl::little_endian::Load32(p)); \
+    p += 4;                                                                    \
+  } while (0)
+#define ABSL_INTERNAL_STEP8(crc, data)                  \
+  do {                                                  \
+    crc = CRC32_u64(static_cast<uint32_t>(crc),         \
+                    absl::little_endian::Load64(data)); \
+    data += 8;                                          \
+  } while (0)
+#define ABSL_INTERNAL_STEP8BY2(crc0, crc1, p0, p1) \
+  do {                                             \
+    ABSL_INTERNAL_STEP8(crc0, p0);                 \
+    ABSL_INTERNAL_STEP8(crc1, p1);                 \
+  } while (0)
+#define ABSL_INTERNAL_STEP8BY3(crc0, crc1, crc2, p0, p1, p2) \
+  do {                                                       \
+    ABSL_INTERNAL_STEP8(crc0, p0);                           \
+    ABSL_INTERNAL_STEP8(crc1, p1);                           \
+    ABSL_INTERNAL_STEP8(crc2, p2);                           \
+  } while (0)
+
+namespace {
+
+uint32_t multiply(uint32_t a, uint32_t b) {
+  V128 shifts = V128_From2x64(0, 1);
+  V128 power = V128_From2x64(0, a);
+  V128 crc = V128_From2x64(0, b);
+  V128 res = V128_PMulLow(power, crc);
+
+  // Combine crc values
+  res = V128_ShiftLeft64(res, shifts);
+  return static_cast<uint32_t>(V128_Extract32<1>(res)) ^
+         CRC32_u32(0, static_cast<uint32_t>(V128_Low64(res)));
+}
+
+// Powers of crc32c polynomial, for faster ExtendByZeros.
+// Verified against folly:
+// folly/hash/detail/Crc32CombineDetail.cpp
+constexpr uint32_t kCRC32CPowers[] = {
+    0x82f63b78, 0x6ea2d55c, 0x18b8ea18, 0x510ac59a, 0xb82be955, 0xb8fdb1e7,
+    0x88e56f72, 0x74c360a4, 0xe4172b16, 0x0d65762a, 0x35d73a62, 0x28461564,
+    0xbf455269, 0xe2ea32dc, 0xfe7740e6, 0xf946610b, 0x3c204f8f, 0x538586e3,
+    0x59726915, 0x734d5309, 0xbc1ac763, 0x7d0722cc, 0xd289cabe, 0xe94ca9bc,
+    0x05b74f3f, 0xa51e1f42, 0x40000000, 0x20000000, 0x08000000, 0x00800000,
+    0x00008000, 0x82f63b78, 0x6ea2d55c, 0x18b8ea18, 0x510ac59a, 0xb82be955,
+    0xb8fdb1e7, 0x88e56f72, 0x74c360a4, 0xe4172b16, 0x0d65762a, 0x35d73a62,
+    0x28461564, 0xbf455269, 0xe2ea32dc, 0xfe7740e6, 0xf946610b, 0x3c204f8f,
+    0x538586e3, 0x59726915, 0x734d5309, 0xbc1ac763, 0x7d0722cc, 0xd289cabe,
+    0xe94ca9bc, 0x05b74f3f, 0xa51e1f42, 0x40000000, 0x20000000, 0x08000000,
+    0x00800000, 0x00008000,
+};
+
+}  // namespace
+
+// Compute a magic constant, so that multiplying by it is the same as
+// extending crc by length zeros.
+uint32_t CRC32AcceleratedX86ARMCombined::ComputeZeroConstant(
+    size_t length) const {
+  // Lowest 2 bits are handled separately in ExtendByZeroes
+  length >>= 2;
+
+  int index = absl::countr_zero(length);
+  uint32_t prev = kCRC32CPowers[index];
+  length &= length - 1;
+
+  while (length) {
+    // For each bit of length, extend by 2**n zeros.
+    index = absl::countr_zero(length);
+    prev = multiply(prev, kCRC32CPowers[index]);
+    length &= length - 1;
+  }
+  return prev;
+}
+
+void CRC32AcceleratedX86ARMCombined::ExtendByZeroes(uint32_t* crc,
+                                                    size_t length) const {
+  uint32_t val = *crc;
+  // Don't bother with multiplication for small length.
+  switch (length & 3) {
+    case 0:
+      break;
+    case 1:
+      val = CRC32_u8(val, 0);
+      break;
+    case 2:
+      val = CRC32_u16(val, 0);
+      break;
+    case 3:
+      val = CRC32_u8(val, 0);
+      val = CRC32_u16(val, 0);
+      break;
+  }
+  if (length > 3) {
+    val = multiply(val, ComputeZeroConstant(length));
+  }
+  *crc = val;
+}
+
+// Taken from Intel paper "Fast CRC Computation for iSCSI Polynomial Using CRC32
+// Instruction"
+// https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/crc-iscsi-polynomial-crc32-instruction-paper.pdf
+// We only need every 4th value, because we unroll loop by 4.
+constexpr uint64_t kClmulConstants[] = {
+    0x09e4addf8, 0x0ba4fc28e, 0x00d3b6092, 0x09e4addf8, 0x0ab7aff2a,
+    0x102f9b8a2, 0x0b9e02b86, 0x00d3b6092, 0x1bf2e8b8a, 0x18266e456,
+    0x0d270f1a2, 0x0ab7aff2a, 0x11eef4f8e, 0x083348832, 0x0dd7e3b0c,
+    0x0b9e02b86, 0x0271d9844, 0x1b331e26a, 0x06b749fb2, 0x1bf2e8b8a,
+    0x0e6fc4e6a, 0x0ce7f39f4, 0x0d7a4825c, 0x0d270f1a2, 0x026f6a60a,
+    0x12ed0daac, 0x068bce87a, 0x11eef4f8e, 0x1329d9f7e, 0x0b3e32c28,
+    0x0170076fa, 0x0dd7e3b0c, 0x1fae1cc66, 0x010746f3c, 0x086d8e4d2,
+    0x0271d9844, 0x0b3af077a, 0x093a5f730, 0x1d88abd4a, 0x06b749fb2,
+    0x0c9c8b782, 0x0cec3662e, 0x1ddffc5d4, 0x0e6fc4e6a, 0x168763fa6,
+    0x0b0cd4768, 0x19b1afbc4, 0x0d7a4825c, 0x123888b7a, 0x00167d312,
+    0x133d7a042, 0x026f6a60a, 0x000bcf5f6, 0x19d34af3a, 0x1af900c24,
+    0x068bce87a, 0x06d390dec, 0x16cba8aca, 0x1f16a3418, 0x1329d9f7e,
+    0x19fb2a8b0, 0x02178513a, 0x1a0f717c4, 0x0170076fa,
+};
+
+enum class CutoffStrategy {
+  // Use 3 CRC streams to fold into 1.
+  Fold3,
+  // Unroll CRC instructions for 64 bytes.
+  Unroll64CRC,
+};
+
+// Base class for CRC32AcceleratedX86ARMCombinedMultipleStreams containing the
+// methods and data that don't need the template arguments.
+class CRC32AcceleratedX86ARMCombinedMultipleStreamsBase
+    : public CRC32AcceleratedX86ARMCombined {
+ protected:
+  // Update partialCRC with crc of 64 byte block. Calling FinalizePclmulStream
+  // would produce a single crc checksum, but it is expensive. PCLMULQDQ has a
+  // high latency, so we run 4 128-bit partial checksums that can be reduced to
+  // a single value by FinalizePclmulStream later. Computing crc for arbitrary
+  // polynomialas with PCLMULQDQ is described in Intel paper "Fast CRC
+  // Computation for Generic Polynomials Using PCLMULQDQ Instruction"
+  // https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf
+  // We are applying it to CRC32C polynomial.
+  ABSL_ATTRIBUTE_ALWAYS_INLINE void Process64BytesPclmul(
+      const uint8_t* p, V128* partialCRC) const {
+    V128 loopMultiplicands = V128_Load(reinterpret_cast<const V128*>(k1k2));
+
+    V128 partialCRC1 = partialCRC[0];
+    V128 partialCRC2 = partialCRC[1];
+    V128 partialCRC3 = partialCRC[2];
+    V128 partialCRC4 = partialCRC[3];
+
+    V128 tmp1 = V128_PMulHi(partialCRC1, loopMultiplicands);
+    V128 tmp2 = V128_PMulHi(partialCRC2, loopMultiplicands);
+    V128 tmp3 = V128_PMulHi(partialCRC3, loopMultiplicands);
+    V128 tmp4 = V128_PMulHi(partialCRC4, loopMultiplicands);
+    V128 data1 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 0));
+    V128 data2 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 1));
+    V128 data3 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 2));
+    V128 data4 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 3));
+    partialCRC1 = V128_PMulLow(partialCRC1, loopMultiplicands);
+    partialCRC2 = V128_PMulLow(partialCRC2, loopMultiplicands);
+    partialCRC3 = V128_PMulLow(partialCRC3, loopMultiplicands);
+    partialCRC4 = V128_PMulLow(partialCRC4, loopMultiplicands);
+    partialCRC1 = V128_Xor(tmp1, partialCRC1);
+    partialCRC2 = V128_Xor(tmp2, partialCRC2);
+    partialCRC3 = V128_Xor(tmp3, partialCRC3);
+    partialCRC4 = V128_Xor(tmp4, partialCRC4);
+    partialCRC1 = V128_Xor(partialCRC1, data1);
+    partialCRC2 = V128_Xor(partialCRC2, data2);
+    partialCRC3 = V128_Xor(partialCRC3, data3);
+    partialCRC4 = V128_Xor(partialCRC4, data4);
+    partialCRC[0] = partialCRC1;
+    partialCRC[1] = partialCRC2;
+    partialCRC[2] = partialCRC3;
+    partialCRC[3] = partialCRC4;
+  }
+
+  // Reduce partialCRC produced by Process64BytesPclmul into a single value,
+  // that represents crc checksum of all the processed bytes.
+  ABSL_ATTRIBUTE_ALWAYS_INLINE uint64_t
+  FinalizePclmulStream(V128* partialCRC) const {
+    V128 partialCRC1 = partialCRC[0];
+    V128 partialCRC2 = partialCRC[1];
+    V128 partialCRC3 = partialCRC[2];
+    V128 partialCRC4 = partialCRC[3];
+
+    // Combine 4 vectors of partial crc into a single vector.
+    V128 reductionMultiplicands =
+        V128_Load(reinterpret_cast<const V128*>(k5k6));
+
+    V128 low = V128_PMulLow(reductionMultiplicands, partialCRC1);
+    V128 high = V128_PMulHi(reductionMultiplicands, partialCRC1);
+
+    partialCRC1 = V128_Xor(low, high);
+    partialCRC1 = V128_Xor(partialCRC1, partialCRC2);
+
+    low = V128_PMulLow(reductionMultiplicands, partialCRC3);
+    high = V128_PMulHi(reductionMultiplicands, partialCRC3);
+
+    partialCRC3 = V128_Xor(low, high);
+    partialCRC3 = V128_Xor(partialCRC3, partialCRC4);
+
+    reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(k3k4));
+
+    low = V128_PMulLow(reductionMultiplicands, partialCRC1);
+    high = V128_PMulHi(reductionMultiplicands, partialCRC1);
+    V128 fullCRC = V128_Xor(low, high);
+    fullCRC = V128_Xor(fullCRC, partialCRC3);
+
+    // Reduce fullCRC into scalar value.
+    reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(k5k6));
+
+    V128 mask = V128_Load(reinterpret_cast<const V128*>(kMask));
+
+    V128 tmp = V128_PMul01(reductionMultiplicands, fullCRC);
+    fullCRC = V128_ShiftRight<8>(fullCRC);
+    fullCRC = V128_Xor(fullCRC, tmp);
+
+    reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(k7k0));
+
+    tmp = V128_ShiftRight<4>(fullCRC);
+    fullCRC = V128_And(fullCRC, mask);
+    fullCRC = V128_PMulLow(reductionMultiplicands, fullCRC);
+    fullCRC = V128_Xor(tmp, fullCRC);
+
+    reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(kPoly));
+
+    tmp = V128_And(fullCRC, mask);
+    tmp = V128_PMul01(reductionMultiplicands, tmp);
+    tmp = V128_And(tmp, mask);
+    tmp = V128_PMulLow(reductionMultiplicands, tmp);
+
+    fullCRC = V128_Xor(tmp, fullCRC);
+
+    return static_cast<uint64_t>(V128_Extract32<1>(fullCRC));
+  }
+
+  // Update crc with 64 bytes of data from p.
+  ABSL_ATTRIBUTE_ALWAYS_INLINE uint64_t Process64BytesCRC(const uint8_t* p,
+                                                          uint64_t crc) const {
+    for (int i = 0; i < 8; i++) {
+      crc =
+          CRC32_u64(static_cast<uint32_t>(crc), absl::little_endian::Load64(p));
+      p += 8;
+    }
+    return crc;
+  }
+
+  // Generated by crc32c_x86_test --crc32c_generate_constants=true
+  // and verified against constants in linux kernel for S390:
+  // https://github.com/torvalds/linux/blob/master/arch/s390/crypto/crc32le-vx.S
+  alignas(16) static constexpr uint64_t k1k2[2] = {0x0740eef02, 0x09e4addf8};
+  alignas(16) static constexpr uint64_t k3k4[2] = {0x1384aa63a, 0x0ba4fc28e};
+  alignas(16) static constexpr uint64_t k5k6[2] = {0x0f20c0dfe, 0x14cd00bd6};
+  alignas(16) static constexpr uint64_t k7k0[2] = {0x0dd45aab8, 0x000000000};
+  alignas(16) static constexpr uint64_t kPoly[2] = {0x105ec76f0, 0x0dea713f1};
+  alignas(16) static constexpr uint32_t kMask[4] = {~0u, 0u, ~0u, 0u};
+
+  // Medium runs of bytes are broken into groups of kGroupsSmall blocks of same
+  // size. Each group is CRCed in parallel then combined at the end of the
+  // block.
+  static constexpr size_t kGroupsSmall = 3;
+  // For large runs we use up to kMaxStreams blocks computed with CRC
+  // instruction, and up to kMaxStreams blocks computed with PCLMULQDQ, which
+  // are combined in the end.
+  static constexpr size_t kMaxStreams = 3;
+};
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+alignas(16) constexpr uint64_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k1k2[2];
+alignas(16) constexpr uint64_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k3k4[2];
+alignas(16) constexpr uint64_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k5k6[2];
+alignas(16) constexpr uint64_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k7k0[2];
+alignas(16) constexpr uint64_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kPoly[2];
+alignas(16) constexpr uint32_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kMask[4];
+constexpr size_t
+    CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kGroupsSmall;
+constexpr size_t CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kMaxStreams;
+#endif  // ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+
+template <size_t num_crc_streams, size_t num_pclmul_streams,
+          CutoffStrategy strategy>
+class CRC32AcceleratedX86ARMCombinedMultipleStreams
+    : public CRC32AcceleratedX86ARMCombinedMultipleStreamsBase {
+  ABSL_ATTRIBUTE_HOT
+  void Extend(uint32_t* crc, const void* bytes, size_t length) const override {
+    static_assert(num_crc_streams >= 1 && num_crc_streams <= kMaxStreams,
+                  "Invalid number of crc streams");
+    static_assert(num_pclmul_streams >= 0 && num_pclmul_streams <= kMaxStreams,
+                  "Invalid number of pclmul streams");
+    const uint8_t* p = static_cast<const uint8_t*>(bytes);
+    const uint8_t* e = p + length;
+    uint32_t l = *crc;
+    uint64_t l64;
+
+    // We have dedicated instruction for 1,2,4 and 8 bytes.
+    if (length & 8) {
+      ABSL_INTERNAL_STEP8(l, p);
+      length &= ~size_t{8};
+    }
+    if (length & 4) {
+      ABSL_INTERNAL_STEP4(l);
+      length &= ~size_t{4};
+    }
+    if (length & 2) {
+      ABSL_INTERNAL_STEP2(l);
+      length &= ~size_t{2};
+    }
+    if (length & 1) {
+      ABSL_INTERNAL_STEP1(l);
+      length &= ~size_t{1};
+    }
+    if (length == 0) {
+      *crc = l;
+      return;
+    }
+    // length is now multiple of 16.
+
+    // For small blocks just run simple loop, because cost of combining multiple
+    // streams is significant.
+    if (strategy != CutoffStrategy::Unroll64CRC) {
+      if (length < kSmallCutoff) {
+        while (length >= 16) {
+          ABSL_INTERNAL_STEP8(l, p);
+          ABSL_INTERNAL_STEP8(l, p);
+          length -= 16;
+        }
+        *crc = l;
+        return;
+      }
+    }
+
+    // For medium blocks we run 3 crc streams and combine them as described in
+    // Intel paper above. Running 4th stream doesn't help, because crc
+    // instruction has latency 3 and throughput 1.
+    if (length < kMediumCutoff) {
+      l64 = l;
+      if (strategy == CutoffStrategy::Fold3) {
+        uint64_t l641 = 0;
+        uint64_t l642 = 0;
+        const size_t blockSize = 32;
+        size_t bs = static_cast<size_t>(e - p) / kGroupsSmall / blockSize;
+        const uint8_t* p1 = p + bs * blockSize;
+        const uint8_t* p2 = p1 + bs * blockSize;
+
+        for (size_t i = 0; i + 1 < bs; ++i) {
+          ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+          ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+          ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+          ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+          PrefetchToLocalCache(
+              reinterpret_cast<const char*>(p + kPrefetchHorizonMedium));
+          PrefetchToLocalCache(
+              reinterpret_cast<const char*>(p1 + kPrefetchHorizonMedium));
+          PrefetchToLocalCache(
+              reinterpret_cast<const char*>(p2 + kPrefetchHorizonMedium));
+        }
+        // Don't run crc on last 8 bytes.
+        ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+        ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+        ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2);
+        ABSL_INTERNAL_STEP8BY2(l64, l641, p, p1);
+
+        V128 magic = *(reinterpret_cast<const V128*>(kClmulConstants) + bs - 1);
+
+        V128 tmp = V128_From2x64(0, l64);
+
+        V128 res1 = V128_PMulLow(tmp, magic);
+
+        tmp = V128_From2x64(0, l641);
+
+        V128 res2 = V128_PMul10(tmp, magic);
+        V128 x = V128_Xor(res1, res2);
+        l64 = static_cast<uint64_t>(V128_Low64(x)) ^
+              absl::little_endian::Load64(p2);
+        l64 = CRC32_u64(static_cast<uint32_t>(l642), l64);
+
+        p = p2 + 8;
+      } else if (strategy == CutoffStrategy::Unroll64CRC) {
+        while ((e - p) >= 64) {
+          l64 = Process64BytesCRC(p, l64);
+          p += 64;
+        }
+      }
+    } else {
+      // There is a lot of data, we can ignore combine costs and run all
+      // requested streams (num_crc_streams + num_pclmul_streams),
+      // using prefetch. CRC and PCLMULQDQ use different cpu execution units,
+      // so on some cpus it makes sense to execute both of them for different
+      // streams.
+
+      // Point x at first 8-byte aligned byte in string.
+      const uint8_t* x = RoundUp<8>(p);
+      // Process bytes until p is 8-byte aligned, if that isn't past the end.
+      while (p != x) {
+        ABSL_INTERNAL_STEP1(l);
+      }
+
+      size_t bs = static_cast<size_t>(e - p) /
+                  (num_crc_streams + num_pclmul_streams) / 64;
+      const uint8_t* crc_streams[kMaxStreams];
+      const uint8_t* pclmul_streams[kMaxStreams];
+      // We are guaranteed to have at least one crc stream.
+      crc_streams[0] = p;
+      for (size_t i = 1; i < num_crc_streams; i++) {
+        crc_streams[i] = crc_streams[i - 1] + bs * 64;
+      }
+      pclmul_streams[0] = crc_streams[num_crc_streams - 1] + bs * 64;
+      for (size_t i = 1; i < num_pclmul_streams; i++) {
+        pclmul_streams[i] = pclmul_streams[i - 1] + bs * 64;
+      }
+
+      // Per stream crc sums.
+      uint64_t l64_crc[kMaxStreams] = {l};
+      uint64_t l64_pclmul[kMaxStreams] = {0};
+
+      // Peel first iteration, because PCLMULQDQ stream, needs setup.
+      for (size_t i = 0; i < num_crc_streams; i++) {
+        l64_crc[i] = Process64BytesCRC(crc_streams[i], l64_crc[i]);
+        crc_streams[i] += 16 * 4;
+      }
+
+      V128 partialCRC[kMaxStreams][4];
+      for (size_t i = 0; i < num_pclmul_streams; i++) {
+        partialCRC[i][0] = V128_LoadU(
+            reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 0));
+        partialCRC[i][1] = V128_LoadU(
+            reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 1));
+        partialCRC[i][2] = V128_LoadU(
+            reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 2));
+        partialCRC[i][3] = V128_LoadU(
+            reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 3));
+        pclmul_streams[i] += 16 * 4;
+      }
+
+      for (size_t i = 1; i < bs; i++) {
+        // Prefetch data for next iterations.
+        for (size_t j = 0; j < num_crc_streams; j++) {
+          PrefetchToLocalCache(
+              reinterpret_cast<const char*>(crc_streams[j] + kPrefetchHorizon));
+        }
+        for (size_t j = 0; j < num_pclmul_streams; j++) {
+          PrefetchToLocalCache(reinterpret_cast<const char*>(pclmul_streams[j] +
+                                                             kPrefetchHorizon));
+        }
+
+        // We process each stream in 64 byte blocks. This can be written as
+        // for (int i = 0; i < num_pclmul_streams; i++) {
+        //   Process64BytesPclmul(pclmul_streams[i], partialCRC[i]);
+        //   pclmul_streams[i] += 16 * 4;
+        // }
+        // for (int i = 0; i < num_crc_streams; i++) {
+        //   l64_crc[i] = Process64BytesCRC(crc_streams[i], l64_crc[i]);
+        //   crc_streams[i] += 16*4;
+        // }
+        // But unrolling and interleaving PCLMULQDQ and CRC blocks manually
+        // gives ~2% performance boost.
+        l64_crc[0] = Process64BytesCRC(crc_streams[0], l64_crc[0]);
+        crc_streams[0] += 16 * 4;
+        if (num_pclmul_streams > 0) {
+          Process64BytesPclmul(pclmul_streams[0], partialCRC[0]);
+          pclmul_streams[0] += 16 * 4;
+        }
+        if (num_crc_streams > 1) {
+          l64_crc[1] = Process64BytesCRC(crc_streams[1], l64_crc[1]);
+          crc_streams[1] += 16 * 4;
+        }
+        if (num_pclmul_streams > 1) {
+          Process64BytesPclmul(pclmul_streams[1], partialCRC[1]);
+          pclmul_streams[1] += 16 * 4;
+        }
+        if (num_crc_streams > 2) {
+          l64_crc[2] = Process64BytesCRC(crc_streams[2], l64_crc[2]);
+          crc_streams[2] += 16 * 4;
+        }
+        if (num_pclmul_streams > 2) {
+          Process64BytesPclmul(pclmul_streams[2], partialCRC[2]);
+          pclmul_streams[2] += 16 * 4;
+        }
+      }
+
+      // PCLMULQDQ based streams require special final step;
+      // CRC based don't.
+      for (size_t i = 0; i < num_pclmul_streams; i++) {
+        l64_pclmul[i] = FinalizePclmulStream(partialCRC[i]);
+      }
+
+      // Combine all streams into single result.
+      uint32_t magic = ComputeZeroConstant(bs * 64);
+      l64 = l64_crc[0];
+      for (size_t i = 1; i < num_crc_streams; i++) {
+        l64 = multiply(static_cast<uint32_t>(l64), magic);
+        l64 ^= l64_crc[i];
+      }
+      for (size_t i = 0; i < num_pclmul_streams; i++) {
+        l64 = multiply(static_cast<uint32_t>(l64), magic);
+        l64 ^= l64_pclmul[i];
+      }
+
+      // Update p.
+      if (num_pclmul_streams > 0) {
+        p = pclmul_streams[num_pclmul_streams - 1];
+      } else {
+        p = crc_streams[num_crc_streams - 1];
+      }
+    }
+    l = static_cast<uint32_t>(l64);
+
+    while ((e - p) >= 16) {
+      ABSL_INTERNAL_STEP8(l, p);
+      ABSL_INTERNAL_STEP8(l, p);
+    }
+    // Process the last few bytes
+    while (p != e) {
+      ABSL_INTERNAL_STEP1(l);
+    }
+
+#undef ABSL_INTERNAL_STEP8BY3
+#undef ABSL_INTERNAL_STEP8BY2
+#undef ABSL_INTERNAL_STEP8
+#undef ABSL_INTERNAL_STEP4
+#undef ABSL_INTERNAL_STEP2
+#undef ABSL_INTERNAL_STEP1
+
+    *crc = l;
+  }
+};
+
+}  // namespace
+
+// Intel processors with SSE4.2 have an instruction for one particular
+// 32-bit CRC polynomial:  crc32c
+CRCImpl* TryNewCRC32AcceleratedX86ARMCombined() {
+  CpuType type = GetCpuType();
+  switch (type) {
+    case CpuType::kIntelHaswell:
+    case CpuType::kAmdRome:
+    case CpuType::kAmdNaples:
+    case CpuType::kAmdMilan:
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          3, 1, CutoffStrategy::Fold3>();
+    // PCLMULQDQ is fast, use combined PCLMULQDQ + CRC implementation.
+    case CpuType::kIntelCascadelakeXeon:
+    case CpuType::kIntelSkylakeXeon:
+    case CpuType::kIntelBroadwell:
+    case CpuType::kIntelSkylake:
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          3, 2, CutoffStrategy::Fold3>();
+    // PCLMULQDQ is slow, don't use it.
+    case CpuType::kIntelIvybridge:
+    case CpuType::kIntelSandybridge:
+    case CpuType::kIntelWestmere:
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          3, 0, CutoffStrategy::Fold3>();
+    case CpuType::kArmNeoverseN1:
+    case CpuType::kArmNeoverseN2:
+    case CpuType::kArmNeoverseV1:
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          1, 1, CutoffStrategy::Unroll64CRC>();
+    case CpuType::kAmpereSiryn:
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          3, 2, CutoffStrategy::Fold3>();
+    case CpuType::kArmNeoverseV2:
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          1, 2, CutoffStrategy::Unroll64CRC>();
+#if defined(__aarch64__)
+    default:
+      // Not all ARM processors support the needed instructions, so check here
+      // before trying to use an accelerated implementation.
+      if (SupportsArmCRC32PMULL()) {
+        return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+            1, 1, CutoffStrategy::Unroll64CRC>();
+      } else {
+        return nullptr;
+      }
+#else
+    default:
+      // Something else, play it safe and assume slow PCLMULQDQ.
+      return new CRC32AcceleratedX86ARMCombinedMultipleStreams<
+          3, 0, CutoffStrategy::Fold3>();
+#endif
+  }
+}
+
+std::vector<std::unique_ptr<CRCImpl>> NewCRC32AcceleratedX86ARMCombinedAll() {
+  auto ret = std::vector<std::unique_ptr<CRCImpl>>();
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 0, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 1, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 2, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 3, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 0, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 1, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 2, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 3, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 0, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 1, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 2, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 3, CutoffStrategy::Fold3>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 0, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 1, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 2, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    1, 3, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 0, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 1, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 2, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    2, 3, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 0, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 1, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 2, CutoffStrategy::Unroll64CRC>>());
+  ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams<
+                    3, 3, CutoffStrategy::Unroll64CRC>>());
+
+  return ret;
+}
+
+#else  // !ABSL_INTERNAL_CAN_USE_SIMD_CRC32C
+
+std::vector<std::unique_ptr<CRCImpl>> NewCRC32AcceleratedX86ARMCombinedAll() {
+  return std::vector<std::unique_ptr<CRCImpl>>();
+}
+
+// no hardware acceleration available
+CRCImpl* TryNewCRC32AcceleratedX86ARMCombined() { return nullptr; }
+
+#endif
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_arm_intrinsics.h b/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_arm_intrinsics.h
new file mode 100644
index 0000000000000000000000000000000000000000..9e5ccfc49d8a3e4130192602731b970f3f917d96
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_arm_intrinsics.h
@@ -0,0 +1,79 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CRC_INTERNAL_NON_TEMPORAL_ARM_INTRINSICS_H_
+#define ABSL_CRC_INTERNAL_NON_TEMPORAL_ARM_INTRINSICS_H_
+
+#include "absl/base/config.h"
+
+#ifdef __aarch64__
+#include <arm_neon.h>
+
+typedef int64x2_t __m128i; /* 128-bit vector containing integers */
+#define vreinterpretq_m128i_s32(x) vreinterpretq_s64_s32(x)
+#define vreinterpretq_s64_m128i(x) (x)
+
+// Guarantees that every preceding store is globally visible before any
+// subsequent store.
+// https://msdn.microsoft.com/en-us/library/5h2w73d1%28v=vs.90%29.aspx
+static inline __attribute__((always_inline)) void _mm_sfence(void) {
+  __sync_synchronize();
+}
+
+// Load 128-bits of integer data from unaligned memory into dst. This intrinsic
+// may perform better than _mm_loadu_si128 when the data crosses a cache line
+// boundary.
+//
+//   dst[127:0] := MEM[mem_addr+127:mem_addr]
+//
+// https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm_lddqu_si128
+#define _mm_lddqu_si128 _mm_loadu_si128
+
+// Loads 128-bit value. :
+// https://msdn.microsoft.com/zh-cn/library/f4k12ae8(v=vs.90).aspx
+static inline __attribute__((always_inline)) __m128i _mm_loadu_si128(
+    const __m128i *p) {
+  return vreinterpretq_m128i_s32(vld1q_s32((const int32_t *)p));
+}
+
+// Stores the data in a to the address p without polluting the caches.  If the
+// cache line containing address p is already in the cache, the cache will be
+// updated.
+// https://msdn.microsoft.com/en-us/library/ba08y07y%28v=vs.90%29.aspx
+static inline __attribute__((always_inline)) void _mm_stream_si128(__m128i *p,
+                                                                   __m128i a) {
+#if ABSL_HAVE_BUILTIN(__builtin_nontemporal_store)
+  __builtin_nontemporal_store(a, p);
+#else
+  vst1q_s64((int64_t *)p, vreinterpretq_s64_m128i(a));
+#endif
+}
+
+// Sets the 16 signed 8-bit integer values.
+// https://msdn.microsoft.com/en-us/library/x0cx8zd3(v=vs.90).aspx
+static inline __attribute__((always_inline)) __m128i _mm_set_epi8(
+    signed char b15, signed char b14, signed char b13, signed char b12,
+    signed char b11, signed char b10, signed char b9, signed char b8,
+    signed char b7, signed char b6, signed char b5, signed char b4,
+    signed char b3, signed char b2, signed char b1, signed char b0) {
+  int8_t __attribute__((aligned(16)))
+  data[16] = {(int8_t)b0,  (int8_t)b1,  (int8_t)b2,  (int8_t)b3,
+              (int8_t)b4,  (int8_t)b5,  (int8_t)b6,  (int8_t)b7,
+              (int8_t)b8,  (int8_t)b9,  (int8_t)b10, (int8_t)b11,
+              (int8_t)b12, (int8_t)b13, (int8_t)b14, (int8_t)b15};
+  return (__m128i)vld1q_s8(data);
+}
+#endif  // __aarch64__
+
+#endif  // ABSL_CRC_INTERNAL_NON_TEMPORAL_ARM_INTRINSICS_H_
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_memcpy.h b/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_memcpy.h
new file mode 100644
index 0000000000000000000000000000000000000000..b3d94badfc161ece52dc6f81be2ee50f9e7e76be
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_memcpy.h
@@ -0,0 +1,180 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_CRC_INTERNAL_NON_TEMPORAL_MEMCPY_H_
+#define ABSL_CRC_INTERNAL_NON_TEMPORAL_MEMCPY_H_
+
+#ifdef _MSC_VER
+#include <intrin.h>
+#endif
+
+#ifdef __SSE__
+#include <xmmintrin.h>
+#endif
+
+#ifdef __SSE2__
+#include <emmintrin.h>
+#endif
+
+#ifdef __SSE3__
+#include <pmmintrin.h>
+#endif
+
+#ifdef __AVX__
+#include <immintrin.h>
+#endif
+
+#ifdef __aarch64__
+#include "absl/crc/internal/non_temporal_arm_intrinsics.h"
+#endif
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+
+#include "absl/base/config.h"
+#include "absl/base/optimization.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+// This non-temporal memcpy does regular load and non-temporal store memory
+// copy. It is compatible to both 16-byte aligned and unaligned addresses. If
+// data at the destination is not immediately accessed, using non-temporal
+// memcpy can save 1 DRAM load of the destination cacheline.
+constexpr size_t kCacheLineSize = ABSL_CACHELINE_SIZE;
+
+// If the objects overlap, the behavior is undefined.
+inline void *non_temporal_store_memcpy(void *__restrict dst,
+                                       const void *__restrict src, size_t len) {
+#if defined(__SSE3__) || defined(__aarch64__) || \
+    (defined(_MSC_VER) && defined(__AVX__))
+  // This implementation requires SSE3.
+  // MSVC cannot target SSE3 directly, but when MSVC targets AVX,
+  // SSE3 support is implied.
+  uint8_t *d = reinterpret_cast<uint8_t *>(dst);
+  const uint8_t *s = reinterpret_cast<const uint8_t *>(src);
+
+  // memcpy() the misaligned header. At the end of this if block, <d> is
+  // aligned to a 64-byte cacheline boundary or <len> == 0.
+  if (reinterpret_cast<uintptr_t>(d) & (kCacheLineSize - 1)) {
+    uintptr_t bytes_before_alignment_boundary =
+        kCacheLineSize -
+        (reinterpret_cast<uintptr_t>(d) & (kCacheLineSize - 1));
+    size_t header_len = (std::min)(bytes_before_alignment_boundary, len);
+    assert(bytes_before_alignment_boundary < kCacheLineSize);
+    memcpy(d, s, header_len);
+    d += header_len;
+    s += header_len;
+    len -= header_len;
+  }
+
+  if (len >= kCacheLineSize) {
+    _mm_sfence();
+    __m128i *dst_cacheline = reinterpret_cast<__m128i *>(d);
+    const __m128i *src_cacheline = reinterpret_cast<const __m128i *>(s);
+    constexpr int kOpsPerCacheLine = kCacheLineSize / sizeof(__m128i);
+    size_t loops = len / kCacheLineSize;
+
+    while (len >= kCacheLineSize) {
+      __m128i temp1, temp2, temp3, temp4;
+      temp1 = _mm_lddqu_si128(src_cacheline + 0);
+      temp2 = _mm_lddqu_si128(src_cacheline + 1);
+      temp3 = _mm_lddqu_si128(src_cacheline + 2);
+      temp4 = _mm_lddqu_si128(src_cacheline + 3);
+      _mm_stream_si128(dst_cacheline + 0, temp1);
+      _mm_stream_si128(dst_cacheline + 1, temp2);
+      _mm_stream_si128(dst_cacheline + 2, temp3);
+      _mm_stream_si128(dst_cacheline + 3, temp4);
+      src_cacheline += kOpsPerCacheLine;
+      dst_cacheline += kOpsPerCacheLine;
+      len -= kCacheLineSize;
+    }
+    d += loops * kCacheLineSize;
+    s += loops * kCacheLineSize;
+    _mm_sfence();
+  }
+
+  // memcpy the tail.
+  if (len) {
+    memcpy(d, s, len);
+  }
+  return dst;
+#else
+  // Fallback to regular memcpy.
+  return memcpy(dst, src, len);
+#endif  // __SSE3__ || __aarch64__ || (_MSC_VER && __AVX__)
+}
+
+inline void *non_temporal_store_memcpy_avx(void *__restrict dst,
+                                           const void *__restrict src,
+                                           size_t len) {
+#ifdef __AVX__
+  uint8_t *d = reinterpret_cast<uint8_t *>(dst);
+  const uint8_t *s = reinterpret_cast<const uint8_t *>(src);
+
+  // memcpy() the misaligned header. At the end of this if block, <d> is
+  // aligned to a 64-byte cacheline boundary or <len> == 0.
+  if (reinterpret_cast<uintptr_t>(d) & (kCacheLineSize - 1)) {
+    uintptr_t bytes_before_alignment_boundary =
+        kCacheLineSize -
+        (reinterpret_cast<uintptr_t>(d) & (kCacheLineSize - 1));
+    size_t header_len = (std::min)(bytes_before_alignment_boundary, len);
+    assert(bytes_before_alignment_boundary < kCacheLineSize);
+    memcpy(d, s, header_len);
+    d += header_len;
+    s += header_len;
+    len -= header_len;
+  }
+
+  if (len >= kCacheLineSize) {
+    _mm_sfence();
+    __m256i *dst_cacheline = reinterpret_cast<__m256i *>(d);
+    const __m256i *src_cacheline = reinterpret_cast<const __m256i *>(s);
+    constexpr int kOpsPerCacheLine = kCacheLineSize / sizeof(__m256i);
+    size_t loops = len / kCacheLineSize;
+
+    while (len >= kCacheLineSize) {
+      __m256i temp1, temp2;
+      temp1 = _mm256_lddqu_si256(src_cacheline + 0);
+      temp2 = _mm256_lddqu_si256(src_cacheline + 1);
+      _mm256_stream_si256(dst_cacheline + 0, temp1);
+      _mm256_stream_si256(dst_cacheline + 1, temp2);
+      src_cacheline += kOpsPerCacheLine;
+      dst_cacheline += kOpsPerCacheLine;
+      len -= kCacheLineSize;
+    }
+    d += loops * kCacheLineSize;
+    s += loops * kCacheLineSize;
+    _mm_sfence();
+  }
+
+  // memcpy the tail.
+  if (len) {
+    memcpy(d, s, len);
+  }
+  return dst;
+#else
+  // Fallback to regular memcpy when AVX is not available.
+  return memcpy(dst, src, len);
+#endif  // __AVX__
+}
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_CRC_INTERNAL_NON_TEMPORAL_MEMCPY_H_
diff --git a/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_memcpy_test.cc b/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_memcpy_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..eb07a559a5346b3969794157ef5974f1af6d552b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/crc/internal/non_temporal_memcpy_test.cc
@@ -0,0 +1,88 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/crc/internal/non_temporal_memcpy.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+struct TestParam {
+  size_t copy_size;
+  uint32_t src_offset;
+  uint32_t dst_offset;
+};
+
+class NonTemporalMemcpyTest : public testing::TestWithParam<TestParam> {
+ protected:
+  void SetUp() override {
+    // Make buf_size multiple of 16 bytes.
+    size_t buf_size = ((std::max(GetParam().src_offset, GetParam().dst_offset) +
+                        GetParam().copy_size) +
+                       15) /
+                      16 * 16;
+    a_.resize(buf_size);
+    b_.resize(buf_size);
+    for (size_t i = 0; i < buf_size; i++) {
+      a_[i] = static_cast<uint8_t>(i % 256);
+      b_[i] = ~a_[i];
+    }
+  }
+
+  std::vector<uint8_t> a_, b_;
+};
+
+TEST_P(NonTemporalMemcpyTest, SSEEquality) {
+  uint8_t *src = a_.data() + GetParam().src_offset;
+  uint8_t *dst = b_.data() + GetParam().dst_offset;
+  absl::crc_internal::non_temporal_store_memcpy(dst, src, GetParam().copy_size);
+  for (size_t i = 0; i < GetParam().copy_size; i++) {
+    EXPECT_EQ(src[i], dst[i]);
+  }
+}
+
+TEST_P(NonTemporalMemcpyTest, AVXEquality) {
+  uint8_t* src = a_.data() + GetParam().src_offset;
+  uint8_t* dst = b_.data() + GetParam().dst_offset;
+
+  absl::crc_internal::non_temporal_store_memcpy_avx(dst, src,
+                                                    GetParam().copy_size);
+  for (size_t i = 0; i < GetParam().copy_size; i++) {
+    EXPECT_EQ(src[i], dst[i]);
+  }
+}
+
+// 63B is smaller than one cacheline operation thus the non-temporal routine
+// will not be called.
+// 4352B is sufficient for testing 4092B data copy with room for offsets.
+constexpr TestParam params[] = {
+    {63, 0, 0},       {58, 5, 5},    {61, 2, 0},    {61, 0, 2},
+    {58, 5, 2},       {4096, 0, 0},  {4096, 0, 1},  {4096, 0, 2},
+    {4096, 0, 3},     {4096, 0, 4},  {4096, 0, 5},  {4096, 0, 6},
+    {4096, 0, 7},     {4096, 0, 8},  {4096, 0, 9},  {4096, 0, 10},
+    {4096, 0, 11},    {4096, 0, 12}, {4096, 0, 13}, {4096, 0, 14},
+    {4096, 0, 15},    {4096, 7, 7},  {4096, 3, 0},  {4096, 1, 0},
+    {4096, 9, 3},     {4096, 9, 11}, {8192, 0, 0},  {8192, 5, 2},
+    {1024768, 7, 11}, {1, 0, 0},     {1, 0, 1},     {1, 1, 0},
+    {1, 1, 1}};
+
+INSTANTIATE_TEST_SUITE_P(ParameterizedNonTemporalMemcpyTest,
+                         NonTemporalMemcpyTest, testing::ValuesIn(params));
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/debugging/BUILD.bazel b/weight/_dep/abseil-cpp/absl/debugging/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..5baff7a116f93c8333a2f50803f82b7f1408da56
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/BUILD.bazel
@@ -0,0 +1,342 @@
+#
+# Copyright 2017 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "stacktrace",
+    srcs = [
+        "internal/stacktrace_aarch64-inl.inc",
+        "internal/stacktrace_arm-inl.inc",
+        "internal/stacktrace_config.h",
+        "internal/stacktrace_emscripten-inl.inc",
+        "internal/stacktrace_generic-inl.inc",
+        "internal/stacktrace_powerpc-inl.inc",
+        "internal/stacktrace_riscv-inl.inc",
+        "internal/stacktrace_unimplemented-inl.inc",
+        "internal/stacktrace_win32-inl.inc",
+        "internal/stacktrace_x86-inl.inc",
+        "stacktrace.cc",
+    ],
+    hdrs = ["stacktrace.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":debugging_internal",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:dynamic_annotations",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_test(
+    name = "stacktrace_test",
+    srcs = ["stacktrace_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":stacktrace",
+        "//absl/base:core_headers",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "symbolize",
+    srcs = [
+        "symbolize.cc",
+        "symbolize_darwin.inc",
+        "symbolize_elf.inc",
+        "symbolize_emscripten.inc",
+        "symbolize_unimplemented.inc",
+        "symbolize_win32.inc",
+    ],
+    hdrs = [
+        "internal/symbolize.h",
+        "symbolize.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS + select({
+        "//absl:msvc_compiler": ["-DEFAULTLIB:dbghelp.lib"],
+        "//absl:clang-cl_compiler": ["-DEFAULTLIB:dbghelp.lib"],
+        "//absl:mingw_compiler": [
+            "-DEFAULTLIB:dbghelp.lib",
+            "-ldbghelp",
+        ],
+        "//conditions:default": [],
+    }),
+    deps = [
+        ":debugging_internal",
+        ":demangle_internal",
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:dynamic_annotations",
+        "//absl/base:malloc_internal",
+        "//absl/base:raw_logging_internal",
+        "//absl/strings",
+    ],
+)
+
+cc_test(
+    name = "symbolize_test",
+    srcs = ["symbolize_test.cc"],
+    copts = ABSL_TEST_COPTS + select({
+        "//absl:msvc_compiler": ["/Z7"],
+        "//absl:clang-cl_compiler": ["/Z7"],
+        "//conditions:default": [],
+    }),
+    linkopts = ABSL_DEFAULT_LINKOPTS + select({
+        "//absl:msvc_compiler": ["/DEBUG"],
+        "//absl:clang-cl_compiler": ["/DEBUG"],
+        "//conditions:default": [],
+    }),
+    deps = [
+        ":stack_consumption",
+        ":symbolize",
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/log",
+        "//absl/log:check",
+        "//absl/memory",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_library(
+    name = "examine_stack",
+    srcs = [
+        "internal/examine_stack.cc",
+    ],
+    hdrs = [
+        "internal/examine_stack.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//absl/log/internal:__pkg__"],
+    deps = [
+        ":stacktrace",
+        ":symbolize",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_library(
+    name = "failure_signal_handler",
+    srcs = ["failure_signal_handler.cc"],
+    hdrs = ["failure_signal_handler.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":examine_stack",
+        ":stacktrace",
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_test(
+    name = "failure_signal_handler_test",
+    srcs = ["failure_signal_handler_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = select({
+        "//absl:msvc_compiler": [],
+        "//absl:clang-cl_compiler": [],
+        "//absl:wasm": [],
+        "//conditions:default": ["-pthread"],
+    }) + ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":failure_signal_handler",
+        ":stacktrace",
+        ":symbolize",
+        "//absl/base:raw_logging_internal",
+        "//absl/log:check",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_library(
+    name = "debugging_internal",
+    srcs = [
+        "internal/address_is_readable.cc",
+        "internal/elf_mem_image.cc",
+        "internal/vdso_support.cc",
+    ],
+    hdrs = [
+        "internal/address_is_readable.h",
+        "internal/elf_mem_image.h",
+        "internal/vdso_support.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:dynamic_annotations",
+        "//absl/base:errno_saver",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_library(
+    name = "demangle_internal",
+    srcs = ["internal/demangle.cc"],
+    hdrs = ["internal/demangle.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        "//absl/container:__pkg__",
+        "//absl/debugging:__pkg__",
+    ],
+    deps = [
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "demangle_test",
+    srcs = ["internal/demangle_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":demangle_internal",
+        ":stack_consumption",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/log",
+        "//absl/memory",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "leak_check",
+    srcs = ["leak_check.cc"],
+    hdrs = ["leak_check.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "leak_check_test",
+    srcs = ["leak_check_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["notsan"],
+    deps = [
+        ":leak_check",
+        "//absl/base:config",
+        "//absl/log",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+# Binary that leaks memory and expects to fail on exit.  This isn't a
+# test that expected to pass on its own; it exists to be called by a
+# script that checks exit status and output.
+# TODO(absl-team): Write a test to run this with a script that
+# verifies that it correctly fails.
+cc_binary(
+    name = "leak_check_fail_test_binary",
+    srcs = ["leak_check_fail_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":leak_check",
+        "//absl/log",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "stack_consumption",
+    testonly = 1,
+    srcs = ["internal/stack_consumption.cc"],
+    hdrs = ["internal/stack_consumption.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_test(
+    name = "stack_consumption_test",
+    srcs = ["internal/stack_consumption_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["notsan"],
+    deps = [
+        ":stack_consumption",
+        "//absl/base:core_headers",
+        "//absl/log",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_binary(
+    name = "stacktrace_benchmark",
+    testonly = 1,
+    srcs = ["stacktrace_benchmark.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    deps = [
+        ":stacktrace",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler.cc b/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..570d1e504d89901f12d838793e4830272c4f7bdd
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler.cc
@@ -0,0 +1,405 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "absl/debugging/failure_signal_handler.h"
+
+#include "absl/base/config.h"
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <sched.h>
+#include <unistd.h>
+#endif
+
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif
+
+#ifdef ABSL_HAVE_MMAP
+#include <sys/mman.h>
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+#endif
+
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
+
+#include <algorithm>
+#include <atomic>
+#include <cerrno>
+#include <csignal>
+#include <cstdio>
+#include <cstring>
+#include <ctime>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/sysinfo.h"
+#include "absl/debugging/internal/examine_stack.h"
+#include "absl/debugging/stacktrace.h"
+
+#if !defined(_WIN32) && !defined(__wasi__)
+#define ABSL_HAVE_SIGACTION
+// Apple WatchOS and TVOS don't allow sigaltstack
+// Apple macOS has sigaltstack, but using it makes backtrace() unusable.
+#if !(defined(TARGET_OS_OSX) && TARGET_OS_OSX) &&     \
+    !(defined(TARGET_OS_WATCH) && TARGET_OS_WATCH) && \
+    !(defined(TARGET_OS_TV) && TARGET_OS_TV) && !defined(__QNX__)
+#define ABSL_HAVE_SIGALTSTACK
+#endif
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+ABSL_CONST_INIT static FailureSignalHandlerOptions fsh_options;
+
+// Resets the signal handler for signo to the default action for that
+// signal, then raises the signal.
+static void RaiseToDefaultHandler(int signo) {
+  signal(signo, SIG_DFL);
+  raise(signo);
+}
+
+struct FailureSignalData {
+  const int signo;
+  const char* const as_string;
+#ifdef ABSL_HAVE_SIGACTION
+  struct sigaction previous_action;
+  // StructSigaction is used to silence -Wmissing-field-initializers.
+  using StructSigaction = struct sigaction;
+#define FSD_PREVIOUS_INIT FailureSignalData::StructSigaction()
+#else
+  void (*previous_handler)(int);
+#define FSD_PREVIOUS_INIT SIG_DFL
+#endif
+};
+
+ABSL_CONST_INIT static FailureSignalData failure_signal_data[] = {
+    {SIGSEGV, "SIGSEGV", FSD_PREVIOUS_INIT},
+    {SIGILL, "SIGILL", FSD_PREVIOUS_INIT},
+    {SIGFPE, "SIGFPE", FSD_PREVIOUS_INIT},
+    {SIGABRT, "SIGABRT", FSD_PREVIOUS_INIT},
+    {SIGTERM, "SIGTERM", FSD_PREVIOUS_INIT},
+#ifndef _WIN32
+    {SIGBUS, "SIGBUS", FSD_PREVIOUS_INIT},
+    {SIGTRAP, "SIGTRAP", FSD_PREVIOUS_INIT},
+#endif
+};
+
+#undef FSD_PREVIOUS_INIT
+
+static void RaiseToPreviousHandler(int signo) {
+  // Search for the previous handler.
+  for (const auto& it : failure_signal_data) {
+    if (it.signo == signo) {
+#ifdef ABSL_HAVE_SIGACTION
+      sigaction(signo, &it.previous_action, nullptr);
+#else
+      signal(signo, it.previous_handler);
+#endif
+      raise(signo);
+      return;
+    }
+  }
+
+  // Not found, use the default handler.
+  RaiseToDefaultHandler(signo);
+}
+
+namespace debugging_internal {
+
+const char* FailureSignalToString(int signo) {
+  for (const auto& it : failure_signal_data) {
+    if (it.signo == signo) {
+      return it.as_string;
+    }
+  }
+  return "";
+}
+
+}  // namespace debugging_internal
+
+#ifdef ABSL_HAVE_SIGALTSTACK
+
+static bool SetupAlternateStackOnce() {
+#if defined(__wasm__) || defined(__asjms__)
+  const size_t page_mask = getpagesize() - 1;
+#else
+  const size_t page_mask = static_cast<size_t>(sysconf(_SC_PAGESIZE)) - 1;
+#endif
+  size_t stack_size =
+      (std::max(static_cast<size_t>(SIGSTKSZ), size_t{65536}) + page_mask) &
+      ~page_mask;
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
+    defined(ABSL_HAVE_MEMORY_SANITIZER) || defined(ABSL_HAVE_THREAD_SANITIZER)
+  // Account for sanitizer instrumentation requiring additional stack space.
+  stack_size *= 5;
+#endif
+
+  stack_t sigstk;
+  memset(&sigstk, 0, sizeof(sigstk));
+  sigstk.ss_size = stack_size;
+
+#ifdef ABSL_HAVE_MMAP
+#ifndef MAP_STACK
+#define MAP_STACK 0
+#endif
+  sigstk.ss_sp = mmap(nullptr, sigstk.ss_size, PROT_READ | PROT_WRITE,
+                      MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
+  if (sigstk.ss_sp == MAP_FAILED) {
+    ABSL_RAW_LOG(FATAL, "mmap() for alternate signal stack failed");
+  }
+#else
+  sigstk.ss_sp = malloc(sigstk.ss_size);
+  if (sigstk.ss_sp == nullptr) {
+    ABSL_RAW_LOG(FATAL, "malloc() for alternate signal stack failed");
+  }
+#endif
+
+  if (sigaltstack(&sigstk, nullptr) != 0) {
+    ABSL_RAW_LOG(FATAL, "sigaltstack() failed with errno=%d", errno);
+  }
+
+#ifdef __linux__
+#if defined(PR_SET_VMA) && defined(PR_SET_VMA_ANON_NAME)
+  // Make a best-effort attempt to name the allocated region in
+  // /proc/$PID/smaps.
+  //
+  // The call to prctl() may fail if the kernel was not configured with the
+  // CONFIG_ANON_VMA_NAME kernel option.  This is OK since the call is
+  // primarily a debugging aid.
+  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, sigstk.ss_sp, sigstk.ss_size,
+        "absl-signalstack");
+#endif
+#endif  // __linux__
+
+  return true;
+}
+
+#endif
+
+#ifdef ABSL_HAVE_SIGACTION
+
+// Sets up an alternate stack for signal handlers once.
+// Returns the appropriate flag for sig_action.sa_flags
+// if the system supports using an alternate stack.
+static int MaybeSetupAlternateStack() {
+#ifdef ABSL_HAVE_SIGALTSTACK
+  ABSL_ATTRIBUTE_UNUSED static const bool kOnce = SetupAlternateStackOnce();
+  return SA_ONSTACK;
+#else
+  return 0;
+#endif
+}
+
+static void InstallOneFailureHandler(FailureSignalData* data,
+                                     void (*handler)(int, siginfo_t*, void*)) {
+  struct sigaction act;
+  memset(&act, 0, sizeof(act));
+  sigemptyset(&act.sa_mask);
+  act.sa_flags |= SA_SIGINFO;
+  // SA_NODEFER is required to handle SIGABRT from
+  // ImmediateAbortSignalHandler().
+  act.sa_flags |= SA_NODEFER;
+  if (fsh_options.use_alternate_stack) {
+    act.sa_flags |= MaybeSetupAlternateStack();
+  }
+  act.sa_sigaction = handler;
+  ABSL_RAW_CHECK(sigaction(data->signo, &act, &data->previous_action) == 0,
+                 "sigaction() failed");
+}
+
+#else
+
+static void InstallOneFailureHandler(FailureSignalData* data,
+                                     void (*handler)(int)) {
+  data->previous_handler = signal(data->signo, handler);
+  ABSL_RAW_CHECK(data->previous_handler != SIG_ERR, "signal() failed");
+}
+
+#endif
+
+static void WriteSignalMessage(int signo, int cpu,
+                               void (*writerfn)(const char*)) {
+  char buf[96];
+  char on_cpu[32] = {0};
+  if (cpu != -1) {
+    snprintf(on_cpu, sizeof(on_cpu), " on cpu %d", cpu);
+  }
+  const char* const signal_string =
+      debugging_internal::FailureSignalToString(signo);
+  if (signal_string != nullptr && signal_string[0] != '\0') {
+    snprintf(buf, sizeof(buf), "*** %s received at time=%ld%s ***\n",
+             signal_string,
+             static_cast<long>(time(nullptr)),  // NOLINT(runtime/int)
+             on_cpu);
+  } else {
+    snprintf(buf, sizeof(buf), "*** Signal %d received at time=%ld%s ***\n",
+             signo, static_cast<long>(time(nullptr)),  // NOLINT(runtime/int)
+             on_cpu);
+  }
+  writerfn(buf);
+}
+
+// `void*` might not be big enough to store `void(*)(const char*)`.
+struct WriterFnStruct {
+  void (*writerfn)(const char*);
+};
+
+// Many of the absl::debugging_internal::Dump* functions in
+// examine_stack.h take a writer function pointer that has a void* arg
+// for historical reasons. failure_signal_handler_writer only takes a
+// data pointer. This function converts between these types.
+static void WriterFnWrapper(const char* data, void* arg) {
+  static_cast<WriterFnStruct*>(arg)->writerfn(data);
+}
+
+// Convenient wrapper around DumpPCAndFrameSizesAndStackTrace() for signal
+// handlers. "noinline" so that GetStackFrames() skips the top-most stack
+// frame for this function.
+ABSL_ATTRIBUTE_NOINLINE static void WriteStackTrace(
+    void* ucontext, bool symbolize_stacktrace,
+    void (*writerfn)(const char*, void*), void* writerfn_arg) {
+  constexpr int kNumStackFrames = 32;
+  void* stack[kNumStackFrames];
+  int frame_sizes[kNumStackFrames];
+  int min_dropped_frames;
+  int depth = absl::GetStackFramesWithContext(
+      stack, frame_sizes, kNumStackFrames,
+      1,  // Do not include this function in stack trace.
+      ucontext, &min_dropped_frames);
+  absl::debugging_internal::DumpPCAndFrameSizesAndStackTrace(
+      absl::debugging_internal::GetProgramCounter(ucontext), stack, frame_sizes,
+      depth, min_dropped_frames, symbolize_stacktrace, writerfn, writerfn_arg);
+}
+
+// Called by AbslFailureSignalHandler() to write the failure info. It is
+// called once with writerfn set to WriteToStderr() and then possibly
+// with writerfn set to the user provided function.
+static void WriteFailureInfo(int signo, void* ucontext, int cpu,
+                             void (*writerfn)(const char*)) {
+  WriterFnStruct writerfn_struct{writerfn};
+  WriteSignalMessage(signo, cpu, writerfn);
+  WriteStackTrace(ucontext, fsh_options.symbolize_stacktrace, WriterFnWrapper,
+                  &writerfn_struct);
+}
+
+// absl::SleepFor() can't be used here since AbslInternalSleepFor()
+// may be overridden to do something that isn't async-signal-safe on
+// some platforms.
+static void PortableSleepForSeconds(int seconds) {
+#ifdef _WIN32
+  Sleep(static_cast<DWORD>(seconds * 1000));
+#else
+  struct timespec sleep_time;
+  sleep_time.tv_sec = seconds;
+  sleep_time.tv_nsec = 0;
+  while (nanosleep(&sleep_time, &sleep_time) != 0 && errno == EINTR) {
+  }
+#endif
+}
+
+#ifdef ABSL_HAVE_ALARM
+// AbslFailureSignalHandler() installs this as a signal handler for
+// SIGALRM, then sets an alarm to be delivered to the program after a
+// set amount of time. If AbslFailureSignalHandler() hangs for more than
+// the alarm timeout, ImmediateAbortSignalHandler() will abort the
+// program.
+static void ImmediateAbortSignalHandler(int) { RaiseToDefaultHandler(SIGABRT); }
+#endif
+
+// absl::base_internal::GetTID() returns pid_t on most platforms, but
+// returns absl::base_internal::pid_t on Windows.
+using GetTidType = decltype(absl::base_internal::GetTID());
+ABSL_CONST_INIT static std::atomic<GetTidType> failed_tid(0);
+
+#ifndef ABSL_HAVE_SIGACTION
+static void AbslFailureSignalHandler(int signo) {
+  void* ucontext = nullptr;
+#else
+static void AbslFailureSignalHandler(int signo, siginfo_t*, void* ucontext) {
+#endif
+
+  const GetTidType this_tid = absl::base_internal::GetTID();
+  GetTidType previous_failed_tid = 0;
+  if (!failed_tid.compare_exchange_strong(previous_failed_tid, this_tid,
+                                          std::memory_order_acq_rel,
+                                          std::memory_order_relaxed)) {
+    ABSL_RAW_LOG(
+        ERROR,
+        "Signal %d raised at PC=%p while already in AbslFailureSignalHandler()",
+        signo, absl::debugging_internal::GetProgramCounter(ucontext));
+    if (this_tid != previous_failed_tid) {
+      // Another thread is already in AbslFailureSignalHandler(), so wait
+      // a bit for it to finish. If the other thread doesn't kill us,
+      // we do so after sleeping.
+      PortableSleepForSeconds(3);
+      RaiseToDefaultHandler(signo);
+      // The recursively raised signal may be blocked until we return.
+      return;
+    }
+  }
+
+  // Increase the chance that the CPU we report was the same CPU on which the
+  // signal was received by doing this as early as possible, i.e. after
+  // verifying that this is not a recursive signal handler invocation.
+  int my_cpu = -1;
+#ifdef ABSL_HAVE_SCHED_GETCPU
+  my_cpu = sched_getcpu();
+#endif
+
+#ifdef ABSL_HAVE_ALARM
+  // Set an alarm to abort the program in case this code hangs or deadlocks.
+  if (fsh_options.alarm_on_failure_secs > 0) {
+    alarm(0);  // Cancel any existing alarms.
+    signal(SIGALRM, ImmediateAbortSignalHandler);
+    alarm(static_cast<unsigned int>(fsh_options.alarm_on_failure_secs));
+  }
+#endif
+
+  // First write to stderr.
+  WriteFailureInfo(
+      signo, ucontext, my_cpu, +[](const char* data) {
+        absl::raw_log_internal::AsyncSignalSafeWriteError(data, strlen(data));
+      });
+
+  // Riskier code (because it is less likely to be async-signal-safe)
+  // goes after this point.
+  if (fsh_options.writerfn != nullptr) {
+    WriteFailureInfo(signo, ucontext, my_cpu, fsh_options.writerfn);
+    fsh_options.writerfn(nullptr);
+  }
+
+  if (fsh_options.call_previous_handler) {
+    RaiseToPreviousHandler(signo);
+  } else {
+    RaiseToDefaultHandler(signo);
+  }
+}
+
+void InstallFailureSignalHandler(const FailureSignalHandlerOptions& options) {
+  fsh_options = options;
+  for (auto& it : failure_signal_data) {
+    InstallOneFailureHandler(&it, AbslFailureSignalHandler);
+  }
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler.h b/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler.h
new file mode 100644
index 0000000000000000000000000000000000000000..5e034785f37bbbe973a29413e979daf40d5e7abc
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler.h
@@ -0,0 +1,121 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: failure_signal_handler.h
+// -----------------------------------------------------------------------------
+//
+// This file configures the Abseil *failure signal handler* to capture and dump
+// useful debugging information (such as a stacktrace) upon program failure.
+//
+// To use the failure signal handler, call `absl::InstallFailureSignalHandler()`
+// very early in your program, usually in the first few lines of main():
+//
+// int main(int argc, char** argv) {
+//   // Initialize the symbolizer to get a human-readable stack trace
+//   absl::InitializeSymbolizer(argv[0]);
+//
+//   absl::FailureSignalHandlerOptions options;
+//   absl::InstallFailureSignalHandler(options);
+//   DoSomethingInteresting();
+//   return 0;
+// }
+//
+// Any program that raises a fatal signal (such as `SIGSEGV`, `SIGILL`,
+// `SIGFPE`, `SIGABRT`, `SIGTERM`, `SIGBUG`, and `SIGTRAP`) will call the
+// installed failure signal handler and provide debugging information to stderr.
+//
+// Note that you should *not* install the Abseil failure signal handler more
+// than once. You may, of course, have another (non-Abseil) failure signal
+// handler installed (which would be triggered if Abseil's failure signal
+// handler sets `call_previous_handler` to `true`).
+
+#ifndef ABSL_DEBUGGING_FAILURE_SIGNAL_HANDLER_H_
+#define ABSL_DEBUGGING_FAILURE_SIGNAL_HANDLER_H_
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// FailureSignalHandlerOptions
+//
+// Struct for holding `absl::InstallFailureSignalHandler()` configuration
+// options.
+struct FailureSignalHandlerOptions {
+  // If true, try to symbolize the stacktrace emitted on failure, provided that
+  // you have initialized a symbolizer for that purpose. (See symbolize.h for
+  // more information.)
+  bool symbolize_stacktrace = true;
+
+  // If true, try to run signal handlers on an alternate stack (if supported on
+  // the given platform). An alternate stack is useful for program crashes due
+  // to a stack overflow; by running on a alternate stack, the signal handler
+  // may run even when normal stack space has been exhausted. The downside of
+  // using an alternate stack is that extra memory for the alternate stack needs
+  // to be pre-allocated.
+  bool use_alternate_stack = true;
+
+  // If positive, indicates the number of seconds after which the failure signal
+  // handler is invoked to abort the program. Setting such an alarm is useful in
+  // cases where the failure signal handler itself may become hung or
+  // deadlocked.
+  int alarm_on_failure_secs = 3;
+
+  // If true, call the previously registered signal handler for the signal that
+  // was received (if one was registered) after the existing signal handler
+  // runs. This mechanism can be used to chain signal handlers together.
+  //
+  // If false, the signal is raised to the default handler for that signal
+  // (which normally terminates the program).
+  //
+  // IMPORTANT: If true, the chained fatal signal handlers must not try to
+  // recover from the fatal signal. Instead, they should terminate the program
+  // via some mechanism, like raising the default handler for the signal, or by
+  // calling `_exit()`. Note that the failure signal handler may put parts of
+  // the Abseil library into a state from which they cannot recover.
+  bool call_previous_handler = false;
+
+  // If non-null, indicates a pointer to a callback function that will be called
+  // upon failure, with a string argument containing failure data. This function
+  // may be used as a hook to write failure data to a secondary location, such
+  // as a log file. This function will also be called with null data, as a hint
+  // to flush any buffered data before the program may be terminated. Consider
+  // flushing any buffered data in all calls to this function.
+  //
+  // Since this function runs within a signal handler, it should be
+  // async-signal-safe if possible.
+  // See http://man7.org/linux/man-pages/man7/signal-safety.7.html
+  void (*writerfn)(const char*) = nullptr;
+};
+
+// InstallFailureSignalHandler()
+//
+// Installs a signal handler for the common failure signals `SIGSEGV`, `SIGILL`,
+// `SIGFPE`, `SIGABRT`, `SIGTERM`, `SIGBUG`, and `SIGTRAP` (provided they exist
+// on the given platform). The failure signal handler dumps program failure data
+// useful for debugging in an unspecified format to stderr. This data may
+// include the program counter, a stacktrace, and register information on some
+// systems; do not rely on an exact format for the output, as it is subject to
+// change.
+void InstallFailureSignalHandler(const FailureSignalHandlerOptions& options);
+
+namespace debugging_internal {
+const char* FailureSignalToString(int signo);
+}  // namespace debugging_internal
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_FAILURE_SIGNAL_HANDLER_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler_test.cc b/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..72816a3e727cb7f5d093e7aa1c26e0f8154f3b94
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/failure_signal_handler_test.cc
@@ -0,0 +1,166 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "absl/debugging/failure_signal_handler.h"
+
+#include <csignal>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <fstream>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+#include "absl/log/check.h"
+#include "absl/strings/match.h"
+#include "absl/strings/str_cat.h"
+
+namespace {
+
+using testing::StartsWith;
+
+#if GTEST_HAS_DEATH_TEST
+
+// For the parameterized death tests. GetParam() returns the signal number.
+using FailureSignalHandlerDeathTest = ::testing::TestWithParam<int>;
+
+// This function runs in a fork()ed process on most systems.
+void InstallHandlerAndRaise(int signo) {
+  absl::InstallFailureSignalHandler(absl::FailureSignalHandlerOptions());
+  raise(signo);
+}
+
+TEST_P(FailureSignalHandlerDeathTest, AbslFailureSignal) {
+  const int signo = GetParam();
+  std::string exit_regex = absl::StrCat(
+      "\\*\\*\\* ", absl::debugging_internal::FailureSignalToString(signo),
+      " received at time=");
+#ifndef _WIN32
+  EXPECT_EXIT(InstallHandlerAndRaise(signo), testing::KilledBySignal(signo),
+              exit_regex);
+#else
+  // Windows doesn't have testing::KilledBySignal().
+  EXPECT_DEATH_IF_SUPPORTED(InstallHandlerAndRaise(signo), exit_regex);
+#endif
+}
+
+ABSL_CONST_INIT FILE* error_file = nullptr;
+
+void WriteToErrorFile(const char* msg) {
+  if (msg != nullptr) {
+    ABSL_RAW_CHECK(fwrite(msg, strlen(msg), 1, error_file) == 1,
+                   "fwrite() failed");
+  }
+  ABSL_RAW_CHECK(fflush(error_file) == 0, "fflush() failed");
+}
+
+std::string GetTmpDir() {
+  // TEST_TMPDIR is set by Bazel. Try the others when not running under Bazel.
+  static const char* const kTmpEnvVars[] = {"TEST_TMPDIR", "TMPDIR", "TEMP",
+                                            "TEMPDIR", "TMP"};
+  for (const char* const var : kTmpEnvVars) {
+    const char* tmp_dir = std::getenv(var);
+    if (tmp_dir != nullptr) {
+      return tmp_dir;
+    }
+  }
+
+  // Try something reasonable.
+  return "/tmp";
+}
+
+// This function runs in a fork()ed process on most systems.
+void InstallHandlerWithWriteToFileAndRaise(const char* file, int signo) {
+  error_file = fopen(file, "w");
+  CHECK_NE(error_file, nullptr) << "Failed create error_file";
+  absl::FailureSignalHandlerOptions options;
+  options.writerfn = WriteToErrorFile;
+  absl::InstallFailureSignalHandler(options);
+  raise(signo);
+}
+
+TEST_P(FailureSignalHandlerDeathTest, AbslFatalSignalsWithWriterFn) {
+  const int signo = GetParam();
+  std::string tmp_dir = GetTmpDir();
+  std::string file = absl::StrCat(tmp_dir, "/signo_", signo);
+
+  std::string exit_regex = absl::StrCat(
+      "\\*\\*\\* ", absl::debugging_internal::FailureSignalToString(signo),
+      " received at time=");
+#ifndef _WIN32
+  EXPECT_EXIT(InstallHandlerWithWriteToFileAndRaise(file.c_str(), signo),
+              testing::KilledBySignal(signo), exit_regex);
+#else
+  // Windows doesn't have testing::KilledBySignal().
+  EXPECT_DEATH_IF_SUPPORTED(
+      InstallHandlerWithWriteToFileAndRaise(file.c_str(), signo), exit_regex);
+#endif
+
+  // Open the file in this process and check its contents.
+  std::fstream error_output(file);
+  ASSERT_TRUE(error_output.is_open()) << file;
+  std::string error_line;
+  std::getline(error_output, error_line);
+  EXPECT_THAT(
+      error_line,
+      StartsWith(absl::StrCat(
+          "*** ", absl::debugging_internal::FailureSignalToString(signo),
+          " received at ")));
+
+  // On platforms where it is possible to get the current CPU, the
+  // CPU number is also logged. Check that it is present in output.
+#if defined(__linux__)
+  EXPECT_THAT(error_line, testing::HasSubstr(" on cpu "));
+#endif
+
+  if (absl::debugging_internal::StackTraceWorksForTest()) {
+    std::getline(error_output, error_line);
+    EXPECT_THAT(error_line, StartsWith("PC: "));
+  }
+}
+
+constexpr int kFailureSignals[] = {
+    SIGSEGV, SIGILL,  SIGFPE, SIGABRT, SIGTERM,
+#ifndef _WIN32
+    SIGBUS,  SIGTRAP,
+#endif
+};
+
+std::string SignalParamToString(const ::testing::TestParamInfo<int>& info) {
+  std::string result =
+      absl::debugging_internal::FailureSignalToString(info.param);
+  if (result.empty()) {
+    result = absl::StrCat(info.param);
+  }
+  return result;
+}
+
+INSTANTIATE_TEST_SUITE_P(AbslDeathTest, FailureSignalHandlerDeathTest,
+                         ::testing::ValuesIn(kFailureSignals),
+                         SignalParamToString);
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+}  // namespace
+
+int main(int argc, char** argv) {
+  absl::InitializeSymbolizer(argv[0]);
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/demangle.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/demangle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..381a2b504bae9459b0af22551c59d1b9fe73e245
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/demangle.cc
@@ -0,0 +1,2012 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// For reference check out:
+// https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling
+//
+// Note that we only have partial C++11 support yet.
+
+#include "absl/debugging/internal/demangle.h"
+
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <limits>
+#include <string>
+
+#include "absl/base/config.h"
+
+#if ABSL_INTERNAL_HAS_CXA_DEMANGLE
+#include <cxxabi.h>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+typedef struct {
+  const char *abbrev;
+  const char *real_name;
+  // Number of arguments in <expression> context, or 0 if disallowed.
+  int arity;
+} AbbrevPair;
+
+// List of operators from Itanium C++ ABI.
+static const AbbrevPair kOperatorList[] = {
+    // New has special syntax (not currently supported).
+    {"nw", "new", 0},
+    {"na", "new[]", 0},
+
+    // Works except that the 'gs' prefix is not supported.
+    {"dl", "delete", 1},
+    {"da", "delete[]", 1},
+
+    {"ps", "+", 1},  // "positive"
+    {"ng", "-", 1},  // "negative"
+    {"ad", "&", 1},  // "address-of"
+    {"de", "*", 1},  // "dereference"
+    {"co", "~", 1},
+
+    {"pl", "+", 2},
+    {"mi", "-", 2},
+    {"ml", "*", 2},
+    {"dv", "/", 2},
+    {"rm", "%", 2},
+    {"an", "&", 2},
+    {"or", "|", 2},
+    {"eo", "^", 2},
+    {"aS", "=", 2},
+    {"pL", "+=", 2},
+    {"mI", "-=", 2},
+    {"mL", "*=", 2},
+    {"dV", "/=", 2},
+    {"rM", "%=", 2},
+    {"aN", "&=", 2},
+    {"oR", "|=", 2},
+    {"eO", "^=", 2},
+    {"ls", "<<", 2},
+    {"rs", ">>", 2},
+    {"lS", "<<=", 2},
+    {"rS", ">>=", 2},
+    {"eq", "==", 2},
+    {"ne", "!=", 2},
+    {"lt", "<", 2},
+    {"gt", ">", 2},
+    {"le", "<=", 2},
+    {"ge", ">=", 2},
+    {"nt", "!", 1},
+    {"aa", "&&", 2},
+    {"oo", "||", 2},
+    {"pp", "++", 1},
+    {"mm", "--", 1},
+    {"cm", ",", 2},
+    {"pm", "->*", 2},
+    {"pt", "->", 0},  // Special syntax
+    {"cl", "()", 0},  // Special syntax
+    {"ix", "[]", 2},
+    {"qu", "?", 3},
+    {"st", "sizeof", 0},  // Special syntax
+    {"sz", "sizeof", 1},  // Not a real operator name, but used in expressions.
+    {nullptr, nullptr, 0},
+};
+
+// List of builtin types from Itanium C++ ABI.
+//
+// Invariant: only one- or two-character type abbreviations here.
+static const AbbrevPair kBuiltinTypeList[] = {
+    {"v", "void", 0},
+    {"w", "wchar_t", 0},
+    {"b", "bool", 0},
+    {"c", "char", 0},
+    {"a", "signed char", 0},
+    {"h", "unsigned char", 0},
+    {"s", "short", 0},
+    {"t", "unsigned short", 0},
+    {"i", "int", 0},
+    {"j", "unsigned int", 0},
+    {"l", "long", 0},
+    {"m", "unsigned long", 0},
+    {"x", "long long", 0},
+    {"y", "unsigned long long", 0},
+    {"n", "__int128", 0},
+    {"o", "unsigned __int128", 0},
+    {"f", "float", 0},
+    {"d", "double", 0},
+    {"e", "long double", 0},
+    {"g", "__float128", 0},
+    {"z", "ellipsis", 0},
+
+    {"De", "decimal128", 0},      // IEEE 754r decimal floating point (128 bits)
+    {"Dd", "decimal64", 0},       // IEEE 754r decimal floating point (64 bits)
+    {"Dc", "decltype(auto)", 0},
+    {"Da", "auto", 0},
+    {"Dn", "std::nullptr_t", 0},  // i.e., decltype(nullptr)
+    {"Df", "decimal32", 0},       // IEEE 754r decimal floating point (32 bits)
+    {"Di", "char32_t", 0},
+    {"Du", "char8_t", 0},
+    {"Ds", "char16_t", 0},
+    {"Dh", "float16", 0},         // IEEE 754r half-precision float (16 bits)
+    {nullptr, nullptr, 0},
+};
+
+// List of substitutions Itanium C++ ABI.
+static const AbbrevPair kSubstitutionList[] = {
+    {"St", "", 0},
+    {"Sa", "allocator", 0},
+    {"Sb", "basic_string", 0},
+    // std::basic_string<char, std::char_traits<char>,std::allocator<char> >
+    {"Ss", "string", 0},
+    // std::basic_istream<char, std::char_traits<char> >
+    {"Si", "istream", 0},
+    // std::basic_ostream<char, std::char_traits<char> >
+    {"So", "ostream", 0},
+    // std::basic_iostream<char, std::char_traits<char> >
+    {"Sd", "iostream", 0},
+    {nullptr, nullptr, 0},
+};
+
+// State needed for demangling.  This struct is copied in almost every stack
+// frame, so every byte counts.
+typedef struct {
+  int mangled_idx;                     // Cursor of mangled name.
+  int out_cur_idx;                     // Cursor of output string.
+  int prev_name_idx;                   // For constructors/destructors.
+  unsigned int prev_name_length : 16;  // For constructors/destructors.
+  signed int nest_level : 15;          // For nested names.
+  unsigned int append : 1;             // Append flag.
+  // Note: for some reason MSVC can't pack "bool append : 1" into the same int
+  // with the above two fields, so we use an int instead.  Amusingly it can pack
+  // "signed bool" as expected, but relying on that to continue to be a legal
+  // type seems ill-advised (as it's illegal in at least clang).
+} ParseState;
+
+static_assert(sizeof(ParseState) == 4 * sizeof(int),
+              "unexpected size of ParseState");
+
+// One-off state for demangling that's not subject to backtracking -- either
+// constant data, data that's intentionally immune to backtracking (steps), or
+// data that would never be changed by backtracking anyway (recursion_depth).
+//
+// Only one copy of this exists for each call to Demangle, so the size of this
+// struct is nearly inconsequential.
+typedef struct {
+  const char *mangled_begin;  // Beginning of input string.
+  char *out;                  // Beginning of output string.
+  int out_end_idx;            // One past last allowed output character.
+  int recursion_depth;        // For stack exhaustion prevention.
+  int steps;               // Cap how much work we'll do, regardless of depth.
+  ParseState parse_state;  // Backtrackable state copied for most frames.
+} State;
+
+namespace {
+// Prevent deep recursion / stack exhaustion.
+// Also prevent unbounded handling of complex inputs.
+class ComplexityGuard {
+ public:
+  explicit ComplexityGuard(State *state) : state_(state) {
+    ++state->recursion_depth;
+    ++state->steps;
+  }
+  ~ComplexityGuard() { --state_->recursion_depth; }
+
+  // 256 levels of recursion seems like a reasonable upper limit on depth.
+  // 128 is not enough to demagle synthetic tests from demangle_unittest.txt:
+  // "_ZaaZZZZ..." and "_ZaaZcvZcvZ..."
+  static constexpr int kRecursionDepthLimit = 256;
+
+  // We're trying to pick a charitable upper-limit on how many parse steps are
+  // necessary to handle something that a human could actually make use of.
+  // This is mostly in place as a bound on how much work we'll do if we are
+  // asked to demangle an mangled name from an untrusted source, so it should be
+  // much larger than the largest expected symbol, but much smaller than the
+  // amount of work we can do in, e.g., a second.
+  //
+  // Some real-world symbols from an arbitrary binary started failing between
+  // 2^12 and 2^13, so we multiply the latter by an extra factor of 16 to set
+  // the limit.
+  //
+  // Spending one second on 2^17 parse steps would require each step to take
+  // 7.6us, or ~30000 clock cycles, so it's safe to say this can be done in
+  // under a second.
+  static constexpr int kParseStepsLimit = 1 << 17;
+
+  bool IsTooComplex() const {
+    return state_->recursion_depth > kRecursionDepthLimit ||
+           state_->steps > kParseStepsLimit;
+  }
+
+ private:
+  State *state_;
+};
+}  // namespace
+
+// We don't use strlen() in libc since it's not guaranteed to be async
+// signal safe.
+static size_t StrLen(const char *str) {
+  size_t len = 0;
+  while (*str != '\0') {
+    ++str;
+    ++len;
+  }
+  return len;
+}
+
+// Returns true if "str" has at least "n" characters remaining.
+static bool AtLeastNumCharsRemaining(const char *str, size_t n) {
+  for (size_t i = 0; i < n; ++i) {
+    if (str[i] == '\0') {
+      return false;
+    }
+  }
+  return true;
+}
+
+// Returns true if "str" has "prefix" as a prefix.
+static bool StrPrefix(const char *str, const char *prefix) {
+  size_t i = 0;
+  while (str[i] != '\0' && prefix[i] != '\0' && str[i] == prefix[i]) {
+    ++i;
+  }
+  return prefix[i] == '\0';  // Consumed everything in "prefix".
+}
+
+static void InitState(State* state,
+                      const char* mangled,
+                      char* out,
+                      size_t out_size) {
+  state->mangled_begin = mangled;
+  state->out = out;
+  state->out_end_idx = static_cast<int>(out_size);
+  state->recursion_depth = 0;
+  state->steps = 0;
+
+  state->parse_state.mangled_idx = 0;
+  state->parse_state.out_cur_idx = 0;
+  state->parse_state.prev_name_idx = 0;
+  state->parse_state.prev_name_length = 0;
+  state->parse_state.nest_level = -1;
+  state->parse_state.append = true;
+}
+
+static inline const char *RemainingInput(State *state) {
+  return &state->mangled_begin[state->parse_state.mangled_idx];
+}
+
+// Returns true and advances "mangled_idx" if we find "one_char_token"
+// at "mangled_idx" position.  It is assumed that "one_char_token" does
+// not contain '\0'.
+static bool ParseOneCharToken(State *state, const char one_char_token) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (RemainingInput(state)[0] == one_char_token) {
+    ++state->parse_state.mangled_idx;
+    return true;
+  }
+  return false;
+}
+
+// Returns true and advances "mangled_cur" if we find "two_char_token"
+// at "mangled_cur" position.  It is assumed that "two_char_token" does
+// not contain '\0'.
+static bool ParseTwoCharToken(State *state, const char *two_char_token) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (RemainingInput(state)[0] == two_char_token[0] &&
+      RemainingInput(state)[1] == two_char_token[1]) {
+    state->parse_state.mangled_idx += 2;
+    return true;
+  }
+  return false;
+}
+
+// Returns true and advances "mangled_cur" if we find any character in
+// "char_class" at "mangled_cur" position.
+static bool ParseCharClass(State *state, const char *char_class) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (RemainingInput(state)[0] == '\0') {
+    return false;
+  }
+  const char *p = char_class;
+  for (; *p != '\0'; ++p) {
+    if (RemainingInput(state)[0] == *p) {
+      ++state->parse_state.mangled_idx;
+      return true;
+    }
+  }
+  return false;
+}
+
+static bool ParseDigit(State *state, int *digit) {
+  char c = RemainingInput(state)[0];
+  if (ParseCharClass(state, "0123456789")) {
+    if (digit != nullptr) {
+      *digit = c - '0';
+    }
+    return true;
+  }
+  return false;
+}
+
+// This function is used for handling an optional non-terminal.
+static bool Optional(bool /*status*/) { return true; }
+
+// This function is used for handling <non-terminal>+ syntax.
+typedef bool (*ParseFunc)(State *);
+static bool OneOrMore(ParseFunc parse_func, State *state) {
+  if (parse_func(state)) {
+    while (parse_func(state)) {
+    }
+    return true;
+  }
+  return false;
+}
+
+// This function is used for handling <non-terminal>* syntax. The function
+// always returns true and must be followed by a termination token or a
+// terminating sequence not handled by parse_func (e.g.
+// ParseOneCharToken(state, 'E')).
+static bool ZeroOrMore(ParseFunc parse_func, State *state) {
+  while (parse_func(state)) {
+  }
+  return true;
+}
+
+// Append "str" at "out_cur_idx".  If there is an overflow, out_cur_idx is
+// set to out_end_idx+1.  The output string is ensured to
+// always terminate with '\0' as long as there is no overflow.
+static void Append(State *state, const char *const str, const size_t length) {
+  for (size_t i = 0; i < length; ++i) {
+    if (state->parse_state.out_cur_idx + 1 <
+        state->out_end_idx) {  // +1 for '\0'
+      state->out[state->parse_state.out_cur_idx++] = str[i];
+    } else {
+      // signal overflow
+      state->parse_state.out_cur_idx = state->out_end_idx + 1;
+      break;
+    }
+  }
+  if (state->parse_state.out_cur_idx < state->out_end_idx) {
+    state->out[state->parse_state.out_cur_idx] =
+        '\0';  // Terminate it with '\0'
+  }
+}
+
+// We don't use equivalents in libc to avoid locale issues.
+static bool IsLower(char c) { return c >= 'a' && c <= 'z'; }
+
+static bool IsAlpha(char c) {
+  return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
+}
+
+static bool IsDigit(char c) { return c >= '0' && c <= '9'; }
+
+// Returns true if "str" is a function clone suffix.  These suffixes are used
+// by GCC 4.5.x and later versions (and our locally-modified version of GCC
+// 4.4.x) to indicate functions which have been cloned during optimization.
+// We treat any sequence (.<alpha>+.<digit>+)+ as a function clone suffix.
+// Additionally, '_' is allowed along with the alphanumeric sequence.
+static bool IsFunctionCloneSuffix(const char *str) {
+  size_t i = 0;
+  while (str[i] != '\0') {
+    bool parsed = false;
+    // Consume a single [.<alpha> | _]*[.<digit>]* sequence.
+    if (str[i] == '.' && (IsAlpha(str[i + 1]) || str[i + 1] == '_')) {
+      parsed = true;
+      i += 2;
+      while (IsAlpha(str[i]) || str[i] == '_') {
+        ++i;
+      }
+    }
+    if (str[i] == '.' && IsDigit(str[i + 1])) {
+      parsed = true;
+      i += 2;
+      while (IsDigit(str[i])) {
+        ++i;
+      }
+    }
+    if (!parsed)
+      return false;
+  }
+  return true;  // Consumed everything in "str".
+}
+
+static bool EndsWith(State *state, const char chr) {
+  return state->parse_state.out_cur_idx > 0 &&
+         state->parse_state.out_cur_idx < state->out_end_idx &&
+         chr == state->out[state->parse_state.out_cur_idx - 1];
+}
+
+// Append "str" with some tweaks, iff "append" state is true.
+static void MaybeAppendWithLength(State *state, const char *const str,
+                                  const size_t length) {
+  if (state->parse_state.append && length > 0) {
+    // Append a space if the output buffer ends with '<' and "str"
+    // starts with '<' to avoid <<<.
+    if (str[0] == '<' && EndsWith(state, '<')) {
+      Append(state, " ", 1);
+    }
+    // Remember the last identifier name for ctors/dtors,
+    // but only if we haven't yet overflown the buffer.
+    if (state->parse_state.out_cur_idx < state->out_end_idx &&
+        (IsAlpha(str[0]) || str[0] == '_')) {
+      state->parse_state.prev_name_idx = state->parse_state.out_cur_idx;
+      state->parse_state.prev_name_length = static_cast<unsigned int>(length);
+    }
+    Append(state, str, length);
+  }
+}
+
+// Appends a positive decimal number to the output if appending is enabled.
+static bool MaybeAppendDecimal(State *state, int val) {
+  // Max {32-64}-bit unsigned int is 20 digits.
+  constexpr size_t kMaxLength = 20;
+  char buf[kMaxLength];
+
+  // We can't use itoa or sprintf as neither is specified to be
+  // async-signal-safe.
+  if (state->parse_state.append) {
+    // We can't have a one-before-the-beginning pointer, so instead start with
+    // one-past-the-end and manipulate one character before the pointer.
+    char *p = &buf[kMaxLength];
+    do {  // val=0 is the only input that should write a leading zero digit.
+      *--p = static_cast<char>((val % 10) + '0');
+      val /= 10;
+    } while (p > buf && val != 0);
+
+    // 'p' landed on the last character we set.  How convenient.
+    Append(state, p, kMaxLength - static_cast<size_t>(p - buf));
+  }
+
+  return true;
+}
+
+// A convenient wrapper around MaybeAppendWithLength().
+// Returns true so that it can be placed in "if" conditions.
+static bool MaybeAppend(State *state, const char *const str) {
+  if (state->parse_state.append) {
+    size_t length = StrLen(str);
+    MaybeAppendWithLength(state, str, length);
+  }
+  return true;
+}
+
+// This function is used for handling nested names.
+static bool EnterNestedName(State *state) {
+  state->parse_state.nest_level = 0;
+  return true;
+}
+
+// This function is used for handling nested names.
+static bool LeaveNestedName(State *state, int16_t prev_value) {
+  state->parse_state.nest_level = prev_value;
+  return true;
+}
+
+// Disable the append mode not to print function parameters, etc.
+static bool DisableAppend(State *state) {
+  state->parse_state.append = false;
+  return true;
+}
+
+// Restore the append mode to the previous state.
+static bool RestoreAppend(State *state, bool prev_value) {
+  state->parse_state.append = prev_value;
+  return true;
+}
+
+// Increase the nest level for nested names.
+static void MaybeIncreaseNestLevel(State *state) {
+  if (state->parse_state.nest_level > -1) {
+    ++state->parse_state.nest_level;
+  }
+}
+
+// Appends :: for nested names if necessary.
+static void MaybeAppendSeparator(State *state) {
+  if (state->parse_state.nest_level >= 1) {
+    MaybeAppend(state, "::");
+  }
+}
+
+// Cancel the last separator if necessary.
+static void MaybeCancelLastSeparator(State *state) {
+  if (state->parse_state.nest_level >= 1 && state->parse_state.append &&
+      state->parse_state.out_cur_idx >= 2) {
+    state->parse_state.out_cur_idx -= 2;
+    state->out[state->parse_state.out_cur_idx] = '\0';
+  }
+}
+
+// Returns true if the identifier of the given length pointed to by
+// "mangled_cur" is anonymous namespace.
+static bool IdentifierIsAnonymousNamespace(State *state, size_t length) {
+  // Returns true if "anon_prefix" is a proper prefix of "mangled_cur".
+  static const char anon_prefix[] = "_GLOBAL__N_";
+  return (length > (sizeof(anon_prefix) - 1) &&
+          StrPrefix(RemainingInput(state), anon_prefix));
+}
+
+// Forward declarations of our parsing functions.
+static bool ParseMangledName(State *state);
+static bool ParseEncoding(State *state);
+static bool ParseName(State *state);
+static bool ParseUnscopedName(State *state);
+static bool ParseNestedName(State *state);
+static bool ParsePrefix(State *state);
+static bool ParseUnqualifiedName(State *state);
+static bool ParseSourceName(State *state);
+static bool ParseLocalSourceName(State *state);
+static bool ParseUnnamedTypeName(State *state);
+static bool ParseNumber(State *state, int *number_out);
+static bool ParseFloatNumber(State *state);
+static bool ParseSeqId(State *state);
+static bool ParseIdentifier(State *state, size_t length);
+static bool ParseOperatorName(State *state, int *arity);
+static bool ParseSpecialName(State *state);
+static bool ParseCallOffset(State *state);
+static bool ParseNVOffset(State *state);
+static bool ParseVOffset(State *state);
+static bool ParseAbiTags(State *state);
+static bool ParseCtorDtorName(State *state);
+static bool ParseDecltype(State *state);
+static bool ParseType(State *state);
+static bool ParseCVQualifiers(State *state);
+static bool ParseBuiltinType(State *state);
+static bool ParseFunctionType(State *state);
+static bool ParseBareFunctionType(State *state);
+static bool ParseClassEnumType(State *state);
+static bool ParseArrayType(State *state);
+static bool ParsePointerToMemberType(State *state);
+static bool ParseTemplateParam(State *state);
+static bool ParseTemplateTemplateParam(State *state);
+static bool ParseTemplateArgs(State *state);
+static bool ParseTemplateArg(State *state);
+static bool ParseBaseUnresolvedName(State *state);
+static bool ParseUnresolvedName(State *state);
+static bool ParseExpression(State *state);
+static bool ParseExprPrimary(State *state);
+static bool ParseExprCastValue(State *state);
+static bool ParseLocalName(State *state);
+static bool ParseLocalNameSuffix(State *state);
+static bool ParseDiscriminator(State *state);
+static bool ParseSubstitution(State *state, bool accept_std);
+
+// Implementation note: the following code is a straightforward
+// translation of the Itanium C++ ABI defined in BNF with a couple of
+// exceptions.
+//
+// - Support GNU extensions not defined in the Itanium C++ ABI
+// - <prefix> and <template-prefix> are combined to avoid infinite loop
+// - Reorder patterns to shorten the code
+// - Reorder patterns to give greedier functions precedence
+//   We'll mark "Less greedy than" for these cases in the code
+//
+// Each parsing function changes the parse state and returns true on
+// success, or returns false and doesn't change the parse state (note:
+// the parse-steps counter increases regardless of success or failure).
+// To ensure that the parse state isn't changed in the latter case, we
+// save the original state before we call multiple parsing functions
+// consecutively with &&, and restore it if unsuccessful.  See
+// ParseEncoding() as an example of this convention.  We follow the
+// convention throughout the code.
+//
+// Originally we tried to do demangling without following the full ABI
+// syntax but it turned out we needed to follow the full syntax to
+// parse complicated cases like nested template arguments.  Note that
+// implementing a full-fledged demangler isn't trivial (libiberty's
+// cp-demangle.c has +4300 lines).
+//
+// Note that (foo) in <(foo) ...> is a modifier to be ignored.
+//
+// Reference:
+// - Itanium C++ ABI
+//   <https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling>
+
+// <mangled-name> ::= _Z <encoding>
+static bool ParseMangledName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  return ParseTwoCharToken(state, "_Z") && ParseEncoding(state);
+}
+
+// <encoding> ::= <(function) name> <bare-function-type>
+//            ::= <(data) name>
+//            ::= <special-name>
+static bool ParseEncoding(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  // Implementing the first two productions together as <name>
+  // [<bare-function-type>] avoids exponential blowup of backtracking.
+  //
+  // Since Optional(...) can't fail, there's no need to copy the state for
+  // backtracking.
+  if (ParseName(state) && Optional(ParseBareFunctionType(state))) {
+    return true;
+  }
+
+  if (ParseSpecialName(state)) {
+    return true;
+  }
+  return false;
+}
+
+// <name> ::= <nested-name>
+//        ::= <unscoped-template-name> <template-args>
+//        ::= <unscoped-name>
+//        ::= <local-name>
+static bool ParseName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseNestedName(state) || ParseLocalName(state)) {
+    return true;
+  }
+
+  // We reorganize the productions to avoid re-parsing unscoped names.
+  // - Inline <unscoped-template-name> productions:
+  //   <name> ::= <substitution> <template-args>
+  //          ::= <unscoped-name> <template-args>
+  //          ::= <unscoped-name>
+  // - Merge the two productions that start with unscoped-name:
+  //   <name> ::= <unscoped-name> [<template-args>]
+
+  ParseState copy = state->parse_state;
+  // "std<...>" isn't a valid name.
+  if (ParseSubstitution(state, /*accept_std=*/false) &&
+      ParseTemplateArgs(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Note there's no need to restore state after this since only the first
+  // subparser can fail.
+  return ParseUnscopedName(state) && Optional(ParseTemplateArgs(state));
+}
+
+// <unscoped-name> ::= <unqualified-name>
+//                 ::= St <unqualified-name>
+static bool ParseUnscopedName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseUnqualifiedName(state)) {
+    return true;
+  }
+
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "St") && MaybeAppend(state, "std::") &&
+      ParseUnqualifiedName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <ref-qualifer> ::= R // lvalue method reference qualifier
+//                ::= O // rvalue method reference qualifier
+static inline bool ParseRefQualifier(State *state) {
+  return ParseCharClass(state, "OR");
+}
+
+// <nested-name> ::= N [<CV-qualifiers>] [<ref-qualifier>] <prefix>
+//                   <unqualified-name> E
+//               ::= N [<CV-qualifiers>] [<ref-qualifier>] <template-prefix>
+//                   <template-args> E
+static bool ParseNestedName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'N') && EnterNestedName(state) &&
+      Optional(ParseCVQualifiers(state)) &&
+      Optional(ParseRefQualifier(state)) && ParsePrefix(state) &&
+      LeaveNestedName(state, copy.nest_level) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// This part is tricky.  If we literally translate them to code, we'll
+// end up infinite loop.  Hence we merge them to avoid the case.
+//
+// <prefix> ::= <prefix> <unqualified-name>
+//          ::= <template-prefix> <template-args>
+//          ::= <template-param>
+//          ::= <substitution>
+//          ::= # empty
+// <template-prefix> ::= <prefix> <(template) unqualified-name>
+//                   ::= <template-param>
+//                   ::= <substitution>
+static bool ParsePrefix(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  bool has_something = false;
+  while (true) {
+    MaybeAppendSeparator(state);
+    if (ParseTemplateParam(state) ||
+        ParseSubstitution(state, /*accept_std=*/true) ||
+        ParseUnscopedName(state) ||
+        (ParseOneCharToken(state, 'M') && ParseUnnamedTypeName(state))) {
+      has_something = true;
+      MaybeIncreaseNestLevel(state);
+      continue;
+    }
+    MaybeCancelLastSeparator(state);
+    if (has_something && ParseTemplateArgs(state)) {
+      return ParsePrefix(state);
+    } else {
+      break;
+    }
+  }
+  return true;
+}
+
+// <unqualified-name> ::= <operator-name> [<abi-tags>]
+//                    ::= <ctor-dtor-name> [<abi-tags>]
+//                    ::= <source-name> [<abi-tags>]
+//                    ::= <local-source-name> [<abi-tags>]
+//                    ::= <unnamed-type-name> [<abi-tags>]
+//
+// <local-source-name> is a GCC extension; see below.
+static bool ParseUnqualifiedName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseOperatorName(state, nullptr) || ParseCtorDtorName(state) ||
+      ParseSourceName(state) || ParseLocalSourceName(state) ||
+      ParseUnnamedTypeName(state)) {
+    return ParseAbiTags(state);
+  }
+  return false;
+}
+
+// <abi-tags> ::= <abi-tag> [<abi-tags>]
+// <abi-tag>  ::= B <source-name>
+static bool ParseAbiTags(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  while (ParseOneCharToken(state, 'B')) {
+    ParseState copy = state->parse_state;
+    MaybeAppend(state, "[abi:");
+
+    if (!ParseSourceName(state)) {
+      state->parse_state = copy;
+      return false;
+    }
+    MaybeAppend(state, "]");
+  }
+
+  return true;
+}
+
+// <source-name> ::= <positive length number> <identifier>
+static bool ParseSourceName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  int length = -1;
+  if (ParseNumber(state, &length) &&
+      ParseIdentifier(state, static_cast<size_t>(length))) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <local-source-name> ::= L <source-name> [<discriminator>]
+//
+// References:
+//   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=31775
+//   https://gcc.gnu.org/viewcvs?view=rev&revision=124467
+static bool ParseLocalSourceName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'L') && ParseSourceName(state) &&
+      Optional(ParseDiscriminator(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <unnamed-type-name> ::= Ut [<(nonnegative) number>] _
+//                     ::= <closure-type-name>
+// <closure-type-name> ::= Ul <lambda-sig> E [<(nonnegative) number>] _
+// <lambda-sig>        ::= <(parameter) type>+
+static bool ParseUnnamedTypeName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  // Type's 1-based index n is encoded as { "", n == 1; itoa(n-2), otherwise }.
+  // Optionally parse the encoded value into 'which' and add 2 to get the index.
+  int which = -1;
+
+  // Unnamed type local to function or class.
+  if (ParseTwoCharToken(state, "Ut") && Optional(ParseNumber(state, &which)) &&
+      which <= std::numeric_limits<int>::max() - 2 &&  // Don't overflow.
+      ParseOneCharToken(state, '_')) {
+    MaybeAppend(state, "{unnamed type#");
+    MaybeAppendDecimal(state, 2 + which);
+    MaybeAppend(state, "}");
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Closure type.
+  which = -1;
+  if (ParseTwoCharToken(state, "Ul") && DisableAppend(state) &&
+      OneOrMore(ParseType, state) && RestoreAppend(state, copy.append) &&
+      ParseOneCharToken(state, 'E') && Optional(ParseNumber(state, &which)) &&
+      which <= std::numeric_limits<int>::max() - 2 &&  // Don't overflow.
+      ParseOneCharToken(state, '_')) {
+    MaybeAppend(state, "{lambda()#");
+    MaybeAppendDecimal(state, 2 + which);
+    MaybeAppend(state, "}");
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <number> ::= [n] <non-negative decimal integer>
+// If "number_out" is non-null, then *number_out is set to the value of the
+// parsed number on success.
+static bool ParseNumber(State *state, int *number_out) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  bool negative = false;
+  if (ParseOneCharToken(state, 'n')) {
+    negative = true;
+  }
+  const char *p = RemainingInput(state);
+  uint64_t number = 0;
+  for (; *p != '\0'; ++p) {
+    if (IsDigit(*p)) {
+      number = number * 10 + static_cast<uint64_t>(*p - '0');
+    } else {
+      break;
+    }
+  }
+  // Apply the sign with uint64_t arithmetic so overflows aren't UB.  Gives
+  // "incorrect" results for out-of-range inputs, but negative values only
+  // appear for literals, which aren't printed.
+  if (negative) {
+    number = ~number + 1;
+  }
+  if (p != RemainingInput(state)) {  // Conversion succeeded.
+    state->parse_state.mangled_idx += p - RemainingInput(state);
+    if (number_out != nullptr) {
+      // Note: possibly truncate "number".
+      *number_out = static_cast<int>(number);
+    }
+    return true;
+  }
+  return false;
+}
+
+// Floating-point literals are encoded using a fixed-length lowercase
+// hexadecimal string.
+static bool ParseFloatNumber(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  const char *p = RemainingInput(state);
+  for (; *p != '\0'; ++p) {
+    if (!IsDigit(*p) && !(*p >= 'a' && *p <= 'f')) {
+      break;
+    }
+  }
+  if (p != RemainingInput(state)) {  // Conversion succeeded.
+    state->parse_state.mangled_idx += p - RemainingInput(state);
+    return true;
+  }
+  return false;
+}
+
+// The <seq-id> is a sequence number in base 36,
+// using digits and upper case letters
+static bool ParseSeqId(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  const char *p = RemainingInput(state);
+  for (; *p != '\0'; ++p) {
+    if (!IsDigit(*p) && !(*p >= 'A' && *p <= 'Z')) {
+      break;
+    }
+  }
+  if (p != RemainingInput(state)) {  // Conversion succeeded.
+    state->parse_state.mangled_idx += p - RemainingInput(state);
+    return true;
+  }
+  return false;
+}
+
+// <identifier> ::= <unqualified source code identifier> (of given length)
+static bool ParseIdentifier(State *state, size_t length) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (!AtLeastNumCharsRemaining(RemainingInput(state), length)) {
+    return false;
+  }
+  if (IdentifierIsAnonymousNamespace(state, length)) {
+    MaybeAppend(state, "(anonymous namespace)");
+  } else {
+    MaybeAppendWithLength(state, RemainingInput(state), length);
+  }
+  state->parse_state.mangled_idx += length;
+  return true;
+}
+
+// <operator-name> ::= nw, and other two letters cases
+//                 ::= cv <type>  # (cast)
+//                 ::= v  <digit> <source-name> # vendor extended operator
+static bool ParseOperatorName(State *state, int *arity) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (!AtLeastNumCharsRemaining(RemainingInput(state), 2)) {
+    return false;
+  }
+  // First check with "cv" (cast) case.
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "cv") && MaybeAppend(state, "operator ") &&
+      EnterNestedName(state) && ParseType(state) &&
+      LeaveNestedName(state, copy.nest_level)) {
+    if (arity != nullptr) {
+      *arity = 1;
+    }
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Then vendor extended operators.
+  if (ParseOneCharToken(state, 'v') && ParseDigit(state, arity) &&
+      ParseSourceName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Other operator names should start with a lower alphabet followed
+  // by a lower/upper alphabet.
+  if (!(IsLower(RemainingInput(state)[0]) &&
+        IsAlpha(RemainingInput(state)[1]))) {
+    return false;
+  }
+  // We may want to perform a binary search if we really need speed.
+  const AbbrevPair *p;
+  for (p = kOperatorList; p->abbrev != nullptr; ++p) {
+    if (RemainingInput(state)[0] == p->abbrev[0] &&
+        RemainingInput(state)[1] == p->abbrev[1]) {
+      if (arity != nullptr) {
+        *arity = p->arity;
+      }
+      MaybeAppend(state, "operator");
+      if (IsLower(*p->real_name)) {  // new, delete, etc.
+        MaybeAppend(state, " ");
+      }
+      MaybeAppend(state, p->real_name);
+      state->parse_state.mangled_idx += 2;
+      return true;
+    }
+  }
+  return false;
+}
+
+// <special-name> ::= TV <type>
+//                ::= TT <type>
+//                ::= TI <type>
+//                ::= TS <type>
+//                ::= TH <type>  # thread-local
+//                ::= Tc <call-offset> <call-offset> <(base) encoding>
+//                ::= GV <(object) name>
+//                ::= T <call-offset> <(base) encoding>
+// G++ extensions:
+//                ::= TC <type> <(offset) number> _ <(base) type>
+//                ::= TF <type>
+//                ::= TJ <type>
+//                ::= GR <name>
+//                ::= GA <encoding>
+//                ::= Th <call-offset> <(base) encoding>
+//                ::= Tv <call-offset> <(base) encoding>
+//
+// Note: we don't care much about them since they don't appear in
+// stack traces.  The are special data.
+static bool ParseSpecialName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "VTISH") &&
+      ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Tc") && ParseCallOffset(state) &&
+      ParseCallOffset(state) && ParseEncoding(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "GV") && ParseName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'T') && ParseCallOffset(state) &&
+      ParseEncoding(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // G++ extensions
+  if (ParseTwoCharToken(state, "TC") && ParseType(state) &&
+      ParseNumber(state, nullptr) && ParseOneCharToken(state, '_') &&
+      DisableAppend(state) && ParseType(state)) {
+    RestoreAppend(state, copy.append);
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "FJ") &&
+      ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "GR") && ParseName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "GA") && ParseEncoding(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "hv") &&
+      ParseCallOffset(state) && ParseEncoding(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <call-offset> ::= h <nv-offset> _
+//               ::= v <v-offset> _
+static bool ParseCallOffset(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'h') && ParseNVOffset(state) &&
+      ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'v') && ParseVOffset(state) &&
+      ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <nv-offset> ::= <(offset) number>
+static bool ParseNVOffset(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  return ParseNumber(state, nullptr);
+}
+
+// <v-offset>  ::= <(offset) number> _ <(virtual offset) number>
+static bool ParseVOffset(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseNumber(state, nullptr) && ParseOneCharToken(state, '_') &&
+      ParseNumber(state, nullptr)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <ctor-dtor-name> ::= C1 | C2 | C3 | CI1 <base-class-type> | CI2
+// <base-class-type>
+//                  ::= D0 | D1 | D2
+// # GCC extensions: "unified" constructor/destructor.  See
+// #
+// https://github.com/gcc-mirror/gcc/blob/7ad17b583c3643bd4557f29b8391ca7ef08391f5/gcc/cp/mangle.c#L1847
+//                  ::= C4 | D4
+static bool ParseCtorDtorName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'C')) {
+    if (ParseCharClass(state, "1234")) {
+      const char *const prev_name =
+          state->out + state->parse_state.prev_name_idx;
+      MaybeAppendWithLength(state, prev_name,
+                            state->parse_state.prev_name_length);
+      return true;
+    } else if (ParseOneCharToken(state, 'I') && ParseCharClass(state, "12") &&
+               ParseClassEnumType(state)) {
+      return true;
+    }
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'D') && ParseCharClass(state, "0124")) {
+    const char *const prev_name = state->out + state->parse_state.prev_name_idx;
+    MaybeAppend(state, "~");
+    MaybeAppendWithLength(state, prev_name,
+                          state->parse_state.prev_name_length);
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <decltype> ::= Dt <expression> E  # decltype of an id-expression or class
+//                                   # member access (C++0x)
+//            ::= DT <expression> E  # decltype of an expression (C++0x)
+static bool ParseDecltype(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'D') && ParseCharClass(state, "tT") &&
+      ParseExpression(state) && ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <type> ::= <CV-qualifiers> <type>
+//        ::= P <type>   # pointer-to
+//        ::= R <type>   # reference-to
+//        ::= O <type>   # rvalue reference-to (C++0x)
+//        ::= C <type>   # complex pair (C 2000)
+//        ::= G <type>   # imaginary (C 2000)
+//        ::= U <source-name> <type>  # vendor extended type qualifier
+//        ::= <builtin-type>
+//        ::= <function-type>
+//        ::= <class-enum-type>  # note: just an alias for <name>
+//        ::= <array-type>
+//        ::= <pointer-to-member-type>
+//        ::= <template-template-param> <template-args>
+//        ::= <template-param>
+//        ::= <decltype>
+//        ::= <substitution>
+//        ::= Dp <type>          # pack expansion of (C++0x)
+//        ::= Dv <num-elems> _   # GNU vector extension
+//
+static bool ParseType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+
+  // We should check CV-qualifers, and PRGC things first.
+  //
+  // CV-qualifiers overlap with some operator names, but an operator name is not
+  // valid as a type.  To avoid an ambiguity that can lead to exponential time
+  // complexity, refuse to backtrack the CV-qualifiers.
+  //
+  // _Z4aoeuIrMvvE
+  //  => _Z 4aoeuI        rM  v     v   E
+  //         aoeu<operator%=, void, void>
+  //  => _Z 4aoeuI r Mv v              E
+  //         aoeu<void void::* restrict>
+  //
+  // By consuming the CV-qualifiers first, the former parse is disabled.
+  if (ParseCVQualifiers(state)) {
+    const bool result = ParseType(state);
+    if (!result) state->parse_state = copy;
+    return result;
+  }
+  state->parse_state = copy;
+
+  // Similarly, these tag characters can overlap with other <name>s resulting in
+  // two different parse prefixes that land on <template-args> in the same
+  // place, such as "C3r1xI...".  So, disable the "ctor-name = C3" parse by
+  // refusing to backtrack the tag characters.
+  if (ParseCharClass(state, "OPRCG")) {
+    const bool result = ParseType(state);
+    if (!result) state->parse_state = copy;
+    return result;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "Dp") && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'U') && ParseSourceName(state) &&
+      ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseBuiltinType(state) || ParseFunctionType(state) ||
+      ParseClassEnumType(state) || ParseArrayType(state) ||
+      ParsePointerToMemberType(state) || ParseDecltype(state) ||
+      // "std" on its own isn't a type.
+      ParseSubstitution(state, /*accept_std=*/false)) {
+    return true;
+  }
+
+  if (ParseTemplateTemplateParam(state) && ParseTemplateArgs(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Less greedy than <template-template-param> <template-args>.
+  if (ParseTemplateParam(state)) {
+    return true;
+  }
+
+  if (ParseTwoCharToken(state, "Dv") && ParseNumber(state, nullptr) &&
+      ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <CV-qualifiers> ::= [r] [V] [K]
+// We don't allow empty <CV-qualifiers> to avoid infinite loop in
+// ParseType().
+static bool ParseCVQualifiers(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  int num_cv_qualifiers = 0;
+  num_cv_qualifiers += ParseOneCharToken(state, 'r');
+  num_cv_qualifiers += ParseOneCharToken(state, 'V');
+  num_cv_qualifiers += ParseOneCharToken(state, 'K');
+  return num_cv_qualifiers > 0;
+}
+
+// <builtin-type> ::= v, etc.  # single-character builtin types
+//                ::= u <source-name>
+//                ::= Dd, etc.  # two-character builtin types
+//
+// Not supported:
+//                ::= DF <number> _ # _FloatN (N bits)
+//
+static bool ParseBuiltinType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  const AbbrevPair *p;
+  for (p = kBuiltinTypeList; p->abbrev != nullptr; ++p) {
+    // Guaranteed only 1- or 2-character strings in kBuiltinTypeList.
+    if (p->abbrev[1] == '\0') {
+      if (ParseOneCharToken(state, p->abbrev[0])) {
+        MaybeAppend(state, p->real_name);
+        return true;
+      }
+    } else if (p->abbrev[2] == '\0' && ParseTwoCharToken(state, p->abbrev)) {
+      MaybeAppend(state, p->real_name);
+      return true;
+    }
+  }
+
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'u') && ParseSourceName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+//  <exception-spec> ::= Do                # non-throwing
+//                                           exception-specification (e.g.,
+//                                           noexcept, throw())
+//                   ::= DO <expression> E # computed (instantiation-dependent)
+//                                           noexcept
+//                   ::= Dw <type>+ E      # dynamic exception specification
+//                                           with instantiation-dependent types
+static bool ParseExceptionSpec(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  if (ParseTwoCharToken(state, "Do")) return true;
+
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "DO") && ParseExpression(state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+  if (ParseTwoCharToken(state, "Dw") && OneOrMore(ParseType, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <function-type> ::= [exception-spec] F [Y] <bare-function-type> [O] E
+static bool ParseFunctionType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (Optional(ParseExceptionSpec(state)) && ParseOneCharToken(state, 'F') &&
+      Optional(ParseOneCharToken(state, 'Y')) && ParseBareFunctionType(state) &&
+      Optional(ParseOneCharToken(state, 'O')) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <bare-function-type> ::= <(signature) type>+
+static bool ParseBareFunctionType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  DisableAppend(state);
+  if (OneOrMore(ParseType, state)) {
+    RestoreAppend(state, copy.append);
+    MaybeAppend(state, "()");
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <class-enum-type> ::= <name>
+static bool ParseClassEnumType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  return ParseName(state);
+}
+
+// <array-type> ::= A <(positive dimension) number> _ <(element) type>
+//              ::= A [<(dimension) expression>] _ <(element) type>
+static bool ParseArrayType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'A') && ParseNumber(state, nullptr) &&
+      ParseOneCharToken(state, '_') && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'A') && Optional(ParseExpression(state)) &&
+      ParseOneCharToken(state, '_') && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <pointer-to-member-type> ::= M <(class) type> <(member) type>
+static bool ParsePointerToMemberType(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'M') && ParseType(state) && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <template-param> ::= T_
+//                  ::= T <parameter-2 non-negative number> _
+static bool ParseTemplateParam(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseTwoCharToken(state, "T_")) {
+    MaybeAppend(state, "?");  // We don't support template substitutions.
+    return true;
+  }
+
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'T') && ParseNumber(state, nullptr) &&
+      ParseOneCharToken(state, '_')) {
+    MaybeAppend(state, "?");  // We don't support template substitutions.
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <template-template-param> ::= <template-param>
+//                           ::= <substitution>
+static bool ParseTemplateTemplateParam(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  return (ParseTemplateParam(state) ||
+          // "std" on its own isn't a template.
+          ParseSubstitution(state, /*accept_std=*/false));
+}
+
+// <template-args> ::= I <template-arg>+ E
+static bool ParseTemplateArgs(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  DisableAppend(state);
+  if (ParseOneCharToken(state, 'I') && OneOrMore(ParseTemplateArg, state) &&
+      ParseOneCharToken(state, 'E')) {
+    RestoreAppend(state, copy.append);
+    MaybeAppend(state, "<>");
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <template-arg>  ::= <type>
+//                 ::= <expr-primary>
+//                 ::= J <template-arg>* E        # argument pack
+//                 ::= X <expression> E
+static bool ParseTemplateArg(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'J') && ZeroOrMore(ParseTemplateArg, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // There can be significant overlap between the following leading to
+  // exponential backtracking:
+  //
+  //   <expr-primary> ::= L <type> <expr-cast-value> E
+  //                 e.g. L 2xxIvE 1                 E
+  //   <type>         ==> <local-source-name> <template-args>
+  //                 e.g. L 2xx               IvE
+  //
+  // This means parsing an entire <type> twice, and <type> can contain
+  // <template-arg>, so this can generate exponential backtracking.  There is
+  // only overlap when the remaining input starts with "L <source-name>", so
+  // parse all cases that can start this way jointly to share the common prefix.
+  //
+  // We have:
+  //
+  //   <template-arg> ::= <type>
+  //                  ::= <expr-primary>
+  //
+  // First, drop all the productions of <type> that must start with something
+  // other than 'L'.  All that's left is <class-enum-type>; inline it.
+  //
+  //   <type> ::= <nested-name> # starts with 'N'
+  //          ::= <unscoped-name>
+  //          ::= <unscoped-template-name> <template-args>
+  //          ::= <local-name> # starts with 'Z'
+  //
+  // Drop and inline again:
+  //
+  //   <type> ::= <unscoped-name>
+  //          ::= <unscoped-name> <template-args>
+  //          ::= <substitution> <template-args> # starts with 'S'
+  //
+  // Merge the first two, inline <unscoped-name>, drop last:
+  //
+  //   <type> ::= <unqualified-name> [<template-args>]
+  //          ::= St <unqualified-name> [<template-args>] # starts with 'S'
+  //
+  // Drop and inline:
+  //
+  //   <type> ::= <operator-name> [<template-args>] # starts with lowercase
+  //          ::= <ctor-dtor-name> [<template-args>] # starts with 'C' or 'D'
+  //          ::= <source-name> [<template-args>] # starts with digit
+  //          ::= <local-source-name> [<template-args>]
+  //          ::= <unnamed-type-name> [<template-args>] # starts with 'U'
+  //
+  // One more time:
+  //
+  //   <type> ::= L <source-name> [<template-args>]
+  //
+  // Likewise with <expr-primary>:
+  //
+  //   <expr-primary> ::= L <type> <expr-cast-value> E
+  //                  ::= LZ <encoding> E # cannot overlap; drop
+  //                  ::= L <mangled_name> E # cannot overlap; drop
+  //
+  // By similar reasoning as shown above, the only <type>s starting with
+  // <source-name> are "<source-name> [<template-args>]".  Inline this.
+  //
+  //   <expr-primary> ::= L <source-name> [<template-args>] <expr-cast-value> E
+  //
+  // Now inline both of these into <template-arg>:
+  //
+  //   <template-arg> ::= L <source-name> [<template-args>]
+  //                  ::= L <source-name> [<template-args>] <expr-cast-value> E
+  //
+  // Merge them and we're done:
+  //   <template-arg>
+  //     ::= L <source-name> [<template-args>] [<expr-cast-value> E]
+  if (ParseLocalSourceName(state) && Optional(ParseTemplateArgs(state))) {
+    copy = state->parse_state;
+    if (ParseExprCastValue(state) && ParseOneCharToken(state, 'E')) {
+      return true;
+    }
+    state->parse_state = copy;
+    return true;
+  }
+
+  // Now that the overlapping cases can't reach this code, we can safely call
+  // both of these.
+  if (ParseType(state) || ParseExprPrimary(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'X') && ParseExpression(state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <unresolved-type> ::= <template-param> [<template-args>]
+//                   ::= <decltype>
+//                   ::= <substitution>
+static inline bool ParseUnresolvedType(State *state) {
+  // No ComplexityGuard because we don't copy the state in this stack frame.
+  return (ParseTemplateParam(state) && Optional(ParseTemplateArgs(state))) ||
+         ParseDecltype(state) || ParseSubstitution(state, /*accept_std=*/false);
+}
+
+// <simple-id> ::= <source-name> [<template-args>]
+static inline bool ParseSimpleId(State *state) {
+  // No ComplexityGuard because we don't copy the state in this stack frame.
+
+  // Note: <simple-id> cannot be followed by a parameter pack; see comment in
+  // ParseUnresolvedType.
+  return ParseSourceName(state) && Optional(ParseTemplateArgs(state));
+}
+
+// <base-unresolved-name> ::= <source-name> [<template-args>]
+//                        ::= on <operator-name> [<template-args>]
+//                        ::= dn <destructor-name>
+static bool ParseBaseUnresolvedName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  if (ParseSimpleId(state)) {
+    return true;
+  }
+
+  ParseState copy = state->parse_state;
+  if (ParseTwoCharToken(state, "on") && ParseOperatorName(state, nullptr) &&
+      Optional(ParseTemplateArgs(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "dn") &&
+      (ParseUnresolvedType(state) || ParseSimpleId(state))) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <unresolved-name> ::= [gs] <base-unresolved-name>
+//                   ::= sr <unresolved-type> <base-unresolved-name>
+//                   ::= srN <unresolved-type> <unresolved-qualifier-level>+ E
+//                         <base-unresolved-name>
+//                   ::= [gs] sr <unresolved-qualifier-level>+ E
+//                         <base-unresolved-name>
+static bool ParseUnresolvedName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  ParseState copy = state->parse_state;
+  if (Optional(ParseTwoCharToken(state, "gs")) &&
+      ParseBaseUnresolvedName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "sr") && ParseUnresolvedType(state) &&
+      ParseBaseUnresolvedName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseTwoCharToken(state, "sr") && ParseOneCharToken(state, 'N') &&
+      ParseUnresolvedType(state) &&
+      OneOrMore(/* <unresolved-qualifier-level> ::= */ ParseSimpleId, state) &&
+      ParseOneCharToken(state, 'E') && ParseBaseUnresolvedName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (Optional(ParseTwoCharToken(state, "gs")) &&
+      ParseTwoCharToken(state, "sr") &&
+      OneOrMore(/* <unresolved-qualifier-level> ::= */ ParseSimpleId, state) &&
+      ParseOneCharToken(state, 'E') && ParseBaseUnresolvedName(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <expression> ::= <1-ary operator-name> <expression>
+//              ::= <2-ary operator-name> <expression> <expression>
+//              ::= <3-ary operator-name> <expression> <expression> <expression>
+//              ::= cl <expression>+ E
+//              ::= cp <simple-id> <expression>* E # Clang-specific.
+//              ::= cv <type> <expression>      # type (expression)
+//              ::= cv <type> _ <expression>* E # type (expr-list)
+//              ::= st <type>
+//              ::= <template-param>
+//              ::= <function-param>
+//              ::= <expr-primary>
+//              ::= dt <expression> <unresolved-name> # expr.name
+//              ::= pt <expression> <unresolved-name> # expr->name
+//              ::= sp <expression>         # argument pack expansion
+//              ::= sr <type> <unqualified-name> <template-args>
+//              ::= sr <type> <unqualified-name>
+// <function-param> ::= fp <(top-level) CV-qualifiers> _
+//                  ::= fp <(top-level) CV-qualifiers> <number> _
+//                  ::= fL <number> p <(top-level) CV-qualifiers> _
+//                  ::= fL <number> p <(top-level) CV-qualifiers> <number> _
+static bool ParseExpression(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseTemplateParam(state) || ParseExprPrimary(state)) {
+    return true;
+  }
+
+  ParseState copy = state->parse_state;
+
+  // Object/function call expression.
+  if (ParseTwoCharToken(state, "cl") && OneOrMore(ParseExpression, state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Clang-specific "cp <simple-id> <expression>* E"
+  //   https://clang.llvm.org/doxygen/ItaniumMangle_8cpp_source.html#l04338
+  if (ParseTwoCharToken(state, "cp") && ParseSimpleId(state) &&
+      ZeroOrMore(ParseExpression, state) && ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Function-param expression (level 0).
+  if (ParseTwoCharToken(state, "fp") && Optional(ParseCVQualifiers(state)) &&
+      Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Function-param expression (level 1+).
+  if (ParseTwoCharToken(state, "fL") && Optional(ParseNumber(state, nullptr)) &&
+      ParseOneCharToken(state, 'p') && Optional(ParseCVQualifiers(state)) &&
+      Optional(ParseNumber(state, nullptr)) && ParseOneCharToken(state, '_')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Parse the conversion expressions jointly to avoid re-parsing the <type> in
+  // their common prefix.  Parsed as:
+  // <expression> ::= cv <type> <conversion-args>
+  // <conversion-args> ::= _ <expression>* E
+  //                   ::= <expression>
+  //
+  // Also don't try ParseOperatorName after seeing "cv", since ParseOperatorName
+  // also needs to accept "cv <type>" in other contexts.
+  if (ParseTwoCharToken(state, "cv")) {
+    if (ParseType(state)) {
+      ParseState copy2 = state->parse_state;
+      if (ParseOneCharToken(state, '_') && ZeroOrMore(ParseExpression, state) &&
+          ParseOneCharToken(state, 'E')) {
+        return true;
+      }
+      state->parse_state = copy2;
+      if (ParseExpression(state)) {
+        return true;
+      }
+    }
+  } else {
+    // Parse unary, binary, and ternary operator expressions jointly, taking
+    // care not to re-parse subexpressions repeatedly. Parse like:
+    //   <expression> ::= <operator-name> <expression>
+    //                    [<one-to-two-expressions>]
+    //   <one-to-two-expressions> ::= <expression> [<expression>]
+    int arity = -1;
+    if (ParseOperatorName(state, &arity) &&
+        arity > 0 &&  // 0 arity => disabled.
+        (arity < 3 || ParseExpression(state)) &&
+        (arity < 2 || ParseExpression(state)) &&
+        (arity < 1 || ParseExpression(state))) {
+      return true;
+    }
+  }
+  state->parse_state = copy;
+
+  // sizeof type
+  if (ParseTwoCharToken(state, "st") && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Object and pointer member access expressions.
+  if ((ParseTwoCharToken(state, "dt") || ParseTwoCharToken(state, "pt")) &&
+      ParseExpression(state) && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Pointer-to-member access expressions.  This parses the same as a binary
+  // operator, but it's implemented separately because "ds" shouldn't be
+  // accepted in other contexts that parse an operator name.
+  if (ParseTwoCharToken(state, "ds") && ParseExpression(state) &&
+      ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Parameter pack expansion
+  if (ParseTwoCharToken(state, "sp") && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return ParseUnresolvedName(state);
+}
+
+// <expr-primary> ::= L <type> <(value) number> E
+//                ::= L <type> <(value) float> E
+//                ::= L <mangled-name> E
+//                // A bug in g++'s C++ ABI version 2 (-fabi-version=2).
+//                ::= LZ <encoding> E
+//
+// Warning, subtle: the "bug" LZ production above is ambiguous with the first
+// production where <type> starts with <local-name>, which can lead to
+// exponential backtracking in two scenarios:
+//
+// - When whatever follows the E in the <local-name> in the first production is
+//   not a name, we backtrack the whole <encoding> and re-parse the whole thing.
+//
+// - When whatever follows the <local-name> in the first production is not a
+//   number and this <expr-primary> may be followed by a name, we backtrack the
+//   <name> and re-parse it.
+//
+// Moreover this ambiguity isn't always resolved -- for example, the following
+// has two different parses:
+//
+//   _ZaaILZ4aoeuE1x1EvE
+//   => operator&&<aoeu, x, E, void>
+//   => operator&&<(aoeu::x)(1), void>
+//
+// To resolve this, we just do what GCC's demangler does, and refuse to parse
+// casts to <local-name> types.
+static bool ParseExprPrimary(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+
+  // The "LZ" special case: if we see LZ, we commit to accept "LZ <encoding> E"
+  // or fail, no backtracking.
+  if (ParseTwoCharToken(state, "LZ")) {
+    if (ParseEncoding(state) && ParseOneCharToken(state, 'E')) {
+      return true;
+    }
+
+    state->parse_state = copy;
+    return false;
+  }
+
+  // The merged cast production.
+  if (ParseOneCharToken(state, 'L') && ParseType(state) &&
+      ParseExprCastValue(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseOneCharToken(state, 'L') && ParseMangledName(state) &&
+      ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <number> or <float>, followed by 'E', as described above ParseExprPrimary.
+static bool ParseExprCastValue(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  // We have to be able to backtrack after accepting a number because we could
+  // have e.g. "7fffE", which will accept "7" as a number but then fail to find
+  // the 'E'.
+  ParseState copy = state->parse_state;
+  if (ParseNumber(state, nullptr) && ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  if (ParseFloatNumber(state) && ParseOneCharToken(state, 'E')) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  return false;
+}
+
+// <local-name> ::= Z <(function) encoding> E <(entity) name> [<discriminator>]
+//              ::= Z <(function) encoding> E s [<discriminator>]
+//
+// Parsing a common prefix of these two productions together avoids an
+// exponential blowup of backtracking.  Parse like:
+//   <local-name> := Z <encoding> E <local-name-suffix>
+//   <local-name-suffix> ::= s [<discriminator>]
+//                       ::= <name> [<discriminator>]
+
+static bool ParseLocalNameSuffix(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+
+  if (MaybeAppend(state, "::") && ParseName(state) &&
+      Optional(ParseDiscriminator(state))) {
+    return true;
+  }
+
+  // Since we're not going to overwrite the above "::" by re-parsing the
+  // <encoding> (whose trailing '\0' byte was in the byte now holding the
+  // first ':'), we have to rollback the "::" if the <name> parse failed.
+  if (state->parse_state.append) {
+    state->out[state->parse_state.out_cur_idx - 2] = '\0';
+  }
+
+  return ParseOneCharToken(state, 's') && Optional(ParseDiscriminator(state));
+}
+
+static bool ParseLocalName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'Z') && ParseEncoding(state) &&
+      ParseOneCharToken(state, 'E') && ParseLocalNameSuffix(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <discriminator> := _ <(non-negative) number>
+static bool ParseDiscriminator(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, '_') && ParseNumber(state, nullptr)) {
+    return true;
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// <substitution> ::= S_
+//                ::= S <seq-id> _
+//                ::= St, etc.
+//
+// "St" is special in that it's not valid as a standalone name, and it *is*
+// allowed to precede a name without being wrapped in "N...E".  This means that
+// if we accept it on its own, we can accept "St1a" and try to parse
+// template-args, then fail and backtrack, accept "St" on its own, then "1a" as
+// an unqualified name and re-parse the same template-args.  To block this
+// exponential backtracking, we disable it with 'accept_std=false' in
+// problematic contexts.
+static bool ParseSubstitution(State *state, bool accept_std) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseTwoCharToken(state, "S_")) {
+    MaybeAppend(state, "?");  // We don't support substitutions.
+    return true;
+  }
+
+  ParseState copy = state->parse_state;
+  if (ParseOneCharToken(state, 'S') && ParseSeqId(state) &&
+      ParseOneCharToken(state, '_')) {
+    MaybeAppend(state, "?");  // We don't support substitutions.
+    return true;
+  }
+  state->parse_state = copy;
+
+  // Expand abbreviations like "St" => "std".
+  if (ParseOneCharToken(state, 'S')) {
+    const AbbrevPair *p;
+    for (p = kSubstitutionList; p->abbrev != nullptr; ++p) {
+      if (RemainingInput(state)[0] == p->abbrev[1] &&
+          (accept_std || p->abbrev[1] != 't')) {
+        MaybeAppend(state, "std");
+        if (p->real_name[0] != '\0') {
+          MaybeAppend(state, "::");
+          MaybeAppend(state, p->real_name);
+        }
+        ++state->parse_state.mangled_idx;
+        return true;
+      }
+    }
+  }
+  state->parse_state = copy;
+  return false;
+}
+
+// Parse <mangled-name>, optionally followed by either a function-clone suffix
+// or version suffix.  Returns true only if all of "mangled_cur" was consumed.
+static bool ParseTopLevelMangledName(State *state) {
+  ComplexityGuard guard(state);
+  if (guard.IsTooComplex()) return false;
+  if (ParseMangledName(state)) {
+    if (RemainingInput(state)[0] != '\0') {
+      // Drop trailing function clone suffix, if any.
+      if (IsFunctionCloneSuffix(RemainingInput(state))) {
+        return true;
+      }
+      // Append trailing version suffix if any.
+      // ex. _Z3foo@@GLIBCXX_3.4
+      if (RemainingInput(state)[0] == '@') {
+        MaybeAppend(state, RemainingInput(state));
+        return true;
+      }
+      return false;  // Unconsumed suffix.
+    }
+    return true;
+  }
+  return false;
+}
+
+static bool Overflowed(const State *state) {
+  return state->parse_state.out_cur_idx >= state->out_end_idx;
+}
+
+// The demangler entry point.
+bool Demangle(const char* mangled, char* out, size_t out_size) {
+  State state;
+  InitState(&state, mangled, out, out_size);
+  return ParseTopLevelMangledName(&state) && !Overflowed(&state) &&
+         state.parse_state.out_cur_idx > 0;
+}
+
+std::string DemangleString(const char* mangled) {
+  std::string out;
+  int status = 0;
+  char* demangled = nullptr;
+#if ABSL_INTERNAL_HAS_CXA_DEMANGLE
+  demangled = abi::__cxa_demangle(mangled, nullptr, nullptr, &status);
+#endif
+  if (status == 0 && demangled != nullptr) {
+    out.append(demangled);
+    free(demangled);
+  } else {
+    out.append(mangled);
+  }
+  return out;
+}
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/demangle.h b/weight/_dep/abseil-cpp/absl/debugging/internal/demangle.h
new file mode 100644
index 0000000000000000000000000000000000000000..146d1150efecddd3e632d2a305b0cdae975cb7f2
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/demangle.h
@@ -0,0 +1,73 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
+#define ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
+
+#include <string>
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// Demangle `mangled`.  On success, return true and write the
+// demangled symbol name to `out`.  Otherwise, return false.
+// `out` is modified even if demangling is unsuccessful.
+//
+// This function provides an alternative to libstdc++'s abi::__cxa_demangle,
+// which is not async signal safe (it uses malloc internally).  It's intended to
+// be used in async signal handlers to symbolize stack traces.
+//
+// Note that this demangler doesn't support full demangling.  More
+// specifically, it doesn't print types of function parameters and
+// types of template arguments.  It just skips them.  However, it's
+// still very useful to extract basic information such as class,
+// function, constructor, destructor, and operator names.
+//
+// See the implementation note in demangle.cc if you are interested.
+//
+// Example:
+//
+// | Mangled Name  | Demangle    | DemangleString
+// |---------------|-------------|-----------------------
+// | _Z1fv         | f()         | f()
+// | _Z1fi         | f()         | f(int)
+// | _Z3foo3bar    | foo()       | foo(bar)
+// | _Z1fIiEvi     | f<>()       | void f<int>(int)
+// | _ZN1N1fE      | N::f        | N::f
+// | _ZN3Foo3BarEv | Foo::Bar()  | Foo::Bar()
+// | _Zrm1XS_"     | operator%() | operator%(X, X)
+// | _ZN3FooC1Ev   | Foo::Foo()  | Foo::Foo()
+// | _Z1fSs        | f()         | f(std::basic_string<char,
+// |               |             |   std::char_traits<char>,
+// |               |             |   std::allocator<char> >)
+//
+// See the unit test for more examples.
+//
+// Note: we might want to write demanglers for ABIs other than Itanium
+// C++ ABI in the future.
+bool Demangle(const char* mangled, char* out, size_t out_size);
+
+// A wrapper around `abi::__cxa_demangle()`.  On success, returns the demangled
+// name.  On failure, returns the input mangled name.
+//
+// This function is not async-signal-safe.
+std::string DemangleString(const char* mangled);
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_DEMANGLE_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/demangle_test.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/demangle_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a16ab75ea8b49a0a2a2813080ca99a9bfa75ae14
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/demangle_test.cc
@@ -0,0 +1,255 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/internal/demangle.h"
+
+#include <cstdlib>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/debugging/internal/stack_consumption.h"
+#include "absl/log/log.h"
+#include "absl/memory/memory.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+namespace {
+
+using ::testing::ContainsRegex;
+
+// Test corner cases of boundary conditions.
+TEST(Demangle, CornerCases) {
+  char tmp[10];
+  EXPECT_TRUE(Demangle("_Z6foobarv", tmp, sizeof(tmp)));
+  // sizeof("foobar()") == 9
+  EXPECT_STREQ("foobar()", tmp);
+  EXPECT_TRUE(Demangle("_Z6foobarv", tmp, 9));
+  EXPECT_STREQ("foobar()", tmp);
+  EXPECT_FALSE(Demangle("_Z6foobarv", tmp, 8));  // Not enough.
+  EXPECT_FALSE(Demangle("_Z6foobarv", tmp, 1));
+  EXPECT_FALSE(Demangle("_Z6foobarv", tmp, 0));
+  EXPECT_FALSE(Demangle("_Z6foobarv", nullptr, 0));  // Should not cause SEGV.
+  EXPECT_FALSE(Demangle("_Z1000000", tmp, 9));
+}
+
+// Test handling of functions suffixed with .clone.N, which is used
+// by GCC 4.5.x (and our locally-modified version of GCC 4.4.x), and
+// .constprop.N and .isra.N, which are used by GCC 4.6.x.  These
+// suffixes are used to indicate functions which have been cloned
+// during optimization.  We ignore these suffixes.
+TEST(Demangle, Clones) {
+  char tmp[20];
+  EXPECT_TRUE(Demangle("_ZL3Foov", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.clone.3", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.constprop.80", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.isra.18", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.isra.2.constprop.18", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // Demangle suffixes produced by -funique-internal-linkage-names.
+  EXPECT_TRUE(Demangle("_ZL3Foov.__uniq.12345", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  EXPECT_TRUE(Demangle("_ZL3Foov.__uniq.12345.isra.2.constprop.18", tmp,
+                       sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // Suffixes without the number should also demangle.
+  EXPECT_TRUE(Demangle("_ZL3Foov.clo", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // Suffixes with just the number should also demangle.
+  EXPECT_TRUE(Demangle("_ZL3Foov.123", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // (.clone. followed by non-number), should also demangle.
+  EXPECT_TRUE(Demangle("_ZL3Foov.clone.foo", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // (.clone. followed by multiple numbers), should also demangle.
+  EXPECT_TRUE(Demangle("_ZL3Foov.clone.123.456", tmp, sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // (a long valid suffix), should demangle.
+  EXPECT_TRUE(Demangle("_ZL3Foov.part.9.165493.constprop.775.31805", tmp,
+                       sizeof(tmp)));
+  EXPECT_STREQ("Foo()", tmp);
+  // Invalid (. without anything else), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.", tmp, sizeof(tmp)));
+  // Invalid (. with mix of alpha and digits), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.abc123", tmp, sizeof(tmp)));
+  // Invalid (.clone. not followed by number), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.clone.", tmp, sizeof(tmp)));
+  // Invalid (.constprop. not followed by number), should not demangle.
+  EXPECT_FALSE(Demangle("_ZL3Foov.isra.2.constprop.", tmp, sizeof(tmp)));
+}
+
+// Test the GNU abi_tag extension.
+TEST(Demangle, AbiTags) {
+  char tmp[80];
+
+  // Mangled name generated via:
+  // struct [[gnu::abi_tag("abc")]] A{};
+  // A a;
+  EXPECT_TRUE(Demangle("_Z1aB3abc", tmp, sizeof(tmp)));
+  EXPECT_STREQ("a[abi:abc]", tmp);
+
+  // Mangled name generated via:
+  // struct B {
+  //   B [[gnu::abi_tag("xyz")]] (){};
+  // };
+  // B b;
+  EXPECT_TRUE(Demangle("_ZN1BC2B3xyzEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("B::B[abi:xyz]()", tmp);
+
+  // Mangled name generated via:
+  // [[gnu::abi_tag("foo", "bar")]] void C() {}
+  EXPECT_TRUE(Demangle("_Z1CB3barB3foov", tmp, sizeof(tmp)));
+  EXPECT_STREQ("C[abi:bar][abi:foo]()", tmp);
+}
+
+// Tests that verify that Demangle footprint is within some limit.
+// They are not to be run under sanitizers as the sanitizers increase
+// stack consumption by about 4x.
+#if defined(ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION) && \
+    !defined(ABSL_HAVE_ADDRESS_SANITIZER) &&                   \
+    !defined(ABSL_HAVE_MEMORY_SANITIZER) &&                    \
+    !defined(ABSL_HAVE_THREAD_SANITIZER)
+
+static const char *g_mangled;
+static char g_demangle_buffer[4096];
+static char *g_demangle_result;
+
+static void DemangleSignalHandler(int signo) {
+  if (Demangle(g_mangled, g_demangle_buffer, sizeof(g_demangle_buffer))) {
+    g_demangle_result = g_demangle_buffer;
+  } else {
+    g_demangle_result = nullptr;
+  }
+}
+
+// Call Demangle and figure out the stack footprint of this call.
+static const char *DemangleStackConsumption(const char *mangled,
+                                            int *stack_consumed) {
+  g_mangled = mangled;
+  *stack_consumed = GetSignalHandlerStackConsumption(DemangleSignalHandler);
+  LOG(INFO) << "Stack consumption of Demangle: " << *stack_consumed;
+  return g_demangle_result;
+}
+
+// Demangle stack consumption should be within 8kB for simple mangled names
+// with some level of nesting. With alternate signal stack we have 64K,
+// but some signal handlers run on thread stack, and could have arbitrarily
+// little space left (so we don't want to make this number too large).
+const int kStackConsumptionUpperLimit = 8192;
+
+// Returns a mangled name nested to the given depth.
+static std::string NestedMangledName(int depth) {
+  std::string mangled_name = "_Z1a";
+  if (depth > 0) {
+    mangled_name += "IXL";
+    mangled_name += NestedMangledName(depth - 1);
+    mangled_name += "EEE";
+  }
+  return mangled_name;
+}
+
+TEST(Demangle, DemangleStackConsumption) {
+  // Measure stack consumption of Demangle for nested mangled names of varying
+  // depth.  Since Demangle is implemented as a recursive descent parser,
+  // stack consumption will grow as the nesting depth increases.  By measuring
+  // the stack consumption for increasing depths, we can see the growing
+  // impact of any stack-saving changes made to the code for Demangle.
+  int stack_consumed = 0;
+
+  const char *demangled =
+      DemangleStackConsumption("_Z6foobarv", &stack_consumed);
+  EXPECT_STREQ("foobar()", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name0 = NestedMangledName(0);
+  demangled = DemangleStackConsumption(nested_mangled_name0.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name1 = NestedMangledName(1);
+  demangled = DemangleStackConsumption(nested_mangled_name1.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a<>", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name2 = NestedMangledName(2);
+  demangled = DemangleStackConsumption(nested_mangled_name2.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a<>", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+
+  const std::string nested_mangled_name3 = NestedMangledName(3);
+  demangled = DemangleStackConsumption(nested_mangled_name3.c_str(),
+                                       &stack_consumed);
+  EXPECT_STREQ("a<>", demangled);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, kStackConsumptionUpperLimit);
+}
+
+#endif  // Stack consumption tests
+
+static void TestOnInput(const char* input) {
+  static const int kOutSize = 1048576;
+  auto out = absl::make_unique<char[]>(kOutSize);
+  Demangle(input, out.get(), kOutSize);
+}
+
+TEST(DemangleRegression, NegativeLength) {
+  TestOnInput("_ZZn4");
+}
+
+TEST(DemangleRegression, DeeplyNestedArrayType) {
+  const int depth = 100000;
+  std::string data = "_ZStI";
+  data.reserve(data.size() + 3 * depth + 1);
+  for (int i = 0; i < depth; i++) {
+    data += "A1_";
+  }
+  TestOnInput(data.c_str());
+}
+
+struct Base {
+  virtual ~Base() = default;
+};
+
+struct Derived : public Base {};
+
+TEST(DemangleStringTest, SupportsSymbolNameReturnedByTypeId) {
+  EXPECT_EQ(DemangleString(typeid(int).name()), "int");
+  // We want to test that `DemangleString` can demangle the symbol names
+  // returned by `typeid`, but without hard-coding the actual demangled values
+  // (because they are platform-specific).
+  EXPECT_THAT(
+      DemangleString(typeid(Base).name()),
+      ContainsRegex("absl.*debugging_internal.*anonymous namespace.*::Base"));
+  EXPECT_THAT(DemangleString(typeid(Derived).name()),
+              ContainsRegex(
+                  "absl.*debugging_internal.*anonymous namespace.*::Derived"));
+}
+
+}  // namespace
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/elf_mem_image.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/elf_mem_image.cc
new file mode 100644
index 0000000000000000000000000000000000000000..42dcd3cde9620a98a0fc4552bb9cb76db6b2fc10
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/elf_mem_image.cc
@@ -0,0 +1,386 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Allow dynamic symbol lookup in an in-memory Elf image.
+//
+
+#include "absl/debugging/internal/elf_mem_image.h"
+
+#ifdef ABSL_HAVE_ELF_MEM_IMAGE  // defined in elf_mem_image.h
+
+#include <string.h>
+#include <cassert>
+#include <cstddef>
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+
+// From binutils/include/elf/common.h (this doesn't appear to be documented
+// anywhere else).
+//
+//   /* This flag appears in a Versym structure.  It means that the symbol
+//      is hidden, and is only visible with an explicit version number.
+//      This is a GNU extension.  */
+//   #define VERSYM_HIDDEN           0x8000
+//
+//   /* This is the mask for the rest of the Versym information.  */
+//   #define VERSYM_VERSION          0x7fff
+
+#define VERSYM_VERSION 0x7fff
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+namespace {
+
+#if __SIZEOF_POINTER__ == 4
+const int kElfClass = ELFCLASS32;
+int ElfBind(const ElfW(Sym) *symbol) { return ELF32_ST_BIND(symbol->st_info); }
+int ElfType(const ElfW(Sym) *symbol) { return ELF32_ST_TYPE(symbol->st_info); }
+#elif __SIZEOF_POINTER__ == 8
+const int kElfClass = ELFCLASS64;
+int ElfBind(const ElfW(Sym) *symbol) { return ELF64_ST_BIND(symbol->st_info); }
+int ElfType(const ElfW(Sym) *symbol) { return ELF64_ST_TYPE(symbol->st_info); }
+#else
+const int kElfClass = -1;
+int ElfBind(const ElfW(Sym) *) {
+  ABSL_RAW_LOG(FATAL, "Unexpected word size");
+  return 0;
+}
+int ElfType(const ElfW(Sym) *) {
+  ABSL_RAW_LOG(FATAL, "Unexpected word size");
+  return 0;
+}
+#endif
+
+// Extract an element from one of the ELF tables, cast it to desired type.
+// This is just a simple arithmetic and a glorified cast.
+// Callers are responsible for bounds checking.
+template <typename T>
+const T *GetTableElement(const ElfW(Ehdr) * ehdr, ElfW(Off) table_offset,
+                         ElfW(Word) element_size, size_t index) {
+  return reinterpret_cast<const T*>(reinterpret_cast<const char *>(ehdr)
+                                    + table_offset
+                                    + index * element_size);
+}
+
+}  // namespace
+
+// The value of this variable doesn't matter; it's used only for its
+// unique address.
+const int ElfMemImage::kInvalidBaseSentinel = 0;
+
+ElfMemImage::ElfMemImage(const void *base) {
+  ABSL_RAW_CHECK(base != kInvalidBase, "bad pointer");
+  Init(base);
+}
+
+int ElfMemImage::GetNumSymbols() const {
+  if (!hash_) {
+    return 0;
+  }
+  // See http://www.caldera.com/developers/gabi/latest/ch5.dynamic.html#hash
+  return static_cast<int>(hash_[1]);
+}
+
+const ElfW(Sym) *ElfMemImage::GetDynsym(int index) const {
+  ABSL_RAW_CHECK(index < GetNumSymbols(), "index out of range");
+  return dynsym_ + index;
+}
+
+const ElfW(Versym) *ElfMemImage::GetVersym(int index) const {
+  ABSL_RAW_CHECK(index < GetNumSymbols(), "index out of range");
+  return versym_ + index;
+}
+
+const ElfW(Phdr) *ElfMemImage::GetPhdr(int index) const {
+  ABSL_RAW_CHECK(index >= 0 && index < ehdr_->e_phnum, "index out of range");
+  return GetTableElement<ElfW(Phdr)>(ehdr_, ehdr_->e_phoff, ehdr_->e_phentsize,
+                                     static_cast<size_t>(index));
+}
+
+const char *ElfMemImage::GetDynstr(ElfW(Word) offset) const {
+  ABSL_RAW_CHECK(offset < strsize_, "offset out of range");
+  return dynstr_ + offset;
+}
+
+const void *ElfMemImage::GetSymAddr(const ElfW(Sym) *sym) const {
+  if (sym->st_shndx == SHN_UNDEF || sym->st_shndx >= SHN_LORESERVE) {
+    // Symbol corresponds to "special" (e.g. SHN_ABS) section.
+    return reinterpret_cast<const void *>(sym->st_value);
+  }
+  ABSL_RAW_CHECK(link_base_ < sym->st_value, "symbol out of range");
+  return GetTableElement<char>(ehdr_, 0, 1, sym->st_value - link_base_);
+}
+
+const ElfW(Verdef) *ElfMemImage::GetVerdef(int index) const {
+  ABSL_RAW_CHECK(0 <= index && static_cast<size_t>(index) <= verdefnum_,
+                 "index out of range");
+  const ElfW(Verdef) *version_definition = verdef_;
+  while (version_definition->vd_ndx < index && version_definition->vd_next) {
+    const char *const version_definition_as_char =
+        reinterpret_cast<const char *>(version_definition);
+    version_definition =
+        reinterpret_cast<const ElfW(Verdef) *>(version_definition_as_char +
+                                               version_definition->vd_next);
+  }
+  return version_definition->vd_ndx == index ? version_definition : nullptr;
+}
+
+const ElfW(Verdaux) *ElfMemImage::GetVerdefAux(
+    const ElfW(Verdef) *verdef) const {
+  return reinterpret_cast<const ElfW(Verdaux) *>(verdef+1);
+}
+
+const char *ElfMemImage::GetVerstr(ElfW(Word) offset) const {
+  ABSL_RAW_CHECK(offset < strsize_, "offset out of range");
+  return dynstr_ + offset;
+}
+
+void ElfMemImage::Init(const void *base) {
+  ehdr_      = nullptr;
+  dynsym_    = nullptr;
+  dynstr_    = nullptr;
+  versym_    = nullptr;
+  verdef_    = nullptr;
+  hash_      = nullptr;
+  strsize_   = 0;
+  verdefnum_ = 0;
+  // Sentinel: PT_LOAD .p_vaddr can't possibly be this.
+  link_base_ = ~ElfW(Addr){0};  // NOLINT(readability/braces)
+  if (!base) {
+    return;
+  }
+  const char *const base_as_char = reinterpret_cast<const char *>(base);
+  if (base_as_char[EI_MAG0] != ELFMAG0 || base_as_char[EI_MAG1] != ELFMAG1 ||
+      base_as_char[EI_MAG2] != ELFMAG2 || base_as_char[EI_MAG3] != ELFMAG3) {
+    assert(false);
+    return;
+  }
+  int elf_class = base_as_char[EI_CLASS];
+  if (elf_class != kElfClass) {
+    assert(false);
+    return;
+  }
+  switch (base_as_char[EI_DATA]) {
+    case ELFDATA2LSB: {
+#ifndef ABSL_IS_LITTLE_ENDIAN
+      assert(false);
+      return;
+#endif
+      break;
+    }
+    case ELFDATA2MSB: {
+#ifndef ABSL_IS_BIG_ENDIAN
+      assert(false);
+      return;
+#endif
+      break;
+    }
+    default: {
+      assert(false);
+      return;
+    }
+  }
+
+  ehdr_ = reinterpret_cast<const ElfW(Ehdr) *>(base);
+  const ElfW(Phdr) *dynamic_program_header = nullptr;
+  for (int i = 0; i < ehdr_->e_phnum; ++i) {
+    const ElfW(Phdr) *const program_header = GetPhdr(i);
+    switch (program_header->p_type) {
+      case PT_LOAD:
+        if (!~link_base_) {
+          link_base_ = program_header->p_vaddr;
+        }
+        break;
+      case PT_DYNAMIC:
+        dynamic_program_header = program_header;
+        break;
+    }
+  }
+  if (!~link_base_ || !dynamic_program_header) {
+    assert(false);
+    // Mark this image as not present. Can not recur infinitely.
+    Init(nullptr);
+    return;
+  }
+  ptrdiff_t relocation =
+      base_as_char - reinterpret_cast<const char *>(link_base_);
+  ElfW(Dyn)* dynamic_entry = reinterpret_cast<ElfW(Dyn)*>(
+      static_cast<intptr_t>(dynamic_program_header->p_vaddr) + relocation);
+  for (; dynamic_entry->d_tag != DT_NULL; ++dynamic_entry) {
+    const auto value =
+        static_cast<intptr_t>(dynamic_entry->d_un.d_val) + relocation;
+    switch (dynamic_entry->d_tag) {
+      case DT_HASH:
+        hash_ = reinterpret_cast<ElfW(Word) *>(value);
+        break;
+      case DT_SYMTAB:
+        dynsym_ = reinterpret_cast<ElfW(Sym) *>(value);
+        break;
+      case DT_STRTAB:
+        dynstr_ = reinterpret_cast<const char *>(value);
+        break;
+      case DT_VERSYM:
+        versym_ = reinterpret_cast<ElfW(Versym) *>(value);
+        break;
+      case DT_VERDEF:
+        verdef_ = reinterpret_cast<ElfW(Verdef) *>(value);
+        break;
+      case DT_VERDEFNUM:
+        verdefnum_ = static_cast<size_t>(dynamic_entry->d_un.d_val);
+        break;
+      case DT_STRSZ:
+        strsize_ = static_cast<size_t>(dynamic_entry->d_un.d_val);
+        break;
+      default:
+        // Unrecognized entries explicitly ignored.
+        break;
+    }
+  }
+  if (!hash_ || !dynsym_ || !dynstr_ || !versym_ ||
+      !verdef_ || !verdefnum_ || !strsize_) {
+    assert(false);  // invalid VDSO
+    // Mark this image as not present. Can not recur infinitely.
+    Init(nullptr);
+    return;
+  }
+}
+
+bool ElfMemImage::LookupSymbol(const char *name,
+                               const char *version,
+                               int type,
+                               SymbolInfo *info_out) const {
+  for (const SymbolInfo& info : *this) {
+    if (strcmp(info.name, name) == 0 && strcmp(info.version, version) == 0 &&
+        ElfType(info.symbol) == type) {
+      if (info_out) {
+        *info_out = info;
+      }
+      return true;
+    }
+  }
+  return false;
+}
+
+bool ElfMemImage::LookupSymbolByAddress(const void *address,
+                                        SymbolInfo *info_out) const {
+  for (const SymbolInfo& info : *this) {
+    const char *const symbol_start =
+        reinterpret_cast<const char *>(info.address);
+    const char *const symbol_end = symbol_start + info.symbol->st_size;
+    if (symbol_start <= address && address < symbol_end) {
+      if (info_out) {
+        // Client wants to know details for that symbol (the usual case).
+        if (ElfBind(info.symbol) == STB_GLOBAL) {
+          // Strong symbol; just return it.
+          *info_out = info;
+          return true;
+        } else {
+          // Weak or local. Record it, but keep looking for a strong one.
+          *info_out = info;
+        }
+      } else {
+        // Client only cares if there is an overlapping symbol.
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+ElfMemImage::SymbolIterator::SymbolIterator(const void *const image, int index)
+    : index_(index), image_(image) {
+}
+
+const ElfMemImage::SymbolInfo *ElfMemImage::SymbolIterator::operator->() const {
+  return &info_;
+}
+
+const ElfMemImage::SymbolInfo& ElfMemImage::SymbolIterator::operator*() const {
+  return info_;
+}
+
+bool ElfMemImage::SymbolIterator::operator==(const SymbolIterator &rhs) const {
+  return this->image_ == rhs.image_ && this->index_ == rhs.index_;
+}
+
+bool ElfMemImage::SymbolIterator::operator!=(const SymbolIterator &rhs) const {
+  return !(*this == rhs);
+}
+
+ElfMemImage::SymbolIterator &ElfMemImage::SymbolIterator::operator++() {
+  this->Update(1);
+  return *this;
+}
+
+ElfMemImage::SymbolIterator ElfMemImage::begin() const {
+  SymbolIterator it(this, 0);
+  it.Update(0);
+  return it;
+}
+
+ElfMemImage::SymbolIterator ElfMemImage::end() const {
+  return SymbolIterator(this, GetNumSymbols());
+}
+
+void ElfMemImage::SymbolIterator::Update(int increment) {
+  const ElfMemImage *image = reinterpret_cast<const ElfMemImage *>(image_);
+  ABSL_RAW_CHECK(image->IsPresent() || increment == 0, "");
+  if (!image->IsPresent()) {
+    return;
+  }
+  index_ += increment;
+  if (index_ >= image->GetNumSymbols()) {
+    index_ = image->GetNumSymbols();
+    return;
+  }
+  const ElfW(Sym)    *symbol = image->GetDynsym(index_);
+  const ElfW(Versym) *version_symbol = image->GetVersym(index_);
+  ABSL_RAW_CHECK(symbol && version_symbol, "");
+  const char *const symbol_name = image->GetDynstr(symbol->st_name);
+#if defined(__NetBSD__)
+  const int version_index = version_symbol->vs_vers & VERSYM_VERSION;
+#else
+  const ElfW(Versym) version_index = version_symbol[0] & VERSYM_VERSION;
+#endif
+  const ElfW(Verdef) *version_definition = nullptr;
+  const char *version_name = "";
+  if (symbol->st_shndx == SHN_UNDEF) {
+    // Undefined symbols reference DT_VERNEED, not DT_VERDEF, and
+    // version_index could well be greater than verdefnum_, so calling
+    // GetVerdef(version_index) may trigger assertion.
+  } else {
+    version_definition = image->GetVerdef(version_index);
+  }
+  if (version_definition) {
+    // I am expecting 1 or 2 auxiliary entries: 1 for the version itself,
+    // optional 2nd if the version has a parent.
+    ABSL_RAW_CHECK(
+        version_definition->vd_cnt == 1 || version_definition->vd_cnt == 2,
+        "wrong number of entries");
+    const ElfW(Verdaux) *version_aux = image->GetVerdefAux(version_definition);
+    version_name = image->GetVerstr(version_aux->vda_name);
+  }
+  info_.name    = symbol_name;
+  info_.version = version_name;
+  info_.address = image->GetSymAddr(symbol);
+  info_.symbol  = symbol;
+}
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HAVE_ELF_MEM_IMAGE
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/elf_mem_image.h b/weight/_dep/abseil-cpp/absl/debugging/internal/elf_mem_image.h
new file mode 100644
index 0000000000000000000000000000000000000000..e7fe6ab06e2ffdf78756f2fd3ebb2f9a78aa784c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/elf_mem_image.h
@@ -0,0 +1,140 @@
+/*
+ * Copyright 2017 The Abseil Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Allow dynamic symbol lookup for in-memory Elf images.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_
+#define ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_
+
+// Including this will define the __GLIBC__ macro if glibc is being
+// used.
+#include <climits>
+
+#include "absl/base/config.h"
+
+// Maybe one day we can rewrite this file not to require the elf
+// symbol extensions in glibc, but for right now we need them.
+#ifdef ABSL_HAVE_ELF_MEM_IMAGE
+#error ABSL_HAVE_ELF_MEM_IMAGE cannot be directly set
+#endif
+
+#if defined(__ELF__) && !defined(__OpenBSD__) && !defined(__QNX__) && \
+    !defined(__native_client__) && !defined(__asmjs__) &&             \
+    !defined(__wasm__) && !defined(__HAIKU__) && !defined(__sun) &&   \
+    !defined(__VXWORKS__) && !defined(__hexagon__)
+#define ABSL_HAVE_ELF_MEM_IMAGE 1
+#endif
+
+#ifdef ABSL_HAVE_ELF_MEM_IMAGE
+
+#include <link.h>  // for ElfW
+
+#if defined(__FreeBSD__) && !defined(ElfW)
+#define ElfW(x) __ElfN(x)
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// An in-memory ELF image (may not exist on disk).
+class ElfMemImage {
+ private:
+  // Sentinel: there could never be an elf image at &kInvalidBaseSentinel.
+  static const int kInvalidBaseSentinel;
+
+ public:
+  // Sentinel: there could never be an elf image at this address.
+  static constexpr const void *const kInvalidBase =
+    static_cast<const void*>(&kInvalidBaseSentinel);
+
+  // Information about a single vdso symbol.
+  // All pointers are into .dynsym, .dynstr, or .text of the VDSO.
+  // Do not free() them or modify through them.
+  struct SymbolInfo {
+    const char      *name;      // E.g. "__vdso_getcpu"
+    const char      *version;   // E.g. "LINUX_2.6", could be ""
+                                // for unversioned symbol.
+    const void      *address;   // Relocated symbol address.
+    const ElfW(Sym) *symbol;    // Symbol in the dynamic symbol table.
+  };
+
+  // Supports iteration over all dynamic symbols.
+  class SymbolIterator {
+   public:
+    friend class ElfMemImage;
+    const SymbolInfo *operator->() const;
+    const SymbolInfo &operator*() const;
+    SymbolIterator& operator++();
+    bool operator!=(const SymbolIterator &rhs) const;
+    bool operator==(const SymbolIterator &rhs) const;
+   private:
+    SymbolIterator(const void *const image, int index);
+    void Update(int incr);
+    SymbolInfo info_;
+    int index_;
+    const void *const image_;
+  };
+
+
+  explicit ElfMemImage(const void *base);
+  void                 Init(const void *base);
+  bool                 IsPresent() const { return ehdr_ != nullptr; }
+  const ElfW(Phdr)*    GetPhdr(int index) const;
+  const ElfW(Sym)*     GetDynsym(int index) const;
+  const ElfW(Versym)*  GetVersym(int index) const;
+  const ElfW(Verdef)*  GetVerdef(int index) const;
+  const ElfW(Verdaux)* GetVerdefAux(const ElfW(Verdef) *verdef) const;
+  const char*          GetDynstr(ElfW(Word) offset) const;
+  const void*          GetSymAddr(const ElfW(Sym) *sym) const;
+  const char*          GetVerstr(ElfW(Word) offset) const;
+  int                  GetNumSymbols() const;
+
+  SymbolIterator begin() const;
+  SymbolIterator end() const;
+
+  // Look up versioned dynamic symbol in the image.
+  // Returns false if image is not present, or doesn't contain given
+  // symbol/version/type combination.
+  // If info_out is non-null, additional details are filled in.
+  bool LookupSymbol(const char *name, const char *version,
+                    int symbol_type, SymbolInfo *info_out) const;
+
+  // Find info about symbol (if any) which overlaps given address.
+  // Returns true if symbol was found; false if image isn't present
+  // or doesn't have a symbol overlapping given address.
+  // If info_out is non-null, additional details are filled in.
+  bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const;
+
+ private:
+  const ElfW(Ehdr) *ehdr_;
+  const ElfW(Sym) *dynsym_;
+  const ElfW(Versym) *versym_;
+  const ElfW(Verdef) *verdef_;
+  const ElfW(Word) *hash_;
+  const char *dynstr_;
+  size_t strsize_;
+  size_t verdefnum_;
+  ElfW(Addr) link_base_;     // Link-time base (p_vaddr of first PT_LOAD).
+};
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HAVE_ELF_MEM_IMAGE
+
+#endif  // ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/examine_stack.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/examine_stack.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3dd6ba1a53ef8842aca8620fe626f4add92fff50
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/examine_stack.cc
@@ -0,0 +1,320 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "absl/debugging/internal/examine_stack.h"
+
+#ifndef _WIN32
+#include <unistd.h>
+#endif
+
+#include "absl/base/config.h"
+
+#ifdef ABSL_HAVE_MMAP
+#include <sys/mman.h>
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+#endif
+
+#if defined(__linux__) || defined(__APPLE__)
+#include <sys/ucontext.h>
+#endif
+
+#include <csignal>
+#include <cstdio>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/macros.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+namespace {
+constexpr int kDefaultDumpStackFramesLimit = 64;
+// The %p field width for printf() functions is two characters per byte,
+// and two extra for the leading "0x".
+constexpr int kPrintfPointerFieldWidth = 2 + 2 * sizeof(void*);
+
+ABSL_CONST_INIT SymbolizeUrlEmitter debug_stack_trace_hook = nullptr;
+
+// Async-signal safe mmap allocator.
+void* Allocate(size_t num_bytes) {
+#ifdef ABSL_HAVE_MMAP
+  void* p = ::mmap(nullptr, num_bytes, PROT_READ | PROT_WRITE,
+                   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  return p == MAP_FAILED ? nullptr : p;
+#else
+  (void)num_bytes;
+  return nullptr;
+#endif  // ABSL_HAVE_MMAP
+}
+
+void Deallocate(void* p, size_t size) {
+#ifdef ABSL_HAVE_MMAP
+  ::munmap(p, size);
+#else
+  (void)p;
+  (void)size;
+#endif  // ABSL_HAVE_MMAP
+}
+
+// Print a program counter only.
+void DumpPC(OutputWriter* writer, void* writer_arg, void* const pc,
+            const char* const prefix) {
+  char buf[100];
+  snprintf(buf, sizeof(buf), "%s@ %*p\n", prefix, kPrintfPointerFieldWidth, pc);
+  writer(buf, writer_arg);
+}
+
+// Print a program counter and the corresponding stack frame size.
+void DumpPCAndFrameSize(OutputWriter* writer, void* writer_arg, void* const pc,
+                        int framesize, const char* const prefix) {
+  char buf[100];
+  if (framesize <= 0) {
+    snprintf(buf, sizeof(buf), "%s@ %*p  (unknown)\n", prefix,
+             kPrintfPointerFieldWidth, pc);
+  } else {
+    snprintf(buf, sizeof(buf), "%s@ %*p  %9d\n", prefix,
+             kPrintfPointerFieldWidth, pc, framesize);
+  }
+  writer(buf, writer_arg);
+}
+
+// Print a program counter and the corresponding symbol.
+void DumpPCAndSymbol(OutputWriter* writer, void* writer_arg, void* const pc,
+                     const char* const prefix) {
+  char tmp[1024];
+  const char* symbol = "(unknown)";
+  // Symbolizes the previous address of pc because pc may be in the
+  // next function.  The overrun happens when the function ends with
+  // a call to a function annotated noreturn (e.g. CHECK).
+  // If symbolization of pc-1 fails, also try pc on the off-chance
+  // that we crashed on the first instruction of a function (that
+  // actually happens very often for e.g. __restore_rt).
+  const uintptr_t prev_pc = reinterpret_cast<uintptr_t>(pc) - 1;
+  if (absl::Symbolize(reinterpret_cast<const char*>(prev_pc), tmp,
+                      sizeof(tmp)) ||
+      absl::Symbolize(pc, tmp, sizeof(tmp))) {
+    symbol = tmp;
+  }
+  char buf[1024];
+  snprintf(buf, sizeof(buf), "%s@ %*p  %s\n", prefix, kPrintfPointerFieldWidth,
+           pc, symbol);
+  writer(buf, writer_arg);
+}
+
+// Print a program counter, its stack frame size, and its symbol name.
+// Note that there is a separate symbolize_pc argument. Return addresses may be
+// at the end of the function, and this allows the caller to back up from pc if
+// appropriate.
+void DumpPCAndFrameSizeAndSymbol(OutputWriter* writer, void* writer_arg,
+                                 void* const pc, void* const symbolize_pc,
+                                 int framesize, const char* const prefix) {
+  char tmp[1024];
+  const char* symbol = "(unknown)";
+  if (absl::Symbolize(symbolize_pc, tmp, sizeof(tmp))) {
+    symbol = tmp;
+  }
+  char buf[1024];
+  if (framesize <= 0) {
+    snprintf(buf, sizeof(buf), "%s@ %*p  (unknown)  %s\n", prefix,
+             kPrintfPointerFieldWidth, pc, symbol);
+  } else {
+    snprintf(buf, sizeof(buf), "%s@ %*p  %9d  %s\n", prefix,
+             kPrintfPointerFieldWidth, pc, framesize, symbol);
+  }
+  writer(buf, writer_arg);
+}
+
+}  // namespace
+
+void RegisterDebugStackTraceHook(SymbolizeUrlEmitter hook) {
+  debug_stack_trace_hook = hook;
+}
+
+SymbolizeUrlEmitter GetDebugStackTraceHook() { return debug_stack_trace_hook; }
+
+// Returns the program counter from signal context, nullptr if
+// unknown. vuc is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* const vuc) {
+#ifdef __linux__
+  if (vuc != nullptr) {
+    ucontext_t* context = reinterpret_cast<ucontext_t*>(vuc);
+#if defined(__aarch64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.pc);
+#elif defined(__alpha__)
+    return reinterpret_cast<void*>(context->uc_mcontext.sc_pc);
+#elif defined(__arm__)
+    return reinterpret_cast<void*>(context->uc_mcontext.arm_pc);
+#elif defined(__hppa__)
+    return reinterpret_cast<void*>(context->uc_mcontext.sc_iaoq[0]);
+#elif defined(__i386__)
+    if (14 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
+      return reinterpret_cast<void*>(context->uc_mcontext.gregs[14]);
+#elif defined(__ia64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.sc_ip);
+#elif defined(__m68k__)
+    return reinterpret_cast<void*>(context->uc_mcontext.gregs[16]);
+#elif defined(__mips__)
+    return reinterpret_cast<void*>(context->uc_mcontext.pc);
+#elif defined(__powerpc64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.gp_regs[32]);
+#elif defined(__powerpc__)
+    return reinterpret_cast<void*>(context->uc_mcontext.uc_regs->gregs[32]);
+#elif defined(__riscv)
+    return reinterpret_cast<void*>(context->uc_mcontext.__gregs[REG_PC]);
+#elif defined(__s390__) && !defined(__s390x__)
+    return reinterpret_cast<void*>(context->uc_mcontext.psw.addr & 0x7fffffff);
+#elif defined(__s390__) && defined(__s390x__)
+    return reinterpret_cast<void*>(context->uc_mcontext.psw.addr);
+#elif defined(__sh__)
+    return reinterpret_cast<void*>(context->uc_mcontext.pc);
+#elif defined(__sparc__) && !defined(__arch64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.gregs[19]);
+#elif defined(__sparc__) && defined(__arch64__)
+    return reinterpret_cast<void*>(context->uc_mcontext.mc_gregs[19]);
+#elif defined(__x86_64__)
+    if (16 < ABSL_ARRAYSIZE(context->uc_mcontext.gregs))
+      return reinterpret_cast<void*>(context->uc_mcontext.gregs[16]);
+#elif defined(__e2k__)
+    return reinterpret_cast<void*>(context->uc_mcontext.cr0_hi);
+#elif defined(__loongarch__)
+    return reinterpret_cast<void*>(context->uc_mcontext.__pc);
+#else
+#error "Undefined Architecture."
+#endif
+  }
+#elif defined(__APPLE__)
+  if (vuc != nullptr) {
+    ucontext_t* signal_ucontext = reinterpret_cast<ucontext_t*>(vuc);
+#if defined(__aarch64__)
+    return reinterpret_cast<void*>(
+        __darwin_arm_thread_state64_get_pc(signal_ucontext->uc_mcontext->__ss));
+#elif defined(__arm__)
+#if __DARWIN_UNIX03
+    return reinterpret_cast<void*>(signal_ucontext->uc_mcontext->__ss.__pc);
+#else
+    return reinterpret_cast<void*>(signal_ucontext->uc_mcontext->ss.pc);
+#endif
+#elif defined(__i386__)
+#if __DARWIN_UNIX03
+    return reinterpret_cast<void*>(signal_ucontext->uc_mcontext->__ss.__eip);
+#else
+    return reinterpret_cast<void*>(signal_ucontext->uc_mcontext->ss.eip);
+#endif
+#elif defined(__x86_64__)
+#if __DARWIN_UNIX03
+    return reinterpret_cast<void*>(signal_ucontext->uc_mcontext->__ss.__rip);
+#else
+    return reinterpret_cast<void*>(signal_ucontext->uc_mcontext->ss.rip);
+#endif
+#endif
+  }
+#elif defined(__akaros__)
+  auto* ctx = reinterpret_cast<struct user_context*>(vuc);
+  return reinterpret_cast<void*>(get_user_ctx_pc(ctx));
+#endif
+  static_cast<void>(vuc);
+  return nullptr;
+}
+
+void DumpPCAndFrameSizesAndStackTrace(void* const pc, void* const stack[],
+                                      int frame_sizes[], int depth,
+                                      int min_dropped_frames,
+                                      bool symbolize_stacktrace,
+                                      OutputWriter* writer, void* writer_arg) {
+  if (pc != nullptr) {
+    // We don't know the stack frame size for PC, use 0.
+    if (symbolize_stacktrace) {
+      DumpPCAndFrameSizeAndSymbol(writer, writer_arg, pc, pc, 0, "PC: ");
+    } else {
+      DumpPCAndFrameSize(writer, writer_arg, pc, 0, "PC: ");
+    }
+  }
+  for (int i = 0; i < depth; i++) {
+    if (symbolize_stacktrace) {
+      // Pass the previous address of pc as the symbol address because pc is a
+      // return address, and an overrun may occur when the function ends with a
+      // call to a function annotated noreturn (e.g. CHECK). Note that we don't
+      // do this for pc above, as the adjustment is only correct for return
+      // addresses.
+      DumpPCAndFrameSizeAndSymbol(writer, writer_arg, stack[i],
+                                  reinterpret_cast<char*>(stack[i]) - 1,
+                                  frame_sizes[i], "    ");
+    } else {
+      DumpPCAndFrameSize(writer, writer_arg, stack[i], frame_sizes[i], "    ");
+    }
+  }
+  if (min_dropped_frames > 0) {
+    char buf[100];
+    snprintf(buf, sizeof(buf), "    @ ... and at least %d more frames\n",
+             min_dropped_frames);
+    writer(buf, writer_arg);
+  }
+}
+
+// Dump current stack trace as directed by writer.
+// Make sure this function is not inlined to avoid skipping too many top frames.
+ABSL_ATTRIBUTE_NOINLINE
+void DumpStackTrace(int min_dropped_frames, int max_num_frames,
+                    bool symbolize_stacktrace, OutputWriter* writer,
+                    void* writer_arg) {
+  // Print stack trace
+  void* stack_buf[kDefaultDumpStackFramesLimit];
+  void** stack = stack_buf;
+  int num_stack = kDefaultDumpStackFramesLimit;
+  size_t allocated_bytes = 0;
+
+  if (num_stack >= max_num_frames) {
+    // User requested fewer frames than we already have space for.
+    num_stack = max_num_frames;
+  } else {
+    const size_t needed_bytes =
+        static_cast<size_t>(max_num_frames) * sizeof(stack[0]);
+    void* p = Allocate(needed_bytes);
+    if (p != nullptr) {  // We got the space.
+      num_stack = max_num_frames;
+      stack = reinterpret_cast<void**>(p);
+      allocated_bytes = needed_bytes;
+    }
+  }
+
+  int depth = absl::GetStackTrace(stack, num_stack, min_dropped_frames + 1);
+  for (int i = 0; i < depth; i++) {
+    if (symbolize_stacktrace) {
+      DumpPCAndSymbol(writer, writer_arg, stack[static_cast<size_t>(i)],
+                      "    ");
+    } else {
+      DumpPC(writer, writer_arg, stack[static_cast<size_t>(i)], "    ");
+    }
+  }
+
+  auto hook = GetDebugStackTraceHook();
+  if (hook != nullptr) {
+    (*hook)(stack, depth, writer, writer_arg);
+  }
+
+  if (allocated_bytes != 0) Deallocate(stack, allocated_bytes);
+}
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/examine_stack.h b/weight/_dep/abseil-cpp/absl/debugging/internal/examine_stack.h
new file mode 100644
index 0000000000000000000000000000000000000000..190af87f1c348a1e85810dfd1e25af099cd2da39
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/examine_stack.h
@@ -0,0 +1,64 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+#define ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// Type of function used for printing in stack trace dumping, etc.
+// We avoid closures to keep things simple.
+typedef void OutputWriter(const char*, void*);
+
+// RegisterDebugStackTraceHook() allows to register a single routine
+// `hook` that is called each time DumpStackTrace() is called.
+// `hook` may be called from a signal handler.
+typedef void (*SymbolizeUrlEmitter)(void* const stack[], int depth,
+                                    OutputWriter* writer, void* writer_arg);
+
+// Registration of SymbolizeUrlEmitter for use inside of a signal handler.
+// This is inherently unsafe and must be signal safe code.
+void RegisterDebugStackTraceHook(SymbolizeUrlEmitter hook);
+SymbolizeUrlEmitter GetDebugStackTraceHook();
+
+// Returns the program counter from signal context, or nullptr if
+// unknown. `vuc` is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* const vuc);
+
+// Uses `writer` to dump the program counter, stack trace, and stack
+// frame sizes.
+void DumpPCAndFrameSizesAndStackTrace(void* const pc, void* const stack[],
+                                      int frame_sizes[], int depth,
+                                      int min_dropped_frames,
+                                      bool symbolize_stacktrace,
+                                      OutputWriter* writer, void* writer_arg);
+
+// Dump current stack trace omitting the topmost `min_dropped_frames` stack
+// frames.
+void DumpStackTrace(int min_dropped_frames, int max_num_frames,
+                    bool symbolize_stacktrace, OutputWriter* writer,
+                    void* writer_arg);
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b54a1b28c01eb26214ab344ec9d038cfd2d2cb4c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption.cc
@@ -0,0 +1,206 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/internal/stack_consumption.h"
+
+#ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+#include <signal.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/raw_logging.h"
+
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+namespace {
+
+// This code requires that we know the direction in which the stack
+// grows. It is commonly believed that this can be detected by putting
+// a variable on the stack and then passing its address to a function
+// that compares the address of this variable to the address of a
+// variable on the function's own stack. However, this is unspecified
+// behavior in C++: If two pointers p and q of the same type point to
+// different objects that are not members of the same object or
+// elements of the same array or to different functions, or if only
+// one of them is null, the results of p<q, p>q, p<=q, and p>=q are
+// unspecified. Therefore, instead we hardcode the direction of the
+// stack on platforms we know about.
+#if defined(__i386__) || defined(__x86_64__) || defined(__ppc__) || \
+    defined(__aarch64__) || defined(__riscv)
+constexpr bool kStackGrowsDown = true;
+#else
+#error Need to define kStackGrowsDown
+#endif
+
+// To measure the stack footprint of some code, we create a signal handler
+// (for SIGUSR2 say) that exercises this code on an alternate stack. This
+// alternate stack is initialized to some known pattern (0x55, 0x55, 0x55,
+// ...). We then self-send this signal, and after the signal handler returns,
+// look at the alternate stack buffer to see what portion has been touched.
+//
+// This trick gives us the the stack footprint of the signal handler.  But the
+// signal handler, even before the code for it is exercised, consumes some
+// stack already. We however only want the stack usage of the code inside the
+// signal handler. To measure this accurately, we install two signal handlers:
+// one that does nothing and just returns, and the user-provided signal
+// handler. The difference between the stack consumption of these two signals
+// handlers should give us the stack foorprint of interest.
+
+void EmptySignalHandler(int) {}
+
+// This is arbitrary value, and could be increase further, at the cost of
+// memset()ting it all to known sentinel value.
+constexpr int kAlternateStackSize = 64 << 10;  // 64KiB
+
+constexpr int kSafetyMargin = 32;
+constexpr char kAlternateStackFillValue = 0x55;
+
+// These helper functions look at the alternate stack buffer, and figure
+// out what portion of this buffer has been touched - this is the stack
+// consumption of the signal handler running on this alternate stack.
+// This function will return -1 if the alternate stack buffer has not been
+// touched. It will abort the program if the buffer has overflowed or is about
+// to overflow.
+int GetStackConsumption(const void* const altstack) {
+  const char* begin;
+  int increment;
+  if (kStackGrowsDown) {
+    begin = reinterpret_cast<const char*>(altstack);
+    increment = 1;
+  } else {
+    begin = reinterpret_cast<const char*>(altstack) + kAlternateStackSize - 1;
+    increment = -1;
+  }
+
+  for (int usage_count = kAlternateStackSize; usage_count > 0; --usage_count) {
+    if (*begin != kAlternateStackFillValue) {
+      ABSL_RAW_CHECK(usage_count <= kAlternateStackSize - kSafetyMargin,
+                     "Buffer has overflowed or is about to overflow");
+      return usage_count;
+    }
+    begin += increment;
+  }
+
+  ABSL_RAW_LOG(FATAL, "Unreachable code");
+  return -1;
+}
+
+}  // namespace
+
+int GetSignalHandlerStackConsumption(void (*signal_handler)(int)) {
+  // The alt-signal-stack cannot be heap allocated because there is a
+  // bug in glibc-2.2 where some signal handler setup code looks at the
+  // current stack pointer to figure out what thread is currently running.
+  // Therefore, the alternate stack must be allocated from the main stack
+  // itself.
+  void* altstack = mmap(nullptr, kAlternateStackSize, PROT_READ | PROT_WRITE,
+                        MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  ABSL_RAW_CHECK(altstack != MAP_FAILED, "mmap() failed");
+
+  // Set up the alt-signal-stack (and save the older one).
+  stack_t sigstk;
+  memset(&sigstk, 0, sizeof(sigstk));
+  sigstk.ss_sp = altstack;
+  sigstk.ss_size = kAlternateStackSize;
+  sigstk.ss_flags = 0;
+  stack_t old_sigstk;
+  memset(&old_sigstk, 0, sizeof(old_sigstk));
+  ABSL_RAW_CHECK(sigaltstack(&sigstk, &old_sigstk) == 0,
+                 "sigaltstack() failed");
+
+  // Set up SIGUSR1 and SIGUSR2 signal handlers (and save the older ones).
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  struct sigaction old_sa1, old_sa2;
+  sigemptyset(&sa.sa_mask);
+  sa.sa_flags = SA_ONSTACK;
+
+  // SIGUSR1 maps to EmptySignalHandler.
+  sa.sa_handler = EmptySignalHandler;
+  ABSL_RAW_CHECK(sigaction(SIGUSR1, &sa, &old_sa1) == 0, "sigaction() failed");
+
+  // SIGUSR2 maps to signal_handler.
+  sa.sa_handler = signal_handler;
+  ABSL_RAW_CHECK(sigaction(SIGUSR2, &sa, &old_sa2) == 0, "sigaction() failed");
+
+  // Send SIGUSR1 signal and measure the stack consumption of the empty
+  // signal handler.
+  // The first signal might use more stack space. Run once and ignore the
+  // results to get that out of the way.
+  ABSL_RAW_CHECK(kill(getpid(), SIGUSR1) == 0, "kill() failed");
+
+  memset(altstack, kAlternateStackFillValue, kAlternateStackSize);
+  ABSL_RAW_CHECK(kill(getpid(), SIGUSR1) == 0, "kill() failed");
+  int base_stack_consumption = GetStackConsumption(altstack);
+
+  // Send SIGUSR2 signal and measure the stack consumption of signal_handler.
+  ABSL_RAW_CHECK(kill(getpid(), SIGUSR2) == 0, "kill() failed");
+  int signal_handler_stack_consumption = GetStackConsumption(altstack);
+
+  // Now restore the old alt-signal-stack and signal handlers.
+  if (old_sigstk.ss_sp == nullptr && old_sigstk.ss_size == 0 &&
+      (old_sigstk.ss_flags & SS_DISABLE)) {
+    // https://git.musl-libc.org/cgit/musl/commit/src/signal/sigaltstack.c?id=7829f42a2c8944555439380498ab8b924d0f2070
+    // The original stack has ss_size==0 and ss_flags==SS_DISABLE, but some
+    // versions of musl have a bug that rejects ss_size==0. Work around this by
+    // setting ss_size to MINSIGSTKSZ, which should be ignored by the kernel
+    // when SS_DISABLE is set.
+    old_sigstk.ss_size = static_cast<size_t>(MINSIGSTKSZ);
+  }
+  ABSL_RAW_CHECK(sigaltstack(&old_sigstk, nullptr) == 0,
+                 "sigaltstack() failed");
+  ABSL_RAW_CHECK(sigaction(SIGUSR1, &old_sa1, nullptr) == 0,
+                 "sigaction() failed");
+  ABSL_RAW_CHECK(sigaction(SIGUSR2, &old_sa2, nullptr) == 0,
+                 "sigaction() failed");
+
+  ABSL_RAW_CHECK(munmap(altstack, kAlternateStackSize) == 0, "munmap() failed");
+  if (signal_handler_stack_consumption != -1 && base_stack_consumption != -1) {
+    return signal_handler_stack_consumption - base_stack_consumption;
+  }
+  return -1;
+}
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#else
+
+// https://github.com/abseil/abseil-cpp/issues/1465
+// CMake builds on Apple platforms error when libraries are empty.
+// Our CMake configuration can avoid this error on header-only libraries,
+// but since this library is conditionally empty, including a single
+// variable is an easy workaround.
+#ifdef __APPLE__
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+extern const char kAvoidEmptyStackConsumptionLibraryWarning;
+const char kAvoidEmptyStackConsumptionLibraryWarning = 0;
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+#endif  // __APPLE__
+
+#endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption.h b/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption.h
new file mode 100644
index 0000000000000000000000000000000000000000..f41b64c39df11181bc9a959bf6c5820153f2137e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption.h
@@ -0,0 +1,50 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Helper function for measuring stack consumption of signal handlers.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACK_CONSUMPTION_H_
+#define ABSL_DEBUGGING_INTERNAL_STACK_CONSUMPTION_H_
+
+#include "absl/base/config.h"
+
+// The code in this module is not portable.
+// Use this feature test macro to detect its availability.
+#ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+#error ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION cannot be set directly
+#elif !defined(__APPLE__) && !defined(_WIN32) &&                     \
+    (defined(__i386__) || defined(__x86_64__) || defined(__ppc__) || \
+     defined(__aarch64__) || defined(__riscv))
+#define ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION 1
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// Returns the stack consumption in bytes for the code exercised by
+// signal_handler.  To measure stack consumption, signal_handler is registered
+// as a signal handler, so the code that it exercises must be async-signal
+// safe.  The argument of signal_handler is an implementation detail of signal
+// handlers and should ignored by the code for signal_handler.  Use global
+// variables to pass information between your test code and signal_handler.
+int GetSignalHandlerStackConsumption(void (*signal_handler)(int));
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACK_CONSUMPTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption_test.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0255ac8f36c80c4cc5fec02c9dd8302e9500f8c5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stack_consumption_test.cc
@@ -0,0 +1,50 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/internal/stack_consumption.h"
+
+#ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+#include <string.h>
+
+#include "gtest/gtest.h"
+#include "absl/log/log.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+namespace {
+
+static void SimpleSignalHandler(int signo) {
+  char buf[100];
+  memset(buf, 'a', sizeof(buf));
+
+  // Never true, but prevents compiler from optimizing buf out.
+  if (signo == 0) {
+    LOG(INFO) << static_cast<void*>(buf);
+  }
+}
+
+TEST(SignalHandlerStackConsumptionTest, MeasuresStackConsumption) {
+  // Our handler should consume reasonable number of bytes.
+  EXPECT_GE(GetSignalHandlerStackConsumption(SimpleSignalHandler), 100);
+}
+
+}  // namespace
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_aarch64-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_aarch64-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..1caf7bbe3591f8a17b46b33d43a52606a74bd339
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_aarch64-inl.inc
@@ -0,0 +1,266 @@
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
+
+// Generate stack tracer for aarch64
+
+#if defined(__linux__)
+#include <signal.h>
+#include <sys/mman.h>
+#include <ucontext.h>
+#include <unistd.h>
+#endif
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <iostream>
+#include <limits>
+
+#include "absl/base/attributes.h"
+#include "absl/debugging/internal/address_is_readable.h"
+#include "absl/debugging/internal/vdso_support.h"  // a no-op on non-elf or non-glibc systems
+#include "absl/debugging/stacktrace.h"
+
+static const size_t kUnknownFrameSize = 0;
+// Stack end to use when we don't know the actual stack end
+// (effectively just the end of address space).
+constexpr uintptr_t kUnknownStackEnd =
+    std::numeric_limits<size_t>::max() - sizeof(void *);
+
+#if defined(__linux__)
+// Returns the address of the VDSO __kernel_rt_sigreturn function, if present.
+static const unsigned char* GetKernelRtSigreturnAddress() {
+  constexpr uintptr_t kImpossibleAddress = 1;
+  ABSL_CONST_INIT static std::atomic<uintptr_t> memoized{kImpossibleAddress};
+  uintptr_t address = memoized.load(std::memory_order_relaxed);
+  if (address != kImpossibleAddress) {
+    return reinterpret_cast<const unsigned char*>(address);
+  }
+
+  address = reinterpret_cast<uintptr_t>(nullptr);
+
+#ifdef ABSL_HAVE_VDSO_SUPPORT
+  absl::debugging_internal::VDSOSupport vdso;
+  if (vdso.IsPresent()) {
+    absl::debugging_internal::VDSOSupport::SymbolInfo symbol_info;
+    auto lookup = [&](int type) {
+      return vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.6.39", type,
+                               &symbol_info);
+    };
+    if ((!lookup(STT_FUNC) && !lookup(STT_NOTYPE)) ||
+        symbol_info.address == nullptr) {
+      // Unexpected: VDSO is present, yet the expected symbol is missing
+      // or null.
+      assert(false && "VDSO is present, but doesn't have expected symbol");
+    } else {
+      if (reinterpret_cast<uintptr_t>(symbol_info.address) !=
+          kImpossibleAddress) {
+        address = reinterpret_cast<uintptr_t>(symbol_info.address);
+      } else {
+        assert(false && "VDSO returned invalid address");
+      }
+    }
+  }
+#endif
+
+  memoized.store(address, std::memory_order_relaxed);
+  return reinterpret_cast<const unsigned char*>(address);
+}
+#endif  // __linux__
+
+// Compute the size of a stack frame in [low..high).  We assume that
+// low < high.  Return size of kUnknownFrameSize.
+template<typename T>
+static size_t ComputeStackFrameSize(const T* low,
+                                           const T* high) {
+  const char* low_char_ptr = reinterpret_cast<const char *>(low);
+  const char* high_char_ptr = reinterpret_cast<const char *>(high);
+  return low < high ? static_cast<size_t>(high_char_ptr - low_char_ptr)
+                    : kUnknownFrameSize;
+}
+
+// Saves stack info that is expensive to calculate to avoid recalculating per frame.
+struct StackInfo {
+  uintptr_t stack_low;
+  uintptr_t stack_high;
+  uintptr_t sig_stack_low;
+  uintptr_t sig_stack_high;
+};
+
+static bool InsideSignalStack(void** ptr, const StackInfo* stack_info) {
+  uintptr_t comparable_ptr = reinterpret_cast<uintptr_t>(ptr);
+  return (comparable_ptr >= stack_info->sig_stack_low &&
+          comparable_ptr < stack_info->sig_stack_high);
+}
+
+// Given a pointer to a stack frame, locate and return the calling
+// stackframe, or return null if no stackframe can be found. Perform sanity
+// checks (the strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template<bool STRICT_UNWINDING, bool WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY  // May read random elements from stack.
+static void **NextStackFrame(void **old_frame_pointer, const void *uc,
+                             const StackInfo *stack_info) {
+  void **new_frame_pointer = reinterpret_cast<void**>(*old_frame_pointer);
+
+#if defined(__linux__)
+  if (WITH_CONTEXT && uc != nullptr) {
+    // Check to see if next frame's return address is __kernel_rt_sigreturn.
+    if (old_frame_pointer[1] == GetKernelRtSigreturnAddress()) {
+      const ucontext_t *ucv = static_cast<const ucontext_t *>(uc);
+      // old_frame_pointer[0] is not suitable for unwinding, look at
+      // ucontext to discover frame pointer before signal.
+      void **const pre_signal_frame_pointer =
+          reinterpret_cast<void **>(ucv->uc_mcontext.regs[29]);
+
+      // The most recent signal always needs special handling to find the frame
+      // pointer, but a nested signal does not.  If pre_signal_frame_pointer is
+      // earlier in the stack than the old_frame_pointer, then use it. If it is
+      // later, then we have already unwound through it and it needs no special
+      // handling.
+      if (pre_signal_frame_pointer >= old_frame_pointer) {
+        new_frame_pointer = pre_signal_frame_pointer;
+      }
+      // Check that alleged frame pointer is actually readable. This is to
+      // prevent "double fault" in case we hit the first fault due to e.g.
+      // stack corruption.
+      if (!absl::debugging_internal::AddressIsReadable(
+              new_frame_pointer))
+        return nullptr;
+    }
+  }
+#endif
+
+  // The frame pointer should be 8-byte aligned.
+  if ((reinterpret_cast<uintptr_t>(new_frame_pointer) & 7) != 0)
+    return nullptr;
+
+  // Only check the size if both frames are in the same stack.
+  if (InsideSignalStack(new_frame_pointer, stack_info) ==
+      InsideSignalStack(old_frame_pointer, stack_info)) {
+    // Check frame size.  In strict mode, we assume frames to be under
+    // 100,000 bytes.  In non-strict mode, we relax the limit to 1MB.
+    const size_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
+    const size_t frame_size =
+        ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
+    if (frame_size == kUnknownFrameSize)
+       return nullptr;
+    // A very large frame may mean corrupt memory or an erroneous frame
+    // pointer. But also maybe just a plain-old large frame.  Assume that if the
+    // frame is within a known stack, then it is valid.
+    if (frame_size > max_size) {
+      size_t stack_low = stack_info->stack_low;
+      size_t stack_high = stack_info->stack_high;
+      if (InsideSignalStack(new_frame_pointer, stack_info)) {
+        stack_low = stack_info->sig_stack_low;
+        stack_high = stack_info->sig_stack_high;
+      }
+      if (stack_high < kUnknownStackEnd &&
+          static_cast<size_t>(getpagesize()) < stack_low) {
+        const uintptr_t new_fp_u =
+            reinterpret_cast<uintptr_t>(new_frame_pointer);
+        // Stack bounds are known.
+        if (!(stack_low < new_fp_u && new_fp_u <= stack_high)) {
+          // new_frame_pointer is not within a known stack.
+          return nullptr;
+        }
+      } else {
+        // Stack bounds are unknown, prefer truncated stack to possible crash.
+        return nullptr;
+      }
+    }
+  }
+
+  return new_frame_pointer;
+}
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+// We count on the bottom frame being this one. See the comment
+// at prev_return_address
+ABSL_ATTRIBUTE_NOINLINE
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+#ifdef __GNUC__
+  void **frame_pointer = reinterpret_cast<void**>(__builtin_frame_address(0));
+#else
+# error reading stack point not yet supported on this platform.
+#endif
+  skip_count++;    // Skip the frame for this function.
+  int n = 0;
+
+  // Assume that the first page is not stack.
+  StackInfo stack_info;
+  stack_info.stack_low = static_cast<uintptr_t>(getpagesize());
+  stack_info.stack_high = kUnknownStackEnd;
+  stack_info.sig_stack_low = stack_info.stack_low;
+  stack_info.sig_stack_high = kUnknownStackEnd;
+
+  // The frame pointer points to low address of a frame.  The first 64-bit
+  // word of a frame points to the next frame up the call chain, which normally
+  // is just after the high address of the current frame.  The second word of
+  // a frame contains return address of to the caller.   To find a pc value
+  // associated with the current frame, we need to go down a level in the call
+  // chain.  So we remember return the address of the last frame seen.  This
+  // does not work for the first stack frame, which belongs to UnwindImp() but
+  // we skip the frame for UnwindImp() anyway.
+  void* prev_return_address = nullptr;
+  // The nth frame size is the difference between the nth frame pointer and the
+  // the frame pointer below it in the call chain. There is no frame below the
+  // leaf frame, but this function is the leaf anyway, and we skip it.
+  void** prev_frame_pointer = nullptr;
+
+   while (frame_pointer && n < max_depth) {
+    if (skip_count > 0) {
+      skip_count--;
+    } else {
+      result[n] = prev_return_address;
+      if (IS_STACK_FRAMES) {
+        sizes[n] = static_cast<int>(
+            ComputeStackFrameSize(prev_frame_pointer, frame_pointer));
+      }
+      n++;
+    }
+    prev_return_address = frame_pointer[1];
+    prev_frame_pointer = frame_pointer;
+    // The absl::GetStackFrames routine is called when we are in some
+    // informational context (the failure signal handler for example).
+    // Use the non-strict unwinding rules to produce a stack trace
+    // that is as complete as possible (even if it contains a few bogus
+    // entries in some rare cases).
+    frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
+        frame_pointer, ucp, &stack_info);
+  }
+
+  if (min_dropped_frames != nullptr) {
+    // Implementation detail: we clamp the max of frames we are willing to
+    // count, so as not to spend too much time in the loop below.
+    const int kMaxUnwind = 200;
+    int num_dropped_frames = 0;
+    for (int j = 0; frame_pointer != nullptr && j < kMaxUnwind; j++) {
+      if (skip_count > 0) {
+        skip_count--;
+      } else {
+        num_dropped_frames++;
+      }
+      frame_pointer = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
+          frame_pointer, ucp, &stack_info);
+    }
+    *min_dropped_frames = num_dropped_frames;
+  }
+  return n;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return true;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_AARCH64_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_arm-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_arm-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..102a2a1251aa980049b99ca553ad31f11e6a6f8d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_arm-inl.inc
@@ -0,0 +1,139 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// This is inspired by Craig Silverstein's PowerPC stacktrace code.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
+
+#include <cstdint>
+
+#include "absl/debugging/stacktrace.h"
+
+// WARNING:
+// This only works if all your code is in either ARM or THUMB mode.  With
+// interworking, the frame pointer of the caller can either be in r11 (ARM
+// mode) or r7 (THUMB mode).  A callee only saves the frame pointer of its
+// mode in a fixed location on its stack frame.  If the caller is a different
+// mode, there is no easy way to find the frame pointer.  It can either be
+// still in the designated register or saved on stack along with other callee
+// saved registers.
+
+// Given a pointer to a stack frame, locate and return the calling
+// stackframe, or return nullptr if no stackframe can be found. Perform sanity
+// checks (the strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template<bool STRICT_UNWINDING>
+static void **NextStackFrame(void **old_sp) {
+  void **new_sp = (void**) old_sp[-1];
+
+  // Check that the transition from frame pointer old_sp to frame
+  // pointer new_sp isn't clearly bogus
+  if (STRICT_UNWINDING) {
+    // With the stack growing downwards, older stack frame must be
+    // at a greater address that the current one.
+    if (new_sp <= old_sp) return nullptr;
+    // Assume stack frames larger than 100,000 bytes are bogus.
+    if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
+  } else {
+    // In the non-strict mode, allow discontiguous stack frames.
+    // (alternate-signal-stacks for example).
+    if (new_sp == old_sp) return nullptr;
+    // And allow frames upto about 1MB.
+    if ((new_sp > old_sp)
+        && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
+  }
+  if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return nullptr;
+  return new_sp;
+}
+
+// This ensures that absl::GetStackTrace sets up the Link Register properly.
+#ifdef __GNUC__
+void StacktraceArmDummyFunction() __attribute__((noinline));
+void StacktraceArmDummyFunction() { __asm__ volatile(""); }
+#else
+# error StacktraceArmDummyFunction() needs to be ported to this platform.
+#endif
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+                      const void * /* ucp */, int *min_dropped_frames) {
+#ifdef __GNUC__
+  void **sp = reinterpret_cast<void**>(__builtin_frame_address(0));
+#else
+# error reading stack point not yet supported on this platform.
+#endif
+
+  // On ARM, the return address is stored in the link register (r14).
+  // This is not saved on the stack frame of a leaf function.  To
+  // simplify code that reads return addresses, we call a dummy
+  // function so that the return address of this function is also
+  // stored in the stack frame.  This works at least for gcc.
+  StacktraceArmDummyFunction();
+
+  int n = 0;
+  while (sp && n < max_depth) {
+    // The absl::GetStackFrames routine is called when we are in some
+    // informational context (the failure signal handler for example).
+    // Use the non-strict unwinding rules to produce a stack trace
+    // that is as complete as possible (even if it contains a few bogus
+    // entries in some rare cases).
+    void **next_sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
+
+    if (skip_count > 0) {
+      skip_count--;
+    } else {
+      result[n] = *sp;
+
+      if (IS_STACK_FRAMES) {
+        if (next_sp > sp) {
+          sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
+        } else {
+          // A frame-size of 0 is used to indicate unknown frame size.
+          sizes[n] = 0;
+        }
+      }
+      n++;
+    }
+    sp = next_sp;
+  }
+  if (min_dropped_frames != nullptr) {
+    // Implementation detail: we clamp the max of frames we are willing to
+    // count, so as not to spend too much time in the loop below.
+    const int kMaxUnwind = 200;
+    int num_dropped_frames = 0;
+    for (int j = 0; sp != nullptr && j < kMaxUnwind; j++) {
+      if (skip_count > 0) {
+        skip_count--;
+      } else {
+        num_dropped_frames++;
+      }
+      sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
+    }
+    *min_dropped_frames = num_dropped_frames;
+  }
+  return n;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return false;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_ARM_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_config.h b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_config.h
new file mode 100644
index 0000000000000000000000000000000000000000..3929b1b734992a65eee9a727c94f826fc3c8eb79
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_config.h
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2017 The Abseil Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+
+ * Defines ABSL_STACKTRACE_INL_HEADER to the *-inl.h containing
+ * actual unwinder implementation.
+ * This header is "private" to stacktrace.cc.
+ * DO NOT include it into any other files.
+*/
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_CONFIG_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_CONFIG_H_
+
+#include "absl/base/config.h"
+
+#if defined(ABSL_STACKTRACE_INL_HEADER)
+#error ABSL_STACKTRACE_INL_HEADER cannot be directly set
+
+#elif defined(_WIN32)
+#define ABSL_STACKTRACE_INL_HEADER \
+    "absl/debugging/internal/stacktrace_win32-inl.inc"
+
+#elif defined(__APPLE__)
+#ifdef ABSL_HAVE_THREAD_LOCAL
+// Thread local support required for UnwindImpl.
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_generic-inl.inc"
+#endif  // defined(ABSL_HAVE_THREAD_LOCAL)
+
+// Emscripten stacktraces rely on JS. Do not use them in standalone mode.
+#elif defined(__EMSCRIPTEN__) && !defined(STANDALONE_WASM)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_emscripten-inl.inc"
+
+#elif defined(__linux__) && !defined(__ANDROID__)
+
+#if defined(NO_FRAME_POINTER) && \
+    (defined(__i386__) || defined(__x86_64__) || defined(__aarch64__))
+// Note: The libunwind-based implementation is not available to open-source
+// users.
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_libunwind-inl.inc"
+#define STACKTRACE_USES_LIBUNWIND 1
+#elif defined(NO_FRAME_POINTER) && defined(__has_include)
+#if __has_include(<execinfo.h>)
+// Note: When using glibc this may require -funwind-tables to function properly.
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_generic-inl.inc"
+#endif  // __has_include(<execinfo.h>)
+#elif defined(__i386__) || defined(__x86_64__)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_x86-inl.inc"
+#elif defined(__ppc__) || defined(__PPC__)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_powerpc-inl.inc"
+#elif defined(__aarch64__)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_aarch64-inl.inc"
+#elif defined(__riscv)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_riscv-inl.inc"
+#elif defined(__has_include)
+#if __has_include(<execinfo.h>)
+// Note: When using glibc this may require -funwind-tables to function properly.
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_generic-inl.inc"
+#endif  // __has_include(<execinfo.h>)
+#endif  // defined(__has_include)
+
+#endif  // defined(__linux__) && !defined(__ANDROID__)
+
+// Fallback to the empty implementation.
+#if !defined(ABSL_STACKTRACE_INL_HEADER)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_unimplemented-inl.inc"
+#endif
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_CONFIG_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..0f44451438624e6db2176aaecce42514aa09617d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc
@@ -0,0 +1,110 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Portable implementation - just use glibc
+//
+// Note:  The glibc implementation may cause a call to malloc.
+// This can cause a deadlock in HeapProfiler.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
+
+#include <emscripten.h>
+
+#include <atomic>
+#include <cstring>
+
+#include "absl/base/attributes.h"
+#include "absl/debugging/stacktrace.h"
+
+extern "C" {
+uintptr_t emscripten_stack_snapshot();
+uint32_t emscripten_stack_unwind_buffer(uintptr_t pc, void *buffer,
+                                        uint32_t depth);
+}
+
+// Sometimes, we can try to get a stack trace from within a stack
+// trace, which can cause a self-deadlock.
+// Protect against such reentrant call by failing to get a stack trace.
+//
+// We use __thread here because the code here is extremely low level -- it is
+// called while collecting stack traces from within malloc and mmap, and thus
+// can not call anything which might call malloc or mmap itself.
+static __thread int recursive = 0;
+
+// The stack trace function might be invoked very early in the program's
+// execution (e.g. from the very first malloc).
+// As such, we suppress usage of backtrace during this early stage of execution.
+static std::atomic<bool> disable_stacktraces(true);  // Disabled until healthy.
+// Waiting until static initializers run seems to be late enough.
+// This file is included into stacktrace.cc so this will only run once.
+ABSL_ATTRIBUTE_UNUSED static int stacktraces_enabler = []() {
+  // Check if we can even create stacktraces. If not, bail early and leave
+  // disable_stacktraces set as-is.
+  // clang-format off
+  if (!EM_ASM_INT({ return (typeof wasmOffsetConverter !== 'undefined'); })) {
+    return 0;
+  }
+  // clang-format on
+  disable_stacktraces.store(false, std::memory_order_relaxed);
+  return 0;
+}();
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+  if (recursive || disable_stacktraces.load(std::memory_order_relaxed)) {
+    return 0;
+  }
+  ++recursive;
+
+  static_cast<void>(ucp);  // Unused.
+  constexpr int kStackLength = 64;
+  void *stack[kStackLength];
+
+  int size;
+  uintptr_t pc = emscripten_stack_snapshot();
+  size = emscripten_stack_unwind_buffer(pc, stack, kStackLength);
+
+  int result_count = size - skip_count;
+  if (result_count < 0) result_count = 0;
+  if (result_count > max_depth) result_count = max_depth;
+  for (int i = 0; i < result_count; i++) result[i] = stack[i + skip_count];
+
+  if (IS_STACK_FRAMES) {
+    // No implementation for finding out the stack frame sizes yet.
+    memset(sizes, 0, sizeof(*sizes) * result_count);
+  }
+  if (min_dropped_frames != nullptr) {
+    if (size - skip_count - max_depth > 0) {
+      *min_dropped_frames = size - skip_count - max_depth;
+    } else {
+      *min_dropped_frames = 0;
+    }
+  }
+
+  --recursive;
+
+  return result_count;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() { return true; }
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_generic-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_generic-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..5fa169a7ec88dfdd820c4646867b37b6fbafd33f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_generic-inl.inc
@@ -0,0 +1,108 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Portable implementation - just use glibc
+//
+// Note:  The glibc implementation may cause a call to malloc.
+// This can cause a deadlock in HeapProfiler.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
+
+#include <execinfo.h>
+#include <atomic>
+#include <cstring>
+
+#include "absl/debugging/stacktrace.h"
+#include "absl/base/attributes.h"
+
+// Sometimes, we can try to get a stack trace from within a stack
+// trace, because we don't block signals inside this code (which would be too
+// expensive: the two extra system calls per stack trace do matter here).
+// That can cause a self-deadlock.
+// Protect against such reentrant call by failing to get a stack trace.
+//
+// We use __thread here because the code here is extremely low level -- it is
+// called while collecting stack traces from within malloc and mmap, and thus
+// can not call anything which might call malloc or mmap itself.
+static __thread int recursive = 0;
+
+// The stack trace function might be invoked very early in the program's
+// execution (e.g. from the very first malloc if using tcmalloc). Also, the
+// glibc implementation itself will trigger malloc the first time it is called.
+// As such, we suppress usage of backtrace during this early stage of execution.
+static std::atomic<bool> disable_stacktraces(true);  // Disabled until healthy.
+// Waiting until static initializers run seems to be late enough.
+// This file is included into stacktrace.cc so this will only run once.
+ABSL_ATTRIBUTE_UNUSED static int stacktraces_enabler = []() {
+  void* unused_stack[1];
+  // Force the first backtrace to happen early to get the one-time shared lib
+  // loading (allocation) out of the way. After the first call it is much safer
+  // to use backtrace from a signal handler if we crash somewhere later.
+  backtrace(unused_stack, 1);
+  disable_stacktraces.store(false, std::memory_order_relaxed);
+  return 0;
+}();
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+  if (recursive || disable_stacktraces.load(std::memory_order_relaxed)) {
+    return 0;
+  }
+  ++recursive;
+
+  static_cast<void>(ucp);  // Unused.
+  static const int kStackLength = 64;
+  void * stack[kStackLength];
+  int size;
+
+  size = backtrace(stack, kStackLength);
+  skip_count++;  // we want to skip the current frame as well
+  int result_count = size - skip_count;
+  if (result_count < 0)
+    result_count = 0;
+  if (result_count > max_depth)
+    result_count = max_depth;
+  for (int i = 0; i < result_count; i++)
+    result[i] = stack[i + skip_count];
+
+  if (IS_STACK_FRAMES) {
+    // No implementation for finding out the stack frame sizes yet.
+    memset(sizes, 0, sizeof(*sizes) * static_cast<size_t>(result_count));
+  }
+  if (min_dropped_frames != nullptr) {
+    if (size - skip_count - max_depth > 0) {
+      *min_dropped_frames = size - skip_count - max_depth;
+    } else {
+      *min_dropped_frames = 0;
+    }
+  }
+
+  --recursive;
+
+  return result_count;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return true;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_powerpc-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_powerpc-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..a49ed2f7f25db0337594707fc7c18a996b9d3b47
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_powerpc-inl.inc
@@ -0,0 +1,258 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Produce stack trace.  I'm guessing (hoping!) the code is much like
+// for x86.  For apple machines, at least, it seems to be; see
+//    https://developer.apple.com/documentation/mac/runtimehtml/RTArch-59.html
+//    https://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
+// Linux has similar code: http://patchwork.ozlabs.org/linuxppc/patch?id=8882
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
+
+#if defined(__linux__)
+#include <asm/ptrace.h>   // for PT_NIP.
+#include <ucontext.h>     // for ucontext_t
+#endif
+
+#include <unistd.h>
+#include <cassert>
+#include <cstdint>
+#include <cstdio>
+
+#include "absl/base/attributes.h"
+#include "absl/base/optimization.h"
+#include "absl/base/port.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/internal/address_is_readable.h"
+#include "absl/debugging/internal/vdso_support.h"  // a no-op on non-elf or non-glibc systems
+
+// Given a stack pointer, return the saved link register value.
+// Note that this is the link register for a callee.
+static inline void *StacktracePowerPCGetLR(void **sp) {
+  // PowerPC has 3 main ABIs, which say where in the stack the
+  // Link Register is.  For DARWIN and AIX (used by apple and
+  // linux ppc64), it's in sp[2].  For SYSV (used by linux ppc),
+  // it's in sp[1].
+#if defined(_CALL_AIX) || defined(_CALL_DARWIN)
+  return *(sp+2);
+#elif defined(_CALL_SYSV)
+  return *(sp+1);
+#elif defined(__APPLE__) || defined(__FreeBSD__) || \
+    (defined(__linux__) && defined(__PPC64__))
+  // This check is in case the compiler doesn't define _CALL_AIX/etc.
+  return *(sp+2);
+#elif defined(__linux)
+  // This check is in case the compiler doesn't define _CALL_SYSV.
+  return *(sp+1);
+#else
+#error Need to specify the PPC ABI for your architecture.
+#endif
+}
+
+// Given a pointer to a stack frame, locate and return the calling
+// stackframe, or return null if no stackframe can be found. Perform sanity
+// checks (the strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template<bool STRICT_UNWINDING, bool IS_WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+static void **NextStackFrame(void **old_sp, const void *uc) {
+  void **new_sp = (void **) *old_sp;
+  enum { kStackAlignment = 16 };
+
+  // Check that the transition from frame pointer old_sp to frame
+  // pointer new_sp isn't clearly bogus
+  if (STRICT_UNWINDING) {
+    // With the stack growing downwards, older stack frame must be
+    // at a greater address that the current one.
+    if (new_sp <= old_sp) return nullptr;
+    // Assume stack frames larger than 100,000 bytes are bogus.
+    if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return nullptr;
+  } else {
+    // In the non-strict mode, allow discontiguous stack frames.
+    // (alternate-signal-stacks for example).
+    if (new_sp == old_sp) return nullptr;
+    // And allow frames upto about 1MB.
+    if ((new_sp > old_sp)
+        && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return nullptr;
+  }
+  if ((uintptr_t)new_sp % kStackAlignment != 0) return nullptr;
+
+#if defined(__linux__)
+  enum StackTraceKernelSymbolStatus {
+      kNotInitialized = 0, kAddressValid, kAddressInvalid };
+
+  if (IS_WITH_CONTEXT && uc != nullptr) {
+    static StackTraceKernelSymbolStatus kernel_symbol_status =
+        kNotInitialized;  // Sentinel: not computed yet.
+    // Initialize with sentinel value: __kernel_rt_sigtramp_rt64 can not
+    // possibly be there.
+    static const unsigned char *kernel_sigtramp_rt64_address = nullptr;
+    if (kernel_symbol_status == kNotInitialized) {
+      absl::debugging_internal::VDSOSupport vdso;
+      if (vdso.IsPresent()) {
+        absl::debugging_internal::VDSOSupport::SymbolInfo
+            sigtramp_rt64_symbol_info;
+        if (!vdso.LookupSymbol(
+                "__kernel_sigtramp_rt64", "LINUX_2.6.15",
+                absl::debugging_internal::VDSOSupport::kVDSOSymbolType,
+                &sigtramp_rt64_symbol_info) ||
+            sigtramp_rt64_symbol_info.address == nullptr) {
+          // Unexpected: VDSO is present, yet the expected symbol is missing
+          // or null.
+          assert(false && "VDSO is present, but doesn't have expected symbol");
+          kernel_symbol_status = kAddressInvalid;
+        } else {
+          kernel_sigtramp_rt64_address =
+              reinterpret_cast<const unsigned char *>(
+                  sigtramp_rt64_symbol_info.address);
+          kernel_symbol_status = kAddressValid;
+        }
+      } else {
+        kernel_symbol_status = kAddressInvalid;
+      }
+    }
+
+    if (new_sp != nullptr &&
+        kernel_symbol_status == kAddressValid &&
+        StacktracePowerPCGetLR(new_sp) == kernel_sigtramp_rt64_address) {
+      const ucontext_t* signal_context =
+          reinterpret_cast<const ucontext_t*>(uc);
+      void **const sp_before_signal =
+#if defined(__PPC64__)
+          reinterpret_cast<void **>(signal_context->uc_mcontext.gp_regs[PT_R1]);
+#else
+          reinterpret_cast<void **>(
+              signal_context->uc_mcontext.uc_regs->gregs[PT_R1]);
+#endif
+      // Check that alleged sp before signal is nonnull and is reasonably
+      // aligned.
+      if (sp_before_signal != nullptr &&
+          ((uintptr_t)sp_before_signal % kStackAlignment) == 0) {
+        // Check that alleged stack pointer is actually readable. This is to
+        // prevent a "double fault" in case we hit the first fault due to e.g.
+        // a stack corruption.
+        if (absl::debugging_internal::AddressIsReadable(sp_before_signal)) {
+          // Alleged stack pointer is readable, use it for further unwinding.
+          new_sp = sp_before_signal;
+        }
+      }
+    }
+  }
+#endif
+
+  return new_sp;
+}
+
+// This ensures that absl::GetStackTrace sets up the Link Register properly.
+ABSL_ATTRIBUTE_NOINLINE static void AbslStacktracePowerPCDummyFunction() {
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+  void **sp;
+  // Apple macOS uses an old version of gnu as -- both Darwin 7.9.0 (Panther)
+  // and Darwin 8.8.1 (Tiger) use as 1.38.  This means we have to use a
+  // different asm syntax.  I don't know quite the best way to discriminate
+  // systems using the old as from the new one; I've gone with __APPLE__.
+#ifdef __APPLE__
+  __asm__ volatile ("mr %0,r1" : "=r" (sp));
+#else
+  __asm__ volatile ("mr %0,1" : "=r" (sp));
+#endif
+
+  // On PowerPC, the "Link Register" or "Link Record" (LR), is a stack
+  // entry that holds the return address of the subroutine call (what
+  // instruction we run after our function finishes).  This is the
+  // same as the stack-pointer of our parent routine, which is what we
+  // want here.  While the compiler will always(?) set up LR for
+  // subroutine calls, it may not for leaf functions (such as this one).
+  // This routine forces the compiler (at least gcc) to push it anyway.
+  AbslStacktracePowerPCDummyFunction();
+
+  // The LR save area is used by the callee, so the top entry is bogus.
+  skip_count++;
+
+  int n = 0;
+
+  // Unlike ABIs of X86 and ARM, PowerPC ABIs say that return address (in
+  // the link register) of a function call is stored in the caller's stack
+  // frame instead of the callee's.  When we look for the return address
+  // associated with a stack frame, we need to make sure that there is a
+  // caller frame before it.  So we call NextStackFrame before entering the
+  // loop below and check next_sp instead of sp for loop termination.
+  // The outermost frame is set up by runtimes and it does not have a
+  // caller frame, so it is skipped.
+
+  // The absl::GetStackFrames routine is called when we are in some
+  // informational context (the failure signal handler for example).
+  // Use the non-strict unwinding rules to produce a stack trace
+  // that is as complete as possible (even if it contains a few
+  // bogus entries in some rare cases).
+  void **next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
+
+  while (next_sp && n < max_depth) {
+    if (skip_count > 0) {
+      skip_count--;
+    } else {
+      result[n] = StacktracePowerPCGetLR(sp);
+      if (IS_STACK_FRAMES) {
+        if (next_sp > sp) {
+          sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
+        } else {
+          // A frame-size of 0 is used to indicate unknown frame size.
+          sizes[n] = 0;
+        }
+      }
+      n++;
+    }
+
+    sp = next_sp;
+    next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(sp, ucp);
+  }
+
+  if (min_dropped_frames != nullptr) {
+    // Implementation detail: we clamp the max of frames we are willing to
+    // count, so as not to spend too much time in the loop below.
+    const int kMaxUnwind = 1000;
+    int num_dropped_frames = 0;
+    for (int j = 0; next_sp != nullptr && j < kMaxUnwind; j++) {
+      if (skip_count > 0) {
+        skip_count--;
+      } else {
+        num_dropped_frames++;
+      }
+      next_sp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(next_sp, ucp);
+    }
+    *min_dropped_frames = num_dropped_frames;
+  }
+  return n;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return true;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_POWERPC_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_riscv-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_riscv-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..20183fa3213b01c9c9d8242d92fe74846c7c5ef6
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_riscv-inl.inc
@@ -0,0 +1,191 @@
+// Copyright 2021 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_RISCV_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_RISCV_INL_H_
+
+// Generate stack trace for riscv
+
+#include <sys/ucontext.h>
+
+#include "absl/base/config.h"
+#if defined(__linux__)
+#include <sys/mman.h>
+#include <ucontext.h>
+#include <unistd.h>
+#endif
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <iostream>
+#include <limits>
+#include <utility>
+
+#include "absl/base/attributes.h"
+#include "absl/debugging/stacktrace.h"
+
+static const uintptr_t kUnknownFrameSize = 0;
+
+// Compute the size of a stack frame in [low..high).  We assume that low < high.
+// Return size of kUnknownFrameSize.
+template <typename T>
+static inline uintptr_t ComputeStackFrameSize(const T *low, const T *high) {
+  const char *low_char_ptr = reinterpret_cast<const char *>(low);
+  const char *high_char_ptr = reinterpret_cast<const char *>(high);
+  return low < high ? high_char_ptr - low_char_ptr : kUnknownFrameSize;
+}
+
+// Given a pointer to a stack frame, locate and return the calling stackframe,
+// or return null if no stackframe can be found. Perform sanity checks (the
+// strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template <bool STRICT_UNWINDING, bool WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+static void ** NextStackFrame(void **old_frame_pointer, const void *uc,
+                              const std::pair<size_t, size_t> range) {
+  //               .
+  //               .
+  //               .
+  //   +-> +----------------+
+  //   |   | return address |
+  //   |   |   previous fp  |
+  //   |   |      ...       |
+  //   |   +----------------+ <-+
+  //   |   | return address |   |
+  //   +---|-  previous fp  |   |
+  //       |      ...       |   |
+  // $fp ->|----------------+   |
+  //       | return address |   |
+  //       |   previous fp -|---+
+  // $sp ->|      ...       |
+  //       +----------------+
+  void **new_frame_pointer = reinterpret_cast<void **>(old_frame_pointer[-2]);
+  uintptr_t frame_pointer = reinterpret_cast<uintptr_t>(new_frame_pointer);
+
+  // The RISCV ELF psABI mandates that the stack pointer is always 16-byte
+  // aligned.
+  // TODO(#1236) this doesn't hold for ILP32E which only mandates a 4-byte
+  // alignment.
+  if (frame_pointer & 15)
+    return nullptr;
+
+  // If the new frame pointer matches the signal context, avoid terminating
+  // early to deal with alternate signal stacks.
+  if (WITH_CONTEXT)
+    if (const ucontext_t *ucv = static_cast<const ucontext_t *>(uc))
+      // RISCV ELF psABI has the frame pointer at x8/fp/s0.
+      // -- RISCV psABI Table 18.2
+      if (ucv->uc_mcontext.__gregs[8] == frame_pointer)
+        return new_frame_pointer;
+
+  // Check frame size.  In strict mode, we assume frames to be under 100,000
+  // bytes.  In non-strict mode, we relax the limit to 1MB.
+  const uintptr_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
+  const uintptr_t frame_size =
+      ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
+  if (frame_size == kUnknownFrameSize) {
+    if (STRICT_UNWINDING)
+      return nullptr;
+
+    // In non-strict mode permit non-contiguous stacks (e.g. alternate signal
+    // frame handling).
+    if (reinterpret_cast<uintptr_t>(new_frame_pointer) < range.first ||
+        reinterpret_cast<uintptr_t>(new_frame_pointer) > range.second)
+      return nullptr;
+  }
+
+  if (frame_size > max_size)
+    return nullptr;
+
+  return new_frame_pointer;
+}
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+  // The `frame_pointer` that is computed here points to the top of the frame.
+  // The two words preceding the address are the return address and the previous
+  // frame pointer.
+#if defined(__GNUC__)
+  void **frame_pointer = reinterpret_cast<void **>(__builtin_frame_address(0));
+#else
+#error reading stack pointer not yet supported on this platform
+#endif
+
+  std::pair<size_t, size_t> stack = {
+      // assume that the first page is not the stack.
+      static_cast<size_t>(sysconf(_SC_PAGESIZE)),
+      std::numeric_limits<size_t>::max() - sizeof(void *)
+  };
+
+  int n = 0;
+  void *return_address = nullptr;
+  while (frame_pointer && n < max_depth) {
+    return_address = frame_pointer[-1];
+
+    // The absl::GetStackFrames routine is called when we are in some
+    // informational context (the failure signal handler for example).  Use the
+    // non-strict unwinding rules to produce a stack trace that is as complete
+    // as possible (even if it contains a few bogus entries in some rare cases).
+    void **next_frame_pointer =
+        NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp,
+                                                          stack);
+
+    if (skip_count > 0) {
+      skip_count--;
+    } else {
+      result[n] = return_address;
+      if (IS_STACK_FRAMES) {
+        sizes[n] = ComputeStackFrameSize(frame_pointer, next_frame_pointer);
+      }
+      n++;
+    }
+
+    frame_pointer = next_frame_pointer;
+  }
+
+  if (min_dropped_frames != nullptr) {
+    // Implementation detail: we clamp the max of frames we are willing to
+    // count, so as not to spend too much time in the loop below.
+    const int kMaxUnwind = 200;
+    int num_dropped_frames = 0;
+    for (int j = 0; frame_pointer != nullptr && j < kMaxUnwind; j++) {
+      if (skip_count > 0) {
+        skip_count--;
+      } else {
+        num_dropped_frames++;
+      }
+      frame_pointer =
+          NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(frame_pointer, ucp,
+                                                            stack);
+    }
+    *min_dropped_frames = num_dropped_frames;
+  }
+
+  return n;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() { return true; }
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_unimplemented-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_unimplemented-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..5b8fb191b65a33000b1c1d2ce53907b4d6e2f2b1
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_unimplemented-inl.inc
@@ -0,0 +1,24 @@
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void** /* result */, int* /* sizes */,
+                      int /* max_depth */, int /* skip_count */,
+                      const void* /* ucp */, int *min_dropped_frames) {
+  if (min_dropped_frames != nullptr) {
+    *min_dropped_frames = 0;
+  }
+  return 0;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return false;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_UNIMPLEMENTED_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_win32-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_win32-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..ef2b973ec3e3dad0cce7b893e98867b5dabd023d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_win32-inl.inc
@@ -0,0 +1,94 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Produces a stack trace for Windows.  Normally, one could use
+// stacktrace_x86-inl.h or stacktrace_x86_64-inl.h -- and indeed, that
+// should work for binaries compiled using MSVC in "debug" mode.
+// However, in "release" mode, Windows uses frame-pointer
+// optimization, which makes getting a stack trace very difficult.
+//
+// There are several approaches one can take.  One is to use Windows
+// intrinsics like StackWalk64.  These can work, but have restrictions
+// on how successful they can be.  Another attempt is to write a
+// version of stacktrace_x86-inl.h that has heuristic support for
+// dealing with FPO, similar to what WinDbg does (see
+// http://www.nynaeve.net/?p=97).  There are (non-working) examples of
+// these approaches, complete with TODOs, in stacktrace_win32-inl.h#1
+//
+// The solution we've ended up doing is to call the undocumented
+// windows function RtlCaptureStackBackTrace, which probably doesn't
+// work with FPO but at least is fast, and doesn't require a symbol
+// server.
+//
+// This code is inspired by a patch from David Vitek:
+//   https://code.google.com/p/google-perftools/issues/detail?id=83
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_
+
+#include <windows.h>    // for GetProcAddress and GetModuleHandle
+#include <cassert>
+
+typedef USHORT NTAPI RtlCaptureStackBackTrace_Function(
+    IN ULONG frames_to_skip,
+    IN ULONG frames_to_capture,
+    OUT PVOID *backtrace,
+    OUT PULONG backtrace_hash);
+
+// It is not possible to load RtlCaptureStackBackTrace at static init time in
+// UWP. CaptureStackBackTrace is the public version of RtlCaptureStackBackTrace
+#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP) && \
+    !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn =
+    &::CaptureStackBackTrace;
+#else
+// Load the function we need at static init time, where we don't have
+// to worry about someone else holding the loader's lock.
+static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn =
+    (RtlCaptureStackBackTrace_Function*)GetProcAddress(
+        GetModuleHandleA("ntdll.dll"), "RtlCaptureStackBackTrace");
+#endif  // WINAPI_PARTITION_APP && !WINAPI_PARTITION_DESKTOP
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
+                      const void*, int* min_dropped_frames) {
+  USHORT n = 0;
+  if (!RtlCaptureStackBackTrace_fn || skip_count < 0 || max_depth < 0) {
+    // can't get a stacktrace with no function/invalid args
+  } else {
+    n = RtlCaptureStackBackTrace_fn(static_cast<ULONG>(skip_count) + 2,
+                                    static_cast<ULONG>(max_depth), result, 0);
+  }
+  if (IS_STACK_FRAMES) {
+    // No implementation for finding out the stack frame sizes yet.
+    memset(sizes, 0, sizeof(*sizes) * n);
+  }
+  if (min_dropped_frames != nullptr) {
+    // Not implemented.
+    *min_dropped_frames = 0;
+  }
+  return n;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return false;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_x86-inl.inc b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_x86-inl.inc
new file mode 100644
index 0000000000000000000000000000000000000000..1975ba74434387d3bba3a8ce4a800271f4606822
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/stacktrace_x86-inl.inc
@@ -0,0 +1,394 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Produce stack trace
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_
+
+#if defined(__linux__) && (defined(__i386__) || defined(__x86_64__))
+#include <ucontext.h>  // for ucontext_t
+#endif
+
+#if !defined(_WIN32)
+#include <unistd.h>
+#endif
+
+#include <cassert>
+#include <cstdint>
+#include <limits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+#include "absl/debugging/internal/address_is_readable.h"
+#include "absl/debugging/internal/vdso_support.h"  // a no-op on non-elf or non-glibc systems
+#include "absl/debugging/stacktrace.h"
+
+using absl::debugging_internal::AddressIsReadable;
+
+#if defined(__linux__) && defined(__i386__)
+// Count "push %reg" instructions in VDSO __kernel_vsyscall(),
+// preceding "syscall" or "sysenter".
+// If __kernel_vsyscall uses frame pointer, answer 0.
+//
+// kMaxBytes tells how many instruction bytes of __kernel_vsyscall
+// to analyze before giving up. Up to kMaxBytes+1 bytes of
+// instructions could be accessed.
+//
+// Here are known __kernel_vsyscall instruction sequences:
+//
+// SYSENTER (linux-2.6.26/arch/x86/vdso/vdso32/sysenter.S).
+// Used on Intel.
+//  0xffffe400 <__kernel_vsyscall+0>:       push   %ecx
+//  0xffffe401 <__kernel_vsyscall+1>:       push   %edx
+//  0xffffe402 <__kernel_vsyscall+2>:       push   %ebp
+//  0xffffe403 <__kernel_vsyscall+3>:       mov    %esp,%ebp
+//  0xffffe405 <__kernel_vsyscall+5>:       sysenter
+//
+// SYSCALL (see linux-2.6.26/arch/x86/vdso/vdso32/syscall.S).
+// Used on AMD.
+//  0xffffe400 <__kernel_vsyscall+0>:       push   %ebp
+//  0xffffe401 <__kernel_vsyscall+1>:       mov    %ecx,%ebp
+//  0xffffe403 <__kernel_vsyscall+3>:       syscall
+//
+
+// The sequence below isn't actually expected in Google fleet,
+// here only for completeness. Remove this comment from OSS release.
+
+// i386 (see linux-2.6.26/arch/x86/vdso/vdso32/int80.S)
+//  0xffffe400 <__kernel_vsyscall+0>:       int $0x80
+//  0xffffe401 <__kernel_vsyscall+1>:       ret
+//
+static const int kMaxBytes = 10;
+
+// We use assert()s instead of DCHECK()s -- this is too low level
+// for DCHECK().
+
+static int CountPushInstructions(const unsigned char *const addr) {
+  int result = 0;
+  for (int i = 0; i < kMaxBytes; ++i) {
+    if (addr[i] == 0x89) {
+      // "mov reg,reg"
+      if (addr[i + 1] == 0xE5) {
+        // Found "mov %esp,%ebp".
+        return 0;
+      }
+      ++i;  // Skip register encoding byte.
+    } else if (addr[i] == 0x0F &&
+               (addr[i + 1] == 0x34 || addr[i + 1] == 0x05)) {
+      // Found "sysenter" or "syscall".
+      return result;
+    } else if ((addr[i] & 0xF0) == 0x50) {
+      // Found "push %reg".
+      ++result;
+    } else if (addr[i] == 0xCD && addr[i + 1] == 0x80) {
+      // Found "int $0x80"
+      assert(result == 0);
+      return 0;
+    } else {
+      // Unexpected instruction.
+      assert(false && "unexpected instruction in __kernel_vsyscall");
+      return 0;
+    }
+  }
+  // Unexpected: didn't find SYSENTER or SYSCALL in
+  // [__kernel_vsyscall, __kernel_vsyscall + kMaxBytes) interval.
+  assert(false && "did not find SYSENTER or SYSCALL in __kernel_vsyscall");
+  return 0;
+}
+#endif
+
+// Assume stack frames larger than 100,000 bytes are bogus.
+static const int kMaxFrameBytes = 100000;
+// Stack end to use when we don't know the actual stack end
+// (effectively just the end of address space).
+constexpr uintptr_t kUnknownStackEnd =
+    std::numeric_limits<size_t>::max() - sizeof(void *);
+
+// Returns the stack frame pointer from signal context, 0 if unknown.
+// vuc is a ucontext_t *.  We use void* to avoid the use
+// of ucontext_t on non-POSIX systems.
+static uintptr_t GetFP(const void *vuc) {
+#if !defined(__linux__)
+  static_cast<void>(vuc);  // Avoid an unused argument compiler warning.
+#else
+  if (vuc != nullptr) {
+    auto *uc = reinterpret_cast<const ucontext_t *>(vuc);
+#if defined(__i386__)
+    const auto bp = uc->uc_mcontext.gregs[REG_EBP];
+    const auto sp = uc->uc_mcontext.gregs[REG_ESP];
+#elif defined(__x86_64__)
+    const auto bp = uc->uc_mcontext.gregs[REG_RBP];
+    const auto sp = uc->uc_mcontext.gregs[REG_RSP];
+#else
+    const uintptr_t bp = 0;
+    const uintptr_t sp = 0;
+#endif
+    // Sanity-check that the base pointer is valid. It's possible that some
+    // code in the process is compiled with --copt=-fomit-frame-pointer or
+    // --copt=-momit-leaf-frame-pointer.
+    //
+    // TODO(bcmills): -momit-leaf-frame-pointer is currently the default
+    // behavior when building with clang.  Talk to the C++ toolchain team about
+    // fixing that.
+    if (bp >= sp && bp - sp <= kMaxFrameBytes)
+      return static_cast<uintptr_t>(bp);
+
+    // If bp isn't a plausible frame pointer, return the stack pointer instead.
+    // If we're lucky, it points to the start of a stack frame; otherwise, we'll
+    // get one frame of garbage in the stack trace and fail the sanity check on
+    // the next iteration.
+    return static_cast<uintptr_t>(sp);
+  }
+#endif
+  return 0;
+}
+
+// Given a pointer to a stack frame, locate and return the calling
+// stackframe, or return null if no stackframe can be found. Perform sanity
+// checks (the strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template <bool STRICT_UNWINDING, bool WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+static void **NextStackFrame(void **old_fp, const void *uc,
+                             size_t stack_low, size_t stack_high) {
+  void **new_fp = (void **)*old_fp;
+
+#if defined(__linux__) && defined(__i386__)
+  if (WITH_CONTEXT && uc != nullptr) {
+    // How many "push %reg" instructions are there at __kernel_vsyscall?
+    // This is constant for a given kernel and processor, so compute
+    // it only once.
+    static int num_push_instructions = -1;  // Sentinel: not computed yet.
+    // Initialize with sentinel value: __kernel_rt_sigreturn can not possibly
+    // be there.
+    static const unsigned char *kernel_rt_sigreturn_address = nullptr;
+    static const unsigned char *kernel_vsyscall_address = nullptr;
+    if (num_push_instructions == -1) {
+#ifdef ABSL_HAVE_VDSO_SUPPORT
+      absl::debugging_internal::VDSOSupport vdso;
+      if (vdso.IsPresent()) {
+        absl::debugging_internal::VDSOSupport::SymbolInfo
+            rt_sigreturn_symbol_info;
+        absl::debugging_internal::VDSOSupport::SymbolInfo vsyscall_symbol_info;
+        if (!vdso.LookupSymbol("__kernel_rt_sigreturn", "LINUX_2.5", STT_FUNC,
+                               &rt_sigreturn_symbol_info) ||
+            !vdso.LookupSymbol("__kernel_vsyscall", "LINUX_2.5", STT_FUNC,
+                               &vsyscall_symbol_info) ||
+            rt_sigreturn_symbol_info.address == nullptr ||
+            vsyscall_symbol_info.address == nullptr) {
+          // Unexpected: 32-bit VDSO is present, yet one of the expected
+          // symbols is missing or null.
+          assert(false && "VDSO is present, but doesn't have expected symbols");
+          num_push_instructions = 0;
+        } else {
+          kernel_rt_sigreturn_address =
+              reinterpret_cast<const unsigned char *>(
+                  rt_sigreturn_symbol_info.address);
+          kernel_vsyscall_address =
+              reinterpret_cast<const unsigned char *>(
+                  vsyscall_symbol_info.address);
+          num_push_instructions =
+              CountPushInstructions(kernel_vsyscall_address);
+        }
+      } else {
+        num_push_instructions = 0;
+      }
+#else  // ABSL_HAVE_VDSO_SUPPORT
+      num_push_instructions = 0;
+#endif  // ABSL_HAVE_VDSO_SUPPORT
+    }
+    if (num_push_instructions != 0 && kernel_rt_sigreturn_address != nullptr &&
+        old_fp[1] == kernel_rt_sigreturn_address) {
+      const ucontext_t *ucv = static_cast<const ucontext_t *>(uc);
+      // This kernel does not use frame pointer in its VDSO code,
+      // and so %ebp is not suitable for unwinding.
+      void **const reg_ebp =
+          reinterpret_cast<void **>(ucv->uc_mcontext.gregs[REG_EBP]);
+      const unsigned char *const reg_eip =
+          reinterpret_cast<unsigned char *>(ucv->uc_mcontext.gregs[REG_EIP]);
+      if (new_fp == reg_ebp && kernel_vsyscall_address <= reg_eip &&
+          reg_eip - kernel_vsyscall_address < kMaxBytes) {
+        // We "stepped up" to __kernel_vsyscall, but %ebp is not usable.
+        // Restore from 'ucv' instead.
+        void **const reg_esp =
+            reinterpret_cast<void **>(ucv->uc_mcontext.gregs[REG_ESP]);
+        // Check that alleged %esp is not null and is reasonably aligned.
+        if (reg_esp &&
+            ((uintptr_t)reg_esp & (sizeof(reg_esp) - 1)) == 0) {
+          // Check that alleged %esp is actually readable. This is to prevent
+          // "double fault" in case we hit the first fault due to e.g. stack
+          // corruption.
+          void *const reg_esp2 = reg_esp[num_push_instructions - 1];
+          if (AddressIsReadable(reg_esp2)) {
+            // Alleged %esp is readable, use it for further unwinding.
+            new_fp = reinterpret_cast<void **>(reg_esp2);
+          }
+        }
+      }
+    }
+  }
+#endif
+
+  const uintptr_t old_fp_u = reinterpret_cast<uintptr_t>(old_fp);
+  const uintptr_t new_fp_u = reinterpret_cast<uintptr_t>(new_fp);
+
+  // Check that the transition from frame pointer old_fp to frame
+  // pointer new_fp isn't clearly bogus.  Skip the checks if new_fp
+  // matches the signal context, so that we don't skip out early when
+  // using an alternate signal stack.
+  //
+  // TODO(bcmills): The GetFP call should be completely unnecessary when
+  // ENABLE_COMBINED_UNWINDER is set (because we should be back in the thread's
+  // stack by this point), but it is empirically still needed (e.g. when the
+  // stack includes a call to abort).  unw_get_reg returns UNW_EBADREG for some
+  // frames.  Figure out why GetValidFrameAddr and/or libunwind isn't doing what
+  // it's supposed to.
+  if (STRICT_UNWINDING &&
+      (!WITH_CONTEXT || uc == nullptr || new_fp_u != GetFP(uc))) {
+    // With the stack growing downwards, older stack frame must be
+    // at a greater address that the current one.
+    if (new_fp_u <= old_fp_u) return nullptr;
+
+    // If we get a very large frame size, it may be an indication that we
+    // guessed frame pointers incorrectly and now risk a paging fault
+    // dereferencing a wrong frame pointer. Or maybe not because large frames
+    // are possible as well. The main stack is assumed to be readable,
+    // so we assume the large frame is legit if we know the real stack bounds
+    // and are within the stack.
+    if (new_fp_u - old_fp_u > kMaxFrameBytes) {
+      if (stack_high < kUnknownStackEnd &&
+          static_cast<size_t>(getpagesize()) < stack_low) {
+        // Stack bounds are known.
+        if (!(stack_low < new_fp_u && new_fp_u <= stack_high)) {
+          // new_fp_u is not within the known stack.
+          return nullptr;
+        }
+      } else {
+        // Stack bounds are unknown, prefer truncated stack to possible crash.
+        return nullptr;
+      }
+    }
+    if (stack_low < old_fp_u && old_fp_u <= stack_high) {
+      // Old BP was in the expected stack region...
+      if (!(stack_low < new_fp_u && new_fp_u <= stack_high)) {
+        // ... but new BP is outside of expected stack region.
+        // It is most likely bogus.
+        return nullptr;
+      }
+    } else {
+      // We may be here if we are executing in a co-routine with a
+      // separate stack. We can't do safety checks in this case.
+    }
+  } else {
+    if (new_fp == nullptr) return nullptr;  // skip AddressIsReadable() below
+    // In the non-strict mode, allow discontiguous stack frames.
+    // (alternate-signal-stacks for example).
+    if (new_fp == old_fp) return nullptr;
+  }
+
+  if (new_fp_u & (sizeof(void *) - 1)) return nullptr;
+#ifdef __i386__
+  // On 32-bit machines, the stack pointer can be very close to
+  // 0xffffffff, so we explicitly check for a pointer into the
+  // last two pages in the address space
+  if (new_fp_u >= 0xffffe000) return nullptr;
+#endif
+#if !defined(_WIN32)
+  if (!STRICT_UNWINDING) {
+    // Lax sanity checks cause a crash in 32-bit tcmalloc/crash_reason_test
+    // on AMD-based machines with VDSO-enabled kernels.
+    // Make an extra sanity check to insure new_fp is readable.
+    // Note: NextStackFrame<false>() is only called while the program
+    //       is already on its last leg, so it's ok to be slow here.
+
+    if (!AddressIsReadable(new_fp)) {
+      return nullptr;
+    }
+  }
+#endif
+  return new_fp;
+}
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS  // May read random elements from stack.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY   // May read random elements from stack.
+ABSL_ATTRIBUTE_NOINLINE
+static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+  int n = 0;
+  void **fp = reinterpret_cast<void **>(__builtin_frame_address(0));
+
+  // Assume that the first page is not stack.
+  size_t stack_low = static_cast<size_t>(getpagesize());
+  size_t stack_high = kUnknownStackEnd;
+
+  while (fp && n < max_depth) {
+    if (*(fp + 1) == reinterpret_cast<void *>(0)) {
+      // In 64-bit code, we often see a frame that
+      // points to itself and has a return address of 0.
+      break;
+    }
+    void **next_fp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(
+        fp, ucp, stack_low, stack_high);
+    if (skip_count > 0) {
+      skip_count--;
+    } else {
+      result[n] = *(fp + 1);
+      if (IS_STACK_FRAMES) {
+        if (next_fp > fp) {
+          sizes[n] = static_cast<int>(
+              reinterpret_cast<uintptr_t>(next_fp) -
+              reinterpret_cast<uintptr_t>(fp));
+        } else {
+          // A frame-size of 0 is used to indicate unknown frame size.
+          sizes[n] = 0;
+        }
+      }
+      n++;
+    }
+    fp = next_fp;
+  }
+  if (min_dropped_frames != nullptr) {
+    // Implementation detail: we clamp the max of frames we are willing to
+    // count, so as not to spend too much time in the loop below.
+    const int kMaxUnwind = 1000;
+    int num_dropped_frames = 0;
+    for (int j = 0; fp != nullptr && j < kMaxUnwind; j++) {
+      if (skip_count > 0) {
+        skip_count--;
+      } else {
+        num_dropped_frames++;
+      }
+      fp = NextStackFrame<!IS_STACK_FRAMES, IS_WITH_CONTEXT>(fp, ucp, stack_low,
+                                                             stack_high);
+    }
+    *min_dropped_frames = num_dropped_frames;
+  }
+  return n;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() {
+  return true;
+}
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_X86_INL_INC_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/symbolize.h b/weight/_dep/abseil-cpp/absl/debugging/internal/symbolize.h
new file mode 100644
index 0000000000000000000000000000000000000000..5593fde6b4ca1f93fe1644b81192590e5036ed3a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/symbolize.h
@@ -0,0 +1,153 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains internal parts of the Abseil symbolizer.
+// Do not depend on the anything in this file, it may change at anytime.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
+#define ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
+
+#ifdef __cplusplus
+
+#include <cstddef>
+#include <cstdint>
+
+#include "absl/base/config.h"
+#include "absl/strings/string_view.h"
+
+#ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+#error ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE cannot be directly set
+#elif defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__) \
+      && !defined(__asmjs__) && !defined(__wasm__)
+#define ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE 1
+
+#include <elf.h>
+#include <link.h>  // For ElfW() macro.
+#include <functional>
+#include <string>
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// Iterates over all sections, invoking callback on each with the section name
+// and the section header.
+//
+// Returns true on success; otherwise returns false in case of errors.
+//
+// This is not async-signal-safe.
+bool ForEachSection(int fd,
+                    const std::function<bool(absl::string_view name,
+                                             const ElfW(Shdr) &)>& callback);
+
+// Gets the section header for the given name, if it exists. Returns true on
+// success. Otherwise, returns false.
+bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
+                            ElfW(Shdr) *out);
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+
+#ifdef ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE
+#error ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE cannot be directly set
+#elif defined(__APPLE__)
+#define ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE 1
+#endif
+
+#ifdef ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
+#error ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE cannot be directly set
+#elif defined(__EMSCRIPTEN__)
+#define ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE 1
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+struct SymbolDecoratorArgs {
+  // The program counter we are getting symbolic name for.
+  const void *pc;
+  // 0 for main executable, load address for shared libraries.
+  ptrdiff_t relocation;
+  // Read-only file descriptor for ELF image covering "pc",
+  // or -1 if no such ELF image exists in /proc/self/maps.
+  int fd;
+  // Output buffer, size.
+  // Note: the buffer may not be empty -- default symbolizer may have already
+  // produced some output, and earlier decorators may have adorned it in
+  // some way. You are free to replace or augment the contents (within the
+  // symbol_buf_size limit).
+  char *const symbol_buf;
+  size_t symbol_buf_size;
+  // Temporary scratch space, size.
+  // Use that space in preference to allocating your own stack buffer to
+  // conserve stack.
+  char *const tmp_buf;
+  size_t tmp_buf_size;
+  // User-provided argument
+  void* arg;
+};
+using SymbolDecorator = void (*)(const SymbolDecoratorArgs *);
+
+// Installs a function-pointer as a decorator. Returns a value less than zero
+// if the system cannot install the decorator. Otherwise, returns a unique
+// identifier corresponding to the decorator. This identifier can be used to
+// uninstall the decorator - See RemoveSymbolDecorator() below.
+int InstallSymbolDecorator(SymbolDecorator decorator, void* arg);
+
+// Removes a previously installed function-pointer decorator. Parameter "ticket"
+// is the return-value from calling InstallSymbolDecorator().
+bool RemoveSymbolDecorator(int ticket);
+
+// Remove all installed decorators.  Returns true if successful, false if
+// symbolization is currently in progress.
+bool RemoveAllSymbolDecorators();
+
+// Registers an address range to a file mapping.
+//
+// Preconditions:
+//   start <= end
+//   filename != nullptr
+//
+// Returns true if the file was successfully registered.
+bool RegisterFileMappingHint(const void* start, const void* end,
+                             uint64_t offset, const char* filename);
+
+// Looks up the file mapping registered by RegisterFileMappingHint for an
+// address range. If there is one, the file name is stored in *filename and
+// *start and *end are modified to reflect the registered mapping. Returns
+// whether any hint was found.
+bool GetFileMappingHint(const void** start, const void** end, uint64_t* offset,
+                        const char** filename);
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // __cplusplus
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C"
+#endif  // __cplusplus
+
+    bool
+    AbslInternalGetFileMappingHint(const void** start, const void** end,
+                                   uint64_t* offset, const char** filename);
+
+#endif  // ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/vdso_support.cc b/weight/_dep/abseil-cpp/absl/debugging/internal/vdso_support.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8a588eaffee6a695183c3753752528f81de78605
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/vdso_support.cc
@@ -0,0 +1,205 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Allow dynamic symbol lookup in the kernel VDSO page.
+//
+// VDSOSupport -- a class representing kernel VDSO (if present).
+
+#include "absl/debugging/internal/vdso_support.h"
+
+#ifdef ABSL_HAVE_VDSO_SUPPORT     // defined in vdso_support.h
+
+#if !defined(__has_include)
+#define __has_include(header) 0
+#endif
+
+#include <errno.h>
+#include <fcntl.h>
+#if __has_include(<syscall.h>)
+#include <syscall.h>
+#elif __has_include(<sys/syscall.h>)
+#include <sys/syscall.h>
+#endif
+#include <unistd.h>
+
+#if !defined(__UCLIBC__) && defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 16))
+#define ABSL_HAVE_GETAUXVAL
+#endif
+
+#ifdef ABSL_HAVE_GETAUXVAL
+#include <sys/auxv.h>
+#endif
+
+#include "absl/base/dynamic_annotations.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/port.h"
+
+#ifndef AT_SYSINFO_EHDR
+#define AT_SYSINFO_EHDR 33  // for crosstoolv10
+#endif
+
+#if defined(__NetBSD__)
+using Elf32_auxv_t = Aux32Info;
+using Elf64_auxv_t = Aux64Info;
+#endif
+#if defined(__FreeBSD__)
+#if defined(__ELF_WORD_SIZE) && __ELF_WORD_SIZE == 64
+using Elf64_auxv_t = Elf64_Auxinfo;
+#endif
+using Elf32_auxv_t = Elf32_Auxinfo;
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+ABSL_CONST_INIT
+std::atomic<const void *> VDSOSupport::vdso_base_(
+    debugging_internal::ElfMemImage::kInvalidBase);
+
+ABSL_CONST_INIT std::atomic<VDSOSupport::GetCpuFn> VDSOSupport::getcpu_fn_(
+    &InitAndGetCPU);
+
+VDSOSupport::VDSOSupport()
+    // If vdso_base_ is still set to kInvalidBase, we got here
+    // before VDSOSupport::Init has been called. Call it now.
+    : image_(vdso_base_.load(std::memory_order_relaxed) ==
+                     debugging_internal::ElfMemImage::kInvalidBase
+                 ? Init()
+                 : vdso_base_.load(std::memory_order_relaxed)) {}
+
+// NOTE: we can't use GoogleOnceInit() below, because we can be
+// called by tcmalloc, and none of the *once* stuff may be functional yet.
+//
+// In addition, we hope that the VDSOSupportHelper constructor
+// causes this code to run before there are any threads, and before
+// InitGoogle() has executed any chroot or setuid calls.
+//
+// Finally, even if there is a race here, it is harmless, because
+// the operation should be idempotent.
+const void *VDSOSupport::Init() {
+  const auto kInvalidBase = debugging_internal::ElfMemImage::kInvalidBase;
+#ifdef ABSL_HAVE_GETAUXVAL
+  if (vdso_base_.load(std::memory_order_relaxed) == kInvalidBase) {
+    errno = 0;
+    const void *const sysinfo_ehdr =
+        reinterpret_cast<const void *>(getauxval(AT_SYSINFO_EHDR));
+    if (errno == 0) {
+      vdso_base_.store(sysinfo_ehdr, std::memory_order_relaxed);
+    }
+  }
+#endif  // ABSL_HAVE_GETAUXVAL
+  if (vdso_base_.load(std::memory_order_relaxed) == kInvalidBase) {
+    int fd = open("/proc/self/auxv", O_RDONLY);
+    if (fd == -1) {
+      // Kernel too old to have a VDSO.
+      vdso_base_.store(nullptr, std::memory_order_relaxed);
+      getcpu_fn_.store(&GetCPUViaSyscall, std::memory_order_relaxed);
+      return nullptr;
+    }
+    ElfW(auxv_t) aux;
+    while (read(fd, &aux, sizeof(aux)) == sizeof(aux)) {
+      if (aux.a_type == AT_SYSINFO_EHDR) {
+#if defined(__NetBSD__)
+        vdso_base_.store(reinterpret_cast<void *>(aux.a_v),
+                         std::memory_order_relaxed);
+#else
+        vdso_base_.store(reinterpret_cast<void *>(aux.a_un.a_val),
+                         std::memory_order_relaxed);
+#endif
+        break;
+      }
+    }
+    close(fd);
+    if (vdso_base_.load(std::memory_order_relaxed) == kInvalidBase) {
+      // Didn't find AT_SYSINFO_EHDR in auxv[].
+      vdso_base_.store(nullptr, std::memory_order_relaxed);
+    }
+  }
+  GetCpuFn fn = &GetCPUViaSyscall;  // default if VDSO not present.
+  if (vdso_base_.load(std::memory_order_relaxed)) {
+    VDSOSupport vdso;
+    SymbolInfo info;
+    if (vdso.LookupSymbol("__vdso_getcpu", "LINUX_2.6", STT_FUNC, &info)) {
+      fn = reinterpret_cast<GetCpuFn>(const_cast<void *>(info.address));
+    }
+  }
+  // Subtle: this code runs outside of any locks; prevent compiler
+  // from assigning to getcpu_fn_ more than once.
+  getcpu_fn_.store(fn, std::memory_order_relaxed);
+  return vdso_base_.load(std::memory_order_relaxed);
+}
+
+const void *VDSOSupport::SetBase(const void *base) {
+  ABSL_RAW_CHECK(base != debugging_internal::ElfMemImage::kInvalidBase,
+                 "internal error");
+  const void *old_base = vdso_base_.load(std::memory_order_relaxed);
+  vdso_base_.store(base, std::memory_order_relaxed);
+  image_.Init(base);
+  // Also reset getcpu_fn_, so GetCPU could be tested with simulated VDSO.
+  getcpu_fn_.store(&InitAndGetCPU, std::memory_order_relaxed);
+  return old_base;
+}
+
+bool VDSOSupport::LookupSymbol(const char *name,
+                               const char *version,
+                               int type,
+                               SymbolInfo *info) const {
+  return image_.LookupSymbol(name, version, type, info);
+}
+
+bool VDSOSupport::LookupSymbolByAddress(const void *address,
+                                        SymbolInfo *info_out) const {
+  return image_.LookupSymbolByAddress(address, info_out);
+}
+
+// NOLINT on 'long' because this routine mimics kernel api.
+long VDSOSupport::GetCPUViaSyscall(unsigned *cpu,  // NOLINT(runtime/int)
+                                   void *, void *) {
+#ifdef SYS_getcpu
+  return syscall(SYS_getcpu, cpu, nullptr, nullptr);
+#else
+  // x86_64 never implemented sys_getcpu(), except as a VDSO call.
+  static_cast<void>(cpu);  // Avoid an unused argument compiler warning.
+  errno = ENOSYS;
+  return -1;
+#endif
+}
+
+// Use fast __vdso_getcpu if available.
+long VDSOSupport::InitAndGetCPU(unsigned *cpu,  // NOLINT(runtime/int)
+                                void *x, void *y) {
+  Init();
+  GetCpuFn fn = getcpu_fn_.load(std::memory_order_relaxed);
+  ABSL_RAW_CHECK(fn != &InitAndGetCPU, "Init() did not set getcpu_fn_");
+  return (*fn)(cpu, x, y);
+}
+
+// This function must be very fast, and may be called from very
+// low level (e.g. tcmalloc). Hence I avoid things like
+// GoogleOnceInit() and ::operator new.
+ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY
+int GetCPU() {
+  unsigned cpu;
+  long ret_code =  // NOLINT(runtime/int)
+      (*VDSOSupport::getcpu_fn_)(&cpu, nullptr, nullptr);
+  return ret_code == 0 ? static_cast<int>(cpu) : static_cast<int>(ret_code);
+}
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HAVE_VDSO_SUPPORT
diff --git a/weight/_dep/abseil-cpp/absl/debugging/internal/vdso_support.h b/weight/_dep/abseil-cpp/absl/debugging/internal/vdso_support.h
new file mode 100644
index 0000000000000000000000000000000000000000..6562c6c2350aaa2d40c5341737c9a6a63589ba47
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/internal/vdso_support.h
@@ -0,0 +1,158 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// Allow dynamic symbol lookup in the kernel VDSO page.
+//
+// VDSO stands for "Virtual Dynamic Shared Object" -- a page of
+// executable code, which looks like a shared library, but doesn't
+// necessarily exist anywhere on disk, and which gets mmap()ed into
+// every process by kernels which support VDSO, such as 2.6.x for 32-bit
+// executables, and 2.6.24 and above for 64-bit executables.
+//
+// More details could be found here:
+// http://www.trilithium.com/johan/2005/08/linux-gate/
+//
+// VDSOSupport -- a class representing kernel VDSO (if present).
+//
+// Example usage:
+//  VDSOSupport vdso;
+//  VDSOSupport::SymbolInfo info;
+//  typedef (*FN)(unsigned *, void *, void *);
+//  FN fn = nullptr;
+//  if (vdso.LookupSymbol("__vdso_getcpu", "LINUX_2.6", STT_FUNC, &info)) {
+//     fn = reinterpret_cast<FN>(info.address);
+//  }
+
+#ifndef ABSL_DEBUGGING_INTERNAL_VDSO_SUPPORT_H_
+#define ABSL_DEBUGGING_INTERNAL_VDSO_SUPPORT_H_
+
+#include <atomic>
+
+#include "absl/base/attributes.h"
+#include "absl/debugging/internal/elf_mem_image.h"
+
+#ifdef ABSL_HAVE_ELF_MEM_IMAGE
+
+#ifdef ABSL_HAVE_VDSO_SUPPORT
+#error ABSL_HAVE_VDSO_SUPPORT cannot be directly set
+#else
+#define ABSL_HAVE_VDSO_SUPPORT 1
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// NOTE: this class may be used from within tcmalloc, and can not
+// use any memory allocation routines.
+class VDSOSupport {
+ public:
+  VDSOSupport();
+
+  typedef ElfMemImage::SymbolInfo SymbolInfo;
+  typedef ElfMemImage::SymbolIterator SymbolIterator;
+
+  // On PowerPC64 VDSO symbols can either be of type STT_FUNC or STT_NOTYPE
+  // depending on how the kernel is built.  The kernel is normally built with
+  // STT_NOTYPE type VDSO symbols.  Let's make things simpler first by using a
+  // compile-time constant.
+#ifdef __powerpc64__
+  enum { kVDSOSymbolType = STT_NOTYPE };
+#else
+  enum { kVDSOSymbolType = STT_FUNC };
+#endif
+
+  // Answers whether we have a vdso at all.
+  bool IsPresent() const { return image_.IsPresent(); }
+
+  // Allow to iterate over all VDSO symbols.
+  SymbolIterator begin() const { return image_.begin(); }
+  SymbolIterator end() const { return image_.end(); }
+
+  // Look up versioned dynamic symbol in the kernel VDSO.
+  // Returns false if VDSO is not present, or doesn't contain given
+  // symbol/version/type combination.
+  // If info_out != nullptr, additional details are filled in.
+  bool LookupSymbol(const char *name, const char *version,
+                    int symbol_type, SymbolInfo *info_out) const;
+
+  // Find info about symbol (if any) which overlaps given address.
+  // Returns true if symbol was found; false if VDSO isn't present
+  // or doesn't have a symbol overlapping given address.
+  // If info_out != nullptr, additional details are filled in.
+  bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const;
+
+  // Used only for testing. Replace real VDSO base with a mock.
+  // Returns previous value of vdso_base_. After you are done testing,
+  // you are expected to call SetBase() with previous value, in order to
+  // reset state to the way it was.
+  const void *SetBase(const void *s);
+
+  // Computes vdso_base_ and returns it. Should be called as early as
+  // possible; before any thread creation, chroot or setuid.
+  static const void *Init();
+
+ private:
+  // image_ represents VDSO ELF image in memory.
+  // image_.ehdr_ == nullptr implies there is no VDSO.
+  ElfMemImage image_;
+
+  // Cached value of auxv AT_SYSINFO_EHDR, computed once.
+  // This is a tri-state:
+  //   kInvalidBase   => value hasn't been determined yet.
+  //              0   => there is no VDSO.
+  //           else   => vma of VDSO Elf{32,64}_Ehdr.
+  //
+  // When testing with mock VDSO, low bit is set.
+  // The low bit is always available because vdso_base_ is
+  // page-aligned.
+  static std::atomic<const void *> vdso_base_;
+
+  // NOLINT on 'long' because these routines mimic kernel api.
+  // The 'cache' parameter may be used by some versions of the kernel,
+  // and should be nullptr or point to a static buffer containing at
+  // least two 'long's.
+  static long InitAndGetCPU(unsigned *cpu, void *cache,     // NOLINT 'long'.
+                            void *unused);
+  static long GetCPUViaSyscall(unsigned *cpu, void *cache,  // NOLINT 'long'.
+                               void *unused);
+  typedef long (*GetCpuFn)(unsigned *cpu, void *cache,      // NOLINT 'long'.
+                           void *unused);
+
+  // This function pointer may point to InitAndGetCPU,
+  // GetCPUViaSyscall, or __vdso_getcpu at different stages of initialization.
+  ABSL_CONST_INIT static std::atomic<GetCpuFn> getcpu_fn_;
+
+  friend int GetCPU(void);  // Needs access to getcpu_fn_.
+
+  VDSOSupport(const VDSOSupport&) = delete;
+  VDSOSupport& operator=(const VDSOSupport&) = delete;
+};
+
+// Same as sched_getcpu() on later glibc versions.
+// Return current CPU, using (fast) __vdso_getcpu@LINUX_2.6 if present,
+// otherwise use syscall(SYS_getcpu,...).
+// May return -1 with errno == ENOSYS if the kernel doesn't
+// support SYS_getcpu.
+int GetCPU();
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HAVE_ELF_MEM_IMAGE
+
+#endif  // ABSL_DEBUGGING_INTERNAL_VDSO_SUPPORT_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/leak_check.cc b/weight/_dep/abseil-cpp/absl/debugging/leak_check.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fdb8798b814b249a7223ab6f68f3de6895255903
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/leak_check.cc
@@ -0,0 +1,73 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Wrappers around lsan_interface functions.
+//
+// These are always-available run-time functions manipulating the LeakSanitizer,
+// even when the lsan_interface (and LeakSanitizer) is not available. When
+// LeakSanitizer is not linked in, these functions become no-op stubs.
+
+#include "absl/debugging/leak_check.h"
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+
+#if defined(ABSL_HAVE_LEAK_SANITIZER)
+
+#include <sanitizer/lsan_interface.h>
+
+#if ABSL_HAVE_ATTRIBUTE_WEAK
+extern "C" ABSL_ATTRIBUTE_WEAK int __lsan_is_turned_off();
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+bool HaveLeakSanitizer() { return true; }
+
+#if ABSL_HAVE_ATTRIBUTE_WEAK
+bool LeakCheckerIsActive() {
+  return !(&__lsan_is_turned_off && __lsan_is_turned_off());
+}
+#else
+bool LeakCheckerIsActive() { return true; }
+#endif
+
+bool FindAndReportLeaks() { return __lsan_do_recoverable_leak_check(); }
+void DoIgnoreLeak(const void* ptr) { __lsan_ignore_object(ptr); }
+void RegisterLivePointers(const void* ptr, size_t size) {
+  __lsan_register_root_region(ptr, size);
+}
+void UnRegisterLivePointers(const void* ptr, size_t size) {
+  __lsan_unregister_root_region(ptr, size);
+}
+LeakCheckDisabler::LeakCheckDisabler() { __lsan_disable(); }
+LeakCheckDisabler::~LeakCheckDisabler() { __lsan_enable(); }
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#else  // defined(ABSL_HAVE_LEAK_SANITIZER)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+bool HaveLeakSanitizer() { return false; }
+bool LeakCheckerIsActive() { return false; }
+void DoIgnoreLeak(const void*) { }
+void RegisterLivePointers(const void*, size_t) { }
+void UnRegisterLivePointers(const void*, size_t) { }
+LeakCheckDisabler::LeakCheckDisabler() = default;
+LeakCheckDisabler::~LeakCheckDisabler() = default;
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // defined(ABSL_HAVE_LEAK_SANITIZER)
diff --git a/weight/_dep/abseil-cpp/absl/debugging/leak_check.h b/weight/_dep/abseil-cpp/absl/debugging/leak_check.h
new file mode 100644
index 0000000000000000000000000000000000000000..6bd794062369a6279573f84511ac9d7e31192f9d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/leak_check.h
@@ -0,0 +1,150 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: leak_check.h
+// -----------------------------------------------------------------------------
+//
+// This file contains functions that affect leak checking behavior within
+// targets built with the LeakSanitizer (LSan), a memory leak detector that is
+// integrated within the AddressSanitizer (ASan) as an additional component, or
+// which can be used standalone. LSan and ASan are included (or can be provided)
+// as additional components for most compilers such as Clang, gcc and MSVC.
+// Note: this leak checking API is not yet supported in MSVC.
+// Leak checking is enabled by default in all ASan builds.
+//
+// https://clang.llvm.org/docs/LeakSanitizer.html
+// https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer
+//
+// GCC and Clang both automatically enable LeakSanitizer when AddressSanitizer
+// is enabled. To use the mode, simply pass `-fsanitize=address` to both the
+// compiler and linker. An example Bazel command could be
+//
+//   $ bazel test --copt=-fsanitize=address --linkopt=-fsanitize=address ...
+//
+// GCC and Clang auto support a standalone LeakSanitizer mode (a mode which does
+// not also use AddressSanitizer). To use the mode, simply pass
+// `-fsanitize=leak` to both the compiler and linker. Since GCC does not
+// currently provide a way of detecting this mode at compile-time, GCC users
+// must also pass -DLEAK_SANITIZER to the compiler. An example Bazel command
+// could be
+//
+//   $ bazel test --copt=-DLEAK_SANITIZER --copt=-fsanitize=leak
+//     --linkopt=-fsanitize=leak ...
+//
+// -----------------------------------------------------------------------------
+#ifndef ABSL_DEBUGGING_LEAK_CHECK_H_
+#define ABSL_DEBUGGING_LEAK_CHECK_H_
+
+#include <cstddef>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// HaveLeakSanitizer()
+//
+// Returns true if a leak-checking sanitizer (either ASan or standalone LSan) is
+// currently built into this target.
+bool HaveLeakSanitizer();
+
+// LeakCheckerIsActive()
+//
+// Returns true if a leak-checking sanitizer (either ASan or standalone LSan) is
+// currently built into this target and is turned on.
+bool LeakCheckerIsActive();
+
+// DoIgnoreLeak()
+//
+// Implements `IgnoreLeak()` below. This function should usually
+// not be called directly; calling `IgnoreLeak()` is preferred.
+void DoIgnoreLeak(const void* ptr);
+
+// IgnoreLeak()
+//
+// Instruct the leak sanitizer to ignore leak warnings on the object referenced
+// by the passed pointer, as well as all heap objects transitively referenced
+// by it. The passed object pointer can point to either the beginning of the
+// object or anywhere within it.
+//
+// Example:
+//
+//   static T* obj = IgnoreLeak(new T(...));
+//
+// If the passed `ptr` does not point to an actively allocated object at the
+// time `IgnoreLeak()` is called, the call is a no-op; if it is actively
+// allocated, leak sanitizer will assume this object is referenced even if
+// there is no actual reference in user memory.
+//
+template <typename T>
+T* IgnoreLeak(T* ptr) {
+  DoIgnoreLeak(ptr);
+  return ptr;
+}
+
+// FindAndReportLeaks()
+//
+// If any leaks are detected, prints a leak report and returns true.  This
+// function may be called repeatedly, and does not affect end-of-process leak
+// checking.
+//
+// Example:
+// if (FindAndReportLeaks()) {
+//   ... diagnostic already printed. Exit with failure code.
+//   exit(1)
+// }
+bool FindAndReportLeaks();
+
+// LeakCheckDisabler
+//
+// This helper class indicates that any heap allocations done in the code block
+// covered by the scoped object, which should be allocated on the stack, will
+// not be reported as leaks. Leak check disabling will occur within the code
+// block and any nested function calls within the code block.
+//
+// Example:
+//
+//   void Foo() {
+//     LeakCheckDisabler disabler;
+//     ... code that allocates objects whose leaks should be ignored ...
+//   }
+//
+// REQUIRES: Destructor runs in same thread as constructor
+class LeakCheckDisabler {
+ public:
+  LeakCheckDisabler();
+  LeakCheckDisabler(const LeakCheckDisabler&) = delete;
+  LeakCheckDisabler& operator=(const LeakCheckDisabler&) = delete;
+  ~LeakCheckDisabler();
+};
+
+// RegisterLivePointers()
+//
+// Registers `ptr[0,size-1]` as pointers to memory that is still actively being
+// referenced and for which leak checking should be ignored. This function is
+// useful if you store pointers in mapped memory, for memory ranges that we know
+// are correct but for which normal analysis would flag as leaked code.
+void RegisterLivePointers(const void* ptr, size_t size);
+
+// UnRegisterLivePointers()
+//
+// Deregisters the pointers previously marked as active in
+// `RegisterLivePointers()`, enabling leak checking of those pointers.
+void UnRegisterLivePointers(const void* ptr, size_t size);
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_LEAK_CHECK_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/leak_check_fail_test.cc b/weight/_dep/abseil-cpp/absl/debugging/leak_check_fail_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..46e9fb6297b497c9547ddf9ee13a065fa5932dad
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/leak_check_fail_test.cc
@@ -0,0 +1,41 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <memory>
+
+#include "gtest/gtest.h"
+#include "absl/debugging/leak_check.h"
+#include "absl/log/log.h"
+
+namespace {
+
+TEST(LeakCheckTest, LeakMemory) {
+  // This test is expected to cause lsan failures on program exit. Therefore the
+  // test will be run only by leak_check_test.sh, which will verify a
+  // failed exit code.
+
+  char* foo = strdup("lsan should complain about this leaked string");
+  LOG(INFO) << "Should detect leaked string " << foo;
+}
+
+TEST(LeakCheckTest, LeakMemoryAfterDisablerScope) {
+  // This test is expected to cause lsan failures on program exit. Therefore the
+  // test will be run only by external_leak_check_test.sh, which will verify a
+  // failed exit code.
+  { absl::LeakCheckDisabler disabler; }
+  char* foo = strdup("lsan should also complain about this leaked string");
+  LOG(INFO) << "Re-enabled leak detection.Should detect leaked string " << foo;
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/debugging/leak_check_test.cc b/weight/_dep/abseil-cpp/absl/debugging/leak_check_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6f0135ed79206d9b0e8f23e664f29d6a4002199b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/leak_check_test.cc
@@ -0,0 +1,41 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/debugging/leak_check.h"
+#include "absl/log/log.h"
+
+namespace {
+
+TEST(LeakCheckTest, IgnoreLeakSuppressesLeakedMemoryErrors) {
+  if (!absl::LeakCheckerIsActive()) {
+    GTEST_SKIP() << "LeakChecker is not active";
+  }
+  auto foo = absl::IgnoreLeak(new std::string("some ignored leaked string"));
+  LOG(INFO) << "Ignoring leaked string " << foo;
+}
+
+TEST(LeakCheckTest, LeakCheckDisablerIgnoresLeak) {
+  if (!absl::LeakCheckerIsActive()) {
+    GTEST_SKIP() << "LeakChecker is not active";
+  }
+  absl::LeakCheckDisabler disabler;
+  auto foo = new std::string("some string leaked while checks are disabled");
+  LOG(INFO) << "Ignoring leaked string " << foo;
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/debugging/stacktrace.cc b/weight/_dep/abseil-cpp/absl/debugging/stacktrace.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ff8069f84310a5f6b96d5c2761fd6f1470ed3535
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/stacktrace.cc
@@ -0,0 +1,142 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Produce stack trace.
+//
+// There are three different ways we can try to get the stack trace:
+//
+// 1) Our hand-coded stack-unwinder.  This depends on a certain stack
+//    layout, which is used by gcc (and those systems using a
+//    gcc-compatible ABI) on x86 systems, at least since gcc 2.95.
+//    It uses the frame pointer to do its work.
+//
+// 2) The libunwind library.  This is still in development, and as a
+//    separate library adds a new dependency, but doesn't need a frame
+//    pointer.  It also doesn't call malloc.
+//
+// 3) The gdb unwinder -- also the one used by the c++ exception code.
+//    It's obviously well-tested, but has a fatal flaw: it can call
+//    malloc() from the unwinder.  This is a problem because we're
+//    trying to use the unwinder to instrument malloc().
+//
+// Note: if you add a new implementation here, make sure it works
+// correctly when absl::GetStackTrace() is called with max_depth == 0.
+// Some code may do that.
+
+#include "absl/debugging/stacktrace.h"
+
+#include <atomic>
+
+#include "absl/base/attributes.h"
+#include "absl/base/port.h"
+#include "absl/debugging/internal/stacktrace_config.h"
+
+#if defined(ABSL_STACKTRACE_INL_HEADER)
+#include ABSL_STACKTRACE_INL_HEADER
+#else
+# error Cannot calculate stack trace: will need to write for your environment
+
+# include "absl/debugging/internal/stacktrace_aarch64-inl.inc"
+# include "absl/debugging/internal/stacktrace_arm-inl.inc"
+# include "absl/debugging/internal/stacktrace_emscripten-inl.inc"
+# include "absl/debugging/internal/stacktrace_generic-inl.inc"
+# include "absl/debugging/internal/stacktrace_powerpc-inl.inc"
+# include "absl/debugging/internal/stacktrace_riscv-inl.inc"
+# include "absl/debugging/internal/stacktrace_unimplemented-inl.inc"
+# include "absl/debugging/internal/stacktrace_win32-inl.inc"
+# include "absl/debugging/internal/stacktrace_x86-inl.inc"
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace {
+
+typedef int (*Unwinder)(void**, int*, int, int, const void*, int*);
+std::atomic<Unwinder> custom;
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+ABSL_ATTRIBUTE_ALWAYS_INLINE inline int Unwind(void** result, int* sizes,
+                                               int max_depth, int skip_count,
+                                               const void* uc,
+                                               int* min_dropped_frames) {
+  Unwinder f = &UnwindImpl<IS_STACK_FRAMES, IS_WITH_CONTEXT>;
+  Unwinder g = custom.load(std::memory_order_acquire);
+  if (g != nullptr) f = g;
+
+  // Add 1 to skip count for the unwinder function itself
+  int size = (*f)(result, sizes, max_depth, skip_count + 1, uc,
+                  min_dropped_frames);
+  // To disable tail call to (*f)(...)
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+  return size;
+}
+
+}  // anonymous namespace
+
+ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int GetStackFrames(
+    void** result, int* sizes, int max_depth, int skip_count) {
+  return Unwind<true, false>(result, sizes, max_depth, skip_count, nullptr,
+                             nullptr);
+}
+
+ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
+GetStackFramesWithContext(void** result, int* sizes, int max_depth,
+                          int skip_count, const void* uc,
+                          int* min_dropped_frames) {
+  return Unwind<true, true>(result, sizes, max_depth, skip_count, uc,
+                            min_dropped_frames);
+}
+
+ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int GetStackTrace(
+    void** result, int max_depth, int skip_count) {
+  return Unwind<false, false>(result, nullptr, max_depth, skip_count, nullptr,
+                              nullptr);
+}
+
+ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
+GetStackTraceWithContext(void** result, int max_depth, int skip_count,
+                         const void* uc, int* min_dropped_frames) {
+  return Unwind<false, true>(result, nullptr, max_depth, skip_count, uc,
+                             min_dropped_frames);
+}
+
+void SetStackUnwinder(Unwinder w) {
+  custom.store(w, std::memory_order_release);
+}
+
+int DefaultStackUnwinder(void** pcs, int* sizes, int depth, int skip,
+                         const void* uc, int* min_dropped_frames) {
+  skip++;  // For this function
+  Unwinder f = nullptr;
+  if (sizes == nullptr) {
+    if (uc == nullptr) {
+      f = &UnwindImpl<false, false>;
+    } else {
+      f = &UnwindImpl<false, true>;
+    }
+  } else {
+    if (uc == nullptr) {
+      f = &UnwindImpl<true, false>;
+    } else {
+      f = &UnwindImpl<true, true>;
+    }
+  }
+  volatile int x = 0;
+  int n = (*f)(pcs, sizes, depth, skip, uc, min_dropped_frames);
+  x = 1; (void) x;  // To disable tail call to (*f)(...)
+  return n;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/stacktrace.h b/weight/_dep/abseil-cpp/absl/debugging/stacktrace.h
new file mode 100644
index 0000000000000000000000000000000000000000..0ec0ffdabd422e07be93660860202c61c4c60406
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/stacktrace.h
@@ -0,0 +1,231 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: stacktrace.h
+// -----------------------------------------------------------------------------
+//
+// This file contains routines to extract the current stack trace and associated
+// stack frames. These functions are thread-safe and async-signal-safe.
+//
+// Note that stack trace functionality is platform dependent and requires
+// additional support from the compiler/build system in most cases. (That is,
+// this functionality generally only works on platforms/builds that have been
+// specifically configured to support it.)
+//
+// Note: stack traces in Abseil that do not utilize a symbolizer will result in
+// frames consisting of function addresses rather than human-readable function
+// names. (See symbolize.h for information on symbolizing these values.)
+
+#ifndef ABSL_DEBUGGING_STACKTRACE_H_
+#define ABSL_DEBUGGING_STACKTRACE_H_
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// GetStackFrames()
+//
+// Records program counter values for up to `max_depth` frames, skipping the
+// most recent `skip_count` stack frames, stores their corresponding values
+// and sizes in `results` and `sizes` buffers, and returns the number of frames
+// stored. (Note that the frame generated for the `absl::GetStackFrames()`
+// routine itself is also skipped.)
+//
+// Example:
+//
+//      main() { foo(); }
+//      foo() { bar(); }
+//      bar() {
+//        void* result[10];
+//        int sizes[10];
+//        int depth = absl::GetStackFrames(result, sizes, 10, 1);
+//      }
+//
+// The current stack frame would consist of three function calls: `bar()`,
+// `foo()`, and then `main()`; however, since the `GetStackFrames()` call sets
+// `skip_count` to `1`, it will skip the frame for `bar()`, the most recently
+// invoked function call. It will therefore return 2 and fill `result` with
+// program counters within the following functions:
+//
+//      result[0]       foo()
+//      result[1]       main()
+//
+// (Note: in practice, a few more entries after `main()` may be added to account
+// for startup processes.)
+//
+// Corresponding stack frame sizes will also be recorded:
+//
+//    sizes[0]       16
+//    sizes[1]       16
+//
+// (Stack frame sizes of `16` above are just for illustration purposes.)
+//
+// Stack frame sizes of 0 or less indicate that those frame sizes couldn't
+// be identified.
+//
+// This routine may return fewer stack frame entries than are
+// available. Also note that `result` and `sizes` must both be non-null.
+extern int GetStackFrames(void** result, int* sizes, int max_depth,
+                          int skip_count);
+
+// GetStackFramesWithContext()
+//
+// Records program counter values obtained from a signal handler. Records
+// program counter values for up to `max_depth` frames, skipping the most recent
+// `skip_count` stack frames, stores their corresponding values and sizes in
+// `results` and `sizes` buffers, and returns the number of frames stored. (Note
+// that the frame generated for the `absl::GetStackFramesWithContext()` routine
+// itself is also skipped.)
+//
+// The `uc` parameter, if non-null, should be a pointer to a `ucontext_t` value
+// passed to a signal handler registered via the `sa_sigaction` field of a
+// `sigaction` struct. (See
+// http://man7.org/linux/man-pages/man2/sigaction.2.html.) The `uc` value may
+// help a stack unwinder to provide a better stack trace under certain
+// conditions. `uc` may safely be null.
+//
+// The `min_dropped_frames` output parameter, if non-null, points to the
+// location to note any dropped stack frames, if any, due to buffer limitations
+// or other reasons. (This value will be set to `0` if no frames were dropped.)
+// The number of total stack frames is guaranteed to be >= skip_count +
+// max_depth + *min_dropped_frames.
+extern int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
+                                     int skip_count, const void* uc,
+                                     int* min_dropped_frames);
+
+// GetStackTrace()
+//
+// Records program counter values for up to `max_depth` frames, skipping the
+// most recent `skip_count` stack frames, stores their corresponding values
+// in `results`, and returns the number of frames
+// stored. Note that this function is similar to `absl::GetStackFrames()`
+// except that it returns the stack trace only, and not stack frame sizes.
+//
+// Example:
+//
+//      main() { foo(); }
+//      foo() { bar(); }
+//      bar() {
+//        void* result[10];
+//        int depth = absl::GetStackTrace(result, 10, 1);
+//      }
+//
+// This produces:
+//
+//      result[0]       foo
+//      result[1]       main
+//           ....       ...
+//
+// `result` must not be null.
+extern int GetStackTrace(void** result, int max_depth, int skip_count);
+
+// GetStackTraceWithContext()
+//
+// Records program counter values obtained from a signal handler. Records
+// program counter values for up to `max_depth` frames, skipping the most recent
+// `skip_count` stack frames, stores their corresponding values in `results`,
+// and returns the number of frames stored. (Note that the frame generated for
+// the `absl::GetStackFramesWithContext()` routine itself is also skipped.)
+//
+// The `uc` parameter, if non-null, should be a pointer to a `ucontext_t` value
+// passed to a signal handler registered via the `sa_sigaction` field of a
+// `sigaction` struct. (See
+// http://man7.org/linux/man-pages/man2/sigaction.2.html.) The `uc` value may
+// help a stack unwinder to provide a better stack trace under certain
+// conditions. `uc` may safely be null.
+//
+// The `min_dropped_frames` output parameter, if non-null, points to the
+// location to note any dropped stack frames, if any, due to buffer limitations
+// or other reasons. (This value will be set to `0` if no frames were dropped.)
+// The number of total stack frames is guaranteed to be >= skip_count +
+// max_depth + *min_dropped_frames.
+extern int GetStackTraceWithContext(void** result, int max_depth,
+                                    int skip_count, const void* uc,
+                                    int* min_dropped_frames);
+
+// SetStackUnwinder()
+//
+// Provides a custom function for unwinding stack frames that will be used in
+// place of the default stack unwinder when invoking the static
+// GetStack{Frames,Trace}{,WithContext}() functions above.
+//
+// The arguments passed to the unwinder function will match the
+// arguments passed to `absl::GetStackFramesWithContext()` except that sizes
+// will be non-null iff the caller is interested in frame sizes.
+//
+// If unwinder is set to null, we revert to the default stack-tracing behavior.
+//
+// *****************************************************************************
+// WARNING
+// *****************************************************************************
+//
+// absl::SetStackUnwinder is not suitable for general purpose use.  It is
+// provided for custom runtimes.
+// Some things to watch out for when calling `absl::SetStackUnwinder()`:
+//
+// (a) The unwinder may be called from within signal handlers and
+// therefore must be async-signal-safe.
+//
+// (b) Even after a custom stack unwinder has been unregistered, other
+// threads may still be in the process of using that unwinder.
+// Therefore do not clean up any state that may be needed by an old
+// unwinder.
+// *****************************************************************************
+extern void SetStackUnwinder(int (*unwinder)(void** pcs, int* sizes,
+                                             int max_depth, int skip_count,
+                                             const void* uc,
+                                             int* min_dropped_frames));
+
+// DefaultStackUnwinder()
+//
+// Records program counter values of up to `max_depth` frames, skipping the most
+// recent `skip_count` stack frames, and stores their corresponding values in
+// `pcs`. (Note that the frame generated for this call itself is also skipped.)
+// This function acts as a generic stack-unwinder; prefer usage of the more
+// specific `GetStack{Trace,Frames}{,WithContext}()` functions above.
+//
+// If you have set your own stack unwinder (with the `SetStackUnwinder()`
+// function above, you can still get the default stack unwinder by calling
+// `DefaultStackUnwinder()`, which will ignore any previously set stack unwinder
+// and use the default one instead.
+//
+// Because this function is generic, only `pcs` is guaranteed to be non-null
+// upon return. It is legal for `sizes`, `uc`, and `min_dropped_frames` to all
+// be null when called.
+//
+// The semantics are the same as the corresponding `GetStack*()` function in the
+// case where `absl::SetStackUnwinder()` was never called. Equivalents are:
+//
+//                       null sizes         |        non-nullptr sizes
+//             |==========================================================|
+//     null uc | GetStackTrace()            | GetStackFrames()            |
+// non-null uc | GetStackTraceWithContext() | GetStackFramesWithContext() |
+//             |==========================================================|
+extern int DefaultStackUnwinder(void** pcs, int* sizes, int max_depth,
+                                int skip_count, const void* uc,
+                                int* min_dropped_frames);
+
+namespace debugging_internal {
+// Returns true for platforms which are expected to have functioning stack trace
+// implementations. Intended to be used for tests which want to exclude
+// verification of logic known to be broken because stack traces are not
+// working.
+extern bool StackTraceWorksForTest();
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_STACKTRACE_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/stacktrace_test.cc b/weight/_dep/abseil-cpp/absl/debugging/stacktrace_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..31f7723cdd3d6903db86c11860bf685992284a55
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/stacktrace_test.cc
@@ -0,0 +1,47 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/stacktrace.h"
+
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+#include "absl/base/optimization.h"
+
+namespace {
+
+// This test is currently only known to pass on Linux x86_64/aarch64.
+#if defined(__linux__) && (defined(__x86_64__) || defined(__aarch64__))
+ABSL_ATTRIBUTE_NOINLINE void Unwind(void* p) {
+  ABSL_ATTRIBUTE_UNUSED static void* volatile sink = p;
+  constexpr int kSize = 16;
+  void* stack[kSize];
+  int frames[kSize];
+  absl::GetStackTrace(stack, kSize, 0);
+  absl::GetStackFrames(stack, frames, kSize, 0);
+}
+
+ABSL_ATTRIBUTE_NOINLINE void HugeFrame() {
+  char buffer[1 << 20];
+  Unwind(buffer);
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+TEST(StackTrace, HugeFrame) {
+  // Ensure that the unwinder is not confused by very large stack frames.
+  HugeFrame();
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+#endif
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize.cc b/weight/_dep/abseil-cpp/absl/debugging/symbolize.cc
new file mode 100644
index 0000000000000000000000000000000000000000..638d3954aeca9a499041c2354af02ec27257cf1d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize.cc
@@ -0,0 +1,43 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/symbolize.h"
+
+#ifdef _WIN32
+#include <winapifamily.h>
+#if !(WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP)) || \
+    WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+// UWP doesn't have access to win32 APIs.
+#define ABSL_INTERNAL_HAVE_SYMBOLIZE_WIN32
+#endif
+#endif
+
+// Emscripten symbolization relies on JS. Do not use them in standalone mode.
+#if defined(__EMSCRIPTEN__) && !defined(STANDALONE_WASM)
+#define ABSL_INTERNAL_HAVE_SYMBOLIZE_WASM
+#endif
+
+#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE)
+#include "absl/debugging/symbolize_elf.inc"
+#elif defined(ABSL_INTERNAL_HAVE_SYMBOLIZE_WIN32)
+// The Windows Symbolizer only works if PDB files containing the debug info
+// are available to the program at runtime.
+#include "absl/debugging/symbolize_win32.inc"
+#elif defined(__APPLE__)
+#include "absl/debugging/symbolize_darwin.inc"
+#elif defined(ABSL_INTERNAL_HAVE_SYMBOLIZE_WASM)
+#include "absl/debugging/symbolize_emscripten.inc"
+#else
+#include "absl/debugging/symbolize_unimplemented.inc"
+#endif
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize.h b/weight/_dep/abseil-cpp/absl/debugging/symbolize.h
new file mode 100644
index 0000000000000000000000000000000000000000..43d93a86822eb5129a9c995bbda54370a973528e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize.h
@@ -0,0 +1,99 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: symbolize.h
+// -----------------------------------------------------------------------------
+//
+// This file configures the Abseil symbolizer for use in converting instruction
+// pointer addresses (program counters) into human-readable names (function
+// calls, etc.) within Abseil code.
+//
+// The symbolizer may be invoked from several sources:
+//
+//   * Implicitly, through the installation of an Abseil failure signal handler.
+//     (See failure_signal_handler.h for more information.)
+//   * By calling `Symbolize()` directly on a program counter you obtain through
+//     `absl::GetStackTrace()` or `absl::GetStackFrames()`. (See stacktrace.h
+//     for more information.
+//   * By calling `Symbolize()` directly on a program counter you obtain through
+//     other means (which would be platform-dependent).
+//
+// In all of the above cases, the symbolizer must first be initialized before
+// any program counter values can be symbolized. If you are installing a failure
+// signal handler, initialize the symbolizer before you do so.
+//
+// Example:
+//
+//   int main(int argc, char** argv) {
+//     // Initialize the Symbolizer before installing the failure signal handler
+//     absl::InitializeSymbolizer(argv[0]);
+//
+//     // Now you may install the failure signal handler
+//     absl::FailureSignalHandlerOptions options;
+//     absl::InstallFailureSignalHandler(options);
+//
+//     // Start running your main program
+//     ...
+//     return 0;
+//  }
+//
+#ifndef ABSL_DEBUGGING_SYMBOLIZE_H_
+#define ABSL_DEBUGGING_SYMBOLIZE_H_
+
+#include "absl/debugging/internal/symbolize.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// InitializeSymbolizer()
+//
+// Initializes the program counter symbolizer, given the path of the program
+// (typically obtained through `main()`s `argv[0]`). The Abseil symbolizer
+// allows you to read program counters (instruction pointer values) using their
+// human-readable names within output such as stack traces.
+//
+// Example:
+//
+// int main(int argc, char *argv[]) {
+//   absl::InitializeSymbolizer(argv[0]);
+//   // Now you can use the symbolizer
+// }
+void InitializeSymbolizer(const char* argv0);
+//
+// Symbolize()
+//
+// Symbolizes a program counter (instruction pointer value) `pc` and, on
+// success, writes the name to `out`. The symbol name is demangled, if possible.
+// Note that the symbolized name may be truncated and will be NUL-terminated.
+// Demangling is supported for symbols generated by GCC 3.x or newer). Returns
+// `false` on failure.
+//
+// Example:
+//
+//   // Print a program counter and its symbol name.
+//   static void DumpPCAndSymbol(void *pc) {
+//     char tmp[1024];
+//     const char *symbol = "(unknown)";
+//     if (absl::Symbolize(pc, tmp, sizeof(tmp))) {
+//       symbol = tmp;
+//     }
+//     absl::PrintF("%p  %s\n", pc, symbol);
+//  }
+bool Symbolize(const void *pc, char *out, int out_size);
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_SYMBOLIZE_H_
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize_darwin.inc b/weight/_dep/abseil-cpp/absl/debugging/symbolize_darwin.inc
new file mode 100644
index 0000000000000000000000000000000000000000..cf63d1919b8fe3fa1111c68c5d35b6b89e18eb1b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize_darwin.inc
@@ -0,0 +1,102 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cxxabi.h>
+#include <execinfo.h>
+
+#include <algorithm>
+#include <cstring>
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/debugging/internal/demangle.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+void InitializeSymbolizer(const char*) {}
+
+namespace debugging_internal {
+namespace {
+
+static std::string GetSymbolString(absl::string_view backtrace_line) {
+  // Example Backtrace lines:
+  // 0   libimaging_shared.dylib             0x018c152a
+  // _ZNSt11_Deque_baseIN3nik7mediadb4PageESaIS2_EE17_M_initialize_mapEm + 3478
+  //
+  // or
+  // 0   libimaging_shared.dylib             0x0000000001895c39
+  // _ZN3nik4util19register_shared_ptrINS_3gpu7TextureEEEvPKvS5_ + 39
+  //
+  // or
+  // 0   mysterious_app                      0x0124000120120009 main + 17
+  auto address_pos = backtrace_line.find(" 0x");
+  if (address_pos == absl::string_view::npos) return std::string();
+  absl::string_view symbol_view = backtrace_line.substr(address_pos + 1);
+
+  auto space_pos = symbol_view.find(" ");
+  if (space_pos == absl::string_view::npos) return std::string();
+  symbol_view = symbol_view.substr(space_pos + 1);  // to mangled symbol
+
+  auto plus_pos = symbol_view.find(" + ");
+  if (plus_pos == absl::string_view::npos) return std::string();
+  symbol_view = symbol_view.substr(0, plus_pos);  // strip remainng
+
+  return std::string(symbol_view);
+}
+
+}  // namespace
+}  // namespace debugging_internal
+
+bool Symbolize(const void* pc, char* out, int out_size) {
+  if (out_size <= 0 || pc == nullptr) {
+    out = nullptr;
+    return false;
+  }
+
+  // This allocates a char* array.
+  char** frame_strings = backtrace_symbols(const_cast<void**>(&pc), 1);
+
+  if (frame_strings == nullptr) return false;
+
+  std::string symbol = debugging_internal::GetSymbolString(frame_strings[0]);
+  free(frame_strings);
+
+  char tmp_buf[1024];
+  if (debugging_internal::Demangle(symbol.c_str(), tmp_buf, sizeof(tmp_buf))) {
+    size_t len = strlen(tmp_buf);
+    if (len + 1 <= static_cast<size_t>(out_size)) {  // +1 for '\0'
+      assert(len < sizeof(tmp_buf));
+      memmove(out, tmp_buf, len + 1);
+    }
+  } else {
+    strncpy(out, symbol.c_str(), static_cast<size_t>(out_size));
+  }
+
+  if (out[out_size - 1] != '\0') {
+    // strncpy() does not '\0' terminate when it truncates.
+    static constexpr char kEllipsis[] = "...";
+    size_t ellipsis_size =
+        std::min(sizeof(kEllipsis) - 1, static_cast<size_t>(out_size) - 1);
+    memcpy(out + out_size - ellipsis_size - 1, kEllipsis, ellipsis_size);
+    out[out_size - 1] = '\0';
+  }
+
+  return true;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize_elf.inc b/weight/_dep/abseil-cpp/absl/debugging/symbolize_elf.inc
new file mode 100644
index 0000000000000000000000000000000000000000..ae75cd4153d25b3363c484e3d5ba32a9970de5a8
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize_elf.inc
@@ -0,0 +1,1725 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This library provides Symbolize() function that symbolizes program
+// counters to their corresponding symbol names on linux platforms.
+// This library has a minimal implementation of an ELF symbol table
+// reader (i.e. it doesn't depend on libelf, etc.).
+//
+// The algorithm used in Symbolize() is as follows.
+//
+//   1. Go through a list of maps in /proc/self/maps and find the map
+//   containing the program counter.
+//
+//   2. Open the mapped file and find a regular symbol table inside.
+//   Iterate over symbols in the symbol table and look for the symbol
+//   containing the program counter.  If such a symbol is found,
+//   obtain the symbol name, and demangle the symbol if possible.
+//   If the symbol isn't found in the regular symbol table (binary is
+//   stripped), try the same thing with a dynamic symbol table.
+//
+// Note that Symbolize() is originally implemented to be used in
+// signal handlers, hence it doesn't use malloc() and other unsafe
+// operations.  It should be both thread-safe and async-signal-safe.
+//
+// Implementation note:
+//
+// We don't use heaps but only use stacks.  We want to reduce the
+// stack consumption so that the symbolizer can run on small stacks.
+//
+// Here are some numbers collected with GCC 4.1.0 on x86:
+// - sizeof(Elf32_Sym)  = 16
+// - sizeof(Elf32_Shdr) = 40
+// - sizeof(Elf64_Sym)  = 24
+// - sizeof(Elf64_Shdr) = 64
+//
+// This implementation is intended to be async-signal-safe but uses some
+// functions which are not guaranteed to be so, such as memchr() and
+// memmove().  We assume they are async-signal-safe.
+
+#include <dlfcn.h>
+#include <elf.h>
+#include <fcntl.h>
+#include <link.h>  // For ElfW() macro.
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <array>
+#include <atomic>
+#include <cerrno>
+#include <cinttypes>
+#include <climits>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+#include "absl/base/casts.h"
+#include "absl/base/dynamic_annotations.h"
+#include "absl/base/internal/low_level_alloc.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/spinlock.h"
+#include "absl/base/port.h"
+#include "absl/debugging/internal/demangle.h"
+#include "absl/debugging/internal/vdso_support.h"
+#include "absl/strings/string_view.h"
+
+#if defined(__FreeBSD__) && !defined(ElfW)
+#define ElfW(x) __ElfN(x)
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Value of argv[0]. Used by MaybeInitializeObjFile().
+static char *argv0_value = nullptr;
+
+void InitializeSymbolizer(const char *argv0) {
+#ifdef ABSL_HAVE_VDSO_SUPPORT
+  // We need to make sure VDSOSupport::Init() is called before any setuid or
+  // chroot calls, so InitializeSymbolizer() should be called very early in the
+  // life of a program.
+  absl::debugging_internal::VDSOSupport::Init();
+#endif
+  if (argv0_value != nullptr) {
+    free(argv0_value);
+    argv0_value = nullptr;
+  }
+  if (argv0 != nullptr && argv0[0] != '\0') {
+    argv0_value = strdup(argv0);
+  }
+}
+
+namespace debugging_internal {
+namespace {
+
+// Re-runs fn until it doesn't cause EINTR.
+#define NO_INTR(fn) \
+  do {              \
+  } while ((fn) < 0 && errno == EINTR)
+
+// On Linux, ELF_ST_* are defined in <linux/elf.h>.  To make this portable
+// we define our own ELF_ST_BIND and ELF_ST_TYPE if not available.
+#ifndef ELF_ST_BIND
+#define ELF_ST_BIND(info) (((unsigned char)(info)) >> 4)
+#endif
+
+#ifndef ELF_ST_TYPE
+#define ELF_ST_TYPE(info) (((unsigned char)(info)) & 0xF)
+#endif
+
+// Some platforms use a special .opd section to store function pointers.
+const char kOpdSectionName[] = ".opd";
+
+#if (defined(__powerpc__) && !(_CALL_ELF > 1)) || defined(__ia64)
+// Use opd section for function descriptors on these platforms, the function
+// address is the first word of the descriptor.
+enum { kPlatformUsesOPDSections = 1 };
+#else  // not PPC or IA64
+enum { kPlatformUsesOPDSections = 0 };
+#endif
+
+// This works for PowerPC & IA64 only.  A function descriptor consist of two
+// pointers and the first one is the function's entry.
+const size_t kFunctionDescriptorSize = sizeof(void *) * 2;
+
+const int kMaxDecorators = 10;  // Seems like a reasonable upper limit.
+
+struct InstalledSymbolDecorator {
+  SymbolDecorator fn;
+  void *arg;
+  int ticket;
+};
+
+int g_num_decorators;
+InstalledSymbolDecorator g_decorators[kMaxDecorators];
+
+struct FileMappingHint {
+  const void *start;
+  const void *end;
+  uint64_t offset;
+  const char *filename;
+};
+
+// Protects g_decorators.
+// We are using SpinLock and not a Mutex here, because we may be called
+// from inside Mutex::Lock itself, and it prohibits recursive calls.
+// This happens in e.g. base/stacktrace_syscall_unittest.
+// Moreover, we are using only TryLock(), if the decorator list
+// is being modified (is busy), we skip all decorators, and possibly
+// loose some info. Sorry, that's the best we could do.
+ABSL_CONST_INIT absl::base_internal::SpinLock g_decorators_mu(
+    absl::kConstInit, absl::base_internal::SCHEDULE_KERNEL_ONLY);
+
+const int kMaxFileMappingHints = 8;
+int g_num_file_mapping_hints;
+FileMappingHint g_file_mapping_hints[kMaxFileMappingHints];
+// Protects g_file_mapping_hints.
+ABSL_CONST_INIT absl::base_internal::SpinLock g_file_mapping_mu(
+    absl::kConstInit, absl::base_internal::SCHEDULE_KERNEL_ONLY);
+
+// Async-signal-safe function to zero a buffer.
+// memset() is not guaranteed to be async-signal-safe.
+static void SafeMemZero(void* p, size_t size) {
+  unsigned char *c = static_cast<unsigned char *>(p);
+  while (size--) {
+    *c++ = 0;
+  }
+}
+
+struct ObjFile {
+  ObjFile()
+      : filename(nullptr),
+        start_addr(nullptr),
+        end_addr(nullptr),
+        offset(0),
+        fd(-1),
+        elf_type(-1) {
+    SafeMemZero(&elf_header, sizeof(elf_header));
+    SafeMemZero(&phdr[0], sizeof(phdr));
+  }
+
+  char *filename;
+  const void *start_addr;
+  const void *end_addr;
+  uint64_t offset;
+
+  // The following fields are initialized on the first access to the
+  // object file.
+  int fd;
+  int elf_type;
+  ElfW(Ehdr) elf_header;
+
+  // PT_LOAD program header describing executable code.
+  // Normally we expect just one, but SWIFT binaries have two.
+  // CUDA binaries have 3 (see cr/473913254 description).
+  std::array<ElfW(Phdr), 4> phdr;
+};
+
+// Build 4-way associative cache for symbols. Within each cache line, symbols
+// are replaced in LRU order.
+enum {
+  ASSOCIATIVITY = 4,
+};
+struct SymbolCacheLine {
+  const void *pc[ASSOCIATIVITY];
+  char *name[ASSOCIATIVITY];
+
+  // age[i] is incremented when a line is accessed. it's reset to zero if the
+  // i'th entry is read.
+  uint32_t age[ASSOCIATIVITY];
+};
+
+// ---------------------------------------------------------------
+// An async-signal-safe arena for LowLevelAlloc
+static std::atomic<base_internal::LowLevelAlloc::Arena *> g_sig_safe_arena;
+
+static base_internal::LowLevelAlloc::Arena *SigSafeArena() {
+  return g_sig_safe_arena.load(std::memory_order_acquire);
+}
+
+static void InitSigSafeArena() {
+  if (SigSafeArena() == nullptr) {
+    base_internal::LowLevelAlloc::Arena *new_arena =
+        base_internal::LowLevelAlloc::NewArena(
+            base_internal::LowLevelAlloc::kAsyncSignalSafe);
+    base_internal::LowLevelAlloc::Arena *old_value = nullptr;
+    if (!g_sig_safe_arena.compare_exchange_strong(old_value, new_arena,
+                                                  std::memory_order_release,
+                                                  std::memory_order_relaxed)) {
+      // We lost a race to allocate an arena; deallocate.
+      base_internal::LowLevelAlloc::DeleteArena(new_arena);
+    }
+  }
+}
+
+// ---------------------------------------------------------------
+// An AddrMap is a vector of ObjFile, using SigSafeArena() for allocation.
+
+class AddrMap {
+ public:
+  AddrMap() : size_(0), allocated_(0), obj_(nullptr) {}
+  ~AddrMap() { base_internal::LowLevelAlloc::Free(obj_); }
+  size_t Size() const { return size_; }
+  ObjFile *At(size_t i) { return &obj_[i]; }
+  ObjFile *Add();
+  void Clear();
+
+ private:
+  size_t size_;       // count of valid elements (<= allocated_)
+  size_t allocated_;  // count of allocated elements
+  ObjFile *obj_;      // array of allocated_ elements
+  AddrMap(const AddrMap &) = delete;
+  AddrMap &operator=(const AddrMap &) = delete;
+};
+
+void AddrMap::Clear() {
+  for (size_t i = 0; i != size_; i++) {
+    At(i)->~ObjFile();
+  }
+  size_ = 0;
+}
+
+ObjFile *AddrMap::Add() {
+  if (size_ == allocated_) {
+    size_t new_allocated = allocated_ * 2 + 50;
+    ObjFile *new_obj_ =
+        static_cast<ObjFile *>(base_internal::LowLevelAlloc::AllocWithArena(
+            new_allocated * sizeof(*new_obj_), SigSafeArena()));
+    if (obj_) {
+      memcpy(new_obj_, obj_, allocated_ * sizeof(*new_obj_));
+      base_internal::LowLevelAlloc::Free(obj_);
+    }
+    obj_ = new_obj_;
+    allocated_ = new_allocated;
+  }
+  return new (&obj_[size_++]) ObjFile;
+}
+
+class CachingFile {
+ public:
+  // Setup reader for fd that uses buf[0, buf_size-1] as a cache.
+  CachingFile(int fd, char *buf, size_t buf_size)
+      : fd_(fd),
+        cache_(buf),
+        cache_size_(buf_size),
+        cache_start_(0),
+        cache_limit_(0) {}
+
+  int fd() const { return fd_; }
+  ssize_t ReadFromOffset(void *buf, size_t count, off_t offset);
+  bool ReadFromOffsetExact(void *buf, size_t count, off_t offset);
+
+ private:
+  // Bytes [cache_start_, cache_limit_-1] from fd_ are stored in
+  // a prefix of cache_[0, cache_size_-1].
+  int fd_;
+  char *cache_;
+  size_t cache_size_;
+  off_t cache_start_;
+  off_t cache_limit_;
+};
+
+// ---------------------------------------------------------------
+
+enum FindSymbolResult { SYMBOL_NOT_FOUND = 1, SYMBOL_TRUNCATED, SYMBOL_FOUND };
+
+class Symbolizer {
+ public:
+  Symbolizer();
+  ~Symbolizer();
+  const char *GetSymbol(const void *const pc);
+
+ private:
+  char *CopyString(const char *s) {
+    size_t len = strlen(s);
+    char *dst = static_cast<char *>(
+        base_internal::LowLevelAlloc::AllocWithArena(len + 1, SigSafeArena()));
+    ABSL_RAW_CHECK(dst != nullptr, "out of memory");
+    memcpy(dst, s, len + 1);
+    return dst;
+  }
+  ObjFile *FindObjFile(const void *const start,
+                       size_t size) ABSL_ATTRIBUTE_NOINLINE;
+  static bool RegisterObjFile(const char *filename,
+                              const void *const start_addr,
+                              const void *const end_addr, uint64_t offset,
+                              void *arg);
+  SymbolCacheLine *GetCacheLine(const void *const pc);
+  const char *FindSymbolInCache(const void *const pc);
+  const char *InsertSymbolInCache(const void *const pc, const char *name);
+  void AgeSymbols(SymbolCacheLine *line);
+  void ClearAddrMap();
+  FindSymbolResult GetSymbolFromObjectFile(const ObjFile &obj,
+                                           const void *const pc,
+                                           const ptrdiff_t relocation,
+                                           char *out, size_t out_size,
+                                           char *tmp_buf, size_t tmp_buf_size);
+  const char *GetUncachedSymbol(const void *pc);
+
+  enum {
+    SYMBOL_BUF_SIZE = 3072,
+    TMP_BUF_SIZE = 1024,
+    SYMBOL_CACHE_LINES = 128,
+    FILE_CACHE_SIZE = 8192,
+  };
+
+  AddrMap addr_map_;
+
+  bool ok_;
+  bool addr_map_read_;
+
+  char symbol_buf_[SYMBOL_BUF_SIZE];
+  char file_cache_[FILE_CACHE_SIZE];
+
+  // tmp_buf_ will be used to store arrays of ElfW(Shdr) and ElfW(Sym)
+  // so we ensure that tmp_buf_ is properly aligned to store either.
+  alignas(16) char tmp_buf_[TMP_BUF_SIZE];
+  static_assert(alignof(ElfW(Shdr)) <= 16,
+                "alignment of tmp buf too small for Shdr");
+  static_assert(alignof(ElfW(Sym)) <= 16,
+                "alignment of tmp buf too small for Sym");
+
+  SymbolCacheLine symbol_cache_[SYMBOL_CACHE_LINES];
+};
+
+static std::atomic<Symbolizer *> g_cached_symbolizer;
+
+}  // namespace
+
+static size_t SymbolizerSize() {
+#if defined(__wasm__) || defined(__asmjs__)
+  auto pagesize = static_cast<size_t>(getpagesize());
+#else
+  auto pagesize = static_cast<size_t>(sysconf(_SC_PAGESIZE));
+#endif
+  return ((sizeof(Symbolizer) - 1) / pagesize + 1) * pagesize;
+}
+
+// Return (and set null) g_cached_symbolized_state if it is not null.
+// Otherwise return a new symbolizer.
+static Symbolizer *AllocateSymbolizer() {
+  InitSigSafeArena();
+  Symbolizer *symbolizer =
+      g_cached_symbolizer.exchange(nullptr, std::memory_order_acquire);
+  if (symbolizer != nullptr) {
+    return symbolizer;
+  }
+  return new (base_internal::LowLevelAlloc::AllocWithArena(
+      SymbolizerSize(), SigSafeArena())) Symbolizer();
+}
+
+// Set g_cached_symbolize_state to s if it is null, otherwise
+// delete s.
+static void FreeSymbolizer(Symbolizer *s) {
+  Symbolizer *old_cached_symbolizer = nullptr;
+  if (!g_cached_symbolizer.compare_exchange_strong(old_cached_symbolizer, s,
+                                                   std::memory_order_release,
+                                                   std::memory_order_relaxed)) {
+    s->~Symbolizer();
+    base_internal::LowLevelAlloc::Free(s);
+  }
+}
+
+Symbolizer::Symbolizer() : ok_(true), addr_map_read_(false) {
+  for (SymbolCacheLine &symbol_cache_line : symbol_cache_) {
+    for (size_t j = 0; j < ABSL_ARRAYSIZE(symbol_cache_line.name); ++j) {
+      symbol_cache_line.pc[j] = nullptr;
+      symbol_cache_line.name[j] = nullptr;
+      symbol_cache_line.age[j] = 0;
+    }
+  }
+}
+
+Symbolizer::~Symbolizer() {
+  for (SymbolCacheLine &symbol_cache_line : symbol_cache_) {
+    for (char *s : symbol_cache_line.name) {
+      base_internal::LowLevelAlloc::Free(s);
+    }
+  }
+  ClearAddrMap();
+}
+
+// We don't use assert() since it's not guaranteed to be
+// async-signal-safe.  Instead we define a minimal assertion
+// macro. So far, we don't need pretty printing for __FILE__, etc.
+#define SAFE_ASSERT(expr) ((expr) ? static_cast<void>(0) : abort())
+
+// Read up to "count" bytes from file descriptor "fd" into the buffer
+// starting at "buf" while handling short reads and EINTR.  On
+// success, return the number of bytes read.  Otherwise, return -1.
+static ssize_t ReadPersistent(int fd, void *buf, size_t count) {
+  SAFE_ASSERT(fd >= 0);
+  SAFE_ASSERT(count <= SSIZE_MAX);
+  char *buf0 = reinterpret_cast<char *>(buf);
+  size_t num_bytes = 0;
+  while (num_bytes < count) {
+    ssize_t len;
+    NO_INTR(len = read(fd, buf0 + num_bytes, count - num_bytes));
+    if (len < 0) {  // There was an error other than EINTR.
+      ABSL_RAW_LOG(WARNING, "read failed: errno=%d", errno);
+      return -1;
+    }
+    if (len == 0) {  // Reached EOF.
+      break;
+    }
+    num_bytes += static_cast<size_t>(len);
+  }
+  SAFE_ASSERT(num_bytes <= count);
+  return static_cast<ssize_t>(num_bytes);
+}
+
+// Read up to "count" bytes from "offset" into the buffer starting at "buf",
+// while handling short reads and EINTR.  On success, return the number of bytes
+// read.  Otherwise, return -1.
+ssize_t CachingFile::ReadFromOffset(void *buf, size_t count, off_t offset) {
+  char *dst = static_cast<char *>(buf);
+  size_t read = 0;
+  while (read < count) {
+    // Look in cache first.
+    if (offset >= cache_start_ && offset < cache_limit_) {
+      const char *hit_start = &cache_[offset - cache_start_];
+      const size_t n =
+          std::min(count - read, static_cast<size_t>(cache_limit_ - offset));
+      memcpy(dst, hit_start, n);
+      dst += n;
+      read += static_cast<size_t>(n);
+      offset += static_cast<off_t>(n);
+      continue;
+    }
+
+    cache_start_ = 0;
+    cache_limit_ = 0;
+    ssize_t n = pread(fd_, cache_, cache_size_, offset);
+    if (n < 0) {
+      if (errno == EINTR) {
+        continue;
+      }
+      ABSL_RAW_LOG(WARNING, "read failed: errno=%d", errno);
+      return -1;
+    }
+    if (n == 0) {  // Reached EOF.
+      break;
+    }
+
+    cache_start_ = offset;
+    cache_limit_ = offset + static_cast<off_t>(n);
+    // Next iteration will copy from cache into dst.
+  }
+  return static_cast<ssize_t>(read);
+}
+
+// Try reading exactly "count" bytes from "offset" bytes into the buffer
+// starting at "buf" while handling short reads and EINTR.  On success, return
+// true. Otherwise, return false.
+bool CachingFile::ReadFromOffsetExact(void *buf, size_t count, off_t offset) {
+  ssize_t len = ReadFromOffset(buf, count, offset);
+  return len >= 0 && static_cast<size_t>(len) == count;
+}
+
+// Returns elf_header.e_type if the file pointed by fd is an ELF binary.
+static int FileGetElfType(CachingFile *file) {
+  ElfW(Ehdr) elf_header;
+  if (!file->ReadFromOffsetExact(&elf_header, sizeof(elf_header), 0)) {
+    return -1;
+  }
+  if (memcmp(elf_header.e_ident, ELFMAG, SELFMAG) != 0) {
+    return -1;
+  }
+  return elf_header.e_type;
+}
+
+// Read the section headers in the given ELF binary, and if a section
+// of the specified type is found, set the output to this section header
+// and return true.  Otherwise, return false.
+// To keep stack consumption low, we would like this function to not get
+// inlined.
+static ABSL_ATTRIBUTE_NOINLINE bool GetSectionHeaderByType(
+    CachingFile *file, ElfW(Half) sh_num, const off_t sh_offset,
+    ElfW(Word) type, ElfW(Shdr) * out, char *tmp_buf, size_t tmp_buf_size) {
+  ElfW(Shdr) *buf = reinterpret_cast<ElfW(Shdr) *>(tmp_buf);
+  const size_t buf_entries = tmp_buf_size / sizeof(buf[0]);
+  const size_t buf_bytes = buf_entries * sizeof(buf[0]);
+
+  for (size_t i = 0; static_cast<int>(i) < sh_num;) {
+    const size_t num_bytes_left =
+        (static_cast<size_t>(sh_num) - i) * sizeof(buf[0]);
+    const size_t num_bytes_to_read =
+        (buf_bytes > num_bytes_left) ? num_bytes_left : buf_bytes;
+    const off_t offset = sh_offset + static_cast<off_t>(i * sizeof(buf[0]));
+    const ssize_t len = file->ReadFromOffset(buf, num_bytes_to_read, offset);
+    if (len < 0) {
+      ABSL_RAW_LOG(
+          WARNING,
+          "Reading %zu bytes from offset %ju returned %zd which is negative.",
+          num_bytes_to_read, static_cast<intmax_t>(offset), len);
+      return false;
+    }
+    if (static_cast<size_t>(len) % sizeof(buf[0]) != 0) {
+      ABSL_RAW_LOG(
+          WARNING,
+          "Reading %zu bytes from offset %jd returned %zd which is not a "
+          "multiple of %zu.",
+          num_bytes_to_read, static_cast<intmax_t>(offset), len,
+          sizeof(buf[0]));
+      return false;
+    }
+    const size_t num_headers_in_buf = static_cast<size_t>(len) / sizeof(buf[0]);
+    SAFE_ASSERT(num_headers_in_buf <= buf_entries);
+    for (size_t j = 0; j < num_headers_in_buf; ++j) {
+      if (buf[j].sh_type == type) {
+        *out = buf[j];
+        return true;
+      }
+    }
+    i += num_headers_in_buf;
+  }
+  return false;
+}
+
+// There is no particular reason to limit section name to 63 characters,
+// but there has (as yet) been no need for anything longer either.
+const int kMaxSectionNameLen = 64;
+
+// Small cache to use for miscellaneous file reads.
+const int kSmallFileCacheSize = 100;
+
+bool ForEachSection(int fd,
+                    const std::function<bool(absl::string_view name,
+                                             const ElfW(Shdr) &)> &callback) {
+  char buf[kSmallFileCacheSize];
+  CachingFile file(fd, buf, sizeof(buf));
+
+  ElfW(Ehdr) elf_header;
+  if (!file.ReadFromOffsetExact(&elf_header, sizeof(elf_header), 0)) {
+    return false;
+  }
+
+  // Technically it can be larger, but in practice this never happens.
+  if (elf_header.e_shentsize != sizeof(ElfW(Shdr))) {
+    return false;
+  }
+
+  ElfW(Shdr) shstrtab;
+  off_t shstrtab_offset = static_cast<off_t>(elf_header.e_shoff) +
+                          elf_header.e_shentsize * elf_header.e_shstrndx;
+  if (!file.ReadFromOffsetExact(&shstrtab, sizeof(shstrtab), shstrtab_offset)) {
+    return false;
+  }
+
+  for (int i = 0; i < elf_header.e_shnum; ++i) {
+    ElfW(Shdr) out;
+    off_t section_header_offset =
+        static_cast<off_t>(elf_header.e_shoff) + elf_header.e_shentsize * i;
+    if (!file.ReadFromOffsetExact(&out, sizeof(out), section_header_offset)) {
+      return false;
+    }
+    off_t name_offset = static_cast<off_t>(shstrtab.sh_offset) + out.sh_name;
+    char header_name[kMaxSectionNameLen];
+    ssize_t n_read =
+        file.ReadFromOffset(&header_name, kMaxSectionNameLen, name_offset);
+    if (n_read < 0) {
+      return false;
+    } else if (n_read > kMaxSectionNameLen) {
+      // Long read?
+      return false;
+    }
+
+    absl::string_view name(header_name,
+                           strnlen(header_name, static_cast<size_t>(n_read)));
+    if (!callback(name, out)) {
+      break;
+    }
+  }
+  return true;
+}
+
+// name_len should include terminating '\0'.
+bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
+                            ElfW(Shdr) * out) {
+  char header_name[kMaxSectionNameLen];
+  if (sizeof(header_name) < name_len) {
+    ABSL_RAW_LOG(WARNING,
+                 "Section name '%s' is too long (%zu); "
+                 "section will not be found (even if present).",
+                 name, name_len);
+    // No point in even trying.
+    return false;
+  }
+
+  char buf[kSmallFileCacheSize];
+  CachingFile file(fd, buf, sizeof(buf));
+  ElfW(Ehdr) elf_header;
+  if (!file.ReadFromOffsetExact(&elf_header, sizeof(elf_header), 0)) {
+    return false;
+  }
+
+  // Technically it can be larger, but in practice this never happens.
+  if (elf_header.e_shentsize != sizeof(ElfW(Shdr))) {
+    return false;
+  }
+
+  ElfW(Shdr) shstrtab;
+  off_t shstrtab_offset = static_cast<off_t>(elf_header.e_shoff) +
+                          elf_header.e_shentsize * elf_header.e_shstrndx;
+  if (!file.ReadFromOffsetExact(&shstrtab, sizeof(shstrtab), shstrtab_offset)) {
+    return false;
+  }
+
+  for (int i = 0; i < elf_header.e_shnum; ++i) {
+    off_t section_header_offset =
+        static_cast<off_t>(elf_header.e_shoff) + elf_header.e_shentsize * i;
+    if (!file.ReadFromOffsetExact(out, sizeof(*out), section_header_offset)) {
+      return false;
+    }
+    off_t name_offset = static_cast<off_t>(shstrtab.sh_offset) + out->sh_name;
+    ssize_t n_read = file.ReadFromOffset(&header_name, name_len, name_offset);
+    if (n_read < 0) {
+      return false;
+    } else if (static_cast<size_t>(n_read) != name_len) {
+      // Short read -- name could be at end of file.
+      continue;
+    }
+    if (memcmp(header_name, name, name_len) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Compare symbols at in the same address.
+// Return true if we should pick symbol1.
+static bool ShouldPickFirstSymbol(const ElfW(Sym) & symbol1,
+                                  const ElfW(Sym) & symbol2) {
+  // If one of the symbols is weak and the other is not, pick the one
+  // this is not a weak symbol.
+  char bind1 = ELF_ST_BIND(symbol1.st_info);
+  char bind2 = ELF_ST_BIND(symbol1.st_info);
+  if (bind1 == STB_WEAK && bind2 != STB_WEAK) return false;
+  if (bind2 == STB_WEAK && bind1 != STB_WEAK) return true;
+
+  // If one of the symbols has zero size and the other is not, pick the
+  // one that has non-zero size.
+  if (symbol1.st_size != 0 && symbol2.st_size == 0) {
+    return true;
+  }
+  if (symbol1.st_size == 0 && symbol2.st_size != 0) {
+    return false;
+  }
+
+  // If one of the symbols has no type and the other is not, pick the
+  // one that has a type.
+  char type1 = ELF_ST_TYPE(symbol1.st_info);
+  char type2 = ELF_ST_TYPE(symbol1.st_info);
+  if (type1 != STT_NOTYPE && type2 == STT_NOTYPE) {
+    return true;
+  }
+  if (type1 == STT_NOTYPE && type2 != STT_NOTYPE) {
+    return false;
+  }
+
+  // Pick the first one, if we still cannot decide.
+  return true;
+}
+
+// Return true if an address is inside a section.
+static bool InSection(const void *address, ptrdiff_t relocation,
+                      const ElfW(Shdr) * section) {
+  const char *start = reinterpret_cast<const char *>(
+      section->sh_addr + static_cast<ElfW(Addr)>(relocation));
+  size_t size = static_cast<size_t>(section->sh_size);
+  return start <= address && address < (start + size);
+}
+
+static const char *ComputeOffset(const char *base, ptrdiff_t offset) {
+  // Note: cast to intptr_t to avoid undefined behavior when base evaluates to
+  // zero and offset is non-zero.
+  return reinterpret_cast<const char *>(reinterpret_cast<intptr_t>(base) +
+                                        offset);
+}
+
+// Read a symbol table and look for the symbol containing the
+// pc. Iterate over symbols in a symbol table and look for the symbol
+// containing "pc".  If the symbol is found, and its name fits in
+// out_size, the name is written into out and SYMBOL_FOUND is returned.
+// If the name does not fit, truncated name is written into out,
+// and SYMBOL_TRUNCATED is returned. Out is NUL-terminated.
+// If the symbol is not found, SYMBOL_NOT_FOUND is returned;
+// To keep stack consumption low, we would like this function to not get
+// inlined.
+static ABSL_ATTRIBUTE_NOINLINE FindSymbolResult FindSymbol(
+    const void *const pc, CachingFile *file, char *out, size_t out_size,
+    ptrdiff_t relocation, const ElfW(Shdr) * strtab, const ElfW(Shdr) * symtab,
+    const ElfW(Shdr) * opd, char *tmp_buf, size_t tmp_buf_size) {
+  if (symtab == nullptr) {
+    return SYMBOL_NOT_FOUND;
+  }
+
+  // Read multiple symbols at once to save read() calls.
+  ElfW(Sym) *buf = reinterpret_cast<ElfW(Sym) *>(tmp_buf);
+  const size_t buf_entries = tmp_buf_size / sizeof(buf[0]);
+
+  const size_t num_symbols = symtab->sh_size / symtab->sh_entsize;
+
+  // On platforms using an .opd section (PowerPC & IA64), a function symbol
+  // has the address of a function descriptor, which contains the real
+  // starting address.  However, we do not always want to use the real
+  // starting address because we sometimes want to symbolize a function
+  // pointer into the .opd section, e.g. FindSymbol(&foo,...).
+  const bool pc_in_opd = kPlatformUsesOPDSections && opd != nullptr &&
+                         InSection(pc, relocation, opd);
+  const bool deref_function_descriptor_pointer =
+      kPlatformUsesOPDSections && opd != nullptr && !pc_in_opd;
+
+  ElfW(Sym) best_match;
+  SafeMemZero(&best_match, sizeof(best_match));
+  bool found_match = false;
+  for (size_t i = 0; i < num_symbols;) {
+    off_t offset =
+        static_cast<off_t>(symtab->sh_offset + i * symtab->sh_entsize);
+    const size_t num_remaining_symbols = num_symbols - i;
+    const size_t entries_in_chunk =
+        std::min(num_remaining_symbols, buf_entries);
+    const size_t bytes_in_chunk = entries_in_chunk * sizeof(buf[0]);
+    const ssize_t len = file->ReadFromOffset(buf, bytes_in_chunk, offset);
+    SAFE_ASSERT(len >= 0);
+    SAFE_ASSERT(static_cast<size_t>(len) % sizeof(buf[0]) == 0);
+    const size_t num_symbols_in_buf = static_cast<size_t>(len) / sizeof(buf[0]);
+    SAFE_ASSERT(num_symbols_in_buf <= entries_in_chunk);
+    for (size_t j = 0; j < num_symbols_in_buf; ++j) {
+      const ElfW(Sym) &symbol = buf[j];
+
+      // For a DSO, a symbol address is relocated by the loading address.
+      // We keep the original address for opd redirection below.
+      const char *const original_start_address =
+          reinterpret_cast<const char *>(symbol.st_value);
+      const char *start_address =
+          ComputeOffset(original_start_address, relocation);
+
+#ifdef __arm__
+      // ARM functions are always aligned to multiples of two bytes; the
+      // lowest-order bit in start_address is ignored by the CPU and indicates
+      // whether the function contains ARM (0) or Thumb (1) code. We don't care
+      // about what encoding is being used; we just want the real start address
+      // of the function.
+      start_address = reinterpret_cast<const char *>(
+          reinterpret_cast<uintptr_t>(start_address) & ~1u);
+#endif
+
+      if (deref_function_descriptor_pointer &&
+          InSection(original_start_address, /*relocation=*/0, opd)) {
+        // The opd section is mapped into memory.  Just dereference
+        // start_address to get the first double word, which points to the
+        // function entry.
+        start_address = *reinterpret_cast<const char *const *>(start_address);
+      }
+
+      // If pc is inside the .opd section, it points to a function descriptor.
+      const size_t size = pc_in_opd ? kFunctionDescriptorSize : symbol.st_size;
+      const void *const end_address =
+          ComputeOffset(start_address, static_cast<ptrdiff_t>(size));
+      if (symbol.st_value != 0 &&  // Skip null value symbols.
+          symbol.st_shndx != 0 &&  // Skip undefined symbols.
+#ifdef STT_TLS
+          ELF_ST_TYPE(symbol.st_info) != STT_TLS &&  // Skip thread-local data.
+#endif                                               // STT_TLS
+          ((start_address <= pc && pc < end_address) ||
+           (start_address == pc && pc == end_address))) {
+        if (!found_match || ShouldPickFirstSymbol(symbol, best_match)) {
+          found_match = true;
+          best_match = symbol;
+        }
+      }
+    }
+    i += num_symbols_in_buf;
+  }
+
+  if (found_match) {
+    const off_t off =
+        static_cast<off_t>(strtab->sh_offset) + best_match.st_name;
+    const ssize_t n_read = file->ReadFromOffset(out, out_size, off);
+    if (n_read <= 0) {
+      // This should never happen.
+      ABSL_RAW_LOG(WARNING,
+                   "Unable to read from fd %d at offset %lld: n_read = %zd",
+                   file->fd(), static_cast<long long>(off), n_read);
+      return SYMBOL_NOT_FOUND;
+    }
+    ABSL_RAW_CHECK(static_cast<size_t>(n_read) <= out_size,
+                   "ReadFromOffset read too much data.");
+
+    // strtab->sh_offset points into .strtab-like section that contains
+    // NUL-terminated strings: '\0foo\0barbaz\0...".
+    //
+    // sh_offset+st_name points to the start of symbol name, but we don't know
+    // how long the symbol is, so we try to read as much as we have space for,
+    // and usually over-read (i.e. there is a NUL somewhere before n_read).
+    if (memchr(out, '\0', static_cast<size_t>(n_read)) == nullptr) {
+      // Either out_size was too small (n_read == out_size and no NUL), or
+      // we tried to read past the EOF (n_read < out_size) and .strtab is
+      // corrupt (missing terminating NUL; should never happen for valid ELF).
+      out[n_read - 1] = '\0';
+      return SYMBOL_TRUNCATED;
+    }
+    return SYMBOL_FOUND;
+  }
+
+  return SYMBOL_NOT_FOUND;
+}
+
+// Get the symbol name of "pc" from the file pointed by "fd".  Process
+// both regular and dynamic symbol tables if necessary.
+// See FindSymbol() comment for description of return value.
+FindSymbolResult Symbolizer::GetSymbolFromObjectFile(
+    const ObjFile &obj, const void *const pc, const ptrdiff_t relocation,
+    char *out, size_t out_size, char *tmp_buf, size_t tmp_buf_size) {
+  ElfW(Shdr) symtab;
+  ElfW(Shdr) strtab;
+  ElfW(Shdr) opd;
+  ElfW(Shdr) *opd_ptr = nullptr;
+
+  // On platforms using an .opd sections for function descriptor, read
+  // the section header.  The .opd section is in data segment and should be
+  // loaded but we check that it is mapped just to be extra careful.
+  if (kPlatformUsesOPDSections) {
+    if (GetSectionHeaderByName(obj.fd, kOpdSectionName,
+                               sizeof(kOpdSectionName) - 1, &opd) &&
+        FindObjFile(reinterpret_cast<const char *>(opd.sh_addr) + relocation,
+                    opd.sh_size) != nullptr) {
+      opd_ptr = &opd;
+    } else {
+      return SYMBOL_NOT_FOUND;
+    }
+  }
+
+  CachingFile file(obj.fd, file_cache_, sizeof(file_cache_));
+
+  // Consult a regular symbol table, then fall back to the dynamic symbol table.
+  for (const auto symbol_table_type : {SHT_SYMTAB, SHT_DYNSYM}) {
+    if (!GetSectionHeaderByType(&file, obj.elf_header.e_shnum,
+                                static_cast<off_t>(obj.elf_header.e_shoff),
+                                static_cast<ElfW(Word)>(symbol_table_type),
+                                &symtab, tmp_buf, tmp_buf_size)) {
+      continue;
+    }
+    if (!file.ReadFromOffsetExact(
+            &strtab, sizeof(strtab),
+            static_cast<off_t>(obj.elf_header.e_shoff +
+                               symtab.sh_link * sizeof(symtab)))) {
+      continue;
+    }
+    const FindSymbolResult rc =
+        FindSymbol(pc, &file, out, out_size, relocation, &strtab, &symtab,
+                   opd_ptr, tmp_buf, tmp_buf_size);
+    if (rc != SYMBOL_NOT_FOUND) {
+      return rc;
+    }
+  }
+
+  return SYMBOL_NOT_FOUND;
+}
+
+namespace {
+// Thin wrapper around a file descriptor so that the file descriptor
+// gets closed for sure.
+class FileDescriptor {
+ public:
+  explicit FileDescriptor(int fd) : fd_(fd) {}
+  FileDescriptor(const FileDescriptor &) = delete;
+  FileDescriptor &operator=(const FileDescriptor &) = delete;
+
+  ~FileDescriptor() {
+    if (fd_ >= 0) {
+      close(fd_);
+    }
+  }
+
+  int get() const { return fd_; }
+
+ private:
+  const int fd_;
+};
+
+// Helper class for reading lines from file.
+//
+// Note: we don't use ProcMapsIterator since the object is big (it has
+// a 5k array member) and uses async-unsafe functions such as sscanf()
+// and snprintf().
+class LineReader {
+ public:
+  explicit LineReader(int fd, char *buf, size_t buf_len)
+      : fd_(fd),
+        buf_len_(buf_len),
+        buf_(buf),
+        bol_(buf),
+        eol_(buf),
+        eod_(buf) {}
+
+  LineReader(const LineReader &) = delete;
+  LineReader &operator=(const LineReader &) = delete;
+
+  // Read '\n'-terminated line from file.  On success, modify "bol"
+  // and "eol", then return true.  Otherwise, return false.
+  //
+  // Note: if the last line doesn't end with '\n', the line will be
+  // dropped.  It's an intentional behavior to make the code simple.
+  bool ReadLine(const char **bol, const char **eol) {
+    if (BufferIsEmpty()) {  // First time.
+      const ssize_t num_bytes = ReadPersistent(fd_, buf_, buf_len_);
+      if (num_bytes <= 0) {  // EOF or error.
+        return false;
+      }
+      eod_ = buf_ + num_bytes;
+      bol_ = buf_;
+    } else {
+      bol_ = eol_ + 1;            // Advance to the next line in the buffer.
+      SAFE_ASSERT(bol_ <= eod_);  // "bol_" can point to "eod_".
+      if (!HasCompleteLine()) {
+        const auto incomplete_line_length = static_cast<size_t>(eod_ - bol_);
+        // Move the trailing incomplete line to the beginning.
+        memmove(buf_, bol_, incomplete_line_length);
+        // Read text from file and append it.
+        char *const append_pos = buf_ + incomplete_line_length;
+        const size_t capacity_left = buf_len_ - incomplete_line_length;
+        const ssize_t num_bytes =
+            ReadPersistent(fd_, append_pos, capacity_left);
+        if (num_bytes <= 0) {  // EOF or error.
+          return false;
+        }
+        eod_ = append_pos + num_bytes;
+        bol_ = buf_;
+      }
+    }
+    eol_ = FindLineFeed();
+    if (eol_ == nullptr) {  // '\n' not found.  Malformed line.
+      return false;
+    }
+    *eol_ = '\0';  // Replace '\n' with '\0'.
+
+    *bol = bol_;
+    *eol = eol_;
+    return true;
+  }
+
+ private:
+  char *FindLineFeed() const {
+    return reinterpret_cast<char *>(
+        memchr(bol_, '\n', static_cast<size_t>(eod_ - bol_)));
+  }
+
+  bool BufferIsEmpty() const { return buf_ == eod_; }
+
+  bool HasCompleteLine() const {
+    return !BufferIsEmpty() && FindLineFeed() != nullptr;
+  }
+
+  const int fd_;
+  const size_t buf_len_;
+  char *const buf_;
+  char *bol_;
+  char *eol_;
+  const char *eod_;  // End of data in "buf_".
+};
+}  // namespace
+
+// Place the hex number read from "start" into "*hex".  The pointer to
+// the first non-hex character or "end" is returned.
+static const char *GetHex(const char *start, const char *end,
+                          uint64_t *const value) {
+  uint64_t hex = 0;
+  const char *p;
+  for (p = start; p < end; ++p) {
+    int ch = *p;
+    if ((ch >= '0' && ch <= '9') || (ch >= 'A' && ch <= 'F') ||
+        (ch >= 'a' && ch <= 'f')) {
+      hex = (hex << 4) |
+            static_cast<uint64_t>(ch < 'A' ? ch - '0' : (ch & 0xF) + 9);
+    } else {  // Encountered the first non-hex character.
+      break;
+    }
+  }
+  SAFE_ASSERT(p <= end);
+  *value = hex;
+  return p;
+}
+
+static const char *GetHex(const char *start, const char *end,
+                          const void **const addr) {
+  uint64_t hex = 0;
+  const char *p = GetHex(start, end, &hex);
+  *addr = reinterpret_cast<void *>(hex);
+  return p;
+}
+
+// Normally we are only interested in "r?x" maps.
+// On the PowerPC, function pointers point to descriptors in the .opd
+// section.  The descriptors themselves are not executable code, so
+// we need to relax the check below to "r??".
+static bool ShouldUseMapping(const char *const flags) {
+  return flags[0] == 'r' && (kPlatformUsesOPDSections || flags[2] == 'x');
+}
+
+// Read /proc/self/maps and run "callback" for each mmapped file found.  If
+// "callback" returns false, stop scanning and return true. Else continue
+// scanning /proc/self/maps. Return true if no parse error is found.
+static ABSL_ATTRIBUTE_NOINLINE bool ReadAddrMap(
+    bool (*callback)(const char *filename, const void *const start_addr,
+                     const void *const end_addr, uint64_t offset, void *arg),
+    void *arg, void *tmp_buf, size_t tmp_buf_size) {
+  // Use /proc/self/task/<pid>/maps instead of /proc/self/maps. The latter
+  // requires kernel to stop all threads, and is significantly slower when there
+  // are 1000s of threads.
+  char maps_path[80];
+  snprintf(maps_path, sizeof(maps_path), "/proc/self/task/%d/maps", getpid());
+
+  int maps_fd;
+  NO_INTR(maps_fd = open(maps_path, O_RDONLY));
+  FileDescriptor wrapped_maps_fd(maps_fd);
+  if (wrapped_maps_fd.get() < 0) {
+    ABSL_RAW_LOG(WARNING, "%s: errno=%d", maps_path, errno);
+    return false;
+  }
+
+  // Iterate over maps and look for the map containing the pc.  Then
+  // look into the symbol tables inside.
+  LineReader reader(wrapped_maps_fd.get(), static_cast<char *>(tmp_buf),
+                    tmp_buf_size);
+  while (true) {
+    const char *cursor;
+    const char *eol;
+    if (!reader.ReadLine(&cursor, &eol)) {  // EOF or malformed line.
+      break;
+    }
+
+    const char *line = cursor;
+    const void *start_address;
+    // Start parsing line in /proc/self/maps.  Here is an example:
+    //
+    // 08048000-0804c000 r-xp 00000000 08:01 2142121    /bin/cat
+    //
+    // We want start address (08048000), end address (0804c000), flags
+    // (r-xp) and file name (/bin/cat).
+
+    // Read start address.
+    cursor = GetHex(cursor, eol, &start_address);
+    if (cursor == eol || *cursor != '-') {
+      ABSL_RAW_LOG(WARNING, "Corrupt /proc/self/maps line: %s", line);
+      return false;
+    }
+    ++cursor;  // Skip '-'.
+
+    // Read end address.
+    const void *end_address;
+    cursor = GetHex(cursor, eol, &end_address);
+    if (cursor == eol || *cursor != ' ') {
+      ABSL_RAW_LOG(WARNING, "Corrupt /proc/self/maps line: %s", line);
+      return false;
+    }
+    ++cursor;  // Skip ' '.
+
+    // Read flags.  Skip flags until we encounter a space or eol.
+    const char *const flags_start = cursor;
+    while (cursor < eol && *cursor != ' ') {
+      ++cursor;
+    }
+    // We expect at least four letters for flags (ex. "r-xp").
+    if (cursor == eol || cursor < flags_start + 4) {
+      ABSL_RAW_LOG(WARNING, "Corrupt /proc/self/maps: %s", line);
+      return false;
+    }
+
+    // Check flags.
+    if (!ShouldUseMapping(flags_start)) {
+      continue;  // We skip this map.
+    }
+    ++cursor;  // Skip ' '.
+
+    // Read file offset.
+    uint64_t offset;
+    cursor = GetHex(cursor, eol, &offset);
+    ++cursor;  // Skip ' '.
+
+    // Skip to file name.  "cursor" now points to dev.  We need to skip at least
+    // two spaces for dev and inode.
+    int num_spaces = 0;
+    while (cursor < eol) {
+      if (*cursor == ' ') {
+        ++num_spaces;
+      } else if (num_spaces >= 2) {
+        // The first non-space character after  skipping two spaces
+        // is the beginning of the file name.
+        break;
+      }
+      ++cursor;
+    }
+
+    // Check whether this entry corresponds to our hint table for the true
+    // filename.
+    bool hinted =
+        GetFileMappingHint(&start_address, &end_address, &offset, &cursor);
+    if (!hinted && (cursor == eol || cursor[0] == '[')) {
+      // not an object file, typically [vdso] or [vsyscall]
+      continue;
+    }
+    if (!callback(cursor, start_address, end_address, offset, arg)) break;
+  }
+  return true;
+}
+
+// Find the objfile mapped in address region containing [addr, addr + len).
+ObjFile *Symbolizer::FindObjFile(const void *const addr, size_t len) {
+  for (int i = 0; i < 2; ++i) {
+    if (!ok_) return nullptr;
+
+    // Read /proc/self/maps if necessary
+    if (!addr_map_read_) {
+      addr_map_read_ = true;
+      if (!ReadAddrMap(RegisterObjFile, this, tmp_buf_, TMP_BUF_SIZE)) {
+        ok_ = false;
+        return nullptr;
+      }
+    }
+
+    size_t lo = 0;
+    size_t hi = addr_map_.Size();
+    while (lo < hi) {
+      size_t mid = (lo + hi) / 2;
+      if (addr < addr_map_.At(mid)->end_addr) {
+        hi = mid;
+      } else {
+        lo = mid + 1;
+      }
+    }
+    if (lo != addr_map_.Size()) {
+      ObjFile *obj = addr_map_.At(lo);
+      SAFE_ASSERT(obj->end_addr > addr);
+      if (addr >= obj->start_addr &&
+          reinterpret_cast<const char *>(addr) + len <= obj->end_addr)
+        return obj;
+    }
+
+    // The address mapping may have changed since it was last read.  Retry.
+    ClearAddrMap();
+  }
+  return nullptr;
+}
+
+void Symbolizer::ClearAddrMap() {
+  for (size_t i = 0; i != addr_map_.Size(); i++) {
+    ObjFile *o = addr_map_.At(i);
+    base_internal::LowLevelAlloc::Free(o->filename);
+    if (o->fd >= 0) {
+      close(o->fd);
+    }
+  }
+  addr_map_.Clear();
+  addr_map_read_ = false;
+}
+
+// Callback for ReadAddrMap to register objfiles in an in-memory table.
+bool Symbolizer::RegisterObjFile(const char *filename,
+                                 const void *const start_addr,
+                                 const void *const end_addr, uint64_t offset,
+                                 void *arg) {
+  Symbolizer *impl = static_cast<Symbolizer *>(arg);
+
+  // Files are supposed to be added in the increasing address order.  Make
+  // sure that's the case.
+  size_t addr_map_size = impl->addr_map_.Size();
+  if (addr_map_size != 0) {
+    ObjFile *old = impl->addr_map_.At(addr_map_size - 1);
+    if (old->end_addr > end_addr) {
+      ABSL_RAW_LOG(ERROR,
+                   "Unsorted addr map entry: 0x%" PRIxPTR ": %s <-> 0x%" PRIxPTR
+                   ": %s",
+                   reinterpret_cast<uintptr_t>(end_addr), filename,
+                   reinterpret_cast<uintptr_t>(old->end_addr), old->filename);
+      return true;
+    } else if (old->end_addr == end_addr) {
+      // The same entry appears twice. This sometimes happens for [vdso].
+      if (old->start_addr != start_addr ||
+          strcmp(old->filename, filename) != 0) {
+        ABSL_RAW_LOG(ERROR,
+                     "Duplicate addr 0x%" PRIxPTR ": %s <-> 0x%" PRIxPTR ": %s",
+                     reinterpret_cast<uintptr_t>(end_addr), filename,
+                     reinterpret_cast<uintptr_t>(old->end_addr), old->filename);
+      }
+      return true;
+    } else if (old->end_addr == start_addr &&
+               reinterpret_cast<uintptr_t>(old->start_addr) - old->offset ==
+                   reinterpret_cast<uintptr_t>(start_addr) - offset &&
+               strcmp(old->filename, filename) == 0) {
+      // Two contiguous map entries that span a contiguous region of the file,
+      // perhaps because some part of the file was mlock()ed. Combine them.
+      old->end_addr = end_addr;
+      return true;
+    }
+  }
+  ObjFile *obj = impl->addr_map_.Add();
+  obj->filename = impl->CopyString(filename);
+  obj->start_addr = start_addr;
+  obj->end_addr = end_addr;
+  obj->offset = offset;
+  obj->elf_type = -1;  // filled on demand
+  obj->fd = -1;        // opened on demand
+  return true;
+}
+
+// This function wraps the Demangle function to provide an interface
+// where the input symbol is demangled in-place.
+// To keep stack consumption low, we would like this function to not
+// get inlined.
+static ABSL_ATTRIBUTE_NOINLINE void DemangleInplace(char *out, size_t out_size,
+                                                    char *tmp_buf,
+                                                    size_t tmp_buf_size) {
+  if (Demangle(out, tmp_buf, tmp_buf_size)) {
+    // Demangling succeeded. Copy to out if the space allows.
+    size_t len = strlen(tmp_buf);
+    if (len + 1 <= out_size) {  // +1 for '\0'.
+      SAFE_ASSERT(len < tmp_buf_size);
+      memmove(out, tmp_buf, len + 1);
+    }
+  }
+}
+
+SymbolCacheLine *Symbolizer::GetCacheLine(const void *const pc) {
+  uintptr_t pc0 = reinterpret_cast<uintptr_t>(pc);
+  pc0 >>= 3;  // drop the low 3 bits
+
+  // Shuffle bits.
+  pc0 ^= (pc0 >> 6) ^ (pc0 >> 12) ^ (pc0 >> 18);
+  return &symbol_cache_[pc0 % SYMBOL_CACHE_LINES];
+}
+
+void Symbolizer::AgeSymbols(SymbolCacheLine *line) {
+  for (uint32_t &age : line->age) {
+    ++age;
+  }
+}
+
+const char *Symbolizer::FindSymbolInCache(const void *const pc) {
+  if (pc == nullptr) return nullptr;
+
+  SymbolCacheLine *line = GetCacheLine(pc);
+  for (size_t i = 0; i < ABSL_ARRAYSIZE(line->pc); ++i) {
+    if (line->pc[i] == pc) {
+      AgeSymbols(line);
+      line->age[i] = 0;
+      return line->name[i];
+    }
+  }
+  return nullptr;
+}
+
+const char *Symbolizer::InsertSymbolInCache(const void *const pc,
+                                            const char *name) {
+  SAFE_ASSERT(pc != nullptr);
+
+  SymbolCacheLine *line = GetCacheLine(pc);
+  uint32_t max_age = 0;
+  size_t oldest_index = 0;
+  bool found_oldest_index = false;
+  for (size_t i = 0; i < ABSL_ARRAYSIZE(line->pc); ++i) {
+    if (line->pc[i] == nullptr) {
+      AgeSymbols(line);
+      line->pc[i] = pc;
+      line->name[i] = CopyString(name);
+      line->age[i] = 0;
+      return line->name[i];
+    }
+    if (line->age[i] >= max_age) {
+      max_age = line->age[i];
+      oldest_index = i;
+      found_oldest_index = true;
+    }
+  }
+
+  AgeSymbols(line);
+  ABSL_RAW_CHECK(found_oldest_index, "Corrupt cache");
+  base_internal::LowLevelAlloc::Free(line->name[oldest_index]);
+  line->pc[oldest_index] = pc;
+  line->name[oldest_index] = CopyString(name);
+  line->age[oldest_index] = 0;
+  return line->name[oldest_index];
+}
+
+static void MaybeOpenFdFromSelfExe(ObjFile *obj) {
+  if (memcmp(obj->start_addr, ELFMAG, SELFMAG) != 0) {
+    return;
+  }
+  int fd = open("/proc/self/exe", O_RDONLY);
+  if (fd == -1) {
+    return;
+  }
+  // Verify that contents of /proc/self/exe matches in-memory image of
+  // the binary. This can fail if the "deleted" binary is in fact not
+  // the main executable, or for binaries that have the first PT_LOAD
+  // segment smaller than 4K. We do it in four steps so that the
+  // buffer is smaller and we don't consume too much stack space.
+  const char *mem = reinterpret_cast<const char *>(obj->start_addr);
+  for (int i = 0; i < 4; ++i) {
+    char buf[1024];
+    ssize_t n = read(fd, buf, sizeof(buf));
+    if (n != sizeof(buf) || memcmp(buf, mem, sizeof(buf)) != 0) {
+      close(fd);
+      return;
+    }
+    mem += sizeof(buf);
+  }
+  obj->fd = fd;
+}
+
+static bool MaybeInitializeObjFile(ObjFile *obj) {
+  if (obj->fd < 0) {
+    obj->fd = open(obj->filename, O_RDONLY);
+
+    if (obj->fd < 0) {
+      // Getting /proc/self/exe here means that we were hinted.
+      if (strcmp(obj->filename, "/proc/self/exe") == 0) {
+        // /proc/self/exe may be inaccessible (due to setuid, etc.), so try
+        // accessing the binary via argv0.
+        if (argv0_value != nullptr) {
+          obj->fd = open(argv0_value, O_RDONLY);
+        }
+      } else {
+        MaybeOpenFdFromSelfExe(obj);
+      }
+    }
+
+    if (obj->fd < 0) {
+      ABSL_RAW_LOG(WARNING, "%s: open failed: errno=%d", obj->filename, errno);
+      return false;
+    }
+
+    char buf[kSmallFileCacheSize];
+    CachingFile file(obj->fd, buf, sizeof(buf));
+
+    obj->elf_type = FileGetElfType(&file);
+    if (obj->elf_type < 0) {
+      ABSL_RAW_LOG(WARNING, "%s: wrong elf type: %d", obj->filename,
+                   obj->elf_type);
+      return false;
+    }
+
+    if (!file.ReadFromOffsetExact(&obj->elf_header, sizeof(obj->elf_header),
+                                  0)) {
+      ABSL_RAW_LOG(WARNING, "%s: failed to read elf header", obj->filename);
+      return false;
+    }
+    const int phnum = obj->elf_header.e_phnum;
+    const int phentsize = obj->elf_header.e_phentsize;
+    auto phoff = static_cast<off_t>(obj->elf_header.e_phoff);
+    size_t num_interesting_load_segments = 0;
+    for (int j = 0; j < phnum; j++) {
+      ElfW(Phdr) phdr;
+      if (!file.ReadFromOffsetExact(&phdr, sizeof(phdr), phoff)) {
+        ABSL_RAW_LOG(WARNING, "%s: failed to read program header %d",
+                     obj->filename, j);
+        return false;
+      }
+      phoff += phentsize;
+
+#if defined(__powerpc__) && !(_CALL_ELF > 1)
+      // On the PowerPC ELF v1 ABI, function pointers actually point to function
+      // descriptors. These descriptors are stored in an .opd section, which is
+      // mapped read-only. We thus need to look at all readable segments, not
+      // just the executable ones.
+      constexpr int interesting = PF_R;
+#else
+      constexpr int interesting = PF_X | PF_R;
+#endif
+
+      if (phdr.p_type != PT_LOAD
+          || (phdr.p_flags & interesting) != interesting) {
+        // Not a LOAD segment, not executable code, and not a function
+        // descriptor.
+        continue;
+      }
+      if (num_interesting_load_segments < obj->phdr.size()) {
+        memcpy(&obj->phdr[num_interesting_load_segments++], &phdr, sizeof(phdr));
+      } else {
+        ABSL_RAW_LOG(
+            WARNING, "%s: too many interesting LOAD segments: %zu >= %zu",
+            obj->filename, num_interesting_load_segments, obj->phdr.size());
+        break;
+      }
+    }
+    if (num_interesting_load_segments == 0) {
+      // This object has no interesting LOAD segments. That's unexpected.
+      ABSL_RAW_LOG(WARNING, "%s: no interesting LOAD segments", obj->filename);
+      return false;
+    }
+  }
+  return true;
+}
+
+// The implementation of our symbolization routine.  If it
+// successfully finds the symbol containing "pc" and obtains the
+// symbol name, returns pointer to that symbol. Otherwise, returns nullptr.
+// If any symbol decorators have been installed via InstallSymbolDecorator(),
+// they are called here as well.
+// To keep stack consumption low, we would like this function to not
+// get inlined.
+const char *Symbolizer::GetUncachedSymbol(const void *pc) {
+  ObjFile *const obj = FindObjFile(pc, 1);
+  ptrdiff_t relocation = 0;
+  int fd = -1;
+  if (obj != nullptr) {
+    if (MaybeInitializeObjFile(obj)) {
+      const size_t start_addr = reinterpret_cast<size_t>(obj->start_addr);
+      if (obj->elf_type == ET_DYN && start_addr >= obj->offset) {
+        // This object was relocated.
+        //
+        // For obj->offset > 0, adjust the relocation since a mapping at offset
+        // X in the file will have a start address of [true relocation]+X.
+        relocation = static_cast<ptrdiff_t>(start_addr - obj->offset);
+
+        // Note: some binaries have multiple LOAD segments that can contain
+        // function pointers. We must find the right one.
+        ElfW(Phdr) *phdr = nullptr;
+        for (size_t j = 0; j < obj->phdr.size(); j++) {
+          ElfW(Phdr) &p = obj->phdr[j];
+          if (p.p_type != PT_LOAD) {
+            // We only expect PT_LOADs. This must be PT_NULL that we didn't
+            // write over (i.e. we exhausted all interesting PT_LOADs).
+            ABSL_RAW_CHECK(p.p_type == PT_NULL, "unexpected p_type");
+            break;
+          }
+          if (pc < reinterpret_cast<void *>(start_addr + p.p_vaddr + p.p_memsz)) {
+            phdr = &p;
+            break;
+          }
+        }
+        if (phdr == nullptr) {
+          // That's unexpected. Hope for the best.
+          ABSL_RAW_LOG(
+              WARNING,
+              "%s: unable to find LOAD segment for pc: %p, start_addr: %zx",
+              obj->filename, pc, start_addr);
+        } else {
+          // Adjust relocation in case phdr.p_vaddr != 0.
+          // This happens for binaries linked with `lld --rosegment`, and for
+          // binaries linked with BFD `ld -z separate-code`.
+          relocation -= phdr->p_vaddr - phdr->p_offset;
+        }
+      }
+
+      fd = obj->fd;
+      if (GetSymbolFromObjectFile(*obj, pc, relocation, symbol_buf_,
+                                  sizeof(symbol_buf_), tmp_buf_,
+                                  sizeof(tmp_buf_)) == SYMBOL_FOUND) {
+        // Only try to demangle the symbol name if it fit into symbol_buf_.
+        DemangleInplace(symbol_buf_, sizeof(symbol_buf_), tmp_buf_,
+                        sizeof(tmp_buf_));
+      }
+    }
+  } else {
+#if ABSL_HAVE_VDSO_SUPPORT
+    VDSOSupport vdso;
+    if (vdso.IsPresent()) {
+      VDSOSupport::SymbolInfo symbol_info;
+      if (vdso.LookupSymbolByAddress(pc, &symbol_info)) {
+        // All VDSO symbols are known to be short.
+        size_t len = strlen(symbol_info.name);
+        ABSL_RAW_CHECK(len + 1 < sizeof(symbol_buf_),
+                       "VDSO symbol unexpectedly long");
+        memcpy(symbol_buf_, symbol_info.name, len + 1);
+      }
+    }
+#endif
+  }
+
+  if (g_decorators_mu.TryLock()) {
+    if (g_num_decorators > 0) {
+      SymbolDecoratorArgs decorator_args = {
+          pc,       relocation,       fd,     symbol_buf_, sizeof(symbol_buf_),
+          tmp_buf_, sizeof(tmp_buf_), nullptr};
+      for (int i = 0; i < g_num_decorators; ++i) {
+        decorator_args.arg = g_decorators[i].arg;
+        g_decorators[i].fn(&decorator_args);
+      }
+    }
+    g_decorators_mu.Unlock();
+  }
+  if (symbol_buf_[0] == '\0') {
+    return nullptr;
+  }
+  symbol_buf_[sizeof(symbol_buf_) - 1] = '\0';  // Paranoia.
+  return InsertSymbolInCache(pc, symbol_buf_);
+}
+
+const char *Symbolizer::GetSymbol(const void *pc) {
+  const char *entry = FindSymbolInCache(pc);
+  if (entry != nullptr) {
+    return entry;
+  }
+  symbol_buf_[0] = '\0';
+
+#ifdef __hppa__
+  {
+    // In some contexts (e.g., return addresses), PA-RISC uses the lowest two
+    // bits of the address to indicate the privilege level. Clear those bits
+    // before trying to symbolize.
+    const auto pc_bits = reinterpret_cast<uintptr_t>(pc);
+    const auto address = pc_bits & ~0x3;
+    entry = GetUncachedSymbol(reinterpret_cast<const void *>(address));
+    if (entry != nullptr) {
+      return entry;
+    }
+
+    // In some contexts, PA-RISC also uses bit 1 of the address to indicate that
+    // this is a cross-DSO function pointer. Such function pointers actually
+    // point to a procedure label, a struct whose first 32-bit (pointer) element
+    // actually points to the function text. With no symbol found for this
+    // address so far, try interpreting it as a cross-DSO function pointer and
+    // see how that goes.
+    if (pc_bits & 0x2) {
+      return GetUncachedSymbol(*reinterpret_cast<const void *const *>(address));
+    }
+
+    return nullptr;
+  }
+#else
+  return GetUncachedSymbol(pc);
+#endif
+}
+
+bool RemoveAllSymbolDecorators(void) {
+  if (!g_decorators_mu.TryLock()) {
+    // Someone else is using decorators. Get out.
+    return false;
+  }
+  g_num_decorators = 0;
+  g_decorators_mu.Unlock();
+  return true;
+}
+
+bool RemoveSymbolDecorator(int ticket) {
+  if (!g_decorators_mu.TryLock()) {
+    // Someone else is using decorators. Get out.
+    return false;
+  }
+  for (int i = 0; i < g_num_decorators; ++i) {
+    if (g_decorators[i].ticket == ticket) {
+      while (i < g_num_decorators - 1) {
+        g_decorators[i] = g_decorators[i + 1];
+        ++i;
+      }
+      g_num_decorators = i;
+      break;
+    }
+  }
+  g_decorators_mu.Unlock();
+  return true;  // Decorator is known to be removed.
+}
+
+int InstallSymbolDecorator(SymbolDecorator decorator, void *arg) {
+  static int ticket = 0;
+
+  if (!g_decorators_mu.TryLock()) {
+    // Someone else is using decorators. Get out.
+    return -2;
+  }
+  int ret = ticket;
+  if (g_num_decorators >= kMaxDecorators) {
+    ret = -1;
+  } else {
+    g_decorators[g_num_decorators] = {decorator, arg, ticket++};
+    ++g_num_decorators;
+  }
+  g_decorators_mu.Unlock();
+  return ret;
+}
+
+bool RegisterFileMappingHint(const void *start, const void *end, uint64_t offset,
+                             const char *filename) {
+  SAFE_ASSERT(start <= end);
+  SAFE_ASSERT(filename != nullptr);
+
+  InitSigSafeArena();
+
+  if (!g_file_mapping_mu.TryLock()) {
+    return false;
+  }
+
+  bool ret = true;
+  if (g_num_file_mapping_hints >= kMaxFileMappingHints) {
+    ret = false;
+  } else {
+    // TODO(ckennelly): Move this into a string copy routine.
+    size_t len = strlen(filename);
+    char *dst = static_cast<char *>(
+        base_internal::LowLevelAlloc::AllocWithArena(len + 1, SigSafeArena()));
+    ABSL_RAW_CHECK(dst != nullptr, "out of memory");
+    memcpy(dst, filename, len + 1);
+
+    auto &hint = g_file_mapping_hints[g_num_file_mapping_hints++];
+    hint.start = start;
+    hint.end = end;
+    hint.offset = offset;
+    hint.filename = dst;
+  }
+
+  g_file_mapping_mu.Unlock();
+  return ret;
+}
+
+bool GetFileMappingHint(const void **start, const void **end, uint64_t *offset,
+                        const char **filename) {
+  if (!g_file_mapping_mu.TryLock()) {
+    return false;
+  }
+  bool found = false;
+  for (int i = 0; i < g_num_file_mapping_hints; i++) {
+    if (g_file_mapping_hints[i].start <= *start &&
+        *end <= g_file_mapping_hints[i].end) {
+      // We assume that the start_address for the mapping is the base
+      // address of the ELF section, but when [start_address,end_address) is
+      // not strictly equal to [hint.start, hint.end), that assumption is
+      // invalid.
+      //
+      // This uses the hint's start address (even though hint.start is not
+      // necessarily equal to start_address) to ensure the correct
+      // relocation is computed later.
+      *start = g_file_mapping_hints[i].start;
+      *end = g_file_mapping_hints[i].end;
+      *offset = g_file_mapping_hints[i].offset;
+      *filename = g_file_mapping_hints[i].filename;
+      found = true;
+      break;
+    }
+  }
+  g_file_mapping_mu.Unlock();
+  return found;
+}
+
+}  // namespace debugging_internal
+
+bool Symbolize(const void *pc, char *out, int out_size) {
+  // Symbolization is very slow under tsan.
+  ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN();
+  SAFE_ASSERT(out_size >= 0);
+  debugging_internal::Symbolizer *s = debugging_internal::AllocateSymbolizer();
+  const char *name = s->GetSymbol(pc);
+  bool ok = false;
+  if (name != nullptr && out_size > 0) {
+    strncpy(out, name, static_cast<size_t>(out_size));
+    ok = true;
+    if (out[static_cast<size_t>(out_size) - 1] != '\0') {
+      // strncpy() does not '\0' terminate when it truncates.  Do so, with
+      // trailing ellipsis.
+      static constexpr char kEllipsis[] = "...";
+      size_t ellipsis_size =
+          std::min(strlen(kEllipsis), static_cast<size_t>(out_size) - 1);
+      memcpy(out + static_cast<size_t>(out_size) - ellipsis_size - 1, kEllipsis,
+             ellipsis_size);
+      out[static_cast<size_t>(out_size) - 1] = '\0';
+    }
+  }
+  debugging_internal::FreeSymbolizer(s);
+  ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_END();
+  return ok;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+extern "C" bool AbslInternalGetFileMappingHint(const void **start,
+                                               const void **end, uint64_t *offset,
+                                               const char **filename) {
+  return absl::debugging_internal::GetFileMappingHint(start, end, offset,
+                                                      filename);
+}
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize_emscripten.inc b/weight/_dep/abseil-cpp/absl/debugging/symbolize_emscripten.inc
new file mode 100644
index 0000000000000000000000000000000000000000..a0f344dd9b509ed3224889a4c7dd23a718e1427e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize_emscripten.inc
@@ -0,0 +1,75 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cxxabi.h>
+#include <emscripten.h>
+
+#include <algorithm>
+#include <cstring>
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/debugging/internal/demangle.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+extern "C" {
+const char* emscripten_pc_get_function(const void* pc);
+}
+
+// clang-format off
+EM_JS(bool, HaveOffsetConverter, (),
+      { return typeof wasmOffsetConverter !== 'undefined'; });
+// clang-format on
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+void InitializeSymbolizer(const char*) {
+  if (!HaveOffsetConverter()) {
+    ABSL_RAW_LOG(INFO,
+                 "Symbolization unavailable. Rebuild with -sWASM=1 "
+                 "and -sUSE_OFFSET_CONVERTER=1.");
+  }
+}
+
+bool Symbolize(const void* pc, char* out, int out_size) {
+  // Check if we have the offset converter necessary for pc_get_function.
+  // Without it, the program will abort().
+  if (!HaveOffsetConverter()) {
+    return false;
+  }
+  if (pc == nullptr || out_size <= 0) {
+    return false;
+  }
+  const char* func_name = emscripten_pc_get_function(pc);
+  if (func_name == nullptr) {
+    return false;
+  }
+
+  strncpy(out, func_name, out_size);
+
+  if (out[out_size - 1] != '\0') {
+    // strncpy() does not '\0' terminate when it truncates.
+    static constexpr char kEllipsis[] = "...";
+    int ellipsis_size = std::min<int>(sizeof(kEllipsis) - 1, out_size - 1);
+    memcpy(out + out_size - ellipsis_size - 1, kEllipsis, ellipsis_size);
+    out[out_size - 1] = '\0';
+  }
+
+  return true;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize_test.cc b/weight/_dep/abseil-cpp/absl/debugging/symbolize_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d0feab2ffa699b92c33872abe24bb5fbcfa3b1da
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize_test.cc
@@ -0,0 +1,638 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/symbolize.h"
+
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
+#ifndef _WIN32
+#include <fcntl.h>
+#include <sys/mman.h>
+#endif
+
+#include <cstring>
+#include <iostream>
+#include <memory>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/casts.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/per_thread_tls.h"
+#include "absl/base/optimization.h"
+#include "absl/debugging/internal/stack_consumption.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+using testing::Contains;
+
+#ifdef _WIN32
+#define ABSL_SYMBOLIZE_TEST_NOINLINE __declspec(noinline)
+#else
+#define ABSL_SYMBOLIZE_TEST_NOINLINE ABSL_ATTRIBUTE_NOINLINE
+#endif
+
+// Functions to symbolize. Use C linkage to avoid mangled names.
+extern "C" {
+ABSL_SYMBOLIZE_TEST_NOINLINE void nonstatic_func() {
+  // The next line makes this a unique function to prevent the compiler from
+  // folding identical functions together.
+  volatile int x = __LINE__;
+  static_cast<void>(x);
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+ABSL_SYMBOLIZE_TEST_NOINLINE static void static_func() {
+  // The next line makes this a unique function to prevent the compiler from
+  // folding identical functions together.
+  volatile int x = __LINE__;
+  static_cast<void>(x);
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+}  // extern "C"
+
+struct Foo {
+  static void func(int x);
+};
+
+// A C++ method that should have a mangled name.
+ABSL_SYMBOLIZE_TEST_NOINLINE void Foo::func(int) {
+  // The next line makes this a unique function to prevent the compiler from
+  // folding identical functions together.
+  volatile int x = __LINE__;
+  static_cast<void>(x);
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+// Create functions that will remain in different text sections in the
+// final binary when linker option "-z,keep-text-section-prefix" is used.
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.unlikely) unlikely_func() {
+  return 0;
+}
+
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.hot) hot_func() { return 0; }
+
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.startup) startup_func() { return 0; }
+
+int ABSL_ATTRIBUTE_SECTION_VARIABLE(.text.exit) exit_func() { return 0; }
+
+int /*ABSL_ATTRIBUTE_SECTION_VARIABLE(.text)*/ regular_func() { return 0; }
+
+// Thread-local data may confuse the symbolizer, ensure that it does not.
+// Variable sizes and order are important.
+#if ABSL_PER_THREAD_TLS
+static ABSL_PER_THREAD_TLS_KEYWORD char symbolize_test_thread_small[1];
+static ABSL_PER_THREAD_TLS_KEYWORD char
+    symbolize_test_thread_big[2 * 1024 * 1024];
+#endif
+
+#if !defined(__EMSCRIPTEN__)
+static void *GetPCFromFnPtr(void *ptr) { return ptr; }
+
+// Used below to hopefully inhibit some compiler/linker optimizations
+// that may remove kHpageTextPadding, kPadding0, and kPadding1 from
+// the binary.
+static volatile bool volatile_bool = false;
+
+// Force the binary to be large enough that a THP .text remap will succeed.
+static constexpr size_t kHpageSize = 1 << 21;
+const char kHpageTextPadding[kHpageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(
+        .text) = "";
+
+#else
+static void *GetPCFromFnPtr(void *ptr) {
+  return EM_ASM_PTR(
+      { return wasmOffsetConverter.convert(wasmTable.get($0).name, 0); }, ptr);
+}
+
+#endif  // !defined(__EMSCRIPTEN__)
+
+static char try_symbolize_buffer[4096];
+
+// A wrapper function for absl::Symbolize() to make the unit test simple.  The
+// limit must be < sizeof(try_symbolize_buffer).  Returns null if
+// absl::Symbolize() returns false, otherwise returns try_symbolize_buffer with
+// the result of absl::Symbolize().
+static const char *TrySymbolizeWithLimit(void *pc, int limit) {
+  CHECK_LE(limit, sizeof(try_symbolize_buffer))
+      << "try_symbolize_buffer is too small";
+
+  // Use the heap to facilitate heap and buffer sanitizer tools.
+  auto heap_buffer = absl::make_unique<char[]>(sizeof(try_symbolize_buffer));
+  bool found = absl::Symbolize(pc, heap_buffer.get(), limit);
+  if (found) {
+    CHECK_LT(static_cast<int>(
+                 strnlen(heap_buffer.get(), static_cast<size_t>(limit))),
+             limit)
+        << "absl::Symbolize() did not properly terminate the string";
+    strncpy(try_symbolize_buffer, heap_buffer.get(),
+            sizeof(try_symbolize_buffer) - 1);
+    try_symbolize_buffer[sizeof(try_symbolize_buffer) - 1] = '\0';
+  }
+
+  return found ? try_symbolize_buffer : nullptr;
+}
+
+// A wrapper for TrySymbolizeWithLimit(), with a large limit.
+static const char *TrySymbolize(void *pc) {
+  return TrySymbolizeWithLimit(pc, sizeof(try_symbolize_buffer));
+}
+
+#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE) ||    \
+    defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE) || \
+    defined(ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE)
+
+// Test with a return address.
+void ABSL_ATTRIBUTE_NOINLINE TestWithReturnAddress() {
+#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
+  void *return_address = __builtin_return_address(0);
+  const char *symbol = TrySymbolize(return_address);
+  CHECK_NE(symbol, nullptr) << "TestWithReturnAddress failed";
+  CHECK_STREQ(symbol, "main") << "TestWithReturnAddress failed";
+  std::cout << "TestWithReturnAddress passed" << std::endl;
+#endif
+}
+
+TEST(Symbolize, Cached) {
+  // Compilers should give us pointers to them.
+  EXPECT_STREQ("nonstatic_func",
+               TrySymbolize(GetPCFromFnPtr((void *)(&nonstatic_func))));
+  // The name of an internal linkage symbol is not specified; allow either a
+  // mangled or an unmangled name here.
+  const char *static_func_symbol =
+      TrySymbolize(GetPCFromFnPtr((void *)(&static_func)));
+  EXPECT_TRUE(strcmp("static_func", static_func_symbol) == 0 ||
+              strcmp("static_func()", static_func_symbol) == 0);
+
+  EXPECT_TRUE(nullptr == TrySymbolize(nullptr));
+}
+
+TEST(Symbolize, Truncation) {
+  constexpr char kNonStaticFunc[] = "nonstatic_func";
+  EXPECT_STREQ("nonstatic_func",
+               TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)),
+                                     strlen(kNonStaticFunc) + 1));
+  EXPECT_STREQ("nonstatic_...",
+               TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)),
+                                     strlen(kNonStaticFunc) + 0));
+  EXPECT_STREQ("nonstatic...",
+               TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)),
+                                     strlen(kNonStaticFunc) - 1));
+  EXPECT_STREQ("n...", TrySymbolizeWithLimit(
+                           GetPCFromFnPtr((void *)(&nonstatic_func)), 5));
+  EXPECT_STREQ("...", TrySymbolizeWithLimit(
+                          GetPCFromFnPtr((void *)(&nonstatic_func)), 4));
+  EXPECT_STREQ("..", TrySymbolizeWithLimit(
+                         GetPCFromFnPtr((void *)(&nonstatic_func)), 3));
+  EXPECT_STREQ(
+      ".", TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)), 2));
+  EXPECT_STREQ(
+      "", TrySymbolizeWithLimit(GetPCFromFnPtr((void *)(&nonstatic_func)), 1));
+  EXPECT_EQ(nullptr, TrySymbolizeWithLimit(
+                         GetPCFromFnPtr((void *)(&nonstatic_func)), 0));
+}
+
+TEST(Symbolize, SymbolizeWithDemangling) {
+  Foo::func(100);
+#ifdef __EMSCRIPTEN__
+  // Emscripten's online symbolizer is more precise with arguments.
+  EXPECT_STREQ("Foo::func(int)",
+               TrySymbolize(GetPCFromFnPtr((void *)(&Foo::func))));
+#else
+  EXPECT_STREQ("Foo::func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&Foo::func))));
+#endif
+}
+
+TEST(Symbolize, SymbolizeSplitTextSections) {
+  EXPECT_STREQ("unlikely_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&unlikely_func))));
+  EXPECT_STREQ("hot_func()", TrySymbolize(GetPCFromFnPtr((void *)(&hot_func))));
+  EXPECT_STREQ("startup_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&startup_func))));
+  EXPECT_STREQ("exit_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&exit_func))));
+  EXPECT_STREQ("regular_func()",
+               TrySymbolize(GetPCFromFnPtr((void *)(&regular_func))));
+}
+
+// Tests that verify that Symbolize stack footprint is within some limit.
+#ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+static void *g_pc_to_symbolize;
+static char g_symbolize_buffer[4096];
+static char *g_symbolize_result;
+
+static void SymbolizeSignalHandler(int signo) {
+  if (absl::Symbolize(g_pc_to_symbolize, g_symbolize_buffer,
+                      sizeof(g_symbolize_buffer))) {
+    g_symbolize_result = g_symbolize_buffer;
+  } else {
+    g_symbolize_result = nullptr;
+  }
+}
+
+// Call Symbolize and figure out the stack footprint of this call.
+static const char *SymbolizeStackConsumption(void *pc, int *stack_consumed) {
+  g_pc_to_symbolize = pc;
+  *stack_consumed = absl::debugging_internal::GetSignalHandlerStackConsumption(
+      SymbolizeSignalHandler);
+  return g_symbolize_result;
+}
+
+static int GetStackConsumptionUpperLimit() {
+  // Symbolize stack consumption should be within 2kB.
+  int stack_consumption_upper_limit = 2048;
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER) || \
+    defined(ABSL_HAVE_MEMORY_SANITIZER) || defined(ABSL_HAVE_THREAD_SANITIZER)
+  // Account for sanitizer instrumentation requiring additional stack space.
+  stack_consumption_upper_limit *= 5;
+#endif
+  return stack_consumption_upper_limit;
+}
+
+TEST(Symbolize, SymbolizeStackConsumption) {
+  int stack_consumed = 0;
+
+  const char *symbol =
+      SymbolizeStackConsumption((void *)(&nonstatic_func), &stack_consumed);
+  EXPECT_STREQ("nonstatic_func", symbol);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, GetStackConsumptionUpperLimit());
+
+  // The name of an internal linkage symbol is not specified; allow either a
+  // mangled or an unmangled name here.
+  symbol = SymbolizeStackConsumption((void *)(&static_func), &stack_consumed);
+  EXPECT_TRUE(strcmp("static_func", symbol) == 0 ||
+              strcmp("static_func()", symbol) == 0);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, GetStackConsumptionUpperLimit());
+}
+
+TEST(Symbolize, SymbolizeWithDemanglingStackConsumption) {
+  Foo::func(100);
+  int stack_consumed = 0;
+
+  const char *symbol =
+      SymbolizeStackConsumption((void *)(&Foo::func), &stack_consumed);
+
+  EXPECT_STREQ("Foo::func()", symbol);
+  EXPECT_GT(stack_consumed, 0);
+  EXPECT_LT(stack_consumed, GetStackConsumptionUpperLimit());
+}
+
+#endif  // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+#if !defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE) && \
+    !defined(ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE)
+// Use a 64K page size for PPC.
+const size_t kPageSize = 64 << 10;
+// We place a read-only symbols into the .text section and verify that we can
+// symbolize them and other symbols after remapping them.
+const char kPadding0[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(.text) = "";
+const char kPadding1[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(.text) = "";
+
+static int FilterElfHeader(struct dl_phdr_info *info, size_t size, void *data) {
+  for (int i = 0; i < info->dlpi_phnum; i++) {
+    if (info->dlpi_phdr[i].p_type == PT_LOAD &&
+        info->dlpi_phdr[i].p_flags == (PF_R | PF_X)) {
+      const void *const vaddr =
+          absl::bit_cast<void *>(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
+      const auto segsize = info->dlpi_phdr[i].p_memsz;
+
+      const char *self_exe;
+      if (info->dlpi_name != nullptr && info->dlpi_name[0] != '\0') {
+        self_exe = info->dlpi_name;
+      } else {
+        self_exe = "/proc/self/exe";
+      }
+
+      absl::debugging_internal::RegisterFileMappingHint(
+          vaddr, reinterpret_cast<const char *>(vaddr) + segsize,
+          info->dlpi_phdr[i].p_offset, self_exe);
+
+      return 1;
+    }
+  }
+
+  return 1;
+}
+
+TEST(Symbolize, SymbolizeWithMultipleMaps) {
+  // Force kPadding0 and kPadding1 to be linked in.
+  if (volatile_bool) {
+    LOG(INFO) << kPadding0;
+    LOG(INFO) << kPadding1;
+  }
+
+  // Verify we can symbolize everything.
+  char buf[512];
+  memset(buf, 0, sizeof(buf));
+  absl::Symbolize(kPadding0, buf, sizeof(buf));
+  EXPECT_STREQ("kPadding0", buf);
+
+  memset(buf, 0, sizeof(buf));
+  absl::Symbolize(kPadding1, buf, sizeof(buf));
+  EXPECT_STREQ("kPadding1", buf);
+
+  // Specify a hint for the executable segment.
+  dl_iterate_phdr(FilterElfHeader, nullptr);
+
+  // Reload at least one page out of kPadding0, kPadding1
+  const char *ptrs[] = {kPadding0, kPadding1};
+
+  for (const char *ptr : ptrs) {
+    const int kMapFlags = MAP_ANONYMOUS | MAP_PRIVATE;
+    void *addr = mmap(nullptr, kPageSize, PROT_READ, kMapFlags, 0, 0);
+    ASSERT_NE(addr, MAP_FAILED);
+
+    // kPadding[0-1] is full of zeroes, so we can remap anywhere within it, but
+    // we ensure there is at least a full page of padding.
+    void *remapped = reinterpret_cast<void *>(
+        reinterpret_cast<uintptr_t>(ptr + kPageSize) & ~(kPageSize - 1ULL));
+
+    const int kMremapFlags = (MREMAP_MAYMOVE | MREMAP_FIXED);
+    void *ret = mremap(addr, kPageSize, kPageSize, kMremapFlags, remapped);
+    ASSERT_NE(ret, MAP_FAILED);
+  }
+
+  // Invalidate the symbolization cache so we are forced to rely on the hint.
+  absl::Symbolize(nullptr, buf, sizeof(buf));
+
+  // Verify we can still symbolize.
+  const char *expected[] = {"kPadding0", "kPadding1"};
+  const size_t offsets[] = {0, kPageSize, 2 * kPageSize, 3 * kPageSize};
+
+  for (int i = 0; i < 2; i++) {
+    for (size_t offset : offsets) {
+      memset(buf, 0, sizeof(buf));
+      absl::Symbolize(ptrs[i] + offset, buf, sizeof(buf));
+      EXPECT_STREQ(expected[i], buf);
+    }
+  }
+}
+
+// Appends string(*args->arg) to args->symbol_buf.
+static void DummySymbolDecorator(
+    const absl::debugging_internal::SymbolDecoratorArgs *args) {
+  std::string *message = static_cast<std::string *>(args->arg);
+  strncat(args->symbol_buf, message->c_str(),
+          args->symbol_buf_size - strlen(args->symbol_buf) - 1);
+}
+
+TEST(Symbolize, InstallAndRemoveSymbolDecorators) {
+  int ticket_a;
+  std::string a_message("a");
+  EXPECT_GE(ticket_a = absl::debugging_internal::InstallSymbolDecorator(
+                DummySymbolDecorator, &a_message),
+            0);
+
+  int ticket_b;
+  std::string b_message("b");
+  EXPECT_GE(ticket_b = absl::debugging_internal::InstallSymbolDecorator(
+                DummySymbolDecorator, &b_message),
+            0);
+
+  int ticket_c;
+  std::string c_message("c");
+  EXPECT_GE(ticket_c = absl::debugging_internal::InstallSymbolDecorator(
+                DummySymbolDecorator, &c_message),
+            0);
+
+  // Use addresses 4 and 8 here to ensure that we always use valid addresses
+  // even on systems that require instructions to be 32-bit aligned.
+  char *address = reinterpret_cast<char *>(4);
+  EXPECT_STREQ("abc", TrySymbolize(address));
+
+  EXPECT_TRUE(absl::debugging_internal::RemoveSymbolDecorator(ticket_b));
+
+  EXPECT_STREQ("ac", TrySymbolize(address + 4));
+
+  // Cleanup: remove all remaining decorators so other stack traces don't
+  // get mystery "ac" decoration.
+  EXPECT_TRUE(absl::debugging_internal::RemoveSymbolDecorator(ticket_a));
+  EXPECT_TRUE(absl::debugging_internal::RemoveSymbolDecorator(ticket_c));
+}
+
+// Some versions of Clang with optimizations enabled seem to be able
+// to optimize away the .data section if no variables live in the
+// section. This variable should get placed in the .data section, and
+// the test below checks for the existence of a .data section.
+static int in_data_section = 1;
+
+TEST(Symbolize, ForEachSection) {
+  int fd = TEMP_FAILURE_RETRY(open("/proc/self/exe", O_RDONLY));
+  ASSERT_NE(fd, -1);
+
+  std::vector<std::string> sections;
+  ASSERT_TRUE(absl::debugging_internal::ForEachSection(
+      fd, [&sections](const absl::string_view name, const ElfW(Shdr) &) {
+        sections.emplace_back(name);
+        return true;
+      }));
+
+  // Check for the presence of common section names.
+  EXPECT_THAT(sections, Contains(".text"));
+  EXPECT_THAT(sections, Contains(".rodata"));
+  EXPECT_THAT(sections, Contains(".bss"));
+  ++in_data_section;
+  EXPECT_THAT(sections, Contains(".data"));
+
+  close(fd);
+}
+#endif  // !ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE &&
+        // !ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
+
+// x86 specific tests.  Uses some inline assembler.
+extern "C" {
+inline void *ABSL_ATTRIBUTE_ALWAYS_INLINE inline_func() {
+  void *pc = nullptr;
+#if defined(__i386__)
+  __asm__ __volatile__("call 1f;\n 1: pop %[PC]" : [PC] "=r"(pc));
+#elif defined(__x86_64__)
+  __asm__ __volatile__("leaq 0(%%rip),%[PC];\n" : [PC] "=r"(pc));
+#endif
+  return pc;
+}
+
+void *ABSL_ATTRIBUTE_NOINLINE non_inline_func() {
+  void *pc = nullptr;
+#if defined(__i386__)
+  __asm__ __volatile__("call 1f;\n 1: pop %[PC]" : [PC] "=r"(pc));
+#elif defined(__x86_64__)
+  __asm__ __volatile__("leaq 0(%%rip),%[PC];\n" : [PC] "=r"(pc));
+#endif
+  return pc;
+}
+
+void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideNonInlineFunction() {
+#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE) && \
+    (defined(__i386__) || defined(__x86_64__))
+  void *pc = non_inline_func();
+  const char *symbol = TrySymbolize(pc);
+  CHECK_NE(symbol, nullptr) << "TestWithPCInsideNonInlineFunction failed";
+  CHECK_STREQ(symbol, "non_inline_func")
+      << "TestWithPCInsideNonInlineFunction failed";
+  std::cout << "TestWithPCInsideNonInlineFunction passed" << std::endl;
+#endif
+}
+
+void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideInlineFunction() {
+#if defined(ABSL_HAVE_ATTRIBUTE_ALWAYS_INLINE) && \
+    (defined(__i386__) || defined(__x86_64__))
+  void *pc = inline_func();  // Must be inlined.
+  const char *symbol = TrySymbolize(pc);
+  CHECK_NE(symbol, nullptr) << "TestWithPCInsideInlineFunction failed";
+  CHECK_STREQ(symbol, __FUNCTION__) << "TestWithPCInsideInlineFunction failed";
+  std::cout << "TestWithPCInsideInlineFunction passed" << std::endl;
+#endif
+}
+}
+
+#if defined(__arm__) && ABSL_HAVE_ATTRIBUTE(target) && \
+    ((__ARM_ARCH >= 7) || !defined(__ARM_PCS_VFP))
+// Test that we correctly identify bounds of Thumb functions on ARM.
+//
+// Thumb functions have the lowest-order bit set in their addresses in the ELF
+// symbol table. This requires some extra logic to properly compute function
+// bounds. To test this logic, nudge a Thumb function right up against an ARM
+// function and try to symbolize the ARM function.
+//
+// A naive implementation will simply use the Thumb function's entry point as
+// written in the symbol table and will therefore treat the Thumb function as
+// extending one byte further in the instruction stream than it actually does.
+// When asked to symbolize the start of the ARM function, it will identify an
+// overlap between the Thumb and ARM functions, and it will return the name of
+// the Thumb function.
+//
+// A correct implementation, on the other hand, will null out the lowest-order
+// bit in the Thumb function's entry point. It will correctly compute the end of
+// the Thumb function, it will find no overlap between the Thumb and ARM
+// functions, and it will return the name of the ARM function.
+//
+// Unfortunately we cannot perform this test on armv6 or lower systems that use
+// the hard float ABI because gcc refuses to compile thumb functions on such
+// systems with a "sorry, unimplemented: Thumb-1 hard-float VFP ABI" error.
+
+__attribute__((target("thumb"))) int ArmThumbOverlapThumb(int x) {
+  return x * x * x;
+}
+
+__attribute__((target("arm"))) int ArmThumbOverlapArm(int x) {
+  return x * x * x;
+}
+
+void ABSL_ATTRIBUTE_NOINLINE TestArmThumbOverlap() {
+#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
+  const char *symbol = TrySymbolize((void *)&ArmThumbOverlapArm);
+  CHECK_NE(symbol, nullptr) << "TestArmThumbOverlap failed";
+  CHECK_STREQ("ArmThumbOverlapArm()", symbol) << "TestArmThumbOverlap failed";
+  std::cout << "TestArmThumbOverlap passed" << std::endl;
+#endif
+}
+
+#endif  // defined(__arm__) && ABSL_HAVE_ATTRIBUTE(target) && ((__ARM_ARCH >= 7)
+        // || !defined(__ARM_PCS_VFP))
+
+#elif defined(_WIN32)
+#if !defined(ABSL_CONSUME_DLL)
+
+TEST(Symbolize, Basics) {
+  EXPECT_STREQ("nonstatic_func", TrySymbolize((void *)(&nonstatic_func)));
+
+  // The name of an internal linkage symbol is not specified; allow either a
+  // mangled or an unmangled name here.
+  const char *static_func_symbol = TrySymbolize((void *)(&static_func));
+  ASSERT_TRUE(static_func_symbol != nullptr);
+  EXPECT_TRUE(strstr(static_func_symbol, "static_func") != nullptr);
+
+  EXPECT_TRUE(nullptr == TrySymbolize(nullptr));
+}
+
+TEST(Symbolize, Truncation) {
+  constexpr char kNonStaticFunc[] = "nonstatic_func";
+  EXPECT_STREQ("nonstatic_func",
+               TrySymbolizeWithLimit((void *)(&nonstatic_func),
+                                     strlen(kNonStaticFunc) + 1));
+  EXPECT_STREQ("nonstatic_...",
+               TrySymbolizeWithLimit((void *)(&nonstatic_func),
+                                     strlen(kNonStaticFunc) + 0));
+  EXPECT_STREQ("nonstatic...",
+               TrySymbolizeWithLimit((void *)(&nonstatic_func),
+                                     strlen(kNonStaticFunc) - 1));
+  EXPECT_STREQ("n...", TrySymbolizeWithLimit((void *)(&nonstatic_func), 5));
+  EXPECT_STREQ("...", TrySymbolizeWithLimit((void *)(&nonstatic_func), 4));
+  EXPECT_STREQ("..", TrySymbolizeWithLimit((void *)(&nonstatic_func), 3));
+  EXPECT_STREQ(".", TrySymbolizeWithLimit((void *)(&nonstatic_func), 2));
+  EXPECT_STREQ("", TrySymbolizeWithLimit((void *)(&nonstatic_func), 1));
+  EXPECT_EQ(nullptr, TrySymbolizeWithLimit((void *)(&nonstatic_func), 0));
+}
+
+TEST(Symbolize, SymbolizeWithDemangling) {
+  const char *result = TrySymbolize((void *)(&Foo::func));
+  ASSERT_TRUE(result != nullptr);
+  EXPECT_TRUE(strstr(result, "Foo::func") != nullptr) << result;
+}
+
+#endif  // !defined(ABSL_CONSUME_DLL)
+#else   // Symbolizer unimplemented
+TEST(Symbolize, Unimplemented) {
+  char buf[64];
+  EXPECT_FALSE(absl::Symbolize((void *)(&nonstatic_func), buf, sizeof(buf)));
+  EXPECT_FALSE(absl::Symbolize((void *)(&static_func), buf, sizeof(buf)));
+  EXPECT_FALSE(absl::Symbolize((void *)(&Foo::func), buf, sizeof(buf)));
+}
+
+#endif
+
+int main(int argc, char **argv) {
+#if !defined(__EMSCRIPTEN__)
+  // Make sure kHpageTextPadding is linked into the binary.
+  if (volatile_bool) {
+    LOG(INFO) << kHpageTextPadding;
+  }
+#endif  // !defined(__EMSCRIPTEN__)
+
+#if ABSL_PER_THREAD_TLS
+  // Touch the per-thread variables.
+  symbolize_test_thread_small[0] = 0;
+  symbolize_test_thread_big[0] = 0;
+#endif
+
+  absl::InitializeSymbolizer(argv[0]);
+  testing::InitGoogleTest(&argc, argv);
+
+#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE) ||        \
+    defined(ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE) || \
+    defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE)
+  TestWithPCInsideInlineFunction();
+  TestWithPCInsideNonInlineFunction();
+  TestWithReturnAddress();
+#if defined(__arm__) && ABSL_HAVE_ATTRIBUTE(target) && \
+    ((__ARM_ARCH >= 7) || !defined(__ARM_PCS_VFP))
+  TestArmThumbOverlap();
+#endif
+#endif
+
+  return RUN_ALL_TESTS();
+}
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize_unimplemented.inc b/weight/_dep/abseil-cpp/absl/debugging/symbolize_unimplemented.inc
new file mode 100644
index 0000000000000000000000000000000000000000..db24456b0afaf974ce063638f1cfb5fce42a93e2
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize_unimplemented.inc
@@ -0,0 +1,40 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdint>
+
+#include "absl/base/internal/raw_logging.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace debugging_internal {
+
+int InstallSymbolDecorator(SymbolDecorator, void*) { return -1; }
+bool RemoveSymbolDecorator(int) { return false; }
+bool RemoveAllSymbolDecorators(void) { return false; }
+bool RegisterFileMappingHint(const void *, const void *, uint64_t, const char *) {
+  return false;
+}
+bool GetFileMappingHint(const void **, const void **, uint64_t *, const char **) {
+  return false;
+}
+
+}  // namespace debugging_internal
+
+void InitializeSymbolizer(const char*) {}
+bool Symbolize(const void *, char *, int) { return false; }
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/debugging/symbolize_win32.inc b/weight/_dep/abseil-cpp/absl/debugging/symbolize_win32.inc
new file mode 100644
index 0000000000000000000000000000000000000000..53a099a1814933cfc25e29be36a94acd3818b77f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/debugging/symbolize_win32.inc
@@ -0,0 +1,82 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// See "Retrieving Symbol Information by Address":
+// https://msdn.microsoft.com/en-us/library/windows/desktop/ms680578(v=vs.85).aspx
+
+#include <windows.h>
+
+// MSVC header dbghelp.h has a warning for an ignored typedef.
+#pragma warning(push)
+#pragma warning(disable:4091)
+#include <dbghelp.h>
+#pragma warning(pop)
+
+#pragma comment(lib, "dbghelp.lib")
+
+#include <algorithm>
+#include <cstring>
+
+#include "absl/base/internal/raw_logging.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+static HANDLE process = NULL;
+
+void InitializeSymbolizer(const char*) {
+  if (process != nullptr) {
+    return;
+  }
+  process = GetCurrentProcess();
+
+  // Symbols are not loaded until a reference is made requiring the
+  // symbols be loaded. This is the fastest, most efficient way to use
+  // the symbol handler.
+  SymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_UNDNAME);
+  if (!SymInitialize(process, nullptr, true)) {
+    // GetLastError() returns a Win32 DWORD, but we assign to
+    // unsigned long long to simplify the ABSL_RAW_LOG case below.  The uniform
+    // initialization guarantees this is not a narrowing conversion.
+    const unsigned long long error{GetLastError()};  // NOLINT(runtime/int)
+    ABSL_RAW_LOG(FATAL, "SymInitialize() failed: %llu", error);
+  }
+}
+
+bool Symbolize(const void* pc, char* out, int out_size) {
+  if (out_size <= 0) {
+    return false;
+  }
+  alignas(SYMBOL_INFO) char buf[sizeof(SYMBOL_INFO) + MAX_SYM_NAME];
+  SYMBOL_INFO* symbol = reinterpret_cast<SYMBOL_INFO*>(buf);
+  symbol->SizeOfStruct = sizeof(SYMBOL_INFO);
+  symbol->MaxNameLen = MAX_SYM_NAME;
+  if (!SymFromAddr(process, reinterpret_cast<DWORD64>(pc), nullptr, symbol)) {
+    return false;
+  }
+  const size_t out_size_t = static_cast<size_t>(out_size);
+  strncpy(out, symbol->Name, out_size_t);
+  if (out[out_size_t - 1] != '\0') {
+    // strncpy() does not '\0' terminate when it truncates.
+    static constexpr char kEllipsis[] = "...";
+    size_t ellipsis_size =
+        std::min(sizeof(kEllipsis) - 1, out_size_t - 1);
+    memcpy(out + out_size_t - ellipsis_size - 1, kEllipsis, ellipsis_size);
+    out[out_size_t - 1] = '\0';
+  }
+  return true;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/functional/BUILD.bazel b/weight/_dep/abseil-cpp/absl/functional/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..1a18af25b9e2791960e760a8e0c1a57f60424960
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/BUILD.bazel
@@ -0,0 +1,168 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "any_invocable",
+    srcs = ["internal/any_invocable.h"],
+    hdrs = ["any_invocable.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:base_internal",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/meta:type_traits",
+        "//absl/utility",
+    ],
+)
+
+cc_test(
+    name = "any_invocable_test",
+    srcs = [
+        "any_invocable_test.cc",
+        "internal/any_invocable.h",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":any_invocable",
+        "//absl/base:base_internal",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/meta:type_traits",
+        "//absl/utility",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "bind_front",
+    srcs = ["internal/front_binder.h"],
+    hdrs = ["bind_front.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:base_internal",
+        "//absl/container:compressed_tuple",
+        "//absl/meta:type_traits",
+        "//absl/utility",
+    ],
+)
+
+cc_test(
+    name = "bind_front_test",
+    srcs = ["bind_front_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":bind_front",
+        "//absl/memory",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "function_ref",
+    srcs = ["internal/function_ref.h"],
+    hdrs = ["function_ref.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":any_invocable",
+        "//absl/base:base_internal",
+        "//absl/base:core_headers",
+        "//absl/meta:type_traits",
+    ],
+)
+
+cc_test(
+    name = "function_ref_test",
+    size = "small",
+    srcs = ["function_ref_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    deps = [
+        ":any_invocable",
+        ":function_ref",
+        "//absl/container:test_instance_tracker",
+        "//absl/memory",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "overload",
+    hdrs = ["overload.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/meta:type_traits",
+    ],
+)
+
+cc_test(
+    name = "overload_test",
+    size = "small",
+    srcs = ["overload_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    deps = [
+        ":overload",
+        "//absl/base:config",
+        "//absl/strings",
+        "//absl/strings:string_view",
+        "//absl/types:variant",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "function_type_benchmark",
+    srcs = [
+        "function_type_benchmark.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    tags = ["benchmark"],
+    visibility = ["//visibility:private"],
+    deps = [
+        ":any_invocable",
+        ":function_ref",
+        "//absl/base:core_headers",
+        "@com_github_google_benchmark//:benchmark_main",
+        "@com_google_googletest//:gtest",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/functional/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/functional/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..602829cb6cc6fc3ff208d4261b811e340ac005be
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/CMakeLists.txt
@@ -0,0 +1,134 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+absl_cc_library(
+  NAME
+    any_invocable
+  SRCS
+    "internal/any_invocable.h"
+  HDRS
+    "any_invocable.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base_internal
+    absl::config
+    absl::core_headers
+    absl::type_traits
+    absl::utility
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    any_invocable_test
+  SRCS
+    "any_invocable_test.cc"
+    "internal/any_invocable.h"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::any_invocable
+    absl::base_internal
+    absl::config
+    absl::core_headers
+    absl::type_traits
+    absl::utility
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    bind_front
+  SRCS
+    "internal/front_binder.h"
+  HDRS
+    "bind_front.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base_internal
+    absl::compressed_tuple
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    bind_front_test
+  SRCS
+    "bind_front_test.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::bind_front
+    absl::memory
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    function_ref
+  SRCS
+    "internal/function_ref.h"
+  HDRS
+    "function_ref.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base_internal
+    absl::core_headers
+    absl::any_invocable
+    absl::meta
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    function_ref_test
+  SRCS
+    "function_ref_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::function_ref
+    absl::memory
+    absl::test_instance_tracker
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    overload
+  HDRS
+    "overload.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::meta
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    overload_test
+  SRCS
+    "overload_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::strings
+    GTest::gmock_main
+)
diff --git a/weight/_dep/abseil-cpp/absl/functional/function_ref.h b/weight/_dep/abseil-cpp/absl/functional/function_ref.h
new file mode 100644
index 0000000000000000000000000000000000000000..96cece551b53693ba93820d5179351cd25ac3cb3
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/function_ref.h
@@ -0,0 +1,151 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: function_ref.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the `absl::FunctionRef` type for holding a
+// non-owning reference to an object of any invocable type. This function
+// reference is typically most useful as a type-erased argument type for
+// accepting function types that neither take ownership nor copy the type; using
+// the reference type in this case avoids a copy and an allocation. Best
+// practices of other non-owning reference-like objects (such as
+// `absl::string_view`) apply here.
+//
+//  An `absl::FunctionRef` is similar in usage to a `std::function` but has the
+//  following differences:
+//
+//  * It doesn't own the underlying object.
+//  * It doesn't have a null or empty state.
+//  * It never performs deep copies or allocations.
+//  * It's much faster and cheaper to construct.
+//  * It's trivially copyable and destructable.
+//
+// Generally, `absl::FunctionRef` should not be used as a return value, data
+// member, or to initialize a `std::function`. Such usages will often lead to
+// problematic lifetime issues. Once you convert something to an
+// `absl::FunctionRef` you cannot make a deep copy later.
+//
+// This class is suitable for use wherever a "const std::function<>&"
+// would be used without making a copy. ForEach functions and other versions of
+// the visitor pattern are a good example of when this class should be used.
+//
+// This class is trivial to copy and should be passed by value.
+#ifndef ABSL_FUNCTIONAL_FUNCTION_REF_H_
+#define ABSL_FUNCTIONAL_FUNCTION_REF_H_
+
+#include <cassert>
+#include <functional>
+#include <type_traits>
+
+#include "absl/base/attributes.h"
+#include "absl/functional/internal/function_ref.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// FunctionRef
+//
+// Dummy class declaration to allow the partial specialization based on function
+// types below.
+template <typename T>
+class FunctionRef;
+
+// FunctionRef
+//
+// An `absl::FunctionRef` is a lightweight wrapper to any invocable object with
+// a compatible signature. Generally, an `absl::FunctionRef` should only be used
+// as an argument type and should be preferred as an argument over a const
+// reference to a `std::function`. `absl::FunctionRef` itself does not allocate,
+// although the wrapped invocable may.
+//
+// Example:
+//
+//   // The following function takes a function callback by const reference
+//   bool Visitor(const std::function<void(my_proto&,
+//                                         absl::string_view)>& callback);
+//
+//   // Assuming that the function is not stored or otherwise copied, it can be
+//   // replaced by an `absl::FunctionRef`:
+//   bool Visitor(absl::FunctionRef<void(my_proto&, absl::string_view)>
+//                  callback);
+//
+// Note: the assignment operator within an `absl::FunctionRef` is intentionally
+// deleted to prevent misuse; because the `absl::FunctionRef` does not own the
+// underlying type, assignment likely indicates misuse.
+template <typename R, typename... Args>
+class FunctionRef<R(Args...)> {
+ private:
+  // Used to disable constructors for objects that are not compatible with the
+  // signature of this FunctionRef.
+  template <typename F,
+            typename FR = absl::base_internal::invoke_result_t<F, Args&&...>>
+  using EnableIfCompatible =
+      typename std::enable_if<std::is_void<R>::value ||
+                              std::is_convertible<FR, R>::value>::type;
+
+ public:
+  // Constructs a FunctionRef from any invocable type.
+  template <typename F, typename = EnableIfCompatible<const F&>>
+  // NOLINTNEXTLINE(runtime/explicit)
+  FunctionRef(const F& f ABSL_ATTRIBUTE_LIFETIME_BOUND)
+      : invoker_(&absl::functional_internal::InvokeObject<F, R, Args...>) {
+    absl::functional_internal::AssertNonNull(f);
+    ptr_.obj = &f;
+  }
+
+  // Overload for function pointers. This eliminates a level of indirection that
+  // would happen if the above overload was used (it lets us store the pointer
+  // instead of a pointer to a pointer).
+  //
+  // This overload is also used for references to functions, since references to
+  // functions can decay to function pointers implicitly.
+  template <
+      typename F, typename = EnableIfCompatible<F*>,
+      absl::functional_internal::EnableIf<absl::is_function<F>::value> = 0>
+  FunctionRef(F* f)  // NOLINT(runtime/explicit)
+      : invoker_(&absl::functional_internal::InvokeFunction<F*, R, Args...>) {
+    assert(f != nullptr);
+    ptr_.fun = reinterpret_cast<decltype(ptr_.fun)>(f);
+  }
+
+  // To help prevent subtle lifetime bugs, FunctionRef is not assignable.
+  // Typically, it should only be used as an argument type.
+  FunctionRef& operator=(const FunctionRef& rhs) = delete;
+  FunctionRef(const FunctionRef& rhs) = default;
+
+  // Call the underlying object.
+  R operator()(Args... args) const {
+    return invoker_(ptr_, std::forward<Args>(args)...);
+  }
+
+ private:
+  absl::functional_internal::VoidPtr ptr_;
+  absl::functional_internal::Invoker<R, Args...> invoker_;
+};
+
+// Allow const qualified function signatures. Since FunctionRef requires
+// constness anyway we can just make this a no-op.
+template <typename R, typename... Args>
+class FunctionRef<R(Args...) const> : public FunctionRef<R(Args...)> {
+ public:
+  using FunctionRef<R(Args...)>::FunctionRef;
+};
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FUNCTIONAL_FUNCTION_REF_H_
diff --git a/weight/_dep/abseil-cpp/absl/functional/function_ref_test.cc b/weight/_dep/abseil-cpp/absl/functional/function_ref_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c0211135a2bf0b2bd0b471ce5141b54b48619e1b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/function_ref_test.cc
@@ -0,0 +1,293 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/functional/function_ref.h"
+
+#include <functional>
+#include <memory>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/test_instance_tracker.h"
+#include "absl/functional/any_invocable.h"
+#include "absl/memory/memory.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace {
+
+void RunFun(FunctionRef<void()> f) { f(); }
+
+TEST(FunctionRefTest, Lambda) {
+  bool ran = false;
+  RunFun([&] { ran = true; });
+  EXPECT_TRUE(ran);
+}
+
+int Function() { return 1337; }
+
+TEST(FunctionRefTest, Function1) {
+  FunctionRef<int()> ref(&Function);
+  EXPECT_EQ(1337, ref());
+}
+
+TEST(FunctionRefTest, Function2) {
+  FunctionRef<int()> ref(Function);
+  EXPECT_EQ(1337, ref());
+}
+
+TEST(FunctionRefTest, ConstFunction) {
+  FunctionRef<int() const> ref(Function);
+  EXPECT_EQ(1337, ref());
+}
+
+int NoExceptFunction() noexcept { return 1337; }
+
+// TODO(jdennett): Add a test for noexcept member functions.
+TEST(FunctionRefTest, NoExceptFunction) {
+  FunctionRef<int()> ref(NoExceptFunction);
+  EXPECT_EQ(1337, ref());
+}
+
+TEST(FunctionRefTest, ForwardsArgs) {
+  auto l = [](std::unique_ptr<int> i) { return *i; };
+  FunctionRef<int(std::unique_ptr<int>)> ref(l);
+  EXPECT_EQ(42, ref(absl::make_unique<int>(42)));
+}
+
+TEST(FunctionRef, ReturnMoveOnly) {
+  auto l = [] { return absl::make_unique<int>(29); };
+  FunctionRef<std::unique_ptr<int>()> ref(l);
+  EXPECT_EQ(29, *ref());
+}
+
+TEST(FunctionRef, ManyArgs) {
+  auto l = [](int a, int b, int c) { return a + b + c; };
+  FunctionRef<int(int, int, int)> ref(l);
+  EXPECT_EQ(6, ref(1, 2, 3));
+}
+
+TEST(FunctionRef, VoidResultFromNonVoidFunctor) {
+  bool ran = false;
+  auto l = [&]() -> int {
+    ran = true;
+    return 2;
+  };
+  FunctionRef<void()> ref(l);
+  ref();
+  EXPECT_TRUE(ran);
+}
+
+TEST(FunctionRef, CastFromDerived) {
+  struct Base {};
+  struct Derived : public Base {};
+
+  Derived d;
+  auto l1 = [&](Base* b) { EXPECT_EQ(&d, b); };
+  FunctionRef<void(Derived*)> ref1(l1);
+  ref1(&d);
+
+  auto l2 = [&]() -> Derived* { return &d; };
+  FunctionRef<Base*()> ref2(l2);
+  EXPECT_EQ(&d, ref2());
+}
+
+TEST(FunctionRef, VoidResultFromNonVoidFuncton) {
+  FunctionRef<void()> ref(Function);
+  ref();
+}
+
+TEST(FunctionRef, MemberPtr) {
+  struct S {
+    int i;
+  };
+
+  S s{1100111};
+  auto mem_ptr = &S::i;
+  FunctionRef<int(const S& s)> ref(mem_ptr);
+  EXPECT_EQ(1100111, ref(s));
+}
+
+TEST(FunctionRef, MemberFun) {
+  struct S {
+    int i;
+    int get_i() const { return i; }
+  };
+
+  S s{22};
+  auto mem_fun_ptr = &S::get_i;
+  FunctionRef<int(const S& s)> ref(mem_fun_ptr);
+  EXPECT_EQ(22, ref(s));
+}
+
+TEST(FunctionRef, MemberFunRefqualified) {
+  struct S {
+    int i;
+    int get_i() && { return i; }
+  };
+  auto mem_fun_ptr = &S::get_i;
+  S s{22};
+  FunctionRef<int(S && s)> ref(mem_fun_ptr);
+  EXPECT_EQ(22, ref(std::move(s)));
+}
+
+#if !defined(_WIN32) && defined(GTEST_HAS_DEATH_TEST)
+
+TEST(FunctionRef, MemberFunRefqualifiedNull) {
+  struct S {
+    int i;
+    int get_i() && { return i; }
+  };
+  auto mem_fun_ptr = &S::get_i;
+  mem_fun_ptr = nullptr;
+  EXPECT_DEBUG_DEATH({ FunctionRef<int(S && s)> ref(mem_fun_ptr); }, "");
+}
+
+TEST(FunctionRef, NullMemberPtrAssertFails) {
+  struct S {
+    int i;
+  };
+  using MemberPtr = int S::*;
+  MemberPtr mem_ptr = nullptr;
+  EXPECT_DEBUG_DEATH({ FunctionRef<int(const S& s)> ref(mem_ptr); }, "");
+}
+
+TEST(FunctionRef, NullStdFunctionAssertPasses) {
+  std::function<void()> function = []() {};
+  FunctionRef<void()> ref(function);
+}
+
+TEST(FunctionRef, NullStdFunctionAssertFails) {
+  std::function<void()> function = nullptr;
+  EXPECT_DEBUG_DEATH({ FunctionRef<void()> ref(function); }, "");
+}
+
+TEST(FunctionRef, NullAnyInvocableAssertPasses) {
+  AnyInvocable<void() const> invocable = []() {};
+  FunctionRef<void()> ref(invocable);
+}
+TEST(FunctionRef, NullAnyInvocableAssertFails) {
+  AnyInvocable<void() const> invocable = nullptr;
+  EXPECT_DEBUG_DEATH({ FunctionRef<void()> ref(invocable); }, "");
+}
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+TEST(FunctionRef, CopiesAndMovesPerPassByValue) {
+  absl::test_internal::InstanceTracker tracker;
+  absl::test_internal::CopyableMovableInstance instance(0);
+  auto l = [](absl::test_internal::CopyableMovableInstance) {};
+  FunctionRef<void(absl::test_internal::CopyableMovableInstance)> ref(l);
+  ref(instance);
+  EXPECT_EQ(tracker.copies(), 1);
+  EXPECT_EQ(tracker.moves(), 1);
+}
+
+TEST(FunctionRef, CopiesAndMovesPerPassByRef) {
+  absl::test_internal::InstanceTracker tracker;
+  absl::test_internal::CopyableMovableInstance instance(0);
+  auto l = [](const absl::test_internal::CopyableMovableInstance&) {};
+  FunctionRef<void(const absl::test_internal::CopyableMovableInstance&)> ref(l);
+  ref(instance);
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 0);
+}
+
+TEST(FunctionRef, CopiesAndMovesPerPassByValueCallByMove) {
+  absl::test_internal::InstanceTracker tracker;
+  absl::test_internal::CopyableMovableInstance instance(0);
+  auto l = [](absl::test_internal::CopyableMovableInstance) {};
+  FunctionRef<void(absl::test_internal::CopyableMovableInstance)> ref(l);
+  ref(std::move(instance));
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 2);
+}
+
+TEST(FunctionRef, CopiesAndMovesPerPassByValueToRef) {
+  absl::test_internal::InstanceTracker tracker;
+  absl::test_internal::CopyableMovableInstance instance(0);
+  auto l = [](const absl::test_internal::CopyableMovableInstance&) {};
+  FunctionRef<void(absl::test_internal::CopyableMovableInstance)> ref(l);
+  ref(std::move(instance));
+  EXPECT_EQ(tracker.copies(), 0);
+  EXPECT_EQ(tracker.moves(), 1);
+}
+
+TEST(FunctionRef, PassByValueTypes) {
+  using absl::functional_internal::Invoker;
+  using absl::functional_internal::VoidPtr;
+  using absl::test_internal::CopyableMovableInstance;
+  struct Trivial {
+    void* p[2];
+  };
+  struct LargeTrivial {
+    void* p[3];
+  };
+
+  static_assert(std::is_same<Invoker<void, int>, void (*)(VoidPtr, int)>::value,
+                "Scalar types should be passed by value");
+  static_assert(
+      std::is_same<Invoker<void, Trivial>, void (*)(VoidPtr, Trivial)>::value,
+      "Small trivial types should be passed by value");
+  static_assert(std::is_same<Invoker<void, LargeTrivial>,
+                             void (*)(VoidPtr, LargeTrivial &&)>::value,
+                "Large trivial types should be passed by rvalue reference");
+  static_assert(
+      std::is_same<Invoker<void, CopyableMovableInstance>,
+                   void (*)(VoidPtr, CopyableMovableInstance &&)>::value,
+      "Types with copy/move ctor should be passed by rvalue reference");
+
+  // References are passed as references.
+  static_assert(
+      std::is_same<Invoker<void, int&>, void (*)(VoidPtr, int&)>::value,
+      "Reference types should be preserved");
+  static_assert(
+      std::is_same<Invoker<void, CopyableMovableInstance&>,
+                   void (*)(VoidPtr, CopyableMovableInstance&)>::value,
+      "Reference types should be preserved");
+  static_assert(
+      std::is_same<Invoker<void, CopyableMovableInstance&&>,
+                   void (*)(VoidPtr, CopyableMovableInstance &&)>::value,
+      "Reference types should be preserved");
+
+  // Make sure the address of an object received by reference is the same as the
+  // address of the object passed by the caller.
+  {
+    LargeTrivial obj;
+    auto test = [&obj](LargeTrivial& input) { ASSERT_EQ(&input, &obj); };
+    absl::FunctionRef<void(LargeTrivial&)> ref(test);
+    ref(obj);
+  }
+
+  {
+    Trivial obj;
+    auto test = [&obj](Trivial& input) { ASSERT_EQ(&input, &obj); };
+    absl::FunctionRef<void(Trivial&)> ref(test);
+    ref(obj);
+  }
+}
+
+TEST(FunctionRef, ReferenceToIncompleteType) {
+  struct IncompleteType;
+  auto test = [](IncompleteType&) {};
+  absl::FunctionRef<void(IncompleteType&)> ref(test);
+
+  struct IncompleteType {};
+  IncompleteType obj;
+  ref(obj);
+}
+
+}  // namespace
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/functional/function_type_benchmark.cc b/weight/_dep/abseil-cpp/absl/functional/function_type_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..03dc31d8cdfb832bf6cecb916c6c5f584b1dca5b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/function_type_benchmark.cc
@@ -0,0 +1,176 @@
+// Copyright 2022 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <functional>
+#include <memory>
+#include <string>
+
+#include "benchmark/benchmark.h"
+#include "absl/base/attributes.h"
+#include "absl/functional/any_invocable.h"
+#include "absl/functional/function_ref.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace {
+
+int dummy = 0;
+
+void FreeFunction() { benchmark::DoNotOptimize(dummy); }
+
+struct TrivialFunctor {
+  void operator()() const { benchmark::DoNotOptimize(dummy); }
+};
+
+struct LargeFunctor {
+  void operator()() const { benchmark::DoNotOptimize(this); }
+  std::string a, b, c;
+};
+
+template <typename Function, typename... Args>
+void ABSL_ATTRIBUTE_NOINLINE CallFunction(Function f, Args&&... args) {
+  f(std::forward<Args>(args)...);
+}
+
+template <typename Function, typename Callable, typename... Args>
+void ConstructAndCallFunctionBenchmark(benchmark::State& state,
+                                       const Callable& c, Args&&... args) {
+  for (auto _ : state) {
+    CallFunction<Function>(c, std::forward<Args>(args)...);
+  }
+}
+
+void BM_TrivialStdFunction(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<std::function<void()>>(state,
+                                                           TrivialFunctor{});
+}
+BENCHMARK(BM_TrivialStdFunction);
+
+void BM_TrivialFunctionRef(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<FunctionRef<void()>>(state,
+                                                         TrivialFunctor{});
+}
+BENCHMARK(BM_TrivialFunctionRef);
+
+void BM_TrivialAnyInvocable(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<AnyInvocable<void()>>(state,
+                                                          TrivialFunctor{});
+}
+BENCHMARK(BM_TrivialAnyInvocable);
+
+void BM_LargeStdFunction(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<std::function<void()>>(state,
+                                                           LargeFunctor{});
+}
+BENCHMARK(BM_LargeStdFunction);
+
+void BM_LargeFunctionRef(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<FunctionRef<void()>>(state, LargeFunctor{});
+}
+BENCHMARK(BM_LargeFunctionRef);
+
+
+void BM_LargeAnyInvocable(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<AnyInvocable<void()>>(state,
+                                                          LargeFunctor{});
+}
+BENCHMARK(BM_LargeAnyInvocable);
+
+void BM_FunPtrStdFunction(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<std::function<void()>>(state, FreeFunction);
+}
+BENCHMARK(BM_FunPtrStdFunction);
+
+void BM_FunPtrFunctionRef(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<FunctionRef<void()>>(state, FreeFunction);
+}
+BENCHMARK(BM_FunPtrFunctionRef);
+
+void BM_FunPtrAnyInvocable(benchmark::State& state) {
+  ConstructAndCallFunctionBenchmark<AnyInvocable<void()>>(state, FreeFunction);
+}
+BENCHMARK(BM_FunPtrAnyInvocable);
+
+// Doesn't include construction or copy overhead in the loop.
+template <typename Function, typename Callable, typename... Args>
+void CallFunctionBenchmark(benchmark::State& state, const Callable& c,
+                           Args... args) {
+  Function f = c;
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(&f);
+    f(args...);
+  }
+}
+
+struct FunctorWithTrivialArgs {
+  void operator()(int a, int b, int c) const {
+    benchmark::DoNotOptimize(a);
+    benchmark::DoNotOptimize(b);
+    benchmark::DoNotOptimize(c);
+  }
+};
+
+void BM_TrivialArgsStdFunction(benchmark::State& state) {
+  CallFunctionBenchmark<std::function<void(int, int, int)>>(
+      state, FunctorWithTrivialArgs{}, 1, 2, 3);
+}
+BENCHMARK(BM_TrivialArgsStdFunction);
+
+void BM_TrivialArgsFunctionRef(benchmark::State& state) {
+  CallFunctionBenchmark<FunctionRef<void(int, int, int)>>(
+      state, FunctorWithTrivialArgs{}, 1, 2, 3);
+}
+BENCHMARK(BM_TrivialArgsFunctionRef);
+
+void BM_TrivialArgsAnyInvocable(benchmark::State& state) {
+  CallFunctionBenchmark<AnyInvocable<void(int, int, int)>>(
+      state, FunctorWithTrivialArgs{}, 1, 2, 3);
+}
+BENCHMARK(BM_TrivialArgsAnyInvocable);
+
+struct FunctorWithNonTrivialArgs {
+  void operator()(std::string a, std::string b, std::string c) const {
+    benchmark::DoNotOptimize(&a);
+    benchmark::DoNotOptimize(&b);
+    benchmark::DoNotOptimize(&c);
+  }
+};
+
+void BM_NonTrivialArgsStdFunction(benchmark::State& state) {
+  std::string a, b, c;
+  CallFunctionBenchmark<
+      std::function<void(std::string, std::string, std::string)>>(
+      state, FunctorWithNonTrivialArgs{}, a, b, c);
+}
+BENCHMARK(BM_NonTrivialArgsStdFunction);
+
+void BM_NonTrivialArgsFunctionRef(benchmark::State& state) {
+  std::string a, b, c;
+  CallFunctionBenchmark<
+      FunctionRef<void(std::string, std::string, std::string)>>(
+      state, FunctorWithNonTrivialArgs{}, a, b, c);
+}
+BENCHMARK(BM_NonTrivialArgsFunctionRef);
+
+void BM_NonTrivialArgsAnyInvocable(benchmark::State& state) {
+  std::string a, b, c;
+  CallFunctionBenchmark<
+      AnyInvocable<void(std::string, std::string, std::string)>>(
+      state, FunctorWithNonTrivialArgs{}, a, b, c);
+}
+BENCHMARK(BM_NonTrivialArgsAnyInvocable);
+
+}  // namespace
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/functional/internal/front_binder.h b/weight/_dep/abseil-cpp/absl/functional/internal/front_binder.h
new file mode 100644
index 0000000000000000000000000000000000000000..45f52de73d25ef73c521a97c265804956051573d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/internal/front_binder.h
@@ -0,0 +1,95 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Implementation details for `absl::bind_front()`.
+
+#ifndef ABSL_FUNCTIONAL_INTERNAL_FRONT_BINDER_H_
+#define ABSL_FUNCTIONAL_INTERNAL_FRONT_BINDER_H_
+
+#include <cstddef>
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/internal/invoke.h"
+#include "absl/container/internal/compressed_tuple.h"
+#include "absl/meta/type_traits.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace functional_internal {
+
+// Invoke the method, expanding the tuple of bound arguments.
+template <class R, class Tuple, size_t... Idx, class... Args>
+R Apply(Tuple&& bound, absl::index_sequence<Idx...>, Args&&... free) {
+  return base_internal::invoke(
+      absl::forward<Tuple>(bound).template get<Idx>()...,
+      absl::forward<Args>(free)...);
+}
+
+template <class F, class... BoundArgs>
+class FrontBinder {
+  using BoundArgsT = absl::container_internal::CompressedTuple<F, BoundArgs...>;
+  using Idx = absl::make_index_sequence<sizeof...(BoundArgs) + 1>;
+
+  BoundArgsT bound_args_;
+
+ public:
+  template <class... Ts>
+  constexpr explicit FrontBinder(absl::in_place_t, Ts&&... ts)
+      : bound_args_(absl::forward<Ts>(ts)...) {}
+
+  template <class... FreeArgs, class R = base_internal::invoke_result_t<
+                                   F&, BoundArgs&..., FreeArgs&&...>>
+  R operator()(FreeArgs&&... free_args) & {
+    return functional_internal::Apply<R>(bound_args_, Idx(),
+                                         absl::forward<FreeArgs>(free_args)...);
+  }
+
+  template <class... FreeArgs,
+            class R = base_internal::invoke_result_t<
+                const F&, const BoundArgs&..., FreeArgs&&...>>
+  R operator()(FreeArgs&&... free_args) const& {
+    return functional_internal::Apply<R>(bound_args_, Idx(),
+                                         absl::forward<FreeArgs>(free_args)...);
+  }
+
+  template <class... FreeArgs, class R = base_internal::invoke_result_t<
+                                   F&&, BoundArgs&&..., FreeArgs&&...>>
+  R operator()(FreeArgs&&... free_args) && {
+    // This overload is called when *this is an rvalue. If some of the bound
+    // arguments are stored by value or rvalue reference, we move them.
+    return functional_internal::Apply<R>(absl::move(bound_args_), Idx(),
+                                         absl::forward<FreeArgs>(free_args)...);
+  }
+
+  template <class... FreeArgs,
+            class R = base_internal::invoke_result_t<
+                const F&&, const BoundArgs&&..., FreeArgs&&...>>
+  R operator()(FreeArgs&&... free_args) const&& {
+    // This overload is called when *this is an rvalue. If some of the bound
+    // arguments are stored by value or rvalue reference, we move them.
+    return functional_internal::Apply<R>(absl::move(bound_args_), Idx(),
+                                         absl::forward<FreeArgs>(free_args)...);
+  }
+};
+
+template <class F, class... BoundArgs>
+using bind_front_t = FrontBinder<decay_t<F>, absl::decay_t<BoundArgs>...>;
+
+}  // namespace functional_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FUNCTIONAL_INTERNAL_FRONT_BINDER_H_
diff --git a/weight/_dep/abseil-cpp/absl/functional/internal/function_ref.h b/weight/_dep/abseil-cpp/absl/functional/internal/function_ref.h
new file mode 100644
index 0000000000000000000000000000000000000000..1cd34a3c766e99aa461c210b08dce96ec73463ae
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/internal/function_ref.h
@@ -0,0 +1,116 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
+#define ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
+
+#include <cassert>
+#include <functional>
+#include <type_traits>
+
+#include "absl/base/internal/invoke.h"
+#include "absl/functional/any_invocable.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace functional_internal {
+
+// Like a void* that can handle function pointers as well. The standard does not
+// allow function pointers to round-trip through void*, but void(*)() is fine.
+//
+// Note: It's important that this class remains trivial and is the same size as
+// a pointer, since this allows the compiler to perform tail-call optimizations
+// when the underlying function is a callable object with a matching signature.
+union VoidPtr {
+  const void* obj;
+  void (*fun)();
+};
+
+// Chooses the best type for passing T as an argument.
+// Attempt to be close to SystemV AMD64 ABI. Objects with trivial copy ctor are
+// passed by value.
+template <typename T,
+          bool IsLValueReference = std::is_lvalue_reference<T>::value>
+struct PassByValue : std::false_type {};
+
+template <typename T>
+struct PassByValue<T, /*IsLValueReference=*/false>
+    : std::integral_constant<bool,
+                             absl::is_trivially_copy_constructible<T>::value &&
+                                 absl::is_trivially_copy_assignable<
+                                     typename std::remove_cv<T>::type>::value &&
+                                 std::is_trivially_destructible<T>::value &&
+                                 sizeof(T) <= 2 * sizeof(void*)> {};
+
+template <typename T>
+struct ForwardT : std::conditional<PassByValue<T>::value, T, T&&> {};
+
+// An Invoker takes a pointer to the type-erased invokable object, followed by
+// the arguments that the invokable object expects.
+//
+// Note: The order of arguments here is an optimization, since member functions
+// have an implicit "this" pointer as their first argument, putting VoidPtr
+// first allows the compiler to perform tail-call optimization in many cases.
+template <typename R, typename... Args>
+using Invoker = R (*)(VoidPtr, typename ForwardT<Args>::type...);
+
+//
+// InvokeObject and InvokeFunction provide static "Invoke" functions that can be
+// used as Invokers for objects or functions respectively.
+//
+// static_cast<R> handles the case the return type is void.
+template <typename Obj, typename R, typename... Args>
+R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) {
+  auto o = static_cast<const Obj*>(ptr.obj);
+  return static_cast<R>(
+      absl::base_internal::invoke(*o, std::forward<Args>(args)...));
+}
+
+template <typename Fun, typename R, typename... Args>
+R InvokeFunction(VoidPtr ptr, typename ForwardT<Args>::type... args) {
+  auto f = reinterpret_cast<Fun>(ptr.fun);
+  return static_cast<R>(
+      absl::base_internal::invoke(f, std::forward<Args>(args)...));
+}
+
+template <typename Sig>
+void AssertNonNull(const std::function<Sig>& f) {
+  assert(f != nullptr);
+  (void)f;
+}
+
+template <typename Sig>
+void AssertNonNull(const AnyInvocable<Sig>& f) {
+  assert(f != nullptr);
+  (void)f;
+}
+
+template <typename F>
+void AssertNonNull(const F&) {}
+
+template <typename F, typename C>
+void AssertNonNull(F C::*f) {
+  assert(f != nullptr);
+  (void)f;
+}
+
+template <bool C>
+using EnableIf = typename ::std::enable_if<C, int>::type;
+
+}  // namespace functional_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
diff --git a/weight/_dep/abseil-cpp/absl/functional/overload.h b/weight/_dep/abseil-cpp/absl/functional/overload.h
new file mode 100644
index 0000000000000000000000000000000000000000..4651f14bd8cdc87e93f0f88bb88e970c8ab431df
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/overload.h
@@ -0,0 +1,75 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: overload.h
+// -----------------------------------------------------------------------------
+//
+// `absl::Overload()` returns a functor that provides overloads based on the
+// functors passed to it.
+// Before using this function, consider whether named function overloads would
+// be a better design.
+// One use case for this is locally defining visitors for `std::visit` inside a
+// function using lambdas.
+
+// Example: Using  `absl::Overload` to define a visitor for `std::variant`.
+//
+// std::variant<int, std::string, double> v(int{1});
+//
+// assert(std::visit(absl::Overload(
+//                        [](int) -> absl::string_view { return "int"; },
+//                        [](const std::string&) -> absl::string_view {
+//                          return "string";
+//                        },
+//                        [](double) -> absl::string_view { return "double"; }),
+//                     v) == "int");
+//
+// Note: This requires C++17.
+
+#ifndef ABSL_FUNCTIONAL_OVERLOAD_H_
+#define ABSL_FUNCTIONAL_OVERLOAD_H_
+
+#include "absl/base/config.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+#if defined(ABSL_INTERNAL_CPLUSPLUS_LANG) && \
+    ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
+
+template <int&... ExplicitArgumentBarrier, typename... T>
+auto Overload(T&&... ts) {
+  struct OverloadImpl : absl::remove_cvref_t<T>... {
+    using absl::remove_cvref_t<T>::operator()...;
+  };
+  return OverloadImpl{std::forward<T>(ts)...};
+}
+#else
+namespace functional_internal {
+template <typename T>
+constexpr bool kDependentFalse = false;
+}
+
+template <typename Dependent = int, typename... T>
+auto Overload(T&&...) {
+  static_assert(functional_internal::kDependentFalse<Dependent>,
+                "Overload is only usable with C++17 or above.");
+}
+
+#endif
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FUNCTIONAL_OVERLOAD_H_
diff --git a/weight/_dep/abseil-cpp/absl/functional/overload_test.cc b/weight/_dep/abseil-cpp/absl/functional/overload_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..739c4c4cab49ed1b3e41e2c724881e583b768f47
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/functional/overload_test.cc
@@ -0,0 +1,130 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/functional/overload.h"
+
+#include <cstdint>
+#include <string>
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/variant.h"
+
+#if defined(ABSL_INTERNAL_CPLUSPLUS_LANG) && \
+    ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
+
+#include "gtest/gtest.h"
+
+namespace {
+
+TEST(OverloadTest, DispatchConsidersType) {
+  auto overloaded = absl::Overload(
+      [](int v) -> std::string { return absl::StrCat("int ", v); },        //
+      [](double v) -> std::string { return absl::StrCat("double ", v); },  //
+      [](const char* v) -> std::string {                                   //
+        return absl::StrCat("const char* ", v);                            //
+      },                                                                   //
+      [](auto v) -> std::string { return absl::StrCat("auto ", v); }       //
+  );
+  EXPECT_EQ("int 1", overloaded(1));
+  EXPECT_EQ("double 2.5", overloaded(2.5));
+  EXPECT_EQ("const char* hello", overloaded("hello"));
+  EXPECT_EQ("auto 1.5", overloaded(1.5f));
+}
+
+TEST(OverloadTest, DispatchConsidersNumberOfArguments) {
+  auto overloaded = absl::Overload(                 //
+      [](int a) { return a + 1; },                  //
+      [](int a, int b) { return a * b; },           //
+      []() -> absl::string_view { return "none"; }  //
+  );
+  EXPECT_EQ(3, overloaded(2));
+  EXPECT_EQ(21, overloaded(3, 7));
+  EXPECT_EQ("none", overloaded());
+}
+
+TEST(OverloadTest, SupportsConstantEvaluation) {
+  auto overloaded = absl::Overload(                 //
+      [](int a) { return a + 1; },                  //
+      [](int a, int b) { return a * b; },           //
+      []() -> absl::string_view { return "none"; }  //
+  );
+  static_assert(overloaded() == "none");
+  static_assert(overloaded(2) == 3);
+  static_assert(overloaded(3, 7) == 21);
+}
+
+TEST(OverloadTest, PropogatesDefaults) {
+  auto overloaded = absl::Overload(            //
+      [](int a, int b = 5) { return a * b; },  //
+      [](double c) { return c; }               //
+  );
+
+  EXPECT_EQ(21, overloaded(3, 7));
+  EXPECT_EQ(35, overloaded(7));
+  EXPECT_EQ(2.5, overloaded(2.5));
+}
+
+TEST(OverloadTest, AmbiguousWithDefaultsNotInvocable) {
+  auto overloaded = absl::Overload(            //
+      [](int a, int b = 5) { return a * b; },  //
+      [](int c) { return c; }                  //
+  );
+  static_assert(!std::is_invocable_v<decltype(overloaded), int>);
+  static_assert(std::is_invocable_v<decltype(overloaded), int, int>);
+}
+
+TEST(OverloadTest, AmbiguousDuplicatesNotInvocable) {
+  auto overloaded = absl::Overload(  //
+      [](int a) { return a; },       //
+      [](int c) { return c; }        //
+  );
+  static_assert(!std::is_invocable_v<decltype(overloaded), int>);
+}
+
+TEST(OverloadTest, AmbiguousConversionNotInvocable) {
+  auto overloaded = absl::Overload(  //
+      [](uint16_t a) { return a; },  //
+      [](uint64_t c) { return c; }   //
+  );
+  static_assert(!std::is_invocable_v<decltype(overloaded), int>);
+}
+
+TEST(OverloadTest, DispatchConsidersSfinae) {
+  auto overloaded = absl::Overload(                    //
+      [](auto a) -> decltype(a + 1) { return a + 1; }  //
+  );
+  static_assert(std::is_invocable_v<decltype(overloaded), int>);
+  static_assert(!std::is_invocable_v<decltype(overloaded), std::string>);
+}
+
+TEST(OverloadTest, VariantVisitDispatchesCorrectly) {
+  absl::variant<int, double, std::string> v(1);
+  auto overloaded = absl::Overload(
+      [](int) -> absl::string_view { return "int"; },                   //
+      [](double) -> absl::string_view { return "double"; },             //
+      [](const std::string&) -> absl::string_view { return "string"; }  //
+  );
+  EXPECT_EQ("int", absl::visit(overloaded, v));
+  v = 1.1;
+  EXPECT_EQ("double", absl::visit(overloaded, v));
+  v = "hello";
+  EXPECT_EQ("string", absl::visit(overloaded, v));
+}
+
+}  // namespace
+
+#endif
diff --git a/weight/_dep/abseil-cpp/absl/hash/BUILD.bazel b/weight/_dep/abseil-cpp/absl/hash/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..1e8ad45131f94301ad6ea7eeee00e33fc8663109
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/BUILD.bazel
@@ -0,0 +1,217 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "hash",
+    srcs = [
+        "internal/hash.cc",
+        "internal/hash.h",
+    ],
+    hdrs = ["hash.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":city",
+        ":low_level_hash",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:endian",
+        "//absl/container:fixed_array",
+        "//absl/functional:function_ref",
+        "//absl/meta:type_traits",
+        "//absl/numeric:bits",
+        "//absl/numeric:int128",
+        "//absl/strings",
+        "//absl/types:optional",
+        "//absl/types:variant",
+        "//absl/utility",
+    ],
+)
+
+cc_library(
+    name = "hash_testing",
+    testonly = 1,
+    hdrs = ["hash_testing.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":spy_hash_state",
+        "//absl/meta:type_traits",
+        "//absl/strings",
+        "//absl/types:variant",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_test(
+    name = "hash_test",
+    srcs = [
+        "hash_test.cc",
+        "internal/hash_test.h",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":hash",
+        ":hash_testing",
+        ":spy_hash_state",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/container:btree",
+        "//absl/container:flat_hash_map",
+        "//absl/container:flat_hash_set",
+        "//absl/container:node_hash_map",
+        "//absl/container:node_hash_set",
+        "//absl/memory",
+        "//absl/meta:type_traits",
+        "//absl/numeric:int128",
+        "//absl/strings:cord_test_helpers",
+        "//absl/strings:string_view",
+        "//absl/types:optional",
+        "//absl/types:variant",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "hash_instantiated_test",
+    srcs = [
+        "hash_instantiated_test.cc",
+        "internal/hash_test.h",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":hash",
+        ":hash_testing",
+        "//absl/base:config",
+        "//absl/container:btree",
+        "//absl/container:flat_hash_map",
+        "//absl/container:flat_hash_set",
+        "//absl/container:node_hash_map",
+        "//absl/container:node_hash_set",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_binary(
+    name = "hash_benchmark",
+    testonly = 1,
+    srcs = ["hash_benchmark.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    visibility = ["//visibility:private"],
+    deps = [
+        ":hash",
+        "//absl/base:core_headers",
+        "//absl/container:flat_hash_set",
+        "//absl/random",
+        "//absl/strings",
+        "//absl/strings:cord",
+        "//absl/strings:cord_test_helpers",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
+
+cc_library(
+    name = "spy_hash_state",
+    testonly = 1,
+    hdrs = ["internal/spy_hash_state.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":hash",
+        "//absl/strings",
+        "//absl/strings:str_format",
+    ],
+)
+
+cc_library(
+    name = "city",
+    srcs = ["internal/city.cc"],
+    hdrs = [
+        "internal/city.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:endian",
+    ],
+)
+
+cc_test(
+    name = "city_test",
+    srcs = ["internal/city_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":city",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "low_level_hash",
+    srcs = ["internal/low_level_hash.cc"],
+    hdrs = ["internal/low_level_hash.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:endian",
+        "//absl/base:prefetch",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_test(
+    name = "low_level_hash_test",
+    srcs = ["internal/low_level_hash_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":low_level_hash",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/hash/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/hash/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..99d6fa1f8dcc637cfa279c974fedc9155cb26d4c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/CMakeLists.txt
@@ -0,0 +1,186 @@
+#
+# Copyright 2018 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+absl_cc_library(
+  NAME
+    hash
+  HDRS
+    "hash.h"
+  SRCS
+    "internal/hash.cc"
+    "internal/hash.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::bits
+    absl::city
+    absl::config
+    absl::core_headers
+    absl::endian
+    absl::fixed_array
+    absl::function_ref
+    absl::meta
+    absl::int128
+    absl::strings
+    absl::optional
+    absl::variant
+    absl::utility
+    absl::low_level_hash
+  PUBLIC
+)
+
+absl_cc_library(
+  NAME
+    hash_testing
+  HDRS
+    "hash_testing.h"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::spy_hash_state
+    absl::meta
+    absl::strings
+    absl::variant
+    GTest::gmock
+  TESTONLY
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    hash_test
+  SRCS
+    "hash_test.cc"
+    "internal/hash_test.h"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::btree
+    absl::cord_test_helpers
+    absl::core_headers
+    absl::flat_hash_map
+    absl::flat_hash_set
+    absl::hash
+    absl::hash_testing
+    absl::int128
+    absl::memory
+    absl::meta
+    absl::node_hash_map
+    absl::node_hash_set
+    absl::optional
+    absl::spy_hash_state
+    absl::string_view
+    absl::variant
+    GTest::gmock_main
+)
+
+absl_cc_test(
+  NAME
+    hash_instantiated_test
+  SRCS
+    "hash_instantiated_test.cc"
+    "internal/hash_test.h"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::hash
+    absl::hash_testing
+    absl::config
+    absl::btree
+    absl::flat_hash_map
+    absl::flat_hash_set
+    absl::node_hash_map
+    absl::node_hash_set
+    GTest::gmock_main
+)
+
+# Internal-only target, do not depend on directly.
+#
+# Note: Even though external code should not depend on this target
+# directly, it must be marked PUBLIC since it is a dependency of
+# hash_testing.
+absl_cc_library(
+  NAME
+    spy_hash_state
+  HDRS
+    "internal/spy_hash_state.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::hash
+    absl::strings
+    absl::str_format
+  TESTONLY
+  PUBLIC
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    city
+  HDRS
+    "internal/city.h"
+  SRCS
+    "internal/city.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+    absl::endian
+)
+
+absl_cc_test(
+  NAME
+    city_test
+  SRCS
+    "internal/city_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::city
+    GTest::gmock_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    low_level_hash
+  HDRS
+    "internal/low_level_hash.h"
+  SRCS
+    "internal/low_level_hash.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::endian
+    absl::int128
+    absl::prefetch
+)
+
+absl_cc_test(
+  NAME
+    low_level_hash_test
+  SRCS
+    "internal/low_level_hash_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::low_level_hash
+    absl::strings
+    GTest::gmock_main
+)
diff --git a/weight/_dep/abseil-cpp/absl/hash/hash.h b/weight/_dep/abseil-cpp/absl/hash/hash.h
new file mode 100644
index 0000000000000000000000000000000000000000..470cca4837a25bfda5d69b6954430cf6c4ba8362
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/hash.h
@@ -0,0 +1,424 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: hash.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the Abseil `hash` library and the Abseil hashing
+// framework. This framework consists of the following:
+//
+//   * The `absl::Hash` functor, which is used to invoke the hasher within the
+//     Abseil hashing framework. `absl::Hash<T>` supports most basic types and
+//     a number of Abseil types out of the box.
+//   * `AbslHashValue`, an extension point that allows you to extend types to
+//     support Abseil hashing without requiring you to define a hashing
+//     algorithm.
+//   * `HashState`, a type-erased class which implements the manipulation of the
+//     hash state (H) itself; contains member functions `combine()`,
+//     `combine_contiguous()`, and `combine_unordered()`; and which you can use
+//     to contribute to an existing hash state when hashing your types.
+//
+// Unlike `std::hash` or other hashing frameworks, the Abseil hashing framework
+// provides most of its utility by abstracting away the hash algorithm (and its
+// implementation) entirely. Instead, a type invokes the Abseil hashing
+// framework by simply combining its state with the state of known, hashable
+// types. Hashing of that combined state is separately done by `absl::Hash`.
+//
+// One should assume that a hash algorithm is chosen randomly at the start of
+// each process.  E.g., `absl::Hash<int>{}(9)` in one process and
+// `absl::Hash<int>{}(9)` in another process are likely to differ.
+//
+// `absl::Hash` may also produce different values from different dynamically
+// loaded libraries. For this reason, `absl::Hash` values must never cross
+// boundaries in dynamically loaded libraries (including when used in types like
+// hash containers.)
+//
+// `absl::Hash` is intended to strongly mix input bits with a target of passing
+// an [Avalanche Test](https://en.wikipedia.org/wiki/Avalanche_effect).
+//
+// Example:
+//
+//   // Suppose we have a class `Circle` for which we want to add hashing:
+//   class Circle {
+//    public:
+//     ...
+//    private:
+//     std::pair<int, int> center_;
+//     int radius_;
+//   };
+//
+//   // To add hashing support to `Circle`, we simply need to add a free
+//   // (non-member) function `AbslHashValue()`, and return the combined hash
+//   // state of the existing hash state and the class state. You can add such a
+//   // free function using a friend declaration within the body of the class:
+//   class Circle {
+//    public:
+//     ...
+//     template <typename H>
+//     friend H AbslHashValue(H h, const Circle& c) {
+//       return H::combine(std::move(h), c.center_, c.radius_);
+//     }
+//     ...
+//   };
+//
+// For more information, see Adding Type Support to `absl::Hash` below.
+//
+#ifndef ABSL_HASH_HASH_H_
+#define ABSL_HASH_HASH_H_
+
+#include <tuple>
+#include <utility>
+
+#include "absl/functional/function_ref.h"
+#include "absl/hash/internal/hash.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// -----------------------------------------------------------------------------
+// `absl::Hash`
+// -----------------------------------------------------------------------------
+//
+// `absl::Hash<T>` is a convenient general-purpose hash functor for any type `T`
+// satisfying any of the following conditions (in order):
+//
+//  * T is an arithmetic or pointer type
+//  * T defines an overload for `AbslHashValue(H, const T&)` for an arbitrary
+//    hash state `H`.
+//  - T defines a specialization of `std::hash<T>`
+//
+// `absl::Hash` intrinsically supports the following types:
+//
+//   * All integral types (including bool)
+//   * All enum types
+//   * All floating-point types (although hashing them is discouraged)
+//   * All pointer types, including nullptr_t
+//   * std::pair<T1, T2>, if T1 and T2 are hashable
+//   * std::tuple<Ts...>, if all the Ts... are hashable
+//   * std::unique_ptr and std::shared_ptr
+//   * All string-like types including:
+//     * absl::Cord
+//     * std::string (as well as any instance of std::basic_string that
+//       uses one of {char, wchar_t, char16_t, char32_t} and its associated
+//       std::char_traits)
+//     * std::string_view (as well as any instance of std::basic_string_view
+//       that uses one of {char, wchar_t, char16_t, char32_t} and its associated
+//       std::char_traits)
+//  * All the standard sequence containers (provided the elements are hashable)
+//  * All the standard associative containers (provided the elements are
+//    hashable)
+//  * absl types such as the following:
+//    * absl::string_view
+//    * absl::uint128
+//    * absl::Time, absl::Duration, and absl::TimeZone
+//  * absl containers (provided the elements are hashable) such as the
+//    following:
+//    * absl::flat_hash_set, absl::node_hash_set, absl::btree_set
+//    * absl::flat_hash_map, absl::node_hash_map, absl::btree_map
+//    * absl::btree_multiset, absl::btree_multimap
+//    * absl::InlinedVector
+//    * absl::FixedArray
+//
+// When absl::Hash is used to hash an unordered container with a custom hash
+// functor, the elements are hashed using default absl::Hash semantics, not
+// the custom hash functor.  This is consistent with the behavior of
+// operator==() on unordered containers, which compares elements pairwise with
+// operator==() rather than the custom equality functor.  It is usually a
+// mistake to use either operator==() or absl::Hash on unordered collections
+// that use functors incompatible with operator==() equality.
+//
+// Note: the list above is not meant to be exhaustive. Additional type support
+// may be added, in which case the above list will be updated.
+//
+// -----------------------------------------------------------------------------
+// absl::Hash Invocation Evaluation
+// -----------------------------------------------------------------------------
+//
+// When invoked, `absl::Hash<T>` searches for supplied hash functions in the
+// following order:
+//
+//   * Natively supported types out of the box (see above)
+//   * Types for which an `AbslHashValue()` overload is provided (such as
+//     user-defined types). See "Adding Type Support to `absl::Hash`" below.
+//   * Types which define a `std::hash<T>` specialization
+//
+// The fallback to legacy hash functions exists mainly for backwards
+// compatibility. If you have a choice, prefer defining an `AbslHashValue`
+// overload instead of specializing any legacy hash functors.
+//
+// -----------------------------------------------------------------------------
+// The Hash State Concept, and using `HashState` for Type Erasure
+// -----------------------------------------------------------------------------
+//
+// The `absl::Hash` framework relies on the Concept of a "hash state." Such a
+// hash state is used in several places:
+//
+// * Within existing implementations of `absl::Hash<T>` to store the hashed
+//   state of an object. Note that it is up to the implementation how it stores
+//   such state. A hash table, for example, may mix the state to produce an
+//   integer value; a testing framework may simply hold a vector of that state.
+// * Within implementations of `AbslHashValue()` used to extend user-defined
+//   types. (See "Adding Type Support to absl::Hash" below.)
+// * Inside a `HashState`, providing type erasure for the concept of a hash
+//   state, which you can use to extend the `absl::Hash` framework for types
+//   that are otherwise difficult to extend using `AbslHashValue()`. (See the
+//   `HashState` class below.)
+//
+// The "hash state" concept contains three member functions for mixing hash
+// state:
+//
+// * `H::combine(state, values...)`
+//
+//   Combines an arbitrary number of values into a hash state, returning the
+//   updated state. Note that the existing hash state is move-only and must be
+//   passed by value.
+//
+//   Each of the value types T must be hashable by H.
+//
+//   NOTE:
+//
+//     state = H::combine(std::move(state), value1, value2, value3);
+//
+//   must be guaranteed to produce the same hash expansion as
+//
+//     state = H::combine(std::move(state), value1);
+//     state = H::combine(std::move(state), value2);
+//     state = H::combine(std::move(state), value3);
+//
+// * `H::combine_contiguous(state, data, size)`
+//
+//    Combines a contiguous array of `size` elements into a hash state,
+//    returning the updated state. Note that the existing hash state is
+//    move-only and must be passed by value.
+//
+//    NOTE:
+//
+//      state = H::combine_contiguous(std::move(state), data, size);
+//
+//    need NOT be guaranteed to produce the same hash expansion as a loop
+//    (it may perform internal optimizations). If you need this guarantee, use a
+//    loop instead.
+//
+// * `H::combine_unordered(state, begin, end)`
+//
+//    Combines a set of elements denoted by an iterator pair into a hash
+//    state, returning the updated state.  Note that the existing hash
+//    state is move-only and must be passed by value.
+//
+//    Unlike the other two methods, the hashing is order-independent.
+//    This can be used to hash unordered collections.
+//
+// -----------------------------------------------------------------------------
+// Adding Type Support to `absl::Hash`
+// -----------------------------------------------------------------------------
+//
+// To add support for your user-defined type, add a proper `AbslHashValue()`
+// overload as a free (non-member) function. The overload will take an
+// existing hash state and should combine that state with state from the type.
+//
+// Example:
+//
+//   template <typename H>
+//   H AbslHashValue(H state, const MyType& v) {
+//     return H::combine(std::move(state), v.field1, ..., v.fieldN);
+//   }
+//
+// where `(field1, ..., fieldN)` are the members you would use on your
+// `operator==` to define equality.
+//
+// Notice that `AbslHashValue` is not a class member, but an ordinary function.
+// An `AbslHashValue` overload for a type should only be declared in the same
+// file and namespace as said type. The proper `AbslHashValue` implementation
+// for a given type will be discovered via ADL.
+//
+// Note: unlike `std::hash', `absl::Hash` should never be specialized. It must
+// only be extended by adding `AbslHashValue()` overloads.
+//
+template <typename T>
+using Hash = absl::hash_internal::Hash<T>;
+
+// HashOf
+//
+// absl::HashOf() is a helper that generates a hash from the values of its
+// arguments.  It dispatches to absl::Hash directly, as follows:
+//  * HashOf(t) == absl::Hash<T>{}(t)
+//  * HashOf(a, b, c) == HashOf(std::make_tuple(a, b, c))
+//
+// HashOf(a1, a2, ...) == HashOf(b1, b2, ...) is guaranteed when
+//  * The argument lists have pairwise identical C++ types
+//  * a1 == b1 && a2 == b2 && ...
+//
+// The requirement that the arguments match in both type and value is critical.
+// It means that `a == b` does not necessarily imply `HashOf(a) == HashOf(b)` if
+// `a` and `b` have different types. For example, `HashOf(2) != HashOf(2.0)`.
+template <int&... ExplicitArgumentBarrier, typename... Types>
+size_t HashOf(const Types&... values) {
+  auto tuple = std::tie(values...);
+  return absl::Hash<decltype(tuple)>{}(tuple);
+}
+
+// HashState
+//
+// A type erased version of the hash state concept, for use in user-defined
+// `AbslHashValue` implementations that can't use templates (such as PImpl
+// classes, virtual functions, etc.). The type erasure adds overhead so it
+// should be avoided unless necessary.
+//
+// Note: This wrapper will only erase calls to
+//     combine_contiguous(H, const unsigned char*, size_t)
+//     RunCombineUnordered(H, CombinerF)
+//
+// All other calls will be handled internally and will not invoke overloads
+// provided by the wrapped class.
+//
+// Users of this class should still define a template `AbslHashValue` function,
+// but can use `absl::HashState::Create(&state)` to erase the type of the hash
+// state and dispatch to their private hashing logic.
+//
+// This state can be used like any other hash state. In particular, you can call
+// `HashState::combine()` and `HashState::combine_contiguous()` on it.
+//
+// Example:
+//
+//   class Interface {
+//    public:
+//     template <typename H>
+//     friend H AbslHashValue(H state, const Interface& value) {
+//       state = H::combine(std::move(state), std::type_index(typeid(*this)));
+//       value.HashValue(absl::HashState::Create(&state));
+//       return state;
+//     }
+//    private:
+//     virtual void HashValue(absl::HashState state) const = 0;
+//   };
+//
+//   class Impl : Interface {
+//    private:
+//     void HashValue(absl::HashState state) const override {
+//       absl::HashState::combine(std::move(state), v1_, v2_);
+//     }
+//     int v1_;
+//     std::string v2_;
+//   };
+class HashState : public hash_internal::HashStateBase<HashState> {
+ public:
+  // HashState::Create()
+  //
+  // Create a new `HashState` instance that wraps `state`. All calls to
+  // `combine()` and `combine_contiguous()` on the new instance will be
+  // redirected to the original `state` object. The `state` object must outlive
+  // the `HashState` instance.
+  template <typename T>
+  static HashState Create(T* state) {
+    HashState s;
+    s.Init(state);
+    return s;
+  }
+
+  HashState(const HashState&) = delete;
+  HashState& operator=(const HashState&) = delete;
+  HashState(HashState&&) = default;
+  HashState& operator=(HashState&&) = default;
+
+  // HashState::combine()
+  //
+  // Combines an arbitrary number of values into a hash state, returning the
+  // updated state.
+  using HashState::HashStateBase::combine;
+
+  // HashState::combine_contiguous()
+  //
+  // Combines a contiguous array of `size` elements into a hash state, returning
+  // the updated state.
+  static HashState combine_contiguous(HashState hash_state,
+                                      const unsigned char* first, size_t size) {
+    hash_state.combine_contiguous_(hash_state.state_, first, size);
+    return hash_state;
+  }
+  using HashState::HashStateBase::combine_contiguous;
+
+ private:
+  HashState() = default;
+
+  friend class HashState::HashStateBase;
+
+  template <typename T>
+  static void CombineContiguousImpl(void* p, const unsigned char* first,
+                                    size_t size) {
+    T& state = *static_cast<T*>(p);
+    state = T::combine_contiguous(std::move(state), first, size);
+  }
+
+  template <typename T>
+  void Init(T* state) {
+    state_ = state;
+    combine_contiguous_ = &CombineContiguousImpl<T>;
+    run_combine_unordered_ = &RunCombineUnorderedImpl<T>;
+  }
+
+  template <typename HS>
+  struct CombineUnorderedInvoker {
+    template <typename T, typename ConsumerT>
+    void operator()(T inner_state, ConsumerT inner_cb) {
+      f(HashState::Create(&inner_state),
+        [&](HashState& inner_erased) { inner_cb(inner_erased.Real<T>()); });
+    }
+
+    absl::FunctionRef<void(HS, absl::FunctionRef<void(HS&)>)> f;
+  };
+
+  template <typename T>
+  static HashState RunCombineUnorderedImpl(
+      HashState state,
+      absl::FunctionRef<void(HashState, absl::FunctionRef<void(HashState&)>)>
+          f) {
+    // Note that this implementation assumes that inner_state and outer_state
+    // are the same type.  This isn't true in the SpyHash case, but SpyHash
+    // types are move-convertible to each other, so this still works.
+    T& real_state = state.Real<T>();
+    real_state = T::RunCombineUnordered(
+        std::move(real_state), CombineUnorderedInvoker<HashState>{f});
+    return state;
+  }
+
+  template <typename CombinerT>
+  static HashState RunCombineUnordered(HashState state, CombinerT combiner) {
+    auto* run = state.run_combine_unordered_;
+    return run(std::move(state), std::ref(combiner));
+  }
+
+  // Do not erase an already erased state.
+  void Init(HashState* state) {
+    state_ = state->state_;
+    combine_contiguous_ = state->combine_contiguous_;
+    run_combine_unordered_ = state->run_combine_unordered_;
+  }
+
+  template <typename T>
+  T& Real() {
+    return *static_cast<T*>(state_);
+  }
+
+  void* state_;
+  void (*combine_contiguous_)(void*, const unsigned char*, size_t);
+  HashState (*run_combine_unordered_)(
+      HashState state,
+      absl::FunctionRef<void(HashState, absl::FunctionRef<void(HashState&)>)>);
+};
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_HASH_H_
diff --git a/weight/_dep/abseil-cpp/absl/hash/hash_benchmark.cc b/weight/_dep/abseil-cpp/absl/hash/hash_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d18ea694aaf76b535e289d7b8fe2ff8880bdacb5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/hash_benchmark.cc
@@ -0,0 +1,323 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <typeindex>
+#include <utility>
+#include <vector>
+
+#include "absl/base/attributes.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/hash/hash.h"
+#include "absl/random/random.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/cord_test_helpers.h"
+#include "absl/strings/string_view.h"
+#include "benchmark/benchmark.h"
+
+namespace {
+
+using absl::Hash;
+
+template <template <typename> class H, typename T>
+void RunBenchmark(benchmark::State& state, T value) {
+  H<T> h;
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(value);
+    benchmark::DoNotOptimize(h(value));
+  }
+}
+
+}  // namespace
+
+template <typename T>
+using AbslHash = absl::Hash<T>;
+
+class TypeErasedInterface {
+ public:
+  virtual ~TypeErasedInterface() = default;
+
+  template <typename H>
+  friend H AbslHashValue(H state, const TypeErasedInterface& wrapper) {
+    state = H::combine(std::move(state), std::type_index(typeid(wrapper)));
+    wrapper.HashValue(absl::HashState::Create(&state));
+    return state;
+  }
+
+ private:
+  virtual void HashValue(absl::HashState state) const = 0;
+};
+
+template <typename T>
+struct TypeErasedAbslHash {
+  class Wrapper : public TypeErasedInterface {
+   public:
+    explicit Wrapper(const T& value) : value_(value) {}
+
+   private:
+    void HashValue(absl::HashState state) const override {
+      absl::HashState::combine(std::move(state), value_);
+    }
+
+    const T& value_;
+  };
+
+  size_t operator()(const T& value) {
+    return absl::Hash<Wrapper>{}(Wrapper(value));
+  }
+};
+
+absl::Cord FlatCord(size_t size) {
+  absl::Cord result(std::string(size, 'a'));
+  result.Flatten();
+  return result;
+}
+
+absl::Cord FragmentedCord(size_t size) {
+  const size_t orig_size = size;
+  std::vector<std::string> chunks;
+  size_t chunk_size = std::max<size_t>(1, size / 10);
+  while (size > chunk_size) {
+    chunks.push_back(std::string(chunk_size, 'a'));
+    size -= chunk_size;
+  }
+  if (size > 0) {
+    chunks.push_back(std::string(size, 'a'));
+  }
+  absl::Cord result = absl::MakeFragmentedCord(chunks);
+  (void) orig_size;
+  assert(result.size() == orig_size);
+  return result;
+}
+
+template <typename T>
+std::vector<T> Vector(size_t count) {
+  std::vector<T> result;
+  for (size_t v = 0; v < count; ++v) {
+    result.push_back(v);
+  }
+  return result;
+}
+
+// Bogus type that replicates an unorderd_set's bit mixing, but with
+// vector-speed iteration. This is intended to measure the overhead of unordered
+// hashing without counting the speed of unordered_set iteration.
+template <typename T>
+struct FastUnorderedSet {
+  explicit FastUnorderedSet(size_t count) {
+    for (size_t v = 0; v < count; ++v) {
+      values.push_back(v);
+    }
+  }
+  std::vector<T> values;
+
+  template <typename H>
+  friend H AbslHashValue(H h, const FastUnorderedSet& fus) {
+    return H::combine(H::combine_unordered(std::move(h), fus.values.begin(),
+                                           fus.values.end()),
+                      fus.values.size());
+  }
+};
+
+template <typename T>
+absl::flat_hash_set<T> FlatHashSet(size_t count) {
+  absl::flat_hash_set<T> result;
+  for (size_t v = 0; v < count; ++v) {
+    result.insert(v);
+  }
+  return result;
+}
+
+// Generates a benchmark and a codegen method for the provided types.  The
+// codegen method provides a well known entrypoint for dumping assembly.
+#define MAKE_BENCHMARK(hash, name, ...)                          \
+  namespace {                                                    \
+  void BM_##hash##_##name(benchmark::State& state) {             \
+    RunBenchmark<hash>(state, __VA_ARGS__);                      \
+  }                                                              \
+  BENCHMARK(BM_##hash##_##name);                                 \
+  }                                                              \
+  size_t Codegen##hash##name(const decltype(__VA_ARGS__)& arg);  \
+  size_t Codegen##hash##name(const decltype(__VA_ARGS__)& arg) { \
+    return hash<decltype(__VA_ARGS__)>{}(arg);                   \
+  }                                                              \
+  bool absl_hash_test_odr_use##hash##name =                      \
+      (benchmark::DoNotOptimize(&Codegen##hash##name), false);
+
+MAKE_BENCHMARK(AbslHash, Int32, int32_t{});
+MAKE_BENCHMARK(AbslHash, Int64, int64_t{});
+MAKE_BENCHMARK(AbslHash, Double, 1.2);
+MAKE_BENCHMARK(AbslHash, DoubleZero, 0.0);
+MAKE_BENCHMARK(AbslHash, PairInt32Int32, std::pair<int32_t, int32_t>{});
+MAKE_BENCHMARK(AbslHash, PairInt64Int64, std::pair<int64_t, int64_t>{});
+MAKE_BENCHMARK(AbslHash, TupleInt32BoolInt64,
+               std::tuple<int32_t, bool, int64_t>{});
+MAKE_BENCHMARK(AbslHash, String_0, std::string());
+MAKE_BENCHMARK(AbslHash, String_10, std::string(10, 'a'));
+MAKE_BENCHMARK(AbslHash, String_30, std::string(30, 'a'));
+MAKE_BENCHMARK(AbslHash, String_90, std::string(90, 'a'));
+MAKE_BENCHMARK(AbslHash, String_200, std::string(200, 'a'));
+MAKE_BENCHMARK(AbslHash, String_5000, std::string(5000, 'a'));
+MAKE_BENCHMARK(AbslHash, Cord_Flat_0, absl::Cord());
+MAKE_BENCHMARK(AbslHash, Cord_Flat_10, FlatCord(10));
+MAKE_BENCHMARK(AbslHash, Cord_Flat_30, FlatCord(30));
+MAKE_BENCHMARK(AbslHash, Cord_Flat_90, FlatCord(90));
+MAKE_BENCHMARK(AbslHash, Cord_Flat_200, FlatCord(200));
+MAKE_BENCHMARK(AbslHash, Cord_Flat_5000, FlatCord(5000));
+MAKE_BENCHMARK(AbslHash, Cord_Fragmented_200, FragmentedCord(200));
+MAKE_BENCHMARK(AbslHash, Cord_Fragmented_5000, FragmentedCord(5000));
+MAKE_BENCHMARK(AbslHash, VectorInt64_10, Vector<int64_t>(10));
+MAKE_BENCHMARK(AbslHash, VectorInt64_100, Vector<int64_t>(100));
+MAKE_BENCHMARK(AbslHash, VectorInt64_1000, Vector<int64_t>(1000));
+MAKE_BENCHMARK(AbslHash, VectorDouble_10, Vector<double>(10));
+MAKE_BENCHMARK(AbslHash, VectorDouble_100, Vector<double>(100));
+MAKE_BENCHMARK(AbslHash, VectorDouble_1000, Vector<double>(1000));
+MAKE_BENCHMARK(AbslHash, FlatHashSetInt64_10, FlatHashSet<int64_t>(10));
+MAKE_BENCHMARK(AbslHash, FlatHashSetInt64_100, FlatHashSet<int64_t>(100));
+MAKE_BENCHMARK(AbslHash, FlatHashSetInt64_1000, FlatHashSet<int64_t>(1000));
+MAKE_BENCHMARK(AbslHash, FlatHashSetDouble_10, FlatHashSet<double>(10));
+MAKE_BENCHMARK(AbslHash, FlatHashSetDouble_100, FlatHashSet<double>(100));
+MAKE_BENCHMARK(AbslHash, FlatHashSetDouble_1000, FlatHashSet<double>(1000));
+MAKE_BENCHMARK(AbslHash, FastUnorderedSetInt64_1000,
+               FastUnorderedSet<int64_t>(1000));
+MAKE_BENCHMARK(AbslHash, FastUnorderedSetDouble_1000,
+               FastUnorderedSet<double>(1000));
+MAKE_BENCHMARK(AbslHash, PairStringString_0,
+               std::make_pair(std::string(), std::string()));
+MAKE_BENCHMARK(AbslHash, PairStringString_10,
+               std::make_pair(std::string(10, 'a'), std::string(10, 'b')));
+MAKE_BENCHMARK(AbslHash, PairStringString_30,
+               std::make_pair(std::string(30, 'a'), std::string(30, 'b')));
+MAKE_BENCHMARK(AbslHash, PairStringString_90,
+               std::make_pair(std::string(90, 'a'), std::string(90, 'b')));
+MAKE_BENCHMARK(AbslHash, PairStringString_200,
+               std::make_pair(std::string(200, 'a'), std::string(200, 'b')));
+MAKE_BENCHMARK(AbslHash, PairStringString_5000,
+               std::make_pair(std::string(5000, 'a'), std::string(5000, 'b')));
+
+MAKE_BENCHMARK(TypeErasedAbslHash, Int32, int32_t{});
+MAKE_BENCHMARK(TypeErasedAbslHash, Int64, int64_t{});
+MAKE_BENCHMARK(TypeErasedAbslHash, PairInt32Int32,
+               std::pair<int32_t, int32_t>{});
+MAKE_BENCHMARK(TypeErasedAbslHash, PairInt64Int64,
+               std::pair<int64_t, int64_t>{});
+MAKE_BENCHMARK(TypeErasedAbslHash, TupleInt32BoolInt64,
+               std::tuple<int32_t, bool, int64_t>{});
+MAKE_BENCHMARK(TypeErasedAbslHash, String_0, std::string());
+MAKE_BENCHMARK(TypeErasedAbslHash, String_10, std::string(10, 'a'));
+MAKE_BENCHMARK(TypeErasedAbslHash, String_30, std::string(30, 'a'));
+MAKE_BENCHMARK(TypeErasedAbslHash, String_90, std::string(90, 'a'));
+MAKE_BENCHMARK(TypeErasedAbslHash, String_200, std::string(200, 'a'));
+MAKE_BENCHMARK(TypeErasedAbslHash, String_5000, std::string(5000, 'a'));
+MAKE_BENCHMARK(TypeErasedAbslHash, VectorDouble_10,
+               std::vector<double>(10, 1.1));
+MAKE_BENCHMARK(TypeErasedAbslHash, VectorDouble_100,
+               std::vector<double>(100, 1.1));
+MAKE_BENCHMARK(TypeErasedAbslHash, VectorDouble_1000,
+               std::vector<double>(1000, 1.1));
+MAKE_BENCHMARK(TypeErasedAbslHash, FlatHashSetInt64_10,
+               FlatHashSet<int64_t>(10));
+MAKE_BENCHMARK(TypeErasedAbslHash, FlatHashSetInt64_100,
+               FlatHashSet<int64_t>(100));
+MAKE_BENCHMARK(TypeErasedAbslHash, FlatHashSetInt64_1000,
+               FlatHashSet<int64_t>(1000));
+MAKE_BENCHMARK(TypeErasedAbslHash, FlatHashSetDouble_10,
+               FlatHashSet<double>(10));
+MAKE_BENCHMARK(TypeErasedAbslHash, FlatHashSetDouble_100,
+               FlatHashSet<double>(100));
+MAKE_BENCHMARK(TypeErasedAbslHash, FlatHashSetDouble_1000,
+               FlatHashSet<double>(1000));
+MAKE_BENCHMARK(TypeErasedAbslHash, FastUnorderedSetInt64_1000,
+               FastUnorderedSet<int64_t>(1000));
+MAKE_BENCHMARK(TypeErasedAbslHash, FastUnorderedSetDouble_1000,
+               FastUnorderedSet<double>(1000));
+
+// The latency benchmark attempts to model the speed of the hash function in
+// production. When a hash function is used for hashtable lookups it is rarely
+// used to hash N items in a tight loop nor on constant sized strings. Instead,
+// after hashing there is a potential equality test plus a (usually) large
+// amount of user code. To simulate this effectively we introduce a data
+// dependency between elements we hash by using the hash of the Nth element as
+// the selector of the N+1th element to hash. This isolates the hash function
+// code much like in production. As a bonus we use the hash to generate strings
+// of size [1,N] (instead of fixed N) to disable perfect branch predictions in
+// hash function implementations.
+namespace {
+// 16kb fits in L1 cache of most CPUs we care about. Keeping memory latency low
+// will allow us to attribute most time to CPU which means more accurate
+// measurements.
+static constexpr size_t kEntropySize = 16 << 10;
+static char entropy[kEntropySize + 1024];
+ABSL_ATTRIBUTE_UNUSED static const bool kInitialized = [] {
+  absl::BitGen gen;
+  static_assert(sizeof(entropy) % sizeof(uint64_t) == 0, "");
+  for (int i = 0; i != sizeof(entropy); i += sizeof(uint64_t)) {
+    auto rand = absl::Uniform<uint64_t>(gen);
+    memcpy(&entropy[i], &rand, sizeof(uint64_t));
+  }
+  return true;
+}();
+}  // namespace
+
+template <class T>
+struct PodRand {
+  static_assert(std::is_pod<T>::value, "");
+  static_assert(kEntropySize + sizeof(T) < sizeof(entropy), "");
+
+  T Get(size_t i) const {
+    T v;
+    memcpy(&v, &entropy[i % kEntropySize], sizeof(T));
+    return v;
+  }
+};
+
+template <size_t N>
+struct StringRand {
+  static_assert(kEntropySize + N < sizeof(entropy), "");
+
+  absl::string_view Get(size_t i) const {
+    // This has a small bias towards small numbers. Because max N is ~200 this
+    // is very small and prefer to be very fast instead of absolutely accurate.
+    // Also we pass N = 2^K+1 so that mod reduces to a bitand.
+    size_t s = (i % (N - 1)) + 1;
+    return {&entropy[i % kEntropySize], s};
+  }
+};
+
+#define MAKE_LATENCY_BENCHMARK(hash, name, ...)              \
+  namespace {                                                \
+  void BM_latency_##hash##_##name(benchmark::State& state) { \
+    __VA_ARGS__ r;                                           \
+    hash<decltype(r.Get(0))> h;                              \
+    size_t i = 871401241;                                    \
+    for (auto _ : state) {                                   \
+      benchmark::DoNotOptimize(i = h(r.Get(i)));             \
+    }                                                        \
+  }                                                          \
+  BENCHMARK(BM_latency_##hash##_##name);                     \
+  }  // namespace
+
+MAKE_LATENCY_BENCHMARK(AbslHash, Int32, PodRand<int32_t>);
+MAKE_LATENCY_BENCHMARK(AbslHash, Int64, PodRand<int64_t>);
+MAKE_LATENCY_BENCHMARK(AbslHash, String9, StringRand<9>);
+MAKE_LATENCY_BENCHMARK(AbslHash, String33, StringRand<33>);
+MAKE_LATENCY_BENCHMARK(AbslHash, String65, StringRand<65>);
+MAKE_LATENCY_BENCHMARK(AbslHash, String257, StringRand<257>);
diff --git a/weight/_dep/abseil-cpp/absl/hash/hash_instantiated_test.cc b/weight/_dep/abseil-cpp/absl/hash/hash_instantiated_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e65de9ca9edfd11c7c9802b322c3c44e47fe78e5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/hash_instantiated_test.cc
@@ -0,0 +1,224 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains a few select absl::Hash tests that, due to their reliance
+// on INSTANTIATE_TYPED_TEST_SUITE_P, require a large amount of memory to
+// compile. Put new tests in hash_test.cc, not this file.
+
+#include "absl/hash/hash.h"
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <deque>
+#include <forward_list>
+#include <initializer_list>
+#include <list>
+#include <map>
+#include <set>
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/container/btree_map.h"
+#include "absl/container/btree_set.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/container/node_hash_map.h"
+#include "absl/container/node_hash_set.h"
+#include "absl/hash/hash_testing.h"
+#include "absl/hash/internal/hash_test.h"
+
+namespace {
+
+using ::absl::hash_test_internal::is_hashable;
+using ::absl::hash_test_internal::TypeErasedContainer;
+
+// Dummy type with unordered equality and hashing semantics.  This preserves
+// input order internally, and is used below to ensure we get test coverage
+// for equal sequences with different iteraton orders.
+template <typename T>
+class UnorderedSequence {
+ public:
+  UnorderedSequence() = default;
+  template <typename TT>
+  UnorderedSequence(std::initializer_list<TT> l)
+      : values_(l.begin(), l.end()) {}
+  template <typename ForwardIterator,
+            typename std::enable_if<!std::is_integral<ForwardIterator>::value,
+                                    bool>::type = true>
+  UnorderedSequence(ForwardIterator begin, ForwardIterator end)
+      : values_(begin, end) {}
+  // one-argument constructor of value type T, to appease older toolchains that
+  // get confused by one-element initializer lists in some contexts
+  explicit UnorderedSequence(const T& v) : values_(&v, &v + 1) {}
+
+  using value_type = T;
+
+  size_t size() const { return values_.size(); }
+  typename std::vector<T>::const_iterator begin() const {
+    return values_.begin();
+  }
+  typename std::vector<T>::const_iterator end() const { return values_.end(); }
+
+  friend bool operator==(const UnorderedSequence& lhs,
+                         const UnorderedSequence& rhs) {
+    return lhs.size() == rhs.size() &&
+           std::is_permutation(lhs.begin(), lhs.end(), rhs.begin());
+  }
+  friend bool operator!=(const UnorderedSequence& lhs,
+                         const UnorderedSequence& rhs) {
+    return !(lhs == rhs);
+  }
+  template <typename H>
+  friend H AbslHashValue(H h, const UnorderedSequence& u) {
+    return H::combine(H::combine_unordered(std::move(h), u.begin(), u.end()),
+                      u.size());
+  }
+
+ private:
+  std::vector<T> values_;
+};
+
+template <typename T>
+class HashValueSequenceTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueSequenceTest);
+
+TYPED_TEST_P(HashValueSequenceTest, BasicUsage) {
+  EXPECT_TRUE((is_hashable<TypeParam>::value));
+
+  using IntType = typename TypeParam::value_type;
+  auto a = static_cast<IntType>(0);
+  auto b = static_cast<IntType>(23);
+  auto c = static_cast<IntType>(42);
+
+  std::vector<TypeParam> exemplars = {
+      TypeParam(),        TypeParam(),        TypeParam{a, b, c},
+      TypeParam{a, c, b}, TypeParam{c, a, b}, TypeParam{a},
+      TypeParam{a, a},    TypeParam{a, a, a}, TypeParam{a, a, b},
+      TypeParam{a, b, a}, TypeParam{b, a, a}, TypeParam{a, b},
+      TypeParam{b, c}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueSequenceTest, BasicUsage);
+using IntSequenceTypes = testing::Types<
+    std::deque<int>, std::forward_list<int>, std::list<int>, std::vector<int>,
+    std::vector<bool>, TypeErasedContainer<std::vector<int>>, std::set<int>,
+    std::multiset<int>, UnorderedSequence<int>,
+    TypeErasedContainer<UnorderedSequence<int>>, std::unordered_set<int>,
+    std::unordered_multiset<int>, absl::flat_hash_set<int>,
+    absl::node_hash_set<int>, absl::btree_set<int>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueSequenceTest, IntSequenceTypes);
+
+template <typename T>
+class HashValueNestedSequenceTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueNestedSequenceTest);
+
+TYPED_TEST_P(HashValueNestedSequenceTest, BasicUsage) {
+  using T = TypeParam;
+  using V = typename T::value_type;
+  std::vector<T> exemplars = {
+      // empty case
+      T{},
+      // sets of empty sets
+      T{V{}}, T{V{}, V{}}, T{V{}, V{}, V{}},
+      // multisets of different values
+      T{V{1}}, T{V{1, 1}, V{1, 1}}, T{V{1, 1, 1}, V{1, 1, 1}, V{1, 1, 1}},
+      // various orderings of same nested sets
+      T{V{}, V{1, 2}}, T{V{}, V{2, 1}}, T{V{1, 2}, V{}}, T{V{2, 1}, V{}},
+      // various orderings of various nested sets, case 2
+      T{V{1, 2}, V{3, 4}}, T{V{1, 2}, V{4, 3}}, T{V{1, 3}, V{2, 4}},
+      T{V{1, 3}, V{4, 2}}, T{V{1, 4}, V{2, 3}}, T{V{1, 4}, V{3, 2}},
+      T{V{2, 3}, V{1, 4}}, T{V{2, 3}, V{4, 1}}, T{V{2, 4}, V{1, 3}},
+      T{V{2, 4}, V{3, 1}}, T{V{3, 4}, V{1, 2}}, T{V{3, 4}, V{2, 1}}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueNestedSequenceTest, BasicUsage);
+template <typename T>
+using TypeErasedSet = TypeErasedContainer<UnorderedSequence<T>>;
+
+using NestedIntSequenceTypes = testing::Types<
+    std::vector<std::vector<int>>, std::vector<UnorderedSequence<int>>,
+    std::vector<TypeErasedSet<int>>, UnorderedSequence<std::vector<int>>,
+    UnorderedSequence<UnorderedSequence<int>>,
+    UnorderedSequence<TypeErasedSet<int>>, TypeErasedSet<std::vector<int>>,
+    TypeErasedSet<UnorderedSequence<int>>, TypeErasedSet<TypeErasedSet<int>>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueNestedSequenceTest,
+                               NestedIntSequenceTypes);
+
+template <typename T>
+class HashValueAssociativeMapTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueAssociativeMapTest);
+
+TYPED_TEST_P(HashValueAssociativeMapTest, BasicUsage) {
+  using M = TypeParam;
+  using V = typename M::value_type;
+  std::vector<M> exemplars{M{},
+                           M{V{0, "foo"}},
+                           M{V{1, "foo"}},
+                           M{V{0, "bar"}},
+                           M{V{1, "bar"}},
+                           M{V{0, "foo"}, V{42, "bar"}},
+                           M{V{42, "bar"}, V{0, "foo"}},
+                           M{V{1, "foo"}, V{42, "bar"}},
+                           M{V{1, "foo"}, V{43, "bar"}},
+                           M{V{1, "foo"}, V{43, "baz"}}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueAssociativeMapTest, BasicUsage);
+using AssociativeMapTypes = testing::Types<
+    std::map<int, std::string>, std::unordered_map<int, std::string>,
+    absl::flat_hash_map<int, std::string>,
+    absl::node_hash_map<int, std::string>, absl::btree_map<int, std::string>,
+    UnorderedSequence<std::pair<const int, std::string>>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueAssociativeMapTest,
+                               AssociativeMapTypes);
+
+template <typename T>
+class HashValueAssociativeMultimapTest : public testing::Test {};
+TYPED_TEST_SUITE_P(HashValueAssociativeMultimapTest);
+
+TYPED_TEST_P(HashValueAssociativeMultimapTest, BasicUsage) {
+  using MM = TypeParam;
+  using V = typename MM::value_type;
+  std::vector<MM> exemplars{MM{},
+                            MM{V{0, "foo"}},
+                            MM{V{1, "foo"}},
+                            MM{V{0, "bar"}},
+                            MM{V{1, "bar"}},
+                            MM{V{0, "foo"}, V{0, "bar"}},
+                            MM{V{0, "bar"}, V{0, "foo"}},
+                            MM{V{0, "foo"}, V{42, "bar"}},
+                            MM{V{1, "foo"}, V{42, "bar"}},
+                            MM{V{1, "foo"}, V{1, "foo"}, V{43, "bar"}},
+                            MM{V{1, "foo"}, V{43, "bar"}, V{1, "foo"}},
+                            MM{V{1, "foo"}, V{43, "baz"}}};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(exemplars));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueAssociativeMultimapTest, BasicUsage);
+using AssociativeMultimapTypes =
+    testing::Types<std::multimap<int, std::string>,
+                   std::unordered_multimap<int, std::string>>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueAssociativeMultimapTest,
+                               AssociativeMultimapTypes);
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/hash/hash_test.cc b/weight/_dep/abseil-cpp/absl/hash/hash_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..59fe8dea933eb6ab2cbb54170d34e81ddefac659
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/hash_test.cc
@@ -0,0 +1,1148 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/hash/hash.h"
+
+#include <algorithm>
+#include <array>
+#include <bitset>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <functional>
+#include <initializer_list>
+#include <ios>
+#include <limits>
+#include <memory>
+#include <ostream>
+#include <set>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/hash/hash_testing.h"
+#include "absl/hash/internal/hash_test.h"
+#include "absl/hash/internal/spy_hash_state.h"
+#include "absl/memory/memory.h"
+#include "absl/meta/type_traits.h"
+#include "absl/strings/cord_test_helpers.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "absl/types/variant.h"
+
+#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
+#include <filesystem>  // NOLINT
+#endif
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
+namespace {
+
+using ::absl::hash_test_internal::is_hashable;
+using ::absl::hash_test_internal::TypeErasedContainer;
+using ::absl::hash_test_internal::TypeErasedValue;
+
+template <typename T>
+using TypeErasedVector = TypeErasedContainer<std::vector<T>>;
+
+using absl::Hash;
+using absl::hash_internal::SpyHashState;
+
+template <typename T>
+class HashValueIntTest : public testing::Test {
+};
+TYPED_TEST_SUITE_P(HashValueIntTest);
+
+template <typename T>
+SpyHashState SpyHash(const T& value) {
+  return SpyHashState::combine(SpyHashState(), value);
+}
+
+TYPED_TEST_P(HashValueIntTest, BasicUsage) {
+  EXPECT_TRUE((is_hashable<TypeParam>::value));
+
+  TypeParam n = 42;
+  EXPECT_EQ(SpyHash(n), SpyHash(TypeParam{42}));
+  EXPECT_NE(SpyHash(n), SpyHash(TypeParam{0}));
+  EXPECT_NE(SpyHash(std::numeric_limits<TypeParam>::max()),
+            SpyHash(std::numeric_limits<TypeParam>::min()));
+}
+
+TYPED_TEST_P(HashValueIntTest, FastPath) {
+  // Test the fast-path to make sure the values are the same.
+  TypeParam n = 42;
+  EXPECT_EQ(absl::Hash<TypeParam>{}(n),
+            absl::Hash<std::tuple<TypeParam>>{}(std::tuple<TypeParam>(n)));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashValueIntTest, BasicUsage, FastPath);
+using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t,
+                                uint32_t, uint64_t, size_t>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashValueIntTest, IntTypes);
+
+enum LegacyEnum { kValue1, kValue2, kValue3 };
+
+enum class EnumClass { kValue4, kValue5, kValue6 };
+
+TEST(HashValueTest, EnumAndBool) {
+  EXPECT_TRUE((is_hashable<LegacyEnum>::value));
+  EXPECT_TRUE((is_hashable<EnumClass>::value));
+  EXPECT_TRUE((is_hashable<bool>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      LegacyEnum::kValue1, LegacyEnum::kValue2, LegacyEnum::kValue3)));
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      EnumClass::kValue4, EnumClass::kValue5, EnumClass::kValue6)));
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(true, false)));
+}
+
+TEST(HashValueTest, FloatingPoint) {
+  EXPECT_TRUE((is_hashable<float>::value));
+  EXPECT_TRUE((is_hashable<double>::value));
+  EXPECT_TRUE((is_hashable<long double>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(42.f, 0.f, -0.f, std::numeric_limits<float>::infinity(),
+                      -std::numeric_limits<float>::infinity())));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(42., 0., -0., std::numeric_limits<double>::infinity(),
+                      -std::numeric_limits<double>::infinity())));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      // Add some values with small exponent to test that NORMAL values also
+      // append their category.
+      .5L, 1.L, 2.L, 4.L, 42.L, 0.L, -0.L,
+      17 * static_cast<long double>(std::numeric_limits<double>::max()),
+      std::numeric_limits<long double>::infinity(),
+      -std::numeric_limits<long double>::infinity())));
+}
+
+TEST(HashValueTest, Pointer) {
+  EXPECT_TRUE((is_hashable<int*>::value));
+  EXPECT_TRUE((is_hashable<int(*)(char, float)>::value));
+  EXPECT_TRUE((is_hashable<void(*)(int, int, ...)>::value));
+
+  int i;
+  int* ptr = &i;
+  int* n = nullptr;
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(&i, ptr, nullptr, ptr + 1, n)));
+}
+
+TEST(HashValueTest, PointerAlignment) {
+  // We want to make sure that pointer alignment will not cause bits to be
+  // stuck.
+
+  constexpr size_t kTotalSize = 1 << 20;
+  std::unique_ptr<char[]> data(new char[kTotalSize]);
+  constexpr size_t kLog2NumValues = 5;
+  constexpr size_t kNumValues = 1 << kLog2NumValues;
+
+  for (size_t align = 1; align < kTotalSize / kNumValues;
+       align < 8 ? align += 1 : align < 1024 ? align += 8 : align += 32) {
+    SCOPED_TRACE(align);
+    ASSERT_LE(align * kNumValues, kTotalSize);
+
+    size_t bits_or = 0;
+    size_t bits_and = ~size_t{};
+
+    for (size_t i = 0; i < kNumValues; ++i) {
+      size_t hash = absl::Hash<void*>()(data.get() + i * align);
+      bits_or |= hash;
+      bits_and &= hash;
+    }
+
+    // Limit the scope to the bits we would be using for Swisstable.
+    constexpr size_t kMask = (1 << (kLog2NumValues + 7)) - 1;
+    size_t stuck_bits = (~bits_or | bits_and) & kMask;
+    EXPECT_EQ(stuck_bits, 0u) << "0x" << std::hex << stuck_bits;
+  }
+}
+
+TEST(HashValueTest, PointerToMember) {
+  struct Bass {
+    void q() {}
+  };
+
+  struct A : Bass {
+    virtual ~A() = default;
+    virtual void vfa() {}
+
+    static auto pq() -> void (A::*)() { return &A::q; }
+  };
+
+  struct B : Bass {
+    virtual ~B() = default;
+    virtual void vfb() {}
+
+    static auto pq() -> void (B::*)() { return &B::q; }
+  };
+
+  struct Foo : A, B {
+    void f1() {}
+    void f2() const {}
+
+    int g1() & { return 0; }
+    int g2() const & { return 0; }
+    int g3() && { return 0; }
+    int g4() const && { return 0; }
+
+    int h1() & { return 0; }
+    int h2() const & { return 0; }
+    int h3() && { return 0; }
+    int h4() const && { return 0; }
+
+    int a;
+    int b;
+
+    const int c = 11;
+    const int d = 22;
+  };
+
+  EXPECT_TRUE((is_hashable<float Foo::*>::value));
+  EXPECT_TRUE((is_hashable<double (Foo::*)(int, int)&&>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(&Foo::a, &Foo::b, static_cast<int Foo::*>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(&Foo::c, &Foo::d, static_cast<const int Foo::*>(nullptr),
+                      &Foo::a, &Foo::b)));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      &Foo::f1, static_cast<void (Foo::*)()>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      &Foo::f2, static_cast<void (Foo::*)() const>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      &Foo::g1, &Foo::h1, static_cast<int (Foo::*)() &>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      &Foo::g2, &Foo::h2, static_cast<int (Foo::*)() const &>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      &Foo::g3, &Foo::h3, static_cast<int (Foo::*)() &&>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      &Foo::g4, &Foo::h4, static_cast<int (Foo::*)() const &&>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(static_cast<void (Foo::*)()>(&Foo::vfa),
+                      static_cast<void (Foo::*)()>(&Foo::vfb),
+                      static_cast<void (Foo::*)()>(nullptr))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(static_cast<void (Foo::*)()>(Foo::A::pq()),
+                      static_cast<void (Foo::*)()>(Foo::B::pq()),
+                      static_cast<void (Foo::*)()>(nullptr))));
+}
+
+TEST(HashValueTest, PairAndTuple) {
+  EXPECT_TRUE((is_hashable<std::pair<int, int>>::value));
+  EXPECT_TRUE((is_hashable<std::pair<const int&, const int&>>::value));
+  EXPECT_TRUE((is_hashable<std::tuple<int&, int&>>::value));
+  EXPECT_TRUE((is_hashable<std::tuple<int&&, int&&>>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::make_pair(0, 42), std::make_pair(0, 42), std::make_pair(42, 0),
+      std::make_pair(0, 0), std::make_pair(42, 42), std::make_pair(1, 42))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::make_tuple(0, 0, 0), std::make_tuple(0, 0, 42),
+                      std::make_tuple(0, 23, 0), std::make_tuple(17, 0, 0),
+                      std::make_tuple(42, 0, 0), std::make_tuple(3, 9, 9),
+                      std::make_tuple(0, 0, -42))));
+
+  // Test that tuples of lvalue references work (so we need a few lvalues):
+  int a = 0, b = 1, c = 17, d = 23;
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::tie(a, a), std::tie(a, b), std::tie(b, c), std::tie(c, d))));
+
+  // Test that tuples of rvalue references work:
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::forward_as_tuple(0, 0, 0), std::forward_as_tuple(0, 0, 42),
+      std::forward_as_tuple(0, 23, 0), std::forward_as_tuple(17, 0, 0),
+      std::forward_as_tuple(42, 0, 0), std::forward_as_tuple(3, 9, 9),
+      std::forward_as_tuple(0, 0, -42))));
+}
+
+TEST(HashValueTest, CombineContiguousWorks) {
+  std::vector<std::tuple<int>> v1 = {std::make_tuple(1), std::make_tuple(3)};
+  std::vector<std::tuple<int>> v2 = {std::make_tuple(1), std::make_tuple(2)};
+
+  auto vh1 = SpyHash(v1);
+  auto vh2 = SpyHash(v2);
+  EXPECT_NE(vh1, vh2);
+}
+
+struct DummyDeleter {
+  template <typename T>
+  void operator() (T* ptr) {}
+};
+
+struct SmartPointerEq {
+  template <typename T, typename U>
+  bool operator()(const T& t, const U& u) const {
+    return GetPtr(t) == GetPtr(u);
+  }
+
+  template <typename T>
+  static auto GetPtr(const T& t) -> decltype(&*t) {
+    return t ? &*t : nullptr;
+  }
+
+  static std::nullptr_t GetPtr(std::nullptr_t) { return nullptr; }
+};
+
+TEST(HashValueTest, SmartPointers) {
+  EXPECT_TRUE((is_hashable<std::unique_ptr<int>>::value));
+  EXPECT_TRUE((is_hashable<std::unique_ptr<int, DummyDeleter>>::value));
+  EXPECT_TRUE((is_hashable<std::shared_ptr<int>>::value));
+
+  int i, j;
+  std::unique_ptr<int, DummyDeleter> unique1(&i);
+  std::unique_ptr<int, DummyDeleter> unique2(&i);
+  std::unique_ptr<int, DummyDeleter> unique_other(&j);
+  std::unique_ptr<int, DummyDeleter> unique_null;
+
+  std::shared_ptr<int> shared1(&i, DummyDeleter());
+  std::shared_ptr<int> shared2(&i, DummyDeleter());
+  std::shared_ptr<int> shared_other(&j, DummyDeleter());
+  std::shared_ptr<int> shared_null;
+
+  // Sanity check of the Eq function.
+  ASSERT_TRUE(SmartPointerEq{}(unique1, shared1));
+  ASSERT_FALSE(SmartPointerEq{}(unique1, shared_other));
+  ASSERT_TRUE(SmartPointerEq{}(unique_null, nullptr));
+  ASSERT_FALSE(SmartPointerEq{}(shared2, nullptr));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::forward_as_tuple(&i, nullptr,                    //
+                            unique1, unique2, unique_null,  //
+                            absl::make_unique<int>(),       //
+                            shared1, shared2, shared_null,  //
+                            std::make_shared<int>()),
+      SmartPointerEq{}));
+}
+
+TEST(HashValueTest, FunctionPointer) {
+  using Func = int (*)();
+  EXPECT_TRUE(is_hashable<Func>::value);
+
+  Func p1 = [] { return 2; }, p2 = [] { return 1; };
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(p1, p2, nullptr)));
+}
+
+struct WrapInTuple {
+  template <typename T>
+  std::tuple<int, T, size_t> operator()(const T& t) const {
+    return std::make_tuple(7, t, 0xdeadbeef);
+  }
+};
+
+absl::Cord FlatCord(absl::string_view sv) {
+  absl::Cord c(sv);
+  c.Flatten();
+  return c;
+}
+
+absl::Cord FragmentedCord(absl::string_view sv) {
+  if (sv.size() < 2) {
+    return absl::Cord(sv);
+  }
+  size_t halfway = sv.size() / 2;
+  std::vector<absl::string_view> parts = {sv.substr(0, halfway),
+                                          sv.substr(halfway)};
+  return absl::MakeFragmentedCord(parts);
+}
+
+TEST(HashValueTest, Strings) {
+  EXPECT_TRUE((is_hashable<std::string>::value));
+
+  const std::string small = "foo";
+  const std::string dup = "foofoo";
+  const std::string large = std::string(2048, 'x');  // multiple of chunk size
+  const std::string huge = std::string(5000, 'a');   // not a multiple
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(  //
+      std::string(), absl::string_view(), absl::Cord(),                     //
+      std::string(""), absl::string_view(""), absl::Cord(""),               //
+      std::string(small), absl::string_view(small), absl::Cord(small),      //
+      std::string(dup), absl::string_view(dup), absl::Cord(dup),            //
+      std::string(large), absl::string_view(large), absl::Cord(large),      //
+      std::string(huge), absl::string_view(huge), FlatCord(huge),           //
+      FragmentedCord(huge))));
+
+  // Also check that nested types maintain the same hash.
+  const WrapInTuple t{};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(  //
+      t(std::string()), t(absl::string_view()), t(absl::Cord()),            //
+      t(std::string("")), t(absl::string_view("")), t(absl::Cord("")),      //
+      t(std::string(small)), t(absl::string_view(small)),                   //
+          t(absl::Cord(small)),                                             //
+      t(std::string(dup)), t(absl::string_view(dup)), t(absl::Cord(dup)),   //
+      t(std::string(large)), t(absl::string_view(large)),                   //
+          t(absl::Cord(large)),                                             //
+      t(std::string(huge)), t(absl::string_view(huge)),                     //
+          t(FlatCord(huge)), t(FragmentedCord(huge)))));
+
+  // Make sure that hashing a `const char*` does not use its string-value.
+  EXPECT_NE(SpyHash(static_cast<const char*>("ABC")),
+            SpyHash(absl::string_view("ABC")));
+}
+
+TEST(HashValueTest, WString) {
+  EXPECT_TRUE((is_hashable<std::wstring>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::wstring(), std::wstring(L"ABC"), std::wstring(L"ABC"),
+      std::wstring(L"Some other different string"),
+      std::wstring(L"Iñtërnâtiônàlizætiøn"))));
+}
+
+TEST(HashValueTest, U16String) {
+  EXPECT_TRUE((is_hashable<std::u16string>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::u16string(), std::u16string(u"ABC"), std::u16string(u"ABC"),
+      std::u16string(u"Some other different string"),
+      std::u16string(u"Iñtërnâtiônàlizætiøn"))));
+}
+
+TEST(HashValueTest, U32String) {
+  EXPECT_TRUE((is_hashable<std::u32string>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::u32string(), std::u32string(U"ABC"), std::u32string(U"ABC"),
+      std::u32string(U"Some other different string"),
+      std::u32string(U"Iñtërnâtiônàlizætiøn"))));
+}
+
+TEST(HashValueTest, WStringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::wstring_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      std::wstring_view(), std::wstring_view(L"ABC"), std::wstring_view(L"ABC"),
+      std::wstring_view(L"Some other different string_view"),
+      std::wstring_view(L"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, U16StringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::u16string_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::u16string_view(), std::u16string_view(u"ABC"),
+                      std::u16string_view(u"ABC"),
+                      std::u16string_view(u"Some other different string_view"),
+                      std::u16string_view(u"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, U32StringView) {
+#ifndef ABSL_HAVE_STD_STRING_VIEW
+  GTEST_SKIP();
+#else
+  EXPECT_TRUE((is_hashable<std::u32string_view>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::u32string_view(), std::u32string_view(U"ABC"),
+                      std::u32string_view(U"ABC"),
+                      std::u32string_view(U"Some other different string_view"),
+                      std::u32string_view(U"Iñtërnâtiônàlizætiøn"))));
+#endif
+}
+
+TEST(HashValueTest, StdFilesystemPath) {
+#ifndef ABSL_INTERNAL_STD_FILESYSTEM_PATH_HASH_AVAILABLE
+  GTEST_SKIP() << "std::filesystem::path is unavailable on this platform";
+#else
+  EXPECT_TRUE((is_hashable<std::filesystem::path>::value));
+
+  // clang-format off
+  const auto kTestCases = std::make_tuple(
+      std::filesystem::path(),
+      std::filesystem::path("/"),
+#ifndef __GLIBCXX__
+      // libstdc++ has a known issue normalizing "//".
+      // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106452
+      std::filesystem::path("//"),
+#endif
+      std::filesystem::path("/a/b"),
+      std::filesystem::path("/a//b"),
+      std::filesystem::path("a/b"),
+      std::filesystem::path("a/b/"),
+      std::filesystem::path("a//b"),
+      std::filesystem::path("a//b/"),
+      std::filesystem::path("c:/"),
+      std::filesystem::path("c:\\"),
+      std::filesystem::path("c:\\/"),
+      std::filesystem::path("c:\\//"),
+      std::filesystem::path("c://"),
+      std::filesystem::path("c://\\"),
+      std::filesystem::path("/e/p"),
+      std::filesystem::path("/s/../e/p"),
+      std::filesystem::path("e/p"),
+      std::filesystem::path("s/../e/p"));
+  // clang-format on
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(kTestCases));
+#endif
+}
+
+TEST(HashValueTest, StdArray) {
+  EXPECT_TRUE((is_hashable<std::array<int, 3>>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::array<int, 3>{}, std::array<int, 3>{{0, 23, 42}})));
+}
+
+TEST(HashValueTest, StdBitset) {
+  EXPECT_TRUE((is_hashable<std::bitset<257>>::value));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      {std::bitset<2>("00"), std::bitset<2>("01"), std::bitset<2>("10"),
+       std::bitset<2>("11")}));
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      {std::bitset<5>("10101"), std::bitset<5>("10001"), std::bitset<5>()}));
+
+  constexpr int kNumBits = 256;
+  std::array<std::string, 6> bit_strings;
+  bit_strings.fill(std::string(kNumBits, '1'));
+  bit_strings[1][0] = '0';
+  bit_strings[2][1] = '0';
+  bit_strings[3][kNumBits / 3] = '0';
+  bit_strings[4][kNumBits - 2] = '0';
+  bit_strings[5][kNumBits - 1] = '0';
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      {std::bitset<kNumBits>(bit_strings[0].c_str()),
+       std::bitset<kNumBits>(bit_strings[1].c_str()),
+       std::bitset<kNumBits>(bit_strings[2].c_str()),
+       std::bitset<kNumBits>(bit_strings[3].c_str()),
+       std::bitset<kNumBits>(bit_strings[4].c_str()),
+       std::bitset<kNumBits>(bit_strings[5].c_str())}));
+}  // namespace
+
+// Private type that only supports AbslHashValue to make sure our chosen hash
+// implementation is recursive within absl::Hash.
+// It uses std::abs() on the value to provide different bitwise representations
+// of the same logical value.
+struct Private {
+  int i;
+  template <typename H>
+  friend H AbslHashValue(H h, Private p) {
+    return H::combine(std::move(h), std::abs(p.i));
+  }
+
+  friend bool operator==(Private a, Private b) {
+    return std::abs(a.i) == std::abs(b.i);
+  }
+
+  friend std::ostream& operator<<(std::ostream& o, Private p) {
+    return o << p.i;
+  }
+};
+
+// Test helper for combine_piecewise_buffer.  It holds a string_view to the
+// buffer-to-be-hashed.  Its AbslHashValue specialization will split up its
+// contents at the character offsets requested.
+class PiecewiseHashTester {
+ public:
+  // Create a hash view of a buffer to be hashed contiguously.
+  explicit PiecewiseHashTester(absl::string_view buf)
+      : buf_(buf), piecewise_(false), split_locations_() {}
+
+  // Create a hash view of a buffer to be hashed piecewise, with breaks at the
+  // given locations.
+  PiecewiseHashTester(absl::string_view buf, std::set<size_t> split_locations)
+      : buf_(buf),
+        piecewise_(true),
+        split_locations_(std::move(split_locations)) {}
+
+  template <typename H>
+  friend H AbslHashValue(H h, const PiecewiseHashTester& p) {
+    if (!p.piecewise_) {
+      return H::combine_contiguous(std::move(h), p.buf_.data(), p.buf_.size());
+    }
+    absl::hash_internal::PiecewiseCombiner combiner;
+    if (p.split_locations_.empty()) {
+      h = combiner.add_buffer(std::move(h), p.buf_.data(), p.buf_.size());
+      return combiner.finalize(std::move(h));
+    }
+    size_t begin = 0;
+    for (size_t next : p.split_locations_) {
+      absl::string_view chunk = p.buf_.substr(begin, next - begin);
+      h = combiner.add_buffer(std::move(h), chunk.data(), chunk.size());
+      begin = next;
+    }
+    absl::string_view last_chunk = p.buf_.substr(begin);
+    if (!last_chunk.empty()) {
+      h = combiner.add_buffer(std::move(h), last_chunk.data(),
+                              last_chunk.size());
+    }
+    return combiner.finalize(std::move(h));
+  }
+
+ private:
+  absl::string_view buf_;
+  bool piecewise_;
+  std::set<size_t> split_locations_;
+};
+
+// Dummy object that hashes as two distinct contiguous buffers, "foo" followed
+// by "bar"
+struct DummyFooBar {
+  template <typename H>
+  friend H AbslHashValue(H h, const DummyFooBar&) {
+    const char* foo = "foo";
+    const char* bar = "bar";
+    h = H::combine_contiguous(std::move(h), foo, 3);
+    h = H::combine_contiguous(std::move(h), bar, 3);
+    return h;
+  }
+};
+
+TEST(HashValueTest, CombinePiecewiseBuffer) {
+  absl::Hash<PiecewiseHashTester> hash;
+
+  // Check that hashing an empty buffer through the piecewise API works.
+  EXPECT_EQ(hash(PiecewiseHashTester("")), hash(PiecewiseHashTester("", {})));
+
+  // Similarly, small buffers should give consistent results
+  EXPECT_EQ(hash(PiecewiseHashTester("foobar")),
+            hash(PiecewiseHashTester("foobar", {})));
+  EXPECT_EQ(hash(PiecewiseHashTester("foobar")),
+            hash(PiecewiseHashTester("foobar", {3})));
+
+  // But hashing "foobar" in pieces gives a different answer than hashing "foo"
+  // contiguously, then "bar" contiguously.
+  EXPECT_NE(hash(PiecewiseHashTester("foobar", {3})),
+            absl::Hash<DummyFooBar>()(DummyFooBar{}));
+
+  // Test hashing a large buffer incrementally, broken up in several different
+  // ways.  Arrange for breaks on and near the stride boundaries to look for
+  // off-by-one errors in the implementation.
+  //
+  // This test is run on a buffer that is a multiple of the stride size, and one
+  // that isn't.
+  for (size_t big_buffer_size : {1024u * 2 + 512u, 1024u * 3}) {
+    SCOPED_TRACE(big_buffer_size);
+    std::string big_buffer;
+    for (size_t i = 0; i < big_buffer_size; ++i) {
+      // Arbitrary string
+      big_buffer.push_back(32 + (i * (i / 3)) % 64);
+    }
+    auto big_buffer_hash = hash(PiecewiseHashTester(big_buffer));
+
+    const int possible_breaks = 9;
+    size_t breaks[possible_breaks] = {1,    512,  1023, 1024, 1025,
+                                      1536, 2047, 2048, 2049};
+    for (unsigned test_mask = 0; test_mask < (1u << possible_breaks);
+         ++test_mask) {
+      SCOPED_TRACE(test_mask);
+      std::set<size_t> break_locations;
+      for (int j = 0; j < possible_breaks; ++j) {
+        if (test_mask & (1u << j)) {
+          break_locations.insert(breaks[j]);
+        }
+      }
+      EXPECT_EQ(
+          hash(PiecewiseHashTester(big_buffer, std::move(break_locations))),
+          big_buffer_hash);
+    }
+  }
+}
+
+TEST(HashValueTest, PrivateSanity) {
+  // Sanity check that Private is working as the tests below expect it to work.
+  EXPECT_TRUE(is_hashable<Private>::value);
+  EXPECT_NE(SpyHash(Private{0}), SpyHash(Private{1}));
+  EXPECT_EQ(SpyHash(Private{1}), SpyHash(Private{1}));
+}
+
+TEST(HashValueTest, Optional) {
+  EXPECT_TRUE(is_hashable<absl::optional<Private>>::value);
+
+  using O = absl::optional<Private>;
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(O{}, O{{1}}, O{{-1}}, O{{10}})));
+}
+
+TEST(HashValueTest, Variant) {
+  using V = absl::variant<Private, std::string>;
+  EXPECT_TRUE(is_hashable<V>::value);
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      V(Private{1}), V(Private{-1}), V(Private{2}), V("ABC"), V("BCD"))));
+
+#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+  struct S {};
+  EXPECT_FALSE(is_hashable<absl::variant<S>>::value);
+#endif
+}
+
+TEST(HashValueTest, ReferenceWrapper) {
+  EXPECT_TRUE(is_hashable<std::reference_wrapper<Private>>::value);
+
+  Private p1{1}, p10{10};
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      p1, p10, std::ref(p1), std::ref(p10), std::cref(p1), std::cref(p10))));
+
+  EXPECT_TRUE(is_hashable<std::reference_wrapper<int>>::value);
+  int one = 1, ten = 10;
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(std::make_tuple(
+      one, ten, std::ref(one), std::ref(ten), std::cref(one), std::cref(ten))));
+
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+      std::make_tuple(std::tuple<std::reference_wrapper<int>>(std::ref(one)),
+                      std::tuple<std::reference_wrapper<int>>(std::ref(ten)),
+                      std::tuple<int>(one), std::tuple<int>(ten))));
+}
+
+template <typename T, typename = void>
+struct IsHashCallable : std::false_type {};
+
+template <typename T>
+struct IsHashCallable<T, absl::void_t<decltype(std::declval<absl::Hash<T>>()(
+                            std::declval<const T&>()))>> : std::true_type {};
+
+template <typename T, typename = void>
+struct IsAggregateInitializable : std::false_type {};
+
+template <typename T>
+struct IsAggregateInitializable<T, absl::void_t<decltype(T{})>>
+    : std::true_type {};
+
+TEST(IsHashableTest, ValidHash) {
+  EXPECT_TRUE((is_hashable<int>::value));
+  EXPECT_TRUE(std::is_default_constructible<absl::Hash<int>>::value);
+  EXPECT_TRUE(std::is_copy_constructible<absl::Hash<int>>::value);
+  EXPECT_TRUE(std::is_move_constructible<absl::Hash<int>>::value);
+  EXPECT_TRUE(absl::is_copy_assignable<absl::Hash<int>>::value);
+  EXPECT_TRUE(absl::is_move_assignable<absl::Hash<int>>::value);
+  EXPECT_TRUE(IsHashCallable<int>::value);
+  EXPECT_TRUE(IsAggregateInitializable<absl::Hash<int>>::value);
+}
+
+#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+TEST(IsHashableTest, PoisonHash) {
+  struct X {};
+  EXPECT_FALSE((is_hashable<X>::value));
+  EXPECT_FALSE(std::is_default_constructible<absl::Hash<X>>::value);
+  EXPECT_FALSE(std::is_copy_constructible<absl::Hash<X>>::value);
+  EXPECT_FALSE(std::is_move_constructible<absl::Hash<X>>::value);
+  EXPECT_FALSE(absl::is_copy_assignable<absl::Hash<X>>::value);
+  EXPECT_FALSE(absl::is_move_assignable<absl::Hash<X>>::value);
+  EXPECT_FALSE(IsHashCallable<X>::value);
+#if !defined(__GNUC__) || defined(__clang__)
+  // TODO(b/144368551): As of GCC 8.4 this does not compile.
+  EXPECT_FALSE(IsAggregateInitializable<absl::Hash<X>>::value);
+#endif
+}
+#endif  // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+
+// Hashable types
+//
+// These types exist simply to exercise various AbslHashValue behaviors, so
+// they are named by what their AbslHashValue overload does.
+struct NoOp {
+  template <typename HashCode>
+  friend HashCode AbslHashValue(HashCode h, NoOp n) {
+    return h;
+  }
+};
+
+struct EmptyCombine {
+  template <typename HashCode>
+  friend HashCode AbslHashValue(HashCode h, EmptyCombine e) {
+    return HashCode::combine(std::move(h));
+  }
+};
+
+template <typename Int>
+struct CombineIterative {
+  template <typename HashCode>
+  friend HashCode AbslHashValue(HashCode h, CombineIterative c) {
+    for (int i = 0; i < 5; ++i) {
+      h = HashCode::combine(std::move(h), Int(i));
+    }
+    return h;
+  }
+};
+
+template <typename Int>
+struct CombineVariadic {
+  template <typename HashCode>
+  friend HashCode AbslHashValue(HashCode h, CombineVariadic c) {
+    return HashCode::combine(std::move(h), Int(0), Int(1), Int(2), Int(3),
+                             Int(4));
+  }
+};
+enum class InvokeTag {
+  kUniquelyRepresented,
+  kHashValue,
+#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+  kLegacyHash,
+#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+  kStdHash,
+  kNone
+};
+
+template <InvokeTag T>
+using InvokeTagConstant = std::integral_constant<InvokeTag, T>;
+
+template <InvokeTag... Tags>
+struct MinTag;
+
+template <InvokeTag a, InvokeTag b, InvokeTag... Tags>
+struct MinTag<a, b, Tags...> : MinTag<(a < b ? a : b), Tags...> {};
+
+template <InvokeTag a>
+struct MinTag<a> : InvokeTagConstant<a> {};
+
+template <InvokeTag... Tags>
+struct CustomHashType {
+  explicit CustomHashType(size_t val) : value(val) {}
+  size_t value;
+};
+
+template <InvokeTag allowed, InvokeTag... tags>
+struct EnableIfContained
+    : std::enable_if<absl::disjunction<
+          std::integral_constant<bool, allowed == tags>...>::value> {};
+
+template <
+    typename H, InvokeTag... Tags,
+    typename = typename EnableIfContained<InvokeTag::kHashValue, Tags...>::type>
+H AbslHashValue(H state, CustomHashType<Tags...> t) {
+  static_assert(MinTag<Tags...>::value == InvokeTag::kHashValue, "");
+  return H::combine(std::move(state),
+                    t.value + static_cast<int>(InvokeTag::kHashValue));
+}
+
+}  // namespace
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+template <InvokeTag... Tags>
+struct is_uniquely_represented<
+    CustomHashType<Tags...>,
+    typename EnableIfContained<InvokeTag::kUniquelyRepresented, Tags...>::type>
+    : std::true_type {};
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+namespace ABSL_INTERNAL_LEGACY_HASH_NAMESPACE {
+template <InvokeTag... Tags>
+struct hash<CustomHashType<Tags...>> {
+  template <InvokeTag... TagsIn, typename = typename EnableIfContained<
+                                     InvokeTag::kLegacyHash, TagsIn...>::type>
+  size_t operator()(CustomHashType<TagsIn...> t) const {
+    static_assert(MinTag<Tags...>::value == InvokeTag::kLegacyHash, "");
+    return t.value + static_cast<int>(InvokeTag::kLegacyHash);
+  }
+};
+}  // namespace ABSL_INTERNAL_LEGACY_HASH_NAMESPACE
+#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+
+namespace std {
+template <InvokeTag... Tags>  // NOLINT
+struct hash<CustomHashType<Tags...>> {
+  template <InvokeTag... TagsIn, typename = typename EnableIfContained<
+                                     InvokeTag::kStdHash, TagsIn...>::type>
+  size_t operator()(CustomHashType<TagsIn...> t) const {
+    static_assert(MinTag<Tags...>::value == InvokeTag::kStdHash, "");
+    return t.value + static_cast<int>(InvokeTag::kStdHash);
+  }
+};
+}  // namespace std
+
+namespace {
+
+template <typename... T>
+void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>, T...) {
+  using type = CustomHashType<T::value...>;
+  SCOPED_TRACE(testing::PrintToString(std::vector<InvokeTag>{T::value...}));
+  EXPECT_TRUE(is_hashable<type>());
+  EXPECT_TRUE(is_hashable<const type>());
+  EXPECT_TRUE(is_hashable<const type&>());
+
+  const size_t offset = static_cast<int>(std::min({T::value...}));
+  EXPECT_EQ(SpyHash(type(7)), SpyHash(size_t{7 + offset}));
+}
+
+void TestCustomHashType(InvokeTagConstant<InvokeTag::kNone>) {
+#if ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+  // is_hashable is false if we don't support any of the hooks.
+  using type = CustomHashType<>;
+  EXPECT_FALSE(is_hashable<type>());
+  EXPECT_FALSE(is_hashable<const type>());
+  EXPECT_FALSE(is_hashable<const type&>());
+#endif  // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+}
+
+template <InvokeTag Tag, typename... T>
+void TestCustomHashType(InvokeTagConstant<Tag> tag, T... t) {
+  constexpr auto next = static_cast<InvokeTag>(static_cast<int>(Tag) + 1);
+  TestCustomHashType(InvokeTagConstant<next>(), tag, t...);
+  TestCustomHashType(InvokeTagConstant<next>(), t...);
+}
+
+TEST(HashTest, CustomHashType) {
+  TestCustomHashType(InvokeTagConstant<InvokeTag{}>());
+}
+
+TEST(HashTest, NoOpsAreEquivalent) {
+  EXPECT_EQ(Hash<NoOp>()({}), Hash<NoOp>()({}));
+  EXPECT_EQ(Hash<NoOp>()({}), Hash<EmptyCombine>()({}));
+}
+
+template <typename T>
+class HashIntTest : public testing::Test {
+};
+TYPED_TEST_SUITE_P(HashIntTest);
+
+TYPED_TEST_P(HashIntTest, BasicUsage) {
+  EXPECT_NE(Hash<NoOp>()({}), Hash<TypeParam>()(0));
+  EXPECT_NE(Hash<NoOp>()({}),
+            Hash<TypeParam>()(std::numeric_limits<TypeParam>::max()));
+  if (std::numeric_limits<TypeParam>::min() != 0) {
+    EXPECT_NE(Hash<NoOp>()({}),
+              Hash<TypeParam>()(std::numeric_limits<TypeParam>::min()));
+  }
+
+  EXPECT_EQ(Hash<CombineIterative<TypeParam>>()({}),
+            Hash<CombineVariadic<TypeParam>>()({}));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(HashIntTest, BasicUsage);
+using IntTypes = testing::Types<unsigned char, char, int, int32_t, int64_t,
+                                uint32_t, uint64_t, size_t>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, HashIntTest, IntTypes);
+
+struct StructWithPadding {
+  char c;
+  int i;
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, const StructWithPadding& s) {
+    return H::combine(std::move(hash_state), s.c, s.i);
+  }
+};
+
+static_assert(sizeof(StructWithPadding) > sizeof(char) + sizeof(int),
+              "StructWithPadding doesn't have padding");
+static_assert(std::is_standard_layout<StructWithPadding>::value, "");
+
+// This check has to be disabled because libstdc++ doesn't support it.
+// static_assert(std::is_trivially_constructible<StructWithPadding>::value, "");
+
+template <typename T>
+struct ArraySlice {
+  T* begin;
+  T* end;
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, const ArraySlice& slice) {
+    for (auto t = slice.begin; t != slice.end; ++t) {
+      hash_state = H::combine(std::move(hash_state), *t);
+    }
+    return hash_state;
+  }
+};
+
+TEST(HashTest, HashNonUniquelyRepresentedType) {
+  // Create equal StructWithPadding objects that are known to have non-equal
+  // padding bytes.
+  static const size_t kNumStructs = 10;
+  unsigned char buffer1[kNumStructs * sizeof(StructWithPadding)];
+  std::memset(buffer1, 0, sizeof(buffer1));
+  auto* s1 = reinterpret_cast<StructWithPadding*>(buffer1);
+
+  unsigned char buffer2[kNumStructs * sizeof(StructWithPadding)];
+  std::memset(buffer2, 255, sizeof(buffer2));
+  auto* s2 = reinterpret_cast<StructWithPadding*>(buffer2);
+  for (size_t i = 0; i < kNumStructs; ++i) {
+    SCOPED_TRACE(i);
+    s1[i].c = s2[i].c = static_cast<char>('0' + i);
+    s1[i].i = s2[i].i = static_cast<int>(i);
+    ASSERT_FALSE(memcmp(buffer1 + i * sizeof(StructWithPadding),
+                        buffer2 + i * sizeof(StructWithPadding),
+                        sizeof(StructWithPadding)) == 0)
+        << "Bug in test code: objects do not have unequal"
+        << " object representations";
+  }
+
+  EXPECT_EQ(Hash<StructWithPadding>()(s1[0]), Hash<StructWithPadding>()(s2[0]));
+  EXPECT_EQ(Hash<ArraySlice<StructWithPadding>>()({s1, s1 + kNumStructs}),
+            Hash<ArraySlice<StructWithPadding>>()({s2, s2 + kNumStructs}));
+}
+
+TEST(HashTest, StandardHashContainerUsage) {
+  std::unordered_map<int, std::string, Hash<int>> map = {{0, "foo"},
+                                                         {42, "bar"}};
+
+  EXPECT_NE(map.find(0), map.end());
+  EXPECT_EQ(map.find(1), map.end());
+  EXPECT_NE(map.find(0u), map.end());
+}
+
+struct ConvertibleFromNoOp {
+  ConvertibleFromNoOp(NoOp) {}  // NOLINT(runtime/explicit)
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, ConvertibleFromNoOp) {
+    return H::combine(std::move(hash_state), 1);
+  }
+};
+
+TEST(HashTest, HeterogeneousCall) {
+  EXPECT_NE(Hash<ConvertibleFromNoOp>()(NoOp()),
+            Hash<NoOp>()(NoOp()));
+}
+
+TEST(IsUniquelyRepresentedTest, SanityTest) {
+  using absl::hash_internal::is_uniquely_represented;
+
+  EXPECT_TRUE(is_uniquely_represented<unsigned char>::value);
+  EXPECT_TRUE(is_uniquely_represented<int>::value);
+  EXPECT_FALSE(is_uniquely_represented<bool>::value);
+  EXPECT_FALSE(is_uniquely_represented<int*>::value);
+}
+
+struct IntAndString {
+  int i;
+  std::string s;
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, IntAndString int_and_string) {
+    return H::combine(std::move(hash_state), int_and_string.s,
+                      int_and_string.i);
+  }
+};
+
+TEST(HashTest, SmallValueOn64ByteBoundary) {
+  Hash<IntAndString>()(IntAndString{0, std::string(63, '0')});
+}
+
+TEST(HashTest, TypeErased) {
+  EXPECT_TRUE((is_hashable<TypeErasedValue<size_t>>::value));
+  EXPECT_TRUE((is_hashable<std::pair<TypeErasedValue<size_t>, int>>::value));
+
+  EXPECT_EQ(SpyHash(TypeErasedValue<size_t>(7)), SpyHash(size_t{7}));
+  EXPECT_NE(SpyHash(TypeErasedValue<size_t>(7)), SpyHash(size_t{13}));
+
+  EXPECT_EQ(SpyHash(std::make_pair(TypeErasedValue<size_t>(7), 17)),
+            SpyHash(std::make_pair(size_t{7}, 17)));
+
+  absl::flat_hash_set<absl::flat_hash_set<int>> ss = {{1, 2}, {3, 4}};
+  TypeErasedContainer<absl::flat_hash_set<absl::flat_hash_set<int>>> es = {
+      absl::flat_hash_set<int>{1, 2}, {3, 4}};
+  absl::flat_hash_set<TypeErasedContainer<absl::flat_hash_set<int>>> se = {
+      {1, 2}, {3, 4}};
+  EXPECT_EQ(SpyHash(ss), SpyHash(es));
+  EXPECT_EQ(SpyHash(ss), SpyHash(se));
+}
+
+struct ValueWithBoolConversion {
+  operator bool() const { return false; }
+  int i;
+};
+
+}  // namespace
+namespace std {
+template <>
+struct hash<ValueWithBoolConversion> {
+  size_t operator()(ValueWithBoolConversion v) {
+    return static_cast<size_t>(v.i);
+  }
+};
+}  // namespace std
+
+namespace {
+
+TEST(HashTest, DoesNotUseImplicitConversionsToBool) {
+  EXPECT_NE(absl::Hash<ValueWithBoolConversion>()(ValueWithBoolConversion{0}),
+            absl::Hash<ValueWithBoolConversion>()(ValueWithBoolConversion{1}));
+}
+
+TEST(HashOf, MatchesHashForSingleArgument) {
+  std::string s = "forty two";
+  double d = 42.0;
+  std::tuple<int, int> t{4, 2};
+  int i = 42;
+  int neg_i = -42;
+  int16_t i16 = 42;
+  int16_t neg_i16 = -42;
+  int8_t i8 = 42;
+  int8_t neg_i8 = -42;
+
+  EXPECT_EQ(absl::HashOf(s), absl::Hash<std::string>{}(s));
+  EXPECT_EQ(absl::HashOf(d), absl::Hash<double>{}(d));
+  EXPECT_EQ(absl::HashOf(t), (absl::Hash<std::tuple<int, int>>{}(t)));
+  EXPECT_EQ(absl::HashOf(i), absl::Hash<int>{}(i));
+  EXPECT_EQ(absl::HashOf(neg_i), absl::Hash<int>{}(neg_i));
+  EXPECT_EQ(absl::HashOf(i16), absl::Hash<int16_t>{}(i16));
+  EXPECT_EQ(absl::HashOf(neg_i16), absl::Hash<int16_t>{}(neg_i16));
+  EXPECT_EQ(absl::HashOf(i8), absl::Hash<int8_t>{}(i8));
+  EXPECT_EQ(absl::HashOf(neg_i8), absl::Hash<int8_t>{}(neg_i8));
+}
+
+TEST(HashOf, MatchesHashOfTupleForMultipleArguments) {
+  std::string hello = "hello";
+  std::string world = "world";
+
+  EXPECT_EQ(absl::HashOf(), absl::HashOf(std::make_tuple()));
+  EXPECT_EQ(absl::HashOf(hello), absl::HashOf(std::make_tuple(hello)));
+  EXPECT_EQ(absl::HashOf(hello, world),
+            absl::HashOf(std::make_tuple(hello, world)));
+}
+
+template <typename T>
+std::true_type HashOfExplicitParameter(decltype(absl::HashOf<T>(0))) {
+  return {};
+}
+template <typename T>
+std::false_type HashOfExplicitParameter(size_t) {
+  return {};
+}
+
+TEST(HashOf, CantPassExplicitTemplateParameters) {
+  EXPECT_FALSE(HashOfExplicitParameter<int>(0));
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/hash/hash_testing.h b/weight/_dep/abseil-cpp/absl/hash/hash_testing.h
new file mode 100644
index 0000000000000000000000000000000000000000..1e1c5741491eaf7c3334e10f590625e839514e1e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/hash_testing.h
@@ -0,0 +1,378 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_HASH_HASH_TESTING_H_
+#define ABSL_HASH_HASH_TESTING_H_
+
+#include <initializer_list>
+#include <tuple>
+#include <type_traits>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/hash/internal/spy_hash_state.h"
+#include "absl/meta/type_traits.h"
+#include "absl/strings/str_cat.h"
+#include "absl/types/variant.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Run the absl::Hash algorithm over all the elements passed in and verify that
+// their hash expansion is congruent with their `==` operator.
+//
+// It is used in conjunction with EXPECT_TRUE. Failures will output information
+// on what requirement failed and on which objects.
+//
+// Users should pass a collection of types as either an initializer list or a
+// container of cases.
+//
+//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+//       {v1, v2, ..., vN}));
+//
+//   std::vector<MyType> cases;
+//   // Fill cases...
+//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(cases));
+//
+// Users can pass a variety of types for testing heterogeneous lookup with
+// `std::make_tuple`:
+//
+//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+//       std::make_tuple(v1, v2, ..., vN)));
+//
+//
+// Ideally, the values passed should provide enough coverage of the `==`
+// operator and the AbslHashValue implementations.
+// For dynamically sized types, the empty state should usually be included in
+// the values.
+//
+// The function accepts an optional comparator function, in case that `==` is
+// not enough for the values provided.
+//
+// Usage:
+//
+//   EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly(
+//       std::make_tuple(v1, v2, ..., vN), MyCustomEq{}));
+//
+// It checks the following requirements:
+//   1. The expansion for a value is deterministic.
+//   2. For any two objects `a` and `b` in the sequence, if `a == b` evaluates
+//      to true, then their hash expansion must be equal.
+//   3. If `a == b` evaluates to false their hash expansion must be unequal.
+//   4. If `a == b` evaluates to false neither hash expansion can be a
+//      suffix of the other.
+//   5. AbslHashValue overloads should not be called by the user. They are only
+//      meant to be called by the framework. Users should call H::combine() and
+//      H::combine_contiguous().
+//   6. No moved-from instance of the hash state is used in the implementation
+//      of AbslHashValue.
+//
+// The values do not have to have the same type. This can be useful for
+// equivalent types that support heterogeneous lookup.
+//
+// A possible reason for breaking (2) is combining state in the hash expansion
+// that was not used in `==`.
+// For example:
+//
+// struct Bad2 {
+//   int a, b;
+//   template <typename H>
+//   friend H AbslHashValue(H state, Bad2 x) {
+//     // Uses a and b.
+//     return H::combine(std::move(state), x.a, x.b);
+//   }
+//   friend bool operator==(Bad2 x, Bad2 y) {
+//     // Only uses a.
+//     return x.a == y.a;
+//   }
+// };
+//
+// As for (3), breaking this usually means that there is state being passed to
+// the `==` operator that is not used in the hash expansion.
+// For example:
+//
+// struct Bad3 {
+//   int a, b;
+//   template <typename H>
+//   friend H AbslHashValue(H state, Bad3 x) {
+//     // Only uses a.
+//     return H::combine(std::move(state), x.a);
+//   }
+//   friend bool operator==(Bad3 x, Bad3 y) {
+//     // Uses a and b.
+//     return x.a == y.a && x.b == y.b;
+//   }
+// };
+//
+// Finally, a common way to break 4 is by combining dynamic ranges without
+// combining the size of the range.
+// For example:
+//
+// struct Bad4 {
+//   int *p, size;
+//   template <typename H>
+//   friend H AbslHashValue(H state, Bad4 x) {
+//     return H::combine_contiguous(std::move(state), x.p, x.p + x.size);
+//   }
+//   friend bool operator==(Bad4 x, Bad4 y) {
+//    // Compare two ranges for equality. C++14 code can instead use std::equal.
+//     return absl::equal(x.p, x.p + x.size, y.p, y.p + y.size);
+//   }
+// };
+//
+// An easy solution to this is to combine the size after combining the range,
+// like so:
+// template <typename H>
+// friend H AbslHashValue(H state, Bad4 x) {
+//   return H::combine(
+//       H::combine_contiguous(std::move(state), x.p, x.p + x.size), x.size);
+// }
+//
+template <int&... ExplicitBarrier, typename Container>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(const Container& values);
+
+template <int&... ExplicitBarrier, typename Container, typename Eq>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals);
+
+template <int&..., typename T>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values);
+
+template <int&..., typename T, typename Eq>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values,
+                                      Eq equals);
+
+namespace hash_internal {
+
+struct PrintVisitor {
+  size_t index;
+  template <typename T>
+  std::string operator()(const T* value) const {
+    return absl::StrCat("#", index, "(", testing::PrintToString(*value), ")");
+  }
+};
+
+template <typename Eq>
+struct EqVisitor {
+  Eq eq;
+  template <typename T, typename U>
+  bool operator()(const T* t, const U* u) const {
+    return eq(*t, *u);
+  }
+};
+
+struct ExpandVisitor {
+  template <typename T>
+  SpyHashState operator()(const T* value) const {
+    return SpyHashState::combine(SpyHashState(), *value);
+  }
+};
+
+template <typename Container, typename Eq>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
+  using V = typename Container::value_type;
+
+  struct Info {
+    const V& value;
+    size_t index;
+    std::string ToString() const {
+      return absl::visit(PrintVisitor{index}, value);
+    }
+    SpyHashState expand() const { return absl::visit(ExpandVisitor{}, value); }
+  };
+
+  using EqClass = std::vector<Info>;
+  std::vector<EqClass> classes;
+
+  // Gather the values in equivalence classes.
+  size_t i = 0;
+  for (const auto& value : values) {
+    EqClass* c = nullptr;
+    for (auto& eqclass : classes) {
+      if (absl::visit(EqVisitor<Eq>{equals}, value, eqclass[0].value)) {
+        c = &eqclass;
+        break;
+      }
+    }
+    if (c == nullptr) {
+      classes.emplace_back();
+      c = &classes.back();
+    }
+    c->push_back({value, i});
+    ++i;
+
+    // Verify potential errors captured by SpyHashState.
+    if (auto error = c->back().expand().error()) {
+      return testing::AssertionFailure() << *error;
+    }
+  }
+
+  if (classes.size() < 2) {
+    return testing::AssertionFailure()
+           << "At least two equivalence classes are expected.";
+  }
+
+  // We assume that equality is correctly implemented.
+  // Now we verify that AbslHashValue is also correctly implemented.
+
+  for (const auto& c : classes) {
+    // All elements of the equivalence class must have the same hash
+    // expansion.
+    const SpyHashState expected = c[0].expand();
+    for (const Info& v : c) {
+      if (v.expand() != v.expand()) {
+        return testing::AssertionFailure()
+               << "Hash expansion for " << v.ToString()
+               << " is non-deterministic.";
+      }
+      if (v.expand() != expected) {
+        return testing::AssertionFailure()
+               << "Values " << c[0].ToString() << " and " << v.ToString()
+               << " evaluate as equal but have an unequal hash expansion.";
+      }
+    }
+
+    // Elements from other classes must have different hash expansion.
+    for (const auto& c2 : classes) {
+      if (&c == &c2) continue;
+      const SpyHashState c2_hash = c2[0].expand();
+      switch (SpyHashState::Compare(expected, c2_hash)) {
+        case SpyHashState::CompareResult::kEqual:
+          return testing::AssertionFailure()
+                 << "Values " << c[0].ToString() << " and " << c2[0].ToString()
+                 << " evaluate as unequal but have an equal hash expansion.";
+        case SpyHashState::CompareResult::kBSuffixA:
+          return testing::AssertionFailure()
+                 << "Hash expansion of " << c2[0].ToString()
+                 << " is a suffix of the hash expansion of " << c[0].ToString()
+                 << ".";
+        case SpyHashState::CompareResult::kASuffixB:
+          return testing::AssertionFailure()
+                 << "Hash expansion of " << c[0].ToString()
+                 << " is a suffix of the hash expansion of " << c2[0].ToString()
+                 << ".";
+        case SpyHashState::CompareResult::kUnequal:
+          break;
+      }
+    }
+  }
+  return testing::AssertionSuccess();
+}
+
+template <typename... T>
+struct TypeSet {
+  template <typename U, bool = disjunction<std::is_same<T, U>...>::value>
+  struct Insert {
+    using type = TypeSet<U, T...>;
+  };
+  template <typename U>
+  struct Insert<U, true> {
+    using type = TypeSet;
+  };
+
+  template <template <typename...> class C>
+  using apply = C<T...>;
+};
+
+template <typename... T>
+struct MakeTypeSet : TypeSet<> {};
+template <typename T, typename... Ts>
+struct MakeTypeSet<T, Ts...> : MakeTypeSet<Ts...>::template Insert<T>::type {};
+
+template <typename... T>
+using VariantForTypes = typename MakeTypeSet<
+    const typename std::decay<T>::type*...>::template apply<absl::variant>;
+
+template <typename Container>
+struct ContainerAsVector {
+  using V = absl::variant<const typename Container::value_type*>;
+  using Out = std::vector<V>;
+
+  static Out Do(const Container& values) {
+    Out out;
+    for (const auto& v : values) out.push_back(&v);
+    return out;
+  }
+};
+
+template <typename... T>
+struct ContainerAsVector<std::tuple<T...>> {
+  using V = VariantForTypes<T...>;
+  using Out = std::vector<V>;
+
+  template <size_t... I>
+  static Out DoImpl(const std::tuple<T...>& tuple, absl::index_sequence<I...>) {
+    return Out{&std::get<I>(tuple)...};
+  }
+
+  static Out Do(const std::tuple<T...>& values) {
+    return DoImpl(values, absl::index_sequence_for<T...>());
+  }
+};
+
+template <>
+struct ContainerAsVector<std::tuple<>> {
+  static std::vector<VariantForTypes<int>> Do(std::tuple<>) { return {}; }
+};
+
+struct DefaultEquals {
+  template <typename T, typename U>
+  bool operator()(const T& t, const U& u) const {
+    return t == u;
+  }
+};
+
+}  // namespace hash_internal
+
+template <int&..., typename Container>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(const Container& values) {
+  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
+      hash_internal::ContainerAsVector<Container>::Do(values),
+      hash_internal::DefaultEquals{});
+}
+
+template <int&..., typename Container, typename Eq>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(const Container& values, Eq equals) {
+  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
+      hash_internal::ContainerAsVector<Container>::Do(values), equals);
+}
+
+template <int&..., typename T>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values) {
+  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
+      hash_internal::ContainerAsVector<std::initializer_list<T>>::Do(values),
+      hash_internal::DefaultEquals{});
+}
+
+template <int&..., typename T, typename Eq>
+ABSL_MUST_USE_RESULT testing::AssertionResult
+VerifyTypeImplementsAbslHashCorrectly(std::initializer_list<T> values,
+                                      Eq equals) {
+  return hash_internal::VerifyTypeImplementsAbslHashCorrectly(
+      hash_internal::ContainerAsVector<std::initializer_list<T>>::Do(values),
+      equals);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_HASH_TESTING_H_
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/city.cc b/weight/_dep/abseil-cpp/absl/hash/internal/city.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f0d3196470df7e0760d77d5b32820c85dc00f396
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/city.cc
@@ -0,0 +1,349 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// This file provides CityHash64() and related functions.
+//
+// It's probably possible to create even faster hash functions by
+// writing a program that systematically explores some of the space of
+// possible hash functions, by using SIMD instructions, or by
+// compromising on hash quality.
+
+#include "absl/hash/internal/city.h"
+
+#include <string.h>  // for memcpy and memset
+#include <algorithm>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/internal/unaligned_access.h"
+#include "absl/base/optimization.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+
+#ifdef ABSL_IS_BIG_ENDIAN
+#define uint32_in_expected_order(x) (absl::gbswap_32(x))
+#define uint64_in_expected_order(x) (absl::gbswap_64(x))
+#else
+#define uint32_in_expected_order(x) (x)
+#define uint64_in_expected_order(x) (x)
+#endif
+
+static uint64_t Fetch64(const char *p) {
+  return uint64_in_expected_order(ABSL_INTERNAL_UNALIGNED_LOAD64(p));
+}
+
+static uint32_t Fetch32(const char *p) {
+  return uint32_in_expected_order(ABSL_INTERNAL_UNALIGNED_LOAD32(p));
+}
+
+// Some primes between 2^63 and 2^64 for various uses.
+static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
+static const uint64_t k1 = 0xb492b66fbe98f273ULL;
+static const uint64_t k2 = 0x9ae16a3b2f90404fULL;
+
+// Magic numbers for 32-bit hashing.  Copied from Murmur3.
+static const uint32_t c1 = 0xcc9e2d51;
+static const uint32_t c2 = 0x1b873593;
+
+// A 32-bit to 32-bit integer hash copied from Murmur3.
+static uint32_t fmix(uint32_t h) {
+  h ^= h >> 16;
+  h *= 0x85ebca6b;
+  h ^= h >> 13;
+  h *= 0xc2b2ae35;
+  h ^= h >> 16;
+  return h;
+}
+
+static uint32_t Rotate32(uint32_t val, int shift) {
+  // Avoid shifting by 32: doing so yields an undefined result.
+  return shift == 0 ? val : ((val >> shift) | (val << (32 - shift)));
+}
+
+#undef PERMUTE3
+#define PERMUTE3(a, b, c) \
+  do {                    \
+    std::swap(a, b);      \
+    std::swap(a, c);      \
+  } while (0)
+
+static uint32_t Mur(uint32_t a, uint32_t h) {
+  // Helper from Murmur3 for combining two 32-bit values.
+  a *= c1;
+  a = Rotate32(a, 17);
+  a *= c2;
+  h ^= a;
+  h = Rotate32(h, 19);
+  return h * 5 + 0xe6546b64;
+}
+
+static uint32_t Hash32Len13to24(const char *s, size_t len) {
+  uint32_t a = Fetch32(s - 4 + (len >> 1));
+  uint32_t b = Fetch32(s + 4);
+  uint32_t c = Fetch32(s + len - 8);
+  uint32_t d = Fetch32(s + (len >> 1));
+  uint32_t e = Fetch32(s);
+  uint32_t f = Fetch32(s + len - 4);
+  uint32_t h = static_cast<uint32_t>(len);
+
+  return fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h)))))));
+}
+
+static uint32_t Hash32Len0to4(const char *s, size_t len) {
+  uint32_t b = 0;
+  uint32_t c = 9;
+  for (size_t i = 0; i < len; i++) {
+    signed char v = static_cast<signed char>(s[i]);
+    b = b * c1 + static_cast<uint32_t>(v);
+    c ^= b;
+  }
+  return fmix(Mur(b, Mur(static_cast<uint32_t>(len), c)));
+}
+
+static uint32_t Hash32Len5to12(const char *s, size_t len) {
+  uint32_t a = static_cast<uint32_t>(len), b = a * 5, c = 9, d = b;
+  a += Fetch32(s);
+  b += Fetch32(s + len - 4);
+  c += Fetch32(s + ((len >> 1) & 4));
+  return fmix(Mur(c, Mur(b, Mur(a, d))));
+}
+
+uint32_t CityHash32(const char *s, size_t len) {
+  if (len <= 24) {
+    return len <= 12
+               ? (len <= 4 ? Hash32Len0to4(s, len) : Hash32Len5to12(s, len))
+               : Hash32Len13to24(s, len);
+  }
+
+  // len > 24
+  uint32_t h = static_cast<uint32_t>(len), g = c1 * h, f = g;
+
+  uint32_t a0 = Rotate32(Fetch32(s + len - 4) * c1, 17) * c2;
+  uint32_t a1 = Rotate32(Fetch32(s + len - 8) * c1, 17) * c2;
+  uint32_t a2 = Rotate32(Fetch32(s + len - 16) * c1, 17) * c2;
+  uint32_t a3 = Rotate32(Fetch32(s + len - 12) * c1, 17) * c2;
+  uint32_t a4 = Rotate32(Fetch32(s + len - 20) * c1, 17) * c2;
+  h ^= a0;
+  h = Rotate32(h, 19);
+  h = h * 5 + 0xe6546b64;
+  h ^= a2;
+  h = Rotate32(h, 19);
+  h = h * 5 + 0xe6546b64;
+  g ^= a1;
+  g = Rotate32(g, 19);
+  g = g * 5 + 0xe6546b64;
+  g ^= a3;
+  g = Rotate32(g, 19);
+  g = g * 5 + 0xe6546b64;
+  f += a4;
+  f = Rotate32(f, 19);
+  f = f * 5 + 0xe6546b64;
+  size_t iters = (len - 1) / 20;
+  do {
+    uint32_t b0 = Rotate32(Fetch32(s) * c1, 17) * c2;
+    uint32_t b1 = Fetch32(s + 4);
+    uint32_t b2 = Rotate32(Fetch32(s + 8) * c1, 17) * c2;
+    uint32_t b3 = Rotate32(Fetch32(s + 12) * c1, 17) * c2;
+    uint32_t b4 = Fetch32(s + 16);
+    h ^= b0;
+    h = Rotate32(h, 18);
+    h = h * 5 + 0xe6546b64;
+    f += b1;
+    f = Rotate32(f, 19);
+    f = f * c1;
+    g += b2;
+    g = Rotate32(g, 18);
+    g = g * 5 + 0xe6546b64;
+    h ^= b3 + b1;
+    h = Rotate32(h, 19);
+    h = h * 5 + 0xe6546b64;
+    g ^= b4;
+    g = absl::gbswap_32(g) * 5;
+    h += b4 * 5;
+    h = absl::gbswap_32(h);
+    f += b0;
+    PERMUTE3(f, h, g);
+    s += 20;
+  } while (--iters != 0);
+  g = Rotate32(g, 11) * c1;
+  g = Rotate32(g, 17) * c1;
+  f = Rotate32(f, 11) * c1;
+  f = Rotate32(f, 17) * c1;
+  h = Rotate32(h + g, 19);
+  h = h * 5 + 0xe6546b64;
+  h = Rotate32(h, 17) * c1;
+  h = Rotate32(h + f, 19);
+  h = h * 5 + 0xe6546b64;
+  h = Rotate32(h, 17) * c1;
+  return h;
+}
+
+// Bitwise right rotate.  Normally this will compile to a single
+// instruction, especially if the shift is a manifest constant.
+static uint64_t Rotate(uint64_t val, int shift) {
+  // Avoid shifting by 64: doing so yields an undefined result.
+  return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
+}
+
+static uint64_t ShiftMix(uint64_t val) { return val ^ (val >> 47); }
+
+static uint64_t HashLen16(uint64_t u, uint64_t v, uint64_t mul) {
+  // Murmur-inspired hashing.
+  uint64_t a = (u ^ v) * mul;
+  a ^= (a >> 47);
+  uint64_t b = (v ^ a) * mul;
+  b ^= (b >> 47);
+  b *= mul;
+  return b;
+}
+
+static uint64_t HashLen16(uint64_t u, uint64_t v) {
+  const uint64_t kMul = 0x9ddfea08eb382d69ULL;
+  return HashLen16(u, v, kMul);
+}
+
+static uint64_t HashLen0to16(const char *s, size_t len) {
+  if (len >= 8) {
+    uint64_t mul = k2 + len * 2;
+    uint64_t a = Fetch64(s) + k2;
+    uint64_t b = Fetch64(s + len - 8);
+    uint64_t c = Rotate(b, 37) * mul + a;
+    uint64_t d = (Rotate(a, 25) + b) * mul;
+    return HashLen16(c, d, mul);
+  }
+  if (len >= 4) {
+    uint64_t mul = k2 + len * 2;
+    uint64_t a = Fetch32(s);
+    return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul);
+  }
+  if (len > 0) {
+    uint8_t a = static_cast<uint8_t>(s[0]);
+    uint8_t b = static_cast<uint8_t>(s[len >> 1]);
+    uint8_t c = static_cast<uint8_t>(s[len - 1]);
+    uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
+    uint32_t z = static_cast<uint32_t>(len) + (static_cast<uint32_t>(c) << 2);
+    return ShiftMix(y * k2 ^ z * k0) * k2;
+  }
+  return k2;
+}
+
+// This probably works well for 16-byte strings as well, but it may be overkill
+// in that case.
+static uint64_t HashLen17to32(const char *s, size_t len) {
+  uint64_t mul = k2 + len * 2;
+  uint64_t a = Fetch64(s) * k1;
+  uint64_t b = Fetch64(s + 8);
+  uint64_t c = Fetch64(s + len - 8) * mul;
+  uint64_t d = Fetch64(s + len - 16) * k2;
+  return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d,
+                   a + Rotate(b + k2, 18) + c, mul);
+}
+
+// Return a 16-byte hash for 48 bytes.  Quick and dirty.
+// Callers do best to use "random-looking" values for a and b.
+static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(
+    uint64_t w, uint64_t x, uint64_t y, uint64_t z, uint64_t a, uint64_t b) {
+  a += w;
+  b = Rotate(b + a + z, 21);
+  uint64_t c = a;
+  a += x;
+  a += y;
+  b += Rotate(a, 44);
+  return std::make_pair(a + z, b + c);
+}
+
+// Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
+static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(const char *s,
+                                                            uint64_t a,
+                                                            uint64_t b) {
+  return WeakHashLen32WithSeeds(Fetch64(s), Fetch64(s + 8), Fetch64(s + 16),
+                                Fetch64(s + 24), a, b);
+}
+
+// Return an 8-byte hash for 33 to 64 bytes.
+static uint64_t HashLen33to64(const char *s, size_t len) {
+  uint64_t mul = k2 + len * 2;
+  uint64_t a = Fetch64(s) * k2;
+  uint64_t b = Fetch64(s + 8);
+  uint64_t c = Fetch64(s + len - 24);
+  uint64_t d = Fetch64(s + len - 32);
+  uint64_t e = Fetch64(s + 16) * k2;
+  uint64_t f = Fetch64(s + 24) * 9;
+  uint64_t g = Fetch64(s + len - 8);
+  uint64_t h = Fetch64(s + len - 16) * mul;
+  uint64_t u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9;
+  uint64_t v = ((a + g) ^ d) + f + 1;
+  uint64_t w = absl::gbswap_64((u + v) * mul) + h;
+  uint64_t x = Rotate(e + f, 42) + c;
+  uint64_t y = (absl::gbswap_64((v + w) * mul) + g) * mul;
+  uint64_t z = e + f + c;
+  a = absl::gbswap_64((x + z) * mul + y) + b;
+  b = ShiftMix((z + a) * mul + d + h) * mul;
+  return b + x;
+}
+
+uint64_t CityHash64(const char *s, size_t len) {
+  if (len <= 32) {
+    if (len <= 16) {
+      return HashLen0to16(s, len);
+    } else {
+      return HashLen17to32(s, len);
+    }
+  } else if (len <= 64) {
+    return HashLen33to64(s, len);
+  }
+
+  // For strings over 64 bytes we hash the end first, and then as we
+  // loop we keep 56 bytes of state: v, w, x, y, and z.
+  uint64_t x = Fetch64(s + len - 40);
+  uint64_t y = Fetch64(s + len - 16) + Fetch64(s + len - 56);
+  uint64_t z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24));
+  std::pair<uint64_t, uint64_t> v =
+      WeakHashLen32WithSeeds(s + len - 64, len, z);
+  std::pair<uint64_t, uint64_t> w =
+      WeakHashLen32WithSeeds(s + len - 32, y + k1, x);
+  x = x * k1 + Fetch64(s);
+
+  // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
+  len = (len - 1) & ~static_cast<size_t>(63);
+  do {
+    x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
+    y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
+    x ^= w.second;
+    y += v.first + Fetch64(s + 40);
+    z = Rotate(z + w.first, 33) * k1;
+    v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
+    w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16));
+    std::swap(z, x);
+    s += 64;
+    len -= 64;
+  } while (len != 0);
+  return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,
+                   HashLen16(v.second, w.second) + x);
+}
+
+uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed) {
+  return CityHash64WithSeeds(s, len, k2, seed);
+}
+
+uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0,
+                             uint64_t seed1) {
+  return HashLen16(CityHash64(s, len) - seed0, seed1);
+}
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/city.h b/weight/_dep/abseil-cpp/absl/hash/internal/city.h
new file mode 100644
index 0000000000000000000000000000000000000000..393da0b95d9f8c13fa5649234f686845fbd7b1ab
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/city.h
@@ -0,0 +1,78 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// https://code.google.com/p/cityhash/
+//
+// This file provides a few functions for hashing strings.  All of them are
+// high-quality functions in the sense that they pass standard tests such
+// as Austin Appleby's SMHasher.  They are also fast.
+//
+// For 64-bit x86 code, on short strings, we don't know of anything faster than
+// CityHash64 that is of comparable quality.  We believe our nearest competitor
+// is Murmur3.  For 64-bit x86 code, CityHash64 is an excellent choice for hash
+// tables and most other hashing (excluding cryptography).
+//
+// For 32-bit x86 code, we don't know of anything faster than CityHash32 that
+// is of comparable quality.  We believe our nearest competitor is Murmur3A.
+// (On 64-bit CPUs, it is typically faster to use the other CityHash variants.)
+//
+// Functions in the CityHash family are not suitable for cryptography.
+//
+// Please see CityHash's README file for more details on our performance
+// measurements and so on.
+//
+// WARNING: This code has been only lightly tested on big-endian platforms!
+// It is known to work well on little-endian platforms that have a small penalty
+// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
+// It should work on all 32-bit and 64-bit platforms that allow unaligned reads;
+// bug reports are welcome.
+//
+// By the way, for some hash functions, given strings a and b, the hash
+// of a+b is easily derived from the hashes of a and b.  This property
+// doesn't hold for any hash functions in this file.
+
+#ifndef ABSL_HASH_INTERNAL_CITY_H_
+#define ABSL_HASH_INTERNAL_CITY_H_
+
+#include <stdint.h>
+#include <stdlib.h>  // for size_t.
+
+#include <utility>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+
+// Hash function for a byte array.
+uint64_t CityHash64(const char *s, size_t len);
+
+// Hash function for a byte array.  For convenience, a 64-bit seed is also
+// hashed into the result.
+uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed);
+
+// Hash function for a byte array.  For convenience, two seeds are also
+// hashed into the result.
+uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0,
+                             uint64_t seed1);
+
+// Hash function for a byte array.  Most useful in 32-bit binaries.
+uint32_t CityHash32(const char *s, size_t len);
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_CITY_H_
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/city_test.cc b/weight/_dep/abseil-cpp/absl/hash/internal/city_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1bbf02e0d1e0a4efe878a78b2bc288bf0c010a75
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/city_test.cc
@@ -0,0 +1,597 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/hash/internal/city.h"
+
+#include <string.h>
+#include <cstdio>
+#include <iostream>
+#include "gtest/gtest.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+namespace {
+
+static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
+static const uint64_t kSeed0 = 1234567;
+static const uint64_t kSeed1 = k0;
+static const int kDataSize = 1 << 20;
+static const int kTestSize = 300;
+
+static char data[kDataSize];
+
+// Initialize data to pseudorandom values.
+void setup() {
+  uint64_t a = 9;
+  uint64_t b = 777;
+  for (int i = 0; i < kDataSize; i++) {
+    a += b;
+    b += a;
+    a = (a ^ (a >> 41)) * k0;
+    b = (b ^ (b >> 41)) * k0 + i;
+    uint8_t u = b >> 37;
+    memcpy(data + i, &u, 1);  // uint8_t -> char
+  }
+}
+
+#define C(x) 0x##x##ULL
+static const uint64_t testdata[kTestSize][4] = {
+    {C(9ae16a3b2f90404f), C(75106db890237a4a), C(3feac5f636039766),
+     C(dc56d17a)},
+    {C(541150e87f415e96), C(1aef0d24b3148a1a), C(bacc300e1e82345a),
+     C(99929334)},
+    {C(f3786a4b25827c1), C(34ee1a2bf767bd1c), C(2f15ca2ebfb631f2), C(4252edb7)},
+    {C(ef923a7a1af78eab), C(79163b1e1e9a9b18), C(df3b2aca6e1e4a30),
+     C(ebc34f3c)},
+    {C(11df592596f41d88), C(843ec0bce9042f9c), C(cce2ea1e08b1eb30),
+     C(26f2b463)},
+    {C(831f448bdc5600b3), C(62a24be3120a6919), C(1b44098a41e010da),
+     C(b042c047)},
+    {C(3eca803e70304894), C(d80de767e4a920a), C(a51cfbb292efd53d), C(e73bb0a8)},
+    {C(1b5a063fb4c7f9f1), C(318dbc24af66dee9), C(10ef7b32d5c719af),
+     C(91dfdd75)},
+    {C(a0f10149a0e538d6), C(69d008c20f87419f), C(41b36376185b3e9e),
+     C(c87f95de)},
+    {C(fb8d9c70660b910b), C(a45b0cc3476bff1b), C(b28d1996144f0207),
+     C(3f5538ef)},
+    {C(236827beae282a46), C(e43970221139c946), C(4f3ac6faa837a3aa),
+     C(70eb1a1f)},
+    {C(c385e435136ecf7c), C(d9d17368ff6c4a08), C(1b31eed4e5251a67),
+     C(cfd63b83)},
+    {C(e3f6828b6017086d), C(21b4d1900554b3b0), C(bef38be1809e24f1),
+     C(894a52ef)},
+    {C(851fff285561dca0), C(4d1277d73cdf416f), C(28ccffa61010ebe2),
+     C(9cde6a54)},
+    {C(61152a63595a96d9), C(d1a3a91ef3a7ba45), C(443b6bb4a493ad0c),
+     C(6c4898d5)},
+    {C(44473e03be306c88), C(30097761f872472a), C(9fd1b669bfad82d7),
+     C(13e1978e)},
+    {C(3ead5f21d344056), C(fb6420393cfb05c3), C(407932394cbbd303), C(51b4ba8)},
+    {C(6abbfde37ee03b5b), C(83febf188d2cc113), C(cda7b62d94d5b8ee),
+     C(b6b06e40)},
+    {C(943e7ed63b3c080), C(1ef207e9444ef7f8), C(ef4a9f9f8c6f9b4a), C(240a2f2)},
+    {C(d72ce05171ef8a1a), C(c6bd6bd869203894), C(c760e6396455d23a),
+     C(5dcefc30)},
+    {C(4182832b52d63735), C(337097e123eea414), C(b5a72ca0456df910),
+     C(7a48b105)},
+    {C(d6cdae892584a2cb), C(58de0fa4eca17dcd), C(43df30b8f5f1cb00),
+     C(fd55007b)},
+    {C(5c8e90bc267c5ee4), C(e9ae044075d992d9), C(f234cbfd1f0a1e59),
+     C(6b95894c)},
+    {C(bbd7f30ac310a6f3), C(b23b570d2666685f), C(fb13fb08c9814fe7),
+     C(3360e827)},
+    {C(36a097aa49519d97), C(8204380a73c4065), C(77c2004bdd9e276a), C(45177e0b)},
+    {C(dc78cb032c49217), C(112464083f83e03a), C(96ae53e28170c0f5), C(7c6fffe4)},
+    {C(441593e0da922dfe), C(936ef46061469b32), C(204a1921197ddd87),
+     C(bbc78da4)},
+    {C(2ba3883d71cc2133), C(72f2bbb32bed1a3c), C(27e1bd96d4843251),
+     C(c5c25d39)},
+    {C(f2b6d2adf8423600), C(7514e2f016a48722), C(43045743a50396ba),
+     C(b6e5d06e)},
+    {C(38fffe7f3680d63c), C(d513325255a7a6d1), C(31ed47790f6ca62f),
+     C(6178504e)},
+    {C(b7477bf0b9ce37c6), C(63b1c580a7fd02a4), C(f6433b9f10a5dac), C(bd4c3637)},
+    {C(55bdb0e71e3edebd), C(c7ab562bcf0568bc), C(43166332f9ee684f),
+     C(6e7ac474)},
+    {C(782fa1b08b475e7), C(fb7138951c61b23b), C(9829105e234fb11e), C(1fb4b518)},
+    {C(c5dc19b876d37a80), C(15ffcff666cfd710), C(e8c30c72003103e2),
+     C(31d13d6d)},
+    {C(5e1141711d2d6706), C(b537f6dee8de6933), C(3af0a1fbbe027c54),
+     C(26fa72e3)},
+    {C(782edf6da001234f), C(f48cbd5c66c48f3), C(808754d1e64e2a32), C(6a7433bf)},
+    {C(d26285842ff04d44), C(8f38d71341eacca9), C(5ca436f4db7a883c),
+     C(4e6df758)},
+    {C(c6ab830865a6bae6), C(6aa8e8dd4b98815c), C(efe3846713c371e5),
+     C(d57f63ea)},
+    {C(44b3a1929232892), C(61dca0e914fc217), C(a607cc142096b964), C(52ef73b3)},
+    {C(4b603d7932a8de4f), C(fae64c464b8a8f45), C(8fafab75661d602a), C(3cb36c3)},
+    {C(4ec0b54cf1566aff), C(30d2c7269b206bf4), C(77c22e82295e1061),
+     C(72c39bea)},
+    {C(ed8b7a4b34954ff7), C(56432de31f4ee757), C(85bd3abaa572b155),
+     C(a65aa25c)},
+    {C(5d28b43694176c26), C(714cc8bc12d060ae), C(3437726273a83fe6),
+     C(74740539)},
+    {C(6a1ef3639e1d202e), C(919bc1bd145ad928), C(30f3f7e48c28a773),
+     C(c3ae3c26)},
+    {C(159f4d9e0307b111), C(3e17914a5675a0c), C(af849bd425047b51), C(f29db8a2)},
+    {C(cc0a840725a7e25b), C(57c69454396e193a), C(976eaf7eee0b4540),
+     C(1ef4cbf4)},
+    {C(a2b27ee22f63c3f1), C(9ebde0ce1b3976b2), C(2fe6a92a257af308),
+     C(a9be6c41)},
+    {C(d8f2f234899bcab3), C(b10b037297c3a168), C(debea2c510ceda7f), C(fa31801)},
+    {C(584f28543864844f), C(d7cee9fc2d46f20d), C(a38dca5657387205),
+     C(8331c5d8)},
+    {C(a94be46dd9aa41af), C(a57e5b7723d3f9bd), C(34bf845a52fd2f), C(e9876db8)},
+    {C(9a87bea227491d20), C(a468657e2b9c43e7), C(af9ba60db8d89ef7),
+     C(27b0604e)},
+    {C(27688c24958d1a5c), C(e3b4a1c9429cf253), C(48a95811f70d64bc),
+     C(dcec07f2)},
+    {C(5d1d37790a1873ad), C(ed9cd4bcc5fa1090), C(ce51cde05d8cd96a),
+     C(cff0a82a)},
+    {C(1f03fd18b711eea9), C(566d89b1946d381a), C(6e96e83fc92563ab),
+     C(fec83621)},
+    {C(f0316f286cf527b6), C(f84c29538de1aa5a), C(7612ed3c923d4a71), C(743d8dc)},
+    {C(297008bcb3e3401d), C(61a8e407f82b0c69), C(a4a35bff0524fa0e),
+     C(64d41d26)},
+    {C(43c6252411ee3be), C(b4ca1b8077777168), C(2746dc3f7da1737f), C(acd90c81)},
+    {C(ce38a9a54fad6599), C(6d6f4a90b9e8755e), C(c3ecc79ff105de3f),
+     C(7c746a4b)},
+    {C(270a9305fef70cf), C(600193999d884f3a), C(f4d49eae09ed8a1), C(b1047e99)},
+    {C(e71be7c28e84d119), C(eb6ace59932736e6), C(70c4397807ba12c5),
+     C(d1fd1068)},
+    {C(b5b58c24b53aaa19), C(d2a6ab0773dd897f), C(ef762fe01ecb5b97),
+     C(56486077)},
+    {C(44dd59bd301995cf), C(3ccabd76493ada1a), C(540db4c87d55ef23),
+     C(6069be80)},
+    {C(b4d4789eb6f2630b), C(bf6973263ce8ef0e), C(d1c75c50844b9d3), C(2078359b)},
+    {C(12807833c463737c), C(58e927ea3b3776b4), C(72dd20ef1c2f8ad0),
+     C(9ea21004)},
+    {C(e88419922b87176f), C(bcf32f41a7ddbf6f), C(d6ebefd8085c1a0f),
+     C(9c9cfe88)},
+    {C(105191e0ec8f7f60), C(5918dbfcca971e79), C(6b285c8a944767b9),
+     C(b70a6ddd)},
+    {C(a5b88bf7399a9f07), C(fca3ddfd96461cc4), C(ebe738fdc0282fc6),
+     C(dea37298)},
+    {C(d08c3f5747d84f50), C(4e708b27d1b6f8ac), C(70f70fd734888606),
+     C(8f480819)},
+    {C(2f72d12a40044b4b), C(889689352fec53de), C(f03e6ad87eb2f36), C(30b3b16)},
+    {C(aa1f61fdc5c2e11e), C(c2c56cd11277ab27), C(a1e73069fdf1f94f),
+     C(f31bc4e8)},
+    {C(9489b36fe2246244), C(3355367033be74b8), C(5f57c2277cbce516),
+     C(419f953b)},
+    {C(358d7c0476a044cd), C(e0b7b47bcbd8854f), C(ffb42ec696705519),
+     C(20e9e76d)},
+    {C(b0c48df14275265a), C(9da4448975905efa), C(d716618e414ceb6d),
+     C(646f0ff8)},
+    {C(daa70bb300956588), C(410ea6883a240c6d), C(f5c8239fb5673eb3),
+     C(eeb7eca8)},
+    {C(4ec97a20b6c4c7c2), C(5913b1cd454f29fd), C(a9629f9daf06d685), C(8112bb9)},
+    {C(5c3323628435a2e8), C(1bea45ce9e72a6e3), C(904f0a7027ddb52e),
+     C(85a6d477)},
+    {C(c1ef26bea260abdb), C(6ee423f2137f9280), C(df2118b946ed0b43),
+     C(56f76c84)},
+    {C(6be7381b115d653a), C(ed046190758ea511), C(de6a45ffc3ed1159),
+     C(9af45d55)},
+    {C(ae3eece1711b2105), C(14fd3f4027f81a4a), C(abb7e45177d151db),
+     C(d1c33760)},
+    {C(376c28588b8fb389), C(6b045e84d8491ed2), C(4e857effb7d4e7dc),
+     C(c56bbf69)},
+    {C(58d943503bb6748f), C(419c6c8e88ac70f6), C(586760cbf3d3d368),
+     C(abecfb9b)},
+    {C(dfff5989f5cfd9a1), C(bcee2e7ea3a96f83), C(681c7874adb29017),
+     C(8de13255)},
+    {C(7fb19eb1a496e8f5), C(d49e5dfdb5c0833f), C(c0d5d7b2f7c48dc7),
+     C(a98ee299)},
+    {C(5dba5b0dadccdbaa), C(4ba8da8ded87fcdc), C(f693fdd25badf2f0),
+     C(3015f556)},
+    {C(688bef4b135a6829), C(8d31d82abcd54e8e), C(f95f8a30d55036d7),
+     C(5a430e29)},
+    {C(d8323be05433a412), C(8d48fa2b2b76141d), C(3d346f23978336a5),
+     C(2797add0)},
+    {C(3b5404278a55a7fc), C(23ca0b327c2d0a81), C(a6d65329571c892c),
+     C(27d55016)},
+    {C(2a96a3f96c5e9bbc), C(8caf8566e212dda8), C(904de559ca16e45e),
+     C(84945a82)},
+    {C(22bebfdcc26d18ff), C(4b4d8dcb10807ba1), C(40265eee30c6b896),
+     C(3ef7e224)},
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+    {C(79f7efe4a80b951a), C(dd3a3fddfc6c9c41), C(ab4c812f9e27aa40),
+     C(a8d123c9)},
+    {C(ae6e59f5f055921a), C(e9d9b7bf68e82), C(5ce4e4a5b269cc59), C(1e80ad7d)},
+    {C(8959dbbf07387d36), C(b4658afce48ea35d), C(8f3f82437d8cb8d6),
+     C(52aeb863)},
+    {C(4739613234278a49), C(99ea5bcd340bf663), C(258640912e712b12),
+     C(ef7c0c18)},
+    {C(420e6c926bc54841), C(96dbbf6f4e7c75cd), C(d8d40fa70c3c67bb),
+     C(b6ad4b68)},
+    {C(c8601bab561bc1b7), C(72b26272a0ff869a), C(56fdfc986d6bc3c4),
+     C(c1e46b17)},
+    {C(b2d294931a0e20eb), C(284ffd9a0815bc38), C(1f8a103aac9bbe6), C(57b8df25)},
+    {C(7966f53c37b6c6d7), C(8e6abcfb3aa2b88f), C(7f2e5e0724e5f345),
+     C(e9fa36d6)},
+    {C(be9bb0abd03b7368), C(13bca93a3031be55), C(e864f4f52b55b472),
+     C(8f8daefc)},
+    {C(a08d128c5f1649be), C(a8166c3dbbe19aad), C(cb9f914f829ec62c), C(6e1bb7e)},
+    {C(7c386f0ffe0465ac), C(530419c9d843dbf3), C(7450e3a4f72b8d8c),
+     C(fd0076f0)},
+    {C(bb362094e7ef4f8), C(ff3c2a48966f9725), C(55152803acd4a7fe), C(899b17b6)},
+    {C(cd80dea24321eea4), C(52b4fdc8130c2b15), C(f3ea100b154bfb82),
+     C(e3e84e31)},
+    {C(d599a04125372c3a), C(313136c56a56f363), C(1e993c3677625832),
+     C(eef79b6b)},
+    {C(dbbf541e9dfda0a), C(1479fceb6db4f844), C(31ab576b59062534), C(868e3315)},
+    {C(c2ee3288be4fe2bf), C(c65d2f5ddf32b92), C(af6ecdf121ba5485), C(4639a426)},
+    {C(d86603ced1ed4730), C(f9de718aaada7709), C(db8b9755194c6535),
+     C(f3213646)},
+    {C(915263c671b28809), C(a815378e7ad762fd), C(abec6dc9b669f559),
+     C(17f148e9)},
+    {C(2b67cdd38c307a5e), C(cb1d45bb5c9fe1c), C(800baf2a02ec18ad), C(bfd94880)},
+    {C(2d107419073b9cd0), C(a96db0740cef8f54), C(ec41ee91b3ecdc1b),
+     C(bb1fa7f3)},
+    {C(f3e9487ec0e26dfc), C(1ab1f63224e837fa), C(119983bb5a8125d8), C(88816b1)},
+    {C(1160987c8fe86f7d), C(879e6db1481eb91b), C(d7dcb802bfe6885d),
+     C(5c2faeb3)},
+    {C(eab8112c560b967b), C(97f550b58e89dbae), C(846ed506d304051f),
+     C(51b5fc6f)},
+    {C(1addcf0386d35351), C(b5f436561f8f1484), C(85d38e22181c9bb1),
+     C(33d94752)},
+    {C(d445ba84bf803e09), C(1216c2497038f804), C(2293216ea2237207),
+     C(b0c92948)},
+    {C(37235a096a8be435), C(d9b73130493589c2), C(3b1024f59378d3be),
+     C(c7171590)},
+    {C(763ad6ea2fe1c99d), C(cf7af5368ac1e26b), C(4d5e451b3bb8d3d4),
+     C(240a67fb)},
+    {C(ea627fc84cd1b857), C(85e372494520071f), C(69ec61800845780b),
+     C(e1843cd5)},
+    {C(1f2ffd79f2cdc0c8), C(726a1bc31b337aaa), C(678b7f275ef96434),
+     C(fda1452b)},
+    {C(39a9e146ec4b3210), C(f63f75802a78b1ac), C(e2e22539c94741c3),
+     C(a2cad330)},
+    {C(74cba303e2dd9d6d), C(692699b83289fad1), C(dfb9aa7874678480),
+     C(53467e16)},
+    {C(4cbc2b73a43071e0), C(56c5db4c4ca4e0b7), C(1b275a162f46bd3d),
+     C(da14a8d0)},
+    {C(875638b9715d2221), C(d9ba0615c0c58740), C(616d4be2dfe825aa),
+     C(67333551)},
+    {C(fb686b2782994a8d), C(edee60693756bb48), C(e6bc3cae0ded2ef5),
+     C(a0ebd66e)},
+    {C(ab21d81a911e6723), C(4c31b07354852f59), C(835da384c9384744),
+     C(4b769593)},
+    {C(33d013cc0cd46ecf), C(3de726423aea122c), C(116af51117fe21a9),
+     C(6aa75624)},
+    {C(8ca92c7cd39fae5d), C(317e620e1bf20f1), C(4f0b33bf2194b97f), C(602a3f96)},
+    {C(fdde3b03f018f43e), C(38f932946c78660), C(c84084ce946851ee), C(cd183c4d)},
+    {C(9c8502050e9c9458), C(d6d2a1a69964beb9), C(1675766f480229b5),
+     C(960a4d07)},
+    {C(348176ca2fa2fdd2), C(3a89c514cc360c2d), C(9f90b8afb318d6d0),
+     C(9ae998c4)},
+    {C(4a3d3dfbbaea130b), C(4e221c920f61ed01), C(553fd6cd1304531f),
+     C(74e2179d)},
+    {C(b371f768cdf4edb9), C(bdef2ace6d2de0f0), C(e05b4100f7f1baec),
+     C(ee9bae25)},
+    {C(7a1d2e96934f61f), C(eb1760ae6af7d961), C(887eb0da063005df), C(b66edf10)},
+    {C(8be53d466d4728f2), C(86a5ac8e0d416640), C(984aa464cdb5c8bb),
+     C(d6209737)},
+    {C(829677eb03abf042), C(43cad004b6bc2c0), C(f2f224756803971a), C(b994a88)},
+    {C(754435bae3496fc), C(5707fc006f094dcf), C(8951c86ab19d8e40), C(a05d43c0)},
+    {C(fda9877ea8e3805f), C(31e868b6ffd521b7), C(b08c90681fb6a0fd),
+     C(c79f73a8)},
+    {C(2e36f523ca8f5eb5), C(8b22932f89b27513), C(331cd6ecbfadc1bb),
+     C(a490aff5)},
+    {C(21a378ef76828208), C(a5c13037fa841da2), C(506d22a53fbe9812),
+     C(dfad65b4)},
+    {C(ccdd5600054b16ca), C(f78846e84204cb7b), C(1f9faec82c24eac9), C(1d07dfb)},
+    {C(7854468f4e0cabd0), C(3a3f6b4f098d0692), C(ae2423ec7799d30d),
+     C(416df9a0)},
+    {C(7f88db5346d8f997), C(88eac9aacc653798), C(68a4d0295f8eefa1),
+     C(1f8fb9cc)},
+    {C(bb3fb5fb01d60fcf), C(1b7cc0847a215eb6), C(1246c994437990a1),
+     C(7abf48e3)},
+    {C(2e783e1761acd84d), C(39158042bac975a0), C(1cd21c5a8071188d),
+     C(dea4e3dd)},
+    {C(392058251cf22acc), C(944ec4475ead4620), C(b330a10b5cb94166),
+     C(c6064f22)},
+    {C(adf5c1e5d6419947), C(2a9747bc659d28aa), C(95c5b8cb1f5d62c), C(743bed9c)},
+    {C(6bc1db2c2bee5aba), C(e63b0ed635307398), C(7b2eca111f30dbbc),
+     C(fce254d5)},
+    {C(b00f898229efa508), C(83b7590ad7f6985c), C(2780e70a0592e41d),
+     C(e47ec9d1)},
+    {C(b56eb769ce0d9a8c), C(ce196117bfbcaf04), C(b26c3c3797d66165),
+     C(334a145c)},
+    {C(70c0637675b94150), C(259e1669305b0a15), C(46e1dd9fd387a58d),
+     C(adec1e3c)},
+    {C(74c0b8a6821faafe), C(abac39d7491370e7), C(faf0b2a48a4e6aed),
+     C(f6a9fbf8)},
+    {C(5fb5e48ac7b7fa4f), C(a96170f08f5acbc7), C(bbf5c63d4f52a1e5),
+     C(5398210c)},
+};
+
+void TestUnchanging(const uint64_t* expected, int offset, int len) {
+  EXPECT_EQ(expected[0], CityHash64(data + offset, len));
+  EXPECT_EQ(expected[3], CityHash32(data + offset, len));
+  EXPECT_EQ(expected[1], CityHash64WithSeed(data + offset, len, kSeed0));
+  EXPECT_EQ(expected[2],
+            CityHash64WithSeeds(data + offset, len, kSeed0, kSeed1));
+}
+
+TEST(CityHashTest, Unchanging) {
+  setup();
+  int i = 0;
+  for (; i < kTestSize - 1; i++) {
+    TestUnchanging(testdata[i], i * i, i);
+  }
+  TestUnchanging(testdata[i], 0, kDataSize);
+}
+
+}  // namespace
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/hash.cc b/weight/_dep/abseil-cpp/absl/hash/internal/hash.cc
new file mode 100644
index 0000000000000000000000000000000000000000..11451e575c0ab9cf7b7877f149b34d092dce6017
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/hash.cc
@@ -0,0 +1,69 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/hash/internal/hash.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+
+uint64_t MixingHashState::CombineLargeContiguousImpl32(
+    uint64_t state, const unsigned char* first, size_t len) {
+  while (len >= PiecewiseChunkSize()) {
+    state = Mix(state,
+                hash_internal::CityHash32(reinterpret_cast<const char*>(first),
+                                          PiecewiseChunkSize()));
+    len -= PiecewiseChunkSize();
+    first += PiecewiseChunkSize();
+  }
+  // Handle the remainder.
+  return CombineContiguousImpl(state, first, len,
+                               std::integral_constant<int, 4>{});
+}
+
+uint64_t MixingHashState::CombineLargeContiguousImpl64(
+    uint64_t state, const unsigned char* first, size_t len) {
+  while (len >= PiecewiseChunkSize()) {
+    state = Mix(state, Hash64(first, PiecewiseChunkSize()));
+    len -= PiecewiseChunkSize();
+    first += PiecewiseChunkSize();
+  }
+  // Handle the remainder.
+  return CombineContiguousImpl(state, first, len,
+                               std::integral_constant<int, 8>{});
+}
+
+ABSL_CONST_INIT const void* const MixingHashState::kSeed = &kSeed;
+
+// The salt array used by LowLevelHash. This array is NOT the mechanism used to
+// make absl::Hash non-deterministic between program invocations.  See `Seed()`
+// for that mechanism.
+//
+// Any random values are fine. These values are just digits from the decimal
+// part of pi.
+// https://en.wikipedia.org/wiki/Nothing-up-my-sleeve_number
+constexpr uint64_t kHashSalt[5] = {
+    uint64_t{0x243F6A8885A308D3}, uint64_t{0x13198A2E03707344},
+    uint64_t{0xA4093822299F31D0}, uint64_t{0x082EFA98EC4E6C89},
+    uint64_t{0x452821E638D01377},
+};
+
+uint64_t MixingHashState::LowLevelHashImpl(const unsigned char* data,
+                                           size_t len) {
+  return LowLevelHash(data, len, Seed(), kHashSalt);
+}
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/hash.h b/weight/_dep/abseil-cpp/absl/hash/internal/hash.h
new file mode 100644
index 0000000000000000000000000000000000000000..f4a94f9129f4443fd60b6cd57146119fd51b319a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/hash.h
@@ -0,0 +1,1375 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: hash.h
+// -----------------------------------------------------------------------------
+//
+#ifndef ABSL_HASH_INTERNAL_HASH_H_
+#define ABSL_HASH_INTERNAL_HASH_H_
+
+#ifdef __APPLE__
+#include <Availability.h>
+#include <TargetConditionals.h>
+#endif
+
+#include <algorithm>
+#include <array>
+#include <bitset>
+#include <cmath>
+#include <cstddef>
+#include <cstring>
+#include <deque>
+#include <forward_list>
+#include <functional>
+#include <iterator>
+#include <limits>
+#include <list>
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/unaligned_access.h"
+#include "absl/base/port.h"
+#include "absl/container/fixed_array.h"
+#include "absl/hash/internal/city.h"
+#include "absl/hash/internal/low_level_hash.h"
+#include "absl/meta/type_traits.h"
+#include "absl/numeric/bits.h"
+#include "absl/numeric/int128.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "absl/types/variant.h"
+#include "absl/utility/utility.h"
+
+#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L && \
+    !defined(_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY)
+#include <filesystem>  // NOLINT
+#endif
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+#include <string_view>
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+class HashState;
+
+namespace hash_internal {
+
+// Internal detail: Large buffers are hashed in smaller chunks.  This function
+// returns the size of these chunks.
+constexpr size_t PiecewiseChunkSize() { return 1024; }
+
+// PiecewiseCombiner
+//
+// PiecewiseCombiner is an internal-only helper class for hashing a piecewise
+// buffer of `char` or `unsigned char` as though it were contiguous.  This class
+// provides two methods:
+//
+//   H add_buffer(state, data, size)
+//   H finalize(state)
+//
+// `add_buffer` can be called zero or more times, followed by a single call to
+// `finalize`.  This will produce the same hash expansion as concatenating each
+// buffer piece into a single contiguous buffer, and passing this to
+// `H::combine_contiguous`.
+//
+//  Example usage:
+//    PiecewiseCombiner combiner;
+//    for (const auto& piece : pieces) {
+//      state = combiner.add_buffer(std::move(state), piece.data, piece.size);
+//    }
+//    return combiner.finalize(std::move(state));
+class PiecewiseCombiner {
+ public:
+  PiecewiseCombiner() : position_(0) {}
+  PiecewiseCombiner(const PiecewiseCombiner&) = delete;
+  PiecewiseCombiner& operator=(const PiecewiseCombiner&) = delete;
+
+  // PiecewiseCombiner::add_buffer()
+  //
+  // Appends the given range of bytes to the sequence to be hashed, which may
+  // modify the provided hash state.
+  template <typename H>
+  H add_buffer(H state, const unsigned char* data, size_t size);
+  template <typename H>
+  H add_buffer(H state, const char* data, size_t size) {
+    return add_buffer(std::move(state),
+                      reinterpret_cast<const unsigned char*>(data), size);
+  }
+
+  // PiecewiseCombiner::finalize()
+  //
+  // Finishes combining the hash sequence, which may may modify the provided
+  // hash state.
+  //
+  // Once finalize() is called, add_buffer() may no longer be called. The
+  // resulting hash state will be the same as if the pieces passed to
+  // add_buffer() were concatenated into a single flat buffer, and then provided
+  // to H::combine_contiguous().
+  template <typename H>
+  H finalize(H state);
+
+ private:
+  unsigned char buf_[PiecewiseChunkSize()];
+  size_t position_;
+};
+
+// is_hashable()
+//
+// Trait class which returns true if T is hashable by the absl::Hash framework.
+// Used for the AbslHashValue implementations for composite types below.
+template <typename T>
+struct is_hashable;
+
+// HashStateBase
+//
+// An internal implementation detail that contains common implementation details
+// for all of the "hash state objects" objects generated by Abseil.  This is not
+// a public API; users should not create classes that inherit from this.
+//
+// A hash state object is the template argument `H` passed to `AbslHashValue`.
+// It represents an intermediate state in the computation of an unspecified hash
+// algorithm. `HashStateBase` provides a CRTP style base class for hash state
+// implementations. Developers adding type support for `absl::Hash` should not
+// rely on any parts of the state object other than the following member
+// functions:
+//
+//   * HashStateBase::combine()
+//   * HashStateBase::combine_contiguous()
+//   * HashStateBase::combine_unordered()
+//
+// A derived hash state class of type `H` must provide a public member function
+// with a signature similar to the following:
+//
+//    `static H combine_contiguous(H state, const unsigned char*, size_t)`.
+//
+// It must also provide a private template method named RunCombineUnordered.
+//
+// A "consumer" is a 1-arg functor returning void.  Its argument is a reference
+// to an inner hash state object, and it may be called multiple times.  When
+// called, the functor consumes the entropy from the provided state object,
+// and resets that object to its empty state.
+//
+// A "combiner" is a stateless 2-arg functor returning void.  Its arguments are
+// an inner hash state object and an ElementStateConsumer functor.  A combiner
+// uses the provided inner hash state object to hash each element of the
+// container, passing the inner hash state object to the consumer after hashing
+// each element.
+//
+// Given these definitions, a derived hash state class of type H
+// must provide a private template method with a signature similar to the
+// following:
+//
+//    `template <typename CombinerT>`
+//    `static H RunCombineUnordered(H outer_state, CombinerT combiner)`
+//
+// This function is responsible for constructing the inner state object and
+// providing a consumer to the combiner.  It uses side effects of the consumer
+// and combiner to mix the state of each element in an order-independent manner,
+// and uses this to return an updated value of `outer_state`.
+//
+// This inside-out approach generates efficient object code in the normal case,
+// but allows us to use stack storage to implement the absl::HashState type
+// erasure mechanism (avoiding heap allocations while hashing).
+//
+// `HashStateBase` will provide a complete implementation for a hash state
+// object in terms of these two methods.
+//
+// Example:
+//
+//   // Use CRTP to define your derived class.
+//   struct MyHashState : HashStateBase<MyHashState> {
+//       static H combine_contiguous(H state, const unsigned char*, size_t);
+//       using MyHashState::HashStateBase::combine;
+//       using MyHashState::HashStateBase::combine_contiguous;
+//       using MyHashState::HashStateBase::combine_unordered;
+//     private:
+//       template <typename CombinerT>
+//       static H RunCombineUnordered(H state, CombinerT combiner);
+//   };
+template <typename H>
+class HashStateBase {
+ public:
+  // HashStateBase::combine()
+  //
+  // Combines an arbitrary number of values into a hash state, returning the
+  // updated state.
+  //
+  // Each of the value types `T` must be separately hashable by the Abseil
+  // hashing framework.
+  //
+  // NOTE:
+  //
+  //   state = H::combine(std::move(state), value1, value2, value3);
+  //
+  // is guaranteed to produce the same hash expansion as:
+  //
+  //   state = H::combine(std::move(state), value1);
+  //   state = H::combine(std::move(state), value2);
+  //   state = H::combine(std::move(state), value3);
+  template <typename T, typename... Ts>
+  static H combine(H state, const T& value, const Ts&... values);
+  static H combine(H state) { return state; }
+
+  // HashStateBase::combine_contiguous()
+  //
+  // Combines a contiguous array of `size` elements into a hash state, returning
+  // the updated state.
+  //
+  // NOTE:
+  //
+  //   state = H::combine_contiguous(std::move(state), data, size);
+  //
+  // is NOT guaranteed to produce the same hash expansion as a for-loop (it may
+  // perform internal optimizations).  If you need this guarantee, use the
+  // for-loop instead.
+  template <typename T>
+  static H combine_contiguous(H state, const T* data, size_t size);
+
+  template <typename I>
+  static H combine_unordered(H state, I begin, I end);
+
+  using AbslInternalPiecewiseCombiner = PiecewiseCombiner;
+
+  template <typename T>
+  using is_hashable = absl::hash_internal::is_hashable<T>;
+
+ private:
+  // Common implementation of the iteration step of a "combiner", as described
+  // above.
+  template <typename I>
+  struct CombineUnorderedCallback {
+    I begin;
+    I end;
+
+    template <typename InnerH, typename ElementStateConsumer>
+    void operator()(InnerH inner_state, ElementStateConsumer cb) {
+      for (; begin != end; ++begin) {
+        inner_state = H::combine(std::move(inner_state), *begin);
+        cb(inner_state);
+      }
+    }
+  };
+};
+
+// is_uniquely_represented
+//
+// `is_uniquely_represented<T>` is a trait class that indicates whether `T`
+// is uniquely represented.
+//
+// A type is "uniquely represented" if two equal values of that type are
+// guaranteed to have the same bytes in their underlying storage. In other
+// words, if `a == b`, then `memcmp(&a, &b, sizeof(T))` is guaranteed to be
+// zero. This property cannot be detected automatically, so this trait is false
+// by default, but can be specialized by types that wish to assert that they are
+// uniquely represented. This makes them eligible for certain optimizations.
+//
+// If you have any doubt whatsoever, do not specialize this template.
+// The default is completely safe, and merely disables some optimizations
+// that will not matter for most types. Specializing this template,
+// on the other hand, can be very hazardous.
+//
+// To be uniquely represented, a type must not have multiple ways of
+// representing the same value; for example, float and double are not
+// uniquely represented, because they have distinct representations for
+// +0 and -0. Furthermore, the type's byte representation must consist
+// solely of user-controlled data, with no padding bits and no compiler-
+// controlled data such as vptrs or sanitizer metadata. This is usually
+// very difficult to guarantee, because in most cases the compiler can
+// insert data and padding bits at its own discretion.
+//
+// If you specialize this template for a type `T`, you must do so in the file
+// that defines that type (or in this file). If you define that specialization
+// anywhere else, `is_uniquely_represented<T>` could have different meanings
+// in different places.
+//
+// The Enable parameter is meaningless; it is provided as a convenience,
+// to support certain SFINAE techniques when defining specializations.
+template <typename T, typename Enable = void>
+struct is_uniquely_represented : std::false_type {};
+
+// is_uniquely_represented<unsigned char>
+//
+// unsigned char is a synonym for "byte", so it is guaranteed to be
+// uniquely represented.
+template <>
+struct is_uniquely_represented<unsigned char> : std::true_type {};
+
+// is_uniquely_represented for non-standard integral types
+//
+// Integral types other than bool should be uniquely represented on any
+// platform that this will plausibly be ported to.
+template <typename Integral>
+struct is_uniquely_represented<
+    Integral, typename std::enable_if<std::is_integral<Integral>::value>::type>
+    : std::true_type {};
+
+// is_uniquely_represented<bool>
+//
+//
+template <>
+struct is_uniquely_represented<bool> : std::false_type {};
+
+// hash_bytes()
+//
+// Convenience function that combines `hash_state` with the byte representation
+// of `value`.
+template <typename H, typename T>
+H hash_bytes(H hash_state, const T& value) {
+  const unsigned char* start = reinterpret_cast<const unsigned char*>(&value);
+  return H::combine_contiguous(std::move(hash_state), start, sizeof(value));
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Basic Types
+// -----------------------------------------------------------------------------
+
+// Note: Default `AbslHashValue` implementations live in `hash_internal`. This
+// allows us to block lexical scope lookup when doing an unqualified call to
+// `AbslHashValue` below. User-defined implementations of `AbslHashValue` can
+// only be found via ADL.
+
+// AbslHashValue() for hashing bool values
+//
+// We use SFINAE to ensure that this overload only accepts bool, not types that
+// are convertible to bool.
+template <typename H, typename B>
+typename std::enable_if<std::is_same<B, bool>::value, H>::type AbslHashValue(
+    H hash_state, B value) {
+  return H::combine(std::move(hash_state),
+                    static_cast<unsigned char>(value ? 1 : 0));
+}
+
+// AbslHashValue() for hashing enum values
+template <typename H, typename Enum>
+typename std::enable_if<std::is_enum<Enum>::value, H>::type AbslHashValue(
+    H hash_state, Enum e) {
+  // In practice, we could almost certainly just invoke hash_bytes directly,
+  // but it's possible that a sanitizer might one day want to
+  // store data in the unused bits of an enum. To avoid that risk, we
+  // convert to the underlying type before hashing. Hopefully this will get
+  // optimized away; if not, we can reopen discussion with c-toolchain-team.
+  return H::combine(std::move(hash_state),
+                    static_cast<typename std::underlying_type<Enum>::type>(e));
+}
+// AbslHashValue() for hashing floating-point values
+template <typename H, typename Float>
+typename std::enable_if<std::is_same<Float, float>::value ||
+                            std::is_same<Float, double>::value,
+                        H>::type
+AbslHashValue(H hash_state, Float value) {
+  return hash_internal::hash_bytes(std::move(hash_state),
+                                   value == 0 ? 0 : value);
+}
+
+// Long double has the property that it might have extra unused bytes in it.
+// For example, in x86 sizeof(long double)==16 but it only really uses 80-bits
+// of it. This means we can't use hash_bytes on a long double and have to
+// convert it to something else first.
+template <typename H, typename LongDouble>
+typename std::enable_if<std::is_same<LongDouble, long double>::value, H>::type
+AbslHashValue(H hash_state, LongDouble value) {
+  const int category = std::fpclassify(value);
+  switch (category) {
+    case FP_INFINITE:
+      // Add the sign bit to differentiate between +Inf and -Inf
+      hash_state = H::combine(std::move(hash_state), std::signbit(value));
+      break;
+
+    case FP_NAN:
+    case FP_ZERO:
+    default:
+      // Category is enough for these.
+      break;
+
+    case FP_NORMAL:
+    case FP_SUBNORMAL:
+      // We can't convert `value` directly to double because this would have
+      // undefined behavior if the value is out of range.
+      // std::frexp gives us a value in the range (-1, -.5] or [.5, 1) that is
+      // guaranteed to be in range for `double`. The truncation is
+      // implementation defined, but that works as long as it is deterministic.
+      int exp;
+      auto mantissa = static_cast<double>(std::frexp(value, &exp));
+      hash_state = H::combine(std::move(hash_state), mantissa, exp);
+  }
+
+  return H::combine(std::move(hash_state), category);
+}
+
+// Without this overload, an array decays to a pointer and we hash that, which
+// is not likely to be what the caller intended.
+template <typename H, typename T, size_t N>
+H AbslHashValue(H hash_state, T (&)[N]) {
+  static_assert(
+      sizeof(T) == -1,
+      "Hashing C arrays is not allowed. For string literals, wrap the literal "
+      "in absl::string_view(). To hash the array contents, use "
+      "absl::MakeSpan() or make the array an std::array. To hash the array "
+      "address, use &array[0].");
+  return hash_state;
+}
+
+// AbslHashValue() for hashing pointers
+template <typename H, typename T>
+std::enable_if_t<std::is_pointer<T>::value, H> AbslHashValue(H hash_state,
+                                                             T ptr) {
+  auto v = reinterpret_cast<uintptr_t>(ptr);
+  // Due to alignment, pointers tend to have low bits as zero, and the next few
+  // bits follow a pattern since they are also multiples of some base value.
+  // Mixing the pointer twice helps prevent stuck low bits for certain alignment
+  // values.
+  return H::combine(std::move(hash_state), v, v);
+}
+
+// AbslHashValue() for hashing nullptr_t
+template <typename H>
+H AbslHashValue(H hash_state, std::nullptr_t) {
+  return H::combine(std::move(hash_state), static_cast<void*>(nullptr));
+}
+
+// AbslHashValue() for hashing pointers-to-member
+template <typename H, typename T, typename C>
+H AbslHashValue(H hash_state, T C::*ptr) {
+  auto salient_ptm_size = [](std::size_t n) -> std::size_t {
+#if defined(_MSC_VER)
+    // Pointers-to-member-function on MSVC consist of one pointer plus 0, 1, 2,
+    // or 3 ints. In 64-bit mode, they are 8-byte aligned and thus can contain
+    // padding (namely when they have 1 or 3 ints). The value below is a lower
+    // bound on the number of salient, non-padding bytes that we use for
+    // hashing.
+    if (alignof(T C::*) == alignof(int)) {
+      // No padding when all subobjects have the same size as the total
+      // alignment. This happens in 32-bit mode.
+      return n;
+    } else {
+      // Padding for 1 int (size 16) or 3 ints (size 24).
+      // With 2 ints, the size is 16 with no padding, which we pessimize.
+      return n == 24 ? 20 : n == 16 ? 12 : n;
+    }
+#else
+  // On other platforms, we assume that pointers-to-members do not have
+  // padding.
+#ifdef __cpp_lib_has_unique_object_representations
+    static_assert(std::has_unique_object_representations<T C::*>::value);
+#endif  // __cpp_lib_has_unique_object_representations
+    return n;
+#endif
+  };
+  return H::combine_contiguous(std::move(hash_state),
+                               reinterpret_cast<unsigned char*>(&ptr),
+                               salient_ptm_size(sizeof ptr));
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Composite Types
+// -----------------------------------------------------------------------------
+
+// AbslHashValue() for hashing pairs
+template <typename H, typename T1, typename T2>
+typename std::enable_if<is_hashable<T1>::value && is_hashable<T2>::value,
+                        H>::type
+AbslHashValue(H hash_state, const std::pair<T1, T2>& p) {
+  return H::combine(std::move(hash_state), p.first, p.second);
+}
+
+// hash_tuple()
+//
+// Helper function for hashing a tuple. The third argument should
+// be an index_sequence running from 0 to tuple_size<Tuple> - 1.
+template <typename H, typename Tuple, size_t... Is>
+H hash_tuple(H hash_state, const Tuple& t, absl::index_sequence<Is...>) {
+  return H::combine(std::move(hash_state), std::get<Is>(t)...);
+}
+
+// AbslHashValue for hashing tuples
+template <typename H, typename... Ts>
+#if defined(_MSC_VER)
+// This SFINAE gets MSVC confused under some conditions. Let's just disable it
+// for now.
+H
+#else   // _MSC_VER
+typename std::enable_if<absl::conjunction<is_hashable<Ts>...>::value, H>::type
+#endif  // _MSC_VER
+AbslHashValue(H hash_state, const std::tuple<Ts...>& t) {
+  return hash_internal::hash_tuple(std::move(hash_state), t,
+                                   absl::make_index_sequence<sizeof...(Ts)>());
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Pointers
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing unique_ptr
+template <typename H, typename T, typename D>
+H AbslHashValue(H hash_state, const std::unique_ptr<T, D>& ptr) {
+  return H::combine(std::move(hash_state), ptr.get());
+}
+
+// AbslHashValue for hashing shared_ptr
+template <typename H, typename T>
+H AbslHashValue(H hash_state, const std::shared_ptr<T>& ptr) {
+  return H::combine(std::move(hash_state), ptr.get());
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for String-Like Types
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing strings
+//
+// All the string-like types supported here provide the same hash expansion for
+// the same character sequence. These types are:
+//
+//  - `absl::Cord`
+//  - `std::string` (and std::basic_string<T, std::char_traits<T>, A> for
+//      any allocator A and any T in {char, wchar_t, char16_t, char32_t})
+//  - `absl::string_view`, `std::string_view`, `std::wstring_view`,
+//    `std::u16string_view`, and `std::u32_string_view`.
+//
+// For simplicity, we currently support only strings built on `char`, `wchar_t`,
+// `char16_t`, or `char32_t`. This support may be broadened, if necessary, but
+// with some caution - this overload would misbehave in cases where the traits'
+// `eq()` member isn't equivalent to `==` on the underlying character type.
+template <typename H>
+H AbslHashValue(H hash_state, absl::string_view str) {
+  return H::combine(
+      H::combine_contiguous(std::move(hash_state), str.data(), str.size()),
+      str.size());
+}
+
+// Support std::wstring, std::u16string and std::u32string.
+template <typename Char, typename Alloc, typename H,
+          typename = absl::enable_if_t<std::is_same<Char, wchar_t>::value ||
+                                       std::is_same<Char, char16_t>::value ||
+                                       std::is_same<Char, char32_t>::value>>
+H AbslHashValue(
+    H hash_state,
+    const std::basic_string<Char, std::char_traits<Char>, Alloc>& str) {
+  return H::combine(
+      H::combine_contiguous(std::move(hash_state), str.data(), str.size()),
+      str.size());
+}
+
+#ifdef ABSL_HAVE_STD_STRING_VIEW
+
+// Support std::wstring_view, std::u16string_view and std::u32string_view.
+template <typename Char, typename H,
+          typename = absl::enable_if_t<std::is_same<Char, wchar_t>::value ||
+                                       std::is_same<Char, char16_t>::value ||
+                                       std::is_same<Char, char32_t>::value>>
+H AbslHashValue(H hash_state, std::basic_string_view<Char> str) {
+  return H::combine(
+      H::combine_contiguous(std::move(hash_state), str.data(), str.size()),
+      str.size());
+}
+
+#endif  // ABSL_HAVE_STD_STRING_VIEW
+
+#if defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L && \
+    !defined(_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY) && \
+    (!defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) ||        \
+     __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 130000)
+
+#define ABSL_INTERNAL_STD_FILESYSTEM_PATH_HASH_AVAILABLE 1
+
+// Support std::filesystem::path. The SFINAE is required because some string
+// types are implicitly convertible to std::filesystem::path.
+template <typename Path, typename H,
+          typename = absl::enable_if_t<
+              std::is_same_v<Path, std::filesystem::path>>>
+H AbslHashValue(H hash_state, const Path& path) {
+  // This is implemented by deferring to the standard library to compute the
+  // hash.  The standard library requires that for two paths, `p1 == p2`, then
+  // `hash_value(p1) == hash_value(p2)`. `AbslHashValue` has the same
+  // requirement. Since `operator==` does platform specific matching, deferring
+  // to the standard library is the simplest approach.
+  return H::combine(std::move(hash_state), std::filesystem::hash_value(path));
+}
+
+#endif  // ABSL_INTERNAL_STD_FILESYSTEM_PATH_HASH_AVAILABLE
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Sequence Containers
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing std::array
+template <typename H, typename T, size_t N>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, const std::array<T, N>& array) {
+  return H::combine_contiguous(std::move(hash_state), array.data(),
+                               array.size());
+}
+
+// AbslHashValue for hashing std::deque
+template <typename H, typename T, typename Allocator>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, const std::deque<T, Allocator>& deque) {
+  // TODO(gromer): investigate a more efficient implementation taking
+  // advantage of the chunk structure.
+  for (const auto& t : deque) {
+    hash_state = H::combine(std::move(hash_state), t);
+  }
+  return H::combine(std::move(hash_state), deque.size());
+}
+
+// AbslHashValue for hashing std::forward_list
+template <typename H, typename T, typename Allocator>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, const std::forward_list<T, Allocator>& list) {
+  size_t size = 0;
+  for (const T& t : list) {
+    hash_state = H::combine(std::move(hash_state), t);
+    ++size;
+  }
+  return H::combine(std::move(hash_state), size);
+}
+
+// AbslHashValue for hashing std::list
+template <typename H, typename T, typename Allocator>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, const std::list<T, Allocator>& list) {
+  for (const auto& t : list) {
+    hash_state = H::combine(std::move(hash_state), t);
+  }
+  return H::combine(std::move(hash_state), list.size());
+}
+
+// AbslHashValue for hashing std::vector
+//
+// Do not use this for vector<bool> on platforms that have a working
+// implementation of std::hash. It does not have a .data(), and a fallback for
+// std::hash<> is most likely faster.
+template <typename H, typename T, typename Allocator>
+typename std::enable_if<is_hashable<T>::value && !std::is_same<T, bool>::value,
+                        H>::type
+AbslHashValue(H hash_state, const std::vector<T, Allocator>& vector) {
+  return H::combine(H::combine_contiguous(std::move(hash_state), vector.data(),
+                                          vector.size()),
+                    vector.size());
+}
+
+// AbslHashValue special cases for hashing std::vector<bool>
+
+#if defined(ABSL_IS_BIG_ENDIAN) && \
+    (defined(__GLIBCXX__) || defined(__GLIBCPP__))
+
+// std::hash in libstdc++ does not work correctly with vector<bool> on Big
+// Endian platforms therefore we need to implement a custom AbslHashValue for
+// it. More details on the bug:
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102531
+template <typename H, typename T, typename Allocator>
+typename std::enable_if<is_hashable<T>::value && std::is_same<T, bool>::value,
+                        H>::type
+AbslHashValue(H hash_state, const std::vector<T, Allocator>& vector) {
+  typename H::AbslInternalPiecewiseCombiner combiner;
+  for (const auto& i : vector) {
+    unsigned char c = static_cast<unsigned char>(i);
+    hash_state = combiner.add_buffer(std::move(hash_state), &c, sizeof(c));
+  }
+  return H::combine(combiner.finalize(std::move(hash_state)), vector.size());
+}
+#else
+// When not working around the libstdc++ bug above, we still have to contend
+// with the fact that std::hash<vector<bool>> is often poor quality, hashing
+// directly on the internal words and on no other state.  On these platforms,
+// vector<bool>{1, 1} and vector<bool>{1, 1, 0} hash to the same value.
+//
+// Mixing in the size (as we do in our other vector<> implementations) on top
+// of the library-provided hash implementation avoids this QOI issue.
+template <typename H, typename T, typename Allocator>
+typename std::enable_if<is_hashable<T>::value && std::is_same<T, bool>::value,
+                        H>::type
+AbslHashValue(H hash_state, const std::vector<T, Allocator>& vector) {
+  return H::combine(std::move(hash_state),
+                    std::hash<std::vector<T, Allocator>>{}(vector),
+                    vector.size());
+}
+#endif
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Ordered Associative Containers
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing std::map
+template <typename H, typename Key, typename T, typename Compare,
+          typename Allocator>
+typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value,
+                        H>::type
+AbslHashValue(H hash_state, const std::map<Key, T, Compare, Allocator>& map) {
+  for (const auto& t : map) {
+    hash_state = H::combine(std::move(hash_state), t);
+  }
+  return H::combine(std::move(hash_state), map.size());
+}
+
+// AbslHashValue for hashing std::multimap
+template <typename H, typename Key, typename T, typename Compare,
+          typename Allocator>
+typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value,
+                        H>::type
+AbslHashValue(H hash_state,
+              const std::multimap<Key, T, Compare, Allocator>& map) {
+  for (const auto& t : map) {
+    hash_state = H::combine(std::move(hash_state), t);
+  }
+  return H::combine(std::move(hash_state), map.size());
+}
+
+// AbslHashValue for hashing std::set
+template <typename H, typename Key, typename Compare, typename Allocator>
+typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(
+    H hash_state, const std::set<Key, Compare, Allocator>& set) {
+  for (const auto& t : set) {
+    hash_state = H::combine(std::move(hash_state), t);
+  }
+  return H::combine(std::move(hash_state), set.size());
+}
+
+// AbslHashValue for hashing std::multiset
+template <typename H, typename Key, typename Compare, typename Allocator>
+typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(
+    H hash_state, const std::multiset<Key, Compare, Allocator>& set) {
+  for (const auto& t : set) {
+    hash_state = H::combine(std::move(hash_state), t);
+  }
+  return H::combine(std::move(hash_state), set.size());
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Unordered Associative Containers
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing std::unordered_set
+template <typename H, typename Key, typename Hash, typename KeyEqual,
+          typename Alloc>
+typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(
+    H hash_state, const std::unordered_set<Key, Hash, KeyEqual, Alloc>& s) {
+  return H::combine(
+      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),
+      s.size());
+}
+
+// AbslHashValue for hashing std::unordered_multiset
+template <typename H, typename Key, typename Hash, typename KeyEqual,
+          typename Alloc>
+typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue(
+    H hash_state,
+    const std::unordered_multiset<Key, Hash, KeyEqual, Alloc>& s) {
+  return H::combine(
+      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),
+      s.size());
+}
+
+// AbslHashValue for hashing std::unordered_set
+template <typename H, typename Key, typename T, typename Hash,
+          typename KeyEqual, typename Alloc>
+typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value,
+                        H>::type
+AbslHashValue(H hash_state,
+              const std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& s) {
+  return H::combine(
+      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),
+      s.size());
+}
+
+// AbslHashValue for hashing std::unordered_multiset
+template <typename H, typename Key, typename T, typename Hash,
+          typename KeyEqual, typename Alloc>
+typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value,
+                        H>::type
+AbslHashValue(H hash_state,
+              const std::unordered_multimap<Key, T, Hash, KeyEqual, Alloc>& s) {
+  return H::combine(
+      H::combine_unordered(std::move(hash_state), s.begin(), s.end()),
+      s.size());
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Wrapper Types
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing std::reference_wrapper
+template <typename H, typename T>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, std::reference_wrapper<T> opt) {
+  return H::combine(std::move(hash_state), opt.get());
+}
+
+// AbslHashValue for hashing absl::optional
+template <typename H, typename T>
+typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue(
+    H hash_state, const absl::optional<T>& opt) {
+  if (opt) hash_state = H::combine(std::move(hash_state), *opt);
+  return H::combine(std::move(hash_state), opt.has_value());
+}
+
+// VariantVisitor
+template <typename H>
+struct VariantVisitor {
+  H&& hash_state;
+  template <typename T>
+  H operator()(const T& t) const {
+    return H::combine(std::move(hash_state), t);
+  }
+};
+
+// AbslHashValue for hashing absl::variant
+template <typename H, typename... T>
+typename std::enable_if<conjunction<is_hashable<T>...>::value, H>::type
+AbslHashValue(H hash_state, const absl::variant<T...>& v) {
+  if (!v.valueless_by_exception()) {
+    hash_state = absl::visit(VariantVisitor<H>{std::move(hash_state)}, v);
+  }
+  return H::combine(std::move(hash_state), v.index());
+}
+
+// -----------------------------------------------------------------------------
+// AbslHashValue for Other Types
+// -----------------------------------------------------------------------------
+
+// AbslHashValue for hashing std::bitset is not defined on Little Endian
+// platforms, for the same reason as for vector<bool> (see std::vector above):
+// It does not expose the raw bytes, and a fallback to std::hash<> is most
+// likely faster.
+
+#if defined(ABSL_IS_BIG_ENDIAN) && \
+    (defined(__GLIBCXX__) || defined(__GLIBCPP__))
+// AbslHashValue for hashing std::bitset
+//
+// std::hash in libstdc++ does not work correctly with std::bitset on Big Endian
+// platforms therefore we need to implement a custom AbslHashValue for it. More
+// details on the bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102531
+template <typename H, size_t N>
+H AbslHashValue(H hash_state, const std::bitset<N>& set) {
+  typename H::AbslInternalPiecewiseCombiner combiner;
+  for (size_t i = 0; i < N; i++) {
+    unsigned char c = static_cast<unsigned char>(set[i]);
+    hash_state = combiner.add_buffer(std::move(hash_state), &c, sizeof(c));
+  }
+  return H::combine(combiner.finalize(std::move(hash_state)), N);
+}
+#endif
+
+// -----------------------------------------------------------------------------
+
+// hash_range_or_bytes()
+//
+// Mixes all values in the range [data, data+size) into the hash state.
+// This overload accepts only uniquely-represented types, and hashes them by
+// hashing the entire range of bytes.
+template <typename H, typename T>
+typename std::enable_if<is_uniquely_represented<T>::value, H>::type
+hash_range_or_bytes(H hash_state, const T* data, size_t size) {
+  const auto* bytes = reinterpret_cast<const unsigned char*>(data);
+  return H::combine_contiguous(std::move(hash_state), bytes, sizeof(T) * size);
+}
+
+// hash_range_or_bytes()
+template <typename H, typename T>
+typename std::enable_if<!is_uniquely_represented<T>::value, H>::type
+hash_range_or_bytes(H hash_state, const T* data, size_t size) {
+  for (const auto end = data + size; data < end; ++data) {
+    hash_state = H::combine(std::move(hash_state), *data);
+  }
+  return hash_state;
+}
+
+#if defined(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE) && \
+    ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+#define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 1
+#else
+#define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 0
+#endif
+
+// HashSelect
+//
+// Type trait to select the appropriate hash implementation to use.
+// HashSelect::type<T> will give the proper hash implementation, to be invoked
+// as:
+//   HashSelect::type<T>::Invoke(state, value)
+// Also, HashSelect::type<T>::value is a boolean equal to `true` if there is a
+// valid `Invoke` function. Types that are not hashable will have a ::value of
+// `false`.
+struct HashSelect {
+ private:
+  struct State : HashStateBase<State> {
+    static State combine_contiguous(State hash_state, const unsigned char*,
+                                    size_t);
+    using State::HashStateBase::combine_contiguous;
+  };
+
+  struct UniquelyRepresentedProbe {
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value)
+        -> absl::enable_if_t<is_uniquely_represented<T>::value, H> {
+      return hash_internal::hash_bytes(std::move(state), value);
+    }
+  };
+
+  struct HashValueProbe {
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value) -> absl::enable_if_t<
+        std::is_same<H,
+                     decltype(AbslHashValue(std::move(state), value))>::value,
+        H> {
+      return AbslHashValue(std::move(state), value);
+    }
+  };
+
+  struct LegacyHashProbe {
+#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value) -> absl::enable_if_t<
+        std::is_convertible<
+            decltype(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>()(value)),
+            size_t>::value,
+        H> {
+      return hash_internal::hash_bytes(
+          std::move(state),
+          ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>{}(value));
+    }
+#endif  // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_
+  };
+
+  struct StdHashProbe {
+    template <typename H, typename T>
+    static auto Invoke(H state, const T& value)
+        -> absl::enable_if_t<type_traits_internal::IsHashable<T>::value, H> {
+      return hash_internal::hash_bytes(std::move(state), std::hash<T>{}(value));
+    }
+  };
+
+  template <typename Hash, typename T>
+  struct Probe : Hash {
+   private:
+    template <typename H, typename = decltype(H::Invoke(
+                              std::declval<State>(), std::declval<const T&>()))>
+    static std::true_type Test(int);
+    template <typename U>
+    static std::false_type Test(char);
+
+   public:
+    static constexpr bool value = decltype(Test<Hash>(0))::value;
+  };
+
+ public:
+  // Probe each implementation in order.
+  // disjunction provides short circuiting wrt instantiation.
+  template <typename T>
+  using Apply = absl::disjunction<         //
+      Probe<UniquelyRepresentedProbe, T>,  //
+      Probe<HashValueProbe, T>,            //
+      Probe<LegacyHashProbe, T>,           //
+      Probe<StdHashProbe, T>,              //
+      std::false_type>;
+};
+
+template <typename T>
+struct is_hashable
+    : std::integral_constant<bool, HashSelect::template Apply<T>::value> {};
+
+// MixingHashState
+class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
+  // absl::uint128 is not an alias or a thin wrapper around the intrinsic.
+  // We use the intrinsic when available to improve performance.
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  using uint128 = __uint128_t;
+#else   // ABSL_HAVE_INTRINSIC_INT128
+  using uint128 = absl::uint128;
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+  static constexpr uint64_t kMul =
+  sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51}
+                      : uint64_t{0x9ddfea08eb382d69};
+
+  template <typename T>
+  using IntegralFastPath =
+      conjunction<std::is_integral<T>, is_uniquely_represented<T>>;
+
+ public:
+  // Move only
+  MixingHashState(MixingHashState&&) = default;
+  MixingHashState& operator=(MixingHashState&&) = default;
+
+  // MixingHashState::combine_contiguous()
+  //
+  // Fundamental base case for hash recursion: mixes the given range of bytes
+  // into the hash state.
+  static MixingHashState combine_contiguous(MixingHashState hash_state,
+                                            const unsigned char* first,
+                                            size_t size) {
+    return MixingHashState(
+        CombineContiguousImpl(hash_state.state_, first, size,
+                              std::integral_constant<int, sizeof(size_t)>{}));
+  }
+  using MixingHashState::HashStateBase::combine_contiguous;
+
+  // MixingHashState::hash()
+  //
+  // For performance reasons in non-opt mode, we specialize this for
+  // integral types.
+  // Otherwise we would be instantiating and calling dozens of functions for
+  // something that is just one multiplication and a couple xor's.
+  // The result should be the same as running the whole algorithm, but faster.
+  template <typename T, absl::enable_if_t<IntegralFastPath<T>::value, int> = 0>
+  static size_t hash(T value) {
+    return static_cast<size_t>(
+        Mix(Seed(), static_cast<std::make_unsigned_t<T>>(value)));
+  }
+
+  // Overload of MixingHashState::hash()
+  template <typename T, absl::enable_if_t<!IntegralFastPath<T>::value, int> = 0>
+  static size_t hash(const T& value) {
+    return static_cast<size_t>(combine(MixingHashState{}, value).state_);
+  }
+
+ private:
+  // Invoked only once for a given argument; that plus the fact that this is
+  // move-only ensures that there is only one non-moved-from object.
+  MixingHashState() : state_(Seed()) {}
+
+  friend class MixingHashState::HashStateBase;
+
+  template <typename CombinerT>
+  static MixingHashState RunCombineUnordered(MixingHashState state,
+                                             CombinerT combiner) {
+    uint64_t unordered_state = 0;
+    combiner(MixingHashState{}, [&](MixingHashState& inner_state) {
+      // Add the hash state of the element to the running total, but mix the
+      // carry bit back into the low bit.  This in intended to avoid losing
+      // entropy to overflow, especially when unordered_multisets contain
+      // multiple copies of the same value.
+      auto element_state = inner_state.state_;
+      unordered_state += element_state;
+      if (unordered_state < element_state) {
+        ++unordered_state;
+      }
+      inner_state = MixingHashState{};
+    });
+    return MixingHashState::combine(std::move(state), unordered_state);
+  }
+
+  // Allow the HashState type-erasure implementation to invoke
+  // RunCombinedUnordered() directly.
+  friend class absl::HashState;
+
+  // Workaround for MSVC bug.
+  // We make the type copyable to fix the calling convention, even though we
+  // never actually copy it. Keep it private to not affect the public API of the
+  // type.
+  MixingHashState(const MixingHashState&) = default;
+
+  explicit MixingHashState(uint64_t state) : state_(state) {}
+
+  // Implementation of the base case for combine_contiguous where we actually
+  // mix the bytes into the state.
+  // Dispatch to different implementations of the combine_contiguous depending
+  // on the value of `sizeof(size_t)`.
+  static uint64_t CombineContiguousImpl(uint64_t state,
+                                        const unsigned char* first, size_t len,
+                                        std::integral_constant<int, 4>
+                                        /* sizeof_size_t */);
+  static uint64_t CombineContiguousImpl(uint64_t state,
+                                        const unsigned char* first, size_t len,
+                                        std::integral_constant<int, 8>
+                                        /* sizeof_size_t */);
+
+  // Slow dispatch path for calls to CombineContiguousImpl with a size argument
+  // larger than PiecewiseChunkSize().  Has the same effect as calling
+  // CombineContiguousImpl() repeatedly with the chunk stride size.
+  static uint64_t CombineLargeContiguousImpl32(uint64_t state,
+                                               const unsigned char* first,
+                                               size_t len);
+  static uint64_t CombineLargeContiguousImpl64(uint64_t state,
+                                               const unsigned char* first,
+                                               size_t len);
+
+  // Reads 9 to 16 bytes from p.
+  // The least significant 8 bytes are in .first, the rest (zero padded) bytes
+  // are in .second.
+  static std::pair<uint64_t, uint64_t> Read9To16(const unsigned char* p,
+                                                 size_t len) {
+    uint64_t low_mem = absl::base_internal::UnalignedLoad64(p);
+    uint64_t high_mem = absl::base_internal::UnalignedLoad64(p + len - 8);
+#ifdef ABSL_IS_LITTLE_ENDIAN
+    uint64_t most_significant = high_mem;
+    uint64_t least_significant = low_mem;
+#else
+    uint64_t most_significant = low_mem;
+    uint64_t least_significant = high_mem;
+#endif
+    return {least_significant, most_significant};
+  }
+
+  // Reads 4 to 8 bytes from p. Zero pads to fill uint64_t.
+  static uint64_t Read4To8(const unsigned char* p, size_t len) {
+    uint32_t low_mem = absl::base_internal::UnalignedLoad32(p);
+    uint32_t high_mem = absl::base_internal::UnalignedLoad32(p + len - 4);
+#ifdef ABSL_IS_LITTLE_ENDIAN
+    uint32_t most_significant = high_mem;
+    uint32_t least_significant = low_mem;
+#else
+    uint32_t most_significant = low_mem;
+    uint32_t least_significant = high_mem;
+#endif
+    return (static_cast<uint64_t>(most_significant) << (len - 4) * 8) |
+           least_significant;
+  }
+
+  // Reads 1 to 3 bytes from p. Zero pads to fill uint32_t.
+  static uint32_t Read1To3(const unsigned char* p, size_t len) {
+    // The trick used by this implementation is to avoid branches if possible.
+    unsigned char mem0 = p[0];
+    unsigned char mem1 = p[len / 2];
+    unsigned char mem2 = p[len - 1];
+#ifdef ABSL_IS_LITTLE_ENDIAN
+    unsigned char significant2 = mem2;
+    unsigned char significant1 = mem1;
+    unsigned char significant0 = mem0;
+#else
+    unsigned char significant2 = mem0;
+    unsigned char significant1 = len == 2 ? mem0 : mem1;
+    unsigned char significant0 = mem2;
+#endif
+    return static_cast<uint32_t>(significant0 |                     //
+                                 (significant1 << (len / 2 * 8)) |  //
+                                 (significant2 << ((len - 1) * 8)));
+  }
+
+  ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Mix(uint64_t state, uint64_t v) {
+    // Though the 128-bit product on AArch64 needs two instructions, it is
+    // still a good balance between speed and hash quality.
+    using MultType =
+        absl::conditional_t<sizeof(size_t) == 4, uint64_t, uint128>;
+    // We do the addition in 64-bit space to make sure the 128-bit
+    // multiplication is fast. If we were to do it as MultType the compiler has
+    // to assume that the high word is non-zero and needs to perform 2
+    // multiplications instead of one.
+    MultType m = state + v;
+    m *= kMul;
+    return static_cast<uint64_t>(m ^ (m >> (sizeof(m) * 8 / 2)));
+  }
+
+  // An extern to avoid bloat on a direct call to LowLevelHash() with fixed
+  // values for both the seed and salt parameters.
+  static uint64_t LowLevelHashImpl(const unsigned char* data, size_t len);
+
+  ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Hash64(const unsigned char* data,
+                                                      size_t len) {
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+    return LowLevelHashImpl(data, len);
+#else
+    return hash_internal::CityHash64(reinterpret_cast<const char*>(data), len);
+#endif
+  }
+
+  // Seed()
+  //
+  // A non-deterministic seed.
+  //
+  // The current purpose of this seed is to generate non-deterministic results
+  // and prevent having users depend on the particular hash values.
+  // It is not meant as a security feature right now, but it leaves the door
+  // open to upgrade it to a true per-process random seed. A true random seed
+  // costs more and we don't need to pay for that right now.
+  //
+  // On platforms with ASLR, we take advantage of it to make a per-process
+  // random value.
+  // See https://en.wikipedia.org/wiki/Address_space_layout_randomization
+  //
+  // On other platforms this is still going to be non-deterministic but most
+  // probably per-build and not per-process.
+  ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Seed() {
+#if (!defined(__clang__) || __clang_major__ > 11) && \
+    (!defined(__apple_build_version__) ||            \
+     __apple_build_version__ >= 19558921)  // Xcode 12
+    return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(&kSeed));
+#else
+    // Workaround the absence of
+    // https://github.com/llvm/llvm-project/commit/bc15bf66dcca76cc06fe71fca35b74dc4d521021.
+    return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(kSeed));
+#endif
+  }
+  static const void* const kSeed;
+
+  uint64_t state_;
+};
+
+// MixingHashState::CombineContiguousImpl()
+inline uint64_t MixingHashState::CombineContiguousImpl(
+    uint64_t state, const unsigned char* first, size_t len,
+    std::integral_constant<int, 4> /* sizeof_size_t */) {
+  // For large values we use CityHash, for small ones we just use a
+  // multiplicative hash.
+  uint64_t v;
+  if (len > 8) {
+    if (ABSL_PREDICT_FALSE(len > PiecewiseChunkSize())) {
+      return CombineLargeContiguousImpl32(state, first, len);
+    }
+    v = hash_internal::CityHash32(reinterpret_cast<const char*>(first), len);
+  } else if (len >= 4) {
+    v = Read4To8(first, len);
+  } else if (len > 0) {
+    v = Read1To3(first, len);
+  } else {
+    // Empty ranges have no effect.
+    return state;
+  }
+  return Mix(state, v);
+}
+
+// Overload of MixingHashState::CombineContiguousImpl()
+inline uint64_t MixingHashState::CombineContiguousImpl(
+    uint64_t state, const unsigned char* first, size_t len,
+    std::integral_constant<int, 8> /* sizeof_size_t */) {
+  // For large values we use LowLevelHash or CityHash depending on the platform,
+  // for small ones we just use a multiplicative hash.
+  uint64_t v;
+  if (len > 16) {
+    if (ABSL_PREDICT_FALSE(len > PiecewiseChunkSize())) {
+      return CombineLargeContiguousImpl64(state, first, len);
+    }
+    v = Hash64(first, len);
+  } else if (len > 8) {
+    // This hash function was constructed by the ML-driven algorithm discovery
+    // using reinforcement learning. We fed the agent lots of inputs from
+    // microbenchmarks, SMHasher, low hamming distance from generated inputs and
+    // picked up the one that was good on micro and macrobenchmarks.
+    auto p = Read9To16(first, len);
+    uint64_t lo = p.first;
+    uint64_t hi = p.second;
+    // Rotation by 53 was found to be most often useful when discovering these
+    // hashing algorithms with ML techniques.
+    lo = absl::rotr(lo, 53);
+    state += kMul;
+    lo += state;
+    state ^= hi;
+    uint128 m = state;
+    m *= lo;
+    return static_cast<uint64_t>(m ^ (m >> 64));
+  } else if (len >= 4) {
+    v = Read4To8(first, len);
+  } else if (len > 0) {
+    v = Read1To3(first, len);
+  } else {
+    // Empty ranges have no effect.
+    return state;
+  }
+  return Mix(state, v);
+}
+
+struct AggregateBarrier {};
+
+// HashImpl
+
+// Add a private base class to make sure this type is not an aggregate.
+// Aggregates can be aggregate initialized even if the default constructor is
+// deleted.
+struct PoisonedHash : private AggregateBarrier {
+  PoisonedHash() = delete;
+  PoisonedHash(const PoisonedHash&) = delete;
+  PoisonedHash& operator=(const PoisonedHash&) = delete;
+};
+
+template <typename T>
+struct HashImpl {
+  size_t operator()(const T& value) const {
+    return MixingHashState::hash(value);
+  }
+};
+
+template <typename T>
+struct Hash
+    : absl::conditional_t<is_hashable<T>::value, HashImpl<T>, PoisonedHash> {};
+
+template <typename H>
+template <typename T, typename... Ts>
+H HashStateBase<H>::combine(H state, const T& value, const Ts&... values) {
+  return H::combine(hash_internal::HashSelect::template Apply<T>::Invoke(
+                        std::move(state), value),
+                    values...);
+}
+
+// HashStateBase::combine_contiguous()
+template <typename H>
+template <typename T>
+H HashStateBase<H>::combine_contiguous(H state, const T* data, size_t size) {
+  return hash_internal::hash_range_or_bytes(std::move(state), data, size);
+}
+
+// HashStateBase::combine_unordered()
+template <typename H>
+template <typename I>
+H HashStateBase<H>::combine_unordered(H state, I begin, I end) {
+  return H::RunCombineUnordered(std::move(state),
+                                CombineUnorderedCallback<I>{begin, end});
+}
+
+// HashStateBase::PiecewiseCombiner::add_buffer()
+template <typename H>
+H PiecewiseCombiner::add_buffer(H state, const unsigned char* data,
+                                size_t size) {
+  if (position_ + size < PiecewiseChunkSize()) {
+    // This partial chunk does not fill our existing buffer
+    memcpy(buf_ + position_, data, size);
+    position_ += size;
+    return state;
+  }
+
+  // If the buffer is partially filled we need to complete the buffer
+  // and hash it.
+  if (position_ != 0) {
+    const size_t bytes_needed = PiecewiseChunkSize() - position_;
+    memcpy(buf_ + position_, data, bytes_needed);
+    state = H::combine_contiguous(std::move(state), buf_, PiecewiseChunkSize());
+    data += bytes_needed;
+    size -= bytes_needed;
+  }
+
+  // Hash whatever chunks we can without copying
+  while (size >= PiecewiseChunkSize()) {
+    state = H::combine_contiguous(std::move(state), data, PiecewiseChunkSize());
+    data += PiecewiseChunkSize();
+    size -= PiecewiseChunkSize();
+  }
+  // Fill the buffer with the remainder
+  memcpy(buf_, data, size);
+  position_ = size;
+  return state;
+}
+
+// HashStateBase::PiecewiseCombiner::finalize()
+template <typename H>
+H PiecewiseCombiner::finalize(H state) {
+  // Hash the remainder left in the buffer, which may be empty
+  return H::combine_contiguous(std::move(state), buf_, position_);
+}
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_HASH_H_
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/hash_test.h b/weight/_dep/abseil-cpp/absl/hash/internal/hash_test.h
new file mode 100644
index 0000000000000000000000000000000000000000..9963dc0b8d95336cfef7fa4273d01738bff71025
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/hash_test.h
@@ -0,0 +1,87 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Common code shared between absl/hash/hash_test.cc and
+// absl/hash/hash_instantiated_test.cc.
+
+#ifndef ABSL_HASH_INTERNAL_HASH_TEST_H_
+#define ABSL_HASH_INTERNAL_HASH_TEST_H_
+
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/config.h"
+#include "absl/hash/hash.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_test_internal {
+
+// Utility wrapper of T for the purposes of testing the `AbslHash` type erasure
+// mechanism.  `TypeErasedValue<T>` can be constructed with a `T`, and can
+// be compared and hashed.  However, all hashing goes through the hashing
+// type-erasure framework.
+template <typename T>
+class TypeErasedValue {
+ public:
+  TypeErasedValue() = default;
+  TypeErasedValue(const TypeErasedValue&) = default;
+  TypeErasedValue(TypeErasedValue&&) = default;
+  explicit TypeErasedValue(const T& n) : n_(n) {}
+
+  template <typename H>
+  friend H AbslHashValue(H hash_state, const TypeErasedValue& v) {
+    v.HashValue(absl::HashState::Create(&hash_state));
+    return hash_state;
+  }
+
+  void HashValue(absl::HashState state) const {
+    absl::HashState::combine(std::move(state), n_);
+  }
+
+  bool operator==(const TypeErasedValue& rhs) const { return n_ == rhs.n_; }
+  bool operator!=(const TypeErasedValue& rhs) const { return !(*this == rhs); }
+
+ private:
+  T n_;
+};
+
+// A TypeErasedValue refinement, for containers.  It exposes the wrapped
+// `value_type` and is constructible from an initializer list.
+template <typename T>
+class TypeErasedContainer : public TypeErasedValue<T> {
+ public:
+  using value_type = typename T::value_type;
+  TypeErasedContainer() = default;
+  TypeErasedContainer(const TypeErasedContainer&) = default;
+  TypeErasedContainer(TypeErasedContainer&&) = default;
+  explicit TypeErasedContainer(const T& n) : TypeErasedValue<T>(n) {}
+  TypeErasedContainer(std::initializer_list<value_type> init_list)
+      : TypeErasedContainer(T(init_list.begin(), init_list.end())) {}
+  // one-argument constructor of value type T, to appease older toolchains that
+  // get confused by one-element initializer lists in some contexts
+  explicit TypeErasedContainer(const value_type& v)
+      : TypeErasedContainer(T(&v, &v + 1)) {}
+};
+
+// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
+// detect it.
+template <typename T>
+using is_hashable = std::is_default_constructible<absl::Hash<T>>;
+
+}  // namespace hash_test_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_HASH_TEST_H_
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash.cc b/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b5db0b89601c812b2a984b7cdd52ae75f09ee226
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash.cc
@@ -0,0 +1,118 @@
+// Copyright 2020 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/hash/internal/low_level_hash.h"
+
+#include "absl/base/internal/unaligned_access.h"
+#include "absl/base/prefetch.h"
+#include "absl/numeric/int128.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+
+static uint64_t Mix(uint64_t v0, uint64_t v1) {
+  absl::uint128 p = v0;
+  p *= v1;
+  return absl::Uint128Low64(p) ^ absl::Uint128High64(p);
+}
+
+uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed,
+                      const uint64_t salt[5]) {
+  // Prefetch the cacheline that data resides in.
+  PrefetchToLocalCache(data);
+  const uint8_t* ptr = static_cast<const uint8_t*>(data);
+  uint64_t starting_length = static_cast<uint64_t>(len);
+  uint64_t current_state = seed ^ salt[0];
+
+  if (len > 64) {
+    // If we have more than 64 bytes, we're going to handle chunks of 64
+    // bytes at a time. We're going to build up two separate hash states
+    // which we will then hash together.
+    uint64_t duplicated_state = current_state;
+
+    do {
+      // Always prefetch the next cacheline.
+      PrefetchToLocalCache(ptr + ABSL_CACHELINE_SIZE);
+
+      uint64_t a = absl::base_internal::UnalignedLoad64(ptr);
+      uint64_t b = absl::base_internal::UnalignedLoad64(ptr + 8);
+      uint64_t c = absl::base_internal::UnalignedLoad64(ptr + 16);
+      uint64_t d = absl::base_internal::UnalignedLoad64(ptr + 24);
+      uint64_t e = absl::base_internal::UnalignedLoad64(ptr + 32);
+      uint64_t f = absl::base_internal::UnalignedLoad64(ptr + 40);
+      uint64_t g = absl::base_internal::UnalignedLoad64(ptr + 48);
+      uint64_t h = absl::base_internal::UnalignedLoad64(ptr + 56);
+
+      uint64_t cs0 = Mix(a ^ salt[1], b ^ current_state);
+      uint64_t cs1 = Mix(c ^ salt[2], d ^ current_state);
+      current_state = (cs0 ^ cs1);
+
+      uint64_t ds0 = Mix(e ^ salt[3], f ^ duplicated_state);
+      uint64_t ds1 = Mix(g ^ salt[4], h ^ duplicated_state);
+      duplicated_state = (ds0 ^ ds1);
+
+      ptr += 64;
+      len -= 64;
+    } while (len > 64);
+
+    current_state = current_state ^ duplicated_state;
+  }
+
+  // We now have a data `ptr` with at most 64 bytes and the current state
+  // of the hashing state machine stored in current_state.
+  while (len > 16) {
+    uint64_t a = absl::base_internal::UnalignedLoad64(ptr);
+    uint64_t b = absl::base_internal::UnalignedLoad64(ptr + 8);
+
+    current_state = Mix(a ^ salt[1], b ^ current_state);
+
+    ptr += 16;
+    len -= 16;
+  }
+
+  // We now have a data `ptr` with at most 16 bytes.
+  uint64_t a = 0;
+  uint64_t b = 0;
+  if (len > 8) {
+    // When we have at least 9 and at most 16 bytes, set A to the first 64
+    // bits of the input and B to the last 64 bits of the input. Yes, they will
+    // overlap in the middle if we are working with less than the full 16
+    // bytes.
+    a = absl::base_internal::UnalignedLoad64(ptr);
+    b = absl::base_internal::UnalignedLoad64(ptr + len - 8);
+  } else if (len > 3) {
+    // If we have at least 4 and at most 8 bytes, set A to the first 32
+    // bits and B to the last 32 bits.
+    a = absl::base_internal::UnalignedLoad32(ptr);
+    b = absl::base_internal::UnalignedLoad32(ptr + len - 4);
+  } else if (len > 0) {
+    // If we have at least 1 and at most 3 bytes, read all of the provided
+    // bits into A, with some adjustments.
+    a = static_cast<uint64_t>((ptr[0] << 16) | (ptr[len >> 1] << 8) |
+                              ptr[len - 1]);
+    b = 0;
+  } else {
+    a = 0;
+    b = 0;
+  }
+
+  uint64_t w = Mix(a ^ salt[1], b ^ current_state);
+  uint64_t z = salt[1] ^ starting_length;
+  return Mix(w, z);
+}
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash.h b/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash.h
new file mode 100644
index 0000000000000000000000000000000000000000..439968aa9808d7aaacb82de872b76c4fc8b5b261
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash.h
@@ -0,0 +1,50 @@
+// Copyright 2020 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// This file provides the Google-internal implementation of LowLevelHash.
+//
+// LowLevelHash is a fast hash function for hash tables, the fastest we've
+// currently (late 2020) found that passes the SMHasher tests. The algorithm
+// relies on intrinsic 128-bit multiplication for speed. This is not meant to be
+// secure - just fast.
+//
+// It is closely based on a version of wyhash, but does not maintain or
+// guarantee future compatibility with it.
+
+#ifndef ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_
+#define ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+
+// Hash function for a byte array. A 64-bit seed and a set of five 64-bit
+// integers are hashed into the result.
+//
+// To allow all hashable types (including string_view and Span) to depend on
+// this algorithm, we keep the API low-level, with as few dependencies as
+// possible.
+uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed,
+                      const uint64_t salt[5]);
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash_test.cc b/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..589a3d8fb3c20ce52b108ab0db8cb39bf44572c8
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/low_level_hash_test.cc
@@ -0,0 +1,532 @@
+// Copyright 2020 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/hash/internal/low_level_hash.h"
+
+#include <cinttypes>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/escaping.h"
+
+#define UPDATE_GOLDEN 0
+
+namespace {
+
+static const uint64_t kSalt[5] = {0xa0761d6478bd642f, 0xe7037ed1a0b428dbl,
+                                  0x8ebc6af09c88c6e3, 0x589965cc75374cc3l,
+                                  0x1d8e4e27c47d124f};
+
+TEST(LowLevelHashTest, VerifyGolden) {
+  constexpr size_t kNumGoldenOutputs = 134;
+  static struct {
+    absl::string_view base64_data;
+    uint64_t seed;
+  } cases[] = {
+      {"", uint64_t{0xec42b7ab404b8acb}},
+      {"ICAg", uint64_t{0}},
+      {"YWFhYQ==", uint64_t{0}},
+      {"AQID", uint64_t{0}},
+      {"AQIDBA==", uint64_t{0}},
+      {"dGhpcmRfcGFydHl8d3loYXNofDY0", uint64_t{0}},
+      {"Zw==", uint64_t{0xeeee074043a3ee0f}},
+      {"xmk=", uint64_t{0x857902089c393de}},
+      {"c1H/", uint64_t{0x993df040024ca3af}},
+      {"SuwpzQ==", uint64_t{0xc4e4c2acea740e96}},
+      {"uqvy++M=", uint64_t{0x6a214b3db872d0cf}},
+      {"RnzCVPgb", uint64_t{0x44343db6a89dba4d}},
+      {"6OeNdlouYw==", uint64_t{0x77b5d6d1ae1dd483}},
+      {"M5/JmmYyDbc=", uint64_t{0x89ab8ecb44d221f1}},
+      {"MVijWiVdBRdY", uint64_t{0x60244b17577ca81b}},
+      {"6V7Uq7LNxpu0VA==", uint64_t{0x59a08dcee0717067}},
+      {"EQ6CdEEhPdyHcOk=", uint64_t{0xf5f20db3ade57396}},
+      {"PqFB4fxnPgF+l+rc", uint64_t{0xbf8dee0751ad3efb}},
+      {"a5aPOFwq7LA7+zKvPA==", uint64_t{0x6b7a06b268d63e30}},
+      {"VOwY21wCGv5D+/qqOvs=", uint64_t{0xb8c37f0ae0f54c82}},
+      {"KdHmBTx8lHXYvmGJ+Vy7", uint64_t{0x9fcbed0c38e50eef}},
+      {"qJkPlbHr8bMF7/cA6aE65Q==", uint64_t{0x2af4bade1d8e3a1d}},
+      {"ygvL0EhHZL0fIx6oHHtkxRQ=", uint64_t{0x714e3aa912da2f2c}},
+      {"c1rFXkt5YztwZCQRngncqtSs", uint64_t{0xf5ee75e3cbb82c1c}},
+      {"8hsQrzszzeNQSEcVXLtvIhm6mw==", uint64_t{0x620e7007321b93b9}},
+      {"ffUL4RocfyP4KfikGxO1yk7omDI=", uint64_t{0xc08528cac2e551fc}},
+      {"OOB5TT00vF9Od/rLbAWshiErqhpV", uint64_t{0x6a1debf9cc3ad39}},
+      {"or5wtXM7BFzTNpSzr+Lw5J5PMhVJ/Q==", uint64_t{0x7e0a3c88111fc226}},
+      {"gk6pCHDUsoopVEiaCrzVDhioRKxb844=", uint64_t{0x1301fef15df39edb}},
+      {"TNctmwlC5QbEM6/No4R/La3UdkfeMhzs", uint64_t{0x64e181f3d5817ab}},
+      {"SsQw9iAjhWz7sgcE9OwLuSC6hsM+BfHs2Q==", uint64_t{0xafafc44961078ecb}},
+      {"ZzO3mVCj4xTT2TT3XqDyEKj2BZQBvrS8RHg=", uint64_t{0x4f7bb45549250094}},
+      {"+klp5iPQGtppan5MflEls0iEUzqU+zGZkDJX", uint64_t{0xa30061abaa2818c}},
+      {"RO6bvOnlJc8I9eniXlNgqtKy0IX6VNg16NRmgg==",
+       uint64_t{0xd902ee3e44a5705f}},
+      {"ZJjZqId1ZXBaij9igClE3nyliU5XWdNRrayGlYA=", uint64_t{0x316d36da516f583}},
+      {"7BfkhfGMDGbxfMB8uyL85GbaYQtjr2K8g7RpLzr/",
+       uint64_t{0x402d83f9f834f616}},
+      {"rycWk6wHH7htETQtje9PidS2YzXBx+Qkg2fY7ZYS7A==",
+       uint64_t{0x9c604164c016b72c}},
+      {"RTkC2OUK+J13CdGllsH0H5WqgspsSa6QzRZouqx6pvI=",
+       uint64_t{0x3f4507e01f9e73ba}},
+      {"tKjKmbLCNyrLCM9hycOAXm4DKNpM12oZ7dLTmUx5iwAi",
+       uint64_t{0xc3fe0d5be8d2c7c7}},
+      {"VprUGNH+5NnNRaORxgH/ySrZFQFDL+4VAodhfBNinmn8cg==",
+       uint64_t{0x531858a40bfa7ea1}},
+      {"gc1xZaY+q0nPcUvOOnWnT3bqfmT/geth/f7Dm2e/DemMfk4=",
+       uint64_t{0x86689478a7a7e8fa}},
+      {"Mr35fIxqx1ukPAL0su1yFuzzAU3wABCLZ8+ZUFsXn47UmAph",
+       uint64_t{0x4ec948b8e7f27288}},
+      {"A9G8pw2+m7+rDtWYAdbl8tb2fT7FFo4hLi2vAsa5Y8mKH3CX3g==",
+       uint64_t{0xce46c7213c10032}},
+      {"DFaJGishGwEHDdj9ixbCoaTjz9KS0phLNWHVVdFsM93CvPft3hM=",
+       uint64_t{0xf63e96ee6f32a8b6}},
+      {"7+Ugx+Kr3aRNgYgcUxru62YkTDt5Hqis+2po81hGBkcrJg4N0uuy",
+       uint64_t{0x1cfe85e65fc5225}},
+      {"H2w6O8BUKqu6Tvj2xxaecxEI2wRgIgqnTTG1WwOgDSINR13Nm4d4Vg==",
+       uint64_t{0x45c474f1cee1d2e8}},
+      {"1XBMnIbqD5jy65xTDaf6WtiwtdtQwv1dCVoqpeKj+7cTR1SaMWMyI04=",
+       uint64_t{0x6e024e14015f329c}},
+      {"znZbdXG2TSFrKHEuJc83gPncYpzXGbAebUpP0XxzH0rpe8BaMQ17nDbt",
+       uint64_t{0x760c40502103ae1c}},
+      {"ylu8Atu13j1StlcC1MRMJJXIl7USgDDS22HgVv0WQ8hx/8pNtaiKB17hCQ==",
+       uint64_t{0x17fd05c3c560c320}},
+      {"M6ZVVzsd7vAvbiACSYHioH/440dp4xG2mLlBnxgiqEvI/aIEGpD0Sf4VS0g=",
+       uint64_t{0x8b34200a6f8e90d9}},
+      {"li3oFSXLXI+ubUVGJ4blP6mNinGKLHWkvGruun85AhVn6iuMtocbZPVhqxzn",
+       uint64_t{0x6be89e50818bdf69}},
+      {"kFuQHuUCqBF3Tc3hO4dgdIp223ShaCoog48d5Do5zMqUXOh5XpGK1t5XtxnfGA==",
+       uint64_t{0xfb389773315b47d8}},
+      {"jWmOad0v0QhXVJd1OdGuBZtDYYS8wBVHlvOeTQx9ZZnm8wLEItPMeihj72E0nWY=",
+       uint64_t{0x4f2512a23f61efee}},
+      {"z+DHU52HaOQdW4JrZwDQAebEA6rm13Zg/9lPYA3txt3NjTBqFZlOMvTRnVzRbl23",
+       uint64_t{0x59ccd92fc16c6fda}},
+      {"MmBiGDfYeTayyJa/tVycg+rN7f9mPDFaDc+23j0TlW9094er0ADigsl4QX7V3gG/qw==",
+       uint64_t{0x25c5a7f5bd330919}},
+      {"774RK+9rOL4iFvs1q2qpo/JVc/I39buvNjqEFDtDvyoB0FXxPI2vXqOrk08VPfIHkmU=",
+       uint64_t{0x51df4174d34c97d7}},
+      {"+slatXiQ7/2lK0BkVUI1qzNxOOLP3I1iK6OfHaoxgqT63FpzbElwEXSwdsryq3UlHK0I",
+       uint64_t{0x80ce6d76f89cb57}},
+      {"64mVTbQ47dHjHlOHGS/hjJwr/"
+       "K2frCNpn87exOqMzNUVYiPKmhCbfS7vBUce5tO6Ec9osQ==",
+       uint64_t{0x20961c911965f684}},
+      {"fIsaG1r530SFrBqaDj1kqE0AJnvvK8MNEZbII2Yw1OK77v0V59xabIh0B5axaz/"
+       "+a2V5WpA=",
+       uint64_t{0x4e5b926ec83868e7}},
+      {"PGih0zDEOWCYGxuHGDFu9Ivbff/"
+       "iE7BNUq65tycTR2R76TerrXALRosnzaNYO5fjFhTi+CiS",
+       uint64_t{0x3927b30b922eecef}},
+      {"RnpA/"
+       "zJnEnnLjmICORByRVb9bCOgxF44p3VMiW10G7PvW7IhwsWajlP9kIwNA9FjAD2GoQHk2Q="
+       "=",
+       uint64_t{0xbd0291284a49b61c}},
+      {"qFklMceaTHqJpy2qavJE+EVBiNFOi6OxjOA3LeIcBop1K7w8xQi3TrDk+"
+       "BrWPRIbfprszSaPfrI=",
+       uint64_t{0x73a77c575bcc956}},
+      {"cLbfUtLl3EcQmITWoTskUR8da/VafRDYF/ylPYwk7/"
+       "zazk6ssyrzxMN3mmSyvrXR2yDGNZ3WDrTT",
+       uint64_t{0x766a0e2ade6d09a6}},
+      {"s/"
+       "Jf1+"
+       "FbsbCpXWPTUSeWyMH6e4CvTFvPE5Fs6Z8hvFITGyr0dtukHzkI84oviVLxhM1xMxrMAy1db"
+       "w==",
+       uint64_t{0x2599f4f905115869}},
+      {"FvyQ00+j7nmYZVQ8hI1Edxd0AWplhTfWuFGiu34AK5X8u2hLX1bE97sZM0CmeLe+"
+       "7LgoUT1fJ/axybE=",
+       uint64_t{0xd8256e5444d21e53}},
+      {"L8ncxMaYLBH3g9buPu8hfpWZNlOF7nvWLNv9IozH07uQsIBWSKxoPy8+"
+       "LW4tTuzC6CIWbRGRRD1sQV/4",
+       uint64_t{0xf664a91333fb8dfd}},
+      {"CDK0meI07yrgV2kQlZZ+"
+       "wuVqhc2NmzqeLH7bmcA6kchsRWFPeVF5Wqjjaj556ABeUoUr3yBmfU3kWOakkg==",
+       uint64_t{0x9625b859be372cd1}},
+      {"d23/vc5ONh/"
+       "HkMiq+gYk4gaCNYyuFKwUkvn46t+dfVcKfBTYykr4kdvAPNXGYLjM4u1YkAEFpJP+"
+       "nX7eOvs=",
+       uint64_t{0x7b99940782e29898}},
+      {"NUR3SRxBkxTSbtQORJpu/GdR6b/h6sSGfsMj/KFd99ahbh+9r7LSgSGmkGVB/"
+       "mGoT0pnMTQst7Lv2q6QN6Vm",
+       uint64_t{0x4fe12fa5383b51a8}},
+      {"2BOFlcI3Z0RYDtS9T9Ie9yJoXlOdigpPeeT+CRujb/"
+       "O39Ih5LPC9hP6RQk1kYESGyaLZZi3jtabHs7DiVx/VDg==",
+       uint64_t{0xe2ccb09ac0f5b4b6}},
+      {"FF2HQE1FxEvWBpg6Z9zAMH+Zlqx8S1JD/"
+       "wIlViL6ZDZY63alMDrxB0GJQahmAtjlm26RGLnjW7jmgQ4Ie3I+014=",
+       uint64_t{0x7d0a37adbd7b753b}},
+      {"tHmO7mqVL/PX11nZrz50Hc+M17Poj5lpnqHkEN+4bpMx/"
+       "YGbkrGOaYjoQjgmt1X2QyypK7xClFrjeWrCMdlVYtbW",
+       uint64_t{0xd3ae96ef9f7185f2}},
+      {"/WiHi9IQcxRImsudkA/KOTqGe8/"
+       "gXkhKIHkjddv5S9hi02M049dIK3EUyAEjkjpdGLUs+BN0QzPtZqjIYPOgwsYE9g==",
+       uint64_t{0x4fb88ea63f79a0d8}},
+      {"qds+1ExSnU11L4fTSDz/QE90g4Jh6ioqSh3KDOTOAo2pQGL1k/"
+       "9CCC7J23YF27dUTzrWsCQA2m4epXoCc3yPHb3xElA=",
+       uint64_t{0xed564e259bb5ebe9}},
+      {"8FVYHx40lSQPTHheh08Oq0/"
+       "pGm2OlG8BEf8ezvAxHuGGdgCkqpXIueJBF2mQJhTfDy5NncO8ntS7vaKs7sCNdDaNGOEi",
+       uint64_t{0x3e3256b60c428000}},
+      {"4ZoEIrJtstiCkeew3oRzmyJHVt/pAs2pj0HgHFrBPztbQ10NsQ/"
+       "lM6DM439QVxpznnBSiHMgMQJhER+70l72LqFTO1JiIQ==",
+       uint64_t{0xfb05bad59ec8705}},
+      {"hQPtaYI+wJyxXgwD5n8jGIKFKaFA/"
+       "P83KqCKZfPthnjwdOFysqEOYwAaZuaaiv4cDyi9TyS8hk5cEbNP/jrI7q6pYGBLbsM=",
+       uint64_t{0xafdc251dbf97b5f8}},
+      {"S4gpMSKzMD7CWPsSfLeYyhSpfWOntyuVZdX1xSBjiGvsspwOZcxNKCRIOqAA0moUfOh3I5+"
+       "juQV4rsqYElMD/gWfDGpsWZKQ",
+       uint64_t{0x10ec9c92ddb5dcbc}},
+      {"oswxop+"
+       "bthuDLT4j0PcoSKby4LhF47ZKg8K17xxHf74UsGCzTBbOz0MM8hQEGlyqDT1iUiAYnaPaUp"
+       "L2mRK0rcIUYA4qLt5uOw==",
+       uint64_t{0x9a767d5822c7dac4}},
+      {"0II/"
+       "697p+"
+       "BtLSjxj5989OXI004TogEb94VUnDzOVSgMXie72cuYRvTFNIBgtXlKfkiUjeqVpd4a+"
+       "n5bxNOD1TGrjQtzKU5r7obo=",
+       uint64_t{0xee46254080d6e2db}},
+      {"E84YZW2qipAlMPmctrg7TKlwLZ68l4L+c0xRDUfyyFrA4MAti0q9sHq3TDFviH0Y+"
+       "Kq3tEE5srWFA8LM9oomtmvm5PYxoaarWPLc",
+       uint64_t{0xbbb669588d8bf398}},
+      {"x3pa4HIElyZG0Nj7Vdy9IdJIR4izLmypXw5PCmZB5y68QQ4uRaVVi3UthsoJROvbjDJkP2D"
+       "Q6L/eN8pFeLFzNPKBYzcmuMOb5Ull7w==",
+       uint64_t{0xdc2afaa529beef44}},
+      {"jVDKGYIuWOP/"
+       "QKLdd2wi8B2VJA8Wh0c8PwrXJVM8FOGM3voPDVPyDJOU6QsBDPseoR8uuKd19OZ/"
+       "zAvSCB+zlf6upAsBlheUKgCfKww=",
+       uint64_t{0xf1f67391d45013a8}},
+      {"mkquunhmYe1aR2wmUz4vcvLEcKBoe6H+kjUok9VUn2+eTSkWs4oDDtJvNCWtY5efJwg/"
+       "j4PgjRYWtqnrCkhaqJaEvkkOwVfgMIwF3e+d",
+       uint64_t{0x16fce2b8c65a3429}},
+      {"fRelvKYonTQ+s+rnnvQw+JzGfFoPixtna0vzcSjiDqX5s2Kg2//"
+       "UGrK+AVCyMUhO98WoB1DDbrsOYSw2QzrcPe0+3ck9sePvb+Q/IRaHbw==",
+       uint64_t{0xf4b096699f49fe67}},
+      {"DUwXFJzagljo44QeJ7/"
+       "6ZKw4QXV18lhkYT2jglMr8WB3CHUU4vdsytvw6AKv42ZcG6fRkZkq9fpnmXy6xG0aO3WPT1"
+       "eHuyFirAlkW+zKtwg=",
+       uint64_t{0xca584c4bc8198682}},
+      {"cYmZCrOOBBongNTr7e4nYn52uQUy2mfe48s50JXx2AZ6cRAt/"
+       "xRHJ5QbEoEJOeOHsJyM4nbzwFm++SlT6gFZZHJpkXJ92JkR86uS/eV1hJUR",
+       uint64_t{0xed269fc3818b6aad}},
+      {"EXeHBDfhwzAKFhsMcH9+2RHwV+mJaN01+9oacF6vgm8mCXRd6jeN9U2oAb0of5c5cO4i+"
+       "Vb/LlHZSMI490SnHU0bejhSCC2gsC5d2K30ER3iNA==",
+       uint64_t{0x33f253cbb8fe66a8}},
+      {"FzkzRYoNjkxFhZDso94IHRZaJUP61nFYrh5MwDwv9FNoJ5jyNCY/"
+       "eazPZk+tbmzDyJIGw2h3GxaWZ9bSlsol/vK98SbkMKCQ/wbfrXRLcDzdd/8=",
+       uint64_t{0xd0b76b2c1523d99c}},
+      {"Re4aXISCMlYY/XsX7zkIFR04ta03u4zkL9dVbLXMa/q6hlY/CImVIIYRN3VKP4pnd0AUr/"
+       "ugkyt36JcstAInb4h9rpAGQ7GMVOgBniiMBZ/MGU7H",
+       uint64_t{0xfd28f0811a2a237f}},
+      {"ueLyMcqJXX+MhO4UApylCN9WlTQ+"
+       "ltJmItgG7vFUtqs2qNwBMjmAvr5u0sAKd8jpzV0dDPTwchbIeAW5zbtkA2NABJV6hFM48ib"
+       "4/J3A5mseA3cS8w==",
+       uint64_t{0x6261fb136482e84}},
+      {"6Si7Yi11L+jZMkwaN+GUuzXMrlvEqviEkGOilNq0h8TdQyYKuFXzkYc/"
+       "q74gP3pVCyiwz9KpVGMM9vfnq36riMHRknkmhQutxLZs5fbmOgEO69HglCU=",
+       uint64_t{0x458efc750bca7c3a}},
+      {"Q6AbOofGuTJOegPh9Clm/"
+       "9crtUMQqylKrTc1fhfJo1tqvpXxhU4k08kntL1RG7woRnFrVh2UoMrL1kjin+s9CanT+"
+       "y4hHwLqRranl9FjvxfVKm3yvg68",
+       uint64_t{0xa7e69ff84e5e7c27}},
+      {"ieQEbIPvqY2YfIjHnqfJiO1/MIVRk0RoaG/WWi3kFrfIGiNLCczYoklgaecHMm/"
+       "1sZ96AjO+a5stQfZbJQwS7Sc1ODABEdJKcTsxeW2hbh9A6CFzpowP1A==",
+       uint64_t{0x3c59bfd0c29efe9e}},
+      {"zQUv8hFB3zh2GGl3KTvCmnfzE+"
+       "SUgQPVaSVIELFX5H9cE3FuVFGmymkPQZJLAyzC90Cmi8GqYCvPqTuAAB//"
+       "XTJxy4bCcVArgZG9zJXpjowpNBfr3ngWrSE=",
+       uint64_t{0x10befacc6afd298d}},
+      {"US4hcC1+op5JKGC7eIs8CUgInjKWKlvKQkapulxW262E/"
+       "B2ye79QxOexf188u2mFwwe3WTISJHRZzS61IwljqAWAWoBAqkUnW8SHmIDwHUP31J0p5sGd"
+       "P47L",
+       uint64_t{0x41d5320b0a38efa7}},
+      {"9bHUWFna2LNaGF6fQLlkx1Hkt24nrkLE2CmFdWgTQV3FFbUe747SSqYw6ebpTa07MWSpWRP"
+       "sHesVo2B9tqHbe7eQmqYebPDFnNqrhSdZwFm9arLQVs+7a3Ic6A==",
+       uint64_t{0x58db1c7450fe17f3}},
+      {"Kb3DpHRUPhtyqgs3RuXjzA08jGb59hjKTOeFt1qhoINfYyfTt2buKhD6YVffRCPsgK9SeqZ"
+       "qRPJSyaqsa0ovyq1WnWW8jI/NhvAkZTVHUrX2pC+cD3OPYT05Dag=",
+       uint64_t{0x6098c055a335b7a6}},
+      {"gzxyMJIPlU+bJBwhFUCHSofZ/"
+       "319LxqMoqnt3+L6h2U2+ZXJCSsYpE80xmR0Ta77Jq54o92SMH87HV8dGOaCTuAYF+"
+       "lDL42SY1P316Cl0sZTS2ow3ZqwGbcPNs/1",
+       uint64_t{0x1bbacec67845a801}},
+      {"uR7V0TW+FGVMpsifnaBAQ3IGlr1wx5sKd7TChuqRe6OvUXTlD4hKWy8S+"
+       "8yyOw8lQabism19vOQxfmocEOW/"
+       "vzY0pEa87qHrAZy4s9fH2Bltu8vaOIe+agYohhYORQ==",
+       uint64_t{0xc419cfc7442190}},
+      {"1UR5eoo2aCwhacjZHaCh9bkOsITp6QunUxHQ2SfeHv0imHetzt/"
+       "Z70mhyWZBalv6eAx+YfWKCUib2SHDtz/"
+       "A2dc3hqUWX5VfAV7FQsghPUAtu6IiRatq4YSLpDvKZBQ=",
+       uint64_t{0xc95e510d94ba270c}},
+      {"opubR7H63BH7OtY+Avd7QyQ25UZ8kLBdFDsBTwZlY6gA/"
+       "u+x+"
+       "czC9AaZMgmQrUy15DH7YMGsvdXnviTtI4eVI4aF1H9Rl3NXMKZgwFOsdTfdcZeeHVRzBBKX"
+       "8jUfh1il",
+       uint64_t{0xff1ae05c98089c3f}},
+      {"DC0kXcSXtfQ9FbSRwirIn5tgPri0sbzHSa78aDZVDUKCMaBGyFU6BmrulywYX8yzvwprdLs"
+       "oOwTWN2wMjHlPDqrvVHNEjnmufRDblW+nSS+xtKNs3N5xsxXdv6JXDrAB/Q==",
+       uint64_t{0x90c02b8dceced493}},
+      {"BXRBk+3wEP3Lpm1y75wjoz+PgB0AMzLe8tQ1AYU2/"
+       "oqrQB2YMC6W+9QDbcOfkGbeH+b7IBkt/"
+       "gwCMw2HaQsRFEsurXtcQ3YwRuPz5XNaw5NAvrNa67Fm7eRzdE1+hWLKtA8=",
+       uint64_t{0x9f8a76697ab1aa36}},
+      {"RRBSvEGYnzR9E45Aps/+WSnpCo/X7gJLO4DRnUqFrJCV/kzWlusLE/"
+       "6ZU6RoUf2ROwcgEvUiXTGjLs7ts3t9SXnJHxC1KiOzxHdYLMhVvgNd3hVSAXODpKFSkVXND"
+       "55G2L1W",
+       uint64_t{0x6ba1bf3d811a531d}},
+      {"jeh6Qazxmdi57pa9S3XSnnZFIRrnc6s8QLrah5OX3SB/V2ErSPoEAumavzQPkdKF1/"
+       "SfvmdL+qgF1C+Yawy562QaFqwVGq7+tW0yxP8FStb56ZRgNI4IOmI30s1Ei7iops9Uuw==",
+       uint64_t{0x6a418974109c67b4}},
+      {"6QO5nnDrY2/"
+       "wrUXpltlKy2dSBcmK15fOY092CR7KxAjNfaY+"
+       "aAmtWbbzQk3MjBg03x39afSUN1fkrWACdyQKRaGxgwq6MGNxI6W+8DLWJBHzIXrntrE/"
+       "ml6fnNXEpxplWJ1vEs4=",
+       uint64_t{0x8472f1c2b3d230a3}},
+      {"0oPxeEHhqhcFuwonNfLd5jF3RNATGZS6NPoS0WklnzyokbTqcl4BeBkMn07+fDQv83j/"
+       "BpGUwcWO05f3+DYzocfnizpFjLJemFGsls3gxcBYxcbqWYev51tG3lN9EvRE+X9+Pwww",
+       uint64_t{0x5e06068f884e73a7}},
+      {"naSBSjtOKgAOg8XVbR5cHAW3Y+QL4Pb/JO9/"
+       "oy6L08wvVRZqo0BrssMwhzBP401Um7A4ppAupbQeJFdMrysY34AuSSNvtNUy5VxjNECwiNt"
+       "gwYHw7yakDUv8WvonctmnoSPKENegQg==",
+       uint64_t{0x55290b1a8f170f59}},
+      {"vPyl8DxVeRe1OpilKb9KNwpGkQRtA94UpAHetNh+"
+       "95V7nIW38v7PpzhnTWIml5kw3So1Si0TXtIUPIbsu32BNhoH7QwFvLM+"
+       "JACgSpc5e3RjsL6Qwxxi11npwxRmRUqATDeMUfRAjxg=",
+       uint64_t{0x5501cfd83dfe706a}},
+      {"QC9i2GjdTMuNC1xQJ74ngKfrlA4w3o58FhvNCltdIpuMhHP1YsDA78scQPLbZ3OCUgeQguY"
+       "f/vw6zAaVKSgwtaykqg5ka/4vhz4hYqWU5ficdXqClHl+zkWEY26slCNYOM5nnDlly8Cj",
+       uint64_t{0xe43ed13d13a66990}},
+      {"7CNIgQhAHX27nxI0HeB5oUTnTdgKpRDYDKwRcXfSFGP1XeT9nQF6WKCMjL1tBV6x7KuJ91G"
+       "Zz11F4c+8s+MfqEAEpd4FHzamrMNjGcjCyrVtU6y+7HscMVzr7Q/"
+       "ODLcPEFztFnwjvCjmHw==",
+       uint64_t{0xdf43bc375cf5283f}},
+      {"Qa/hC2RPXhANSospe+gUaPfjdK/yhQvfm4cCV6/pdvCYWPv8p1kMtKOX3h5/"
+       "8oZ31fsmx4Axphu5qXJokuhZKkBUJueuMpxRyXpwSWz2wELx5glxF7CM0Fn+"
+       "OevnkhUn5jsPlG2r5jYlVn8=",
+       uint64_t{0x8112b806d288d7b5}},
+      {"kUw/0z4l3a89jTwN5jpG0SHY5km/"
+       "IVhTjgM5xCiPRLncg40aqWrJ5vcF891AOq5hEpSq0bUCJUMFXgct7kvnys905HjerV7Vs1G"
+       "y84tgVJ70/2+pAZTsB/PzNOE/G6sOj4+GbTzkQu819OLB",
+       uint64_t{0xd52a18abb001cb46}},
+      {"VDdfSDbO8Tdj3T5W0XM3EI7iHh5xpIutiM6dvcJ/fhe23V/srFEkDy5iZf/"
+       "VnA9kfi2C79ENnFnbOReeuZW1b3MUXB9lgC6U4pOTuC+"
+       "jHK3Qnpyiqzj7h3ISJSuo2pob7vY6VHZo6Fn7exEqHg==",
+       uint64_t{0xe12b76a2433a1236}},
+      {"Ldfvy3ORdquM/R2fIkhH/ONi69mcP1AEJ6n/"
+       "oropwecAsLJzQSgezSY8bEiEs0VnFTBBsW+RtZY6tDj03fnb3amNUOq1b7jbqyQkL9hpl+"
+       "2Z2J8IaVSeownWl+bQcsR5/xRktIMckC5AtF4YHfU=",
+       uint64_t{0x175bf7319cf1fa00}},
+      {"BrbNpb42+"
+       "VzZAjJw6QLirXzhweCVRfwlczzZ0VX2xluskwBqyfnGovz5EuX79JJ31VNXa5hTkAyQat3l"
+       "YKRADTdAdwE5PqM1N7YaMqqsqoAAAeuYVXuk5eWCykYmClNdSspegwgCuT+403JigBzi",
+       uint64_t{0xd63d57b3f67525ae}},
+      {"gB3NGHJJvVcuPyF0ZSvHwnWSIfmaI7La24VMPQVoIIWF7Z74NltPZZpx2f+cocESM+"
+       "ILzQW9p+BC8x5IWz7N4Str2WLGKMdgmaBfNkEhSHQDU0IJEOnpUt0HmjhFaBlx0/"
+       "LTmhua+rQ6Wup8ezLwfg==",
+       uint64_t{0x933faea858832b73}},
+      {"hTKHlRxx6Pl4gjG+6ksvvj0CWFicUg3WrPdSJypDpq91LUWRni2KF6+"
+       "81ZoHBFhEBrCdogKqeK+hy9bLDnx7g6rAFUjtn1+cWzQ2YjiOpz4+"
+       "ROBB7lnwjyTGWzJD1rXtlso1g2qVH8XJVigC5M9AIxM=",
+       uint64_t{0x53d061e5f8e7c04f}},
+      {"IWQBelSQnhrr0F3BhUpXUIDauhX6f95Qp+A0diFXiUK7irwPG1oqBiqHyK/SH/"
+       "9S+"
+       "rln9DlFROAmeFdH0OCJi2tFm4afxYzJTFR4HnR4cG4x12JqHaZLQx6iiu6CE3rtWBVz99oA"
+       "wCZUOEXIsLU24o2Y",
+       uint64_t{0xdb4124556dd515e0}},
+      {"TKo+l+"
+       "1dOXdLvIrFqeLaHdm0HZnbcdEgOoLVcGRiCbAMR0j5pIFw8D36tefckAS1RCFOH5IgP8yiF"
+       "T0Gd0a2hI3+"
+       "fTKA7iK96NekxWeoeqzJyctc6QsoiyBlkZerRxs5RplrxoeNg29kKDTM0K94mnhD9g==",
+       uint64_t{0x4fb31a0dd681ee71}},
+      {"YU4e7G6EfQYvxCFoCrrT0EFgVLHFfOWRTJQJ5gxM3G2b+"
+       "1kJf9YPrpsxF6Xr6nYtS8reEEbDoZJYqnlk9lXSkVArm88Cqn6d25VCx3+"
+       "49MqC0trIlXtb7SXUUhwpJK16T0hJUfPH7s5cMZXc6YmmbFuBNPE=",
+       uint64_t{0x27cc72eefa138e4c}},
+      {"/I/"
+       "eImMwPo1U6wekNFD1Jxjk9XQVi1D+"
+       "FPdqcHifYXQuP5aScNQfxMAmaPR2XhuOQhADV5tTVbBKwCDCX4E3jcDNHzCiPvViZF1W27t"
+       "xaf2BbFQdwKrNCmrtzcluBFYu0XZfc7RU1RmxK/RtnF1qHsq/O4pp",
+       uint64_t{0x44bc2dfba4bd3ced}},
+      {"CJTT9WGcY2XykTdo8KodRIA29qsqY0iHzWZRjKHb9alwyJ7RZAE3V5Juv4MY3MeYEr1EPCC"
+       "MxO7yFXqT8XA8YTjaMp3bafRt17Pw8JC4iKJ1zN+WWKOESrj+"
+       "3aluGQqn8z1EzqY4PH7rLG575PYeWsP98BugdA==",
+       uint64_t{0x242da1e3a439bed8}},
+      {"ZlhyQwLhXQyIUEnMH/"
+       "AEW27vh9xrbNKJxpWGtrEmKhd+nFqAfbeNBQjW0SfG1YI0xQkQMHXjuTt4P/"
+       "EpZRtA47ibZDVS8TtaxwyBjuIDwqcN09eCtpC+Ls+"
+       "vWDTLmBeDM3u4hmzz4DQAYsLiZYSJcldg9Q3wszw=",
+       uint64_t{0xdc559c746e35c139}},
+      {"v2KU8y0sCrBghmnm8lzGJlwo6D6ObccAxCf10heoDtYLosk4ztTpLlpSFEyu23MLA1tJkcg"
+       "Rko04h19QMG0mOw/"
+       "wc93EXAweriBqXfvdaP85sZABwiKO+6rtS9pacRVpYYhHJeVTQ5NzrvBvi1huxAr+"
+       "xswhVMfL",
+       uint64_t{0xd0b0350275b9989}},
+      {"QhKlnIS6BuVCTQsnoE67E/"
+       "yrgogE8EwO7xLaEGei26m0gEU4OksefJgppDh3X0x0Cs78Dr9IHK5b977CmZlrTRmwhlP8p"
+       "M+UzXPNRNIZuN3ntOum/QhUWP8SGpirheXENWsXMQ/"
+       "nxtxakyEtrNkKk471Oov9juP8oQ==",
+       uint64_t{0xb04489e41d17730c}},
+      {"/ZRMgnoRt+Uo6fUPr9FqQvKX7syhgVqWu+"
+       "WUSsiQ68UlN0efSP6Eced5gJZL6tg9gcYJIkhjuQNITU0Q3TjVAnAcobgbJikCn6qZ6pRxK"
+       "BY4MTiAlfGD3T7R7hwJwx554MAy++Zb/YUFlnCaCJiwQMnowF7aQzwYFCo=",
+       uint64_t{0x2217285eb4572156}},
+      {"NB7tU5fNE8nI+SXGfipc7sRkhnSkUF1krjeo6k+8FITaAtdyz+"
+       "o7mONgXmGLulBPH9bEwyYhKNVY0L+njNQrZ9YC2aXsFD3PdZsxAFaBT3VXEzh+"
+       "NGBTjDASNL3mXyS8Yv1iThGfHoY7T4aR0NYGJ+k+pR6f+KrPC96M",
+       uint64_t{0x12c2e8e68aede73b}},
+      {"8T6wrqCtEO6/rwxF6lvMeyuigVOLwPipX/FULvwyu+1wa5sQGav/"
+       "2FsLHUVn6cGSi0LlFwLewGHPFJDLR0u4t7ZUyM//"
+       "x6da0sWgOa5hzDqjsVGmjxEHXiaXKW3i4iSZNuxoNbMQkIbVML+"
+       "DkYu9ND0O2swg4itGeVSzXA==",
+       uint64_t{0x4d612125bdc4fd00}},
+      {"Ntf1bMRdondtMv1CYr3G80iDJ4WSAlKy5H34XdGruQiCrnRGDBa+"
+       "eUi7vKp4gp3BBcVGl8eYSasVQQjn7MLvb3BjtXx6c/"
+       "bCL7JtpzQKaDnPr9GWRxpBXVxKREgMM7d8lm35EODv0w+"
+       "hQLfVSh8OGs7fsBb68nNWPLeeSOo=",
+       uint64_t{0x81826b553954464e}},
+      {"VsSAw72Ro6xks02kaiLuiTEIWBC5bgqr4WDnmP8vglXzAhixk7td926rm9jNimL+"
+       "kroPSygZ9gl63aF5DCPOACXmsbmhDrAQuUzoh9ZKhWgElLQsrqo1KIjWoZT5b5QfVUXY9lS"
+       "IBg3U75SqORoTPq7HalxxoIT5diWOcJQi",
+       uint64_t{0xc2e5d345dc0ddd2d}},
+      {"j+loZ+C87+"
+       "bJxNVebg94gU0mSLeDulcHs84tQT7BZM2rzDSLiCNxUedHr1ZWJ9ejTiBa0dqy2I2ABc++"
+       "xzOLcv+//YfibtjKtYggC6/3rv0XCc7xu6d/"
+       "O6xO+XOBhOWAQ+IHJVHf7wZnDxIXB8AUHsnjEISKj7823biqXjyP3g==",
+       uint64_t{0x3da6830a9e32631e}},
+      {"f3LlpcPElMkspNtDq5xXyWU62erEaKn7RWKlo540gR6mZsNpK1czV/"
+       "sOmqaq8XAQLEn68LKj6/"
+       "cFkJukxRzCa4OF1a7cCAXYFp9+wZDu0bw4y63qbpjhdCl8GO6Z2lkcXy7KOzbPE01ukg7+"
+       "gN+7uKpoohgAhIwpAKQXmX5xtd0=",
+       uint64_t{0xc9ae5c8759b4877a}},
+  };
+
+#if defined(ABSL_IS_BIG_ENDIAN)
+  constexpr uint64_t kGolden[kNumGoldenOutputs] = {
+      0xe5a40d39ab796423, 0x1766974bf7527d81, 0x5c3bbbe230db17a8,
+      0xa6630143a7e6aa6f, 0x17645cb7318b86b,  0x218b175f30ba61f8,
+      0xa6564b468248c683, 0xef192f401b116e1c, 0xbe8dc0c54617639d,
+      0xe7b01610fc22dbb8, 0x99d9f694404af913, 0xf4eecd37464b45c5,
+      0x7d2c653d63596d9b, 0x3f15c8544ec5393a, 0x6b9dc0c1704f796c,
+      0xf1ded7a7eae5ed5a, 0x2db2fd7c6dd4641b, 0x151ca2d3d4cd33ab,
+      0xa5af5994ac2ccd64, 0x2b2a4ca3191d2fce, 0xf89e68c9364e7c05,
+      0x71724c70b799c21,  0x70536fabfd157369, 0xdee92794c3c3082b,
+      0xac033a6743d3b3eb, 0xed2956b506cd5151, 0xbd669644755264b6,
+      0x6ab1ff5d5f549a63, 0xf6bd551a2e3e04e,  0x7b5a8cef6875ea73,
+      0x22bccf4d4db0a91c, 0x4f2bc07754c7c7eb, 0xfb6b8342a86725db,
+      0x13a1a0d4c5854da,  0x5f6e44655f7dedac, 0x54a9198dff2bdf85,
+      0xdb17e6915d4e4042, 0xa69926cf5c3b89f,  0xf77f031bfd74c096,
+      0x1d6f916fdd50ec3c, 0x334ac76013ade393, 0x99370f899111de15,
+      0x352457a03ada6de,  0x341974d4f42d854d, 0xda89ab02872aeb5,
+      0x6ec2b74e143b10d9, 0x6f284c0b5cd60522, 0xf9670de353438f88,
+      0xde920913adf0a2b4, 0xb7a07d7c0c17a8ec, 0x879a69f558ba3a98,
+      0x360cf6d802df20f9, 0x53530f8046673738, 0xbd8f5f2bcf35e483,
+      0x3f171f047144b983, 0x644d04e820823465, 0x50e44773a20b2702,
+      0xe584ed4c05c745dd, 0x9a825c85b95ab6c0, 0xbce2931deb74e775,
+      0x10468e9e705c7cfe, 0x12e01de3104141e2, 0x5c11ae2ee3713abd,
+      0x6ac5ffb0860319e6, 0xc1e6da1849d30fc9, 0xa0e4d247a458b447,
+      0x4530d4615c32b89b, 0x116aa09107a76505, 0xf941339d00d9bb73,
+      0x573a0fc1615afb33, 0xa975c81dc868b258, 0x3ab2c5250ab54bda,
+      0x37f99f208a3e3b11, 0x4b49b0ff706689d,  0x30bafa0b8f0a87fe,
+      0xea6787a65cc20cdd, 0x55861729f1fc3ab8, 0xea38e009c5be9b72,
+      0xcb8522cba33c3c66, 0x352e77653fe306f3, 0xe0bb760793bac064,
+      0xf66ec59322662956, 0x637aa320455d56f8, 0x46ee546be5824a89,
+      0x9e6842421e83d8a4, 0xf98ac2bc96b9fb8c, 0xf2c1002fd9a70b99,
+      0x4c2b62b1e39e9405, 0x3248555fa3ade9c4, 0xd4d04c37f6417c21,
+      0xf40cd506b1bf5653, 0x6c45d6005c760d2f, 0x61d88a7e61ff0d7e,
+      0x131591e8a53cc967, 0xdae85cb9bc29bab6, 0xe98835334905e626,
+      0x7cce50a2b66b8754, 0x5b0b3d0c5ac498ae, 0xd35a218c974d1756,
+      0xfce436ddc1d003c,  0xd183901de90bb741, 0x9378f8f34974a66,
+      0x21f11ae0a0402368, 0xf2fbd7c94ef89cb6, 0xc329c69d0f0d080b,
+      0xf2841cba16216a61, 0x47aba97b44916df1, 0x724d4e00a8019fcf,
+      0x2df9005c2a728d63, 0xc788892a1a5d7515, 0x9e993a65f9df0480,
+      0x76876721ff49f969, 0xbe7a796cfba15bf5, 0xa4c8bd54586f5488,
+      0xb390a325275501ab, 0x893f11317427ccf1, 0x92f2bb57da5695b9,
+      0x30985b90da88269f, 0x2c690e268e086de8, 0x1c02df6097997196,
+      0x1f9778f8bbdf6455, 0x7d57378c7bf8416d, 0xba8582a5f8d84d38,
+      0xe8ca43b85050be4e, 0x5048cf6bed8a5d9f, 0xfbc5ba80917d0ea4,
+      0x8011026525bf1691, 0x26b8dc6aed9fb50d, 0x191f5bfee77c1fe3,
+      0xdd497891465a2cc1, 0x6f1fe8c57a33072e, 0x2c9f4ec078c460c0,
+      0x9a725bde8f6a1437, 0x6ce545fa3ef61e4d,
+  };
+#else
+  constexpr uint64_t kGolden[kNumGoldenOutputs] = {
+      0xe5a40d39ab796423, 0x1766974bf7527d81, 0x5c3bbbe230db17a8,
+      0xa6630143a7e6aa6f, 0x8787cb2d04b0c984, 0x33603654ff574ac2,
+      0xa6564b468248c683, 0xef192f401b116e1c, 0xbe8dc0c54617639d,
+      0x93d7f665b5521c8e, 0x646d70bb42445f28, 0x96a7b1e3cc9bd426,
+      0x76020289ab0790c4, 0x39f842e4133b9b44, 0x2b8d7047be4bcaab,
+      0x99628abef6716a97, 0x4432e02ba42b2740, 0x74d810efcad7918a,
+      0x88c84e986002507f, 0x4f99acf193cf39b9, 0xd90e7a3655891e37,
+      0x3bb378b1d4df8fcf, 0xf78e94045c052d47, 0x26da0b2130da6b40,
+      0x30b4d426af8c6986, 0x5413b4aaf3baaeae, 0x756ab265370a1597,
+      0xdaf5f4b7d09814fb, 0x8f874ae37742b75e, 0x8fecd03956121ce8,
+      0x229c292ea7a08285, 0x0bb4bf0692d14bae, 0x207b24ca3bdac1db,
+      0x64f6cd6745d3825b, 0xa2b2e1656b58df1e, 0x0d01d30d9ee7a148,
+      0x1cb4cd00ab804e3b, 0x4697f2637fd90999, 0x8383a756b5688c07,
+      0x695c29cb3696a975, 0xda2e5a5a5e971521, 0x7935d4befa056b2b,
+      0x38dd541ca95420fe, 0xcc06c7a4963f967f, 0xbf0f6f66e232fb20,
+      0xf7efb32d373fe71a, 0xe2e64634b1c12660, 0x285b8fd1638e306d,
+      0x658e8a4e3b714d6c, 0xf391fb968e0eb398, 0x744a9ea0cc144bf2,
+      0x12636f2be11012f1, 0x29c57de825948f80, 0x58c6f99ab0d1c021,
+      0x13e7b5a7b82fe3bb, 0x10fbc87901e02b63, 0xa24c9184901b748b,
+      0xcac4fd4c5080e581, 0xc38bdb7483ba68e1, 0xdb2a8069b2ceaffa,
+      0xdf9fe91d0d1c7887, 0xe83f49e96e2e6a08, 0x0c69e61b62ca2b62,
+      0xb4a4f3f85f8298fe, 0x167a1b39e1e95f41, 0xf8a2a5649855ee41,
+      0x27992565b595c498, 0x3e08cca5b71f9346, 0xad406b10c770a6d2,
+      0xd1713ce6e552bcf2, 0x753b287194c73ad3, 0x5ae41a95f600af1c,
+      0x4a61163b86a8bb4c, 0x42eeaa79e760c7e4, 0x698df622ef465b0a,
+      0x157583111e1a6026, 0xaa1388f078e793e0, 0xf10d68d0f3309360,
+      0x2af056184457a3de, 0x6d0058e1590b2489, 0x638f287f68817f12,
+      0xc46b71fecefd5467, 0x2c8e94679d964e0a, 0x8612b797ce22503a,
+      0x59f929babfba7170, 0x9527556923fb49a0, 0x1039ab644f5e150b,
+      0x7816c83f3aa05e6d, 0xf51d2f564518c619, 0x67d494cff03ac004,
+      0x2802d636ced1cfbb, 0xf64e20bad771cb12, 0x0b9a6cf84a83e15e,
+      0x8da6630319609301, 0x40946a86e2a996f3, 0xcab7f5997953fa76,
+      0x39129ca0e04fc465, 0x5238221fd685e1b8, 0x175130c407dbcaab,
+      0x02f20e7536c0b0df, 0x2742cb488a04ad56, 0xd6afb593879ff93b,
+      0xf50ad64caac0ca7f, 0x2ade95c4261364ae, 0x5c4f3299faacd07a,
+      0xfffe3bff0ae5e9bc, 0x1db785c0005166e4, 0xea000d962ad18418,
+      0xe42aef38359362d9, 0xc8e95657348a3891, 0xc162eca864f238c6,
+      0xbe1fb373e20579ad, 0x628a1d4f40aa6ffd, 0xa87bdb7456340f90,
+      0x5960ef3ba982c801, 0x5026586df9a431ec, 0xfe4b8a20fdf0840b,
+      0xdcb761867da7072f, 0xc10d4653667275b7, 0x727720deec13110b,
+      0x710b009662858dc9, 0xfbf8f7a3ecac1eb7, 0xb6fc4fcd0722e3df,
+      0x7cb86dcc55104aac, 0x19e71e9b45c3a51e, 0x51de38573c2bea48,
+      0xa73ab6996d6df158, 0x55ef2b8c930817b2, 0xb2850bf5fae87157,
+      0xecf3de1acd04651f, 0xcc0a40552559ff32, 0xc385c374f20315b1,
+      0xb90208a4c7234183, 0x58aa1ca7a4c075d9,
+  };
+#endif
+
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    std::string str;
+    ASSERT_TRUE(absl::Base64Unescape(cases[i].base64_data, &str));
+    uint64_t h = absl::hash_internal::LowLevelHash(str.data(), str.size(),
+                                                   cases[i].seed, kSalt);
+    printf("0x%016" PRIx64 ", ", h);
+    if (i % 3 == 2) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+  EXPECT_FALSE(true);
+#else
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    SCOPED_TRACE(::testing::Message()
+                 << "i = " << i << "; input = " << cases[i].base64_data);
+    std::string str;
+    ASSERT_TRUE(absl::Base64Unescape(cases[i].base64_data, &str));
+    EXPECT_EQ(absl::hash_internal::LowLevelHash(str.data(), str.size(),
+                                                cases[i].seed, kSalt),
+              kGolden[i]);
+  }
+#endif
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/print_hash_of.cc b/weight/_dep/abseil-cpp/absl/hash/internal/print_hash_of.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c392125a69faf6b58592ed122e953964113cb83b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/print_hash_of.cc
@@ -0,0 +1,23 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdlib>
+
+#include "absl/hash/hash.h"
+
+// Prints the hash of argv[1].
+int main(int argc, char** argv) {
+  if (argc < 2) return 1;
+  printf("%zu\n", absl::Hash<int>{}(std::atoi(argv[1])));  // NOLINT
+}
diff --git a/weight/_dep/abseil-cpp/absl/hash/internal/spy_hash_state.h b/weight/_dep/abseil-cpp/absl/hash/internal/spy_hash_state.h
new file mode 100644
index 0000000000000000000000000000000000000000..09728266212d59559ff5779b21883029dd842801
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/hash/internal/spy_hash_state.h
@@ -0,0 +1,266 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_
+#define ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_
+
+#include <algorithm>
+#include <ostream>
+#include <string>
+#include <vector>
+
+#include "absl/hash/hash.h"
+#include "absl/strings/match.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/str_join.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace hash_internal {
+
+// SpyHashState is an implementation of the HashState API that simply
+// accumulates all input bytes in an internal buffer. This makes it useful
+// for testing AbslHashValue overloads (so long as they are templated on the
+// HashState parameter), since it can report the exact hash representation
+// that the AbslHashValue overload produces.
+//
+// Sample usage:
+// EXPECT_EQ(SpyHashState::combine(SpyHashState(), foo),
+//           SpyHashState::combine(SpyHashState(), bar));
+template <typename T>
+class SpyHashStateImpl : public HashStateBase<SpyHashStateImpl<T>> {
+ public:
+  SpyHashStateImpl() : error_(std::make_shared<absl::optional<std::string>>()) {
+    static_assert(std::is_void<T>::value, "");
+  }
+
+  // Move-only
+  SpyHashStateImpl(const SpyHashStateImpl&) = delete;
+  SpyHashStateImpl& operator=(const SpyHashStateImpl&) = delete;
+
+  SpyHashStateImpl(SpyHashStateImpl&& other) noexcept {
+    *this = std::move(other);
+  }
+
+  SpyHashStateImpl& operator=(SpyHashStateImpl&& other) noexcept {
+    hash_representation_ = std::move(other.hash_representation_);
+    error_ = other.error_;
+    moved_from_ = other.moved_from_;
+    other.moved_from_ = true;
+    return *this;
+  }
+
+  template <typename U>
+  SpyHashStateImpl(SpyHashStateImpl<U>&& other) {  // NOLINT
+    hash_representation_ = std::move(other.hash_representation_);
+    error_ = other.error_;
+    moved_from_ = other.moved_from_;
+    other.moved_from_ = true;
+  }
+
+  template <typename A, typename... Args>
+  static SpyHashStateImpl combine(SpyHashStateImpl s, const A& a,
+                                  const Args&... args) {
+    // Pass an instance of SpyHashStateImpl<A> when trying to combine `A`. This
+    // allows us to test that the user only uses this instance for combine calls
+    // and does not call AbslHashValue directly.
+    // See AbslHashValue implementation at the bottom.
+    s = SpyHashStateImpl<A>::HashStateBase::combine(std::move(s), a);
+    return SpyHashStateImpl::combine(std::move(s), args...);
+  }
+  static SpyHashStateImpl combine(SpyHashStateImpl s) {
+    if (direct_absl_hash_value_error_) {
+      *s.error_ = "AbslHashValue should not be invoked directly.";
+    } else if (s.moved_from_) {
+      *s.error_ = "Used moved-from instance of the hash state object.";
+    }
+    return s;
+  }
+
+  static void SetDirectAbslHashValueError() {
+    direct_absl_hash_value_error_ = true;
+  }
+
+  // Two SpyHashStateImpl objects are equal if they hold equal hash
+  // representations.
+  friend bool operator==(const SpyHashStateImpl& lhs,
+                         const SpyHashStateImpl& rhs) {
+    return lhs.hash_representation_ == rhs.hash_representation_;
+  }
+
+  friend bool operator!=(const SpyHashStateImpl& lhs,
+                         const SpyHashStateImpl& rhs) {
+    return !(lhs == rhs);
+  }
+
+  enum class CompareResult {
+    kEqual,
+    kASuffixB,
+    kBSuffixA,
+    kUnequal,
+  };
+
+  static CompareResult Compare(const SpyHashStateImpl& a,
+                               const SpyHashStateImpl& b) {
+    const std::string a_flat = absl::StrJoin(a.hash_representation_, "");
+    const std::string b_flat = absl::StrJoin(b.hash_representation_, "");
+    if (a_flat == b_flat) return CompareResult::kEqual;
+    if (absl::EndsWith(a_flat, b_flat)) return CompareResult::kBSuffixA;
+    if (absl::EndsWith(b_flat, a_flat)) return CompareResult::kASuffixB;
+    return CompareResult::kUnequal;
+  }
+
+  // operator<< prints the hash representation as a hex and ASCII dump, to
+  // facilitate debugging.
+  friend std::ostream& operator<<(std::ostream& out,
+                                  const SpyHashStateImpl& hash_state) {
+    out << "[\n";
+    for (auto& s : hash_state.hash_representation_) {
+      size_t offset = 0;
+      for (char c : s) {
+        if (offset % 16 == 0) {
+          out << absl::StreamFormat("\n0x%04x: ", offset);
+        }
+        if (offset % 2 == 0) {
+          out << " ";
+        }
+        out << absl::StreamFormat("%02x", c);
+        ++offset;
+      }
+      out << "\n";
+    }
+    return out << "]";
+  }
+
+  // The base case of the combine recursion, which writes raw bytes into the
+  // internal buffer.
+  static SpyHashStateImpl combine_contiguous(SpyHashStateImpl hash_state,
+                                             const unsigned char* begin,
+                                             size_t size) {
+    const size_t large_chunk_stride = PiecewiseChunkSize();
+    if (size > large_chunk_stride) {
+      // Combining a large contiguous buffer must have the same effect as
+      // doing it piecewise by the stride length, followed by the (possibly
+      // empty) remainder.
+      while (size >= large_chunk_stride) {
+        hash_state = SpyHashStateImpl::combine_contiguous(
+            std::move(hash_state), begin, large_chunk_stride);
+        begin += large_chunk_stride;
+        size -= large_chunk_stride;
+      }
+    }
+
+    hash_state.hash_representation_.emplace_back(
+        reinterpret_cast<const char*>(begin), size);
+    return hash_state;
+  }
+
+  using SpyHashStateImpl::HashStateBase::combine_contiguous;
+
+  template <typename CombinerT>
+  static SpyHashStateImpl RunCombineUnordered(SpyHashStateImpl state,
+                                              CombinerT combiner) {
+    UnorderedCombinerCallback cb;
+
+    combiner(SpyHashStateImpl<void>{}, std::ref(cb));
+
+    std::sort(cb.element_hash_representations.begin(),
+              cb.element_hash_representations.end());
+    state.hash_representation_.insert(state.hash_representation_.end(),
+                                      cb.element_hash_representations.begin(),
+                                      cb.element_hash_representations.end());
+    if (cb.error && cb.error->has_value()) {
+      state.error_ = std::move(cb.error);
+    }
+    return state;
+  }
+
+  absl::optional<std::string> error() const {
+    if (moved_from_) {
+      return "Returned a moved-from instance of the hash state object.";
+    }
+    return *error_;
+  }
+
+ private:
+  template <typename U>
+  friend class SpyHashStateImpl;
+
+  struct UnorderedCombinerCallback {
+    std::vector<std::string> element_hash_representations;
+    std::shared_ptr<absl::optional<std::string>> error;
+
+    // The inner spy can have a different type.
+    template <typename U>
+    void operator()(SpyHashStateImpl<U>& inner) {
+      element_hash_representations.push_back(
+          absl::StrJoin(inner.hash_representation_, ""));
+      if (inner.error_->has_value()) {
+        error = std::move(inner.error_);
+      }
+      inner = SpyHashStateImpl<void>{};
+    }
+  };
+
+  // This is true if SpyHashStateImpl<T> has been passed to a call of
+  // AbslHashValue with the wrong type. This detects that the user called
+  // AbslHashValue directly (because the hash state type does not match).
+  static bool direct_absl_hash_value_error_;
+
+  std::vector<std::string> hash_representation_;
+  // This is a shared_ptr because we want all instances of the particular
+  // SpyHashState run to share the field. This way we can set the error for
+  // use-after-move and all the copies will see it.
+  std::shared_ptr<absl::optional<std::string>> error_;
+  bool moved_from_ = false;
+};
+
+template <typename T>
+bool SpyHashStateImpl<T>::direct_absl_hash_value_error_;
+
+template <bool& B>
+struct OdrUse {
+  constexpr OdrUse() {}
+  bool& b = B;
+};
+
+template <void (*)()>
+struct RunOnStartup {
+  static bool run;
+  static constexpr OdrUse<run> kOdrUse{};
+};
+
+template <void (*f)()>
+bool RunOnStartup<f>::run = (f(), true);
+
+template <
+    typename T, typename U,
+    // Only trigger for when (T != U),
+    typename = absl::enable_if_t<!std::is_same<T, U>::value>,
+    // This statement works in two ways:
+    //  - First, it instantiates RunOnStartup and forces the initialization of
+    //    `run`, which set the global variable.
+    //  - Second, it triggers a SFINAE error disabling the overload to prevent
+    //    compile time errors. If we didn't disable the overload we would get
+    //    ambiguous overload errors, which we don't want.
+    int = RunOnStartup<SpyHashStateImpl<T>::SetDirectAbslHashValueError>::run>
+void AbslHashValue(SpyHashStateImpl<T>, const U&);
+
+using SpyHashState = SpyHashStateImpl<void>;
+
+}  // namespace hash_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_
diff --git a/weight/_dep/abseil-cpp/absl/meta/BUILD.bazel b/weight/_dep/abseil-cpp/absl/meta/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..cf5df9b88eb5f766fed78cb6ff83919d90e724d6
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/meta/BUILD.bazel
@@ -0,0 +1,59 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "type_traits",
+    hdrs = ["type_traits.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "type_traits_test",
+    srcs = ["type_traits_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":type_traits",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/time",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/meta/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/meta/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..d509114c0ee7180f4b09e12f80c05acacd4294fb
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/meta/CMakeLists.txt
@@ -0,0 +1,54 @@
+#
+# Copyright 2017 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+absl_cc_library(
+  NAME
+    type_traits
+  HDRS
+    "type_traits.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    type_traits_test
+  SRCS
+    "type_traits_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::config
+    absl::time
+    absl::core_headers
+    absl::type_traits
+    GTest::gmock_main
+)
+
+# component target
+absl_cc_library(
+  NAME
+    meta
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::type_traits
+  PUBLIC
+)
diff --git a/weight/_dep/abseil-cpp/absl/meta/type_traits.h b/weight/_dep/abseil-cpp/absl/meta/type_traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..cf71164b3861322aee7b4332dc8df4dd39d7f262
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/meta/type_traits.h
@@ -0,0 +1,564 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// type_traits.h
+// -----------------------------------------------------------------------------
+//
+// This file contains C++11-compatible versions of standard <type_traits> API
+// functions for determining the characteristics of types. Such traits can
+// support type inference, classification, and transformation, as well as
+// make it easier to write templates based on generic type behavior.
+//
+// See https://en.cppreference.com/w/cpp/header/type_traits
+//
+// WARNING: use of many of the constructs in this header will count as "complex
+// template metaprogramming", so before proceeding, please carefully consider
+// https://google.github.io/styleguide/cppguide.html#Template_metaprogramming
+//
+// WARNING: using template metaprogramming to detect or depend on API
+// features is brittle and not guaranteed. Neither the standard library nor
+// Abseil provides any guarantee that APIs are stable in the face of template
+// metaprogramming. Use with caution.
+#ifndef ABSL_META_TYPE_TRAITS_H_
+#define ABSL_META_TYPE_TRAITS_H_
+
+#include <cstddef>
+#include <functional>
+#include <type_traits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+
+// Defines the default alignment. `__STDCPP_DEFAULT_NEW_ALIGNMENT__` is a C++17
+// feature.
+#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+#define ABSL_INTERNAL_DEFAULT_NEW_ALIGNMENT __STDCPP_DEFAULT_NEW_ALIGNMENT__
+#else  // defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+#define ABSL_INTERNAL_DEFAULT_NEW_ALIGNMENT alignof(std::max_align_t)
+#endif  // defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace type_traits_internal {
+
+template <typename... Ts>
+struct VoidTImpl {
+  using type = void;
+};
+
+////////////////////////////////
+// Library Fundamentals V2 TS //
+////////////////////////////////
+
+// NOTE: The `is_detected` family of templates here differ from the library
+// fundamentals specification in that for library fundamentals, `Op<Args...>` is
+// evaluated as soon as the type `is_detected<Op, Args...>` undergoes
+// substitution, regardless of whether or not the `::value` is accessed. That
+// is inconsistent with all other standard traits and prevents lazy evaluation
+// in larger contexts (such as if the `is_detected` check is a trailing argument
+// of a `conjunction`. This implementation opts to instead be lazy in the same
+// way that the standard traits are (this "defect" of the detection idiom
+// specifications has been reported).
+
+template <class Enabler, template <class...> class Op, class... Args>
+struct is_detected_impl {
+  using type = std::false_type;
+};
+
+template <template <class...> class Op, class... Args>
+struct is_detected_impl<typename VoidTImpl<Op<Args...>>::type, Op, Args...> {
+  using type = std::true_type;
+};
+
+template <template <class...> class Op, class... Args>
+struct is_detected : is_detected_impl<void, Op, Args...>::type {};
+
+template <class Enabler, class To, template <class...> class Op, class... Args>
+struct is_detected_convertible_impl {
+  using type = std::false_type;
+};
+
+template <class To, template <class...> class Op, class... Args>
+struct is_detected_convertible_impl<
+    typename std::enable_if<std::is_convertible<Op<Args...>, To>::value>::type,
+    To, Op, Args...> {
+  using type = std::true_type;
+};
+
+template <class To, template <class...> class Op, class... Args>
+struct is_detected_convertible
+    : is_detected_convertible_impl<void, To, Op, Args...>::type {};
+
+}  // namespace type_traits_internal
+
+// void_t()
+//
+// Ignores the type of any its arguments and returns `void`. In general, this
+// metafunction allows you to create a general case that maps to `void` while
+// allowing specializations that map to specific types.
+//
+// This metafunction is designed to be a drop-in replacement for the C++17
+// `std::void_t` metafunction.
+//
+// NOTE: `absl::void_t` does not use the standard-specified implementation so
+// that it can remain compatible with gcc < 5.1. This can introduce slightly
+// different behavior, such as when ordering partial specializations.
+template <typename... Ts>
+using void_t = typename type_traits_internal::VoidTImpl<Ts...>::type;
+
+// conjunction
+//
+// Performs a compile-time logical AND operation on the passed types (which
+// must have  `::value` members convertible to `bool`. Short-circuits if it
+// encounters any `false` members (and does not compare the `::value` members
+// of any remaining arguments).
+//
+// This metafunction is designed to be a drop-in replacement for the C++17
+// `std::conjunction` metafunction.
+template <typename... Ts>
+struct conjunction : std::true_type {};
+
+template <typename T, typename... Ts>
+struct conjunction<T, Ts...>
+    : std::conditional<T::value, conjunction<Ts...>, T>::type {};
+
+template <typename T>
+struct conjunction<T> : T {};
+
+// disjunction
+//
+// Performs a compile-time logical OR operation on the passed types (which
+// must have  `::value` members convertible to `bool`. Short-circuits if it
+// encounters any `true` members (and does not compare the `::value` members
+// of any remaining arguments).
+//
+// This metafunction is designed to be a drop-in replacement for the C++17
+// `std::disjunction` metafunction.
+template <typename... Ts>
+struct disjunction : std::false_type {};
+
+template <typename T, typename... Ts>
+struct disjunction<T, Ts...> :
+      std::conditional<T::value, T, disjunction<Ts...>>::type {};
+
+template <typename T>
+struct disjunction<T> : T {};
+
+// negation
+//
+// Performs a compile-time logical NOT operation on the passed type (which
+// must have  `::value` members convertible to `bool`.
+//
+// This metafunction is designed to be a drop-in replacement for the C++17
+// `std::negation` metafunction.
+template <typename T>
+struct negation : std::integral_constant<bool, !T::value> {};
+
+// is_function()
+//
+// Determines whether the passed type `T` is a function type.
+//
+// This metafunction is designed to be a drop-in replacement for the C++11
+// `std::is_function()` metafunction for platforms that have incomplete C++11
+// support (such as libstdc++ 4.x).
+//
+// This metafunction works because appending `const` to a type does nothing to
+// function types and reference types (and forms a const-qualified type
+// otherwise).
+template <typename T>
+struct is_function
+    : std::integral_constant<
+          bool, !(std::is_reference<T>::value ||
+                  std::is_const<typename std::add_const<T>::type>::value)> {};
+
+// is_copy_assignable()
+// is_move_assignable()
+// is_trivially_destructible()
+// is_trivially_default_constructible()
+// is_trivially_move_constructible()
+// is_trivially_copy_constructible()
+// is_trivially_move_assignable()
+// is_trivially_copy_assignable()
+//
+// Historical note: Abseil once provided implementations of these type traits
+// for platforms that lacked full support. New code should prefer to use the
+// std variants.
+//
+// See the documentation for the STL <type_traits> header for more information:
+// https://en.cppreference.com/w/cpp/header/type_traits
+using std::is_copy_assignable;
+using std::is_move_assignable;
+using std::is_trivially_copy_assignable;
+using std::is_trivially_copy_constructible;
+using std::is_trivially_default_constructible;
+using std::is_trivially_destructible;
+using std::is_trivially_move_assignable;
+using std::is_trivially_move_constructible;
+
+#if defined(__cpp_lib_remove_cvref) && __cpp_lib_remove_cvref >= 201711L
+template <typename T>
+using remove_cvref = std::remove_cvref<T>;
+
+template <typename T>
+using remove_cvref_t = typename std::remove_cvref<T>::type;
+#else
+// remove_cvref()
+//
+// C++11 compatible implementation of std::remove_cvref which was added in
+// C++20.
+template <typename T>
+struct remove_cvref {
+  using type =
+      typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+};
+
+template <typename T>
+using remove_cvref_t = typename remove_cvref<T>::type;
+#endif
+
+// -----------------------------------------------------------------------------
+// C++14 "_t" trait aliases
+// -----------------------------------------------------------------------------
+
+template <typename T>
+using remove_cv_t = typename std::remove_cv<T>::type;
+
+template <typename T>
+using remove_const_t = typename std::remove_const<T>::type;
+
+template <typename T>
+using remove_volatile_t = typename std::remove_volatile<T>::type;
+
+template <typename T>
+using add_cv_t = typename std::add_cv<T>::type;
+
+template <typename T>
+using add_const_t = typename std::add_const<T>::type;
+
+template <typename T>
+using add_volatile_t = typename std::add_volatile<T>::type;
+
+template <typename T>
+using remove_reference_t = typename std::remove_reference<T>::type;
+
+template <typename T>
+using add_lvalue_reference_t = typename std::add_lvalue_reference<T>::type;
+
+template <typename T>
+using add_rvalue_reference_t = typename std::add_rvalue_reference<T>::type;
+
+template <typename T>
+using remove_pointer_t = typename std::remove_pointer<T>::type;
+
+template <typename T>
+using add_pointer_t = typename std::add_pointer<T>::type;
+
+template <typename T>
+using make_signed_t = typename std::make_signed<T>::type;
+
+template <typename T>
+using make_unsigned_t = typename std::make_unsigned<T>::type;
+
+template <typename T>
+using remove_extent_t = typename std::remove_extent<T>::type;
+
+template <typename T>
+using remove_all_extents_t = typename std::remove_all_extents<T>::type;
+
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+namespace type_traits_internal {
+// This trick to retrieve a default alignment is necessary for our
+// implementation of aligned_storage_t to be consistent with any
+// implementation of std::aligned_storage.
+template <size_t Len, typename T = std::aligned_storage<Len>>
+struct default_alignment_of_aligned_storage;
+
+template <size_t Len, size_t Align>
+struct default_alignment_of_aligned_storage<
+    Len, std::aligned_storage<Len, Align>> {
+  static constexpr size_t value = Align;
+};
+}  // namespace type_traits_internal
+
+// TODO(b/260219225): std::aligned_storage(_t) is deprecated in C++23.
+template <size_t Len, size_t Align = type_traits_internal::
+                          default_alignment_of_aligned_storage<Len>::value>
+using aligned_storage_t = typename std::aligned_storage<Len, Align>::type;
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+
+template <typename T>
+using decay_t = typename std::decay<T>::type;
+
+template <bool B, typename T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+
+template <bool B, typename T, typename F>
+using conditional_t = typename std::conditional<B, T, F>::type;
+
+template <typename... T>
+using common_type_t = typename std::common_type<T...>::type;
+
+template <typename T>
+using underlying_type_t = typename std::underlying_type<T>::type;
+
+
+namespace type_traits_internal {
+
+#if (defined(__cpp_lib_is_invocable) && __cpp_lib_is_invocable >= 201703L) || \
+    (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+// std::result_of is deprecated (C++17) or removed (C++20)
+template<typename> struct result_of;
+template<typename F, typename... Args>
+struct result_of<F(Args...)> : std::invoke_result<F, Args...> {};
+#else
+template<typename F> using result_of = std::result_of<F>;
+#endif
+
+}  // namespace type_traits_internal
+
+template<typename F>
+using result_of_t = typename type_traits_internal::result_of<F>::type;
+
+namespace type_traits_internal {
+// In MSVC we can't probe std::hash or stdext::hash because it triggers a
+// static_assert instead of failing substitution. Libc++ prior to 4.0
+// also used a static_assert.
+//
+#if defined(_MSC_VER) || (defined(_LIBCPP_VERSION) && \
+                          _LIBCPP_VERSION < 4000 && _LIBCPP_STD_VER > 11)
+#define ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_ 0
+#else
+#define ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_ 1
+#endif
+
+#if !ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+template <typename Key, typename = size_t>
+struct IsHashable : std::true_type {};
+#else   // ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+template <typename Key, typename = void>
+struct IsHashable : std::false_type {};
+
+template <typename Key>
+struct IsHashable<
+    Key,
+    absl::enable_if_t<std::is_convertible<
+        decltype(std::declval<std::hash<Key>&>()(std::declval<Key const&>())),
+        std::size_t>::value>> : std::true_type {};
+#endif  // !ABSL_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_
+
+struct AssertHashEnabledHelper {
+ private:
+  static void Sink(...) {}
+  struct NAT {};
+
+  template <class Key>
+  static auto GetReturnType(int)
+      -> decltype(std::declval<std::hash<Key>>()(std::declval<Key const&>()));
+  template <class Key>
+  static NAT GetReturnType(...);
+
+  template <class Key>
+  static std::nullptr_t DoIt() {
+    static_assert(IsHashable<Key>::value,
+                  "std::hash<Key> does not provide a call operator");
+    static_assert(
+        std::is_default_constructible<std::hash<Key>>::value,
+        "std::hash<Key> must be default constructible when it is enabled");
+    static_assert(
+        std::is_copy_constructible<std::hash<Key>>::value,
+        "std::hash<Key> must be copy constructible when it is enabled");
+    static_assert(absl::is_copy_assignable<std::hash<Key>>::value,
+                  "std::hash<Key> must be copy assignable when it is enabled");
+    // is_destructible is unchecked as it's implied by each of the
+    // is_constructible checks.
+    using ReturnType = decltype(GetReturnType<Key>(0));
+    static_assert(std::is_same<ReturnType, NAT>::value ||
+                      std::is_same<ReturnType, size_t>::value,
+                  "std::hash<Key> must return size_t");
+    return nullptr;
+  }
+
+  template <class... Ts>
+  friend void AssertHashEnabled();
+};
+
+template <class... Ts>
+inline void AssertHashEnabled() {
+  using Helper = AssertHashEnabledHelper;
+  Helper::Sink(Helper::DoIt<Ts>()...);
+}
+
+}  // namespace type_traits_internal
+
+// An internal namespace that is required to implement the C++17 swap traits.
+// It is not further nested in type_traits_internal to avoid long symbol names.
+namespace swap_internal {
+
+// Necessary for the traits.
+using std::swap;
+
+// This declaration prevents global `swap` and `absl::swap` overloads from being
+// considered unless ADL picks them up.
+void swap();
+
+template <class T>
+using IsSwappableImpl = decltype(swap(std::declval<T&>(), std::declval<T&>()));
+
+// NOTE: This dance with the default template parameter is for MSVC.
+template <class T,
+          class IsNoexcept = std::integral_constant<
+              bool, noexcept(swap(std::declval<T&>(), std::declval<T&>()))>>
+using IsNothrowSwappableImpl = typename std::enable_if<IsNoexcept::value>::type;
+
+// IsSwappable
+//
+// Determines whether the standard swap idiom is a valid expression for
+// arguments of type `T`.
+template <class T>
+struct IsSwappable
+    : absl::type_traits_internal::is_detected<IsSwappableImpl, T> {};
+
+// IsNothrowSwappable
+//
+// Determines whether the standard swap idiom is a valid expression for
+// arguments of type `T` and is noexcept.
+template <class T>
+struct IsNothrowSwappable
+    : absl::type_traits_internal::is_detected<IsNothrowSwappableImpl, T> {};
+
+// Swap()
+//
+// Performs the swap idiom from a namespace where valid candidates may only be
+// found in `std` or via ADL.
+template <class T, absl::enable_if_t<IsSwappable<T>::value, int> = 0>
+void Swap(T& lhs, T& rhs) noexcept(IsNothrowSwappable<T>::value) {
+  swap(lhs, rhs);
+}
+
+// StdSwapIsUnconstrained
+//
+// Some standard library implementations are broken in that they do not
+// constrain `std::swap`. This will effectively tell us if we are dealing with
+// one of those implementations.
+using StdSwapIsUnconstrained = IsSwappable<void()>;
+
+}  // namespace swap_internal
+
+namespace type_traits_internal {
+
+// Make the swap-related traits/function accessible from this namespace.
+using swap_internal::IsNothrowSwappable;
+using swap_internal::IsSwappable;
+using swap_internal::Swap;
+using swap_internal::StdSwapIsUnconstrained;
+
+}  // namespace type_traits_internal
+
+// absl::is_trivially_relocatable<T>
+//
+// Detects whether a type is known to be "trivially relocatable" -- meaning it
+// can be relocated without invoking the constructor/destructor, using a form of
+// move elision.
+//
+// This trait is conservative, for backwards compatibility. If it's true then
+// the type is definitely trivially relocatable, but if it's false then the type
+// may or may not be.
+//
+// Example:
+//
+// if constexpr (absl::is_trivially_relocatable<T>::value) {
+//   memcpy(new_location, old_location, sizeof(T));
+// } else {
+//   new(new_location) T(std::move(*old_location));
+//   old_location->~T();
+// }
+//
+// Upstream documentation:
+//
+// https://clang.llvm.org/docs/LanguageExtensions.html#:~:text=__is_trivially_relocatable
+
+// If the compiler offers a builtin that tells us the answer, we can use that.
+// This covers all of the cases in the fallback below, plus types that opt in
+// using e.g. [[clang::trivial_abi]].
+//
+// Clang on Windows has the builtin, but it falsely claims types with a
+// user-provided destructor are trivial (http://b/275003464). So we opt out
+// there.
+//
+// TODO(b/275003464): remove the opt-out once the bug is fixed.
+//
+// According to https://github.com/abseil/abseil-cpp/issues/1479, this does not
+// work with NVCC either.
+#if ABSL_HAVE_BUILTIN(__is_trivially_relocatable) &&                 \
+    !(defined(__clang__) && (defined(_WIN32) || defined(_WIN64))) && \
+    !defined(__NVCC__)
+template <class T>
+struct is_trivially_relocatable
+    : std::integral_constant<bool, __is_trivially_relocatable(T)> {};
+#else
+// Otherwise we use a fallback that detects only those types we can feasibly
+// detect. Any time that has trivial move-construction and destruction
+// operations is by definition trivially relocatable.
+template <class T>
+struct is_trivially_relocatable
+    : absl::conjunction<absl::is_trivially_move_constructible<T>,
+                        absl::is_trivially_destructible<T>> {};
+#endif
+
+// absl::is_constant_evaluated()
+//
+// Detects whether the function call occurs within a constant-evaluated context.
+// Returns true if the evaluation of the call occurs within the evaluation of an
+// expression or conversion that is manifestly constant-evaluated; otherwise
+// returns false.
+//
+// This function is implemented in terms of `std::is_constant_evaluated` for
+// c++20 and up. For older c++ versions, the function is implemented in terms
+// of `__builtin_is_constant_evaluated` if available, otherwise the function
+// will fail to compile.
+//
+// Applications can inspect `ABSL_HAVE_CONSTANT_EVALUATED` at compile time
+// to check if this function is supported.
+//
+// Example:
+//
+// constexpr MyClass::MyClass(int param) {
+// #ifdef ABSL_HAVE_CONSTANT_EVALUATED
+//   if (!absl::is_constant_evaluated()) {
+//     ABSL_LOG(INFO) << "MyClass(" << param << ")";
+//   }
+// #endif  // ABSL_HAVE_CONSTANT_EVALUATED
+// }
+//
+// Upstream documentation:
+//
+// http://en.cppreference.com/w/cpp/types/is_constant_evaluated
+// http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#:~:text=__builtin_is_constant_evaluated
+//
+#if defined(ABSL_HAVE_CONSTANT_EVALUATED)
+constexpr bool is_constant_evaluated() noexcept {
+#ifdef __cpp_lib_is_constant_evaluated
+  return std::is_constant_evaluated();
+#elif ABSL_HAVE_BUILTIN(__builtin_is_constant_evaluated)
+  return __builtin_is_constant_evaluated();
+#endif
+}
+#endif  // ABSL_HAVE_CONSTANT_EVALUATED
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_META_TYPE_TRAITS_H_
diff --git a/weight/_dep/abseil-cpp/absl/meta/type_traits_test.cc b/weight/_dep/abseil-cpp/absl/meta/type_traits_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7412f33de32669e4c6cbd52d99c8fb93718c9dfc
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/meta/type_traits_test.cc
@@ -0,0 +1,841 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/meta/type_traits.h"
+
+#include <cstdint>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+
+namespace {
+
+using ::testing::StaticAssertTypeEq;
+
+template <class T, class U>
+struct simple_pair {
+  T first;
+  U second;
+};
+
+struct Dummy {};
+
+struct ReturnType {};
+struct ConvertibleToReturnType {
+  operator ReturnType() const;  // NOLINT
+};
+
+// Unique types used as parameter types for testing the detection idiom.
+struct StructA {};
+struct StructB {};
+struct StructC {};
+
+struct TypeWithBarFunction {
+  template <class T,
+            absl::enable_if_t<std::is_same<T&&, StructA&>::value, int> = 0>
+  ReturnType bar(T&&, const StructB&, StructC&&) &&;  // NOLINT
+};
+
+struct TypeWithBarFunctionAndConvertibleReturnType {
+  template <class T,
+            absl::enable_if_t<std::is_same<T&&, StructA&>::value, int> = 0>
+  ConvertibleToReturnType bar(T&&, const StructB&, StructC&&) &&;  // NOLINT
+};
+
+template <class Class, class... Ts>
+using BarIsCallableImpl =
+    decltype(std::declval<Class>().bar(std::declval<Ts>()...));
+
+template <class Class, class... T>
+using BarIsCallable =
+    absl::type_traits_internal::is_detected<BarIsCallableImpl, Class, T...>;
+
+template <class Class, class... T>
+using BarIsCallableConv = absl::type_traits_internal::is_detected_convertible<
+    ReturnType, BarIsCallableImpl, Class, T...>;
+
+// NOTE: Test of detail type_traits_internal::is_detected.
+TEST(IsDetectedTest, BasicUsage) {
+  EXPECT_TRUE((BarIsCallable<TypeWithBarFunction, StructA&, const StructB&,
+                             StructC>::value));
+  EXPECT_TRUE(
+      (BarIsCallable<TypeWithBarFunction, StructA&, StructB&, StructC>::value));
+  EXPECT_TRUE(
+      (BarIsCallable<TypeWithBarFunction, StructA&, StructB, StructC>::value));
+
+  EXPECT_FALSE((BarIsCallable<int, StructA&, const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallable<TypeWithBarFunction&, StructA&, const StructB&,
+                              StructC>::value));
+  EXPECT_FALSE((BarIsCallable<TypeWithBarFunction, StructA, const StructB&,
+                              StructC>::value));
+}
+
+// NOTE: Test of detail type_traits_internal::is_detected_convertible.
+TEST(IsDetectedConvertibleTest, BasicUsage) {
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, const StructB&,
+                                 StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, StructB&,
+                                 StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, StructB,
+                                 StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                 StructA&, const StructB&, StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                 StructA&, StructB&, StructC>::value));
+  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                 StructA&, StructB, StructC>::value));
+
+  EXPECT_FALSE(
+      (BarIsCallableConv<int, StructA&, const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunction&, StructA&,
+                                  const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunction, StructA, const StructB&,
+                                  StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType&,
+                                  StructA&, const StructB&, StructC>::value));
+  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
+                                  StructA, const StructB&, StructC>::value));
+}
+
+TEST(VoidTTest, BasicUsage) {
+  StaticAssertTypeEq<void, absl::void_t<Dummy>>();
+  StaticAssertTypeEq<void, absl::void_t<Dummy, Dummy, Dummy>>();
+}
+
+TEST(ConjunctionTest, BasicBooleanLogic) {
+  EXPECT_TRUE(absl::conjunction<>::value);
+  EXPECT_TRUE(absl::conjunction<std::true_type>::value);
+  EXPECT_TRUE((absl::conjunction<std::true_type, std::true_type>::value));
+  EXPECT_FALSE((absl::conjunction<std::true_type, std::false_type>::value));
+  EXPECT_FALSE((absl::conjunction<std::false_type, std::true_type>::value));
+  EXPECT_FALSE((absl::conjunction<std::false_type, std::false_type>::value));
+}
+
+struct MyTrueType {
+  static constexpr bool value = true;
+};
+
+struct MyFalseType {
+  static constexpr bool value = false;
+};
+
+TEST(ConjunctionTest, ShortCircuiting) {
+  EXPECT_FALSE(
+      (absl::conjunction<std::true_type, std::false_type, Dummy>::value));
+  EXPECT_TRUE((std::is_base_of<MyFalseType,
+                               absl::conjunction<std::true_type, MyFalseType,
+                                                 std::false_type>>::value));
+  EXPECT_TRUE(
+      (std::is_base_of<MyTrueType,
+                       absl::conjunction<std::true_type, MyTrueType>>::value));
+}
+
+TEST(DisjunctionTest, BasicBooleanLogic) {
+  EXPECT_FALSE(absl::disjunction<>::value);
+  EXPECT_FALSE(absl::disjunction<std::false_type>::value);
+  EXPECT_TRUE((absl::disjunction<std::true_type, std::true_type>::value));
+  EXPECT_TRUE((absl::disjunction<std::true_type, std::false_type>::value));
+  EXPECT_TRUE((absl::disjunction<std::false_type, std::true_type>::value));
+  EXPECT_FALSE((absl::disjunction<std::false_type, std::false_type>::value));
+}
+
+TEST(DisjunctionTest, ShortCircuiting) {
+  EXPECT_TRUE(
+      (absl::disjunction<std::false_type, std::true_type, Dummy>::value));
+  EXPECT_TRUE((
+      std::is_base_of<MyTrueType, absl::disjunction<std::false_type, MyTrueType,
+                                                    std::true_type>>::value));
+  EXPECT_TRUE((
+      std::is_base_of<MyFalseType,
+                      absl::disjunction<std::false_type, MyFalseType>>::value));
+}
+
+TEST(NegationTest, BasicBooleanLogic) {
+  EXPECT_FALSE(absl::negation<std::true_type>::value);
+  EXPECT_FALSE(absl::negation<MyTrueType>::value);
+  EXPECT_TRUE(absl::negation<std::false_type>::value);
+  EXPECT_TRUE(absl::negation<MyFalseType>::value);
+}
+
+// all member functions are trivial
+class Trivial {
+  int n_;
+};
+
+struct TrivialDestructor {
+  ~TrivialDestructor() = default;
+};
+
+struct NontrivialDestructor {
+  ~NontrivialDestructor() {}
+};
+
+struct DeletedDestructor {
+  ~DeletedDestructor() = delete;
+};
+
+class TrivialDefaultCtor {
+ public:
+  TrivialDefaultCtor() = default;
+  explicit TrivialDefaultCtor(int n) : n_(n) {}
+
+ private:
+  int n_;
+};
+
+class NontrivialDefaultCtor {
+ public:
+  NontrivialDefaultCtor() : n_(1) {}
+
+ private:
+  int n_;
+};
+
+class DeletedDefaultCtor {
+ public:
+  DeletedDefaultCtor() = delete;
+  explicit DeletedDefaultCtor(int n) : n_(n) {}
+
+ private:
+  int n_;
+};
+
+class TrivialMoveCtor {
+ public:
+  explicit TrivialMoveCtor(int n) : n_(n) {}
+  TrivialMoveCtor(TrivialMoveCtor&&) = default;
+  TrivialMoveCtor& operator=(const TrivialMoveCtor& t) {
+    n_ = t.n_;
+    return *this;
+  }
+
+ private:
+  int n_;
+};
+
+class NontrivialMoveCtor {
+ public:
+  explicit NontrivialMoveCtor(int n) : n_(n) {}
+  NontrivialMoveCtor(NontrivialMoveCtor&& t) noexcept : n_(t.n_) {}
+  NontrivialMoveCtor& operator=(const NontrivialMoveCtor&) = default;
+
+ private:
+  int n_;
+};
+
+class TrivialCopyCtor {
+ public:
+  explicit TrivialCopyCtor(int n) : n_(n) {}
+  TrivialCopyCtor(const TrivialCopyCtor&) = default;
+  TrivialCopyCtor& operator=(const TrivialCopyCtor& t) {
+    n_ = t.n_;
+    return *this;
+  }
+
+ private:
+  int n_;
+};
+
+class NontrivialCopyCtor {
+ public:
+  explicit NontrivialCopyCtor(int n) : n_(n) {}
+  NontrivialCopyCtor(const NontrivialCopyCtor& t) : n_(t.n_) {}
+  NontrivialCopyCtor& operator=(const NontrivialCopyCtor&) = default;
+
+ private:
+  int n_;
+};
+
+class DeletedCopyCtor {
+ public:
+  explicit DeletedCopyCtor(int n) : n_(n) {}
+  DeletedCopyCtor(const DeletedCopyCtor&) = delete;
+  DeletedCopyCtor& operator=(const DeletedCopyCtor&) = default;
+
+ private:
+  int n_;
+};
+
+class TrivialMoveAssign {
+ public:
+  explicit TrivialMoveAssign(int n) : n_(n) {}
+  TrivialMoveAssign(const TrivialMoveAssign& t) : n_(t.n_) {}
+  TrivialMoveAssign& operator=(TrivialMoveAssign&&) = default;
+  ~TrivialMoveAssign() {}  // can have nontrivial destructor
+ private:
+  int n_;
+};
+
+class NontrivialMoveAssign {
+ public:
+  explicit NontrivialMoveAssign(int n) : n_(n) {}
+  NontrivialMoveAssign(const NontrivialMoveAssign&) = default;
+  NontrivialMoveAssign& operator=(NontrivialMoveAssign&& t) noexcept {
+    n_ = t.n_;
+    return *this;
+  }
+
+ private:
+  int n_;
+};
+
+class TrivialCopyAssign {
+ public:
+  explicit TrivialCopyAssign(int n) : n_(n) {}
+  TrivialCopyAssign(const TrivialCopyAssign& t) : n_(t.n_) {}
+  TrivialCopyAssign& operator=(const TrivialCopyAssign& t) = default;
+  ~TrivialCopyAssign() {}  // can have nontrivial destructor
+ private:
+  int n_;
+};
+
+class NontrivialCopyAssign {
+ public:
+  explicit NontrivialCopyAssign(int n) : n_(n) {}
+  NontrivialCopyAssign(const NontrivialCopyAssign&) = default;
+  NontrivialCopyAssign& operator=(const NontrivialCopyAssign& t) {
+    n_ = t.n_;
+    return *this;
+  }
+
+ private:
+  int n_;
+};
+
+class DeletedCopyAssign {
+ public:
+  explicit DeletedCopyAssign(int n) : n_(n) {}
+  DeletedCopyAssign(const DeletedCopyAssign&) = default;
+  DeletedCopyAssign& operator=(const DeletedCopyAssign&) = delete;
+
+ private:
+  int n_;
+};
+
+struct MovableNonCopyable {
+  MovableNonCopyable() = default;
+  MovableNonCopyable(const MovableNonCopyable&) = delete;
+  MovableNonCopyable(MovableNonCopyable&&) = default;
+  MovableNonCopyable& operator=(const MovableNonCopyable&) = delete;
+  MovableNonCopyable& operator=(MovableNonCopyable&&) = default;
+};
+
+struct NonCopyableOrMovable {
+  NonCopyableOrMovable() = default;
+  virtual ~NonCopyableOrMovable() = default;
+  NonCopyableOrMovable(const NonCopyableOrMovable&) = delete;
+  NonCopyableOrMovable(NonCopyableOrMovable&&) = delete;
+  NonCopyableOrMovable& operator=(const NonCopyableOrMovable&) = delete;
+  NonCopyableOrMovable& operator=(NonCopyableOrMovable&&) = delete;
+};
+
+class Base {
+ public:
+  virtual ~Base() {}
+};
+
+TEST(TypeTraitsTest, TestIsFunction) {
+  struct Callable {
+    void operator()() {}
+  };
+  EXPECT_TRUE(absl::is_function<void()>::value);
+  EXPECT_TRUE(absl::is_function<void()&>::value);
+  EXPECT_TRUE(absl::is_function<void() const>::value);
+  EXPECT_TRUE(absl::is_function<void() noexcept>::value);
+  EXPECT_TRUE(absl::is_function<void(...) noexcept>::value);
+
+  EXPECT_FALSE(absl::is_function<void(*)()>::value);
+  EXPECT_FALSE(absl::is_function<void(&)()>::value);
+  EXPECT_FALSE(absl::is_function<int>::value);
+  EXPECT_FALSE(absl::is_function<Callable>::value);
+}
+
+TEST(TypeTraitsTest, TestRemoveCVRef) {
+  EXPECT_TRUE(
+      (std::is_same<typename absl::remove_cvref<int>::type, int>::value));
+  EXPECT_TRUE(
+      (std::is_same<typename absl::remove_cvref<int&>::type, int>::value));
+  EXPECT_TRUE(
+      (std::is_same<typename absl::remove_cvref<int&&>::type, int>::value));
+  EXPECT_TRUE((
+      std::is_same<typename absl::remove_cvref<const int&>::type, int>::value));
+  EXPECT_TRUE(
+      (std::is_same<typename absl::remove_cvref<int*>::type, int*>::value));
+  // Does not remove const in this case.
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<const int*>::type,
+                            const int*>::value));
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<int[2]>::type,
+                            int[2]>::value));
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<int(&)[2]>::type,
+                            int[2]>::value));
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<int(&&)[2]>::type,
+                            int[2]>::value));
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<const int[2]>::type,
+                            int[2]>::value));
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<const int(&)[2]>::type,
+                            int[2]>::value));
+  EXPECT_TRUE((std::is_same<typename absl::remove_cvref<const int(&&)[2]>::type,
+                            int[2]>::value));
+}
+
+#define ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(trait_name, ...)          \
+  EXPECT_TRUE((std::is_same<typename std::trait_name<__VA_ARGS__>::type, \
+                            absl::trait_name##_t<__VA_ARGS__>>::value))
+
+TEST(TypeTraitsTest, TestRemoveCVAliases) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, const volatile int);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, const volatile int);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, const volatile int);
+}
+
+TEST(TypeTraitsTest, TestAddCVAliases) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, const volatile int);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, const volatile int);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, const volatile int);
+}
+
+TEST(TypeTraitsTest, TestReferenceAliases) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, volatile int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, int&&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, volatile int&&);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, volatile int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, int&&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, volatile int&&);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, volatile int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, int&&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, volatile int&&);
+}
+
+TEST(TypeTraitsTest, TestPointerAliases) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_pointer, int*);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_pointer, volatile int*);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_pointer, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_pointer, volatile int);
+}
+
+TEST(TypeTraitsTest, TestSignednessAliases) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, unsigned);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, volatile unsigned);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, unsigned);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, volatile unsigned);
+}
+
+TEST(TypeTraitsTest, TestExtentAliases) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[1]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[1][1]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[][1]);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[1]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[1][1]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[][1]);
+}
+
+TEST(TypeTraitsTest, TestAlignedStorageAlias) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 1);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 2);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 3);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 4);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 5);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 6);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 7);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 8);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 9);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 10);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 11);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 12);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 13);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 14);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 15);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 16);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 17);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 18);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 19);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 20);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 21);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 22);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 23);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 24);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 25);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 26);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 27);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 28);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 29);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 30);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 31);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 32);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 33);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 1, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 2, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 3, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 4, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 5, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 6, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 7, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 8, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 9, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 10, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 11, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 12, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 13, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 14, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 15, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 16, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 17, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 18, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 19, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 20, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 21, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 22, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 23, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 24, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 25, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 26, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 27, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 28, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 29, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 30, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 31, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 32, 128);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 33, 128);
+}
+
+TEST(TypeTraitsTest, TestDecay) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, volatile int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const volatile int);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, volatile int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const volatile int&);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, volatile int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const volatile int&);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[1]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[1][1]);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[][1]);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int());
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(float));  // NOLINT
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(char, ...));  // NOLINT
+}
+
+struct TypeA {};
+struct TypeB {};
+struct TypeC {};
+struct TypeD {};
+
+template <typename T>
+struct Wrap {};
+
+enum class TypeEnum { A, B, C, D };
+
+struct GetTypeT {
+  template <typename T,
+            absl::enable_if_t<std::is_same<T, TypeA>::value, int> = 0>
+  TypeEnum operator()(Wrap<T>) const {
+    return TypeEnum::A;
+  }
+
+  template <typename T,
+            absl::enable_if_t<std::is_same<T, TypeB>::value, int> = 0>
+  TypeEnum operator()(Wrap<T>) const {
+    return TypeEnum::B;
+  }
+
+  template <typename T,
+            absl::enable_if_t<std::is_same<T, TypeC>::value, int> = 0>
+  TypeEnum operator()(Wrap<T>) const {
+    return TypeEnum::C;
+  }
+
+  // NOTE: TypeD is intentionally not handled
+} constexpr GetType = {};
+
+TEST(TypeTraitsTest, TestEnableIf) {
+  EXPECT_EQ(TypeEnum::A, GetType(Wrap<TypeA>()));
+  EXPECT_EQ(TypeEnum::B, GetType(Wrap<TypeB>()));
+  EXPECT_EQ(TypeEnum::C, GetType(Wrap<TypeC>()));
+}
+
+TEST(TypeTraitsTest, TestConditional) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(conditional, true, int, char);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(conditional, false, int, char);
+}
+
+// TODO(calabrese) Check with specialized std::common_type
+TEST(TypeTraitsTest, TestCommonType) {
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char, int);
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char&);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char, int&);
+}
+
+TEST(TypeTraitsTest, TestUnderlyingType) {
+  enum class enum_char : char {};
+  enum class enum_long_long : long long {};  // NOLINT(runtime/int)
+
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(underlying_type, enum_char);
+  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(underlying_type, enum_long_long);
+}
+
+struct GetTypeExtT {
+  template <typename T>
+  absl::result_of_t<const GetTypeT&(T)> operator()(T&& arg) const {
+    return GetType(std::forward<T>(arg));
+  }
+
+  TypeEnum operator()(Wrap<TypeD>) const { return TypeEnum::D; }
+} constexpr GetTypeExt = {};
+
+TEST(TypeTraitsTest, TestResultOf) {
+  EXPECT_EQ(TypeEnum::A, GetTypeExt(Wrap<TypeA>()));
+  EXPECT_EQ(TypeEnum::B, GetTypeExt(Wrap<TypeB>()));
+  EXPECT_EQ(TypeEnum::C, GetTypeExt(Wrap<TypeC>()));
+  EXPECT_EQ(TypeEnum::D, GetTypeExt(Wrap<TypeD>()));
+}
+
+namespace adl_namespace {
+
+struct DeletedSwap {
+};
+
+void swap(DeletedSwap&, DeletedSwap&) = delete;
+
+struct SpecialNoexceptSwap {
+  SpecialNoexceptSwap(SpecialNoexceptSwap&&) {}
+  SpecialNoexceptSwap& operator=(SpecialNoexceptSwap&&) { return *this; }
+  ~SpecialNoexceptSwap() = default;
+};
+
+void swap(SpecialNoexceptSwap&, SpecialNoexceptSwap&) noexcept {}
+
+}  // namespace adl_namespace
+
+TEST(TypeTraitsTest, IsSwappable) {
+  using absl::type_traits_internal::IsSwappable;
+  using absl::type_traits_internal::StdSwapIsUnconstrained;
+
+  EXPECT_TRUE(IsSwappable<int>::value);
+
+  struct S {};
+  EXPECT_TRUE(IsSwappable<S>::value);
+
+  struct NoConstruct {
+    NoConstruct(NoConstruct&&) = delete;
+    NoConstruct& operator=(NoConstruct&&) { return *this; }
+    ~NoConstruct() = default;
+  };
+
+  EXPECT_EQ(IsSwappable<NoConstruct>::value, StdSwapIsUnconstrained::value);
+  struct NoAssign {
+    NoAssign(NoAssign&&) {}
+    NoAssign& operator=(NoAssign&&) = delete;
+    ~NoAssign() = default;
+  };
+
+  EXPECT_EQ(IsSwappable<NoAssign>::value, StdSwapIsUnconstrained::value);
+
+  EXPECT_FALSE(IsSwappable<adl_namespace::DeletedSwap>::value);
+
+  EXPECT_TRUE(IsSwappable<adl_namespace::SpecialNoexceptSwap>::value);
+}
+
+TEST(TypeTraitsTest, IsNothrowSwappable) {
+  using absl::type_traits_internal::IsNothrowSwappable;
+  using absl::type_traits_internal::StdSwapIsUnconstrained;
+
+  EXPECT_TRUE(IsNothrowSwappable<int>::value);
+
+  struct NonNoexceptMoves {
+    NonNoexceptMoves(NonNoexceptMoves&&) {}
+    NonNoexceptMoves& operator=(NonNoexceptMoves&&) { return *this; }
+    ~NonNoexceptMoves() = default;
+  };
+
+  EXPECT_FALSE(IsNothrowSwappable<NonNoexceptMoves>::value);
+
+  struct NoConstruct {
+    NoConstruct(NoConstruct&&) = delete;
+    NoConstruct& operator=(NoConstruct&&) { return *this; }
+    ~NoConstruct() = default;
+  };
+
+  EXPECT_FALSE(IsNothrowSwappable<NoConstruct>::value);
+
+  struct NoAssign {
+    NoAssign(NoAssign&&) {}
+    NoAssign& operator=(NoAssign&&) = delete;
+    ~NoAssign() = default;
+  };
+
+  EXPECT_FALSE(IsNothrowSwappable<NoAssign>::value);
+
+  EXPECT_FALSE(IsNothrowSwappable<adl_namespace::DeletedSwap>::value);
+
+  EXPECT_TRUE(IsNothrowSwappable<adl_namespace::SpecialNoexceptSwap>::value);
+}
+
+TEST(TriviallyRelocatable, PrimitiveTypes) {
+  static_assert(absl::is_trivially_relocatable<int>::value, "");
+  static_assert(absl::is_trivially_relocatable<char>::value, "");
+  static_assert(absl::is_trivially_relocatable<void*>::value, "");
+}
+
+// User-defined types can be trivially relocatable as long as they don't have a
+// user-provided move constructor or destructor.
+TEST(TriviallyRelocatable, UserDefinedTriviallyReconstructible) {
+  struct S {
+    int x;
+    int y;
+  };
+
+  static_assert(absl::is_trivially_relocatable<S>::value, "");
+}
+
+// A user-provided move constructor disqualifies a type from being trivially
+// relocatable.
+TEST(TriviallyRelocatable, UserProvidedMoveConstructor) {
+  struct S {
+    S(S&&) {}  // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(!absl::is_trivially_relocatable<S>::value, "");
+}
+
+// A user-provided copy constructor disqualifies a type from being trivially
+// relocatable.
+TEST(TriviallyRelocatable, UserProvidedCopyConstructor) {
+  struct S {
+    S(const S&) {}  // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(!absl::is_trivially_relocatable<S>::value, "");
+}
+
+// A user-provided destructor disqualifies a type from being trivially
+// relocatable.
+TEST(TriviallyRelocatable, UserProvidedDestructor) {
+  struct S {
+    ~S() {}  // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(!absl::is_trivially_relocatable<S>::value, "");
+}
+
+// TODO(b/275003464): remove the opt-out for Clang on Windows once
+// __is_trivially_relocatable is used there again.
+#if defined(ABSL_HAVE_ATTRIBUTE_TRIVIAL_ABI) &&      \
+    ABSL_HAVE_BUILTIN(__is_trivially_relocatable) && \
+    !(defined(__clang__) && (defined(_WIN32) || defined(_WIN64)))
+// A type marked with the "trivial ABI" attribute is trivially relocatable even
+// if it has user-provided move/copy constructors and a user-provided
+// destructor.
+TEST(TrivallyRelocatable, TrivialAbi) {
+  struct ABSL_ATTRIBUTE_TRIVIAL_ABI S {
+    S(S&&) {}       // NOLINT(modernize-use-equals-default)
+    S(const S&) {}  // NOLINT(modernize-use-equals-default)
+    ~S() {}         // NOLINT(modernize-use-equals-default)
+  };
+
+  static_assert(absl::is_trivially_relocatable<S>::value, "");
+}
+#endif
+
+#ifdef ABSL_HAVE_CONSTANT_EVALUATED
+
+constexpr int64_t NegateIfConstantEvaluated(int64_t i) {
+  if (absl::is_constant_evaluated()) {
+    return -i;
+  } else {
+    return i;
+  }
+}
+
+#endif  // ABSL_HAVE_CONSTANT_EVALUATED
+
+TEST(TrivallyRelocatable, is_constant_evaluated) {
+#ifdef ABSL_HAVE_CONSTANT_EVALUATED
+  constexpr int64_t constant = NegateIfConstantEvaluated(42);
+  EXPECT_EQ(constant, -42);
+
+  int64_t now = absl::ToUnixSeconds(absl::Now());
+  int64_t not_constant = NegateIfConstantEvaluated(now);
+  EXPECT_EQ(not_constant, now);
+
+  static int64_t const_init = NegateIfConstantEvaluated(42);
+  EXPECT_EQ(const_init, -42);
+#else
+  GTEST_SKIP() << "absl::is_constant_evaluated is not defined";
+#endif  // ABSL_HAVE_CONSTANT_EVALUATED
+}
+
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/numeric/BUILD.bazel b/weight/_dep/abseil-cpp/absl/numeric/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..db02b9c047be6edf1edce217c47dc885d5beadc9
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/BUILD.bazel
@@ -0,0 +1,139 @@
+# Copyright 2018 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "bits",
+    hdrs = [
+        "bits.h",
+        "internal/bits.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_binary(
+    name = "bits_benchmark",
+    testonly = 1,
+    srcs = ["bits_benchmark.cc"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":bits",
+        "//absl/base:core_headers",
+        "//absl/random",
+        "@com_github_google_benchmark//:benchmark_main",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_test(
+    name = "bits_test",
+    size = "small",
+    srcs = [
+        "bits_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":bits",
+        "//absl/random",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "int128",
+    srcs = [
+        "int128.cc",
+        "int128_have_intrinsic.inc",
+        "int128_no_intrinsic.inc",
+    ],
+    hdrs = ["int128.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":bits",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "int128_test",
+    size = "small",
+    srcs = [
+        "int128_stream_test.cc",
+        "int128_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":int128",
+        "//absl/base",
+        "//absl/hash:hash_testing",
+        "//absl/meta:type_traits",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "int128_benchmark",
+    srcs = ["int128_benchmark.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    deps = [
+        ":int128",
+        "//absl/base:config",
+        "@com_github_google_benchmark//:benchmark_main",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_library(
+    name = "representation",
+    hdrs = [
+        "internal/representation.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/numeric/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/numeric/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..7181b91ab5a8f24ab64a1f22fee06362186ddf5b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/CMakeLists.txt
@@ -0,0 +1,100 @@
+#
+# Copyright 2017 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+absl_cc_library(
+  NAME
+    bits
+  HDRS
+    "bits.h"
+    "internal/bits.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::core_headers
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    bits_test
+  SRCS
+    "bits_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::bits
+    absl::core_headers
+    absl::random_random
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    int128
+  HDRS
+    "int128.h"
+  SRCS
+    "int128.cc"
+    "int128_have_intrinsic.inc"
+    "int128_no_intrinsic.inc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+    absl::bits
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    int128_test
+  SRCS
+    "int128_stream_test.cc"
+    "int128_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::int128
+    absl::base
+    absl::hash_testing
+    absl::type_traits
+    absl::strings
+    GTest::gmock_main
+)
+
+# component target
+absl_cc_library(
+  NAME
+    numeric
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::int128
+  PUBLIC
+)
+
+absl_cc_library(
+  NAME
+    numeric_representation
+  HDRS
+    "internal/representation.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+  PUBLIC
+)
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128.cc b/weight/_dep/abseil-cpp/absl/numeric/int128.cc
new file mode 100644
index 0000000000000000000000000000000000000000..daa32b518338ad2063c564701d629a8ccefe9b05
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128.cc
@@ -0,0 +1,399 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/numeric/int128.h"
+
+#include <stddef.h>
+
+#include <cassert>
+#include <iomanip>
+#include <ostream>  // NOLINT(readability/streams)
+#include <sstream>
+#include <string>
+#include <type_traits>
+
+#include "absl/base/optimization.h"
+#include "absl/numeric/bits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+ABSL_DLL const uint128 kuint128max = MakeUint128(
+    std::numeric_limits<uint64_t>::max(), std::numeric_limits<uint64_t>::max());
+
+namespace {
+
+// Returns the 0-based position of the last set bit (i.e., most significant bit)
+// in the given uint128. The argument is not 0.
+//
+// For example:
+//   Given: 5 (decimal) == 101 (binary)
+//   Returns: 2
+inline ABSL_ATTRIBUTE_ALWAYS_INLINE int Fls128(uint128 n) {
+  if (uint64_t hi = Uint128High64(n)) {
+    ABSL_ASSUME(hi != 0);
+    return 127 - countl_zero(hi);
+  }
+  const uint64_t low = Uint128Low64(n);
+  ABSL_ASSUME(low != 0);
+  return 63 - countl_zero(low);
+}
+
+// Long division/modulo for uint128 implemented using the shift-subtract
+// division algorithm adapted from:
+// https://stackoverflow.com/questions/5386377/division-without-using
+inline void DivModImpl(uint128 dividend, uint128 divisor, uint128* quotient_ret,
+                       uint128* remainder_ret) {
+  assert(divisor != 0);
+
+  if (divisor > dividend) {
+    *quotient_ret = 0;
+    *remainder_ret = dividend;
+    return;
+  }
+
+  if (divisor == dividend) {
+    *quotient_ret = 1;
+    *remainder_ret = 0;
+    return;
+  }
+
+  uint128 denominator = divisor;
+  uint128 quotient = 0;
+
+  // Left aligns the MSB of the denominator and the dividend.
+  const int shift = Fls128(dividend) - Fls128(denominator);
+  denominator <<= shift;
+
+  // Uses shift-subtract algorithm to divide dividend by denominator. The
+  // remainder will be left in dividend.
+  for (int i = 0; i <= shift; ++i) {
+    quotient <<= 1;
+    if (dividend >= denominator) {
+      dividend -= denominator;
+      quotient |= 1;
+    }
+    denominator >>= 1;
+  }
+
+  *quotient_ret = quotient;
+  *remainder_ret = dividend;
+}
+
+template <typename T>
+uint128 MakeUint128FromFloat(T v) {
+  static_assert(std::is_floating_point<T>::value, "");
+
+  // Rounding behavior is towards zero, same as for built-in types.
+
+  // Undefined behavior if v is NaN or cannot fit into uint128.
+  assert(std::isfinite(v) && v > -1 &&
+         (std::numeric_limits<T>::max_exponent <= 128 ||
+          v < std::ldexp(static_cast<T>(1), 128)));
+
+  if (v >= std::ldexp(static_cast<T>(1), 64)) {
+    uint64_t hi = static_cast<uint64_t>(std::ldexp(v, -64));
+    uint64_t lo = static_cast<uint64_t>(v - std::ldexp(static_cast<T>(hi), 64));
+    return MakeUint128(hi, lo);
+  }
+
+  return MakeUint128(0, static_cast<uint64_t>(v));
+}
+
+#if defined(__clang__) && (__clang_major__ < 9) && !defined(__SSE3__)
+// Workaround for clang bug: https://bugs.llvm.org/show_bug.cgi?id=38289
+// Casting from long double to uint64_t is miscompiled and drops bits.
+// It is more work, so only use when we need the workaround.
+uint128 MakeUint128FromFloat(long double v) {
+  // Go 50 bits at a time, that fits in a double
+  static_assert(std::numeric_limits<double>::digits >= 50, "");
+  static_assert(std::numeric_limits<long double>::digits <= 150, "");
+  // Undefined behavior if v is not finite or cannot fit into uint128.
+  assert(std::isfinite(v) && v > -1 && v < std::ldexp(1.0L, 128));
+
+  v = std::ldexp(v, -100);
+  uint64_t w0 = static_cast<uint64_t>(static_cast<double>(std::trunc(v)));
+  v = std::ldexp(v - static_cast<double>(w0), 50);
+  uint64_t w1 = static_cast<uint64_t>(static_cast<double>(std::trunc(v)));
+  v = std::ldexp(v - static_cast<double>(w1), 50);
+  uint64_t w2 = static_cast<uint64_t>(static_cast<double>(std::trunc(v)));
+  return (static_cast<uint128>(w0) << 100) | (static_cast<uint128>(w1) << 50) |
+         static_cast<uint128>(w2);
+}
+#endif  // __clang__ && (__clang_major__ < 9) && !__SSE3__
+}  // namespace
+
+uint128::uint128(float v) : uint128(MakeUint128FromFloat(v)) {}
+uint128::uint128(double v) : uint128(MakeUint128FromFloat(v)) {}
+uint128::uint128(long double v) : uint128(MakeUint128FromFloat(v)) {}
+
+#if !defined(ABSL_HAVE_INTRINSIC_INT128)
+uint128 operator/(uint128 lhs, uint128 rhs) {
+  uint128 quotient = 0;
+  uint128 remainder = 0;
+  DivModImpl(lhs, rhs, &quotient, &remainder);
+  return quotient;
+}
+
+uint128 operator%(uint128 lhs, uint128 rhs) {
+  uint128 quotient = 0;
+  uint128 remainder = 0;
+  DivModImpl(lhs, rhs, &quotient, &remainder);
+  return remainder;
+}
+#endif  // !defined(ABSL_HAVE_INTRINSIC_INT128)
+
+namespace {
+
+std::string Uint128ToFormattedString(uint128 v, std::ios_base::fmtflags flags) {
+  // Select a divisor which is the largest power of the base < 2^64.
+  uint128 div;
+  int div_base_log;
+  switch (flags & std::ios::basefield) {
+    case std::ios::hex:
+      div = 0x1000000000000000;  // 16^15
+      div_base_log = 15;
+      break;
+    case std::ios::oct:
+      div = 01000000000000000000000;  // 8^21
+      div_base_log = 21;
+      break;
+    default:  // std::ios::dec
+      div = 10000000000000000000u;  // 10^19
+      div_base_log = 19;
+      break;
+  }
+
+  // Now piece together the uint128 representation from three chunks of the
+  // original value, each less than "div" and therefore representable as a
+  // uint64_t.
+  std::ostringstream os;
+  std::ios_base::fmtflags copy_mask =
+      std::ios::basefield | std::ios::showbase | std::ios::uppercase;
+  os.setf(flags & copy_mask, copy_mask);
+  uint128 high = v;
+  uint128 low;
+  DivModImpl(high, div, &high, &low);
+  uint128 mid;
+  DivModImpl(high, div, &high, &mid);
+  if (Uint128Low64(high) != 0) {
+    os << Uint128Low64(high);
+    os << std::noshowbase << std::setfill('0') << std::setw(div_base_log);
+    os << Uint128Low64(mid);
+    os << std::setw(div_base_log);
+  } else if (Uint128Low64(mid) != 0) {
+    os << Uint128Low64(mid);
+    os << std::noshowbase << std::setfill('0') << std::setw(div_base_log);
+  }
+  os << Uint128Low64(low);
+  return os.str();
+}
+
+}  // namespace
+
+std::string uint128::ToString() const {
+  return Uint128ToFormattedString(*this, std::ios_base::dec);
+}
+
+std::ostream& operator<<(std::ostream& os, uint128 v) {
+  std::ios_base::fmtflags flags = os.flags();
+  std::string rep = Uint128ToFormattedString(v, flags);
+
+  // Add the requisite padding.
+  std::streamsize width = os.width(0);
+  if (static_cast<size_t>(width) > rep.size()) {
+    const size_t count = static_cast<size_t>(width) - rep.size();
+    std::ios::fmtflags adjustfield = flags & std::ios::adjustfield;
+    if (adjustfield == std::ios::left) {
+      rep.append(count, os.fill());
+    } else if (adjustfield == std::ios::internal &&
+               (flags & std::ios::showbase) &&
+               (flags & std::ios::basefield) == std::ios::hex && v != 0) {
+      rep.insert(size_t{2}, count, os.fill());
+    } else {
+      rep.insert(size_t{0}, count, os.fill());
+    }
+  }
+
+  return os << rep;
+}
+
+namespace {
+
+uint128 UnsignedAbsoluteValue(int128 v) {
+  // Cast to uint128 before possibly negating because -Int128Min() is undefined.
+  return Int128High64(v) < 0 ? -uint128(v) : uint128(v);
+}
+
+}  // namespace
+
+#if !defined(ABSL_HAVE_INTRINSIC_INT128)
+namespace {
+
+template <typename T>
+int128 MakeInt128FromFloat(T v) {
+  // Conversion when v is NaN or cannot fit into int128 would be undefined
+  // behavior if using an intrinsic 128-bit integer.
+  assert(std::isfinite(v) && (std::numeric_limits<T>::max_exponent <= 127 ||
+                              (v >= -std::ldexp(static_cast<T>(1), 127) &&
+                               v < std::ldexp(static_cast<T>(1), 127))));
+
+  // We must convert the absolute value and then negate as needed, because
+  // floating point types are typically sign-magnitude. Otherwise, the
+  // difference between the high and low 64 bits when interpreted as two's
+  // complement overwhelms the precision of the mantissa.
+  uint128 result = v < 0 ? -MakeUint128FromFloat(-v) : MakeUint128FromFloat(v);
+  return MakeInt128(int128_internal::BitCastToSigned(Uint128High64(result)),
+                    Uint128Low64(result));
+}
+
+}  // namespace
+
+int128::int128(float v) : int128(MakeInt128FromFloat(v)) {}
+int128::int128(double v) : int128(MakeInt128FromFloat(v)) {}
+int128::int128(long double v) : int128(MakeInt128FromFloat(v)) {}
+
+int128 operator/(int128 lhs, int128 rhs) {
+  assert(lhs != Int128Min() || rhs != -1);  // UB on two's complement.
+
+  uint128 quotient = 0;
+  uint128 remainder = 0;
+  DivModImpl(UnsignedAbsoluteValue(lhs), UnsignedAbsoluteValue(rhs),
+             &quotient, &remainder);
+  if ((Int128High64(lhs) < 0) != (Int128High64(rhs) < 0)) quotient = -quotient;
+  return MakeInt128(int128_internal::BitCastToSigned(Uint128High64(quotient)),
+                    Uint128Low64(quotient));
+}
+
+int128 operator%(int128 lhs, int128 rhs) {
+  assert(lhs != Int128Min() || rhs != -1);  // UB on two's complement.
+
+  uint128 quotient = 0;
+  uint128 remainder = 0;
+  DivModImpl(UnsignedAbsoluteValue(lhs), UnsignedAbsoluteValue(rhs),
+             &quotient, &remainder);
+  if (Int128High64(lhs) < 0) remainder = -remainder;
+  return MakeInt128(int128_internal::BitCastToSigned(Uint128High64(remainder)),
+                    Uint128Low64(remainder));
+}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+std::string int128::ToString() const {
+  std::string rep;
+  if (Int128High64(*this) < 0) rep = "-";
+  rep.append(Uint128ToFormattedString(UnsignedAbsoluteValue(*this),
+                                      std::ios_base::dec));
+  return rep;
+}
+
+std::ostream& operator<<(std::ostream& os, int128 v) {
+  std::ios_base::fmtflags flags = os.flags();
+  std::string rep;
+
+  // Add the sign if needed.
+  bool print_as_decimal =
+      (flags & std::ios::basefield) == std::ios::dec ||
+      (flags & std::ios::basefield) == std::ios_base::fmtflags();
+  if (print_as_decimal) {
+    if (Int128High64(v) < 0) {
+      rep = "-";
+    } else if (flags & std::ios::showpos) {
+      rep = "+";
+    }
+  }
+
+  rep.append(Uint128ToFormattedString(
+      print_as_decimal ? UnsignedAbsoluteValue(v) : uint128(v), os.flags()));
+
+  // Add the requisite padding.
+  std::streamsize width = os.width(0);
+  if (static_cast<size_t>(width) > rep.size()) {
+    const size_t count = static_cast<size_t>(width) - rep.size();
+    switch (flags & std::ios::adjustfield) {
+      case std::ios::left:
+        rep.append(count, os.fill());
+        break;
+      case std::ios::internal:
+        if (print_as_decimal && (rep[0] == '+' || rep[0] == '-')) {
+          rep.insert(size_t{1}, count, os.fill());
+        } else if ((flags & std::ios::basefield) == std::ios::hex &&
+                   (flags & std::ios::showbase) && v != 0) {
+          rep.insert(size_t{2}, count, os.fill());
+        } else {
+          rep.insert(size_t{0}, count, os.fill());
+        }
+        break;
+      default:  // std::ios::right
+        rep.insert(size_t{0}, count, os.fill());
+        break;
+    }
+  }
+
+  return os << rep;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+namespace std {
+constexpr bool numeric_limits<absl::uint128>::is_specialized;
+constexpr bool numeric_limits<absl::uint128>::is_signed;
+constexpr bool numeric_limits<absl::uint128>::is_integer;
+constexpr bool numeric_limits<absl::uint128>::is_exact;
+constexpr bool numeric_limits<absl::uint128>::has_infinity;
+constexpr bool numeric_limits<absl::uint128>::has_quiet_NaN;
+constexpr bool numeric_limits<absl::uint128>::has_signaling_NaN;
+constexpr float_denorm_style numeric_limits<absl::uint128>::has_denorm;
+constexpr bool numeric_limits<absl::uint128>::has_denorm_loss;
+constexpr float_round_style numeric_limits<absl::uint128>::round_style;
+constexpr bool numeric_limits<absl::uint128>::is_iec559;
+constexpr bool numeric_limits<absl::uint128>::is_bounded;
+constexpr bool numeric_limits<absl::uint128>::is_modulo;
+constexpr int numeric_limits<absl::uint128>::digits;
+constexpr int numeric_limits<absl::uint128>::digits10;
+constexpr int numeric_limits<absl::uint128>::max_digits10;
+constexpr int numeric_limits<absl::uint128>::radix;
+constexpr int numeric_limits<absl::uint128>::min_exponent;
+constexpr int numeric_limits<absl::uint128>::min_exponent10;
+constexpr int numeric_limits<absl::uint128>::max_exponent;
+constexpr int numeric_limits<absl::uint128>::max_exponent10;
+constexpr bool numeric_limits<absl::uint128>::traps;
+constexpr bool numeric_limits<absl::uint128>::tinyness_before;
+
+constexpr bool numeric_limits<absl::int128>::is_specialized;
+constexpr bool numeric_limits<absl::int128>::is_signed;
+constexpr bool numeric_limits<absl::int128>::is_integer;
+constexpr bool numeric_limits<absl::int128>::is_exact;
+constexpr bool numeric_limits<absl::int128>::has_infinity;
+constexpr bool numeric_limits<absl::int128>::has_quiet_NaN;
+constexpr bool numeric_limits<absl::int128>::has_signaling_NaN;
+constexpr float_denorm_style numeric_limits<absl::int128>::has_denorm;
+constexpr bool numeric_limits<absl::int128>::has_denorm_loss;
+constexpr float_round_style numeric_limits<absl::int128>::round_style;
+constexpr bool numeric_limits<absl::int128>::is_iec559;
+constexpr bool numeric_limits<absl::int128>::is_bounded;
+constexpr bool numeric_limits<absl::int128>::is_modulo;
+constexpr int numeric_limits<absl::int128>::digits;
+constexpr int numeric_limits<absl::int128>::digits10;
+constexpr int numeric_limits<absl::int128>::max_digits10;
+constexpr int numeric_limits<absl::int128>::radix;
+constexpr int numeric_limits<absl::int128>::min_exponent;
+constexpr int numeric_limits<absl::int128>::min_exponent10;
+constexpr int numeric_limits<absl::int128>::max_exponent;
+constexpr int numeric_limits<absl::int128>::max_exponent10;
+constexpr bool numeric_limits<absl::int128>::traps;
+constexpr bool numeric_limits<absl::int128>::tinyness_before;
+}  // namespace std
+#endif
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128.h b/weight/_dep/abseil-cpp/absl/numeric/int128.h
new file mode 100644
index 0000000000000000000000000000000000000000..7530a7934106420f81254c0de00140fb8f62d4a2
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128.h
@@ -0,0 +1,1162 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: int128.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines 128-bit integer types, `uint128` and `int128`.
+//
+// TODO(absl-team): This module is inconsistent as many inline `uint128` methods
+// are defined in this file, while many inline `int128` methods are defined in
+// the `int128_*_intrinsic.inc` files.
+
+#ifndef ABSL_NUMERIC_INT128_H_
+#define ABSL_NUMERIC_INT128_H_
+
+#include <cassert>
+#include <cmath>
+#include <cstdint>
+#include <cstring>
+#include <iosfwd>
+#include <limits>
+#include <string>
+#include <utility>
+
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+
+#if defined(_MSC_VER)
+// In very old versions of MSVC and when the /Zc:wchar_t flag is off, wchar_t is
+// a typedef for unsigned short.  Otherwise wchar_t is mapped to the __wchar_t
+// builtin type.  We need to make sure not to define operator wchar_t()
+// alongside operator unsigned short() in these instances.
+#define ABSL_INTERNAL_WCHAR_T __wchar_t
+#if defined(_M_X64) && !defined(_M_ARM64EC)
+#include <intrin.h>
+#pragma intrinsic(_umul128)
+#endif  // defined(_M_X64)
+#else   // defined(_MSC_VER)
+#define ABSL_INTERNAL_WCHAR_T wchar_t
+#endif  // defined(_MSC_VER)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+class int128;
+
+// uint128
+//
+// An unsigned 128-bit integer type. The API is meant to mimic an intrinsic type
+// as closely as is practical, including exhibiting undefined behavior in
+// analogous cases (e.g. division by zero). This type is intended to be a
+// drop-in replacement once C++ supports an intrinsic `uint128_t` type; when
+// that occurs, existing well-behaved uses of `uint128` will continue to work
+// using that new type.
+//
+// Note: code written with this type will continue to compile once `uint128_t`
+// is introduced, provided the replacement helper functions
+// `Uint128(Low|High)64()` and `MakeUint128()` are made.
+//
+// A `uint128` supports the following:
+//
+//   * Implicit construction from integral types
+//   * Explicit conversion to integral types
+//
+// Additionally, if your compiler supports `__int128`, `uint128` is
+// interoperable with that type. (Abseil checks for this compatibility through
+// the `ABSL_HAVE_INTRINSIC_INT128` macro.)
+//
+// However, a `uint128` differs from intrinsic integral types in the following
+// ways:
+//
+//   * Errors on implicit conversions that do not preserve value (such as
+//     loss of precision when converting to float values).
+//   * Requires explicit construction from and conversion to floating point
+//     types.
+//   * Conversion to integral types requires an explicit static_cast() to
+//     mimic use of the `-Wnarrowing` compiler flag.
+//   * The alignment requirement of `uint128` may differ from that of an
+//     intrinsic 128-bit integer type depending on platform and build
+//     configuration.
+//
+// Example:
+//
+//     float y = absl::Uint128Max();  // Error. uint128 cannot be implicitly
+//                                    // converted to float.
+//
+//     absl::uint128 v;
+//     uint64_t i = v;                         // Error
+//     uint64_t i = static_cast<uint64_t>(v);  // OK
+//
+class
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+    alignas(unsigned __int128)
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+        uint128 {
+ public:
+  uint128() = default;
+
+  // Constructors from arithmetic types
+  constexpr uint128(int v);                 // NOLINT(runtime/explicit)
+  constexpr uint128(unsigned int v);        // NOLINT(runtime/explicit)
+  constexpr uint128(long v);                // NOLINT(runtime/int)
+  constexpr uint128(unsigned long v);       // NOLINT(runtime/int)
+  constexpr uint128(long long v);           // NOLINT(runtime/int)
+  constexpr uint128(unsigned long long v);  // NOLINT(runtime/int)
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  constexpr uint128(__int128 v);           // NOLINT(runtime/explicit)
+  constexpr uint128(unsigned __int128 v);  // NOLINT(runtime/explicit)
+#endif                                     // ABSL_HAVE_INTRINSIC_INT128
+  constexpr uint128(int128 v);             // NOLINT(runtime/explicit)
+  explicit uint128(float v);
+  explicit uint128(double v);
+  explicit uint128(long double v);
+
+  // Assignment operators from arithmetic types
+  uint128& operator=(int v);
+  uint128& operator=(unsigned int v);
+  uint128& operator=(long v);                // NOLINT(runtime/int)
+  uint128& operator=(unsigned long v);       // NOLINT(runtime/int)
+  uint128& operator=(long long v);           // NOLINT(runtime/int)
+  uint128& operator=(unsigned long long v);  // NOLINT(runtime/int)
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  uint128& operator=(__int128 v);
+  uint128& operator=(unsigned __int128 v);
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+  uint128& operator=(int128 v);
+
+  // Conversion operators to other arithmetic types
+  constexpr explicit operator bool() const;
+  constexpr explicit operator char() const;
+  constexpr explicit operator signed char() const;
+  constexpr explicit operator unsigned char() const;
+  constexpr explicit operator char16_t() const;
+  constexpr explicit operator char32_t() const;
+  constexpr explicit operator ABSL_INTERNAL_WCHAR_T() const;
+  constexpr explicit operator short() const;  // NOLINT(runtime/int)
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator unsigned short() const;
+  constexpr explicit operator int() const;
+  constexpr explicit operator unsigned int() const;
+  constexpr explicit operator long() const;  // NOLINT(runtime/int)
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator unsigned long() const;
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator long long() const;
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator unsigned long long() const;
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  constexpr explicit operator __int128() const;
+  constexpr explicit operator unsigned __int128() const;
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+  explicit operator float() const;
+  explicit operator double() const;
+  explicit operator long double() const;
+
+  // Trivial copy constructor, assignment operator and destructor.
+
+  // Arithmetic operators.
+  uint128& operator+=(uint128 other);
+  uint128& operator-=(uint128 other);
+  uint128& operator*=(uint128 other);
+  // Long division/modulo for uint128.
+  uint128& operator/=(uint128 other);
+  uint128& operator%=(uint128 other);
+  uint128 operator++(int);
+  uint128 operator--(int);
+  uint128& operator<<=(int);
+  uint128& operator>>=(int);
+  uint128& operator&=(uint128 other);
+  uint128& operator|=(uint128 other);
+  uint128& operator^=(uint128 other);
+  uint128& operator++();
+  uint128& operator--();
+
+  // Uint128Low64()
+  //
+  // Returns the lower 64-bit value of a `uint128` value.
+  friend constexpr uint64_t Uint128Low64(uint128 v);
+
+  // Uint128High64()
+  //
+  // Returns the higher 64-bit value of a `uint128` value.
+  friend constexpr uint64_t Uint128High64(uint128 v);
+
+  // MakeUInt128()
+  //
+  // Constructs a `uint128` numeric value from two 64-bit unsigned integers.
+  // Note that this factory function is the only way to construct a `uint128`
+  // from integer values greater than 2^64.
+  //
+  // Example:
+  //
+  //   absl::uint128 big = absl::MakeUint128(1, 0);
+  friend constexpr uint128 MakeUint128(uint64_t high, uint64_t low);
+
+  // Uint128Max()
+  //
+  // Returns the highest value for a 128-bit unsigned integer.
+  friend constexpr uint128 Uint128Max();
+
+  // Support for absl::Hash.
+  template <typename H>
+  friend H AbslHashValue(H h, uint128 v) {
+    return H::combine(std::move(h), Uint128High64(v), Uint128Low64(v));
+  }
+
+  // Support for absl::StrCat() etc.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, uint128 v) {
+    sink.Append(v.ToString());
+  }
+
+ private:
+  constexpr uint128(uint64_t high, uint64_t low);
+
+  std::string ToString() const;
+
+  // TODO(strel) Update implementation to use __int128 once all users of
+  // uint128 are fixed to not depend on alignof(uint128) == 8. Also add
+  // alignas(16) to class definition to keep alignment consistent across
+  // platforms.
+#if defined(ABSL_IS_LITTLE_ENDIAN)
+  uint64_t lo_;
+  uint64_t hi_;
+#elif defined(ABSL_IS_BIG_ENDIAN)
+  uint64_t hi_;
+  uint64_t lo_;
+#else  // byte order
+#error "Unsupported byte order: must be little-endian or big-endian."
+#endif  // byte order
+};
+
+// Prefer to use the constexpr `Uint128Max()`.
+//
+// TODO(absl-team) deprecate kuint128max once migration tool is released.
+ABSL_DLL extern const uint128 kuint128max;
+
+// allow uint128 to be logged
+std::ostream& operator<<(std::ostream& os, uint128 v);
+
+// TODO(strel) add operator>>(std::istream&, uint128)
+
+constexpr uint128 Uint128Max() {
+  return uint128((std::numeric_limits<uint64_t>::max)(),
+                 (std::numeric_limits<uint64_t>::max)());
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// Specialized numeric_limits for uint128.
+namespace std {
+template <>
+class numeric_limits<absl::uint128> {
+ public:
+  static constexpr bool is_specialized = true;
+  static constexpr bool is_signed = false;
+  static constexpr bool is_integer = true;
+  static constexpr bool is_exact = true;
+  static constexpr bool has_infinity = false;
+  static constexpr bool has_quiet_NaN = false;
+  static constexpr bool has_signaling_NaN = false;
+  static constexpr float_denorm_style has_denorm = denorm_absent;
+  static constexpr bool has_denorm_loss = false;
+  static constexpr float_round_style round_style = round_toward_zero;
+  static constexpr bool is_iec559 = false;
+  static constexpr bool is_bounded = true;
+  static constexpr bool is_modulo = true;
+  static constexpr int digits = 128;
+  static constexpr int digits10 = 38;
+  static constexpr int max_digits10 = 0;
+  static constexpr int radix = 2;
+  static constexpr int min_exponent = 0;
+  static constexpr int min_exponent10 = 0;
+  static constexpr int max_exponent = 0;
+  static constexpr int max_exponent10 = 0;
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  static constexpr bool traps = numeric_limits<unsigned __int128>::traps;
+#else   // ABSL_HAVE_INTRINSIC_INT128
+  static constexpr bool traps = numeric_limits<uint64_t>::traps;
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+  static constexpr bool tinyness_before = false;
+
+  static constexpr absl::uint128(min)() { return 0; }
+  static constexpr absl::uint128 lowest() { return 0; }
+  static constexpr absl::uint128(max)() { return absl::Uint128Max(); }
+  static constexpr absl::uint128 epsilon() { return 0; }
+  static constexpr absl::uint128 round_error() { return 0; }
+  static constexpr absl::uint128 infinity() { return 0; }
+  static constexpr absl::uint128 quiet_NaN() { return 0; }
+  static constexpr absl::uint128 signaling_NaN() { return 0; }
+  static constexpr absl::uint128 denorm_min() { return 0; }
+};
+}  // namespace std
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// int128
+//
+// A signed 128-bit integer type. The API is meant to mimic an intrinsic
+// integral type as closely as is practical, including exhibiting undefined
+// behavior in analogous cases (e.g. division by zero).
+//
+// An `int128` supports the following:
+//
+//   * Implicit construction from integral types
+//   * Explicit conversion to integral types
+//
+// However, an `int128` differs from intrinsic integral types in the following
+// ways:
+//
+//   * It is not implicitly convertible to other integral types.
+//   * Requires explicit construction from and conversion to floating point
+//     types.
+
+// Additionally, if your compiler supports `__int128`, `int128` is
+// interoperable with that type. (Abseil checks for this compatibility through
+// the `ABSL_HAVE_INTRINSIC_INT128` macro.)
+//
+// The design goal for `int128` is that it will be compatible with a future
+// `int128_t`, if that type becomes a part of the standard.
+//
+// Example:
+//
+//     float y = absl::int128(17);  // Error. int128 cannot be implicitly
+//                                  // converted to float.
+//
+//     absl::int128 v;
+//     int64_t i = v;                        // Error
+//     int64_t i = static_cast<int64_t>(v);  // OK
+//
+class int128 {
+ public:
+  int128() = default;
+
+  // Constructors from arithmetic types
+  constexpr int128(int v);                 // NOLINT(runtime/explicit)
+  constexpr int128(unsigned int v);        // NOLINT(runtime/explicit)
+  constexpr int128(long v);                // NOLINT(runtime/int)
+  constexpr int128(unsigned long v);       // NOLINT(runtime/int)
+  constexpr int128(long long v);           // NOLINT(runtime/int)
+  constexpr int128(unsigned long long v);  // NOLINT(runtime/int)
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  constexpr int128(__int128 v);  // NOLINT(runtime/explicit)
+  constexpr explicit int128(unsigned __int128 v);
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+  constexpr explicit int128(uint128 v);
+  explicit int128(float v);
+  explicit int128(double v);
+  explicit int128(long double v);
+
+  // Assignment operators from arithmetic types
+  int128& operator=(int v);
+  int128& operator=(unsigned int v);
+  int128& operator=(long v);                // NOLINT(runtime/int)
+  int128& operator=(unsigned long v);       // NOLINT(runtime/int)
+  int128& operator=(long long v);           // NOLINT(runtime/int)
+  int128& operator=(unsigned long long v);  // NOLINT(runtime/int)
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  int128& operator=(__int128 v);
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+  // Conversion operators to other arithmetic types
+  constexpr explicit operator bool() const;
+  constexpr explicit operator char() const;
+  constexpr explicit operator signed char() const;
+  constexpr explicit operator unsigned char() const;
+  constexpr explicit operator char16_t() const;
+  constexpr explicit operator char32_t() const;
+  constexpr explicit operator ABSL_INTERNAL_WCHAR_T() const;
+  constexpr explicit operator short() const;  // NOLINT(runtime/int)
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator unsigned short() const;
+  constexpr explicit operator int() const;
+  constexpr explicit operator unsigned int() const;
+  constexpr explicit operator long() const;  // NOLINT(runtime/int)
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator unsigned long() const;
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator long long() const;
+  // NOLINTNEXTLINE(runtime/int)
+  constexpr explicit operator unsigned long long() const;
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  constexpr explicit operator __int128() const;
+  constexpr explicit operator unsigned __int128() const;
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+  explicit operator float() const;
+  explicit operator double() const;
+  explicit operator long double() const;
+
+  // Trivial copy constructor, assignment operator and destructor.
+
+  // Arithmetic operators
+  int128& operator+=(int128 other);
+  int128& operator-=(int128 other);
+  int128& operator*=(int128 other);
+  int128& operator/=(int128 other);
+  int128& operator%=(int128 other);
+  int128 operator++(int);  // postfix increment: i++
+  int128 operator--(int);  // postfix decrement: i--
+  int128& operator++();    // prefix increment:  ++i
+  int128& operator--();    // prefix decrement:  --i
+  int128& operator&=(int128 other);
+  int128& operator|=(int128 other);
+  int128& operator^=(int128 other);
+  int128& operator<<=(int amount);
+  int128& operator>>=(int amount);
+
+  // Int128Low64()
+  //
+  // Returns the lower 64-bit value of a `int128` value.
+  friend constexpr uint64_t Int128Low64(int128 v);
+
+  // Int128High64()
+  //
+  // Returns the higher 64-bit value of a `int128` value.
+  friend constexpr int64_t Int128High64(int128 v);
+
+  // MakeInt128()
+  //
+  // Constructs a `int128` numeric value from two 64-bit integers. Note that
+  // signedness is conveyed in the upper `high` value.
+  //
+  //   (absl::int128(1) << 64) * high + low
+  //
+  // Note that this factory function is the only way to construct a `int128`
+  // from integer values greater than 2^64 or less than -2^64.
+  //
+  // Example:
+  //
+  //   absl::int128 big = absl::MakeInt128(1, 0);
+  //   absl::int128 big_n = absl::MakeInt128(-1, 0);
+  friend constexpr int128 MakeInt128(int64_t high, uint64_t low);
+
+  // Int128Max()
+  //
+  // Returns the maximum value for a 128-bit signed integer.
+  friend constexpr int128 Int128Max();
+
+  // Int128Min()
+  //
+  // Returns the minimum value for a 128-bit signed integer.
+  friend constexpr int128 Int128Min();
+
+  // Support for absl::Hash.
+  template <typename H>
+  friend H AbslHashValue(H h, int128 v) {
+    return H::combine(std::move(h), Int128High64(v), Int128Low64(v));
+  }
+
+  // Support for absl::StrCat() etc.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, int128 v) {
+    sink.Append(v.ToString());
+  }
+
+ private:
+  constexpr int128(int64_t high, uint64_t low);
+
+  std::string ToString() const;
+
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  __int128 v_;
+#else  // ABSL_HAVE_INTRINSIC_INT128
+#if defined(ABSL_IS_LITTLE_ENDIAN)
+  uint64_t lo_;
+  int64_t hi_;
+#elif defined(ABSL_IS_BIG_ENDIAN)
+  int64_t hi_;
+  uint64_t lo_;
+#else  // byte order
+#error "Unsupported byte order: must be little-endian or big-endian."
+#endif  // byte order
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+};
+
+std::ostream& operator<<(std::ostream& os, int128 v);
+
+// TODO(absl-team) add operator>>(std::istream&, int128)
+
+constexpr int128 Int128Max() {
+  return int128((std::numeric_limits<int64_t>::max)(),
+                (std::numeric_limits<uint64_t>::max)());
+}
+
+constexpr int128 Int128Min() {
+  return int128((std::numeric_limits<int64_t>::min)(), 0);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// Specialized numeric_limits for int128.
+namespace std {
+template <>
+class numeric_limits<absl::int128> {
+ public:
+  static constexpr bool is_specialized = true;
+  static constexpr bool is_signed = true;
+  static constexpr bool is_integer = true;
+  static constexpr bool is_exact = true;
+  static constexpr bool has_infinity = false;
+  static constexpr bool has_quiet_NaN = false;
+  static constexpr bool has_signaling_NaN = false;
+  static constexpr float_denorm_style has_denorm = denorm_absent;
+  static constexpr bool has_denorm_loss = false;
+  static constexpr float_round_style round_style = round_toward_zero;
+  static constexpr bool is_iec559 = false;
+  static constexpr bool is_bounded = true;
+  static constexpr bool is_modulo = false;
+  static constexpr int digits = 127;
+  static constexpr int digits10 = 38;
+  static constexpr int max_digits10 = 0;
+  static constexpr int radix = 2;
+  static constexpr int min_exponent = 0;
+  static constexpr int min_exponent10 = 0;
+  static constexpr int max_exponent = 0;
+  static constexpr int max_exponent10 = 0;
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  static constexpr bool traps = numeric_limits<__int128>::traps;
+#else   // ABSL_HAVE_INTRINSIC_INT128
+  static constexpr bool traps = numeric_limits<uint64_t>::traps;
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+  static constexpr bool tinyness_before = false;
+
+  static constexpr absl::int128(min)() { return absl::Int128Min(); }
+  static constexpr absl::int128 lowest() { return absl::Int128Min(); }
+  static constexpr absl::int128(max)() { return absl::Int128Max(); }
+  static constexpr absl::int128 epsilon() { return 0; }
+  static constexpr absl::int128 round_error() { return 0; }
+  static constexpr absl::int128 infinity() { return 0; }
+  static constexpr absl::int128 quiet_NaN() { return 0; }
+  static constexpr absl::int128 signaling_NaN() { return 0; }
+  static constexpr absl::int128 denorm_min() { return 0; }
+};
+}  // namespace std
+
+// --------------------------------------------------------------------------
+//                      Implementation details follow
+// --------------------------------------------------------------------------
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+constexpr uint128 MakeUint128(uint64_t high, uint64_t low) {
+  return uint128(high, low);
+}
+
+// Assignment from integer types.
+
+inline uint128& uint128::operator=(int v) { return *this = uint128(v); }
+
+inline uint128& uint128::operator=(unsigned int v) {
+  return *this = uint128(v);
+}
+
+inline uint128& uint128::operator=(long v) {  // NOLINT(runtime/int)
+  return *this = uint128(v);
+}
+
+// NOLINTNEXTLINE(runtime/int)
+inline uint128& uint128::operator=(unsigned long v) {
+  return *this = uint128(v);
+}
+
+// NOLINTNEXTLINE(runtime/int)
+inline uint128& uint128::operator=(long long v) { return *this = uint128(v); }
+
+// NOLINTNEXTLINE(runtime/int)
+inline uint128& uint128::operator=(unsigned long long v) {
+  return *this = uint128(v);
+}
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+inline uint128& uint128::operator=(__int128 v) { return *this = uint128(v); }
+
+inline uint128& uint128::operator=(unsigned __int128 v) {
+  return *this = uint128(v);
+}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+inline uint128& uint128::operator=(int128 v) { return *this = uint128(v); }
+
+// Arithmetic operators.
+
+constexpr uint128 operator<<(uint128 lhs, int amount);
+constexpr uint128 operator>>(uint128 lhs, int amount);
+constexpr uint128 operator+(uint128 lhs, uint128 rhs);
+constexpr uint128 operator-(uint128 lhs, uint128 rhs);
+uint128 operator*(uint128 lhs, uint128 rhs);
+uint128 operator/(uint128 lhs, uint128 rhs);
+uint128 operator%(uint128 lhs, uint128 rhs);
+
+inline uint128& uint128::operator<<=(int amount) {
+  *this = *this << amount;
+  return *this;
+}
+
+inline uint128& uint128::operator>>=(int amount) {
+  *this = *this >> amount;
+  return *this;
+}
+
+inline uint128& uint128::operator+=(uint128 other) {
+  *this = *this + other;
+  return *this;
+}
+
+inline uint128& uint128::operator-=(uint128 other) {
+  *this = *this - other;
+  return *this;
+}
+
+inline uint128& uint128::operator*=(uint128 other) {
+  *this = *this * other;
+  return *this;
+}
+
+inline uint128& uint128::operator/=(uint128 other) {
+  *this = *this / other;
+  return *this;
+}
+
+inline uint128& uint128::operator%=(uint128 other) {
+  *this = *this % other;
+  return *this;
+}
+
+constexpr uint64_t Uint128Low64(uint128 v) { return v.lo_; }
+
+constexpr uint64_t Uint128High64(uint128 v) { return v.hi_; }
+
+// Constructors from integer types.
+
+#if defined(ABSL_IS_LITTLE_ENDIAN)
+
+constexpr uint128::uint128(uint64_t high, uint64_t low) : lo_{low}, hi_{high} {}
+
+constexpr uint128::uint128(int v)
+    : lo_{static_cast<uint64_t>(v)},
+      hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0} {}
+constexpr uint128::uint128(long v)  // NOLINT(runtime/int)
+    : lo_{static_cast<uint64_t>(v)},
+      hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0} {}
+constexpr uint128::uint128(long long v)  // NOLINT(runtime/int)
+    : lo_{static_cast<uint64_t>(v)},
+      hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0} {}
+
+constexpr uint128::uint128(unsigned int v) : lo_{v}, hi_{0} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr uint128::uint128(unsigned long v) : lo_{v}, hi_{0} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr uint128::uint128(unsigned long long v) : lo_{v}, hi_{0} {}
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+constexpr uint128::uint128(__int128 v)
+    : lo_{static_cast<uint64_t>(v & ~uint64_t{0})},
+      hi_{static_cast<uint64_t>(static_cast<unsigned __int128>(v) >> 64)} {}
+constexpr uint128::uint128(unsigned __int128 v)
+    : lo_{static_cast<uint64_t>(v & ~uint64_t{0})},
+      hi_{static_cast<uint64_t>(v >> 64)} {}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+constexpr uint128::uint128(int128 v)
+    : lo_{Int128Low64(v)}, hi_{static_cast<uint64_t>(Int128High64(v))} {}
+
+#elif defined(ABSL_IS_BIG_ENDIAN)
+
+constexpr uint128::uint128(uint64_t high, uint64_t low) : hi_{high}, lo_{low} {}
+
+constexpr uint128::uint128(int v)
+    : hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0},
+      lo_{static_cast<uint64_t>(v)} {}
+constexpr uint128::uint128(long v)  // NOLINT(runtime/int)
+    : hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0},
+      lo_{static_cast<uint64_t>(v)} {}
+constexpr uint128::uint128(long long v)  // NOLINT(runtime/int)
+    : hi_{v < 0 ? (std::numeric_limits<uint64_t>::max)() : 0},
+      lo_{static_cast<uint64_t>(v)} {}
+
+constexpr uint128::uint128(unsigned int v) : hi_{0}, lo_{v} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr uint128::uint128(unsigned long v) : hi_{0}, lo_{v} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr uint128::uint128(unsigned long long v) : hi_{0}, lo_{v} {}
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+constexpr uint128::uint128(__int128 v)
+    : hi_{static_cast<uint64_t>(static_cast<unsigned __int128>(v) >> 64)},
+      lo_{static_cast<uint64_t>(v & ~uint64_t{0})} {}
+constexpr uint128::uint128(unsigned __int128 v)
+    : hi_{static_cast<uint64_t>(v >> 64)},
+      lo_{static_cast<uint64_t>(v & ~uint64_t{0})} {}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+constexpr uint128::uint128(int128 v)
+    : hi_{static_cast<uint64_t>(Int128High64(v))}, lo_{Int128Low64(v)} {}
+
+#else  // byte order
+#error "Unsupported byte order: must be little-endian or big-endian."
+#endif  // byte order
+
+// Conversion operators to integer types.
+
+constexpr uint128::operator bool() const { return lo_ || hi_; }
+
+constexpr uint128::operator char() const { return static_cast<char>(lo_); }
+
+constexpr uint128::operator signed char() const {
+  return static_cast<signed char>(lo_);
+}
+
+constexpr uint128::operator unsigned char() const {
+  return static_cast<unsigned char>(lo_);
+}
+
+constexpr uint128::operator char16_t() const {
+  return static_cast<char16_t>(lo_);
+}
+
+constexpr uint128::operator char32_t() const {
+  return static_cast<char32_t>(lo_);
+}
+
+constexpr uint128::operator ABSL_INTERNAL_WCHAR_T() const {
+  return static_cast<ABSL_INTERNAL_WCHAR_T>(lo_);
+}
+
+// NOLINTNEXTLINE(runtime/int)
+constexpr uint128::operator short() const { return static_cast<short>(lo_); }
+
+constexpr uint128::operator unsigned short() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned short>(lo_);            // NOLINT(runtime/int)
+}
+
+constexpr uint128::operator int() const { return static_cast<int>(lo_); }
+
+constexpr uint128::operator unsigned int() const {
+  return static_cast<unsigned int>(lo_);
+}
+
+// NOLINTNEXTLINE(runtime/int)
+constexpr uint128::operator long() const { return static_cast<long>(lo_); }
+
+constexpr uint128::operator unsigned long() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned long>(lo_);            // NOLINT(runtime/int)
+}
+
+constexpr uint128::operator long long() const {  // NOLINT(runtime/int)
+  return static_cast<long long>(lo_);            // NOLINT(runtime/int)
+}
+
+constexpr uint128::operator unsigned long long() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned long long>(lo_);            // NOLINT(runtime/int)
+}
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+constexpr uint128::operator __int128() const {
+  return (static_cast<__int128>(hi_) << 64) + lo_;
+}
+
+constexpr uint128::operator unsigned __int128() const {
+  return (static_cast<unsigned __int128>(hi_) << 64) + lo_;
+}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+// Conversion operators to floating point types.
+
+inline uint128::operator float() const {
+  return static_cast<float>(lo_) + std::ldexp(static_cast<float>(hi_), 64);
+}
+
+inline uint128::operator double() const {
+  return static_cast<double>(lo_) + std::ldexp(static_cast<double>(hi_), 64);
+}
+
+inline uint128::operator long double() const {
+  return static_cast<long double>(lo_) +
+         std::ldexp(static_cast<long double>(hi_), 64);
+}
+
+// Comparison operators.
+
+constexpr bool operator==(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) ==
+         static_cast<unsigned __int128>(rhs);
+#else
+  return (Uint128Low64(lhs) == Uint128Low64(rhs) &&
+          Uint128High64(lhs) == Uint128High64(rhs));
+#endif
+}
+
+constexpr bool operator!=(uint128 lhs, uint128 rhs) { return !(lhs == rhs); }
+
+constexpr bool operator<(uint128 lhs, uint128 rhs) {
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  return static_cast<unsigned __int128>(lhs) <
+         static_cast<unsigned __int128>(rhs);
+#else
+  return (Uint128High64(lhs) == Uint128High64(rhs))
+             ? (Uint128Low64(lhs) < Uint128Low64(rhs))
+             : (Uint128High64(lhs) < Uint128High64(rhs));
+#endif
+}
+
+constexpr bool operator>(uint128 lhs, uint128 rhs) { return rhs < lhs; }
+
+constexpr bool operator<=(uint128 lhs, uint128 rhs) { return !(rhs < lhs); }
+
+constexpr bool operator>=(uint128 lhs, uint128 rhs) { return !(lhs < rhs); }
+
+// Unary operators.
+
+constexpr inline uint128 operator+(uint128 val) { return val; }
+
+constexpr inline int128 operator+(int128 val) { return val; }
+
+constexpr uint128 operator-(uint128 val) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return -static_cast<unsigned __int128>(val);
+#else
+  return MakeUint128(
+      ~Uint128High64(val) + static_cast<unsigned long>(Uint128Low64(val) == 0),
+      ~Uint128Low64(val) + 1);
+#endif
+}
+
+constexpr inline bool operator!(uint128 val) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return !static_cast<unsigned __int128>(val);
+#else
+  return !Uint128High64(val) && !Uint128Low64(val);
+#endif
+}
+
+// Logical operators.
+
+constexpr inline uint128 operator~(uint128 val) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return ~static_cast<unsigned __int128>(val);
+#else
+  return MakeUint128(~Uint128High64(val), ~Uint128Low64(val));
+#endif
+}
+
+constexpr inline uint128 operator|(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) |
+         static_cast<unsigned __int128>(rhs);
+#else
+  return MakeUint128(Uint128High64(lhs) | Uint128High64(rhs),
+                     Uint128Low64(lhs) | Uint128Low64(rhs));
+#endif
+}
+
+constexpr inline uint128 operator&(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) &
+         static_cast<unsigned __int128>(rhs);
+#else
+  return MakeUint128(Uint128High64(lhs) & Uint128High64(rhs),
+                     Uint128Low64(lhs) & Uint128Low64(rhs));
+#endif
+}
+
+constexpr inline uint128 operator^(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) ^
+         static_cast<unsigned __int128>(rhs);
+#else
+  return MakeUint128(Uint128High64(lhs) ^ Uint128High64(rhs),
+                     Uint128Low64(lhs) ^ Uint128Low64(rhs));
+#endif
+}
+
+inline uint128& uint128::operator|=(uint128 other) {
+  *this = *this | other;
+  return *this;
+}
+
+inline uint128& uint128::operator&=(uint128 other) {
+  *this = *this & other;
+  return *this;
+}
+
+inline uint128& uint128::operator^=(uint128 other) {
+  *this = *this ^ other;
+  return *this;
+}
+
+// Arithmetic operators.
+
+constexpr uint128 operator<<(uint128 lhs, int amount) {
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  return static_cast<unsigned __int128>(lhs) << amount;
+#else
+  // uint64_t shifts of >= 64 are undefined, so we will need some
+  // special-casing.
+  return amount >= 64  ? MakeUint128(Uint128Low64(lhs) << (amount - 64), 0)
+         : amount == 0 ? lhs
+                       : MakeUint128((Uint128High64(lhs) << amount) |
+                                         (Uint128Low64(lhs) >> (64 - amount)),
+                                     Uint128Low64(lhs) << amount);
+#endif
+}
+
+constexpr uint128 operator>>(uint128 lhs, int amount) {
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  return static_cast<unsigned __int128>(lhs) >> amount;
+#else
+  // uint64_t shifts of >= 64 are undefined, so we will need some
+  // special-casing.
+  return amount >= 64  ? MakeUint128(0, Uint128High64(lhs) >> (amount - 64))
+         : amount == 0 ? lhs
+                       : MakeUint128(Uint128High64(lhs) >> amount,
+                                     (Uint128Low64(lhs) >> amount) |
+                                         (Uint128High64(lhs) << (64 - amount)));
+#endif
+}
+
+#if !defined(ABSL_HAVE_INTRINSIC_INT128)
+namespace int128_internal {
+constexpr uint128 AddResult(uint128 result, uint128 lhs) {
+  // check for carry
+  return (Uint128Low64(result) < Uint128Low64(lhs))
+             ? MakeUint128(Uint128High64(result) + 1, Uint128Low64(result))
+             : result;
+}
+}  // namespace int128_internal
+#endif
+
+constexpr uint128 operator+(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) +
+         static_cast<unsigned __int128>(rhs);
+#else
+  return int128_internal::AddResult(
+      MakeUint128(Uint128High64(lhs) + Uint128High64(rhs),
+                  Uint128Low64(lhs) + Uint128Low64(rhs)),
+      lhs);
+#endif
+}
+
+#if !defined(ABSL_HAVE_INTRINSIC_INT128)
+namespace int128_internal {
+constexpr uint128 SubstructResult(uint128 result, uint128 lhs, uint128 rhs) {
+  // check for carry
+  return (Uint128Low64(lhs) < Uint128Low64(rhs))
+             ? MakeUint128(Uint128High64(result) - 1, Uint128Low64(result))
+             : result;
+}
+}  // namespace int128_internal
+#endif
+
+constexpr uint128 operator-(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) -
+         static_cast<unsigned __int128>(rhs);
+#else
+  return int128_internal::SubstructResult(
+      MakeUint128(Uint128High64(lhs) - Uint128High64(rhs),
+                  Uint128Low64(lhs) - Uint128Low64(rhs)),
+      lhs, rhs);
+#endif
+}
+
+inline uint128 operator*(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  // TODO(strel) Remove once alignment issues are resolved and unsigned __int128
+  // can be used for uint128 storage.
+  return static_cast<unsigned __int128>(lhs) *
+         static_cast<unsigned __int128>(rhs);
+#elif defined(_MSC_VER) && defined(_M_X64) && !defined(_M_ARM64EC)
+  uint64_t carry;
+  uint64_t low = _umul128(Uint128Low64(lhs), Uint128Low64(rhs), &carry);
+  return MakeUint128(Uint128Low64(lhs) * Uint128High64(rhs) +
+                         Uint128High64(lhs) * Uint128Low64(rhs) + carry,
+                     low);
+#else   // ABSL_HAVE_INTRINSIC128
+  uint64_t a32 = Uint128Low64(lhs) >> 32;
+  uint64_t a00 = Uint128Low64(lhs) & 0xffffffff;
+  uint64_t b32 = Uint128Low64(rhs) >> 32;
+  uint64_t b00 = Uint128Low64(rhs) & 0xffffffff;
+  uint128 result =
+      MakeUint128(Uint128High64(lhs) * Uint128Low64(rhs) +
+                      Uint128Low64(lhs) * Uint128High64(rhs) + a32 * b32,
+                  a00 * b00);
+  result += uint128(a32 * b00) << 32;
+  result += uint128(a00 * b32) << 32;
+  return result;
+#endif  // ABSL_HAVE_INTRINSIC128
+}
+
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+inline uint128 operator/(uint128 lhs, uint128 rhs) {
+  return static_cast<unsigned __int128>(lhs) /
+         static_cast<unsigned __int128>(rhs);
+}
+
+inline uint128 operator%(uint128 lhs, uint128 rhs) {
+  return static_cast<unsigned __int128>(lhs) %
+         static_cast<unsigned __int128>(rhs);
+}
+#endif
+
+// Increment/decrement operators.
+
+inline uint128 uint128::operator++(int) {
+  uint128 tmp(*this);
+  *this += 1;
+  return tmp;
+}
+
+inline uint128 uint128::operator--(int) {
+  uint128 tmp(*this);
+  *this -= 1;
+  return tmp;
+}
+
+inline uint128& uint128::operator++() {
+  *this += 1;
+  return *this;
+}
+
+inline uint128& uint128::operator--() {
+  *this -= 1;
+  return *this;
+}
+
+constexpr int128 MakeInt128(int64_t high, uint64_t low) {
+  return int128(high, low);
+}
+
+// Assignment from integer types.
+inline int128& int128::operator=(int v) { return *this = int128(v); }
+
+inline int128& int128::operator=(unsigned int v) { return *this = int128(v); }
+
+inline int128& int128::operator=(long v) {  // NOLINT(runtime/int)
+  return *this = int128(v);
+}
+
+// NOLINTNEXTLINE(runtime/int)
+inline int128& int128::operator=(unsigned long v) { return *this = int128(v); }
+
+// NOLINTNEXTLINE(runtime/int)
+inline int128& int128::operator=(long long v) { return *this = int128(v); }
+
+// NOLINTNEXTLINE(runtime/int)
+inline int128& int128::operator=(unsigned long long v) {
+  return *this = int128(v);
+}
+
+// Arithmetic operators.
+constexpr int128 operator-(int128 v);
+constexpr int128 operator+(int128 lhs, int128 rhs);
+constexpr int128 operator-(int128 lhs, int128 rhs);
+int128 operator*(int128 lhs, int128 rhs);
+int128 operator/(int128 lhs, int128 rhs);
+int128 operator%(int128 lhs, int128 rhs);
+constexpr int128 operator|(int128 lhs, int128 rhs);
+constexpr int128 operator&(int128 lhs, int128 rhs);
+constexpr int128 operator^(int128 lhs, int128 rhs);
+constexpr int128 operator<<(int128 lhs, int amount);
+constexpr int128 operator>>(int128 lhs, int amount);
+
+inline int128& int128::operator+=(int128 other) {
+  *this = *this + other;
+  return *this;
+}
+
+inline int128& int128::operator-=(int128 other) {
+  *this = *this - other;
+  return *this;
+}
+
+inline int128& int128::operator*=(int128 other) {
+  *this = *this * other;
+  return *this;
+}
+
+inline int128& int128::operator/=(int128 other) {
+  *this = *this / other;
+  return *this;
+}
+
+inline int128& int128::operator%=(int128 other) {
+  *this = *this % other;
+  return *this;
+}
+
+inline int128& int128::operator|=(int128 other) {
+  *this = *this | other;
+  return *this;
+}
+
+inline int128& int128::operator&=(int128 other) {
+  *this = *this & other;
+  return *this;
+}
+
+inline int128& int128::operator^=(int128 other) {
+  *this = *this ^ other;
+  return *this;
+}
+
+inline int128& int128::operator<<=(int amount) {
+  *this = *this << amount;
+  return *this;
+}
+
+inline int128& int128::operator>>=(int amount) {
+  *this = *this >> amount;
+  return *this;
+}
+
+// Forward declaration for comparison operators.
+constexpr bool operator!=(int128 lhs, int128 rhs);
+
+namespace int128_internal {
+
+// Casts from unsigned to signed while preserving the underlying binary
+// representation.
+constexpr int64_t BitCastToSigned(uint64_t v) {
+  // Casting an unsigned integer to a signed integer of the same
+  // width is implementation defined behavior if the source value would not fit
+  // in the destination type. We step around it with a roundtrip bitwise not
+  // operation to make sure this function remains constexpr. Clang, GCC, and
+  // MSVC optimize this to a no-op on x86-64.
+  return v & (uint64_t{1} << 63) ? ~static_cast<int64_t>(~v)
+                                 : static_cast<int64_t>(v);
+}
+
+}  // namespace int128_internal
+
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+#include "absl/numeric/int128_have_intrinsic.inc"  // IWYU pragma: export
+#else  // ABSL_HAVE_INTRINSIC_INT128
+#include "absl/numeric/int128_no_intrinsic.inc"  // IWYU pragma: export
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#undef ABSL_INTERNAL_WCHAR_T
+
+#endif  // ABSL_NUMERIC_INT128_H_
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128_benchmark.cc b/weight/_dep/abseil-cpp/absl/numeric/int128_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..eab1515c0ad8d08ae7af97523b4396766ea3bb97
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128_benchmark.cc
@@ -0,0 +1,282 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+#include <cstdint>
+#include <limits>
+#include <random>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "absl/base/config.h"
+#include "absl/numeric/int128.h"
+
+namespace {
+
+constexpr size_t kSampleSize = 1000000;
+
+std::mt19937 MakeRandomEngine() {
+  std::random_device r;
+  std::seed_seq seed({r(), r(), r(), r(), r(), r(), r(), r()});
+  return std::mt19937(seed);
+}
+
+template <typename T,
+          typename H = typename std::conditional<
+              std::numeric_limits<T>::is_signed, int64_t, uint64_t>::type>
+std::vector<std::pair<T, T>> GetRandomClass128SampleUniformDivisor() {
+  std::vector<std::pair<T, T>> values;
+  std::mt19937 random = MakeRandomEngine();
+  std::uniform_int_distribution<H> uniform_h;
+  values.reserve(kSampleSize);
+  for (size_t i = 0; i < kSampleSize; ++i) {
+    T a{absl::MakeUint128(uniform_h(random), uniform_h(random))};
+    T b{absl::MakeUint128(uniform_h(random), uniform_h(random))};
+    values.emplace_back(std::max(a, b), std::max(T(2), std::min(a, b)));
+  }
+  return values;
+}
+
+template <typename T>
+void BM_DivideClass128UniformDivisor(benchmark::State& state) {
+  auto values = GetRandomClass128SampleUniformDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first / pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_DivideClass128UniformDivisor, absl::uint128);
+BENCHMARK_TEMPLATE(BM_DivideClass128UniformDivisor, absl::int128);
+
+template <typename T>
+void BM_RemainderClass128UniformDivisor(benchmark::State& state) {
+  auto values = GetRandomClass128SampleUniformDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first % pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_RemainderClass128UniformDivisor, absl::uint128);
+BENCHMARK_TEMPLATE(BM_RemainderClass128UniformDivisor, absl::int128);
+
+template <typename T,
+          typename H = typename std::conditional<
+              std::numeric_limits<T>::is_signed, int64_t, uint64_t>::type>
+std::vector<std::pair<T, H>> GetRandomClass128SampleSmallDivisor() {
+  std::vector<std::pair<T, H>> values;
+  std::mt19937 random = MakeRandomEngine();
+  std::uniform_int_distribution<H> uniform_h;
+  values.reserve(kSampleSize);
+  for (size_t i = 0; i < kSampleSize; ++i) {
+    T a{absl::MakeUint128(uniform_h(random), uniform_h(random))};
+    H b{std::max(H{2}, uniform_h(random))};
+    values.emplace_back(std::max(a, T(b)), b);
+  }
+  return values;
+}
+
+template <typename T>
+void BM_DivideClass128SmallDivisor(benchmark::State& state) {
+  auto values = GetRandomClass128SampleSmallDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first / pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_DivideClass128SmallDivisor, absl::uint128);
+BENCHMARK_TEMPLATE(BM_DivideClass128SmallDivisor, absl::int128);
+
+template <typename T>
+void BM_RemainderClass128SmallDivisor(benchmark::State& state) {
+  auto values = GetRandomClass128SampleSmallDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first % pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_RemainderClass128SmallDivisor, absl::uint128);
+BENCHMARK_TEMPLATE(BM_RemainderClass128SmallDivisor, absl::int128);
+
+std::vector<std::pair<absl::uint128, absl::uint128>> GetRandomClass128Sample() {
+  std::vector<std::pair<absl::uint128, absl::uint128>> values;
+  std::mt19937 random = MakeRandomEngine();
+  std::uniform_int_distribution<uint64_t> uniform_uint64;
+  values.reserve(kSampleSize);
+  for (size_t i = 0; i < kSampleSize; ++i) {
+    values.emplace_back(
+        absl::MakeUint128(uniform_uint64(random), uniform_uint64(random)),
+        absl::MakeUint128(uniform_uint64(random), uniform_uint64(random)));
+  }
+  return values;
+}
+
+void BM_MultiplyClass128(benchmark::State& state) {
+  auto values = GetRandomClass128Sample();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first * pair.second);
+    }
+  }
+}
+BENCHMARK(BM_MultiplyClass128);
+
+void BM_AddClass128(benchmark::State& state) {
+  auto values = GetRandomClass128Sample();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first + pair.second);
+    }
+  }
+}
+BENCHMARK(BM_AddClass128);
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+
+// Some implementations of <random> do not support __int128 when it is
+// available, so we make our own uniform_int_distribution-like type.
+template <typename T,
+          typename H = typename std::conditional<
+              std::is_same<T, __int128>::value, int64_t, uint64_t>::type>
+class UniformIntDistribution128 {
+ public:
+  // NOLINTNEXTLINE: mimicking std::uniform_int_distribution API
+  T operator()(std::mt19937& generator) {
+    return (static_cast<T>(dist64_(generator)) << 64) | dist64_(generator);
+  }
+
+ private:
+  std::uniform_int_distribution<H> dist64_;
+};
+
+template <typename T,
+          typename H = typename std::conditional<
+              std::is_same<T, __int128>::value, int64_t, uint64_t>::type>
+std::vector<std::pair<T, T>> GetRandomIntrinsic128SampleUniformDivisor() {
+  std::vector<std::pair<T, T>> values;
+  std::mt19937 random = MakeRandomEngine();
+  UniformIntDistribution128<T> uniform_128;
+  values.reserve(kSampleSize);
+  for (size_t i = 0; i < kSampleSize; ++i) {
+    T a = uniform_128(random);
+    T b = uniform_128(random);
+    values.emplace_back(std::max(a, b),
+                        std::max(static_cast<T>(2), std::min(a, b)));
+  }
+  return values;
+}
+
+template <typename T>
+void BM_DivideIntrinsic128UniformDivisor(benchmark::State& state) {
+  auto values = GetRandomIntrinsic128SampleUniformDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first / pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_DivideIntrinsic128UniformDivisor, unsigned __int128);
+BENCHMARK_TEMPLATE(BM_DivideIntrinsic128UniformDivisor, __int128);
+
+template <typename T>
+void BM_RemainderIntrinsic128UniformDivisor(benchmark::State& state) {
+  auto values = GetRandomIntrinsic128SampleUniformDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first % pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_RemainderIntrinsic128UniformDivisor, unsigned __int128);
+BENCHMARK_TEMPLATE(BM_RemainderIntrinsic128UniformDivisor, __int128);
+
+template <typename T,
+          typename H = typename std::conditional<
+              std::is_same<T, __int128>::value, int64_t, uint64_t>::type>
+std::vector<std::pair<T, H>> GetRandomIntrinsic128SampleSmallDivisor() {
+  std::vector<std::pair<T, H>> values;
+  std::mt19937 random = MakeRandomEngine();
+  UniformIntDistribution128<T> uniform_int128;
+  std::uniform_int_distribution<H> uniform_int64;
+  values.reserve(kSampleSize);
+  for (size_t i = 0; i < kSampleSize; ++i) {
+    T a = uniform_int128(random);
+    H b = std::max(H{2}, uniform_int64(random));
+    values.emplace_back(std::max(a, static_cast<T>(b)), b);
+  }
+  return values;
+}
+
+template <typename T>
+void BM_DivideIntrinsic128SmallDivisor(benchmark::State& state) {
+  auto values = GetRandomIntrinsic128SampleSmallDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first / pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_DivideIntrinsic128SmallDivisor, unsigned __int128);
+BENCHMARK_TEMPLATE(BM_DivideIntrinsic128SmallDivisor, __int128);
+
+template <typename T>
+void BM_RemainderIntrinsic128SmallDivisor(benchmark::State& state) {
+  auto values = GetRandomIntrinsic128SampleSmallDivisor<T>();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first % pair.second);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_RemainderIntrinsic128SmallDivisor, unsigned __int128);
+BENCHMARK_TEMPLATE(BM_RemainderIntrinsic128SmallDivisor, __int128);
+
+std::vector<std::pair<unsigned __int128, unsigned __int128>>
+      GetRandomIntrinsic128Sample() {
+  std::vector<std::pair<unsigned __int128, unsigned __int128>> values;
+  std::mt19937 random = MakeRandomEngine();
+  UniformIntDistribution128<unsigned __int128> uniform_uint128;
+  values.reserve(kSampleSize);
+  for (size_t i = 0; i < kSampleSize; ++i) {
+    values.emplace_back(uniform_uint128(random), uniform_uint128(random));
+  }
+  return values;
+}
+
+void BM_MultiplyIntrinsic128(benchmark::State& state) {
+  auto values = GetRandomIntrinsic128Sample();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first * pair.second);
+    }
+  }
+}
+BENCHMARK(BM_MultiplyIntrinsic128);
+
+void BM_AddIntrinsic128(benchmark::State& state) {
+  auto values = GetRandomIntrinsic128Sample();
+  while (state.KeepRunningBatch(values.size())) {
+    for (const auto& pair : values) {
+      benchmark::DoNotOptimize(pair.first + pair.second);
+    }
+  }
+}
+BENCHMARK(BM_AddIntrinsic128);
+
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128_have_intrinsic.inc b/weight/_dep/abseil-cpp/absl/numeric/int128_have_intrinsic.inc
new file mode 100644
index 0000000000000000000000000000000000000000..6f1ac644141e937baaf8b95aa6662bba4cd0d36a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128_have_intrinsic.inc
@@ -0,0 +1,293 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains :int128 implementation details that depend on internal
+// representation when ABSL_HAVE_INTRINSIC_INT128 is defined. This file is
+// included by int128.h and relies on ABSL_INTERNAL_WCHAR_T being defined.
+
+namespace int128_internal {
+
+// Casts from unsigned to signed while preserving the underlying binary
+// representation.
+constexpr __int128 BitCastToSigned(unsigned __int128 v) {
+  // Casting an unsigned integer to a signed integer of the same
+  // width is implementation defined behavior if the source value would not fit
+  // in the destination type. We step around it with a roundtrip bitwise not
+  // operation to make sure this function remains constexpr. Clang and GCC
+  // optimize this to a no-op on x86-64.
+  return v & (static_cast<unsigned __int128>(1) << 127)
+             ? ~static_cast<__int128>(~v)
+             : static_cast<__int128>(v);
+}
+
+}  // namespace int128_internal
+
+inline int128& int128::operator=(__int128 v) {
+  v_ = v;
+  return *this;
+}
+
+constexpr uint64_t Int128Low64(int128 v) {
+  return static_cast<uint64_t>(v.v_ & ~uint64_t{0});
+}
+
+constexpr int64_t Int128High64(int128 v) {
+  // Initially cast to unsigned to prevent a right shift on a negative value.
+  return int128_internal::BitCastToSigned(
+      static_cast<uint64_t>(static_cast<unsigned __int128>(v.v_) >> 64));
+}
+
+constexpr int128::int128(int64_t high, uint64_t low)
+    // Initially cast to unsigned to prevent a left shift that overflows.
+    : v_(int128_internal::BitCastToSigned(static_cast<unsigned __int128>(high)
+                                           << 64) |
+         low) {}
+
+
+constexpr int128::int128(int v) : v_{v} {}
+
+constexpr int128::int128(long v) : v_{v} {}       // NOLINT(runtime/int)
+
+constexpr int128::int128(long long v) : v_{v} {}  // NOLINT(runtime/int)
+
+constexpr int128::int128(__int128 v) : v_{v} {}
+
+constexpr int128::int128(unsigned int v) : v_{v} {}
+
+constexpr int128::int128(unsigned long v) : v_{v} {}  // NOLINT(runtime/int)
+
+// NOLINTNEXTLINE(runtime/int)
+constexpr int128::int128(unsigned long long v) : v_{v} {}
+
+constexpr int128::int128(unsigned __int128 v) : v_{static_cast<__int128>(v)} {}
+
+inline int128::int128(float v) {
+  v_ = static_cast<__int128>(v);
+}
+
+inline int128::int128(double v) {
+  v_ = static_cast<__int128>(v);
+}
+
+inline int128::int128(long double v) {
+  v_ = static_cast<__int128>(v);
+}
+
+constexpr int128::int128(uint128 v) : v_{static_cast<__int128>(v)} {}
+
+constexpr int128::operator bool() const { return static_cast<bool>(v_); }
+
+constexpr int128::operator char() const { return static_cast<char>(v_); }
+
+constexpr int128::operator signed char() const {
+  return static_cast<signed char>(v_);
+}
+
+constexpr int128::operator unsigned char() const {
+  return static_cast<unsigned char>(v_);
+}
+
+constexpr int128::operator char16_t() const {
+  return static_cast<char16_t>(v_);
+}
+
+constexpr int128::operator char32_t() const {
+  return static_cast<char32_t>(v_);
+}
+
+constexpr int128::operator ABSL_INTERNAL_WCHAR_T() const {
+  return static_cast<ABSL_INTERNAL_WCHAR_T>(v_);
+}
+
+constexpr int128::operator short() const {  // NOLINT(runtime/int)
+  return static_cast<short>(v_);            // NOLINT(runtime/int)
+}
+
+constexpr int128::operator unsigned short() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned short>(v_);            // NOLINT(runtime/int)
+}
+
+constexpr int128::operator int() const {
+  return static_cast<int>(v_);
+}
+
+constexpr int128::operator unsigned int() const {
+  return static_cast<unsigned int>(v_);
+}
+
+constexpr int128::operator long() const {  // NOLINT(runtime/int)
+  return static_cast<long>(v_);            // NOLINT(runtime/int)
+}
+
+constexpr int128::operator unsigned long() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned long>(v_);            // NOLINT(runtime/int)
+}
+
+constexpr int128::operator long long() const {  // NOLINT(runtime/int)
+  return static_cast<long long>(v_);            // NOLINT(runtime/int)
+}
+
+constexpr int128::operator unsigned long long() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned long long>(v_);            // NOLINT(runtime/int)
+}
+
+constexpr int128::operator __int128() const { return v_; }
+
+constexpr int128::operator unsigned __int128() const {
+  return static_cast<unsigned __int128>(v_);
+}
+
+// Clang on PowerPC sometimes produces incorrect __int128 to floating point
+// conversions. In that case, we do the conversion with a similar implementation
+// to the conversion operators in int128_no_intrinsic.inc.
+#if defined(__clang__) && !defined(__ppc64__)
+inline int128::operator float() const { return static_cast<float>(v_); }
+
+inline int128::operator double() const { return static_cast<double>(v_); }
+
+inline int128::operator long double() const {
+  return static_cast<long double>(v_);
+}
+
+#else  // Clang on PowerPC
+
+inline int128::operator float() const {
+  // We must convert the absolute value and then negate as needed, because
+  // floating point types are typically sign-magnitude. Otherwise, the
+  // difference between the high and low 64 bits when interpreted as two's
+  // complement overwhelms the precision of the mantissa.
+  //
+  // Also check to make sure we don't negate Int128Min()
+  return v_ < 0 && *this != Int128Min()
+             ? -static_cast<float>(-*this)
+             : static_cast<float>(Int128Low64(*this)) +
+                   std::ldexp(static_cast<float>(Int128High64(*this)), 64);
+}
+
+inline int128::operator double() const {
+  // See comment in int128::operator float() above.
+  return v_ < 0 && *this != Int128Min()
+             ? -static_cast<double>(-*this)
+             : static_cast<double>(Int128Low64(*this)) +
+                   std::ldexp(static_cast<double>(Int128High64(*this)), 64);
+}
+
+inline int128::operator long double() const {
+  // See comment in int128::operator float() above.
+  return v_ < 0 && *this != Int128Min()
+             ? -static_cast<long double>(-*this)
+             : static_cast<long double>(Int128Low64(*this)) +
+                   std::ldexp(static_cast<long double>(Int128High64(*this)),
+                              64);
+}
+#endif  // Clang on PowerPC
+
+// Comparison operators.
+
+constexpr bool operator==(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) == static_cast<__int128>(rhs);
+}
+
+constexpr bool operator!=(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) != static_cast<__int128>(rhs);
+}
+
+constexpr bool operator<(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) < static_cast<__int128>(rhs);
+}
+
+constexpr bool operator>(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) > static_cast<__int128>(rhs);
+}
+
+constexpr bool operator<=(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) <= static_cast<__int128>(rhs);
+}
+
+constexpr bool operator>=(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) >= static_cast<__int128>(rhs);
+}
+
+// Unary operators.
+
+constexpr int128 operator-(int128 v) { return -static_cast<__int128>(v); }
+
+constexpr bool operator!(int128 v) { return !static_cast<__int128>(v); }
+
+constexpr int128 operator~(int128 val) { return ~static_cast<__int128>(val); }
+
+// Arithmetic operators.
+
+constexpr int128 operator+(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) + static_cast<__int128>(rhs);
+}
+
+constexpr int128 operator-(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) - static_cast<__int128>(rhs);
+}
+
+inline int128 operator*(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) * static_cast<__int128>(rhs);
+}
+
+inline int128 operator/(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) / static_cast<__int128>(rhs);
+}
+
+inline int128 operator%(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) % static_cast<__int128>(rhs);
+}
+
+inline int128 int128::operator++(int) {
+  int128 tmp(*this);
+  ++v_;
+  return tmp;
+}
+
+inline int128 int128::operator--(int) {
+  int128 tmp(*this);
+  --v_;
+  return tmp;
+}
+
+inline int128& int128::operator++() {
+  ++v_;
+  return *this;
+}
+
+inline int128& int128::operator--() {
+  --v_;
+  return *this;
+}
+
+constexpr int128 operator|(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) | static_cast<__int128>(rhs);
+}
+
+constexpr int128 operator&(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) & static_cast<__int128>(rhs);
+}
+
+constexpr int128 operator^(int128 lhs, int128 rhs) {
+  return static_cast<__int128>(lhs) ^ static_cast<__int128>(rhs);
+}
+
+constexpr int128 operator<<(int128 lhs, int amount) {
+  return static_cast<__int128>(lhs) << amount;
+}
+
+constexpr int128 operator>>(int128 lhs, int amount) {
+  return static_cast<__int128>(lhs) >> amount;
+}
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128_no_intrinsic.inc b/weight/_dep/abseil-cpp/absl/numeric/int128_no_intrinsic.inc
new file mode 100644
index 0000000000000000000000000000000000000000..6f5d83777c05578a705957e9f98b3798b6e45627
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128_no_intrinsic.inc
@@ -0,0 +1,328 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains :int128 implementation details that depend on internal
+// representation when ABSL_HAVE_INTRINSIC_INT128 is *not* defined. This file
+// is included by int128.h and relies on ABSL_INTERNAL_WCHAR_T being defined.
+
+constexpr uint64_t Int128Low64(int128 v) { return v.lo_; }
+
+constexpr int64_t Int128High64(int128 v) { return v.hi_; }
+
+#if defined(ABSL_IS_LITTLE_ENDIAN)
+
+constexpr int128::int128(int64_t high, uint64_t low) : lo_(low), hi_(high) {}
+
+constexpr int128::int128(int v)
+    : lo_{static_cast<uint64_t>(v)}, hi_{v < 0 ? ~int64_t{0} : 0} {}
+constexpr int128::int128(long v)  // NOLINT(runtime/int)
+    : lo_{static_cast<uint64_t>(v)}, hi_{v < 0 ? ~int64_t{0} : 0} {}
+constexpr int128::int128(long long v)  // NOLINT(runtime/int)
+    : lo_{static_cast<uint64_t>(v)}, hi_{v < 0 ? ~int64_t{0} : 0} {}
+
+constexpr int128::int128(unsigned int v) : lo_{v}, hi_{0} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr int128::int128(unsigned long v) : lo_{v}, hi_{0} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr int128::int128(unsigned long long v) : lo_{v}, hi_{0} {}
+
+constexpr int128::int128(uint128 v)
+    : lo_{Uint128Low64(v)}, hi_{static_cast<int64_t>(Uint128High64(v))} {}
+
+#elif defined(ABSL_IS_BIG_ENDIAN)
+
+constexpr int128::int128(int64_t high, uint64_t low) : hi_{high}, lo_{low} {}
+
+constexpr int128::int128(int v)
+    : hi_{v < 0 ? ~int64_t{0} : 0}, lo_{static_cast<uint64_t>(v)} {}
+constexpr int128::int128(long v)  // NOLINT(runtime/int)
+    : hi_{v < 0 ? ~int64_t{0} : 0}, lo_{static_cast<uint64_t>(v)} {}
+constexpr int128::int128(long long v)  // NOLINT(runtime/int)
+    : hi_{v < 0 ? ~int64_t{0} : 0}, lo_{static_cast<uint64_t>(v)} {}
+
+constexpr int128::int128(unsigned int v) : hi_{0}, lo_{v} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr int128::int128(unsigned long v) : hi_{0}, lo_{v} {}
+// NOLINTNEXTLINE(runtime/int)
+constexpr int128::int128(unsigned long long v) : hi_{0}, lo_{v} {}
+
+constexpr int128::int128(uint128 v)
+    : hi_{static_cast<int64_t>(Uint128High64(v))}, lo_{Uint128Low64(v)} {}
+
+#else  // byte order
+#error "Unsupported byte order: must be little-endian or big-endian."
+#endif  // byte order
+
+constexpr int128::operator bool() const { return lo_ || hi_; }
+
+constexpr int128::operator char() const {
+  // NOLINTNEXTLINE(runtime/int)
+  return static_cast<char>(static_cast<long long>(*this));
+}
+
+constexpr int128::operator signed char() const {
+  // NOLINTNEXTLINE(runtime/int)
+  return static_cast<signed char>(static_cast<long long>(*this));
+}
+
+constexpr int128::operator unsigned char() const {
+  return static_cast<unsigned char>(lo_);
+}
+
+constexpr int128::operator char16_t() const {
+  return static_cast<char16_t>(lo_);
+}
+
+constexpr int128::operator char32_t() const {
+  return static_cast<char32_t>(lo_);
+}
+
+constexpr int128::operator ABSL_INTERNAL_WCHAR_T() const {
+  // NOLINTNEXTLINE(runtime/int)
+  return static_cast<ABSL_INTERNAL_WCHAR_T>(static_cast<long long>(*this));
+}
+
+constexpr int128::operator short() const {  // NOLINT(runtime/int)
+  // NOLINTNEXTLINE(runtime/int)
+  return static_cast<short>(static_cast<long long>(*this));
+}
+
+constexpr int128::operator unsigned short() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned short>(lo_);           // NOLINT(runtime/int)
+}
+
+constexpr int128::operator int() const {
+  // NOLINTNEXTLINE(runtime/int)
+  return static_cast<int>(static_cast<long long>(*this));
+}
+
+constexpr int128::operator unsigned int() const {
+  return static_cast<unsigned int>(lo_);
+}
+
+constexpr int128::operator long() const {  // NOLINT(runtime/int)
+  // NOLINTNEXTLINE(runtime/int)
+  return static_cast<long>(static_cast<long long>(*this));
+}
+
+constexpr int128::operator unsigned long() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned long>(lo_);           // NOLINT(runtime/int)
+}
+
+constexpr int128::operator long long() const {  // NOLINT(runtime/int)
+  // We don't bother checking the value of hi_. If *this < 0, lo_'s high bit
+  // must be set in order for the value to fit into a long long. Conversely, if
+  // lo_'s high bit is set, *this must be < 0 for the value to fit.
+  return int128_internal::BitCastToSigned(lo_);
+}
+
+constexpr int128::operator unsigned long long() const {  // NOLINT(runtime/int)
+  return static_cast<unsigned long long>(lo_);           // NOLINT(runtime/int)
+}
+
+inline int128::operator float() const {
+  // We must convert the absolute value and then negate as needed, because
+  // floating point types are typically sign-magnitude. Otherwise, the
+  // difference between the high and low 64 bits when interpreted as two's
+  // complement overwhelms the precision of the mantissa.
+  //
+  // Also check to make sure we don't negate Int128Min()
+  return hi_ < 0 && *this != Int128Min()
+             ? -static_cast<float>(-*this)
+             : static_cast<float>(lo_) +
+                   std::ldexp(static_cast<float>(hi_), 64);
+}
+
+inline int128::operator double() const {
+  // See comment in int128::operator float() above.
+  return hi_ < 0 && *this != Int128Min()
+             ? -static_cast<double>(-*this)
+             : static_cast<double>(lo_) +
+                   std::ldexp(static_cast<double>(hi_), 64);
+}
+
+inline int128::operator long double() const {
+  // See comment in int128::operator float() above.
+  return hi_ < 0 && *this != Int128Min()
+             ? -static_cast<long double>(-*this)
+             : static_cast<long double>(lo_) +
+                   std::ldexp(static_cast<long double>(hi_), 64);
+}
+
+// Comparison operators.
+
+constexpr bool operator==(int128 lhs, int128 rhs) {
+  return (Int128Low64(lhs) == Int128Low64(rhs) &&
+          Int128High64(lhs) == Int128High64(rhs));
+}
+
+constexpr bool operator!=(int128 lhs, int128 rhs) { return !(lhs == rhs); }
+
+constexpr bool operator<(int128 lhs, int128 rhs) {
+  return (Int128High64(lhs) == Int128High64(rhs))
+             ? (Int128Low64(lhs) < Int128Low64(rhs))
+             : (Int128High64(lhs) < Int128High64(rhs));
+}
+
+constexpr bool operator>(int128 lhs, int128 rhs) {
+  return (Int128High64(lhs) == Int128High64(rhs))
+             ? (Int128Low64(lhs) > Int128Low64(rhs))
+             : (Int128High64(lhs) > Int128High64(rhs));
+}
+
+constexpr bool operator<=(int128 lhs, int128 rhs) { return !(lhs > rhs); }
+
+constexpr bool operator>=(int128 lhs, int128 rhs) { return !(lhs < rhs); }
+
+// Unary operators.
+
+constexpr int128 operator-(int128 v) {
+  return MakeInt128(~Int128High64(v) + (Int128Low64(v) == 0),
+                    ~Int128Low64(v) + 1);
+}
+
+constexpr bool operator!(int128 v) {
+  return !Int128Low64(v) && !Int128High64(v);
+}
+
+constexpr int128 operator~(int128 val) {
+  return MakeInt128(~Int128High64(val), ~Int128Low64(val));
+}
+
+// Arithmetic operators.
+
+namespace int128_internal {
+constexpr int128 SignedAddResult(int128 result, int128 lhs) {
+  // check for carry
+  return (Int128Low64(result) < Int128Low64(lhs))
+             ? MakeInt128(Int128High64(result) + 1, Int128Low64(result))
+             : result;
+}
+}  // namespace int128_internal
+constexpr int128 operator+(int128 lhs, int128 rhs) {
+  return int128_internal::SignedAddResult(
+      MakeInt128(Int128High64(lhs) + Int128High64(rhs),
+                 Int128Low64(lhs) + Int128Low64(rhs)),
+      lhs);
+}
+
+namespace int128_internal {
+constexpr int128 SignedSubstructResult(int128 result, int128 lhs, int128 rhs) {
+  // check for carry
+  return (Int128Low64(lhs) < Int128Low64(rhs))
+             ? MakeInt128(Int128High64(result) - 1, Int128Low64(result))
+             : result;
+}
+}  // namespace int128_internal
+constexpr int128 operator-(int128 lhs, int128 rhs) {
+  return int128_internal::SignedSubstructResult(
+      MakeInt128(Int128High64(lhs) - Int128High64(rhs),
+                 Int128Low64(lhs) - Int128Low64(rhs)),
+      lhs, rhs);
+}
+
+inline int128 operator*(int128 lhs, int128 rhs) {
+  return MakeInt128(
+      int128_internal::BitCastToSigned(Uint128High64(uint128(lhs) * rhs)),
+      Uint128Low64(uint128(lhs) * rhs));
+}
+
+inline int128 int128::operator++(int) {
+  int128 tmp(*this);
+  *this += 1;
+  return tmp;
+}
+
+inline int128 int128::operator--(int) {
+  int128 tmp(*this);
+  *this -= 1;
+  return tmp;
+}
+
+inline int128& int128::operator++() {
+  *this += 1;
+  return *this;
+}
+
+inline int128& int128::operator--() {
+  *this -= 1;
+  return *this;
+}
+
+constexpr int128 operator|(int128 lhs, int128 rhs) {
+  return MakeInt128(Int128High64(lhs) | Int128High64(rhs),
+                    Int128Low64(lhs) | Int128Low64(rhs));
+}
+
+constexpr int128 operator&(int128 lhs, int128 rhs) {
+  return MakeInt128(Int128High64(lhs) & Int128High64(rhs),
+                    Int128Low64(lhs) & Int128Low64(rhs));
+}
+
+constexpr int128 operator^(int128 lhs, int128 rhs) {
+  return MakeInt128(Int128High64(lhs) ^ Int128High64(rhs),
+                    Int128Low64(lhs) ^ Int128Low64(rhs));
+}
+
+constexpr int128 operator<<(int128 lhs, int amount) {
+  // int64_t shifts of >= 63 are undefined, so we need some special-casing.
+  assert(amount >= 0 && amount < 127);
+  if (amount <= 0) {
+    return lhs;
+  } else if (amount < 63) {
+    return MakeInt128(
+        (Int128High64(lhs) << amount) |
+            static_cast<int64_t>(Int128Low64(lhs) >> (64 - amount)),
+        Int128Low64(lhs) << amount);
+  } else if (amount == 63) {
+    return MakeInt128(((Int128High64(lhs) << 32) << 31) |
+                          static_cast<int64_t>(Int128Low64(lhs) >> 1),
+                      (Int128Low64(lhs) << 32) << 31);
+  } else if (amount == 127) {
+    return MakeInt128(static_cast<int64_t>(Int128Low64(lhs) << 63), 0);
+  } else if (amount > 127) {
+    return MakeInt128(0, 0);
+  } else {
+    // amount >= 64 && amount < 127
+    return MakeInt128(static_cast<int64_t>(Int128Low64(lhs) << (amount - 64)),
+                      0);
+  }
+}
+
+constexpr int128 operator>>(int128 lhs, int amount) {
+  // int64_t shifts of >= 63 are undefined, so we need some special-casing.
+  assert(amount >= 0 && amount < 127);
+  if (amount <= 0) {
+    return lhs;
+  } else if (amount < 63) {
+    return MakeInt128(
+        Int128High64(lhs) >> amount,
+        Int128Low64(lhs) >> amount | static_cast<uint64_t>(Int128High64(lhs))
+                                         << (64 - amount));
+  } else if (amount == 63) {
+    return MakeInt128((Int128High64(lhs) >> 32) >> 31,
+                      static_cast<uint64_t>(Int128High64(lhs) << 1) |
+                          (Int128Low64(lhs) >> 32) >> 31);
+
+  } else if (amount >= 127) {
+    return MakeInt128((Int128High64(lhs) >> 32) >> 31,
+                      static_cast<uint64_t>((Int128High64(lhs) >> 32) >> 31));
+  } else {
+    // amount >= 64 && amount < 127
+    return MakeInt128(
+        (Int128High64(lhs) >> 32) >> 31,
+        static_cast<uint64_t>(Int128High64(lhs) >> (amount - 64)));
+  }
+}
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128_stream_test.cc b/weight/_dep/abseil-cpp/absl/numeric/int128_stream_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bd937847d0aa32a7c5d10f1e30d11af6c3d6024e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128_stream_test.cc
@@ -0,0 +1,1400 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/numeric/int128.h"
+
+#include <sstream>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/strings/str_cat.h"
+
+namespace {
+
+struct Uint128TestCase {
+  absl::uint128 value;
+  std::ios_base::fmtflags flags;
+  std::streamsize width;
+  const char* expected;
+};
+
+constexpr char kFill = '_';
+
+std::string StreamFormatToString(std::ios_base::fmtflags flags,
+                                 std::streamsize width) {
+  std::vector<const char*> flagstr;
+  switch (flags & std::ios::basefield) {
+    case std::ios::dec:
+      flagstr.push_back("std::ios::dec");
+      break;
+    case std::ios::oct:
+      flagstr.push_back("std::ios::oct");
+      break;
+    case std::ios::hex:
+      flagstr.push_back("std::ios::hex");
+      break;
+    default:  // basefield not specified
+      break;
+  }
+  switch (flags & std::ios::adjustfield) {
+    case std::ios::left:
+      flagstr.push_back("std::ios::left");
+      break;
+    case std::ios::internal:
+      flagstr.push_back("std::ios::internal");
+      break;
+    case std::ios::right:
+      flagstr.push_back("std::ios::right");
+      break;
+    default:  // adjustfield not specified
+      break;
+  }
+  if (flags & std::ios::uppercase) flagstr.push_back("std::ios::uppercase");
+  if (flags & std::ios::showbase) flagstr.push_back("std::ios::showbase");
+  if (flags & std::ios::showpos) flagstr.push_back("std::ios::showpos");
+
+  std::ostringstream msg;
+  msg << "\n  StreamFormatToString(test_case.flags, test_case.width)\n    "
+         "flags: ";
+  if (!flagstr.empty()) {
+    for (size_t i = 0; i < flagstr.size() - 1; ++i) msg << flagstr[i] << " | ";
+    msg << flagstr.back();
+  } else {
+    msg << "(default)";
+  }
+  msg << "\n    width: " << width << "\n    fill: '" << kFill << "'";
+  return msg.str();
+}
+
+constexpr std::ios::fmtflags kDec = std::ios::dec;
+constexpr std::ios::fmtflags kOct = std::ios::oct;
+constexpr std::ios::fmtflags kHex = std::ios::hex;
+constexpr std::ios::fmtflags kLeft = std::ios::left;
+constexpr std::ios::fmtflags kInt = std::ios::internal;
+constexpr std::ios::fmtflags kRight = std::ios::right;
+constexpr std::ios::fmtflags kUpper = std::ios::uppercase;
+constexpr std::ios::fmtflags kBase = std::ios::showbase;
+constexpr std::ios::fmtflags kPos = std::ios::showpos;
+
+void CheckUint128Case(const Uint128TestCase& test_case) {
+  if (test_case.flags == kDec && test_case.width == 0) {
+    EXPECT_EQ(absl::StrCat(test_case.value), test_case.expected);
+  }
+  std::ostringstream os;
+  os.flags(test_case.flags);
+  os.width(test_case.width);
+  os.fill(kFill);
+  os << test_case.value;
+  SCOPED_TRACE(StreamFormatToString(test_case.flags, test_case.width));
+  EXPECT_EQ(os.str(), test_case.expected);
+}
+
+TEST(Uint128, OStreamValueTest) {
+  CheckUint128Case({1, kDec, /*width = */ 0, "1"});
+  CheckUint128Case({1, kOct, /*width = */ 0, "1"});
+  CheckUint128Case({1, kHex, /*width = */ 0, "1"});
+  CheckUint128Case({9, kDec, /*width = */ 0, "9"});
+  CheckUint128Case({9, kOct, /*width = */ 0, "11"});
+  CheckUint128Case({9, kHex, /*width = */ 0, "9"});
+  CheckUint128Case({12345, kDec, /*width = */ 0, "12345"});
+  CheckUint128Case({12345, kOct, /*width = */ 0, "30071"});
+  CheckUint128Case({12345, kHex, /*width = */ 0, "3039"});
+  CheckUint128Case(
+      {0x8000000000000000, kDec, /*width = */ 0, "9223372036854775808"});
+  CheckUint128Case(
+      {0x8000000000000000, kOct, /*width = */ 0, "1000000000000000000000"});
+  CheckUint128Case(
+      {0x8000000000000000, kHex, /*width = */ 0, "8000000000000000"});
+  CheckUint128Case({std::numeric_limits<uint64_t>::max(), kDec,
+                    /*width = */ 0, "18446744073709551615"});
+  CheckUint128Case({std::numeric_limits<uint64_t>::max(), kOct,
+                    /*width = */ 0, "1777777777777777777777"});
+  CheckUint128Case({std::numeric_limits<uint64_t>::max(), kHex,
+                    /*width = */ 0, "ffffffffffffffff"});
+  CheckUint128Case(
+      {absl::MakeUint128(1, 0), kDec, /*width = */ 0, "18446744073709551616"});
+  CheckUint128Case({absl::MakeUint128(1, 0), kOct, /*width = */ 0,
+                    "2000000000000000000000"});
+  CheckUint128Case(
+      {absl::MakeUint128(1, 0), kHex, /*width = */ 0, "10000000000000000"});
+  CheckUint128Case({absl::MakeUint128(0x8000000000000000, 0), kDec,
+                    /*width = */ 0, "170141183460469231731687303715884105728"});
+  CheckUint128Case({absl::MakeUint128(0x8000000000000000, 0), kOct,
+                    /*width = */ 0,
+                    "2000000000000000000000000000000000000000000"});
+  CheckUint128Case({absl::MakeUint128(0x8000000000000000, 0), kHex,
+                    /*width = */ 0, "80000000000000000000000000000000"});
+  CheckUint128Case({absl::kuint128max, kDec, /*width = */ 0,
+                    "340282366920938463463374607431768211455"});
+  CheckUint128Case({absl::kuint128max, kOct, /*width = */ 0,
+                    "3777777777777777777777777777777777777777777"});
+  CheckUint128Case({absl::kuint128max, kHex, /*width = */ 0,
+                    "ffffffffffffffffffffffffffffffff"});
+}
+
+std::vector<Uint128TestCase> GetUint128FormatCases();
+
+TEST(Uint128, OStreamFormatTest) {
+  for (const Uint128TestCase& test_case : GetUint128FormatCases()) {
+    CheckUint128Case(test_case);
+  }
+}
+
+struct Int128TestCase {
+  absl::int128 value;
+  std::ios_base::fmtflags flags;
+  std::streamsize width;
+  const char* expected;
+};
+
+void CheckInt128Case(const Int128TestCase& test_case) {
+  if (test_case.flags == kDec && test_case.width == 0) {
+    EXPECT_EQ(absl::StrCat(test_case.value), test_case.expected);
+  }
+  std::ostringstream os;
+  os.flags(test_case.flags);
+  os.width(test_case.width);
+  os.fill(kFill);
+  os << test_case.value;
+  SCOPED_TRACE(StreamFormatToString(test_case.flags, test_case.width));
+  EXPECT_EQ(os.str(), test_case.expected);
+}
+
+TEST(Int128, OStreamValueTest) {
+  CheckInt128Case({1, kDec, /*width = */ 0, "1"});
+  CheckInt128Case({1, kOct, /*width = */ 0, "1"});
+  CheckInt128Case({1, kHex, /*width = */ 0, "1"});
+  CheckInt128Case({9, kDec, /*width = */ 0, "9"});
+  CheckInt128Case({9, kOct, /*width = */ 0, "11"});
+  CheckInt128Case({9, kHex, /*width = */ 0, "9"});
+  CheckInt128Case({12345, kDec, /*width = */ 0, "12345"});
+  CheckInt128Case({12345, kOct, /*width = */ 0, "30071"});
+  CheckInt128Case({12345, kHex, /*width = */ 0, "3039"});
+  CheckInt128Case(
+      {0x8000000000000000, kDec, /*width = */ 0, "9223372036854775808"});
+  CheckInt128Case(
+      {0x8000000000000000, kOct, /*width = */ 0, "1000000000000000000000"});
+  CheckInt128Case(
+      {0x8000000000000000, kHex, /*width = */ 0, "8000000000000000"});
+  CheckInt128Case({std::numeric_limits<uint64_t>::max(), kDec,
+                   /*width = */ 0, "18446744073709551615"});
+  CheckInt128Case({std::numeric_limits<uint64_t>::max(), kOct,
+                   /*width = */ 0, "1777777777777777777777"});
+  CheckInt128Case({std::numeric_limits<uint64_t>::max(), kHex,
+                   /*width = */ 0, "ffffffffffffffff"});
+  CheckInt128Case(
+      {absl::MakeInt128(1, 0), kDec, /*width = */ 0, "18446744073709551616"});
+  CheckInt128Case(
+      {absl::MakeInt128(1, 0), kOct, /*width = */ 0, "2000000000000000000000"});
+  CheckInt128Case(
+      {absl::MakeInt128(1, 0), kHex, /*width = */ 0, "10000000000000000"});
+  CheckInt128Case({absl::MakeInt128(std::numeric_limits<int64_t>::max(),
+                                    std::numeric_limits<uint64_t>::max()),
+                   kDec, /*width = */ 0,
+                   "170141183460469231731687303715884105727"});
+  CheckInt128Case({absl::MakeInt128(std::numeric_limits<int64_t>::max(),
+                                    std::numeric_limits<uint64_t>::max()),
+                   kOct, /*width = */ 0,
+                   "1777777777777777777777777777777777777777777"});
+  CheckInt128Case({absl::MakeInt128(std::numeric_limits<int64_t>::max(),
+                                    std::numeric_limits<uint64_t>::max()),
+                   kHex, /*width = */ 0, "7fffffffffffffffffffffffffffffff"});
+  CheckInt128Case({absl::MakeInt128(std::numeric_limits<int64_t>::min(), 0),
+                   kDec, /*width = */ 0,
+                   "-170141183460469231731687303715884105728"});
+  CheckInt128Case({absl::MakeInt128(std::numeric_limits<int64_t>::min(), 0),
+                   kOct, /*width = */ 0,
+                   "2000000000000000000000000000000000000000000"});
+  CheckInt128Case({absl::MakeInt128(std::numeric_limits<int64_t>::min(), 0),
+                   kHex, /*width = */ 0, "80000000000000000000000000000000"});
+  CheckInt128Case({-1, kDec, /*width = */ 0, "-1"});
+  CheckInt128Case({-1, kOct, /*width = */ 0,
+                   "3777777777777777777777777777777777777777777"});
+  CheckInt128Case(
+      {-1, kHex, /*width = */ 0, "ffffffffffffffffffffffffffffffff"});
+  CheckInt128Case({-12345, kDec, /*width = */ 0, "-12345"});
+  CheckInt128Case({-12345, kOct, /*width = */ 0,
+                   "3777777777777777777777777777777777777747707"});
+  CheckInt128Case(
+      {-12345, kHex, /*width = */ 0, "ffffffffffffffffffffffffffffcfc7"});
+}
+
+std::vector<Int128TestCase> GetInt128FormatCases();
+TEST(Int128, OStreamFormatTest) {
+  for (const Int128TestCase& test_case : GetInt128FormatCases()) {
+    CheckInt128Case(test_case);
+  }
+}
+
+std::vector<Int128TestCase> GetInt128FormatCases() {
+  return {
+      {0, std::ios_base::fmtflags(), /*width = */ 0, "0"},
+      {0, std::ios_base::fmtflags(), /*width = */ 6, "_____0"},
+      {0, kPos, /*width = */ 0, "+0"},
+      {0, kPos, /*width = */ 6, "____+0"},
+      {0, kBase, /*width = */ 0, "0"},
+      {0, kBase, /*width = */ 6, "_____0"},
+      {0, kBase | kPos, /*width = */ 0, "+0"},
+      {0, kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kUpper, /*width = */ 0, "0"},
+      {0, kUpper, /*width = */ 6, "_____0"},
+      {0, kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kUpper | kPos, /*width = */ 6, "____+0"},
+      {0, kUpper | kBase, /*width = */ 0, "0"},
+      {0, kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kUpper | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kLeft, /*width = */ 0, "0"},
+      {0, kLeft, /*width = */ 6, "0_____"},
+      {0, kLeft | kPos, /*width = */ 0, "+0"},
+      {0, kLeft | kPos, /*width = */ 6, "+0____"},
+      {0, kLeft | kBase, /*width = */ 0, "0"},
+      {0, kLeft | kBase, /*width = */ 6, "0_____"},
+      {0, kLeft | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kLeft | kBase | kPos, /*width = */ 6, "+0____"},
+      {0, kLeft | kUpper, /*width = */ 0, "0"},
+      {0, kLeft | kUpper, /*width = */ 6, "0_____"},
+      {0, kLeft | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kLeft | kUpper | kPos, /*width = */ 6, "+0____"},
+      {0, kLeft | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kLeft | kUpper | kBase, /*width = */ 6, "0_____"},
+      {0, kLeft | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kLeft | kUpper | kBase | kPos, /*width = */ 6, "+0____"},
+      {0, kInt, /*width = */ 0, "0"},
+      {0, kInt, /*width = */ 6, "_____0"},
+      {0, kInt | kPos, /*width = */ 0, "+0"},
+      {0, kInt | kPos, /*width = */ 6, "+____0"},
+      {0, kInt | kBase, /*width = */ 0, "0"},
+      {0, kInt | kBase, /*width = */ 6, "_____0"},
+      {0, kInt | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kInt | kBase | kPos, /*width = */ 6, "+____0"},
+      {0, kInt | kUpper, /*width = */ 0, "0"},
+      {0, kInt | kUpper, /*width = */ 6, "_____0"},
+      {0, kInt | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kInt | kUpper | kPos, /*width = */ 6, "+____0"},
+      {0, kInt | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kInt | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kInt | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kInt | kUpper | kBase | kPos, /*width = */ 6, "+____0"},
+      {0, kRight, /*width = */ 0, "0"},
+      {0, kRight, /*width = */ 6, "_____0"},
+      {0, kRight | kPos, /*width = */ 0, "+0"},
+      {0, kRight | kPos, /*width = */ 6, "____+0"},
+      {0, kRight | kBase, /*width = */ 0, "0"},
+      {0, kRight | kBase, /*width = */ 6, "_____0"},
+      {0, kRight | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kRight | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kRight | kUpper, /*width = */ 0, "0"},
+      {0, kRight | kUpper, /*width = */ 6, "_____0"},
+      {0, kRight | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kRight | kUpper | kPos, /*width = */ 6, "____+0"},
+      {0, kRight | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kRight | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kRight | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kRight | kUpper | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kDec, /*width = */ 0, "0"},
+      {0, kDec, /*width = */ 6, "_____0"},
+      {0, kDec | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kBase, /*width = */ 0, "0"},
+      {0, kDec | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kUpper, /*width = */ 6, "_____0"},
+      {0, kDec | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kUpper | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kUpper | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kLeft, /*width = */ 0, "0"},
+      {0, kDec | kLeft, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kLeft | kPos, /*width = */ 6, "+0____"},
+      {0, kDec | kLeft | kBase, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kBase, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kLeft | kBase | kPos, /*width = */ 6, "+0____"},
+      {0, kDec | kLeft | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kUpper, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kLeft | kUpper | kPos, /*width = */ 6, "+0____"},
+      {0, kDec | kLeft | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kUpper | kBase, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kLeft | kUpper | kBase | kPos, /*width = */ 6, "+0____"},
+      {0, kDec | kInt, /*width = */ 0, "0"},
+      {0, kDec | kInt, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kInt | kPos, /*width = */ 6, "+____0"},
+      {0, kDec | kInt | kBase, /*width = */ 0, "0"},
+      {0, kDec | kInt | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kInt | kBase | kPos, /*width = */ 6, "+____0"},
+      {0, kDec | kInt | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kInt | kUpper, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kInt | kUpper | kPos, /*width = */ 6, "+____0"},
+      {0, kDec | kInt | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kInt | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kInt | kUpper | kBase | kPos, /*width = */ 6, "+____0"},
+      {0, kDec | kRight, /*width = */ 0, "0"},
+      {0, kDec | kRight, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kRight | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kRight | kBase, /*width = */ 0, "0"},
+      {0, kDec | kRight | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kRight | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kRight | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kRight | kUpper, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kUpper | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kRight | kUpper | kPos, /*width = */ 6, "____+0"},
+      {0, kDec | kRight | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kRight | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kUpper | kBase | kPos, /*width = */ 0, "+0"},
+      {0, kDec | kRight | kUpper | kBase | kPos, /*width = */ 6, "____+0"},
+      {0, kOct, /*width = */ 0, "0"},
+      {0, kOct, /*width = */ 6, "_____0"},
+      {0, kOct | kPos, /*width = */ 0, "0"},
+      {0, kOct | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kBase, /*width = */ 0, "0"},
+      {0, kOct | kBase, /*width = */ 6, "_____0"},
+      {0, kOct | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper, /*width = */ 0, "0"},
+      {0, kOct | kUpper, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kOct | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kOct | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kLeft, /*width = */ 0, "0"},
+      {0, kOct | kLeft, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kPos, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kPos, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kBase, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kBase, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kUpper, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kUpper, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kUpper | kPos, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kUpper | kBase, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kUpper | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kOct | kInt, /*width = */ 0, "0"},
+      {0, kOct | kInt, /*width = */ 6, "_____0"},
+      {0, kOct | kInt | kPos, /*width = */ 0, "0"},
+      {0, kOct | kInt | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kInt | kBase, /*width = */ 0, "0"},
+      {0, kOct | kInt | kBase, /*width = */ 6, "_____0"},
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+      {42, kHex | kLeft | kUpper | kBase, /*width = */ 0, "0X2A"},
+      {42, kHex | kLeft | kUpper | kBase, /*width = */ 6, "0X2A__"},
+      {42, kHex | kLeft | kUpper | kBase | kPos, /*width = */ 0, "0X2A"},
+      {42, kHex | kLeft | kUpper | kBase | kPos, /*width = */ 6, "0X2A__"},
+      {42, kHex | kInt, /*width = */ 0, "2a"},
+      {42, kHex | kInt, /*width = */ 6, "____2a"},
+      {42, kHex | kInt | kPos, /*width = */ 0, "2a"},
+      {42, kHex | kInt | kPos, /*width = */ 6, "____2a"},
+      {42, kHex | kInt | kBase, /*width = */ 0, "0x2a"},
+      {42, kHex | kInt | kBase, /*width = */ 6, "0x__2a"},
+      {42, kHex | kInt | kBase | kPos, /*width = */ 0, "0x2a"},
+      {42, kHex | kInt | kBase | kPos, /*width = */ 6, "0x__2a"},
+      {42, kHex | kInt | kUpper, /*width = */ 0, "2A"},
+      {42, kHex | kInt | kUpper, /*width = */ 6, "____2A"},
+      {42, kHex | kInt | kUpper | kPos, /*width = */ 0, "2A"},
+      {42, kHex | kInt | kUpper | kPos, /*width = */ 6, "____2A"},
+      {42, kHex | kInt | kUpper | kBase, /*width = */ 0, "0X2A"},
+      {42, kHex | kInt | kUpper | kBase, /*width = */ 6, "0X__2A"},
+      {42, kHex | kInt | kUpper | kBase | kPos, /*width = */ 0, "0X2A"},
+      {42, kHex | kInt | kUpper | kBase | kPos, /*width = */ 6, "0X__2A"},
+      {42, kHex | kRight, /*width = */ 0, "2a"},
+      {42, kHex | kRight, /*width = */ 6, "____2a"},
+      {42, kHex | kRight | kPos, /*width = */ 0, "2a"},
+      {42, kHex | kRight | kPos, /*width = */ 6, "____2a"},
+      {42, kHex | kRight | kBase, /*width = */ 0, "0x2a"},
+      {42, kHex | kRight | kBase, /*width = */ 6, "__0x2a"},
+      {42, kHex | kRight | kBase | kPos, /*width = */ 0, "0x2a"},
+      {42, kHex | kRight | kBase | kPos, /*width = */ 6, "__0x2a"},
+      {42, kHex | kRight | kUpper, /*width = */ 0, "2A"},
+      {42, kHex | kRight | kUpper, /*width = */ 6, "____2A"},
+      {42, kHex | kRight | kUpper | kPos, /*width = */ 0, "2A"},
+      {42, kHex | kRight | kUpper | kPos, /*width = */ 6, "____2A"},
+      {42, kHex | kRight | kUpper | kBase, /*width = */ 0, "0X2A"},
+      {42, kHex | kRight | kUpper | kBase, /*width = */ 6, "__0X2A"},
+      {42, kHex | kRight | kUpper | kBase | kPos, /*width = */ 0, "0X2A"},
+      {42, kHex | kRight | kUpper | kBase | kPos, /*width = */ 6, "__0X2A"},
+      {-321, std::ios_base::fmtflags(), /*width = */ 0, "-321"},
+      {-321, std::ios_base::fmtflags(), /*width = */ 6, "__-321"},
+      {-321, kPos, /*width = */ 0, "-321"},
+      {-321, kPos, /*width = */ 6, "__-321"},
+      {-321, kBase, /*width = */ 0, "-321"},
+      {-321, kBase, /*width = */ 6, "__-321"},
+      {-321, kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kUpper, /*width = */ 0, "-321"},
+      {-321, kUpper, /*width = */ 6, "__-321"},
+      {-321, kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kUpper | kPos, /*width = */ 6, "__-321"},
+      {-321, kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kUpper | kBase, /*width = */ 6, "__-321"},
+      {-321, kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kUpper | kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kLeft, /*width = */ 0, "-321"},
+      {-321, kLeft, /*width = */ 6, "-321__"},
+      {-321, kLeft | kPos, /*width = */ 0, "-321"},
+      {-321, kLeft | kPos, /*width = */ 6, "-321__"},
+      {-321, kLeft | kBase, /*width = */ 0, "-321"},
+      {-321, kLeft | kBase, /*width = */ 6, "-321__"},
+      {-321, kLeft | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kLeft | kBase | kPos, /*width = */ 6, "-321__"},
+      {-321, kLeft | kUpper, /*width = */ 0, "-321"},
+      {-321, kLeft | kUpper, /*width = */ 6, "-321__"},
+      {-321, kLeft | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kLeft | kUpper | kPos, /*width = */ 6, "-321__"},
+      {-321, kLeft | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kLeft | kUpper | kBase, /*width = */ 6, "-321__"},
+      {-321, kLeft | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kLeft | kUpper | kBase | kPos, /*width = */ 6, "-321__"},
+      {-321, kInt, /*width = */ 0, "-321"},
+      {-321, kInt, /*width = */ 6, "-__321"},
+      {-321, kInt | kPos, /*width = */ 0, "-321"},
+      {-321, kInt | kPos, /*width = */ 6, "-__321"},
+      {-321, kInt | kBase, /*width = */ 0, "-321"},
+      {-321, kInt | kBase, /*width = */ 6, "-__321"},
+      {-321, kInt | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kInt | kBase | kPos, /*width = */ 6, "-__321"},
+      {-321, kInt | kUpper, /*width = */ 0, "-321"},
+      {-321, kInt | kUpper, /*width = */ 6, "-__321"},
+      {-321, kInt | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kInt | kUpper | kPos, /*width = */ 6, "-__321"},
+      {-321, kInt | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kInt | kUpper | kBase, /*width = */ 6, "-__321"},
+      {-321, kInt | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kInt | kUpper | kBase | kPos, /*width = */ 6, "-__321"},
+      {-321, kRight, /*width = */ 0, "-321"},
+      {-321, kRight, /*width = */ 6, "__-321"},
+      {-321, kRight | kPos, /*width = */ 0, "-321"},
+      {-321, kRight | kPos, /*width = */ 6, "__-321"},
+      {-321, kRight | kBase, /*width = */ 0, "-321"},
+      {-321, kRight | kBase, /*width = */ 6, "__-321"},
+      {-321, kRight | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kRight | kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kRight | kUpper, /*width = */ 0, "-321"},
+      {-321, kRight | kUpper, /*width = */ 6, "__-321"},
+      {-321, kRight | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kRight | kUpper | kPos, /*width = */ 6, "__-321"},
+      {-321, kRight | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kRight | kUpper | kBase, /*width = */ 6, "__-321"},
+      {-321, kRight | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kRight | kUpper | kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec, /*width = */ 0, "-321"},
+      {-321, kDec, /*width = */ 6, "__-321"},
+      {-321, kDec | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kBase, /*width = */ 6, "__-321"},
+      {-321, kDec | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kUpper, /*width = */ 0, "-321"},
+      {-321, kDec | kUpper, /*width = */ 6, "__-321"},
+      {-321, kDec | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kUpper | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kUpper | kBase, /*width = */ 6, "__-321"},
+      {-321, kDec | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kUpper | kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kLeft, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kPos, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kBase, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kBase | kPos, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kUpper, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kUpper, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kUpper | kPos, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kUpper | kBase, /*width = */ 6, "-321__"},
+      {-321, kDec | kLeft | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kLeft | kUpper | kBase | kPos, /*width = */ 6, "-321__"},
+      {-321, kDec | kInt, /*width = */ 0, "-321"},
+      {-321, kDec | kInt, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kPos, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kBase, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kBase | kPos, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kUpper, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kUpper, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kUpper | kPos, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kUpper | kBase, /*width = */ 6, "-__321"},
+      {-321, kDec | kInt | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kInt | kUpper | kBase | kPos, /*width = */ 6, "-__321"},
+      {-321, kDec | kRight, /*width = */ 0, "-321"},
+      {-321, kDec | kRight, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kBase, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kBase | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kUpper, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kUpper, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kUpper | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kUpper | kPos, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kUpper | kBase, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kUpper | kBase, /*width = */ 6, "__-321"},
+      {-321, kDec | kRight | kUpper | kBase | kPos, /*width = */ 0, "-321"},
+      {-321, kDec | kRight | kUpper | kBase | kPos, /*width = */ 6, "__-321"}};
+}
+
+std::vector<Uint128TestCase> GetUint128FormatCases() {
+  return {
+      {0, std::ios_base::fmtflags(), /*width = */ 0, "0"},
+      {0, std::ios_base::fmtflags(), /*width = */ 6, "_____0"},
+      {0, kPos, /*width = */ 0, "0"},
+      {0, kPos, /*width = */ 6, "_____0"},
+      {0, kBase, /*width = */ 0, "0"},
+      {0, kBase, /*width = */ 6, "_____0"},
+      {0, kBase | kPos, /*width = */ 0, "0"},
+      {0, kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kUpper, /*width = */ 0, "0"},
+      {0, kUpper, /*width = */ 6, "_____0"},
+      {0, kUpper | kPos, /*width = */ 0, "0"},
+      {0, kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kUpper | kBase, /*width = */ 0, "0"},
+      {0, kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kLeft, /*width = */ 0, "0"},
+      {0, kLeft, /*width = */ 6, "0_____"},
+      {0, kLeft | kPos, /*width = */ 0, "0"},
+      {0, kLeft | kPos, /*width = */ 6, "0_____"},
+      {0, kLeft | kBase, /*width = */ 0, "0"},
+      {0, kLeft | kBase, /*width = */ 6, "0_____"},
+      {0, kLeft | kBase | kPos, /*width = */ 0, "0"},
+      {0, kLeft | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kLeft | kUpper, /*width = */ 0, "0"},
+      {0, kLeft | kUpper, /*width = */ 6, "0_____"},
+      {0, kLeft | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kLeft | kUpper | kPos, /*width = */ 6, "0_____"},
+      {0, kLeft | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kLeft | kUpper | kBase, /*width = */ 6, "0_____"},
+      {0, kLeft | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kLeft | kUpper | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kInt, /*width = */ 0, "0"},
+      {0, kInt, /*width = */ 6, "_____0"},
+      {0, kInt | kPos, /*width = */ 0, "0"},
+      {0, kInt | kPos, /*width = */ 6, "_____0"},
+      {0, kInt | kBase, /*width = */ 0, "0"},
+      {0, kInt | kBase, /*width = */ 6, "_____0"},
+      {0, kInt | kBase | kPos, /*width = */ 0, "0"},
+      {0, kInt | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kInt | kUpper, /*width = */ 0, "0"},
+      {0, kInt | kUpper, /*width = */ 6, "_____0"},
+      {0, kInt | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kInt | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kInt | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kInt | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kInt | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kInt | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kRight, /*width = */ 0, "0"},
+      {0, kRight, /*width = */ 6, "_____0"},
+      {0, kRight | kPos, /*width = */ 0, "0"},
+      {0, kRight | kPos, /*width = */ 6, "_____0"},
+      {0, kRight | kBase, /*width = */ 0, "0"},
+      {0, kRight | kBase, /*width = */ 6, "_____0"},
+      {0, kRight | kBase | kPos, /*width = */ 0, "0"},
+      {0, kRight | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kRight | kUpper, /*width = */ 0, "0"},
+      {0, kRight | kUpper, /*width = */ 6, "_____0"},
+      {0, kRight | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kRight | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kRight | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kRight | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kRight | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kRight | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kDec, /*width = */ 0, "0"},
+      {0, kDec, /*width = */ 6, "_____0"},
+      {0, kDec | kPos, /*width = */ 0, "0"},
+      {0, kDec | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kBase, /*width = */ 0, "0"},
+      {0, kDec | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kUpper, /*width = */ 6, "_____0"},
+      {0, kDec | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kDec | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kLeft, /*width = */ 0, "0"},
+      {0, kDec | kLeft, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kPos, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kPos, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kBase, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kBase, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kUpper, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kUpper | kPos, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kUpper | kBase, /*width = */ 6, "0_____"},
+      {0, kDec | kLeft | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kLeft | kUpper | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kDec | kInt, /*width = */ 0, "0"},
+      {0, kDec | kInt, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kPos, /*width = */ 0, "0"},
+      {0, kDec | kInt | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kBase, /*width = */ 0, "0"},
+      {0, kDec | kInt | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kInt | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kInt | kUpper, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kDec | kInt | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kInt | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kInt | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kInt | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kRight, /*width = */ 0, "0"},
+      {0, kDec | kRight, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kPos, /*width = */ 0, "0"},
+      {0, kDec | kRight | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kBase, /*width = */ 0, "0"},
+      {0, kDec | kRight | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kRight | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kUpper, /*width = */ 0, "0"},
+      {0, kDec | kRight | kUpper, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kDec | kRight | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kDec | kRight | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kDec | kRight | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kDec | kRight | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kOct, /*width = */ 0, "0"},
+      {0, kOct, /*width = */ 6, "_____0"},
+      {0, kOct | kPos, /*width = */ 0, "0"},
+      {0, kOct | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kBase, /*width = */ 0, "0"},
+      {0, kOct | kBase, /*width = */ 6, "_____0"},
+      {0, kOct | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper, /*width = */ 0, "0"},
+      {0, kOct | kUpper, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper | kPos, /*width = */ 0, "0"},
+      {0, kOct | kUpper | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper | kBase, /*width = */ 0, "0"},
+      {0, kOct | kUpper | kBase, /*width = */ 6, "_____0"},
+      {0, kOct | kUpper | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kUpper | kBase | kPos, /*width = */ 6, "_____0"},
+      {0, kOct | kLeft, /*width = */ 0, "0"},
+      {0, kOct | kLeft, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kPos, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kPos, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kBase, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kBase, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kBase | kPos, /*width = */ 0, "0"},
+      {0, kOct | kLeft | kBase | kPos, /*width = */ 6, "0_____"},
+      {0, kOct | kLeft | kUpper, /*width = */ 0, "0"},
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+      {37, kHex | kLeft, /*width = */ 6, "25____"},
+      {37, kHex | kLeft | kPos, /*width = */ 0, "25"},
+      {37, kHex | kLeft | kPos, /*width = */ 6, "25____"},
+      {37, kHex | kLeft | kBase, /*width = */ 0, "0x25"},
+      {37, kHex | kLeft | kBase, /*width = */ 6, "0x25__"},
+      {37, kHex | kLeft | kBase | kPos, /*width = */ 0, "0x25"},
+      {37, kHex | kLeft | kBase | kPos, /*width = */ 6, "0x25__"},
+      {37, kHex | kLeft | kUpper, /*width = */ 0, "25"},
+      {37, kHex | kLeft | kUpper, /*width = */ 6, "25____"},
+      {37, kHex | kLeft | kUpper | kPos, /*width = */ 0, "25"},
+      {37, kHex | kLeft | kUpper | kPos, /*width = */ 6, "25____"},
+      {37, kHex | kLeft | kUpper | kBase, /*width = */ 0, "0X25"},
+      {37, kHex | kLeft | kUpper | kBase, /*width = */ 6, "0X25__"},
+      {37, kHex | kLeft | kUpper | kBase | kPos, /*width = */ 0, "0X25"},
+      {37, kHex | kLeft | kUpper | kBase | kPos, /*width = */ 6, "0X25__"},
+      {37, kHex | kInt, /*width = */ 0, "25"},
+      {37, kHex | kInt, /*width = */ 6, "____25"},
+      {37, kHex | kInt | kPos, /*width = */ 0, "25"},
+      {37, kHex | kInt | kPos, /*width = */ 6, "____25"},
+      {37, kHex | kInt | kBase, /*width = */ 0, "0x25"},
+      {37, kHex | kInt | kBase, /*width = */ 6, "0x__25"},
+      {37, kHex | kInt | kBase | kPos, /*width = */ 0, "0x25"},
+      {37, kHex | kInt | kBase | kPos, /*width = */ 6, "0x__25"},
+      {37, kHex | kInt | kUpper, /*width = */ 0, "25"},
+      {37, kHex | kInt | kUpper, /*width = */ 6, "____25"},
+      {37, kHex | kInt | kUpper | kPos, /*width = */ 0, "25"},
+      {37, kHex | kInt | kUpper | kPos, /*width = */ 6, "____25"},
+      {37, kHex | kInt | kUpper | kBase, /*width = */ 0, "0X25"},
+      {37, kHex | kInt | kUpper | kBase, /*width = */ 6, "0X__25"},
+      {37, kHex | kInt | kUpper | kBase | kPos, /*width = */ 0, "0X25"},
+      {37, kHex | kInt | kUpper | kBase | kPos, /*width = */ 6, "0X__25"},
+      {37, kHex | kRight, /*width = */ 0, "25"},
+      {37, kHex | kRight, /*width = */ 6, "____25"},
+      {37, kHex | kRight | kPos, /*width = */ 0, "25"},
+      {37, kHex | kRight | kPos, /*width = */ 6, "____25"},
+      {37, kHex | kRight | kBase, /*width = */ 0, "0x25"},
+      {37, kHex | kRight | kBase, /*width = */ 6, "__0x25"},
+      {37, kHex | kRight | kBase | kPos, /*width = */ 0, "0x25"},
+      {37, kHex | kRight | kBase | kPos, /*width = */ 6, "__0x25"},
+      {37, kHex | kRight | kUpper, /*width = */ 0, "25"},
+      {37, kHex | kRight | kUpper, /*width = */ 6, "____25"},
+      {37, kHex | kRight | kUpper | kPos, /*width = */ 0, "25"},
+      {37, kHex | kRight | kUpper | kPos, /*width = */ 6, "____25"},
+      {37, kHex | kRight | kUpper | kBase, /*width = */ 0, "0X25"},
+      {37, kHex | kRight | kUpper | kBase, /*width = */ 6, "__0X25"},
+      {37, kHex | kRight | kUpper | kBase | kPos, /*width = */ 0, "0X25"},
+      {37, kHex | kRight | kUpper | kBase | kPos, /*width = */ 6, "__0X25"}};
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/numeric/int128_test.cc b/weight/_dep/abseil-cpp/absl/numeric/int128_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..01e3eb5c98bb727988532e49bb6d892e1ba1fc7a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/int128_test.cc
@@ -0,0 +1,1285 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/numeric/int128.h"
+
+#include <algorithm>
+#include <limits>
+#include <random>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/base/internal/cycleclock.h"
+#include "absl/hash/hash_testing.h"
+#include "absl/meta/type_traits.h"
+
+#if defined(_MSC_VER) && _MSC_VER == 1900
+// Disable "unary minus operator applied to unsigned type" warnings in Microsoft
+// Visual C++ 14 (2015).
+#pragma warning(disable:4146)
+#endif
+
+#define MAKE_INT128(HI, LO) absl::MakeInt128(static_cast<int64_t>(HI), LO)
+
+namespace {
+
+template <typename T>
+class Uint128IntegerTraitsTest : public ::testing::Test {};
+typedef ::testing::Types<bool, char, signed char, unsigned char, char16_t,
+                         char32_t, wchar_t,
+                         short,           // NOLINT(runtime/int)
+                         unsigned short,  // NOLINT(runtime/int)
+                         int, unsigned int,
+                         long,                // NOLINT(runtime/int)
+                         unsigned long,       // NOLINT(runtime/int)
+                         long long,           // NOLINT(runtime/int)
+                         unsigned long long>  // NOLINT(runtime/int)
+    IntegerTypes;
+
+template <typename T>
+class Uint128FloatTraitsTest : public ::testing::Test {};
+typedef ::testing::Types<float, double, long double> FloatingPointTypes;
+
+TYPED_TEST_SUITE(Uint128IntegerTraitsTest, IntegerTypes);
+
+TYPED_TEST(Uint128IntegerTraitsTest, ConstructAssignTest) {
+  static_assert(std::is_constructible<absl::uint128, TypeParam>::value,
+                "absl::uint128 must be constructible from TypeParam");
+  static_assert(std::is_assignable<absl::uint128&, TypeParam>::value,
+                "absl::uint128 must be assignable from TypeParam");
+  static_assert(!std::is_assignable<TypeParam&, absl::uint128>::value,
+                "TypeParam must not be assignable from absl::uint128");
+}
+
+TYPED_TEST_SUITE(Uint128FloatTraitsTest, FloatingPointTypes);
+
+TYPED_TEST(Uint128FloatTraitsTest, ConstructAssignTest) {
+  static_assert(std::is_constructible<absl::uint128, TypeParam>::value,
+                "absl::uint128 must be constructible from TypeParam");
+  static_assert(!std::is_assignable<absl::uint128&, TypeParam>::value,
+                "absl::uint128 must not be assignable from TypeParam");
+  static_assert(!std::is_assignable<TypeParam&, absl::uint128>::value,
+                "TypeParam must not be assignable from absl::uint128");
+}
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+// These type traits done separately as TYPED_TEST requires typeinfo, and not
+// all platforms have this for __int128 even though they define the type.
+TEST(Uint128, IntrinsicTypeTraitsTest) {
+  static_assert(std::is_constructible<absl::uint128, __int128>::value,
+                "absl::uint128 must be constructible from __int128");
+  static_assert(std::is_assignable<absl::uint128&, __int128>::value,
+                "absl::uint128 must be assignable from __int128");
+  static_assert(!std::is_assignable<__int128&, absl::uint128>::value,
+                "__int128 must not be assignable from absl::uint128");
+
+  static_assert(std::is_constructible<absl::uint128, unsigned __int128>::value,
+                "absl::uint128 must be constructible from unsigned __int128");
+  static_assert(std::is_assignable<absl::uint128&, unsigned __int128>::value,
+                "absl::uint128 must be assignable from unsigned __int128");
+  static_assert(!std::is_assignable<unsigned __int128&, absl::uint128>::value,
+                "unsigned __int128 must not be assignable from absl::uint128");
+}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+TEST(Uint128, TrivialTraitsTest) {
+  static_assert(absl::is_trivially_default_constructible<absl::uint128>::value,
+                "");
+  static_assert(absl::is_trivially_copy_constructible<absl::uint128>::value,
+                "");
+  static_assert(absl::is_trivially_copy_assignable<absl::uint128>::value, "");
+  static_assert(std::is_trivially_destructible<absl::uint128>::value, "");
+}
+
+TEST(Uint128, AllTests) {
+  absl::uint128 zero = 0;
+  absl::uint128 one = 1;
+  absl::uint128 one_2arg = absl::MakeUint128(0, 1);
+  absl::uint128 two = 2;
+  absl::uint128 three = 3;
+  absl::uint128 big = absl::MakeUint128(2000, 2);
+  absl::uint128 big_minus_one = absl::MakeUint128(2000, 1);
+  absl::uint128 bigger = absl::MakeUint128(2001, 1);
+  absl::uint128 biggest = absl::Uint128Max();
+  absl::uint128 high_low = absl::MakeUint128(1, 0);
+  absl::uint128 low_high =
+      absl::MakeUint128(0, std::numeric_limits<uint64_t>::max());
+  EXPECT_LT(one, two);
+  EXPECT_GT(two, one);
+  EXPECT_LT(one, big);
+  EXPECT_LT(one, big);
+  EXPECT_EQ(one, one_2arg);
+  EXPECT_NE(one, two);
+  EXPECT_GT(big, one);
+  EXPECT_GE(big, two);
+  EXPECT_GE(big, big_minus_one);
+  EXPECT_GT(big, big_minus_one);
+  EXPECT_LT(big_minus_one, big);
+  EXPECT_LE(big_minus_one, big);
+  EXPECT_NE(big_minus_one, big);
+  EXPECT_LT(big, biggest);
+  EXPECT_LE(big, biggest);
+  EXPECT_GT(biggest, big);
+  EXPECT_GE(biggest, big);
+  EXPECT_EQ(big, ~~big);
+  EXPECT_EQ(one, one | one);
+  EXPECT_EQ(big, big | big);
+  EXPECT_EQ(one, one | zero);
+  EXPECT_EQ(one, one & one);
+  EXPECT_EQ(big, big & big);
+  EXPECT_EQ(zero, one & zero);
+  EXPECT_EQ(zero, big & ~big);
+  EXPECT_EQ(zero, one ^ one);
+  EXPECT_EQ(zero, big ^ big);
+  EXPECT_EQ(one, one ^ zero);
+
+  // Shift operators.
+  EXPECT_EQ(big, big << 0);
+  EXPECT_EQ(big, big >> 0);
+  EXPECT_GT(big << 1, big);
+  EXPECT_LT(big >> 1, big);
+  EXPECT_EQ(big, (big << 10) >> 10);
+  EXPECT_EQ(big, (big >> 1) << 1);
+  EXPECT_EQ(one, (one << 80) >> 80);
+  EXPECT_EQ(zero, (one >> 80) << 80);
+
+  // Shift assignments.
+  absl::uint128 big_copy = big;
+  EXPECT_EQ(big << 0, big_copy <<= 0);
+  big_copy = big;
+  EXPECT_EQ(big >> 0, big_copy >>= 0);
+  big_copy = big;
+  EXPECT_EQ(big << 1, big_copy <<= 1);
+  big_copy = big;
+  EXPECT_EQ(big >> 1, big_copy >>= 1);
+  big_copy = big;
+  EXPECT_EQ(big << 10, big_copy <<= 10);
+  big_copy = big;
+  EXPECT_EQ(big >> 10, big_copy >>= 10);
+  big_copy = big;
+  EXPECT_EQ(big << 64, big_copy <<= 64);
+  big_copy = big;
+  EXPECT_EQ(big >> 64, big_copy >>= 64);
+  big_copy = big;
+  EXPECT_EQ(big << 73, big_copy <<= 73);
+  big_copy = big;
+  EXPECT_EQ(big >> 73, big_copy >>= 73);
+
+  EXPECT_EQ(absl::Uint128High64(biggest), std::numeric_limits<uint64_t>::max());
+  EXPECT_EQ(absl::Uint128Low64(biggest), std::numeric_limits<uint64_t>::max());
+  EXPECT_EQ(zero + one, one);
+  EXPECT_EQ(one + one, two);
+  EXPECT_EQ(big_minus_one + one, big);
+  EXPECT_EQ(one - one, zero);
+  EXPECT_EQ(one - zero, one);
+  EXPECT_EQ(zero - one, biggest);
+  EXPECT_EQ(big - big, zero);
+  EXPECT_EQ(big - one, big_minus_one);
+  EXPECT_EQ(big + std::numeric_limits<uint64_t>::max(), bigger);
+  EXPECT_EQ(biggest + 1, zero);
+  EXPECT_EQ(zero - 1, biggest);
+  EXPECT_EQ(high_low - one, low_high);
+  EXPECT_EQ(low_high + one, high_low);
+  EXPECT_EQ(absl::Uint128High64((absl::uint128(1) << 64) - 1), 0);
+  EXPECT_EQ(absl::Uint128Low64((absl::uint128(1) << 64) - 1),
+            std::numeric_limits<uint64_t>::max());
+  EXPECT_TRUE(!!one);
+  EXPECT_TRUE(!!high_low);
+  EXPECT_FALSE(!!zero);
+  EXPECT_FALSE(!one);
+  EXPECT_FALSE(!high_low);
+  EXPECT_TRUE(!zero);
+  EXPECT_TRUE(zero == 0);       // NOLINT(readability/check)
+  EXPECT_FALSE(zero != 0);      // NOLINT(readability/check)
+  EXPECT_FALSE(one == 0);       // NOLINT(readability/check)
+  EXPECT_TRUE(one != 0);        // NOLINT(readability/check)
+  EXPECT_FALSE(high_low == 0);  // NOLINT(readability/check)
+  EXPECT_TRUE(high_low != 0);   // NOLINT(readability/check)
+
+  absl::uint128 test = zero;
+  EXPECT_EQ(++test, one);
+  EXPECT_EQ(test, one);
+  EXPECT_EQ(test++, one);
+  EXPECT_EQ(test, two);
+  EXPECT_EQ(test -= 2, zero);
+  EXPECT_EQ(test, zero);
+  EXPECT_EQ(test += 2, two);
+  EXPECT_EQ(test, two);
+  EXPECT_EQ(--test, one);
+  EXPECT_EQ(test, one);
+  EXPECT_EQ(test--, one);
+  EXPECT_EQ(test, zero);
+  EXPECT_EQ(test |= three, three);
+  EXPECT_EQ(test &= one, one);
+  EXPECT_EQ(test ^= three, two);
+  EXPECT_EQ(test >>= 1, one);
+  EXPECT_EQ(test <<= 1, two);
+
+  EXPECT_EQ(big, +big);
+  EXPECT_EQ(two, +two);
+  EXPECT_EQ(absl::Uint128Max(), +absl::Uint128Max());
+  EXPECT_EQ(zero, +zero);
+
+  EXPECT_EQ(big, -(-big));
+  EXPECT_EQ(two, -((-one) - 1));
+  EXPECT_EQ(absl::Uint128Max(), -one);
+  EXPECT_EQ(zero, -zero);
+
+  EXPECT_EQ(absl::Uint128Max(), absl::kuint128max);
+}
+
+TEST(Int128, RightShiftOfNegativeNumbers) {
+  absl::int128 minus_six = -6;
+  absl::int128 minus_three = -3;
+  absl::int128 minus_two = -2;
+  absl::int128 minus_one = -1;
+  if ((-6 >> 1) == -3) {
+    // Right shift is arithmetic (sign propagates)
+    EXPECT_EQ(minus_six >> 1, minus_three);
+    EXPECT_EQ(minus_six >> 2, minus_two);
+    EXPECT_EQ(minus_six >> 65, minus_one);
+  } else {
+    // Right shift is logical (zeros shifted in at MSB)
+    EXPECT_EQ(minus_six >> 1, absl::int128(absl::uint128(minus_six) >> 1));
+    EXPECT_EQ(minus_six >> 2, absl::int128(absl::uint128(minus_six) >> 2));
+    EXPECT_EQ(minus_six >> 65, absl::int128(absl::uint128(minus_six) >> 65));
+  }
+}
+
+TEST(Uint128, ConversionTests) {
+  EXPECT_TRUE(absl::MakeUint128(1, 0));
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+  unsigned __int128 intrinsic =
+      (static_cast<unsigned __int128>(0x3a5b76c209de76f6) << 64) +
+      0x1f25e1d63a2b46c5;
+  absl::uint128 custom =
+      absl::MakeUint128(0x3a5b76c209de76f6, 0x1f25e1d63a2b46c5);
+
+  EXPECT_EQ(custom, absl::uint128(intrinsic));
+  EXPECT_EQ(custom, absl::uint128(static_cast<__int128>(intrinsic)));
+  EXPECT_EQ(intrinsic, static_cast<unsigned __int128>(custom));
+  EXPECT_EQ(intrinsic, static_cast<__int128>(custom));
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+  // verify that an integer greater than 2**64 that can be stored precisely
+  // inside a double is converted to a absl::uint128 without loss of
+  // information.
+  double precise_double = 0x530e * std::pow(2.0, 64.0) + 0xda74000000000000;
+  absl::uint128 from_precise_double(precise_double);
+  absl::uint128 from_precise_ints =
+      absl::MakeUint128(0x530e, 0xda74000000000000);
+  EXPECT_EQ(from_precise_double, from_precise_ints);
+  EXPECT_DOUBLE_EQ(static_cast<double>(from_precise_ints), precise_double);
+
+  double approx_double =
+      static_cast<double>(0xffffeeeeddddcccc) * std::pow(2.0, 64.0) +
+      static_cast<double>(0xbbbbaaaa99998888);
+  absl::uint128 from_approx_double(approx_double);
+  EXPECT_DOUBLE_EQ(static_cast<double>(from_approx_double), approx_double);
+
+  double round_to_zero = 0.7;
+  double round_to_five = 5.8;
+  double round_to_nine = 9.3;
+  EXPECT_EQ(static_cast<absl::uint128>(round_to_zero), 0);
+  EXPECT_EQ(static_cast<absl::uint128>(round_to_five), 5);
+  EXPECT_EQ(static_cast<absl::uint128>(round_to_nine), 9);
+
+  absl::uint128 highest_precision_in_long_double =
+      ~absl::uint128{} >> (128 - std::numeric_limits<long double>::digits);
+  EXPECT_EQ(highest_precision_in_long_double,
+            static_cast<absl::uint128>(
+                static_cast<long double>(highest_precision_in_long_double)));
+  // Apply a mask just to make sure all the bits are the right place.
+  const absl::uint128 arbitrary_mask =
+      absl::MakeUint128(0xa29f622677ded751, 0xf8ca66add076f468);
+  EXPECT_EQ(highest_precision_in_long_double & arbitrary_mask,
+            static_cast<absl::uint128>(static_cast<long double>(
+                highest_precision_in_long_double & arbitrary_mask)));
+
+  EXPECT_EQ(static_cast<absl::uint128>(-0.1L), 0);
+}
+
+TEST(Uint128, OperatorAssignReturnRef) {
+  absl::uint128 v(1);
+  (v += 4) -= 3;
+  EXPECT_EQ(2, v);
+}
+
+TEST(Uint128, Multiply) {
+  absl::uint128 a, b, c;
+
+  // Zero test.
+  a = 0;
+  b = 0;
+  c = a * b;
+  EXPECT_EQ(0, c);
+
+  // Max carries.
+  a = absl::uint128(0) - 1;
+  b = absl::uint128(0) - 1;
+  c = a * b;
+  EXPECT_EQ(1, c);
+
+  // Self-operation with max carries.
+  c = absl::uint128(0) - 1;
+  c *= c;
+  EXPECT_EQ(1, c);
+
+  // 1-bit x 1-bit.
+  for (int i = 0; i < 64; ++i) {
+    for (int j = 0; j < 64; ++j) {
+      a = absl::uint128(1) << i;
+      b = absl::uint128(1) << j;
+      c = a * b;
+      EXPECT_EQ(absl::uint128(1) << (i + j), c);
+    }
+  }
+
+  // Verified with dc.
+  a = absl::MakeUint128(0xffffeeeeddddcccc, 0xbbbbaaaa99998888);
+  b = absl::MakeUint128(0x7777666655554444, 0x3333222211110000);
+  c = a * b;
+  EXPECT_EQ(absl::MakeUint128(0x530EDA741C71D4C3, 0xBF25975319080000), c);
+  EXPECT_EQ(0, c - b * a);
+  EXPECT_EQ(a*a - b*b, (a+b) * (a-b));
+
+  // Verified with dc.
+  a = absl::MakeUint128(0x0123456789abcdef, 0xfedcba9876543210);
+  b = absl::MakeUint128(0x02468ace13579bdf, 0xfdb97531eca86420);
+  c = a * b;
+  EXPECT_EQ(absl::MakeUint128(0x97a87f4f261ba3f2, 0x342d0bbf48948200), c);
+  EXPECT_EQ(0, c - b * a);
+  EXPECT_EQ(a*a - b*b, (a+b) * (a-b));
+}
+
+TEST(Uint128, AliasTests) {
+  absl::uint128 x1 = absl::MakeUint128(1, 2);
+  absl::uint128 x2 = absl::MakeUint128(2, 4);
+  x1 += x1;
+  EXPECT_EQ(x2, x1);
+
+  absl::uint128 x3 = absl::MakeUint128(1, static_cast<uint64_t>(1) << 63);
+  absl::uint128 x4 = absl::MakeUint128(3, 0);
+  x3 += x3;
+  EXPECT_EQ(x4, x3);
+}
+
+TEST(Uint128, DivideAndMod) {
+  using std::swap;
+
+  // a := q * b + r
+  absl::uint128 a, b, q, r;
+
+  // Zero test.
+  a = 0;
+  b = 123;
+  q = a / b;
+  r = a % b;
+  EXPECT_EQ(0, q);
+  EXPECT_EQ(0, r);
+
+  a = absl::MakeUint128(0x530eda741c71d4c3, 0xbf25975319080000);
+  q = absl::MakeUint128(0x4de2cab081, 0x14c34ab4676e4bab);
+  b = absl::uint128(0x1110001);
+  r = absl::uint128(0x3eb455);
+  ASSERT_EQ(a, q * b + r);  // Sanity-check.
+
+  absl::uint128 result_q, result_r;
+  result_q = a / b;
+  result_r = a % b;
+  EXPECT_EQ(q, result_q);
+  EXPECT_EQ(r, result_r);
+
+  // Try the other way around.
+  swap(q, b);
+  result_q = a / b;
+  result_r = a % b;
+  EXPECT_EQ(q, result_q);
+  EXPECT_EQ(r, result_r);
+  // Restore.
+  swap(b, q);
+
+  // Dividend < divisor; result should be q:0 r:<dividend>.
+  swap(a, b);
+  result_q = a / b;
+  result_r = a % b;
+  EXPECT_EQ(0, result_q);
+  EXPECT_EQ(a, result_r);
+  // Try the other way around.
+  swap(a, q);
+  result_q = a / b;
+  result_r = a % b;
+  EXPECT_EQ(0, result_q);
+  EXPECT_EQ(a, result_r);
+  // Restore.
+  swap(q, a);
+  swap(b, a);
+
+  // Try a large remainder.
+  b = a / 2 + 1;
+  absl::uint128 expected_r =
+      absl::MakeUint128(0x29876d3a0e38ea61, 0xdf92cba98c83ffff);
+  // Sanity checks.
+  ASSERT_EQ(a / 2 - 1, expected_r);
+  ASSERT_EQ(a, b + expected_r);
+  result_q = a / b;
+  result_r = a % b;
+  EXPECT_EQ(1, result_q);
+  EXPECT_EQ(expected_r, result_r);
+}
+
+TEST(Uint128, DivideAndModRandomInputs) {
+  const int kNumIters = 1 << 18;
+  std::minstd_rand random(testing::UnitTest::GetInstance()->random_seed());
+  std::uniform_int_distribution<uint64_t> uniform_uint64;
+  for (int i = 0; i < kNumIters; ++i) {
+    const absl::uint128 a =
+        absl::MakeUint128(uniform_uint64(random), uniform_uint64(random));
+    const absl::uint128 b =
+        absl::MakeUint128(uniform_uint64(random), uniform_uint64(random));
+    if (b == 0) {
+      continue;  // Avoid a div-by-zero.
+    }
+    const absl::uint128 q = a / b;
+    const absl::uint128 r = a % b;
+    ASSERT_EQ(a, b * q + r);
+  }
+}
+
+TEST(Uint128, ConstexprTest) {
+  constexpr absl::uint128 zero = absl::uint128();
+  constexpr absl::uint128 one = 1;
+  constexpr absl::uint128 minus_two = -2;
+  EXPECT_EQ(zero, absl::uint128(0));
+  EXPECT_EQ(one, absl::uint128(1));
+  EXPECT_EQ(minus_two, absl::MakeUint128(-1, -2));
+}
+
+TEST(Uint128, NumericLimitsTest) {
+  static_assert(std::numeric_limits<absl::uint128>::is_specialized, "");
+  static_assert(!std::numeric_limits<absl::uint128>::is_signed, "");
+  static_assert(std::numeric_limits<absl::uint128>::is_integer, "");
+  EXPECT_EQ(static_cast<int>(128 * std::log10(2)),
+            std::numeric_limits<absl::uint128>::digits10);
+  EXPECT_EQ(0, std::numeric_limits<absl::uint128>::min());
+  EXPECT_EQ(0, std::numeric_limits<absl::uint128>::lowest());
+  EXPECT_EQ(absl::Uint128Max(), std::numeric_limits<absl::uint128>::max());
+}
+
+TEST(Uint128, Hash) {
+  EXPECT_TRUE(absl::VerifyTypeImplementsAbslHashCorrectly({
+      // Some simple values
+      absl::uint128{0},
+      absl::uint128{1},
+      ~absl::uint128{},
+      // 64 bit limits
+      absl::uint128{std::numeric_limits<int64_t>::max()},
+      absl::uint128{std::numeric_limits<uint64_t>::max()} + 0,
+      absl::uint128{std::numeric_limits<uint64_t>::max()} + 1,
+      absl::uint128{std::numeric_limits<uint64_t>::max()} + 2,
+      // Keeping high same
+      absl::uint128{1} << 62,
+      absl::uint128{1} << 63,
+      // Keeping low same
+      absl::uint128{1} << 64,
+      absl::uint128{1} << 65,
+      // 128 bit limits
+      std::numeric_limits<absl::uint128>::max(),
+      std::numeric_limits<absl::uint128>::max() - 1,
+      std::numeric_limits<absl::uint128>::min() + 1,
+      std::numeric_limits<absl::uint128>::min(),
+  }));
+}
+
+
+TEST(Int128Uint128, ConversionTest) {
+  absl::int128 nonnegative_signed_values[] = {
+      0,
+      1,
+      0xffeeddccbbaa9988,
+      absl::MakeInt128(0x7766554433221100, 0),
+      absl::MakeInt128(0x1234567890abcdef, 0xfedcba0987654321),
+      absl::Int128Max()};
+  for (absl::int128 value : nonnegative_signed_values) {
+    EXPECT_EQ(value, absl::int128(absl::uint128(value)));
+
+    absl::uint128 assigned_value;
+    assigned_value = value;
+    EXPECT_EQ(value, absl::int128(assigned_value));
+  }
+
+  absl::int128 negative_values[] = {
+      -1, -0x1234567890abcdef,
+      absl::MakeInt128(-0x5544332211ffeedd, 0),
+      -absl::MakeInt128(0x76543210fedcba98, 0xabcdef0123456789)};
+  for (absl::int128 value : negative_values) {
+    EXPECT_EQ(absl::uint128(-value), -absl::uint128(value));
+
+    absl::uint128 assigned_value;
+    assigned_value = value;
+    EXPECT_EQ(absl::uint128(-value), -assigned_value);
+  }
+}
+
+template <typename T>
+class Int128IntegerTraitsTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE(Int128IntegerTraitsTest, IntegerTypes);
+
+TYPED_TEST(Int128IntegerTraitsTest, ConstructAssignTest) {
+  static_assert(std::is_constructible<absl::int128, TypeParam>::value,
+                "absl::int128 must be constructible from TypeParam");
+  static_assert(std::is_assignable<absl::int128&, TypeParam>::value,
+                "absl::int128 must be assignable from TypeParam");
+  static_assert(!std::is_assignable<TypeParam&, absl::int128>::value,
+                "TypeParam must not be assignable from absl::int128");
+}
+
+template <typename T>
+class Int128FloatTraitsTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE(Int128FloatTraitsTest, FloatingPointTypes);
+
+TYPED_TEST(Int128FloatTraitsTest, ConstructAssignTest) {
+  static_assert(std::is_constructible<absl::int128, TypeParam>::value,
+                "absl::int128 must be constructible from TypeParam");
+  static_assert(!std::is_assignable<absl::int128&, TypeParam>::value,
+                "absl::int128 must not be assignable from TypeParam");
+  static_assert(!std::is_assignable<TypeParam&, absl::int128>::value,
+                "TypeParam must not be assignable from absl::int128");
+}
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+// These type traits done separately as TYPED_TEST requires typeinfo, and not
+// all platforms have this for __int128 even though they define the type.
+TEST(Int128, IntrinsicTypeTraitsTest) {
+  static_assert(std::is_constructible<absl::int128, __int128>::value,
+                "absl::int128 must be constructible from __int128");
+  static_assert(std::is_assignable<absl::int128&, __int128>::value,
+                "absl::int128 must be assignable from __int128");
+  static_assert(!std::is_assignable<__int128&, absl::int128>::value,
+                "__int128 must not be assignable from absl::int128");
+
+  static_assert(std::is_constructible<absl::int128, unsigned __int128>::value,
+                "absl::int128 must be constructible from unsigned __int128");
+  static_assert(!std::is_assignable<absl::int128&, unsigned __int128>::value,
+                "absl::int128 must be assignable from unsigned __int128");
+  static_assert(!std::is_assignable<unsigned __int128&, absl::int128>::value,
+                "unsigned __int128 must not be assignable from absl::int128");
+}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+TEST(Int128, TrivialTraitsTest) {
+  static_assert(absl::is_trivially_default_constructible<absl::int128>::value,
+                "");
+  static_assert(absl::is_trivially_copy_constructible<absl::int128>::value, "");
+  static_assert(absl::is_trivially_copy_assignable<absl::int128>::value, "");
+  static_assert(std::is_trivially_destructible<absl::int128>::value, "");
+}
+
+TEST(Int128, BoolConversionTest) {
+  EXPECT_FALSE(absl::int128(0));
+  for (int i = 0; i < 64; ++i) {
+    EXPECT_TRUE(absl::MakeInt128(0, uint64_t{1} << i));
+  }
+  for (int i = 0; i < 63; ++i) {
+    EXPECT_TRUE(absl::MakeInt128(int64_t{1} << i, 0));
+  }
+  EXPECT_TRUE(absl::Int128Min());
+
+  EXPECT_EQ(absl::int128(1), absl::int128(true));
+  EXPECT_EQ(absl::int128(0), absl::int128(false));
+}
+
+template <typename T>
+class Int128IntegerConversionTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE(Int128IntegerConversionTest, IntegerTypes);
+
+TYPED_TEST(Int128IntegerConversionTest, RoundTripTest) {
+  EXPECT_EQ(TypeParam{0}, static_cast<TypeParam>(absl::int128(0)));
+  EXPECT_EQ(std::numeric_limits<TypeParam>::min(),
+            static_cast<TypeParam>(
+                absl::int128(std::numeric_limits<TypeParam>::min())));
+  EXPECT_EQ(std::numeric_limits<TypeParam>::max(),
+            static_cast<TypeParam>(
+                absl::int128(std::numeric_limits<TypeParam>::max())));
+}
+
+template <typename T>
+class Int128FloatConversionTest : public ::testing::Test {};
+
+TYPED_TEST_SUITE(Int128FloatConversionTest, FloatingPointTypes);
+
+TYPED_TEST(Int128FloatConversionTest, ConstructAndCastTest) {
+  // Conversions where the floating point values should be exactly the same.
+  // 0x9f5b is a randomly chosen small value.
+  for (int i = 0; i < 110; ++i) {  // 110 = 126 - #bits in 0x9f5b
+    SCOPED_TRACE(::testing::Message() << "i = " << i);
+
+    TypeParam float_value = std::ldexp(static_cast<TypeParam>(0x9f5b), i);
+    absl::int128 int_value = absl::int128(0x9f5b) << i;
+
+    EXPECT_EQ(float_value, static_cast<TypeParam>(int_value));
+    EXPECT_EQ(-float_value, static_cast<TypeParam>(-int_value));
+    EXPECT_EQ(int_value, absl::int128(float_value));
+    EXPECT_EQ(-int_value, absl::int128(-float_value));
+  }
+
+  // Round trip conversions with a small sample of randomly generated uint64_t
+  // values (less than int64_t max so that value * 2^64 fits into int128).
+  uint64_t values[] = {0x6d4492c24fb86199, 0x26ead65e4cb359b5,
+                       0x2c43407433ba3fd1, 0x3b574ec668df6b55,
+                       0x1c750e55a29f4f0f};
+  for (uint64_t value : values) {
+    for (int i = 0; i <= 64; ++i) {
+      SCOPED_TRACE(::testing::Message()
+                   << "value = " << value << "; i = " << i);
+
+      TypeParam fvalue = std::ldexp(static_cast<TypeParam>(value), i);
+      EXPECT_DOUBLE_EQ(fvalue, static_cast<TypeParam>(absl::int128(fvalue)));
+      EXPECT_DOUBLE_EQ(-fvalue, static_cast<TypeParam>(-absl::int128(fvalue)));
+      EXPECT_DOUBLE_EQ(-fvalue, static_cast<TypeParam>(absl::int128(-fvalue)));
+      EXPECT_DOUBLE_EQ(fvalue, static_cast<TypeParam>(-absl::int128(-fvalue)));
+    }
+  }
+
+  // Round trip conversions with a small sample of random large positive values.
+  absl::int128 large_values[] = {
+      absl::MakeInt128(0x5b0640d96c7b3d9f, 0xb7a7189e51d18622),
+      absl::MakeInt128(0x34bed042c6f65270, 0x73b236570669a089),
+      absl::MakeInt128(0x43deba9e6da12724, 0xf7f0f83da686797d),
+      absl::MakeInt128(0x71e8d383be4e5589, 0x75c3f96fb00752b6)};
+  for (absl::int128 value : large_values) {
+    // Make value have as many significant bits as can be represented by
+    // the mantissa, also making sure the highest and lowest bit in the range
+    // are set.
+    value >>= (127 - std::numeric_limits<TypeParam>::digits);
+    value |= absl::int128(1) << (std::numeric_limits<TypeParam>::digits - 1);
+    value |= 1;
+    for (int i = 0; i < 127 - std::numeric_limits<TypeParam>::digits; ++i) {
+      absl::int128 int_value = value << i;
+      EXPECT_EQ(int_value,
+                static_cast<absl::int128>(static_cast<TypeParam>(int_value)));
+      EXPECT_EQ(-int_value,
+                static_cast<absl::int128>(static_cast<TypeParam>(-int_value)));
+    }
+  }
+
+  // Small sample of checks that rounding is toward zero
+  EXPECT_EQ(0, absl::int128(TypeParam(0.1)));
+  EXPECT_EQ(17, absl::int128(TypeParam(17.8)));
+  EXPECT_EQ(0, absl::int128(TypeParam(-0.8)));
+  EXPECT_EQ(-53, absl::int128(TypeParam(-53.1)));
+  EXPECT_EQ(0, absl::int128(TypeParam(0.5)));
+  EXPECT_EQ(0, absl::int128(TypeParam(-0.5)));
+  TypeParam just_lt_one = std::nexttoward(TypeParam(1), TypeParam(0));
+  EXPECT_EQ(0, absl::int128(just_lt_one));
+  TypeParam just_gt_minus_one = std::nexttoward(TypeParam(-1), TypeParam(0));
+  EXPECT_EQ(0, absl::int128(just_gt_minus_one));
+
+  // Check limits
+  EXPECT_DOUBLE_EQ(std::ldexp(static_cast<TypeParam>(1), 127),
+                   static_cast<TypeParam>(absl::Int128Max()));
+  EXPECT_DOUBLE_EQ(-std::ldexp(static_cast<TypeParam>(1), 127),
+                   static_cast<TypeParam>(absl::Int128Min()));
+}
+
+TEST(Int128, FactoryTest) {
+  EXPECT_EQ(absl::int128(-1), absl::MakeInt128(-1, -1));
+  EXPECT_EQ(absl::int128(-31), absl::MakeInt128(-1, -31));
+  EXPECT_EQ(absl::int128(std::numeric_limits<int64_t>::min()),
+            absl::MakeInt128(-1, std::numeric_limits<int64_t>::min()));
+  EXPECT_EQ(absl::int128(0), absl::MakeInt128(0, 0));
+  EXPECT_EQ(absl::int128(1), absl::MakeInt128(0, 1));
+  EXPECT_EQ(absl::int128(std::numeric_limits<int64_t>::max()),
+            absl::MakeInt128(0, std::numeric_limits<int64_t>::max()));
+}
+
+TEST(Int128, HighLowTest) {
+  struct HighLowPair {
+    int64_t high;
+    uint64_t low;
+  };
+  HighLowPair values[]{{0, 0}, {0, 1}, {1, 0}, {123, 456}, {-654, 321}};
+  for (const HighLowPair& pair : values) {
+    absl::int128 value = absl::MakeInt128(pair.high, pair.low);
+    EXPECT_EQ(pair.low, absl::Int128Low64(value));
+    EXPECT_EQ(pair.high, absl::Int128High64(value));
+  }
+}
+
+TEST(Int128, LimitsTest) {
+  EXPECT_EQ(absl::MakeInt128(0x7fffffffffffffff, 0xffffffffffffffff),
+            absl::Int128Max());
+  EXPECT_EQ(absl::Int128Max(), ~absl::Int128Min());
+}
+
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+TEST(Int128, IntrinsicConversionTest) {
+  __int128 intrinsic =
+      (static_cast<__int128>(0x3a5b76c209de76f6) << 64) + 0x1f25e1d63a2b46c5;
+  absl::int128 custom =
+      absl::MakeInt128(0x3a5b76c209de76f6, 0x1f25e1d63a2b46c5);
+
+  EXPECT_EQ(custom, absl::int128(intrinsic));
+  EXPECT_EQ(intrinsic, static_cast<__int128>(custom));
+}
+#endif  // ABSL_HAVE_INTRINSIC_INT128
+
+TEST(Int128, ConstexprTest) {
+  constexpr absl::int128 zero = absl::int128();
+  constexpr absl::int128 one = 1;
+  constexpr absl::int128 minus_two = -2;
+  constexpr absl::int128 min = absl::Int128Min();
+  constexpr absl::int128 max = absl::Int128Max();
+  EXPECT_EQ(zero, absl::int128(0));
+  EXPECT_EQ(one, absl::int128(1));
+  EXPECT_EQ(minus_two, absl::MakeInt128(-1, -2));
+  EXPECT_GT(max, one);
+  EXPECT_LT(min, minus_two);
+}
+
+TEST(Int128, ComparisonTest) {
+  struct TestCase {
+    absl::int128 smaller;
+    absl::int128 larger;
+  };
+  TestCase cases[] = {
+      {absl::int128(0), absl::int128(123)},
+      {absl::MakeInt128(-12, 34), absl::MakeInt128(12, 34)},
+      {absl::MakeInt128(1, 1000), absl::MakeInt128(1000, 1)},
+      {absl::MakeInt128(-1000, 1000), absl::MakeInt128(-1, 1)},
+  };
+  for (const TestCase& pair : cases) {
+    SCOPED_TRACE(::testing::Message() << "pair.smaller = " << pair.smaller
+                                      << "; pair.larger = " << pair.larger);
+
+    EXPECT_TRUE(pair.smaller == pair.smaller);  // NOLINT(readability/check)
+    EXPECT_TRUE(pair.larger == pair.larger);    // NOLINT(readability/check)
+    EXPECT_FALSE(pair.smaller == pair.larger);  // NOLINT(readability/check)
+
+    EXPECT_TRUE(pair.smaller != pair.larger);    // NOLINT(readability/check)
+    EXPECT_FALSE(pair.smaller != pair.smaller);  // NOLINT(readability/check)
+    EXPECT_FALSE(pair.larger != pair.larger);    // NOLINT(readability/check)
+
+    EXPECT_TRUE(pair.smaller < pair.larger);   // NOLINT(readability/check)
+    EXPECT_FALSE(pair.larger < pair.smaller);  // NOLINT(readability/check)
+
+    EXPECT_TRUE(pair.larger > pair.smaller);   // NOLINT(readability/check)
+    EXPECT_FALSE(pair.smaller > pair.larger);  // NOLINT(readability/check)
+
+    EXPECT_TRUE(pair.smaller <= pair.larger);   // NOLINT(readability/check)
+    EXPECT_FALSE(pair.larger <= pair.smaller);  // NOLINT(readability/check)
+    EXPECT_TRUE(pair.smaller <= pair.smaller);  // NOLINT(readability/check)
+    EXPECT_TRUE(pair.larger <= pair.larger);    // NOLINT(readability/check)
+
+    EXPECT_TRUE(pair.larger >= pair.smaller);   // NOLINT(readability/check)
+    EXPECT_FALSE(pair.smaller >= pair.larger);  // NOLINT(readability/check)
+    EXPECT_TRUE(pair.smaller >= pair.smaller);  // NOLINT(readability/check)
+    EXPECT_TRUE(pair.larger >= pair.larger);    // NOLINT(readability/check)
+  }
+}
+
+TEST(Int128, UnaryPlusTest) {
+  int64_t values64[] = {0, 1, 12345, 0x4000000000000000,
+                        std::numeric_limits<int64_t>::max()};
+  for (int64_t value : values64) {
+    SCOPED_TRACE(::testing::Message() << "value = " << value);
+
+    EXPECT_EQ(absl::int128(value), +absl::int128(value));
+    EXPECT_EQ(absl::int128(-value), +absl::int128(-value));
+    EXPECT_EQ(absl::MakeInt128(value, 0), +absl::MakeInt128(value, 0));
+    EXPECT_EQ(absl::MakeInt128(-value, 0), +absl::MakeInt128(-value, 0));
+  }
+}
+
+TEST(Int128, UnaryNegationTest) {
+  int64_t values64[] = {0, 1, 12345, 0x4000000000000000,
+                        std::numeric_limits<int64_t>::max()};
+  for (int64_t value : values64) {
+    SCOPED_TRACE(::testing::Message() << "value = " << value);
+
+    EXPECT_EQ(absl::int128(-value), -absl::int128(value));
+    EXPECT_EQ(absl::int128(value), -absl::int128(-value));
+    EXPECT_EQ(absl::MakeInt128(-value, 0), -absl::MakeInt128(value, 0));
+    EXPECT_EQ(absl::MakeInt128(value, 0), -absl::MakeInt128(-value, 0));
+  }
+}
+
+TEST(Int128, LogicalNotTest) {
+  EXPECT_TRUE(!absl::int128(0));
+  for (int i = 0; i < 64; ++i) {
+    EXPECT_FALSE(!absl::MakeInt128(0, uint64_t{1} << i));
+  }
+  for (int i = 0; i < 63; ++i) {
+    EXPECT_FALSE(!absl::MakeInt128(int64_t{1} << i, 0));
+  }
+}
+
+TEST(Int128, AdditionSubtractionTest) {
+  // 64 bit pairs that will not cause overflow / underflow. These test negative
+  // carry; positive carry must be checked separately.
+  std::pair<int64_t, int64_t> cases[]{
+      {0, 0},                              // 0, 0
+      {0, 2945781290834},                  // 0, +
+      {1908357619234, 0},                  // +, 0
+      {0, -1204895918245},                 // 0, -
+      {-2957928523560, 0},                 // -, 0
+      {89023982312461, 98346012567134},    // +, +
+      {-63454234568239, -23456235230773},  // -, -
+      {98263457263502, -21428561935925},   // +, -
+      {-88235237438467, 15923659234573},   // -, +
+  };
+  for (const auto& pair : cases) {
+    SCOPED_TRACE(::testing::Message()
+                 << "pair = {" << pair.first << ", " << pair.second << '}');
+
+    EXPECT_EQ(absl::int128(pair.first + pair.second),
+              absl::int128(pair.first) + absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.second + pair.first),
+              absl::int128(pair.second) += absl::int128(pair.first));
+
+    EXPECT_EQ(absl::int128(pair.first - pair.second),
+              absl::int128(pair.first) - absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.second - pair.first),
+              absl::int128(pair.second) -= absl::int128(pair.first));
+
+    EXPECT_EQ(
+        absl::MakeInt128(pair.second + pair.first, 0),
+        absl::MakeInt128(pair.second, 0) + absl::MakeInt128(pair.first, 0));
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first + pair.second, 0),
+        absl::MakeInt128(pair.first, 0) += absl::MakeInt128(pair.second, 0));
+
+    EXPECT_EQ(
+        absl::MakeInt128(pair.second - pair.first, 0),
+        absl::MakeInt128(pair.second, 0) - absl::MakeInt128(pair.first, 0));
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first - pair.second, 0),
+        absl::MakeInt128(pair.first, 0) -= absl::MakeInt128(pair.second, 0));
+  }
+
+  // check positive carry
+  EXPECT_EQ(absl::MakeInt128(31, 0),
+            absl::MakeInt128(20, 1) +
+                absl::MakeInt128(10, std::numeric_limits<uint64_t>::max()));
+}
+
+TEST(Int128, IncrementDecrementTest) {
+  absl::int128 value = 0;
+  EXPECT_EQ(0, value++);
+  EXPECT_EQ(1, value);
+  EXPECT_EQ(1, value--);
+  EXPECT_EQ(0, value);
+  EXPECT_EQ(-1, --value);
+  EXPECT_EQ(-1, value);
+  EXPECT_EQ(0, ++value);
+  EXPECT_EQ(0, value);
+}
+
+TEST(Int128, MultiplicationTest) {
+  // 1 bit x 1 bit, and negative combinations
+  for (int i = 0; i < 64; ++i) {
+    for (int j = 0; j < 127 - i; ++j) {
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      absl::int128 a = absl::int128(1) << i;
+      absl::int128 b = absl::int128(1) << j;
+      absl::int128 c = absl::int128(1) << (i + j);
+
+      EXPECT_EQ(c, a * b);
+      EXPECT_EQ(-c, -a * b);
+      EXPECT_EQ(-c, a * -b);
+      EXPECT_EQ(c, -a * -b);
+
+      EXPECT_EQ(c, absl::int128(a) *= b);
+      EXPECT_EQ(-c, absl::int128(-a) *= b);
+      EXPECT_EQ(-c, absl::int128(a) *= -b);
+      EXPECT_EQ(c, absl::int128(-a) *= -b);
+    }
+  }
+
+  // Pairs of random values that will not overflow signed 64-bit multiplication
+  std::pair<int64_t, int64_t> small_values[] = {
+      {0x5e61, 0xf29f79ca14b4},    // +, +
+      {0x3e033b, -0x612c0ee549},   // +, -
+      {-0x052ce7e8, 0x7c728f0f},   // -, +
+      {-0x3af7054626, -0xfb1e1d},  // -, -
+  };
+  for (const std::pair<int64_t, int64_t>& pair : small_values) {
+    SCOPED_TRACE(::testing::Message()
+                 << "pair = {" << pair.first << ", " << pair.second << '}');
+
+    EXPECT_EQ(absl::int128(pair.first * pair.second),
+              absl::int128(pair.first) * absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.first * pair.second),
+              absl::int128(pair.first) *= absl::int128(pair.second));
+
+    EXPECT_EQ(absl::MakeInt128(pair.first * pair.second, 0),
+              absl::MakeInt128(pair.first, 0) * absl::int128(pair.second));
+    EXPECT_EQ(absl::MakeInt128(pair.first * pair.second, 0),
+              absl::MakeInt128(pair.first, 0) *= absl::int128(pair.second));
+  }
+
+  // Pairs of positive random values that will not overflow 64-bit
+  // multiplication and can be left shifted by 32 without overflow
+  std::pair<int64_t, int64_t> small_values2[] = {
+      {0x1bb0a110, 0x31487671},
+      {0x4792784e, 0x28add7d7},
+      {0x7b66553a, 0x11dff8ef},
+  };
+  for (const std::pair<int64_t, int64_t>& pair : small_values2) {
+    SCOPED_TRACE(::testing::Message()
+                 << "pair = {" << pair.first << ", " << pair.second << '}');
+
+    absl::int128 a = absl::int128(pair.first << 32);
+    absl::int128 b = absl::int128(pair.second << 32);
+    absl::int128 c = absl::MakeInt128(pair.first * pair.second, 0);
+
+    EXPECT_EQ(c, a * b);
+    EXPECT_EQ(-c, -a * b);
+    EXPECT_EQ(-c, a * -b);
+    EXPECT_EQ(c, -a * -b);
+
+    EXPECT_EQ(c, absl::int128(a) *= b);
+    EXPECT_EQ(-c, absl::int128(-a) *= b);
+    EXPECT_EQ(-c, absl::int128(a) *= -b);
+    EXPECT_EQ(c, absl::int128(-a) *= -b);
+  }
+
+  // check 0, 1, and -1 behavior with large values
+  absl::int128 large_values[] = {
+      {absl::MakeInt128(0xd66f061af02d0408, 0x727d2846cb475b53)},
+      {absl::MakeInt128(0x27b8d5ed6104452d, 0x03f8a33b0ee1df4f)},
+      {-absl::MakeInt128(0x621b6626b9e8d042, 0x27311ac99df00938)},
+      {-absl::MakeInt128(0x34e0656f1e95fb60, 0x4281cfd731257a47)},
+  };
+  for (absl::int128 value : large_values) {
+    EXPECT_EQ(0, 0 * value);
+    EXPECT_EQ(0, value * 0);
+    EXPECT_EQ(0, absl::int128(0) *= value);
+    EXPECT_EQ(0, value *= 0);
+
+    EXPECT_EQ(value, 1 * value);
+    EXPECT_EQ(value, value * 1);
+    EXPECT_EQ(value, absl::int128(1) *= value);
+    EXPECT_EQ(value, value *= 1);
+
+    EXPECT_EQ(-value, -1 * value);
+    EXPECT_EQ(-value, value * -1);
+    EXPECT_EQ(-value, absl::int128(-1) *= value);
+    EXPECT_EQ(-value, value *= -1);
+  }
+
+  // Manually calculated random large value cases
+  EXPECT_EQ(absl::MakeInt128(0xcd0efd3442219bb, 0xde47c05bcd9df6e1),
+            absl::MakeInt128(0x7c6448, 0x3bc4285c47a9d253) * 0x1a6037537b);
+  EXPECT_EQ(-absl::MakeInt128(0x1f8f149850b1e5e6, 0x1e50d6b52d272c3e),
+            -absl::MakeInt128(0x23, 0x2e68a513ca1b8859) * 0xe5a434cd14866e);
+  EXPECT_EQ(-absl::MakeInt128(0x55cae732029d1fce, 0xca6474b6423263e4),
+            0xa9b98a8ddf66bc * -absl::MakeInt128(0x81, 0x672e58231e2469d7));
+  EXPECT_EQ(absl::MakeInt128(0x19c8b7620b507dc4, 0xfec042b71a5f29a4),
+            -0x3e39341147 * -absl::MakeInt128(0x6a14b2, 0x5ed34cca42327b3c));
+
+  EXPECT_EQ(absl::MakeInt128(0xcd0efd3442219bb, 0xde47c05bcd9df6e1),
+            absl::MakeInt128(0x7c6448, 0x3bc4285c47a9d253) *= 0x1a6037537b);
+  EXPECT_EQ(-absl::MakeInt128(0x1f8f149850b1e5e6, 0x1e50d6b52d272c3e),
+            -absl::MakeInt128(0x23, 0x2e68a513ca1b8859) *= 0xe5a434cd14866e);
+  EXPECT_EQ(-absl::MakeInt128(0x55cae732029d1fce, 0xca6474b6423263e4),
+            absl::int128(0xa9b98a8ddf66bc) *=
+            -absl::MakeInt128(0x81, 0x672e58231e2469d7));
+  EXPECT_EQ(absl::MakeInt128(0x19c8b7620b507dc4, 0xfec042b71a5f29a4),
+            absl::int128(-0x3e39341147) *=
+            -absl::MakeInt128(0x6a14b2, 0x5ed34cca42327b3c));
+}
+
+TEST(Int128, DivisionAndModuloTest) {
+  // Check against 64 bit division and modulo operators with a sample of
+  // randomly generated pairs.
+  std::pair<int64_t, int64_t> small_pairs[] = {
+      {0x15f2a64138, 0x67da05},    {0x5e56d194af43045f, 0xcf1543fb99},
+      {0x15e61ed052036a, -0xc8e6}, {0x88125a341e85, -0xd23fb77683},
+      {-0xc06e20, 0x5a},           {-0x4f100219aea3e85d, 0xdcc56cb4efe993},
+      {-0x168d629105, -0xa7},      {-0x7b44e92f03ab2375, -0x6516},
+  };
+  for (const std::pair<int64_t, int64_t>& pair : small_pairs) {
+    SCOPED_TRACE(::testing::Message()
+                 << "pair = {" << pair.first << ", " << pair.second << '}');
+
+    absl::int128 dividend = pair.first;
+    absl::int128 divisor = pair.second;
+    int64_t quotient = pair.first / pair.second;
+    int64_t remainder = pair.first % pair.second;
+
+    EXPECT_EQ(quotient, dividend / divisor);
+    EXPECT_EQ(quotient, absl::int128(dividend) /= divisor);
+    EXPECT_EQ(remainder, dividend % divisor);
+    EXPECT_EQ(remainder, absl::int128(dividend) %= divisor);
+  }
+
+  // Test behavior with 0, 1, and -1 with a sample of randomly generated large
+  // values.
+  absl::int128 values[] = {
+      absl::MakeInt128(0x63d26ee688a962b2, 0x9e1411abda5c1d70),
+      absl::MakeInt128(0x152f385159d6f986, 0xbf8d48ef63da395d),
+      -absl::MakeInt128(0x3098d7567030038c, 0x14e7a8a098dc2164),
+      -absl::MakeInt128(0x49a037aca35c809f, 0xa6a87525480ef330),
+  };
+  for (absl::int128 value : values) {
+    SCOPED_TRACE(::testing::Message() << "value = " << value);
+
+    EXPECT_EQ(0, 0 / value);
+    EXPECT_EQ(0, absl::int128(0) /= value);
+    EXPECT_EQ(0, 0 % value);
+    EXPECT_EQ(0, absl::int128(0) %= value);
+
+    EXPECT_EQ(value, value / 1);
+    EXPECT_EQ(value, absl::int128(value) /= 1);
+    EXPECT_EQ(0, value % 1);
+    EXPECT_EQ(0, absl::int128(value) %= 1);
+
+    EXPECT_EQ(-value, value / -1);
+    EXPECT_EQ(-value, absl::int128(value) /= -1);
+    EXPECT_EQ(0, value % -1);
+    EXPECT_EQ(0, absl::int128(value) %= -1);
+  }
+
+  // Min and max values
+  EXPECT_EQ(0, absl::Int128Max() / absl::Int128Min());
+  EXPECT_EQ(absl::Int128Max(), absl::Int128Max() % absl::Int128Min());
+  EXPECT_EQ(-1, absl::Int128Min() / absl::Int128Max());
+  EXPECT_EQ(-1, absl::Int128Min() % absl::Int128Max());
+
+  // Power of two division and modulo of random large dividends
+  absl::int128 positive_values[] = {
+      absl::MakeInt128(0x21e1a1cc69574620, 0xe7ac447fab2fc869),
+      absl::MakeInt128(0x32c2ff3ab89e66e8, 0x03379a613fd1ce74),
+      absl::MakeInt128(0x6f32ca786184dcaf, 0x046f9c9ecb3a9ce1),
+      absl::MakeInt128(0x1aeb469dd990e0ee, 0xda2740f243cd37eb),
+  };
+  for (absl::int128 value : positive_values) {
+    for (int i = 0; i < 127; ++i) {
+      SCOPED_TRACE(::testing::Message()
+                   << "value = " << value << "; i = " << i);
+      absl::int128 power_of_two = absl::int128(1) << i;
+
+      EXPECT_EQ(value >> i, value / power_of_two);
+      EXPECT_EQ(value >> i, absl::int128(value) /= power_of_two);
+      EXPECT_EQ(value & (power_of_two - 1), value % power_of_two);
+      EXPECT_EQ(value & (power_of_two - 1),
+                absl::int128(value) %= power_of_two);
+    }
+  }
+
+  // Manually calculated cases with random large dividends
+  struct DivisionModCase {
+    absl::int128 dividend;
+    absl::int128 divisor;
+    absl::int128 quotient;
+    absl::int128 remainder;
+  };
+  DivisionModCase manual_cases[] = {
+      {absl::MakeInt128(0x6ada48d489007966, 0x3c9c5c98150d5d69),
+       absl::MakeInt128(0x8bc308fb, 0x8cb9cc9a3b803344), 0xc3b87e08,
+       absl::MakeInt128(0x1b7db5e1, 0xd9eca34b7af04b49)},
+      {absl::MakeInt128(0xd6946511b5b, 0x4886c5c96546bf5f),
+       -absl::MakeInt128(0x263b, 0xfd516279efcfe2dc), -0x59cbabf0,
+       absl::MakeInt128(0x622, 0xf462909155651d1f)},
+      {-absl::MakeInt128(0x33db734f9e8d1399, 0x8447ac92482bca4d), 0x37495078240,
+       -absl::MakeInt128(0xf01f1, 0xbc0368bf9a77eae8), -0x21a508f404d},
+      {-absl::MakeInt128(0x13f837b409a07e7d, 0x7fc8e248a7d73560), -0x1b9f,
+       absl::MakeInt128(0xb9157556d724, 0xb14f635714d7563e), -0x1ade},
+  };
+  for (const DivisionModCase test_case : manual_cases) {
+    EXPECT_EQ(test_case.quotient, test_case.dividend / test_case.divisor);
+    EXPECT_EQ(test_case.quotient,
+              absl::int128(test_case.dividend) /= test_case.divisor);
+    EXPECT_EQ(test_case.remainder, test_case.dividend % test_case.divisor);
+    EXPECT_EQ(test_case.remainder,
+              absl::int128(test_case.dividend) %= test_case.divisor);
+  }
+}
+
+TEST(Int128, BitwiseLogicTest) {
+  EXPECT_EQ(absl::int128(-1), ~absl::int128(0));
+
+  absl::int128 values[]{
+      0, -1, 0xde400bee05c3ff6b, absl::MakeInt128(0x7f32178dd81d634a, 0),
+      absl::MakeInt128(0xaf539057055613a9, 0x7d104d7d946c2e4d)};
+  for (absl::int128 value : values) {
+    EXPECT_EQ(value, ~~value);
+
+    EXPECT_EQ(value, value | value);
+    EXPECT_EQ(value, value & value);
+    EXPECT_EQ(0, value ^ value);
+
+    EXPECT_EQ(value, absl::int128(value) |= value);
+    EXPECT_EQ(value, absl::int128(value) &= value);
+    EXPECT_EQ(0, absl::int128(value) ^= value);
+
+    EXPECT_EQ(value, value | 0);
+    EXPECT_EQ(0, value & 0);
+    EXPECT_EQ(value, value ^ 0);
+
+    EXPECT_EQ(absl::int128(-1), value | absl::int128(-1));
+    EXPECT_EQ(value, value & absl::int128(-1));
+    EXPECT_EQ(~value, value ^ absl::int128(-1));
+  }
+
+  // small sample of randomly generated int64_t's
+  std::pair<int64_t, int64_t> pairs64[]{
+      {0x7f86797f5e991af4, 0x1ee30494fb007c97},
+      {0x0b278282bacf01af, 0x58780e0a57a49e86},
+      {0x059f266ccb93a666, 0x3d5b731bae9286f5},
+      {0x63c0c4820f12108c, 0x58166713c12e1c3a},
+      {0x381488bb2ed2a66e, 0x2220a3eb76a3698c},
+      {0x2a0a0dfb81e06f21, 0x4b60585927f5523c},
+      {0x555b1c3a03698537, 0x25478cd19d8e53cb},
+      {0x4750f6f27d779225, 0x16397553c6ff05fc},
+  };
+  for (const std::pair<int64_t, int64_t>& pair : pairs64) {
+    SCOPED_TRACE(::testing::Message()
+                 << "pair = {" << pair.first << ", " << pair.second << '}');
+
+    EXPECT_EQ(absl::MakeInt128(~pair.first, ~pair.second),
+              ~absl::MakeInt128(pair.first, pair.second));
+
+    EXPECT_EQ(absl::int128(pair.first & pair.second),
+              absl::int128(pair.first) & absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.first | pair.second),
+              absl::int128(pair.first) | absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.first ^ pair.second),
+              absl::int128(pair.first) ^ absl::int128(pair.second));
+
+    EXPECT_EQ(absl::int128(pair.first & pair.second),
+              absl::int128(pair.first) &= absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.first | pair.second),
+              absl::int128(pair.first) |= absl::int128(pair.second));
+    EXPECT_EQ(absl::int128(pair.first ^ pair.second),
+              absl::int128(pair.first) ^= absl::int128(pair.second));
+
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first & pair.second, 0),
+        absl::MakeInt128(pair.first, 0) & absl::MakeInt128(pair.second, 0));
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first | pair.second, 0),
+        absl::MakeInt128(pair.first, 0) | absl::MakeInt128(pair.second, 0));
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first ^ pair.second, 0),
+        absl::MakeInt128(pair.first, 0) ^ absl::MakeInt128(pair.second, 0));
+
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first & pair.second, 0),
+        absl::MakeInt128(pair.first, 0) &= absl::MakeInt128(pair.second, 0));
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first | pair.second, 0),
+        absl::MakeInt128(pair.first, 0) |= absl::MakeInt128(pair.second, 0));
+    EXPECT_EQ(
+        absl::MakeInt128(pair.first ^ pair.second, 0),
+        absl::MakeInt128(pair.first, 0) ^= absl::MakeInt128(pair.second, 0));
+  }
+}
+
+TEST(Int128, BitwiseShiftTest) {
+  for (int i = 0; i < 64; ++i) {
+    for (int j = 0; j <= i; ++j) {
+      // Left shift from j-th bit to i-th bit.
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      EXPECT_EQ(uint64_t{1} << i, absl::int128(uint64_t{1} << j) << (i - j));
+      EXPECT_EQ(uint64_t{1} << i, absl::int128(uint64_t{1} << j) <<= (i - j));
+    }
+  }
+  for (int i = 0; i < 63; ++i) {
+    for (int j = 0; j < 64; ++j) {
+      // Left shift from j-th bit to (i + 64)-th bit.
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      EXPECT_EQ(absl::MakeInt128(uint64_t{1} << i, 0),
+                absl::int128(uint64_t{1} << j) << (i + 64 - j));
+      EXPECT_EQ(absl::MakeInt128(uint64_t{1} << i, 0),
+                absl::int128(uint64_t{1} << j) <<= (i + 64 - j));
+    }
+    for (int j = 0; j <= i; ++j) {
+      // Left shift from (j + 64)-th bit to (i + 64)-th bit.
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      EXPECT_EQ(absl::MakeInt128(uint64_t{1} << i, 0),
+                absl::MakeInt128(uint64_t{1} << j, 0) << (i - j));
+      EXPECT_EQ(absl::MakeInt128(uint64_t{1} << i, 0),
+                absl::MakeInt128(uint64_t{1} << j, 0) <<= (i - j));
+    }
+  }
+
+  for (int i = 0; i < 64; ++i) {
+    for (int j = i; j < 64; ++j) {
+      // Right shift from j-th bit to i-th bit.
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      EXPECT_EQ(uint64_t{1} << i, absl::int128(uint64_t{1} << j) >> (j - i));
+      EXPECT_EQ(uint64_t{1} << i, absl::int128(uint64_t{1} << j) >>= (j - i));
+    }
+    for (int j = 0; j < 63; ++j) {
+      // Right shift from (j + 64)-th bit to i-th bit.
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      EXPECT_EQ(uint64_t{1} << i,
+                absl::MakeInt128(uint64_t{1} << j, 0) >> (j + 64 - i));
+      EXPECT_EQ(uint64_t{1} << i,
+                absl::MakeInt128(uint64_t{1} << j, 0) >>= (j + 64 - i));
+    }
+  }
+  for (int i = 0; i < 63; ++i) {
+    for (int j = i; j < 63; ++j) {
+      // Right shift from (j + 64)-th bit to (i + 64)-th bit.
+      SCOPED_TRACE(::testing::Message() << "i = " << i << "; j = " << j);
+      EXPECT_EQ(absl::MakeInt128(uint64_t{1} << i, 0),
+                absl::MakeInt128(uint64_t{1} << j, 0) >> (j - i));
+      EXPECT_EQ(absl::MakeInt128(uint64_t{1} << i, 0),
+                absl::MakeInt128(uint64_t{1} << j, 0) >>= (j - i));
+    }
+  }
+
+  // Manually calculated cases with shift count for positive (val1) and negative
+  // (val2) values
+  absl::int128 val1 = MAKE_INT128(0x123456789abcdef0, 0x123456789abcdef0);
+  absl::int128 val2 = MAKE_INT128(0xfedcba0987654321, 0xfedcba0987654321);
+
+  EXPECT_EQ(val1 << 63, MAKE_INT128(0x91a2b3c4d5e6f78, 0x0));
+  EXPECT_EQ(val1 << 64, MAKE_INT128(0x123456789abcdef0, 0x0));
+  EXPECT_EQ(val2 << 63, MAKE_INT128(0xff6e5d04c3b2a190, 0x8000000000000000));
+  EXPECT_EQ(val2 << 64, MAKE_INT128(0xfedcba0987654321, 0x0));
+
+  EXPECT_EQ(val1 << 126, MAKE_INT128(0x0, 0x0));
+  EXPECT_EQ(val2 << 126, MAKE_INT128(0x4000000000000000, 0x0));
+
+  EXPECT_EQ(val1 >> 63, MAKE_INT128(0x0, 0x2468acf13579bde0));
+  EXPECT_EQ(val1 >> 64, MAKE_INT128(0x0, 0x123456789abcdef0));
+  EXPECT_EQ(val2 >> 63, MAKE_INT128(0xffffffffffffffff, 0xfdb974130eca8643));
+  EXPECT_EQ(val2 >> 64, MAKE_INT128(0xffffffffffffffff, 0xfedcba0987654321));
+
+  EXPECT_EQ(val1 >> 126, MAKE_INT128(0x0, 0x0));
+  EXPECT_EQ(val2 >> 126, MAKE_INT128(0xffffffffffffffff, 0xffffffffffffffff));
+}
+
+TEST(Int128, NumericLimitsTest) {
+  static_assert(std::numeric_limits<absl::int128>::is_specialized, "");
+  static_assert(std::numeric_limits<absl::int128>::is_signed, "");
+  static_assert(std::numeric_limits<absl::int128>::is_integer, "");
+  EXPECT_EQ(static_cast<int>(127 * std::log10(2)),
+            std::numeric_limits<absl::int128>::digits10);
+  EXPECT_EQ(absl::Int128Min(), std::numeric_limits<absl::int128>::min());
+  EXPECT_EQ(absl::Int128Min(), std::numeric_limits<absl::int128>::lowest());
+  EXPECT_EQ(absl::Int128Max(), std::numeric_limits<absl::int128>::max());
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/numeric/internal/representation.h b/weight/_dep/abseil-cpp/absl/numeric/internal/representation.h
new file mode 100644
index 0000000000000000000000000000000000000000..82d332fdde31a97d887b791c1a1c8d7195e26261
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/numeric/internal/representation.h
@@ -0,0 +1,55 @@
+// Copyright 2021 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_NUMERIC_INTERNAL_REPRESENTATION_H_
+#define ABSL_NUMERIC_INTERNAL_REPRESENTATION_H_
+
+#include <limits>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace numeric_internal {
+
+// Returns true iff long double is represented as a pair of doubles added
+// together.
+inline constexpr bool IsDoubleDouble() {
+  // A double-double value always has exactly twice the precision of a double
+  // value--one double carries the high digits and one double carries the low
+  // digits. This property is not shared with any other common floating-point
+  // representation, so this test won't trigger false positives. For reference,
+  // this table gives the number of bits of precision of each common
+  // floating-point representation:
+  //
+  //                type     precision
+  //         IEEE single          24 b
+  //         IEEE double          53
+  //     x86 long double          64
+  //       double-double         106
+  //      IEEE quadruple         113
+  //
+  // Note in particular that a quadruple-precision float has greater precision
+  // than a double-double float despite taking up the same amount of memory; the
+  // quad has more of its bits allocated to the mantissa than the double-double
+  // has.
+  return std::numeric_limits<long double>::digits ==
+         2 * std::numeric_limits<double>::digits;
+}
+
+}  // namespace numeric_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_NUMERIC_INTERNAL_REPRESENTATION_H_
diff --git a/weight/_dep/abseil-cpp/absl/profiling/BUILD.bazel b/weight/_dep/abseil-cpp/absl/profiling/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..86f205f9665067a0052ea507e4320a9923088924
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/BUILD.bazel
@@ -0,0 +1,140 @@
+# Copyright 2021 The Abseil Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:private"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "sample_recorder",
+    hdrs = ["internal/sample_recorder.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        "//absl:__subpackages__",
+    ],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/synchronization",
+        "//absl/time",
+    ],
+)
+
+cc_test(
+    name = "sample_recorder_test",
+    srcs = ["internal/sample_recorder_test.cc"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_wasm",
+    ],
+    deps = [
+        ":sample_recorder",
+        "//absl/base:core_headers",
+        "//absl/synchronization",
+        "//absl/synchronization:thread_pool",
+        "//absl/time",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "exponential_biased",
+    srcs = ["internal/exponential_biased.cc"],
+    hdrs = ["internal/exponential_biased.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        "//absl:__subpackages__",
+    ],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "exponential_biased_test",
+    size = "small",
+    srcs = ["internal/exponential_biased_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":exponential_biased",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "periodic_sampler",
+    srcs = ["internal/periodic_sampler.cc"],
+    hdrs = ["internal/periodic_sampler.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        # TODO(b/304670045): remove after periodic_sampler moves to //spanner/common.
+        "//absl:__subpackages__",
+    ],
+    deps = [
+        ":exponential_biased",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "periodic_sampler_test",
+    size = "small",
+    srcs = ["internal/periodic_sampler_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":periodic_sampler",
+        "//absl/base:core_headers",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_binary(
+    name = "periodic_sampler_benchmark",
+    testonly = 1,
+    srcs = ["internal/periodic_sampler_benchmark.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    visibility = ["//visibility:private"],
+    deps = [
+        ":periodic_sampler",
+        "//absl/base:core_headers",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/profiling/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/profiling/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..9b3a71021c44ad8af253b0637397a2bfc657c1ea
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/CMakeLists.txt
@@ -0,0 +1,93 @@
+# Copyright 2021 The Abseil Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+absl_cc_library(
+  NAME
+    sample_recorder
+  HDRS
+    "internal/sample_recorder.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::synchronization
+)
+
+absl_cc_test(
+  NAME
+    sample_recorder_test
+  SRCS
+    "internal/sample_recorder_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::sample_recorder
+    absl::time
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    exponential_biased
+  SRCS
+    "internal/exponential_biased.cc"
+  HDRS
+    "internal/exponential_biased.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+)
+
+absl_cc_test(
+  NAME
+    exponential_biased_test
+  SRCS
+    "internal/exponential_biased_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::exponential_biased
+    absl::strings
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    periodic_sampler
+  SRCS
+    "internal/periodic_sampler.cc"
+  HDRS
+    "internal/periodic_sampler.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::core_headers
+    absl::exponential_biased
+)
+
+absl_cc_test(
+  NAME
+    periodic_sampler_test
+  SRCS
+    "internal/periodic_sampler_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::core_headers
+    absl::periodic_sampler
+    GTest::gmock_main
+)
+
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased.cc b/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased.cc
new file mode 100644
index 0000000000000000000000000000000000000000..81d9a75765263106d9e76380323611df6685eea5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased.cc
@@ -0,0 +1,93 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/profiling/internal/exponential_biased.h"
+
+#include <stdint.h>
+
+#include <algorithm>
+#include <atomic>
+#include <cmath>
+#include <limits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/optimization.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+
+// The algorithm generates a random number between 0 and 1 and applies the
+// inverse cumulative distribution function for an exponential. Specifically:
+// Let m be the inverse of the sample period, then the probability
+// distribution function is m*exp(-mx) so the CDF is
+// p = 1 - exp(-mx), so
+// q = 1 - p = exp(-mx)
+// log_e(q) = -mx
+// -log_e(q)/m = x
+// log_2(q) * (-log_e(2) * 1/m) = x
+// In the code, q is actually in the range 1 to 2**26, hence the -26 below
+int64_t ExponentialBiased::GetSkipCount(int64_t mean) {
+  if (ABSL_PREDICT_FALSE(!initialized_)) {
+    Initialize();
+  }
+
+  uint64_t rng = NextRandom(rng_);
+  rng_ = rng;
+
+  // Take the top 26 bits as the random number
+  // (This plus the 1<<58 sampling bound give a max possible step of
+  // 5194297183973780480 bytes.)
+  // The uint32_t cast is to prevent a (hard-to-reproduce) NAN
+  // under piii debug for some binaries.
+  double q = static_cast<uint32_t>(rng >> (kPrngNumBits - 26)) + 1.0;
+  // Put the computed p-value through the CDF of a geometric.
+  double interval = bias_ + (std::log2(q) - 26) * (-std::log(2.0) * mean);
+  // Very large values of interval overflow int64_t. To avoid that, we will
+  // cheat and clamp any huge values to (int64_t max)/2. This is a potential
+  // source of bias, but the mean would need to be such a large value that it's
+  // not likely to come up. For example, with a mean of 1e18, the probability of
+  // hitting this condition is about 1/1000. For a mean of 1e17, standard
+  // calculators claim that this event won't happen.
+  if (interval > static_cast<double>(std::numeric_limits<int64_t>::max() / 2)) {
+    // Assume huge values are bias neutral, retain bias for next call.
+    return std::numeric_limits<int64_t>::max() / 2;
+  }
+  double value = std::rint(interval);
+  bias_ = interval - value;
+  return value;
+}
+
+int64_t ExponentialBiased::GetStride(int64_t mean) {
+  return GetSkipCount(mean - 1) + 1;
+}
+
+void ExponentialBiased::Initialize() {
+  // We don't get well distributed numbers from `this` so we call NextRandom() a
+  // bunch to mush the bits around. We use a global_rand to handle the case
+  // where the same thread (by memory address) gets created and destroyed
+  // repeatedly.
+  ABSL_CONST_INIT static std::atomic<uint32_t> global_rand(0);
+  uint64_t r = reinterpret_cast<uint64_t>(this) +
+               global_rand.fetch_add(1, std::memory_order_relaxed);
+  for (int i = 0; i < 20; ++i) {
+    r = NextRandom(r);
+  }
+  rng_ = r;
+  initialized_ = true;
+}
+
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased.h b/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased.h
new file mode 100644
index 0000000000000000000000000000000000000000..d31f7782e83dca4461073c443b9b04582a5921df
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased.h
@@ -0,0 +1,130 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_PROFILING_INTERNAL_EXPONENTIAL_BIASED_H_
+#define ABSL_PROFILING_INTERNAL_EXPONENTIAL_BIASED_H_
+
+#include <stdint.h>
+
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+
+// ExponentialBiased provides a small and fast random number generator for a
+// rounded exponential distribution. This generator manages very little state,
+// and imposes no synchronization overhead. This makes it useful in specialized
+// scenarios requiring minimum overhead, such as stride based periodic sampling.
+//
+// ExponentialBiased provides two closely related functions, GetSkipCount() and
+// GetStride(), both returning a rounded integer defining a number of events
+// required before some event with a given mean probability occurs.
+//
+// The distribution is useful to generate a random wait time or some periodic
+// event with a given mean probability. For example, if an action is supposed to
+// happen on average once every 'N' events, then we can get a random 'stride'
+// counting down how long before the event to happen. For example, if we'd want
+// to sample one in every 1000 'Frobber' calls, our code could look like this:
+//
+//   Frobber::Frobber() {
+//     stride_ = exponential_biased_.GetStride(1000);
+//   }
+//
+//   void Frobber::Frob(int arg) {
+//     if (--stride == 0) {
+//       SampleFrob(arg);
+//       stride_ = exponential_biased_.GetStride(1000);
+//     }
+//     ...
+//   }
+//
+// The rounding of the return value creates a bias, especially for smaller means
+// where the distribution of the fraction is not evenly distributed. We correct
+// this bias by tracking the fraction we rounded up or down on each iteration,
+// effectively tracking the distance between the cumulative value, and the
+// rounded cumulative value. For example, given a mean of 2:
+//
+//   raw = 1.63076, cumulative = 1.63076, rounded = 2, bias = -0.36923
+//   raw = 0.14624, cumulative = 1.77701, rounded = 2, bias =  0.14624
+//   raw = 4.93194, cumulative = 6.70895, rounded = 7, bias = -0.06805
+//   raw = 0.24206, cumulative = 6.95101, rounded = 7, bias =  0.24206
+//   etc...
+//
+// Adjusting with rounding bias is relatively trivial:
+//
+//    double value = bias_ + exponential_distribution(mean)();
+//    double rounded_value = std::rint(value);
+//    bias_ = value - rounded_value;
+//    return rounded_value;
+//
+// This class is thread-compatible.
+class ExponentialBiased {
+ public:
+  // The number of bits set by NextRandom.
+  static constexpr int kPrngNumBits = 48;
+
+  // `GetSkipCount()` returns the number of events to skip before some chosen
+  // event happens. For example, randomly tossing a coin, we will on average
+  // throw heads once before we get tails. We can simulate random coin tosses
+  // using GetSkipCount() as:
+  //
+  //   ExponentialBiased eb;
+  //   for (...) {
+  //     int number_of_heads_before_tail = eb.GetSkipCount(1);
+  //     for (int flips = 0; flips < number_of_heads_before_tail; ++flips) {
+  //       printf("head...");
+  //     }
+  //     printf("tail\n");
+  //   }
+  //
+  int64_t GetSkipCount(int64_t mean);
+
+  // GetStride() returns the number of events required for a specific event to
+  // happen. See the class comments for a usage example. `GetStride()` is
+  // equivalent to `GetSkipCount(mean - 1) + 1`. When to use `GetStride()` or
+  // `GetSkipCount()` depends mostly on what best fits the use case.
+  int64_t GetStride(int64_t mean);
+
+  // Computes a random number in the range [0, 1<<(kPrngNumBits+1) - 1]
+  //
+  // This is public to enable testing.
+  static uint64_t NextRandom(uint64_t rnd);
+
+ private:
+  void Initialize();
+
+  uint64_t rng_{0};
+  double bias_{0};
+  bool initialized_{false};
+};
+
+// Returns the next prng value.
+// pRNG is: aX+b mod c with a = 0x5DEECE66D, b =  0xB, c = 1<<48
+// This is the lrand64 generator.
+inline uint64_t ExponentialBiased::NextRandom(uint64_t rnd) {
+  const uint64_t prng_mult = uint64_t{0x5DEECE66D};
+  const uint64_t prng_add = 0xB;
+  const uint64_t prng_mod_power = 48;
+  const uint64_t prng_mod_mask =
+      ~((~static_cast<uint64_t>(0)) << prng_mod_power);
+  return (prng_mult * rnd + prng_add) & prng_mod_mask;
+}
+
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_PROFILING_INTERNAL_EXPONENTIAL_BIASED_H_
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased_test.cc b/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ebfbcad4f001384cf9a18d6245bbc9d89371fe78
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/exponential_biased_test.cc
@@ -0,0 +1,203 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/profiling/internal/exponential_biased.h"
+
+#include <stddef.h>
+
+#include <cmath>
+#include <cstdint>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/str_cat.h"
+
+using ::testing::Ge;
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+namespace {
+
+MATCHER_P2(IsBetween, a, b,
+           absl::StrCat(std::string(negation ? "isn't" : "is"), " between ", a,
+                        " and ", b)) {
+  return a <= arg && arg <= b;
+}
+
+// Tests of the quality of the random numbers generated
+// This uses the Anderson Darling test for uniformity.
+// See "Evaluating the Anderson-Darling Distribution" by Marsaglia
+// for details.
+
+// Short cut version of ADinf(z), z>0 (from Marsaglia)
+// This returns the p-value for Anderson Darling statistic in
+// the limit as n-> infinity. For finite n, apply the error fix below.
+double AndersonDarlingInf(double z) {
+  if (z < 2) {
+    return exp(-1.2337141 / z) / sqrt(z) *
+           (2.00012 +
+            (0.247105 -
+             (0.0649821 - (0.0347962 - (0.011672 - 0.00168691 * z) * z) * z) *
+                 z) *
+                z);
+  }
+  return exp(
+      -exp(1.0776 -
+           (2.30695 -
+            (0.43424 - (0.082433 - (0.008056 - 0.0003146 * z) * z) * z) * z) *
+               z));
+}
+
+// Corrects the approximation error in AndersonDarlingInf for small values of n
+// Add this to AndersonDarlingInf to get a better approximation
+// (from Marsaglia)
+double AndersonDarlingErrFix(int n, double x) {
+  if (x > 0.8) {
+    return (-130.2137 +
+            (745.2337 -
+             (1705.091 - (1950.646 - (1116.360 - 255.7844 * x) * x) * x) * x) *
+                x) /
+           n;
+  }
+  double cutoff = 0.01265 + 0.1757 / n;
+  if (x < cutoff) {
+    double t = x / cutoff;
+    t = sqrt(t) * (1 - t) * (49 * t - 102);
+    return t * (0.0037 / (n * n) + 0.00078 / n + 0.00006) / n;
+  } else {
+    double t = (x - cutoff) / (0.8 - cutoff);
+    t = -0.00022633 +
+        (6.54034 - (14.6538 - (14.458 - (8.259 - 1.91864 * t) * t) * t) * t) *
+            t;
+    return t * (0.04213 + 0.01365 / n) / n;
+  }
+}
+
+// Returns the AndersonDarling p-value given n and the value of the statistic
+double AndersonDarlingPValue(int n, double z) {
+  double ad = AndersonDarlingInf(z);
+  double errfix = AndersonDarlingErrFix(n, ad);
+  return ad + errfix;
+}
+
+double AndersonDarlingStatistic(const std::vector<double>& random_sample) {
+  size_t n = random_sample.size();
+  double ad_sum = 0;
+  for (size_t i = 0; i < n; i++) {
+    ad_sum += (2 * i + 1) *
+              std::log(random_sample[i] * (1 - random_sample[n - 1 - i]));
+  }
+  const auto n_as_double = static_cast<double>(n);
+  double ad_statistic = -n_as_double - 1 / n_as_double * ad_sum;
+  return ad_statistic;
+}
+
+// Tests if the array of doubles is uniformly distributed.
+// Returns the p-value of the Anderson Darling Statistic
+// for the given set of sorted random doubles
+// See "Evaluating the Anderson-Darling Distribution" by
+// Marsaglia and Marsaglia for details.
+double AndersonDarlingTest(const std::vector<double>& random_sample) {
+  double ad_statistic = AndersonDarlingStatistic(random_sample);
+  double p = AndersonDarlingPValue(static_cast<int>(random_sample.size()),
+                                   ad_statistic);
+  return p;
+}
+
+TEST(ExponentialBiasedTest, CoinTossDemoWithGetSkipCount) {
+  ExponentialBiased eb;
+  for (int runs = 0; runs < 10; ++runs) {
+    for (int64_t flips = eb.GetSkipCount(1); flips > 0; --flips) {
+      printf("head...");
+    }
+    printf("tail\n");
+  }
+  int heads = 0;
+  for (int i = 0; i < 10000000; i += 1 + eb.GetSkipCount(1)) {
+    ++heads;
+  }
+  printf("Heads = %d (%f%%)\n", heads, 100.0 * heads / 10000000);
+}
+
+TEST(ExponentialBiasedTest, SampleDemoWithStride) {
+  ExponentialBiased eb;
+  int64_t stride = eb.GetStride(10);
+  int samples = 0;
+  for (int i = 0; i < 10000000; ++i) {
+    if (--stride == 0) {
+      ++samples;
+      stride = eb.GetStride(10);
+    }
+  }
+  printf("Samples = %d (%f%%)\n", samples, 100.0 * samples / 10000000);
+}
+
+
+// Testing that NextRandom generates uniform random numbers. Applies the
+// Anderson-Darling test for uniformity
+TEST(ExponentialBiasedTest, TestNextRandom) {
+  for (auto n : std::vector<size_t>({
+           10,  // Check short-range correlation
+           100, 1000,
+           10000  // Make sure there's no systemic error
+       })) {
+    uint64_t x = 1;
+    // This assumes that the prng returns 48 bit numbers
+    uint64_t max_prng_value = static_cast<uint64_t>(1) << 48;
+    // Initialize.
+    for (int i = 1; i <= 20; i++) {
+      x = ExponentialBiased::NextRandom(x);
+    }
+    std::vector<uint64_t> int_random_sample(n);
+    // Collect samples
+    for (size_t i = 0; i < n; i++) {
+      int_random_sample[i] = x;
+      x = ExponentialBiased::NextRandom(x);
+    }
+    // First sort them...
+    std::sort(int_random_sample.begin(), int_random_sample.end());
+    std::vector<double> random_sample(n);
+    // Convert them to uniform randoms (in the range [0,1])
+    for (size_t i = 0; i < n; i++) {
+      random_sample[i] =
+          static_cast<double>(int_random_sample[i]) / max_prng_value;
+    }
+    // Now compute the Anderson-Darling statistic
+    double ad_pvalue = AndersonDarlingTest(random_sample);
+    EXPECT_GT(std::min(ad_pvalue, 1 - ad_pvalue), 0.0001)
+        << "prng is not uniform: n = " << n << " p = " << ad_pvalue;
+  }
+}
+
+// The generator needs to be available as a thread_local and as a static
+// variable.
+TEST(ExponentialBiasedTest, InitializationModes) {
+  ABSL_CONST_INIT static ExponentialBiased eb_static;
+  EXPECT_THAT(eb_static.GetSkipCount(2), Ge(0));
+
+#ifdef ABSL_HAVE_THREAD_LOCAL
+  thread_local ExponentialBiased eb_thread;
+  EXPECT_THAT(eb_thread.GetSkipCount(2), Ge(0));
+#endif
+
+  ExponentialBiased eb_stack;
+  EXPECT_THAT(eb_stack.GetSkipCount(2), Ge(0));
+}
+
+}  // namespace
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler.cc b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a738a82c865dc43ffd3c92dc62cc42132595c3f5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler.cc
@@ -0,0 +1,53 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/profiling/internal/periodic_sampler.h"
+
+#include <atomic>
+
+#include "absl/profiling/internal/exponential_biased.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+
+int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
+  return rng_.GetStride(period);
+}
+
+bool PeriodicSamplerBase::SubtleConfirmSample() noexcept {
+  int current_period = period();
+
+  // Deal with period case 0 (always off) and 1 (always on)
+  if (ABSL_PREDICT_FALSE(current_period < 2)) {
+    stride_ = 0;
+    return current_period == 1;
+  }
+
+  // Check if this is the first call to Sample()
+  if (ABSL_PREDICT_FALSE(stride_ == 1)) {
+    stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period));
+    if (static_cast<int64_t>(stride_) < -1) {
+      ++stride_;
+      return false;
+    }
+  }
+
+  stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period));
+  return true;
+}
+
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler.h b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler.h
new file mode 100644
index 0000000000000000000000000000000000000000..54f0af452b82f8f3a7aafea43bbcdd11672e4d94
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler.h
@@ -0,0 +1,211 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_PROFILING_INTERNAL_PERIODIC_SAMPLER_H_
+#define ABSL_PROFILING_INTERNAL_PERIODIC_SAMPLER_H_
+
+#include <stdint.h>
+
+#include <atomic>
+
+#include "absl/base/optimization.h"
+#include "absl/profiling/internal/exponential_biased.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+
+// PeriodicSamplerBase provides the basic period sampler implementation.
+//
+// This is the base class for the templated PeriodicSampler class, which holds
+// a global std::atomic value identified by a user defined tag, such that
+// each specific PeriodSampler implementation holds its own global period.
+//
+// PeriodicSamplerBase is thread-compatible except where stated otherwise.
+class PeriodicSamplerBase {
+ public:
+  // PeriodicSamplerBase is trivial / copyable / movable / destructible.
+  PeriodicSamplerBase() = default;
+  PeriodicSamplerBase(PeriodicSamplerBase&&) = default;
+  PeriodicSamplerBase(const PeriodicSamplerBase&) = default;
+
+  // Returns true roughly once every `period` calls. This is established by a
+  // randomly picked `stride` that is counted down on each call to `Sample`.
+  // This stride is picked such that the probability of `Sample()` returning
+  // true is 1 in `period`.
+  inline bool Sample() noexcept;
+
+  // The below methods are intended for optimized use cases where the
+  // size of the inlined fast path code is highly important. Applications
+  // should use the `Sample()` method unless they have proof that their
+  // specific use case requires the optimizations offered by these methods.
+  //
+  // An example of such a use case is SwissTable sampling. All sampling checks
+  // are in inlined SwissTable methods, and the number of call sites is huge.
+  // In this case, the inlined code size added to each translation unit calling
+  // SwissTable methods is non-trivial.
+  //
+  // The `SubtleMaybeSample()` function spuriously returns true even if the
+  // function should not be sampled, applications MUST match each call to
+  // 'SubtleMaybeSample()' returning true with a `SubtleConfirmSample()` call,
+  // and use the result of the latter as the sampling decision.
+  // In other words: the code should logically be equivalent to:
+  //
+  //    if (SubtleMaybeSample() && SubtleConfirmSample()) {
+  //      // Sample this call
+  //    }
+  //
+  // In the 'inline-size' optimized case, the `SubtleConfirmSample()` call can
+  // be placed out of line, for example, the typical use case looks as follows:
+  //
+  //   // --- frobber.h -----------
+  //   void FrobberSampled();
+  //
+  //   inline void FrobberImpl() {
+  //     // ...
+  //   }
+  //
+  //   inline void Frobber() {
+  //     if (ABSL_PREDICT_FALSE(sampler.SubtleMaybeSample())) {
+  //       FrobberSampled();
+  //     } else {
+  //       FrobberImpl();
+  //     }
+  //   }
+  //
+  //   // --- frobber.cc -----------
+  //   void FrobberSampled() {
+  //     if (!sampler.SubtleConfirmSample())) {
+  //       // Spurious false positive
+  //       FrobberImpl();
+  //       return;
+  //     }
+  //
+  //     // Sampled execution
+  //     // ...
+  //   }
+  inline bool SubtleMaybeSample() noexcept;
+  bool SubtleConfirmSample() noexcept;
+
+ protected:
+  // We explicitly don't use a virtual destructor as this class is never
+  // virtually destroyed, and it keeps the class trivial, which avoids TLS
+  // prologue and epilogue code for our TLS instances.
+  ~PeriodicSamplerBase() = default;
+
+  // Returns the next stride for our sampler.
+  // This function is virtual for testing purposes only.
+  virtual int64_t GetExponentialBiased(int period) noexcept;
+
+ private:
+  // Returns the current period of this sampler. Thread-safe.
+  virtual int period() const noexcept = 0;
+
+  // Keep and decrement stride_ as an unsigned integer, but compare the value
+  // to zero casted as a signed int. clang and msvc do not create optimum code
+  // if we use signed for the combined decrement and sign comparison.
+  //
+  // Below 3 alternative options, all compiles generate the best code
+  // using the unsigned increment <---> signed int comparison option.
+  //
+  // Option 1:
+  //   int64_t stride_;
+  //   if (ABSL_PREDICT_TRUE(++stride_ < 0)) { ... }
+  //
+  //   GCC   x64 (OK) : https://gcc.godbolt.org/z/R5MzzA
+  //   GCC   ppc (OK) : https://gcc.godbolt.org/z/z7NZAt
+  //   Clang x64 (BAD): https://gcc.godbolt.org/z/t4gPsd
+  //   ICC   x64 (OK) : https://gcc.godbolt.org/z/rE6s8W
+  //   MSVC  x64 (OK) : https://gcc.godbolt.org/z/ARMXqS
+  //
+  // Option 2:
+  //   int64_t stride_ = 0;
+  //   if (ABSL_PREDICT_TRUE(--stride_ >= 0)) { ... }
+  //
+  //   GCC   x64 (OK) : https://gcc.godbolt.org/z/jSQxYK
+  //   GCC   ppc (OK) : https://gcc.godbolt.org/z/VJdYaA
+  //   Clang x64 (BAD): https://gcc.godbolt.org/z/Xm4NjX
+  //   ICC   x64 (OK) : https://gcc.godbolt.org/z/4snaFd
+  //   MSVC  x64 (BAD): https://gcc.godbolt.org/z/BgnEKE
+  //
+  // Option 3:
+  //   uint64_t stride_;
+  //   if (ABSL_PREDICT_TRUE(static_cast<int64_t>(++stride_) < 0)) { ... }
+  //
+  //   GCC   x64 (OK) : https://gcc.godbolt.org/z/bFbfPy
+  //   GCC   ppc (OK) : https://gcc.godbolt.org/z/S9KkUE
+  //   Clang x64 (OK) : https://gcc.godbolt.org/z/UYzRb4
+  //   ICC   x64 (OK) : https://gcc.godbolt.org/z/ptTNfD
+  //   MSVC  x64 (OK) : https://gcc.godbolt.org/z/76j4-5
+  uint64_t stride_ = 0;
+  absl::profiling_internal::ExponentialBiased rng_;
+};
+
+inline bool PeriodicSamplerBase::SubtleMaybeSample() noexcept {
+  // See comments on `stride_` for the unsigned increment / signed compare.
+  if (ABSL_PREDICT_TRUE(static_cast<int64_t>(++stride_) < 0)) {
+    return false;
+  }
+  return true;
+}
+
+inline bool PeriodicSamplerBase::Sample() noexcept {
+  return ABSL_PREDICT_FALSE(SubtleMaybeSample()) ? SubtleConfirmSample()
+                                                 : false;
+}
+
+// PeriodicSampler is a concreted periodic sampler implementation.
+// The user provided Tag identifies the implementation, and is required to
+// isolate the global state of this instance from other instances.
+//
+// Typical use case:
+//
+//   struct HashTablezTag {};
+//   thread_local PeriodicSampler sampler;
+//
+//   void HashTableSamplingLogic(...) {
+//     if (sampler.Sample()) {
+//       HashTableSlowSamplePath(...);
+//     }
+//   }
+//
+template <typename Tag, int default_period = 0>
+class PeriodicSampler final : public PeriodicSamplerBase {
+ public:
+  ~PeriodicSampler() = default;
+
+  int period() const noexcept final {
+    return period_.load(std::memory_order_relaxed);
+  }
+
+  // Sets the global period for this sampler. Thread-safe.
+  // Setting a period of 0 disables the sampler, i.e., every call to Sample()
+  // will return false. Setting a period of 1 puts the sampler in 'always on'
+  // mode, i.e., every call to Sample() returns true.
+  static void SetGlobalPeriod(int period) {
+    period_.store(period, std::memory_order_relaxed);
+  }
+
+ private:
+  static std::atomic<int> period_;
+};
+
+template <typename Tag, int default_period>
+std::atomic<int> PeriodicSampler<Tag, default_period>::period_(default_period);
+
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_PROFILING_INTERNAL_PERIODIC_SAMPLER_H_
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler_benchmark.cc b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8f0e5574c3b78f481a4f6a5320ced34ea96978d9
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler_benchmark.cc
@@ -0,0 +1,79 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/profiling/internal/periodic_sampler.h"
+#include "benchmark/benchmark.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+namespace {
+
+template <typename Sampler>
+void BM_Sample(Sampler* sampler, benchmark::State& state) {
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(sampler);
+    benchmark::DoNotOptimize(sampler->Sample());
+  }
+}
+
+template <typename Sampler>
+void BM_SampleMinunumInlined(Sampler* sampler, benchmark::State& state) {
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(sampler);
+    if (ABSL_PREDICT_FALSE(sampler->SubtleMaybeSample())) {
+      benchmark::DoNotOptimize(sampler->SubtleConfirmSample());
+    }
+  }
+}
+
+void BM_PeriodicSampler_TinySample(benchmark::State& state) {
+  struct Tag {};
+  PeriodicSampler<Tag, 10> sampler;
+  BM_Sample(&sampler, state);
+}
+BENCHMARK(BM_PeriodicSampler_TinySample);
+
+void BM_PeriodicSampler_ShortSample(benchmark::State& state) {
+  struct Tag {};
+  PeriodicSampler<Tag, 1024> sampler;
+  BM_Sample(&sampler, state);
+}
+BENCHMARK(BM_PeriodicSampler_ShortSample);
+
+void BM_PeriodicSampler_LongSample(benchmark::State& state) {
+  struct Tag {};
+  PeriodicSampler<Tag, 1024 * 1024> sampler;
+  BM_Sample(&sampler, state);
+}
+BENCHMARK(BM_PeriodicSampler_LongSample);
+
+void BM_PeriodicSampler_LongSampleMinunumInlined(benchmark::State& state) {
+  struct Tag {};
+  PeriodicSampler<Tag, 1024 * 1024> sampler;
+  BM_SampleMinunumInlined(&sampler, state);
+}
+BENCHMARK(BM_PeriodicSampler_LongSampleMinunumInlined);
+
+void BM_PeriodicSampler_Disabled(benchmark::State& state) {
+  struct Tag {};
+  PeriodicSampler<Tag, 0> sampler;
+  BM_Sample(&sampler, state);
+}
+BENCHMARK(BM_PeriodicSampler_Disabled);
+
+}  // namespace
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler_test.cc b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ef986f3878bfef820d769fd6a16901a39553eb54
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/periodic_sampler_test.cc
@@ -0,0 +1,177 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/profiling/internal/periodic_sampler.h"
+
+#include <thread>  // NOLINT(build/c++11)
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/macros.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+namespace {
+
+using testing::Eq;
+using testing::Return;
+using testing::StrictMock;
+
+class MockPeriodicSampler : public PeriodicSamplerBase {
+ public:
+  virtual ~MockPeriodicSampler() = default;
+
+  MOCK_METHOD(int, period, (), (const, noexcept));
+  MOCK_METHOD(int64_t, GetExponentialBiased, (int), (noexcept));
+};
+
+TEST(PeriodicSamplerBaseTest, Sample) {
+  StrictMock<MockPeriodicSampler> sampler;
+
+  EXPECT_CALL(sampler, period()).Times(3).WillRepeatedly(Return(16));
+  EXPECT_CALL(sampler, GetExponentialBiased(16))
+      .WillOnce(Return(2))
+      .WillOnce(Return(3))
+      .WillOnce(Return(4));
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_TRUE(sampler.Sample());
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_TRUE(sampler.Sample());
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+}
+
+TEST(PeriodicSamplerBaseTest, ImmediatelySample) {
+  StrictMock<MockPeriodicSampler> sampler;
+
+  EXPECT_CALL(sampler, period()).Times(2).WillRepeatedly(Return(16));
+  EXPECT_CALL(sampler, GetExponentialBiased(16))
+      .WillOnce(Return(1))
+      .WillOnce(Return(2))
+      .WillOnce(Return(3));
+
+  EXPECT_TRUE(sampler.Sample());
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_TRUE(sampler.Sample());
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+}
+
+TEST(PeriodicSamplerBaseTest, Disabled) {
+  StrictMock<MockPeriodicSampler> sampler;
+
+  EXPECT_CALL(sampler, period()).Times(3).WillRepeatedly(Return(0));
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+}
+
+TEST(PeriodicSamplerBaseTest, AlwaysOn) {
+  StrictMock<MockPeriodicSampler> sampler;
+
+  EXPECT_CALL(sampler, period()).Times(3).WillRepeatedly(Return(1));
+
+  EXPECT_TRUE(sampler.Sample());
+  EXPECT_TRUE(sampler.Sample());
+  EXPECT_TRUE(sampler.Sample());
+}
+
+TEST(PeriodicSamplerBaseTest, Disable) {
+  StrictMock<MockPeriodicSampler> sampler;
+
+  EXPECT_CALL(sampler, period()).WillOnce(Return(16));
+  EXPECT_CALL(sampler, GetExponentialBiased(16)).WillOnce(Return(3));
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+
+  EXPECT_CALL(sampler, period()).Times(2).WillRepeatedly(Return(0));
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+}
+
+TEST(PeriodicSamplerBaseTest, Enable) {
+  StrictMock<MockPeriodicSampler> sampler;
+
+  EXPECT_CALL(sampler, period()).WillOnce(Return(0));
+  EXPECT_FALSE(sampler.Sample());
+
+  EXPECT_CALL(sampler, period()).Times(2).WillRepeatedly(Return(16));
+  EXPECT_CALL(sampler, GetExponentialBiased(16))
+      .Times(2)
+      .WillRepeatedly(Return(3));
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_TRUE(sampler.Sample());
+
+  EXPECT_FALSE(sampler.Sample());
+  EXPECT_FALSE(sampler.Sample());
+}
+
+TEST(PeriodicSamplerTest, ConstructConstInit) {
+  struct Tag {};
+  ABSL_CONST_INIT static PeriodicSampler<Tag> sampler;
+  (void)sampler;
+}
+
+TEST(PeriodicSamplerTest, DefaultPeriod0) {
+  struct Tag {};
+  PeriodicSampler<Tag> sampler;
+  EXPECT_THAT(sampler.period(), Eq(0));
+}
+
+TEST(PeriodicSamplerTest, DefaultPeriod) {
+  struct Tag {};
+  PeriodicSampler<Tag, 100> sampler;
+  EXPECT_THAT(sampler.period(), Eq(100));
+}
+
+TEST(PeriodicSamplerTest, SetGlobalPeriod) {
+  struct Tag1 {};
+  struct Tag2 {};
+  PeriodicSampler<Tag1, 25> sampler1;
+  PeriodicSampler<Tag2, 50> sampler2;
+
+  EXPECT_THAT(sampler1.period(), Eq(25));
+  EXPECT_THAT(sampler2.period(), Eq(50));
+
+  std::thread thread([] {
+    PeriodicSampler<Tag1, 25> sampler1;
+    PeriodicSampler<Tag2, 50> sampler2;
+    EXPECT_THAT(sampler1.period(), Eq(25));
+    EXPECT_THAT(sampler2.period(), Eq(50));
+    sampler1.SetGlobalPeriod(10);
+    sampler2.SetGlobalPeriod(20);
+  });
+  thread.join();
+
+  EXPECT_THAT(sampler1.period(), Eq(10));
+  EXPECT_THAT(sampler2.period(), Eq(20));
+}
+
+}  // namespace
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/sample_recorder.h b/weight/_dep/abseil-cpp/absl/profiling/internal/sample_recorder.h
new file mode 100644
index 0000000000000000000000000000000000000000..371f6c473ffc0fb9050a48a4dc40d2db44abdc68
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/sample_recorder.h
@@ -0,0 +1,253 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: sample_recorder.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines a lock-free linked list for recording samples
+// collected from a random/stochastic process.
+//
+// This utility is internal-only. Use at your own risk.
+
+#ifndef ABSL_PROFILING_INTERNAL_SAMPLE_RECORDER_H_
+#define ABSL_PROFILING_INTERNAL_SAMPLE_RECORDER_H_
+
+#include <atomic>
+#include <cstddef>
+#include <functional>
+
+#include "absl/base/config.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+
+// Sample<T> that has members required for linking samples in the linked list of
+// samples maintained by the SampleRecorder.  Type T defines the sampled data.
+template <typename T>
+struct Sample {
+  // Guards the ability to restore the sample to a pristine state.  This
+  // prevents races with sampling and resurrecting an object.
+  absl::Mutex init_mu;
+  T* next = nullptr;
+  T* dead ABSL_GUARDED_BY(init_mu) = nullptr;
+  int64_t weight;  // How many sampling events were required to sample this one.
+};
+
+// Holds samples and their associated stack traces with a soft limit of
+// `SetHashtablezMaxSamples()`.
+//
+// Thread safe.
+template <typename T>
+class SampleRecorder {
+ public:
+  SampleRecorder();
+  ~SampleRecorder();
+
+  // Registers for sampling.  Returns an opaque registration info.
+  template <typename... Targs>
+  T* Register(Targs&&... args);
+
+  // Unregisters the sample.
+  void Unregister(T* sample);
+
+  // The dispose callback will be called on all samples the moment they are
+  // being unregistered. Only affects samples that are unregistered after the
+  // callback has been set.
+  // Returns the previous callback.
+  using DisposeCallback = void (*)(const T&);
+  DisposeCallback SetDisposeCallback(DisposeCallback f);
+
+  // Iterates over all the registered `StackInfo`s.  Returning the number of
+  // samples that have been dropped.
+  int64_t Iterate(const std::function<void(const T& stack)>& f);
+
+  size_t GetMaxSamples() const;
+  void SetMaxSamples(size_t max);
+
+ private:
+  void PushNew(T* sample);
+  void PushDead(T* sample);
+  template <typename... Targs>
+  T* PopDead(Targs... args);
+
+  std::atomic<size_t> dropped_samples_;
+  std::atomic<size_t> size_estimate_;
+  std::atomic<size_t> max_samples_{1 << 20};
+
+  // Intrusive lock free linked lists for tracking samples.
+  //
+  // `all_` records all samples (they are never removed from this list) and is
+  // terminated with a `nullptr`.
+  //
+  // `graveyard_.dead` is a circular linked list.  When it is empty,
+  // `graveyard_.dead == &graveyard`.  The list is circular so that
+  // every item on it (even the last) has a non-null dead pointer.  This allows
+  // `Iterate` to determine if a given sample is live or dead using only
+  // information on the sample itself.
+  //
+  // For example, nodes [A, B, C, D, E] with [A, C, E] alive and [B, D] dead
+  // looks like this (G is the Graveyard):
+  //
+  //           +---+    +---+    +---+    +---+    +---+
+  //    all -->| A |--->| B |--->| C |--->| D |--->| E |
+  //           |   |    |   |    |   |    |   |    |   |
+  //   +---+   |   | +->|   |-+  |   | +->|   |-+  |   |
+  //   | G |   +---+ |  +---+ |  +---+ |  +---+ |  +---+
+  //   |   |         |        |        |        |
+  //   |   | --------+        +--------+        |
+  //   +---+                                    |
+  //     ^                                      |
+  //     +--------------------------------------+
+  //
+  std::atomic<T*> all_;
+  T graveyard_;
+
+  std::atomic<DisposeCallback> dispose_;
+};
+
+template <typename T>
+typename SampleRecorder<T>::DisposeCallback
+SampleRecorder<T>::SetDisposeCallback(DisposeCallback f) {
+  return dispose_.exchange(f, std::memory_order_relaxed);
+}
+
+template <typename T>
+SampleRecorder<T>::SampleRecorder()
+    : dropped_samples_(0), size_estimate_(0), all_(nullptr), dispose_(nullptr) {
+  absl::MutexLock l(&graveyard_.init_mu);
+  graveyard_.dead = &graveyard_;
+}
+
+template <typename T>
+SampleRecorder<T>::~SampleRecorder() {
+  T* s = all_.load(std::memory_order_acquire);
+  while (s != nullptr) {
+    T* next = s->next;
+    delete s;
+    s = next;
+  }
+}
+
+template <typename T>
+void SampleRecorder<T>::PushNew(T* sample) {
+  sample->next = all_.load(std::memory_order_relaxed);
+  while (!all_.compare_exchange_weak(sample->next, sample,
+                                     std::memory_order_release,
+                                     std::memory_order_relaxed)) {
+  }
+}
+
+template <typename T>
+void SampleRecorder<T>::PushDead(T* sample) {
+  if (auto* dispose = dispose_.load(std::memory_order_relaxed)) {
+    dispose(*sample);
+  }
+
+  absl::MutexLock graveyard_lock(&graveyard_.init_mu);
+  absl::MutexLock sample_lock(&sample->init_mu);
+  sample->dead = graveyard_.dead;
+  graveyard_.dead = sample;
+}
+
+template <typename T>
+template <typename... Targs>
+T* SampleRecorder<T>::PopDead(Targs... args) {
+  absl::MutexLock graveyard_lock(&graveyard_.init_mu);
+
+  // The list is circular, so eventually it collapses down to
+  //   graveyard_.dead == &graveyard_
+  // when it is empty.
+  T* sample = graveyard_.dead;
+  if (sample == &graveyard_) return nullptr;
+
+  absl::MutexLock sample_lock(&sample->init_mu);
+  graveyard_.dead = sample->dead;
+  sample->dead = nullptr;
+  sample->PrepareForSampling(std::forward<Targs>(args)...);
+  return sample;
+}
+
+template <typename T>
+template <typename... Targs>
+T* SampleRecorder<T>::Register(Targs&&... args) {
+  size_t size = size_estimate_.fetch_add(1, std::memory_order_relaxed);
+  if (size > max_samples_.load(std::memory_order_relaxed)) {
+    size_estimate_.fetch_sub(1, std::memory_order_relaxed);
+    dropped_samples_.fetch_add(1, std::memory_order_relaxed);
+    return nullptr;
+  }
+
+  T* sample = PopDead(args...);
+  if (sample == nullptr) {
+    // Resurrection failed.  Hire a new warlock.
+    sample = new T();
+    {
+      absl::MutexLock sample_lock(&sample->init_mu);
+      // If flag initialization happens to occur (perhaps in another thread)
+      // while in this block, it will lock `graveyard_` which is usually always
+      // locked before any sample. This will appear as a lock inversion.
+      // However, this code is run exactly once per sample, and this sample
+      // cannot be accessed until after it is returned from this method.  This
+      // means that this lock state can never be recreated, so we can safely
+      // inform the deadlock detector to ignore it.
+      sample->init_mu.ForgetDeadlockInfo();
+      sample->PrepareForSampling(std::forward<Targs>(args)...);
+    }
+    PushNew(sample);
+  }
+
+  return sample;
+}
+
+template <typename T>
+void SampleRecorder<T>::Unregister(T* sample) {
+  PushDead(sample);
+  size_estimate_.fetch_sub(1, std::memory_order_relaxed);
+}
+
+template <typename T>
+int64_t SampleRecorder<T>::Iterate(
+    const std::function<void(const T& stack)>& f) {
+  T* s = all_.load(std::memory_order_acquire);
+  while (s != nullptr) {
+    absl::MutexLock l(&s->init_mu);
+    if (s->dead == nullptr) {
+      f(*s);
+    }
+    s = s->next;
+  }
+
+  return dropped_samples_.load(std::memory_order_relaxed);
+}
+
+template <typename T>
+void SampleRecorder<T>::SetMaxSamples(size_t max) {
+  max_samples_.store(max, std::memory_order_release);
+}
+
+template <typename T>
+size_t SampleRecorder<T>::GetMaxSamples() const {
+  return max_samples_.load(std::memory_order_acquire);
+}
+
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_PROFILING_INTERNAL_SAMPLE_RECORDER_H_
diff --git a/weight/_dep/abseil-cpp/absl/profiling/internal/sample_recorder_test.cc b/weight/_dep/abseil-cpp/absl/profiling/internal/sample_recorder_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3373329a8acd74b9d0d417c61576080ace356462
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/profiling/internal/sample_recorder_test.cc
@@ -0,0 +1,184 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/profiling/internal/sample_recorder.h"
+
+#include <atomic>
+#include <random>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "absl/base/thread_annotations.h"
+#include "absl/synchronization/internal/thread_pool.h"
+#include "absl/synchronization/mutex.h"
+#include "absl/synchronization/notification.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace profiling_internal {
+
+namespace {
+using ::absl::synchronization_internal::ThreadPool;
+using ::testing::IsEmpty;
+using ::testing::UnorderedElementsAre;
+
+struct Info : public Sample<Info> {
+ public:
+  void PrepareForSampling(int64_t w) { weight = w; }
+  std::atomic<size_t> size;
+  absl::Time create_time;
+};
+
+std::vector<size_t> GetSizes(SampleRecorder<Info>* s) {
+  std::vector<size_t> res;
+  s->Iterate([&](const Info& info) {
+    res.push_back(info.size.load(std::memory_order_acquire));
+  });
+  return res;
+}
+
+std::vector<int64_t> GetWeights(SampleRecorder<Info>* s) {
+  std::vector<int64_t> res;
+  s->Iterate([&](const Info& info) { res.push_back(info.weight); });
+  return res;
+}
+
+Info* Register(SampleRecorder<Info>* s, int64_t weight, size_t size) {
+  auto* info = s->Register(weight);
+  assert(info != nullptr);
+  info->size.store(size);
+  return info;
+}
+
+TEST(SampleRecorderTest, Registration) {
+  SampleRecorder<Info> sampler;
+  auto* info1 = Register(&sampler, 31, 1);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(1));
+  EXPECT_THAT(GetWeights(&sampler), UnorderedElementsAre(31));
+
+  auto* info2 = Register(&sampler, 32, 2);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(1, 2));
+  info1->size.store(3);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(3, 2));
+  EXPECT_THAT(GetWeights(&sampler), UnorderedElementsAre(31, 32));
+
+  sampler.Unregister(info1);
+  sampler.Unregister(info2);
+}
+
+TEST(SampleRecorderTest, Unregistration) {
+  SampleRecorder<Info> sampler;
+  std::vector<Info*> infos;
+  for (size_t i = 0; i < 3; ++i) {
+    infos.push_back(Register(&sampler, 33 + i, i));
+  }
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 1, 2));
+  EXPECT_THAT(GetWeights(&sampler), UnorderedElementsAre(33, 34, 35));
+
+  sampler.Unregister(infos[1]);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 2));
+  EXPECT_THAT(GetWeights(&sampler), UnorderedElementsAre(33, 35));
+
+  infos.push_back(Register(&sampler, 36, 3));
+  infos.push_back(Register(&sampler, 37, 4));
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 2, 3, 4));
+  EXPECT_THAT(GetWeights(&sampler), UnorderedElementsAre(33, 35, 36, 37));
+  sampler.Unregister(infos[3]);
+  EXPECT_THAT(GetSizes(&sampler), UnorderedElementsAre(0, 2, 4));
+  EXPECT_THAT(GetWeights(&sampler), UnorderedElementsAre(33, 35, 37));
+
+  sampler.Unregister(infos[0]);
+  sampler.Unregister(infos[2]);
+  sampler.Unregister(infos[4]);
+  EXPECT_THAT(GetSizes(&sampler), IsEmpty());
+}
+
+TEST(SampleRecorderTest, MultiThreaded) {
+  SampleRecorder<Info> sampler;
+  Notification stop;
+  ThreadPool pool(10);
+
+  for (int i = 0; i < 10; ++i) {
+    pool.Schedule([&sampler, &stop, i]() {
+      std::random_device rd;
+      std::mt19937 gen(rd());
+
+      std::vector<Info*> infoz;
+      while (!stop.HasBeenNotified()) {
+        if (infoz.empty()) {
+          infoz.push_back(sampler.Register(i));
+        }
+        switch (std::uniform_int_distribution<>(0, 2)(gen)) {
+          case 0: {
+            infoz.push_back(sampler.Register(i));
+            break;
+          }
+          case 1: {
+            size_t p =
+                std::uniform_int_distribution<>(0, infoz.size() - 1)(gen);
+            Info* info = infoz[p];
+            infoz[p] = infoz.back();
+            infoz.pop_back();
+            EXPECT_EQ(info->weight, i);
+            sampler.Unregister(info);
+            break;
+          }
+          case 2: {
+            absl::Duration oldest = absl::ZeroDuration();
+            sampler.Iterate([&](const Info& info) {
+              oldest = std::max(oldest, absl::Now() - info.create_time);
+            });
+            ASSERT_GE(oldest, absl::ZeroDuration());
+            break;
+          }
+        }
+      }
+    });
+  }
+  // The threads will hammer away.  Give it a little bit of time for tsan to
+  // spot errors.
+  absl::SleepFor(absl::Seconds(3));
+  stop.Notify();
+}
+
+TEST(SampleRecorderTest, Callback) {
+  SampleRecorder<Info> sampler;
+
+  auto* info1 = Register(&sampler, 39, 1);
+  auto* info2 = Register(&sampler, 40, 2);
+
+  static const Info* expected;
+
+  auto callback = [](const Info& info) {
+    // We can't use `info` outside of this callback because the object will be
+    // disposed as soon as we return from here.
+    EXPECT_EQ(&info, expected);
+  };
+
+  // Set the callback.
+  EXPECT_EQ(sampler.SetDisposeCallback(callback), nullptr);
+  expected = info1;
+  sampler.Unregister(info1);
+
+  // Unset the callback.
+  EXPECT_EQ(callback, sampler.SetDisposeCallback(nullptr));
+  expected = nullptr;  // no more calls.
+  sampler.Unregister(info2);
+}
+
+}  // namespace
+}  // namespace profiling_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/BUILD.bazel b/weight/_dep/abseil-cpp/absl/random/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..80c4f0552171f189a46f67931893fef00a7e4e4c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/BUILD.bazel
@@ -0,0 +1,541 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# ABSL random-number generation libraries.
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "random",
+    hdrs = ["random.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":seed_sequences",
+        "//absl/random/internal:nonsecure_base",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:pool_urbg",
+        "//absl/random/internal:randen_engine",
+    ],
+)
+
+cc_library(
+    name = "distributions",
+    srcs = [
+        "discrete_distribution.cc",
+        "gaussian_distribution.cc",
+    ],
+    hdrs = [
+        "bernoulli_distribution.h",
+        "beta_distribution.h",
+        "discrete_distribution.h",
+        "distributions.h",
+        "exponential_distribution.h",
+        "gaussian_distribution.h",
+        "log_uniform_int_distribution.h",
+        "poisson_distribution.h",
+        "uniform_int_distribution.h",
+        "uniform_real_distribution.h",
+        "zipf_distribution.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:base_internal",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/meta:type_traits",
+        "//absl/numeric:bits",
+        "//absl/random/internal:distribution_caller",
+        "//absl/random/internal:fast_uniform_bits",
+        "//absl/random/internal:fastmath",
+        "//absl/random/internal:generate_real",
+        "//absl/random/internal:iostream_state_saver",
+        "//absl/random/internal:traits",
+        "//absl/random/internal:uniform_helper",
+        "//absl/random/internal:wide_multiply",
+        "//absl/strings",
+    ],
+)
+
+cc_library(
+    name = "seed_gen_exception",
+    srcs = ["seed_gen_exception.cc"],
+    hdrs = ["seed_gen_exception.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/base:config"],
+)
+
+cc_library(
+    name = "seed_sequences",
+    srcs = ["seed_sequences.cc"],
+    hdrs = [
+        "seed_sequences.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":seed_gen_exception",
+        "//absl/base:config",
+        "//absl/random/internal:pool_urbg",
+        "//absl/random/internal:salted_seed_seq",
+        "//absl/random/internal:seed_material",
+        "//absl/types:span",
+    ],
+)
+
+cc_library(
+    name = "bit_gen_ref",
+    hdrs = ["bit_gen_ref.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":random",
+        "//absl/base:core_headers",
+        "//absl/base:fast_type_id",
+        "//absl/meta:type_traits",
+        "//absl/random/internal:distribution_caller",
+        "//absl/random/internal:fast_uniform_bits",
+    ],
+)
+
+cc_library(
+    name = "mock_distributions",
+    testonly = 1,
+    hdrs = ["mock_distributions.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":mocking_bit_gen",
+        "//absl/meta:type_traits",
+        "//absl/random/internal:mock_overload_set",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_library(
+    name = "mocking_bit_gen",
+    testonly = 1,
+    hdrs = [
+        "mocking_bit_gen.h",
+    ],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/base:fast_type_id",
+        "//absl/container:flat_hash_map",
+        "//absl/meta:type_traits",
+        "//absl/random/internal:distribution_caller",
+        "//absl/strings",
+        "//absl/types:span",
+        "//absl/types:variant",
+        "//absl/utility",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_test(
+    name = "bernoulli_distribution_test",
+    size = "small",
+    timeout = "eternal",  # Android can take a very long time
+    srcs = ["bernoulli_distribution_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "beta_distribution_test",
+    size = "small",
+    timeout = "eternal",  # Android can take a very long time
+    srcs = ["beta_distribution_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    flaky = 1,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_wasm",
+    ],
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/log",
+        "//absl/numeric:representation",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "distributions_test",
+    size = "small",
+    timeout = "moderate",
+    srcs = [
+        "distributions_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/random/internal:distribution_test_util",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "generators_test",
+    size = "small",
+    srcs = ["generators_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "log_uniform_int_distribution_test",
+    size = "medium",
+    srcs = [
+        "log_uniform_int_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_wasm",  # Does not converge on WASM.
+    ],
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/log",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "discrete_distribution_test",
+    size = "medium",
+    srcs = [
+        "discrete_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/log",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "poisson_distribution_test",
+    size = "small",
+    timeout = "eternal",  # Android can take a very long time
+    srcs = [
+        "poisson_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        # Too Slow.
+        "no_test_android_arm",
+        "no_test_loonix",
+    ],
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/base:core_headers",
+        "//absl/container:flat_hash_map",
+        "//absl/log",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "exponential_distribution_test",
+    size = "small",
+    timeout = "moderate",
+    srcs = ["exponential_distribution_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/base:core_headers",
+        "//absl/log",
+        "//absl/numeric:representation",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "gaussian_distribution_test",
+    size = "small",
+    timeout = "eternal",  # Android can take a very long time
+    srcs = [
+        "gaussian_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/base:core_headers",
+        "//absl/log",
+        "//absl/numeric:representation",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "uniform_int_distribution_test",
+    size = "medium",
+    timeout = "long",
+    srcs = [
+        "uniform_int_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/log",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "uniform_real_distribution_test",
+    size = "medium",
+    srcs = [
+        "uniform_real_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_android_arm",
+        "no_test_android_arm64",
+        "no_test_android_x86",
+    ],
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/log",
+        "//absl/numeric:representation",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "zipf_distribution_test",
+    size = "medium",
+    srcs = [
+        "zipf_distribution_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distributions",
+        ":random",
+        "//absl/log",
+        "//absl/random/internal:distribution_test_util",
+        "//absl/random/internal:pcg_engine",
+        "//absl/random/internal:sequence_urbg",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "bit_gen_ref_test",
+    size = "small",
+    srcs = ["bit_gen_ref_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":bit_gen_ref",
+        ":random",
+        "//absl/base:fast_type_id",
+        "//absl/random/internal:sequence_urbg",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "mocking_bit_gen_test",
+    size = "small",
+    srcs = ["mocking_bit_gen_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_wasm",
+    ],
+    deps = [
+        ":bit_gen_ref",
+        ":mock_distributions",
+        ":mocking_bit_gen",
+        ":random",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "mock_distributions_test",
+    size = "small",
+    srcs = ["mock_distributions_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_wasm",
+    ],
+    deps = [
+        ":mock_distributions",
+        ":mocking_bit_gen",
+        ":random",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "examples_test",
+    size = "small",
+    srcs = ["examples_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_wasm",
+    ],
+    deps = [
+        ":random",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "seed_sequences_test",
+    size = "small",
+    srcs = ["seed_sequences_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":random",
+        ":seed_sequences",
+        "//absl/random/internal:nonsecure_base",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+# Benchmarks for various methods / test utilities
+cc_binary(
+    name = "benchmarks",
+    testonly = 1,
+    srcs = [
+        "benchmarks.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    deps = [
+        ":distributions",
+        ":random",
+        ":seed_sequences",
+        "//absl/base:core_headers",
+        "//absl/meta:type_traits",
+        "//absl/random/internal:fast_uniform_bits",
+        "//absl/random/internal:randen_engine",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/random/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/random/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..bd363d881cba448849838ce3c7cf9f960eea1e47
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/CMakeLists.txt
@@ -0,0 +1,1219 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+absl_cc_library(
+  NAME
+    random_random
+  HDRS
+    "random.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_distributions
+    absl::random_internal_nonsecure_base
+    absl::random_internal_pcg_engine
+    absl::random_internal_pool_urbg
+    absl::random_internal_randen_engine
+    absl::random_seed_sequences
+)
+
+absl_cc_library(
+  NAME
+    random_bit_gen_ref
+  HDRS
+    "bit_gen_ref.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::core_headers
+    absl::random_internal_distribution_caller
+    absl::random_internal_fast_uniform_bits
+    absl::type_traits
+)
+
+absl_cc_test(
+  NAME
+    random_bit_gen_ref_test
+  SRCS
+    "bit_gen_ref_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_bit_gen_ref
+    absl::random_random
+    absl::random_internal_sequence_urbg
+    absl::fast_type_id
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_mock_helpers
+  HDRS
+    "internal/mock_helpers.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::fast_type_id
+    absl::optional
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_mock_overload_set
+  HDRS
+    "internal/mock_overload_set.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_mocking_bit_gen
+    absl::random_internal_mock_helpers
+  TESTONLY
+)
+
+absl_cc_library(
+  NAME
+    random_mocking_bit_gen
+  HDRS
+    "mock_distributions.h"
+    "mocking_bit_gen.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::flat_hash_map
+    absl::raw_logging_internal
+    absl::random_distributions
+    absl::random_internal_distribution_caller
+    absl::random_internal_mock_overload_set
+    absl::random_random
+    absl::strings
+    absl::span
+    absl::type_traits
+    absl::utility
+    absl::variant
+    GTest::gmock
+    GTest::gtest
+  PUBLIC
+  TESTONLY
+)
+
+absl_cc_test(
+  NAME
+    random_mock_distributions_test
+  SRCS
+    "mock_distributions_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_mocking_bit_gen
+    absl::random_random
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_mocking_bit_gen_test
+  SRCS
+    "mocking_bit_gen_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_bit_gen_ref
+    absl::random_mocking_bit_gen
+    absl::random_random
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_library(
+  NAME
+    random_distributions
+  SRCS
+    "discrete_distribution.cc"
+    "gaussian_distribution.cc"
+  HDRS
+    "bernoulli_distribution.h"
+    "beta_distribution.h"
+    "discrete_distribution.h"
+    "distributions.h"
+    "exponential_distribution.h"
+    "gaussian_distribution.h"
+    "log_uniform_int_distribution.h"
+    "poisson_distribution.h"
+    "uniform_int_distribution.h"
+    "uniform_real_distribution.h"
+    "zipf_distribution.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::base_internal
+    absl::config
+    absl::core_headers
+    absl::random_internal_generate_real
+    absl::random_internal_distribution_caller
+    absl::random_internal_fast_uniform_bits
+    absl::random_internal_fastmath
+    absl::random_internal_iostream_state_saver
+    absl::random_internal_traits
+    absl::random_internal_uniform_helper
+    absl::random_internal_wide_multiply
+    absl::strings
+    absl::type_traits
+)
+
+absl_cc_library(
+  NAME
+    random_seed_gen_exception
+  SRCS
+    "seed_gen_exception.cc"
+  HDRS
+    "seed_gen_exception.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+)
+
+absl_cc_library(
+  NAME
+    random_seed_sequences
+  SRCS
+    "seed_sequences.cc"
+  HDRS
+    "seed_sequences.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+    absl::inlined_vector
+    absl::random_internal_pool_urbg
+    absl::random_internal_salted_seed_seq
+    absl::random_internal_seed_material
+    absl::random_seed_gen_exception
+    absl::span
+)
+
+absl_cc_test(
+  NAME
+    random_bernoulli_distribution_test
+  SRCS
+    "bernoulli_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_distributions
+    absl::random_random
+    absl::random_internal_sequence_urbg
+    absl::random_internal_pcg_engine
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_beta_distribution_test
+  SRCS
+    "beta_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::numeric_representation
+    absl::random_distributions
+    absl::random_random
+    absl::random_internal_distribution_test_util
+    absl::random_internal_sequence_urbg
+    absl::random_internal_pcg_engine
+    absl::strings
+    absl::str_format
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_distributions_test
+  SRCS
+    "distributions_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_distributions
+    absl::random_random
+    absl::random_internal_distribution_test_util
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_generators_test
+  SRCS
+    "generators_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_distributions
+    absl::random_random
+    absl::raw_logging_internal
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_log_uniform_int_distribution_test
+  SRCS
+    "log_uniform_int_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    absl::str_format
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_discrete_distribution_test
+  SRCS
+    "discrete_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_poisson_distribution_test
+  SRCS
+    "poisson_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_distributions
+    absl::random_random
+    absl::core_headers
+    absl::flat_hash_map
+    absl::log
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::strings
+    absl::str_format
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_exponential_distribution_test
+  SRCS
+    "exponential_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::core_headers
+    absl::log
+    absl::numeric_representation
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    absl::str_format
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_gaussian_distribution_test
+  SRCS
+    "gaussian_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::core_headers
+    absl::log
+    absl::numeric_representation
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    absl::str_format
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_uniform_int_distribution_test
+  SRCS
+    "uniform_int_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_uniform_real_distribution_test
+  SRCS
+    "uniform_real_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::numeric_representation
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_zipf_distribution_test
+  SRCS
+    "zipf_distribution_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::random_distributions
+    absl::random_internal_distribution_test_util
+    absl::random_internal_pcg_engine
+    absl::random_internal_sequence_urbg
+    absl::random_random
+    absl::strings
+    GTest::gmock
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_examples_test
+  SRCS
+    "examples_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_random
+    GTest::gtest_main
+)
+
+absl_cc_test(
+  NAME
+    random_seed_sequences_test
+  SRCS
+    "seed_sequences_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_seed_sequences
+    absl::random_internal_nonsecure_base
+    absl::random_random
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_traits
+  HDRS
+    "internal/traits.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_distribution_caller
+  HDRS
+    "internal/distribution_caller.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+    absl::utility
+    absl::fast_type_id
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_fast_uniform_bits
+  HDRS
+    "internal/fast_uniform_bits.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_seed_material
+  SRCS
+    "internal/seed_material.cc"
+  HDRS
+    "internal/seed_material.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+    $<$<BOOL:${MINGW}>:-lbcrypt>
+  DEPS
+    absl::core_headers
+    absl::optional
+    absl::random_internal_fast_uniform_bits
+    absl::raw_logging_internal
+    absl::span
+    absl::strings
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_pool_urbg
+  SRCS
+    "internal/pool_urbg.cc"
+  HDRS
+    "internal/pool_urbg.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::base
+    absl::config
+    absl::core_headers
+    absl::endian
+    absl::random_internal_randen
+    absl::random_internal_seed_material
+    absl::random_internal_traits
+    absl::random_seed_gen_exception
+    absl::raw_logging_internal
+    absl::span
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_explicit_seed_seq
+  HDRS
+      "internal/random_internal_explicit_seed_seq.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+    absl::endian
+  TESTONLY
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_sequence_urbg
+  HDRS
+    "internal/sequence_urbg.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+  TESTONLY
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_salted_seed_seq
+  HDRS
+    "internal/salted_seed_seq.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::inlined_vector
+    absl::optional
+    absl::span
+    absl::random_internal_seed_material
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_iostream_state_saver
+  HDRS
+    "internal/iostream_state_saver.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::int128
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_generate_real
+  HDRS
+    "internal/generate_real.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::bits
+    absl::random_internal_fastmath
+    absl::random_internal_traits
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_wide_multiply
+  HDRS
+    "internal/wide_multiply.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::bits
+    absl::config
+    absl::int128
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_fastmath
+  HDRS
+    "internal/fastmath.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::bits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_nonsecure_base
+  HDRS
+    "internal/nonsecure_base.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::core_headers
+    absl::inlined_vector
+    absl::random_internal_pool_urbg
+    absl::random_internal_salted_seed_seq
+    absl::random_internal_seed_material
+    absl::span
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_pcg_engine
+  HDRS
+    "internal/pcg_engine.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+    absl::int128
+    absl::random_internal_fastmath
+    absl::random_internal_iostream_state_saver
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_randen_engine
+  HDRS
+    "internal/randen_engine.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::endian
+    absl::random_internal_iostream_state_saver
+    absl::random_internal_randen
+    absl::raw_logging_internal
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_platform
+  HDRS
+    "internal/randen_traits.h"
+    "internal/platform.h"
+  SRCS
+    "internal/randen_round_keys.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_randen
+  SRCS
+    "internal/randen.cc"
+  HDRS
+    "internal/randen.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_platform
+    absl::random_internal_randen_hwaes
+    absl::random_internal_randen_slow
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_randen_slow
+  SRCS
+    "internal/randen_slow.cc"
+  HDRS
+    "internal/randen_slow.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_platform
+    absl::config
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_randen_hwaes
+  SRCS
+    "internal/randen_detect.cc"
+  HDRS
+    "internal/randen_detect.h"
+    "internal/randen_hwaes.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+    ${ABSL_RANDOM_RANDEN_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_platform
+    absl::random_internal_randen_hwaes_impl
+    absl::config
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_randen_hwaes_impl
+  SRCS
+    "internal/randen_hwaes.cc"
+    "internal/randen_hwaes.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+    ${ABSL_RANDOM_RANDEN_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_platform
+    absl::config
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_distribution_test_util
+  SRCS
+    "internal/chi_square.cc"
+    "internal/distribution_test_util.cc"
+  HDRS
+    "internal/chi_square.h"
+    "internal/distribution_test_util.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+    absl::raw_logging_internal
+    absl::strings
+    absl::str_format
+    absl::span
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_traits_test
+  SRCS
+    "internal/traits_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_traits
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_generate_real_test
+  SRCS
+    "internal/generate_real_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::bits
+    absl::flags
+    absl::random_internal_generate_real
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_distribution_test_util_test
+  SRCS
+    "internal/distribution_test_util_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_distribution_test_util
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_fastmath_test
+  SRCS
+    "internal/fastmath_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_fastmath
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_explicit_seed_seq_test
+  SRCS
+    "internal/explicit_seed_seq_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_explicit_seed_seq
+    absl::random_seed_sequences
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_salted_seed_seq_test
+  SRCS
+    "internal/salted_seed_seq_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_salted_seed_seq
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_chi_square_test
+  SRCS
+    "internal/chi_square_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::core_headers
+    absl::random_internal_distribution_test_util
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_fast_uniform_bits_test
+  SRCS
+    "internal/fast_uniform_bits_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_fast_uniform_bits
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_nonsecure_base_test
+  SRCS
+    "internal/nonsecure_base_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_nonsecure_base
+    absl::random_random
+    absl::random_distributions
+    absl::random_seed_sequences
+    absl::strings
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_seed_material_test
+  SRCS
+    "internal/seed_material_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_seed_material
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_pool_urbg_test
+  SRCS
+    "internal/pool_urbg_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_pool_urbg
+    absl::span
+    absl::type_traits
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_pcg_engine_test
+  SRCS
+    "internal/pcg_engine_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_explicit_seed_seq
+    absl::random_internal_pcg_engine
+    absl::time
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_randen_engine_test
+  SRCS
+    "internal/randen_engine_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::random_internal_explicit_seed_seq
+    absl::random_internal_randen_engine
+    absl::strings
+    absl::time
+    GTest::gmock
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_randen_test
+  SRCS
+    "internal/randen_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_randen
+    absl::type_traits
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_randen_slow_test
+  SRCS
+    "internal/randen_slow_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::endian
+    absl::random_internal_randen_slow
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_randen_hwaes_test
+  SRCS
+    "internal/randen_hwaes_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::log
+    absl::random_internal_platform
+    absl::random_internal_randen_hwaes
+    absl::random_internal_randen_hwaes_impl
+    absl::str_format
+    GTest::gmock
+    GTest::gtest
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    random_internal_uniform_helper
+  HDRS
+    "internal/uniform_helper.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::config
+    absl::random_internal_traits
+    absl::type_traits
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_uniform_helper_test
+  SRCS
+    "internal/uniform_helper_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_uniform_helper
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_iostream_state_saver_test
+  SRCS
+    "internal/iostream_state_saver_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_iostream_state_saver
+    GTest::gtest_main
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_test(
+  NAME
+    random_internal_wide_multiply_test
+  SRCS
+      internal/wide_multiply_test.cc
+  COPTS
+    ${ABSL_TEST_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::random_internal_wide_multiply
+    absl::bits
+    absl::int128
+    GTest::gmock
+    GTest::gtest_main
+)
diff --git a/weight/_dep/abseil-cpp/absl/random/discrete_distribution.cc b/weight/_dep/abseil-cpp/absl/random/discrete_distribution.cc
new file mode 100644
index 0000000000000000000000000000000000000000..081accee52a4eb8fb30bc836c58cb0fc829bd4e5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/discrete_distribution.cc
@@ -0,0 +1,98 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/discrete_distribution.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// Initializes the distribution table for Walker's Aliasing algorithm, described
+// in Knuth, Vol 2. as well as in https://en.wikipedia.org/wiki/Alias_method
+std::vector<std::pair<double, size_t>> InitDiscreteDistribution(
+    std::vector<double>* probabilities) {
+  // The empty-case should already be handled by the constructor.
+  assert(probabilities);
+  assert(!probabilities->empty());
+
+  // Step 1. Normalize the input probabilities to 1.0.
+  double sum = std::accumulate(std::begin(*probabilities),
+                               std::end(*probabilities), 0.0);
+  if (std::fabs(sum - 1.0) > 1e-6) {
+    // Scale `probabilities` only when the sum is too far from 1.0.  Scaling
+    // unconditionally will alter the probabilities slightly.
+    for (double& item : *probabilities) {
+      item = item / sum;
+    }
+  }
+
+  // Step 2. At this point `probabilities` is set to the conditional
+  // probabilities of each element which sum to 1.0, to within reasonable error.
+  // These values are used to construct the proportional probability tables for
+  // the selection phases of Walker's Aliasing algorithm.
+  //
+  // To construct the table, pick an element which is under-full (i.e., an
+  // element for which `(*probabilities)[i] < 1.0/n`), and pair it with an
+  // element which is over-full (i.e., an element for which
+  // `(*probabilities)[i] > 1.0/n`). The smaller value can always be retired.
+  // The larger may still be greater than 1.0/n, or may now be less than 1.0/n,
+  // and put back onto the appropriate collection.
+  const size_t n = probabilities->size();
+  std::vector<std::pair<double, size_t>> q;
+  q.reserve(n);
+
+  std::vector<size_t> over;
+  std::vector<size_t> under;
+  size_t idx = 0;
+  for (const double item : *probabilities) {
+    assert(item >= 0);
+    const double v = item * n;
+    q.emplace_back(v, 0);
+    if (v < 1.0) {
+      under.push_back(idx++);
+    } else {
+      over.push_back(idx++);
+    }
+  }
+  while (!over.empty() && !under.empty()) {
+    auto lo = under.back();
+    under.pop_back();
+    auto hi = over.back();
+    over.pop_back();
+
+    q[lo].second = hi;
+    const double r = q[hi].first - (1.0 - q[lo].first);
+    q[hi].first = r;
+    if (r < 1.0) {
+      under.push_back(hi);
+    } else {
+      over.push_back(hi);
+    }
+  }
+
+  // Due to rounding errors, there may be un-paired elements in either
+  // collection; these should all be values near 1.0.  For these values, set `q`
+  // to 1.0 and set the alternate to the identity.
+  for (auto i : over) {
+    q[i] = {1.0, i};
+  }
+  for (auto i : under) {
+    q[i] = {1.0, i};
+  }
+  return q;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/discrete_distribution.h b/weight/_dep/abseil-cpp/absl/random/discrete_distribution.h
new file mode 100644
index 0000000000000000000000000000000000000000..171aa11a1eb439abc62a8b47a8e98c2113c21de4
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/discrete_distribution.h
@@ -0,0 +1,247 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_
+#define ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_
+
+#include <cassert>
+#include <cmath>
+#include <istream>
+#include <limits>
+#include <numeric>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "absl/random/bernoulli_distribution.h"
+#include "absl/random/internal/iostream_state_saver.h"
+#include "absl/random/uniform_int_distribution.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::discrete_distribution
+//
+// A discrete distribution produces random integers i, where 0 <= i < n
+// distributed according to the discrete probability function:
+//
+//     P(i|p0,...,pn−1)=pi
+//
+// This class is an implementation of discrete_distribution (see
+// [rand.dist.samp.discrete]).
+//
+// The algorithm used is Walker's Aliasing algorithm, described in Knuth, Vol 2.
+// absl::discrete_distribution takes O(N) time to precompute the probabilities
+// (where N is the number of possible outcomes in the distribution) at
+// construction, and then takes O(1) time for each variate generation.  Many
+// other implementations also take O(N) time to construct an ordered sequence of
+// partial sums, plus O(log N) time per variate to binary search.
+//
+template <typename IntType = int>
+class discrete_distribution {
+ public:
+  using result_type = IntType;
+
+  class param_type {
+   public:
+    using distribution_type = discrete_distribution;
+
+    param_type() { init(); }
+
+    template <typename InputIterator>
+    explicit param_type(InputIterator begin, InputIterator end)
+        : p_(begin, end) {
+      init();
+    }
+
+    explicit param_type(std::initializer_list<double> weights) : p_(weights) {
+      init();
+    }
+
+    template <class UnaryOperation>
+    explicit param_type(size_t nw, double xmin, double xmax,
+                        UnaryOperation fw) {
+      if (nw > 0) {
+        p_.reserve(nw);
+        double delta = (xmax - xmin) / static_cast<double>(nw);
+        assert(delta > 0);
+        double t = delta * 0.5;
+        for (size_t i = 0; i < nw; ++i) {
+          p_.push_back(fw(xmin + i * delta + t));
+        }
+      }
+      init();
+    }
+
+    const std::vector<double>& probabilities() const { return p_; }
+    size_t n() const { return p_.size() - 1; }
+
+    friend bool operator==(const param_type& a, const param_type& b) {
+      return a.probabilities() == b.probabilities();
+    }
+
+    friend bool operator!=(const param_type& a, const param_type& b) {
+      return !(a == b);
+    }
+
+   private:
+    friend class discrete_distribution;
+
+    void init();
+
+    std::vector<double> p_;                     // normalized probabilities
+    std::vector<std::pair<double, size_t>> q_;  // (acceptance, alternate) pairs
+
+    static_assert(std::is_integral<result_type>::value,
+                  "Class-template absl::discrete_distribution<> must be "
+                  "parameterized using an integral type.");
+  };
+
+  discrete_distribution() : param_() {}
+
+  explicit discrete_distribution(const param_type& p) : param_(p) {}
+
+  template <typename InputIterator>
+  explicit discrete_distribution(InputIterator begin, InputIterator end)
+      : param_(begin, end) {}
+
+  explicit discrete_distribution(std::initializer_list<double> weights)
+      : param_(weights) {}
+
+  template <class UnaryOperation>
+  explicit discrete_distribution(size_t nw, double xmin, double xmax,
+                                 UnaryOperation fw)
+      : param_(nw, xmin, xmax, std::move(fw)) {}
+
+  void reset() {}
+
+  // generating functions
+  template <typename URBG>
+  result_type operator()(URBG& g) {  // NOLINT(runtime/references)
+    return (*this)(g, param_);
+  }
+
+  template <typename URBG>
+  result_type operator()(URBG& g,  // NOLINT(runtime/references)
+                         const param_type& p);
+
+  const param_type& param() const { return param_; }
+  void param(const param_type& p) { param_ = p; }
+
+  result_type(min)() const { return 0; }
+  result_type(max)() const {
+    return static_cast<result_type>(param_.n());
+  }  // inclusive
+
+  // NOTE [rand.dist.sample.discrete] returns a std::vector<double> not a
+  // const std::vector<double>&.
+  const std::vector<double>& probabilities() const {
+    return param_.probabilities();
+  }
+
+  friend bool operator==(const discrete_distribution& a,
+                         const discrete_distribution& b) {
+    return a.param_ == b.param_;
+  }
+  friend bool operator!=(const discrete_distribution& a,
+                         const discrete_distribution& b) {
+    return a.param_ != b.param_;
+  }
+
+ private:
+  param_type param_;
+};
+
+// --------------------------------------------------------------------------
+// Implementation details only below
+// --------------------------------------------------------------------------
+
+namespace random_internal {
+
+// Using the vector `*probabilities`, whose values are the weights or
+// probabilities of an element being selected, constructs the proportional
+// probabilities used by the discrete distribution.  `*probabilities` will be
+// scaled, if necessary, so that its entries sum to a value sufficiently close
+// to 1.0.
+std::vector<std::pair<double, size_t>> InitDiscreteDistribution(
+    std::vector<double>* probabilities);
+
+}  // namespace random_internal
+
+template <typename IntType>
+void discrete_distribution<IntType>::param_type::init() {
+  if (p_.empty()) {
+    p_.push_back(1.0);
+    q_.emplace_back(1.0, 0);
+  } else {
+    assert(n() <= (std::numeric_limits<IntType>::max)());
+    q_ = random_internal::InitDiscreteDistribution(&p_);
+  }
+}
+
+template <typename IntType>
+template <typename URBG>
+typename discrete_distribution<IntType>::result_type
+discrete_distribution<IntType>::operator()(
+    URBG& g,  // NOLINT(runtime/references)
+    const param_type& p) {
+  const auto idx = absl::uniform_int_distribution<result_type>(0, p.n())(g);
+  const auto& q = p.q_[idx];
+  const bool selected = absl::bernoulli_distribution(q.first)(g);
+  return selected ? idx : static_cast<result_type>(q.second);
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_ostream<CharT, Traits>& operator<<(
+    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+    const discrete_distribution<IntType>& x) {
+  auto saver = random_internal::make_ostream_state_saver(os);
+  const auto& probabilities = x.param().probabilities();
+  os << probabilities.size();
+
+  os.precision(random_internal::stream_precision_helper<double>::kPrecision);
+  for (const auto& p : probabilities) {
+    os << os.fill() << p;
+  }
+  return os;
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_istream<CharT, Traits>& operator>>(
+    std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+    discrete_distribution<IntType>& x) {    // NOLINT(runtime/references)
+  using param_type = typename discrete_distribution<IntType>::param_type;
+  auto saver = random_internal::make_istream_state_saver(is);
+
+  size_t n;
+  std::vector<double> p;
+
+  is >> n;
+  if (is.fail()) return is;
+  if (n > 0) {
+    p.reserve(n);
+    for (IntType i = 0; i < n && !is.fail(); ++i) {
+      auto tmp = random_internal::read_floating_point<double>(is);
+      if (is.fail()) return is;
+      p.push_back(tmp);
+    }
+  }
+  x.param(param_type(p.begin(), p.end()));
+  return is;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/discrete_distribution_test.cc b/weight/_dep/abseil-cpp/absl/random/discrete_distribution_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..32405ea9ed634a20a750258efa9ad0a31454dbb5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/discrete_distribution_test.cc
@@ -0,0 +1,251 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/discrete_distribution.h"
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+#include <numeric>
+#include <random>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/log/log.h"
+#include "absl/random/internal/chi_square.h"
+#include "absl/random/internal/distribution_test_util.h"
+#include "absl/random/internal/pcg_engine.h"
+#include "absl/random/internal/sequence_urbg.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/strip.h"
+
+namespace {
+
+template <typename IntType>
+class DiscreteDistributionTypeTest : public ::testing::Test {};
+
+using IntTypes = ::testing::Types<int8_t, uint8_t, int16_t, uint16_t, int32_t,
+                                  uint32_t, int64_t, uint64_t>;
+TYPED_TEST_SUITE(DiscreteDistributionTypeTest, IntTypes);
+
+TYPED_TEST(DiscreteDistributionTypeTest, ParamSerializeTest) {
+  using param_type =
+      typename absl::discrete_distribution<TypeParam>::param_type;
+
+  absl::discrete_distribution<TypeParam> empty;
+  EXPECT_THAT(empty.probabilities(), testing::ElementsAre(1.0));
+
+  absl::discrete_distribution<TypeParam> before({1.0, 2.0, 1.0});
+
+  // Validate that the probabilities sum to 1.0. We picked values which
+  // can be represented exactly to avoid floating-point roundoff error.
+  double s = 0;
+  for (const auto& x : before.probabilities()) {
+    s += x;
+  }
+  EXPECT_EQ(s, 1.0);
+  EXPECT_THAT(before.probabilities(), testing::ElementsAre(0.25, 0.5, 0.25));
+
+  // Validate the same data via an initializer list.
+  {
+    std::vector<double> data({1.0, 2.0, 1.0});
+
+    absl::discrete_distribution<TypeParam> via_param{
+        param_type(std::begin(data), std::end(data))};
+
+    EXPECT_EQ(via_param, before);
+  }
+
+  std::stringstream ss;
+  ss << before;
+  absl::discrete_distribution<TypeParam> after;
+
+  EXPECT_NE(before, after);
+
+  ss >> after;
+
+  EXPECT_EQ(before, after);
+}
+
+TYPED_TEST(DiscreteDistributionTypeTest, Constructor) {
+  auto fn = [](double x) { return x; };
+  {
+    absl::discrete_distribution<int> unary(0, 1.0, 9.0, fn);
+    EXPECT_THAT(unary.probabilities(), testing::ElementsAre(1.0));
+  }
+
+  {
+    absl::discrete_distribution<int> unary(2, 1.0, 9.0, fn);
+    // => fn(1.0 + 0 * 4 + 2) => 3
+    // => fn(1.0 + 1 * 4 + 2) => 7
+    EXPECT_THAT(unary.probabilities(), testing::ElementsAre(0.3, 0.7));
+  }
+}
+
+TEST(DiscreteDistributionTest, InitDiscreteDistribution) {
+  using testing::_;
+  using testing::Pair;
+
+  {
+    std::vector<double> p({1.0, 2.0, 3.0});
+    std::vector<std::pair<double, size_t>> q =
+        absl::random_internal::InitDiscreteDistribution(&p);
+
+    EXPECT_THAT(p, testing::ElementsAre(1 / 6.0, 2 / 6.0, 3 / 6.0));
+
+    // Each bucket is p=1/3, so bucket 0 will send half it's traffic
+    // to bucket 2, while the rest will retain all of their traffic.
+    EXPECT_THAT(q, testing::ElementsAre(Pair(0.5, 2),  //
+                                        Pair(1.0, _),  //
+                                        Pair(1.0, _)));
+  }
+
+  {
+    std::vector<double> p({1.0, 2.0, 3.0, 5.0, 2.0});
+
+    std::vector<std::pair<double, size_t>> q =
+        absl::random_internal::InitDiscreteDistribution(&p);
+
+    EXPECT_THAT(p, testing::ElementsAre(1 / 13.0, 2 / 13.0, 3 / 13.0, 5 / 13.0,
+                                        2 / 13.0));
+
+    // A more complex bucketing solution: Each bucket has p=0.2
+    // So buckets 0, 1, 4 will send their alternate traffic elsewhere, which
+    // happens to be bucket 3.
+    // However, summing up that alternate traffic gives bucket 3 too much
+    // traffic, so it will send some traffic to bucket 2.
+    constexpr double b0 = 1.0 / 13.0 / 0.2;
+    constexpr double b1 = 2.0 / 13.0 / 0.2;
+    constexpr double b3 = (5.0 / 13.0 / 0.2) - ((1 - b0) + (1 - b1) + (1 - b1));
+
+    EXPECT_THAT(q, testing::ElementsAre(Pair(b0, 3),   //
+                                        Pair(b1, 3),   //
+                                        Pair(1.0, _),  //
+                                        Pair(b3, 2),   //
+                                        Pair(b1, 3)));
+  }
+}
+
+TEST(DiscreteDistributionTest, ChiSquaredTest50) {
+  using absl::random_internal::kChiSquared;
+
+  constexpr size_t kTrials = 10000;
+  constexpr int kBuckets = 50;  // inclusive, so actually +1
+
+  // 1-in-100000 threshold, but remember, there are about 8 tests
+  // in this file. And the test could fail for other reasons.
+  // Empirically validated with --runs_per_test=10000.
+  const int kThreshold =
+      absl::random_internal::ChiSquareValue(kBuckets, 0.99999);
+
+  std::vector<double> weights(kBuckets, 0);
+  std::iota(std::begin(weights), std::end(weights), 1);
+  absl::discrete_distribution<int> dist(std::begin(weights), std::end(weights));
+
+  // We use a fixed bit generator for distribution accuracy tests.  This allows
+  // these tests to be deterministic, while still testing the qualify of the
+  // implementation.
+  absl::random_internal::pcg64_2018_engine rng(0x2B7E151628AED2A6);
+
+  std::vector<int32_t> counts(kBuckets, 0);
+  for (size_t i = 0; i < kTrials; i++) {
+    auto x = dist(rng);
+    counts[x]++;
+  }
+
+  // Scale weights.
+  double sum = 0;
+  for (double x : weights) {
+    sum += x;
+  }
+  for (double& x : weights) {
+    x = kTrials * (x / sum);
+  }
+
+  double chi_square =
+      absl::random_internal::ChiSquare(std::begin(counts), std::end(counts),
+                                       std::begin(weights), std::end(weights));
+
+  if (chi_square > kThreshold) {
+    double p_value =
+        absl::random_internal::ChiSquarePValue(chi_square, kBuckets);
+
+    // Chi-squared test failed. Output does not appear to be uniform.
+    std::string msg;
+    for (size_t i = 0; i < counts.size(); i++) {
+      absl::StrAppend(&msg, i, ": ", counts[i], " vs ", weights[i], "\n");
+    }
+    absl::StrAppend(&msg, kChiSquared, " p-value ", p_value, "\n");
+    absl::StrAppend(&msg, "High ", kChiSquared, " value: ", chi_square, " > ",
+                    kThreshold);
+    LOG(INFO) << msg;
+    FAIL() << msg;
+  }
+}
+
+TEST(DiscreteDistributionTest, StabilityTest) {
+  // absl::discrete_distribution stabilitiy relies on
+  // absl::uniform_int_distribution and absl::bernoulli_distribution.
+  absl::random_internal::sequence_urbg urbg(
+      {0x0003eb76f6f7f755ull, 0xFFCEA50FDB2F953Bull, 0xC332DDEFBE6C5AA5ull,
+       0x6558218568AB9702ull, 0x2AEF7DAD5B6E2F84ull, 0x1521B62829076170ull,
+       0xECDD4775619F1510ull, 0x13CCA830EB61BD96ull, 0x0334FE1EAA0363CFull,
+       0xB5735C904C70A239ull, 0xD59E9E0BCBAADE14ull, 0xEECC86BC60622CA7ull});
+
+  std::vector<int> output(6);
+
+  {
+    absl::discrete_distribution<int32_t> dist({1.0, 2.0, 3.0, 5.0, 2.0});
+    EXPECT_EQ(0, dist.min());
+    EXPECT_EQ(4, dist.max());
+    for (auto& v : output) {
+      v = dist(urbg);
+    }
+    EXPECT_EQ(12, urbg.invocations());
+  }
+
+  // With 12 calls to urbg, each call into discrete_distribution consumes
+  // precisely 2 values: one for the uniform call, and a second for the
+  // bernoulli.
+  //
+  // Given the alt mapping: 0=>3, 1=>3, 2=>2, 3=>2, 4=>3, we can
+  //
+  // uniform:      443210143131
+  // bernoulli: b0 000011100101
+  // bernoulli: b1 001111101101
+  // bernoulli: b2 111111111111
+  // bernoulli: b3 001111101111
+  // bernoulli: b4 001111101101
+  // ...
+  EXPECT_THAT(output, testing::ElementsAre(3, 3, 1, 3, 3, 3));
+
+  {
+    urbg.reset();
+    absl::discrete_distribution<int64_t> dist({1.0, 2.0, 3.0, 5.0, 2.0});
+    EXPECT_EQ(0, dist.min());
+    EXPECT_EQ(4, dist.max());
+    for (auto& v : output) {
+      v = dist(urbg);
+    }
+    EXPECT_EQ(12, urbg.invocations());
+  }
+  EXPECT_THAT(output, testing::ElementsAre(3, 3, 0, 3, 0, 4));
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/distributions.h b/weight/_dep/abseil-cpp/absl/random/distributions.h
new file mode 100644
index 0000000000000000000000000000000000000000..4e3b332e0f072b14063528054652ff3bf78ecec7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/distributions.h
@@ -0,0 +1,452 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: distributions.h
+// -----------------------------------------------------------------------------
+//
+// This header defines functions representing distributions, which you use in
+// combination with an Abseil random bit generator to produce random values
+// according to the rules of that distribution.
+//
+// The Abseil random library defines the following distributions within this
+// file:
+//
+//   * `absl::Uniform` for uniform (constant) distributions having constant
+//     probability
+//   * `absl::Bernoulli` for discrete distributions having exactly two outcomes
+//   * `absl::Beta` for continuous distributions parameterized through two
+//     free parameters
+//   * `absl::Exponential` for discrete distributions of events occurring
+//     continuously and independently at a constant average rate
+//   * `absl::Gaussian` (also known as "normal distributions") for continuous
+//     distributions using an associated quadratic function
+//   * `absl::LogUniform` for continuous uniform distributions where the log
+//     to the given base of all values is uniform
+//   * `absl::Poisson` for discrete probability distributions that express the
+//     probability of a given number of events occurring within a fixed interval
+//   * `absl::Zipf` for discrete probability distributions commonly used for
+//     modelling of rare events
+//
+// Prefer use of these distribution function classes over manual construction of
+// your own distribution classes, as it allows library maintainers greater
+// flexibility to change the underlying implementation in the future.
+
+#ifndef ABSL_RANDOM_DISTRIBUTIONS_H_
+#define ABSL_RANDOM_DISTRIBUTIONS_H_
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+#include <random>
+#include <type_traits>
+
+#include "absl/base/internal/inline_variable.h"
+#include "absl/random/bernoulli_distribution.h"
+#include "absl/random/beta_distribution.h"
+#include "absl/random/exponential_distribution.h"
+#include "absl/random/gaussian_distribution.h"
+#include "absl/random/internal/distribution_caller.h"  // IWYU pragma: export
+#include "absl/random/internal/uniform_helper.h"  // IWYU pragma: export
+#include "absl/random/log_uniform_int_distribution.h"
+#include "absl/random/poisson_distribution.h"
+#include "absl/random/uniform_int_distribution.h"
+#include "absl/random/uniform_real_distribution.h"
+#include "absl/random/zipf_distribution.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalClosedClosedTag, IntervalClosedClosed,
+                               {});
+ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalClosedClosedTag, IntervalClosed, {});
+ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalClosedOpenTag, IntervalClosedOpen, {});
+ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalOpenOpenTag, IntervalOpenOpen, {});
+ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalOpenOpenTag, IntervalOpen, {});
+ABSL_INTERNAL_INLINE_CONSTEXPR(IntervalOpenClosedTag, IntervalOpenClosed, {});
+
+// -----------------------------------------------------------------------------
+// absl::Uniform<T>(tag, bitgen, lo, hi)
+// -----------------------------------------------------------------------------
+//
+// `absl::Uniform()` produces random values of type `T` uniformly distributed in
+// a defined interval {lo, hi}. The interval `tag` defines the type of interval
+// which should be one of the following possible values:
+//
+//   * `absl::IntervalOpenOpen`
+//   * `absl::IntervalOpenClosed`
+//   * `absl::IntervalClosedOpen`
+//   * `absl::IntervalClosedClosed`
+//
+// where "open" refers to an exclusive value (excluded) from the output, while
+// "closed" refers to an inclusive value (included) from the output.
+//
+// In the absence of an explicit return type `T`, `absl::Uniform()` will deduce
+// the return type based on the provided endpoint arguments {A lo, B hi}.
+// Given these endpoints, one of {A, B} will be chosen as the return type, if
+// a type can be implicitly converted into the other in a lossless way. The
+// lack of any such implicit conversion between {A, B} will produce a
+// compile-time error
+//
+// See https://en.wikipedia.org/wiki/Uniform_distribution_(continuous)
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//
+//   // Produce a random float value between 0.0 and 1.0, inclusive
+//   auto x = absl::Uniform(absl::IntervalClosedClosed, bitgen, 0.0f, 1.0f);
+//
+//   // The most common interval of `absl::IntervalClosedOpen` is available by
+//   // default:
+//
+//   auto x = absl::Uniform(bitgen, 0.0f, 1.0f);
+//
+//   // Return-types are typically inferred from the arguments, however callers
+//   // can optionally provide an explicit return-type to the template.
+//
+//   auto x = absl::Uniform<float>(bitgen, 0, 1);
+//
+template <typename R = void, typename TagType, typename URBG>
+typename absl::enable_if_t<!std::is_same<R, void>::value, R>  //
+Uniform(TagType tag,
+        URBG&& urbg,  // NOLINT(runtime/references)
+        R lo, R hi) {
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = random_internal::UniformDistributionWrapper<R>;
+
+  auto a = random_internal::uniform_lower_bound(tag, lo, hi);
+  auto b = random_internal::uniform_upper_bound(tag, lo, hi);
+  if (!random_internal::is_uniform_range_valid(a, b)) return lo;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, tag, lo, hi);
+}
+
+// absl::Uniform<T>(bitgen, lo, hi)
+//
+// Overload of `Uniform()` using the default closed-open interval of [lo, hi),
+// and returning values of type `T`
+template <typename R = void, typename URBG>
+typename absl::enable_if_t<!std::is_same<R, void>::value, R>  //
+Uniform(URBG&& urbg,  // NOLINT(runtime/references)
+        R lo, R hi) {
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = random_internal::UniformDistributionWrapper<R>;
+  constexpr auto tag = absl::IntervalClosedOpen;
+
+  auto a = random_internal::uniform_lower_bound(tag, lo, hi);
+  auto b = random_internal::uniform_upper_bound(tag, lo, hi);
+  if (!random_internal::is_uniform_range_valid(a, b)) return lo;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, lo, hi);
+}
+
+// absl::Uniform(tag, bitgen, lo, hi)
+//
+// Overload of `Uniform()` using different (but compatible) lo, hi types. Note
+// that a compile-error will result if the return type cannot be deduced
+// correctly from the passed types.
+template <typename R = void, typename TagType, typename URBG, typename A,
+          typename B>
+typename absl::enable_if_t<std::is_same<R, void>::value,
+                           random_internal::uniform_inferred_return_t<A, B>>
+Uniform(TagType tag,
+        URBG&& urbg,  // NOLINT(runtime/references)
+        A lo, B hi) {
+  using gen_t = absl::decay_t<URBG>;
+  using return_t = typename random_internal::uniform_inferred_return_t<A, B>;
+  using distribution_t = random_internal::UniformDistributionWrapper<return_t>;
+
+  auto a = random_internal::uniform_lower_bound<return_t>(tag, lo, hi);
+  auto b = random_internal::uniform_upper_bound<return_t>(tag, lo, hi);
+  if (!random_internal::is_uniform_range_valid(a, b)) return lo;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, tag, static_cast<return_t>(lo),
+                                static_cast<return_t>(hi));
+}
+
+// absl::Uniform(bitgen, lo, hi)
+//
+// Overload of `Uniform()` using different (but compatible) lo, hi types and the
+// default closed-open interval of [lo, hi). Note that a compile-error will
+// result if the return type cannot be deduced correctly from the passed types.
+template <typename R = void, typename URBG, typename A, typename B>
+typename absl::enable_if_t<std::is_same<R, void>::value,
+                           random_internal::uniform_inferred_return_t<A, B>>
+Uniform(URBG&& urbg,  // NOLINT(runtime/references)
+        A lo, B hi) {
+  using gen_t = absl::decay_t<URBG>;
+  using return_t = typename random_internal::uniform_inferred_return_t<A, B>;
+  using distribution_t = random_internal::UniformDistributionWrapper<return_t>;
+
+  constexpr auto tag = absl::IntervalClosedOpen;
+  auto a = random_internal::uniform_lower_bound<return_t>(tag, lo, hi);
+  auto b = random_internal::uniform_upper_bound<return_t>(tag, lo, hi);
+  if (!random_internal::is_uniform_range_valid(a, b)) return lo;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, static_cast<return_t>(lo),
+                                static_cast<return_t>(hi));
+}
+
+// absl::Uniform<unsigned T>(bitgen)
+//
+// Overload of Uniform() using the minimum and maximum values of a given type
+// `T` (which must be unsigned), returning a value of type `unsigned T`
+template <typename R, typename URBG>
+typename absl::enable_if_t<!std::is_signed<R>::value, R>  //
+Uniform(URBG&& urbg) {  // NOLINT(runtime/references)
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = random_internal::UniformDistributionWrapper<R>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg);
+}
+
+// -----------------------------------------------------------------------------
+// absl::Bernoulli(bitgen, p)
+// -----------------------------------------------------------------------------
+//
+// `absl::Bernoulli` produces a random boolean value, with probability `p`
+// (where 0.0 <= p <= 1.0) equaling `true`.
+//
+// Prefer `absl::Bernoulli` to produce boolean values over other alternatives
+// such as comparing an `absl::Uniform()` value to a specific output.
+//
+// See https://en.wikipedia.org/wiki/Bernoulli_distribution
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   if (absl::Bernoulli(bitgen, 1.0/3721.0)) {
+//     std::cout << "Asteroid field navigation successful.";
+//   }
+//
+template <typename URBG>
+bool Bernoulli(URBG&& urbg,  // NOLINT(runtime/references)
+               double p) {
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = absl::bernoulli_distribution;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, p);
+}
+
+// -----------------------------------------------------------------------------
+// absl::Beta<T>(bitgen, alpha, beta)
+// -----------------------------------------------------------------------------
+//
+// `absl::Beta` produces a floating point number distributed in the closed
+// interval [0,1] and parameterized by two values `alpha` and `beta` as per a
+// Beta distribution. `T` must be a floating point type, but may be inferred
+// from the types of `alpha` and `beta`.
+//
+// See https://en.wikipedia.org/wiki/Beta_distribution.
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   double sample = absl::Beta(bitgen, 3.0, 2.0);
+//
+template <typename RealType, typename URBG>
+RealType Beta(URBG&& urbg,  // NOLINT(runtime/references)
+              RealType alpha, RealType beta) {
+  static_assert(
+      std::is_floating_point<RealType>::value,
+      "Template-argument 'RealType' must be a floating-point type, in "
+      "absl::Beta<RealType, URBG>(...)");
+
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = typename absl::beta_distribution<RealType>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, alpha, beta);
+}
+
+// -----------------------------------------------------------------------------
+// absl::Exponential<T>(bitgen, lambda = 1)
+// -----------------------------------------------------------------------------
+//
+// `absl::Exponential` produces a floating point number representing the
+// distance (time) between two consecutive events in a point process of events
+// occurring continuously and independently at a constant average rate. `T` must
+// be a floating point type, but may be inferred from the type of `lambda`.
+//
+// See https://en.wikipedia.org/wiki/Exponential_distribution.
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   double call_length = absl::Exponential(bitgen, 7.0);
+//
+template <typename RealType, typename URBG>
+RealType Exponential(URBG&& urbg,  // NOLINT(runtime/references)
+                     RealType lambda = 1) {
+  static_assert(
+      std::is_floating_point<RealType>::value,
+      "Template-argument 'RealType' must be a floating-point type, in "
+      "absl::Exponential<RealType, URBG>(...)");
+
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = typename absl::exponential_distribution<RealType>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, lambda);
+}
+
+// -----------------------------------------------------------------------------
+// absl::Gaussian<T>(bitgen, mean = 0, stddev = 1)
+// -----------------------------------------------------------------------------
+//
+// `absl::Gaussian` produces a floating point number selected from the Gaussian
+// (ie. "Normal") distribution. `T` must be a floating point type, but may be
+// inferred from the types of `mean` and `stddev`.
+//
+// See https://en.wikipedia.org/wiki/Normal_distribution
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   double giraffe_height = absl::Gaussian(bitgen, 16.3, 3.3);
+//
+template <typename RealType, typename URBG>
+RealType Gaussian(URBG&& urbg,  // NOLINT(runtime/references)
+                  RealType mean = 0, RealType stddev = 1) {
+  static_assert(
+      std::is_floating_point<RealType>::value,
+      "Template-argument 'RealType' must be a floating-point type, in "
+      "absl::Gaussian<RealType, URBG>(...)");
+
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = typename absl::gaussian_distribution<RealType>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, mean, stddev);
+}
+
+// -----------------------------------------------------------------------------
+// absl::LogUniform<T>(bitgen, lo, hi, base = 2)
+// -----------------------------------------------------------------------------
+//
+// `absl::LogUniform` produces random values distributed where the log to a
+// given base of all values is uniform in a closed interval [lo, hi]. `T` must
+// be an integral type, but may be inferred from the types of `lo` and `hi`.
+//
+// I.e., `LogUniform(0, n, b)` is uniformly distributed across buckets
+// [0], [1, b-1], [b, b^2-1] .. [b^(k-1), (b^k)-1] .. [b^floor(log(n, b)), n]
+// and is uniformly distributed within each bucket.
+//
+// The resulting probability density is inversely related to bucket size, though
+// values in the final bucket may be more likely than previous values. (In the
+// extreme case where n = b^i the final value will be tied with zero as the most
+// probable result.
+//
+// If `lo` is nonzero then this distribution is shifted to the desired interval,
+// so LogUniform(lo, hi, b) is equivalent to LogUniform(0, hi-lo, b)+lo.
+//
+// See https://en.wikipedia.org/wiki/Log-normal_distribution
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   int v = absl::LogUniform(bitgen, 0, 1000);
+//
+template <typename IntType, typename URBG>
+IntType LogUniform(URBG&& urbg,  // NOLINT(runtime/references)
+                   IntType lo, IntType hi, IntType base = 2) {
+  static_assert(random_internal::IsIntegral<IntType>::value,
+                "Template-argument 'IntType' must be an integral type, in "
+                "absl::LogUniform<IntType, URBG>(...)");
+
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = typename absl::log_uniform_int_distribution<IntType>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, lo, hi, base);
+}
+
+// -----------------------------------------------------------------------------
+// absl::Poisson<T>(bitgen, mean = 1)
+// -----------------------------------------------------------------------------
+//
+// `absl::Poisson` produces discrete probabilities for a given number of events
+// occurring within a fixed interval within the closed interval [0, max]. `T`
+// must be an integral type.
+//
+// See https://en.wikipedia.org/wiki/Poisson_distribution
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   int requests_per_minute = absl::Poisson<int>(bitgen, 3.2);
+//
+template <typename IntType, typename URBG>
+IntType Poisson(URBG&& urbg,  // NOLINT(runtime/references)
+                double mean = 1.0) {
+  static_assert(random_internal::IsIntegral<IntType>::value,
+                "Template-argument 'IntType' must be an integral type, in "
+                "absl::Poisson<IntType, URBG>(...)");
+
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = typename absl::poisson_distribution<IntType>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, mean);
+}
+
+// -----------------------------------------------------------------------------
+// absl::Zipf<T>(bitgen, hi = max, q = 2, v = 1)
+// -----------------------------------------------------------------------------
+//
+// `absl::Zipf` produces discrete probabilities commonly used for modelling of
+// rare events over the closed interval [0, hi]. The parameters `v` and `q`
+// determine the skew of the distribution. `T`  must be an integral type, but
+// may be inferred from the type of `hi`.
+//
+// See http://mathworld.wolfram.com/ZipfDistribution.html
+//
+// Example:
+//
+//   absl::BitGen bitgen;
+//   ...
+//   int term_rank = absl::Zipf<int>(bitgen);
+//
+template <typename IntType, typename URBG>
+IntType Zipf(URBG&& urbg,  // NOLINT(runtime/references)
+             IntType hi = (std::numeric_limits<IntType>::max)(), double q = 2.0,
+             double v = 1.0) {
+  static_assert(random_internal::IsIntegral<IntType>::value,
+                "Template-argument 'IntType' must be an integral type, in "
+                "absl::Zipf<IntType, URBG>(...)");
+
+  using gen_t = absl::decay_t<URBG>;
+  using distribution_t = typename absl::zipf_distribution<IntType>;
+
+  return random_internal::DistributionCaller<gen_t>::template Call<
+      distribution_t>(&urbg, hi, q, v);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_DISTRIBUTIONS_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/examples_test.cc b/weight/_dep/abseil-cpp/absl/random/examples_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1dcb5146f3d036554f3c133598a20c54a9ac7025
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/examples_test.cc
@@ -0,0 +1,99 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cinttypes>
+#include <random>
+#include <sstream>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/random/random.h"
+
+template <typename T>
+void Use(T) {}
+
+TEST(Examples, Basic) {
+  absl::BitGen gen;
+  std::vector<int> objs = {10, 20, 30, 40, 50};
+
+  // Choose an element from a set.
+  auto elem = objs[absl::Uniform(gen, 0u, objs.size())];
+  Use(elem);
+
+  // Generate a uniform value between 1 and 6.
+  auto dice_roll = absl::Uniform<int>(absl::IntervalClosedClosed, gen, 1, 6);
+  Use(dice_roll);
+
+  // Generate a random byte.
+  auto byte = absl::Uniform<uint8_t>(gen);
+  Use(byte);
+
+  // Generate a fractional value from [0f, 1f).
+  auto fraction = absl::Uniform<float>(gen, 0, 1);
+  Use(fraction);
+
+  // Toss a fair coin; 50/50 probability.
+  bool coin_toss = absl::Bernoulli(gen, 0.5);
+  Use(coin_toss);
+
+  // Select a file size between 1k and 10MB, biased towards smaller file sizes.
+  auto file_size = absl::LogUniform<size_t>(gen, 1000, 10 * 1000 * 1000);
+  Use(file_size);
+
+  // Randomize (shuffle) a collection.
+  std::shuffle(std::begin(objs), std::end(objs), gen);
+}
+
+TEST(Examples, CreateingCorrelatedVariateSequences) {
+  // Unexpected PRNG correlation is often a source of bugs,
+  // so when using absl::BitGen it must be an intentional choice.
+  // NOTE: All of these only exhibit process-level stability.
+
+  // Create a correlated sequence from system entropy.
+  {
+    auto my_seed = absl::MakeSeedSeq();
+
+    absl::BitGen gen_1(my_seed);
+    absl::BitGen gen_2(my_seed);  // Produces same variates as gen_1.
+
+    EXPECT_EQ(absl::Bernoulli(gen_1, 0.5), absl::Bernoulli(gen_2, 0.5));
+    EXPECT_EQ(absl::Uniform<uint32_t>(gen_1), absl::Uniform<uint32_t>(gen_2));
+  }
+
+  // Create a correlated sequence from an existing URBG.
+  {
+    absl::BitGen gen;
+
+    auto my_seed = absl::CreateSeedSeqFrom(&gen);
+    absl::BitGen gen_1(my_seed);
+    absl::BitGen gen_2(my_seed);
+
+    EXPECT_EQ(absl::Bernoulli(gen_1, 0.5), absl::Bernoulli(gen_2, 0.5));
+    EXPECT_EQ(absl::Uniform<uint32_t>(gen_1), absl::Uniform<uint32_t>(gen_2));
+  }
+
+  // An alternate construction which uses user-supplied data
+  // instead of a random seed.
+  {
+    const char kData[] = "A simple seed string";
+    std::seed_seq my_seed(std::begin(kData), std::end(kData));
+
+    absl::BitGen gen_1(my_seed);
+    absl::BitGen gen_2(my_seed);
+
+    EXPECT_EQ(absl::Bernoulli(gen_1, 0.5), absl::Bernoulli(gen_2, 0.5));
+    EXPECT_EQ(absl::Uniform<uint32_t>(gen_1), absl::Uniform<uint32_t>(gen_2));
+  }
+}
+
diff --git a/weight/_dep/abseil-cpp/absl/random/gaussian_distribution.cc b/weight/_dep/abseil-cpp/absl/random/gaussian_distribution.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c7a72cb2f61ce4d0ad8e7bd3ec9fd216f3e156bd
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/gaussian_distribution.cc
@@ -0,0 +1,104 @@
+// BEGIN GENERATED CODE; DO NOT EDIT
+// clang-format off
+
+#include "absl/random/gaussian_distribution.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+const gaussian_distribution_base::Tables
+    gaussian_distribution_base::zg_ = {
+    {3.7130862467425505, 3.442619855899000214, 3.223084984581141565,
+     3.083228858216868318, 2.978696252647779819, 2.894344007021528942,
+     2.82312535054891045, 2.761169372387176857, 2.706113573121819549,
+     2.656406411261359679, 2.610972248431847387, 2.56903362592493778,
+     2.530009672388827457, 2.493454522095372106, 2.459018177411830486,
+     2.426420645533749809, 2.395434278011062457, 2.365871370117638595,
+     2.337575241339236776, 2.310413683698762988, 2.284274059677471769,
+     2.25905957386919809, 2.234686395590979036, 2.21108140887870297,
+     2.188180432076048731, 2.165926793748921497, 2.144270182360394905,
+     2.123165708673976138, 2.102573135189237608, 2.082456237992015957,
+     2.062782274508307978, 2.043521536655067194, 2.02464697337738464,
+     2.006133869963471206, 1.987959574127619033, 1.970103260854325633,
+     1.952545729553555764, 1.935269228296621957, 1.918257300864508963,
+     1.901494653105150423, 1.884967035707758143, 1.868661140994487768,
+     1.852564511728090002, 1.836665460258444904, 1.820952996596124418,
+     1.805416764219227366, 1.790046982599857506, 1.77483439558606837,
+     1.759770224899592339, 1.744846128113799244, 1.730054160563729182,
+     1.71538674071366648, 1.700836618569915748, 1.686396846779167014,
+     1.6720607540975998, 1.657821920954023254, 1.643674156862867441,
+     1.629611479470633562, 1.615628095043159629, 1.601718380221376581,
+     1.587876864890574558, 1.574098216022999264, 1.560377222366167382,
+     1.546708779859908844, 1.533087877674041755, 1.519509584765938559,
+     1.505969036863201937, 1.492461423781352714, 1.478981976989922842,
+     1.465525957342709296, 1.452088642889222792, 1.438665316684561546,
+     1.425251254514058319, 1.411841712447055919, 1.398431914131003539,
+     1.385017037732650058, 1.371592202427340812, 1.358152454330141534,
+     1.34469275175354519, 1.331207949665625279, 1.317692783209412299,
+     1.304141850128615054, 1.290549591926194894, 1.27691027356015363,
+     1.263217961454619287, 1.249466499573066436, 1.23564948326336066,
+     1.221760230539994385, 1.207791750415947662, 1.193736707833126465,
+     1.17958738466398616, 1.165335636164750222, 1.150972842148865416,
+     1.136489852013158774, 1.121876922582540237, 1.107123647534034028,
+     1.092218876907275371, 1.077150624892893482, 1.061905963694822042,
+     1.046470900764042922, 1.030830236068192907, 1.014967395251327842,
+     0.9988642334929808131, 0.9825008035154263464, 0.9658550794011470098,
+     0.9489026255113034436, 0.9316161966151479401, 0.9139652510230292792,
+     0.8959153525809346874, 0.8774274291129204872, 0.8584568431938099931,
+     0.8389522142975741614, 0.8188539067003538507, 0.7980920606440534693,
+     0.7765839878947563557, 0.7542306644540520688, 0.7309119106424850631,
+     0.7064796113354325779, 0.6807479186691505202, 0.6534786387399710295,
+     0.6243585973360461505, 0.5929629424714434327, 0.5586921784081798625,
+     0.5206560387620546848, 0.4774378372966830431, 0.4265479863554152429,
+     0.3628714310970211909, 0.2723208648139477384, 0},
+    {0.001014352564120377413, 0.002669629083880922793, 0.005548995220771345792,
+     0.008624484412859888607, 0.01183947865788486861, 0.01516729801054656976,
+     0.01859210273701129151, 0.02210330461592709475, 0.02569329193593428151,
+     0.02935631744000685023, 0.03308788614622575758, 0.03688438878665621645,
+     0.04074286807444417458, 0.04466086220049143157, 0.04863629585986780496,
+     0.05266740190305100461, 0.05675266348104984759, 0.06089077034804041277,
+     0.06508058521306804567, 0.06932111739357792179, 0.07361150188411341722,
+     0.07795098251397346301, 0.08233889824223575293, 0.08677467189478028919,
+     0.09125780082683036809, 0.095787849121731522, 0.1003644410286559929,
+     0.1049872554094214289, 0.1096560210148404546, 0.1143705124488661323,
+     0.1191305467076509556, 0.1239359802028679736, 0.1287867061959434012,
+     0.1336826525834396151, 0.1386237799845948804, 0.1436100800906280339,
+     0.1486415742423425057, 0.1537183122081819397, 0.1588403711394795748,
+     0.1640078546834206341, 0.1692208922373653057, 0.1744796383307898324,
+     0.1797842721232958407, 0.1851349970089926078, 0.1905320403191375633,
+     0.1959756531162781534, 0.2014661100743140865, 0.2070037094399269362,
+     0.2125887730717307134, 0.2182216465543058426, 0.2239026993850088965,
+     0.229632325232116602, 0.2354109422634795556, 0.2412389935454402889,
+     0.2471169475123218551, 0.2530452985073261551, 0.2590245673962052742,
+     0.2650553022555897087, 0.271138079138385224, 0.2772735029191887857,
+     0.2834622082232336471, 0.2897048604429605656, 0.2960021568469337061,
+     0.3023548277864842593, 0.3087636380061818397, 0.3152293880650116065,
+     0.3217529158759855901, 0.3283350983728509642, 0.3349768533135899506,
+     0.3416791412315512977, 0.3484429675463274756, 0.355269384847918035,
+     0.3621594953693184626, 0.3691144536644731522, 0.376135469510563536,
+     0.3832238110559021416, 0.3903808082373155797, 0.3976078564938743676,
+     0.404906420807223999, 0.4122780401026620578, 0.4197243320495753771,
+     0.4272469983049970721, 0.4348478302499918513, 0.4425287152754694975,
+     0.4502916436820402768, 0.458138716267873114, 0.4660721526894572309,
+     0.4740943006930180559, 0.4822076463294863724, 0.4904148252838453348,
+     0.4987186354709807201, 0.5071220510755701794, 0.5156282382440030565,
+     0.5242405726729852944, 0.5329626593838373561, 0.5417983550254266145,
+     0.5507517931146057588, 0.5598274127040882009, 0.5690299910679523787,
+     0.5783646811197646898, 0.5878370544347081283, 0.5974531509445183408,
+     0.6072195366251219584, 0.6171433708188825973, 0.6272324852499290282,
+     0.6374954773350440806, 0.6479418211102242475, 0.6585820000500898219,
+     0.6694276673488921414, 0.6804918409973358395, 0.6917891434366769676,
+     0.7033360990161600101, 0.7151515074105005976, 0.7272569183441868201,
+     0.7396772436726493094, 0.7524415591746134169, 0.7655841738977066102,
+     0.7791460859296898134, 0.7931770117713072832, 0.8077382946829627652,
+     0.8229072113814113187, 0.8387836052959920519, 0.8555006078694531446,
+     0.873243048910072206, 0.8922816507840289901, 0.9130436479717434217,
+     0.9362826816850632339, 0.9635996931270905952, 1}};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// clang-format on
+// END GENERATED CODE
diff --git a/weight/_dep/abseil-cpp/absl/random/gaussian_distribution.h b/weight/_dep/abseil-cpp/absl/random/gaussian_distribution.h
new file mode 100644
index 0000000000000000000000000000000000000000..4b07a5c0af9d5e09a20658e7a64207ef93822d88
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/gaussian_distribution.h
@@ -0,0 +1,275 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_GAUSSIAN_DISTRIBUTION_H_
+#define ABSL_RANDOM_GAUSSIAN_DISTRIBUTION_H_
+
+// absl::gaussian_distribution implements the Ziggurat algorithm
+// for generating random gaussian numbers.
+//
+// Implementation based on "The Ziggurat Method for Generating Random Variables"
+// by George Marsaglia and Wai Wan Tsang: http://www.jstatsoft.org/v05/i08/
+//
+
+#include <cmath>
+#include <cstdint>
+#include <istream>
+#include <limits>
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/random/internal/fast_uniform_bits.h"
+#include "absl/random/internal/generate_real.h"
+#include "absl/random/internal/iostream_state_saver.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// absl::gaussian_distribution_base implements the underlying ziggurat algorithm
+// using the ziggurat tables generated by the gaussian_distribution_gentables
+// binary.
+//
+// The specific algorithm has some of the improvements suggested by the
+// 2005 paper, "An Improved Ziggurat Method to Generate Normal Random Samples",
+// Jurgen A Doornik.  (https://www.doornik.com/research/ziggurat.pdf)
+class ABSL_DLL gaussian_distribution_base {
+ public:
+  template <typename URBG>
+  inline double zignor(URBG& g);  // NOLINT(runtime/references)
+
+ private:
+  friend class TableGenerator;
+
+  template <typename URBG>
+  inline double zignor_fallback(URBG& g,  // NOLINT(runtime/references)
+                                bool neg);
+
+  // Constants used for the gaussian distribution.
+  static constexpr double kR = 3.442619855899;  // Start of the tail.
+  static constexpr double kRInv = 0.29047645161474317;  // ~= (1.0 / kR) .
+  static constexpr double kV = 9.91256303526217e-3;
+  static constexpr uint64_t kMask = 0x07f;
+
+  // The ziggurat tables store the pdf(f) and inverse-pdf(x) for equal-area
+  // points on one-half of the normal distribution, where the pdf function,
+  // pdf = e ^ (-1/2 *x^2), assumes that the mean = 0 & stddev = 1.
+  //
+  // These tables are just over 2kb in size; larger tables might improve the
+  // distributions, but also lead to more cache pollution.
+  //
+  // x = {3.71308, 3.44261, 3.22308, ..., 0}
+  // f = {0.00101, 0.00266, 0.00554, ..., 1}
+  struct Tables {
+    double x[kMask + 2];
+    double f[kMask + 2];
+  };
+  static const Tables zg_;
+  random_internal::FastUniformBits<uint64_t> fast_u64_;
+};
+
+}  // namespace random_internal
+
+// absl::gaussian_distribution:
+// Generates a number conforming to a Gaussian distribution.
+template <typename RealType = double>
+class gaussian_distribution : random_internal::gaussian_distribution_base {
+ public:
+  using result_type = RealType;
+
+  class param_type {
+   public:
+    using distribution_type = gaussian_distribution;
+
+    explicit param_type(result_type mean = 0, result_type stddev = 1)
+        : mean_(mean), stddev_(stddev) {}
+
+    // Returns the mean distribution parameter.  The mean specifies the location
+    // of the peak.  The default value is 0.0.
+    result_type mean() const { return mean_; }
+
+    // Returns the deviation distribution parameter.  The default value is 1.0.
+    result_type stddev() const { return stddev_; }
+
+    friend bool operator==(const param_type& a, const param_type& b) {
+      return a.mean_ == b.mean_ && a.stddev_ == b.stddev_;
+    }
+
+    friend bool operator!=(const param_type& a, const param_type& b) {
+      return !(a == b);
+    }
+
+   private:
+    result_type mean_;
+    result_type stddev_;
+
+    static_assert(
+        std::is_floating_point<RealType>::value,
+        "Class-template absl::gaussian_distribution<> must be parameterized "
+        "using a floating-point type.");
+  };
+
+  gaussian_distribution() : gaussian_distribution(0) {}
+
+  explicit gaussian_distribution(result_type mean, result_type stddev = 1)
+      : param_(mean, stddev) {}
+
+  explicit gaussian_distribution(const param_type& p) : param_(p) {}
+
+  void reset() {}
+
+  // Generating functions
+  template <typename URBG>
+  result_type operator()(URBG& g) {  // NOLINT(runtime/references)
+    return (*this)(g, param_);
+  }
+
+  template <typename URBG>
+  result_type operator()(URBG& g,  // NOLINT(runtime/references)
+                         const param_type& p);
+
+  param_type param() const { return param_; }
+  void param(const param_type& p) { param_ = p; }
+
+  result_type(min)() const {
+    return -std::numeric_limits<result_type>::infinity();
+  }
+  result_type(max)() const {
+    return std::numeric_limits<result_type>::infinity();
+  }
+
+  result_type mean() const { return param_.mean(); }
+  result_type stddev() const { return param_.stddev(); }
+
+  friend bool operator==(const gaussian_distribution& a,
+                         const gaussian_distribution& b) {
+    return a.param_ == b.param_;
+  }
+  friend bool operator!=(const gaussian_distribution& a,
+                         const gaussian_distribution& b) {
+    return a.param_ != b.param_;
+  }
+
+ private:
+  param_type param_;
+};
+
+// --------------------------------------------------------------------------
+// Implementation details only below
+// --------------------------------------------------------------------------
+
+template <typename RealType>
+template <typename URBG>
+typename gaussian_distribution<RealType>::result_type
+gaussian_distribution<RealType>::operator()(
+    URBG& g,  // NOLINT(runtime/references)
+    const param_type& p) {
+  return p.mean() + p.stddev() * static_cast<result_type>(zignor(g));
+}
+
+template <typename CharT, typename Traits, typename RealType>
+std::basic_ostream<CharT, Traits>& operator<<(
+    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+    const gaussian_distribution<RealType>& x) {
+  auto saver = random_internal::make_ostream_state_saver(os);
+  os.precision(random_internal::stream_precision_helper<RealType>::kPrecision);
+  os << x.mean() << os.fill() << x.stddev();
+  return os;
+}
+
+template <typename CharT, typename Traits, typename RealType>
+std::basic_istream<CharT, Traits>& operator>>(
+    std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+    gaussian_distribution<RealType>& x) {   // NOLINT(runtime/references)
+  using result_type = typename gaussian_distribution<RealType>::result_type;
+  using param_type = typename gaussian_distribution<RealType>::param_type;
+
+  auto saver = random_internal::make_istream_state_saver(is);
+  auto mean = random_internal::read_floating_point<result_type>(is);
+  if (is.fail()) return is;
+  auto stddev = random_internal::read_floating_point<result_type>(is);
+  if (!is.fail()) {
+    x.param(param_type(mean, stddev));
+  }
+  return is;
+}
+
+namespace random_internal {
+
+template <typename URBG>
+inline double gaussian_distribution_base::zignor_fallback(URBG& g, bool neg) {
+  using random_internal::GeneratePositiveTag;
+  using random_internal::GenerateRealFromBits;
+
+  // This fallback path happens approximately 0.05% of the time.
+  double x, y;
+  do {
+    // kRInv = 1/r, U(0, 1)
+    x = kRInv *
+        std::log(GenerateRealFromBits<double, GeneratePositiveTag, false>(
+            fast_u64_(g)));
+    y = -std::log(
+        GenerateRealFromBits<double, GeneratePositiveTag, false>(fast_u64_(g)));
+  } while ((y + y) < (x * x));
+  return neg ? (x - kR) : (kR - x);
+}
+
+template <typename URBG>
+inline double gaussian_distribution_base::zignor(
+    URBG& g) {  // NOLINT(runtime/references)
+  using random_internal::GeneratePositiveTag;
+  using random_internal::GenerateRealFromBits;
+  using random_internal::GenerateSignedTag;
+
+  while (true) {
+    // We use a single uint64_t to generate both a double and a strip.
+    // These bits are unused when the generated double is > 1/2^5.
+    // This may introduce some bias from the duplicated low bits of small
+    // values (those smaller than 1/2^5, which all end up on the left tail).
+    uint64_t bits = fast_u64_(g);
+    int i = static_cast<int>(bits & kMask);  // pick a random strip
+    double j = GenerateRealFromBits<double, GenerateSignedTag, false>(
+        bits);  // U(-1, 1)
+    const double x = j * zg_.x[i];
+
+    // Retangular box. Handles >97% of all cases.
+    // For any given box, this handles between 75% and 99% of values.
+    // Equivalent to U(01) < (x[i+1] / x[i]), and when i == 0, ~93.5%
+    if (std::abs(x) < zg_.x[i + 1]) {
+      return x;
+    }
+
+    // i == 0: Base box. Sample using a ratio of uniforms.
+    if (i == 0) {
+      // This path happens about 0.05% of the time.
+      return zignor_fallback(g, j < 0);
+    }
+
+    // i > 0: Wedge samples using precomputed values.
+    double v = GenerateRealFromBits<double, GeneratePositiveTag, false>(
+        fast_u64_(g));  // U(0, 1)
+    if ((zg_.f[i + 1] + v * (zg_.f[i] - zg_.f[i + 1])) <
+        std::exp(-0.5 * x * x)) {
+      return x;
+    }
+
+    // The wedge was missed; reject the value and try again.
+  }
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_GAUSSIAN_DISTRIBUTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/BUILD.bazel b/weight/_dep/abseil-cpp/absl/random/internal/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..71a742ee954ddbf4903043daf747e9e672ab01ed
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/BUILD.bazel
@@ -0,0 +1,784 @@
+#
+# Copyright 2019 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# Internal-only implementation classes for Abseil Random
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_RANDOM_RANDEN_COPTS",
+    "ABSL_TEST_COPTS",
+    "absl_random_randen_copts_init",
+)
+
+default_package_visibility = [
+    "//absl/random:__pkg__",
+]
+
+package(
+    default_visibility = default_package_visibility,
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "traits",
+    hdrs = ["traits.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/numeric:bits",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_library(
+    name = "distribution_caller",
+    hdrs = ["distribution_caller.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:fast_type_id",
+        "//absl/utility",
+    ],
+)
+
+cc_library(
+    name = "fast_uniform_bits",
+    hdrs = [
+        "fast_uniform_bits.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":traits",
+        "//absl/base:config",
+        "//absl/meta:type_traits",
+    ],
+)
+
+cc_library(
+    name = "seed_material",
+    srcs = [
+        "seed_material.cc",
+    ],
+    hdrs = [
+        "seed_material.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS + select({
+        "//absl:msvc_compiler": ["-DEFAULTLIB:bcrypt.lib"],
+        "//absl:clang-cl_compiler": ["-DEFAULTLIB:bcrypt.lib"],
+        "//absl:mingw_compiler": [
+            "-DEFAULTLIB:bcrypt.lib",
+            "-lbcrypt",
+        ],
+        "//conditions:default": [],
+    }),
+    deps = [
+        ":fast_uniform_bits",
+        "//absl/base:core_headers",
+        "//absl/base:dynamic_annotations",
+        "//absl/base:raw_logging_internal",
+        "//absl/strings",
+        "//absl/types:optional",
+        "//absl/types:span",
+    ],
+)
+
+cc_library(
+    name = "pool_urbg",
+    srcs = [
+        "pool_urbg.cc",
+    ],
+    hdrs = [
+        "pool_urbg.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = select({
+        "//absl:msvc_compiler": [],
+        "//absl:clang-cl_compiler": [],
+        "//absl:wasm": [],
+        "//conditions:default": ["-pthread"],
+    }) + ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":randen",
+        ":seed_material",
+        ":traits",
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:endian",
+        "//absl/base:raw_logging_internal",
+        "//absl/random:seed_gen_exception",
+        "//absl/types:span",
+    ],
+)
+
+cc_library(
+    name = "explicit_seed_seq",
+    testonly = 1,
+    hdrs = [
+        "explicit_seed_seq.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:endian",
+    ],
+)
+
+cc_library(
+    name = "sequence_urbg",
+    testonly = 1,
+    hdrs = [
+        "sequence_urbg.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/base:config"],
+)
+
+cc_library(
+    name = "salted_seed_seq",
+    hdrs = [
+        "salted_seed_seq.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":seed_material",
+        "//absl/container:inlined_vector",
+        "//absl/meta:type_traits",
+        "//absl/types:optional",
+        "//absl/types:span",
+    ],
+)
+
+cc_library(
+    name = "iostream_state_saver",
+    hdrs = ["iostream_state_saver.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/meta:type_traits",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_library(
+    name = "generate_real",
+    hdrs = [
+        "generate_real.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":fastmath",
+        ":traits",
+        "//absl/meta:type_traits",
+        "//absl/numeric:bits",
+    ],
+)
+
+cc_library(
+    name = "fastmath",
+    hdrs = [
+        "fastmath.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = ["//absl/numeric:bits"],
+)
+
+cc_library(
+    name = "wide_multiply",
+    hdrs = ["wide_multiply.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":traits",
+        "//absl/base:config",
+        "//absl/numeric:bits",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_library(
+    name = "nonsecure_base",
+    hdrs = ["nonsecure_base.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":pool_urbg",
+        ":salted_seed_seq",
+        ":seed_material",
+        "//absl/base:core_headers",
+        "//absl/container:inlined_vector",
+        "//absl/meta:type_traits",
+        "//absl/types:span",
+    ],
+)
+
+cc_library(
+    name = "pcg_engine",
+    hdrs = ["pcg_engine.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":fastmath",
+        ":iostream_state_saver",
+        "//absl/base:config",
+        "//absl/meta:type_traits",
+        "//absl/numeric:bits",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_library(
+    name = "randen_engine",
+    hdrs = ["randen_engine.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = default_package_visibility + [
+    ],
+    deps = [
+        ":iostream_state_saver",
+        ":randen",
+        "//absl/base:endian",
+        "//absl/meta:type_traits",
+    ],
+)
+
+cc_library(
+    name = "platform",
+    srcs = [
+        "randen_round_keys.cc",
+    ],
+    hdrs = [
+        "randen_traits.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    textual_hdrs = [
+        "platform.h",
+    ],
+    deps = ["//absl/base:config"],
+)
+
+cc_library(
+    name = "randen",
+    srcs = [
+        "randen.cc",
+    ],
+    hdrs = [
+        "randen.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":platform",
+        ":randen_hwaes",
+        ":randen_slow",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_library(
+    name = "randen_slow",
+    srcs = ["randen_slow.cc"],
+    hdrs = ["randen_slow.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":platform",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:endian",
+        "//absl/numeric:int128",
+    ],
+)
+
+absl_random_randen_copts_init()
+
+cc_library(
+    name = "randen_hwaes",
+    srcs = [
+        "randen_detect.cc",
+    ],
+    hdrs = [
+        "randen_detect.h",
+        "randen_hwaes.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":platform",
+        ":randen_hwaes_impl",
+        "//absl/base:config",
+    ],
+)
+
+# build with --save_temps to see assembly language output.
+cc_library(
+    name = "randen_hwaes_impl",
+    srcs = [
+        "randen_hwaes.cc",
+        "randen_hwaes.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS + ABSL_RANDOM_RANDEN_COPTS + select({
+        "//absl:msvc_compiler": [],
+        "//absl:clang-cl_compiler": [],
+        "//conditions:default": ["-Wno-pass-failed"],
+    }),
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":platform",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_binary(
+    name = "gaussian_distribution_gentables",
+    srcs = [
+        "gaussian_distribution_gentables.cc",
+    ],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:core_headers",
+        "//absl/random:distributions",
+    ],
+)
+
+cc_library(
+    name = "distribution_test_util",
+    testonly = 1,
+    srcs = [
+        "chi_square.cc",
+        "distribution_test_util.cc",
+    ],
+    hdrs = [
+        "chi_square.h",
+        "distribution_test_util.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
+        "//absl/strings",
+        "//absl/strings:str_format",
+        "//absl/types:span",
+    ],
+)
+
+# Common tags for tests, etc.
+ABSL_RANDOM_NONPORTABLE_TAGS = [
+    "no_test_android_arm",
+    "no_test_android_arm64",
+    "no_test_android_x86",
+    "no_test_darwin_x86_64",
+    "no_test_ios_x86_64",
+    "no_test_loonix",
+    "no_test_lexan",
+    "no_test_wasm",
+]
+
+cc_test(
+    name = "traits_test",
+    size = "small",
+    srcs = ["traits_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":traits",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "generate_real_test",
+    size = "small",
+    srcs = [
+        "generate_real_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":generate_real",
+        "//absl/flags:flag",
+        "//absl/numeric:bits",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "distribution_test_util_test",
+    size = "small",
+    srcs = ["distribution_test_util_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distribution_test_util",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "fastmath_test",
+    size = "small",
+    srcs = ["fastmath_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":fastmath",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "explicit_seed_seq_test",
+    size = "small",
+    srcs = ["explicit_seed_seq_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":explicit_seed_seq",
+        "//absl/random:seed_sequences",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "salted_seed_seq_test",
+    size = "small",
+    srcs = ["salted_seed_seq_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":salted_seed_seq",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "chi_square_test",
+    size = "small",
+    srcs = [
+        "chi_square_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":distribution_test_util",
+        "//absl/base:core_headers",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "fast_uniform_bits_test",
+    size = "small",
+    srcs = [
+        "fast_uniform_bits_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":fast_uniform_bits",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "mock_helpers",
+    hdrs = ["mock_helpers.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:fast_type_id",
+        "//absl/types:optional",
+    ],
+)
+
+cc_library(
+    name = "mock_overload_set",
+    testonly = 1,
+    hdrs = ["mock_overload_set.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":mock_helpers",
+        "//absl/random:mocking_bit_gen",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_test(
+    name = "nonsecure_base_test",
+    size = "small",
+    srcs = [
+        "nonsecure_base_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":nonsecure_base",
+        "//absl/random",
+        "//absl/random:distributions",
+        "//absl/random:seed_sequences",
+        "//absl/strings",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "seed_material_test",
+    size = "small",
+    srcs = ["seed_material_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":seed_material",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "pool_urbg_test",
+    size = "small",
+    srcs = [
+        "pool_urbg_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":pool_urbg",
+        "//absl/meta:type_traits",
+        "//absl/types:span",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "pcg_engine_test",
+    size = "medium",  # Trying to measure accuracy.
+    srcs = ["pcg_engine_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    flaky = 1,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":explicit_seed_seq",
+        ":pcg_engine",
+        "//absl/time",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "randen_engine_test",
+    size = "medium",
+    srcs = [
+        "randen_engine_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":explicit_seed_seq",
+        ":randen_engine",
+        "//absl/log",
+        "//absl/strings",
+        "//absl/time",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "randen_test",
+    size = "small",
+    srcs = ["randen_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":randen",
+        "//absl/meta:type_traits",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "randen_slow_test",
+    size = "small",
+    srcs = ["randen_slow_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":platform",
+        ":randen_slow",
+        "//absl/base:endian",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "randen_hwaes_test",
+    size = "small",
+    srcs = ["randen_hwaes_test.cc"],
+    copts = ABSL_TEST_COPTS + ABSL_RANDOM_RANDEN_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ABSL_RANDOM_NONPORTABLE_TAGS,
+    deps = [
+        ":platform",
+        ":randen_hwaes",
+        ":randen_hwaes_impl",  # build_cleaner: keep
+        "//absl/log",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+cc_test(
+    name = "wide_multiply_test",
+    size = "small",
+    srcs = ["wide_multiply_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":wide_multiply",
+        "//absl/numeric:bits",
+        "//absl/numeric:int128",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "nanobenchmark",
+    srcs = ["nanobenchmark.cc"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    textual_hdrs = ["nanobenchmark.h"],
+    deps = [
+        ":platform",
+        ":randen_engine",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_library(
+    name = "uniform_helper",
+    hdrs = ["uniform_helper.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":traits",
+        "//absl/base:config",
+        "//absl/meta:type_traits",
+        "//absl/numeric:int128",
+    ],
+)
+
+cc_test(
+    name = "nanobenchmark_test",
+    size = "small",
+    srcs = ["nanobenchmark_test.cc"],
+    flaky = 1,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "benchmark",
+        "no_test_ios_x86_64",
+        "no_test_loonix",  # Crashing.
+        "no_test_wasm",
+    ],
+    deps = [
+        ":nanobenchmark",
+        "//absl/log",
+        "//absl/log:check",
+        "//absl/strings",
+        "//absl/strings:str_format",
+    ],
+)
+
+cc_test(
+    name = "randen_benchmarks",
+    size = "medium",
+    timeout = "long",
+    srcs = ["randen_benchmarks.cc"],
+    copts = ABSL_TEST_COPTS + ABSL_RANDOM_RANDEN_COPTS,
+    flaky = 1,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ABSL_RANDOM_NONPORTABLE_TAGS + ["benchmark"],
+    deps = [
+        ":nanobenchmark",
+        ":platform",
+        ":randen",
+        ":randen_engine",
+        ":randen_hwaes",
+        ":randen_hwaes_impl",
+        ":randen_slow",
+        "//absl/base:raw_logging_internal",
+        "//absl/strings",
+    ],
+)
+
+cc_test(
+    name = "iostream_state_saver_test",
+    srcs = ["iostream_state_saver_test.cc"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":iostream_state_saver",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "uniform_helper_test",
+    size = "small",
+    srcs = ["uniform_helper_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":uniform_helper",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/chi_square.cc b/weight/_dep/abseil-cpp/absl/random/internal/chi_square.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fbe0173299b9bc61e52fbc64c66431b67836f20f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/chi_square.cc
@@ -0,0 +1,233 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/chi_square.h"
+
+#include <cmath>
+
+#include "absl/random/internal/distribution_test_util.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+namespace {
+
+#if defined(__EMSCRIPTEN__)
+// Workaround __EMSCRIPTEN__ error: llvm_fma_f64 not found.
+inline double fma(double x, double y, double z) {
+  return (x * y) + z;
+}
+#endif
+
+// Use Horner's method to evaluate a polynomial.
+template <typename T, unsigned N>
+inline T EvaluatePolynomial(T x, const T (&poly)[N]) {
+#if !defined(__EMSCRIPTEN__)
+  using std::fma;
+#endif
+  T p = poly[N - 1];
+  for (unsigned i = 2; i <= N; i++) {
+    p = fma(p, x, poly[N - i]);
+  }
+  return p;
+}
+
+static constexpr int kLargeDOF = 150;
+
+// Returns the probability of a normal z-value.
+//
+// Adapted from the POZ function in:
+//     Ibbetson D, Algorithm 209
+//     Collected Algorithms of the CACM 1963 p. 616
+//
+double POZ(double z) {
+  static constexpr double kP1[] = {
+      0.797884560593,  -0.531923007300, 0.319152932694,
+      -0.151968751364, 0.059054035642,  -0.019198292004,
+      0.005198775019,  -0.001075204047, 0.000124818987,
+  };
+  static constexpr double kP2[] = {
+      0.999936657524,  0.000535310849,  -0.002141268741, 0.005353579108,
+      -0.009279453341, 0.011630447319,  -0.010557625006, 0.006549791214,
+      -0.002034254874, -0.000794620820, 0.001390604284,  -0.000676904986,
+      -0.000019538132, 0.000152529290,  -0.000045255659,
+  };
+
+  const double kZMax = 6.0;  // Maximum meaningful z-value.
+  if (z == 0.0) {
+    return 0.5;
+  }
+  double x;
+  double y = 0.5 * std::fabs(z);
+  if (y >= (kZMax * 0.5)) {
+    x = 1.0;
+  } else if (y < 1.0) {
+    double w = y * y;
+    x = EvaluatePolynomial(w, kP1) * y * 2.0;
+  } else {
+    y -= 2.0;
+    x = EvaluatePolynomial(y, kP2);
+  }
+  return z > 0.0 ? ((x + 1.0) * 0.5) : ((1.0 - x) * 0.5);
+}
+
+// Approximates the survival function of the normal distribution.
+//
+// Algorithm 26.2.18, from:
+// [Abramowitz and Stegun, Handbook of Mathematical Functions,p.932]
+// http://people.math.sfu.ca/~cbm/aands/abramowitz_and_stegun.pdf
+//
+double normal_survival(double z) {
+  // Maybe replace with the alternate formulation.
+  // 0.5 * erfc((x - mean)/(sqrt(2) * sigma))
+  static constexpr double kR[] = {
+      1.0, 0.196854, 0.115194, 0.000344, 0.019527,
+  };
+  double r = EvaluatePolynomial(z, kR);
+  r *= r;
+  return 0.5 / (r * r);
+}
+
+}  // namespace
+
+// Calculates the critical chi-square value given degrees-of-freedom and a
+// p-value, usually using bisection. Also known by the name CRITCHI.
+double ChiSquareValue(int dof, double p) {
+  static constexpr double kChiEpsilon =
+      0.000001;  // Accuracy of the approximation.
+  static constexpr double kChiMax =
+      99999.0;  // Maximum chi-squared value.
+
+  const double p_value = 1.0 - p;
+  if (dof < 1 || p_value > 1.0) {
+    return 0.0;
+  }
+
+  if (dof > kLargeDOF) {
+    // For large degrees of freedom, use the normal approximation by
+    //     Wilson, E. B. and Hilferty, M. M. (1931)
+    //                     chi^2 - mean
+    //                Z = --------------
+    //                        stddev
+    const double z = InverseNormalSurvival(p_value);
+    const double mean = 1 - 2.0 / (9 * dof);
+    const double variance = 2.0 / (9 * dof);
+    // Cannot use this method if the variance is 0.
+    if (variance != 0) {
+      double term = z * std::sqrt(variance) + mean;
+      return dof * (term * term * term);
+    }
+  }
+
+  if (p_value <= 0.0) return kChiMax;
+
+  // Otherwise search for the p value by bisection
+  double min_chisq = 0.0;
+  double max_chisq = kChiMax;
+  double current = dof / std::sqrt(p_value);
+  while ((max_chisq - min_chisq) > kChiEpsilon) {
+    if (ChiSquarePValue(current, dof) < p_value) {
+      max_chisq = current;
+    } else {
+      min_chisq = current;
+    }
+    current = (max_chisq + min_chisq) * 0.5;
+  }
+  return current;
+}
+
+// Calculates the p-value (probability) of a given chi-square value
+// and degrees of freedom.
+//
+// Adapted from the POCHISQ function from:
+//     Hill, I. D. and Pike, M. C.  Algorithm 299
+//     Collected Algorithms of the CACM 1963 p. 243
+//
+double ChiSquarePValue(double chi_square, int dof) {
+  static constexpr double kLogSqrtPi =
+      0.5723649429247000870717135;  // Log[Sqrt[Pi]]
+  static constexpr double kInverseSqrtPi =
+      0.5641895835477562869480795;  // 1/(Sqrt[Pi])
+
+  // For large degrees of freedom, use the normal approximation by
+  //     Wilson, E. B. and Hilferty, M. M. (1931)
+  // Via Wikipedia:
+  //   By the Central Limit Theorem, because the chi-square distribution is the
+  //   sum of k independent random variables with finite mean and variance, it
+  //   converges to a normal distribution for large k.
+  if (dof > kLargeDOF) {
+    // Re-scale everything.
+    const double chi_square_scaled = std::pow(chi_square / dof, 1.0 / 3);
+    const double mean = 1 - 2.0 / (9 * dof);
+    const double variance = 2.0 / (9 * dof);
+    // If variance is 0, this method cannot be used.
+    if (variance != 0) {
+      const double z = (chi_square_scaled - mean) / std::sqrt(variance);
+      if (z > 0) {
+        return normal_survival(z);
+      } else if (z < 0) {
+        return 1.0 - normal_survival(-z);
+      } else {
+        return 0.5;
+      }
+    }
+  }
+
+  // The chi square function is >= 0 for any degrees of freedom.
+  // In other words, probability that the chi square function >= 0 is 1.
+  if (chi_square <= 0.0) return 1.0;
+
+  // If the degrees of freedom is zero, the chi square function is always 0 by
+  // definition. In other words, the probability that the chi square function
+  // is > 0 is zero (chi square values <= 0 have been filtered above).
+  if (dof < 1) return 0;
+
+  auto capped_exp = [](double x) { return x < -20 ? 0.0 : std::exp(x); };
+  static constexpr double kBigX = 20;
+
+  double a = 0.5 * chi_square;
+  const bool even = !(dof & 1);  // True if dof is an even number.
+  const double y = capped_exp(-a);
+  double s = even ? y : (2.0 * POZ(-std::sqrt(chi_square)));
+
+  if (dof <= 2) {
+    return s;
+  }
+
+  chi_square = 0.5 * (dof - 1.0);
+  double z = (even ? 1.0 : 0.5);
+  if (a > kBigX) {
+    double e = (even ? 0.0 : kLogSqrtPi);
+    double c = std::log(a);
+    while (z <= chi_square) {
+      e = std::log(z) + e;
+      s += capped_exp(c * z - a - e);
+      z += 1.0;
+    }
+    return s;
+  }
+
+  double e = (even ? 1.0 : (kInverseSqrtPi / std::sqrt(a)));
+  double c = 0.0;
+  while (z <= chi_square) {
+    e = e * (a / z);
+    c = c + e;
+    z += 1.0;
+  }
+  return c * y + s;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/chi_square.h b/weight/_dep/abseil-cpp/absl/random/internal/chi_square.h
new file mode 100644
index 0000000000000000000000000000000000000000..07f4fbe5229825ba2207fbd6d1688c535e5f80a9
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/chi_square.h
@@ -0,0 +1,89 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
+#define ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
+
+// The chi-square statistic.
+//
+// Useful for evaluating if `D` independent random variables are behaving as
+// expected, or if two distributions are similar.  (`D` is the degrees of
+// freedom).
+//
+// Each bucket should have an expected count of 10 or more for the chi square to
+// be meaningful.
+
+#include <cassert>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+constexpr const char kChiSquared[] = "chi-squared";
+
+// Returns the measured chi square value, using a single expected value.  This
+// assumes that the values in [begin, end) are uniformly distributed.
+template <typename Iterator>
+double ChiSquareWithExpected(Iterator begin, Iterator end, double expected) {
+  // Compute the sum and the number of buckets.
+  assert(expected >= 10);  // require at least 10 samples per bucket.
+  double chi_square = 0;
+  for (auto it = begin; it != end; it++) {
+    double d = static_cast<double>(*it) - expected;
+    chi_square += d * d;
+  }
+  chi_square = chi_square / expected;
+  return chi_square;
+}
+
+// Returns the measured chi square value, taking the actual value of each bucket
+// from the first set of iterators, and the expected value of each bucket from
+// the second set of iterators.
+template <typename Iterator, typename Expected>
+double ChiSquare(Iterator it, Iterator end, Expected eit, Expected eend) {
+  double chi_square = 0;
+  for (; it != end && eit != eend; ++it, ++eit) {
+    if (*it > 0) {
+      assert(*eit > 0);
+    }
+    double e = static_cast<double>(*eit);
+    double d = static_cast<double>(*it - *eit);
+    if (d != 0) {
+      assert(e > 0);
+      chi_square += (d * d) / e;
+    }
+  }
+  assert(it == end && eit == eend);
+  return chi_square;
+}
+
+// ======================================================================
+// The following methods can be used for an arbitrary significance level.
+//
+
+// Calculates critical chi-square values to produce the given p-value using a
+// bisection search for a value within epsilon, relying on the monotonicity of
+// ChiSquarePValue().
+double ChiSquareValue(int dof, double p);
+
+// Calculates the p-value (probability) of a given chi-square value.
+double ChiSquarePValue(double chi_square, int dof);
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_CHI_SQUARE_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/chi_square_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/chi_square_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5025defac12ce06bb7b97d0a5ba0a3fcf2851ad0
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/chi_square_test.cc
@@ -0,0 +1,365 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/chi_square.h"
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+#include <numeric>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+
+using absl::random_internal::ChiSquare;
+using absl::random_internal::ChiSquarePValue;
+using absl::random_internal::ChiSquareValue;
+using absl::random_internal::ChiSquareWithExpected;
+
+namespace {
+
+TEST(ChiSquare, Value) {
+  struct {
+    int line;
+    double chi_square;
+    int df;
+    double confidence;
+  } const specs[] = {
+      // Testing lookup at 1% confidence
+      {__LINE__, 0, 0, 0.01},
+      {__LINE__, 0.00016, 1, 0.01},
+      {__LINE__, 1.64650, 8, 0.01},
+      {__LINE__, 5.81221, 16, 0.01},
+      {__LINE__, 156.4319, 200, 0.01},
+      {__LINE__, 1121.3784, 1234, 0.01},
+      {__LINE__, 53557.1629, 54321, 0.01},
+      {__LINE__, 651662.6647, 654321, 0.01},
+
+      // Testing lookup at 99% confidence
+      {__LINE__, 0, 0, 0.99},
+      {__LINE__, 6.635, 1, 0.99},
+      {__LINE__, 20.090, 8, 0.99},
+      {__LINE__, 32.000, 16, 0.99},
+      {__LINE__, 249.4456, 200, 0.99},
+      {__LINE__, 1131.1573, 1023, 0.99},
+      {__LINE__, 1352.5038, 1234, 0.99},
+      {__LINE__, 55090.7356, 54321, 0.99},
+      {__LINE__, 656985.1514, 654321, 0.99},
+
+      // Testing lookup at 99.9% confidence
+      {__LINE__, 16.2659, 3, 0.999},
+      {__LINE__, 22.4580, 6, 0.999},
+      {__LINE__, 267.5409, 200, 0.999},
+      {__LINE__, 1168.5033, 1023, 0.999},
+      {__LINE__, 55345.1741, 54321, 0.999},
+      {__LINE__, 657861.7284, 654321, 0.999},
+      {__LINE__, 51.1772, 24, 0.999},
+      {__LINE__, 59.7003, 30, 0.999},
+      {__LINE__, 37.6984, 15, 0.999},
+      {__LINE__, 29.5898, 10, 0.999},
+      {__LINE__, 27.8776, 9, 0.999},
+
+      // Testing lookup at random confidences
+      {__LINE__, 0.000157088, 1, 0.01},
+      {__LINE__, 5.31852, 2, 0.93},
+      {__LINE__, 1.92256, 4, 0.25},
+      {__LINE__, 10.7709, 13, 0.37},
+      {__LINE__, 26.2514, 17, 0.93},
+      {__LINE__, 36.4799, 29, 0.84},
+      {__LINE__, 25.818, 31, 0.27},
+      {__LINE__, 63.3346, 64, 0.50},
+      {__LINE__, 196.211, 128, 0.9999},
+      {__LINE__, 215.21, 243, 0.10},
+      {__LINE__, 285.393, 256, 0.90},
+      {__LINE__, 984.504, 1024, 0.1923},
+      {__LINE__, 2043.85, 2048, 0.4783},
+      {__LINE__, 48004.6, 48273, 0.194},
+  };
+  for (const auto& spec : specs) {
+    SCOPED_TRACE(spec.line);
+    // Verify all values are have at most a 1% relative error.
+    const double val = ChiSquareValue(spec.df, spec.confidence);
+    const double err = std::max(5e-6, spec.chi_square / 5e3);  // 1 part in 5000
+    EXPECT_NEAR(spec.chi_square, val, err) << spec.line;
+  }
+
+  // Relaxed test for extreme values, from
+  //  http://www.ciphersbyritter.com/JAVASCRP/NORMCHIK.HTM#ChiSquare
+  EXPECT_NEAR(49.2680, ChiSquareValue(100, 1e-6), 5);  // 0.000'005 mark
+  EXPECT_NEAR(123.499, ChiSquareValue(200, 1e-6), 5);  // 0.000'005 mark
+
+  EXPECT_NEAR(149.449, ChiSquareValue(100, 0.999), 0.01);
+  EXPECT_NEAR(161.318, ChiSquareValue(100, 0.9999), 0.01);
+  EXPECT_NEAR(172.098, ChiSquareValue(100, 0.99999), 0.01);
+
+  EXPECT_NEAR(381.426, ChiSquareValue(300, 0.999), 0.05);
+  EXPECT_NEAR(399.756, ChiSquareValue(300, 0.9999), 0.1);
+  EXPECT_NEAR(416.126, ChiSquareValue(300, 0.99999), 0.2);
+}
+
+TEST(ChiSquareTest, PValue) {
+  struct {
+    int line;
+    double pval;
+    double chi_square;
+    int df;
+  } static const specs[] = {
+      {__LINE__, 1, 0, 0},
+      {__LINE__, 0, 0.001, 0},
+      {__LINE__, 1.000, 0, 453},
+      {__LINE__, 0.134471, 7972.52, 7834},
+      {__LINE__, 0.203922, 28.32, 23},
+      {__LINE__, 0.737171, 48274, 48472},
+      {__LINE__, 0.444146, 583.1234, 579},
+      {__LINE__, 0.294814, 138.2, 130},
+      {__LINE__, 0.0816532, 12.63, 7},
+      {__LINE__, 0, 682.32, 67},
+      {__LINE__, 0.49405, 999, 999},
+      {__LINE__, 1.000, 0, 9999},
+      {__LINE__, 0.997477, 0.00001, 1},
+      {__LINE__, 0, 5823.21, 5040},
+  };
+  for (const auto& spec : specs) {
+    SCOPED_TRACE(spec.line);
+    const double pval = ChiSquarePValue(spec.chi_square, spec.df);
+    EXPECT_NEAR(spec.pval, pval, 1e-3);
+  }
+}
+
+TEST(ChiSquareTest, CalcChiSquare) {
+  struct {
+    int line;
+    std::vector<int> expected;
+    std::vector<int> actual;
+  } const specs[] = {
+      {__LINE__,
+       {56, 234, 76, 1, 546, 1, 87, 345, 1, 234},
+       {2, 132, 4, 43, 234, 8, 345, 8, 236, 56}},
+      {__LINE__,
+       {123, 36, 234, 367, 345, 2, 456, 567, 234, 567},
+       {123, 56, 2345, 8, 345, 8, 2345, 23, 48, 267}},
+      {__LINE__,
+       {123, 234, 345, 456, 567, 678, 789, 890, 98, 76},
+       {123, 234, 345, 456, 567, 678, 789, 890, 98, 76}},
+      {__LINE__, {3, 675, 23, 86, 2, 8, 2}, {456, 675, 23, 86, 23, 65, 2}},
+      {__LINE__, {1}, {23}},
+  };
+  for (const auto& spec : specs) {
+    SCOPED_TRACE(spec.line);
+    double chi_square = 0;
+    for (int i = 0; i < spec.expected.size(); ++i) {
+      const double diff = spec.actual[i] - spec.expected[i];
+      chi_square += (diff * diff) / spec.expected[i];
+    }
+    EXPECT_NEAR(chi_square,
+                ChiSquare(std::begin(spec.actual), std::end(spec.actual),
+                          std::begin(spec.expected), std::end(spec.expected)),
+                1e-5);
+  }
+}
+
+TEST(ChiSquareTest, CalcChiSquareInt64) {
+  const int64_t data[3] = {910293487, 910292491, 910216780};
+  // $ python -c "import scipy.stats
+  // > print scipy.stats.chisquare([910293487, 910292491, 910216780])[0]"
+  // 4.25410123524
+  double sum = std::accumulate(std::begin(data), std::end(data), double{0});
+  size_t n = std::distance(std::begin(data), std::end(data));
+  double a = ChiSquareWithExpected(std::begin(data), std::end(data), sum / n);
+  EXPECT_NEAR(4.254101, a, 1e-6);
+
+  // ... Or with known values.
+  double b =
+      ChiSquareWithExpected(std::begin(data), std::end(data), 910267586.0);
+  EXPECT_NEAR(4.254101, b, 1e-6);
+}
+
+TEST(ChiSquareTest, TableData) {
+  // Test data from
+  // http://www.itl.nist.gov/div898/handbook/eda/section3/eda3674.htm
+  //    0.90      0.95     0.975      0.99     0.999
+  const double data[100][5] = {
+      /* 1*/ {2.706, 3.841, 5.024, 6.635, 10.828},
+      /* 2*/ {4.605, 5.991, 7.378, 9.210, 13.816},
+      /* 3*/ {6.251, 7.815, 9.348, 11.345, 16.266},
+      /* 4*/ {7.779, 9.488, 11.143, 13.277, 18.467},
+      /* 5*/ {9.236, 11.070, 12.833, 15.086, 20.515},
+      /* 6*/ {10.645, 12.592, 14.449, 16.812, 22.458},
+      /* 7*/ {12.017, 14.067, 16.013, 18.475, 24.322},
+      /* 8*/ {13.362, 15.507, 17.535, 20.090, 26.125},
+      /* 9*/ {14.684, 16.919, 19.023, 21.666, 27.877},
+      /*10*/ {15.987, 18.307, 20.483, 23.209, 29.588},
+      /*11*/ {17.275, 19.675, 21.920, 24.725, 31.264},
+      /*12*/ {18.549, 21.026, 23.337, 26.217, 32.910},
+      /*13*/ {19.812, 22.362, 24.736, 27.688, 34.528},
+      /*14*/ {21.064, 23.685, 26.119, 29.141, 36.123},
+      /*15*/ {22.307, 24.996, 27.488, 30.578, 37.697},
+      /*16*/ {23.542, 26.296, 28.845, 32.000, 39.252},
+      /*17*/ {24.769, 27.587, 30.191, 33.409, 40.790},
+      /*18*/ {25.989, 28.869, 31.526, 34.805, 42.312},
+      /*19*/ {27.204, 30.144, 32.852, 36.191, 43.820},
+      /*20*/ {28.412, 31.410, 34.170, 37.566, 45.315},
+      /*21*/ {29.615, 32.671, 35.479, 38.932, 46.797},
+      /*22*/ {30.813, 33.924, 36.781, 40.289, 48.268},
+      /*23*/ {32.007, 35.172, 38.076, 41.638, 49.728},
+      /*24*/ {33.196, 36.415, 39.364, 42.980, 51.179},
+      /*25*/ {34.382, 37.652, 40.646, 44.314, 52.620},
+      /*26*/ {35.563, 38.885, 41.923, 45.642, 54.052},
+      /*27*/ {36.741, 40.113, 43.195, 46.963, 55.476},
+      /*28*/ {37.916, 41.337, 44.461, 48.278, 56.892},
+      /*29*/ {39.087, 42.557, 45.722, 49.588, 58.301},
+      /*30*/ {40.256, 43.773, 46.979, 50.892, 59.703},
+      /*31*/ {41.422, 44.985, 48.232, 52.191, 61.098},
+      /*32*/ {42.585, 46.194, 49.480, 53.486, 62.487},
+      /*33*/ {43.745, 47.400, 50.725, 54.776, 63.870},
+      /*34*/ {44.903, 48.602, 51.966, 56.061, 65.247},
+      /*35*/ {46.059, 49.802, 53.203, 57.342, 66.619},
+      /*36*/ {47.212, 50.998, 54.437, 58.619, 67.985},
+      /*37*/ {48.363, 52.192, 55.668, 59.893, 69.347},
+      /*38*/ {49.513, 53.384, 56.896, 61.162, 70.703},
+      /*39*/ {50.660, 54.572, 58.120, 62.428, 72.055},
+      /*40*/ {51.805, 55.758, 59.342, 63.691, 73.402},
+      /*41*/ {52.949, 56.942, 60.561, 64.950, 74.745},
+      /*42*/ {54.090, 58.124, 61.777, 66.206, 76.084},
+      /*43*/ {55.230, 59.304, 62.990, 67.459, 77.419},
+      /*44*/ {56.369, 60.481, 64.201, 68.710, 78.750},
+      /*45*/ {57.505, 61.656, 65.410, 69.957, 80.077},
+      /*46*/ {58.641, 62.830, 66.617, 71.201, 81.400},
+      /*47*/ {59.774, 64.001, 67.821, 72.443, 82.720},
+      /*48*/ {60.907, 65.171, 69.023, 73.683, 84.037},
+      /*49*/ {62.038, 66.339, 70.222, 74.919, 85.351},
+      /*50*/ {63.167, 67.505, 71.420, 76.154, 86.661},
+      /*51*/ {64.295, 68.669, 72.616, 77.386, 87.968},
+      /*52*/ {65.422, 69.832, 73.810, 78.616, 89.272},
+      /*53*/ {66.548, 70.993, 75.002, 79.843, 90.573},
+      /*54*/ {67.673, 72.153, 76.192, 81.069, 91.872},
+      /*55*/ {68.796, 73.311, 77.380, 82.292, 93.168},
+      /*56*/ {69.919, 74.468, 78.567, 83.513, 94.461},
+      /*57*/ {71.040, 75.624, 79.752, 84.733, 95.751},
+      /*58*/ {72.160, 76.778, 80.936, 85.950, 97.039},
+      /*59*/ {73.279, 77.931, 82.117, 87.166, 98.324},
+      /*60*/ {74.397, 79.082, 83.298, 88.379, 99.607},
+      /*61*/ {75.514, 80.232, 84.476, 89.591, 100.888},
+      /*62*/ {76.630, 81.381, 85.654, 90.802, 102.166},
+      /*63*/ {77.745, 82.529, 86.830, 92.010, 103.442},
+      /*64*/ {78.860, 83.675, 88.004, 93.217, 104.716},
+      /*65*/ {79.973, 84.821, 89.177, 94.422, 105.988},
+      /*66*/ {81.085, 85.965, 90.349, 95.626, 107.258},
+      /*67*/ {82.197, 87.108, 91.519, 96.828, 108.526},
+      /*68*/ {83.308, 88.250, 92.689, 98.028, 109.791},
+      /*69*/ {84.418, 89.391, 93.856, 99.228, 111.055},
+      /*70*/ {85.527, 90.531, 95.023, 100.425, 112.317},
+      /*71*/ {86.635, 91.670, 96.189, 101.621, 113.577},
+      /*72*/ {87.743, 92.808, 97.353, 102.816, 114.835},
+      /*73*/ {88.850, 93.945, 98.516, 104.010, 116.092},
+      /*74*/ {89.956, 95.081, 99.678, 105.202, 117.346},
+      /*75*/ {91.061, 96.217, 100.839, 106.393, 118.599},
+      /*76*/ {92.166, 97.351, 101.999, 107.583, 119.850},
+      /*77*/ {93.270, 98.484, 103.158, 108.771, 121.100},
+      /*78*/ {94.374, 99.617, 104.316, 109.958, 122.348},
+      /*79*/ {95.476, 100.749, 105.473, 111.144, 123.594},
+      /*80*/ {96.578, 101.879, 106.629, 112.329, 124.839},
+      /*81*/ {97.680, 103.010, 107.783, 113.512, 126.083},
+      /*82*/ {98.780, 104.139, 108.937, 114.695, 127.324},
+      /*83*/ {99.880, 105.267, 110.090, 115.876, 128.565},
+      /*84*/ {100.980, 106.395, 111.242, 117.057, 129.804},
+      /*85*/ {102.079, 107.522, 112.393, 118.236, 131.041},
+      /*86*/ {103.177, 108.648, 113.544, 119.414, 132.277},
+      /*87*/ {104.275, 109.773, 114.693, 120.591, 133.512},
+      /*88*/ {105.372, 110.898, 115.841, 121.767, 134.746},
+      /*89*/ {106.469, 112.022, 116.989, 122.942, 135.978},
+      /*90*/ {107.565, 113.145, 118.136, 124.116, 137.208},
+      /*91*/ {108.661, 114.268, 119.282, 125.289, 138.438},
+      /*92*/ {109.756, 115.390, 120.427, 126.462, 139.666},
+      /*93*/ {110.850, 116.511, 121.571, 127.633, 140.893},
+      /*94*/ {111.944, 117.632, 122.715, 128.803, 142.119},
+      /*95*/ {113.038, 118.752, 123.858, 129.973, 143.344},
+      /*96*/ {114.131, 119.871, 125.000, 131.141, 144.567},
+      /*97*/ {115.223, 120.990, 126.141, 132.309, 145.789},
+      /*98*/ {116.315, 122.108, 127.282, 133.476, 147.010},
+      /*99*/ {117.407, 123.225, 128.422, 134.642, 148.230},
+      /*100*/ {118.498, 124.342, 129.561, 135.807, 149.449}
+      /**/};
+
+  //    0.90      0.95     0.975      0.99     0.999
+  for (int i = 0; i < ABSL_ARRAYSIZE(data); i++) {
+    const double E = 0.0001;
+    EXPECT_NEAR(ChiSquarePValue(data[i][0], i + 1), 0.10, E)
+        << i << " " << data[i][0];
+    EXPECT_NEAR(ChiSquarePValue(data[i][1], i + 1), 0.05, E)
+        << i << " " << data[i][1];
+    EXPECT_NEAR(ChiSquarePValue(data[i][2], i + 1), 0.025, E)
+        << i << " " << data[i][2];
+    EXPECT_NEAR(ChiSquarePValue(data[i][3], i + 1), 0.01, E)
+        << i << " " << data[i][3];
+    EXPECT_NEAR(ChiSquarePValue(data[i][4], i + 1), 0.001, E)
+        << i << " " << data[i][4];
+
+    const double F = 0.1;
+    EXPECT_NEAR(ChiSquareValue(i + 1, 0.90), data[i][0], F) << i;
+    EXPECT_NEAR(ChiSquareValue(i + 1, 0.95), data[i][1], F) << i;
+    EXPECT_NEAR(ChiSquareValue(i + 1, 0.975), data[i][2], F) << i;
+    EXPECT_NEAR(ChiSquareValue(i + 1, 0.99), data[i][3], F) << i;
+    EXPECT_NEAR(ChiSquareValue(i + 1, 0.999), data[i][4], F) << i;
+  }
+}
+
+TEST(ChiSquareTest, ChiSquareTwoIterator) {
+  // Test data from http://www.stat.yale.edu/Courses/1997-98/101/chigf.htm
+  // Null-hypothesis: This data is normally distributed.
+  const int counts[10] = {6, 6, 18, 33, 38, 38, 28, 21, 9, 3};
+  const double expected[10] = {4.6,  8.8,  18.4, 30.0, 38.2,
+                               38.2, 30.0, 18.4, 8.8,  4.6};
+  double chi_square = ChiSquare(std::begin(counts), std::end(counts),
+                                std::begin(expected), std::end(expected));
+  EXPECT_NEAR(chi_square, 2.69, 0.001);
+
+  // Degrees of freedom: 10 bins. two estimated parameters. = 10 - 2 - 1.
+  const int dof = 7;
+  // The critical value of 7, 95% => 14.067 (see above test)
+  double p_value_05 = ChiSquarePValue(14.067, dof);
+  EXPECT_NEAR(p_value_05, 0.05, 0.001);  // 95%-ile p-value
+
+  double p_actual = ChiSquarePValue(chi_square, dof);
+  EXPECT_GT(p_actual, 0.05);  // Accept the null hypothesis.
+}
+
+TEST(ChiSquareTest, DiceRolls) {
+  // Assume we are testing 102 fair dice rolls.
+  // Null-hypothesis: This data is fairly distributed.
+  //
+  // The dof value of 4, @95% = 9.488 (see above test)
+  // The dof value of 5, @95% = 11.070
+  const int rolls[6] = {22, 11, 17, 14, 20, 18};
+  double sum = std::accumulate(std::begin(rolls), std::end(rolls), double{0});
+  size_t n = std::distance(std::begin(rolls), std::end(rolls));
+
+  double a = ChiSquareWithExpected(std::begin(rolls), std::end(rolls), sum / n);
+  EXPECT_NEAR(a, 4.70588, 1e-5);
+  EXPECT_LT(a, ChiSquareValue(4, 0.95));
+
+  double p_a = ChiSquarePValue(a, 4);
+  EXPECT_NEAR(p_a, 0.318828, 1e-5);  // Accept the null hypothesis.
+
+  double b = ChiSquareWithExpected(std::begin(rolls), std::end(rolls), 17.0);
+  EXPECT_NEAR(b, 4.70588, 1e-5);
+  EXPECT_LT(b, ChiSquareValue(5, 0.95));
+
+  double p_b = ChiSquarePValue(b, 5);
+  EXPECT_NEAR(p_b, 0.4528180, 1e-5);  // Accept the null hypothesis.
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/distribution_caller.h b/weight/_dep/abseil-cpp/absl/random/internal/distribution_caller.h
new file mode 100644
index 0000000000000000000000000000000000000000..0f162a4e29f3129f934cfb0aa299447ed956c65e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/distribution_caller.h
@@ -0,0 +1,95 @@
+//
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_
+#define ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_
+
+#include <utility>
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/fast_type_id.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// DistributionCaller provides an opportunity to overload the general
+// mechanism for calling a distribution, allowing for mock-RNG classes
+// to intercept such calls.
+template <typename URBG>
+struct DistributionCaller {
+  static_assert(!std::is_pointer<URBG>::value,
+                "You must pass a reference, not a pointer.");
+  // SFINAE to detect whether the URBG type includes a member matching
+  // bool InvokeMock(base_internal::FastTypeIdType, void*, void*).
+  //
+  // These live inside BitGenRef so that they have friend access
+  // to MockingBitGen. (see similar methods in DistributionCaller).
+  template <template <class...> class Trait, class AlwaysVoid, class... Args>
+  struct detector : std::false_type {};
+  template <template <class...> class Trait, class... Args>
+  struct detector<Trait, absl::void_t<Trait<Args...>>, Args...>
+      : std::true_type {};
+
+  template <class T>
+  using invoke_mock_t = decltype(std::declval<T*>()->InvokeMock(
+      std::declval<::absl::base_internal::FastTypeIdType>(),
+      std::declval<void*>(), std::declval<void*>()));
+
+  using HasInvokeMock = typename detector<invoke_mock_t, void, URBG>::type;
+
+  // Default implementation of distribution caller.
+  template <typename DistrT, typename... Args>
+  static typename DistrT::result_type Impl(std::false_type, URBG* urbg,
+                                           Args&&... args) {
+    DistrT dist(std::forward<Args>(args)...);
+    return dist(*urbg);
+  }
+
+  // Mock implementation of distribution caller.
+  // The underlying KeyT must match the KeyT constructed by MockOverloadSet.
+  template <typename DistrT, typename... Args>
+  static typename DistrT::result_type Impl(std::true_type, URBG* urbg,
+                                           Args&&... args) {
+    using ResultT = typename DistrT::result_type;
+    using ArgTupleT = std::tuple<absl::decay_t<Args>...>;
+    using KeyT = ResultT(DistrT, ArgTupleT);
+
+    ArgTupleT arg_tuple(std::forward<Args>(args)...);
+    ResultT result;
+    if (!urbg->InvokeMock(::absl::base_internal::FastTypeId<KeyT>(), &arg_tuple,
+                          &result)) {
+      auto dist = absl::make_from_tuple<DistrT>(arg_tuple);
+      result = dist(*urbg);
+    }
+    return result;
+  }
+
+  // Default implementation of distribution caller.
+  template <typename DistrT, typename... Args>
+  static typename DistrT::result_type Call(URBG* urbg, Args&&... args) {
+    return Impl<DistrT, Args...>(HasInvokeMock{}, urbg,
+                                 std::forward<Args>(args)...);
+  }
+};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util.cc b/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9fa37bd69a03f4158ee3be8eec86bee9bea66f6f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util.cc
@@ -0,0 +1,418 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/distribution_test_util.h"
+
+#include <cassert>
+#include <cmath>
+#include <string>
+#include <vector>
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/macros.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+namespace {
+
+#if defined(__EMSCRIPTEN__)
+// Workaround __EMSCRIPTEN__ error: llvm_fma_f64 not found.
+inline double fma(double x, double y, double z) { return (x * y) + z; }
+#endif
+
+}  // namespace
+
+DistributionMoments ComputeDistributionMoments(
+    absl::Span<const double> data_points) {
+  DistributionMoments result;
+
+  // Compute m1
+  for (double x : data_points) {
+    result.n++;
+    result.mean += x;
+  }
+  result.mean /= static_cast<double>(result.n);
+
+  // Compute m2, m3, m4
+  for (double x : data_points) {
+    double v = x - result.mean;
+    result.variance += v * v;
+    result.skewness += v * v * v;
+    result.kurtosis += v * v * v * v;
+  }
+  result.variance /= static_cast<double>(result.n - 1);
+
+  result.skewness /= static_cast<double>(result.n);
+  result.skewness /= std::pow(result.variance, 1.5);
+
+  result.kurtosis /= static_cast<double>(result.n);
+  result.kurtosis /= std::pow(result.variance, 2.0);
+  return result;
+
+  // When validating the min/max count, the following confidence intervals may
+  // be of use:
+  // 3.291 * stddev = 99.9% CI
+  // 2.576 * stddev = 99% CI
+  // 1.96 * stddev  = 95% CI
+  // 1.65 * stddev  = 90% CI
+}
+
+std::ostream& operator<<(std::ostream& os, const DistributionMoments& moments) {
+  return os << absl::StrFormat("mean=%f, stddev=%f, skewness=%f, kurtosis=%f",
+                               moments.mean, std::sqrt(moments.variance),
+                               moments.skewness, moments.kurtosis);
+}
+
+double InverseNormalSurvival(double x) {
+  // inv_sf(u) = -sqrt(2) * erfinv(2u-1)
+  static constexpr double kSqrt2 = 1.4142135623730950488;
+  return -kSqrt2 * absl::random_internal::erfinv(2 * x - 1.0);
+}
+
+bool Near(absl::string_view msg, double actual, double expected, double bound) {
+  assert(bound > 0.0);
+  double delta = fabs(expected - actual);
+  if (delta < bound) {
+    return true;
+  }
+
+  std::string formatted = absl::StrCat(
+      msg, " actual=", actual, " expected=", expected, " err=", delta / bound);
+  ABSL_RAW_LOG(INFO, "%s", formatted.c_str());
+  return false;
+}
+
+// TODO(absl-team): Replace with an "ABSL_HAVE_SPECIAL_MATH" and try
+// to use std::beta().  As of this writing P0226R1 is not implemented
+// in libc++: http://libcxx.llvm.org/cxx1z_status.html
+double beta(double p, double q) {
+  // Beta(x, y) = Gamma(x) * Gamma(y) / Gamma(x+y)
+  double lbeta = std::lgamma(p) + std::lgamma(q) - std::lgamma(p + q);
+  return std::exp(lbeta);
+}
+
+// Approximation to inverse of the Error Function in double precision.
+// (http://people.maths.ox.ac.uk/gilesm/files/gems_erfinv.pdf)
+double erfinv(double x) {
+#if !defined(__EMSCRIPTEN__)
+  using std::fma;
+#endif
+
+  double w = 0.0;
+  double p = 0.0;
+  w = -std::log((1.0 - x) * (1.0 + x));
+  if (w < 6.250000) {
+    w = w - 3.125000;
+    p = -3.6444120640178196996e-21;
+    p = fma(p, w, -1.685059138182016589e-19);
+    p = fma(p, w, 1.2858480715256400167e-18);
+    p = fma(p, w, 1.115787767802518096e-17);
+    p = fma(p, w, -1.333171662854620906e-16);
+    p = fma(p, w, 2.0972767875968561637e-17);
+    p = fma(p, w, 6.6376381343583238325e-15);
+    p = fma(p, w, -4.0545662729752068639e-14);
+    p = fma(p, w, -8.1519341976054721522e-14);
+    p = fma(p, w, 2.6335093153082322977e-12);
+    p = fma(p, w, -1.2975133253453532498e-11);
+    p = fma(p, w, -5.4154120542946279317e-11);
+    p = fma(p, w, 1.051212273321532285e-09);
+    p = fma(p, w, -4.1126339803469836976e-09);
+    p = fma(p, w, -2.9070369957882005086e-08);
+    p = fma(p, w, 4.2347877827932403518e-07);
+    p = fma(p, w, -1.3654692000834678645e-06);
+    p = fma(p, w, -1.3882523362786468719e-05);
+    p = fma(p, w, 0.0001867342080340571352);
+    p = fma(p, w, -0.00074070253416626697512);
+    p = fma(p, w, -0.0060336708714301490533);
+    p = fma(p, w, 0.24015818242558961693);
+    p = fma(p, w, 1.6536545626831027356);
+  } else if (w < 16.000000) {
+    w = std::sqrt(w) - 3.250000;
+    p = 2.2137376921775787049e-09;
+    p = fma(p, w, 9.0756561938885390979e-08);
+    p = fma(p, w, -2.7517406297064545428e-07);
+    p = fma(p, w, 1.8239629214389227755e-08);
+    p = fma(p, w, 1.5027403968909827627e-06);
+    p = fma(p, w, -4.013867526981545969e-06);
+    p = fma(p, w, 2.9234449089955446044e-06);
+    p = fma(p, w, 1.2475304481671778723e-05);
+    p = fma(p, w, -4.7318229009055733981e-05);
+    p = fma(p, w, 6.8284851459573175448e-05);
+    p = fma(p, w, 2.4031110387097893999e-05);
+    p = fma(p, w, -0.0003550375203628474796);
+    p = fma(p, w, 0.00095328937973738049703);
+    p = fma(p, w, -0.0016882755560235047313);
+    p = fma(p, w, 0.0024914420961078508066);
+    p = fma(p, w, -0.0037512085075692412107);
+    p = fma(p, w, 0.005370914553590063617);
+    p = fma(p, w, 1.0052589676941592334);
+    p = fma(p, w, 3.0838856104922207635);
+  } else {
+    w = std::sqrt(w) - 5.000000;
+    p = -2.7109920616438573243e-11;
+    p = fma(p, w, -2.5556418169965252055e-10);
+    p = fma(p, w, 1.5076572693500548083e-09);
+    p = fma(p, w, -3.7894654401267369937e-09);
+    p = fma(p, w, 7.6157012080783393804e-09);
+    p = fma(p, w, -1.4960026627149240478e-08);
+    p = fma(p, w, 2.9147953450901080826e-08);
+    p = fma(p, w, -6.7711997758452339498e-08);
+    p = fma(p, w, 2.2900482228026654717e-07);
+    p = fma(p, w, -9.9298272942317002539e-07);
+    p = fma(p, w, 4.5260625972231537039e-06);
+    p = fma(p, w, -1.9681778105531670567e-05);
+    p = fma(p, w, 7.5995277030017761139e-05);
+    p = fma(p, w, -0.00021503011930044477347);
+    p = fma(p, w, -0.00013871931833623122026);
+    p = fma(p, w, 1.0103004648645343977);
+    p = fma(p, w, 4.8499064014085844221);
+  }
+  return p * x;
+}
+
+namespace {
+
+// Direct implementation of AS63, BETAIN()
+// https://www.jstor.org/stable/2346797?seq=3#page_scan_tab_contents.
+//
+// BETAIN(x, p, q, beta)
+//  x:     the value of the upper limit x.
+//  p:     the value of the parameter p.
+//  q:     the value of the parameter q.
+//  beta:  the value of ln B(p, q)
+//
+double BetaIncompleteImpl(const double x, const double p, const double q,
+                          const double beta) {
+  if (p < (p + q) * x) {
+    // Incomplete beta function is symmetrical, so return the complement.
+    return 1. - BetaIncompleteImpl(1.0 - x, q, p, beta);
+  }
+
+  double psq = p + q;
+  const double kErr = 1e-14;
+  const double xc = 1. - x;
+  const double pre =
+      std::exp(p * std::log(x) + (q - 1.) * std::log(xc) - beta) / p;
+
+  double term = 1.;
+  double ai = 1.;
+  double result = 1.;
+  int ns = static_cast<int>(q + xc * psq);
+
+  // Use the soper reduction formula.
+  double rx = (ns == 0) ? x : x / xc;
+  double temp = q - ai;
+  for (;;) {
+    term = term * temp * rx / (p + ai);
+    result = result + term;
+    temp = std::fabs(term);
+    if (temp < kErr && temp < kErr * result) {
+      return result * pre;
+    }
+    ai = ai + 1.;
+    --ns;
+    if (ns >= 0) {
+      temp = q - ai;
+      if (ns == 0) {
+        rx = x;
+      }
+    } else {
+      temp = psq;
+      psq = psq + 1.;
+    }
+  }
+
+  // NOTE: See also TOMS Algorithm 708.
+  // http://www.netlib.org/toms/index.html
+  //
+  // NOTE: The NWSC library also includes BRATIO / ISUBX (p87)
+  // https://archive.org/details/DTIC_ADA261511/page/n75
+}
+
+// Direct implementation of AS109, XINBTA(p, q, beta, alpha)
+// https://www.jstor.org/stable/2346798?read-now=1&seq=4#page_scan_tab_contents
+// https://www.jstor.org/stable/2346887?seq=1#page_scan_tab_contents
+//
+// XINBTA(p, q, beta, alpha)
+//  p:     the value of the parameter p.
+//  q:     the value of the parameter q.
+//  beta:  the value of ln B(p, q)
+//  alpha: the value of the lower tail area.
+//
+double BetaIncompleteInvImpl(const double p, const double q, const double beta,
+                             const double alpha) {
+  if (alpha < 0.5) {
+    // Inverse Incomplete beta function is symmetrical, return the complement.
+    return 1. - BetaIncompleteInvImpl(q, p, beta, 1. - alpha);
+  }
+  const double kErr = 1e-14;
+  double value = kErr;
+
+  // Compute the initial estimate.
+  {
+    double r = std::sqrt(-std::log(alpha * alpha));
+    double y =
+        r - fma(r, 0.27061, 2.30753) / fma(r, fma(r, 0.04481, 0.99229), 1.0);
+    if (p > 1. && q > 1.) {
+      r = (y * y - 3.) / 6.;
+      double s = 1. / (p + p - 1.);
+      double t = 1. / (q + q - 1.);
+      double h = 2. / s + t;
+      double w =
+          y * std::sqrt(h + r) / h - (t - s) * (r + 5. / 6. - t / (3. * h));
+      value = p / (p + q * std::exp(w + w));
+    } else {
+      r = q + q;
+      double t = 1.0 / (9. * q);
+      double u = 1.0 - t + y * std::sqrt(t);
+      t = r * (u * u * u);
+      if (t <= 0) {
+        value = 1.0 - std::exp((std::log((1.0 - alpha) * q) + beta) / q);
+      } else {
+        t = (4.0 * p + r - 2.0) / t;
+        if (t <= 1) {
+          value = std::exp((std::log(alpha * p) + beta) / p);
+        } else {
+          value = 1.0 - 2.0 / (t + 1.0);
+        }
+      }
+    }
+  }
+
+  // Solve for x using a modified newton-raphson method using the function
+  // BetaIncomplete.
+  {
+    value = std::max(value, kErr);
+    value = std::min(value, 1.0 - kErr);
+
+    const double r = 1.0 - p;
+    const double t = 1.0 - q;
+    double y;
+    double yprev = 0;
+    double sq = 1;
+    double prev = 1;
+    for (;;) {
+      if (value < 0 || value > 1.0) {
+        // Error case; value went infinite.
+        return std::numeric_limits<double>::infinity();
+      } else if (value == 0 || value == 1) {
+        y = value;
+      } else {
+        y = BetaIncompleteImpl(value, p, q, beta);
+        if (!std::isfinite(y)) {
+          return y;
+        }
+      }
+      y = (y - alpha) *
+          std::exp(beta + r * std::log(value) + t * std::log(1.0 - value));
+      if (y * yprev <= 0) {
+        prev = std::max(sq, std::numeric_limits<double>::min());
+      }
+      double g = 1.0;
+      for (;;) {
+        const double adj = g * y;
+        const double adj_sq = adj * adj;
+        if (adj_sq >= prev) {
+          g = g / 3.0;
+          continue;
+        }
+        const double tx = value - adj;
+        if (tx < 0 || tx > 1) {
+          g = g / 3.0;
+          continue;
+        }
+        if (prev < kErr) {
+          return value;
+        }
+        if (y * y < kErr) {
+          return value;
+        }
+        if (tx == value) {
+          return value;
+        }
+        if (tx == 0 || tx == 1) {
+          g = g / 3.0;
+          continue;
+        }
+        value = tx;
+        yprev = y;
+        break;
+      }
+    }
+  }
+
+  // NOTES: See also: Asymptotic inversion of the incomplete beta function.
+  // https://core.ac.uk/download/pdf/82140723.pdf
+  //
+  // NOTE: See the Boost library documentation as well:
+  // https://www.boost.org/doc/libs/1_52_0/libs/math/doc/sf_and_dist/html/math_toolkit/special/sf_beta/ibeta_function.html
+}
+
+}  // namespace
+
+double BetaIncomplete(const double x, const double p, const double q) {
+  // Error cases.
+  if (p < 0 || q < 0 || x < 0 || x > 1.0) {
+    return std::numeric_limits<double>::infinity();
+  }
+  if (x == 0 || x == 1) {
+    return x;
+  }
+  // ln(Beta(p, q))
+  double beta = std::lgamma(p) + std::lgamma(q) - std::lgamma(p + q);
+  return BetaIncompleteImpl(x, p, q, beta);
+}
+
+double BetaIncompleteInv(const double p, const double q, const double alpha) {
+  // Error cases.
+  if (p < 0 || q < 0 || alpha < 0 || alpha > 1.0) {
+    return std::numeric_limits<double>::infinity();
+  }
+  if (alpha == 0 || alpha == 1) {
+    return alpha;
+  }
+  // ln(Beta(p, q))
+  double beta = std::lgamma(p) + std::lgamma(q) - std::lgamma(p + q);
+  return BetaIncompleteInvImpl(p, q, beta, alpha);
+}
+
+// Given `num_trials` trials each with probability `p` of success, the
+// probability of no failures is `p^k`. To ensure the probability of a failure
+// is no more than `p_fail`, it must be that `p^k == 1 - p_fail`. This function
+// computes `p` from that equation.
+double RequiredSuccessProbability(const double p_fail, const int num_trials) {
+  double p = std::exp(std::log(1.0 - p_fail) / static_cast<double>(num_trials));
+  ABSL_ASSERT(p > 0);
+  return p;
+}
+
+double ZScore(double expected_mean, const DistributionMoments& moments) {
+  return (moments.mean - expected_mean) /
+         (std::sqrt(moments.variance) /
+          std::sqrt(static_cast<double>(moments.n)));
+}
+
+double MaxErrorTolerance(double acceptance_probability) {
+  double one_sided_pvalue = 0.5 * (1.0 - acceptance_probability);
+  const double max_err = InverseNormalSurvival(one_sided_pvalue);
+  ABSL_ASSERT(max_err > 0);
+  return max_err;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util.h b/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..6d94cf6c97bf030102d639f34b2a3fc491b70ef5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util.h
@@ -0,0 +1,113 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_DISTRIBUTION_TEST_UTIL_H_
+#define ABSL_RANDOM_INTERNAL_DISTRIBUTION_TEST_UTIL_H_
+
+#include <cstddef>
+#include <iostream>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/span.h"
+
+// NOTE: The functions in this file are test only, and are should not be used in
+// non-test code.
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// http://webspace.ship.edu/pgmarr/Geo441/Lectures/Lec%205%20-%20Normality%20Testing.pdf
+
+// Compute the 1st to 4th standard moments:
+// mean, variance, skewness, and kurtosis.
+// http://www.itl.nist.gov/div898/handbook/eda/section3/eda35b.htm
+struct DistributionMoments {
+  size_t n = 0;
+  double mean = 0.0;
+  double variance = 0.0;
+  double skewness = 0.0;
+  double kurtosis = 0.0;
+};
+DistributionMoments ComputeDistributionMoments(
+    absl::Span<const double> data_points);
+
+std::ostream& operator<<(std::ostream& os, const DistributionMoments& moments);
+
+// Computes the Z-score for a set of data with the given distribution moments
+// compared against `expected_mean`.
+double ZScore(double expected_mean, const DistributionMoments& moments);
+
+// Returns the probability of success required for a single trial to ensure that
+// after `num_trials` trials, the probability of at least one failure is no more
+// than `p_fail`.
+double RequiredSuccessProbability(double p_fail, int num_trials);
+
+// Computes the maximum distance from the mean tolerable, for Z-Tests that are
+// expected to pass with `acceptance_probability`. Will terminate if the
+// resulting tolerance is zero (due to passing in 0.0 for
+// `acceptance_probability` or rounding errors).
+//
+// For example,
+// MaxErrorTolerance(0.001) = 0.0
+// MaxErrorTolerance(0.5) = ~0.47
+// MaxErrorTolerance(1.0) = inf
+double MaxErrorTolerance(double acceptance_probability);
+
+// Approximation to inverse of the Error Function in double precision.
+// (http://people.maths.ox.ac.uk/gilesm/files/gems_erfinv.pdf)
+double erfinv(double x);
+
+// Beta(p, q) = Gamma(p) * Gamma(q) / Gamma(p+q)
+double beta(double p, double q);
+
+// The inverse of the normal survival function.
+double InverseNormalSurvival(double x);
+
+// Returns whether actual is "near" expected, based on the bound.
+bool Near(absl::string_view msg, double actual, double expected, double bound);
+
+// Implements the incomplete regularized beta function, AS63, BETAIN.
+//    https://www.jstor.org/stable/2346797
+//
+// BetaIncomplete(x, p, q), where
+//   `x` is the value of the upper limit
+//   `p` is beta parameter p, `q` is beta parameter q.
+//
+// NOTE: This is a test-only function which is only accurate to within, at most,
+// 1e-13 of the actual value.
+//
+double BetaIncomplete(double x, double p, double q);
+
+// Implements the inverse of the incomplete regularized beta function, AS109,
+// XINBTA.
+//   https://www.jstor.org/stable/2346798
+//   https://www.jstor.org/stable/2346887
+//
+// BetaIncompleteInv(p, q, beta, alhpa)
+//   `p` is beta parameter p, `q` is beta parameter q.
+//   `alpha` is the value of the lower tail area.
+//
+// NOTE: This is a test-only function and, when successful, is only accurate to
+// within ~1e-6 of the actual value; there are some cases where it diverges from
+// the actual value by much more than that.  The function uses Newton's method,
+// and thus the runtime is highly variable.
+double BetaIncompleteInv(double p, double q, double alpha);
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_DISTRIBUTION_TEST_UTIL_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c49d44fb4796954d8cd47d6c93468836c9c9640a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/distribution_test_util_test.cc
@@ -0,0 +1,193 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/distribution_test_util.h"
+
+#include "gtest/gtest.h"
+
+namespace {
+
+TEST(TestUtil, InverseErf) {
+  const struct {
+    const double z;
+    const double value;
+  } kErfInvTable[] = {
+      {0.0000001, 8.86227e-8},
+      {0.00001, 8.86227e-6},
+      {0.5, 0.4769362762044},
+      {0.6, 0.5951160814499},
+      {0.99999, 3.1234132743},
+      {0.9999999, 3.7665625816},
+      {0.999999944, 3.8403850690566985},  // = log((1-x) * (1+x)) =~ 16.004
+      {0.999999999, 4.3200053849134452},
+  };
+
+  for (const auto& data : kErfInvTable) {
+    auto value = absl::random_internal::erfinv(data.z);
+
+    // Log using the Wolfram-alpha function name & parameters.
+    EXPECT_NEAR(value, data.value, 1e-8)
+        << " InverseErf[" << data.z << "]  (expected=" << data.value << ")  -> "
+        << value;
+  }
+}
+
+const struct {
+  const double p;
+  const double q;
+  const double x;
+  const double alpha;
+} kBetaTable[] = {
+    {0.5, 0.5, 0.01, 0.06376856085851985},
+    {0.5, 0.5, 0.1, 0.2048327646991335},
+    {0.5, 0.5, 1, 1},
+    {1, 0.5, 0, 0},
+    {1, 0.5, 0.01, 0.005012562893380045},
+    {1, 0.5, 0.1, 0.0513167019494862},
+    {1, 0.5, 0.5, 0.2928932188134525},
+    {1, 1, 0.5, 0.5},
+    {2, 2, 0.1, 0.028},
+    {2, 2, 0.2, 0.104},
+    {2, 2, 0.3, 0.216},
+    {2, 2, 0.4, 0.352},
+    {2, 2, 0.5, 0.5},
+    {2, 2, 0.6, 0.648},
+    {2, 2, 0.7, 0.784},
+    {2, 2, 0.8, 0.896},
+    {2, 2, 0.9, 0.972},
+    {5.5, 5, 0.5, 0.4361908850559777},
+    {10, 0.5, 0.9, 0.1516409096346979},
+    {10, 5, 0.5, 0.08978271484375},
+    {10, 5, 1, 1},
+    {10, 10, 0.5, 0.5},
+    {20, 5, 0.8, 0.4598773297575791},
+    {20, 10, 0.6, 0.2146816102371739},
+    {20, 10, 0.8, 0.9507364826957875},
+    {20, 20, 0.5, 0.5},
+    {20, 20, 0.6, 0.8979413687105918},
+    {30, 10, 0.7, 0.2241297491808366},
+    {30, 10, 0.8, 0.7586405487192086},
+    {40, 20, 0.7, 0.7001783247477069},
+    {1, 0.5, 0.1, 0.0513167019494862},
+    {1, 0.5, 0.2, 0.1055728090000841},
+    {1, 0.5, 0.3, 0.1633399734659245},
+    {1, 0.5, 0.4, 0.2254033307585166},
+    {1, 2, 0.2, 0.36},
+    {1, 3, 0.2, 0.488},
+    {1, 4, 0.2, 0.5904},
+    {1, 5, 0.2, 0.67232},
+    {2, 2, 0.3, 0.216},
+    {3, 2, 0.3, 0.0837},
+    {4, 2, 0.3, 0.03078},
+    {5, 2, 0.3, 0.010935},
+
+    // These values test small & large points along the range of the Beta
+    // function.
+    //
+    // When selecting test points, remember that if BetaIncomplete(x, p, q)
+    // returns the same value to within the limits of precision over a large
+    // domain of the input, x, then BetaIncompleteInv(alpha, p, q) may return an
+    // essentially arbitrary value where BetaIncomplete(x, p, q) =~ alpha.
+
+    // BetaRegularized[x, 0.00001, 0.00001],
+    // For x in {~0.001 ... ~0.999}, => ~0.5
+    {1e-5, 1e-5, 1e-5, 0.4999424388184638311},
+    {1e-5, 1e-5, (1.0 - 1e-8), 0.5000920948389232964},
+
+    // BetaRegularized[x, 0.00001, 10000].
+    // For x in {~epsilon ... 1.0}, => ~1
+    {1e-5, 1e5, 1e-6, 0.9999817708130066936},
+    {1e-5, 1e5, (1.0 - 1e-7), 1.0},
+
+    // BetaRegularized[x, 10000, 0.00001].
+    // For x in {0 .. 1-epsilon}, => ~0
+    {1e5, 1e-5, 1e-6, 0},
+    {1e5, 1e-5, (1.0 - 1e-6), 1.8229186993306369e-5},
+};
+
+TEST(BetaTest, BetaIncomplete) {
+  for (const auto& data : kBetaTable) {
+    auto value = absl::random_internal::BetaIncomplete(data.x, data.p, data.q);
+
+    // Log using the Wolfram-alpha function name & parameters.
+    EXPECT_NEAR(value, data.alpha, 1e-12)
+        << " BetaRegularized[" << data.x << ", " << data.p << ", " << data.q
+        << "]  (expected=" << data.alpha << ")  -> " << value;
+  }
+}
+
+TEST(BetaTest, BetaIncompleteInv) {
+  for (const auto& data : kBetaTable) {
+    auto value =
+        absl::random_internal::BetaIncompleteInv(data.p, data.q, data.alpha);
+
+    // Log using the Wolfram-alpha function name & parameters.
+    EXPECT_NEAR(value, data.x, 1e-6)
+        << " InverseBetaRegularized[" << data.alpha << ", " << data.p << ", "
+        << data.q << "]  (expected=" << data.x << ")  -> " << value;
+  }
+}
+
+TEST(MaxErrorTolerance, MaxErrorTolerance) {
+  std::vector<std::pair<double, double>> cases = {
+      {0.0000001, 8.86227e-8 * 1.41421356237},
+      {0.00001, 8.86227e-6 * 1.41421356237},
+      {0.5, 0.4769362762044 * 1.41421356237},
+      {0.6, 0.5951160814499 * 1.41421356237},
+      {0.99999, 3.1234132743 * 1.41421356237},
+      {0.9999999, 3.7665625816 * 1.41421356237},
+      {0.999999944, 3.8403850690566985 * 1.41421356237},
+      {0.999999999, 4.3200053849134452 * 1.41421356237}};
+  for (auto entry : cases) {
+    EXPECT_NEAR(absl::random_internal::MaxErrorTolerance(entry.first),
+                entry.second, 1e-8);
+  }
+}
+
+TEST(ZScore, WithSameMean) {
+  absl::random_internal::DistributionMoments m;
+  m.n = 100;
+  m.mean = 5;
+  m.variance = 1;
+  EXPECT_NEAR(absl::random_internal::ZScore(5, m), 0, 1e-12);
+
+  m.n = 1;
+  m.mean = 0;
+  m.variance = 1;
+  EXPECT_NEAR(absl::random_internal::ZScore(0, m), 0, 1e-12);
+
+  m.n = 10000;
+  m.mean = -5;
+  m.variance = 100;
+  EXPECT_NEAR(absl::random_internal::ZScore(-5, m), 0, 1e-12);
+}
+
+TEST(ZScore, DifferentMean) {
+  absl::random_internal::DistributionMoments m;
+  m.n = 100;
+  m.mean = 5;
+  m.variance = 1;
+  EXPECT_NEAR(absl::random_internal::ZScore(4, m), 10, 1e-12);
+
+  m.n = 1;
+  m.mean = 0;
+  m.variance = 1;
+  EXPECT_NEAR(absl::random_internal::ZScore(-1, m), 1, 1e-12);
+
+  m.n = 10000;
+  m.mean = -5;
+  m.variance = 100;
+  EXPECT_NEAR(absl::random_internal::ZScore(-4, m), -10, 1e-12);
+}
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/explicit_seed_seq.h b/weight/_dep/abseil-cpp/absl/random/internal/explicit_seed_seq.h
new file mode 100644
index 0000000000000000000000000000000000000000..25f791535f81abb118757bd40ab147525e543c5b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/explicit_seed_seq.h
@@ -0,0 +1,92 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_
+#define ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <initializer_list>
+#include <iterator>
+#include <vector>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/endian.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// This class conforms to the C++ Standard "Seed Sequence" concept
+// [rand.req.seedseq].
+//
+// An "ExplicitSeedSeq" is meant to provide a conformant interface for
+// forwarding pre-computed seed material to the constructor of a class
+// conforming to the "Uniform Random Bit Generator" concept. This class makes no
+// attempt to mutate the state provided by its constructor, and returns it
+// directly via ExplicitSeedSeq::generate().
+//
+// If this class is asked to generate more seed material than was provided to
+// the constructor, then the remaining bytes will be filled with deterministic,
+// nonrandom data.
+class ExplicitSeedSeq {
+ public:
+  using result_type = uint32_t;
+
+  ExplicitSeedSeq() : state_() {}
+
+  // Copy and move both allowed.
+  ExplicitSeedSeq(const ExplicitSeedSeq& other) = default;
+  ExplicitSeedSeq& operator=(const ExplicitSeedSeq& other) = default;
+  ExplicitSeedSeq(ExplicitSeedSeq&& other) = default;
+  ExplicitSeedSeq& operator=(ExplicitSeedSeq&& other) = default;
+
+  template <typename Iterator>
+  ExplicitSeedSeq(Iterator begin, Iterator end) {
+    for (auto it = begin; it != end; it++) {
+      state_.push_back(*it & 0xffffffff);
+    }
+  }
+
+  template <typename T>
+  ExplicitSeedSeq(std::initializer_list<T> il)
+      : ExplicitSeedSeq(il.begin(), il.end()) {}
+
+  size_t size() const { return state_.size(); }
+
+  template <typename OutIterator>
+  void param(OutIterator out) const {
+    std::copy(std::begin(state_), std::end(state_), out);
+  }
+
+  template <typename OutIterator>
+  void generate(OutIterator begin, OutIterator end) {
+    for (size_t index = 0; begin != end; begin++) {
+      *begin = state_.empty() ? 0 : state_[index++];
+      if (index >= state_.size()) {
+        index = 0;
+      }
+    }
+  }
+
+ protected:
+  std::vector<uint32_t> state_;
+};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/explicit_seed_seq_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/explicit_seed_seq_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e36d5fa028db9f73ffe60a6ececb39949e1b2250
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/explicit_seed_seq_test.cc
@@ -0,0 +1,237 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/explicit_seed_seq.h"
+
+#include <iterator>
+#include <random>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/random/seed_sequences.h"
+
+namespace {
+
+using ::absl::random_internal::ExplicitSeedSeq;
+
+template <typename Sseq>
+bool ConformsToInterface() {
+  // Check that the SeedSequence can be default-constructed.
+  { Sseq default_constructed_seq; }
+  // Check that the SeedSequence can be constructed with two iterators.
+  {
+    uint32_t init_array[] = {1, 3, 5, 7, 9};
+    Sseq iterator_constructed_seq(init_array, &init_array[5]);
+  }
+  // Check that the SeedSequence can be std::initializer_list-constructed.
+  { Sseq list_constructed_seq = {1, 3, 5, 7, 9, 11, 13}; }
+  // Check that param() and size() return state provided to constructor.
+  {
+    uint32_t init_array[] = {1, 2, 3, 4, 5};
+    Sseq seq(init_array, &init_array[ABSL_ARRAYSIZE(init_array)]);
+    EXPECT_EQ(seq.size(), ABSL_ARRAYSIZE(init_array));
+
+    uint32_t state_array[ABSL_ARRAYSIZE(init_array)];
+    seq.param(state_array);
+
+    for (int i = 0; i < ABSL_ARRAYSIZE(state_array); i++) {
+      EXPECT_EQ(state_array[i], i + 1);
+    }
+  }
+  // Check for presence of generate() method.
+  {
+    Sseq seq;
+    uint32_t seeds[5];
+
+    seq.generate(seeds, &seeds[ABSL_ARRAYSIZE(seeds)]);
+  }
+  return true;
+}
+}  // namespace
+
+TEST(SeedSequences, CheckInterfaces) {
+  // Control case
+  EXPECT_TRUE(ConformsToInterface<std::seed_seq>());
+
+  // Abseil classes
+  EXPECT_TRUE(ConformsToInterface<ExplicitSeedSeq>());
+}
+
+TEST(ExplicitSeedSeq, DefaultConstructorGeneratesZeros) {
+  const size_t kNumBlocks = 128;
+
+  uint32_t outputs[kNumBlocks];
+  ExplicitSeedSeq seq;
+  seq.generate(outputs, &outputs[kNumBlocks]);
+
+  for (uint32_t& seed : outputs) {
+    EXPECT_EQ(seed, 0);
+  }
+}
+
+TEST(ExplicitSeeqSeq, SeedMaterialIsForwardedIdentically) {
+  const size_t kNumBlocks = 128;
+
+  uint32_t seed_material[kNumBlocks];
+  std::random_device urandom{"/dev/urandom"};
+  for (uint32_t& seed : seed_material) {
+    seed = urandom();
+  }
+  ExplicitSeedSeq seq(seed_material, &seed_material[kNumBlocks]);
+
+  // Check that output is same as seed-material provided to constructor.
+  {
+    const size_t kNumGenerated = kNumBlocks / 2;
+    uint32_t outputs[kNumGenerated];
+    seq.generate(outputs, &outputs[kNumGenerated]);
+    for (size_t i = 0; i < kNumGenerated; i++) {
+      EXPECT_EQ(outputs[i], seed_material[i]);
+    }
+  }
+  // Check that SeedSequence is stateless between invocations: Despite the last
+  // invocation of generate() only consuming half of the input-entropy, the same
+  // entropy will be recycled for the next invocation.
+  {
+    const size_t kNumGenerated = kNumBlocks;
+    uint32_t outputs[kNumGenerated];
+    seq.generate(outputs, &outputs[kNumGenerated]);
+    for (size_t i = 0; i < kNumGenerated; i++) {
+      EXPECT_EQ(outputs[i], seed_material[i]);
+    }
+  }
+  // Check that when more seed-material is asked for than is provided, nonzero
+  // values are still written.
+  {
+    const size_t kNumGenerated = kNumBlocks * 2;
+    uint32_t outputs[kNumGenerated];
+    seq.generate(outputs, &outputs[kNumGenerated]);
+    for (size_t i = 0; i < kNumGenerated; i++) {
+      EXPECT_EQ(outputs[i], seed_material[i % kNumBlocks]);
+    }
+  }
+}
+
+TEST(ExplicitSeedSeq, CopyAndMoveConstructors) {
+  using testing::Each;
+  using testing::Eq;
+  using testing::Not;
+  using testing::Pointwise;
+
+  uint32_t entropy[4];
+  std::random_device urandom("/dev/urandom");
+  for (uint32_t& entry : entropy) {
+    entry = urandom();
+  }
+  ExplicitSeedSeq seq_from_entropy(std::begin(entropy), std::end(entropy));
+  // Copy constructor.
+  {
+    ExplicitSeedSeq seq_copy(seq_from_entropy);
+    EXPECT_EQ(seq_copy.size(), seq_from_entropy.size());
+
+    std::vector<uint32_t> seeds_1(1000, 0);
+    std::vector<uint32_t> seeds_2(1000, 1);
+
+    seq_from_entropy.generate(seeds_1.begin(), seeds_1.end());
+    seq_copy.generate(seeds_2.begin(), seeds_2.end());
+
+    EXPECT_THAT(seeds_1, Pointwise(Eq(), seeds_2));
+  }
+  // Assignment operator.
+  {
+    for (uint32_t& entry : entropy) {
+      entry = urandom();
+    }
+    ExplicitSeedSeq another_seq(std::begin(entropy), std::end(entropy));
+
+    std::vector<uint32_t> seeds_1(1000, 0);
+    std::vector<uint32_t> seeds_2(1000, 0);
+
+    seq_from_entropy.generate(seeds_1.begin(), seeds_1.end());
+    another_seq.generate(seeds_2.begin(), seeds_2.end());
+
+    // Assert precondition: Sequences generated by seed-sequences are not equal.
+    EXPECT_THAT(seeds_1, Not(Pointwise(Eq(), seeds_2)));
+
+    // Apply the assignment-operator.
+    // GCC 12 has a false-positive -Wstringop-overflow warning here.
+#if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(12, 0)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstringop-overflow"
+#endif
+    another_seq = seq_from_entropy;
+#if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(12, 0)
+#pragma GCC diagnostic pop
+#endif
+
+    // Re-generate seeds.
+    seq_from_entropy.generate(seeds_1.begin(), seeds_1.end());
+    another_seq.generate(seeds_2.begin(), seeds_2.end());
+
+    // Seeds generated by seed-sequences should now be equal.
+    EXPECT_THAT(seeds_1, Pointwise(Eq(), seeds_2));
+  }
+  // Move constructor.
+  {
+    // Get seeds from seed-sequence constructed from entropy.
+    std::vector<uint32_t> seeds_1(1000, 0);
+    seq_from_entropy.generate(seeds_1.begin(), seeds_1.end());
+
+    // Apply move-constructor move the sequence to another instance.
+    absl::random_internal::ExplicitSeedSeq moved_seq(
+        std::move(seq_from_entropy));
+    std::vector<uint32_t> seeds_2(1000, 1);
+    moved_seq.generate(seeds_2.begin(), seeds_2.end());
+    // Verify that seeds produced by moved-instance are the same as original.
+    EXPECT_THAT(seeds_1, Pointwise(Eq(), seeds_2));
+
+    // Verify that the moved-from instance now behaves like a
+    // default-constructed instance.
+    EXPECT_EQ(seq_from_entropy.size(), 0);
+    seq_from_entropy.generate(seeds_1.begin(), seeds_1.end());
+    EXPECT_THAT(seeds_1, Each(Eq(0)));
+  }
+}
+
+TEST(ExplicitSeedSeq, StdURBGGoldenTests) {
+  // Verify that for std::- URBG instances the results are stable across
+  // platforms (these should have deterministic output).
+  {
+    ExplicitSeedSeq seed_sequence{12, 34, 56};
+    std::minstd_rand rng(seed_sequence);
+
+    std::minstd_rand::result_type values[4] = {rng(), rng(), rng(), rng()};
+    EXPECT_THAT(values,
+                testing::ElementsAre(579252, 43785881, 464353103, 1501811174));
+  }
+
+  {
+    ExplicitSeedSeq seed_sequence{12, 34, 56};
+    std::mt19937 rng(seed_sequence);
+
+    std::mt19937::result_type values[4] = {rng(), rng(), rng(), rng()};
+    EXPECT_THAT(values, testing::ElementsAre(138416803, 151130212, 33817739,
+                                             138416803));
+  }
+
+  {
+    ExplicitSeedSeq seed_sequence{12, 34, 56};
+    std::mt19937_64 rng(seed_sequence);
+
+    std::mt19937_64::result_type values[4] = {rng(), rng(), rng(), rng()};
+    EXPECT_THAT(values,
+                testing::ElementsAre(19738651785169348, 1464811352364190456,
+                                     18054685302720800, 19738651785169348));
+  }
+}
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/fast_uniform_bits.h b/weight/_dep/abseil-cpp/absl/random/internal/fast_uniform_bits.h
new file mode 100644
index 0000000000000000000000000000000000000000..83ee5c0fea532529f7c0fb54dc93349ea1a2261c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/fast_uniform_bits.h
@@ -0,0 +1,271 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_FAST_UNIFORM_BITS_H_
+#define ABSL_RANDOM_INTERNAL_FAST_UNIFORM_BITS_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/meta/type_traits.h"
+#include "absl/random/internal/traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+// Returns true if the input value is zero or a power of two. Useful for
+// determining if the range of output values in a URBG
+template <typename UIntType>
+constexpr bool IsPowerOfTwoOrZero(UIntType n) {
+  return (n == 0) || ((n & (n - 1)) == 0);
+}
+
+// Computes the length of the range of values producible by the URBG, or returns
+// zero if that would encompass the entire range of representable values in
+// URBG::result_type.
+template <typename URBG>
+constexpr typename URBG::result_type RangeSize() {
+  using result_type = typename URBG::result_type;
+  static_assert((URBG::max)() != (URBG::min)(), "URBG range cannot be 0.");
+  return ((URBG::max)() == (std::numeric_limits<result_type>::max)() &&
+          (URBG::min)() == std::numeric_limits<result_type>::lowest())
+             ? result_type{0}
+             : ((URBG::max)() - (URBG::min)() + result_type{1});
+}
+
+// Computes the floor of the log. (i.e., std::floor(std::log2(N));
+template <typename UIntType>
+constexpr UIntType IntegerLog2(UIntType n) {
+  return (n <= 1) ? 0 : 1 + IntegerLog2(n >> 1);
+}
+
+// Returns the number of bits of randomness returned through
+// `PowerOfTwoVariate(urbg)`.
+template <typename URBG>
+constexpr size_t NumBits() {
+  return static_cast<size_t>(
+      RangeSize<URBG>() == 0
+          ? std::numeric_limits<typename URBG::result_type>::digits
+          : IntegerLog2(RangeSize<URBG>()));
+}
+
+// Given a shift value `n`, constructs a mask with exactly the low `n` bits set.
+// If `n == 0`, all bits are set.
+template <typename UIntType>
+constexpr UIntType MaskFromShift(size_t n) {
+  return ((n % std::numeric_limits<UIntType>::digits) == 0)
+             ? ~UIntType{0}
+             : (UIntType{1} << n) - UIntType{1};
+}
+
+// Tags used to dispatch FastUniformBits::generate to the simple or more complex
+// entropy extraction algorithm.
+struct SimplifiedLoopTag {};
+struct RejectionLoopTag {};
+
+// FastUniformBits implements a fast path to acquire uniform independent bits
+// from a type which conforms to the [rand.req.urbg] concept.
+// Parameterized by:
+//  `UIntType`: the result (output) type
+//
+// The std::independent_bits_engine [rand.adapt.ibits] adaptor can be
+// instantiated from an existing generator through a copy or a move. It does
+// not, however, facilitate the production of pseudorandom bits from an un-owned
+// generator that will outlive the std::independent_bits_engine instance.
+template <typename UIntType = uint64_t>
+class FastUniformBits {
+ public:
+  using result_type = UIntType;
+
+  static constexpr result_type(min)() { return 0; }
+  static constexpr result_type(max)() {
+    return (std::numeric_limits<result_type>::max)();
+  }
+
+  template <typename URBG>
+  result_type operator()(URBG& g);  // NOLINT(runtime/references)
+
+ private:
+  static_assert(IsUnsigned<UIntType>::value,
+                "Class-template FastUniformBits<> must be parameterized using "
+                "an unsigned type.");
+
+  // Generate() generates a random value, dispatched on whether
+  // the underlying URBG must use rejection sampling to generate a value,
+  // or whether a simplified loop will suffice.
+  template <typename URBG>
+  result_type Generate(URBG& g,  // NOLINT(runtime/references)
+                       SimplifiedLoopTag);
+
+  template <typename URBG>
+  result_type Generate(URBG& g,  // NOLINT(runtime/references)
+                       RejectionLoopTag);
+};
+
+template <typename UIntType>
+template <typename URBG>
+typename FastUniformBits<UIntType>::result_type
+FastUniformBits<UIntType>::operator()(URBG& g) {  // NOLINT(runtime/references)
+  // kRangeMask is the mask used when sampling variates from the URBG when the
+  // width of the URBG range is not a power of 2.
+  // Y = (2 ^ kRange) - 1
+  static_assert((URBG::max)() > (URBG::min)(),
+                "URBG::max and URBG::min may not be equal.");
+
+  using tag = absl::conditional_t<IsPowerOfTwoOrZero(RangeSize<URBG>()),
+                                  SimplifiedLoopTag, RejectionLoopTag>;
+  return Generate(g, tag{});
+}
+
+template <typename UIntType>
+template <typename URBG>
+typename FastUniformBits<UIntType>::result_type
+FastUniformBits<UIntType>::Generate(URBG& g,  // NOLINT(runtime/references)
+                                    SimplifiedLoopTag) {
+  // The simplified version of FastUniformBits works only on URBGs that have
+  // a range that is a power of 2. In this case we simply loop and shift without
+  // attempting to balance the bits across calls.
+  static_assert(IsPowerOfTwoOrZero(RangeSize<URBG>()),
+                "incorrect Generate tag for URBG instance");
+
+  static constexpr size_t kResultBits =
+      std::numeric_limits<result_type>::digits;
+  static constexpr size_t kUrbgBits = NumBits<URBG>();
+  static constexpr size_t kIters =
+      (kResultBits / kUrbgBits) + (kResultBits % kUrbgBits != 0);
+  static constexpr size_t kShift = (kIters == 1) ? 0 : kUrbgBits;
+  static constexpr auto kMin = (URBG::min)();
+
+  result_type r = static_cast<result_type>(g() - kMin);
+  for (size_t n = 1; n < kIters; ++n) {
+    r = static_cast<result_type>(r << kShift) +
+        static_cast<result_type>(g() - kMin);
+  }
+  return r;
+}
+
+template <typename UIntType>
+template <typename URBG>
+typename FastUniformBits<UIntType>::result_type
+FastUniformBits<UIntType>::Generate(URBG& g,  // NOLINT(runtime/references)
+                                    RejectionLoopTag) {
+  static_assert(!IsPowerOfTwoOrZero(RangeSize<URBG>()),
+                "incorrect Generate tag for URBG instance");
+  using urbg_result_type = typename URBG::result_type;
+
+  // See [rand.adapt.ibits] for more details on the constants calculated below.
+  //
+  // It is preferable to use roughly the same number of bits from each generator
+  // call, however this is only possible when the number of bits provided by the
+  // URBG is a divisor of the number of bits in `result_type`. In all other
+  // cases, the number of bits used cannot always be the same, but it can be
+  // guaranteed to be off by at most 1. Thus we run two loops, one with a
+  // smaller bit-width size (`kSmallWidth`) and one with a larger width size
+  // (satisfying `kLargeWidth == kSmallWidth + 1`). The loops are run
+  // `kSmallIters` and `kLargeIters` times respectively such
+  // that
+  //
+  //    `kResultBits == kSmallIters * kSmallBits
+  //                    + kLargeIters * kLargeBits`
+  //
+  // where `kResultBits` is the total number of bits in `result_type`.
+  //
+  static constexpr size_t kResultBits =
+      std::numeric_limits<result_type>::digits;                      // w
+  static constexpr urbg_result_type kUrbgRange = RangeSize<URBG>();  // R
+  static constexpr size_t kUrbgBits = NumBits<URBG>();               // m
+
+  // compute the initial estimate of the bits used.
+  // [rand.adapt.ibits] 2 (c)
+  static constexpr size_t kA =  // ceil(w/m)
+      (kResultBits / kUrbgBits) + ((kResultBits % kUrbgBits) != 0);  // n'
+
+  static constexpr size_t kABits = kResultBits / kA;  // w0'
+  static constexpr urbg_result_type kARejection =
+      ((kUrbgRange >> kABits) << kABits);  // y0'
+
+  // refine the selection to reduce the rejection frequency.
+  static constexpr size_t kTotalIters =
+      ((kUrbgRange - kARejection) <= (kARejection / kA)) ? kA : (kA + 1);  // n
+
+  // [rand.adapt.ibits] 2 (b)
+  static constexpr size_t kSmallIters =
+      kTotalIters - (kResultBits % kTotalIters);                   // n0
+  static constexpr size_t kSmallBits = kResultBits / kTotalIters;  // w0
+  static constexpr urbg_result_type kSmallRejection =
+      ((kUrbgRange >> kSmallBits) << kSmallBits);  // y0
+
+  static constexpr size_t kLargeBits = kSmallBits + 1;  // w0+1
+  static constexpr urbg_result_type kLargeRejection =
+      ((kUrbgRange >> kLargeBits) << kLargeBits);  // y1
+
+  //
+  // Because `kLargeBits == kSmallBits + 1`, it follows that
+  //
+  //     `kResultBits == kSmallIters * kSmallBits + kLargeIters`
+  //
+  // and therefore
+  //
+  //     `kLargeIters == kTotalWidth % kSmallWidth`
+  //
+  // Intuitively, each iteration with the large width accounts for one unit
+  // of the remainder when `kTotalWidth` is divided by `kSmallWidth`. As
+  // mentioned above, if the URBG width is a divisor of `kTotalWidth`, then
+  // there would be no need for any large iterations (i.e., one loop would
+  // suffice), and indeed, in this case, `kLargeIters` would be zero.
+  static_assert(kResultBits == kSmallIters * kSmallBits +
+                                   (kTotalIters - kSmallIters) * kLargeBits,
+                "Error in looping constant calculations.");
+
+  // The small shift is essentially small bits, but due to the potential
+  // of generating a smaller result_type from a larger urbg type, the actual
+  // shift might be 0.
+  static constexpr size_t kSmallShift = kSmallBits % kResultBits;
+  static constexpr auto kSmallMask =
+      MaskFromShift<urbg_result_type>(kSmallShift);
+  static constexpr size_t kLargeShift = kLargeBits % kResultBits;
+  static constexpr auto kLargeMask =
+      MaskFromShift<urbg_result_type>(kLargeShift);
+
+  static constexpr auto kMin = (URBG::min)();
+
+  result_type s = 0;
+  for (size_t n = 0; n < kSmallIters; ++n) {
+    urbg_result_type v;
+    do {
+      v = g() - kMin;
+    } while (v >= kSmallRejection);
+
+    s = (s << kSmallShift) + static_cast<result_type>(v & kSmallMask);
+  }
+
+  for (size_t n = kSmallIters; n < kTotalIters; ++n) {
+    urbg_result_type v;
+    do {
+      v = g() - kMin;
+    } while (v >= kLargeRejection);
+
+    s = (s << kLargeShift) + static_cast<result_type>(v & kLargeMask);
+  }
+  return s;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_FAST_UNIFORM_BITS_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/fast_uniform_bits_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/fast_uniform_bits_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..34c25206b3b1812e13d7cab426ef3ccd7b6022b4
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/fast_uniform_bits_test.cc
@@ -0,0 +1,336 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/fast_uniform_bits.h"
+
+#include <random>
+
+#include "gtest/gtest.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+namespace {
+
+template <typename IntType>
+class FastUniformBitsTypedTest : public ::testing::Test {};
+
+using IntTypes = ::testing::Types<uint8_t, uint16_t, uint32_t, uint64_t>;
+
+TYPED_TEST_SUITE(FastUniformBitsTypedTest, IntTypes);
+
+TYPED_TEST(FastUniformBitsTypedTest, BasicTest) {
+  using Limits = std::numeric_limits<TypeParam>;
+  using FastBits = FastUniformBits<TypeParam>;
+
+  EXPECT_EQ(0, (FastBits::min)());
+  EXPECT_EQ((Limits::max)(), (FastBits::max)());
+
+  constexpr int kIters = 10000;
+  std::random_device rd;
+  std::mt19937 gen(rd());
+  FastBits fast;
+  for (int i = 0; i < kIters; i++) {
+    const auto v = fast(gen);
+    EXPECT_LE(v, (FastBits::max)());
+    EXPECT_GE(v, (FastBits::min)());
+  }
+}
+
+template <typename UIntType, UIntType Lo, UIntType Hi, UIntType Val = Lo>
+struct FakeUrbg {
+  using result_type = UIntType;
+
+  FakeUrbg() = default;
+  explicit FakeUrbg(bool r) : reject(r) {}
+
+  static constexpr result_type(max)() { return Hi; }
+  static constexpr result_type(min)() { return Lo; }
+  result_type operator()() {
+    // when reject is set, return Hi half the time.
+    return ((++calls % 2) == 1 && reject) ? Hi : Val;
+  }
+
+  bool reject = false;
+  size_t calls = 0;
+};
+
+TEST(FastUniformBitsTest, IsPowerOfTwoOrZero) {
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint8_t{0}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint8_t{1}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint8_t{2}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint8_t{3}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint8_t{4}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint8_t{16}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint8_t{17}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero((std::numeric_limits<uint8_t>::max)()));
+
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint16_t{0}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint16_t{1}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint16_t{2}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint16_t{3}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint16_t{4}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint16_t{16}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint16_t{17}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero((std::numeric_limits<uint16_t>::max)()));
+
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint32_t{0}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint32_t{1}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint32_t{2}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint32_t{3}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint32_t{32}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint32_t{17}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero((std::numeric_limits<uint32_t>::max)()));
+
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint64_t{0}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint64_t{1}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint64_t{2}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint64_t{3}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint64_t{4}));
+  EXPECT_TRUE(IsPowerOfTwoOrZero(uint64_t{64}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero(uint64_t{17}));
+  EXPECT_FALSE(IsPowerOfTwoOrZero((std::numeric_limits<uint64_t>::max)()));
+}
+
+TEST(FastUniformBitsTest, IntegerLog2) {
+  EXPECT_EQ(0, IntegerLog2(uint16_t{0}));
+  EXPECT_EQ(0, IntegerLog2(uint16_t{1}));
+  EXPECT_EQ(1, IntegerLog2(uint16_t{2}));
+  EXPECT_EQ(1, IntegerLog2(uint16_t{3}));
+  EXPECT_EQ(2, IntegerLog2(uint16_t{4}));
+  EXPECT_EQ(2, IntegerLog2(uint16_t{5}));
+  EXPECT_EQ(2, IntegerLog2(uint16_t{7}));
+  EXPECT_EQ(3, IntegerLog2(uint16_t{8}));
+  EXPECT_EQ(63, IntegerLog2((std::numeric_limits<uint64_t>::max)()));
+}
+
+TEST(FastUniformBitsTest, RangeSize) {
+  EXPECT_EQ(2, (RangeSize<FakeUrbg<uint8_t, 0, 1>>()));
+  EXPECT_EQ(3, (RangeSize<FakeUrbg<uint8_t, 0, 2>>()));
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint8_t, 0, 3>>()));
+  //  EXPECT_EQ(0, (RangeSize<FakeUrbg<uint8_t, 2, 2>>()));
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint8_t, 2, 5>>()));
+  EXPECT_EQ(5, (RangeSize<FakeUrbg<uint8_t, 2, 6>>()));
+  EXPECT_EQ(9, (RangeSize<FakeUrbg<uint8_t, 2, 10>>()));
+  EXPECT_EQ(
+      0, (RangeSize<
+             FakeUrbg<uint8_t, 0, (std::numeric_limits<uint8_t>::max)()>>()));
+
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint16_t, 0, 3>>()));
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint16_t, 2, 5>>()));
+  EXPECT_EQ(5, (RangeSize<FakeUrbg<uint16_t, 2, 6>>()));
+  EXPECT_EQ(18, (RangeSize<FakeUrbg<uint16_t, 1000, 1017>>()));
+  EXPECT_EQ(
+      0, (RangeSize<
+             FakeUrbg<uint16_t, 0, (std::numeric_limits<uint16_t>::max)()>>()));
+
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint32_t, 0, 3>>()));
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint32_t, 2, 5>>()));
+  EXPECT_EQ(5, (RangeSize<FakeUrbg<uint32_t, 2, 6>>()));
+  EXPECT_EQ(18, (RangeSize<FakeUrbg<uint32_t, 1000, 1017>>()));
+  EXPECT_EQ(0, (RangeSize<FakeUrbg<uint32_t, 0, 0xffffffff>>()));
+  EXPECT_EQ(0xffffffff, (RangeSize<FakeUrbg<uint32_t, 1, 0xffffffff>>()));
+  EXPECT_EQ(0xfffffffe, (RangeSize<FakeUrbg<uint32_t, 1, 0xfffffffe>>()));
+  EXPECT_EQ(0xfffffffd, (RangeSize<FakeUrbg<uint32_t, 2, 0xfffffffe>>()));
+  EXPECT_EQ(
+      0, (RangeSize<
+             FakeUrbg<uint32_t, 0, (std::numeric_limits<uint32_t>::max)()>>()));
+
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint64_t, 0, 3>>()));
+  EXPECT_EQ(4, (RangeSize<FakeUrbg<uint64_t, 2, 5>>()));
+  EXPECT_EQ(5, (RangeSize<FakeUrbg<uint64_t, 2, 6>>()));
+  EXPECT_EQ(18, (RangeSize<FakeUrbg<uint64_t, 1000, 1017>>()));
+  EXPECT_EQ(0x100000000, (RangeSize<FakeUrbg<uint64_t, 0, 0xffffffff>>()));
+  EXPECT_EQ(0xffffffff, (RangeSize<FakeUrbg<uint64_t, 1, 0xffffffff>>()));
+  EXPECT_EQ(0xfffffffe, (RangeSize<FakeUrbg<uint64_t, 1, 0xfffffffe>>()));
+  EXPECT_EQ(0xfffffffd, (RangeSize<FakeUrbg<uint64_t, 2, 0xfffffffe>>()));
+  EXPECT_EQ(0, (RangeSize<FakeUrbg<uint64_t, 0, 0xffffffffffffffff>>()));
+  EXPECT_EQ(0xffffffffffffffff,
+            (RangeSize<FakeUrbg<uint64_t, 1, 0xffffffffffffffff>>()));
+  EXPECT_EQ(0xfffffffffffffffe,
+            (RangeSize<FakeUrbg<uint64_t, 1, 0xfffffffffffffffe>>()));
+  EXPECT_EQ(0xfffffffffffffffd,
+            (RangeSize<FakeUrbg<uint64_t, 2, 0xfffffffffffffffe>>()));
+  EXPECT_EQ(
+      0, (RangeSize<
+             FakeUrbg<uint64_t, 0, (std::numeric_limits<uint64_t>::max)()>>()));
+}
+
+// The constants need to be chosen so that an infinite rejection loop doesn't
+// happen...
+using Urng1_5bit = FakeUrbg<uint8_t, 0, 2, 0>;  // ~1.5 bits (range 3)
+using Urng4bits = FakeUrbg<uint8_t, 1, 0x10, 2>;
+using Urng22bits = FakeUrbg<uint32_t, 0, 0x3fffff, 0x301020>;
+using Urng31bits = FakeUrbg<uint32_t, 1, 0xfffffffe, 0x60070f03>;  // ~31.9 bits
+using Urng32bits = FakeUrbg<uint32_t, 0, 0xffffffff, 0x74010f01>;
+using Urng33bits =
+    FakeUrbg<uint64_t, 1, 0x1ffffffff, 0x013301033>;  // ~32.9 bits
+using Urng63bits = FakeUrbg<uint64_t, 1, 0xfffffffffffffffe,
+                            0xfedcba9012345678>;  // ~63.9 bits
+using Urng64bits =
+    FakeUrbg<uint64_t, 0, 0xffffffffffffffff, 0x123456780fedcba9>;
+
+TEST(FastUniformBitsTest, OutputsUpTo32Bits) {
+  // Tests that how values are composed; the single-bit deltas should be spread
+  // across each invocation.
+  Urng1_5bit urng1_5;
+  Urng4bits urng4;
+  Urng22bits urng22;
+  Urng31bits urng31;
+  Urng32bits urng32;
+  Urng33bits urng33;
+  Urng63bits urng63;
+  Urng64bits urng64;
+
+  // 8-bit types
+  {
+    FastUniformBits<uint8_t> fast8;
+    EXPECT_EQ(0x0, fast8(urng1_5));
+    EXPECT_EQ(0x11, fast8(urng4));
+    EXPECT_EQ(0x20, fast8(urng22));
+    EXPECT_EQ(0x2, fast8(urng31));
+    EXPECT_EQ(0x1, fast8(urng32));
+    EXPECT_EQ(0x32, fast8(urng33));
+    EXPECT_EQ(0x77, fast8(urng63));
+    EXPECT_EQ(0xa9, fast8(urng64));
+  }
+
+  // 16-bit types
+  {
+    FastUniformBits<uint16_t> fast16;
+    EXPECT_EQ(0x0, fast16(urng1_5));
+    EXPECT_EQ(0x1111, fast16(urng4));
+    EXPECT_EQ(0x1020, fast16(urng22));
+    EXPECT_EQ(0x0f02, fast16(urng31));
+    EXPECT_EQ(0x0f01, fast16(urng32));
+    EXPECT_EQ(0x1032, fast16(urng33));
+    EXPECT_EQ(0x5677, fast16(urng63));
+    EXPECT_EQ(0xcba9, fast16(urng64));
+  }
+
+  // 32-bit types
+  {
+    FastUniformBits<uint32_t> fast32;
+    EXPECT_EQ(0x0, fast32(urng1_5));
+    EXPECT_EQ(0x11111111, fast32(urng4));
+    EXPECT_EQ(0x08301020, fast32(urng22));
+    EXPECT_EQ(0x0f020f02, fast32(urng31));
+    EXPECT_EQ(0x74010f01, fast32(urng32));
+    EXPECT_EQ(0x13301032, fast32(urng33));
+    EXPECT_EQ(0x12345677, fast32(urng63));
+    EXPECT_EQ(0x0fedcba9, fast32(urng64));
+  }
+}
+
+TEST(FastUniformBitsTest, Outputs64Bits) {
+  // Tests that how values are composed; the single-bit deltas should be spread
+  // across each invocation.
+  FastUniformBits<uint64_t> fast64;
+
+  {
+    FakeUrbg<uint8_t, 0, 1, 0> urng0;
+    FakeUrbg<uint8_t, 0, 1, 1> urng1;
+    Urng4bits urng4;
+    Urng22bits urng22;
+    Urng31bits urng31;
+    Urng32bits urng32;
+    Urng33bits urng33;
+    Urng63bits urng63;
+    Urng64bits urng64;
+
+    // somewhat degenerate cases only create a single bit.
+    EXPECT_EQ(0x0, fast64(urng0));
+    EXPECT_EQ(64, urng0.calls);
+    EXPECT_EQ(0xffffffffffffffff, fast64(urng1));
+    EXPECT_EQ(64, urng1.calls);
+
+    // less degenerate cases.
+    EXPECT_EQ(0x1111111111111111, fast64(urng4));
+    EXPECT_EQ(16, urng4.calls);
+    EXPECT_EQ(0x01020c0408301020, fast64(urng22));
+    EXPECT_EQ(3, urng22.calls);
+    EXPECT_EQ(0x387811c3c0870f02, fast64(urng31));
+    EXPECT_EQ(3, urng31.calls);
+    EXPECT_EQ(0x74010f0174010f01, fast64(urng32));
+    EXPECT_EQ(2, urng32.calls);
+    EXPECT_EQ(0x808194040cb01032, fast64(urng33));
+    EXPECT_EQ(3, urng33.calls);
+    EXPECT_EQ(0x1234567712345677, fast64(urng63));
+    EXPECT_EQ(2, urng63.calls);
+    EXPECT_EQ(0x123456780fedcba9, fast64(urng64));
+    EXPECT_EQ(1, urng64.calls);
+  }
+
+  // The 1.5 bit case is somewhat interesting in that the algorithm refinement
+  // causes one extra small sample. Comments here reference the names used in
+  // [rand.adapt.ibits] that correspond to this case.
+  {
+    Urng1_5bit urng1_5;
+
+    // w = 64
+    // R = 3
+    // m = 1
+    // n' = 64
+    // w0' = 1
+    // y0' = 2
+    // n = (1 <= 0) > 64 : 65 = 65
+    // n0 = 65 - (64%65) = 1
+    // n1 = 64
+    // w0 = 0
+    // y0 = 3
+    // w1 = 1
+    // y1 = 2
+    EXPECT_EQ(0x0, fast64(urng1_5));
+    EXPECT_EQ(65, urng1_5.calls);
+  }
+
+  // Validate rejections for non-power-of-2 cases.
+  {
+    Urng1_5bit urng1_5(true);
+    Urng31bits urng31(true);
+    Urng33bits urng33(true);
+    Urng63bits urng63(true);
+
+    // For 1.5 bits, there would be 1+2*64, except the first
+    // value was accepted and shifted off the end.
+    EXPECT_EQ(0, fast64(urng1_5));
+    EXPECT_EQ(128, urng1_5.calls);
+    EXPECT_EQ(0x387811c3c0870f02, fast64(urng31));
+    EXPECT_EQ(6, urng31.calls);
+    EXPECT_EQ(0x808194040cb01032, fast64(urng33));
+    EXPECT_EQ(6, urng33.calls);
+    EXPECT_EQ(0x1234567712345677, fast64(urng63));
+    EXPECT_EQ(4, urng63.calls);
+  }
+}
+
+TEST(FastUniformBitsTest, URBG32bitRegression) {
+  // Validate with deterministic 32-bit std::minstd_rand
+  // to ensure that operator() performs as expected.
+
+  EXPECT_EQ(2147483646, RangeSize<std::minstd_rand>());
+  EXPECT_EQ(30, IntegerLog2(RangeSize<std::minstd_rand>()));
+
+  std::minstd_rand gen(1);
+  FastUniformBits<uint64_t> fast64;
+
+  EXPECT_EQ(0x05e47095f8791f45, fast64(gen));
+  EXPECT_EQ(0x028be17e3c07c122, fast64(gen));
+  EXPECT_EQ(0x55d2847c1626e8c2, fast64(gen));
+}
+
+}  // namespace
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/fastmath.h b/weight/_dep/abseil-cpp/absl/random/internal/fastmath.h
new file mode 100644
index 0000000000000000000000000000000000000000..963b7690f1a9fb3551933935723aff1c682a1803
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/fastmath.h
@@ -0,0 +1,57 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_FASTMATH_H_
+#define ABSL_RANDOM_INTERNAL_FASTMATH_H_
+
+// This file contains fast math functions (bitwise ops as well as some others)
+// which are implementation details of various absl random number distributions.
+
+#include <cassert>
+#include <cmath>
+#include <cstdint>
+
+#include "absl/numeric/bits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// Compute log2(n) using integer operations.
+// While std::log2 is more accurate than std::log(n) / std::log(2), for
+// very large numbers--those close to std::numeric_limits<uint64_t>::max() - 2,
+// for instance--std::log2 rounds up rather than down, which introduces
+// definite skew in the results.
+inline int IntLog2Floor(uint64_t n) {
+  return (n <= 1) ? 0 : (63 - countl_zero(n));
+}
+inline int IntLog2Ceil(uint64_t n) {
+  return (n <= 1) ? 0 : (64 - countl_zero(n - 1));
+}
+
+inline double StirlingLogFactorial(double n) {
+  assert(n >= 1);
+  // Using Stirling's approximation.
+  constexpr double kLog2PI = 1.83787706640934548356;
+  const double logn = std::log(n);
+  const double ninv = 1.0 / static_cast<double>(n);
+  return n * logn - n + 0.5 * (kLog2PI + logn) + (1.0 / 12.0) * ninv -
+         (1.0 / 360.0) * ninv * ninv * ninv;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_FASTMATH_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/fastmath_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/fastmath_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0d6f9dc15772c97ad747d07b2c21989dbf89253a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/fastmath_test.cc
@@ -0,0 +1,97 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/fastmath.h"
+
+#include "gtest/gtest.h"
+
+#if defined(__native_client__) || defined(__EMSCRIPTEN__)
+// NACL has a less accurate implementation of std::log2 than most of
+// the other platforms. For some values which should have integral results,
+// sometimes NACL returns slightly larger values.
+//
+// The MUSL libc used by emscripten also has a similar bug.
+#define ABSL_RANDOM_INACCURATE_LOG2
+#endif
+
+namespace {
+
+TEST(FastMathTest, IntLog2FloorTest) {
+  using absl::random_internal::IntLog2Floor;
+  constexpr uint64_t kZero = 0;
+  EXPECT_EQ(0, IntLog2Floor(0));  // boundary. return 0.
+  EXPECT_EQ(0, IntLog2Floor(1));
+  EXPECT_EQ(1, IntLog2Floor(2));
+  EXPECT_EQ(63, IntLog2Floor(~kZero));
+
+  // A boundary case: Converting 0xffffffffffffffff requires > 53
+  // bits of precision, so the conversion to double rounds up,
+  // and the result of std::log2(x) > IntLog2Floor(x).
+  EXPECT_LT(IntLog2Floor(~kZero), static_cast<int>(std::log2(~kZero)));
+
+  for (int i = 0; i < 64; i++) {
+    const uint64_t i_pow_2 = static_cast<uint64_t>(1) << i;
+    EXPECT_EQ(i, IntLog2Floor(i_pow_2));
+    EXPECT_EQ(i, static_cast<int>(std::log2(i_pow_2)));
+
+    uint64_t y = i_pow_2;
+    for (int j = i - 1; j > 0; --j) {
+      y = y | (i_pow_2 >> j);
+      EXPECT_EQ(i, IntLog2Floor(y));
+    }
+  }
+}
+
+TEST(FastMathTest, IntLog2CeilTest) {
+  using absl::random_internal::IntLog2Ceil;
+  constexpr uint64_t kZero = 0;
+  EXPECT_EQ(0, IntLog2Ceil(0));  // boundary. return 0.
+  EXPECT_EQ(0, IntLog2Ceil(1));
+  EXPECT_EQ(1, IntLog2Ceil(2));
+  EXPECT_EQ(64, IntLog2Ceil(~kZero));
+
+  // A boundary case: Converting 0xffffffffffffffff requires > 53
+  // bits of precision, so the conversion to double rounds up,
+  // and the result of std::log2(x) > IntLog2Floor(x).
+  EXPECT_LE(IntLog2Ceil(~kZero), static_cast<int>(std::log2(~kZero)));
+
+  for (int i = 0; i < 64; i++) {
+    const uint64_t i_pow_2 = static_cast<uint64_t>(1) << i;
+    EXPECT_EQ(i, IntLog2Ceil(i_pow_2));
+#ifndef ABSL_RANDOM_INACCURATE_LOG2
+    EXPECT_EQ(i, static_cast<int>(std::ceil(std::log2(i_pow_2))));
+#endif
+
+    uint64_t y = i_pow_2;
+    for (int j = i - 1; j > 0; --j) {
+      y = y | (i_pow_2 >> j);
+      EXPECT_EQ(i + 1, IntLog2Ceil(y));
+    }
+  }
+}
+
+TEST(FastMathTest, StirlingLogFactorial) {
+  using absl::random_internal::StirlingLogFactorial;
+
+  EXPECT_NEAR(StirlingLogFactorial(1.0), 0, 1e-3);
+  EXPECT_NEAR(StirlingLogFactorial(1.50), 0.284683, 1e-3);
+  EXPECT_NEAR(StirlingLogFactorial(2.0), 0.69314718056, 1e-4);
+
+  for (int i = 2; i < 50; i++) {
+    double d = static_cast<double>(i);
+    EXPECT_NEAR(StirlingLogFactorial(d), std::lgamma(d + 1), 3e-5);
+  }
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/gaussian_distribution_gentables.cc b/weight/_dep/abseil-cpp/absl/random/internal/gaussian_distribution_gentables.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a95333d55f55d0724c9ab0ead2c51ce23ff05c23
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/gaussian_distribution_gentables.cc
@@ -0,0 +1,143 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Generates gaussian_distribution.cc
+//
+// $ blaze run :gaussian_distribution_gentables > gaussian_distribution.cc
+//
+#include "absl/random/gaussian_distribution.h"
+
+#include <cmath>
+#include <cstddef>
+#include <iostream>
+#include <limits>
+#include <string>
+
+#include "absl/base/macros.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+namespace {
+
+template <typename T, size_t N>
+void FormatArrayContents(std::ostream* os, T (&data)[N]) {
+  if (!std::numeric_limits<T>::is_exact) {
+    // Note: T is either an integer or a float.
+    // float requires higher precision to ensure that values are
+    // reproduced exactly.
+    // Trivia: C99 has hexadecimal floating point literals, but C++11 does not.
+    // Using them would remove all concern of precision loss.
+    os->precision(std::numeric_limits<T>::max_digits10 + 2);
+  }
+  *os << "    {";
+  std::string separator = "";
+  for (size_t i = 0; i < N; ++i) {
+    *os << separator << data[i];
+    if ((i + 1) % 3 != 0) {
+      separator = ", ";
+    } else {
+      separator = ",\n     ";
+    }
+  }
+  *os << "}";
+}
+
+}  // namespace
+
+class TableGenerator : public gaussian_distribution_base {
+ public:
+  TableGenerator();
+  void Print(std::ostream* os);
+
+  using gaussian_distribution_base::kMask;
+  using gaussian_distribution_base::kR;
+  using gaussian_distribution_base::kV;
+
+ private:
+  Tables tables_;
+};
+
+// Ziggurat gaussian initialization.  For an explanation of the algorithm, see
+// the Marsaglia paper, "The Ziggurat Method for Generating Random Variables".
+//   http://www.jstatsoft.org/v05/i08/
+//
+// Further details are available in the Doornik paper
+//   https://www.doornik.com/research/ziggurat.pdf
+//
+TableGenerator::TableGenerator() {
+  // The constants here should match the values in gaussian_distribution.h
+  static constexpr int kC = kMask + 1;
+
+  static_assert((ABSL_ARRAYSIZE(tables_.x) == kC + 1),
+                "xArray must be length kMask + 2");
+
+  static_assert((ABSL_ARRAYSIZE(tables_.x) == ABSL_ARRAYSIZE(tables_.f)),
+                "fx and x arrays must be identical length");
+
+  auto f = [](double x) { return std::exp(-0.5 * x * x); };
+  auto f_inv = [](double x) { return std::sqrt(-2.0 * std::log(x)); };
+
+  tables_.x[0] = kV / f(kR);
+  tables_.f[0] = f(tables_.x[0]);
+
+  tables_.x[1] = kR;
+  tables_.f[1] = f(tables_.x[1]);
+
+  tables_.x[kC] = 0.0;
+  tables_.f[kC] = f(tables_.x[kC]);  // 1.0
+
+  for (int i = 2; i < kC; i++) {
+    double v = (kV / tables_.x[i - 1]) + tables_.f[i - 1];
+    tables_.x[i] = f_inv(v);
+    tables_.f[i] = v;
+  }
+}
+
+void TableGenerator::Print(std::ostream* os) {
+  *os << "// BEGIN GENERATED CODE; DO NOT EDIT\n"
+         "// clang-format off\n"
+         "\n"
+         "#include \"absl/random/gaussian_distribution.h\"\n"
+         "\n"
+         "namespace absl {\n"
+         "ABSL_NAMESPACE_BEGIN\n"
+         "namespace random_internal {\n"
+         "\n"
+         "const gaussian_distribution_base::Tables\n"
+         "    gaussian_distribution_base::zg_ = {\n";
+  FormatArrayContents(os, tables_.x);
+  *os << ",\n";
+  FormatArrayContents(os, tables_.f);
+  *os << "};\n"
+         "\n"
+         "}  // namespace random_internal\n"
+         "ABSL_NAMESPACE_END\n"
+         "}  // namespace absl\n"
+         "\n"
+         "// clang-format on\n"
+         "// END GENERATED CODE";
+  *os << std::endl;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+int main(int, char**) {
+  std::cerr << "\nCopy the output to gaussian_distribution.cc" << std::endl;
+  absl::random_internal::TableGenerator generator;
+  generator.Print(&std::cout);
+  return 0;
+}
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/generate_real.h b/weight/_dep/abseil-cpp/absl/random/internal/generate_real.h
new file mode 100644
index 0000000000000000000000000000000000000000..9a6f4005ceda9f41351b63c9021223894c46439f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/generate_real.h
@@ -0,0 +1,144 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_GENERATE_REAL_H_
+#define ABSL_RANDOM_INTERNAL_GENERATE_REAL_H_
+
+// This file contains some implementation details which are used by one or more
+// of the absl random number distributions.
+
+#include <cstdint>
+#include <cstring>
+#include <limits>
+#include <type_traits>
+
+#include "absl/meta/type_traits.h"
+#include "absl/numeric/bits.h"
+#include "absl/random/internal/fastmath.h"
+#include "absl/random/internal/traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// Tristate tag types controlling the output of GenerateRealFromBits.
+struct GeneratePositiveTag {};
+struct GenerateNegativeTag {};
+struct GenerateSignedTag {};
+
+// GenerateRealFromBits generates a single real value from a single 64-bit
+// `bits` with template fields controlling the output.
+//
+// The `SignedTag` parameter controls whether positive, negative,
+// or either signed/unsigned may be returned.
+//   When SignedTag == GeneratePositiveTag, range is U(0, 1)
+//   When SignedTag == GenerateNegativeTag, range is U(-1, 0)
+//   When SignedTag == GenerateSignedTag, range is U(-1, 1)
+//
+// When the `IncludeZero` parameter is true, the function may return 0 for some
+// inputs, otherwise it never returns 0.
+//
+// When a value in U(0,1) is required, use:
+//   GenerateRealFromBits<double, PositiveValueT, true>;
+//
+// When a value in U(-1,1) is required, use:
+//   GenerateRealFromBits<double, SignedValueT, false>;
+//
+//   This generates more distinct values than the mathematical equivalent
+//   `U(0, 1) * 2.0 - 1.0`.
+//
+// Scaling the result by powers of 2 (and avoiding a multiply) is also possible:
+//   GenerateRealFromBits<double>(..., -1);  => U(0, 0.5)
+//   GenerateRealFromBits<double>(..., 1);   => U(0, 2)
+//
+template <typename RealType,  // Real type, either float or double.
+          typename SignedTag = GeneratePositiveTag,  // Whether a positive,
+                                                     // negative, or signed
+                                                     // value is generated.
+          bool IncludeZero = true>
+inline RealType GenerateRealFromBits(uint64_t bits, int exp_bias = 0) {
+  using real_type = RealType;
+  using uint_type = absl::conditional_t<std::is_same<real_type, float>::value,
+                                        uint32_t, uint64_t>;
+
+  static_assert(
+      (std::is_same<double, real_type>::value ||
+       std::is_same<float, real_type>::value),
+      "GenerateRealFromBits must be parameterized by either float or double.");
+
+  static_assert(sizeof(uint_type) == sizeof(real_type),
+                "Mismatched unsigned and real types.");
+
+  static_assert((std::numeric_limits<real_type>::is_iec559 &&
+                 std::numeric_limits<real_type>::radix == 2),
+                "RealType representation is not IEEE 754 binary.");
+
+  static_assert((std::is_same<SignedTag, GeneratePositiveTag>::value ||
+                 std::is_same<SignedTag, GenerateNegativeTag>::value ||
+                 std::is_same<SignedTag, GenerateSignedTag>::value),
+                "");
+
+  static constexpr int kExp = std::numeric_limits<real_type>::digits - 1;
+  static constexpr uint_type kMask = (static_cast<uint_type>(1) << kExp) - 1u;
+  static constexpr int kUintBits = sizeof(uint_type) * 8;
+
+  int exp = exp_bias + int{std::numeric_limits<real_type>::max_exponent - 2};
+
+  // Determine the sign bit.
+  // Depending on the SignedTag, this may use the left-most bit
+  // or it may be a constant value.
+  uint_type sign = std::is_same<SignedTag, GenerateNegativeTag>::value
+                       ? (static_cast<uint_type>(1) << (kUintBits - 1))
+                       : 0;
+  if (std::is_same<SignedTag, GenerateSignedTag>::value) {
+    if (std::is_same<uint_type, uint64_t>::value) {
+      sign = bits & uint64_t{0x8000000000000000};
+    }
+    if (std::is_same<uint_type, uint32_t>::value) {
+      const uint64_t tmp = bits & uint64_t{0x8000000000000000};
+      sign = static_cast<uint32_t>(tmp >> 32);
+    }
+    // adjust the bits and the exponent to account for removing
+    // the leading bit.
+    bits = bits & uint64_t{0x7FFFFFFFFFFFFFFF};
+    exp++;
+  }
+  if (IncludeZero) {
+    if (bits == 0u) return 0;
+  }
+
+  // Number of leading zeros is mapped to the exponent: 2^-clz
+  // bits is 0..01xxxxxx. After shifting, we're left with 1xxx...0..0
+  int clz = countl_zero(bits);
+  bits <<= (IncludeZero ? clz : (clz & 63));  // remove 0-bits.
+  exp -= clz;                                 // set the exponent.
+  bits >>= (63 - kExp);
+
+  // Construct the 32-bit or 64-bit IEEE 754 floating-point value from
+  // the individual fields: sign, exp, mantissa(bits).
+  uint_type val = sign | (static_cast<uint_type>(exp) << kExp) |
+                  (static_cast<uint_type>(bits) & kMask);
+
+  // bit_cast to the output-type
+  real_type result;
+  memcpy(static_cast<void*>(&result), static_cast<const void*>(&val),
+         sizeof(result));
+  return result;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_GENERATE_REAL_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/generate_real_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/generate_real_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b099dbf35fec119feba7169c2e5c25df69733e0a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/generate_real_test.cc
@@ -0,0 +1,496 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/generate_real.h"
+
+#include <cfloat>
+#include <cstddef>
+#include <cstdint>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/flags/flag.h"
+#include "absl/numeric/bits.h"
+
+ABSL_FLAG(int64_t, absl_random_test_trials, 50000,
+          "Number of trials for the probability tests.");
+
+using absl::random_internal::GenerateNegativeTag;
+using absl::random_internal::GeneratePositiveTag;
+using absl::random_internal::GenerateRealFromBits;
+using absl::random_internal::GenerateSignedTag;
+
+namespace {
+
+TEST(GenerateRealTest, U64ToFloat_Positive_NoZero_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GeneratePositiveTag, false>(a);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), 2.710505431e-20f);
+  EXPECT_EQ(ToFloat(0x0000000000000001), 5.421010862e-20f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), 0.5);
+  EXPECT_EQ(ToFloat(0x8000000000000001), 0.5);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), 0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloat_Positive_Zero_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GeneratePositiveTag, true>(a);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), 0.0);
+  EXPECT_EQ(ToFloat(0x0000000000000001), 5.421010862e-20f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), 0.5);
+  EXPECT_EQ(ToFloat(0x8000000000000001), 0.5);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), 0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloat_Negative_NoZero_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GenerateNegativeTag, false>(a);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), -2.710505431e-20f);
+  EXPECT_EQ(ToFloat(0x0000000000000001), -5.421010862e-20f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), -0.5);
+  EXPECT_EQ(ToFloat(0x8000000000000001), -0.5);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), -0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloat_Negative_Zero_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GenerateNegativeTag, true>(a);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), 0.0);
+  EXPECT_EQ(ToFloat(0x0000000000000001), -5.421010862e-20f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), -0.5);
+  EXPECT_EQ(ToFloat(0x8000000000000001), -0.5);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), -0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloat_Signed_NoZero_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GenerateSignedTag, false>(a);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), 5.421010862e-20f);
+  EXPECT_EQ(ToFloat(0x0000000000000001), 1.084202172e-19f);
+  EXPECT_EQ(ToFloat(0x7FFFFFFFFFFFFFFF), 0.9999999404f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), -5.421010862e-20f);
+  EXPECT_EQ(ToFloat(0x8000000000000001), -1.084202172e-19f);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), -0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloat_Signed_Zero_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GenerateSignedTag, true>(a);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), 0);
+  EXPECT_EQ(ToFloat(0x0000000000000001), 1.084202172e-19f);
+  EXPECT_EQ(ToFloat(0x7FFFFFFFFFFFFFFF), 0.9999999404f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), 0);
+  EXPECT_EQ(ToFloat(0x8000000000000001), -1.084202172e-19f);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), -0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloat_Signed_Bias_Test) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GenerateSignedTag, true>(a, 1);
+  };
+  EXPECT_EQ(ToFloat(0x0000000000000000), 0);
+  EXPECT_EQ(ToFloat(0x0000000000000001), 2 * 1.084202172e-19f);
+  EXPECT_EQ(ToFloat(0x7FFFFFFFFFFFFFFF), 2 * 0.9999999404f);
+  EXPECT_EQ(ToFloat(0x8000000000000000), 0);
+  EXPECT_EQ(ToFloat(0x8000000000000001), 2 * -1.084202172e-19f);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), 2 * -0.9999999404f);
+}
+
+TEST(GenerateRealTest, U64ToFloatTest) {
+  auto ToFloat = [](uint64_t a) -> float {
+    return GenerateRealFromBits<float, GeneratePositiveTag, true>(a);
+  };
+
+  EXPECT_EQ(ToFloat(0x0000000000000000), 0.0f);
+
+  EXPECT_EQ(ToFloat(0x8000000000000000), 0.5f);
+  EXPECT_EQ(ToFloat(0x8000000000000001), 0.5f);
+  EXPECT_EQ(ToFloat(0x800000FFFFFFFFFF), 0.5f);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), 0.9999999404f);
+
+  EXPECT_GT(ToFloat(0x0000000000000001), 0.0f);
+
+  EXPECT_NE(ToFloat(0x7FFFFF0000000000), ToFloat(0x7FFFFEFFFFFFFFFF));
+
+  EXPECT_LT(ToFloat(0xFFFFFFFFFFFFFFFF), 1.0f);
+  int32_t two_to_24 = 1 << 24;
+  EXPECT_EQ(static_cast<int32_t>(ToFloat(0xFFFFFFFFFFFFFFFF) * two_to_24),
+            two_to_24 - 1);
+  EXPECT_NE(static_cast<int32_t>(ToFloat(0xFFFFFFFFFFFFFFFF) * two_to_24 * 2),
+            two_to_24 * 2 - 1);
+  EXPECT_EQ(ToFloat(0xFFFFFFFFFFFFFFFF), ToFloat(0xFFFFFF0000000000));
+  EXPECT_NE(ToFloat(0xFFFFFFFFFFFFFFFF), ToFloat(0xFFFFFEFFFFFFFFFF));
+  EXPECT_EQ(ToFloat(0x7FFFFFFFFFFFFFFF), ToFloat(0x7FFFFF8000000000));
+  EXPECT_NE(ToFloat(0x7FFFFFFFFFFFFFFF), ToFloat(0x7FFFFF7FFFFFFFFF));
+  EXPECT_EQ(ToFloat(0x3FFFFFFFFFFFFFFF), ToFloat(0x3FFFFFC000000000));
+  EXPECT_NE(ToFloat(0x3FFFFFFFFFFFFFFF), ToFloat(0x3FFFFFBFFFFFFFFF));
+
+  // For values where every bit counts, the values scale as multiples of the
+  // input.
+  for (int i = 0; i < 100; ++i) {
+    EXPECT_EQ(i * ToFloat(0x0000000000000001), ToFloat(i));
+  }
+
+  // For each i: value generated from (1 << i).
+  float exp_values[64];
+  exp_values[63] = 0.5f;
+  for (int i = 62; i >= 0; --i) exp_values[i] = 0.5f * exp_values[i + 1];
+  constexpr uint64_t one = 1;
+  for (int i = 0; i < 64; ++i) {
+    EXPECT_EQ(ToFloat(one << i), exp_values[i]);
+    for (int j = 1; j < FLT_MANT_DIG && i - j >= 0; ++j) {
+      EXPECT_NE(exp_values[i] + exp_values[i - j], exp_values[i]);
+      EXPECT_EQ(ToFloat((one << i) + (one << (i - j))),
+                exp_values[i] + exp_values[i - j]);
+    }
+    for (int j = FLT_MANT_DIG; i - j >= 0; ++j) {
+      EXPECT_EQ(exp_values[i] + exp_values[i - j], exp_values[i]);
+      EXPECT_EQ(ToFloat((one << i) + (one << (i - j))), exp_values[i]);
+    }
+  }
+}
+
+TEST(GenerateRealTest, U64ToDouble_Positive_NoZero_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GeneratePositiveTag, false>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), 2.710505431213761085e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000001), 5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000002), 1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0x8000000000000000), 0.5);
+  EXPECT_EQ(ToDouble(0x8000000000000001), 0.5);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), 0.999999999999999888978);
+}
+
+TEST(GenerateRealTest, U64ToDouble_Positive_Zero_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GeneratePositiveTag, true>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), 0.0);
+  EXPECT_EQ(ToDouble(0x0000000000000001), 5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x8000000000000000), 0.5);
+  EXPECT_EQ(ToDouble(0x8000000000000001), 0.5);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), 0.999999999999999888978);
+}
+
+TEST(GenerateRealTest, U64ToDouble_Negative_NoZero_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GenerateNegativeTag, false>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), -2.710505431213761085e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000001), -5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000002), -1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0x8000000000000000), -0.5);
+  EXPECT_EQ(ToDouble(0x8000000000000001), -0.5);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), -0.999999999999999888978);
+}
+
+TEST(GenerateRealTest, U64ToDouble_Negative_Zero_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GenerateNegativeTag, true>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), 0.0);
+  EXPECT_EQ(ToDouble(0x0000000000000001), -5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000002), -1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0x8000000000000000), -0.5);
+  EXPECT_EQ(ToDouble(0x8000000000000001), -0.5);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), -0.999999999999999888978);
+}
+
+TEST(GenerateRealTest, U64ToDouble_Signed_NoZero_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GenerateSignedTag, false>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), 5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000001), 1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0x7FFFFFFFFFFFFFFF), 0.999999999999999888978);
+  EXPECT_EQ(ToDouble(0x8000000000000000), -5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x8000000000000001), -1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), -0.999999999999999888978);
+}
+
+TEST(GenerateRealTest, U64ToDouble_Signed_Zero_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GenerateSignedTag, true>(a);
+  };
+  EXPECT_EQ(ToDouble(0x0000000000000000), 0);
+  EXPECT_EQ(ToDouble(0x0000000000000001), 1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0x7FFFFFFFFFFFFFFF), 0.999999999999999888978);
+  EXPECT_EQ(ToDouble(0x8000000000000000), 0);
+  EXPECT_EQ(ToDouble(0x8000000000000001), -1.084202172485504434e-19);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), -0.999999999999999888978);
+}
+
+TEST(GenerateRealTest, U64ToDouble_GenerateSignedTag_Bias_Test) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GenerateSignedTag, true>(a, -1);
+  };
+  EXPECT_EQ(ToDouble(0x0000000000000000), 0);
+  EXPECT_EQ(ToDouble(0x0000000000000001), 1.084202172485504434e-19 / 2);
+  EXPECT_EQ(ToDouble(0x7FFFFFFFFFFFFFFF), 0.999999999999999888978 / 2);
+  EXPECT_EQ(ToDouble(0x8000000000000000), 0);
+  EXPECT_EQ(ToDouble(0x8000000000000001), -1.084202172485504434e-19 / 2);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), -0.999999999999999888978 / 2);
+}
+
+TEST(GenerateRealTest, U64ToDoubleTest) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GeneratePositiveTag, true>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), 0.0);
+  EXPECT_EQ(ToDouble(0x0000000000000000), 0.0);
+
+  EXPECT_EQ(ToDouble(0x0000000000000001), 5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x7fffffffffffffef), 0.499999999999999944489);
+  EXPECT_EQ(ToDouble(0x8000000000000000), 0.5);
+
+  // For values > 0.5, RandU64ToDouble discards up to 11 bits. (64-53).
+  EXPECT_EQ(ToDouble(0x8000000000000001), 0.5);
+  EXPECT_EQ(ToDouble(0x80000000000007FF), 0.5);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), 0.999999999999999888978);
+  EXPECT_NE(ToDouble(0x7FFFFFFFFFFFF800), ToDouble(0x7FFFFFFFFFFFF7FF));
+
+  EXPECT_LT(ToDouble(0xFFFFFFFFFFFFFFFF), 1.0);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFF), ToDouble(0xFFFFFFFFFFFFF800));
+  EXPECT_NE(ToDouble(0xFFFFFFFFFFFFFFFF), ToDouble(0xFFFFFFFFFFFFF7FF));
+  EXPECT_EQ(ToDouble(0x7FFFFFFFFFFFFFFF), ToDouble(0x7FFFFFFFFFFFFC00));
+  EXPECT_NE(ToDouble(0x7FFFFFFFFFFFFFFF), ToDouble(0x7FFFFFFFFFFFFBFF));
+  EXPECT_EQ(ToDouble(0x3FFFFFFFFFFFFFFF), ToDouble(0x3FFFFFFFFFFFFE00));
+  EXPECT_NE(ToDouble(0x3FFFFFFFFFFFFFFF), ToDouble(0x3FFFFFFFFFFFFDFF));
+
+  EXPECT_EQ(ToDouble(0x1000000000000001), 0.0625);
+  EXPECT_EQ(ToDouble(0x2000000000000001), 0.125);
+  EXPECT_EQ(ToDouble(0x3000000000000001), 0.1875);
+  EXPECT_EQ(ToDouble(0x4000000000000001), 0.25);
+  EXPECT_EQ(ToDouble(0x5000000000000001), 0.3125);
+  EXPECT_EQ(ToDouble(0x6000000000000001), 0.375);
+  EXPECT_EQ(ToDouble(0x7000000000000001), 0.4375);
+  EXPECT_EQ(ToDouble(0x8000000000000001), 0.5);
+  EXPECT_EQ(ToDouble(0x9000000000000001), 0.5625);
+  EXPECT_EQ(ToDouble(0xa000000000000001), 0.625);
+  EXPECT_EQ(ToDouble(0xb000000000000001), 0.6875);
+  EXPECT_EQ(ToDouble(0xc000000000000001), 0.75);
+  EXPECT_EQ(ToDouble(0xd000000000000001), 0.8125);
+  EXPECT_EQ(ToDouble(0xe000000000000001), 0.875);
+  EXPECT_EQ(ToDouble(0xf000000000000001), 0.9375);
+
+  // Large powers of 2.
+  int64_t two_to_53 = int64_t{1} << 53;
+  EXPECT_EQ(static_cast<int64_t>(ToDouble(0xFFFFFFFFFFFFFFFF) * two_to_53),
+            two_to_53 - 1);
+  EXPECT_NE(static_cast<int64_t>(ToDouble(0xFFFFFFFFFFFFFFFF) * two_to_53 * 2),
+            two_to_53 * 2 - 1);
+
+  // For values where every bit counts, the values scale as multiples of the
+  // input.
+  for (int i = 0; i < 100; ++i) {
+    EXPECT_EQ(i * ToDouble(0x0000000000000001), ToDouble(i));
+  }
+
+  // For each i: value generated from (1 << i).
+  double exp_values[64];
+  exp_values[63] = 0.5;
+  for (int i = 62; i >= 0; --i) exp_values[i] = 0.5 * exp_values[i + 1];
+  constexpr uint64_t one = 1;
+  for (int i = 0; i < 64; ++i) {
+    EXPECT_EQ(ToDouble(one << i), exp_values[i]);
+    for (int j = 1; j < DBL_MANT_DIG && i - j >= 0; ++j) {
+      EXPECT_NE(exp_values[i] + exp_values[i - j], exp_values[i]);
+      EXPECT_EQ(ToDouble((one << i) + (one << (i - j))),
+                exp_values[i] + exp_values[i - j]);
+    }
+    for (int j = DBL_MANT_DIG; i - j >= 0; ++j) {
+      EXPECT_EQ(exp_values[i] + exp_values[i - j], exp_values[i]);
+      EXPECT_EQ(ToDouble((one << i) + (one << (i - j))), exp_values[i]);
+    }
+  }
+}
+
+TEST(GenerateRealTest, U64ToDoubleSignedTest) {
+  auto ToDouble = [](uint64_t a) {
+    return GenerateRealFromBits<double, GenerateSignedTag, false>(a);
+  };
+
+  EXPECT_EQ(ToDouble(0x0000000000000000), 5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x0000000000000001), 1.084202172485504434e-19);
+
+  EXPECT_EQ(ToDouble(0x8000000000000000), -5.42101086242752217004e-20);
+  EXPECT_EQ(ToDouble(0x8000000000000001), -1.084202172485504434e-19);
+
+  const double e_plus = ToDouble(0x0000000000000001);
+  const double e_minus = ToDouble(0x8000000000000001);
+  EXPECT_EQ(e_plus, 1.084202172485504434e-19);
+  EXPECT_EQ(e_minus, -1.084202172485504434e-19);
+
+  EXPECT_EQ(ToDouble(0x3fffffffffffffef), 0.499999999999999944489);
+  EXPECT_EQ(ToDouble(0xbfffffffffffffef), -0.499999999999999944489);
+
+  // For values > 0.5, RandU64ToDouble discards up to 10 bits. (63-53).
+  EXPECT_EQ(ToDouble(0x4000000000000000), 0.5);
+  EXPECT_EQ(ToDouble(0x4000000000000001), 0.5);
+  EXPECT_EQ(ToDouble(0x40000000000003FF), 0.5);
+
+  EXPECT_EQ(ToDouble(0xC000000000000000), -0.5);
+  EXPECT_EQ(ToDouble(0xC000000000000001), -0.5);
+  EXPECT_EQ(ToDouble(0xC0000000000003FF), -0.5);
+
+  EXPECT_EQ(ToDouble(0x7FFFFFFFFFFFFFFe), 0.999999999999999888978);
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFe), -0.999999999999999888978);
+
+  EXPECT_NE(ToDouble(0x7FFFFFFFFFFFF800), ToDouble(0x7FFFFFFFFFFFF7FF));
+
+  EXPECT_LT(ToDouble(0x7FFFFFFFFFFFFFFF), 1.0);
+  EXPECT_GT(ToDouble(0x7FFFFFFFFFFFFFFF), 0.9999999999);
+
+  EXPECT_GT(ToDouble(0xFFFFFFFFFFFFFFFe), -1.0);
+  EXPECT_LT(ToDouble(0xFFFFFFFFFFFFFFFe), -0.999999999);
+
+  EXPECT_EQ(ToDouble(0xFFFFFFFFFFFFFFFe), ToDouble(0xFFFFFFFFFFFFFC00));
+  EXPECT_EQ(ToDouble(0x7FFFFFFFFFFFFFFF), ToDouble(0x7FFFFFFFFFFFFC00));
+  EXPECT_NE(ToDouble(0xFFFFFFFFFFFFFFFe), ToDouble(0xFFFFFFFFFFFFF3FF));
+  EXPECT_NE(ToDouble(0x7FFFFFFFFFFFFFFF), ToDouble(0x7FFFFFFFFFFFF3FF));
+
+  EXPECT_EQ(ToDouble(0x1000000000000001), 0.125);
+  EXPECT_EQ(ToDouble(0x2000000000000001), 0.25);
+  EXPECT_EQ(ToDouble(0x3000000000000001), 0.375);
+  EXPECT_EQ(ToDouble(0x4000000000000001), 0.5);
+  EXPECT_EQ(ToDouble(0x5000000000000001), 0.625);
+  EXPECT_EQ(ToDouble(0x6000000000000001), 0.75);
+  EXPECT_EQ(ToDouble(0x7000000000000001), 0.875);
+  EXPECT_EQ(ToDouble(0x7800000000000001), 0.9375);
+  EXPECT_EQ(ToDouble(0x7c00000000000001), 0.96875);
+  EXPECT_EQ(ToDouble(0x7e00000000000001), 0.984375);
+  EXPECT_EQ(ToDouble(0x7f00000000000001), 0.9921875);
+
+  // 0x8000000000000000 ~= 0
+  EXPECT_EQ(ToDouble(0x9000000000000001), -0.125);
+  EXPECT_EQ(ToDouble(0xa000000000000001), -0.25);
+  EXPECT_EQ(ToDouble(0xb000000000000001), -0.375);
+  EXPECT_EQ(ToDouble(0xc000000000000001), -0.5);
+  EXPECT_EQ(ToDouble(0xd000000000000001), -0.625);
+  EXPECT_EQ(ToDouble(0xe000000000000001), -0.75);
+  EXPECT_EQ(ToDouble(0xf000000000000001), -0.875);
+
+  // Large powers of 2.
+  int64_t two_to_53 = int64_t{1} << 53;
+  EXPECT_EQ(static_cast<int64_t>(ToDouble(0x7FFFFFFFFFFFFFFF) * two_to_53),
+            two_to_53 - 1);
+  EXPECT_EQ(static_cast<int64_t>(ToDouble(0xFFFFFFFFFFFFFFFF) * two_to_53),
+            -(two_to_53 - 1));
+
+  EXPECT_NE(static_cast<int64_t>(ToDouble(0x7FFFFFFFFFFFFFFF) * two_to_53 * 2),
+            two_to_53 * 2 - 1);
+
+  // For values where every bit counts, the values scale as multiples of the
+  // input.
+  for (int i = 1; i < 100; ++i) {
+    EXPECT_EQ(i * e_plus, ToDouble(i)) << i;
+    EXPECT_EQ(i * e_minus, ToDouble(0x8000000000000000 | i)) << i;
+  }
+}
+
+TEST(GenerateRealTest, ExhaustiveFloat) {
+  auto ToFloat = [](uint64_t a) {
+    return GenerateRealFromBits<float, GeneratePositiveTag, true>(a);
+  };
+
+  // Rely on RandU64ToFloat generating values from greatest to least when
+  // supplied with uint64_t values from greatest (0xfff...) to least (0x0).
+  // Thus, this algorithm stores the previous value, and if the new value is at
+  // greater than or equal to the previous value, then there is a collision in
+  // the generation algorithm.
+  //
+  // Use the computation below to convert the random value into a result:
+  //   double res = a() * (1.0f - sample) + b() * sample;
+  float last_f = 1.0, last_g = 2.0;
+  uint64_t f_collisions = 0, g_collisions = 0;
+  uint64_t f_unique = 0, g_unique = 0;
+  uint64_t total = 0;
+  auto count = [&](const float r) {
+    total++;
+    // `f` is mapped to the range [0, 1) (default)
+    const float f = 0.0f * (1.0f - r) + 1.0f * r;
+    if (f >= last_f) {
+      f_collisions++;
+    } else {
+      f_unique++;
+      last_f = f;
+    }
+    // `g` is mapped to the range [1, 2)
+    const float g = 1.0f * (1.0f - r) + 2.0f * r;
+    if (g >= last_g) {
+      g_collisions++;
+    } else {
+      g_unique++;
+      last_g = g;
+    }
+  };
+
+  size_t limit = absl::GetFlag(FLAGS_absl_random_test_trials);
+
+  // Generate all uint64_t which have unique floating point values.
+  // Counting down from 0xFFFFFFFFFFFFFFFFu ... 0x0u
+  uint64_t x = ~uint64_t(0);
+  for (; x != 0 && limit > 0;) {
+    constexpr int kDig = (64 - FLT_MANT_DIG);
+    // Set a decrement value & the next point at which to change
+    // the decrement value. By default these are 1, 0.
+    uint64_t dec = 1;
+    uint64_t chk = 0;
+
+    // Adjust decrement and check value based on how many leading 0
+    // bits are set in the current value.
+    const int clz = absl::countl_zero(x);
+    if (clz < kDig) {
+      dec <<= (kDig - clz);
+      chk = (~uint64_t(0)) >> (clz + 1);
+    }
+    for (; x > chk && limit > 0; x -= dec) {
+      count(ToFloat(x));
+      --limit;
+    }
+  }
+
+  static_assert(FLT_MANT_DIG == 24,
+                "The float type is expected to have a 24 bit mantissa.");
+
+  if (limit != 0) {
+    // There are between 2^28 and 2^29 unique values in the range [0, 1).  For
+    // the low values of x, there are 2^24 -1 unique values.  Once x > 2^24,
+    // there are 40 * 2^24 unique values. Thus:
+    // (2 + 4 + 8 ... + 2^23) + 40 * 2^23
+    EXPECT_LT(1 << 28, f_unique);
+    EXPECT_EQ((1 << 24) + 40 * (1 << 23) - 1, f_unique);
+    EXPECT_EQ(total, f_unique);
+    EXPECT_EQ(0, f_collisions);
+
+    // Expect at least 2^23 unique values for the range [1, 2)
+    EXPECT_LE(1 << 23, g_unique);
+    EXPECT_EQ(total - g_unique, g_collisions);
+  }
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/iostream_state_saver.h b/weight/_dep/abseil-cpp/absl/random/internal/iostream_state_saver.h
new file mode 100644
index 0000000000000000000000000000000000000000..e6e242ee1e669afff1532941918fbfc5642a7302
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/iostream_state_saver.h
@@ -0,0 +1,245 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_
+#define ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_
+
+#include <cmath>
+#include <iostream>
+#include <limits>
+#include <type_traits>
+
+#include "absl/meta/type_traits.h"
+#include "absl/numeric/int128.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// The null_state_saver does nothing.
+template <typename T>
+class null_state_saver {
+ public:
+  using stream_type = T;
+  using flags_type = std::ios_base::fmtflags;
+
+  null_state_saver(T&, flags_type) {}
+  ~null_state_saver() {}
+};
+
+// ostream_state_saver is a RAII object to save and restore the common
+// basic_ostream flags used when implementing `operator <<()` on any of
+// the absl random distributions.
+template <typename OStream>
+class ostream_state_saver {
+ public:
+  using ostream_type = OStream;
+  using flags_type = std::ios_base::fmtflags;
+  using fill_type = typename ostream_type::char_type;
+  using precision_type = std::streamsize;
+
+  ostream_state_saver(ostream_type& os,  // NOLINT(runtime/references)
+                      flags_type flags, fill_type fill)
+      : os_(os),
+        flags_(os.flags(flags)),
+        fill_(os.fill(fill)),
+        precision_(os.precision()) {
+    // Save state in initialized variables.
+  }
+
+  ~ostream_state_saver() {
+    // Restore saved state.
+    os_.precision(precision_);
+    os_.fill(fill_);
+    os_.flags(flags_);
+  }
+
+ private:
+  ostream_type& os_;
+  const flags_type flags_;
+  const fill_type fill_;
+  const precision_type precision_;
+};
+
+#if defined(__NDK_MAJOR__) && __NDK_MAJOR__ < 16
+#define ABSL_RANDOM_INTERNAL_IOSTREAM_HEXFLOAT 1
+#else
+#define ABSL_RANDOM_INTERNAL_IOSTREAM_HEXFLOAT 0
+#endif
+
+template <typename CharT, typename Traits>
+ostream_state_saver<std::basic_ostream<CharT, Traits>> make_ostream_state_saver(
+    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+    std::ios_base::fmtflags flags = std::ios_base::dec | std::ios_base::left |
+#if ABSL_RANDOM_INTERNAL_IOSTREAM_HEXFLOAT
+                                    std::ios_base::fixed |
+#endif
+                                    std::ios_base::scientific) {
+  using result_type = ostream_state_saver<std::basic_ostream<CharT, Traits>>;
+  return result_type(os, flags, os.widen(' '));
+}
+
+template <typename T>
+typename absl::enable_if_t<!std::is_base_of<std::ios_base, T>::value,
+                           null_state_saver<T>>
+make_ostream_state_saver(T& is,  // NOLINT(runtime/references)
+                         std::ios_base::fmtflags flags = std::ios_base::dec) {
+  std::cerr << "null_state_saver";
+  using result_type = null_state_saver<T>;
+  return result_type(is, flags);
+}
+
+// stream_precision_helper<type>::kPrecision returns the base 10 precision
+// required to stream and reconstruct a real type exact binary value through
+// a binary->decimal->binary transition.
+template <typename T>
+struct stream_precision_helper {
+  // max_digits10 may be 0 on MSVC; if so, use digits10 + 3.
+  static constexpr int kPrecision =
+      (std::numeric_limits<T>::max_digits10 > std::numeric_limits<T>::digits10)
+          ? std::numeric_limits<T>::max_digits10
+          : (std::numeric_limits<T>::digits10 + 3);
+};
+
+template <>
+struct stream_precision_helper<float> {
+  static constexpr int kPrecision = 9;
+};
+template <>
+struct stream_precision_helper<double> {
+  static constexpr int kPrecision = 17;
+};
+template <>
+struct stream_precision_helper<long double> {
+  static constexpr int kPrecision = 36;  // assuming fp128
+};
+
+// istream_state_saver is a RAII object to save and restore the common
+// std::basic_istream<> flags used when implementing `operator >>()` on any of
+// the absl random distributions.
+template <typename IStream>
+class istream_state_saver {
+ public:
+  using istream_type = IStream;
+  using flags_type = std::ios_base::fmtflags;
+
+  istream_state_saver(istream_type& is,  // NOLINT(runtime/references)
+                      flags_type flags)
+      : is_(is), flags_(is.flags(flags)) {}
+
+  ~istream_state_saver() { is_.flags(flags_); }
+
+ private:
+  istream_type& is_;
+  flags_type flags_;
+};
+
+template <typename CharT, typename Traits>
+istream_state_saver<std::basic_istream<CharT, Traits>> make_istream_state_saver(
+    std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+    std::ios_base::fmtflags flags = std::ios_base::dec |
+                                    std::ios_base::scientific |
+                                    std::ios_base::skipws) {
+  using result_type = istream_state_saver<std::basic_istream<CharT, Traits>>;
+  return result_type(is, flags);
+}
+
+template <typename T>
+typename absl::enable_if_t<!std::is_base_of<std::ios_base, T>::value,
+                           null_state_saver<T>>
+make_istream_state_saver(T& is,  // NOLINT(runtime/references)
+                         std::ios_base::fmtflags flags = std::ios_base::dec) {
+  using result_type = null_state_saver<T>;
+  return result_type(is, flags);
+}
+
+// stream_format_type<T> is a helper struct to convert types which
+// basic_iostream cannot output as decimal numbers into types which
+// basic_iostream can output as decimal numbers. Specifically:
+// * signed/unsigned char-width types are converted to int.
+// * TODO(lar): __int128 => uint128, except there is no operator << yet.
+//
+template <typename T>
+struct stream_format_type
+    : public std::conditional<(sizeof(T) == sizeof(char)), int, T> {};
+
+// stream_u128_helper allows us to write out either absl::uint128 or
+// __uint128_t types in the same way, which enables their use as internal
+// state of PRNG engines.
+template <typename T>
+struct stream_u128_helper;
+
+template <>
+struct stream_u128_helper<absl::uint128> {
+  template <typename IStream>
+  inline absl::uint128 read(IStream& in) {
+    uint64_t h = 0;
+    uint64_t l = 0;
+    in >> h >> l;
+    return absl::MakeUint128(h, l);
+  }
+
+  template <typename OStream>
+  inline void write(absl::uint128 val, OStream& out) {
+    uint64_t h = absl::Uint128High64(val);
+    uint64_t l = absl::Uint128Low64(val);
+    out << h << out.fill() << l;
+  }
+};
+
+#ifdef ABSL_HAVE_INTRINSIC_INT128
+template <>
+struct stream_u128_helper<__uint128_t> {
+  template <typename IStream>
+  inline __uint128_t read(IStream& in) {
+    uint64_t h = 0;
+    uint64_t l = 0;
+    in >> h >> l;
+    return (static_cast<__uint128_t>(h) << 64) | l;
+  }
+
+  template <typename OStream>
+  inline void write(__uint128_t val, OStream& out) {
+    uint64_t h = static_cast<uint64_t>(val >> 64u);
+    uint64_t l = static_cast<uint64_t>(val);
+    out << h << out.fill() << l;
+  }
+};
+#endif
+
+template <typename FloatType, typename IStream>
+inline FloatType read_floating_point(IStream& is) {
+  static_assert(std::is_floating_point<FloatType>::value, "");
+  FloatType dest;
+  is >> dest;
+  // Parsing a double value may report a subnormal value as an error
+  // despite being able to represent it.
+  // See https://stackoverflow.com/q/52410931/3286653
+  // It may also report an underflow when parsing DOUBLE_MIN as an
+  // ERANGE error, as the parsed value may be smaller than DOUBLE_MIN
+  // and rounded up.
+  // See: https://stackoverflow.com/q/42005462
+  if (is.fail() &&
+      (std::fabs(dest) == (std::numeric_limits<FloatType>::min)() ||
+       std::fpclassify(dest) == FP_SUBNORMAL)) {
+    is.clear(is.rdstate() & (~std::ios_base::failbit));
+  }
+  return dest;
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_IOSTREAM_STATE_SAVER_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/iostream_state_saver_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/iostream_state_saver_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ea9d2af05cbab7c6f53e53803fafa49d16d71292
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/iostream_state_saver_test.cc
@@ -0,0 +1,373 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/iostream_state_saver.h"
+
+#include <errno.h>
+#include <stdio.h>
+
+#include <sstream>
+#include <string>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+using absl::random_internal::make_istream_state_saver;
+using absl::random_internal::make_ostream_state_saver;
+using absl::random_internal::stream_precision_helper;
+
+template <typename T>
+typename absl::enable_if_t<std::is_integral<T>::value, T>  //
+StreamRoundTrip(T t) {
+  std::stringstream ss;
+  {
+    auto saver = make_ostream_state_saver(ss);
+    ss.precision(stream_precision_helper<T>::kPrecision);
+    ss << t;
+  }
+  T result = 0;
+  {
+    auto saver = make_istream_state_saver(ss);
+    ss >> result;
+  }
+  EXPECT_FALSE(ss.fail())            //
+      << ss.str() << " "             //
+      << (ss.good() ? "good " : "")  //
+      << (ss.bad() ? "bad " : "")    //
+      << (ss.eof() ? "eof " : "")    //
+      << (ss.fail() ? "fail " : "");
+
+  return result;
+}
+
+template <typename T>
+typename absl::enable_if_t<std::is_floating_point<T>::value, T>  //
+StreamRoundTrip(T t) {
+  std::stringstream ss;
+  {
+    auto saver = make_ostream_state_saver(ss);
+    ss.precision(stream_precision_helper<T>::kPrecision);
+    ss << t;
+  }
+  T result = 0;
+  {
+    auto saver = make_istream_state_saver(ss);
+    result = absl::random_internal::read_floating_point<T>(ss);
+  }
+  EXPECT_FALSE(ss.fail())            //
+      << ss.str() << " "             //
+      << (ss.good() ? "good " : "")  //
+      << (ss.bad() ? "bad " : "")    //
+      << (ss.eof() ? "eof " : "")    //
+      << (ss.fail() ? "fail " : "");
+
+  return result;
+}
+
+TEST(IOStreamStateSaver, BasicSaverState) {
+  std::stringstream ss;
+  ss.precision(2);
+  ss.fill('x');
+  ss.flags(std::ios_base::dec | std::ios_base::right);
+
+  {
+    auto saver = make_ostream_state_saver(ss);
+    ss.precision(10);
+    EXPECT_NE('x', ss.fill());
+    EXPECT_EQ(10, ss.precision());
+    EXPECT_NE(std::ios_base::dec | std::ios_base::right, ss.flags());
+
+    ss << 1.23;
+  }
+
+  EXPECT_EQ('x', ss.fill());
+  EXPECT_EQ(2, ss.precision());
+  EXPECT_EQ(std::ios_base::dec | std::ios_base::right, ss.flags());
+}
+
+TEST(IOStreamStateSaver, RoundTripInts) {
+  const uint64_t kUintValues[] = {
+      0,
+      1,
+      static_cast<uint64_t>(-1),
+      2,
+      static_cast<uint64_t>(-2),
+
+      1 << 7,
+      1 << 8,
+      1 << 16,
+      1ull << 32,
+      1ull << 50,
+      1ull << 62,
+      1ull << 63,
+
+      (1 << 7) - 1,
+      (1 << 8) - 1,
+      (1 << 16) - 1,
+      (1ull << 32) - 1,
+      (1ull << 50) - 1,
+      (1ull << 62) - 1,
+      (1ull << 63) - 1,
+
+      static_cast<uint64_t>(-(1 << 8)),
+      static_cast<uint64_t>(-(1 << 16)),
+      static_cast<uint64_t>(-(1ll << 32)),
+      static_cast<uint64_t>(-(1ll << 50)),
+      static_cast<uint64_t>(-(1ll << 62)),
+
+      static_cast<uint64_t>(-(1 << 8) - 1),
+      static_cast<uint64_t>(-(1 << 16) - 1),
+      static_cast<uint64_t>(-(1ll << 32) - 1),
+      static_cast<uint64_t>(-(1ll << 50) - 1),
+      static_cast<uint64_t>(-(1ll << 62) - 1),
+  };
+
+  for (const uint64_t u : kUintValues) {
+    EXPECT_EQ(u, StreamRoundTrip<uint64_t>(u));
+
+    int64_t x = static_cast<int64_t>(u);
+    EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
+
+    double d = static_cast<double>(x);
+    EXPECT_EQ(d, StreamRoundTrip<double>(d));
+
+    float f = d;
+    EXPECT_EQ(f, StreamRoundTrip<float>(f));
+  }
+}
+
+TEST(IOStreamStateSaver, RoundTripFloats) {
+  static_assert(
+      stream_precision_helper<float>::kPrecision >= 9,
+      "stream_precision_helper<float>::kPrecision should be at least 9");
+
+  const float kValues[] = {
+      1,
+      std::nextafter(1.0f, 0.0f),  // 1 - epsilon
+      std::nextafter(1.0f, 2.0f),  // 1 + epsilon
+
+      1.0e+1f,
+      1.0e-1f,
+      1.0e+2f,
+      1.0e-2f,
+      1.0e+10f,
+      1.0e-10f,
+
+      0.00000051110000111311111111f,
+      -0.00000051110000111211111111f,
+
+      1.234678912345678912345e+6f,
+      1.234678912345678912345e-6f,
+      1.234678912345678912345e+30f,
+      1.234678912345678912345e-30f,
+      1.234678912345678912345e+38f,
+      1.0234678912345678912345e-38f,
+
+      // Boundary cases.
+      std::numeric_limits<float>::max(),
+      std::numeric_limits<float>::lowest(),
+      std::numeric_limits<float>::epsilon(),
+      std::nextafter(std::numeric_limits<float>::min(),
+                     1.0f),               // min + epsilon
+      std::numeric_limits<float>::min(),  // smallest normal
+      // There are some errors dealing with denorms on apple platforms.
+      std::numeric_limits<float>::denorm_min(),  // smallest denorm
+      std::numeric_limits<float>::min() / 2,
+      std::nextafter(std::numeric_limits<float>::min(),
+                     0.0f),  // denorm_max
+      std::nextafter(std::numeric_limits<float>::denorm_min(), 1.0f),
+  };
+
+  for (const float f : kValues) {
+    EXPECT_EQ(f, StreamRoundTrip<float>(f));
+    EXPECT_EQ(-f, StreamRoundTrip<float>(-f));
+
+    double d = f;
+    EXPECT_EQ(d, StreamRoundTrip<double>(d));
+    EXPECT_EQ(-d, StreamRoundTrip<double>(-d));
+
+    // Avoid undefined behavior (overflow/underflow).
+    if (f <= static_cast<float>(std::numeric_limits<int64_t>::max()) &&
+        f >= static_cast<float>(std::numeric_limits<int64_t>::lowest())) {
+      int64_t x = static_cast<int64_t>(f);
+      EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
+    }
+  }
+}
+
+TEST(IOStreamStateSaver, RoundTripDoubles) {
+  static_assert(
+      stream_precision_helper<double>::kPrecision >= 17,
+      "stream_precision_helper<double>::kPrecision should be at least 17");
+
+  const double kValues[] = {
+      1,
+      std::nextafter(1.0, 0.0),  // 1 - epsilon
+      std::nextafter(1.0, 2.0),  // 1 + epsilon
+
+      1.0e+1,
+      1.0e-1,
+      1.0e+2,
+      1.0e-2,
+      1.0e+10,
+      1.0e-10,
+
+      0.00000051110000111311111111,
+      -0.00000051110000111211111111,
+
+      1.234678912345678912345e+6,
+      1.234678912345678912345e-6,
+      1.234678912345678912345e+30,
+      1.234678912345678912345e-30,
+      1.234678912345678912345e+38,
+      1.0234678912345678912345e-38,
+
+      1.0e+100,
+      1.0e-100,
+      1.234678912345678912345e+308,
+      1.0234678912345678912345e-308,
+      2.22507385850720138e-308,
+
+      // Boundary cases.
+      std::numeric_limits<double>::max(),
+      std::numeric_limits<double>::lowest(),
+      std::numeric_limits<double>::epsilon(),
+      std::nextafter(std::numeric_limits<double>::min(),
+                     1.0),                 // min + epsilon
+      std::numeric_limits<double>::min(),  // smallest normal
+      // There are some errors dealing with denorms on apple platforms.
+      std::numeric_limits<double>::denorm_min(),  // smallest denorm
+      std::numeric_limits<double>::min() / 2,
+      std::nextafter(std::numeric_limits<double>::min(),
+                     0.0),  // denorm_max
+      std::nextafter(std::numeric_limits<double>::denorm_min(), 1.0f),
+  };
+
+  for (const double d : kValues) {
+    EXPECT_EQ(d, StreamRoundTrip<double>(d));
+    EXPECT_EQ(-d, StreamRoundTrip<double>(-d));
+
+    // Avoid undefined behavior (overflow/underflow).
+    if (d <= std::numeric_limits<float>::max() &&
+        d >= std::numeric_limits<float>::lowest()) {
+      float f = static_cast<float>(d);
+      EXPECT_EQ(f, StreamRoundTrip<float>(f));
+    }
+
+    // Avoid undefined behavior (overflow/underflow).
+    if (d <= static_cast<double>(std::numeric_limits<int64_t>::max()) &&
+        d >= static_cast<double>(std::numeric_limits<int64_t>::lowest())) {
+      int64_t x = static_cast<int64_t>(d);
+      EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
+    }
+  }
+}
+
+TEST(IOStreamStateSaver, RoundTripLongDoubles) {
+  // Technically, C++ only guarantees that long double is at least as large as a
+  // double.  Practically it varies from 64-bits to 128-bits.
+  //
+  // So it is best to consider long double a best-effort extended precision
+  // type.
+
+  static_assert(
+      stream_precision_helper<long double>::kPrecision >= 36,
+      "stream_precision_helper<long double>::kPrecision should be at least 36");
+
+  using real_type = long double;
+  const real_type kValues[] = {
+      1,
+      std::nextafter(1.0, 0.0),  // 1 - epsilon
+      std::nextafter(1.0, 2.0),  // 1 + epsilon
+
+      1.0e+1,
+      1.0e-1,
+      1.0e+2,
+      1.0e-2,
+      1.0e+10,
+      1.0e-10,
+
+      0.00000051110000111311111111,
+      -0.00000051110000111211111111,
+
+      1.2346789123456789123456789123456789e+6,
+      1.2346789123456789123456789123456789e-6,
+      1.2346789123456789123456789123456789e+30,
+      1.2346789123456789123456789123456789e-30,
+      1.2346789123456789123456789123456789e+38,
+      1.2346789123456789123456789123456789e-38,
+      1.2346789123456789123456789123456789e+308,
+      1.2346789123456789123456789123456789e-308,
+
+      1.0e+100,
+      1.0e-100,
+      1.234678912345678912345e+308,
+      1.0234678912345678912345e-308,
+
+      // Boundary cases.
+      std::numeric_limits<real_type>::max(),
+      std::numeric_limits<real_type>::lowest(),
+      std::numeric_limits<real_type>::epsilon(),
+      std::nextafter(std::numeric_limits<real_type>::min(),
+                     real_type(1)),           // min + epsilon
+      std::numeric_limits<real_type>::min(),  // smallest normal
+      // There are some errors dealing with denorms on apple platforms.
+      std::numeric_limits<real_type>::denorm_min(),  // smallest denorm
+      std::numeric_limits<real_type>::min() / 2,
+      std::nextafter(std::numeric_limits<real_type>::min(),
+                     0.0),  // denorm_max
+      std::nextafter(std::numeric_limits<real_type>::denorm_min(), 1.0f),
+  };
+
+  int index = -1;
+  for (const long double dd : kValues) {
+    index++;
+    EXPECT_EQ(dd, StreamRoundTrip<real_type>(dd)) << index;
+    EXPECT_EQ(-dd, StreamRoundTrip<real_type>(-dd)) << index;
+
+    // Avoid undefined behavior (overflow/underflow).
+    if (dd <= std::numeric_limits<double>::max() &&
+        dd >= std::numeric_limits<double>::lowest()) {
+      double d = static_cast<double>(dd);
+      EXPECT_EQ(d, StreamRoundTrip<double>(d));
+    }
+
+    // Avoid undefined behavior (overflow/underflow).
+    if (dd <= static_cast<long double>(std::numeric_limits<int64_t>::max()) &&
+        dd >=
+            static_cast<long double>(std::numeric_limits<int64_t>::lowest())) {
+      int64_t x = static_cast<int64_t>(dd);
+      EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
+    }
+  }
+}
+
+TEST(StrToDTest, DoubleMin) {
+  const char kV[] = "2.22507385850720138e-308";
+  char* end;
+  double x = std::strtod(kV, &end);
+  EXPECT_EQ(std::numeric_limits<double>::min(), x);
+  // errno may equal ERANGE.
+}
+
+TEST(StrToDTest, DoubleDenormMin) {
+  const char kV[] = "4.94065645841246544e-324";
+  char* end;
+  double x = std::strtod(kV, &end);
+  EXPECT_EQ(std::numeric_limits<double>::denorm_min(), x);
+  // errno may equal ERANGE.
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/mock_helpers.h b/weight/_dep/abseil-cpp/absl/random/internal/mock_helpers.h
new file mode 100644
index 0000000000000000000000000000000000000000..a7a97bfc390646277bb83f028eeed8ed824251b1
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/mock_helpers.h
@@ -0,0 +1,135 @@
+//
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_MOCK_HELPERS_H_
+#define ABSL_RANDOM_INTERNAL_MOCK_HELPERS_H_
+
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/internal/fast_type_id.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// MockHelpers works in conjunction with MockOverloadSet, MockingBitGen, and
+// BitGenRef to enable the mocking capability for absl distribution functions.
+//
+// MockingBitGen registers mocks based on the typeid of a mock signature, KeyT,
+// which is used to generate a unique id.
+//
+// KeyT is a signature of the form:
+//   result_type(discriminator_type, std::tuple<args...>)
+// The mocked function signature will be composed from KeyT as:
+//   result_type(args...)
+//
+class MockHelpers {
+  using IdType = ::absl::base_internal::FastTypeIdType;
+
+  // Given a key signature type used to index the mock, extract the components.
+  // KeyT is expected to have the form:
+  //   result_type(discriminator_type, arg_tuple_type)
+  template <typename KeyT>
+  struct KeySignature;
+
+  template <typename ResultT, typename DiscriminatorT, typename ArgTupleT>
+  struct KeySignature<ResultT(DiscriminatorT, ArgTupleT)> {
+    using result_type = ResultT;
+    using discriminator_type = DiscriminatorT;
+    using arg_tuple_type = ArgTupleT;
+  };
+
+  // Detector for InvokeMock.
+  template <class T>
+  using invoke_mock_t = decltype(std::declval<T*>()->InvokeMock(
+      std::declval<IdType>(), std::declval<void*>(), std::declval<void*>()));
+
+  // Empty implementation of InvokeMock.
+  template <typename KeyT, typename ReturnT, typename ArgTupleT, typename URBG,
+            typename... Args>
+  static absl::optional<ReturnT> InvokeMockImpl(char, URBG*, Args&&...) {
+    return absl::nullopt;
+  }
+
+  // Non-empty implementation of InvokeMock.
+  template <typename KeyT, typename ReturnT, typename ArgTupleT, typename URBG,
+            typename = invoke_mock_t<URBG>, typename... Args>
+  static absl::optional<ReturnT> InvokeMockImpl(int, URBG* urbg,
+                                                Args&&... args) {
+    ArgTupleT arg_tuple(std::forward<Args>(args)...);
+    ReturnT result;
+    if (urbg->InvokeMock(::absl::base_internal::FastTypeId<KeyT>(), &arg_tuple,
+                         &result)) {
+      return result;
+    }
+    return absl::nullopt;
+  }
+
+ public:
+  // InvokeMock is private; this provides access for some specialized use cases.
+  template <typename URBG>
+  static inline bool PrivateInvokeMock(URBG* urbg, IdType type,
+                                       void* args_tuple, void* result) {
+    return urbg->InvokeMock(type, args_tuple, result);
+  }
+
+  // Invoke a mock for the KeyT (may or may not be a signature).
+  //
+  // KeyT is used to generate a typeid-based lookup key for the mock.
+  // KeyT is a signature of the form:
+  //   result_type(discriminator_type, std::tuple<args...>)
+  // The mocked function signature will be composed from KeyT as:
+  //   result_type(args...)
+  //
+  // An instance of arg_tuple_type must be constructable from Args..., since
+  // the underlying mechanism requires a pointer to an argument tuple.
+  template <typename KeyT, typename URBG, typename... Args>
+  static auto MaybeInvokeMock(URBG* urbg, Args&&... args)
+      -> absl::optional<typename KeySignature<KeyT>::result_type> {
+    // Use function overloading to dispatch to the implementation since
+    // more modern patterns (e.g. require + constexpr) are not supported in all
+    // compiler configurations.
+    return InvokeMockImpl<KeyT, typename KeySignature<KeyT>::result_type,
+                          typename KeySignature<KeyT>::arg_tuple_type, URBG>(
+        0, urbg, std::forward<Args>(args)...);
+  }
+
+  // Acquire a mock for the KeyT (may or may not be a signature).
+  //
+  // KeyT is used to generate a typeid-based lookup for the mock.
+  // KeyT is a signature of the form:
+  //   result_type(discriminator_type, std::tuple<args...>)
+  // The mocked function signature will be composed from KeyT as:
+  //   result_type(args...)
+  template <typename KeyT, typename MockURBG>
+  static auto MockFor(MockURBG& m)
+      -> decltype(m.template RegisterMock<
+                  typename KeySignature<KeyT>::result_type,
+                  typename KeySignature<KeyT>::arg_tuple_type>(
+          m, std::declval<IdType>())) {
+    return m.template RegisterMock<typename KeySignature<KeyT>::result_type,
+                                   typename KeySignature<KeyT>::arg_tuple_type>(
+        m, ::absl::base_internal::FastTypeId<KeyT>());
+  }
+};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_MOCK_HELPERS_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/nanobenchmark.cc b/weight/_dep/abseil-cpp/absl/random/internal/nanobenchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0f31a7d5d2d13b5dc2a4472b709a92e2fd3b97cd
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/nanobenchmark.cc
@@ -0,0 +1,804 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/nanobenchmark.h"
+
+#include <sys/types.h>
+
+#include <algorithm>  // sort
+#include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>  // memcpy
+#include <limits>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/base/attributes.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/random/internal/platform.h"
+#include "absl/random/internal/randen_engine.h"
+
+// OS
+#if defined(_WIN32) || defined(_WIN64)
+#define ABSL_OS_WIN
+#include <windows.h>  // NOLINT
+
+#elif defined(__ANDROID__)
+#define ABSL_OS_ANDROID
+
+#elif defined(__linux__)
+#define ABSL_OS_LINUX
+#include <sched.h>        // NOLINT
+#include <sys/syscall.h>  // NOLINT
+#endif
+
+#if defined(ABSL_ARCH_X86_64) && !defined(ABSL_OS_WIN)
+#include <cpuid.h>  // NOLINT
+#endif
+
+// __ppc_get_timebase_freq
+#if defined(ABSL_ARCH_PPC)
+#include <sys/platform/ppc.h>  // NOLINT
+#endif
+
+// clock_gettime
+#if defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
+#include <time.h>  // NOLINT
+#endif
+
+// ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE prevents inlining of the method.
+#if ABSL_HAVE_ATTRIBUTE(noinline) || (defined(__GNUC__) && !defined(__clang__))
+#define ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE __attribute__((noinline))
+#elif defined(_MSC_VER)
+#define ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE __declspec(noinline)
+#else
+#define ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal_nanobenchmark {
+namespace {
+
+// For code folding.
+namespace platform {
+#if defined(ABSL_ARCH_X86_64)
+
+// TODO(janwas): Merge with the one in randen_hwaes.cc?
+void Cpuid(const uint32_t level, const uint32_t count,
+           uint32_t* ABSL_RANDOM_INTERNAL_RESTRICT abcd) {
+#if defined(ABSL_OS_WIN)
+  int regs[4];
+  __cpuidex(regs, level, count);
+  for (int i = 0; i < 4; ++i) {
+    abcd[i] = regs[i];
+  }
+#else
+  uint32_t a, b, c, d;
+  __cpuid_count(level, count, a, b, c, d);
+  abcd[0] = a;
+  abcd[1] = b;
+  abcd[2] = c;
+  abcd[3] = d;
+#endif
+}
+
+std::string BrandString() {
+  char brand_string[49];
+  uint32_t abcd[4];
+
+  // Check if brand string is supported (it is on all reasonable Intel/AMD)
+  Cpuid(0x80000000U, 0, abcd);
+  if (abcd[0] < 0x80000004U) {
+    return std::string();
+  }
+
+  for (int i = 0; i < 3; ++i) {
+    Cpuid(0x80000002U + i, 0, abcd);
+    memcpy(brand_string + i * 16, &abcd, sizeof(abcd));
+  }
+  brand_string[48] = 0;
+  return brand_string;
+}
+
+// Returns the frequency quoted inside the brand string. This does not
+// account for throttling nor Turbo Boost.
+double NominalClockRate() {
+  const std::string& brand_string = BrandString();
+  // Brand strings include the maximum configured frequency. These prefixes are
+  // defined by Intel CPUID documentation.
+  const char* prefixes[3] = {"MHz", "GHz", "THz"};
+  const double multipliers[3] = {1E6, 1E9, 1E12};
+  for (size_t i = 0; i < 3; ++i) {
+    const size_t pos_prefix = brand_string.find(prefixes[i]);
+    if (pos_prefix != std::string::npos) {
+      const size_t pos_space = brand_string.rfind(' ', pos_prefix - 1);
+      if (pos_space != std::string::npos) {
+        const std::string digits =
+            brand_string.substr(pos_space + 1, pos_prefix - pos_space - 1);
+        return std::stod(digits) * multipliers[i];
+      }
+    }
+  }
+
+  return 0.0;
+}
+
+#endif  // ABSL_ARCH_X86_64
+}  // namespace platform
+
+// Prevents the compiler from eliding the computations that led to "output".
+template <class T>
+inline void PreventElision(T&& output) {
+#ifndef ABSL_OS_WIN
+  // Works by indicating to the compiler that "output" is being read and
+  // modified. The +r constraint avoids unnecessary writes to memory, but only
+  // works for built-in types (typically FuncOutput).
+  asm volatile("" : "+r"(output) : : "memory");
+#else
+  // MSVC does not support inline assembly anymore (and never supported GCC's
+  // RTL constraints). Self-assignment with #pragma optimize("off") might be
+  // expected to prevent elision, but it does not with MSVC 2015. Type-punning
+  // with volatile pointers generates inefficient code on MSVC 2017.
+  static std::atomic<T> dummy(T{});
+  dummy.store(output, std::memory_order_relaxed);
+#endif
+}
+
+namespace timer {
+
+// Start/Stop return absolute timestamps and must be placed immediately before
+// and after the region to measure. We provide separate Start/Stop functions
+// because they use different fences.
+//
+// Background: RDTSC is not 'serializing'; earlier instructions may complete
+// after it, and/or later instructions may complete before it. 'Fences' ensure
+// regions' elapsed times are independent of such reordering. The only
+// documented unprivileged serializing instruction is CPUID, which acts as a
+// full fence (no reordering across it in either direction). Unfortunately
+// the latency of CPUID varies wildly (perhaps made worse by not initializing
+// its EAX input). Because it cannot reliably be deducted from the region's
+// elapsed time, it must not be included in the region to measure (i.e.
+// between the two RDTSC).
+//
+// The newer RDTSCP is sometimes described as serializing, but it actually
+// only serves as a half-fence with release semantics. Although all
+// instructions in the region will complete before the final timestamp is
+// captured, subsequent instructions may leak into the region and increase the
+// elapsed time. Inserting another fence after the final RDTSCP would prevent
+// such reordering without affecting the measured region.
+//
+// Fortunately, such a fence exists. The LFENCE instruction is only documented
+// to delay later loads until earlier loads are visible. However, Intel's
+// reference manual says it acts as a full fence (waiting until all earlier
+// instructions have completed, and delaying later instructions until it
+// completes). AMD assigns the same behavior to MFENCE.
+//
+// We need a fence before the initial RDTSC to prevent earlier instructions
+// from leaking into the region, and arguably another after RDTSC to avoid
+// region instructions from completing before the timestamp is recorded.
+// When surrounded by fences, the additional RDTSCP half-fence provides no
+// benefit, so the initial timestamp can be recorded via RDTSC, which has
+// lower overhead than RDTSCP because it does not read TSC_AUX. In summary,
+// we define Start = LFENCE/RDTSC/LFENCE; Stop = RDTSCP/LFENCE.
+//
+// Using Start+Start leads to higher variance and overhead than Stop+Stop.
+// However, Stop+Stop includes an LFENCE in the region measurements, which
+// adds a delay dependent on earlier loads. The combination of Start+Stop
+// is faster than Start+Start and more consistent than Stop+Stop because
+// the first LFENCE already delayed subsequent loads before the measured
+// region. This combination seems not to have been considered in prior work:
+// http://akaros.cs.berkeley.edu/lxr/akaros/kern/arch/x86/rdtsc_test.c
+//
+// Note: performance counters can measure 'exact' instructions-retired or
+// (unhalted) cycle counts. The RDPMC instruction is not serializing and also
+// requires fences. Unfortunately, it is not accessible on all OSes and we
+// prefer to avoid kernel-mode drivers. Performance counters are also affected
+// by several under/over-count errata, so we use the TSC instead.
+
+// Returns a 64-bit timestamp in unit of 'ticks'; to convert to seconds,
+// divide by InvariantTicksPerSecond.
+inline uint64_t Start64() {
+  uint64_t t;
+#if defined(ABSL_ARCH_PPC)
+  asm volatile("mfspr %0, %1" : "=r"(t) : "i"(268));
+#elif defined(ABSL_ARCH_X86_64)
+#if defined(ABSL_OS_WIN)
+  _ReadWriteBarrier();
+  _mm_lfence();
+  _ReadWriteBarrier();
+  t = __rdtsc();
+  _ReadWriteBarrier();
+  _mm_lfence();
+  _ReadWriteBarrier();
+#else
+  asm volatile(
+      "lfence\n\t"
+      "rdtsc\n\t"
+      "shl $32, %%rdx\n\t"
+      "or %%rdx, %0\n\t"
+      "lfence"
+      : "=a"(t)
+      :
+      // "memory" avoids reordering. rdx = TSC >> 32.
+      // "cc" = flags modified by SHL.
+      : "rdx", "memory", "cc");
+#endif
+#else
+  // Fall back to OS - unsure how to reliably query cntvct_el0 frequency.
+  timespec ts;
+  clock_gettime(CLOCK_REALTIME, &ts);
+  t = ts.tv_sec * 1000000000LL + ts.tv_nsec;
+#endif
+  return t;
+}
+
+inline uint64_t Stop64() {
+  uint64_t t;
+#if defined(ABSL_ARCH_X86_64)
+#if defined(ABSL_OS_WIN)
+  _ReadWriteBarrier();
+  unsigned aux;
+  t = __rdtscp(&aux);
+  _ReadWriteBarrier();
+  _mm_lfence();
+  _ReadWriteBarrier();
+#else
+  // Use inline asm because __rdtscp generates code to store TSC_AUX (ecx).
+  asm volatile(
+      "rdtscp\n\t"
+      "shl $32, %%rdx\n\t"
+      "or %%rdx, %0\n\t"
+      "lfence"
+      : "=a"(t)
+      :
+      // "memory" avoids reordering. rcx = TSC_AUX. rdx = TSC >> 32.
+      // "cc" = flags modified by SHL.
+      : "rcx", "rdx", "memory", "cc");
+#endif
+#else
+  t = Start64();
+#endif
+  return t;
+}
+
+// Returns a 32-bit timestamp with about 4 cycles less overhead than
+// Start64. Only suitable for measuring very short regions because the
+// timestamp overflows about once a second.
+inline uint32_t Start32() {
+  uint32_t t;
+#if defined(ABSL_ARCH_X86_64)
+#if defined(ABSL_OS_WIN)
+  _ReadWriteBarrier();
+  _mm_lfence();
+  _ReadWriteBarrier();
+  t = static_cast<uint32_t>(__rdtsc());
+  _ReadWriteBarrier();
+  _mm_lfence();
+  _ReadWriteBarrier();
+#else
+  asm volatile(
+      "lfence\n\t"
+      "rdtsc\n\t"
+      "lfence"
+      : "=a"(t)
+      :
+      // "memory" avoids reordering. rdx = TSC >> 32.
+      : "rdx", "memory");
+#endif
+#else
+  t = static_cast<uint32_t>(Start64());
+#endif
+  return t;
+}
+
+inline uint32_t Stop32() {
+  uint32_t t;
+#if defined(ABSL_ARCH_X86_64)
+#if defined(ABSL_OS_WIN)
+  _ReadWriteBarrier();
+  unsigned aux;
+  t = static_cast<uint32_t>(__rdtscp(&aux));
+  _ReadWriteBarrier();
+  _mm_lfence();
+  _ReadWriteBarrier();
+#else
+  // Use inline asm because __rdtscp generates code to store TSC_AUX (ecx).
+  asm volatile(
+      "rdtscp\n\t"
+      "lfence"
+      : "=a"(t)
+      :
+      // "memory" avoids reordering. rcx = TSC_AUX. rdx = TSC >> 32.
+      : "rcx", "rdx", "memory");
+#endif
+#else
+  t = static_cast<uint32_t>(Stop64());
+#endif
+  return t;
+}
+
+}  // namespace timer
+
+namespace robust_statistics {
+
+// Sorts integral values in ascending order (e.g. for Mode). About 3x faster
+// than std::sort for input distributions with very few unique values.
+template <class T>
+void CountingSort(T* values, size_t num_values) {
+  // Unique values and their frequency (similar to flat_map).
+  using Unique = std::pair<T, int>;
+  std::vector<Unique> unique;
+  for (size_t i = 0; i < num_values; ++i) {
+    const T value = values[i];
+    const auto pos =
+        std::find_if(unique.begin(), unique.end(),
+                     [value](const Unique u) { return u.first == value; });
+    if (pos == unique.end()) {
+      unique.push_back(std::make_pair(value, 1));
+    } else {
+      ++pos->second;
+    }
+  }
+
+  // Sort in ascending order of value (pair.first).
+  std::sort(unique.begin(), unique.end());
+
+  // Write that many copies of each unique value to the array.
+  T* ABSL_RANDOM_INTERNAL_RESTRICT p = values;
+  for (const auto& value_count : unique) {
+    std::fill_n(p, value_count.second, value_count.first);
+    p += value_count.second;
+  }
+  ABSL_RAW_CHECK(p == values + num_values, "Did not produce enough output");
+}
+
+// @return i in [idx_begin, idx_begin + half_count) that minimizes
+// sorted[i + half_count] - sorted[i].
+template <typename T>
+size_t MinRange(const T* const ABSL_RANDOM_INTERNAL_RESTRICT sorted,
+                const size_t idx_begin, const size_t half_count) {
+  T min_range = (std::numeric_limits<T>::max)();
+  size_t min_idx = 0;
+
+  for (size_t idx = idx_begin; idx < idx_begin + half_count; ++idx) {
+    ABSL_RAW_CHECK(sorted[idx] <= sorted[idx + half_count], "Not sorted");
+    const T range = sorted[idx + half_count] - sorted[idx];
+    if (range < min_range) {
+      min_range = range;
+      min_idx = idx;
+    }
+  }
+
+  return min_idx;
+}
+
+// Returns an estimate of the mode by calling MinRange on successively
+// halved intervals. "sorted" must be in ascending order. This is the
+// Half Sample Mode estimator proposed by Bickel in "On a fast, robust
+// estimator of the mode", with complexity O(N log N). The mode is less
+// affected by outliers in highly-skewed distributions than the median.
+// The averaging operation below assumes "T" is an unsigned integer type.
+template <typename T>
+T ModeOfSorted(const T* const ABSL_RANDOM_INTERNAL_RESTRICT sorted,
+               const size_t num_values) {
+  size_t idx_begin = 0;
+  size_t half_count = num_values / 2;
+  while (half_count > 1) {
+    idx_begin = MinRange(sorted, idx_begin, half_count);
+    half_count >>= 1;
+  }
+
+  const T x = sorted[idx_begin + 0];
+  if (half_count == 0) {
+    return x;
+  }
+  ABSL_RAW_CHECK(half_count == 1, "Should stop at half_count=1");
+  const T average = (x + sorted[idx_begin + 1] + 1) / 2;
+  return average;
+}
+
+// Returns the mode. Side effect: sorts "values".
+template <typename T>
+T Mode(T* values, const size_t num_values) {
+  CountingSort(values, num_values);
+  return ModeOfSorted(values, num_values);
+}
+
+template <typename T, size_t N>
+T Mode(T (&values)[N]) {
+  return Mode(&values[0], N);
+}
+
+// Returns the median value. Side effect: sorts "values".
+template <typename T>
+T Median(T* values, const size_t num_values) {
+  ABSL_RAW_CHECK(num_values != 0, "Empty input");
+  std::sort(values, values + num_values);
+  const size_t half = num_values / 2;
+  // Odd count: return middle
+  if (num_values % 2) {
+    return values[half];
+  }
+  // Even count: return average of middle two.
+  return (values[half] + values[half - 1] + 1) / 2;
+}
+
+// Returns a robust measure of variability.
+template <typename T>
+T MedianAbsoluteDeviation(const T* values, const size_t num_values,
+                          const T median) {
+  ABSL_RAW_CHECK(num_values != 0, "Empty input");
+  std::vector<T> abs_deviations;
+  abs_deviations.reserve(num_values);
+  for (size_t i = 0; i < num_values; ++i) {
+    const int64_t abs = std::abs(int64_t(values[i]) - int64_t(median));
+    abs_deviations.push_back(static_cast<T>(abs));
+  }
+  return Median(abs_deviations.data(), num_values);
+}
+
+}  // namespace robust_statistics
+
+// Ticks := platform-specific timer values (CPU cycles on x86). Must be
+// unsigned to guarantee wraparound on overflow. 32 bit timers are faster to
+// read than 64 bit.
+using Ticks = uint32_t;
+
+// Returns timer overhead / minimum measurable difference.
+Ticks TimerResolution() {
+  // Nested loop avoids exceeding stack/L1 capacity.
+  Ticks repetitions[Params::kTimerSamples];
+  for (size_t rep = 0; rep < Params::kTimerSamples; ++rep) {
+    Ticks samples[Params::kTimerSamples];
+    for (size_t i = 0; i < Params::kTimerSamples; ++i) {
+      const Ticks t0 = timer::Start32();
+      const Ticks t1 = timer::Stop32();
+      samples[i] = t1 - t0;
+    }
+    repetitions[rep] = robust_statistics::Mode(samples);
+  }
+  return robust_statistics::Mode(repetitions);
+}
+
+static const Ticks timer_resolution = TimerResolution();
+
+// Estimates the expected value of "lambda" values with a variable number of
+// samples until the variability "rel_mad" is less than "max_rel_mad".
+template <class Lambda>
+Ticks SampleUntilStable(const double max_rel_mad, double* rel_mad,
+                        const Params& p, const Lambda& lambda) {
+  auto measure_duration = [&lambda]() -> Ticks {
+    const Ticks t0 = timer::Start32();
+    lambda();
+    const Ticks t1 = timer::Stop32();
+    return t1 - t0;
+  };
+
+  // Choose initial samples_per_eval based on a single estimated duration.
+  Ticks est = measure_duration();
+  static const double ticks_per_second = InvariantTicksPerSecond();
+  const size_t ticks_per_eval = ticks_per_second * p.seconds_per_eval;
+  size_t samples_per_eval = ticks_per_eval / est;
+  samples_per_eval = (std::max)(samples_per_eval, p.min_samples_per_eval);
+
+  std::vector<Ticks> samples;
+  samples.reserve(1 + samples_per_eval);
+  samples.push_back(est);
+
+  // Percentage is too strict for tiny differences, so also allow a small
+  // absolute "median absolute deviation".
+  const Ticks max_abs_mad = (timer_resolution + 99) / 100;
+  *rel_mad = 0.0;  // ensure initialized
+
+  for (size_t eval = 0; eval < p.max_evals; ++eval, samples_per_eval *= 2) {
+    samples.reserve(samples.size() + samples_per_eval);
+    for (size_t i = 0; i < samples_per_eval; ++i) {
+      const Ticks r = measure_duration();
+      samples.push_back(r);
+    }
+
+    if (samples.size() >= p.min_mode_samples) {
+      est = robust_statistics::Mode(samples.data(), samples.size());
+    } else {
+      // For "few" (depends also on the variance) samples, Median is safer.
+      est = robust_statistics::Median(samples.data(), samples.size());
+    }
+    ABSL_RAW_CHECK(est != 0, "Estimator returned zero duration");
+
+    // Median absolute deviation (mad) is a robust measure of 'variability'.
+    const Ticks abs_mad = robust_statistics::MedianAbsoluteDeviation(
+        samples.data(), samples.size(), est);
+    *rel_mad = static_cast<double>(static_cast<int>(abs_mad)) / est;
+
+    if (*rel_mad <= max_rel_mad || abs_mad <= max_abs_mad) {
+      if (p.verbose) {
+        ABSL_RAW_LOG(INFO,
+                     "%6zu samples => %5u (abs_mad=%4u, rel_mad=%4.2f%%)\n",
+                     samples.size(), est, abs_mad, *rel_mad * 100.0);
+      }
+      return est;
+    }
+  }
+
+  if (p.verbose) {
+    ABSL_RAW_LOG(WARNING,
+                 "rel_mad=%4.2f%% still exceeds %4.2f%% after %6zu samples.\n",
+                 *rel_mad * 100.0, max_rel_mad * 100.0, samples.size());
+  }
+  return est;
+}
+
+using InputVec = std::vector<FuncInput>;
+
+// Returns vector of unique input values.
+InputVec UniqueInputs(const FuncInput* inputs, const size_t num_inputs) {
+  InputVec unique(inputs, inputs + num_inputs);
+  std::sort(unique.begin(), unique.end());
+  unique.erase(std::unique(unique.begin(), unique.end()), unique.end());
+  return unique;
+}
+
+// Returns how often we need to call func for sufficient precision, or zero
+// on failure (e.g. the elapsed time is too long for a 32-bit tick count).
+size_t NumSkip(const Func func, const void* arg, const InputVec& unique,
+               const Params& p) {
+  // Min elapsed ticks for any input.
+  Ticks min_duration = ~0u;
+
+  for (const FuncInput input : unique) {
+    // Make sure a 32-bit timer is sufficient.
+    const uint64_t t0 = timer::Start64();
+    PreventElision(func(arg, input));
+    const uint64_t t1 = timer::Stop64();
+    const uint64_t elapsed = t1 - t0;
+    if (elapsed >= (1ULL << 30)) {
+      ABSL_RAW_LOG(WARNING,
+                   "Measurement failed: need 64-bit timer for input=%zu\n",
+                   static_cast<size_t>(input));
+      return 0;
+    }
+
+    double rel_mad;
+    const Ticks total = SampleUntilStable(
+        p.target_rel_mad, &rel_mad, p,
+        [func, arg, input]() { PreventElision(func(arg, input)); });
+    min_duration = (std::min)(min_duration, total - timer_resolution);
+  }
+
+  // Number of repetitions required to reach the target resolution.
+  const size_t max_skip = p.precision_divisor;
+  // Number of repetitions given the estimated duration.
+  const size_t num_skip =
+      min_duration == 0 ? 0 : (max_skip + min_duration - 1) / min_duration;
+  if (p.verbose) {
+    ABSL_RAW_LOG(INFO, "res=%u max_skip=%zu min_dur=%u num_skip=%zu\n",
+                 timer_resolution, max_skip, min_duration, num_skip);
+  }
+  return num_skip;
+}
+
+// Replicates inputs until we can omit "num_skip" occurrences of an input.
+InputVec ReplicateInputs(const FuncInput* inputs, const size_t num_inputs,
+                         const size_t num_unique, const size_t num_skip,
+                         const Params& p) {
+  InputVec full;
+  if (num_unique == 1) {
+    full.assign(p.subset_ratio * num_skip, inputs[0]);
+    return full;
+  }
+
+  full.reserve(p.subset_ratio * num_skip * num_inputs);
+  for (size_t i = 0; i < p.subset_ratio * num_skip; ++i) {
+    full.insert(full.end(), inputs, inputs + num_inputs);
+  }
+  absl::random_internal::randen_engine<uint32_t> rng;
+  std::shuffle(full.begin(), full.end(), rng);
+  return full;
+}
+
+// Copies the "full" to "subset" in the same order, but with "num_skip"
+// randomly selected occurrences of "input_to_skip" removed.
+void FillSubset(const InputVec& full, const FuncInput input_to_skip,
+                const size_t num_skip, InputVec* subset) {
+  const size_t count = std::count(full.begin(), full.end(), input_to_skip);
+  // Generate num_skip random indices: which occurrence to skip.
+  std::vector<uint32_t> omit;
+  // Replacement for std::iota, not yet available in MSVC builds.
+  omit.reserve(count);
+  for (size_t i = 0; i < count; ++i) {
+    omit.push_back(i);
+  }
+  // omit[] is the same on every call, but that's OK because they identify the
+  // Nth instance of input_to_skip, so the position within full[] differs.
+  absl::random_internal::randen_engine<uint32_t> rng;
+  std::shuffle(omit.begin(), omit.end(), rng);
+  omit.resize(num_skip);
+  std::sort(omit.begin(), omit.end());
+
+  uint32_t occurrence = ~0u;  // 0 after preincrement
+  size_t idx_omit = 0;        // cursor within omit[]
+  size_t idx_subset = 0;      // cursor within *subset
+  for (const FuncInput next : full) {
+    if (next == input_to_skip) {
+      ++occurrence;
+      // Haven't removed enough already
+      if (idx_omit < num_skip) {
+        // This one is up for removal
+        if (occurrence == omit[idx_omit]) {
+          ++idx_omit;
+          continue;
+        }
+      }
+    }
+    if (idx_subset < subset->size()) {
+      (*subset)[idx_subset++] = next;
+    }
+  }
+  ABSL_RAW_CHECK(idx_subset == subset->size(), "idx_subset not at end");
+  ABSL_RAW_CHECK(idx_omit == omit.size(), "idx_omit not at end");
+  ABSL_RAW_CHECK(occurrence == count - 1, "occurrence not at end");
+}
+
+// Returns total ticks elapsed for all inputs.
+Ticks TotalDuration(const Func func, const void* arg, const InputVec* inputs,
+                    const Params& p, double* max_rel_mad) {
+  double rel_mad;
+  const Ticks duration =
+      SampleUntilStable(p.target_rel_mad, &rel_mad, p, [func, arg, inputs]() {
+        for (const FuncInput input : *inputs) {
+          PreventElision(func(arg, input));
+        }
+      });
+  *max_rel_mad = (std::max)(*max_rel_mad, rel_mad);
+  return duration;
+}
+
+// (Nearly) empty Func for measuring timer overhead/resolution.
+ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE FuncOutput
+EmptyFunc(const void* arg, const FuncInput input) {
+  return input;
+}
+
+// Returns overhead of accessing inputs[] and calling a function; this will
+// be deducted from future TotalDuration return values.
+Ticks Overhead(const void* arg, const InputVec* inputs, const Params& p) {
+  double rel_mad;
+  // Zero tolerance because repeatability is crucial and EmptyFunc is fast.
+  return SampleUntilStable(0.0, &rel_mad, p, [arg, inputs]() {
+    for (const FuncInput input : *inputs) {
+      PreventElision(EmptyFunc(arg, input));
+    }
+  });
+}
+
+}  // namespace
+
+void PinThreadToCPU(int cpu) {
+  // We might migrate to another CPU before pinning below, but at least cpu
+  // will be one of the CPUs on which this thread ran.
+#if defined(ABSL_OS_WIN)
+  if (cpu < 0) {
+    cpu = static_cast<int>(GetCurrentProcessorNumber());
+    ABSL_RAW_CHECK(cpu >= 0, "PinThreadToCPU detect failed");
+    if (cpu >= 64) {
+      // NOTE: On wine, at least, GetCurrentProcessorNumber() sometimes returns
+      // a value > 64, which is out of range. When this happens, log a message
+      // and don't set a cpu affinity.
+      ABSL_RAW_LOG(ERROR, "Invalid CPU number: %d", cpu);
+      return;
+    }
+  } else if (cpu >= 64) {
+    // User specified an explicit CPU affinity > the valid range.
+    ABSL_RAW_LOG(FATAL, "Invalid CPU number: %d", cpu);
+  }
+  const DWORD_PTR prev = SetThreadAffinityMask(GetCurrentThread(), 1ULL << cpu);
+  ABSL_RAW_CHECK(prev != 0, "SetAffinity failed");
+#elif defined(ABSL_OS_LINUX) && !defined(ABSL_OS_ANDROID)
+  if (cpu < 0) {
+    cpu = sched_getcpu();
+    ABSL_RAW_CHECK(cpu >= 0, "PinThreadToCPU detect failed");
+  }
+  const pid_t pid = 0;  // current thread
+  cpu_set_t set;
+  CPU_ZERO(&set);
+  CPU_SET(cpu, &set);
+  const int err = sched_setaffinity(pid, sizeof(set), &set);
+  ABSL_RAW_CHECK(err == 0, "SetAffinity failed");
+#endif
+}
+
+// Returns tick rate. Invariant means the tick counter frequency is independent
+// of CPU throttling or sleep. May be expensive, caller should cache the result.
+double InvariantTicksPerSecond() {
+#if defined(ABSL_ARCH_PPC)
+  return __ppc_get_timebase_freq();
+#elif defined(ABSL_ARCH_X86_64)
+  // We assume the TSC is invariant; it is on all recent Intel/AMD CPUs.
+  return platform::NominalClockRate();
+#else
+  // Fall back to clock_gettime nanoseconds.
+  return 1E9;
+#endif
+}
+
+size_t MeasureImpl(const Func func, const void* arg, const size_t num_skip,
+                   const InputVec& unique, const InputVec& full,
+                   const Params& p, Result* results) {
+  const float mul = 1.0f / static_cast<int>(num_skip);
+
+  InputVec subset(full.size() - num_skip);
+  const Ticks overhead = Overhead(arg, &full, p);
+  const Ticks overhead_skip = Overhead(arg, &subset, p);
+  if (overhead < overhead_skip) {
+    ABSL_RAW_LOG(WARNING, "Measurement failed: overhead %u < %u\n", overhead,
+                 overhead_skip);
+    return 0;
+  }
+
+  if (p.verbose) {
+    ABSL_RAW_LOG(INFO, "#inputs=%5zu,%5zu overhead=%5u,%5u\n", full.size(),
+                 subset.size(), overhead, overhead_skip);
+  }
+
+  double max_rel_mad = 0.0;
+  const Ticks total = TotalDuration(func, arg, &full, p, &max_rel_mad);
+
+  for (size_t i = 0; i < unique.size(); ++i) {
+    FillSubset(full, unique[i], num_skip, &subset);
+    const Ticks total_skip = TotalDuration(func, arg, &subset, p, &max_rel_mad);
+
+    if (total < total_skip) {
+      ABSL_RAW_LOG(WARNING, "Measurement failed: total %u < %u\n", total,
+                   total_skip);
+      return 0;
+    }
+
+    const Ticks duration = (total - overhead) - (total_skip - overhead_skip);
+    results[i].input = unique[i];
+    results[i].ticks = duration * mul;
+    results[i].variability = max_rel_mad;
+  }
+
+  return unique.size();
+}
+
+size_t Measure(const Func func, const void* arg, const FuncInput* inputs,
+               const size_t num_inputs, Result* results, const Params& p) {
+  ABSL_RAW_CHECK(num_inputs != 0, "No inputs");
+
+  const InputVec unique = UniqueInputs(inputs, num_inputs);
+  const size_t num_skip = NumSkip(func, arg, unique, p);  // never 0
+  if (num_skip == 0) return 0;  // NumSkip already printed error message
+
+  const InputVec full =
+      ReplicateInputs(inputs, num_inputs, unique.size(), num_skip, p);
+
+  // MeasureImpl may fail up to p.max_measure_retries times.
+  for (size_t i = 0; i < p.max_measure_retries; i++) {
+    auto result = MeasureImpl(func, arg, num_skip, unique, full, p, results);
+    if (result != 0) {
+      return result;
+    }
+  }
+  // All retries failed. (Unusual)
+  return 0;
+}
+
+}  // namespace random_internal_nanobenchmark
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/nanobenchmark_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/nanobenchmark_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d4f1028dbd3c609e6f571f2c0038c030476864ce
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/nanobenchmark_test.cc
@@ -0,0 +1,79 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/nanobenchmark.h"
+
+#include "absl/log/check.h"
+#include "absl/log/log.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_format.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal_nanobenchmark {
+namespace {
+
+uint64_t Div(const void*, FuncInput in) {
+  // Here we're measuring the throughput because benchmark invocations are
+  // independent.
+  const int64_t d1 = 0xFFFFFFFFFFll / int64_t(in);  // IDIV
+  return d1;
+}
+
+template <size_t N>
+void MeasureDiv(const FuncInput (&inputs)[N]) {
+  Result results[N];
+  Params params;
+  params.max_evals = 6;  // avoid test timeout
+  const size_t num_results = Measure(&Div, nullptr, inputs, N, results, params);
+  if (num_results == 0) {
+    LOG(WARNING)
+        << "WARNING: Measurement failed, should not happen when using "
+           "PinThreadToCPU unless the region to measure takes > 1 second.";
+    return;
+  }
+  for (size_t i = 0; i < num_results; ++i) {
+    LOG(INFO) << absl::StreamFormat("%5u: %6.2f ticks; MAD=%4.2f%%\n",
+                                    results[i].input, results[i].ticks,
+                                    results[i].variability * 100.0);
+    CHECK_NE(results[i].ticks, 0.0f) << "Zero duration";
+  }
+}
+
+void RunAll(const int argc, char* argv[]) {
+  // Avoid migrating between cores - important on multi-socket systems.
+  int cpu = -1;
+  if (argc == 2) {
+    if (!absl::SimpleAtoi(argv[1], &cpu)) {
+      LOG(FATAL) << "The optional argument must be a CPU number >= 0.";
+    }
+  }
+  PinThreadToCPU(cpu);
+
+  // unpredictable == 1 but the compiler doesn't know that.
+  const FuncInput unpredictable = argc != 999;
+  static const FuncInput inputs[] = {unpredictable * 10, unpredictable * 100};
+
+  MeasureDiv(inputs);
+}
+
+}  // namespace
+}  // namespace random_internal_nanobenchmark
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+int main(int argc, char* argv[]) {
+  absl::random_internal_nanobenchmark::RunAll(argc, argv);
+  return 0;
+}
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/nonsecure_base.h b/weight/_dep/abseil-cpp/absl/random/internal/nonsecure_base.h
new file mode 100644
index 0000000000000000000000000000000000000000..c3b80335aed8536ad41831aebfd1e21128c12335
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/nonsecure_base.h
@@ -0,0 +1,161 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_NONSECURE_BASE_H_
+#define ABSL_RANDOM_INTERNAL_NONSECURE_BASE_H_
+
+#include <algorithm>
+#include <cstdint>
+#include <iterator>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "absl/base/macros.h"
+#include "absl/container/inlined_vector.h"
+#include "absl/meta/type_traits.h"
+#include "absl/random/internal/pool_urbg.h"
+#include "absl/random/internal/salted_seed_seq.h"
+#include "absl/random/internal/seed_material.h"
+#include "absl/types/span.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// RandenPoolSeedSeq is a custom seed sequence type where generate() fills the
+// provided buffer via the RandenPool entropy source.
+class RandenPoolSeedSeq {
+ private:
+  struct ContiguousTag {};
+  struct BufferTag {};
+
+  // Generate random unsigned values directly into the buffer.
+  template <typename Contiguous>
+  void generate_impl(ContiguousTag, Contiguous begin, Contiguous end) {
+    const size_t n = static_cast<size_t>(std::distance(begin, end));
+    auto* a = &(*begin);
+    RandenPool<uint8_t>::Fill(
+        absl::MakeSpan(reinterpret_cast<uint8_t*>(a), sizeof(*a) * n));
+  }
+
+  // Construct a buffer of size n and fill it with values, then copy
+  // those values into the seed iterators.
+  template <typename RandomAccessIterator>
+  void generate_impl(BufferTag, RandomAccessIterator begin,
+                     RandomAccessIterator end) {
+    const size_t n = std::distance(begin, end);
+    absl::InlinedVector<uint32_t, 8> data(n, 0);
+    RandenPool<uint32_t>::Fill(absl::MakeSpan(data.begin(), data.end()));
+    std::copy(std::begin(data), std::end(data), begin);
+  }
+
+ public:
+  using result_type = uint32_t;
+
+  size_t size() { return 0; }
+
+  template <typename OutIterator>
+  void param(OutIterator) const {}
+
+  template <typename RandomAccessIterator>
+  void generate(RandomAccessIterator begin, RandomAccessIterator end) {
+    // RandomAccessIterator must be assignable from uint32_t
+    if (begin != end) {
+      using U = typename std::iterator_traits<RandomAccessIterator>::value_type;
+      // ContiguousTag indicates the common case of a known contiguous buffer,
+      // which allows directly filling the buffer. In C++20,
+      // std::contiguous_iterator_tag provides a mechanism for testing this
+      // capability, however until Abseil's support requirements allow us to
+      // assume C++20, limit checks to a few common cases.
+      using TagType = absl::conditional_t<
+          (std::is_pointer<RandomAccessIterator>::value ||
+           std::is_same<RandomAccessIterator,
+                        typename std::vector<U>::iterator>::value),
+          ContiguousTag, BufferTag>;
+
+      generate_impl(TagType{}, begin, end);
+    }
+  }
+};
+
+// Each instance of NonsecureURBGBase<URBG> will be seeded by variates produced
+// by a thread-unique URBG-instance.
+template <typename URBG, typename Seeder = RandenPoolSeedSeq>
+class NonsecureURBGBase {
+ public:
+  using result_type = typename URBG::result_type;
+
+  // Default constructor
+  NonsecureURBGBase() : urbg_(ConstructURBG()) {}
+
+  // Copy disallowed, move allowed.
+  NonsecureURBGBase(const NonsecureURBGBase&) = delete;
+  NonsecureURBGBase& operator=(const NonsecureURBGBase&) = delete;
+  NonsecureURBGBase(NonsecureURBGBase&&) = default;
+  NonsecureURBGBase& operator=(NonsecureURBGBase&&) = default;
+
+  // Constructor using a seed
+  template <class SSeq, typename = typename absl::enable_if_t<
+                            !std::is_same<SSeq, NonsecureURBGBase>::value>>
+  explicit NonsecureURBGBase(SSeq&& seq)
+      : urbg_(ConstructURBG(std::forward<SSeq>(seq))) {}
+
+  // Note: on MSVC, min() or max() can be interpreted as MIN() or MAX(), so we
+  // enclose min() or max() in parens as (min)() and (max)().
+  // Additionally, clang-format requires no space before this construction.
+
+  // NonsecureURBGBase::min()
+  static constexpr result_type(min)() { return (URBG::min)(); }
+
+  // NonsecureURBGBase::max()
+  static constexpr result_type(max)() { return (URBG::max)(); }
+
+  // NonsecureURBGBase::operator()()
+  result_type operator()() { return urbg_(); }
+
+  // NonsecureURBGBase::discard()
+  void discard(unsigned long long values) {  // NOLINT(runtime/int)
+    urbg_.discard(values);
+  }
+
+  bool operator==(const NonsecureURBGBase& other) const {
+    return urbg_ == other.urbg_;
+  }
+
+  bool operator!=(const NonsecureURBGBase& other) const {
+    return !(urbg_ == other.urbg_);
+  }
+
+ private:
+  static URBG ConstructURBG() {
+    Seeder seeder;
+    return URBG(seeder);
+  }
+
+  template <typename SSeq>
+  static URBG ConstructURBG(SSeq&& seq) {  // NOLINT(runtime/references)
+    auto salted_seq =
+        random_internal::MakeSaltedSeedSeq(std::forward<SSeq>(seq));
+    return URBG(salted_seq);
+  }
+
+  URBG urbg_;
+};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_NONSECURE_BASE_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/nonsecure_base_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/nonsecure_base_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3502243e151ab1fbcbb3b76a192a5e6d074b04cd
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/nonsecure_base_test.cc
@@ -0,0 +1,227 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/nonsecure_base.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <memory>
+#include <random>
+#include <sstream>
+
+#include "gtest/gtest.h"
+#include "absl/random/distributions.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+
+namespace {
+
+using ExampleNonsecureURBG =
+    absl::random_internal::NonsecureURBGBase<std::mt19937>;
+
+template <typename T>
+void Use(const T&) {}
+
+}  // namespace
+
+TEST(NonsecureURBGBase, DefaultConstructorIsValid) {
+  ExampleNonsecureURBG urbg;
+}
+
+// Ensure that the recommended template-instantiations are valid.
+TEST(RecommendedTemplates, CanBeConstructed) {
+  absl::BitGen default_generator;
+  absl::InsecureBitGen insecure_generator;
+}
+
+TEST(RecommendedTemplates, CanDiscardValues) {
+  absl::BitGen default_generator;
+  absl::InsecureBitGen insecure_generator;
+
+  default_generator.discard(5);
+  insecure_generator.discard(5);
+}
+
+TEST(NonsecureURBGBase, StandardInterface) {
+  // Names after definition of [rand.req.urbg] in C++ standard.
+  // e us a value of E
+  // v is a lvalue of E
+  // x, y are possibly const values of E
+  // s is a value of T
+  // q is a value satisfying requirements of seed_sequence
+  // z is a value of type unsigned long long
+  // os is a some specialization of basic_ostream
+  // is is a some specialization of basic_istream
+
+  using E = absl::random_internal::NonsecureURBGBase<std::minstd_rand>;
+
+  using T = typename E::result_type;
+
+  static_assert(!std::is_copy_constructible<E>::value,
+                "NonsecureURBGBase should not be copy constructible");
+
+  static_assert(!absl::is_copy_assignable<E>::value,
+                "NonsecureURBGBase should not be copy assignable");
+
+  static_assert(std::is_move_constructible<E>::value,
+                "NonsecureURBGBase should be move constructible");
+
+  static_assert(absl::is_move_assignable<E>::value,
+                "NonsecureURBGBase should be move assignable");
+
+  static_assert(std::is_same<decltype(std::declval<E>()()), T>::value,
+                "return type of operator() must be result_type");
+
+  {
+    const E x, y;
+    Use(x);
+    Use(y);
+
+    static_assert(std::is_same<decltype(x == y), bool>::value,
+                  "return type of operator== must be bool");
+
+    static_assert(std::is_same<decltype(x != y), bool>::value,
+                  "return type of operator== must be bool");
+  }
+
+  E e;
+  std::seed_seq q{1, 2, 3};
+
+  E{};
+  E{q};
+
+  // Copy constructor not supported.
+  // E{x};
+
+  // result_type seed constructor not supported.
+  // E{T{1}};
+
+  // Move constructors are supported.
+  {
+    E tmp(q);
+    E m = std::move(tmp);
+    E n(std::move(m));
+    EXPECT_TRUE(e != n);
+  }
+
+  // Comparisons work.
+  {
+    // MSVC emits error 2718 when using EXPECT_EQ(e, x)
+    //  * actual parameter with __declspec(align('#')) won't be aligned
+    E a(q);
+    E b(q);
+
+    EXPECT_TRUE(a != e);
+    EXPECT_TRUE(a == b);
+
+    a();
+    EXPECT_TRUE(a != b);
+  }
+
+  // e.seed(s) not supported.
+
+  // [rand.req.eng] specifies the parameter as 'unsigned long long'
+  // e.discard(unsigned long long) is supported.
+  unsigned long long z = 1;  // NOLINT(runtime/int)
+  e.discard(z);
+}
+
+TEST(NonsecureURBGBase, SeedSeqConstructorIsValid) {
+  std::seed_seq seq;
+  ExampleNonsecureURBG rbg(seq);
+}
+
+TEST(NonsecureURBGBase, CompatibleWithDistributionUtils) {
+  ExampleNonsecureURBG rbg;
+
+  absl::Uniform(rbg, 0, 100);
+  absl::Uniform(rbg, 0.5, 0.7);
+  absl::Poisson<uint32_t>(rbg);
+  absl::Exponential<float>(rbg);
+}
+
+TEST(NonsecureURBGBase, CompatibleWithStdDistributions) {
+  ExampleNonsecureURBG rbg;
+
+  // Cast to void to suppress [[nodiscard]] warnings
+  static_cast<void>(std::uniform_int_distribution<uint32_t>(0, 100)(rbg));
+  static_cast<void>(std::uniform_real_distribution<float>()(rbg));
+  static_cast<void>(std::bernoulli_distribution(0.2)(rbg));
+}
+
+TEST(NonsecureURBGBase, ConsecutiveDefaultInstancesYieldUniqueVariates) {
+  const size_t kNumSamples = 128;
+
+  ExampleNonsecureURBG rbg1;
+  ExampleNonsecureURBG rbg2;
+
+  for (size_t i = 0; i < kNumSamples; i++) {
+    EXPECT_NE(rbg1(), rbg2());
+  }
+}
+
+TEST(NonsecureURBGBase, EqualSeedSequencesYieldEqualVariates) {
+  std::seed_seq seq;
+
+  ExampleNonsecureURBG rbg1(seq);
+  ExampleNonsecureURBG rbg2(seq);
+
+  // ExampleNonsecureURBG rbg3({1, 2, 3});  // Should not compile.
+
+  for (uint32_t i = 0; i < 1000; i++) {
+    EXPECT_EQ(rbg1(), rbg2());
+  }
+
+  rbg1.discard(100);
+  rbg2.discard(100);
+
+  // The sequences should continue after discarding
+  for (uint32_t i = 0; i < 1000; i++) {
+    EXPECT_EQ(rbg1(), rbg2());
+  }
+}
+
+TEST(RandenPoolSeedSeqTest, SeederWorksForU32) {
+  absl::random_internal::RandenPoolSeedSeq seeder;
+
+  uint32_t state[2] = {0, 0};
+  seeder.generate(std::begin(state), std::end(state));
+  EXPECT_FALSE(state[0] == 0 && state[1] == 0);
+}
+
+TEST(RandenPoolSeedSeqTest, SeederWorksForU64) {
+  absl::random_internal::RandenPoolSeedSeq seeder;
+
+  uint64_t state[2] = {0, 0};
+  seeder.generate(std::begin(state), std::end(state));
+  EXPECT_FALSE(state[0] == 0 && state[1] == 0);
+  EXPECT_FALSE((state[0] >> 32) == 0 && (state[1] >> 32) == 0);
+}
+
+TEST(RandenPoolSeedSeqTest, SeederWorksForS32) {
+  absl::random_internal::RandenPoolSeedSeq seeder;
+
+  int32_t state[2] = {0, 0};
+  seeder.generate(std::begin(state), std::end(state));
+  EXPECT_FALSE(state[0] == 0 && state[1] == 0);
+}
+
+TEST(RandenPoolSeedSeqTest, SeederWorksForVector) {
+  absl::random_internal::RandenPoolSeedSeq seeder;
+
+  std::vector<uint32_t> state(2);
+  seeder.generate(std::begin(state), std::end(state));
+  EXPECT_FALSE(state[0] == 0 && state[1] == 0);
+}
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/pcg_engine.h b/weight/_dep/abseil-cpp/absl/random/internal/pcg_engine.h
new file mode 100644
index 0000000000000000000000000000000000000000..e1f4ef3317146298058352df64b484096c892e9c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/pcg_engine.h
@@ -0,0 +1,287 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_PCG_ENGINE_H_
+#define ABSL_RANDOM_INTERNAL_PCG_ENGINE_H_
+
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/meta/type_traits.h"
+#include "absl/numeric/bits.h"
+#include "absl/numeric/int128.h"
+#include "absl/random/internal/fastmath.h"
+#include "absl/random/internal/iostream_state_saver.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// pcg_engine is a simplified implementation of Melissa O'Neil's PCG engine in
+// C++.  PCG combines a linear congruential generator (LCG) with output state
+// mixing functions to generate each random variate.  pcg_engine supports only a
+// single sequence (oneseq), and does not support streams.
+//
+// pcg_engine is parameterized by two types:
+//   Params, which provides the multiplier and increment values;
+//   Mix, which mixes the state into the result.
+//
+template <typename Params, typename Mix>
+class pcg_engine {
+  static_assert(std::is_same<typename Params::state_type,
+                             typename Mix::state_type>::value,
+                "Class-template absl::pcg_engine must be parameterized by "
+                "Params and Mix with identical state_type");
+
+  static_assert(std::is_unsigned<typename Mix::result_type>::value,
+                "Class-template absl::pcg_engine must be parameterized by "
+                "an unsigned Mix::result_type");
+
+  using params_type = Params;
+  using mix_type = Mix;
+  using state_type = typename Mix::state_type;
+
+ public:
+  // C++11 URBG interface:
+  using result_type = typename Mix::result_type;
+
+  static constexpr result_type(min)() {
+    return (std::numeric_limits<result_type>::min)();
+  }
+
+  static constexpr result_type(max)() {
+    return (std::numeric_limits<result_type>::max)();
+  }
+
+  explicit pcg_engine(uint64_t seed_value = 0) { seed(seed_value); }
+
+  template <class SeedSequence,
+            typename = typename absl::enable_if_t<
+                !std::is_same<SeedSequence, pcg_engine>::value>>
+  explicit pcg_engine(SeedSequence&& seq) {
+    seed(seq);
+  }
+
+  pcg_engine(const pcg_engine&) = default;
+  pcg_engine& operator=(const pcg_engine&) = default;
+  pcg_engine(pcg_engine&&) = default;
+  pcg_engine& operator=(pcg_engine&&) = default;
+
+  result_type operator()() {
+    // Advance the LCG state, always using the new value to generate the output.
+    state_ = lcg(state_);
+    return Mix{}(state_);
+  }
+
+  void seed(uint64_t seed_value = 0) {
+    state_type tmp = seed_value;
+    state_ = lcg(tmp + Params::increment());
+  }
+
+  template <class SeedSequence>
+  typename absl::enable_if_t<
+      !std::is_convertible<SeedSequence, uint64_t>::value, void>
+  seed(SeedSequence&& seq) {
+    reseed(seq);
+  }
+
+  void discard(uint64_t count) { state_ = advance(state_, count); }
+
+  bool operator==(const pcg_engine& other) const {
+    return state_ == other.state_;
+  }
+
+  bool operator!=(const pcg_engine& other) const { return !(*this == other); }
+
+  template <class CharT, class Traits>
+  friend typename absl::enable_if_t<(sizeof(state_type) == 16),
+                                    std::basic_ostream<CharT, Traits>&>
+  operator<<(
+      std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+      const pcg_engine& engine) {
+    auto saver = random_internal::make_ostream_state_saver(os);
+    random_internal::stream_u128_helper<state_type> helper;
+    helper.write(pcg_engine::params_type::multiplier(), os);
+    os << os.fill();
+    helper.write(pcg_engine::params_type::increment(), os);
+    os << os.fill();
+    helper.write(engine.state_, os);
+    return os;
+  }
+
+  template <class CharT, class Traits>
+  friend typename absl::enable_if_t<(sizeof(state_type) <= 8),
+                                    std::basic_ostream<CharT, Traits>&>
+  operator<<(
+      std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+      const pcg_engine& engine) {
+    auto saver = random_internal::make_ostream_state_saver(os);
+    os << pcg_engine::params_type::multiplier() << os.fill();
+    os << pcg_engine::params_type::increment() << os.fill();
+    os << engine.state_;
+    return os;
+  }
+
+  template <class CharT, class Traits>
+  friend typename absl::enable_if_t<(sizeof(state_type) == 16),
+                                    std::basic_istream<CharT, Traits>&>
+  operator>>(
+      std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+      pcg_engine& engine) {                   // NOLINT(runtime/references)
+    random_internal::stream_u128_helper<state_type> helper;
+    auto mult = helper.read(is);
+    auto inc = helper.read(is);
+    auto tmp = helper.read(is);
+    if (mult != pcg_engine::params_type::multiplier() ||
+        inc != pcg_engine::params_type::increment()) {
+      // signal failure by setting the failbit.
+      is.setstate(is.rdstate() | std::ios_base::failbit);
+    }
+    if (!is.fail()) {
+      engine.state_ = tmp;
+    }
+    return is;
+  }
+
+  template <class CharT, class Traits>
+  friend typename absl::enable_if_t<(sizeof(state_type) <= 8),
+                                    std::basic_istream<CharT, Traits>&>
+  operator>>(
+      std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+      pcg_engine& engine) {                   // NOLINT(runtime/references)
+    state_type mult{}, inc{}, tmp{};
+    is >> mult >> inc >> tmp;
+    if (mult != pcg_engine::params_type::multiplier() ||
+        inc != pcg_engine::params_type::increment()) {
+      // signal failure by setting the failbit.
+      is.setstate(is.rdstate() | std::ios_base::failbit);
+    }
+    if (!is.fail()) {
+      engine.state_ = tmp;
+    }
+    return is;
+  }
+
+ private:
+  state_type state_;
+
+  // Returns the linear-congruential generator next state.
+  static inline constexpr state_type lcg(state_type s) {
+    return s * Params::multiplier() + Params::increment();
+  }
+
+  // Returns the linear-congruential arbitrary seek state.
+  inline state_type advance(state_type s, uint64_t n) const {
+    state_type mult = Params::multiplier();
+    state_type inc = Params::increment();
+    state_type m = 1;
+    state_type i = 0;
+    while (n > 0) {
+      if (n & 1) {
+        m *= mult;
+        i = i * mult + inc;
+      }
+      inc = (mult + 1) * inc;
+      mult *= mult;
+      n >>= 1;
+    }
+    return m * s + i;
+  }
+
+  template <class SeedSequence>
+  void reseed(SeedSequence& seq) {
+    using sequence_result_type = typename SeedSequence::result_type;
+    constexpr size_t kBufferSize =
+        sizeof(state_type) / sizeof(sequence_result_type);
+    sequence_result_type buffer[kBufferSize];
+    seq.generate(std::begin(buffer), std::end(buffer));
+    // Convert the seed output to a single state value.
+    state_type tmp = buffer[0];
+    for (size_t i = 1; i < kBufferSize; i++) {
+      tmp <<= (sizeof(sequence_result_type) * 8);
+      tmp |= buffer[i];
+    }
+    state_ = lcg(tmp + params_type::increment());
+  }
+};
+
+// Parameterized implementation of the PCG 128-bit oneseq state.
+// This provides state_type, multiplier, and increment for pcg_engine.
+template <uint64_t kMultA, uint64_t kMultB, uint64_t kIncA, uint64_t kIncB>
+class pcg128_params {
+ public:
+  using state_type = absl::uint128;
+  static inline constexpr state_type multiplier() {
+    return absl::MakeUint128(kMultA, kMultB);
+  }
+  static inline constexpr state_type increment() {
+    return absl::MakeUint128(kIncA, kIncB);
+  }
+};
+
+// Implementation of the PCG xsl_rr_128_64 128-bit mixing function, which
+// accepts an input of state_type and mixes it into an output of result_type.
+struct pcg_xsl_rr_128_64 {
+  using state_type = absl::uint128;
+  using result_type = uint64_t;
+
+  inline uint64_t operator()(state_type state) {
+    // This is equivalent to the xsl_rr_128_64 mixing function.
+    uint64_t rotate = static_cast<uint64_t>(state >> 122u);
+    state ^= state >> 64;
+    uint64_t s = static_cast<uint64_t>(state);
+    return rotr(s, static_cast<int>(rotate));
+  }
+};
+
+// Parameterized implementation of the PCG 64-bit oneseq state.
+// This provides state_type, multiplier, and increment for pcg_engine.
+template <uint64_t kMult, uint64_t kInc>
+class pcg64_params {
+ public:
+  using state_type = uint64_t;
+  static inline constexpr state_type multiplier() { return kMult; }
+  static inline constexpr state_type increment() { return kInc; }
+};
+
+// Implementation of the PCG xsh_rr_64_32 64-bit mixing function, which accepts
+// an input of state_type and mixes it into an output of result_type.
+struct pcg_xsh_rr_64_32 {
+  using state_type = uint64_t;
+  using result_type = uint32_t;
+  inline uint32_t operator()(uint64_t state) {
+    return rotr(static_cast<uint32_t>(((state >> 18) ^ state) >> 27),
+                state >> 59);
+  }
+};
+
+// Stable pcg_engine implementations:
+// This is a 64-bit generator using 128-bits of state.
+// The output sequence is equivalent to Melissa O'Neil's pcg64_oneseq.
+using pcg64_2018_engine = pcg_engine<
+    random_internal::pcg128_params<0x2360ed051fc65da4ull, 0x4385df649fccf645ull,
+                                   0x5851f42d4c957f2d, 0x14057b7ef767814f>,
+    random_internal::pcg_xsl_rr_128_64>;
+
+// This is a 32-bit generator using 64-bits of state.
+// This is equivalent to Melissa O'Neil's pcg32_oneseq.
+using pcg32_2018_engine = pcg_engine<
+    random_internal::pcg64_params<0x5851f42d4c957f2dull, 0x14057b7ef767814full>,
+    random_internal::pcg_xsh_rr_64_32>;
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_PCG_ENGINE_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/pcg_engine_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/pcg_engine_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4d763e89eb5805d0ba36726f34c6d2c303fadd45
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/pcg_engine_test.cc
@@ -0,0 +1,638 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/pcg_engine.h"
+
+#include <algorithm>
+#include <bitset>
+#include <random>
+#include <sstream>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/random/internal/explicit_seed_seq.h"
+#include "absl/time/clock.h"
+
+#define UPDATE_GOLDEN 0
+
+namespace {
+
+using absl::random_internal::ExplicitSeedSeq;
+using absl::random_internal::pcg32_2018_engine;
+using absl::random_internal::pcg64_2018_engine;
+
+template <typename EngineType>
+class PCGEngineTest : public ::testing::Test {};
+
+using EngineTypes = ::testing::Types<pcg64_2018_engine, pcg32_2018_engine>;
+
+TYPED_TEST_SUITE(PCGEngineTest, EngineTypes);
+
+TYPED_TEST(PCGEngineTest, VerifyReseedChangesAllValues) {
+  using engine_type = TypeParam;
+  using result_type = typename engine_type::result_type;
+
+  const size_t kNumOutputs = 16;
+  engine_type engine;
+
+  // MSVC emits error 2719 without the use of std::ref below.
+  //  * formal parameter with __declspec(align('#')) won't be aligned
+
+  {
+    std::seed_seq seq1{1, 2, 3, 4, 5, 6, 7};
+    engine.seed(seq1);
+  }
+  result_type a[kNumOutputs];
+  std::generate(std::begin(a), std::end(a), std::ref(engine));
+
+  {
+    std::random_device rd;
+    std::seed_seq seq2{rd(), rd(), rd()};
+    engine.seed(seq2);
+  }
+  result_type b[kNumOutputs];
+  std::generate(std::begin(b), std::end(b), std::ref(engine));
+
+  // Verify that two uncorrelated values have ~50% of there bits in common. Use
+  // a 10% margin-of-error to reduce flakiness.
+  size_t changed_bits = 0;
+  size_t unchanged_bits = 0;
+  size_t total_set = 0;
+  size_t total_bits = 0;
+  size_t equal_count = 0;
+  for (size_t i = 0; i < kNumOutputs; ++i) {
+    equal_count += (a[i] == b[i]) ? 1 : 0;
+    std::bitset<sizeof(result_type) * 8> bitset(a[i] ^ b[i]);
+    changed_bits += bitset.count();
+    unchanged_bits += bitset.size() - bitset.count();
+
+    std::bitset<sizeof(result_type) * 8> a_set(a[i]);
+    std::bitset<sizeof(result_type) * 8> b_set(b[i]);
+    total_set += a_set.count() + b_set.count();
+    total_bits += 2 * 8 * sizeof(result_type);
+  }
+  // On average, half the bits are changed between two calls.
+  EXPECT_LE(changed_bits, 0.60 * (changed_bits + unchanged_bits));
+  EXPECT_GE(changed_bits, 0.40 * (changed_bits + unchanged_bits));
+
+  // verify using a quick normal-approximation to the binomial.
+  EXPECT_NEAR(total_set, total_bits * 0.5, 4 * std::sqrt(total_bits))
+      << "@" << total_set / static_cast<double>(total_bits);
+
+  // Also, A[i] == B[i] with probability (1/range) * N.
+  // Give this a pretty wide latitude, though.
+  const double kExpected = kNumOutputs / (1.0 * sizeof(result_type) * 8);
+  EXPECT_LE(equal_count, 1.0 + kExpected);
+}
+
+// Number of values that needs to be consumed to clean two sizes of buffer
+// and trigger third refresh. (slightly overestimates the actual state size).
+constexpr size_t kTwoBufferValues = 16;
+
+TYPED_TEST(PCGEngineTest, VerifyDiscard) {
+  using engine_type = TypeParam;
+
+  for (size_t num_used = 0; num_used < kTwoBufferValues; ++num_used) {
+    engine_type engine_used;
+    for (size_t i = 0; i < num_used; ++i) {
+      engine_used();
+    }
+
+    for (size_t num_discard = 0; num_discard < kTwoBufferValues;
+         ++num_discard) {
+      engine_type engine1 = engine_used;
+      engine_type engine2 = engine_used;
+      for (size_t i = 0; i < num_discard; ++i) {
+        engine1();
+      }
+      engine2.discard(num_discard);
+      for (size_t i = 0; i < kTwoBufferValues; ++i) {
+        const auto r1 = engine1();
+        const auto r2 = engine2();
+        ASSERT_EQ(r1, r2) << "used=" << num_used << " discard=" << num_discard;
+      }
+    }
+  }
+}
+
+TYPED_TEST(PCGEngineTest, StreamOperatorsResult) {
+  using engine_type = TypeParam;
+
+  std::wostringstream os;
+  std::wistringstream is;
+  engine_type engine;
+
+  EXPECT_EQ(&(os << engine), &os);
+  EXPECT_EQ(&(is >> engine), &is);
+}
+
+TYPED_TEST(PCGEngineTest, StreamSerialization) {
+  using engine_type = TypeParam;
+
+  for (size_t discard = 0; discard < kTwoBufferValues; ++discard) {
+    ExplicitSeedSeq seed_sequence{12, 34, 56};
+    engine_type engine(seed_sequence);
+    engine.discard(discard);
+
+    std::stringstream stream;
+    stream << engine;
+
+    engine_type new_engine;
+    stream >> new_engine;
+    for (size_t i = 0; i < 64; ++i) {
+      EXPECT_EQ(engine(), new_engine()) << " " << i;
+    }
+  }
+}
+
+constexpr size_t kNumGoldenOutputs = 127;
+
+// This test is checking if randen_engine is meets interface requirements
+// defined in [rand.req.urbg].
+TYPED_TEST(PCGEngineTest, RandomNumberEngineInterface) {
+  using engine_type = TypeParam;
+
+  using E = engine_type;
+  using T = typename E::result_type;
+
+  static_assert(std::is_copy_constructible<E>::value,
+                "engine_type must be copy constructible");
+
+  static_assert(absl::is_copy_assignable<E>::value,
+                "engine_type must be copy assignable");
+
+  static_assert(std::is_move_constructible<E>::value,
+                "engine_type must be move constructible");
+
+  static_assert(absl::is_move_assignable<E>::value,
+                "engine_type must be move assignable");
+
+  static_assert(std::is_same<decltype(std::declval<E>()()), T>::value,
+                "return type of operator() must be result_type");
+
+  // Names after definition of [rand.req.urbg] in C++ standard.
+  // e us a value of E
+  // v is a lvalue of E
+  // x, y are possibly const values of E
+  // s is a value of T
+  // q is a value satisfying requirements of seed_sequence
+  // z is a value of type unsigned long long
+  // os is a some specialization of basic_ostream
+  // is is a some specialization of basic_istream
+
+  E e, v;
+  const E x, y;
+  T s = 1;
+  std::seed_seq q{1, 2, 3};
+  unsigned long long z = 1;  // NOLINT(runtime/int)
+  std::wostringstream os;
+  std::wistringstream is;
+
+  E{};
+  E{x};
+  E{s};
+  E{q};
+
+  e.seed();
+
+  // MSVC emits error 2718 when using EXPECT_EQ(e, x)
+  //  * actual parameter with __declspec(align('#')) won't be aligned
+  EXPECT_TRUE(e == x);
+
+  e.seed(q);
+  {
+    E tmp(q);
+    EXPECT_TRUE(e == tmp);
+  }
+
+  e();
+  {
+    E tmp(q);
+    EXPECT_TRUE(e != tmp);
+  }
+
+  e.discard(z);
+
+  static_assert(std::is_same<decltype(x == y), bool>::value,
+                "return type of operator== must be bool");
+
+  static_assert(std::is_same<decltype(x != y), bool>::value,
+                "return type of operator== must be bool");
+}
+
+TYPED_TEST(PCGEngineTest, RandenEngineSFINAETest) {
+  using engine_type = TypeParam;
+  using result_type = typename engine_type::result_type;
+
+  {
+    engine_type engine(result_type(1));
+    engine.seed(result_type(1));
+  }
+
+  {
+    result_type n = 1;
+    engine_type engine(n);
+    engine.seed(n);
+  }
+
+  {
+    engine_type engine(1);
+    engine.seed(1);
+  }
+
+  {
+    int n = 1;
+    engine_type engine(n);
+    engine.seed(n);
+  }
+
+  {
+    std::seed_seq seed_seq;
+    engine_type engine(seed_seq);
+    engine.seed(seed_seq);
+  }
+
+  {
+    engine_type engine{std::seed_seq()};
+    engine.seed(std::seed_seq());
+  }
+}
+
+// ------------------------------------------------------------------
+// Stability tests for pcg64_2018_engine
+// ------------------------------------------------------------------
+TEST(PCG642018EngineTest, VerifyGolden) {
+  constexpr uint64_t kGolden[kNumGoldenOutputs] = {
+      0x01070196e695f8f1, 0x703ec840c59f4493, 0xe54954914b3a44fa,
+      0x96130ff204b9285e, 0x7d9fdef535ceb21a, 0x666feed42e1219a0,
+      0x981f685721c8326f, 0xad80710d6eab4dda, 0xe202c480b037a029,
+      0x5d3390eaedd907e2, 0x0756befb39c6b8aa, 0x1fb44ba6634d62a3,
+      0x8d20423662426642, 0x34ea910167a39fb4, 0x93010b43a80d0ab6,
+      0x663db08a98fc568a, 0x720b0a1335956fae, 0x2c35483e31e1d3ba,
+      0x429f39776337409d, 0xb46d99e638687344, 0x105370b96aedcaee,
+      0x3999e92f811cff71, 0xd230f8bcb591cfc9, 0x0dce3db2ba7bdea5,
+      0xcf2f52c91eec99af, 0x2bc7c24a8b998a39, 0xbd8af1b0d599a19c,
+      0x56bc45abc66059f5, 0x170a46dc170f7f1e, 0xc25daf5277b85fad,
+      0xe629c2e0c948eadb, 0x1720a796915542ed, 0x22fb0caa4f909951,
+      0x7e0c0f4175acd83d, 0xd9fcab37ff2a860c, 0xab2280fb2054bad1,
+      0x58e8a06f37fa9e99, 0xc3a52a30b06528c7, 0x0175f773a13fc1bd,
+      0x731cfc584b00e840, 0x404cc7b2648069cb, 0x5bc29153b0b7f783,
+      0x771310a38cc999d1, 0x766a572f0a71a916, 0x90f450fb4fc48348,
+      0xf080ea3e1c7b1a0d, 0x15471a4507d66a44, 0x7d58e55a78f3df69,
+      0x0130a094576ac99c, 0x46669cb2d04b1d87, 0x17ab5bed20191840,
+      0x95b177d260adff3e, 0x025fb624b6ee4c07, 0xb35de4330154a95f,
+      0xe8510fff67e24c79, 0x132c3cbcd76ed2d3, 0x35e7cc145a093904,
+      0x9f5b5b5f81583b79, 0x3ee749a533966233, 0x4af85886cdeda8cd,
+      0x0ca5380ecb3ef3aa, 0x4f674eb7661d3192, 0x88a29aad00cd7733,
+      0x70b627ca045ffac6, 0x5912b43ea887623d, 0x95dc9fc6f62cf221,
+      0x926081a12a5c905b, 0x9c57d4cd7dfce651, 0x85ab2cbf23e3bb5d,
+      0xc5cd669f63023152, 0x3067be0fad5d898e, 0x12b56f444cb53d05,
+      0xbc2e5a640c3434fc, 0x9280bff0e4613fe1, 0x98819094c528743e,
+      0x999d1c98d829df33, 0x9ff82a012dc89242, 0xf99183ed39c8be94,
+      0xf0f59161cd421c55, 0x3c705730c2f6c48d, 0x66ad85c6e9278a61,
+      0x2a3428e4a428d5d0, 0x79207d68fd04940d, 0xea7f2b402edc8430,
+      0xa06b419ac857f63b, 0xcb1dd0e6fbc47e1c, 0x4f55229200ada6a4,
+      0x9647b5e6359c927f, 0x30bf8f9197c7efe5, 0xa79519529cc384d0,
+      0xbb22c4f339ad6497, 0xd7b9782f59d14175, 0x0dff12fff2ec0118,
+      0xa331ad8305343a7c, 0x48dad7e3f17e0862, 0x324c6fb3fd3c9665,
+      0xf0e4350e7933dfc4, 0x7ccda2f30b8b03b6, 0xa0afc6179005de40,
+      0xee65da6d063b3a30, 0xb9506f42f2bfe87a, 0xc9a2e26b0ef5baa0,
+      0x39fa9d4f495011d6, 0xbecc21a45d023948, 0x6bf484c6593f737f,
+      0x8065e0070cadc3b7, 0x9ef617ed8d419799, 0xac692cf8c233dd15,
+      0xd2ed87583c4ebb98, 0xad95ba1bebfedc62, 0x9b60b160a8264e43,
+      0x0bc8c45f71fcf25b, 0x4a78035cdf1c9931, 0x4602dc106667e029,
+      0xb335a3c250498ac8, 0x0256ebc4df20cab8, 0x0c61efd153f0c8d9,
+      0xe5d0150a4f806f88, 0x99d6521d351e7d87, 0x8d4888c9f80f4325,
+      0x106c5735c1ba868d, 0x73414881b880a878, 0x808a9a58a3064751,
+      0x339a29f3746de3d5, 0x5410d7fa4f873896, 0xd84623c81d7b8a03,
+      0x1f7c7e7a7f47f462,
+  };
+
+  pcg64_2018_engine engine(0);
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    printf("0x%016lx, ", engine());
+    if (i % 3 == 2) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+#else
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+  engine.seed();
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+#endif
+}
+
+TEST(PCG642018EngineTest, VerifyGoldenSeeded) {
+  constexpr uint64_t kGolden[kNumGoldenOutputs] = {
+      0xb03988f1e39691ee, 0xbd2a1eb5ac31e97a, 0x8f00d6d433634d02,
+      0x1823c28d483d5776, 0x000c3ee3e1aeb74a, 0xfa82ef27a4f3df9c,
+      0xc6f382308654e454, 0x414afb1a238996c2, 0x4703a4bc252eb411,
+      0x99d64f62c8f7f654, 0xbb07ebe11a34fa44, 0x79eb06a363c06131,
+      0xf66ad3756f1c6b21, 0x130c01d5e869f457, 0x5ca2b9963aecbc81,
+      0xfef7bebc1de27e6c, 0x1d174faa5ed2cdbf, 0xd75b7a773f2bb889,
+      0xc35c872327a170a5, 0x46da6d88646a42fe, 0x4622985e0442dae2,
+      0xbe3cbd67297f1f9b, 0xe7c37b4a4798bfd1, 0x173d5dfad15a25c3,
+      0x0eb6849ba2961522, 0xb0ff7246e6700d73, 0x88cb9c42d3afa577,
+      0xb609731dbd94d917, 0xd3941cda04b40081, 0x28d140f7409bea3a,
+      0x3c96699a920a124a, 0xdb28be521958b2fd, 0x0a3f44db3d4c5124,
+      0x7ac8e60ba13b70d2, 0x75f03a41ded5195a, 0xaed10ac7c4e4825d,
+      0xb92a3b18aadb7adc, 0xda45e0081f2bca46, 0x74d39ab3753143fc,
+      0xb686038018fac9ca, 0x4cc309fe99542dbb, 0xf3e1a4fcb311097c,
+      0x58763d6fa698d69d, 0xd11c365dbecd8d60, 0x2c15d55725b1dee7,
+      0x89805f254d85658c, 0x2374c44dfc62158b, 0x9a8350fa7995328d,
+      0x198f838970cf91da, 0x96aff569562c0e53, 0xd76c8c52b7ec6e3f,
+      0x23a01cd9ae4baa81, 0x3adb366b6d02a893, 0xb3313e2a4c5b333f,
+      0x04c11230b96a5425, 0x1f7f7af04787d571, 0xaddb019365275ec7,
+      0x5c960468ccb09f42, 0x8438db698c69a44a, 0x492be1e46111637e,
+      0x9c6c01e18100c610, 0xbfe48e75b7d0aceb, 0xb5e0b89ec1ce6a00,
+      0x9d280ecbc2fe8997, 0x290d9e991ba5fcab, 0xeec5bec7d9d2a4f0,
+      0x726e81488f19150e, 0x1a6df7955a7e462c, 0x37a12d174ba46bb5,
+      0x3cdcdffd96b1b5c5, 0x2c5d5ac10661a26e, 0xa742ed18f22e50c4,
+      0x00e0ed88ff0d8a35, 0x3d3c1718cb1efc0b, 0x1d70c51ffbccbf11,
+      0xfbbb895132a4092f, 0x619d27f2fb095f24, 0x69af68200985e5c4,
+      0xbee4885f57373f8d, 0x10b7a6bfe0587e40, 0xa885e6cf2f7e5f0a,
+      0x59f879464f767550, 0x24e805d69056990d, 0x860970b911095891,
+      0xca3189954f84170d, 0x6652a5edd4590134, 0x5e1008cef76174bf,
+      0xcbd417881f2bcfe5, 0xfd49fc9d706ecd17, 0xeebf540221ebd066,
+      0x46af7679464504cb, 0xd4028486946956f1, 0xd4f41864b86c2103,
+      0x7af090e751583372, 0x98cdaa09278cb642, 0xffd42b921215602f,
+      0x1d05bec8466b1740, 0xf036fa78a0132044, 0x787880589d1ecc78,
+      0x5644552cfef33230, 0x0a97e275fe06884b, 0x96d1b13333d470b5,
+      0xc8b3cdad52d3b034, 0x091357b9db7376fd, 0xa5fe4232555edf8c,
+      0x3371bc3b6ada76b5, 0x7deeb2300477c995, 0x6fc6d4244f2849c1,
+      0x750e8cc797ca340a, 0x81728613cd79899f, 0x3467f4ee6f9aeb93,
+      0x5ef0a905f58c640f, 0x432db85e5101c98a, 0x6488e96f46ac80c2,
+      0x22fddb282625048c, 0x15b287a0bc2d4c5d, 0xa7e2343ef1f28bce,
+      0xc87ee1aa89bed09e, 0x220610107812c5e9, 0xcbdab6fcd640f586,
+      0x8d41047970928784, 0x1aa431509ec1ade0, 0xac3f0be53f518ddc,
+      0x16f4428ad81d0cbb, 0x675b13c2736fc4bb, 0x6db073afdd87e32d,
+      0x572f3ca2f1a078c6,
+  };
+
+  ExplicitSeedSeq seed_sequence{12, 34, 56};
+  pcg64_2018_engine engine(seed_sequence);
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    printf("0x%016lx, ", engine());
+    if (i % 3 == 2) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+#else
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+  engine.seed(seed_sequence);
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+#endif
+}
+
+TEST(PCG642018EngineTest, VerifyGoldenFromDeserializedEngine) {
+  constexpr uint64_t kGolden[kNumGoldenOutputs] = {
+      0xdd425b47b4113dea, 0x1b07176479d444b0, 0x6b391027586f2e42,
+      0xa166f2b15f4a2143, 0xffb6dbd7a179ee97, 0xb2c00035365bf0b1,
+      0x8fbb518b45855521, 0xfc789a55ddf87c3b, 0x429531f0f17ff355,
+      0xbe708560d603d283, 0x5bff415175c5cb6b, 0xe813491f4ad45394,
+      0xa853f4506d55880d, 0x7e538453e568172e, 0xe101f1e098ddd0ec,
+      0x6ee31266ee4c766d, 0xa8786d92d66b39d7, 0xfee622a2acf5e5b0,
+      0x5fe8e82c102fa7b3, 0x01f10be4cdb53c9d, 0xbe0545366f857022,
+      0x12e74f010a339bca, 0xb10d85ca40d5ce34, 0xe80d6feba5054875,
+      0x2b7c1ee6d567d4ee, 0x2a9cd043bfd03b66, 0x5cfc531bd239f3f1,
+      0x1c4734e4647d70f5, 0x85a8f60f006b5760, 0x6a4239ce76dca387,
+      0x8da0f86d7339335c, 0xf055b0468551374d, 0x486e8567e9bea9a0,
+      0x4cb531b8405192dd, 0xf813b1ee3157110b, 0x214c2a664a875d8e,
+      0x74531237b29b35f7, 0xa6f0267bb77a771e, 0x64b552bff54184a4,
+      0xa2d6f7af2d75b6fc, 0x460a10018e03b5ab, 0x76fd1fdcb81d0800,
+      0x76f5f81805070d9d, 0x1fb75cb1a70b289a, 0x9dfd25a022c4b27f,
+      0x9a31a14a80528e9e, 0x910dc565ddc25820, 0xd6aef8e2b0936c10,
+      0xe1773c507fe70225, 0xe027fd7aadd632bc, 0xc1fecb427089c8b8,
+      0xb5c74c69fa9dbf26, 0x71bf9b0e4670227d, 0x25f48fad205dcfdd,
+      0x905248ec4d689c56, 0x5c2b7631b0de5c9d, 0x9f2ee0f8f485036c,
+      0xfd6ce4ebb90bf7ea, 0xd435d20046085574, 0x6b7eadcb0625f986,
+      0x679d7d44b48be89e, 0x49683b8e1cdc49de, 0x4366cf76e9a2f4ca,
+      0x54026ec1cdad7bed, 0xa9a04385207f28d3, 0xc8e66de4eba074b2,
+      0x40b08c42de0f4cc0, 0x1d4c5e0e93c5bbc0, 0x19b80792e470ae2d,
+      0x6fcaaeaa4c2a5bd9, 0xa92cb07c4238438e, 0x8bb5c918a007e298,
+      0x7cd671e944874cf4, 0x88166470b1ba3cac, 0xd013d476eaeeade6,
+      0xcee416947189b3c3, 0x5d7c16ab0dce6088, 0xd3578a5c32b13d27,
+      0x3875db5adc9cc973, 0xfbdaba01c5b5dc56, 0xffc4fdd391b231c3,
+      0x2334520ecb164fec, 0x361c115e7b6de1fa, 0xeee58106cc3563d7,
+      0x8b7f35a8db25ebb8, 0xb29d00211e2cafa6, 0x22a39fe4614b646b,
+      0x92ca6de8b998506d, 0x40922fe3d388d1db, 0x9da47f1e540f802a,
+      0x811dceebf16a25db, 0xf6524ae22e0e53a9, 0x52d9e780a16eb99d,
+      0x4f504286bb830207, 0xf6654d4786bd5cc3, 0x00bd98316003a7e1,
+      0xefda054a6ab8f5f3, 0x46cfb0f4c1872827, 0xc22b316965c0f3b2,
+      0xd1a28087c7e7562a, 0xaa4f6a094b7f5cff, 0xfe2bc853a041f7da,
+      0xe9d531402a83c3ba, 0xe545d8663d3ce4dd, 0xfa2dcd7d91a13fa8,
+      0xda1a080e52a127b8, 0x19c98f1f809c3d84, 0x2cef109af4678c88,
+      0x53462accab3b9132, 0x176b13a80415394e, 0xea70047ef6bc178b,
+      0x57bca80506d6dcdf, 0xd853ba09ff09f5c4, 0x75f4df3a7ddd4775,
+      0x209c367ade62f4fe, 0xa9a0bbc74d5f4682, 0x5dfe34bada86c21a,
+      0xc2c05bbcd38566d1, 0x6de8088e348c916a, 0x6a7001c6000c2196,
+      0xd9fb51865fc4a367, 0x12f320e444ece8ff, 0x6d56f7f793d65035,
+      0x138f31b7a865f8aa, 0x58fc68b4026b9adf, 0xcd48954b79fb6436,
+      0x27dfce4a0232af87,
+  };
+
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  std::seed_seq seed_sequence{1, 2, 3};
+  pcg64_2018_engine engine(seed_sequence);
+  std::ostringstream stream;
+  stream << engine;
+  auto str = stream.str();
+  printf("%s\n\n", str.c_str());
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    printf("0x%016lx, ", engine());
+    if (i % 3 == 2) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+#else
+  pcg64_2018_engine engine;
+  std::istringstream stream(
+      "2549297995355413924 4865540595714422341 6364136223846793005 "
+      "1442695040888963407 18088519957565336995 4845369368158826708");
+  stream >> engine;
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+#endif
+}
+
+// ------------------------------------------------------------------
+// Stability tests for pcg32_2018_engine
+// ------------------------------------------------------------------
+TEST(PCG322018EngineTest, VerifyGolden) {
+  constexpr uint32_t kGolden[kNumGoldenOutputs] = {
+      0x7a7ecbd9, 0x89fd6c06, 0xae646aa8, 0xcd3cf945, 0x6204b303, 0x198c8585,
+      0x49fce611, 0xd1e9297a, 0x142d9440, 0xee75f56b, 0x473a9117, 0xe3a45903,
+      0xbce807a1, 0xe54e5f4d, 0x497d6c51, 0x61829166, 0xa740474b, 0x031912a8,
+      0x9de3defa, 0xd266dbf1, 0x0f38bebb, 0xec3c4f65, 0x07c5057d, 0xbbce03c8,
+      0xfd2ac7a8, 0xffcf4773, 0x5b10affb, 0xede1c842, 0xe22b01b7, 0xda133c8c,
+      0xaf89b0f4, 0x25d1b8bc, 0x9f625482, 0x7bfd6882, 0x2e2210c0, 0x2c8fb9a6,
+      0x42cb3b83, 0x40ce0dab, 0x644a3510, 0x36230ef2, 0xe2cb6d43, 0x1012b343,
+      0x746c6c9f, 0x36714cf8, 0xed1f5026, 0x8bbbf83e, 0xe98710f4, 0x8a2afa36,
+      0x09035349, 0x6dc1a487, 0x682b634b, 0xc106794f, 0x7dd78beb, 0x628c262b,
+      0x852fb232, 0xb153ac4c, 0x4f169d1b, 0xa69ab774, 0x4bd4b6f2, 0xdc351dd3,
+      0x93ff3c8c, 0xa30819ab, 0xff07758c, 0x5ab13c62, 0xd16d7fb5, 0xc4950ffa,
+      0xd309ae49, 0xb9677a87, 0x4464e317, 0x90dc44f1, 0xc694c1d4, 0x1d5e1168,
+      0xadf37a2d, 0xda38990d, 0x1ec4bd33, 0x36ca25ce, 0xfa0dc76a, 0x968a9d43,
+      0x6950ac39, 0xdd3276bc, 0x06d5a71e, 0x1f6f282d, 0x5c626c62, 0xdde3fc31,
+      0x152194ce, 0xc35ed14c, 0xb1f7224e, 0x47f76bb8, 0xb34fdd08, 0x7011395e,
+      0x162d2a49, 0x0d1bf09f, 0x9428a952, 0x03c5c344, 0xd3525616, 0x7816fff3,
+      0x6bceb8a8, 0x8345a081, 0x366420fd, 0x182abeda, 0x70f82745, 0xaf15ded8,
+      0xc7f52ca2, 0xa98db9c5, 0x919d99ba, 0x9c376c1c, 0xed8d34c2, 0x716ae9f5,
+      0xef062fa5, 0xee3b6c56, 0x52325658, 0x61afa9c3, 0xfdaf02f0, 0x961cf3ab,
+      0x9f291565, 0x4fbf3045, 0x0590c899, 0xde901385, 0x45005ffb, 0x509db162,
+      0x262fa941, 0x4c421653, 0x4b17c21e, 0xea0d1530, 0xde803845, 0x61bfd515,
+      0x438523ef,
+  };
+
+  pcg32_2018_engine engine(0);
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    printf("0x%08x, ", engine());
+    if (i % 6 == 5) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+#else
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+  engine.seed();
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+#endif
+}
+
+TEST(PCG322018EngineTest, VerifyGoldenSeeded) {
+  constexpr uint32_t kGolden[kNumGoldenOutputs] = {
+      0x60b5a64c, 0x978502f9, 0x80a75f60, 0x241f1158, 0xa4cd1dbb, 0xe7284017,
+      0x3b678da5, 0x5223ec99, 0xe4bdd5d9, 0x72190e6d, 0xe6e702c9, 0xff80c768,
+      0xcf126ed3, 0x1fbd20ab, 0x60980489, 0xbc72bf89, 0x407ac6c0, 0x00bf3c51,
+      0xf9087897, 0x172e4eb6, 0xe9e4f443, 0x1a6098bf, 0xbf44f8c2, 0xdd84a0e5,
+      0xd9a52364, 0xc0e2e786, 0x061ae2ba, 0x9facb8e3, 0x6109432d, 0xd4e0a013,
+      0xbd8eb9a6, 0x7e86c3b6, 0x629c0e68, 0x05337430, 0xb495b9f4, 0x11ccd65d,
+      0xb578db25, 0x66f1246d, 0x6ef20a7f, 0x5e429812, 0x11772130, 0xb944b5c2,
+      0x01624128, 0xa2385ab7, 0xd3e10d35, 0xbe570ec3, 0xc951656f, 0xbe8944a0,
+      0x7be41062, 0x5709f919, 0xd745feda, 0x9870b9ae, 0xb44b8168, 0x19e7683b,
+      0xded8017f, 0xc6e4d544, 0x91ae4225, 0xd6745fba, 0xb992f284, 0x65b12b33,
+      0xa9d5fdb4, 0xf105ce1a, 0x35ca1a6e, 0x2ff70dd0, 0xd8335e49, 0xfb71ddf2,
+      0xcaeabb89, 0x5c6f5f84, 0x9a811a7d, 0xbcecbbd1, 0x0f661ba0, 0x9ad93b9d,
+      0xedd23e0b, 0x42062f48, 0xd38dd7e4, 0x6cd63c9c, 0x640b98ae, 0x4bff5653,
+      0x12626371, 0x13266017, 0xe7a698d8, 0x39c74667, 0xe8fdf2e3, 0x52803bf8,
+      0x2af6895b, 0x91335b7b, 0x699e4961, 0x00a40fff, 0x253ff2b6, 0x4a6cf672,
+      0x9584e85f, 0xf2a5000c, 0x4d58aba8, 0xb8513e6a, 0x767fad65, 0x8e326f9e,
+      0x182f15a1, 0x163dab52, 0xdf99c780, 0x047282a1, 0xee4f90dd, 0xd50394ae,
+      0x6c9fd5f0, 0xb06a9194, 0x387e3840, 0x04a9487b, 0xf678a4c2, 0xd0a78810,
+      0xd502c97e, 0xd6a9b12a, 0x4accc5dc, 0x416ed53e, 0x50411536, 0xeeb89c24,
+      0x813a7902, 0x034ebca6, 0xffa52e7c, 0x7ecd3d0e, 0xfa37a0d2, 0xb1fbe2c1,
+      0xb7efc6d1, 0xefa4ccee, 0xf6f80424, 0x2283f3d9, 0x68732284, 0x94f3b5c8,
+      0xbbdeceb9,
+  };
+
+  ExplicitSeedSeq seed_sequence{12, 34, 56};
+  pcg32_2018_engine engine(seed_sequence);
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    printf("0x%08x, ", engine());
+    if (i % 6 == 5) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+#else
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+  engine.seed(seed_sequence);
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+#endif
+}
+
+TEST(PCG322018EngineTest, VerifyGoldenFromDeserializedEngine) {
+  constexpr uint64_t kGolden[kNumGoldenOutputs] = {
+      0x780f7042, 0xba137215, 0x43ab6f22, 0x0cb55f46, 0x44b2627d, 0x835597af,
+      0xea973ea1, 0x0d2abd35, 0x4fdd601c, 0xac4342fe, 0x7db7e93c, 0xe56ebcaf,
+      0x3596470a, 0x7770a9ad, 0x9b893320, 0x57db3415, 0xb432de54, 0xa02baf71,
+      0xa256aadb, 0x88921fc7, 0xa35fa6b3, 0xde3eca46, 0x605739a7, 0xa890b82b,
+      0xe457b7ad, 0x335fb903, 0xeb06790c, 0xb3c54bf6, 0x6141e442, 0xa599a482,
+      0xb78987cc, 0xc61dfe9d, 0x0f1d6ace, 0x17460594, 0x8f6a5061, 0x083dc354,
+      0xe9c337fb, 0xcfd105f7, 0x926764b6, 0x638d24dc, 0xeaac650a, 0x67d2cb9c,
+      0xd807733c, 0x205fc52e, 0xf5399e2e, 0x6c46ddcc, 0xb603e875, 0xce113a25,
+      0x3c8d4813, 0xfb584db8, 0xf6d255ff, 0xea80954f, 0x42e8be85, 0xb2feee72,
+      0x62bd8d16, 0x1be4a142, 0x97dca1a4, 0xdd6e7333, 0xb2caa20e, 0xa12b1588,
+      0xeb3a5a1a, 0x6fa5ba89, 0x077ea931, 0x8ddb1713, 0x0dd03079, 0x2c2ba965,
+      0xa77fac17, 0xc8325742, 0x8bb893bf, 0xc2315741, 0xeaceee92, 0x81dd2ee2,
+      0xe5214216, 0x1b9b8fb2, 0x01646d03, 0x24facc25, 0xd8c0e0bb, 0xa33fe106,
+      0xf34fe976, 0xb3b4b44e, 0x65618fed, 0x032c6192, 0xa9dd72ce, 0xf391887b,
+      0xf41c6a6e, 0x05c4bd6d, 0x37fa260e, 0x46b05659, 0xb5f6348a, 0x62d26d89,
+      0x39f6452d, 0xb17b30a2, 0xbdd82743, 0x38ecae3b, 0xfe90f0a2, 0xcb2d226d,
+      0xcf8a0b1c, 0x0eed3d4d, 0xa1f69cfc, 0xd7ac3ba5, 0xce9d9a6b, 0x121deb4c,
+      0x4a0d03f3, 0xc1821ed1, 0x59c249ac, 0xc0abb474, 0x28149985, 0xfd9a82ba,
+      0x5960c3b2, 0xeff00cba, 0x6073aa17, 0x25dc0919, 0x9976626e, 0xdd2ccc33,
+      0x39ecb6ec, 0xc6e15d13, 0xfac94cfd, 0x28cfd34f, 0xf2d2c32d, 0x51c23d08,
+      0x4fdb2f48, 0x97baa807, 0xf2c1004c, 0xc4ae8136, 0x71f31c94, 0x8c92d601,
+      0x36caf5cd,
+  };
+
+#if UPDATE_GOLDEN
+  (void)kGolden;  // Silence warning.
+  std::seed_seq seed_sequence{1, 2, 3};
+  pcg32_2018_engine engine(seed_sequence);
+  std::ostringstream stream;
+  stream << engine;
+  auto str = stream.str();
+  printf("%s\n\n", str.c_str());
+  for (size_t i = 0; i < kNumGoldenOutputs; ++i) {
+    printf("0x%08x, ", engine());
+    if (i % 6 == 5) {
+      printf("\n");
+    }
+  }
+  printf("\n\n\n");
+
+  EXPECT_FALSE(true);
+#else
+  pcg32_2018_engine engine;
+  std::istringstream stream(
+      "6364136223846793005 1442695040888963407 6537028157270659894");
+  stream >> engine;
+  for (const auto& elem : kGolden) {
+    EXPECT_EQ(elem, engine());
+  }
+#endif
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/platform.h b/weight/_dep/abseil-cpp/absl/random/internal/platform.h
new file mode 100644
index 0000000000000000000000000000000000000000..d779f481dd3f85b686f8c1855cfae0b32a09a800
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/platform.h
@@ -0,0 +1,171 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_PLATFORM_H_
+#define ABSL_RANDOM_INTERNAL_PLATFORM_H_
+
+// HERMETIC NOTE: The randen_hwaes target must not introduce duplicate
+// symbols from arbitrary system and other headers, since it may be built
+// with different flags from other targets, using different levels of
+// optimization, potentially introducing ODR violations.
+
+// -----------------------------------------------------------------------------
+// Platform Feature Checks
+// -----------------------------------------------------------------------------
+
+// Currently supported operating systems and associated preprocessor
+// symbols:
+//
+//   Linux and Linux-derived           __linux__
+//   Android                           __ANDROID__ (implies __linux__)
+//   Linux (non-Android)               __linux__ && !__ANDROID__
+//   Darwin (macOS and iOS)            __APPLE__
+//   Akaros (http://akaros.org)        __ros__
+//   Windows                           _WIN32
+//   NaCL                              __native_client__
+//   AsmJS                             __asmjs__
+//   WebAssembly                       __wasm__
+//   Fuchsia                           __Fuchsia__
+//
+// Note that since Android defines both __ANDROID__ and __linux__, one
+// may probe for either Linux or Android by simply testing for __linux__.
+//
+// NOTE: For __APPLE__ platforms, we use #include <TargetConditionals.h>
+// to distinguish os variants.
+//
+// http://nadeausoftware.com/articles/2012/01/c_c_tip_how_use_compiler_predefined_macros_detect_operating_system
+
+#if defined(__APPLE__)
+#include <TargetConditionals.h>
+#endif
+
+// -----------------------------------------------------------------------------
+// Architecture Checks
+// -----------------------------------------------------------------------------
+
+// These preprocessor directives are trying to determine CPU architecture,
+// including necessary headers to support hardware AES.
+//
+// ABSL_ARCH_{X86/PPC/ARM} macros determine the platform.
+#if defined(__x86_64__) || defined(__x86_64) || defined(_M_AMD64) || \
+    defined(_M_X64)
+#define ABSL_ARCH_X86_64
+#elif defined(__i386) || defined(_M_IX86)
+#define ABSL_ARCH_X86_32
+#elif defined(__aarch64__) || defined(__arm64__) || defined(_M_ARM64)
+#define ABSL_ARCH_AARCH64
+#elif defined(__arm__) || defined(__ARMEL__) || defined(_M_ARM)
+#define ABSL_ARCH_ARM
+#elif defined(__powerpc64__) || defined(__PPC64__) || defined(__powerpc__) || \
+    defined(__ppc__) || defined(__PPC__)
+#define ABSL_ARCH_PPC
+#else
+// Unsupported architecture.
+//  * https://sourceforge.net/p/predef/wiki/Architectures/
+//  * https://msdn.microsoft.com/en-us/library/b0084kay.aspx
+//  * for gcc, clang: "echo | gcc -E -dM -"
+#endif
+
+// -----------------------------------------------------------------------------
+// Attribute Checks
+// -----------------------------------------------------------------------------
+
+// ABSL_RANDOM_INTERNAL_RESTRICT annotates whether pointers may be considered
+// to be unaliased.
+#if defined(__clang__) || defined(__GNUC__)
+#define ABSL_RANDOM_INTERNAL_RESTRICT __restrict__
+#elif defined(_MSC_VER)
+#define ABSL_RANDOM_INTERNAL_RESTRICT __restrict
+#else
+#define ABSL_RANDOM_INTERNAL_RESTRICT
+#endif
+
+// ABSL_HAVE_ACCELERATED_AES indicates whether the currently active compiler
+// flags (e.g. -maes) allow using hardware accelerated AES instructions, which
+// implies us assuming that the target platform supports them.
+#define ABSL_HAVE_ACCELERATED_AES 0
+
+#if defined(ABSL_ARCH_X86_64)
+
+#if defined(__AES__) || defined(__AVX__)
+#undef ABSL_HAVE_ACCELERATED_AES
+#define ABSL_HAVE_ACCELERATED_AES 1
+#endif
+
+#elif defined(ABSL_ARCH_PPC)
+
+// Rely on VSX and CRYPTO extensions for vcipher on PowerPC.
+#if (defined(__VEC__) || defined(__ALTIVEC__)) && defined(__VSX__) && \
+    defined(__CRYPTO__)
+#undef ABSL_HAVE_ACCELERATED_AES
+#define ABSL_HAVE_ACCELERATED_AES 1
+#endif
+
+#elif defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
+
+// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053c/IHI0053C_acle_2_0.pdf
+// Rely on NEON+CRYPTO extensions for ARM.
+#if defined(__ARM_NEON) && defined(__ARM_FEATURE_CRYPTO)
+#undef ABSL_HAVE_ACCELERATED_AES
+#define ABSL_HAVE_ACCELERATED_AES 1
+#endif
+
+#endif
+
+// NaCl does not allow AES.
+#if defined(__native_client__)
+#undef ABSL_HAVE_ACCELERATED_AES
+#define ABSL_HAVE_ACCELERATED_AES 0
+#endif
+
+// ABSL_RANDOM_INTERNAL_AES_DISPATCH indicates whether the currently active
+// platform has, or should use run-time dispatch for selecting the
+// accelerated Randen implementation.
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
+
+#if defined(ABSL_ARCH_X86_64)
+// Dispatch is available on x86_64
+#undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
+#elif defined(__linux__) && defined(ABSL_ARCH_PPC)
+// Or when running linux PPC
+#undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
+#elif defined(__linux__) && defined(ABSL_ARCH_AARCH64)
+// Or when running linux AArch64
+#undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
+#elif defined(__linux__) && defined(ABSL_ARCH_ARM) && (__ARM_ARCH >= 8)
+// Or when running linux ARM v8 or higher.
+// (This captures a lot of Android configurations.)
+#undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 1
+#endif
+
+// NaCl does not allow dispatch.
+#if defined(__native_client__)
+#undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
+#endif
+
+// iOS does not support dispatch, even on x86, since applications
+// should be bundled as fat binaries, with a different build tailored for
+// each specific supported platform/architecture.
+#if (defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE) || \
+    (defined(TARGET_OS_IPHONE_SIMULATOR) && TARGET_OS_IPHONE_SIMULATOR)
+#undef ABSL_RANDOM_INTERNAL_AES_DISPATCH
+#define ABSL_RANDOM_INTERNAL_AES_DISPATCH 0
+#endif
+
+#endif  // ABSL_RANDOM_INTERNAL_PLATFORM_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg.cc b/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5aefa7d97b50c940446e9caac9ef66e6e1006acf
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg.cc
@@ -0,0 +1,253 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/pool_urbg.h"
+
+#include <algorithm>
+#include <atomic>
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+
+#include "absl/base/attributes.h"
+#include "absl/base/call_once.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/spinlock.h"
+#include "absl/base/internal/sysinfo.h"
+#include "absl/base/internal/unaligned_access.h"
+#include "absl/base/optimization.h"
+#include "absl/random/internal/randen.h"
+#include "absl/random/internal/seed_material.h"
+#include "absl/random/seed_gen_exception.h"
+
+using absl::base_internal::SpinLock;
+using absl::base_internal::SpinLockHolder;
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+namespace {
+
+// RandenPoolEntry is a thread-safe pseudorandom bit generator, implementing a
+// single generator within a RandenPool<T>. It is an internal implementation
+// detail, and does not aim to conform to [rand.req.urng].
+//
+// NOTE: There are alignment issues when used on ARM, for instance.
+// See the allocation code in PoolAlignedAlloc().
+class RandenPoolEntry {
+ public:
+  static constexpr size_t kState = RandenTraits::kStateBytes / sizeof(uint32_t);
+  static constexpr size_t kCapacity =
+      RandenTraits::kCapacityBytes / sizeof(uint32_t);
+
+  void Init(absl::Span<const uint32_t> data) {
+    SpinLockHolder l(&mu_);  // Always uncontested.
+    std::copy(data.begin(), data.end(), std::begin(state_));
+    next_ = kState;
+  }
+
+  // Copy bytes into out.
+  void Fill(uint8_t* out, size_t bytes) ABSL_LOCKS_EXCLUDED(mu_);
+
+  // Returns random bits from the buffer in units of T.
+  template <typename T>
+  inline T Generate() ABSL_LOCKS_EXCLUDED(mu_);
+
+  inline void MaybeRefill() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
+    if (next_ >= kState) {
+      next_ = kCapacity;
+      impl_.Generate(state_);
+    }
+  }
+
+ private:
+  // Randen URBG state.
+  uint32_t state_[kState] ABSL_GUARDED_BY(mu_);  // First to satisfy alignment.
+  SpinLock mu_;
+  const Randen impl_;
+  size_t next_ ABSL_GUARDED_BY(mu_);
+};
+
+template <>
+inline uint8_t RandenPoolEntry::Generate<uint8_t>() {
+  SpinLockHolder l(&mu_);
+  MaybeRefill();
+  return static_cast<uint8_t>(state_[next_++]);
+}
+
+template <>
+inline uint16_t RandenPoolEntry::Generate<uint16_t>() {
+  SpinLockHolder l(&mu_);
+  MaybeRefill();
+  return static_cast<uint16_t>(state_[next_++]);
+}
+
+template <>
+inline uint32_t RandenPoolEntry::Generate<uint32_t>() {
+  SpinLockHolder l(&mu_);
+  MaybeRefill();
+  return state_[next_++];
+}
+
+template <>
+inline uint64_t RandenPoolEntry::Generate<uint64_t>() {
+  SpinLockHolder l(&mu_);
+  if (next_ >= kState - 1) {
+    next_ = kCapacity;
+    impl_.Generate(state_);
+  }
+  auto p = state_ + next_;
+  next_ += 2;
+
+  uint64_t result;
+  std::memcpy(&result, p, sizeof(result));
+  return result;
+}
+
+void RandenPoolEntry::Fill(uint8_t* out, size_t bytes) {
+  SpinLockHolder l(&mu_);
+  while (bytes > 0) {
+    MaybeRefill();
+    size_t remaining = (kState - next_) * sizeof(state_[0]);
+    size_t to_copy = std::min(bytes, remaining);
+    std::memcpy(out, &state_[next_], to_copy);
+    out += to_copy;
+    bytes -= to_copy;
+    next_ += (to_copy + sizeof(state_[0]) - 1) / sizeof(state_[0]);
+  }
+}
+
+// Number of pooled urbg entries.
+static constexpr size_t kPoolSize = 8;
+
+// Shared pool entries.
+static absl::once_flag pool_once;
+ABSL_CACHELINE_ALIGNED static RandenPoolEntry* shared_pools[kPoolSize];
+
+// Returns an id in the range [0 ... kPoolSize), which indexes into the
+// pool of random engines.
+//
+// Each thread to access the pool is assigned a sequential ID (without reuse)
+// from the pool-id space; the id is cached in a thread_local variable.
+// This id is assigned based on the arrival-order of the thread to the
+// GetPoolID call; this has no binary, CL, or runtime stability because
+// on subsequent runs the order within the same program may be significantly
+// different. However, as other thread IDs are not assigned sequentially,
+// this is not expected to matter.
+size_t GetPoolID() {
+  static_assert(kPoolSize >= 1,
+                "At least one urbg instance is required for PoolURBG");
+
+  ABSL_CONST_INIT static std::atomic<uint64_t> sequence{0};
+
+#ifdef ABSL_HAVE_THREAD_LOCAL
+  static thread_local size_t my_pool_id = kPoolSize;
+  if (ABSL_PREDICT_FALSE(my_pool_id == kPoolSize)) {
+    my_pool_id = (sequence++ % kPoolSize);
+  }
+  return my_pool_id;
+#else
+  static pthread_key_t tid_key = [] {
+    pthread_key_t tmp_key;
+    int err = pthread_key_create(&tmp_key, nullptr);
+    if (err) {
+      ABSL_RAW_LOG(FATAL, "pthread_key_create failed with %d", err);
+    }
+    return tmp_key;
+  }();
+
+  // Store the value in the pthread_{get/set}specific. However an uninitialized
+  // value is 0, so add +1 to distinguish from the null value.
+  uintptr_t my_pool_id =
+      reinterpret_cast<uintptr_t>(pthread_getspecific(tid_key));
+  if (ABSL_PREDICT_FALSE(my_pool_id == 0)) {
+    // No allocated ID, allocate the next value, cache it, and return.
+    my_pool_id = (sequence++ % kPoolSize) + 1;
+    int err = pthread_setspecific(tid_key, reinterpret_cast<void*>(my_pool_id));
+    if (err) {
+      ABSL_RAW_LOG(FATAL, "pthread_setspecific failed with %d", err);
+    }
+  }
+  return my_pool_id - 1;
+#endif
+}
+
+// Allocate a RandenPoolEntry with at least 32-byte alignment, which is required
+// by ARM platform code.
+RandenPoolEntry* PoolAlignedAlloc() {
+  constexpr size_t kAlignment =
+      ABSL_CACHELINE_SIZE > 32 ? ABSL_CACHELINE_SIZE : 32;
+
+  // Not all the platforms that we build for have std::aligned_alloc, however
+  // since we never free these objects, we can over allocate and munge the
+  // pointers to the correct alignment.
+  uintptr_t x = reinterpret_cast<uintptr_t>(
+      new char[sizeof(RandenPoolEntry) + kAlignment]);
+  auto y = x % kAlignment;
+  void* aligned = reinterpret_cast<void*>(y == 0 ? x : (x + kAlignment - y));
+  return new (aligned) RandenPoolEntry();
+}
+
+// Allocate and initialize kPoolSize objects of type RandenPoolEntry.
+//
+// The initialization strategy is to initialize one object directly from
+// OS entropy, then to use that object to seed all of the individual
+// pool instances.
+void InitPoolURBG() {
+  static constexpr size_t kSeedSize =
+      RandenTraits::kStateBytes / sizeof(uint32_t);
+  // Read the seed data from OS entropy once.
+  uint32_t seed_material[kPoolSize * kSeedSize];
+  if (!random_internal::ReadSeedMaterialFromOSEntropy(
+          absl::MakeSpan(seed_material))) {
+    random_internal::ThrowSeedGenException();
+  }
+  for (size_t i = 0; i < kPoolSize; i++) {
+    shared_pools[i] = PoolAlignedAlloc();
+    shared_pools[i]->Init(
+        absl::MakeSpan(&seed_material[i * kSeedSize], kSeedSize));
+  }
+}
+
+// Returns the pool entry for the current thread.
+RandenPoolEntry* GetPoolForCurrentThread() {
+  absl::call_once(pool_once, InitPoolURBG);
+  return shared_pools[GetPoolID()];
+}
+
+}  // namespace
+
+template <typename T>
+typename RandenPool<T>::result_type RandenPool<T>::Generate() {
+  auto* pool = GetPoolForCurrentThread();
+  return pool->Generate<T>();
+}
+
+template <typename T>
+void RandenPool<T>::Fill(absl::Span<result_type> data) {
+  auto* pool = GetPoolForCurrentThread();
+  pool->Fill(reinterpret_cast<uint8_t*>(data.data()),
+             data.size() * sizeof(result_type));
+}
+
+template class RandenPool<uint8_t>;
+template class RandenPool<uint16_t>;
+template class RandenPool<uint32_t>;
+template class RandenPool<uint64_t>;
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg.h b/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg.h
new file mode 100644
index 0000000000000000000000000000000000000000..05721929f54e6a5fb1adfa467de3c37d0bf49f23
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg.h
@@ -0,0 +1,131 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_POOL_URBG_H_
+#define ABSL_RANDOM_INTERNAL_POOL_URBG_H_
+
+#include <cinttypes>
+#include <limits>
+
+#include "absl/random/internal/traits.h"
+#include "absl/types/span.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// RandenPool is a thread-safe random number generator [random.req.urbg] that
+// uses an underlying pool of Randen generators to generate values.  Each thread
+// has affinity to one instance of the underlying pool generators.  Concurrent
+// access is guarded by a spin-lock.
+template <typename T>
+class RandenPool {
+ public:
+  using result_type = T;
+  static_assert(std::is_unsigned<result_type>::value,
+                "RandenPool template argument must be a built-in unsigned "
+                "integer type");
+
+  static constexpr result_type(min)() {
+    return (std::numeric_limits<result_type>::min)();
+  }
+
+  static constexpr result_type(max)() {
+    return (std::numeric_limits<result_type>::max)();
+  }
+
+  RandenPool() {}
+
+  // Returns a single value.
+  inline result_type operator()() { return Generate(); }
+
+  // Fill data with random values.
+  static void Fill(absl::Span<result_type> data);
+
+ protected:
+  // Generate returns a single value.
+  static result_type Generate();
+};
+
+extern template class RandenPool<uint8_t>;
+extern template class RandenPool<uint16_t>;
+extern template class RandenPool<uint32_t>;
+extern template class RandenPool<uint64_t>;
+
+// PoolURBG uses an underlying pool of random generators to implement a
+// thread-compatible [random.req.urbg] interface with an internal cache of
+// values.
+template <typename T, size_t kBufferSize>
+class PoolURBG {
+  // Inheritance to access the protected static members of RandenPool.
+  using unsigned_type = typename make_unsigned_bits<T>::type;
+  using PoolType = RandenPool<unsigned_type>;
+  using SpanType = absl::Span<unsigned_type>;
+
+  static constexpr size_t kInitialBuffer = kBufferSize + 1;
+  static constexpr size_t kHalfBuffer = kBufferSize / 2;
+
+ public:
+  using result_type = T;
+
+  static_assert(std::is_unsigned<result_type>::value,
+                "PoolURBG must be parameterized by an unsigned integer type");
+
+  static_assert(kBufferSize > 1,
+                "PoolURBG must be parameterized by a buffer-size > 1");
+
+  static_assert(kBufferSize <= 256,
+                "PoolURBG must be parameterized by a buffer-size <= 256");
+
+  static constexpr result_type(min)() {
+    return (std::numeric_limits<result_type>::min)();
+  }
+
+  static constexpr result_type(max)() {
+    return (std::numeric_limits<result_type>::max)();
+  }
+
+  PoolURBG() : next_(kInitialBuffer) {}
+
+  // copy-constructor does not copy cache.
+  PoolURBG(const PoolURBG&) : next_(kInitialBuffer) {}
+  const PoolURBG& operator=(const PoolURBG&) {
+    next_ = kInitialBuffer;
+    return *this;
+  }
+
+  // move-constructor does move cache.
+  PoolURBG(PoolURBG&&) = default;
+  PoolURBG& operator=(PoolURBG&&) = default;
+
+  inline result_type operator()() {
+    if (next_ >= kBufferSize) {
+      next_ = (kBufferSize > 2 && next_ > kBufferSize) ? kHalfBuffer : 0;
+      PoolType::Fill(SpanType(reinterpret_cast<unsigned_type*>(state_ + next_),
+                              kBufferSize - next_));
+    }
+    return state_[next_++];
+  }
+
+ private:
+  // Buffer size.
+  size_t next_;  // index within state_
+  result_type state_[kBufferSize];
+};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_POOL_URBG_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..53f4eacf16fe64892230f61e41d970c872212f75
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/pool_urbg_test.cc
@@ -0,0 +1,182 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/pool_urbg.h"
+
+#include <algorithm>
+#include <bitset>
+#include <cmath>
+#include <cstdint>
+#include <iterator>
+
+#include "gtest/gtest.h"
+#include "absl/meta/type_traits.h"
+#include "absl/types/span.h"
+
+using absl::random_internal::PoolURBG;
+using absl::random_internal::RandenPool;
+
+namespace {
+
+// is_randen_pool trait is true when parameterized by an RandenPool
+template <typename T>
+using is_randen_pool = typename absl::disjunction<  //
+    std::is_same<T, RandenPool<uint8_t>>,           //
+    std::is_same<T, RandenPool<uint16_t>>,          //
+    std::is_same<T, RandenPool<uint32_t>>,          //
+    std::is_same<T, RandenPool<uint64_t>>>;         //
+
+// MyFill either calls RandenPool::Fill() or std::generate(..., rng)
+template <typename T, typename V>
+typename absl::enable_if_t<absl::negation<is_randen_pool<T>>::value, void>  //
+MyFill(T& rng, absl::Span<V> data) {  // NOLINT(runtime/references)
+  std::generate(std::begin(data), std::end(data), rng);
+}
+
+template <typename T, typename V>
+typename absl::enable_if_t<is_randen_pool<T>::value, void>  //
+MyFill(T& rng, absl::Span<V> data) {  // NOLINT(runtime/references)
+  rng.Fill(data);
+}
+
+template <typename EngineType>
+class PoolURBGTypedTest : public ::testing::Test {};
+
+using EngineTypes = ::testing::Types<  //
+    RandenPool<uint8_t>,               //
+    RandenPool<uint16_t>,              //
+    RandenPool<uint32_t>,              //
+    RandenPool<uint64_t>,              //
+    PoolURBG<uint8_t, 2>,              //
+    PoolURBG<uint16_t, 2>,             //
+    PoolURBG<uint32_t, 2>,             //
+    PoolURBG<uint64_t, 2>,             //
+    PoolURBG<unsigned int, 8>,         // NOLINT(runtime/int)
+    PoolURBG<unsigned long, 8>,        // NOLINT(runtime/int)
+    PoolURBG<unsigned long int, 4>,    // NOLINT(runtime/int)
+    PoolURBG<unsigned long long, 4>>;  // NOLINT(runtime/int)
+
+TYPED_TEST_SUITE(PoolURBGTypedTest, EngineTypes);
+
+// This test is checks that the engines meet the URBG interface requirements
+// defined in [rand.req.urbg].
+TYPED_TEST(PoolURBGTypedTest, URBGInterface) {
+  using E = TypeParam;
+  using T = typename E::result_type;
+
+  static_assert(std::is_copy_constructible<E>::value,
+                "engine must be copy constructible");
+
+  static_assert(absl::is_copy_assignable<E>::value,
+                "engine must be copy assignable");
+
+  E e;
+  const E x;
+
+  e();
+
+  static_assert(std::is_same<decltype(e()), T>::value,
+                "return type of operator() must be result_type");
+
+  E u0(x);
+  u0();
+
+  E u1 = e;
+  u1();
+}
+
+// This validates that sequences are independent.
+TYPED_TEST(PoolURBGTypedTest, VerifySequences) {
+  using E = TypeParam;
+  using result_type = typename E::result_type;
+
+  E rng;
+  (void)rng();  // Discard one value.
+
+  constexpr int kNumOutputs = 64;
+  result_type a[kNumOutputs];
+  result_type b[kNumOutputs];
+  std::fill(std::begin(b), std::end(b), 0);
+
+  // Fill a using Fill or generate, depending on the engine type.
+  {
+    E x = rng;
+    MyFill(x, absl::MakeSpan(a));
+  }
+
+  // Fill b using std::generate().
+  {
+    E x = rng;
+    std::generate(std::begin(b), std::end(b), x);
+  }
+
+  // Test that generated sequence changed as sequence of bits, i.e. if about
+  // half of the bites were flipped between two non-correlated values.
+  size_t changed_bits = 0;
+  size_t unchanged_bits = 0;
+  size_t total_set = 0;
+  size_t total_bits = 0;
+  size_t equal_count = 0;
+  for (size_t i = 0; i < kNumOutputs; ++i) {
+    equal_count += (a[i] == b[i]) ? 1 : 0;
+    std::bitset<sizeof(result_type) * 8> bitset(a[i] ^ b[i]);
+    changed_bits += bitset.count();
+    unchanged_bits += bitset.size() - bitset.count();
+
+    std::bitset<sizeof(result_type) * 8> a_set(a[i]);
+    std::bitset<sizeof(result_type) * 8> b_set(b[i]);
+    total_set += a_set.count() + b_set.count();
+    total_bits += 2 * 8 * sizeof(result_type);
+  }
+  // On average, half the bits are changed between two calls.
+  EXPECT_LE(changed_bits, 0.60 * (changed_bits + unchanged_bits));
+  EXPECT_GE(changed_bits, 0.40 * (changed_bits + unchanged_bits));
+
+  // verify using a quick normal-approximation to the binomial.
+  EXPECT_NEAR(total_set, total_bits * 0.5, 4 * std::sqrt(total_bits))
+      << "@" << total_set / static_cast<double>(total_bits);
+
+  // Also, A[i] == B[i] with probability (1/range) * N.
+  // Give this a pretty wide latitude, though.
+  const double kExpected = kNumOutputs / (1.0 * sizeof(result_type) * 8);
+  EXPECT_LE(equal_count, 1.0 + kExpected);
+}
+
+}  // namespace
+
+/*
+$ nanobenchmarks 1 RandenPool construct
+$ nanobenchmarks 1 PoolURBG construct
+
+RandenPool<uint32_t> | 1    | 1000 |    48482.00 ticks | 48.48 ticks | 13.9 ns
+RandenPool<uint32_t> | 10   | 2000 |  1028795.00 ticks | 51.44 ticks | 14.7 ns
+RandenPool<uint32_t> | 100  | 1000 |  5119968.00 ticks | 51.20 ticks | 14.6 ns
+RandenPool<uint32_t> | 1000 |  500 | 25867936.00 ticks | 51.74 ticks | 14.8 ns
+
+RandenPool<uint64_t> | 1    | 1000 |    49921.00 ticks | 49.92 ticks | 14.3 ns
+RandenPool<uint64_t> | 10   | 2000 |  1208269.00 ticks | 60.41 ticks | 17.3 ns
+RandenPool<uint64_t> | 100  | 1000 |  5844955.00 ticks | 58.45 ticks | 16.7 ns
+RandenPool<uint64_t> | 1000 |  500 | 28767404.00 ticks | 57.53 ticks | 16.4 ns
+
+PoolURBG<uint32_t,8> | 1    | 1000 |    86431.00 ticks | 86.43 ticks | 24.7 ns
+PoolURBG<uint32_t,8> | 10   | 1000 |   206191.00 ticks | 20.62 ticks |  5.9 ns
+PoolURBG<uint32_t,8> | 100  | 1000 |  1516049.00 ticks | 15.16 ticks |  4.3 ns
+PoolURBG<uint32_t,8> | 1000 |  500 |  7613936.00 ticks | 15.23 ticks |  4.4 ns
+
+PoolURBG<uint64_t,4> | 1    | 1000 |    96668.00 ticks | 96.67 ticks | 27.6 ns
+PoolURBG<uint64_t,4> | 10   | 1000 |   282423.00 ticks | 28.24 ticks |  8.1 ns
+PoolURBG<uint64_t,4> | 100  | 1000 |  2609587.00 ticks | 26.10 ticks |  7.5 ns
+PoolURBG<uint64_t,4> | 1000 |  500 | 12408757.00 ticks | 24.82 ticks |  7.1 ns
+
+*/
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/randen_benchmarks.cc b/weight/_dep/abseil-cpp/absl/random/internal/randen_benchmarks.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ec086cea49d74e42ab5cbfc21298e6c96597185b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/randen_benchmarks.cc
@@ -0,0 +1,176 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#include "absl/random/internal/randen.h"
+
+#include <cstdint>
+#include <cstdio>
+#include <cstring>
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/random/internal/nanobenchmark.h"
+#include "absl/random/internal/platform.h"
+#include "absl/random/internal/randen_engine.h"
+#include "absl/random/internal/randen_hwaes.h"
+#include "absl/random/internal/randen_slow.h"
+#include "absl/strings/numbers.h"
+
+namespace {
+
+using absl::random_internal::Randen;
+using absl::random_internal::RandenHwAes;
+using absl::random_internal::RandenSlow;
+
+using absl::random_internal_nanobenchmark::FuncInput;
+using absl::random_internal_nanobenchmark::FuncOutput;
+using absl::random_internal_nanobenchmark::InvariantTicksPerSecond;
+using absl::random_internal_nanobenchmark::MeasureClosure;
+using absl::random_internal_nanobenchmark::Params;
+using absl::random_internal_nanobenchmark::PinThreadToCPU;
+using absl::random_internal_nanobenchmark::Result;
+
+// Local state parameters.
+static constexpr size_t kStateSizeT = Randen::kStateBytes / sizeof(uint64_t);
+static constexpr size_t kSeedSizeT = Randen::kSeedBytes / sizeof(uint32_t);
+
+// Randen implementation benchmarks.
+template <typename T>
+struct AbsorbFn : public T {
+  // These are both cast to uint128* in the RandenHwAes implementation, so
+  // ensure they are 16 byte aligned.
+  alignas(16) mutable uint64_t state[kStateSizeT] = {};
+  alignas(16) mutable uint32_t seed[kSeedSizeT] = {};
+
+  static constexpr size_t bytes() { return sizeof(seed); }
+
+  FuncOutput operator()(const FuncInput num_iters) const {
+    for (size_t i = 0; i < num_iters; ++i) {
+      this->Absorb(seed, state);
+    }
+    return state[0];
+  }
+};
+
+template <typename T>
+struct GenerateFn : public T {
+  mutable uint64_t state[kStateSizeT];
+  GenerateFn() { std::memset(state, 0, sizeof(state)); }
+
+  static constexpr size_t bytes() { return sizeof(state); }
+
+  FuncOutput operator()(const FuncInput num_iters) const {
+    const auto* keys = this->GetKeys();
+    for (size_t i = 0; i < num_iters; ++i) {
+      this->Generate(keys, state);
+    }
+    return state[0];
+  }
+};
+
+template <typename UInt>
+struct Engine {
+  mutable absl::random_internal::randen_engine<UInt> rng;
+
+  static constexpr size_t bytes() { return sizeof(UInt); }
+
+  FuncOutput operator()(const FuncInput num_iters) const {
+    for (size_t i = 0; i < num_iters - 1; ++i) {
+      rng();
+    }
+    return rng();
+  }
+};
+
+template <size_t N>
+void Print(const char* name, const size_t n, const Result (&results)[N],
+           const size_t bytes) {
+  if (n == 0) {
+    ABSL_RAW_LOG(
+        WARNING,
+        "WARNING: Measurement failed, should not happen when using "
+        "PinThreadToCPU unless the region to measure takes > 1 second.\n");
+    return;
+  }
+
+  static const double ns_per_tick = 1e9 / InvariantTicksPerSecond();
+  static constexpr const double kNsPerS = 1e9;                 // ns/s
+  static constexpr const double kMBPerByte = 1.0 / 1048576.0;  // Mb / b
+  static auto header = [] {
+    return printf("%20s %8s: %12s ticks; %9s  (%9s) %8s\n", "Name", "Count",
+                  "Total", "Variance", "Time", "bytes/s");
+  }();
+  (void)header;
+
+  for (size_t i = 0; i < n; ++i) {
+    const double ticks_per_call = results[i].ticks / results[i].input;
+    const double ns_per_call = ns_per_tick * ticks_per_call;
+    const double bytes_per_ns = bytes / ns_per_call;
+    const double mb_per_s = bytes_per_ns * kNsPerS * kMBPerByte;
+    // Output
+    printf("%20s %8zu: %12.2f ticks; MAD=%4.2f%%  (%6.1f ns) %8.1f Mb/s\n",
+           name, results[i].input, results[i].ticks,
+           results[i].variability * 100.0, ns_per_call, mb_per_s);
+  }
+}
+
+// Fails here
+template <typename Op, size_t N>
+void Measure(const char* name, const FuncInput (&inputs)[N]) {
+  Op op;
+
+  Result results[N];
+  Params params;
+  params.verbose = false;
+  params.max_evals = 6;  // avoid test timeout
+  const size_t num_results = MeasureClosure(op, inputs, N, results, params);
+  Print(name, num_results, results, op.bytes());
+}
+
+// unpredictable == 1 but the compiler does not know that.
+void RunAll(const int argc, char* argv[]) {
+  if (argc == 2) {
+    int cpu = -1;
+    if (!absl::SimpleAtoi(argv[1], &cpu)) {
+      ABSL_RAW_LOG(FATAL, "The optional argument must be a CPU number >= 0.\n");
+    }
+    PinThreadToCPU(cpu);
+  }
+
+  // The compiler cannot reduce this to a constant.
+  const FuncInput unpredictable = (argc != 999);
+  static const FuncInput inputs[] = {unpredictable * 100, unpredictable * 1000};
+
+#if !defined(ABSL_INTERNAL_DISABLE_AES) && ABSL_HAVE_ACCELERATED_AES
+  Measure<AbsorbFn<RandenHwAes>>("Absorb (HwAes)", inputs);
+#endif
+  Measure<AbsorbFn<RandenSlow>>("Absorb (Slow)", inputs);
+
+#if !defined(ABSL_INTERNAL_DISABLE_AES) && ABSL_HAVE_ACCELERATED_AES
+  Measure<GenerateFn<RandenHwAes>>("Generate (HwAes)", inputs);
+#endif
+  Measure<GenerateFn<RandenSlow>>("Generate (Slow)", inputs);
+
+  // Measure the production engine.
+  static const FuncInput inputs1[] = {unpredictable * 1000,
+                                      unpredictable * 10000};
+  Measure<Engine<uint64_t>>("randen_engine<uint64_t>", inputs1);
+  Measure<Engine<uint32_t>>("randen_engine<uint32_t>", inputs1);
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+  RunAll(argc, argv);
+  return 0;
+}
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/randen_detect.h b/weight/_dep/abseil-cpp/absl/random/internal/randen_detect.h
new file mode 100644
index 0000000000000000000000000000000000000000..f283f4322647d102383d3903185fcc8df05f962a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/randen_detect.h
@@ -0,0 +1,33 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_RANDEN_DETECT_H_
+#define ABSL_RANDOM_INTERNAL_RANDEN_DETECT_H_
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// Returns whether the current CPU supports RandenHwAes implementation.
+// This typically involves supporting cryptographic extensions on whichever
+// platform is currently running.
+bool CPUSupportsRandenHwAes();
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_RANDEN_DETECT_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/randen_hwaes.cc b/weight/_dep/abseil-cpp/absl/random/internal/randen_hwaes.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f535f4c53aade1e6e8a4f550e784c20ee6d406f8
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/randen_hwaes.cc
@@ -0,0 +1,526 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// HERMETIC NOTE: The randen_hwaes target must not introduce duplicate
+// symbols from arbitrary system and other headers, since it may be built
+// with different flags from other targets, using different levels of
+// optimization, potentially introducing ODR violations.
+
+#include "absl/random/internal/randen_hwaes.h"
+
+#include <cstdint>
+#include <cstring>
+
+#include "absl/base/attributes.h"
+#include "absl/numeric/int128.h"
+#include "absl/random/internal/platform.h"
+#include "absl/random/internal/randen_traits.h"
+
+// ABSL_RANDEN_HWAES_IMPL indicates whether this file will contain
+// a hardware accelerated implementation of randen, or whether it
+// will contain stubs that exit the process.
+#if ABSL_HAVE_ACCELERATED_AES
+// The following platforms have implemented RandenHwAes.
+#if defined(ABSL_ARCH_X86_64) || defined(ABSL_ARCH_X86_32) || \
+    defined(ABSL_ARCH_PPC) || defined(ABSL_ARCH_ARM) ||       \
+    defined(ABSL_ARCH_AARCH64)
+#define ABSL_RANDEN_HWAES_IMPL 1
+#endif
+#endif
+
+#if !defined(ABSL_RANDEN_HWAES_IMPL)
+// No accelerated implementation is supported.
+// The RandenHwAes functions are stubs that print an error and exit.
+
+#include <cstdio>
+#include <cstdlib>
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// No accelerated implementation.
+bool HasRandenHwAesImplementation() { return false; }
+
+// NOLINTNEXTLINE
+const void* RandenHwAes::GetKeys() {
+  // Attempted to dispatch to an unsupported dispatch target.
+  const int d = ABSL_RANDOM_INTERNAL_AES_DISPATCH;
+  fprintf(stderr, "AES Hardware detection failed (%d).\n", d);
+  exit(1);
+  return nullptr;
+}
+
+// NOLINTNEXTLINE
+void RandenHwAes::Absorb(const void*, void*) {
+  // Attempted to dispatch to an unsupported dispatch target.
+  const int d = ABSL_RANDOM_INTERNAL_AES_DISPATCH;
+  fprintf(stderr, "AES Hardware detection failed (%d).\n", d);
+  exit(1);
+}
+
+// NOLINTNEXTLINE
+void RandenHwAes::Generate(const void*, void*) {
+  // Attempted to dispatch to an unsupported dispatch target.
+  const int d = ABSL_RANDOM_INTERNAL_AES_DISPATCH;
+  fprintf(stderr, "AES Hardware detection failed (%d).\n", d);
+  exit(1);
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#else  // defined(ABSL_RANDEN_HWAES_IMPL)
+//
+// Accelerated implementations are supported.
+// We need the per-architecture includes and defines.
+//
+namespace {
+
+using absl::random_internal::RandenTraits;
+
+}  // namespace
+
+// TARGET_CRYPTO defines a crypto attribute for each architecture.
+//
+// NOTE: Evaluate whether we should eliminate ABSL_TARGET_CRYPTO.
+#if (defined(__clang__) || defined(__GNUC__))
+#if defined(ABSL_ARCH_X86_64) || defined(ABSL_ARCH_X86_32)
+#define ABSL_TARGET_CRYPTO __attribute__((target("aes")))
+#elif defined(ABSL_ARCH_PPC)
+#define ABSL_TARGET_CRYPTO __attribute__((target("crypto")))
+#else
+#define ABSL_TARGET_CRYPTO
+#endif
+#else
+#define ABSL_TARGET_CRYPTO
+#endif
+
+#if defined(ABSL_ARCH_PPC)
+// NOTE: Keep in mind that PPC can operate in little-endian or big-endian mode,
+// however the PPC altivec vector registers (and thus the AES instructions)
+// always operate in big-endian mode.
+
+#include <altivec.h>
+// <altivec.h> #defines vector __vector; in C++, this is bad form.
+#undef vector
+#undef bool
+
+// Rely on the PowerPC AltiVec vector operations for accelerated AES
+// instructions. GCC support of the PPC vector types is described in:
+// https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/PowerPC-AltiVec_002fVSX-Built-in-Functions.html
+//
+// Already provides operator^=.
+using Vector128 = __vector unsigned long long;  // NOLINT(runtime/int)
+
+namespace {
+inline ABSL_TARGET_CRYPTO Vector128 ReverseBytes(const Vector128& v) {
+  // Reverses the bytes of the vector.
+  const __vector unsigned char perm = {15, 14, 13, 12, 11, 10, 9, 8,
+                                       7,  6,  5,  4,  3,  2,  1, 0};
+  return vec_perm(v, v, perm);
+}
+
+// WARNING: these load/store in native byte order. It is OK to load and then
+// store an unchanged vector, but interpreting the bits as a number or input
+// to AES will have undefined results.
+inline ABSL_TARGET_CRYPTO Vector128 Vector128Load(const void* from) {
+  return vec_vsx_ld(0, reinterpret_cast<const Vector128*>(from));
+}
+
+inline ABSL_TARGET_CRYPTO void Vector128Store(const Vector128& v, void* to) {
+  vec_vsx_st(v, 0, reinterpret_cast<Vector128*>(to));
+}
+
+// One round of AES. "round_key" is a public constant for breaking the
+// symmetry of AES (ensures previously equal columns differ afterwards).
+inline ABSL_TARGET_CRYPTO Vector128 AesRound(const Vector128& state,
+                                             const Vector128& round_key) {
+  return Vector128(__builtin_crypto_vcipher(state, round_key));
+}
+
+// Enables native loads in the round loop by pre-swapping.
+inline ABSL_TARGET_CRYPTO void SwapEndian(absl::uint128* state) {
+  for (uint32_t block = 0; block < RandenTraits::kFeistelBlocks; ++block) {
+    Vector128Store(ReverseBytes(Vector128Load(state + block)), state + block);
+  }
+}
+
+}  // namespace
+
+#elif defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
+
+// Rely on the ARM NEON+Crypto advanced simd types, defined in <arm_neon.h>.
+// uint8x16_t is the user alias for underlying __simd128_uint8_t type.
+// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0073a/IHI0073A_arm_neon_intrinsics_ref.pdf
+//
+// <arm_neon> defines the following
+//
+// typedef __attribute__((neon_vector_type(16))) uint8_t uint8x16_t;
+// typedef __attribute__((neon_vector_type(16))) int8_t int8x16_t;
+// typedef __attribute__((neon_polyvector_type(16))) int8_t poly8x16_t;
+//
+// vld1q_v
+// vst1q_v
+// vaeseq_v
+// vaesmcq_v
+#include <arm_neon.h>
+
+// Already provides operator^=.
+using Vector128 = uint8x16_t;
+
+namespace {
+
+inline ABSL_TARGET_CRYPTO Vector128 Vector128Load(const void* from) {
+  return vld1q_u8(reinterpret_cast<const uint8_t*>(from));
+}
+
+inline ABSL_TARGET_CRYPTO void Vector128Store(const Vector128& v, void* to) {
+  vst1q_u8(reinterpret_cast<uint8_t*>(to), v);
+}
+
+// One round of AES. "round_key" is a public constant for breaking the
+// symmetry of AES (ensures previously equal columns differ afterwards).
+inline ABSL_TARGET_CRYPTO Vector128 AesRound(const Vector128& state,
+                                             const Vector128& round_key) {
+  // It is important to always use the full round function - omitting the
+  // final MixColumns reduces security [https://eprint.iacr.org/2010/041.pdf]
+  // and does not help because we never decrypt.
+  //
+  // Note that ARM divides AES instructions differently than x86 / PPC,
+  // And we need to skip the first AddRoundKey step and add an extra
+  // AddRoundKey step to the end. Lucky for us this is just XOR.
+  return vaesmcq_u8(vaeseq_u8(state, uint8x16_t{})) ^ round_key;
+}
+
+inline ABSL_TARGET_CRYPTO void SwapEndian(void*) {}
+
+}  // namespace
+
+#elif defined(ABSL_ARCH_X86_64) || defined(ABSL_ARCH_X86_32)
+// On x86 we rely on the aesni instructions
+#include <immintrin.h>
+
+namespace {
+
+// Vector128 class is only wrapper for __m128i, benchmark indicates that it's
+// faster than using __m128i directly.
+class Vector128 {
+ public:
+  // Convert from/to intrinsics.
+  inline explicit Vector128(const __m128i& v) : data_(v) {}
+
+  inline __m128i data() const { return data_; }
+
+  inline Vector128& operator^=(const Vector128& other) {
+    data_ = _mm_xor_si128(data_, other.data());
+    return *this;
+  }
+
+ private:
+  __m128i data_;
+};
+
+inline ABSL_TARGET_CRYPTO Vector128 Vector128Load(const void* from) {
+  return Vector128(_mm_load_si128(reinterpret_cast<const __m128i*>(from)));
+}
+
+inline ABSL_TARGET_CRYPTO void Vector128Store(const Vector128& v, void* to) {
+  _mm_store_si128(reinterpret_cast<__m128i*>(to), v.data());
+}
+
+// One round of AES. "round_key" is a public constant for breaking the
+// symmetry of AES (ensures previously equal columns differ afterwards).
+inline ABSL_TARGET_CRYPTO Vector128 AesRound(const Vector128& state,
+                                             const Vector128& round_key) {
+  // It is important to always use the full round function - omitting the
+  // final MixColumns reduces security [https://eprint.iacr.org/2010/041.pdf]
+  // and does not help because we never decrypt.
+  return Vector128(_mm_aesenc_si128(state.data(), round_key.data()));
+}
+
+inline ABSL_TARGET_CRYPTO void SwapEndian(void*) {}
+
+}  // namespace
+
+#endif
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunknown-pragmas"
+#endif
+
+// At this point, all of the platform-specific features have been defined /
+// implemented.
+//
+// REQUIRES: using Vector128 = ...
+// REQUIRES: Vector128 Vector128Load(void*) {...}
+// REQUIRES: void Vector128Store(Vector128, void*) {...}
+// REQUIRES: Vector128 AesRound(Vector128, Vector128) {...}
+// REQUIRES: void SwapEndian(uint64_t*) {...}
+//
+// PROVIDES: absl::random_internal::RandenHwAes::Absorb
+// PROVIDES: absl::random_internal::RandenHwAes::Generate
+namespace {
+
+// Block shuffles applies a shuffle to the entire state between AES rounds.
+// Improved odd-even shuffle from "New criterion for diffusion property".
+inline ABSL_TARGET_CRYPTO void BlockShuffle(absl::uint128* state) {
+  static_assert(RandenTraits::kFeistelBlocks == 16,
+                "Expecting 16 FeistelBlocks.");
+
+  constexpr size_t shuffle[RandenTraits::kFeistelBlocks] = {
+      7, 2, 13, 4, 11, 8, 3, 6, 15, 0, 9, 10, 1, 14, 5, 12};
+
+  const Vector128 v0 = Vector128Load(state + shuffle[0]);
+  const Vector128 v1 = Vector128Load(state + shuffle[1]);
+  const Vector128 v2 = Vector128Load(state + shuffle[2]);
+  const Vector128 v3 = Vector128Load(state + shuffle[3]);
+  const Vector128 v4 = Vector128Load(state + shuffle[4]);
+  const Vector128 v5 = Vector128Load(state + shuffle[5]);
+  const Vector128 v6 = Vector128Load(state + shuffle[6]);
+  const Vector128 v7 = Vector128Load(state + shuffle[7]);
+  const Vector128 w0 = Vector128Load(state + shuffle[8]);
+  const Vector128 w1 = Vector128Load(state + shuffle[9]);
+  const Vector128 w2 = Vector128Load(state + shuffle[10]);
+  const Vector128 w3 = Vector128Load(state + shuffle[11]);
+  const Vector128 w4 = Vector128Load(state + shuffle[12]);
+  const Vector128 w5 = Vector128Load(state + shuffle[13]);
+  const Vector128 w6 = Vector128Load(state + shuffle[14]);
+  const Vector128 w7 = Vector128Load(state + shuffle[15]);
+
+  Vector128Store(v0, state + 0);
+  Vector128Store(v1, state + 1);
+  Vector128Store(v2, state + 2);
+  Vector128Store(v3, state + 3);
+  Vector128Store(v4, state + 4);
+  Vector128Store(v5, state + 5);
+  Vector128Store(v6, state + 6);
+  Vector128Store(v7, state + 7);
+  Vector128Store(w0, state + 8);
+  Vector128Store(w1, state + 9);
+  Vector128Store(w2, state + 10);
+  Vector128Store(w3, state + 11);
+  Vector128Store(w4, state + 12);
+  Vector128Store(w5, state + 13);
+  Vector128Store(w6, state + 14);
+  Vector128Store(w7, state + 15);
+}
+
+// Feistel round function using two AES subrounds. Very similar to F()
+// from Simpira v2, but with independent subround keys. Uses 17 AES rounds
+// per 16 bytes (vs. 10 for AES-CTR). Computing eight round functions in
+// parallel hides the 7-cycle AESNI latency on HSW. Note that the Feistel
+// XORs are 'free' (included in the second AES instruction).
+inline ABSL_TARGET_CRYPTO const absl::uint128* FeistelRound(
+    absl::uint128* state,
+    const absl::uint128* ABSL_RANDOM_INTERNAL_RESTRICT keys) {
+  static_assert(RandenTraits::kFeistelBlocks == 16,
+                "Expecting 16 FeistelBlocks.");
+
+  // MSVC does a horrible job at unrolling loops.
+  // So we unroll the loop by hand to improve the performance.
+  const Vector128 s0 = Vector128Load(state + 0);
+  const Vector128 s1 = Vector128Load(state + 1);
+  const Vector128 s2 = Vector128Load(state + 2);
+  const Vector128 s3 = Vector128Load(state + 3);
+  const Vector128 s4 = Vector128Load(state + 4);
+  const Vector128 s5 = Vector128Load(state + 5);
+  const Vector128 s6 = Vector128Load(state + 6);
+  const Vector128 s7 = Vector128Load(state + 7);
+  const Vector128 s8 = Vector128Load(state + 8);
+  const Vector128 s9 = Vector128Load(state + 9);
+  const Vector128 s10 = Vector128Load(state + 10);
+  const Vector128 s11 = Vector128Load(state + 11);
+  const Vector128 s12 = Vector128Load(state + 12);
+  const Vector128 s13 = Vector128Load(state + 13);
+  const Vector128 s14 = Vector128Load(state + 14);
+  const Vector128 s15 = Vector128Load(state + 15);
+
+  // Encode even blocks with keys.
+  const Vector128 e0 = AesRound(s0, Vector128Load(keys + 0));
+  const Vector128 e2 = AesRound(s2, Vector128Load(keys + 1));
+  const Vector128 e4 = AesRound(s4, Vector128Load(keys + 2));
+  const Vector128 e6 = AesRound(s6, Vector128Load(keys + 3));
+  const Vector128 e8 = AesRound(s8, Vector128Load(keys + 4));
+  const Vector128 e10 = AesRound(s10, Vector128Load(keys + 5));
+  const Vector128 e12 = AesRound(s12, Vector128Load(keys + 6));
+  const Vector128 e14 = AesRound(s14, Vector128Load(keys + 7));
+
+  // Encode odd blocks with even output from above.
+  const Vector128 o1 = AesRound(e0, s1);
+  const Vector128 o3 = AesRound(e2, s3);
+  const Vector128 o5 = AesRound(e4, s5);
+  const Vector128 o7 = AesRound(e6, s7);
+  const Vector128 o9 = AesRound(e8, s9);
+  const Vector128 o11 = AesRound(e10, s11);
+  const Vector128 o13 = AesRound(e12, s13);
+  const Vector128 o15 = AesRound(e14, s15);
+
+  // Store odd blocks. (These will be shuffled later).
+  Vector128Store(o1, state + 1);
+  Vector128Store(o3, state + 3);
+  Vector128Store(o5, state + 5);
+  Vector128Store(o7, state + 7);
+  Vector128Store(o9, state + 9);
+  Vector128Store(o11, state + 11);
+  Vector128Store(o13, state + 13);
+  Vector128Store(o15, state + 15);
+
+  return keys + 8;
+}
+
+// Cryptographic permutation based via type-2 Generalized Feistel Network.
+// Indistinguishable from ideal by chosen-ciphertext adversaries using less than
+// 2^64 queries if the round function is a PRF. This is similar to the b=8 case
+// of Simpira v2, but more efficient than its generic construction for b=16.
+inline ABSL_TARGET_CRYPTO void Permute(
+    absl::uint128* state,
+    const absl::uint128* ABSL_RANDOM_INTERNAL_RESTRICT keys) {
+  // (Successfully unrolled; the first iteration jumps into the second half)
+#ifdef __clang__
+#pragma clang loop unroll_count(2)
+#endif
+  for (size_t round = 0; round < RandenTraits::kFeistelRounds; ++round) {
+    keys = FeistelRound(state, keys);
+    BlockShuffle(state);
+  }
+}
+
+}  // namespace
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+bool HasRandenHwAesImplementation() { return true; }
+
+const void* ABSL_TARGET_CRYPTO RandenHwAes::GetKeys() {
+  // Round keys for one AES per Feistel round and branch.
+  // The canonical implementation uses first digits of Pi.
+#if defined(ABSL_ARCH_PPC)
+  return kRandenRoundKeysBE;
+#else
+  return kRandenRoundKeys;
+#endif
+}
+
+// NOLINTNEXTLINE
+void ABSL_TARGET_CRYPTO RandenHwAes::Absorb(const void* seed_void,
+                                            void* state_void) {
+  static_assert(RandenTraits::kCapacityBytes / sizeof(Vector128) == 1,
+                "Unexpected Randen kCapacityBlocks");
+  static_assert(RandenTraits::kStateBytes / sizeof(Vector128) == 16,
+                "Unexpected Randen kStateBlocks");
+
+  auto* state = reinterpret_cast<absl::uint128 * ABSL_RANDOM_INTERNAL_RESTRICT>(
+      state_void);
+  const auto* seed =
+      reinterpret_cast<const absl::uint128 * ABSL_RANDOM_INTERNAL_RESTRICT>(
+          seed_void);
+
+  Vector128 b1 = Vector128Load(state + 1);
+  b1 ^= Vector128Load(seed + 0);
+  Vector128Store(b1, state + 1);
+
+  Vector128 b2 = Vector128Load(state + 2);
+  b2 ^= Vector128Load(seed + 1);
+  Vector128Store(b2, state + 2);
+
+  Vector128 b3 = Vector128Load(state + 3);
+  b3 ^= Vector128Load(seed + 2);
+  Vector128Store(b3, state + 3);
+
+  Vector128 b4 = Vector128Load(state + 4);
+  b4 ^= Vector128Load(seed + 3);
+  Vector128Store(b4, state + 4);
+
+  Vector128 b5 = Vector128Load(state + 5);
+  b5 ^= Vector128Load(seed + 4);
+  Vector128Store(b5, state + 5);
+
+  Vector128 b6 = Vector128Load(state + 6);
+  b6 ^= Vector128Load(seed + 5);
+  Vector128Store(b6, state + 6);
+
+  Vector128 b7 = Vector128Load(state + 7);
+  b7 ^= Vector128Load(seed + 6);
+  Vector128Store(b7, state + 7);
+
+  Vector128 b8 = Vector128Load(state + 8);
+  b8 ^= Vector128Load(seed + 7);
+  Vector128Store(b8, state + 8);
+
+  Vector128 b9 = Vector128Load(state + 9);
+  b9 ^= Vector128Load(seed + 8);
+  Vector128Store(b9, state + 9);
+
+  Vector128 b10 = Vector128Load(state + 10);
+  b10 ^= Vector128Load(seed + 9);
+  Vector128Store(b10, state + 10);
+
+  Vector128 b11 = Vector128Load(state + 11);
+  b11 ^= Vector128Load(seed + 10);
+  Vector128Store(b11, state + 11);
+
+  Vector128 b12 = Vector128Load(state + 12);
+  b12 ^= Vector128Load(seed + 11);
+  Vector128Store(b12, state + 12);
+
+  Vector128 b13 = Vector128Load(state + 13);
+  b13 ^= Vector128Load(seed + 12);
+  Vector128Store(b13, state + 13);
+
+  Vector128 b14 = Vector128Load(state + 14);
+  b14 ^= Vector128Load(seed + 13);
+  Vector128Store(b14, state + 14);
+
+  Vector128 b15 = Vector128Load(state + 15);
+  b15 ^= Vector128Load(seed + 14);
+  Vector128Store(b15, state + 15);
+}
+
+// NOLINTNEXTLINE
+void ABSL_TARGET_CRYPTO RandenHwAes::Generate(const void* keys_void,
+                                              void* state_void) {
+  static_assert(RandenTraits::kCapacityBytes == sizeof(Vector128),
+                "Capacity mismatch");
+
+  auto* state = reinterpret_cast<absl::uint128*>(state_void);
+  const auto* keys = reinterpret_cast<const absl::uint128*>(keys_void);
+
+  const Vector128 prev_inner = Vector128Load(state);
+
+  SwapEndian(state);
+
+  Permute(state, keys);
+
+  SwapEndian(state);
+
+  // Ensure backtracking resistance.
+  Vector128 inner = Vector128Load(state);
+  inner ^= prev_inner;
+  Vector128Store(inner, state);
+}
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // (ABSL_RANDEN_HWAES_IMPL)
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/salted_seed_seq.h b/weight/_dep/abseil-cpp/absl/random/internal/salted_seed_seq.h
new file mode 100644
index 0000000000000000000000000000000000000000..06291865e3dcf370923fd2d16df6bccf6e762697
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/salted_seed_seq.h
@@ -0,0 +1,165 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_SALTED_SEED_SEQ_H_
+#define ABSL_RANDOM_INTERNAL_SALTED_SEED_SEQ_H_
+
+#include <cstdint>
+#include <cstdlib>
+#include <initializer_list>
+#include <iterator>
+#include <memory>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/meta/type_traits.h"
+#include "absl/random/internal/seed_material.h"
+#include "absl/types/optional.h"
+#include "absl/types/span.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// This class conforms to the C++ Standard "Seed Sequence" concept
+// [rand.req.seedseq].
+//
+// A `SaltedSeedSeq` is meant to wrap an existing seed sequence and modify
+// generated sequence by mixing with extra entropy. This entropy may be
+// build-dependent or process-dependent. The implementation may change to be
+// have either or both kinds of entropy. If salt is not available sequence is
+// not modified.
+template <typename SSeq>
+class SaltedSeedSeq {
+ public:
+  using inner_sequence_type = SSeq;
+  using result_type = typename SSeq::result_type;
+
+  SaltedSeedSeq() : seq_(absl::make_unique<SSeq>()) {}
+
+  template <typename Iterator>
+  SaltedSeedSeq(Iterator begin, Iterator end)
+      : seq_(absl::make_unique<SSeq>(begin, end)) {}
+
+  template <typename T>
+  SaltedSeedSeq(std::initializer_list<T> il)
+      : SaltedSeedSeq(il.begin(), il.end()) {}
+
+  SaltedSeedSeq(const SaltedSeedSeq&) = delete;
+  SaltedSeedSeq& operator=(const SaltedSeedSeq&) = delete;
+
+  SaltedSeedSeq(SaltedSeedSeq&&) = default;
+  SaltedSeedSeq& operator=(SaltedSeedSeq&&) = default;
+
+  template <typename RandomAccessIterator>
+  void generate(RandomAccessIterator begin, RandomAccessIterator end) {
+    using U = typename std::iterator_traits<RandomAccessIterator>::value_type;
+
+    // The common case is that generate is called with ContiguousIterators
+    // to uint arrays. Such contiguous memory regions may be optimized,
+    // which we detect here.
+    using TagType = absl::conditional_t<
+        (std::is_same<U, uint32_t>::value &&
+         (std::is_pointer<RandomAccessIterator>::value ||
+          std::is_same<RandomAccessIterator,
+                       typename std::vector<U>::iterator>::value)),
+        ContiguousAndUint32Tag, DefaultTag>;
+    if (begin != end) {
+      generate_impl(TagType{}, begin, end, std::distance(begin, end));
+    }
+  }
+
+  template <typename OutIterator>
+  void param(OutIterator out) const {
+    seq_->param(out);
+  }
+
+  size_t size() const { return seq_->size(); }
+
+ private:
+  struct ContiguousAndUint32Tag {};
+  struct DefaultTag {};
+
+  // Generate which requires the iterators are contiguous pointers to uint32_t.
+  // Fills the initial seed buffer the underlying SSeq::generate() call,
+  // then mixes in the salt material.
+  template <typename Contiguous>
+  void generate_impl(ContiguousAndUint32Tag, Contiguous begin, Contiguous end,
+                     size_t n) {
+    seq_->generate(begin, end);
+    const uint32_t salt = absl::random_internal::GetSaltMaterial().value_or(0);
+    auto span = absl::Span<uint32_t>(&*begin, n);
+    MixIntoSeedMaterial(absl::MakeConstSpan(&salt, 1), span);
+  }
+
+  // The uncommon case for generate is that it is called with iterators over
+  // some other buffer type which is assignable from a 32-bit value. In this
+  // case we allocate a temporary 32-bit buffer and then copy-assign back
+  // to the initial inputs.
+  template <typename RandomAccessIterator>
+  void generate_impl(DefaultTag, RandomAccessIterator begin,
+                     RandomAccessIterator, size_t n) {
+    // Allocates a seed buffer of `n` elements, generates the seed, then
+    // copies the result into the `out` iterator.
+    absl::InlinedVector<uint32_t, 8> data(n, 0);
+    generate_impl(ContiguousAndUint32Tag{}, data.begin(), data.end(), n);
+    std::copy(data.begin(), data.end(), begin);
+  }
+
+  // Because [rand.req.seedseq] is not required to be copy-constructible,
+  // copy-assignable nor movable, we wrap it with unique pointer to be able
+  // to move SaltedSeedSeq.
+  std::unique_ptr<SSeq> seq_;
+};
+
+// is_salted_seed_seq indicates whether the type is a SaltedSeedSeq.
+template <typename T, typename = void>
+struct is_salted_seed_seq : public std::false_type {};
+
+template <typename T>
+struct is_salted_seed_seq<
+    T, typename std::enable_if<std::is_same<
+           T, SaltedSeedSeq<typename T::inner_sequence_type>>::value>::type>
+    : public std::true_type {};
+
+// MakeSaltedSeedSeq returns a salted variant of the seed sequence.
+// When provided with an existing SaltedSeedSeq, returns the input parameter,
+// otherwise constructs a new SaltedSeedSeq which embodies the original
+// non-salted seed parameters.
+template <
+    typename SSeq,  //
+    typename EnableIf = absl::enable_if_t<is_salted_seed_seq<SSeq>::value>>
+SSeq MakeSaltedSeedSeq(SSeq&& seq) {
+  return SSeq(std::forward<SSeq>(seq));
+}
+
+template <
+    typename SSeq,  //
+    typename EnableIf = absl::enable_if_t<!is_salted_seed_seq<SSeq>::value>>
+SaltedSeedSeq<typename std::decay<SSeq>::type> MakeSaltedSeedSeq(SSeq&& seq) {
+  using sseq_type = typename std::decay<SSeq>::type;
+  using result_type = typename sseq_type::result_type;
+
+  absl::InlinedVector<result_type, 8> data;
+  seq.param(std::back_inserter(data));
+  return SaltedSeedSeq<sseq_type>(data.begin(), data.end());
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_SALTED_SEED_SEQ_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/seed_material_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/seed_material_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6db2820ec707cc2ffa33e63588fda6390f72d379
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/seed_material_test.cc
@@ -0,0 +1,202 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/seed_material.h"
+
+#include <bitset>
+#include <cstdlib>
+#include <cstring>
+#include <random>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#ifdef __ANDROID__
+// Android assert messages only go to system log, so death tests cannot inspect
+// the message for matching.
+#define ABSL_EXPECT_DEATH_IF_SUPPORTED(statement, regex) \
+  EXPECT_DEATH_IF_SUPPORTED(statement, ".*")
+#else
+#define ABSL_EXPECT_DEATH_IF_SUPPORTED(statement, regex) \
+  EXPECT_DEATH_IF_SUPPORTED(statement, regex)
+#endif
+
+namespace {
+
+using testing::Each;
+using testing::ElementsAre;
+using testing::Eq;
+using testing::Ne;
+using testing::Pointwise;
+
+TEST(SeedBitsToBlocks, VerifyCases) {
+  EXPECT_EQ(0, absl::random_internal::SeedBitsToBlocks(0));
+  EXPECT_EQ(1, absl::random_internal::SeedBitsToBlocks(1));
+  EXPECT_EQ(1, absl::random_internal::SeedBitsToBlocks(31));
+  EXPECT_EQ(1, absl::random_internal::SeedBitsToBlocks(32));
+  EXPECT_EQ(2, absl::random_internal::SeedBitsToBlocks(33));
+  EXPECT_EQ(4, absl::random_internal::SeedBitsToBlocks(127));
+  EXPECT_EQ(4, absl::random_internal::SeedBitsToBlocks(128));
+  EXPECT_EQ(5, absl::random_internal::SeedBitsToBlocks(129));
+}
+
+TEST(ReadSeedMaterialFromOSEntropy, SuccessiveReadsAreDistinct) {
+  constexpr size_t kSeedMaterialSize = 64;
+  uint32_t seed_material_1[kSeedMaterialSize] = {};
+  uint32_t seed_material_2[kSeedMaterialSize] = {};
+
+  EXPECT_TRUE(absl::random_internal::ReadSeedMaterialFromOSEntropy(
+      absl::Span<uint32_t>(seed_material_1, kSeedMaterialSize)));
+  EXPECT_TRUE(absl::random_internal::ReadSeedMaterialFromOSEntropy(
+      absl::Span<uint32_t>(seed_material_2, kSeedMaterialSize)));
+
+  EXPECT_THAT(seed_material_1, Pointwise(Ne(), seed_material_2));
+}
+
+TEST(ReadSeedMaterialFromOSEntropy, ReadZeroBytesIsNoOp) {
+  uint32_t seed_material[32] = {};
+  std::memset(seed_material, 0xAA, sizeof(seed_material));
+  EXPECT_TRUE(absl::random_internal::ReadSeedMaterialFromOSEntropy(
+      absl::Span<uint32_t>(seed_material, 0)));
+
+  EXPECT_THAT(seed_material, Each(Eq(0xAAAAAAAA)));
+}
+
+TEST(ReadSeedMaterialFromOSEntropy, NullPtrVectorArgument) {
+#ifdef NDEBUG
+  EXPECT_FALSE(absl::random_internal::ReadSeedMaterialFromOSEntropy(
+      absl::Span<uint32_t>(nullptr, 32)));
+#else
+  bool result;
+  ABSL_EXPECT_DEATH_IF_SUPPORTED(
+      result = absl::random_internal::ReadSeedMaterialFromOSEntropy(
+          absl::Span<uint32_t>(nullptr, 32)),
+      "!= nullptr");
+  (void)result;  // suppress unused-variable warning
+#endif
+}
+
+TEST(ReadSeedMaterialFromURBG, SeedMaterialEqualsVariateSequence) {
+  // Two default-constructed instances of std::mt19937_64 are guaranteed to
+  // produce equal variate-sequences.
+  std::mt19937 urbg_1;
+  std::mt19937 urbg_2;
+  constexpr size_t kSeedMaterialSize = 1024;
+  uint32_t seed_material[kSeedMaterialSize] = {};
+
+  EXPECT_TRUE(absl::random_internal::ReadSeedMaterialFromURBG(
+      &urbg_1, absl::Span<uint32_t>(seed_material, kSeedMaterialSize)));
+  for (uint32_t seed : seed_material) {
+    EXPECT_EQ(seed, urbg_2());
+  }
+}
+
+TEST(ReadSeedMaterialFromURBG, ReadZeroBytesIsNoOp) {
+  std::mt19937_64 urbg;
+  uint32_t seed_material[32];
+  std::memset(seed_material, 0xAA, sizeof(seed_material));
+  EXPECT_TRUE(absl::random_internal::ReadSeedMaterialFromURBG(
+      &urbg, absl::Span<uint32_t>(seed_material, 0)));
+
+  EXPECT_THAT(seed_material, Each(Eq(0xAAAAAAAA)));
+}
+
+TEST(ReadSeedMaterialFromURBG, NullUrbgArgument) {
+  constexpr size_t kSeedMaterialSize = 32;
+  uint32_t seed_material[kSeedMaterialSize];
+#ifdef NDEBUG
+  EXPECT_FALSE(absl::random_internal::ReadSeedMaterialFromURBG<std::mt19937_64>(
+      nullptr, absl::Span<uint32_t>(seed_material, kSeedMaterialSize)));
+#else
+  bool result;
+  ABSL_EXPECT_DEATH_IF_SUPPORTED(
+      result = absl::random_internal::ReadSeedMaterialFromURBG<std::mt19937_64>(
+          nullptr, absl::Span<uint32_t>(seed_material, kSeedMaterialSize)),
+      "!= nullptr");
+  (void)result;  // suppress unused-variable warning
+#endif
+}
+
+TEST(ReadSeedMaterialFromURBG, NullPtrVectorArgument) {
+  std::mt19937_64 urbg;
+#ifdef NDEBUG
+  EXPECT_FALSE(absl::random_internal::ReadSeedMaterialFromURBG(
+      &urbg, absl::Span<uint32_t>(nullptr, 32)));
+#else
+  bool result;
+  ABSL_EXPECT_DEATH_IF_SUPPORTED(
+      result = absl::random_internal::ReadSeedMaterialFromURBG(
+          &urbg, absl::Span<uint32_t>(nullptr, 32)),
+      "!= nullptr");
+  (void)result;  // suppress unused-variable warning
+#endif
+}
+
+// The avalanche effect is a desirable cryptographic property of hashes in which
+// changing a single bit in the input causes each bit of the output to be
+// changed with probability near 50%.
+//
+// https://en.wikipedia.org/wiki/Avalanche_effect
+
+TEST(MixSequenceIntoSeedMaterial, AvalancheEffectTestOneBitLong) {
+  std::vector<uint32_t> seed_material = {1, 2, 3, 4, 5, 6, 7, 8};
+
+  // For every 32-bit number with exactly one bit set, verify the avalanche
+  // effect holds.  In order to reduce flakiness of tests, accept values
+  // anywhere in the range of 30%-70%.
+  for (uint32_t v = 1; v != 0; v <<= 1) {
+    std::vector<uint32_t> seed_material_copy = seed_material;
+    absl::random_internal::MixIntoSeedMaterial(
+        absl::Span<uint32_t>(&v, 1),
+        absl::Span<uint32_t>(seed_material_copy.data(),
+                             seed_material_copy.size()));
+
+    uint32_t changed_bits = 0;
+    for (size_t i = 0; i < seed_material.size(); i++) {
+      std::bitset<sizeof(uint32_t) * 8> bitset(seed_material[i] ^
+                                               seed_material_copy[i]);
+      changed_bits += bitset.count();
+    }
+
+    EXPECT_LE(changed_bits, 0.7 * sizeof(uint32_t) * 8 * seed_material.size());
+    EXPECT_GE(changed_bits, 0.3 * sizeof(uint32_t) * 8 * seed_material.size());
+  }
+}
+
+TEST(MixSequenceIntoSeedMaterial, AvalancheEffectTestOneBitShort) {
+  std::vector<uint32_t> seed_material = {1};
+
+  // For every 32-bit number with exactly one bit set, verify the avalanche
+  // effect holds.  In order to reduce flakiness of tests, accept values
+  // anywhere in the range of 30%-70%.
+  for (uint32_t v = 1; v != 0; v <<= 1) {
+    std::vector<uint32_t> seed_material_copy = seed_material;
+    absl::random_internal::MixIntoSeedMaterial(
+        absl::Span<uint32_t>(&v, 1),
+        absl::Span<uint32_t>(seed_material_copy.data(),
+                             seed_material_copy.size()));
+
+    uint32_t changed_bits = 0;
+    for (size_t i = 0; i < seed_material.size(); i++) {
+      std::bitset<sizeof(uint32_t) * 8> bitset(seed_material[i] ^
+                                               seed_material_copy[i]);
+      changed_bits += bitset.count();
+    }
+
+    EXPECT_LE(changed_bits, 0.7 * sizeof(uint32_t) * 8 * seed_material.size());
+    EXPECT_GE(changed_bits, 0.3 * sizeof(uint32_t) * 8 * seed_material.size());
+  }
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/sequence_urbg.h b/weight/_dep/abseil-cpp/absl/random/internal/sequence_urbg.h
new file mode 100644
index 0000000000000000000000000000000000000000..bc96a12cd29ccb692ce2a25f858ecf24ee1f55b3
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/sequence_urbg.h
@@ -0,0 +1,60 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_SEQUENCE_URBG_H_
+#define ABSL_RANDOM_INTERNAL_SEQUENCE_URBG_H_
+
+#include <cstdint>
+#include <cstring>
+#include <limits>
+#include <type_traits>
+#include <vector>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// `sequence_urbg` is a simple random number generator which meets the
+// requirements of [rand.req.urbg], and is solely for testing absl
+// distributions.
+class sequence_urbg {
+ public:
+  using result_type = uint64_t;
+
+  static constexpr result_type(min)() {
+    return (std::numeric_limits<result_type>::min)();
+  }
+  static constexpr result_type(max)() {
+    return (std::numeric_limits<result_type>::max)();
+  }
+
+  sequence_urbg(std::initializer_list<result_type> data) : i_(0), data_(data) {}
+  void reset() { i_ = 0; }
+
+  result_type operator()() { return data_[i_++ % data_.size()]; }
+
+  size_t invocations() const { return i_; }
+
+ private:
+  size_t i_;
+  std::vector<result_type> data_;
+};
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_SEQUENCE_URBG_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/traits.h b/weight/_dep/abseil-cpp/absl/random/internal/traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..f874a0f78b0a61c0c7a0aa44825d569e8363fdb9
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/traits.h
@@ -0,0 +1,149 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_INTERNAL_TRAITS_H_
+#define ABSL_RANDOM_INTERNAL_TRAITS_H_
+
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+
+#include "absl/base/config.h"
+#include "absl/numeric/bits.h"
+#include "absl/numeric/int128.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace random_internal {
+
+// random_internal::is_widening_convertible<A, B>
+//
+// Returns whether a type A is widening-convertible to a type B.
+//
+// A is widening-convertible to B means:
+//   A a = <any number>;
+//   B b = a;
+//   A c = b;
+//   EXPECT_EQ(a, c);
+template <typename A, typename B>
+class is_widening_convertible {
+  // As long as there are enough bits in the exact part of a number:
+  // - unsigned can fit in float, signed, unsigned
+  // - signed can fit in float, signed
+  // - float can fit in float
+  // So we define rank to be:
+  // - rank(float) -> 2
+  // - rank(signed) -> 1
+  // - rank(unsigned) -> 0
+  template <class T>
+  static constexpr int rank() {
+    return !std::numeric_limits<T>::is_integer +
+           std::numeric_limits<T>::is_signed;
+  }
+
+ public:
+  // If an arithmetic-type B can represent at least as many digits as a type A,
+  // and B belongs to a rank no lower than A, then A can be safely represented
+  // by B through a widening-conversion.
+  static constexpr bool value =
+      std::numeric_limits<A>::digits <= std::numeric_limits<B>::digits &&
+      rank<A>() <= rank<B>();
+};
+
+template <typename T>
+struct IsIntegral : std::is_integral<T> {};
+template <>
+struct IsIntegral<absl::int128> : std::true_type {};
+template <>
+struct IsIntegral<absl::uint128> : std::true_type {};
+
+template <typename T>
+struct MakeUnsigned : std::make_unsigned<T> {};
+template <>
+struct MakeUnsigned<absl::int128> {
+  using type = absl::uint128;
+};
+template <>
+struct MakeUnsigned<absl::uint128> {
+  using type = absl::uint128;
+};
+
+template <typename T>
+struct IsUnsigned : std::is_unsigned<T> {};
+template <>
+struct IsUnsigned<absl::int128> : std::false_type {};
+template <>
+struct IsUnsigned<absl::uint128> : std::true_type {};
+
+// unsigned_bits<N>::type returns the unsigned int type with the indicated
+// number of bits.
+template <size_t N>
+struct unsigned_bits;
+
+template <>
+struct unsigned_bits<8> {
+  using type = uint8_t;
+};
+template <>
+struct unsigned_bits<16> {
+  using type = uint16_t;
+};
+template <>
+struct unsigned_bits<32> {
+  using type = uint32_t;
+};
+template <>
+struct unsigned_bits<64> {
+  using type = uint64_t;
+};
+
+template <>
+struct unsigned_bits<128> {
+  using type = absl::uint128;
+};
+
+// 256-bit wrapper for wide multiplications.
+struct U256 {
+  uint128 hi;
+  uint128 lo;
+};
+template <>
+struct unsigned_bits<256> {
+  using type = U256;
+};
+
+template <typename IntType>
+struct make_unsigned_bits {
+  using type = typename unsigned_bits<
+      std::numeric_limits<typename MakeUnsigned<IntType>::type>::digits>::type;
+};
+
+template <typename T>
+int BitWidth(T v) {
+  // Workaround for bit_width not supporting int128.
+  // Don't hardcode `64` to make sure this code does not trigger compiler
+  // warnings in smaller types.
+  constexpr int half_bits = sizeof(T) * 8 / 2;
+  if (sizeof(T) == 16 && (v >> half_bits) != 0) {
+    return bit_width(static_cast<uint64_t>(v >> half_bits)) + half_bits;
+  } else {
+    return bit_width(static_cast<uint64_t>(v));
+  }
+}
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_TRAITS_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/uniform_helper_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/uniform_helper_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..173c49b0b7f8d61af24b45ce6eb8824abbdd0a21
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/uniform_helper_test.cc
@@ -0,0 +1,279 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/uniform_helper.h"
+
+#include <cmath>
+#include <cstdint>
+#include <random>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+using absl::IntervalClosedClosedTag;
+using absl::IntervalClosedOpenTag;
+using absl::IntervalOpenClosedTag;
+using absl::IntervalOpenOpenTag;
+using absl::random_internal::uniform_inferred_return_t;
+using absl::random_internal::uniform_lower_bound;
+using absl::random_internal::uniform_upper_bound;
+
+class UniformHelperTest : public testing::Test {};
+
+TEST_F(UniformHelperTest, UniformBoundFunctionsGeneral) {
+  constexpr IntervalClosedClosedTag IntervalClosedClosed;
+  constexpr IntervalClosedOpenTag IntervalClosedOpen;
+  constexpr IntervalOpenClosedTag IntervalOpenClosed;
+  constexpr IntervalOpenOpenTag IntervalOpenOpen;
+
+  // absl::uniform_int_distribution natively assumes IntervalClosedClosed
+  // absl::uniform_real_distribution natively assumes IntervalClosedOpen
+
+  EXPECT_EQ(uniform_lower_bound(IntervalOpenClosed, 0, 100), 1);
+  EXPECT_EQ(uniform_lower_bound(IntervalOpenOpen, 0, 100), 1);
+  EXPECT_GT(uniform_lower_bound<float>(IntervalOpenClosed, 0, 1.0), 0);
+  EXPECT_GT(uniform_lower_bound<float>(IntervalOpenOpen, 0, 1.0), 0);
+  EXPECT_GT(uniform_lower_bound<double>(IntervalOpenClosed, 0, 1.0), 0);
+  EXPECT_GT(uniform_lower_bound<double>(IntervalOpenOpen, 0, 1.0), 0);
+
+  EXPECT_EQ(uniform_lower_bound(IntervalClosedClosed, 0, 100), 0);
+  EXPECT_EQ(uniform_lower_bound(IntervalClosedOpen, 0, 100), 0);
+  EXPECT_EQ(uniform_lower_bound<float>(IntervalClosedClosed, 0, 1.0), 0);
+  EXPECT_EQ(uniform_lower_bound<float>(IntervalClosedOpen, 0, 1.0), 0);
+  EXPECT_EQ(uniform_lower_bound<double>(IntervalClosedClosed, 0, 1.0), 0);
+  EXPECT_EQ(uniform_lower_bound<double>(IntervalClosedOpen, 0, 1.0), 0);
+
+  EXPECT_EQ(uniform_upper_bound(IntervalOpenOpen, 0, 100), 99);
+  EXPECT_EQ(uniform_upper_bound(IntervalClosedOpen, 0, 100), 99);
+  EXPECT_EQ(uniform_upper_bound<float>(IntervalOpenOpen, 0, 1.0), 1.0);
+  EXPECT_EQ(uniform_upper_bound<float>(IntervalClosedOpen, 0, 1.0), 1.0);
+  EXPECT_EQ(uniform_upper_bound<double>(IntervalOpenOpen, 0, 1.0), 1.0);
+  EXPECT_EQ(uniform_upper_bound<double>(IntervalClosedOpen, 0, 1.0), 1.0);
+
+  EXPECT_EQ(uniform_upper_bound(IntervalOpenClosed, 0, 100), 100);
+  EXPECT_EQ(uniform_upper_bound(IntervalClosedClosed, 0, 100), 100);
+  EXPECT_GT(uniform_upper_bound<float>(IntervalOpenClosed, 0, 1.0), 1.0);
+  EXPECT_GT(uniform_upper_bound<float>(IntervalClosedClosed, 0, 1.0), 1.0);
+  EXPECT_GT(uniform_upper_bound<double>(IntervalOpenClosed, 0, 1.0), 1.0);
+  EXPECT_GT(uniform_upper_bound<double>(IntervalClosedClosed, 0, 1.0), 1.0);
+
+  // Negative value tests
+  EXPECT_EQ(uniform_lower_bound(IntervalOpenClosed, -100, -1), -99);
+  EXPECT_EQ(uniform_lower_bound(IntervalOpenOpen, -100, -1), -99);
+  EXPECT_GT(uniform_lower_bound<float>(IntervalOpenClosed, -2.0, -1.0), -2.0);
+  EXPECT_GT(uniform_lower_bound<float>(IntervalOpenOpen, -2.0, -1.0), -2.0);
+  EXPECT_GT(uniform_lower_bound<double>(IntervalOpenClosed, -2.0, -1.0), -2.0);
+  EXPECT_GT(uniform_lower_bound<double>(IntervalOpenOpen, -2.0, -1.0), -2.0);
+
+  EXPECT_EQ(uniform_lower_bound(IntervalClosedClosed, -100, -1), -100);
+  EXPECT_EQ(uniform_lower_bound(IntervalClosedOpen, -100, -1), -100);
+  EXPECT_EQ(uniform_lower_bound<float>(IntervalClosedClosed, -2.0, -1.0), -2.0);
+  EXPECT_EQ(uniform_lower_bound<float>(IntervalClosedOpen, -2.0, -1.0), -2.0);
+  EXPECT_EQ(uniform_lower_bound<double>(IntervalClosedClosed, -2.0, -1.0),
+            -2.0);
+  EXPECT_EQ(uniform_lower_bound<double>(IntervalClosedOpen, -2.0, -1.0), -2.0);
+
+  EXPECT_EQ(uniform_upper_bound(IntervalOpenOpen, -100, -1), -2);
+  EXPECT_EQ(uniform_upper_bound(IntervalClosedOpen, -100, -1), -2);
+  EXPECT_EQ(uniform_upper_bound<float>(IntervalOpenOpen, -2.0, -1.0), -1.0);
+  EXPECT_EQ(uniform_upper_bound<float>(IntervalClosedOpen, -2.0, -1.0), -1.0);
+  EXPECT_EQ(uniform_upper_bound<double>(IntervalOpenOpen, -2.0, -1.0), -1.0);
+  EXPECT_EQ(uniform_upper_bound<double>(IntervalClosedOpen, -2.0, -1.0), -1.0);
+
+  EXPECT_EQ(uniform_upper_bound(IntervalOpenClosed, -100, -1), -1);
+  EXPECT_EQ(uniform_upper_bound(IntervalClosedClosed, -100, -1), -1);
+  EXPECT_GT(uniform_upper_bound<float>(IntervalOpenClosed, -2.0, -1.0), -1.0);
+  EXPECT_GT(uniform_upper_bound<float>(IntervalClosedClosed, -2.0, -1.0), -1.0);
+  EXPECT_GT(uniform_upper_bound<double>(IntervalOpenClosed, -2.0, -1.0), -1.0);
+  EXPECT_GT(uniform_upper_bound<double>(IntervalClosedClosed, -2.0, -1.0),
+            -1.0);
+
+  EXPECT_GT(uniform_lower_bound(IntervalOpenClosed, 1.0, 2.0), 1.0);
+  EXPECT_LT(uniform_lower_bound(IntervalOpenClosed, 1.0, +0.0), 1.0);
+  EXPECT_LT(uniform_lower_bound(IntervalOpenClosed, 1.0, -0.0), 1.0);
+  EXPECT_LT(uniform_lower_bound(IntervalOpenClosed, 1.0, -1.0), 1.0);
+}
+
+TEST_F(UniformHelperTest, UniformBoundFunctionsIntBounds) {
+  // Verifies the saturating nature of uniform_lower_bound and
+  // uniform_upper_bound
+  constexpr IntervalOpenOpenTag IntervalOpenOpen;
+
+  // uint max.
+  constexpr auto m = (std::numeric_limits<uint64_t>::max)();
+
+  EXPECT_EQ(1, uniform_lower_bound(IntervalOpenOpen, 0u, 0u));
+  EXPECT_EQ(m, uniform_lower_bound(IntervalOpenOpen, m, m));
+  EXPECT_EQ(m, uniform_lower_bound(IntervalOpenOpen, m - 1, m - 1));
+  EXPECT_EQ(0, uniform_upper_bound(IntervalOpenOpen, 0u, 0u));
+  EXPECT_EQ(m - 1, uniform_upper_bound(IntervalOpenOpen, m, m));
+
+  // int min/max
+  constexpr auto l = (std::numeric_limits<int64_t>::min)();
+  constexpr auto r = (std::numeric_limits<int64_t>::max)();
+  EXPECT_EQ(1, uniform_lower_bound(IntervalOpenOpen, 0, 0));
+  EXPECT_EQ(l + 1, uniform_lower_bound(IntervalOpenOpen, l, l));
+  EXPECT_EQ(r, uniform_lower_bound(IntervalOpenOpen, r - 1, r - 1));
+  EXPECT_EQ(r, uniform_lower_bound(IntervalOpenOpen, r, r));
+  EXPECT_EQ(-1, uniform_upper_bound(IntervalOpenOpen, 0, 0));
+  EXPECT_EQ(l, uniform_upper_bound(IntervalOpenOpen, l, l));
+  EXPECT_EQ(r - 1, uniform_upper_bound(IntervalOpenOpen, r, r));
+}
+
+TEST_F(UniformHelperTest, UniformBoundFunctionsRealBounds) {
+  // absl::uniform_real_distribution natively assumes IntervalClosedOpen;
+  // use the inverse here so each bound has to change.
+  constexpr IntervalOpenClosedTag IntervalOpenClosed;
+
+  // Edge cases: the next value toward itself is itself.
+  EXPECT_EQ(1.0, uniform_lower_bound(IntervalOpenClosed, 1.0, 1.0));
+  EXPECT_EQ(1.0f, uniform_lower_bound(IntervalOpenClosed, 1.0f, 1.0f));
+
+  // rightmost and leftmost finite values.
+  constexpr auto r = (std::numeric_limits<double>::max)();
+  const auto re = std::nexttoward(r, 0.0);
+  constexpr auto l = -r;
+  const auto le = std::nexttoward(l, 0.0);
+
+  EXPECT_EQ(l, uniform_lower_bound(IntervalOpenClosed, l, l));     // (l,l)
+  EXPECT_EQ(r, uniform_lower_bound(IntervalOpenClosed, r, r));     // (r,r)
+  EXPECT_EQ(le, uniform_lower_bound(IntervalOpenClosed, l, r));    // (l,r)
+  EXPECT_EQ(le, uniform_lower_bound(IntervalOpenClosed, l, 0.0));  // (l, 0)
+  EXPECT_EQ(le, uniform_lower_bound(IntervalOpenClosed, l, le));   // (l, le)
+  EXPECT_EQ(r, uniform_lower_bound(IntervalOpenClosed, re, r));    // (re, r)
+
+  EXPECT_EQ(le, uniform_upper_bound(IntervalOpenClosed, l, l));   // (l,l)
+  EXPECT_EQ(r, uniform_upper_bound(IntervalOpenClosed, r, r));    // (r,r)
+  EXPECT_EQ(r, uniform_upper_bound(IntervalOpenClosed, l, r));    // (l,r)
+  EXPECT_EQ(r, uniform_upper_bound(IntervalOpenClosed, l, re));   // (l,re)
+  EXPECT_EQ(r, uniform_upper_bound(IntervalOpenClosed, 0.0, r));  // (0, r)
+  EXPECT_EQ(r, uniform_upper_bound(IntervalOpenClosed, re, r));   // (re, r)
+  EXPECT_EQ(r, uniform_upper_bound(IntervalOpenClosed, le, re));  // (le, re)
+
+  const double e = std::nextafter(1.0, 2.0);  // 1 + epsilon
+  const double f = std::nextafter(1.0, 0.0);  // 1 - epsilon
+
+  // (1.0, 1.0 + epsilon)
+  EXPECT_EQ(e, uniform_lower_bound(IntervalOpenClosed, 1.0, e));
+  EXPECT_EQ(std::nextafter(e, 2.0),
+            uniform_upper_bound(IntervalOpenClosed, 1.0, e));
+
+  // (1.0-epsilon, 1.0)
+  EXPECT_EQ(1.0, uniform_lower_bound(IntervalOpenClosed, f, 1.0));
+  EXPECT_EQ(e, uniform_upper_bound(IntervalOpenClosed, f, 1.0));
+
+  // denorm cases.
+  const double g = std::numeric_limits<double>::denorm_min();
+  const double h = std::nextafter(g, 1.0);
+
+  // (0, denorm_min)
+  EXPECT_EQ(g, uniform_lower_bound(IntervalOpenClosed, 0.0, g));
+  EXPECT_EQ(h, uniform_upper_bound(IntervalOpenClosed, 0.0, g));
+
+  // (denorm_min, 1.0)
+  EXPECT_EQ(h, uniform_lower_bound(IntervalOpenClosed, g, 1.0));
+  EXPECT_EQ(e, uniform_upper_bound(IntervalOpenClosed, g, 1.0));
+
+  // Edge cases: invalid bounds.
+  EXPECT_EQ(f, uniform_lower_bound(IntervalOpenClosed, 1.0, -1.0));
+}
+
+struct Invalid {};
+
+template <typename A, typename B>
+auto InferredUniformReturnT(int) -> uniform_inferred_return_t<A, B>;
+
+template <typename, typename>
+Invalid InferredUniformReturnT(...);
+
+// Given types <A, B, Expect>, CheckArgsInferType() verifies that
+//
+//   uniform_inferred_return_t<A, B> and
+//   uniform_inferred_return_t<B, A>
+//
+// returns the type "Expect".
+//
+// This interface can also be used to assert that a given inferred return types
+// are invalid. Writing:
+//
+//   CheckArgsInferType<float, int, Invalid>()
+//
+// will assert that this overload does not exist.
+template <typename A, typename B, typename Expect>
+void CheckArgsInferType() {
+  static_assert(
+      absl::conjunction<
+          std::is_same<Expect, decltype(InferredUniformReturnT<A, B>(0))>,
+          std::is_same<Expect,
+                       decltype(InferredUniformReturnT<B, A>(0))>>::value,
+      "");
+}
+
+TEST_F(UniformHelperTest, UniformTypeInference) {
+  // Infers common types.
+  CheckArgsInferType<uint16_t, uint16_t, uint16_t>();
+  CheckArgsInferType<uint32_t, uint32_t, uint32_t>();
+  CheckArgsInferType<uint64_t, uint64_t, uint64_t>();
+  CheckArgsInferType<int16_t, int16_t, int16_t>();
+  CheckArgsInferType<int32_t, int32_t, int32_t>();
+  CheckArgsInferType<int64_t, int64_t, int64_t>();
+  CheckArgsInferType<float, float, float>();
+  CheckArgsInferType<double, double, double>();
+
+  // Properly promotes uint16_t.
+  CheckArgsInferType<uint16_t, uint32_t, uint32_t>();
+  CheckArgsInferType<uint16_t, uint64_t, uint64_t>();
+  CheckArgsInferType<uint16_t, int32_t, int32_t>();
+  CheckArgsInferType<uint16_t, int64_t, int64_t>();
+  CheckArgsInferType<uint16_t, float, float>();
+  CheckArgsInferType<uint16_t, double, double>();
+
+  // Properly promotes int16_t.
+  CheckArgsInferType<int16_t, int32_t, int32_t>();
+  CheckArgsInferType<int16_t, int64_t, int64_t>();
+  CheckArgsInferType<int16_t, float, float>();
+  CheckArgsInferType<int16_t, double, double>();
+
+  // Invalid (u)int16_t-pairings do not compile.
+  // See "CheckArgsInferType" comments above, for how this is achieved.
+  CheckArgsInferType<uint16_t, int16_t, Invalid>();
+  CheckArgsInferType<int16_t, uint32_t, Invalid>();
+  CheckArgsInferType<int16_t, uint64_t, Invalid>();
+
+  // Properly promotes uint32_t.
+  CheckArgsInferType<uint32_t, uint64_t, uint64_t>();
+  CheckArgsInferType<uint32_t, int64_t, int64_t>();
+  CheckArgsInferType<uint32_t, double, double>();
+
+  // Properly promotes int32_t.
+  CheckArgsInferType<int32_t, int64_t, int64_t>();
+  CheckArgsInferType<int32_t, double, double>();
+
+  // Invalid (u)int32_t-pairings do not compile.
+  CheckArgsInferType<uint32_t, int32_t, Invalid>();
+  CheckArgsInferType<int32_t, uint64_t, Invalid>();
+  CheckArgsInferType<int32_t, float, Invalid>();
+  CheckArgsInferType<uint32_t, float, Invalid>();
+
+  // Invalid (u)int64_t-pairings do not compile.
+  CheckArgsInferType<uint64_t, int64_t, Invalid>();
+  CheckArgsInferType<int64_t, float, Invalid>();
+  CheckArgsInferType<int64_t, double, Invalid>();
+
+  // Properly promotes float.
+  CheckArgsInferType<float, double, double>();
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/internal/wide_multiply_test.cc b/weight/_dep/abseil-cpp/absl/random/internal/wide_multiply_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f8ee35c03ea00789f9b89e7cd065cf14e6d8a1d5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/internal/wide_multiply_test.cc
@@ -0,0 +1,119 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/internal/wide_multiply.h"
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/numeric/int128.h"
+
+using absl::random_internal::MultiplyU128ToU256;
+using absl::random_internal::U256;
+
+namespace {
+
+U256 LeftShift(U256 v, int s) {
+  if (s == 0) {
+    return v;
+  } else if (s < 128) {
+    return {(v.hi << s) | (v.lo >> (128 - s)), v.lo << s};
+  } else {
+    return {v.lo << (s - 128), 0};
+  }
+}
+
+MATCHER_P2(Eq256, hi, lo, "") { return arg.hi == hi && arg.lo == lo; }
+MATCHER_P(Eq256, v, "") { return arg.hi == v.hi && arg.lo == v.lo; }
+
+TEST(WideMultiplyTest, MultiplyU128ToU256Test) {
+  using absl::uint128;
+  constexpr uint128 k1 = 1;
+  constexpr uint128 kMax = ~static_cast<uint128>(0);
+
+  EXPECT_THAT(MultiplyU128ToU256(0, 0), Eq256(0, 0));
+
+  // Max uin128_t
+  EXPECT_THAT(MultiplyU128ToU256(kMax, kMax), Eq256(kMax << 1, 1));
+  EXPECT_THAT(MultiplyU128ToU256(kMax, 1), Eq256(0, kMax));
+  EXPECT_THAT(MultiplyU128ToU256(1, kMax), Eq256(0, kMax));
+  for (int i = 0; i < 64; ++i) {
+    SCOPED_TRACE(i);
+    EXPECT_THAT(MultiplyU128ToU256(kMax, k1 << i),
+                Eq256(LeftShift({0, kMax}, i)));
+    EXPECT_THAT(MultiplyU128ToU256(k1 << i, kMax),
+                Eq256(LeftShift({0, kMax}, i)));
+  }
+
+  // 1-bit x 1-bit.
+  for (int i = 0; i < 64; ++i) {
+    for (int j = 0; j < 64; ++j) {
+      EXPECT_THAT(MultiplyU128ToU256(k1 << i, k1 << j),
+                  Eq256(LeftShift({0, 1}, i + j)));
+    }
+  }
+
+  // Verified multiplies
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0xc502da0d6ea99fe8, 0xfa3c9141a1f50912),
+                  absl::MakeUint128(0x96bcf1ac37f97bd6, 0x27e2cdeb5fb2299e)),
+              Eq256(absl::MakeUint128(0x740113d838f96a64, 0x22e8cfa4d71f89ea),
+                    absl::MakeUint128(0x19184a345c62e993, 0x237871b630337b1c)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0x6f29e670cee07230, 0xc3d8e6c3e4d86759),
+                  absl::MakeUint128(0x3227d29fa6386db1, 0x231682bb1e4b764f)),
+              Eq256(absl::MakeUint128(0x15c779d9d5d3b07c, 0xd7e6c827f0c81cbe),
+                    absl::MakeUint128(0xf88e3914f7fa287a, 0x15b79975137dea77)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0xafb77107215646e1, 0x3b844cb1ac5769e7),
+                  absl::MakeUint128(0x1ff7b2d888b62479, 0x92f758ae96fcba0b)),
+              Eq256(absl::MakeUint128(0x15f13b70181f6985, 0x2adb36bbabce7d02),
+                    absl::MakeUint128(0x6c470d72e13aad04, 0x63fba3f5841762ed)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0xd85d5558d67ac905, 0xf88c70654dae19b1),
+                  absl::MakeUint128(0x17252c6727db3738, 0x399ff658c511eedc)),
+              Eq256(absl::MakeUint128(0x138fcdaf8b0421ee, 0x1b465ddf2a0d03f6),
+                    absl::MakeUint128(0x8f573ba68296860f, 0xf327d2738741a21c)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0x46f0421a37ff6bee, 0xa61df89f09d140b1),
+                  absl::MakeUint128(0x3d712ec9f37ca2e1, 0x9658a2cba47ef4b1)),
+              Eq256(absl::MakeUint128(0x11069cc48ee7c95d, 0xd35fb1c7aa91c978),
+                    absl::MakeUint128(0xbe2f4a6de874b015, 0xd2f7ac1b76746e61)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0x730d27c72d58fa49, 0x3ebeda7498f8827c),
+                  absl::MakeUint128(0xa2c959eca9f503af, 0x189c687eb842bbd8)),
+              Eq256(absl::MakeUint128(0x4928d0ea356ba022, 0x1546d34a2963393),
+                    absl::MakeUint128(0x7481531e1e0a16d1, 0xdd8025015cf6aca0)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0x6ca41020f856d2f1, 0xb9b0838c04a7f4aa),
+                  absl::MakeUint128(0x9cf41d28a8396f54, 0x1d681695e377ffe6)),
+              Eq256(absl::MakeUint128(0x429b92934d9be6f1, 0xea182877157c1e7),
+                    absl::MakeUint128(0x7135c23f0a4a475, 0xc1adc366f4a126bc)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0x57472833797c332, 0x6c79272fdec4687a),
+                  absl::MakeUint128(0xb5f022ea3838e46b, 0x16face2f003e27a6)),
+              Eq256(absl::MakeUint128(0x3e072e0962b3400, 0x5d9fe8fdc3d0e1f4),
+                    absl::MakeUint128(0x7dc0df47cedafd62, 0xbe6501f1acd2551c)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0xf0fb4198322eb1c2, 0xfe7f5f31f3885938),
+                  absl::MakeUint128(0xd99012b71bb7aa31, 0xac7a6f9eb190789)),
+              Eq256(absl::MakeUint128(0xcccc998cf075ca01, 0x642d144322fb873a),
+                    absl::MakeUint128(0xc79dc12b69d91ed4, 0xa83459132ce046f8)));
+  EXPECT_THAT(MultiplyU128ToU256(
+                  absl::MakeUint128(0xb5c04120848cdb47, 0x8aa62a827bf52635),
+                  absl::MakeUint128(0x8d07a359be2f1380, 0x467bb90d59da0dea)),
+              Eq256(absl::MakeUint128(0x64205019d139a9ce, 0x99425c5fb6e7a977),
+                    absl::MakeUint128(0xd3e99628a9e5fca7, 0x9c7824cb7279d72)));
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/mock_distributions.h b/weight/_dep/abseil-cpp/absl/random/mock_distributions.h
new file mode 100644
index 0000000000000000000000000000000000000000..764ab370abebcb1b12687e4d8fc8bc6f36de60e0
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/mock_distributions.h
@@ -0,0 +1,266 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: mock_distributions.h
+// -----------------------------------------------------------------------------
+//
+// This file contains mock distribution functions for use alongside an
+// `absl::MockingBitGen` object within the Googletest testing framework. Such
+// mocks are useful to provide deterministic values as return values within
+// (otherwise random) Abseil distribution functions.
+//
+// The return type of each function is a mock expectation object which
+// is used to set the match result.
+//
+// More information about the Googletest testing framework is available at
+// https://github.com/google/googletest
+//
+// EXPECT_CALL and ON_CALL need to be made within the same DLL component as
+// the call to absl::Uniform and related methods, otherwise mocking will fail
+// since the  underlying implementation creates a type-specific pointer which
+// will be distinct across different DLL boundaries.
+//
+// Example:
+//
+//   absl::MockingBitGen mock;
+//   EXPECT_CALL(absl::MockUniform<int>(), Call(mock, 1, 1000))
+//     .WillRepeatedly(testing::ReturnRoundRobin({20, 40}));
+//
+//   EXPECT_EQ(absl::Uniform<int>(gen, 1, 1000), 20);
+//   EXPECT_EQ(absl::Uniform<int>(gen, 1, 1000), 40);
+//   EXPECT_EQ(absl::Uniform<int>(gen, 1, 1000), 20);
+//   EXPECT_EQ(absl::Uniform<int>(gen, 1, 1000), 40);
+
+#ifndef ABSL_RANDOM_MOCK_DISTRIBUTIONS_H_
+#define ABSL_RANDOM_MOCK_DISTRIBUTIONS_H_
+
+#include <limits>
+#include <type_traits>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/meta/type_traits.h"
+#include "absl/random/distributions.h"
+#include "absl/random/internal/mock_overload_set.h"
+#include "absl/random/mocking_bit_gen.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// -----------------------------------------------------------------------------
+// absl::MockUniform
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Uniform.
+//
+// `absl::MockUniform` is a class template used in conjunction with Googletest's
+// `ON_CALL()` and `EXPECT_CALL()` macros. To use it, default-construct an
+// instance of it inside `ON_CALL()` or `EXPECT_CALL()`, and use `Call(...)` the
+// same way one would define mocks on a Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockUniform<uint32_t>(), Call(mock))
+//     .WillOnce(Return(123456));
+//  auto x = absl::Uniform<uint32_t>(mock);
+//  assert(x == 123456)
+//
+template <typename R>
+using MockUniform = random_internal::MockOverloadSet<
+    random_internal::UniformDistributionWrapper<R>,
+    R(IntervalClosedOpenTag, MockingBitGen&, R, R),
+    R(IntervalClosedClosedTag, MockingBitGen&, R, R),
+    R(IntervalOpenOpenTag, MockingBitGen&, R, R),
+    R(IntervalOpenClosedTag, MockingBitGen&, R, R), R(MockingBitGen&, R, R),
+    R(MockingBitGen&)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockBernoulli
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Bernoulli.
+//
+// `absl::MockBernoulli` is a class used in conjunction with Googletest's
+// `ON_CALL()` and `EXPECT_CALL()` macros. To use it, default-construct an
+// instance of it inside `ON_CALL()` or `EXPECT_CALL()`, and use `Call(...)` the
+// same way one would define mocks on a Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockBernoulli(), Call(mock, testing::_))
+//     .WillOnce(Return(false));
+//  assert(absl::Bernoulli(mock, 0.5) == false);
+//
+using MockBernoulli =
+    random_internal::MockOverloadSet<absl::bernoulli_distribution,
+                                     bool(MockingBitGen&, double)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockBeta
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Beta.
+//
+// `absl::MockBeta` is a class used in conjunction with Googletest's `ON_CALL()`
+// and `EXPECT_CALL()` macros. To use it, default-construct an instance of it
+// inside `ON_CALL()` or `EXPECT_CALL()`, and use `Call(...)` the same way one
+// would define mocks on a Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockBeta(), Call(mock, 3.0, 2.0))
+//     .WillOnce(Return(0.567));
+//  auto x = absl::Beta<double>(mock, 3.0, 2.0);
+//  assert(x == 0.567);
+//
+template <typename RealType>
+using MockBeta =
+    random_internal::MockOverloadSet<absl::beta_distribution<RealType>,
+                                     RealType(MockingBitGen&, RealType,
+                                              RealType)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockExponential
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Exponential.
+//
+// `absl::MockExponential` is a class template used in conjunction with
+// Googletest's `ON_CALL()` and `EXPECT_CALL()` macros. To use it,
+// default-construct an instance of it inside `ON_CALL()` or `EXPECT_CALL()`,
+// and use `Call(...)` the same way one would define mocks on a
+// Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockExponential<double>(), Call(mock, 0.5))
+//     .WillOnce(Return(12.3456789));
+//  auto x = absl::Exponential<double>(mock, 0.5);
+//  assert(x == 12.3456789)
+//
+template <typename RealType>
+using MockExponential =
+    random_internal::MockOverloadSet<absl::exponential_distribution<RealType>,
+                                     RealType(MockingBitGen&, RealType)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockGaussian
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Gaussian.
+//
+// `absl::MockGaussian` is a class template used in conjunction with
+// Googletest's `ON_CALL()` and `EXPECT_CALL()` macros. To use it,
+// default-construct an instance of it inside `ON_CALL()` or `EXPECT_CALL()`,
+// and use `Call(...)` the same way one would define mocks on a
+// Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockGaussian<double>(), Call(mock, 16.3, 3.3))
+//     .WillOnce(Return(12.3456789));
+//  auto x = absl::Gaussian<double>(mock, 16.3, 3.3);
+//  assert(x == 12.3456789)
+//
+template <typename RealType>
+using MockGaussian =
+    random_internal::MockOverloadSet<absl::gaussian_distribution<RealType>,
+                                     RealType(MockingBitGen&, RealType,
+                                              RealType)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockLogUniform
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::LogUniform.
+//
+// `absl::MockLogUniform` is a class template used in conjunction with
+// Googletest's `ON_CALL()` and `EXPECT_CALL()` macros. To use it,
+// default-construct an instance of it inside `ON_CALL()` or `EXPECT_CALL()`,
+// and use `Call(...)` the same way one would define mocks on a
+// Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockLogUniform<int>(), Call(mock, 10, 10000, 10))
+//     .WillOnce(Return(1221));
+//  auto x = absl::LogUniform<int>(mock, 10, 10000, 10);
+//  assert(x == 1221)
+//
+template <typename IntType>
+using MockLogUniform = random_internal::MockOverloadSet<
+    absl::log_uniform_int_distribution<IntType>,
+    IntType(MockingBitGen&, IntType, IntType, IntType)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockPoisson
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Poisson.
+//
+// `absl::MockPoisson` is a class template used in conjunction with Googletest's
+// `ON_CALL()` and `EXPECT_CALL()` macros. To use it, default-construct an
+// instance of it inside `ON_CALL()` or `EXPECT_CALL()`, and use `Call(...)` the
+// same way one would define mocks on a Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockPoisson<int>(), Call(mock, 2.0))
+//     .WillOnce(Return(1221));
+//  auto x = absl::Poisson<int>(mock, 2.0);
+//  assert(x == 1221)
+//
+template <typename IntType>
+using MockPoisson =
+    random_internal::MockOverloadSet<absl::poisson_distribution<IntType>,
+                                     IntType(MockingBitGen&, double)>;
+
+// -----------------------------------------------------------------------------
+// absl::MockZipf
+// -----------------------------------------------------------------------------
+//
+// Matches calls to absl::Zipf.
+//
+// `absl::MockZipf` is a class template used in conjunction with Googletest's
+// `ON_CALL()` and `EXPECT_CALL()` macros. To use it, default-construct an
+// instance of it inside `ON_CALL()` or `EXPECT_CALL()`, and use `Call(...)` the
+// same way one would define mocks on a Googletest `MockFunction()`.
+//
+// Example:
+//
+//  absl::MockingBitGen mock;
+//  EXPECT_CALL(absl::MockZipf<int>(), Call(mock, 1000000, 2.0, 1.0))
+//     .WillOnce(Return(1221));
+//  auto x = absl::Zipf<int>(mock, 1000000, 2.0, 1.0);
+//  assert(x == 1221)
+//
+template <typename IntType>
+using MockZipf =
+    random_internal::MockOverloadSet<absl::zipf_distribution<IntType>,
+                                     IntType(MockingBitGen&, IntType, double,
+                                             double)>;
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_MOCK_DISTRIBUTIONS_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/mocking_bit_gen.h b/weight/_dep/abseil-cpp/absl/random/mocking_bit_gen.h
new file mode 100644
index 0000000000000000000000000000000000000000..89fa5a47a6e25d44aa086456ea56ce9e0e1a20f0
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/mocking_bit_gen.h
@@ -0,0 +1,240 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// mocking_bit_gen.h
+// -----------------------------------------------------------------------------
+//
+// This file includes an `absl::MockingBitGen` class to use as a mock within the
+// Googletest testing framework. Such a mock is useful to provide deterministic
+// values as return values within (otherwise random) Abseil distribution
+// functions. Such determinism within a mock is useful within testing frameworks
+// to test otherwise indeterminate APIs.
+//
+// More information about the Googletest testing framework is available at
+// https://github.com/google/googletest
+
+#ifndef ABSL_RANDOM_MOCKING_BIT_GEN_H_
+#define ABSL_RANDOM_MOCKING_BIT_GEN_H_
+
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/internal/fast_type_id.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/meta/type_traits.h"
+#include "absl/random/distributions.h"
+#include "absl/random/internal/distribution_caller.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_join.h"
+#include "absl/types/span.h"
+#include "absl/types/variant.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace random_internal {
+template <typename>
+struct DistributionCaller;
+class MockHelpers;
+
+}  // namespace random_internal
+class BitGenRef;
+
+// MockingBitGen
+//
+// `absl::MockingBitGen` is a mock Uniform Random Bit Generator (URBG) class
+// which can act in place of an `absl::BitGen` URBG within tests using the
+// Googletest testing framework.
+//
+// Usage:
+//
+// Use an `absl::MockingBitGen` along with a mock distribution object (within
+// mock_distributions.h) inside Googletest constructs such as ON_CALL(),
+// EXPECT_TRUE(), etc. to produce deterministic results conforming to the
+// distribution's API contract.
+//
+// Example:
+//
+//  // Mock a call to an `absl::Bernoulli` distribution using Googletest
+//   absl::MockingBitGen bitgen;
+//
+//   ON_CALL(absl::MockBernoulli(), Call(bitgen, 0.5))
+//       .WillByDefault(testing::Return(true));
+//   EXPECT_TRUE(absl::Bernoulli(bitgen, 0.5));
+//
+//  // Mock a call to an `absl::Uniform` distribution within Googletest
+//  absl::MockingBitGen bitgen;
+//
+//   ON_CALL(absl::MockUniform<int>(), Call(bitgen, testing::_, testing::_))
+//       .WillByDefault([] (int low, int high) {
+//           return low + (high - low) / 2;
+//       });
+//
+//   EXPECT_EQ(absl::Uniform<int>(gen, 0, 10), 5);
+//   EXPECT_EQ(absl::Uniform<int>(gen, 30, 40), 35);
+//
+// At this time, only mock distributions supplied within the Abseil random
+// library are officially supported.
+//
+// EXPECT_CALL and ON_CALL need to be made within the same DLL component as
+// the call to absl::Uniform and related methods, otherwise mocking will fail
+// since the  underlying implementation creates a type-specific pointer which
+// will be distinct across different DLL boundaries.
+//
+class MockingBitGen {
+ public:
+  MockingBitGen() = default;
+  ~MockingBitGen() = default;
+
+  // URBG interface
+  using result_type = absl::BitGen::result_type;
+
+  static constexpr result_type(min)() { return (absl::BitGen::min)(); }
+  static constexpr result_type(max)() { return (absl::BitGen::max)(); }
+  result_type operator()() { return gen_(); }
+
+ private:
+  // GetMockFnType returns the testing::MockFunction for a result and tuple.
+  // This method only exists for type deduction and is otherwise unimplemented.
+  template <typename ResultT, typename... Args>
+  static auto GetMockFnType(ResultT, std::tuple<Args...>)
+      -> ::testing::MockFunction<ResultT(Args...)>;
+
+  // MockFnCaller is a helper method for use with absl::apply to
+  // apply an ArgTupleT to a compatible MockFunction.
+  // NOTE: MockFnCaller is essentially equivalent to the lambda:
+  // [fn](auto... args) { return fn->Call(std::move(args)...)}
+  // however that fails to build on some supported platforms.
+  template <typename MockFnType, typename ResultT, typename Tuple>
+  struct MockFnCaller;
+
+  // specialization for std::tuple.
+  template <typename MockFnType, typename ResultT, typename... Args>
+  struct MockFnCaller<MockFnType, ResultT, std::tuple<Args...>> {
+    MockFnType* fn;
+    inline ResultT operator()(Args... args) {
+      return fn->Call(std::move(args)...);
+    }
+  };
+
+  // FunctionHolder owns a particular ::testing::MockFunction associated with
+  // a mocked type signature, and implement the type-erased Apply call, which
+  // applies type-erased arguments to the mock.
+  class FunctionHolder {
+   public:
+    virtual ~FunctionHolder() = default;
+
+    // Call is a dispatch function which converts the
+    // generic type-erased parameters into a specific mock invocation call.
+    virtual void Apply(/*ArgTupleT*/ void* args_tuple,
+                       /*ResultT*/ void* result) = 0;
+  };
+
+  template <typename MockFnType, typename ResultT, typename ArgTupleT>
+  class FunctionHolderImpl final : public FunctionHolder {
+   public:
+    void Apply(void* args_tuple, void* result) override {
+      // Requires tuple_args to point to a ArgTupleT, which is a
+      // std::tuple<Args...> used to invoke the mock function. Requires result
+      // to point to a ResultT, which is the result of the call.
+      *static_cast<ResultT*>(result) =
+          absl::apply(MockFnCaller<MockFnType, ResultT, ArgTupleT>{&mock_fn_},
+                      *static_cast<ArgTupleT*>(args_tuple));
+    }
+
+    MockFnType mock_fn_;
+  };
+
+  // MockingBitGen::RegisterMock
+  //
+  // RegisterMock<ResultT, ArgTupleT>(FastTypeIdType) is the main extension
+  // point for extending the MockingBitGen framework. It provides a mechanism to
+  // install a mock expectation for a function like ResultT(Args...) keyed by
+  // type_idex onto the MockingBitGen context. The key is that the type_index
+  // used to register must match the type index used to call the mock.
+  //
+  // The returned MockFunction<...> type can be used to setup additional
+  // distribution parameters of the expectation.
+  template <typename ResultT, typename ArgTupleT, typename SelfT>
+  auto RegisterMock(SelfT&, base_internal::FastTypeIdType type)
+      -> decltype(GetMockFnType(std::declval<ResultT>(),
+                                std::declval<ArgTupleT>()))& {
+    using MockFnType = decltype(GetMockFnType(std::declval<ResultT>(),
+                                              std::declval<ArgTupleT>()));
+
+    using WrappedFnType = absl::conditional_t<
+        std::is_same<SelfT, ::testing::NiceMock<absl::MockingBitGen>>::value,
+        ::testing::NiceMock<MockFnType>,
+        absl::conditional_t<
+            std::is_same<SelfT,
+                         ::testing::NaggyMock<absl::MockingBitGen>>::value,
+            ::testing::NaggyMock<MockFnType>,
+            absl::conditional_t<
+                std::is_same<SelfT,
+                             ::testing::StrictMock<absl::MockingBitGen>>::value,
+                ::testing::StrictMock<MockFnType>, MockFnType>>>;
+
+    using ImplT = FunctionHolderImpl<WrappedFnType, ResultT, ArgTupleT>;
+    auto& mock = mocks_[type];
+    if (!mock) {
+      mock = absl::make_unique<ImplT>();
+    }
+    return static_cast<ImplT*>(mock.get())->mock_fn_;
+  }
+
+  // MockingBitGen::InvokeMock
+  //
+  // InvokeMock(FastTypeIdType, args, result) is the entrypoint for invoking
+  // mocks registered on MockingBitGen.
+  //
+  // When no mocks are registered on the provided FastTypeIdType, returns false.
+  // Otherwise attempts to invoke the mock function ResultT(Args...) that
+  // was previously registered via the type_index.
+  // Requires tuple_args to point to a ArgTupleT, which is a std::tuple<Args...>
+  // used to invoke the mock function.
+  // Requires result to point to a ResultT, which is the result of the call.
+  inline bool InvokeMock(base_internal::FastTypeIdType type, void* args_tuple,
+                         void* result) {
+    // Trigger a mock, if there exists one that matches `param`.
+    auto it = mocks_.find(type);
+    if (it == mocks_.end()) return false;
+    it->second->Apply(args_tuple, result);
+    return true;
+  }
+
+  absl::flat_hash_map<base_internal::FastTypeIdType,
+                      std::unique_ptr<FunctionHolder>>
+      mocks_;
+  absl::BitGen gen_;
+
+  template <typename>
+  friend struct ::absl::random_internal::DistributionCaller;  // for InvokeMock
+  friend class ::absl::BitGenRef;                             // for InvokeMock
+  friend class ::absl::random_internal::MockHelpers;  // for RegisterMock,
+                                                      // InvokeMock
+};
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_MOCKING_BIT_GEN_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/poisson_distribution.h b/weight/_dep/abseil-cpp/absl/random/poisson_distribution.h
new file mode 100644
index 0000000000000000000000000000000000000000..f4573082e10804fb7deeb4c21fcf40706d3167f6
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/poisson_distribution.h
@@ -0,0 +1,261 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_POISSON_DISTRIBUTION_H_
+#define ABSL_RANDOM_POISSON_DISTRIBUTION_H_
+
+#include <cassert>
+#include <cmath>
+#include <istream>
+#include <limits>
+#include <ostream>
+#include <type_traits>
+
+#include "absl/random/internal/fast_uniform_bits.h"
+#include "absl/random/internal/fastmath.h"
+#include "absl/random/internal/generate_real.h"
+#include "absl/random/internal/iostream_state_saver.h"
+#include "absl/random/internal/traits.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::poisson_distribution:
+// Generates discrete variates conforming to a Poisson distribution.
+//   p(n) = (mean^n / n!) exp(-mean)
+//
+// Depending on the parameter, the distribution selects one of the following
+// algorithms:
+// * The standard algorithm, attributed to Knuth, extended using a split method
+// for larger values
+// * The "Ratio of Uniforms as a convenient method for sampling from classical
+// discrete distributions", Stadlober, 1989.
+// http://www.sciencedirect.com/science/article/pii/0377042790903495
+//
+// NOTE: param_type.mean() is a double, which permits values larger than
+// poisson_distribution<IntType>::max(), however this should be avoided and
+// the distribution results are limited to the max() value.
+//
+// The goals of this implementation are to provide good performance while still
+// beig thread-safe: This limits the implementation to not using lgamma provided
+// by <math.h>.
+//
+template <typename IntType = int>
+class poisson_distribution {
+ public:
+  using result_type = IntType;
+
+  class param_type {
+   public:
+    using distribution_type = poisson_distribution;
+    explicit param_type(double mean = 1.0);
+
+    double mean() const { return mean_; }
+
+    friend bool operator==(const param_type& a, const param_type& b) {
+      return a.mean_ == b.mean_;
+    }
+
+    friend bool operator!=(const param_type& a, const param_type& b) {
+      return !(a == b);
+    }
+
+   private:
+    friend class poisson_distribution;
+
+    double mean_;
+    double emu_;  // e ^ -mean_
+    double lmu_;  // ln(mean_)
+    double s_;
+    double log_k_;
+    int split_;
+
+    static_assert(random_internal::IsIntegral<IntType>::value,
+                  "Class-template absl::poisson_distribution<> must be "
+                  "parameterized using an integral type.");
+  };
+
+  poisson_distribution() : poisson_distribution(1.0) {}
+
+  explicit poisson_distribution(double mean) : param_(mean) {}
+
+  explicit poisson_distribution(const param_type& p) : param_(p) {}
+
+  void reset() {}
+
+  // generating functions
+  template <typename URBG>
+  result_type operator()(URBG& g) {  // NOLINT(runtime/references)
+    return (*this)(g, param_);
+  }
+
+  template <typename URBG>
+  result_type operator()(URBG& g,  // NOLINT(runtime/references)
+                         const param_type& p);
+
+  param_type param() const { return param_; }
+  void param(const param_type& p) { param_ = p; }
+
+  result_type(min)() const { return 0; }
+  result_type(max)() const { return (std::numeric_limits<result_type>::max)(); }
+
+  double mean() const { return param_.mean(); }
+
+  friend bool operator==(const poisson_distribution& a,
+                         const poisson_distribution& b) {
+    return a.param_ == b.param_;
+  }
+  friend bool operator!=(const poisson_distribution& a,
+                         const poisson_distribution& b) {
+    return a.param_ != b.param_;
+  }
+
+ private:
+  param_type param_;
+  random_internal::FastUniformBits<uint64_t> fast_u64_;
+};
+
+// -----------------------------------------------------------------------------
+// Implementation details follow
+// -----------------------------------------------------------------------------
+
+template <typename IntType>
+poisson_distribution<IntType>::param_type::param_type(double mean)
+    : mean_(mean), split_(0) {
+  assert(mean >= 0);
+  assert(mean <=
+         static_cast<double>((std::numeric_limits<result_type>::max)()));
+  // As a defensive measure, avoid large values of the mean.  The rejection
+  // algorithm used does not support very large values well.  It my be worth
+  // changing algorithms to better deal with these cases.
+  assert(mean <= 1e10);
+  if (mean_ < 10) {
+    // For small lambda, use the knuth method.
+    split_ = 1;
+    emu_ = std::exp(-mean_);
+  } else if (mean_ <= 50) {
+    // Use split-knuth method.
+    split_ = 1 + static_cast<int>(mean_ / 10.0);
+    emu_ = std::exp(-mean_ / static_cast<double>(split_));
+  } else {
+    // Use ratio of uniforms method.
+    constexpr double k2E = 0.7357588823428846;
+    constexpr double kSA = 0.4494580810294493;
+
+    lmu_ = std::log(mean_);
+    double a = mean_ + 0.5;
+    s_ = kSA + std::sqrt(k2E * a);
+    const double mode = std::ceil(mean_) - 1;
+    log_k_ = lmu_ * mode - absl::random_internal::StirlingLogFactorial(mode);
+  }
+}
+
+template <typename IntType>
+template <typename URBG>
+typename poisson_distribution<IntType>::result_type
+poisson_distribution<IntType>::operator()(
+    URBG& g,  // NOLINT(runtime/references)
+    const param_type& p) {
+  using random_internal::GeneratePositiveTag;
+  using random_internal::GenerateRealFromBits;
+  using random_internal::GenerateSignedTag;
+
+  if (p.split_ != 0) {
+    // Use Knuth's algorithm with range splitting to avoid floating-point
+    // errors. Knuth's algorithm is: Ui is a sequence of uniform variates on
+    // (0,1); return the number of variates required for product(Ui) <
+    // exp(-lambda).
+    //
+    // The expected number of variates required for Knuth's method can be
+    // computed as follows:
+    // The expected value of U is 0.5, so solving for 0.5^n < exp(-lambda) gives
+    // the expected number of uniform variates
+    // required for a given lambda, which is:
+    //  lambda = [2, 5,  9, 10, 11, 12, 13, 14, 15, 16, 17]
+    //  n      = [3, 8, 13, 15, 16, 18, 19, 21, 22, 24, 25]
+    //
+    result_type n = 0;
+    for (int split = p.split_; split > 0; --split) {
+      double r = 1.0;
+      do {
+        r *= GenerateRealFromBits<double, GeneratePositiveTag, true>(
+            fast_u64_(g));  // U(-1, 0)
+        ++n;
+      } while (r > p.emu_);
+      --n;
+    }
+    return n;
+  }
+
+  // Use ratio of uniforms method.
+  //
+  // Let u ~ Uniform(0, 1), v ~ Uniform(-1, 1),
+  //     a = lambda + 1/2,
+  //     s = 1.5 - sqrt(3/e) + sqrt(2(lambda + 1/2)/e),
+  //     x = s * v/u + a.
+  // P(floor(x) = k | u^2 < f(floor(x))/k), where
+  // f(m) = lambda^m exp(-lambda)/ m!, for 0 <= m, and f(m) = 0 otherwise,
+  // and k = max(f).
+  const double a = p.mean_ + 0.5;
+  for (;;) {
+    const double u = GenerateRealFromBits<double, GeneratePositiveTag, false>(
+        fast_u64_(g));  // U(0, 1)
+    const double v = GenerateRealFromBits<double, GenerateSignedTag, false>(
+        fast_u64_(g));  // U(-1, 1)
+
+    const double x = std::floor(p.s_ * v / u + a);
+    if (x < 0) continue;  // f(negative) = 0
+    const double rhs = x * p.lmu_;
+    // clang-format off
+    double s = (x <= 1.0) ? 0.0
+             : (x == 2.0) ? 0.693147180559945
+             : absl::random_internal::StirlingLogFactorial(x);
+    // clang-format on
+    const double lhs = 2.0 * std::log(u) + p.log_k_ + s;
+    if (lhs < rhs) {
+      return x > static_cast<double>((max)())
+                 ? (max)()
+                 : static_cast<result_type>(x);  // f(x)/k >= u^2
+    }
+  }
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_ostream<CharT, Traits>& operator<<(
+    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+    const poisson_distribution<IntType>& x) {
+  auto saver = random_internal::make_ostream_state_saver(os);
+  os.precision(random_internal::stream_precision_helper<double>::kPrecision);
+  os << x.mean();
+  return os;
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_istream<CharT, Traits>& operator>>(
+    std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+    poisson_distribution<IntType>& x) {     // NOLINT(runtime/references)
+  using param_type = typename poisson_distribution<IntType>::param_type;
+
+  auto saver = random_internal::make_istream_state_saver(is);
+  double mean = random_internal::read_floating_point<double>(is);
+  if (!is.fail()) {
+    x.param(param_type(mean));
+  }
+  return is;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_POISSON_DISTRIBUTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/poisson_distribution_test.cc b/weight/_dep/abseil-cpp/absl/random/poisson_distribution_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..54755960e108a0a5e642f1b6aaf4f6a594585f22
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/poisson_distribution_test.cc
@@ -0,0 +1,570 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/poisson_distribution.h"
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+#include <random>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+#include "absl/container/flat_hash_map.h"
+#include "absl/log/log.h"
+#include "absl/random/internal/chi_square.h"
+#include "absl/random/internal/distribution_test_util.h"
+#include "absl/random/internal/pcg_engine.h"
+#include "absl/random/internal/sequence_urbg.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/str_replace.h"
+#include "absl/strings/strip.h"
+
+// Notes about generating poisson variates:
+//
+// It is unlikely that any implementation of std::poisson_distribution
+// will be stable over time and across library implementations. For instance
+// the three different poisson variate generators listed below all differ:
+//
+// https://github.com/ampl/gsl/tree/master/randist/poisson.c
+// * GSL uses a gamma + binomial + knuth method to compute poisson variates.
+//
+// https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/bits/random.tcc
+// * GCC uses the Devroye rejection algorithm, based on
+// Devroye, L. Non-Uniform Random Variates Generation. Springer-Verlag,
+// New York, 1986, Ch. X, Sects. 3.3 & 3.4 (+ Errata!), ~p.511
+//   http://www.nrbook.com/devroye/
+//
+// https://github.com/llvm-mirror/libcxx/blob/master/include/random
+// * CLANG uses a different rejection method, which appears to include a
+// normal-distribution approximation and an exponential distribution to
+// compute the threshold, including a similar factorial approximation to this
+// one, but it is unclear where the algorithm comes from, exactly.
+//
+
+namespace {
+
+using absl::random_internal::kChiSquared;
+
+// The PoissonDistributionInterfaceTest provides a basic test that
+// absl::poisson_distribution conforms to the interface and serialization
+// requirements imposed by [rand.req.dist] for the common integer types.
+
+template <typename IntType>
+class PoissonDistributionInterfaceTest : public ::testing::Test {};
+
+using IntTypes = ::testing::Types<int, int8_t, int16_t, int32_t, int64_t,
+                                  uint8_t, uint16_t, uint32_t, uint64_t>;
+TYPED_TEST_SUITE(PoissonDistributionInterfaceTest, IntTypes);
+
+TYPED_TEST(PoissonDistributionInterfaceTest, SerializeTest) {
+  using param_type = typename absl::poisson_distribution<TypeParam>::param_type;
+  const double kMax =
+      std::min(1e10 /* assertion limit */,
+               static_cast<double>(std::numeric_limits<TypeParam>::max()));
+
+  const double kParams[] = {
+      // Cases around 1.
+      1,                         //
+      std::nextafter(1.0, 0.0),  // 1 - epsilon
+      std::nextafter(1.0, 2.0),  // 1 + epsilon
+      // Arbitrary values.
+      1e-8, 1e-4,
+      0.0000005,  // ~7.2e-7
+      0.2,        // ~0.2x
+      0.5,        // 0.72
+      2,          // ~2.8
+      20,         // 3x ~9.6
+      100, 1e4, 1e8, 1.5e9, 1e20,
+      // Boundary cases.
+      std::numeric_limits<double>::max(),
+      std::numeric_limits<double>::epsilon(),
+      std::nextafter(std::numeric_limits<double>::min(),
+                     1.0),                        // min + epsilon
+      std::numeric_limits<double>::min(),         // smallest normal
+      std::numeric_limits<double>::denorm_min(),  // smallest denorm
+      std::numeric_limits<double>::min() / 2,     // denorm
+      std::nextafter(std::numeric_limits<double>::min(),
+                     0.0),  // denorm_max
+  };
+
+
+  constexpr int kCount = 1000;
+  absl::InsecureBitGen gen;
+  for (const double m : kParams) {
+    const double mean = std::min(kMax, m);
+    const param_type param(mean);
+
+    // Validate parameters.
+    absl::poisson_distribution<TypeParam> before(mean);
+    EXPECT_EQ(before.mean(), param.mean());
+
+    {
+      absl::poisson_distribution<TypeParam> via_param(param);
+      EXPECT_EQ(via_param, before);
+      EXPECT_EQ(via_param.param(), before.param());
+    }
+
+    // Smoke test.
+    auto sample_min = before.max();
+    auto sample_max = before.min();
+    for (int i = 0; i < kCount; i++) {
+      auto sample = before(gen);
+      EXPECT_GE(sample, before.min());
+      EXPECT_LE(sample, before.max());
+      if (sample > sample_max) sample_max = sample;
+      if (sample < sample_min) sample_min = sample;
+    }
+
+    LOG(INFO) << "Range {" << param.mean() << "}: " << sample_min << ", "
+              << sample_max;
+
+    // Validate stream serialization.
+    std::stringstream ss;
+    ss << before;
+
+    absl::poisson_distribution<TypeParam> after(3.8);
+
+    EXPECT_NE(before.mean(), after.mean());
+    EXPECT_NE(before.param(), after.param());
+    EXPECT_NE(before, after);
+
+    ss >> after;
+
+    EXPECT_EQ(before.mean(), after.mean())  //
+        << ss.str() << " "                  //
+        << (ss.good() ? "good " : "")       //
+        << (ss.bad() ? "bad " : "")         //
+        << (ss.eof() ? "eof " : "")         //
+        << (ss.fail() ? "fail " : "");
+  }
+}
+
+// See http://www.itl.nist.gov/div898/handbook/eda/section3/eda366j.htm
+
+class PoissonModel {
+ public:
+  explicit PoissonModel(double mean) : mean_(mean) {}
+
+  double mean() const { return mean_; }
+  double variance() const { return mean_; }
+  double stddev() const { return std::sqrt(variance()); }
+  double skew() const { return 1.0 / mean_; }
+  double kurtosis() const { return 3.0 + 1.0 / mean_; }
+
+  // InitCDF() initializes the CDF for the distribution parameters.
+  void InitCDF();
+
+  // The InverseCDF, or the Percent-point function returns x, P(x) < v.
+  struct CDF {
+    size_t index;
+    double pmf;
+    double cdf;
+  };
+  CDF InverseCDF(double p) {
+    CDF target{0, 0, p};
+    auto it = std::upper_bound(
+        std::begin(cdf_), std::end(cdf_), target,
+        [](const CDF& a, const CDF& b) { return a.cdf < b.cdf; });
+    return *it;
+  }
+
+  void LogCDF() {
+    LOG(INFO) << "CDF (mean = " << mean_ << ")";
+    for (const auto c : cdf_) {
+      LOG(INFO) << c.index << ": pmf=" << c.pmf << " cdf=" << c.cdf;
+    }
+  }
+
+ private:
+  const double mean_;
+
+  std::vector<CDF> cdf_;
+};
+
+// The goal is to compute an InverseCDF function, or percent point function for
+// the poisson distribution, and use that to partition our output into equal
+// range buckets.  However there is no closed form solution for the inverse cdf
+// for poisson distributions (the closest is the incomplete gamma function).
+// Instead, `InitCDF` iteratively computes the PMF and the CDF. This enables
+// searching for the bucket points.
+void PoissonModel::InitCDF() {
+  if (!cdf_.empty()) {
+    // State already initialized.
+    return;
+  }
+  ABSL_ASSERT(mean_ < 201.0);
+
+  const size_t max_i = 50 * stddev() + mean();
+  const double e_neg_mean = std::exp(-mean());
+  ABSL_ASSERT(e_neg_mean > 0);
+
+  double d = 1;
+  double last_result = e_neg_mean;
+  double cumulative = e_neg_mean;
+  if (e_neg_mean > 1e-10) {
+    cdf_.push_back({0, e_neg_mean, cumulative});
+  }
+  for (size_t i = 1; i < max_i; i++) {
+    d *= (mean() / i);
+    double result = e_neg_mean * d;
+    cumulative += result;
+    if (result < 1e-10 && result < last_result && cumulative > 0.999999) {
+      break;
+    }
+    if (result > 1e-7) {
+      cdf_.push_back({i, result, cumulative});
+    }
+    last_result = result;
+  }
+  ABSL_ASSERT(!cdf_.empty());
+}
+
+// PoissonDistributionZTest implements a z-test for the poisson distribution.
+
+struct ZParam {
+  double mean;
+  double p_fail;   // Z-Test probability of failure.
+  int trials;      // Z-Test trials.
+  size_t samples;  // Z-Test samples.
+};
+
+class PoissonDistributionZTest : public testing::TestWithParam<ZParam>,
+                                 public PoissonModel {
+ public:
+  PoissonDistributionZTest() : PoissonModel(GetParam().mean) {}
+
+  // ZTestImpl provides a basic z-squared test of the mean vs. expected
+  // mean for data generated by the poisson distribution.
+  template <typename D>
+  bool SingleZTest(const double p, const size_t samples);
+
+  // We use a fixed bit generator for distribution accuracy tests.  This allows
+  // these tests to be deterministic, while still testing the qualify of the
+  // implementation.
+  absl::random_internal::pcg64_2018_engine rng_{0x2B7E151628AED2A6};
+};
+
+template <typename D>
+bool PoissonDistributionZTest::SingleZTest(const double p,
+                                           const size_t samples) {
+  D dis(mean());
+
+  absl::flat_hash_map<int32_t, int> buckets;
+  std::vector<double> data;
+  data.reserve(samples);
+  for (int j = 0; j < samples; j++) {
+    const auto x = dis(rng_);
+    buckets[x]++;
+    data.push_back(x);
+  }
+
+  // The null-hypothesis is that the distribution is a poisson distribution with
+  // the provided mean (not estimated from the data).
+  const auto m = absl::random_internal::ComputeDistributionMoments(data);
+  const double max_err = absl::random_internal::MaxErrorTolerance(p);
+  const double z = absl::random_internal::ZScore(mean(), m);
+  const bool pass = absl::random_internal::Near("z", z, 0.0, max_err);
+
+  if (!pass) {
+    // clang-format off
+    LOG(INFO)
+        << "p=" << p << " max_err=" << max_err << "\n"
+           " mean=" << m.mean << " vs. " << mean() << "\n"
+           " stddev=" << std::sqrt(m.variance) << " vs. " << stddev() << "\n"
+           " skewness=" << m.skewness << " vs. " << skew() << "\n"
+           " kurtosis=" << m.kurtosis << " vs. " << kurtosis() << "\n"
+           " z=" << z;
+    // clang-format on
+  }
+  return pass;
+}
+
+TEST_P(PoissonDistributionZTest, AbslPoissonDistribution) {
+  const auto& param = GetParam();
+  const int expected_failures =
+      std::max(1, static_cast<int>(std::ceil(param.trials * param.p_fail)));
+  const double p = absl::random_internal::RequiredSuccessProbability(
+      param.p_fail, param.trials);
+
+  int failures = 0;
+  for (int i = 0; i < param.trials; i++) {
+    failures +=
+        SingleZTest<absl::poisson_distribution<int32_t>>(p, param.samples) ? 0
+                                                                           : 1;
+  }
+  EXPECT_LE(failures, expected_failures);
+}
+
+std::vector<ZParam> GetZParams() {
+  // These values have been adjusted from the "exact" computed values to reduce
+  // failure rates.
+  //
+  // It turns out that the actual values are not as close to the expected values
+  // as would be ideal.
+  return std::vector<ZParam>({
+      // Knuth method.
+      ZParam{0.5, 0.01, 100, 1000},
+      ZParam{1.0, 0.01, 100, 1000},
+      ZParam{10.0, 0.01, 100, 5000},
+      // Split-knuth method.
+      ZParam{20.0, 0.01, 100, 10000},
+      ZParam{50.0, 0.01, 100, 10000},
+      // Ratio of gaussians method.
+      ZParam{51.0, 0.01, 100, 10000},
+      ZParam{200.0, 0.05, 10, 100000},
+      ZParam{100000.0, 0.05, 10, 1000000},
+  });
+}
+
+std::string ZParamName(const ::testing::TestParamInfo<ZParam>& info) {
+  const auto& p = info.param;
+  std::string name = absl::StrCat("mean_", absl::SixDigits(p.mean));
+  return absl::StrReplaceAll(name, {{"+", "_"}, {"-", "_"}, {".", "_"}});
+}
+
+INSTANTIATE_TEST_SUITE_P(All, PoissonDistributionZTest,
+                         ::testing::ValuesIn(GetZParams()), ZParamName);
+
+// The PoissonDistributionChiSquaredTest class provides a basic test framework
+// for variates generated by a conforming poisson_distribution.
+class PoissonDistributionChiSquaredTest : public testing::TestWithParam<double>,
+                                          public PoissonModel {
+ public:
+  PoissonDistributionChiSquaredTest() : PoissonModel(GetParam()) {}
+
+  // The ChiSquaredTestImpl provides a chi-squared goodness of fit test for data
+  // generated by the poisson distribution.
+  template <typename D>
+  double ChiSquaredTestImpl();
+
+ private:
+  void InitChiSquaredTest(const double buckets);
+
+  std::vector<size_t> cutoffs_;
+  std::vector<double> expected_;
+
+  // We use a fixed bit generator for distribution accuracy tests.  This allows
+  // these tests to be deterministic, while still testing the qualify of the
+  // implementation.
+  absl::random_internal::pcg64_2018_engine rng_{0x2B7E151628AED2A6};
+};
+
+void PoissonDistributionChiSquaredTest::InitChiSquaredTest(
+    const double buckets) {
+  if (!cutoffs_.empty() && !expected_.empty()) {
+    return;
+  }
+  InitCDF();
+
+  // The code below finds cuttoffs that yield approximately equally-sized
+  // buckets to the extent that it is possible. However for poisson
+  // distributions this is particularly challenging for small mean parameters.
+  // Track the expected proportion of items in each bucket.
+  double last_cdf = 0;
+  const double inc = 1.0 / buckets;
+  for (double p = inc; p <= 1.0; p += inc) {
+    auto result = InverseCDF(p);
+    if (!cutoffs_.empty() && cutoffs_.back() == result.index) {
+      continue;
+    }
+    double d = result.cdf - last_cdf;
+    cutoffs_.push_back(result.index);
+    expected_.push_back(d);
+    last_cdf = result.cdf;
+  }
+  cutoffs_.push_back(std::numeric_limits<size_t>::max());
+  expected_.push_back(std::max(0.0, 1.0 - last_cdf));
+}
+
+template <typename D>
+double PoissonDistributionChiSquaredTest::ChiSquaredTestImpl() {
+  const int kSamples = 2000;
+  const int kBuckets = 50;
+
+  // The poisson CDF fails for large mean values, since e^-mean exceeds the
+  // machine precision. For these cases, using a normal approximation would be
+  // appropriate.
+  ABSL_ASSERT(mean() <= 200);
+  InitChiSquaredTest(kBuckets);
+
+  D dis(mean());
+
+  std::vector<int32_t> counts(cutoffs_.size(), 0);
+  for (int j = 0; j < kSamples; j++) {
+    const size_t x = dis(rng_);
+    auto it = std::lower_bound(std::begin(cutoffs_), std::end(cutoffs_), x);
+    counts[std::distance(cutoffs_.begin(), it)]++;
+  }
+
+  // Normalize the counts.
+  std::vector<int32_t> e(expected_.size(), 0);
+  for (int i = 0; i < e.size(); i++) {
+    e[i] = kSamples * expected_[i];
+  }
+
+  // The null-hypothesis is that the distribution is a poisson distribution with
+  // the provided mean (not estimated from the data).
+  const int dof = static_cast<int>(counts.size()) - 1;
+
+  // The threshold for logging is 1-in-50.
+  const double threshold = absl::random_internal::ChiSquareValue(dof, 0.98);
+
+  const double chi_square = absl::random_internal::ChiSquare(
+      std::begin(counts), std::end(counts), std::begin(e), std::end(e));
+
+  const double p = absl::random_internal::ChiSquarePValue(chi_square, dof);
+
+  // Log if the chi_squared value is above the threshold.
+  if (chi_square > threshold) {
+    LogCDF();
+
+    LOG(INFO) << "VALUES  buckets=" << counts.size()
+              << "  samples=" << kSamples;
+    for (size_t i = 0; i < counts.size(); i++) {
+      LOG(INFO) << cutoffs_[i] << ": " << counts[i] << " vs. E=" << e[i];
+    }
+
+    LOG(INFO) << kChiSquared << "(data, dof=" << dof << ") = " << chi_square
+              << " (" << p << ")\n"
+              << " vs.\n"
+              << kChiSquared << " @ 0.98 = " << threshold;
+  }
+  return p;
+}
+
+TEST_P(PoissonDistributionChiSquaredTest, AbslPoissonDistribution) {
+  const int kTrials = 20;
+
+  // Large values are not yet supported -- this requires estimating the cdf
+  // using the normal distribution instead of the poisson in this case.
+  ASSERT_LE(mean(), 200.0);
+  if (mean() > 200.0) {
+    return;
+  }
+
+  int failures = 0;
+  for (int i = 0; i < kTrials; i++) {
+    double p_value = ChiSquaredTestImpl<absl::poisson_distribution<int32_t>>();
+    if (p_value < 0.005) {
+      failures++;
+    }
+  }
+  // There is a 0.10% chance of producing at least one failure, so raise the
+  // failure threshold high enough to allow for a flake rate < 10,000.
+  EXPECT_LE(failures, 4);
+}
+
+INSTANTIATE_TEST_SUITE_P(All, PoissonDistributionChiSquaredTest,
+                         ::testing::Values(0.5, 1.0, 2.0, 10.0, 50.0, 51.0,
+                                           200.0));
+
+// NOTE: absl::poisson_distribution is not guaranteed to be stable.
+TEST(PoissonDistributionTest, StabilityTest) {
+  using testing::ElementsAre;
+  // absl::poisson_distribution stability relies on stability of
+  // std::exp, std::log, std::sqrt, std::ceil, std::floor, and
+  // absl::FastUniformBits, absl::StirlingLogFactorial, absl::RandU64ToDouble.
+  absl::random_internal::sequence_urbg urbg({
+      0x035b0dc7e0a18acfull, 0x06cebe0d2653682eull, 0x0061e9b23861596bull,
+      0x0003eb76f6f7f755ull, 0xFFCEA50FDB2F953Bull, 0xC332DDEFBE6C5AA5ull,
+      0x6558218568AB9702ull, 0x2AEF7DAD5B6E2F84ull, 0x1521B62829076170ull,
+      0xECDD4775619F1510ull, 0x13CCA830EB61BD96ull, 0x0334FE1EAA0363CFull,
+      0xB5735C904C70A239ull, 0xD59E9E0BCBAADE14ull, 0xEECC86BC60622CA7ull,
+      0x4864f22c059bf29eull, 0x247856d8b862665cull, 0xe46e86e9a1337e10ull,
+      0xd8c8541f3519b133ull, 0xe75b5162c567b9e4ull, 0xf732e5ded7009c5bull,
+      0xb170b98353121eacull, 0x1ec2e8986d2362caull, 0x814c8e35fe9a961aull,
+      0x0c3cd59c9b638a02ull, 0xcb3bb6478a07715cull, 0x1224e62c978bbc7full,
+      0x671ef2cb04e81f6eull, 0x3c1cbd811eaf1808ull, 0x1bbc23cfa8fac721ull,
+      0xa4c2cda65e596a51ull, 0xb77216fad37adf91ull, 0x836d794457c08849ull,
+      0xe083df03475f49d7ull, 0xbc9feb512e6b0d6cull, 0xb12d74fdd718c8c5ull,
+      0x12ff09653bfbe4caull, 0x8dd03a105bc4ee7eull, 0x5738341045ba0d85ull,
+      0xf3fd722dc65ad09eull, 0xfa14fd21ea2a5705ull, 0xffe6ea4d6edb0c73ull,
+      0xD07E9EFE2BF11FB4ull, 0x95DBDA4DAE909198ull, 0xEAAD8E716B93D5A0ull,
+      0xD08ED1D0AFC725E0ull, 0x8E3C5B2F8E7594B7ull, 0x8FF6E2FBF2122B64ull,
+      0x8888B812900DF01Cull, 0x4FAD5EA0688FC31Cull, 0xD1CFF191B3A8C1ADull,
+      0x2F2F2218BE0E1777ull, 0xEA752DFE8B021FA1ull, 0xE5A0CC0FB56F74E8ull,
+      0x18ACF3D6CE89E299ull, 0xB4A84FE0FD13E0B7ull, 0x7CC43B81D2ADA8D9ull,
+      0x165FA26680957705ull, 0x93CC7314211A1477ull, 0xE6AD206577B5FA86ull,
+      0xC75442F5FB9D35CFull, 0xEBCDAF0C7B3E89A0ull, 0xD6411BD3AE1E7E49ull,
+      0x00250E2D2071B35Eull, 0x226800BB57B8E0AFull, 0x2464369BF009B91Eull,
+      0x5563911D59DFA6AAull, 0x78C14389D95A537Full, 0x207D5BA202E5B9C5ull,
+      0x832603766295CFA9ull, 0x11C819684E734A41ull, 0xB3472DCA7B14A94Aull,
+  });
+
+  std::vector<int> output(10);
+
+  // Method 1.
+  {
+    absl::poisson_distribution<int> dist(5);
+    std::generate(std::begin(output), std::end(output),
+                  [&] { return dist(urbg); });
+  }
+  EXPECT_THAT(output,  // mean = 4.2
+              ElementsAre(1, 0, 0, 4, 2, 10, 3, 3, 7, 12));
+
+  // Method 2.
+  {
+    urbg.reset();
+    absl::poisson_distribution<int> dist(25);
+    std::generate(std::begin(output), std::end(output),
+                  [&] { return dist(urbg); });
+  }
+  EXPECT_THAT(output,  // mean = 19.8
+              ElementsAre(9, 35, 18, 10, 35, 18, 10, 35, 18, 10));
+
+  // Method 3.
+  {
+    urbg.reset();
+    absl::poisson_distribution<int> dist(121);
+    std::generate(std::begin(output), std::end(output),
+                  [&] { return dist(urbg); });
+  }
+  EXPECT_THAT(output,  // mean = 124.1
+              ElementsAre(161, 122, 129, 124, 112, 112, 117, 120, 130, 114));
+}
+
+TEST(PoissonDistributionTest, AlgorithmExpectedValue_1) {
+  // This tests small values of the Knuth method.
+  // The underlying uniform distribution will generate exactly 0.5.
+  absl::random_internal::sequence_urbg urbg({0x8000000000000001ull});
+  absl::poisson_distribution<int> dist(5);
+  EXPECT_EQ(7, dist(urbg));
+}
+
+TEST(PoissonDistributionTest, AlgorithmExpectedValue_2) {
+  // This tests larger values of the Knuth method.
+  // The underlying uniform distribution will generate exactly 0.5.
+  absl::random_internal::sequence_urbg urbg({0x8000000000000001ull});
+  absl::poisson_distribution<int> dist(25);
+  EXPECT_EQ(36, dist(urbg));
+}
+
+TEST(PoissonDistributionTest, AlgorithmExpectedValue_3) {
+  // This variant uses the ratio of uniforms method.
+  absl::random_internal::sequence_urbg urbg(
+      {0x7fffffffffffffffull, 0x8000000000000000ull});
+
+  absl::poisson_distribution<int> dist(121);
+  EXPECT_EQ(121, dist(urbg));
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/seed_gen_exception.h b/weight/_dep/abseil-cpp/absl/random/seed_gen_exception.h
new file mode 100644
index 0000000000000000000000000000000000000000..5353900564372008d26542d10a9ba336d1b055ca
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/seed_gen_exception.h
@@ -0,0 +1,55 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: seed_gen_exception.h
+// -----------------------------------------------------------------------------
+//
+// This header defines an exception class which may be thrown if unpredictable
+// events prevent the derivation of suitable seed-material for constructing a
+// bit generator conforming to [rand.req.urng] (eg. entropy cannot be read from
+// /dev/urandom on a Unix-based system).
+//
+// Note: if exceptions are disabled, `std::terminate()` is called instead.
+
+#ifndef ABSL_RANDOM_SEED_GEN_EXCEPTION_H_
+#define ABSL_RANDOM_SEED_GEN_EXCEPTION_H_
+
+#include <exception>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+//------------------------------------------------------------------------------
+// SeedGenException
+//------------------------------------------------------------------------------
+class SeedGenException : public std::exception {
+ public:
+  SeedGenException() = default;
+  ~SeedGenException() override;
+  const char* what() const noexcept override;
+};
+
+namespace random_internal {
+
+// throw delegator
+[[noreturn]] void ThrowSeedGenException();
+
+}  // namespace random_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_SEED_GEN_EXCEPTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/seed_sequences.cc b/weight/_dep/abseil-cpp/absl/random/seed_sequences.cc
new file mode 100644
index 0000000000000000000000000000000000000000..426eafd3c8de4b43b13f5f420e77038f437c2a8d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/seed_sequences.cc
@@ -0,0 +1,29 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/seed_sequences.h"
+
+#include "absl/random/internal/pool_urbg.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+SeedSeq MakeSeedSeq() {
+  SeedSeq::result_type seed_material[8];
+  random_internal::RandenPool<uint32_t>::Fill(absl::MakeSpan(seed_material));
+  return SeedSeq(std::begin(seed_material), std::end(seed_material));
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/random/seed_sequences.h b/weight/_dep/abseil-cpp/absl/random/seed_sequences.h
new file mode 100644
index 0000000000000000000000000000000000000000..c3af4b00a477ce9588a4206342cc68e7a5e38e53
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/seed_sequences.h
@@ -0,0 +1,111 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: seed_sequences.h
+// -----------------------------------------------------------------------------
+//
+// This header contains utilities for creating and working with seed sequences
+// conforming to [rand.req.seedseq]. In general, direct construction of seed
+// sequences is discouraged, but use-cases for construction of identical bit
+// generators (using the same seed sequence) may be helpful (e.g. replaying a
+// simulation whose state is derived from variates of a bit generator).
+
+#ifndef ABSL_RANDOM_SEED_SEQUENCES_H_
+#define ABSL_RANDOM_SEED_SEQUENCES_H_
+
+#include <iterator>
+#include <random>
+
+#include "absl/base/config.h"
+#include "absl/random/internal/salted_seed_seq.h"
+#include "absl/random/internal/seed_material.h"
+#include "absl/random/seed_gen_exception.h"
+#include "absl/types/span.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// -----------------------------------------------------------------------------
+// absl::SeedSeq
+// -----------------------------------------------------------------------------
+//
+// `absl::SeedSeq` constructs a seed sequence according to [rand.req.seedseq]
+// for use within bit generators. `absl::SeedSeq`, unlike `std::seed_seq`
+// additionally salts the generated seeds with extra implementation-defined
+// entropy. For that reason, you can use `absl::SeedSeq` in combination with
+// standard library bit generators (e.g. `std::mt19937`) to introduce
+// non-determinism in your seeds.
+//
+// Example:
+//
+//   absl::SeedSeq my_seed_seq({a, b, c});
+//   std::mt19937 my_bitgen(my_seed_seq);
+//
+using SeedSeq = random_internal::SaltedSeedSeq<std::seed_seq>;
+
+// -----------------------------------------------------------------------------
+// absl::CreateSeedSeqFrom(bitgen*)
+// -----------------------------------------------------------------------------
+//
+// Constructs a seed sequence conforming to [rand.req.seedseq] using variates
+// produced by a provided bit generator.
+//
+// You should generally avoid direct construction of seed sequences, but
+// use-cases for reuse of a seed sequence to construct identical bit generators
+// may be helpful (eg. replaying a simulation whose state is derived from bit
+// generator values).
+//
+// If bitgen == nullptr, then behavior is undefined.
+//
+// Example:
+//
+//   absl::BitGen my_bitgen;
+//   auto seed_seq = absl::CreateSeedSeqFrom(&my_bitgen);
+//   absl::BitGen new_engine(seed_seq); // derived from my_bitgen, but not
+//                                      // correlated.
+//
+template <typename URBG>
+SeedSeq CreateSeedSeqFrom(URBG* urbg) {
+  SeedSeq::result_type
+      seed_material[random_internal::kEntropyBlocksNeeded];
+
+  if (!random_internal::ReadSeedMaterialFromURBG(
+          urbg, absl::MakeSpan(seed_material))) {
+    random_internal::ThrowSeedGenException();
+  }
+  return SeedSeq(std::begin(seed_material), std::end(seed_material));
+}
+
+// -----------------------------------------------------------------------------
+// absl::MakeSeedSeq()
+// -----------------------------------------------------------------------------
+//
+// Constructs an `absl::SeedSeq` salting the generated values using
+// implementation-defined entropy. The returned sequence can be used to create
+// equivalent bit generators correlated using this sequence.
+//
+// Example:
+//
+//   auto my_seed_seq = absl::MakeSeedSeq();
+//   std::mt19937 rng1(my_seed_seq);
+//   std::mt19937 rng2(my_seed_seq);
+//   EXPECT_EQ(rng1(), rng2());
+//
+SeedSeq MakeSeedSeq();
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_SEED_SEQUENCES_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/seed_sequences_test.cc b/weight/_dep/abseil-cpp/absl/random/seed_sequences_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fe1100bda0d59f89714cc90e51c459dd9399b9fd
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/seed_sequences_test.cc
@@ -0,0 +1,126 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/seed_sequences.h"
+
+#include <iterator>
+#include <random>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/random/internal/nonsecure_base.h"
+#include "absl/random/random.h"
+namespace {
+
+TEST(SeedSequences, Examples) {
+  {
+    absl::SeedSeq seed_seq({1, 2, 3});
+    absl::BitGen bitgen(seed_seq);
+
+    EXPECT_NE(0, bitgen());
+  }
+  {
+    absl::BitGen engine;
+    auto seed_seq = absl::CreateSeedSeqFrom(&engine);
+    absl::BitGen bitgen(seed_seq);
+
+    EXPECT_NE(engine(), bitgen());
+  }
+  {
+    auto seed_seq = absl::MakeSeedSeq();
+    std::mt19937 random(seed_seq);
+
+    EXPECT_NE(0, random());
+  }
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithStdTypes) {
+  using ExampleNonsecureURBG =
+      absl::random_internal::NonsecureURBGBase<std::minstd_rand0>;
+
+  // Construct a URBG instance.
+  ExampleNonsecureURBG rng;
+
+  // Construct a Seed Sequence from its variates.
+  auto seq_from_rng = absl::CreateSeedSeqFrom(&rng);
+
+  // Ensure that another URBG can be validly constructed from the Seed Sequence.
+  std::mt19937_64{seq_from_rng};
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithBitGenerator) {
+  // Construct a URBG instance.
+  absl::BitGen rng;
+
+  // Construct a Seed Sequence from its variates.
+  auto seq_from_rng = absl::CreateSeedSeqFrom(&rng);
+
+  // Ensure that another URBG can be validly constructed from the Seed Sequence.
+  std::mt19937_64{seq_from_rng};
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithInsecureBitGen) {
+  // Construct a URBG instance.
+  absl::InsecureBitGen rng;
+
+  // Construct a Seed Sequence from its variates.
+  auto seq_from_rng = absl::CreateSeedSeqFrom(&rng);
+
+  // Ensure that another URBG can be validly constructed from the Seed Sequence.
+  std::mt19937_64{seq_from_rng};
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithRawURBG) {
+  // Construct a URBG instance.
+  std::random_device urandom;
+
+  // Construct a Seed Sequence from its variates, using 64b of seed-material.
+  auto seq_from_rng = absl::CreateSeedSeqFrom(&urandom);
+
+  // Ensure that another URBG can be validly constructed from the Seed Sequence.
+  std::mt19937_64{seq_from_rng};
+}
+
+template <typename URBG>
+void TestReproducibleVariateSequencesForNonsecureURBG() {
+  const size_t kNumVariates = 1000;
+
+  URBG rng;
+  // Reused for both RNG instances.
+  auto reusable_seed = absl::CreateSeedSeqFrom(&rng);
+
+  typename URBG::result_type variates[kNumVariates];
+  {
+    URBG child(reusable_seed);
+    for (auto& variate : variates) {
+      variate = child();
+    }
+  }
+  // Ensure that variate-sequence can be "replayed" by identical RNG.
+  {
+    URBG child(reusable_seed);
+    for (auto& variate : variates) {
+      ASSERT_EQ(variate, child());
+    }
+  }
+}
+
+TEST(CreateSeedSeqFrom, ReproducesVariateSequencesForInsecureBitGen) {
+  TestReproducibleVariateSequencesForNonsecureURBG<absl::InsecureBitGen>();
+}
+
+TEST(CreateSeedSeqFrom, ReproducesVariateSequencesForBitGenerator) {
+  TestReproducibleVariateSequencesForNonsecureURBG<absl::BitGen>();
+}
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/uniform_int_distribution.h b/weight/_dep/abseil-cpp/absl/random/uniform_int_distribution.h
new file mode 100644
index 0000000000000000000000000000000000000000..fae80252e39b5e9456ba929aba0c4cd82329395b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/uniform_int_distribution.h
@@ -0,0 +1,275 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: uniform_int_distribution.h
+// -----------------------------------------------------------------------------
+//
+// This header defines a class for representing a uniform integer distribution
+// over the closed (inclusive) interval [a,b]. You use this distribution in
+// combination with an Abseil random bit generator to produce random values
+// according to the rules of the distribution.
+//
+// `absl::uniform_int_distribution` is a drop-in replacement for the C++11
+// `std::uniform_int_distribution` [rand.dist.uni.int] but is considerably
+// faster than the libstdc++ implementation.
+
+#ifndef ABSL_RANDOM_UNIFORM_INT_DISTRIBUTION_H_
+#define ABSL_RANDOM_UNIFORM_INT_DISTRIBUTION_H_
+
+#include <cassert>
+#include <istream>
+#include <limits>
+#include <type_traits>
+
+#include "absl/base/optimization.h"
+#include "absl/random/internal/fast_uniform_bits.h"
+#include "absl/random/internal/iostream_state_saver.h"
+#include "absl/random/internal/traits.h"
+#include "absl/random/internal/wide_multiply.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::uniform_int_distribution<T>
+//
+// This distribution produces random integer values uniformly distributed in the
+// closed (inclusive) interval [a, b].
+//
+// Example:
+//
+//   absl::BitGen gen;
+//
+//   // Use the distribution to produce a value between 1 and 6, inclusive.
+//   int die_roll = absl::uniform_int_distribution<int>(1, 6)(gen);
+//
+template <typename IntType = int>
+class uniform_int_distribution {
+ private:
+  using unsigned_type =
+      typename random_internal::make_unsigned_bits<IntType>::type;
+
+ public:
+  using result_type = IntType;
+
+  class param_type {
+   public:
+    using distribution_type = uniform_int_distribution;
+
+    explicit param_type(
+        result_type lo = 0,
+        result_type hi = (std::numeric_limits<result_type>::max)())
+        : lo_(lo),
+          range_(static_cast<unsigned_type>(hi) -
+                 static_cast<unsigned_type>(lo)) {
+      // [rand.dist.uni.int] precondition 2
+      assert(lo <= hi);
+    }
+
+    result_type a() const { return lo_; }
+    result_type b() const {
+      return static_cast<result_type>(static_cast<unsigned_type>(lo_) + range_);
+    }
+
+    friend bool operator==(const param_type& a, const param_type& b) {
+      return a.lo_ == b.lo_ && a.range_ == b.range_;
+    }
+
+    friend bool operator!=(const param_type& a, const param_type& b) {
+      return !(a == b);
+    }
+
+   private:
+    friend class uniform_int_distribution;
+    unsigned_type range() const { return range_; }
+
+    result_type lo_;
+    unsigned_type range_;
+
+    static_assert(random_internal::IsIntegral<result_type>::value,
+                  "Class-template absl::uniform_int_distribution<> must be "
+                  "parameterized using an integral type.");
+  };  // param_type
+
+  uniform_int_distribution() : uniform_int_distribution(0) {}
+
+  explicit uniform_int_distribution(
+      result_type lo,
+      result_type hi = (std::numeric_limits<result_type>::max)())
+      : param_(lo, hi) {}
+
+  explicit uniform_int_distribution(const param_type& param) : param_(param) {}
+
+  // uniform_int_distribution<T>::reset()
+  //
+  // Resets the uniform int distribution. Note that this function has no effect
+  // because the distribution already produces independent values.
+  void reset() {}
+
+  template <typename URBG>
+  result_type operator()(URBG& gen) {  // NOLINT(runtime/references)
+    return (*this)(gen, param());
+  }
+
+  template <typename URBG>
+  result_type operator()(
+      URBG& gen, const param_type& param) {  // NOLINT(runtime/references)
+    return static_cast<result_type>(param.a() + Generate(gen, param.range()));
+  }
+
+  result_type a() const { return param_.a(); }
+  result_type b() const { return param_.b(); }
+
+  param_type param() const { return param_; }
+  void param(const param_type& params) { param_ = params; }
+
+  result_type(min)() const { return a(); }
+  result_type(max)() const { return b(); }
+
+  friend bool operator==(const uniform_int_distribution& a,
+                         const uniform_int_distribution& b) {
+    return a.param_ == b.param_;
+  }
+  friend bool operator!=(const uniform_int_distribution& a,
+                         const uniform_int_distribution& b) {
+    return !(a == b);
+  }
+
+ private:
+  // Generates a value in the *closed* interval [0, R]
+  template <typename URBG>
+  unsigned_type Generate(URBG& g,  // NOLINT(runtime/references)
+                         unsigned_type R);
+  param_type param_;
+};
+
+// -----------------------------------------------------------------------------
+// Implementation details follow
+// -----------------------------------------------------------------------------
+template <typename CharT, typename Traits, typename IntType>
+std::basic_ostream<CharT, Traits>& operator<<(
+    std::basic_ostream<CharT, Traits>& os,
+    const uniform_int_distribution<IntType>& x) {
+  using stream_type =
+      typename random_internal::stream_format_type<IntType>::type;
+  auto saver = random_internal::make_ostream_state_saver(os);
+  os << static_cast<stream_type>(x.a()) << os.fill()
+     << static_cast<stream_type>(x.b());
+  return os;
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_istream<CharT, Traits>& operator>>(
+    std::basic_istream<CharT, Traits>& is,
+    uniform_int_distribution<IntType>& x) {
+  using param_type = typename uniform_int_distribution<IntType>::param_type;
+  using result_type = typename uniform_int_distribution<IntType>::result_type;
+  using stream_type =
+      typename random_internal::stream_format_type<IntType>::type;
+
+  stream_type a;
+  stream_type b;
+
+  auto saver = random_internal::make_istream_state_saver(is);
+  is >> a >> b;
+  if (!is.fail()) {
+    x.param(
+        param_type(static_cast<result_type>(a), static_cast<result_type>(b)));
+  }
+  return is;
+}
+
+template <typename IntType>
+template <typename URBG>
+typename random_internal::make_unsigned_bits<IntType>::type
+uniform_int_distribution<IntType>::Generate(
+    URBG& g,  // NOLINT(runtime/references)
+    typename random_internal::make_unsigned_bits<IntType>::type R) {
+  random_internal::FastUniformBits<unsigned_type> fast_bits;
+  unsigned_type bits = fast_bits(g);
+  const unsigned_type Lim = R + 1;
+  if ((R & Lim) == 0) {
+    // If the interval's length is a power of two range, just take the low bits.
+    return bits & R;
+  }
+
+  // Generates a uniform variate on [0, Lim) using fixed-point multiplication.
+  // The above fast-path guarantees that Lim is representable in unsigned_type.
+  //
+  // Algorithm adapted from
+  // http://lemire.me/blog/2016/06/30/fast-random-shuffling/, with added
+  // explanation.
+  //
+  // The algorithm creates a uniform variate `bits` in the interval [0, 2^N),
+  // and treats it as the fractional part of a fixed-point real value in [0, 1),
+  // multiplied by 2^N.  For example, 0.25 would be represented as 2^(N - 2),
+  // because 2^N * 0.25 == 2^(N - 2).
+  //
+  // Next, `bits` and `Lim` are multiplied with a wide-multiply to bring the
+  // value into the range [0, Lim).  The integral part (the high word of the
+  // multiplication result) is then very nearly the desired result.  However,
+  // this is not quite accurate; viewing the multiplication result as one
+  // double-width integer, the resulting values for the sample are mapped as
+  // follows:
+  //
+  // If the result lies in this interval:       Return this value:
+  //        [0, 2^N)                                    0
+  //        [2^N, 2 * 2^N)                              1
+  //        ...                                         ...
+  //        [K * 2^N, (K + 1) * 2^N)                    K
+  //        ...                                         ...
+  //        [(Lim - 1) * 2^N, Lim * 2^N)                Lim - 1
+  //
+  // While all of these intervals have the same size, the result of `bits * Lim`
+  // must be a multiple of `Lim`, and not all of these intervals contain the
+  // same number of multiples of `Lim`.  In particular, some contain
+  // `F = floor(2^N / Lim)` and some contain `F + 1 = ceil(2^N / Lim)`.  This
+  // difference produces a small nonuniformity, which is corrected by applying
+  // rejection sampling to one of the values in the "larger intervals" (i.e.,
+  // the intervals containing `F + 1` multiples of `Lim`.
+  //
+  // An interval contains `F + 1` multiples of `Lim` if and only if its smallest
+  // value modulo 2^N is less than `2^N % Lim`.  The unique value satisfying
+  // this property is used as the one for rejection.  That is, a value of
+  // `bits * Lim` is rejected if `(bit * Lim) % 2^N < (2^N % Lim)`.
+
+  using helper = random_internal::wide_multiply<unsigned_type>;
+  auto product = helper::multiply(bits, Lim);
+
+  // Two optimizations here:
+  // * Rejection occurs with some probability less than 1/2, and for reasonable
+  //   ranges considerably less (in particular, less than 1/(F+1)), so
+  //   ABSL_PREDICT_FALSE is apt.
+  // * `Lim` is an overestimate of `threshold`, and doesn't require a divide.
+  if (ABSL_PREDICT_FALSE(helper::lo(product) < Lim)) {
+    // This quantity is exactly equal to `2^N % Lim`, but does not require high
+    // precision calculations: `2^N % Lim` is congruent to `(2^N - Lim) % Lim`.
+    // Ideally this could be expressed simply as `-X` rather than `2^N - X`, but
+    // for types smaller than int, this calculation is incorrect due to integer
+    // promotion rules.
+    const unsigned_type threshold =
+        ((std::numeric_limits<unsigned_type>::max)() - Lim + 1) % Lim;
+    while (helper::lo(product) < threshold) {
+      bits = fast_bits(g);
+      product = helper::multiply(bits, Lim);
+    }
+  }
+
+  return helper::hi(product);
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_UNIFORM_INT_DISTRIBUTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/uniform_real_distribution.h b/weight/_dep/abseil-cpp/absl/random/uniform_real_distribution.h
new file mode 100644
index 0000000000000000000000000000000000000000..196833415e86c33f335dc778d1f020762d31311e
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/uniform_real_distribution.h
@@ -0,0 +1,202 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: uniform_real_distribution.h
+// -----------------------------------------------------------------------------
+//
+// This header defines a class for representing a uniform floating-point
+// distribution over a half-open interval [a,b). You use this distribution in
+// combination with an Abseil random bit generator to produce random values
+// according to the rules of the distribution.
+//
+// `absl::uniform_real_distribution` is a drop-in replacement for the C++11
+// `std::uniform_real_distribution` [rand.dist.uni.real] but is considerably
+// faster than the libstdc++ implementation.
+//
+// Note: the standard-library version may occasionally return `1.0` when
+// default-initialized. See https://bugs.llvm.org//show_bug.cgi?id=18767
+// `absl::uniform_real_distribution` does not exhibit this behavior.
+
+#ifndef ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_
+#define ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_
+
+#include <cassert>
+#include <cmath>
+#include <cstdint>
+#include <istream>
+#include <limits>
+#include <type_traits>
+
+#include "absl/meta/type_traits.h"
+#include "absl/random/internal/fast_uniform_bits.h"
+#include "absl/random/internal/generate_real.h"
+#include "absl/random/internal/iostream_state_saver.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::uniform_real_distribution<T>
+//
+// This distribution produces random floating-point values uniformly distributed
+// over the half-open interval [a, b).
+//
+// Example:
+//
+//   absl::BitGen gen;
+//
+//   // Use the distribution to produce a value between 0.0 (inclusive)
+//   // and 1.0 (exclusive).
+//   double value = absl::uniform_real_distribution<double>(0, 1)(gen);
+//
+template <typename RealType = double>
+class uniform_real_distribution {
+ public:
+  using result_type = RealType;
+
+  class param_type {
+   public:
+    using distribution_type = uniform_real_distribution;
+
+    explicit param_type(result_type lo = 0, result_type hi = 1)
+        : lo_(lo), hi_(hi), range_(hi - lo) {
+      // [rand.dist.uni.real] preconditions 2 & 3
+      assert(lo <= hi);
+
+      // NOTE: For integral types, we can promote the range to an unsigned type,
+      // which gives full width of the range. However for real (fp) types, this
+      // is not possible, so value generation cannot use the full range of the
+      // real type.
+      assert(range_ <= (std::numeric_limits<result_type>::max)());
+    }
+
+    result_type a() const { return lo_; }
+    result_type b() const { return hi_; }
+
+    friend bool operator==(const param_type& a, const param_type& b) {
+      return a.lo_ == b.lo_ && a.hi_ == b.hi_;
+    }
+
+    friend bool operator!=(const param_type& a, const param_type& b) {
+      return !(a == b);
+    }
+
+   private:
+    friend class uniform_real_distribution;
+    result_type lo_, hi_, range_;
+
+    static_assert(std::is_floating_point<RealType>::value,
+                  "Class-template absl::uniform_real_distribution<> must be "
+                  "parameterized using a floating-point type.");
+  };
+
+  uniform_real_distribution() : uniform_real_distribution(0) {}
+
+  explicit uniform_real_distribution(result_type lo, result_type hi = 1)
+      : param_(lo, hi) {}
+
+  explicit uniform_real_distribution(const param_type& param) : param_(param) {}
+
+  // uniform_real_distribution<T>::reset()
+  //
+  // Resets the uniform real distribution. Note that this function has no effect
+  // because the distribution already produces independent values.
+  void reset() {}
+
+  template <typename URBG>
+  result_type operator()(URBG& gen) {  // NOLINT(runtime/references)
+    return operator()(gen, param_);
+  }
+
+  template <typename URBG>
+  result_type operator()(URBG& gen,  // NOLINT(runtime/references)
+                         const param_type& p);
+
+  result_type a() const { return param_.a(); }
+  result_type b() const { return param_.b(); }
+
+  param_type param() const { return param_; }
+  void param(const param_type& params) { param_ = params; }
+
+  result_type(min)() const { return a(); }
+  result_type(max)() const { return b(); }
+
+  friend bool operator==(const uniform_real_distribution& a,
+                         const uniform_real_distribution& b) {
+    return a.param_ == b.param_;
+  }
+  friend bool operator!=(const uniform_real_distribution& a,
+                         const uniform_real_distribution& b) {
+    return a.param_ != b.param_;
+  }
+
+ private:
+  param_type param_;
+  random_internal::FastUniformBits<uint64_t> fast_u64_;
+};
+
+// -----------------------------------------------------------------------------
+// Implementation details follow
+// -----------------------------------------------------------------------------
+template <typename RealType>
+template <typename URBG>
+typename uniform_real_distribution<RealType>::result_type
+uniform_real_distribution<RealType>::operator()(
+    URBG& gen, const param_type& p) {  // NOLINT(runtime/references)
+  using random_internal::GeneratePositiveTag;
+  using random_internal::GenerateRealFromBits;
+  using real_type =
+      absl::conditional_t<std::is_same<RealType, float>::value, float, double>;
+
+  while (true) {
+    const result_type sample =
+        GenerateRealFromBits<real_type, GeneratePositiveTag, true>(
+            fast_u64_(gen));
+    const result_type res = p.a() + (sample * p.range_);
+    if (res < p.b() || p.range_ <= 0 || !std::isfinite(p.range_)) {
+      return res;
+    }
+    // else sample rejected, try again.
+  }
+}
+
+template <typename CharT, typename Traits, typename RealType>
+std::basic_ostream<CharT, Traits>& operator<<(
+    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+    const uniform_real_distribution<RealType>& x) {
+  auto saver = random_internal::make_ostream_state_saver(os);
+  os.precision(random_internal::stream_precision_helper<RealType>::kPrecision);
+  os << x.a() << os.fill() << x.b();
+  return os;
+}
+
+template <typename CharT, typename Traits, typename RealType>
+std::basic_istream<CharT, Traits>& operator>>(
+    std::basic_istream<CharT, Traits>& is,     // NOLINT(runtime/references)
+    uniform_real_distribution<RealType>& x) {  // NOLINT(runtime/references)
+  using param_type = typename uniform_real_distribution<RealType>::param_type;
+  using result_type = typename uniform_real_distribution<RealType>::result_type;
+  auto saver = random_internal::make_istream_state_saver(is);
+  auto a = random_internal::read_floating_point<result_type>(is);
+  if (is.fail()) return is;
+  auto b = random_internal::read_floating_point<result_type>(is);
+  if (!is.fail()) {
+    x.param(param_type(a, b));
+  }
+  return is;
+}
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_UNIFORM_REAL_DISTRIBUTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/uniform_real_distribution_test.cc b/weight/_dep/abseil-cpp/absl/random/uniform_real_distribution_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..260aac96f7e3e219cc60e2dd4b1ae6fd53cce442
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/uniform_real_distribution_test.cc
@@ -0,0 +1,394 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/uniform_real_distribution.h"
+
+#include <cfloat>
+#include <cmath>
+#include <cstdint>
+#include <iterator>
+#include <random>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/log/log.h"
+#include "absl/numeric/internal/representation.h"
+#include "absl/random/internal/chi_square.h"
+#include "absl/random/internal/distribution_test_util.h"
+#include "absl/random/internal/pcg_engine.h"
+#include "absl/random/internal/sequence_urbg.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+
+// NOTES:
+// * Some documentation on generating random real values suggests that
+//   it is possible to use std::nextafter(b, DBL_MAX) to generate a value on
+//   the closed range [a, b]. Unfortunately, that technique is not universally
+//   reliable due to floating point quantization.
+//
+// * absl::uniform_real_distribution<float> generates between 2^28 and 2^29
+//   distinct floating point values in the range [0, 1).
+//
+// * absl::uniform_real_distribution<float> generates at least 2^23 distinct
+//   floating point values in the range [1, 2). This should be the same as
+//   any other range covered by a single exponent in IEEE 754.
+//
+// * absl::uniform_real_distribution<double> generates more than 2^52 distinct
+//   values in the range [0, 1), and should generate at least 2^52 distinct
+//   values in the range of [1, 2).
+//
+
+namespace {
+
+template <typename RealType>
+class UniformRealDistributionTest : public ::testing::Test {};
+
+// double-double arithmetic is not supported well by either GCC or Clang; see
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99048,
+// https://bugs.llvm.org/show_bug.cgi?id=49131, and
+// https://bugs.llvm.org/show_bug.cgi?id=49132. Don't bother running these tests
+// with double doubles until compiler support is better.
+using RealTypes =
+    std::conditional<absl::numeric_internal::IsDoubleDouble(),
+                     ::testing::Types<float, double>,
+                     ::testing::Types<float, double, long double>>::type;
+
+TYPED_TEST_SUITE(UniformRealDistributionTest, RealTypes);
+
+TYPED_TEST(UniformRealDistributionTest, ParamSerializeTest) {
+#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0
+  // We're using an x87-compatible FPU, and intermediate operations are
+  // performed with 80-bit floats. This produces slightly different results from
+  // what we expect below.
+  GTEST_SKIP()
+      << "Skipping the test because we detected x87 floating-point semantics";
+#endif
+  using DistributionType = absl::uniform_real_distribution<TypeParam>;
+  using real_type = TypeParam;
+  using param_type = typename DistributionType::param_type;
+
+  constexpr const real_type kMax = std::numeric_limits<real_type>::max();
+  constexpr const real_type kMin = std::numeric_limits<real_type>::min();
+  constexpr const real_type kEpsilon =
+      std::numeric_limits<real_type>::epsilon();
+  constexpr const real_type kLowest =
+      std::numeric_limits<real_type>::lowest();  // -max
+
+  const real_type kDenormMax = std::nextafter(kMin, real_type{0});
+  const real_type kOneMinusE =
+      std::nextafter(real_type{1}, real_type{0});  // 1 - epsilon
+
+  constexpr const real_type kTwo60{1152921504606846976};  // 2^60
+
+  constexpr int kCount = 1000;
+  absl::InsecureBitGen gen;
+  for (const auto& param : {
+           param_type(),
+           param_type(real_type{0}, real_type{1}),
+           param_type(real_type(-0.1), real_type(0.1)),
+           param_type(real_type(0.05), real_type(0.12)),
+           param_type(real_type(-0.05), real_type(0.13)),
+           param_type(real_type(-0.05), real_type(-0.02)),
+           // range = 0
+           param_type(real_type(2.0), real_type(2.0)),  // Same
+           // double range = 0
+           // 2^60 , 2^60 + 2^6
+           param_type(kTwo60, real_type(1152921504606847040)),
+           // 2^60 , 2^60 + 2^7
+           param_type(kTwo60, real_type(1152921504606847104)),
+           // double range = 2^8
+           // 2^60 , 2^60 + 2^8
+           param_type(kTwo60, real_type(1152921504606847232)),
+           // float range = 0
+           // 2^60 , 2^60 + 2^36
+           param_type(kTwo60, real_type(1152921573326323712)),
+           // 2^60 , 2^60 + 2^37
+           param_type(kTwo60, real_type(1152921642045800448)),
+           // float range = 2^38
+           // 2^60 , 2^60 + 2^38
+           param_type(kTwo60, real_type(1152921779484753920)),
+           // Limits
+           param_type(0, kMax),
+           param_type(kLowest, 0),
+           param_type(0, kMin),
+           param_type(0, kEpsilon),
+           param_type(-kEpsilon, kEpsilon),
+           param_type(0, kOneMinusE),
+           param_type(0, kDenormMax),
+       }) {
+    // Validate parameters.
+    const auto a = param.a();
+    const auto b = param.b();
+    DistributionType before(a, b);
+    EXPECT_EQ(before.a(), param.a());
+    EXPECT_EQ(before.b(), param.b());
+
+    {
+      DistributionType via_param(param);
+      EXPECT_EQ(via_param, before);
+    }
+
+    std::stringstream ss;
+    ss << before;
+    DistributionType after(real_type(1.0), real_type(3.1));
+
+    EXPECT_NE(before.a(), after.a());
+    EXPECT_NE(before.b(), after.b());
+    EXPECT_NE(before.param(), after.param());
+    EXPECT_NE(before, after);
+
+    ss >> after;
+
+    EXPECT_EQ(before.a(), after.a());
+    EXPECT_EQ(before.b(), after.b());
+    EXPECT_EQ(before.param(), after.param());
+    EXPECT_EQ(before, after);
+
+    // Smoke test.
+    auto sample_min = after.max();
+    auto sample_max = after.min();
+    for (int i = 0; i < kCount; i++) {
+      auto sample = after(gen);
+      // Failure here indicates a bug in uniform_real_distribution::operator(),
+      // or bad parameters--range too large, etc.
+      if (after.min() == after.max()) {
+        EXPECT_EQ(sample, after.min());
+      } else {
+        EXPECT_GE(sample, after.min());
+        EXPECT_LT(sample, after.max());
+      }
+      if (sample > sample_max) {
+        sample_max = sample;
+      }
+      if (sample < sample_min) {
+        sample_min = sample;
+      }
+    }
+
+    if (!std::is_same<real_type, long double>::value) {
+      // static_cast<double>(long double) can overflow.
+      LOG(INFO) << "Range: " << static_cast<double>(sample_min) << ", "
+                << static_cast<double>(sample_max);
+    }
+  }
+}
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable:4756)  // Constant arithmetic overflow.
+#endif
+TYPED_TEST(UniformRealDistributionTest, ViolatesPreconditionsDeathTest) {
+  using DistributionType = absl::uniform_real_distribution<TypeParam>;
+  using real_type = TypeParam;
+
+#if GTEST_HAS_DEATH_TEST
+  // Hi < Lo
+  EXPECT_DEBUG_DEATH({ DistributionType dist(10.0, 1.0); }, "");
+
+  // Hi - Lo > numeric_limits<>::max()
+  EXPECT_DEBUG_DEATH(
+      {
+        DistributionType dist(std::numeric_limits<real_type>::lowest(),
+                              std::numeric_limits<real_type>::max());
+      },
+      "");
+
+  // kEpsilon guarantees that max + kEpsilon = inf.
+  const auto kEpsilon = std::nexttoward(
+      (std::numeric_limits<real_type>::max() -
+       std::nexttoward(std::numeric_limits<real_type>::max(), 0.0)) /
+          2,
+      std::numeric_limits<real_type>::max());
+  EXPECT_DEBUG_DEATH(
+      {
+        DistributionType dist(-kEpsilon, std::numeric_limits<real_type>::max());
+      },
+      "");
+  EXPECT_DEBUG_DEATH(
+      {
+        DistributionType dist(std::numeric_limits<real_type>::lowest(),
+                              kEpsilon);
+      },
+      "");
+
+#endif  // GTEST_HAS_DEATH_TEST
+#if defined(NDEBUG)
+  // opt-mode, for invalid parameters, will generate a garbage value,
+  // but should not enter an infinite loop.
+  absl::InsecureBitGen gen;
+  {
+    DistributionType dist(10.0, 1.0);
+    auto x = dist(gen);
+    EXPECT_FALSE(std::isnan(x)) << x;
+  }
+  {
+    DistributionType dist(std::numeric_limits<real_type>::lowest(),
+                          std::numeric_limits<real_type>::max());
+    auto x = dist(gen);
+    // Infinite result.
+    EXPECT_FALSE(std::isfinite(x)) << x;
+  }
+#endif  // NDEBUG
+}
+#ifdef _MSC_VER
+#pragma warning(pop)  // warning(disable:4756)
+#endif
+
+TYPED_TEST(UniformRealDistributionTest, TestMoments) {
+  using DistributionType = absl::uniform_real_distribution<TypeParam>;
+
+  constexpr int kSize = 1000000;
+  std::vector<double> values(kSize);
+
+  // We use a fixed bit generator for distribution accuracy tests.  This allows
+  // these tests to be deterministic, while still testing the qualify of the
+  // implementation.
+  absl::random_internal::pcg64_2018_engine rng{0x2B7E151628AED2A6};
+
+  DistributionType dist;
+  for (int i = 0; i < kSize; i++) {
+    values[i] = dist(rng);
+  }
+
+  const auto moments =
+      absl::random_internal::ComputeDistributionMoments(values);
+  EXPECT_NEAR(0.5, moments.mean, 0.01);
+  EXPECT_NEAR(1 / 12.0, moments.variance, 0.015);
+  EXPECT_NEAR(0.0, moments.skewness, 0.02);
+  EXPECT_NEAR(9 / 5.0, moments.kurtosis, 0.015);
+}
+
+TYPED_TEST(UniformRealDistributionTest, ChiSquaredTest50) {
+  using DistributionType = absl::uniform_real_distribution<TypeParam>;
+  using param_type = typename DistributionType::param_type;
+
+  using absl::random_internal::kChiSquared;
+
+  constexpr size_t kTrials = 100000;
+  constexpr int kBuckets = 50;
+  constexpr double kExpected =
+      static_cast<double>(kTrials) / static_cast<double>(kBuckets);
+
+  // 1-in-100000 threshold, but remember, there are about 8 tests
+  // in this file. And the test could fail for other reasons.
+  // Empirically validated with --runs_per_test=10000.
+  const int kThreshold =
+      absl::random_internal::ChiSquareValue(kBuckets - 1, 0.999999);
+
+  // We use a fixed bit generator for distribution accuracy tests.  This allows
+  // these tests to be deterministic, while still testing the qualify of the
+  // implementation.
+  absl::random_internal::pcg64_2018_engine rng{0x2B7E151628AED2A6};
+
+  for (const auto& param : {param_type(0, 1), param_type(5, 12),
+                            param_type(-5, 13), param_type(-5, -2)}) {
+    const double min_val = param.a();
+    const double max_val = param.b();
+    const double factor = kBuckets / (max_val - min_val);
+
+    std::vector<int32_t> counts(kBuckets, 0);
+    DistributionType dist(param);
+    for (size_t i = 0; i < kTrials; i++) {
+      auto x = dist(rng);
+      auto bucket = static_cast<size_t>((x - min_val) * factor);
+      counts[bucket]++;
+    }
+
+    double chi_square = absl::random_internal::ChiSquareWithExpected(
+        std::begin(counts), std::end(counts), kExpected);
+    if (chi_square > kThreshold) {
+      double p_value =
+          absl::random_internal::ChiSquarePValue(chi_square, kBuckets);
+
+      // Chi-squared test failed. Output does not appear to be uniform.
+      std::string msg;
+      for (const auto& a : counts) {
+        absl::StrAppend(&msg, a, "\n");
+      }
+      absl::StrAppend(&msg, kChiSquared, " p-value ", p_value, "\n");
+      absl::StrAppend(&msg, "High ", kChiSquared, " value: ", chi_square, " > ",
+                      kThreshold);
+      LOG(INFO) << msg;
+      FAIL() << msg;
+    }
+  }
+}
+
+TYPED_TEST(UniformRealDistributionTest, StabilityTest) {
+  using DistributionType = absl::uniform_real_distribution<TypeParam>;
+  using real_type = TypeParam;
+
+  // absl::uniform_real_distribution stability relies only on
+  // random_internal::GenerateRealFromBits.
+  absl::random_internal::sequence_urbg urbg(
+      {0x0003eb76f6f7f755ull, 0xFFCEA50FDB2F953Bull, 0xC332DDEFBE6C5AA5ull,
+       0x6558218568AB9702ull, 0x2AEF7DAD5B6E2F84ull, 0x1521B62829076170ull,
+       0xECDD4775619F1510ull, 0x13CCA830EB61BD96ull, 0x0334FE1EAA0363CFull,
+       0xB5735C904C70A239ull, 0xD59E9E0BCBAADE14ull, 0xEECC86BC60622CA7ull});
+
+  std::vector<int> output(12);
+
+  DistributionType dist;
+  std::generate(std::begin(output), std::end(output), [&] {
+    return static_cast<int>(real_type(1000000) * dist(urbg));
+  });
+
+  EXPECT_THAT(
+      output,  //
+      testing::ElementsAre(59, 999246, 762494, 395876, 167716, 82545, 925251,
+                           77341, 12527, 708791, 834451, 932808));
+}
+
+TEST(UniformRealDistributionTest, AlgorithmBounds) {
+  absl::uniform_real_distribution<double> dist;
+
+  {
+    // This returns the smallest value >0 from absl::uniform_real_distribution.
+    absl::random_internal::sequence_urbg urbg({0x0000000000000001ull});
+    double a = dist(urbg);
+    EXPECT_EQ(a, 5.42101086242752217004e-20);
+  }
+
+  {
+    // This returns a value very near 0.5 from absl::uniform_real_distribution.
+    absl::random_internal::sequence_urbg urbg({0x7fffffffffffffefull});
+    double a = dist(urbg);
+    EXPECT_EQ(a, 0.499999999999999944489);
+  }
+  {
+    // This returns a value very near 0.5 from absl::uniform_real_distribution.
+    absl::random_internal::sequence_urbg urbg({0x8000000000000000ull});
+    double a = dist(urbg);
+    EXPECT_EQ(a, 0.5);
+  }
+
+  {
+    // This returns the largest value <1 from absl::uniform_real_distribution.
+    absl::random_internal::sequence_urbg urbg({0xFFFFFFFFFFFFFFEFull});
+    double a = dist(urbg);
+    EXPECT_EQ(a, 0.999999999999999888978);
+  }
+  {
+    // This *ALSO* returns the largest value <1.
+    absl::random_internal::sequence_urbg urbg({0xFFFFFFFFFFFFFFFFull});
+    double a = dist(urbg);
+    EXPECT_EQ(a, 0.999999999999999888978);
+  }
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/random/zipf_distribution.h b/weight/_dep/abseil-cpp/absl/random/zipf_distribution.h
new file mode 100644
index 0000000000000000000000000000000000000000..03497b1b26a2934e4c2bd6c90dc063a87f6ecb99
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/zipf_distribution.h
@@ -0,0 +1,272 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_RANDOM_ZIPF_DISTRIBUTION_H_
+#define ABSL_RANDOM_ZIPF_DISTRIBUTION_H_
+
+#include <cassert>
+#include <cmath>
+#include <istream>
+#include <limits>
+#include <ostream>
+#include <type_traits>
+
+#include "absl/random/internal/iostream_state_saver.h"
+#include "absl/random/internal/traits.h"
+#include "absl/random/uniform_real_distribution.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::zipf_distribution produces random integer-values in the range [0, k],
+// distributed according to the unnormalized discrete probability function:
+//
+//  P(x) = (v + x) ^ -q
+//
+// The parameter `v` must be greater than 0 and the parameter `q` must be
+// greater than 1. If either of these parameters take invalid values then the
+// behavior is undefined.
+//
+// IntType is the result_type generated by the generator. It must be of integral
+// type; a static_assert ensures this is the case.
+//
+// The implementation is based on W.Hormann, G.Derflinger:
+//
+// "Rejection-Inversion to Generate Variates from Monotone Discrete
+// Distributions"
+//
+// http://eeyore.wu-wien.ac.at/papers/96-04-04.wh-der.ps.gz
+//
+template <typename IntType = int>
+class zipf_distribution {
+ public:
+  using result_type = IntType;
+
+  class param_type {
+   public:
+    using distribution_type = zipf_distribution;
+
+    // Preconditions: k > 0, v > 0, q > 1
+    // The precondidtions are validated when NDEBUG is not defined via
+    // a pair of assert() directives.
+    // If NDEBUG is defined and either or both of these parameters take invalid
+    // values, the behavior of the class is undefined.
+    explicit param_type(result_type k = (std::numeric_limits<IntType>::max)(),
+                        double q = 2.0, double v = 1.0);
+
+    result_type k() const { return k_; }
+    double q() const { return q_; }
+    double v() const { return v_; }
+
+    friend bool operator==(const param_type& a, const param_type& b) {
+      return a.k_ == b.k_ && a.q_ == b.q_ && a.v_ == b.v_;
+    }
+    friend bool operator!=(const param_type& a, const param_type& b) {
+      return !(a == b);
+    }
+
+   private:
+    friend class zipf_distribution;
+    inline double h(double x) const;
+    inline double hinv(double x) const;
+    inline double compute_s() const;
+    inline double pow_negative_q(double x) const;
+
+    // Parameters here are exactly the same as the parameters of Algorithm ZRI
+    // in the paper.
+    IntType k_;
+    double q_;
+    double v_;
+
+    double one_minus_q_;  // 1-q
+    double s_;
+    double one_minus_q_inv_;  // 1 / 1-q
+    double hxm_;              // h(k + 0.5)
+    double hx0_minus_hxm_;    // h(x0) - h(k + 0.5)
+
+    static_assert(random_internal::IsIntegral<IntType>::value,
+                  "Class-template absl::zipf_distribution<> must be "
+                  "parameterized using an integral type.");
+  };
+
+  zipf_distribution()
+      : zipf_distribution((std::numeric_limits<IntType>::max)()) {}
+
+  explicit zipf_distribution(result_type k, double q = 2.0, double v = 1.0)
+      : param_(k, q, v) {}
+
+  explicit zipf_distribution(const param_type& p) : param_(p) {}
+
+  void reset() {}
+
+  template <typename URBG>
+  result_type operator()(URBG& g) {  // NOLINT(runtime/references)
+    return (*this)(g, param_);
+  }
+
+  template <typename URBG>
+  result_type operator()(URBG& g,  // NOLINT(runtime/references)
+                         const param_type& p);
+
+  result_type k() const { return param_.k(); }
+  double q() const { return param_.q(); }
+  double v() const { return param_.v(); }
+
+  param_type param() const { return param_; }
+  void param(const param_type& p) { param_ = p; }
+
+  result_type(min)() const { return 0; }
+  result_type(max)() const { return k(); }
+
+  friend bool operator==(const zipf_distribution& a,
+                         const zipf_distribution& b) {
+    return a.param_ == b.param_;
+  }
+  friend bool operator!=(const zipf_distribution& a,
+                         const zipf_distribution& b) {
+    return a.param_ != b.param_;
+  }
+
+ private:
+  param_type param_;
+};
+
+// --------------------------------------------------------------------------
+// Implementation details follow
+// --------------------------------------------------------------------------
+
+template <typename IntType>
+zipf_distribution<IntType>::param_type::param_type(
+    typename zipf_distribution<IntType>::result_type k, double q, double v)
+    : k_(k), q_(q), v_(v), one_minus_q_(1 - q) {
+  assert(q > 1);
+  assert(v > 0);
+  assert(k > 0);
+  one_minus_q_inv_ = 1 / one_minus_q_;
+
+  // Setup for the ZRI algorithm (pg 17 of the paper).
+  // Compute: h(i max) => h(k + 0.5)
+  constexpr double kMax = 18446744073709549568.0;
+  double kd = static_cast<double>(k);
+  // TODO(absl-team): Determine if this check is needed, and if so, add a test
+  // that fails for k > kMax
+  if (kd > kMax) {
+    // Ensure that our maximum value is capped to a value which will
+    // round-trip back through double.
+    kd = kMax;
+  }
+  hxm_ = h(kd + 0.5);
+
+  // Compute: h(0)
+  const bool use_precomputed = (v == 1.0 && q == 2.0);
+  const double h0x5 = use_precomputed ? (-1.0 / 1.5)  // exp(-log(1.5))
+                                      : h(0.5);
+  const double elogv_q = (v_ == 1.0) ? 1 : pow_negative_q(v_);
+
+  // h(0) = h(0.5) - exp(log(v) * -q)
+  hx0_minus_hxm_ = (h0x5 - elogv_q) - hxm_;
+
+  // And s
+  s_ = use_precomputed ? 0.46153846153846123 : compute_s();
+}
+
+template <typename IntType>
+double zipf_distribution<IntType>::param_type::h(double x) const {
+  // std::exp(one_minus_q_ * std::log(v_ + x)) * one_minus_q_inv_;
+  x += v_;
+  return (one_minus_q_ == -1.0)
+             ? (-1.0 / x)  // -exp(-log(x))
+             : (std::exp(std::log(x) * one_minus_q_) * one_minus_q_inv_);
+}
+
+template <typename IntType>
+double zipf_distribution<IntType>::param_type::hinv(double x) const {
+  // std::exp(one_minus_q_inv_ * std::log(one_minus_q_ * x)) - v_;
+  return -v_ + ((one_minus_q_ == -1.0)
+                    ? (-1.0 / x)  // exp(-log(-x))
+                    : std::exp(one_minus_q_inv_ * std::log(one_minus_q_ * x)));
+}
+
+template <typename IntType>
+double zipf_distribution<IntType>::param_type::compute_s() const {
+  // 1 - hinv(h(1.5) - std::exp(std::log(v_ + 1) * -q_));
+  return 1.0 - hinv(h(1.5) - pow_negative_q(v_ + 1.0));
+}
+
+template <typename IntType>
+double zipf_distribution<IntType>::param_type::pow_negative_q(double x) const {
+  // std::exp(std::log(x) * -q_);
+  return q_ == 2.0 ? (1.0 / (x * x)) : std::exp(std::log(x) * -q_);
+}
+
+template <typename IntType>
+template <typename URBG>
+typename zipf_distribution<IntType>::result_type
+zipf_distribution<IntType>::operator()(
+    URBG& g, const param_type& p) {  // NOLINT(runtime/references)
+  absl::uniform_real_distribution<double> uniform_double;
+  double k;
+  for (;;) {
+    const double v = uniform_double(g);
+    const double u = p.hxm_ + v * p.hx0_minus_hxm_;
+    const double x = p.hinv(u);
+    k = rint(x);              // std::floor(x + 0.5);
+    if (k > static_cast<double>(p.k())) continue;  // reject k > max_k
+    if (k - x <= p.s_) break;
+    const double h = p.h(k + 0.5);
+    const double r = p.pow_negative_q(p.v_ + k);
+    if (u >= h - r) break;
+  }
+  IntType ki = static_cast<IntType>(k);
+  assert(ki <= p.k_);
+  return ki;
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_ostream<CharT, Traits>& operator<<(
+    std::basic_ostream<CharT, Traits>& os,  // NOLINT(runtime/references)
+    const zipf_distribution<IntType>& x) {
+  using stream_type =
+      typename random_internal::stream_format_type<IntType>::type;
+  auto saver = random_internal::make_ostream_state_saver(os);
+  os.precision(random_internal::stream_precision_helper<double>::kPrecision);
+  os << static_cast<stream_type>(x.k()) << os.fill() << x.q() << os.fill()
+     << x.v();
+  return os;
+}
+
+template <typename CharT, typename Traits, typename IntType>
+std::basic_istream<CharT, Traits>& operator>>(
+    std::basic_istream<CharT, Traits>& is,  // NOLINT(runtime/references)
+    zipf_distribution<IntType>& x) {        // NOLINT(runtime/references)
+  using result_type = typename zipf_distribution<IntType>::result_type;
+  using param_type = typename zipf_distribution<IntType>::param_type;
+  using stream_type =
+      typename random_internal::stream_format_type<IntType>::type;
+  stream_type k;
+  double q;
+  double v;
+
+  auto saver = random_internal::make_istream_state_saver(is);
+  is >> k >> q >> v;
+  if (!is.fail()) {
+    x.param(param_type(static_cast<result_type>(k), q, v));
+  }
+  return is;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_ZIPF_DISTRIBUTION_H_
diff --git a/weight/_dep/abseil-cpp/absl/random/zipf_distribution_test.cc b/weight/_dep/abseil-cpp/absl/random/zipf_distribution_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..801ec4f62267415cdeb73bf603eac3152ec5fe54
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/random/zipf_distribution_test.cc
@@ -0,0 +1,423 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/random/zipf_distribution.h"
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+#include <random>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/log/log.h"
+#include "absl/random/internal/chi_square.h"
+#include "absl/random/internal/pcg_engine.h"
+#include "absl/random/internal/sequence_urbg.h"
+#include "absl/random/random.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_replace.h"
+#include "absl/strings/strip.h"
+
+namespace {
+
+using ::absl::random_internal::kChiSquared;
+using ::testing::ElementsAre;
+
+template <typename IntType>
+class ZipfDistributionTypedTest : public ::testing::Test {};
+
+using IntTypes = ::testing::Types<int, int8_t, int16_t, int32_t, int64_t,
+                                  uint8_t, uint16_t, uint32_t, uint64_t>;
+TYPED_TEST_SUITE(ZipfDistributionTypedTest, IntTypes);
+
+TYPED_TEST(ZipfDistributionTypedTest, SerializeTest) {
+  using param_type = typename absl::zipf_distribution<TypeParam>::param_type;
+
+  constexpr int kCount = 1000;
+  absl::InsecureBitGen gen;
+  for (const auto& param : {
+           param_type(),
+           param_type(32),
+           param_type(100, 3, 2),
+           param_type(std::numeric_limits<TypeParam>::max(), 4, 3),
+           param_type(std::numeric_limits<TypeParam>::max() / 2),
+       }) {
+    // Validate parameters.
+    const auto k = param.k();
+    const auto q = param.q();
+    const auto v = param.v();
+
+    absl::zipf_distribution<TypeParam> before(k, q, v);
+    EXPECT_EQ(before.k(), param.k());
+    EXPECT_EQ(before.q(), param.q());
+    EXPECT_EQ(before.v(), param.v());
+
+    {
+      absl::zipf_distribution<TypeParam> via_param(param);
+      EXPECT_EQ(via_param, before);
+    }
+
+    // Validate stream serialization.
+    std::stringstream ss;
+    ss << before;
+    absl::zipf_distribution<TypeParam> after(4, 5.5, 4.4);
+
+    EXPECT_NE(before.k(), after.k());
+    EXPECT_NE(before.q(), after.q());
+    EXPECT_NE(before.v(), after.v());
+    EXPECT_NE(before.param(), after.param());
+    EXPECT_NE(before, after);
+
+    ss >> after;
+
+    EXPECT_EQ(before.k(), after.k());
+    EXPECT_EQ(before.q(), after.q());
+    EXPECT_EQ(before.v(), after.v());
+    EXPECT_EQ(before.param(), after.param());
+    EXPECT_EQ(before, after);
+
+    // Smoke test.
+    auto sample_min = after.max();
+    auto sample_max = after.min();
+    for (int i = 0; i < kCount; i++) {
+      auto sample = after(gen);
+      EXPECT_GE(sample, after.min());
+      EXPECT_LE(sample, after.max());
+      if (sample > sample_max) sample_max = sample;
+      if (sample < sample_min) sample_min = sample;
+    }
+    LOG(INFO) << "Range: " << sample_min << ", " << sample_max;
+  }
+}
+
+class ZipfModel {
+ public:
+  ZipfModel(size_t k, double q, double v) : k_(k), q_(q), v_(v) {}
+
+  double mean() const { return mean_; }
+
+  // For the other moments of the Zipf distribution, see, for example,
+  // http://mathworld.wolfram.com/ZipfDistribution.html
+
+  // PMF(k) = (1 / k^s) / H(N,s)
+  // Returns the probability that any single invocation returns k.
+  double PMF(size_t i) { return i >= hnq_.size() ? 0.0 : hnq_[i] / sum_hnq_; }
+
+  // CDF = H(k, s) / H(N,s)
+  double CDF(size_t i) {
+    if (i >= hnq_.size()) {
+      return 1.0;
+    }
+    auto it = std::begin(hnq_);
+    double h = 0.0;
+    for (const auto end = it; it != end; it++) {
+      h += *it;
+    }
+    return h / sum_hnq_;
+  }
+
+  // The InverseCDF returns the k values which bound p on the upper and lower
+  // bound. Since there is no closed-form solution, this is implemented as a
+  // bisction of the cdf.
+  std::pair<size_t, size_t> InverseCDF(double p) {
+    size_t min = 0;
+    size_t max = hnq_.size();
+    while (max > min + 1) {
+      size_t target = (max + min) >> 1;
+      double x = CDF(target);
+      if (x > p) {
+        max = target;
+      } else {
+        min = target;
+      }
+    }
+    return {min, max};
+  }
+
+  // Compute the probability totals, which are based on the generalized harmonic
+  // number, H(N,s).
+  //   H(N,s) == SUM(k=1..N, 1 / k^s)
+  //
+  // In the limit, H(N,s) == zetac(s) + 1.
+  //
+  // NOTE: The mean of a zipf distribution could be computed here as well.
+  // Mean :=  H(N, s-1) / H(N,s).
+  // Given the parameter v = 1, this gives the following function:
+  // (Hn(100, 1) - Hn(1,1)) / (Hn(100,2) - Hn(1,2)) = 6.5944
+  //
+  void Init() {
+    if (!hnq_.empty()) {
+      return;
+    }
+    hnq_.clear();
+    hnq_.reserve(std::min(k_, size_t{1000}));
+
+    sum_hnq_ = 0;
+    double qm1 = q_ - 1.0;
+    double sum_hnq_m1 = 0;
+    for (size_t i = 0; i < k_; i++) {
+      // Partial n-th generalized harmonic number
+      const double x = v_ + i;
+
+      // H(n, q-1)
+      const double hnqm1 =
+          (q_ == 2.0) ? (1.0 / x)
+                      : (q_ == 3.0) ? (1.0 / (x * x)) : std::pow(x, -qm1);
+      sum_hnq_m1 += hnqm1;
+
+      // H(n, q)
+      const double hnq =
+          (q_ == 2.0) ? (1.0 / (x * x))
+                      : (q_ == 3.0) ? (1.0 / (x * x * x)) : std::pow(x, -q_);
+      sum_hnq_ += hnq;
+      hnq_.push_back(hnq);
+      if (i > 1000 && hnq <= 1e-10) {
+        // The harmonic number is too small.
+        break;
+      }
+    }
+    assert(sum_hnq_ > 0);
+    mean_ = sum_hnq_m1 / sum_hnq_;
+  }
+
+ private:
+  const size_t k_;
+  const double q_;
+  const double v_;
+
+  double mean_;
+  std::vector<double> hnq_;
+  double sum_hnq_;
+};
+
+using zipf_u64 = absl::zipf_distribution<uint64_t>;
+
+class ZipfTest : public testing::TestWithParam<zipf_u64::param_type>,
+                 public ZipfModel {
+ public:
+  ZipfTest() : ZipfModel(GetParam().k(), GetParam().q(), GetParam().v()) {}
+
+  // We use a fixed bit generator for distribution accuracy tests.  This allows
+  // these tests to be deterministic, while still testing the qualify of the
+  // implementation.
+  absl::random_internal::pcg64_2018_engine rng_{0x2B7E151628AED2A6};
+};
+
+TEST_P(ZipfTest, ChiSquaredTest) {
+  const auto& param = GetParam();
+  Init();
+
+  size_t trials = 10000;
+
+  // Find the split-points for the buckets.
+  std::vector<size_t> points;
+  std::vector<double> expected;
+  {
+    double last_cdf = 0.0;
+    double min_p = 1.0;
+    for (double p = 0.01; p < 1.0; p += 0.01) {
+      auto x = InverseCDF(p);
+      if (points.empty() || points.back() < x.second) {
+        const double p = CDF(x.second);
+        points.push_back(x.second);
+        double q = p - last_cdf;
+        expected.push_back(q);
+        last_cdf = p;
+        if (q < min_p) {
+          min_p = q;
+        }
+      }
+    }
+    if (last_cdf < 0.999) {
+      points.push_back(std::numeric_limits<size_t>::max());
+      double q = 1.0 - last_cdf;
+      expected.push_back(q);
+      if (q < min_p) {
+        min_p = q;
+      }
+    } else {
+      points.back() = std::numeric_limits<size_t>::max();
+      expected.back() += (1.0 - last_cdf);
+    }
+    // The Chi-Squared score is not completely scale-invariant; it works best
+    // when the small values are in the small digits.
+    trials = static_cast<size_t>(8.0 / min_p);
+  }
+  ASSERT_GT(points.size(), 0);
+
+  // Generate n variates and fill the counts vector with the count of their
+  // occurrences.
+  std::vector<int64_t> buckets(points.size(), 0);
+  double avg = 0;
+  {
+    zipf_u64 dis(param);
+    for (size_t i = 0; i < trials; i++) {
+      uint64_t x = dis(rng_);
+      ASSERT_LE(x, dis.max());
+      ASSERT_GE(x, dis.min());
+      avg += static_cast<double>(x);
+      auto it = std::upper_bound(std::begin(points), std::end(points),
+                                 static_cast<size_t>(x));
+      buckets[std::distance(std::begin(points), it)]++;
+    }
+    avg = avg / static_cast<double>(trials);
+  }
+
+  // Validate the output using the Chi-Squared test.
+  for (auto& e : expected) {
+    e *= trials;
+  }
+
+  // The null-hypothesis is that the distribution is a poisson distribution with
+  // the provided mean (not estimated from the data).
+  const int dof = static_cast<int>(expected.size()) - 1;
+
+  // NOTE: This test runs about 15x per invocation, so a value of 0.9995 is
+  // approximately correct for a test suite failure rate of 1 in 100.  In
+  // practice we see failures slightly higher than that.
+  const double threshold = absl::random_internal::ChiSquareValue(dof, 0.9999);
+
+  const double chi_square = absl::random_internal::ChiSquare(
+      std::begin(buckets), std::end(buckets), std::begin(expected),
+      std::end(expected));
+
+  const double p_actual =
+      absl::random_internal::ChiSquarePValue(chi_square, dof);
+
+  // Log if the chi_squared value is above the threshold.
+  if (chi_square > threshold) {
+    LOG(INFO) << "values";
+    for (size_t i = 0; i < expected.size(); i++) {
+      LOG(INFO) << points[i] << ": " << buckets[i] << " vs. E=" << expected[i];
+    }
+    LOG(INFO) << "trials " << trials;
+    LOG(INFO) << "mean " << avg << " vs. expected " << mean();
+    LOG(INFO) << kChiSquared << "(data, " << dof << ") = " << chi_square << " ("
+              << p_actual << ")";
+    LOG(INFO) << kChiSquared << " @ 0.9995 = " << threshold;
+    FAIL() << kChiSquared << " value of " << chi_square
+           << " is above the threshold.";
+  }
+}
+
+std::vector<zipf_u64::param_type> GenParams() {
+  using param = zipf_u64::param_type;
+  const auto k = param().k();
+  const auto q = param().q();
+  const auto v = param().v();
+  const uint64_t k2 = 1 << 10;
+  return std::vector<zipf_u64::param_type>{
+      // Default
+      param(k, q, v),
+      // vary K
+      param(4, q, v), param(1 << 4, q, v), param(k2, q, v),
+      // vary V
+      param(k2, q, 0.5), param(k2, q, 1.5), param(k2, q, 2.5), param(k2, q, 10),
+      // vary Q
+      param(k2, 1.5, v), param(k2, 3, v), param(k2, 5, v), param(k2, 10, v),
+      // Vary V & Q
+      param(k2, 1.5, 0.5), param(k2, 3, 1.5), param(k, 10, 10)};
+}
+
+std::string ParamName(
+    const ::testing::TestParamInfo<zipf_u64::param_type>& info) {
+  const auto& p = info.param;
+  std::string name = absl::StrCat("k_", p.k(), "__q_", absl::SixDigits(p.q()),
+                                  "__v_", absl::SixDigits(p.v()));
+  return absl::StrReplaceAll(name, {{"+", "_"}, {"-", "_"}, {".", "_"}});
+}
+
+INSTANTIATE_TEST_SUITE_P(All, ZipfTest, ::testing::ValuesIn(GenParams()),
+                         ParamName);
+
+// NOTE: absl::zipf_distribution is not guaranteed to be stable.
+TEST(ZipfDistributionTest, StabilityTest) {
+  // absl::zipf_distribution stability relies on
+  // absl::uniform_real_distribution, std::log, std::exp, std::log1p
+  absl::random_internal::sequence_urbg urbg(
+      {0x0003eb76f6f7f755ull, 0xFFCEA50FDB2F953Bull, 0xC332DDEFBE6C5AA5ull,
+       0x6558218568AB9702ull, 0x2AEF7DAD5B6E2F84ull, 0x1521B62829076170ull,
+       0xECDD4775619F1510ull, 0x13CCA830EB61BD96ull, 0x0334FE1EAA0363CFull,
+       0xB5735C904C70A239ull, 0xD59E9E0BCBAADE14ull, 0xEECC86BC60622CA7ull});
+
+  std::vector<int> output(10);
+
+  {
+    absl::zipf_distribution<int32_t> dist;
+    std::generate(std::begin(output), std::end(output),
+                  [&] { return dist(urbg); });
+    EXPECT_THAT(output, ElementsAre(10031, 0, 0, 3, 6, 0, 7, 47, 0, 0));
+  }
+  urbg.reset();
+  {
+    absl::zipf_distribution<int32_t> dist(std::numeric_limits<int32_t>::max(),
+                                          3.3);
+    std::generate(std::begin(output), std::end(output),
+                  [&] { return dist(urbg); });
+    EXPECT_THAT(output, ElementsAre(44, 0, 0, 0, 0, 1, 0, 1, 3, 0));
+  }
+}
+
+TEST(ZipfDistributionTest, AlgorithmBounds) {
+  absl::zipf_distribution<int32_t> dist;
+
+  // Small values from absl::uniform_real_distribution map to larger Zipf
+  // distribution values.
+  const std::pair<uint64_t, int32_t> kInputs[] = {
+      {0xffffffffffffffff, 0x0}, {0x7fffffffffffffff, 0x0},
+      {0x3ffffffffffffffb, 0x1}, {0x1ffffffffffffffd, 0x4},
+      {0xffffffffffffffe, 0x9},  {0x7ffffffffffffff, 0x12},
+      {0x3ffffffffffffff, 0x25}, {0x1ffffffffffffff, 0x4c},
+      {0xffffffffffffff, 0x99},  {0x7fffffffffffff, 0x132},
+      {0x3fffffffffffff, 0x265}, {0x1fffffffffffff, 0x4cc},
+      {0xfffffffffffff, 0x999},  {0x7ffffffffffff, 0x1332},
+      {0x3ffffffffffff, 0x2665}, {0x1ffffffffffff, 0x4ccc},
+      {0xffffffffffff, 0x9998},  {0x7fffffffffff, 0x1332f},
+      {0x3fffffffffff, 0x2665a}, {0x1fffffffffff, 0x4cc9e},
+      {0xfffffffffff, 0x998e0},  {0x7ffffffffff, 0x133051},
+      {0x3ffffffffff, 0x265ae4}, {0x1ffffffffff, 0x4c9ed3},
+      {0xffffffffff, 0x98e223},  {0x7fffffffff, 0x13058c4},
+      {0x3fffffffff, 0x25b178e}, {0x1fffffffff, 0x4a062b2},
+      {0xfffffffff, 0x8ee23b8},  {0x7ffffffff, 0x10b21642},
+      {0x3ffffffff, 0x1d89d89d}, {0x1ffffffff, 0x2fffffff},
+      {0xffffffff, 0x45d1745d},  {0x7fffffff, 0x5a5a5a5a},
+      {0x3fffffff, 0x69ee5846},  {0x1fffffff, 0x73ecade3},
+      {0xfffffff, 0x79a9d260},   {0x7ffffff, 0x7cc0532b},
+      {0x3ffffff, 0x7e5ad146},   {0x1ffffff, 0x7f2c0bec},
+      {0xffffff, 0x7f95adef},    {0x7fffff, 0x7fcac0da},
+      {0x3fffff, 0x7fe55ae2},    {0x1fffff, 0x7ff2ac0e},
+      {0xfffff, 0x7ff955ae},     {0x7ffff, 0x7ffcaac1},
+      {0x3ffff, 0x7ffe555b},     {0x1ffff, 0x7fff2aac},
+      {0xffff, 0x7fff9556},      {0x7fff, 0x7fffcaab},
+      {0x3fff, 0x7fffe555},      {0x1fff, 0x7ffff2ab},
+      {0xfff, 0x7ffff955},       {0x7ff, 0x7ffffcab},
+      {0x3ff, 0x7ffffe55},       {0x1ff, 0x7fffff2b},
+      {0xff, 0x7fffff95},        {0x7f, 0x7fffffcb},
+      {0x3f, 0x7fffffe5},        {0x1f, 0x7ffffff3},
+      {0xf, 0x7ffffff9},         {0x7, 0x7ffffffd},
+      {0x3, 0x7ffffffe},         {0x1, 0x7fffffff},
+  };
+
+  for (const auto& instance : kInputs) {
+    absl::random_internal::sequence_urbg urbg({instance.first});
+    EXPECT_EQ(instance.second, dist(urbg));
+  }
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/status/BUILD.bazel b/weight/_dep/abseil-cpp/absl/status/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..981b37fda7edaf582ee2e63977b31871a5bb27dc
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/BUILD.bazel
@@ -0,0 +1,131 @@
+#
+# Copyright 2017 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This package contains `absl::Status`.
+# It will expand later to have utilities around `Status` like `StatusOr`,
+# `StatusBuilder` and macros.
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "status",
+    srcs = [
+        "internal/status_internal.cc",
+        "internal/status_internal.h",
+        "status.cc",
+        "status_payload_printer.cc",
+    ],
+    hdrs = [
+        "status.h",
+        "status_payload_printer.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base:atomic_hook",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:no_destructor",
+        "//absl/base:nullability",
+        "//absl/base:raw_logging_internal",
+        "//absl/base:strerror",
+        "//absl/container:inlined_vector",
+        "//absl/debugging:stacktrace",
+        "//absl/debugging:symbolize",
+        "//absl/functional:function_ref",
+        "//absl/memory",
+        "//absl/strings",
+        "//absl/strings:cord",
+        "//absl/strings:str_format",
+        "//absl/types:optional",
+        "//absl/types:span",
+    ],
+)
+
+cc_test(
+    name = "status_test",
+    srcs = ["status_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":status",
+        "//absl/strings",
+        "//absl/strings:cord",
+        "//absl/strings:str_format",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "statusor",
+    srcs = [
+        "internal/statusor_internal.h",
+        "statusor.cc",
+    ],
+    hdrs = [
+        "statusor.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":status",
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:nullability",
+        "//absl/base:raw_logging_internal",
+        "//absl/meta:type_traits",
+        "//absl/strings",
+        "//absl/strings:has_ostream_operator",
+        "//absl/strings:str_format",
+        "//absl/types:variant",
+        "//absl/utility",
+    ],
+)
+
+cc_test(
+    name = "statusor_test",
+    size = "small",
+    srcs = ["statusor_test.cc"],
+    deps = [
+        ":status",
+        ":statusor",
+        "//absl/base",
+        "//absl/memory",
+        "//absl/strings",
+        "//absl/types:any",
+        "//absl/types:variant",
+        "//absl/utility",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/status/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/status/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..00415ab94dad832aaa8c2ccf59251f085c07561c
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/CMakeLists.txt
@@ -0,0 +1,104 @@
+#
+# Copyright 2020 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+absl_cc_library(
+  NAME
+    status
+  HDRS
+    "status.h"
+  SRCS
+    "internal/status_internal.h"
+    "internal/status_internal.cc"
+    "status.cc"
+    "status_payload_printer.h"
+    "status_payload_printer.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEFINES
+    "$<$<PLATFORM_ID:AIX>:_LINUX_SOURCE_COMPAT>"
+  DEPS
+    absl::atomic_hook
+    absl::config
+    absl::cord
+    absl::core_headers
+    absl::function_ref
+    absl::inlined_vector
+    absl::memory
+    absl::no_destructor
+    absl::nullability
+    absl::optional
+    absl::raw_logging_internal
+    absl::span
+    absl::stacktrace
+    absl::strerror
+    absl::str_format
+    absl::strings
+    absl::symbolize
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    status_test
+  SRCS
+   "status_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::status
+    absl::str_format
+    absl::strings
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    statusor
+  HDRS
+    "statusor.h"
+  SRCS
+    "statusor.cc"
+    "internal/statusor_internal.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::config
+    absl::core_headers
+    absl::has_ostream_operator
+    absl::nullability
+    absl::raw_logging_internal
+    absl::status
+    absl::str_format
+    absl::strings
+    absl::type_traits
+    absl::utility
+    absl::variant
+  PUBLIC
+)
+
+absl_cc_test(
+  NAME
+    statusor_test
+  SRCS
+   "statusor_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::status
+    absl::statusor
+    absl::strings
+    GTest::gmock_main
+)
diff --git a/weight/_dep/abseil-cpp/absl/status/status.cc b/weight/_dep/abseil-cpp/absl/status/status.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4dd5ae06ced2dfc608df58d92f30bba69c9af106
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/status.cc
@@ -0,0 +1,425 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#include "absl/status/status.h"
+
+#include <errno.h>
+
+#include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <memory>
+#include <ostream>
+#include <string>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/strerror.h"
+#include "absl/base/macros.h"
+#include "absl/base/no_destructor.h"
+#include "absl/base/nullability.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+#include "absl/status/internal/status_internal.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/str_split.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+static_assert(
+    alignof(status_internal::StatusRep) >= 4,
+    "absl::Status assumes it can use the bottom 2 bits of a StatusRep*.");
+
+std::string StatusCodeToString(StatusCode code) {
+  switch (code) {
+    case StatusCode::kOk:
+      return "OK";
+    case StatusCode::kCancelled:
+      return "CANCELLED";
+    case StatusCode::kUnknown:
+      return "UNKNOWN";
+    case StatusCode::kInvalidArgument:
+      return "INVALID_ARGUMENT";
+    case StatusCode::kDeadlineExceeded:
+      return "DEADLINE_EXCEEDED";
+    case StatusCode::kNotFound:
+      return "NOT_FOUND";
+    case StatusCode::kAlreadyExists:
+      return "ALREADY_EXISTS";
+    case StatusCode::kPermissionDenied:
+      return "PERMISSION_DENIED";
+    case StatusCode::kUnauthenticated:
+      return "UNAUTHENTICATED";
+    case StatusCode::kResourceExhausted:
+      return "RESOURCE_EXHAUSTED";
+    case StatusCode::kFailedPrecondition:
+      return "FAILED_PRECONDITION";
+    case StatusCode::kAborted:
+      return "ABORTED";
+    case StatusCode::kOutOfRange:
+      return "OUT_OF_RANGE";
+    case StatusCode::kUnimplemented:
+      return "UNIMPLEMENTED";
+    case StatusCode::kInternal:
+      return "INTERNAL";
+    case StatusCode::kUnavailable:
+      return "UNAVAILABLE";
+    case StatusCode::kDataLoss:
+      return "DATA_LOSS";
+    default:
+      return "";
+  }
+}
+
+std::ostream& operator<<(std::ostream& os, StatusCode code) {
+  return os << StatusCodeToString(code);
+}
+
+absl::Nonnull<const std::string*> Status::EmptyString() {
+  static const absl::NoDestructor<std::string> kEmpty;
+  return kEmpty.get();
+}
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr const char Status::kMovedFromString[];
+#endif
+
+absl::Nonnull<const std::string*> Status::MovedFromString() {
+  static const absl::NoDestructor<std::string> kMovedFrom(kMovedFromString);
+  return kMovedFrom.get();
+}
+
+Status::Status(absl::StatusCode code, absl::string_view msg)
+    : rep_(CodeToInlinedRep(code)) {
+  if (code != absl::StatusCode::kOk && !msg.empty()) {
+    rep_ = PointerToRep(new status_internal::StatusRep(code, msg, nullptr));
+  }
+}
+
+absl::Nonnull<status_internal::StatusRep*> Status::PrepareToModify(
+    uintptr_t rep) {
+  if (IsInlined(rep)) {
+    return new status_internal::StatusRep(InlinedRepToCode(rep),
+                                          absl::string_view(), nullptr);
+  }
+  return RepToPointer(rep)->CloneAndUnref();
+}
+
+std::string Status::ToStringSlow(uintptr_t rep, StatusToStringMode mode) {
+  if (IsInlined(rep)) {
+    return absl::StrCat(absl::StatusCodeToString(InlinedRepToCode(rep)), ": ");
+  }
+  return RepToPointer(rep)->ToString(mode);
+}
+
+std::ostream& operator<<(std::ostream& os, const Status& x) {
+  os << x.ToString(StatusToStringMode::kWithEverything);
+  return os;
+}
+
+Status AbortedError(absl::string_view message) {
+  return Status(absl::StatusCode::kAborted, message);
+}
+
+Status AlreadyExistsError(absl::string_view message) {
+  return Status(absl::StatusCode::kAlreadyExists, message);
+}
+
+Status CancelledError(absl::string_view message) {
+  return Status(absl::StatusCode::kCancelled, message);
+}
+
+Status DataLossError(absl::string_view message) {
+  return Status(absl::StatusCode::kDataLoss, message);
+}
+
+Status DeadlineExceededError(absl::string_view message) {
+  return Status(absl::StatusCode::kDeadlineExceeded, message);
+}
+
+Status FailedPreconditionError(absl::string_view message) {
+  return Status(absl::StatusCode::kFailedPrecondition, message);
+}
+
+Status InternalError(absl::string_view message) {
+  return Status(absl::StatusCode::kInternal, message);
+}
+
+Status InvalidArgumentError(absl::string_view message) {
+  return Status(absl::StatusCode::kInvalidArgument, message);
+}
+
+Status NotFoundError(absl::string_view message) {
+  return Status(absl::StatusCode::kNotFound, message);
+}
+
+Status OutOfRangeError(absl::string_view message) {
+  return Status(absl::StatusCode::kOutOfRange, message);
+}
+
+Status PermissionDeniedError(absl::string_view message) {
+  return Status(absl::StatusCode::kPermissionDenied, message);
+}
+
+Status ResourceExhaustedError(absl::string_view message) {
+  return Status(absl::StatusCode::kResourceExhausted, message);
+}
+
+Status UnauthenticatedError(absl::string_view message) {
+  return Status(absl::StatusCode::kUnauthenticated, message);
+}
+
+Status UnavailableError(absl::string_view message) {
+  return Status(absl::StatusCode::kUnavailable, message);
+}
+
+Status UnimplementedError(absl::string_view message) {
+  return Status(absl::StatusCode::kUnimplemented, message);
+}
+
+Status UnknownError(absl::string_view message) {
+  return Status(absl::StatusCode::kUnknown, message);
+}
+
+bool IsAborted(const Status& status) {
+  return status.code() == absl::StatusCode::kAborted;
+}
+
+bool IsAlreadyExists(const Status& status) {
+  return status.code() == absl::StatusCode::kAlreadyExists;
+}
+
+bool IsCancelled(const Status& status) {
+  return status.code() == absl::StatusCode::kCancelled;
+}
+
+bool IsDataLoss(const Status& status) {
+  return status.code() == absl::StatusCode::kDataLoss;
+}
+
+bool IsDeadlineExceeded(const Status& status) {
+  return status.code() == absl::StatusCode::kDeadlineExceeded;
+}
+
+bool IsFailedPrecondition(const Status& status) {
+  return status.code() == absl::StatusCode::kFailedPrecondition;
+}
+
+bool IsInternal(const Status& status) {
+  return status.code() == absl::StatusCode::kInternal;
+}
+
+bool IsInvalidArgument(const Status& status) {
+  return status.code() == absl::StatusCode::kInvalidArgument;
+}
+
+bool IsNotFound(const Status& status) {
+  return status.code() == absl::StatusCode::kNotFound;
+}
+
+bool IsOutOfRange(const Status& status) {
+  return status.code() == absl::StatusCode::kOutOfRange;
+}
+
+bool IsPermissionDenied(const Status& status) {
+  return status.code() == absl::StatusCode::kPermissionDenied;
+}
+
+bool IsResourceExhausted(const Status& status) {
+  return status.code() == absl::StatusCode::kResourceExhausted;
+}
+
+bool IsUnauthenticated(const Status& status) {
+  return status.code() == absl::StatusCode::kUnauthenticated;
+}
+
+bool IsUnavailable(const Status& status) {
+  return status.code() == absl::StatusCode::kUnavailable;
+}
+
+bool IsUnimplemented(const Status& status) {
+  return status.code() == absl::StatusCode::kUnimplemented;
+}
+
+bool IsUnknown(const Status& status) {
+  return status.code() == absl::StatusCode::kUnknown;
+}
+
+StatusCode ErrnoToStatusCode(int error_number) {
+  switch (error_number) {
+    case 0:
+      return StatusCode::kOk;
+    case EINVAL:        // Invalid argument
+    case ENAMETOOLONG:  // Filename too long
+    case E2BIG:         // Argument list too long
+    case EDESTADDRREQ:  // Destination address required
+    case EDOM:          // Mathematics argument out of domain of function
+    case EFAULT:        // Bad address
+    case EILSEQ:        // Illegal byte sequence
+    case ENOPROTOOPT:   // Protocol not available
+    case ENOSTR:        // Not a STREAM
+    case ENOTSOCK:      // Not a socket
+    case ENOTTY:        // Inappropriate I/O control operation
+    case EPROTOTYPE:    // Protocol wrong type for socket
+    case ESPIPE:        // Invalid seek
+      return StatusCode::kInvalidArgument;
+    case ETIMEDOUT:  // Connection timed out
+    case ETIME:      // Timer expired
+      return StatusCode::kDeadlineExceeded;
+    case ENODEV:  // No such device
+    case ENOENT:  // No such file or directory
+#ifdef ENOMEDIUM
+    case ENOMEDIUM:  // No medium found
+#endif
+    case ENXIO:  // No such device or address
+    case ESRCH:  // No such process
+      return StatusCode::kNotFound;
+    case EEXIST:         // File exists
+    case EADDRNOTAVAIL:  // Address not available
+    case EALREADY:       // Connection already in progress
+#ifdef ENOTUNIQ
+    case ENOTUNIQ:  // Name not unique on network
+#endif
+      return StatusCode::kAlreadyExists;
+    case EPERM:   // Operation not permitted
+    case EACCES:  // Permission denied
+#ifdef ENOKEY
+    case ENOKEY:  // Required key not available
+#endif
+    case EROFS:  // Read only file system
+      return StatusCode::kPermissionDenied;
+    case ENOTEMPTY:   // Directory not empty
+    case EISDIR:      // Is a directory
+    case ENOTDIR:     // Not a directory
+    case EADDRINUSE:  // Address already in use
+    case EBADF:       // Invalid file descriptor
+#ifdef EBADFD
+    case EBADFD:  // File descriptor in bad state
+#endif
+    case EBUSY:    // Device or resource busy
+    case ECHILD:   // No child processes
+    case EISCONN:  // Socket is connected
+#ifdef EISNAM
+    case EISNAM:  // Is a named type file
+#endif
+#ifdef ENOTBLK
+    case ENOTBLK:  // Block device required
+#endif
+    case ENOTCONN:  // The socket is not connected
+    case EPIPE:     // Broken pipe
+#ifdef ESHUTDOWN
+    case ESHUTDOWN:  // Cannot send after transport endpoint shutdown
+#endif
+    case ETXTBSY:  // Text file busy
+#ifdef EUNATCH
+    case EUNATCH:  // Protocol driver not attached
+#endif
+      return StatusCode::kFailedPrecondition;
+    case ENOSPC:  // No space left on device
+#ifdef EDQUOT
+    case EDQUOT:  // Disk quota exceeded
+#endif
+    case EMFILE:   // Too many open files
+    case EMLINK:   // Too many links
+    case ENFILE:   // Too many open files in system
+    case ENOBUFS:  // No buffer space available
+    case ENODATA:  // No message is available on the STREAM read queue
+    case ENOMEM:   // Not enough space
+    case ENOSR:    // No STREAM resources
+#ifdef EUSERS
+    case EUSERS:  // Too many users
+#endif
+      return StatusCode::kResourceExhausted;
+#ifdef ECHRNG
+    case ECHRNG:  // Channel number out of range
+#endif
+    case EFBIG:      // File too large
+    case EOVERFLOW:  // Value too large to be stored in data type
+    case ERANGE:     // Result too large
+      return StatusCode::kOutOfRange;
+#ifdef ENOPKG
+    case ENOPKG:  // Package not installed
+#endif
+    case ENOSYS:        // Function not implemented
+    case ENOTSUP:       // Operation not supported
+    case EAFNOSUPPORT:  // Address family not supported
+#ifdef EPFNOSUPPORT
+    case EPFNOSUPPORT:  // Protocol family not supported
+#endif
+    case EPROTONOSUPPORT:  // Protocol not supported
+#ifdef ESOCKTNOSUPPORT
+    case ESOCKTNOSUPPORT:  // Socket type not supported
+#endif
+    case EXDEV:  // Improper link
+      return StatusCode::kUnimplemented;
+    case EAGAIN:  // Resource temporarily unavailable
+#ifdef ECOMM
+    case ECOMM:  // Communication error on send
+#endif
+    case ECONNREFUSED:  // Connection refused
+    case ECONNABORTED:  // Connection aborted
+    case ECONNRESET:    // Connection reset
+    case EINTR:         // Interrupted function call
+#ifdef EHOSTDOWN
+    case EHOSTDOWN:  // Host is down
+#endif
+    case EHOSTUNREACH:  // Host is unreachable
+    case ENETDOWN:      // Network is down
+    case ENETRESET:     // Connection aborted by network
+    case ENETUNREACH:   // Network unreachable
+    case ENOLCK:        // No locks available
+    case ENOLINK:       // Link has been severed
+#ifdef ENONET
+    case ENONET:  // Machine is not on the network
+#endif
+      return StatusCode::kUnavailable;
+    case EDEADLK:  // Resource deadlock avoided
+#ifdef ESTALE
+    case ESTALE:  // Stale file handle
+#endif
+      return StatusCode::kAborted;
+    case ECANCELED:  // Operation cancelled
+      return StatusCode::kCancelled;
+    default:
+      return StatusCode::kUnknown;
+  }
+}
+
+namespace {
+std::string MessageForErrnoToStatus(int error_number,
+                                    absl::string_view message) {
+  return absl::StrCat(message, ": ",
+                      absl::base_internal::StrError(error_number));
+}
+}  // namespace
+
+Status ErrnoToStatus(int error_number, absl::string_view message) {
+  return Status(ErrnoToStatusCode(error_number),
+                MessageForErrnoToStatus(error_number, message));
+}
+
+absl::Nonnull<const char*> StatusMessageAsCStr(const Status& status) {
+  // As an internal implementation detail, we guarantee that if status.message()
+  // is non-empty, then the resulting string_view is null terminated.
+  auto sv_message = status.message();
+  return sv_message.empty() ? "" : sv_message.data();
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/status/status.h b/weight/_dep/abseil-cpp/absl/status/status.h
new file mode 100644
index 0000000000000000000000000000000000000000..9ce16db9619a520d0429ba0c981cdf7bb1e80bf6
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/status.h
@@ -0,0 +1,943 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: status.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the Abseil `status` library, consisting of:
+//
+//   * An `absl::Status` class for holding error handling information
+//   * A set of canonical `absl::StatusCode` error codes, and associated
+//     utilities for generating and propagating status codes.
+//   * A set of helper functions for creating status codes and checking their
+//     values
+//
+// Within Google, `absl::Status` is the primary mechanism for communicating
+// errors in C++, and is used to represent error state in both in-process
+// library calls as well as RPC calls. Some of these errors may be recoverable,
+// but others may not. Most functions that can produce a recoverable error
+// should be designed to return an `absl::Status` (or `absl::StatusOr`).
+//
+// Example:
+//
+// absl::Status myFunction(absl::string_view fname, ...) {
+//   ...
+//   // encounter error
+//   if (error condition) {
+//     return absl::InvalidArgumentError("bad mode");
+//   }
+//   // else, return OK
+//   return absl::OkStatus();
+// }
+//
+// An `absl::Status` is designed to either return "OK" or one of a number of
+// different error codes, corresponding to typical error conditions.
+// In almost all cases, when using `absl::Status` you should use the canonical
+// error codes (of type `absl::StatusCode`) enumerated in this header file.
+// These canonical codes are understood across the codebase and will be
+// accepted across all API and RPC boundaries.
+#ifndef ABSL_STATUS_STATUS_H_
+#define ABSL_STATUS_STATUS_H_
+
+#include <cassert>
+#include <cstdint>
+#include <ostream>
+#include <string>
+#include <utility>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+#include "absl/base/nullability.h"
+#include "absl/base/optimization.h"
+#include "absl/functional/function_ref.h"
+#include "absl/status/internal/status_internal.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::StatusCode
+//
+// An `absl::StatusCode` is an enumerated type indicating either no error ("OK")
+// or an error condition. In most cases, an `absl::Status` indicates a
+// recoverable error, and the purpose of signalling an error is to indicate what
+// action to take in response to that error. These error codes map to the proto
+// RPC error codes indicated in https://cloud.google.com/apis/design/errors.
+//
+// The errors listed below are the canonical errors associated with
+// `absl::Status` and are used throughout the codebase. As a result, these
+// error codes are somewhat generic.
+//
+// In general, try to return the most specific error that applies if more than
+// one error may pertain. For example, prefer `kOutOfRange` over
+// `kFailedPrecondition` if both codes apply. Similarly prefer `kNotFound` or
+// `kAlreadyExists` over `kFailedPrecondition`.
+//
+// Because these errors may cross RPC boundaries, these codes are tied to the
+// `google.rpc.Code` definitions within
+// https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto
+// The string value of these RPC codes is denoted within each enum below.
+//
+// If your error handling code requires more context, you can attach payloads
+// to your status. See `absl::Status::SetPayload()` and
+// `absl::Status::GetPayload()` below.
+enum class StatusCode : int {
+  // StatusCode::kOk
+  //
+  // kOK (gRPC code "OK") does not indicate an error; this value is returned on
+  // success. It is typical to check for this value before proceeding on any
+  // given call across an API or RPC boundary. To check this value, use the
+  // `absl::Status::ok()` member function rather than inspecting the raw code.
+  kOk = 0,
+
+  // StatusCode::kCancelled
+  //
+  // kCancelled (gRPC code "CANCELLED") indicates the operation was cancelled,
+  // typically by the caller.
+  kCancelled = 1,
+
+  // StatusCode::kUnknown
+  //
+  // kUnknown (gRPC code "UNKNOWN") indicates an unknown error occurred. In
+  // general, more specific errors should be raised, if possible. Errors raised
+  // by APIs that do not return enough error information may be converted to
+  // this error.
+  kUnknown = 2,
+
+  // StatusCode::kInvalidArgument
+  //
+  // kInvalidArgument (gRPC code "INVALID_ARGUMENT") indicates the caller
+  // specified an invalid argument, such as a malformed filename. Note that use
+  // of such errors should be narrowly limited to indicate the invalid nature of
+  // the arguments themselves. Errors with validly formed arguments that may
+  // cause errors with the state of the receiving system should be denoted with
+  // `kFailedPrecondition` instead.
+  kInvalidArgument = 3,
+
+  // StatusCode::kDeadlineExceeded
+  //
+  // kDeadlineExceeded (gRPC code "DEADLINE_EXCEEDED") indicates a deadline
+  // expired before the operation could complete. For operations that may change
+  // state within a system, this error may be returned even if the operation has
+  // completed successfully. For example, a successful response from a server
+  // could have been delayed long enough for the deadline to expire.
+  kDeadlineExceeded = 4,
+
+  // StatusCode::kNotFound
+  //
+  // kNotFound (gRPC code "NOT_FOUND") indicates some requested entity (such as
+  // a file or directory) was not found.
+  //
+  // `kNotFound` is useful if a request should be denied for an entire class of
+  // users, such as during a gradual feature rollout or undocumented allow list.
+  // If a request should be denied for specific sets of users, such as through
+  // user-based access control, use `kPermissionDenied` instead.
+  kNotFound = 5,
+
+  // StatusCode::kAlreadyExists
+  //
+  // kAlreadyExists (gRPC code "ALREADY_EXISTS") indicates that the entity a
+  // caller attempted to create (such as a file or directory) is already
+  // present.
+  kAlreadyExists = 6,
+
+  // StatusCode::kPermissionDenied
+  //
+  // kPermissionDenied (gRPC code "PERMISSION_DENIED") indicates that the caller
+  // does not have permission to execute the specified operation. Note that this
+  // error is different than an error due to an *un*authenticated user. This
+  // error code does not imply the request is valid or the requested entity
+  // exists or satisfies any other pre-conditions.
+  //
+  // `kPermissionDenied` must not be used for rejections caused by exhausting
+  // some resource. Instead, use `kResourceExhausted` for those errors.
+  // `kPermissionDenied` must not be used if the caller cannot be identified.
+  // Instead, use `kUnauthenticated` for those errors.
+  kPermissionDenied = 7,
+
+  // StatusCode::kResourceExhausted
+  //
+  // kResourceExhausted (gRPC code "RESOURCE_EXHAUSTED") indicates some resource
+  // has been exhausted, perhaps a per-user quota, or perhaps the entire file
+  // system is out of space.
+  kResourceExhausted = 8,
+
+  // StatusCode::kFailedPrecondition
+  //
+  // kFailedPrecondition (gRPC code "FAILED_PRECONDITION") indicates that the
+  // operation was rejected because the system is not in a state required for
+  // the operation's execution. For example, a directory to be deleted may be
+  // non-empty, an "rmdir" operation is applied to a non-directory, etc.
+  //
+  // Some guidelines that may help a service implementer in deciding between
+  // `kFailedPrecondition`, `kAborted`, and `kUnavailable`:
+  //
+  //  (a) Use `kUnavailable` if the client can retry just the failing call.
+  //  (b) Use `kAborted` if the client should retry at a higher transaction
+  //      level (such as when a client-specified test-and-set fails, indicating
+  //      the client should restart a read-modify-write sequence).
+  //  (c) Use `kFailedPrecondition` if the client should not retry until
+  //      the system state has been explicitly fixed. For example, if a "rmdir"
+  //      fails because the directory is non-empty, `kFailedPrecondition`
+  //      should be returned since the client should not retry unless
+  //      the files are deleted from the directory.
+  kFailedPrecondition = 9,
+
+  // StatusCode::kAborted
+  //
+  // kAborted (gRPC code "ABORTED") indicates the operation was aborted,
+  // typically due to a concurrency issue such as a sequencer check failure or a
+  // failed transaction.
+  //
+  // See the guidelines above for deciding between `kFailedPrecondition`,
+  // `kAborted`, and `kUnavailable`.
+  kAborted = 10,
+
+  // StatusCode::kOutOfRange
+  //
+  // kOutOfRange (gRPC code "OUT_OF_RANGE") indicates the operation was
+  // attempted past the valid range, such as seeking or reading past an
+  // end-of-file.
+  //
+  // Unlike `kInvalidArgument`, this error indicates a problem that may
+  // be fixed if the system state changes. For example, a 32-bit file
+  // system will generate `kInvalidArgument` if asked to read at an
+  // offset that is not in the range [0,2^32-1], but it will generate
+  // `kOutOfRange` if asked to read from an offset past the current
+  // file size.
+  //
+  // There is a fair bit of overlap between `kFailedPrecondition` and
+  // `kOutOfRange`.  We recommend using `kOutOfRange` (the more specific
+  // error) when it applies so that callers who are iterating through
+  // a space can easily look for an `kOutOfRange` error to detect when
+  // they are done.
+  kOutOfRange = 11,
+
+  // StatusCode::kUnimplemented
+  //
+  // kUnimplemented (gRPC code "UNIMPLEMENTED") indicates the operation is not
+  // implemented or supported in this service. In this case, the operation
+  // should not be re-attempted.
+  kUnimplemented = 12,
+
+  // StatusCode::kInternal
+  //
+  // kInternal (gRPC code "INTERNAL") indicates an internal error has occurred
+  // and some invariants expected by the underlying system have not been
+  // satisfied. This error code is reserved for serious errors.
+  kInternal = 13,
+
+  // StatusCode::kUnavailable
+  //
+  // kUnavailable (gRPC code "UNAVAILABLE") indicates the service is currently
+  // unavailable and that this is most likely a transient condition. An error
+  // such as this can be corrected by retrying with a backoff scheme. Note that
+  // it is not always safe to retry non-idempotent operations.
+  //
+  // See the guidelines above for deciding between `kFailedPrecondition`,
+  // `kAborted`, and `kUnavailable`.
+  kUnavailable = 14,
+
+  // StatusCode::kDataLoss
+  //
+  // kDataLoss (gRPC code "DATA_LOSS") indicates that unrecoverable data loss or
+  // corruption has occurred. As this error is serious, proper alerting should
+  // be attached to errors such as this.
+  kDataLoss = 15,
+
+  // StatusCode::kUnauthenticated
+  //
+  // kUnauthenticated (gRPC code "UNAUTHENTICATED") indicates that the request
+  // does not have valid authentication credentials for the operation. Correct
+  // the authentication and try again.
+  kUnauthenticated = 16,
+
+  // StatusCode::DoNotUseReservedForFutureExpansionUseDefaultInSwitchInstead_
+  //
+  // NOTE: this error code entry should not be used and you should not rely on
+  // its value, which may change.
+  //
+  // The purpose of this enumerated value is to force people who handle status
+  // codes with `switch()` statements to *not* simply enumerate all possible
+  // values, but instead provide a "default:" case. Providing such a default
+  // case ensures that code will compile when new codes are added.
+  kDoNotUseReservedForFutureExpansionUseDefaultInSwitchInstead_ = 20
+};
+
+// StatusCodeToString()
+//
+// Returns the name for the status code, or "" if it is an unknown value.
+std::string StatusCodeToString(StatusCode code);
+
+// operator<<
+//
+// Streams StatusCodeToString(code) to `os`.
+std::ostream& operator<<(std::ostream& os, StatusCode code);
+
+// absl::StatusToStringMode
+//
+// An `absl::StatusToStringMode` is an enumerated type indicating how
+// `absl::Status::ToString()` should construct the output string for a non-ok
+// status.
+enum class StatusToStringMode : int {
+  // ToString will not contain any extra data (such as payloads). It will only
+  // contain the error code and message, if any.
+  kWithNoExtraData = 0,
+  // ToString will contain the payloads.
+  kWithPayload = 1 << 0,
+  // ToString will include all the extra data this Status has.
+  kWithEverything = ~kWithNoExtraData,
+  // Default mode used by ToString. Its exact value might change in the future.
+  kDefault = kWithPayload,
+};
+
+// absl::StatusToStringMode is specified as a bitmask type, which means the
+// following operations must be provided:
+inline constexpr StatusToStringMode operator&(StatusToStringMode lhs,
+                                              StatusToStringMode rhs) {
+  return static_cast<StatusToStringMode>(static_cast<int>(lhs) &
+                                         static_cast<int>(rhs));
+}
+inline constexpr StatusToStringMode operator|(StatusToStringMode lhs,
+                                              StatusToStringMode rhs) {
+  return static_cast<StatusToStringMode>(static_cast<int>(lhs) |
+                                         static_cast<int>(rhs));
+}
+inline constexpr StatusToStringMode operator^(StatusToStringMode lhs,
+                                              StatusToStringMode rhs) {
+  return static_cast<StatusToStringMode>(static_cast<int>(lhs) ^
+                                         static_cast<int>(rhs));
+}
+inline constexpr StatusToStringMode operator~(StatusToStringMode arg) {
+  return static_cast<StatusToStringMode>(~static_cast<int>(arg));
+}
+inline StatusToStringMode& operator&=(StatusToStringMode& lhs,
+                                      StatusToStringMode rhs) {
+  lhs = lhs & rhs;
+  return lhs;
+}
+inline StatusToStringMode& operator|=(StatusToStringMode& lhs,
+                                      StatusToStringMode rhs) {
+  lhs = lhs | rhs;
+  return lhs;
+}
+inline StatusToStringMode& operator^=(StatusToStringMode& lhs,
+                                      StatusToStringMode rhs) {
+  lhs = lhs ^ rhs;
+  return lhs;
+}
+
+// absl::Status
+//
+// The `absl::Status` class is generally used to gracefully handle errors
+// across API boundaries (and in particular across RPC boundaries). Some of
+// these errors may be recoverable, but others may not. Most
+// functions which can produce a recoverable error should be designed to return
+// either an `absl::Status` (or the similar `absl::StatusOr<T>`, which holds
+// either an object of type `T` or an error).
+//
+// API developers should construct their functions to return `absl::OkStatus()`
+// upon success, or an `absl::StatusCode` upon another type of error (e.g
+// an `absl::StatusCode::kInvalidArgument` error). The API provides convenience
+// functions to construct each status code.
+//
+// Example:
+//
+// absl::Status myFunction(absl::string_view fname, ...) {
+//   ...
+//   // encounter error
+//   if (error condition) {
+//     // Construct an absl::StatusCode::kInvalidArgument error
+//     return absl::InvalidArgumentError("bad mode");
+//   }
+//   // else, return OK
+//   return absl::OkStatus();
+// }
+//
+// Users handling status error codes should prefer checking for an OK status
+// using the `ok()` member function. Handling multiple error codes may justify
+// use of switch statement, but only check for error codes you know how to
+// handle; do not try to exhaustively match against all canonical error codes.
+// Errors that cannot be handled should be logged and/or propagated for higher
+// levels to deal with. If you do use a switch statement, make sure that you
+// also provide a `default:` switch case, so that code does not break as other
+// canonical codes are added to the API.
+//
+// Example:
+//
+//   absl::Status result = DoSomething();
+//   if (!result.ok()) {
+//     LOG(ERROR) << result;
+//   }
+//
+//   // Provide a default if switching on multiple error codes
+//   switch (result.code()) {
+//     // The user hasn't authenticated. Ask them to reauth
+//     case absl::StatusCode::kUnauthenticated:
+//       DoReAuth();
+//       break;
+//     // The user does not have permission. Log an error.
+//     case absl::StatusCode::kPermissionDenied:
+//       LOG(ERROR) << result;
+//       break;
+//     // Propagate the error otherwise.
+//     default:
+//       return true;
+//   }
+//
+// An `absl::Status` can optionally include a payload with more information
+// about the error. Typically, this payload serves one of several purposes:
+//
+//   * It may provide more fine-grained semantic information about the error to
+//     facilitate actionable remedies.
+//   * It may provide human-readable contextual information that is more
+//     appropriate to display to an end user.
+//
+// Example:
+//
+//   absl::Status result = DoSomething();
+//   // Inform user to retry after 30 seconds
+//   // See more error details in googleapis/google/rpc/error_details.proto
+//   if (absl::IsResourceExhausted(result)) {
+//     google::rpc::RetryInfo info;
+//     info.retry_delay().seconds() = 30;
+//     // Payloads require a unique key (a URL to ensure no collisions with
+//     // other payloads), and an `absl::Cord` to hold the encoded data.
+//     absl::string_view url = "type.googleapis.com/google.rpc.RetryInfo";
+//     result.SetPayload(url, info.SerializeAsCord());
+//     return result;
+//   }
+//
+// For documentation see https://abseil.io/docs/cpp/guides/status.
+//
+// Returned Status objects may not be ignored. status_internal.h has a forward
+// declaration of the form
+// class ABSL_MUST_USE_RESULT Status;
+class ABSL_ATTRIBUTE_TRIVIAL_ABI Status final {
+ public:
+  // Constructors
+
+  // This default constructor creates an OK status with no message or payload.
+  // Avoid this constructor and prefer explicit construction of an OK status
+  // with `absl::OkStatus()`.
+  Status();
+
+  // Creates a status in the canonical error space with the specified
+  // `absl::StatusCode` and error message.  If `code == absl::StatusCode::kOk`,  // NOLINT
+  // `msg` is ignored and an object identical to an OK status is constructed.
+  //
+  // The `msg` string must be in UTF-8. The implementation may complain (e.g.,  // NOLINT
+  // by printing a warning) if it is not.
+  Status(absl::StatusCode code, absl::string_view msg);
+
+  Status(const Status&);
+  Status& operator=(const Status& x);
+
+  // Move operators
+
+  // The moved-from state is valid but unspecified.
+  Status(Status&&) noexcept;
+  Status& operator=(Status&&);
+
+  ~Status();
+
+  // Status::Update()
+  //
+  // Updates the existing status with `new_status` provided that `this->ok()`.
+  // If the existing status already contains a non-OK error, this update has no
+  // effect and preserves the current data. Note that this behavior may change
+  // in the future to augment a current non-ok status with additional
+  // information about `new_status`.
+  //
+  // `Update()` provides a convenient way of keeping track of the first error
+  // encountered.
+  //
+  // Example:
+  //   // Instead of "if (overall_status.ok()) overall_status = new_status"
+  //   overall_status.Update(new_status);
+  //
+  void Update(const Status& new_status);
+  void Update(Status&& new_status);
+
+  // Status::ok()
+  //
+  // Returns `true` if `this->code()` == `absl::StatusCode::kOk`,
+  // indicating the absence of an error.
+  // Prefer checking for an OK status using this member function.
+  ABSL_MUST_USE_RESULT bool ok() const;
+
+  // Status::code()
+  //
+  // Returns the canonical error code of type `absl::StatusCode` of this status.
+  absl::StatusCode code() const;
+
+  // Status::raw_code()
+  //
+  // Returns a raw (canonical) error code corresponding to the enum value of
+  // `google.rpc.Code` definitions within
+  // https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto.
+  // These values could be out of the range of canonical `absl::StatusCode`
+  // enum values.
+  //
+  // NOTE: This function should only be called when converting to an associated
+  // wire format. Use `Status::code()` for error handling.
+  int raw_code() const;
+
+  // Status::message()
+  //
+  // Returns the error message associated with this error code, if available.
+  // Note that this message rarely describes the error code.  It is not unusual
+  // for the error message to be the empty string. As a result, prefer
+  // `operator<<` or `Status::ToString()` for debug logging.
+  absl::string_view message() const;
+
+  friend bool operator==(const Status&, const Status&);
+  friend bool operator!=(const Status&, const Status&);
+
+  // Status::ToString()
+  //
+  // Returns a string based on the `mode`. By default, it returns combination of
+  // the error code name, the message and any associated payload messages. This
+  // string is designed simply to be human readable and its exact format should
+  // not be load bearing. Do not depend on the exact format of the result of
+  // `ToString()` which is subject to change.
+  //
+  // The printed code name and the message are generally substrings of the
+  // result, and the payloads to be printed use the status payload printer
+  // mechanism (which is internal).
+  std::string ToString(
+      StatusToStringMode mode = StatusToStringMode::kDefault) const;
+
+  // Support `absl::StrCat`, `absl::StrFormat`, etc.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const Status& status) {
+    sink.Append(status.ToString(StatusToStringMode::kWithEverything));
+  }
+
+  // Status::IgnoreError()
+  //
+  // Ignores any errors. This method does nothing except potentially suppress
+  // complaints from any tools that are checking that errors are not dropped on
+  // the floor.
+  void IgnoreError() const;
+
+  // swap()
+  //
+  // Swap the contents of one status with another.
+  friend void swap(Status& a, Status& b);
+
+  //----------------------------------------------------------------------------
+  // Payload Management APIs
+  //----------------------------------------------------------------------------
+
+  // A payload may be attached to a status to provide additional context to an
+  // error that may not be satisfied by an existing `absl::StatusCode`.
+  // Typically, this payload serves one of several purposes:
+  //
+  //   * It may provide more fine-grained semantic information about the error
+  //     to facilitate actionable remedies.
+  //   * It may provide human-readable contextual information that is more
+  //     appropriate to display to an end user.
+  //
+  // A payload consists of a [key,value] pair, where the key is a string
+  // referring to a unique "type URL" and the value is an object of type
+  // `absl::Cord` to hold the contextual data.
+  //
+  // The "type URL" should be unique and follow the format of a URL
+  // (https://en.wikipedia.org/wiki/URL) and, ideally, provide some
+  // documentation or schema on how to interpret its associated data. For
+  // example, the default type URL for a protobuf message type is
+  // "type.googleapis.com/packagename.messagename". Other custom wire formats
+  // should define the format of type URL in a similar practice so as to
+  // minimize the chance of conflict between type URLs.
+  // Users should ensure that the type URL can be mapped to a concrete
+  // C++ type if they want to deserialize the payload and read it effectively.
+  //
+  // To attach a payload to a status object, call `Status::SetPayload()`,
+  // passing it the type URL and an `absl::Cord` of associated data. Similarly,
+  // to extract the payload from a status, call `Status::GetPayload()`. You
+  // may attach multiple payloads (with differing type URLs) to any given
+  // status object, provided that the status is currently exhibiting an error
+  // code (i.e. is not OK).
+
+  // Status::GetPayload()
+  //
+  // Gets the payload of a status given its unique `type_url` key, if present.
+  absl::optional<absl::Cord> GetPayload(absl::string_view type_url) const;
+
+  // Status::SetPayload()
+  //
+  // Sets the payload for a non-ok status using a `type_url` key, overwriting
+  // any existing payload for that `type_url`.
+  //
+  // NOTE: This function does nothing if the Status is ok.
+  void SetPayload(absl::string_view type_url, absl::Cord payload);
+
+  // Status::ErasePayload()
+  //
+  // Erases the payload corresponding to the `type_url` key.  Returns `true` if
+  // the payload was present.
+  bool ErasePayload(absl::string_view type_url);
+
+  // Status::ForEachPayload()
+  //
+  // Iterates over the stored payloads and calls the
+  // `visitor(type_key, payload)` callable for each one.
+  //
+  // NOTE: The order of calls to `visitor()` is not specified and may change at
+  // any time.
+  //
+  // NOTE: Any mutation on the same 'absl::Status' object during visitation is
+  // forbidden and could result in undefined behavior.
+  void ForEachPayload(
+      absl::FunctionRef<void(absl::string_view, const absl::Cord&)> visitor)
+      const;
+
+ private:
+  friend Status CancelledError();
+
+  // Creates a status in the canonical error space with the specified
+  // code, and an empty error message.
+  explicit Status(absl::StatusCode code);
+
+  // Underlying constructor for status from a rep_.
+  explicit Status(uintptr_t rep) : rep_(rep) {}
+
+  static void Ref(uintptr_t rep);
+  static void Unref(uintptr_t rep);
+
+  // REQUIRES: !ok()
+  // Ensures rep is not inlined or shared with any other Status.
+  static absl::Nonnull<status_internal::StatusRep*> PrepareToModify(
+      uintptr_t rep);
+
+  // MSVC 14.0 limitation requires the const.
+  static constexpr const char kMovedFromString[] =
+      "Status accessed after move.";
+
+  static absl::Nonnull<const std::string*> EmptyString();
+  static absl::Nonnull<const std::string*> MovedFromString();
+
+  // Returns whether rep contains an inlined representation.
+  // See rep_ for details.
+  static constexpr bool IsInlined(uintptr_t rep);
+
+  // Indicates whether this Status was the rhs of a move operation. See rep_
+  // for details.
+  static constexpr bool IsMovedFrom(uintptr_t rep);
+  static constexpr uintptr_t MovedFromRep();
+
+  // Convert between error::Code and the inlined uintptr_t representation used
+  // by rep_. See rep_ for details.
+  static constexpr uintptr_t CodeToInlinedRep(absl::StatusCode code);
+  static constexpr absl::StatusCode InlinedRepToCode(uintptr_t rep);
+
+  // Converts between StatusRep* and the external uintptr_t representation used
+  // by rep_. See rep_ for details.
+  static uintptr_t PointerToRep(status_internal::StatusRep* r);
+  static absl::Nonnull<const status_internal::StatusRep*> RepToPointer(
+      uintptr_t r);
+
+  static std::string ToStringSlow(uintptr_t rep, StatusToStringMode mode);
+
+  // Status supports two different representations.
+  //  - When the low bit is set it is an inlined representation.
+  //    It uses the canonical error space, no message or payload.
+  //    The error code is (rep_ >> 2).
+  //    The (rep_ & 2) bit is the "moved from" indicator, used in IsMovedFrom().
+  //  - When the low bit is off it is an external representation.
+  //    In this case all the data comes from a heap allocated Rep object.
+  //    rep_ is a status_internal::StatusRep* pointer to that structure.
+  uintptr_t rep_;
+
+  friend class status_internal::StatusRep;
+};
+
+// OkStatus()
+//
+// Returns an OK status, equivalent to a default constructed instance. Prefer
+// usage of `absl::OkStatus()` when constructing such an OK status.
+Status OkStatus();
+
+// operator<<()
+//
+// Prints a human-readable representation of `x` to `os`.
+std::ostream& operator<<(std::ostream& os, const Status& x);
+
+// IsAborted()
+// IsAlreadyExists()
+// IsCancelled()
+// IsDataLoss()
+// IsDeadlineExceeded()
+// IsFailedPrecondition()
+// IsInternal()
+// IsInvalidArgument()
+// IsNotFound()
+// IsOutOfRange()
+// IsPermissionDenied()
+// IsResourceExhausted()
+// IsUnauthenticated()
+// IsUnavailable()
+// IsUnimplemented()
+// IsUnknown()
+//
+// These convenience functions return `true` if a given status matches the
+// `absl::StatusCode` error code of its associated function.
+ABSL_MUST_USE_RESULT bool IsAborted(const Status& status);
+ABSL_MUST_USE_RESULT bool IsAlreadyExists(const Status& status);
+ABSL_MUST_USE_RESULT bool IsCancelled(const Status& status);
+ABSL_MUST_USE_RESULT bool IsDataLoss(const Status& status);
+ABSL_MUST_USE_RESULT bool IsDeadlineExceeded(const Status& status);
+ABSL_MUST_USE_RESULT bool IsFailedPrecondition(const Status& status);
+ABSL_MUST_USE_RESULT bool IsInternal(const Status& status);
+ABSL_MUST_USE_RESULT bool IsInvalidArgument(const Status& status);
+ABSL_MUST_USE_RESULT bool IsNotFound(const Status& status);
+ABSL_MUST_USE_RESULT bool IsOutOfRange(const Status& status);
+ABSL_MUST_USE_RESULT bool IsPermissionDenied(const Status& status);
+ABSL_MUST_USE_RESULT bool IsResourceExhausted(const Status& status);
+ABSL_MUST_USE_RESULT bool IsUnauthenticated(const Status& status);
+ABSL_MUST_USE_RESULT bool IsUnavailable(const Status& status);
+ABSL_MUST_USE_RESULT bool IsUnimplemented(const Status& status);
+ABSL_MUST_USE_RESULT bool IsUnknown(const Status& status);
+
+// AbortedError()
+// AlreadyExistsError()
+// CancelledError()
+// DataLossError()
+// DeadlineExceededError()
+// FailedPreconditionError()
+// InternalError()
+// InvalidArgumentError()
+// NotFoundError()
+// OutOfRangeError()
+// PermissionDeniedError()
+// ResourceExhaustedError()
+// UnauthenticatedError()
+// UnavailableError()
+// UnimplementedError()
+// UnknownError()
+//
+// These convenience functions create an `absl::Status` object with an error
+// code as indicated by the associated function name, using the error message
+// passed in `message`.
+Status AbortedError(absl::string_view message);
+Status AlreadyExistsError(absl::string_view message);
+Status CancelledError(absl::string_view message);
+Status DataLossError(absl::string_view message);
+Status DeadlineExceededError(absl::string_view message);
+Status FailedPreconditionError(absl::string_view message);
+Status InternalError(absl::string_view message);
+Status InvalidArgumentError(absl::string_view message);
+Status NotFoundError(absl::string_view message);
+Status OutOfRangeError(absl::string_view message);
+Status PermissionDeniedError(absl::string_view message);
+Status ResourceExhaustedError(absl::string_view message);
+Status UnauthenticatedError(absl::string_view message);
+Status UnavailableError(absl::string_view message);
+Status UnimplementedError(absl::string_view message);
+Status UnknownError(absl::string_view message);
+
+// ErrnoToStatusCode()
+//
+// Returns the StatusCode for `error_number`, which should be an `errno` value.
+// See https://en.cppreference.com/w/cpp/error/errno_macros and similar
+// references.
+absl::StatusCode ErrnoToStatusCode(int error_number);
+
+// ErrnoToStatus()
+//
+// Convenience function that creates a `absl::Status` using an `error_number`,
+// which should be an `errno` value.
+Status ErrnoToStatus(int error_number, absl::string_view message);
+
+//------------------------------------------------------------------------------
+// Implementation details follow
+//------------------------------------------------------------------------------
+
+inline Status::Status() : Status(absl::StatusCode::kOk) {}
+
+inline Status::Status(absl::StatusCode code) : Status(CodeToInlinedRep(code)) {}
+
+inline Status::Status(const Status& x) : Status(x.rep_) { Ref(rep_); }
+
+inline Status& Status::operator=(const Status& x) {
+  uintptr_t old_rep = rep_;
+  if (x.rep_ != old_rep) {
+    Ref(x.rep_);
+    rep_ = x.rep_;
+    Unref(old_rep);
+  }
+  return *this;
+}
+
+inline Status::Status(Status&& x) noexcept : Status(x.rep_) {
+  x.rep_ = MovedFromRep();
+}
+
+inline Status& Status::operator=(Status&& x) {
+  uintptr_t old_rep = rep_;
+  if (x.rep_ != old_rep) {
+    rep_ = x.rep_;
+    x.rep_ = MovedFromRep();
+    Unref(old_rep);
+  }
+  return *this;
+}
+
+inline void Status::Update(const Status& new_status) {
+  if (ok()) {
+    *this = new_status;
+  }
+}
+
+inline void Status::Update(Status&& new_status) {
+  if (ok()) {
+    *this = std::move(new_status);
+  }
+}
+
+inline Status::~Status() { Unref(rep_); }
+
+inline bool Status::ok() const {
+  return rep_ == CodeToInlinedRep(absl::StatusCode::kOk);
+}
+
+inline absl::StatusCode Status::code() const {
+  return status_internal::MapToLocalCode(raw_code());
+}
+
+inline int Status::raw_code() const {
+  if (IsInlined(rep_)) return static_cast<int>(InlinedRepToCode(rep_));
+  return static_cast<int>(RepToPointer(rep_)->code());
+}
+
+inline absl::string_view Status::message() const {
+  return !IsInlined(rep_)
+             ? RepToPointer(rep_)->message()
+             : (IsMovedFrom(rep_) ? absl::string_view(kMovedFromString)
+                                  : absl::string_view());
+}
+
+inline bool operator==(const Status& lhs, const Status& rhs) {
+  if (lhs.rep_ == rhs.rep_) return true;
+  if (Status::IsInlined(lhs.rep_)) return false;
+  if (Status::IsInlined(rhs.rep_)) return false;
+  return *Status::RepToPointer(lhs.rep_) == *Status::RepToPointer(rhs.rep_);
+}
+
+inline bool operator!=(const Status& lhs, const Status& rhs) {
+  return !(lhs == rhs);
+}
+
+inline std::string Status::ToString(StatusToStringMode mode) const {
+  return ok() ? "OK" : ToStringSlow(rep_, mode);
+}
+
+inline void Status::IgnoreError() const {
+  // no-op
+}
+
+inline void swap(absl::Status& a, absl::Status& b) {
+  using std::swap;
+  swap(a.rep_, b.rep_);
+}
+
+inline absl::optional<absl::Cord> Status::GetPayload(
+    absl::string_view type_url) const {
+  if (IsInlined(rep_)) return absl::nullopt;
+  return RepToPointer(rep_)->GetPayload(type_url);
+}
+
+inline void Status::SetPayload(absl::string_view type_url, absl::Cord payload) {
+  if (ok()) return;
+  status_internal::StatusRep* rep = PrepareToModify(rep_);
+  rep->SetPayload(type_url, std::move(payload));
+  rep_ = PointerToRep(rep);
+}
+
+inline bool Status::ErasePayload(absl::string_view type_url) {
+  if (IsInlined(rep_)) return false;
+  status_internal::StatusRep* rep = PrepareToModify(rep_);
+  auto res = rep->ErasePayload(type_url);
+  rep_ = res.new_rep;
+  return res.erased;
+}
+
+inline void Status::ForEachPayload(
+    absl::FunctionRef<void(absl::string_view, const absl::Cord&)> visitor)
+    const {
+  if (IsInlined(rep_)) return;
+  RepToPointer(rep_)->ForEachPayload(visitor);
+}
+
+constexpr bool Status::IsInlined(uintptr_t rep) { return (rep & 1) != 0; }
+
+constexpr bool Status::IsMovedFrom(uintptr_t rep) { return (rep & 2) != 0; }
+
+constexpr uintptr_t Status::CodeToInlinedRep(absl::StatusCode code) {
+  return (static_cast<uintptr_t>(code) << 2) + 1;
+}
+
+constexpr absl::StatusCode Status::InlinedRepToCode(uintptr_t rep) {
+  ABSL_ASSERT(IsInlined(rep));
+  return static_cast<absl::StatusCode>(rep >> 2);
+}
+
+constexpr uintptr_t Status::MovedFromRep() {
+  return CodeToInlinedRep(absl::StatusCode::kInternal) | 2;
+}
+
+inline absl::Nonnull<const status_internal::StatusRep*> Status::RepToPointer(
+    uintptr_t rep) {
+  assert(!IsInlined(rep));
+  return reinterpret_cast<const status_internal::StatusRep*>(rep);
+}
+
+inline uintptr_t Status::PointerToRep(
+    absl::Nonnull<status_internal::StatusRep*> rep) {
+  return reinterpret_cast<uintptr_t>(rep);
+}
+
+inline void Status::Ref(uintptr_t rep) {
+  if (!IsInlined(rep)) RepToPointer(rep)->Ref();
+}
+
+inline void Status::Unref(uintptr_t rep) {
+  if (!IsInlined(rep)) RepToPointer(rep)->Unref();
+}
+
+inline Status OkStatus() { return Status(); }
+
+// Creates a `Status` object with the `absl::StatusCode::kCancelled` error code
+// and an empty message. It is provided only for efficiency, given that
+// message-less kCancelled errors are common in the infrastructure.
+inline Status CancelledError() { return Status(absl::StatusCode::kCancelled); }
+
+// Retrieves a message's status as a null terminated C string. The lifetime of
+// this string is tied to the lifetime of the status object itself.
+//
+// If the status's message is empty, the empty string is returned.
+//
+// StatusMessageAsCStr exists for C support. Use `status.message()` in C++.
+absl::Nonnull<const char*> StatusMessageAsCStr(
+    const Status& status ABSL_ATTRIBUTE_LIFETIME_BOUND);
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STATUS_STATUS_H_
diff --git a/weight/_dep/abseil-cpp/absl/status/status_payload_printer.cc b/weight/_dep/abseil-cpp/absl/status/status_payload_printer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..98401e9072216e70307c70cfc3b9ad69f530dd7a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/status_payload_printer.cc
@@ -0,0 +1,36 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#include "absl/status/status_payload_printer.h"
+
+#include "absl/base/config.h"
+#include "absl/base/internal/atomic_hook.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace status_internal {
+
+ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
+static absl::base_internal::AtomicHook<StatusPayloadPrinter> storage;
+
+void SetStatusPayloadPrinter(StatusPayloadPrinter printer) {
+  storage.Store(printer);
+}
+
+StatusPayloadPrinter GetStatusPayloadPrinter() {
+  return storage.Load();
+}
+
+}  // namespace status_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/status/status_payload_printer.h b/weight/_dep/abseil-cpp/absl/status/status_payload_printer.h
new file mode 100644
index 0000000000000000000000000000000000000000..f22255e1c6cd27dc64c903419afaab19b5a4c3f0
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/status_payload_printer.h
@@ -0,0 +1,52 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#ifndef ABSL_STATUS_STATUS_PAYLOAD_PRINTER_H_
+#define ABSL_STATUS_STATUS_PAYLOAD_PRINTER_H_
+
+#include <string>
+
+#include "absl/base/nullability.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace status_internal {
+
+// By default, `Status::ToString` and `operator<<(Status)` print a payload by
+// dumping the type URL and the raw bytes. To help debugging, we provide an
+// extension point, which is a global printer function that can be set by users
+// to specify how to print payloads. The function takes the type URL and the
+// payload as input, and should return a valid human-readable string on success
+// or `absl::nullopt` on failure (in which case it falls back to the default
+// approach of printing the raw bytes).
+// NOTE: This is an internal API and the design is subject to change in the
+// future in a non-backward-compatible way. Since it's only meant for debugging
+// purpose, you should not rely on it in any critical logic.
+using StatusPayloadPrinter = absl::Nullable<absl::optional<std::string> (*)(
+    absl::string_view, const absl::Cord&)>;
+
+// Sets the global payload printer. Only one printer should be set per process.
+// If multiple printers are set, it's undefined which one will be used.
+void SetStatusPayloadPrinter(StatusPayloadPrinter);
+
+// Returns the global payload printer if previously set, otherwise `nullptr`.
+StatusPayloadPrinter GetStatusPayloadPrinter();
+
+}  // namespace status_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STATUS_STATUS_PAYLOAD_PRINTER_H_
diff --git a/weight/_dep/abseil-cpp/absl/status/status_test.cc b/weight/_dep/abseil-cpp/absl/status/status_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..585e78076c1628e45a8e2b00bae7c3d332d570c9
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/status_test.cc
@@ -0,0 +1,579 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/status/status.h"
+
+#include <errno.h>
+
+#include <array>
+#include <cstddef>
+#include <sstream>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+
+namespace {
+
+using ::testing::Eq;
+using ::testing::HasSubstr;
+using ::testing::Optional;
+using ::testing::UnorderedElementsAreArray;
+
+TEST(StatusCode, InsertionOperator) {
+  const absl::StatusCode code = absl::StatusCode::kUnknown;
+  std::ostringstream oss;
+  oss << code;
+  EXPECT_EQ(oss.str(), absl::StatusCodeToString(code));
+}
+
+// This structure holds the details for testing a single error code,
+// its creator, and its classifier.
+struct ErrorTest {
+  absl::StatusCode code;
+  using Creator = absl::Status (*)(
+      absl::string_view
+  );
+  using Classifier = bool (*)(const absl::Status&);
+  Creator creator;
+  Classifier classifier;
+};
+
+constexpr ErrorTest kErrorTests[]{
+    {absl::StatusCode::kCancelled, absl::CancelledError, absl::IsCancelled},
+    {absl::StatusCode::kUnknown, absl::UnknownError, absl::IsUnknown},
+    {absl::StatusCode::kInvalidArgument, absl::InvalidArgumentError,
+     absl::IsInvalidArgument},
+    {absl::StatusCode::kDeadlineExceeded, absl::DeadlineExceededError,
+     absl::IsDeadlineExceeded},
+    {absl::StatusCode::kNotFound, absl::NotFoundError, absl::IsNotFound},
+    {absl::StatusCode::kAlreadyExists, absl::AlreadyExistsError,
+     absl::IsAlreadyExists},
+    {absl::StatusCode::kPermissionDenied, absl::PermissionDeniedError,
+     absl::IsPermissionDenied},
+    {absl::StatusCode::kResourceExhausted, absl::ResourceExhaustedError,
+     absl::IsResourceExhausted},
+    {absl::StatusCode::kFailedPrecondition, absl::FailedPreconditionError,
+     absl::IsFailedPrecondition},
+    {absl::StatusCode::kAborted, absl::AbortedError, absl::IsAborted},
+    {absl::StatusCode::kOutOfRange, absl::OutOfRangeError, absl::IsOutOfRange},
+    {absl::StatusCode::kUnimplemented, absl::UnimplementedError,
+     absl::IsUnimplemented},
+    {absl::StatusCode::kInternal, absl::InternalError, absl::IsInternal},
+    {absl::StatusCode::kUnavailable, absl::UnavailableError,
+     absl::IsUnavailable},
+    {absl::StatusCode::kDataLoss, absl::DataLossError, absl::IsDataLoss},
+    {absl::StatusCode::kUnauthenticated, absl::UnauthenticatedError,
+     absl::IsUnauthenticated},
+};
+
+TEST(Status, CreateAndClassify) {
+  for (const auto& test : kErrorTests) {
+    SCOPED_TRACE(absl::StatusCodeToString(test.code));
+
+    // Ensure that the creator does, in fact, create status objects with the
+    // expected error code and message.
+    std::string message =
+        absl::StrCat("error code ", test.code, " test message");
+    absl::Status status = test.creator(
+        message
+    );
+    EXPECT_EQ(test.code, status.code());
+    EXPECT_EQ(message, status.message());
+
+    // Ensure that the classifier returns true for a status produced by the
+    // creator.
+    EXPECT_TRUE(test.classifier(status));
+
+    // Ensure that the classifier returns false for status with a different
+    // code.
+    for (const auto& other : kErrorTests) {
+      if (other.code != test.code) {
+        EXPECT_FALSE(test.classifier(absl::Status(other.code, "")))
+            << " other.code = " << other.code;
+      }
+    }
+  }
+}
+
+TEST(Status, DefaultConstructor) {
+  absl::Status status;
+  EXPECT_TRUE(status.ok());
+  EXPECT_EQ(absl::StatusCode::kOk, status.code());
+  EXPECT_EQ("", status.message());
+}
+
+TEST(Status, OkStatus) {
+  absl::Status status = absl::OkStatus();
+  EXPECT_TRUE(status.ok());
+  EXPECT_EQ(absl::StatusCode::kOk, status.code());
+  EXPECT_EQ("", status.message());
+}
+
+TEST(Status, ConstructorWithCodeMessage) {
+  {
+    absl::Status status(absl::StatusCode::kCancelled, "");
+    EXPECT_FALSE(status.ok());
+    EXPECT_EQ(absl::StatusCode::kCancelled, status.code());
+    EXPECT_EQ("", status.message());
+  }
+  {
+    absl::Status status(absl::StatusCode::kInternal, "message");
+    EXPECT_FALSE(status.ok());
+    EXPECT_EQ(absl::StatusCode::kInternal, status.code());
+    EXPECT_EQ("message", status.message());
+  }
+}
+
+TEST(Status, StatusMessageCStringTest) {
+  {
+    absl::Status status = absl::OkStatus();
+    EXPECT_EQ(status.message(), "");
+    EXPECT_STREQ(absl::StatusMessageAsCStr(status), "");
+    EXPECT_EQ(status.message(), absl::StatusMessageAsCStr(status));
+    EXPECT_NE(absl::StatusMessageAsCStr(status), nullptr);
+  }
+  {
+    absl::Status status;
+    EXPECT_EQ(status.message(), "");
+    EXPECT_NE(absl::StatusMessageAsCStr(status), nullptr);
+    EXPECT_STREQ(absl::StatusMessageAsCStr(status), "");
+  }
+  {
+    absl::Status status(absl::StatusCode::kInternal, "message");
+    EXPECT_FALSE(status.ok());
+    EXPECT_EQ(absl::StatusCode::kInternal, status.code());
+    EXPECT_EQ("message", status.message());
+    EXPECT_STREQ("message", absl::StatusMessageAsCStr(status));
+  }
+}
+
+TEST(Status, ConstructOutOfRangeCode) {
+  const int kRawCode = 9999;
+  absl::Status status(static_cast<absl::StatusCode>(kRawCode), "");
+  EXPECT_EQ(absl::StatusCode::kUnknown, status.code());
+  EXPECT_EQ(kRawCode, status.raw_code());
+}
+
+constexpr char kUrl1[] = "url.payload.1";
+constexpr char kUrl2[] = "url.payload.2";
+constexpr char kUrl3[] = "url.payload.3";
+constexpr char kUrl4[] = "url.payload.xx";
+
+constexpr char kPayload1[] = "aaaaa";
+constexpr char kPayload2[] = "bbbbb";
+constexpr char kPayload3[] = "ccccc";
+
+using PayloadsVec = std::vector<std::pair<std::string, absl::Cord>>;
+
+TEST(Status, TestGetSetPayload) {
+  absl::Status ok_status = absl::OkStatus();
+  ok_status.SetPayload(kUrl1, absl::Cord(kPayload1));
+  ok_status.SetPayload(kUrl2, absl::Cord(kPayload2));
+
+  EXPECT_FALSE(ok_status.GetPayload(kUrl1));
+  EXPECT_FALSE(ok_status.GetPayload(kUrl2));
+
+  absl::Status bad_status(absl::StatusCode::kInternal, "fail");
+  bad_status.SetPayload(kUrl1, absl::Cord(kPayload1));
+  bad_status.SetPayload(kUrl2, absl::Cord(kPayload2));
+
+  EXPECT_THAT(bad_status.GetPayload(kUrl1), Optional(Eq(kPayload1)));
+  EXPECT_THAT(bad_status.GetPayload(kUrl2), Optional(Eq(kPayload2)));
+
+  EXPECT_FALSE(bad_status.GetPayload(kUrl3));
+
+  bad_status.SetPayload(kUrl1, absl::Cord(kPayload3));
+  EXPECT_THAT(bad_status.GetPayload(kUrl1), Optional(Eq(kPayload3)));
+
+  // Testing dynamically generated type_url
+  bad_status.SetPayload(absl::StrCat(kUrl1, ".1"), absl::Cord(kPayload1));
+  EXPECT_THAT(bad_status.GetPayload(absl::StrCat(kUrl1, ".1")),
+              Optional(Eq(kPayload1)));
+}
+
+TEST(Status, TestErasePayload) {
+  absl::Status bad_status(absl::StatusCode::kInternal, "fail");
+  bad_status.SetPayload(kUrl1, absl::Cord(kPayload1));
+  bad_status.SetPayload(kUrl2, absl::Cord(kPayload2));
+  bad_status.SetPayload(kUrl3, absl::Cord(kPayload3));
+
+  EXPECT_FALSE(bad_status.ErasePayload(kUrl4));
+
+  EXPECT_TRUE(bad_status.GetPayload(kUrl2));
+  EXPECT_TRUE(bad_status.ErasePayload(kUrl2));
+  EXPECT_FALSE(bad_status.GetPayload(kUrl2));
+  EXPECT_FALSE(bad_status.ErasePayload(kUrl2));
+
+  EXPECT_TRUE(bad_status.ErasePayload(kUrl1));
+  EXPECT_TRUE(bad_status.ErasePayload(kUrl3));
+
+  bad_status.SetPayload(kUrl1, absl::Cord(kPayload1));
+  EXPECT_TRUE(bad_status.ErasePayload(kUrl1));
+}
+
+TEST(Status, TestComparePayloads) {
+  absl::Status bad_status1(absl::StatusCode::kInternal, "fail");
+  bad_status1.SetPayload(kUrl1, absl::Cord(kPayload1));
+  bad_status1.SetPayload(kUrl2, absl::Cord(kPayload2));
+  bad_status1.SetPayload(kUrl3, absl::Cord(kPayload3));
+
+  absl::Status bad_status2(absl::StatusCode::kInternal, "fail");
+  bad_status2.SetPayload(kUrl2, absl::Cord(kPayload2));
+  bad_status2.SetPayload(kUrl3, absl::Cord(kPayload3));
+  bad_status2.SetPayload(kUrl1, absl::Cord(kPayload1));
+
+  EXPECT_EQ(bad_status1, bad_status2);
+}
+
+TEST(Status, TestComparePayloadsAfterErase) {
+  absl::Status payload_status(absl::StatusCode::kInternal, "");
+  payload_status.SetPayload(kUrl1, absl::Cord(kPayload1));
+  payload_status.SetPayload(kUrl2, absl::Cord(kPayload2));
+
+  absl::Status empty_status(absl::StatusCode::kInternal, "");
+
+  // Different payloads, not equal
+  EXPECT_NE(payload_status, empty_status);
+  EXPECT_TRUE(payload_status.ErasePayload(kUrl1));
+
+  // Still Different payloads, still not equal.
+  EXPECT_NE(payload_status, empty_status);
+  EXPECT_TRUE(payload_status.ErasePayload(kUrl2));
+
+  // Both empty payloads, should be equal
+  EXPECT_EQ(payload_status, empty_status);
+}
+
+PayloadsVec AllVisitedPayloads(const absl::Status& s) {
+  PayloadsVec result;
+
+  s.ForEachPayload([&](absl::string_view type_url, const absl::Cord& payload) {
+    result.push_back(std::make_pair(std::string(type_url), payload));
+  });
+
+  return result;
+}
+
+TEST(Status, TestForEachPayload) {
+  absl::Status bad_status(absl::StatusCode::kInternal, "fail");
+  bad_status.SetPayload(kUrl1, absl::Cord(kPayload1));
+  bad_status.SetPayload(kUrl2, absl::Cord(kPayload2));
+  bad_status.SetPayload(kUrl3, absl::Cord(kPayload3));
+
+  int count = 0;
+
+  bad_status.ForEachPayload(
+      [&count](absl::string_view, const absl::Cord&) { ++count; });
+
+  EXPECT_EQ(count, 3);
+
+  PayloadsVec expected_payloads = {{kUrl1, absl::Cord(kPayload1)},
+                                   {kUrl2, absl::Cord(kPayload2)},
+                                   {kUrl3, absl::Cord(kPayload3)}};
+
+  // Test that we visit all the payloads in the status.
+  PayloadsVec visited_payloads = AllVisitedPayloads(bad_status);
+  EXPECT_THAT(visited_payloads, UnorderedElementsAreArray(expected_payloads));
+
+  // Test that visitation order is not consistent between run.
+  std::vector<absl::Status> scratch;
+  while (true) {
+    scratch.emplace_back(absl::StatusCode::kInternal, "fail");
+
+    scratch.back().SetPayload(kUrl1, absl::Cord(kPayload1));
+    scratch.back().SetPayload(kUrl2, absl::Cord(kPayload2));
+    scratch.back().SetPayload(kUrl3, absl::Cord(kPayload3));
+
+    if (AllVisitedPayloads(scratch.back()) != visited_payloads) {
+      break;
+    }
+  }
+}
+
+TEST(Status, ToString) {
+  absl::Status status(absl::StatusCode::kInternal, "fail");
+  EXPECT_EQ("INTERNAL: fail", status.ToString());
+  status.SetPayload("foo", absl::Cord("bar"));
+  EXPECT_EQ("INTERNAL: fail [foo='bar']", status.ToString());
+  status.SetPayload("bar", absl::Cord("\377"));
+  EXPECT_THAT(status.ToString(),
+              AllOf(HasSubstr("INTERNAL: fail"), HasSubstr("[foo='bar']"),
+                    HasSubstr("[bar='\\xff']")));
+}
+
+TEST(Status, ToStringMode) {
+  absl::Status status(absl::StatusCode::kInternal, "fail");
+  status.SetPayload("foo", absl::Cord("bar"));
+  status.SetPayload("bar", absl::Cord("\377"));
+
+  EXPECT_EQ("INTERNAL: fail",
+            status.ToString(absl::StatusToStringMode::kWithNoExtraData));
+
+  EXPECT_THAT(status.ToString(absl::StatusToStringMode::kWithPayload),
+              AllOf(HasSubstr("INTERNAL: fail"), HasSubstr("[foo='bar']"),
+                    HasSubstr("[bar='\\xff']")));
+
+  EXPECT_THAT(status.ToString(absl::StatusToStringMode::kWithEverything),
+              AllOf(HasSubstr("INTERNAL: fail"), HasSubstr("[foo='bar']"),
+                    HasSubstr("[bar='\\xff']")));
+
+  EXPECT_THAT(status.ToString(~absl::StatusToStringMode::kWithPayload),
+              AllOf(HasSubstr("INTERNAL: fail"), Not(HasSubstr("[foo='bar']")),
+                    Not(HasSubstr("[bar='\\xff']"))));
+}
+
+TEST(Status, OstreamOperator) {
+  absl::Status status(absl::StatusCode::kInternal, "fail");
+  { std::stringstream stream;
+    stream << status;
+    EXPECT_EQ("INTERNAL: fail", stream.str());
+  }
+  status.SetPayload("foo", absl::Cord("bar"));
+  { std::stringstream stream;
+    stream << status;
+    EXPECT_EQ("INTERNAL: fail [foo='bar']", stream.str());
+  }
+  status.SetPayload("bar", absl::Cord("\377"));
+  { std::stringstream stream;
+    stream << status;
+    EXPECT_THAT(stream.str(),
+                AllOf(HasSubstr("INTERNAL: fail"), HasSubstr("[foo='bar']"),
+                      HasSubstr("[bar='\\xff']")));
+  }
+}
+
+TEST(Status, AbslStringify) {
+  absl::Status status(absl::StatusCode::kInternal, "fail");
+  EXPECT_EQ("INTERNAL: fail", absl::StrCat(status));
+  EXPECT_EQ("INTERNAL: fail", absl::StrFormat("%v", status));
+  status.SetPayload("foo", absl::Cord("bar"));
+  EXPECT_EQ("INTERNAL: fail [foo='bar']", absl::StrCat(status));
+  status.SetPayload("bar", absl::Cord("\377"));
+  EXPECT_THAT(absl::StrCat(status),
+              AllOf(HasSubstr("INTERNAL: fail"), HasSubstr("[foo='bar']"),
+                    HasSubstr("[bar='\\xff']")));
+}
+
+TEST(Status, OstreamEqStringify) {
+  absl::Status status(absl::StatusCode::kUnknown, "fail");
+  status.SetPayload("foo", absl::Cord("bar"));
+  std::stringstream stream;
+  stream << status;
+  EXPECT_EQ(stream.str(), absl::StrCat(status));
+}
+
+absl::Status EraseAndReturn(const absl::Status& base) {
+  absl::Status copy = base;
+  EXPECT_TRUE(copy.ErasePayload(kUrl1));
+  return copy;
+}
+
+TEST(Status, CopyOnWriteForErasePayload) {
+  {
+    absl::Status base(absl::StatusCode::kInvalidArgument, "fail");
+    base.SetPayload(kUrl1, absl::Cord(kPayload1));
+    EXPECT_TRUE(base.GetPayload(kUrl1).has_value());
+    absl::Status copy = EraseAndReturn(base);
+    EXPECT_TRUE(base.GetPayload(kUrl1).has_value());
+    EXPECT_FALSE(copy.GetPayload(kUrl1).has_value());
+  }
+  {
+    absl::Status base(absl::StatusCode::kInvalidArgument, "fail");
+    base.SetPayload(kUrl1, absl::Cord(kPayload1));
+    absl::Status copy = base;
+
+    EXPECT_TRUE(base.GetPayload(kUrl1).has_value());
+    EXPECT_TRUE(copy.GetPayload(kUrl1).has_value());
+
+    EXPECT_TRUE(base.ErasePayload(kUrl1));
+
+    EXPECT_FALSE(base.GetPayload(kUrl1).has_value());
+    EXPECT_TRUE(copy.GetPayload(kUrl1).has_value());
+  }
+}
+
+TEST(Status, CopyConstructor) {
+  {
+    absl::Status status;
+    absl::Status copy(status);
+    EXPECT_EQ(copy, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    absl::Status copy(status);
+    EXPECT_EQ(copy, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    status.SetPayload(kUrl1, absl::Cord(kPayload1));
+    absl::Status copy(status);
+    EXPECT_EQ(copy, status);
+  }
+}
+
+TEST(Status, CopyAssignment) {
+  absl::Status assignee;
+  {
+    absl::Status status;
+    assignee = status;
+    EXPECT_EQ(assignee, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    assignee = status;
+    EXPECT_EQ(assignee, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    status.SetPayload(kUrl1, absl::Cord(kPayload1));
+    assignee = status;
+    EXPECT_EQ(assignee, status);
+  }
+}
+
+TEST(Status, CopyAssignmentIsNotRef) {
+  const absl::Status status_orig(absl::StatusCode::kInvalidArgument, "message");
+  absl::Status status_copy = status_orig;
+  EXPECT_EQ(status_orig, status_copy);
+  status_copy.SetPayload(kUrl1, absl::Cord(kPayload1));
+  EXPECT_NE(status_orig, status_copy);
+}
+
+TEST(Status, MoveConstructor) {
+  {
+    absl::Status status;
+    absl::Status copy(absl::Status{});
+    EXPECT_EQ(copy, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    absl::Status copy(
+        absl::Status(absl::StatusCode::kInvalidArgument, "message"));
+    EXPECT_EQ(copy, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    status.SetPayload(kUrl1, absl::Cord(kPayload1));
+    absl::Status copy1(status);
+    absl::Status copy2(std::move(status));
+    EXPECT_EQ(copy1, copy2);
+  }
+}
+
+TEST(Status, MoveAssignment) {
+  absl::Status assignee;
+  {
+    absl::Status status;
+    assignee = absl::Status();
+    EXPECT_EQ(assignee, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    assignee = absl::Status(absl::StatusCode::kInvalidArgument, "message");
+    EXPECT_EQ(assignee, status);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    status.SetPayload(kUrl1, absl::Cord(kPayload1));
+    absl::Status copy(status);
+    assignee = std::move(status);
+    EXPECT_EQ(assignee, copy);
+  }
+  {
+    absl::Status status(absl::StatusCode::kInvalidArgument, "message");
+    absl::Status copy(status);
+    status = static_cast<absl::Status&&>(status);
+    EXPECT_EQ(status, copy);
+  }
+}
+
+TEST(Status, Update) {
+  absl::Status s;
+  s.Update(absl::OkStatus());
+  EXPECT_TRUE(s.ok());
+  const absl::Status a(absl::StatusCode::kCancelled, "message");
+  s.Update(a);
+  EXPECT_EQ(s, a);
+  const absl::Status b(absl::StatusCode::kInternal, "other message");
+  s.Update(b);
+  EXPECT_EQ(s, a);
+  s.Update(absl::OkStatus());
+  EXPECT_EQ(s, a);
+  EXPECT_FALSE(s.ok());
+}
+
+TEST(Status, Equality) {
+  absl::Status ok;
+  absl::Status no_payload = absl::CancelledError("no payload");
+  absl::Status one_payload = absl::InvalidArgumentError("one payload");
+  one_payload.SetPayload(kUrl1, absl::Cord(kPayload1));
+  absl::Status two_payloads = one_payload;
+  two_payloads.SetPayload(kUrl2, absl::Cord(kPayload2));
+  const std::array<absl::Status, 4> status_arr = {ok, no_payload, one_payload,
+                                                  two_payloads};
+  for (int i = 0; i < status_arr.size(); i++) {
+    for (int j = 0; j < status_arr.size(); j++) {
+      if (i == j) {
+        EXPECT_TRUE(status_arr[i] == status_arr[j]);
+        EXPECT_FALSE(status_arr[i] != status_arr[j]);
+      } else {
+        EXPECT_TRUE(status_arr[i] != status_arr[j]);
+        EXPECT_FALSE(status_arr[i] == status_arr[j]);
+      }
+    }
+  }
+}
+
+TEST(Status, Swap) {
+  auto test_swap = [](const absl::Status& s1, const absl::Status& s2) {
+    absl::Status copy1 = s1, copy2 = s2;
+    swap(copy1, copy2);
+    EXPECT_EQ(copy1, s2);
+    EXPECT_EQ(copy2, s1);
+  };
+  const absl::Status ok;
+  const absl::Status no_payload(absl::StatusCode::kAlreadyExists, "no payload");
+  absl::Status with_payload(absl::StatusCode::kInternal, "with payload");
+  with_payload.SetPayload(kUrl1, absl::Cord(kPayload1));
+  test_swap(ok, no_payload);
+  test_swap(no_payload, ok);
+  test_swap(ok, with_payload);
+  test_swap(with_payload, ok);
+  test_swap(no_payload, with_payload);
+  test_swap(with_payload, no_payload);
+}
+
+TEST(StatusErrno, ErrnoToStatusCode) {
+  EXPECT_EQ(absl::ErrnoToStatusCode(0), absl::StatusCode::kOk);
+
+  // Spot-check a few errno values.
+  EXPECT_EQ(absl::ErrnoToStatusCode(EINVAL),
+            absl::StatusCode::kInvalidArgument);
+  EXPECT_EQ(absl::ErrnoToStatusCode(ENOENT), absl::StatusCode::kNotFound);
+
+  // We'll pick a very large number so it hopefully doesn't collide to errno.
+  EXPECT_EQ(absl::ErrnoToStatusCode(19980927), absl::StatusCode::kUnknown);
+}
+
+TEST(StatusErrno, ErrnoToStatus) {
+  absl::Status status = absl::ErrnoToStatus(ENOENT, "Cannot open 'path'");
+  EXPECT_EQ(status.code(), absl::StatusCode::kNotFound);
+  EXPECT_EQ(status.message(), "Cannot open 'path': No such file or directory");
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/status/statusor_test.cc b/weight/_dep/abseil-cpp/absl/status/statusor_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..09ffc65889e46a87478ade3f221436fd8739e59a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/status/statusor_test.cc
@@ -0,0 +1,1921 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/status/statusor.h"
+
+#include <array>
+#include <cstddef>
+#include <initializer_list>
+#include <map>
+#include <memory>
+#include <ostream>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/casts.h"
+#include "absl/memory/memory.h"
+#include "absl/status/status.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/any.h"
+#include "absl/types/variant.h"
+#include "absl/utility/utility.h"
+
+namespace {
+
+using ::testing::AllOf;
+using ::testing::AnyOf;
+using ::testing::AnyWith;
+using ::testing::ElementsAre;
+using ::testing::EndsWith;
+using ::testing::Field;
+using ::testing::HasSubstr;
+using ::testing::Ne;
+using ::testing::Not;
+using ::testing::Pointee;
+using ::testing::StartsWith;
+using ::testing::VariantWith;
+
+#ifdef GTEST_HAS_STATUS_MATCHERS
+using ::testing::status::IsOk;
+using ::testing::status::IsOkAndHolds;
+#else  // GTEST_HAS_STATUS_MATCHERS
+inline const ::absl::Status& GetStatus(const ::absl::Status& status) {
+  return status;
+}
+
+template <typename T>
+inline const ::absl::Status& GetStatus(const ::absl::StatusOr<T>& status) {
+  return status.status();
+}
+
+// Monomorphic implementation of matcher IsOkAndHolds(m).  StatusOrType is a
+// reference to StatusOr<T>.
+template <typename StatusOrType>
+class IsOkAndHoldsMatcherImpl
+    : public ::testing::MatcherInterface<StatusOrType> {
+ public:
+  typedef
+      typename std::remove_reference<StatusOrType>::type::value_type value_type;
+
+  template <typename InnerMatcher>
+  explicit IsOkAndHoldsMatcherImpl(InnerMatcher&& inner_matcher)
+      : inner_matcher_(::testing::SafeMatcherCast<const value_type&>(
+            std::forward<InnerMatcher>(inner_matcher))) {}
+
+  void DescribeTo(std::ostream* os) const override {
+    *os << "is OK and has a value that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const override {
+    *os << "isn't OK or has a value that ";
+    inner_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(
+      StatusOrType actual_value,
+      ::testing::MatchResultListener* result_listener) const override {
+    if (!actual_value.ok()) {
+      *result_listener << "which has status " << actual_value.status();
+      return false;
+    }
+
+    ::testing::StringMatchResultListener inner_listener;
+    const bool matches =
+        inner_matcher_.MatchAndExplain(*actual_value, &inner_listener);
+    const std::string inner_explanation = inner_listener.str();
+    if (!inner_explanation.empty()) {
+      *result_listener << "which contains value "
+                       << ::testing::PrintToString(*actual_value) << ", "
+                       << inner_explanation;
+    }
+    return matches;
+  }
+
+ private:
+  const ::testing::Matcher<const value_type&> inner_matcher_;
+};
+
+// Implements IsOkAndHolds(m) as a polymorphic matcher.
+template <typename InnerMatcher>
+class IsOkAndHoldsMatcher {
+ public:
+  explicit IsOkAndHoldsMatcher(InnerMatcher inner_matcher)
+      : inner_matcher_(std::move(inner_matcher)) {}
+
+  // Converts this polymorphic matcher to a monomorphic matcher of the
+  // given type.  StatusOrType can be either StatusOr<T> or a
+  // reference to StatusOr<T>.
+  template <typename StatusOrType>
+  operator ::testing::Matcher<StatusOrType>() const {  // NOLINT
+    return ::testing::Matcher<StatusOrType>(
+        new IsOkAndHoldsMatcherImpl<const StatusOrType&>(inner_matcher_));
+  }
+
+ private:
+  const InnerMatcher inner_matcher_;
+};
+
+// Monomorphic implementation of matcher IsOk() for a given type T.
+// T can be Status, StatusOr<>, or a reference to either of them.
+template <typename T>
+class MonoIsOkMatcherImpl : public ::testing::MatcherInterface<T> {
+ public:
+  void DescribeTo(std::ostream* os) const override { *os << "is OK"; }
+  void DescribeNegationTo(std::ostream* os) const override {
+    *os << "is not OK";
+  }
+  bool MatchAndExplain(T actual_value,
+                       ::testing::MatchResultListener*) const override {
+    return GetStatus(actual_value).ok();
+  }
+};
+
+// Implements IsOk() as a polymorphic matcher.
+class IsOkMatcher {
+ public:
+  template <typename T>
+  operator ::testing::Matcher<T>() const {  // NOLINT
+    return ::testing::Matcher<T>(new MonoIsOkMatcherImpl<T>());
+  }
+};
+
+// Macros for testing the results of functions that return absl::Status or
+// absl::StatusOr<T> (for any type T).
+#define EXPECT_OK(expression) EXPECT_THAT(expression, IsOk())
+
+// Returns a gMock matcher that matches a StatusOr<> whose status is
+// OK and whose value matches the inner matcher.
+template <typename InnerMatcher>
+IsOkAndHoldsMatcher<typename std::decay<InnerMatcher>::type> IsOkAndHolds(
+    InnerMatcher&& inner_matcher) {
+  return IsOkAndHoldsMatcher<typename std::decay<InnerMatcher>::type>(
+      std::forward<InnerMatcher>(inner_matcher));
+}
+
+// Returns a gMock matcher that matches a Status or StatusOr<> which is OK.
+inline IsOkMatcher IsOk() { return IsOkMatcher(); }
+#endif  // GTEST_HAS_STATUS_MATCHERS
+
+struct CopyDetector {
+  CopyDetector() = default;
+  explicit CopyDetector(int xx) : x(xx) {}
+  CopyDetector(CopyDetector&& d) noexcept
+      : x(d.x), copied(false), moved(true) {}
+  CopyDetector(const CopyDetector& d) : x(d.x), copied(true), moved(false) {}
+  CopyDetector& operator=(const CopyDetector& c) {
+    x = c.x;
+    copied = true;
+    moved = false;
+    return *this;
+  }
+  CopyDetector& operator=(CopyDetector&& c) noexcept {
+    x = c.x;
+    copied = false;
+    moved = true;
+    return *this;
+  }
+  int x = 0;
+  bool copied = false;
+  bool moved = false;
+};
+
+testing::Matcher<const CopyDetector&> CopyDetectorHas(int a, bool b, bool c) {
+  return AllOf(Field(&CopyDetector::x, a), Field(&CopyDetector::moved, b),
+               Field(&CopyDetector::copied, c));
+}
+
+class Base1 {
+ public:
+  virtual ~Base1() {}
+  int pad;
+};
+
+class Base2 {
+ public:
+  virtual ~Base2() {}
+  int yetotherpad;
+};
+
+class Derived : public Base1, public Base2 {
+ public:
+  virtual ~Derived() {}
+  int evenmorepad;
+};
+
+class CopyNoAssign {
+ public:
+  explicit CopyNoAssign(int value) : foo(value) {}
+  CopyNoAssign(const CopyNoAssign& other) : foo(other.foo) {}
+  int foo;
+
+ private:
+  const CopyNoAssign& operator=(const CopyNoAssign&);
+};
+
+absl::StatusOr<std::unique_ptr<int>> ReturnUniquePtr() {
+  // Uses implicit constructor from T&&
+  return absl::make_unique<int>(0);
+}
+
+TEST(StatusOr, ElementType) {
+  static_assert(std::is_same<absl::StatusOr<int>::value_type, int>(), "");
+  static_assert(std::is_same<absl::StatusOr<char>::value_type, char>(), "");
+}
+
+TEST(StatusOr, TestMoveOnlyInitialization) {
+  absl::StatusOr<std::unique_ptr<int>> thing(ReturnUniquePtr());
+  ASSERT_TRUE(thing.ok());
+  EXPECT_EQ(0, **thing);
+  int* previous = thing->get();
+
+  thing = ReturnUniquePtr();
+  EXPECT_TRUE(thing.ok());
+  EXPECT_EQ(0, **thing);
+  EXPECT_NE(previous, thing->get());
+}
+
+TEST(StatusOr, TestMoveOnlyValueExtraction) {
+  absl::StatusOr<std::unique_ptr<int>> thing(ReturnUniquePtr());
+  ASSERT_TRUE(thing.ok());
+  std::unique_ptr<int> ptr = *std::move(thing);
+  EXPECT_EQ(0, *ptr);
+
+  thing = std::move(ptr);
+  ptr = std::move(*thing);
+  EXPECT_EQ(0, *ptr);
+}
+
+TEST(StatusOr, TestMoveOnlyInitializationFromTemporaryByValueOrDie) {
+  std::unique_ptr<int> ptr(*ReturnUniquePtr());
+  EXPECT_EQ(0, *ptr);
+}
+
+TEST(StatusOr, TestValueOrDieOverloadForConstTemporary) {
+  static_assert(
+      std::is_same<
+          const int&&,
+          decltype(std::declval<const absl::StatusOr<int>&&>().value())>(),
+      "value() for const temporaries should return const T&&");
+}
+
+TEST(StatusOr, TestMoveOnlyConversion) {
+  absl::StatusOr<std::unique_ptr<const int>> const_thing(ReturnUniquePtr());
+  EXPECT_TRUE(const_thing.ok());
+  EXPECT_EQ(0, **const_thing);
+
+  // Test rvalue converting assignment
+  const int* const_previous = const_thing->get();
+  const_thing = ReturnUniquePtr();
+  EXPECT_TRUE(const_thing.ok());
+  EXPECT_EQ(0, **const_thing);
+  EXPECT_NE(const_previous, const_thing->get());
+}
+
+TEST(StatusOr, TestMoveOnlyVector) {
+  // Sanity check that absl::StatusOr<MoveOnly> works in vector.
+  std::vector<absl::StatusOr<std::unique_ptr<int>>> vec;
+  vec.push_back(ReturnUniquePtr());
+  vec.resize(2);
+  auto another_vec = std::move(vec);
+  EXPECT_EQ(0, **another_vec[0]);
+  EXPECT_EQ(absl::UnknownError(""), another_vec[1].status());
+}
+
+TEST(StatusOr, TestDefaultCtor) {
+  absl::StatusOr<int> thing;
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(thing.status().code(), absl::StatusCode::kUnknown);
+}
+
+TEST(StatusOr, StatusCtorForwards) {
+  absl::Status status(absl::StatusCode::kInternal, "Some error");
+
+  EXPECT_EQ(absl::StatusOr<int>(status).status().message(), "Some error");
+  EXPECT_EQ(status.message(), "Some error");
+
+  EXPECT_EQ(absl::StatusOr<int>(std::move(status)).status().message(),
+            "Some error");
+  EXPECT_NE(status.message(), "Some error");
+}
+
+TEST(BadStatusOrAccessTest, CopyConstructionWhatOk) {
+  absl::Status error =
+      absl::InternalError("some arbitrary message too big for the sso buffer");
+  absl::BadStatusOrAccess e1{error};
+  absl::BadStatusOrAccess e2{e1};
+  EXPECT_THAT(e1.what(), HasSubstr(error.ToString()));
+  EXPECT_THAT(e2.what(), HasSubstr(error.ToString()));
+}
+
+TEST(BadStatusOrAccessTest, CopyAssignmentWhatOk) {
+  absl::Status error =
+      absl::InternalError("some arbitrary message too big for the sso buffer");
+  absl::BadStatusOrAccess e1{error};
+  absl::BadStatusOrAccess e2{absl::InternalError("other")};
+  e2 = e1;
+  EXPECT_THAT(e1.what(), HasSubstr(error.ToString()));
+  EXPECT_THAT(e2.what(), HasSubstr(error.ToString()));
+}
+
+TEST(BadStatusOrAccessTest, MoveConstructionWhatOk) {
+  absl::Status error =
+      absl::InternalError("some arbitrary message too big for the sso buffer");
+  absl::BadStatusOrAccess e1{error};
+  absl::BadStatusOrAccess e2{std::move(e1)};
+  EXPECT_THAT(e2.what(), HasSubstr(error.ToString()));
+}
+
+TEST(BadStatusOrAccessTest, MoveAssignmentWhatOk) {
+  absl::Status error =
+      absl::InternalError("some arbitrary message too big for the sso buffer");
+  absl::BadStatusOrAccess e1{error};
+  absl::BadStatusOrAccess e2{absl::InternalError("other")};
+  e2 = std::move(e1);
+  EXPECT_THAT(e2.what(), HasSubstr(error.ToString()));
+}
+
+// Define `EXPECT_DEATH_OR_THROW` to test the behavior of `StatusOr::value`,
+// which either throws `BadStatusOrAccess` or `LOG(FATAL)` based on whether
+// exceptions are enabled.
+#ifdef ABSL_HAVE_EXCEPTIONS
+#define EXPECT_DEATH_OR_THROW(statement, status_)                  \
+  EXPECT_THROW(                                                    \
+      {                                                            \
+        try {                                                      \
+          statement;                                               \
+        } catch (const absl::BadStatusOrAccess& e) {               \
+          EXPECT_EQ(e.status(), status_);                          \
+          EXPECT_THAT(e.what(), HasSubstr(e.status().ToString())); \
+          throw;                                                   \
+        }                                                          \
+      },                                                           \
+      absl::BadStatusOrAccess);
+#else  // ABSL_HAVE_EXCEPTIONS
+#define EXPECT_DEATH_OR_THROW(statement, status) \
+  EXPECT_DEATH_IF_SUPPORTED(statement, status.ToString());
+#endif  // ABSL_HAVE_EXCEPTIONS
+
+TEST(StatusOrDeathTest, TestDefaultCtorValue) {
+  absl::StatusOr<int> thing;
+  EXPECT_DEATH_OR_THROW(thing.value(), absl::UnknownError(""));
+  const absl::StatusOr<int> thing2;
+  EXPECT_DEATH_OR_THROW(thing2.value(), absl::UnknownError(""));
+}
+
+TEST(StatusOrDeathTest, TestValueNotOk) {
+  absl::StatusOr<int> thing(absl::CancelledError());
+  EXPECT_DEATH_OR_THROW(thing.value(), absl::CancelledError());
+}
+
+TEST(StatusOrDeathTest, TestValueNotOkConst) {
+  const absl::StatusOr<int> thing(absl::UnknownError(""));
+  EXPECT_DEATH_OR_THROW(thing.value(), absl::UnknownError(""));
+}
+
+TEST(StatusOrDeathTest, TestPointerDefaultCtorValue) {
+  absl::StatusOr<int*> thing;
+  EXPECT_DEATH_OR_THROW(thing.value(), absl::UnknownError(""));
+}
+
+TEST(StatusOrDeathTest, TestPointerValueNotOk) {
+  absl::StatusOr<int*> thing(absl::CancelledError());
+  EXPECT_DEATH_OR_THROW(thing.value(), absl::CancelledError());
+}
+
+TEST(StatusOrDeathTest, TestPointerValueNotOkConst) {
+  const absl::StatusOr<int*> thing(absl::CancelledError());
+  EXPECT_DEATH_OR_THROW(thing.value(), absl::CancelledError());
+}
+
+#if GTEST_HAS_DEATH_TEST
+TEST(StatusOrDeathTest, TestStatusCtorStatusOk) {
+  EXPECT_DEBUG_DEATH(
+      {
+        // This will DCHECK
+        absl::StatusOr<int> thing(absl::OkStatus());
+        // In optimized mode, we are actually going to get error::INTERNAL for
+        // status here, rather than crashing, so check that.
+        EXPECT_FALSE(thing.ok());
+        EXPECT_EQ(thing.status().code(), absl::StatusCode::kInternal);
+      },
+      "An OK status is not a valid constructor argument");
+}
+
+TEST(StatusOrDeathTest, TestPointerStatusCtorStatusOk) {
+  EXPECT_DEBUG_DEATH(
+      {
+        absl::StatusOr<int*> thing(absl::OkStatus());
+        // In optimized mode, we are actually going to get error::INTERNAL for
+        // status here, rather than crashing, so check that.
+        EXPECT_FALSE(thing.ok());
+        EXPECT_EQ(thing.status().code(), absl::StatusCode::kInternal);
+      },
+      "An OK status is not a valid constructor argument");
+}
+#endif
+
+TEST(StatusOr, ValueAccessor) {
+  const int kIntValue = 110;
+  {
+    absl::StatusOr<int> status_or(kIntValue);
+    EXPECT_EQ(kIntValue, status_or.value());
+    EXPECT_EQ(kIntValue, std::move(status_or).value());
+  }
+  {
+    absl::StatusOr<CopyDetector> status_or(kIntValue);
+    EXPECT_THAT(status_or,
+                IsOkAndHolds(CopyDetectorHas(kIntValue, false, false)));
+    CopyDetector copy_detector = status_or.value();
+    EXPECT_THAT(copy_detector, CopyDetectorHas(kIntValue, false, true));
+    copy_detector = std::move(status_or).value();
+    EXPECT_THAT(copy_detector, CopyDetectorHas(kIntValue, true, false));
+  }
+}
+
+TEST(StatusOr, BadValueAccess) {
+  const absl::Status kError = absl::CancelledError("message");
+  absl::StatusOr<int> status_or(kError);
+  EXPECT_DEATH_OR_THROW(status_or.value(), kError);
+}
+
+TEST(StatusOr, TestStatusCtor) {
+  absl::StatusOr<int> thing(absl::CancelledError());
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(thing.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestValueCtor) {
+  const int kI = 4;
+  const absl::StatusOr<int> thing(kI);
+  EXPECT_TRUE(thing.ok());
+  EXPECT_EQ(kI, *thing);
+}
+
+struct Foo {
+  const int x;
+  explicit Foo(int y) : x(y) {}
+};
+
+TEST(StatusOr, InPlaceConstruction) {
+  EXPECT_THAT(absl::StatusOr<Foo>(absl::in_place, 10),
+              IsOkAndHolds(Field(&Foo::x, 10)));
+}
+
+struct InPlaceHelper {
+  InPlaceHelper(std::initializer_list<int> xs, std::unique_ptr<int> yy)
+      : x(xs), y(std::move(yy)) {}
+  const std::vector<int> x;
+  std::unique_ptr<int> y;
+};
+
+TEST(StatusOr, InPlaceInitListConstruction) {
+  absl::StatusOr<InPlaceHelper> status_or(absl::in_place, {10, 11, 12},
+                                          absl::make_unique<int>(13));
+  EXPECT_THAT(status_or, IsOkAndHolds(AllOf(
+                             Field(&InPlaceHelper::x, ElementsAre(10, 11, 12)),
+                             Field(&InPlaceHelper::y, Pointee(13)))));
+}
+
+TEST(StatusOr, Emplace) {
+  absl::StatusOr<Foo> status_or_foo(10);
+  status_or_foo.emplace(20);
+  EXPECT_THAT(status_or_foo, IsOkAndHolds(Field(&Foo::x, 20)));
+  status_or_foo = absl::InvalidArgumentError("msg");
+  EXPECT_FALSE(status_or_foo.ok());
+  EXPECT_EQ(status_or_foo.status().code(), absl::StatusCode::kInvalidArgument);
+  EXPECT_EQ(status_or_foo.status().message(), "msg");
+  status_or_foo.emplace(20);
+  EXPECT_THAT(status_or_foo, IsOkAndHolds(Field(&Foo::x, 20)));
+}
+
+TEST(StatusOr, EmplaceInitializerList) {
+  absl::StatusOr<InPlaceHelper> status_or(absl::in_place, {10, 11, 12},
+                                          absl::make_unique<int>(13));
+  status_or.emplace({1, 2, 3}, absl::make_unique<int>(4));
+  EXPECT_THAT(status_or,
+              IsOkAndHolds(AllOf(Field(&InPlaceHelper::x, ElementsAre(1, 2, 3)),
+                                 Field(&InPlaceHelper::y, Pointee(4)))));
+  status_or = absl::InvalidArgumentError("msg");
+  EXPECT_FALSE(status_or.ok());
+  EXPECT_EQ(status_or.status().code(), absl::StatusCode::kInvalidArgument);
+  EXPECT_EQ(status_or.status().message(), "msg");
+  status_or.emplace({1, 2, 3}, absl::make_unique<int>(4));
+  EXPECT_THAT(status_or,
+              IsOkAndHolds(AllOf(Field(&InPlaceHelper::x, ElementsAre(1, 2, 3)),
+                                 Field(&InPlaceHelper::y, Pointee(4)))));
+}
+
+TEST(StatusOr, TestCopyCtorStatusOk) {
+  const int kI = 4;
+  const absl::StatusOr<int> original(kI);
+  const absl::StatusOr<int> copy(original);
+  EXPECT_OK(copy.status());
+  EXPECT_EQ(*original, *copy);
+}
+
+TEST(StatusOr, TestCopyCtorStatusNotOk) {
+  absl::StatusOr<int> original(absl::CancelledError());
+  absl::StatusOr<int> copy(original);
+  EXPECT_EQ(copy.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestCopyCtorNonAssignable) {
+  const int kI = 4;
+  CopyNoAssign value(kI);
+  absl::StatusOr<CopyNoAssign> original(value);
+  absl::StatusOr<CopyNoAssign> copy(original);
+  EXPECT_OK(copy.status());
+  EXPECT_EQ(original->foo, copy->foo);
+}
+
+TEST(StatusOr, TestCopyCtorStatusOKConverting) {
+  const int kI = 4;
+  absl::StatusOr<int> original(kI);
+  absl::StatusOr<double> copy(original);
+  EXPECT_OK(copy.status());
+  EXPECT_DOUBLE_EQ(*original, *copy);
+}
+
+TEST(StatusOr, TestCopyCtorStatusNotOkConverting) {
+  absl::StatusOr<int> original(absl::CancelledError());
+  absl::StatusOr<double> copy(original);
+  EXPECT_EQ(copy.status(), original.status());
+}
+
+TEST(StatusOr, TestAssignmentStatusOk) {
+  // Copy assignmment
+  {
+    const auto p = std::make_shared<int>(17);
+    absl::StatusOr<std::shared_ptr<int>> source(p);
+
+    absl::StatusOr<std::shared_ptr<int>> target;
+    target = source;
+
+    ASSERT_TRUE(target.ok());
+    EXPECT_OK(target.status());
+    EXPECT_EQ(p, *target);
+
+    ASSERT_TRUE(source.ok());
+    EXPECT_OK(source.status());
+    EXPECT_EQ(p, *source);
+  }
+
+  // Move asssignment
+  {
+    const auto p = std::make_shared<int>(17);
+    absl::StatusOr<std::shared_ptr<int>> source(p);
+
+    absl::StatusOr<std::shared_ptr<int>> target;
+    target = std::move(source);
+
+    ASSERT_TRUE(target.ok());
+    EXPECT_OK(target.status());
+    EXPECT_EQ(p, *target);
+
+    ASSERT_TRUE(source.ok());
+    EXPECT_OK(source.status());
+    EXPECT_EQ(nullptr, *source);
+  }
+}
+
+TEST(StatusOr, TestAssignmentStatusNotOk) {
+  // Copy assignment
+  {
+    const absl::Status expected = absl::CancelledError();
+    absl::StatusOr<int> source(expected);
+
+    absl::StatusOr<int> target;
+    target = source;
+
+    EXPECT_FALSE(target.ok());
+    EXPECT_EQ(expected, target.status());
+
+    EXPECT_FALSE(source.ok());
+    EXPECT_EQ(expected, source.status());
+  }
+
+  // Move assignment
+  {
+    const absl::Status expected = absl::CancelledError();
+    absl::StatusOr<int> source(expected);
+
+    absl::StatusOr<int> target;
+    target = std::move(source);
+
+    EXPECT_FALSE(target.ok());
+    EXPECT_EQ(expected, target.status());
+
+    EXPECT_FALSE(source.ok());
+    EXPECT_EQ(source.status().code(), absl::StatusCode::kInternal);
+  }
+}
+
+TEST(StatusOr, TestAssignmentStatusOKConverting) {
+  // Copy assignment
+  {
+    const int kI = 4;
+    absl::StatusOr<int> source(kI);
+
+    absl::StatusOr<double> target;
+    target = source;
+
+    ASSERT_TRUE(target.ok());
+    EXPECT_OK(target.status());
+    EXPECT_DOUBLE_EQ(kI, *target);
+
+    ASSERT_TRUE(source.ok());
+    EXPECT_OK(source.status());
+    EXPECT_DOUBLE_EQ(kI, *source);
+  }
+
+  // Move assignment
+  {
+    const auto p = new int(17);
+    absl::StatusOr<std::unique_ptr<int>> source(absl::WrapUnique(p));
+
+    absl::StatusOr<std::shared_ptr<int>> target;
+    target = std::move(source);
+
+    ASSERT_TRUE(target.ok());
+    EXPECT_OK(target.status());
+    EXPECT_EQ(p, target->get());
+
+    ASSERT_TRUE(source.ok());
+    EXPECT_OK(source.status());
+    EXPECT_EQ(nullptr, source->get());
+  }
+}
+
+struct A {
+  int x;
+};
+
+struct ImplicitConstructibleFromA {
+  int x;
+  bool moved;
+  ImplicitConstructibleFromA(const A& a)  // NOLINT
+      : x(a.x), moved(false) {}
+  ImplicitConstructibleFromA(A&& a)  // NOLINT
+      : x(a.x), moved(true) {}
+};
+
+TEST(StatusOr, ImplicitConvertingConstructor) {
+  EXPECT_THAT(
+      absl::implicit_cast<absl::StatusOr<ImplicitConstructibleFromA>>(
+          absl::StatusOr<A>(A{11})),
+      IsOkAndHolds(AllOf(Field(&ImplicitConstructibleFromA::x, 11),
+                         Field(&ImplicitConstructibleFromA::moved, true))));
+  absl::StatusOr<A> a(A{12});
+  EXPECT_THAT(
+      absl::implicit_cast<absl::StatusOr<ImplicitConstructibleFromA>>(a),
+      IsOkAndHolds(AllOf(Field(&ImplicitConstructibleFromA::x, 12),
+                         Field(&ImplicitConstructibleFromA::moved, false))));
+}
+
+struct ExplicitConstructibleFromA {
+  int x;
+  bool moved;
+  explicit ExplicitConstructibleFromA(const A& a) : x(a.x), moved(false) {}
+  explicit ExplicitConstructibleFromA(A&& a) : x(a.x), moved(true) {}
+};
+
+TEST(StatusOr, ExplicitConvertingConstructor) {
+  EXPECT_FALSE(
+      (std::is_convertible<const absl::StatusOr<A>&,
+                           absl::StatusOr<ExplicitConstructibleFromA>>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::StatusOr<A>&&,
+                           absl::StatusOr<ExplicitConstructibleFromA>>::value));
+  EXPECT_THAT(
+      absl::StatusOr<ExplicitConstructibleFromA>(absl::StatusOr<A>(A{11})),
+      IsOkAndHolds(AllOf(Field(&ExplicitConstructibleFromA::x, 11),
+                         Field(&ExplicitConstructibleFromA::moved, true))));
+  absl::StatusOr<A> a(A{12});
+  EXPECT_THAT(
+      absl::StatusOr<ExplicitConstructibleFromA>(a),
+      IsOkAndHolds(AllOf(Field(&ExplicitConstructibleFromA::x, 12),
+                         Field(&ExplicitConstructibleFromA::moved, false))));
+}
+
+struct ImplicitConstructibleFromBool {
+  ImplicitConstructibleFromBool(bool y) : x(y) {}  // NOLINT
+  bool x = false;
+};
+
+struct ConvertibleToBool {
+  explicit ConvertibleToBool(bool y) : x(y) {}
+  operator bool() const { return x; }  // NOLINT
+  bool x = false;
+};
+
+TEST(StatusOr, ImplicitBooleanConstructionWithImplicitCasts) {
+  EXPECT_THAT(absl::StatusOr<bool>(absl::StatusOr<ConvertibleToBool>(true)),
+              IsOkAndHolds(true));
+  EXPECT_THAT(absl::StatusOr<bool>(absl::StatusOr<ConvertibleToBool>(false)),
+              IsOkAndHolds(false));
+  EXPECT_THAT(
+      absl::implicit_cast<absl::StatusOr<ImplicitConstructibleFromBool>>(
+          absl::StatusOr<bool>(false)),
+      IsOkAndHolds(Field(&ImplicitConstructibleFromBool::x, false)));
+  EXPECT_FALSE((std::is_convertible<
+                absl::StatusOr<ConvertibleToBool>,
+                absl::StatusOr<ImplicitConstructibleFromBool>>::value));
+}
+
+TEST(StatusOr, BooleanConstructionWithImplicitCasts) {
+  EXPECT_THAT(absl::StatusOr<bool>(absl::StatusOr<ConvertibleToBool>(true)),
+              IsOkAndHolds(true));
+  EXPECT_THAT(absl::StatusOr<bool>(absl::StatusOr<ConvertibleToBool>(false)),
+              IsOkAndHolds(false));
+  EXPECT_THAT(
+      absl::StatusOr<ImplicitConstructibleFromBool>{
+          absl::StatusOr<bool>(false)},
+      IsOkAndHolds(Field(&ImplicitConstructibleFromBool::x, false)));
+  EXPECT_THAT(
+      absl::StatusOr<ImplicitConstructibleFromBool>{
+          absl::StatusOr<bool>(absl::InvalidArgumentError(""))},
+      Not(IsOk()));
+
+  EXPECT_THAT(
+      absl::StatusOr<ImplicitConstructibleFromBool>{
+          absl::StatusOr<ConvertibleToBool>(ConvertibleToBool{false})},
+      IsOkAndHolds(Field(&ImplicitConstructibleFromBool::x, false)));
+  EXPECT_THAT(
+      absl::StatusOr<ImplicitConstructibleFromBool>{
+          absl::StatusOr<ConvertibleToBool>(absl::InvalidArgumentError(""))},
+      Not(IsOk()));
+}
+
+TEST(StatusOr, ConstImplicitCast) {
+  EXPECT_THAT(absl::implicit_cast<absl::StatusOr<bool>>(
+                  absl::StatusOr<const bool>(true)),
+              IsOkAndHolds(true));
+  EXPECT_THAT(absl::implicit_cast<absl::StatusOr<bool>>(
+                  absl::StatusOr<const bool>(false)),
+              IsOkAndHolds(false));
+  EXPECT_THAT(absl::implicit_cast<absl::StatusOr<const bool>>(
+                  absl::StatusOr<bool>(true)),
+              IsOkAndHolds(true));
+  EXPECT_THAT(absl::implicit_cast<absl::StatusOr<const bool>>(
+                  absl::StatusOr<bool>(false)),
+              IsOkAndHolds(false));
+  EXPECT_THAT(absl::implicit_cast<absl::StatusOr<const std::string>>(
+                  absl::StatusOr<std::string>("foo")),
+              IsOkAndHolds("foo"));
+  EXPECT_THAT(absl::implicit_cast<absl::StatusOr<std::string>>(
+                  absl::StatusOr<const std::string>("foo")),
+              IsOkAndHolds("foo"));
+  EXPECT_THAT(
+      absl::implicit_cast<absl::StatusOr<std::shared_ptr<const std::string>>>(
+          absl::StatusOr<std::shared_ptr<std::string>>(
+              std::make_shared<std::string>("foo"))),
+      IsOkAndHolds(Pointee(std::string("foo"))));
+}
+
+TEST(StatusOr, ConstExplicitConstruction) {
+  EXPECT_THAT(absl::StatusOr<bool>(absl::StatusOr<const bool>(true)),
+              IsOkAndHolds(true));
+  EXPECT_THAT(absl::StatusOr<bool>(absl::StatusOr<const bool>(false)),
+              IsOkAndHolds(false));
+  EXPECT_THAT(absl::StatusOr<const bool>(absl::StatusOr<bool>(true)),
+              IsOkAndHolds(true));
+  EXPECT_THAT(absl::StatusOr<const bool>(absl::StatusOr<bool>(false)),
+              IsOkAndHolds(false));
+}
+
+struct ExplicitConstructibleFromInt {
+  int x;
+  explicit ExplicitConstructibleFromInt(int y) : x(y) {}
+};
+
+TEST(StatusOr, ExplicitConstruction) {
+  EXPECT_THAT(absl::StatusOr<ExplicitConstructibleFromInt>(10),
+              IsOkAndHolds(Field(&ExplicitConstructibleFromInt::x, 10)));
+}
+
+TEST(StatusOr, ImplicitConstruction) {
+  // Check implicit casting works.
+  auto status_or =
+      absl::implicit_cast<absl::StatusOr<absl::variant<int, std::string>>>(10);
+  EXPECT_THAT(status_or, IsOkAndHolds(VariantWith<int>(10)));
+}
+
+TEST(StatusOr, ImplicitConstructionFromInitliazerList) {
+  // Note: dropping the explicit std::initializer_list<int> is not supported
+  // by absl::StatusOr or absl::optional.
+  auto status_or =
+      absl::implicit_cast<absl::StatusOr<std::vector<int>>>({{10, 20, 30}});
+  EXPECT_THAT(status_or, IsOkAndHolds(ElementsAre(10, 20, 30)));
+}
+
+TEST(StatusOr, UniquePtrImplicitConstruction) {
+  auto status_or = absl::implicit_cast<absl::StatusOr<std::unique_ptr<Base1>>>(
+      absl::make_unique<Derived>());
+  EXPECT_THAT(status_or, IsOkAndHolds(Ne(nullptr)));
+}
+
+TEST(StatusOr, NestedStatusOrCopyAndMoveConstructorTests) {
+  absl::StatusOr<absl::StatusOr<CopyDetector>> status_or = CopyDetector(10);
+  absl::StatusOr<absl::StatusOr<CopyDetector>> status_error =
+      absl::InvalidArgumentError("foo");
+  EXPECT_THAT(status_or,
+              IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, true, false))));
+  absl::StatusOr<absl::StatusOr<CopyDetector>> a = status_or;
+  EXPECT_THAT(a, IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, false, true))));
+  absl::StatusOr<absl::StatusOr<CopyDetector>> a_err = status_error;
+  EXPECT_THAT(a_err, Not(IsOk()));
+
+  const absl::StatusOr<absl::StatusOr<CopyDetector>>& cref = status_or;
+  absl::StatusOr<absl::StatusOr<CopyDetector>> b = cref;  // NOLINT
+  EXPECT_THAT(b, IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, false, true))));
+  const absl::StatusOr<absl::StatusOr<CopyDetector>>& cref_err = status_error;
+  absl::StatusOr<absl::StatusOr<CopyDetector>> b_err = cref_err;  // NOLINT
+  EXPECT_THAT(b_err, Not(IsOk()));
+
+  absl::StatusOr<absl::StatusOr<CopyDetector>> c = std::move(status_or);
+  EXPECT_THAT(c, IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, true, false))));
+  absl::StatusOr<absl::StatusOr<CopyDetector>> c_err = std::move(status_error);
+  EXPECT_THAT(c_err, Not(IsOk()));
+}
+
+TEST(StatusOr, NestedStatusOrCopyAndMoveAssignment) {
+  absl::StatusOr<absl::StatusOr<CopyDetector>> status_or = CopyDetector(10);
+  absl::StatusOr<absl::StatusOr<CopyDetector>> status_error =
+      absl::InvalidArgumentError("foo");
+  absl::StatusOr<absl::StatusOr<CopyDetector>> a;
+  a = status_or;
+  EXPECT_THAT(a, IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, false, true))));
+  a = status_error;
+  EXPECT_THAT(a, Not(IsOk()));
+
+  const absl::StatusOr<absl::StatusOr<CopyDetector>>& cref = status_or;
+  a = cref;
+  EXPECT_THAT(a, IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, false, true))));
+  const absl::StatusOr<absl::StatusOr<CopyDetector>>& cref_err = status_error;
+  a = cref_err;
+  EXPECT_THAT(a, Not(IsOk()));
+  a = std::move(status_or);
+  EXPECT_THAT(a, IsOkAndHolds(IsOkAndHolds(CopyDetectorHas(10, true, false))));
+  a = std::move(status_error);
+  EXPECT_THAT(a, Not(IsOk()));
+}
+
+struct Copyable {
+  Copyable() {}
+  Copyable(const Copyable&) {}
+  Copyable& operator=(const Copyable&) { return *this; }
+};
+
+struct MoveOnly {
+  MoveOnly() {}
+  MoveOnly(MoveOnly&&) {}
+  MoveOnly& operator=(MoveOnly&&) { return *this; }
+};
+
+struct NonMovable {
+  NonMovable() {}
+  NonMovable(const NonMovable&) = delete;
+  NonMovable(NonMovable&&) = delete;
+  NonMovable& operator=(const NonMovable&) = delete;
+  NonMovable& operator=(NonMovable&&) = delete;
+};
+
+TEST(StatusOr, CopyAndMoveAbility) {
+  EXPECT_TRUE(std::is_copy_constructible<Copyable>::value);
+  EXPECT_TRUE(std::is_copy_assignable<Copyable>::value);
+  EXPECT_TRUE(std::is_move_constructible<Copyable>::value);
+  EXPECT_TRUE(std::is_move_assignable<Copyable>::value);
+  EXPECT_FALSE(std::is_copy_constructible<MoveOnly>::value);
+  EXPECT_FALSE(std::is_copy_assignable<MoveOnly>::value);
+  EXPECT_TRUE(std::is_move_constructible<MoveOnly>::value);
+  EXPECT_TRUE(std::is_move_assignable<MoveOnly>::value);
+  EXPECT_FALSE(std::is_copy_constructible<NonMovable>::value);
+  EXPECT_FALSE(std::is_copy_assignable<NonMovable>::value);
+  EXPECT_FALSE(std::is_move_constructible<NonMovable>::value);
+  EXPECT_FALSE(std::is_move_assignable<NonMovable>::value);
+}
+
+TEST(StatusOr, StatusOrAnyCopyAndMoveConstructorTests) {
+  absl::StatusOr<absl::any> status_or = CopyDetector(10);
+  absl::StatusOr<absl::any> status_error = absl::InvalidArgumentError("foo");
+  EXPECT_THAT(
+      status_or,
+      IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, true, false))));
+  absl::StatusOr<absl::any> a = status_or;
+  EXPECT_THAT(
+      a, IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, false, true))));
+  absl::StatusOr<absl::any> a_err = status_error;
+  EXPECT_THAT(a_err, Not(IsOk()));
+
+  const absl::StatusOr<absl::any>& cref = status_or;
+  // No lint for no-change copy.
+  absl::StatusOr<absl::any> b = cref;  // NOLINT
+  EXPECT_THAT(
+      b, IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, false, true))));
+  const absl::StatusOr<absl::any>& cref_err = status_error;
+  // No lint for no-change copy.
+  absl::StatusOr<absl::any> b_err = cref_err;  // NOLINT
+  EXPECT_THAT(b_err, Not(IsOk()));
+
+  absl::StatusOr<absl::any> c = std::move(status_or);
+  EXPECT_THAT(
+      c, IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, true, false))));
+  absl::StatusOr<absl::any> c_err = std::move(status_error);
+  EXPECT_THAT(c_err, Not(IsOk()));
+}
+
+TEST(StatusOr, StatusOrAnyCopyAndMoveAssignment) {
+  absl::StatusOr<absl::any> status_or = CopyDetector(10);
+  absl::StatusOr<absl::any> status_error = absl::InvalidArgumentError("foo");
+  absl::StatusOr<absl::any> a;
+  a = status_or;
+  EXPECT_THAT(
+      a, IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, false, true))));
+  a = status_error;
+  EXPECT_THAT(a, Not(IsOk()));
+
+  const absl::StatusOr<absl::any>& cref = status_or;
+  a = cref;
+  EXPECT_THAT(
+      a, IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, false, true))));
+  const absl::StatusOr<absl::any>& cref_err = status_error;
+  a = cref_err;
+  EXPECT_THAT(a, Not(IsOk()));
+  a = std::move(status_or);
+  EXPECT_THAT(
+      a, IsOkAndHolds(AnyWith<CopyDetector>(CopyDetectorHas(10, true, false))));
+  a = std::move(status_error);
+  EXPECT_THAT(a, Not(IsOk()));
+}
+
+TEST(StatusOr, StatusOrCopyAndMoveTestsConstructor) {
+  absl::StatusOr<CopyDetector> status_or(10);
+  ASSERT_THAT(status_or, IsOkAndHolds(CopyDetectorHas(10, false, false)));
+  absl::StatusOr<CopyDetector> a(status_or);
+  EXPECT_THAT(a, IsOkAndHolds(CopyDetectorHas(10, false, true)));
+  const absl::StatusOr<CopyDetector>& cref = status_or;
+  absl::StatusOr<CopyDetector> b(cref);  // NOLINT
+  EXPECT_THAT(b, IsOkAndHolds(CopyDetectorHas(10, false, true)));
+  absl::StatusOr<CopyDetector> c(std::move(status_or));
+  EXPECT_THAT(c, IsOkAndHolds(CopyDetectorHas(10, true, false)));
+}
+
+TEST(StatusOr, StatusOrCopyAndMoveTestsAssignment) {
+  absl::StatusOr<CopyDetector> status_or(10);
+  ASSERT_THAT(status_or, IsOkAndHolds(CopyDetectorHas(10, false, false)));
+  absl::StatusOr<CopyDetector> a;
+  a = status_or;
+  EXPECT_THAT(a, IsOkAndHolds(CopyDetectorHas(10, false, true)));
+  const absl::StatusOr<CopyDetector>& cref = status_or;
+  absl::StatusOr<CopyDetector> b;
+  b = cref;
+  EXPECT_THAT(b, IsOkAndHolds(CopyDetectorHas(10, false, true)));
+  absl::StatusOr<CopyDetector> c;
+  c = std::move(status_or);
+  EXPECT_THAT(c, IsOkAndHolds(CopyDetectorHas(10, true, false)));
+}
+
+TEST(StatusOr, AbslAnyAssignment) {
+  EXPECT_FALSE((std::is_assignable<absl::StatusOr<absl::any>,
+                                   absl::StatusOr<int>>::value));
+  absl::StatusOr<absl::any> status_or;
+  status_or = absl::InvalidArgumentError("foo");
+  EXPECT_THAT(status_or, Not(IsOk()));
+}
+
+TEST(StatusOr, ImplicitAssignment) {
+  absl::StatusOr<absl::variant<int, std::string>> status_or;
+  status_or = 10;
+  EXPECT_THAT(status_or, IsOkAndHolds(VariantWith<int>(10)));
+}
+
+TEST(StatusOr, SelfDirectInitAssignment) {
+  absl::StatusOr<std::vector<int>> status_or = {{10, 20, 30}};
+  status_or = *status_or;
+  EXPECT_THAT(status_or, IsOkAndHolds(ElementsAre(10, 20, 30)));
+}
+
+TEST(StatusOr, ImplicitCastFromInitializerList) {
+  absl::StatusOr<std::vector<int>> status_or = {{10, 20, 30}};
+  EXPECT_THAT(status_or, IsOkAndHolds(ElementsAre(10, 20, 30)));
+}
+
+TEST(StatusOr, UniquePtrImplicitAssignment) {
+  absl::StatusOr<std::unique_ptr<Base1>> status_or;
+  status_or = absl::make_unique<Derived>();
+  EXPECT_THAT(status_or, IsOkAndHolds(Ne(nullptr)));
+}
+
+TEST(StatusOr, Pointer) {
+  struct A {};
+  struct B : public A {};
+  struct C : private A {};
+
+  EXPECT_TRUE((std::is_constructible<absl::StatusOr<A*>, B*>::value));
+  EXPECT_TRUE((std::is_convertible<B*, absl::StatusOr<A*>>::value));
+  EXPECT_FALSE((std::is_constructible<absl::StatusOr<A*>, C*>::value));
+  EXPECT_FALSE((std::is_convertible<C*, absl::StatusOr<A*>>::value));
+}
+
+TEST(StatusOr, TestAssignmentStatusNotOkConverting) {
+  // Copy assignment
+  {
+    const absl::Status expected = absl::CancelledError();
+    absl::StatusOr<int> source(expected);
+
+    absl::StatusOr<double> target;
+    target = source;
+
+    EXPECT_FALSE(target.ok());
+    EXPECT_EQ(expected, target.status());
+
+    EXPECT_FALSE(source.ok());
+    EXPECT_EQ(expected, source.status());
+  }
+
+  // Move assignment
+  {
+    const absl::Status expected = absl::CancelledError();
+    absl::StatusOr<int> source(expected);
+
+    absl::StatusOr<double> target;
+    target = std::move(source);
+
+    EXPECT_FALSE(target.ok());
+    EXPECT_EQ(expected, target.status());
+
+    EXPECT_FALSE(source.ok());
+    EXPECT_EQ(source.status().code(), absl::StatusCode::kInternal);
+  }
+}
+
+TEST(StatusOr, SelfAssignment) {
+  // Copy-assignment, status OK
+  {
+    // A string long enough that it's likely to defeat any inline representation
+    // optimization.
+    const std::string long_str(128, 'a');
+
+    absl::StatusOr<std::string> so = long_str;
+    so = *&so;
+
+    ASSERT_TRUE(so.ok());
+    EXPECT_OK(so.status());
+    EXPECT_EQ(long_str, *so);
+  }
+
+  // Copy-assignment, error status
+  {
+    absl::StatusOr<int> so = absl::NotFoundError("taco");
+    so = *&so;
+
+    EXPECT_FALSE(so.ok());
+    EXPECT_EQ(so.status().code(), absl::StatusCode::kNotFound);
+    EXPECT_EQ(so.status().message(), "taco");
+  }
+
+  // Move-assignment with copyable type, status OK
+  {
+    absl::StatusOr<int> so = 17;
+
+    // Fool the compiler, which otherwise complains.
+    auto& same = so;
+    so = std::move(same);
+
+    ASSERT_TRUE(so.ok());
+    EXPECT_OK(so.status());
+    EXPECT_EQ(17, *so);
+  }
+
+  // Move-assignment with copyable type, error status
+  {
+    absl::StatusOr<int> so = absl::NotFoundError("taco");
+
+    // Fool the compiler, which otherwise complains.
+    auto& same = so;
+    so = std::move(same);
+
+    EXPECT_FALSE(so.ok());
+    EXPECT_EQ(so.status().code(), absl::StatusCode::kNotFound);
+    EXPECT_EQ(so.status().message(), "taco");
+  }
+
+  // Move-assignment with non-copyable type, status OK
+  {
+    const auto raw = new int(17);
+    absl::StatusOr<std::unique_ptr<int>> so = absl::WrapUnique(raw);
+
+    // Fool the compiler, which otherwise complains.
+    auto& same = so;
+    so = std::move(same);
+
+    ASSERT_TRUE(so.ok());
+    EXPECT_OK(so.status());
+    EXPECT_EQ(raw, so->get());
+  }
+
+  // Move-assignment with non-copyable type, error status
+  {
+    absl::StatusOr<std::unique_ptr<int>> so = absl::NotFoundError("taco");
+
+    // Fool the compiler, which otherwise complains.
+    auto& same = so;
+    so = std::move(same);
+
+    EXPECT_FALSE(so.ok());
+    EXPECT_EQ(so.status().code(), absl::StatusCode::kNotFound);
+    EXPECT_EQ(so.status().message(), "taco");
+  }
+}
+
+// These types form the overload sets of the constructors and the assignment
+// operators of `MockValue`. They distinguish construction from assignment,
+// lvalue from rvalue.
+struct FromConstructibleAssignableLvalue {};
+struct FromConstructibleAssignableRvalue {};
+struct FromImplicitConstructibleOnly {};
+struct FromAssignableOnly {};
+
+// This class is for testing the forwarding value assignments of `StatusOr`.
+// `from_rvalue` indicates whether the constructor or the assignment taking
+// rvalue reference is called. `from_assignment` indicates whether any
+// assignment is called.
+struct MockValue {
+  // Constructs `MockValue` from `FromConstructibleAssignableLvalue`.
+  MockValue(const FromConstructibleAssignableLvalue&)  // NOLINT
+      : from_rvalue(false), assigned(false) {}
+  // Constructs `MockValue` from `FromConstructibleAssignableRvalue`.
+  MockValue(FromConstructibleAssignableRvalue&&)  // NOLINT
+      : from_rvalue(true), assigned(false) {}
+  // Constructs `MockValue` from `FromImplicitConstructibleOnly`.
+  // `MockValue` is not assignable from `FromImplicitConstructibleOnly`.
+  MockValue(const FromImplicitConstructibleOnly&)  // NOLINT
+      : from_rvalue(false), assigned(false) {}
+  // Assigns `FromConstructibleAssignableLvalue`.
+  MockValue& operator=(const FromConstructibleAssignableLvalue&) {
+    from_rvalue = false;
+    assigned = true;
+    return *this;
+  }
+  // Assigns `FromConstructibleAssignableRvalue` (rvalue only).
+  MockValue& operator=(FromConstructibleAssignableRvalue&&) {
+    from_rvalue = true;
+    assigned = true;
+    return *this;
+  }
+  // Assigns `FromAssignableOnly`, but not constructible from
+  // `FromAssignableOnly`.
+  MockValue& operator=(const FromAssignableOnly&) {
+    from_rvalue = false;
+    assigned = true;
+    return *this;
+  }
+  bool from_rvalue;
+  bool assigned;
+};
+
+// operator=(U&&)
+TEST(StatusOr, PerfectForwardingAssignment) {
+  // U == T
+  constexpr int kValue1 = 10, kValue2 = 20;
+  absl::StatusOr<CopyDetector> status_or;
+  CopyDetector lvalue(kValue1);
+  status_or = lvalue;
+  EXPECT_THAT(status_or, IsOkAndHolds(CopyDetectorHas(kValue1, false, true)));
+  status_or = CopyDetector(kValue2);
+  EXPECT_THAT(status_or, IsOkAndHolds(CopyDetectorHas(kValue2, true, false)));
+
+  // U != T
+  EXPECT_TRUE(
+      (std::is_assignable<absl::StatusOr<MockValue>&,
+                          const FromConstructibleAssignableLvalue&>::value));
+  EXPECT_TRUE((std::is_assignable<absl::StatusOr<MockValue>&,
+                                  FromConstructibleAssignableLvalue&&>::value));
+  EXPECT_FALSE(
+      (std::is_assignable<absl::StatusOr<MockValue>&,
+                          const FromConstructibleAssignableRvalue&>::value));
+  EXPECT_TRUE((std::is_assignable<absl::StatusOr<MockValue>&,
+                                  FromConstructibleAssignableRvalue&&>::value));
+  EXPECT_TRUE(
+      (std::is_assignable<absl::StatusOr<MockValue>&,
+                          const FromImplicitConstructibleOnly&>::value));
+  EXPECT_FALSE((std::is_assignable<absl::StatusOr<MockValue>&,
+                                   const FromAssignableOnly&>::value));
+
+  absl::StatusOr<MockValue> from_lvalue(FromConstructibleAssignableLvalue{});
+  EXPECT_FALSE(from_lvalue->from_rvalue);
+  EXPECT_FALSE(from_lvalue->assigned);
+  from_lvalue = FromConstructibleAssignableLvalue{};
+  EXPECT_FALSE(from_lvalue->from_rvalue);
+  EXPECT_TRUE(from_lvalue->assigned);
+
+  absl::StatusOr<MockValue> from_rvalue(FromConstructibleAssignableRvalue{});
+  EXPECT_TRUE(from_rvalue->from_rvalue);
+  EXPECT_FALSE(from_rvalue->assigned);
+  from_rvalue = FromConstructibleAssignableRvalue{};
+  EXPECT_TRUE(from_rvalue->from_rvalue);
+  EXPECT_TRUE(from_rvalue->assigned);
+
+  absl::StatusOr<MockValue> from_implicit_constructible(
+      FromImplicitConstructibleOnly{});
+  EXPECT_FALSE(from_implicit_constructible->from_rvalue);
+  EXPECT_FALSE(from_implicit_constructible->assigned);
+  // construct a temporary `StatusOr` object and invoke the `StatusOr` move
+  // assignment operator.
+  from_implicit_constructible = FromImplicitConstructibleOnly{};
+  EXPECT_FALSE(from_implicit_constructible->from_rvalue);
+  EXPECT_FALSE(from_implicit_constructible->assigned);
+}
+
+TEST(StatusOr, TestStatus) {
+  absl::StatusOr<int> good(4);
+  EXPECT_TRUE(good.ok());
+  absl::StatusOr<int> bad(absl::CancelledError());
+  EXPECT_FALSE(bad.ok());
+  EXPECT_EQ(bad.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, OperatorStarRefQualifiers) {
+  static_assert(
+      std::is_same<const int&,
+                   decltype(*std::declval<const absl::StatusOr<int>&>())>(),
+      "Unexpected ref-qualifiers");
+  static_assert(
+      std::is_same<int&, decltype(*std::declval<absl::StatusOr<int>&>())>(),
+      "Unexpected ref-qualifiers");
+  static_assert(
+      std::is_same<const int&&,
+                   decltype(*std::declval<const absl::StatusOr<int>&&>())>(),
+      "Unexpected ref-qualifiers");
+  static_assert(
+      std::is_same<int&&, decltype(*std::declval<absl::StatusOr<int>&&>())>(),
+      "Unexpected ref-qualifiers");
+}
+
+TEST(StatusOr, OperatorStar) {
+  const absl::StatusOr<std::string> const_lvalue("hello");
+  EXPECT_EQ("hello", *const_lvalue);
+
+  absl::StatusOr<std::string> lvalue("hello");
+  EXPECT_EQ("hello", *lvalue);
+
+  // Note: Recall that std::move() is equivalent to a static_cast to an rvalue
+  // reference type.
+  const absl::StatusOr<std::string> const_rvalue("hello");
+  EXPECT_EQ("hello", *std::move(const_rvalue));  // NOLINT
+
+  absl::StatusOr<std::string> rvalue("hello");
+  EXPECT_EQ("hello", *std::move(rvalue));
+}
+
+TEST(StatusOr, OperatorArrowQualifiers) {
+  static_assert(
+      std::is_same<
+          const int*,
+          decltype(std::declval<const absl::StatusOr<int>&>().operator->())>(),
+      "Unexpected qualifiers");
+  static_assert(
+      std::is_same<
+          int*, decltype(std::declval<absl::StatusOr<int>&>().operator->())>(),
+      "Unexpected qualifiers");
+  static_assert(
+      std::is_same<
+          const int*,
+          decltype(std::declval<const absl::StatusOr<int>&&>().operator->())>(),
+      "Unexpected qualifiers");
+  static_assert(
+      std::is_same<
+          int*, decltype(std::declval<absl::StatusOr<int>&&>().operator->())>(),
+      "Unexpected qualifiers");
+}
+
+TEST(StatusOr, OperatorArrow) {
+  const absl::StatusOr<std::string> const_lvalue("hello");
+  EXPECT_EQ(std::string("hello"), const_lvalue->c_str());
+
+  absl::StatusOr<std::string> lvalue("hello");
+  EXPECT_EQ(std::string("hello"), lvalue->c_str());
+}
+
+TEST(StatusOr, RValueStatus) {
+  absl::StatusOr<int> so(absl::NotFoundError("taco"));
+  const absl::Status s = std::move(so).status();
+
+  EXPECT_EQ(s.code(), absl::StatusCode::kNotFound);
+  EXPECT_EQ(s.message(), "taco");
+
+  // Check that !ok() still implies !status().ok(), even after moving out of the
+  // object. See the note on the rvalue ref-qualified status method.
+  EXPECT_FALSE(so.ok());  // NOLINT
+  EXPECT_FALSE(so.status().ok());
+  EXPECT_EQ(so.status().code(), absl::StatusCode::kInternal);
+  EXPECT_EQ(so.status().message(), "Status accessed after move.");
+}
+
+TEST(StatusOr, TestValue) {
+  const int kI = 4;
+  absl::StatusOr<int> thing(kI);
+  EXPECT_EQ(kI, *thing);
+}
+
+TEST(StatusOr, TestValueConst) {
+  const int kI = 4;
+  const absl::StatusOr<int> thing(kI);
+  EXPECT_EQ(kI, *thing);
+}
+
+TEST(StatusOr, TestPointerDefaultCtor) {
+  absl::StatusOr<int*> thing;
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(thing.status().code(), absl::StatusCode::kUnknown);
+}
+
+TEST(StatusOr, TestPointerStatusCtor) {
+  absl::StatusOr<int*> thing(absl::CancelledError());
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(thing.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestPointerValueCtor) {
+  const int kI = 4;
+
+  // Construction from a non-null pointer
+  {
+    absl::StatusOr<const int*> so(&kI);
+    EXPECT_TRUE(so.ok());
+    EXPECT_OK(so.status());
+    EXPECT_EQ(&kI, *so);
+  }
+
+  // Construction from a null pointer constant
+  {
+    absl::StatusOr<const int*> so(nullptr);
+    EXPECT_TRUE(so.ok());
+    EXPECT_OK(so.status());
+    EXPECT_EQ(nullptr, *so);
+  }
+
+  // Construction from a non-literal null pointer
+  {
+    const int* const p = nullptr;
+
+    absl::StatusOr<const int*> so(p);
+    EXPECT_TRUE(so.ok());
+    EXPECT_OK(so.status());
+    EXPECT_EQ(nullptr, *so);
+  }
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusOk) {
+  const int kI = 0;
+  absl::StatusOr<const int*> original(&kI);
+  absl::StatusOr<const int*> copy(original);
+  EXPECT_OK(copy.status());
+  EXPECT_EQ(*original, *copy);
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusNotOk) {
+  absl::StatusOr<int*> original(absl::CancelledError());
+  absl::StatusOr<int*> copy(original);
+  EXPECT_EQ(copy.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusOKConverting) {
+  Derived derived;
+  absl::StatusOr<Derived*> original(&derived);
+  absl::StatusOr<Base2*> copy(original);
+  EXPECT_OK(copy.status());
+  EXPECT_EQ(static_cast<const Base2*>(*original), *copy);
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusNotOkConverting) {
+  absl::StatusOr<Derived*> original(absl::CancelledError());
+  absl::StatusOr<Base2*> copy(original);
+  EXPECT_EQ(copy.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusOk) {
+  const int kI = 0;
+  absl::StatusOr<const int*> source(&kI);
+  absl::StatusOr<const int*> target;
+  target = source;
+  EXPECT_OK(target.status());
+  EXPECT_EQ(*source, *target);
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusNotOk) {
+  absl::StatusOr<int*> source(absl::CancelledError());
+  absl::StatusOr<int*> target;
+  target = source;
+  EXPECT_EQ(target.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusOKConverting) {
+  Derived derived;
+  absl::StatusOr<Derived*> source(&derived);
+  absl::StatusOr<Base2*> target;
+  target = source;
+  EXPECT_OK(target.status());
+  EXPECT_EQ(static_cast<const Base2*>(*source), *target);
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusNotOkConverting) {
+  absl::StatusOr<Derived*> source(absl::CancelledError());
+  absl::StatusOr<Base2*> target;
+  target = source;
+  EXPECT_EQ(target.status(), source.status());
+}
+
+TEST(StatusOr, TestPointerStatus) {
+  const int kI = 0;
+  absl::StatusOr<const int*> good(&kI);
+  EXPECT_TRUE(good.ok());
+  absl::StatusOr<const int*> bad(absl::CancelledError());
+  EXPECT_EQ(bad.status().code(), absl::StatusCode::kCancelled);
+}
+
+TEST(StatusOr, TestPointerValue) {
+  const int kI = 0;
+  absl::StatusOr<const int*> thing(&kI);
+  EXPECT_EQ(&kI, *thing);
+}
+
+TEST(StatusOr, TestPointerValueConst) {
+  const int kI = 0;
+  const absl::StatusOr<const int*> thing(&kI);
+  EXPECT_EQ(&kI, *thing);
+}
+
+TEST(StatusOr, StatusOrVectorOfUniquePointerCanReserveAndResize) {
+  using EvilType = std::vector<std::unique_ptr<int>>;
+  static_assert(std::is_copy_constructible<EvilType>::value, "");
+  std::vector<::absl::StatusOr<EvilType>> v(5);
+  v.reserve(v.capacity() + 10);
+  v.resize(v.capacity() + 10);
+}
+
+TEST(StatusOr, ConstPayload) {
+  // A reduced version of a problematic type found in the wild. All of the
+  // operations below should compile.
+  absl::StatusOr<const int> a;
+
+  // Copy-construction
+  absl::StatusOr<const int> b(a);
+
+  // Copy-assignment
+  EXPECT_FALSE(std::is_copy_assignable<absl::StatusOr<const int>>::value);
+
+  // Move-construction
+  absl::StatusOr<const int> c(std::move(a));
+
+  // Move-assignment
+  EXPECT_FALSE(std::is_move_assignable<absl::StatusOr<const int>>::value);
+}
+
+TEST(StatusOr, MapToStatusOrUniquePtr) {
+  // A reduced version of a problematic type found in the wild. All of the
+  // operations below should compile.
+  using MapType = std::map<std::string, absl::StatusOr<std::unique_ptr<int>>>;
+
+  MapType a;
+
+  // Move-construction
+  MapType b(std::move(a));
+
+  // Move-assignment
+  a = std::move(b);
+}
+
+TEST(StatusOr, ValueOrOk) {
+  const absl::StatusOr<int> status_or = 0;
+  EXPECT_EQ(status_or.value_or(-1), 0);
+}
+
+TEST(StatusOr, ValueOrDefault) {
+  const absl::StatusOr<int> status_or = absl::CancelledError();
+  EXPECT_EQ(status_or.value_or(-1), -1);
+}
+
+TEST(StatusOr, MoveOnlyValueOrOk) {
+  EXPECT_THAT(absl::StatusOr<std::unique_ptr<int>>(absl::make_unique<int>(0))
+                  .value_or(absl::make_unique<int>(-1)),
+              Pointee(0));
+}
+
+TEST(StatusOr, MoveOnlyValueOrDefault) {
+  EXPECT_THAT(absl::StatusOr<std::unique_ptr<int>>(absl::CancelledError())
+                  .value_or(absl::make_unique<int>(-1)),
+              Pointee(-1));
+}
+
+static absl::StatusOr<int> MakeStatus() { return 100; }
+
+TEST(StatusOr, TestIgnoreError) { MakeStatus().IgnoreError(); }
+
+TEST(StatusOr, EqualityOperator) {
+  constexpr size_t kNumCases = 4;
+  std::array<absl::StatusOr<int>, kNumCases> group1 = {
+      absl::StatusOr<int>(1), absl::StatusOr<int>(2),
+      absl::StatusOr<int>(absl::InvalidArgumentError("msg")),
+      absl::StatusOr<int>(absl::InternalError("msg"))};
+  std::array<absl::StatusOr<int>, kNumCases> group2 = {
+      absl::StatusOr<int>(1), absl::StatusOr<int>(2),
+      absl::StatusOr<int>(absl::InvalidArgumentError("msg")),
+      absl::StatusOr<int>(absl::InternalError("msg"))};
+  for (size_t i = 0; i < kNumCases; ++i) {
+    for (size_t j = 0; j < kNumCases; ++j) {
+      if (i == j) {
+        EXPECT_TRUE(group1[i] == group2[j]);
+        EXPECT_FALSE(group1[i] != group2[j]);
+      } else {
+        EXPECT_FALSE(group1[i] == group2[j]);
+        EXPECT_TRUE(group1[i] != group2[j]);
+      }
+    }
+  }
+}
+
+struct MyType {
+  bool operator==(const MyType&) const { return true; }
+};
+
+enum class ConvTraits { kNone = 0, kImplicit = 1, kExplicit = 2 };
+
+// This class has conversion operator to `StatusOr<T>` based on value of
+// `conv_traits`.
+template <typename T, ConvTraits conv_traits = ConvTraits::kNone>
+struct StatusOrConversionBase {};
+
+template <typename T>
+struct StatusOrConversionBase<T, ConvTraits::kImplicit> {
+  operator absl::StatusOr<T>() const& {  // NOLINT
+    return absl::InvalidArgumentError("conversion to absl::StatusOr");
+  }
+  operator absl::StatusOr<T>() && {  // NOLINT
+    return absl::InvalidArgumentError("conversion to absl::StatusOr");
+  }
+};
+
+template <typename T>
+struct StatusOrConversionBase<T, ConvTraits::kExplicit> {
+  explicit operator absl::StatusOr<T>() const& {
+    return absl::InvalidArgumentError("conversion to absl::StatusOr");
+  }
+  explicit operator absl::StatusOr<T>() && {
+    return absl::InvalidArgumentError("conversion to absl::StatusOr");
+  }
+};
+
+// This class has conversion operator to `T` based on the value of
+// `conv_traits`.
+template <typename T, ConvTraits conv_traits = ConvTraits::kNone>
+struct ConversionBase {};
+
+template <typename T>
+struct ConversionBase<T, ConvTraits::kImplicit> {
+  operator T() const& { return t; }         // NOLINT
+  operator T() && { return std::move(t); }  // NOLINT
+  T t;
+};
+
+template <typename T>
+struct ConversionBase<T, ConvTraits::kExplicit> {
+  explicit operator T() const& { return t; }
+  explicit operator T() && { return std::move(t); }
+  T t;
+};
+
+// This class has conversion operator to `absl::Status` based on the value of
+// `conv_traits`.
+template <ConvTraits conv_traits = ConvTraits::kNone>
+struct StatusConversionBase {};
+
+template <>
+struct StatusConversionBase<ConvTraits::kImplicit> {
+  operator absl::Status() const& {  // NOLINT
+    return absl::InternalError("conversion to Status");
+  }
+  operator absl::Status() && {  // NOLINT
+    return absl::InternalError("conversion to Status");
+  }
+};
+
+template <>
+struct StatusConversionBase<ConvTraits::kExplicit> {
+  explicit operator absl::Status() const& {  // NOLINT
+    return absl::InternalError("conversion to Status");
+  }
+  explicit operator absl::Status() && {  // NOLINT
+    return absl::InternalError("conversion to Status");
+  }
+};
+
+static constexpr int kConvToStatus = 1;
+static constexpr int kConvToStatusOr = 2;
+static constexpr int kConvToT = 4;
+static constexpr int kConvExplicit = 8;
+
+constexpr ConvTraits GetConvTraits(int bit, int config) {
+  return (config & bit) == 0
+             ? ConvTraits::kNone
+             : ((config & kConvExplicit) == 0 ? ConvTraits::kImplicit
+                                              : ConvTraits::kExplicit);
+}
+
+// This class conditionally has conversion operator to `absl::Status`, `T`,
+// `StatusOr<T>`, based on values of the template parameters.
+template <typename T, int config>
+struct CustomType
+    : StatusOrConversionBase<T, GetConvTraits(kConvToStatusOr, config)>,
+      ConversionBase<T, GetConvTraits(kConvToT, config)>,
+      StatusConversionBase<GetConvTraits(kConvToStatus, config)> {};
+
+struct ConvertibleToAnyStatusOr {
+  template <typename T>
+  operator absl::StatusOr<T>() const {  // NOLINT
+    return absl::InvalidArgumentError("Conversion to absl::StatusOr");
+  }
+};
+
+// Test the rank of overload resolution for `StatusOr<T>` constructor and
+// assignment, from highest to lowest:
+// 1. T/Status
+// 2. U that has conversion operator to absl::StatusOr<T>
+// 3. U that is convertible to Status
+// 4. U that is convertible to T
+TEST(StatusOr, ConstructionFromT) {
+  // Construct absl::StatusOr<T> from T when T is convertible to
+  // absl::StatusOr<T>
+  {
+    ConvertibleToAnyStatusOr v;
+    absl::StatusOr<ConvertibleToAnyStatusOr> statusor(v);
+    EXPECT_TRUE(statusor.ok());
+  }
+  {
+    ConvertibleToAnyStatusOr v;
+    absl::StatusOr<ConvertibleToAnyStatusOr> statusor = v;
+    EXPECT_TRUE(statusor.ok());
+  }
+  // Construct absl::StatusOr<T> from T when T is explicitly convertible to
+  // Status
+  {
+    CustomType<MyType, kConvToStatus | kConvExplicit> v;
+    absl::StatusOr<CustomType<MyType, kConvToStatus | kConvExplicit>> statusor(
+        v);
+    EXPECT_TRUE(statusor.ok());
+  }
+  {
+    CustomType<MyType, kConvToStatus | kConvExplicit> v;
+    absl::StatusOr<CustomType<MyType, kConvToStatus | kConvExplicit>> statusor =
+        v;
+    EXPECT_TRUE(statusor.ok());
+  }
+}
+
+// Construct absl::StatusOr<T> from U when U is explicitly convertible to T
+TEST(StatusOr, ConstructionFromTypeConvertibleToT) {
+  {
+    CustomType<MyType, kConvToT | kConvExplicit> v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_TRUE(statusor.ok());
+  }
+  {
+    CustomType<MyType, kConvToT> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_TRUE(statusor.ok());
+  }
+}
+
+// Construct absl::StatusOr<T> from U when U has explicit conversion operator to
+// absl::StatusOr<T>
+TEST(StatusOr, ConstructionFromTypeWithConversionOperatorToStatusOrT) {
+  {
+    CustomType<MyType, kConvToStatusOr | kConvExplicit> v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatusOr | kConvExplicit> v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToStatusOr | kConvToStatus | kConvExplicit> v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType,
+               kConvToT | kConvToStatusOr | kConvToStatus | kConvExplicit>
+        v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToStatusOr> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatusOr> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToStatusOr | kConvToStatus> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatusOr | kConvToStatus> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+}
+
+TEST(StatusOr, ConstructionFromTypeConvertibleToStatus) {
+  // Construction fails because conversion to `Status` is explicit.
+  {
+    CustomType<MyType, kConvToStatus | kConvExplicit> v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_FALSE(statusor.ok());
+    EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatus | kConvExplicit> v;
+    absl::StatusOr<MyType> statusor(v);
+    EXPECT_FALSE(statusor.ok());
+    EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+  }
+  {
+    CustomType<MyType, kConvToStatus> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_FALSE(statusor.ok());
+    EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatus> v;
+    absl::StatusOr<MyType> statusor = v;
+    EXPECT_FALSE(statusor.ok());
+    EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+  }
+}
+
+TEST(StatusOr, AssignmentFromT) {
+  // Assign to absl::StatusOr<T> from T when T is convertible to
+  // absl::StatusOr<T>
+  {
+    ConvertibleToAnyStatusOr v;
+    absl::StatusOr<ConvertibleToAnyStatusOr> statusor;
+    statusor = v;
+    EXPECT_TRUE(statusor.ok());
+  }
+  // Assign to absl::StatusOr<T> from T when T is convertible to Status
+  {
+    CustomType<MyType, kConvToStatus> v;
+    absl::StatusOr<CustomType<MyType, kConvToStatus>> statusor;
+    statusor = v;
+    EXPECT_TRUE(statusor.ok());
+  }
+}
+
+TEST(StatusOr, AssignmentFromTypeConvertibleToT) {
+  // Assign to absl::StatusOr<T> from U when U is convertible to T
+  {
+    CustomType<MyType, kConvToT> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_TRUE(statusor.ok());
+  }
+}
+
+TEST(StatusOr, AssignmentFromTypeWithConversionOperatortoStatusOrT) {
+  // Assign to absl::StatusOr<T> from U when U has conversion operator to
+  // absl::StatusOr<T>
+  {
+    CustomType<MyType, kConvToStatusOr> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatusOr> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToStatusOr | kConvToStatus> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatusOr | kConvToStatus> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_EQ(statusor, v.operator absl::StatusOr<MyType>());
+  }
+}
+
+TEST(StatusOr, AssignmentFromTypeConvertibleToStatus) {
+  // Assign to absl::StatusOr<T> from U when U is convertible to Status
+  {
+    CustomType<MyType, kConvToStatus> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_FALSE(statusor.ok());
+    EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+  }
+  {
+    CustomType<MyType, kConvToT | kConvToStatus> v;
+    absl::StatusOr<MyType> statusor;
+    statusor = v;
+    EXPECT_FALSE(statusor.ok());
+    EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+  }
+}
+
+TEST(StatusOr, StatusAssignmentFromStatusError) {
+  absl::StatusOr<absl::Status> statusor;
+  statusor.AssignStatus(absl::CancelledError());
+
+  EXPECT_FALSE(statusor.ok());
+  EXPECT_EQ(statusor.status(), absl::CancelledError());
+}
+
+#if GTEST_HAS_DEATH_TEST
+TEST(StatusOr, StatusAssignmentFromStatusOk) {
+  EXPECT_DEBUG_DEATH(
+      {
+        absl::StatusOr<absl::Status> statusor;
+        // This will DCHECK.
+        statusor.AssignStatus(absl::OkStatus());
+        // In optimized mode, we are actually going to get error::INTERNAL for
+        // status here, rather than crashing, so check that.
+        EXPECT_FALSE(statusor.ok());
+        EXPECT_EQ(statusor.status().code(), absl::StatusCode::kInternal);
+      },
+      "An OK status is not a valid constructor argument to StatusOr<T>");
+}
+#endif
+
+TEST(StatusOr, StatusAssignmentFromTypeConvertibleToStatus) {
+  CustomType<MyType, kConvToStatus> v;
+  absl::StatusOr<MyType> statusor;
+  statusor.AssignStatus(v);
+
+  EXPECT_FALSE(statusor.ok());
+  EXPECT_EQ(statusor.status(), static_cast<absl::Status>(v));
+}
+
+struct PrintTestStruct {
+  friend std::ostream& operator<<(std::ostream& os, const PrintTestStruct&) {
+    return os << "ostream";
+  }
+
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const PrintTestStruct&) {
+    sink.Append("stringify");
+  }
+};
+
+TEST(StatusOr, OkPrinting) {
+  absl::StatusOr<PrintTestStruct> print_me = PrintTestStruct{};
+  std::stringstream stream;
+  stream << print_me;
+  EXPECT_EQ(stream.str(), "ostream");
+  EXPECT_EQ(absl::StrCat(print_me), "stringify");
+}
+
+TEST(StatusOr, ErrorPrinting) {
+  absl::StatusOr<PrintTestStruct> print_me = absl::UnknownError("error");
+  std::stringstream stream;
+  stream << print_me;
+  const auto error_matcher =
+      AllOf(HasSubstr("UNKNOWN"), HasSubstr("error"),
+            AnyOf(AllOf(StartsWith("("), EndsWith(")")),
+                  AllOf(StartsWith("["), EndsWith("]"))));
+  EXPECT_THAT(stream.str(), error_matcher);
+  EXPECT_THAT(absl::StrCat(print_me), error_matcher);
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/cord_rep_consume.cc b/weight/_dep/abseil-cpp/absl/strings/internal/cord_rep_consume.cc
new file mode 100644
index 0000000000000000000000000000000000000000..db7d4fefc4b16c0a35f03974fb3a742816ba9c4b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/cord_rep_consume.cc
@@ -0,0 +1,64 @@
+// Copyright 2021 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/cord_rep_consume.h"
+
+#include <array>
+#include <utility>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/functional/function_ref.h"
+#include "absl/strings/internal/cord_internal.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace cord_internal {
+
+namespace {
+
+// Unrefs the provided `substring`, and returns `substring->child`
+// Adds or assumes a reference on `substring->child`
+CordRep* ClipSubstring(CordRepSubstring* substring) {
+  CordRep* child = substring->child;
+  if (substring->refcount.IsOne()) {
+    delete substring;
+  } else {
+    CordRep::Ref(child);
+    CordRep::Unref(substring);
+  }
+  return child;
+}
+
+}  // namespace
+
+void Consume(CordRep* rep,
+             FunctionRef<void(CordRep*, size_t, size_t)> consume_fn) {
+  size_t offset = 0;
+  size_t length = rep->length;
+
+  if (rep->tag == SUBSTRING) {
+    offset += rep->substring()->start;
+    rep = ClipSubstring(rep->substring());
+  }
+  consume_fn(rep, offset, length);
+}
+
+void ReverseConsume(CordRep* rep,
+                    FunctionRef<void(CordRep*, size_t, size_t)> consume_fn) {
+  return Consume(rep, consume_fn);
+}
+
+}  // namespace cord_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/cord_rep_flat.h b/weight/_dep/abseil-cpp/absl/strings/internal/cord_rep_flat.h
new file mode 100644
index 0000000000000000000000000000000000000000..27c4b21eb5f79250bcdb4c99c9524d927852e161
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/cord_rep_flat.h
@@ -0,0 +1,195 @@
+// Copyright 2020 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_FLAT_H_
+#define ABSL_STRINGS_INTERNAL_CORD_REP_FLAT_H_
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+#include "absl/strings/internal/cord_internal.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace cord_internal {
+
+// Note: all constants below are never ODR used and internal to cord, we define
+// these as static constexpr to avoid 'in struct' definition and usage clutter.
+
+// Largest and smallest flat node lengths we are willing to allocate
+// Flat allocation size is stored in tag, which currently can encode sizes up
+// to 4K, encoded as multiple of either 8 or 32 bytes.
+// If we allow for larger sizes, we need to change this to 8/64, 16/128, etc.
+// kMinFlatSize is bounded by tag needing to be at least FLAT * 8 bytes, and
+// ideally a 'nice' size aligning with allocation and cacheline sizes like 32.
+// kMaxFlatSize is bounded by the size resulting in a computed tag no greater
+// than MAX_FLAT_TAG. MAX_FLAT_TAG provides for additional 'high' tag values.
+static constexpr size_t kFlatOverhead = offsetof(CordRep, storage);
+static constexpr size_t kMinFlatSize = 32;
+static constexpr size_t kMaxFlatSize = 4096;
+static constexpr size_t kMaxFlatLength = kMaxFlatSize - kFlatOverhead;
+static constexpr size_t kMinFlatLength = kMinFlatSize - kFlatOverhead;
+static constexpr size_t kMaxLargeFlatSize = 256 * 1024;
+static constexpr size_t kMaxLargeFlatLength = kMaxLargeFlatSize - kFlatOverhead;
+
+// kTagBase should make the Size <--> Tag computation resilient
+// against changes to the value of FLAT when we add a new tag..
+static constexpr uint8_t kTagBase = FLAT - 4;
+
+// Converts the provided rounded size to the corresponding tag
+constexpr uint8_t AllocatedSizeToTagUnchecked(size_t size) {
+  return static_cast<uint8_t>(size <= 512 ? kTagBase + size / 8
+                              : size <= 8192
+                                  ? kTagBase + 512 / 8 + size / 64 - 512 / 64
+                                  : kTagBase + 512 / 8 + ((8192 - 512) / 64) +
+                                        size / 4096 - 8192 / 4096);
+}
+
+// Converts the provided tag to the corresponding allocated size
+constexpr size_t TagToAllocatedSize(uint8_t tag) {
+  return (tag <= kTagBase + 512 / 8) ? tag * 8 - kTagBase * 8
+         : (tag <= kTagBase + (512 / 8) + ((8192 - 512) / 64))
+             ? 512 + tag * 64 - kTagBase * 64 - 512 / 8 * 64
+             : 8192 + tag * 4096 - kTagBase * 4096 -
+                   ((512 / 8) + ((8192 - 512) / 64)) * 4096;
+}
+
+static_assert(AllocatedSizeToTagUnchecked(kMinFlatSize) == FLAT, "");
+static_assert(AllocatedSizeToTagUnchecked(kMaxLargeFlatSize) == MAX_FLAT_TAG,
+              "");
+
+// RoundUp logically performs `((n + m - 1) / m) * m` to round up to the nearest
+// multiple of `m`, optimized for the invariant that `m` is a power of 2.
+constexpr size_t RoundUp(size_t n, size_t m) {
+  return (n + m - 1) & (0 - m);
+}
+
+// Returns the size to the nearest equal or larger value that can be
+// expressed exactly as a tag value.
+inline size_t RoundUpForTag(size_t size) {
+  return RoundUp(size, (size <= 512) ? 8 : (size <= 8192 ? 64 : 4096));
+}
+
+// Converts the allocated size to a tag, rounding down if the size
+// does not exactly match a 'tag expressible' size value. The result is
+// undefined if the size exceeds the maximum size that can be encoded in
+// a tag, i.e., if size is larger than TagToAllocatedSize(<max tag>).
+inline uint8_t AllocatedSizeToTag(size_t size) {
+  const uint8_t tag = AllocatedSizeToTagUnchecked(size);
+  assert(tag <= MAX_FLAT_TAG);
+  return tag;
+}
+
+// Converts the provided tag to the corresponding available data length
+constexpr size_t TagToLength(uint8_t tag) {
+  return TagToAllocatedSize(tag) - kFlatOverhead;
+}
+
+// Enforce that kMaxFlatSize maps to a well-known exact tag value.
+static_assert(TagToAllocatedSize(MAX_FLAT_TAG) == kMaxLargeFlatSize,
+              "Bad tag logic");
+
+struct CordRepFlat : public CordRep {
+  // Tag for explicit 'large flat' allocation
+  struct Large {};
+
+  // Creates a new flat node.
+  template <size_t max_flat_size, typename... Args>
+  static CordRepFlat* NewImpl(size_t len, Args... args ABSL_ATTRIBUTE_UNUSED) {
+    if (len <= kMinFlatLength) {
+      len = kMinFlatLength;
+    } else if (len > max_flat_size - kFlatOverhead) {
+      len = max_flat_size - kFlatOverhead;
+    }
+
+    // Round size up so it matches a size we can exactly express in a tag.
+    const size_t size = RoundUpForTag(len + kFlatOverhead);
+    void* const raw_rep = ::operator new(size);
+    // GCC 13 has a false-positive -Wstringop-overflow warning here.
+    #if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(13, 0)
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wstringop-overflow"
+    #endif
+    CordRepFlat* rep = new (raw_rep) CordRepFlat();
+    rep->tag = AllocatedSizeToTag(size);
+    #if ABSL_INTERNAL_HAVE_MIN_GNUC_VERSION(13, 0)
+    #pragma GCC diagnostic pop
+    #endif
+    return rep;
+  }
+
+  static CordRepFlat* New(size_t len) { return NewImpl<kMaxFlatSize>(len); }
+
+  static CordRepFlat* New(Large, size_t len) {
+    return NewImpl<kMaxLargeFlatSize>(len);
+  }
+
+  // Deletes a CordRepFlat instance created previously through a call to New().
+  // Flat CordReps are allocated and constructed with raw ::operator new and
+  // placement new, and must be destructed and deallocated accordingly.
+  static void Delete(CordRep*rep) {
+    assert(rep->tag >= FLAT && rep->tag <= MAX_FLAT_TAG);
+
+#if defined(__cpp_sized_deallocation)
+    size_t size = TagToAllocatedSize(rep->tag);
+    rep->~CordRep();
+    ::operator delete(rep, size);
+#else
+    rep->~CordRep();
+    ::operator delete(rep);
+#endif
+  }
+
+  // Create a CordRepFlat containing `data`, with an optional additional
+  // extra capacity of up to `extra` bytes. Requires that `data.size()`
+  // is less than kMaxFlatLength.
+  static CordRepFlat* Create(absl::string_view data, size_t extra = 0) {
+    assert(data.size() <= kMaxFlatLength);
+    CordRepFlat* flat = New(data.size() + (std::min)(extra, kMaxFlatLength));
+    memcpy(flat->Data(), data.data(), data.size());
+    flat->length = data.size();
+    return flat;
+  }
+
+  // Returns a pointer to the data inside this flat rep.
+  char* Data() { return reinterpret_cast<char*>(storage); }
+  const char* Data() const { return reinterpret_cast<const char*>(storage); }
+
+  // Returns the maximum capacity (payload size) of this instance.
+  size_t Capacity() const { return TagToLength(tag); }
+
+  // Returns the allocated size (payload + overhead) of this instance.
+  size_t AllocatedSize() const { return TagToAllocatedSize(tag); }
+};
+
+// Now that CordRepFlat is defined, we can define CordRep's helper casts:
+inline CordRepFlat* CordRep::flat() {
+  assert(tag >= FLAT && tag <= MAX_FLAT_TAG);
+  return reinterpret_cast<CordRepFlat*>(this);
+}
+
+inline const CordRepFlat* CordRep::flat() const {
+  assert(tag >= FLAT && tag <= MAX_FLAT_TAG);
+  return reinterpret_cast<const CordRepFlat*>(this);
+}
+
+}  // namespace cord_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_CORD_REP_FLAT_H_
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/damerau_levenshtein_distance_test.cc b/weight/_dep/abseil-cpp/absl/strings/internal/damerau_levenshtein_distance_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..49dd105bfdcfdbd51bfca42886017e171b86e704
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/damerau_levenshtein_distance_test.cc
@@ -0,0 +1,99 @@
+// Copyright 2022 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/damerau_levenshtein_distance.h"
+
+#include <cstdint>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+using absl::strings_internal::CappedDamerauLevenshteinDistance;
+
+TEST(Distance, TestDistances) {
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("ab", "ab", 6), uint8_t{0});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("a", "b", 6), uint8_t{1});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("ca", "abc", 6), uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "ad", 6), uint8_t{2});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "cadb", 6), uint8_t{4});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "bdac", 6), uint8_t{4});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("ab", "ab", 0), uint8_t{0});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("", "", 0), uint8_t{0});
+  // combinations for 3-character strings:
+  // 1, 2, 3 removals, insertions or replacements and transpositions
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abc", "abc", 6), uint8_t{0});
+  for (auto res :
+       {"", "ca", "efg", "ea", "ce", "ceb", "eca", "cae", "cea", "bea"}) {
+    EXPECT_THAT(CappedDamerauLevenshteinDistance("abc", res, 6), uint8_t{3});
+    EXPECT_THAT(CappedDamerauLevenshteinDistance(res, "abc", 6), uint8_t{3});
+  }
+  for (auto res :
+       {"a",   "b",   "c",   "ba",  "cb",  "bca", "cab", "cba", "ace",
+        "efc", "ebf", "aef", "ae",  "be",  "eb",  "ec",  "ecb", "bec",
+        "bce", "cbe", "ace", "eac", "aeb", "bae", "eab", "eba"}) {
+    EXPECT_THAT(CappedDamerauLevenshteinDistance("abc", res, 6), uint8_t{2});
+    EXPECT_THAT(CappedDamerauLevenshteinDistance(res, "abc", 6), uint8_t{2});
+  }
+  for (auto res : {"ab", "ac", "bc", "acb", "bac", "ebc", "aec", "abe"}) {
+    EXPECT_THAT(CappedDamerauLevenshteinDistance("abc", res, 6), uint8_t{1});
+    EXPECT_THAT(CappedDamerauLevenshteinDistance(res, "abc", 6), uint8_t{1});
+  }
+}
+
+TEST(Distance, TestCutoff) {
+  // Returning cutoff + 1 if the value is larger than cutoff or string longer
+  // than MAX_SIZE.
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "a", 3), uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "a", 2), uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcd", "a", 1), uint8_t{2});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("abcdefg", "a", 2), uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance("a", "abcde", 2), uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(102, 'a'),
+                                               std::string(102, 'a'), 105),
+              uint8_t{101});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(100, 'a'),
+                                               std::string(100, 'a'), 100),
+              uint8_t{0});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(100, 'a'),
+                                               std::string(100, 'b'), 100),
+              uint8_t{100});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(100, 'a'),
+                                               std::string(99, 'a'), 2),
+              uint8_t{1});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(100, 'a'),
+                                               std::string(101, 'a'), 2),
+              uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(100, 'a'),
+                                               std::string(101, 'a'), 2),
+              uint8_t{3});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(UINT8_MAX + 1, 'a'),
+                                               std::string(UINT8_MAX + 1, 'b'),
+                                               UINT8_MAX),
+              uint8_t{101});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(UINT8_MAX - 1, 'a'),
+                                               std::string(UINT8_MAX - 1, 'b'),
+                                               UINT8_MAX),
+              uint8_t{101});
+  EXPECT_THAT(
+      CappedDamerauLevenshteinDistance(std::string(UINT8_MAX, 'a'),
+                                       std::string(UINT8_MAX, 'b'), UINT8_MAX),
+      uint8_t{101});
+  EXPECT_THAT(CappedDamerauLevenshteinDistance(std::string(UINT8_MAX - 1, 'a'),
+                                               std::string(UINT8_MAX - 1, 'a'),
+                                               UINT8_MAX),
+              uint8_t{101});
+}
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/escaping.h b/weight/_dep/abseil-cpp/absl/strings/internal/escaping.h
new file mode 100644
index 0000000000000000000000000000000000000000..2186f7787df3369fca7542cebd81519b59d1c326
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/escaping.h
@@ -0,0 +1,57 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_ESCAPING_H_
+#define ABSL_STRINGS_INTERNAL_ESCAPING_H_
+
+#include <cassert>
+
+#include "absl/strings/internal/resize_uninitialized.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace strings_internal {
+
+ABSL_CONST_INIT extern const char kBase64Chars[];
+ABSL_CONST_INIT extern const char kWebSafeBase64Chars[];
+
+// Calculates the length of a Base64 encoding (RFC 4648) of a string of length
+// `input_len`, with or without padding per `do_padding`. Note that 'web-safe'
+// encoding (section 5 of the RFC) does not change this length.
+size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding);
+
+// Base64-encodes `src` using the alphabet provided in `base64` (which
+// determines whether to do web-safe encoding or not) and writes the result to
+// `dest`. If `do_padding` is true, `dest` is padded with '=' chars until its
+// length is a multiple of 3. Returns the length of `dest`.
+size_t Base64EscapeInternal(const unsigned char* src, size_t szsrc, char* dest,
+                            size_t szdest, const char* base64, bool do_padding);
+template <typename String>
+void Base64EscapeInternal(const unsigned char* src, size_t szsrc, String* dest,
+                          bool do_padding, const char* base64_chars) {
+  const size_t calc_escaped_size =
+      CalculateBase64EscapedLenInternal(szsrc, do_padding);
+  STLStringResizeUninitialized(dest, calc_escaped_size);
+
+  const size_t escaped_len = Base64EscapeInternal(
+      src, szsrc, &(*dest)[0], dest->size(), base64_chars, do_padding);
+  assert(calc_escaped_size == escaped_len);
+  dest->erase(escaped_len);
+}
+
+}  // namespace strings_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_ESCAPING_H_
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/ostringstream_test.cc b/weight/_dep/abseil-cpp/absl/strings/internal/ostringstream_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ef3ad573e90802721b26cad9082ecd92c13fa40d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/ostringstream_test.cc
@@ -0,0 +1,131 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/ostringstream.h"
+
+#include <ios>
+#include <memory>
+#include <ostream>
+#include <string>
+#include <type_traits>
+#include <utility>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+TEST(OStringStream, IsOStream) {
+  static_assert(
+      std::is_base_of<std::ostream, absl::strings_internal::OStringStream>(),
+      "");
+}
+
+TEST(OStringStream, ConstructNullptr) {
+  absl::strings_internal::OStringStream strm(nullptr);
+  EXPECT_EQ(nullptr, strm.str());
+}
+
+TEST(OStringStream, ConstructStr) {
+  std::string s = "abc";
+  {
+    absl::strings_internal::OStringStream strm(&s);
+    EXPECT_EQ(&s, strm.str());
+  }
+  EXPECT_EQ("abc", s);
+}
+
+TEST(OStringStream, Destroy) {
+  std::unique_ptr<std::string> s(new std::string);
+  absl::strings_internal::OStringStream strm(s.get());
+  s.reset();
+}
+
+TEST(OStringStream, MoveConstruct) {
+  std::string s = "abc";
+  {
+    absl::strings_internal::OStringStream strm1(&s);
+    strm1 << std::hex << 16;
+    EXPECT_EQ(&s, strm1.str());
+    absl::strings_internal::OStringStream strm2(std::move(strm1));
+    strm2 << 16;  // We should still be in base 16.
+    EXPECT_EQ(&s, strm2.str());
+  }
+  EXPECT_EQ("abc1010", s);
+}
+
+TEST(OStringStream, MoveAssign) {
+  std::string s = "abc";
+  {
+    absl::strings_internal::OStringStream strm1(&s);
+    strm1 << std::hex << 16;
+    EXPECT_EQ(&s, strm1.str());
+    absl::strings_internal::OStringStream strm2(nullptr);
+    strm2 = std::move(strm1);
+    strm2 << 16;  // We should still be in base 16.
+    EXPECT_EQ(&s, strm2.str());
+  }
+  EXPECT_EQ("abc1010", s);
+}
+
+TEST(OStringStream, Str) {
+  std::string s1;
+  absl::strings_internal::OStringStream strm(&s1);
+  const absl::strings_internal::OStringStream& c_strm(strm);
+
+  static_assert(std::is_same<decltype(strm.str()), std::string*>(), "");
+  static_assert(std::is_same<decltype(c_strm.str()), const std::string*>(), "");
+
+  EXPECT_EQ(&s1, strm.str());
+  EXPECT_EQ(&s1, c_strm.str());
+
+  strm.str(&s1);
+  EXPECT_EQ(&s1, strm.str());
+  EXPECT_EQ(&s1, c_strm.str());
+
+  std::string s2;
+  strm.str(&s2);
+  EXPECT_EQ(&s2, strm.str());
+  EXPECT_EQ(&s2, c_strm.str());
+
+  strm.str(nullptr);
+  EXPECT_EQ(nullptr, strm.str());
+  EXPECT_EQ(nullptr, c_strm.str());
+}
+
+TEST(OStreamStream, WriteToLValue) {
+  std::string s = "abc";
+  {
+    absl::strings_internal::OStringStream strm(&s);
+    EXPECT_EQ("abc", s);
+    strm << "";
+    EXPECT_EQ("abc", s);
+    strm << 42;
+    EXPECT_EQ("abc42", s);
+    strm << 'x' << 'y';
+    EXPECT_EQ("abc42xy", s);
+  }
+  EXPECT_EQ("abc42xy", s);
+}
+
+TEST(OStreamStream, WriteToRValue) {
+  std::string s = "abc";
+  absl::strings_internal::OStringStream(&s) << "";
+  EXPECT_EQ("abc", s);
+  absl::strings_internal::OStringStream(&s) << 42;
+  EXPECT_EQ("abc42", s);
+  absl::strings_internal::OStringStream(&s) << 'x' << 'y';
+  EXPECT_EQ("abc42xy", s);
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/resize_uninitialized_test.cc b/weight/_dep/abseil-cpp/absl/strings/internal/resize_uninitialized_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ad1b9c58f33bcda106bd048ec43045e30a56f8be
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/resize_uninitialized_test.cc
@@ -0,0 +1,133 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/resize_uninitialized.h"
+
+#include "gtest/gtest.h"
+
+namespace {
+
+int resize_call_count = 0;
+int append_call_count = 0;
+
+// A mock string class whose only purpose is to track how many times its
+// resize()/append() methods have been called.
+struct resizable_string {
+  using value_type = char;
+  size_t size() const { return 0; }
+  size_t capacity() const { return 0; }
+  char& operator[](size_t) {
+    static char c = '\0';
+    return c;
+  }
+  void resize(size_t) { resize_call_count += 1; }
+  void append(size_t, value_type) { append_call_count += 1; }
+  void reserve(size_t) {}
+  resizable_string& erase(size_t = 0, size_t = 0) { return *this; }
+};
+
+int resize_default_init_call_count = 0;
+int append_default_init_call_count = 0;
+
+// A mock string class whose only purpose is to track how many times its
+// resize()/__resize_default_init()/append()/__append_default_init() methods
+// have been called.
+struct default_init_string {
+  size_t size() const { return 0; }
+  size_t capacity() const { return 0; }
+  char& operator[](size_t) {
+    static char c = '\0';
+    return c;
+  }
+  void resize(size_t) { resize_call_count += 1; }
+  void __resize_default_init(size_t) { resize_default_init_call_count += 1; }
+  void __append_default_init(size_t) { append_default_init_call_count += 1; }
+  void reserve(size_t) {}
+  default_init_string& erase(size_t = 0, size_t = 0) { return *this; }
+};
+
+TEST(ResizeUninit, WithAndWithout) {
+  resize_call_count = 0;
+  append_call_count = 0;
+  resize_default_init_call_count = 0;
+  append_default_init_call_count = 0;
+  {
+    resizable_string rs;
+
+    EXPECT_EQ(resize_call_count, 0);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 0);
+    EXPECT_EQ(append_default_init_call_count, 0);
+    EXPECT_FALSE(
+        absl::strings_internal::STLStringSupportsNontrashingResize(&rs));
+    EXPECT_EQ(resize_call_count, 0);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 0);
+    EXPECT_EQ(append_default_init_call_count, 0);
+    absl::strings_internal::STLStringResizeUninitialized(&rs, 237);
+    EXPECT_EQ(resize_call_count, 1);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 0);
+    EXPECT_EQ(append_default_init_call_count, 0);
+    absl::strings_internal::STLStringResizeUninitializedAmortized(&rs, 1000);
+    EXPECT_EQ(resize_call_count, 1);
+    EXPECT_EQ(append_call_count, 1);
+    EXPECT_EQ(resize_default_init_call_count, 0);
+    EXPECT_EQ(append_default_init_call_count, 0);
+  }
+
+  resize_call_count = 0;
+  append_call_count = 0;
+  resize_default_init_call_count = 0;
+  append_default_init_call_count = 0;
+  {
+    default_init_string rus;
+
+    EXPECT_EQ(resize_call_count, 0);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 0);
+    EXPECT_EQ(append_default_init_call_count, 0);
+    EXPECT_TRUE(
+        absl::strings_internal::STLStringSupportsNontrashingResize(&rus));
+    EXPECT_EQ(resize_call_count, 0);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 0);
+    EXPECT_EQ(append_default_init_call_count, 0);
+    absl::strings_internal::STLStringResizeUninitialized(&rus, 237);
+    EXPECT_EQ(resize_call_count, 0);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 1);
+    EXPECT_EQ(append_default_init_call_count, 0);
+    absl::strings_internal::STLStringResizeUninitializedAmortized(&rus, 1000);
+    EXPECT_EQ(resize_call_count, 0);
+    EXPECT_EQ(append_call_count, 0);
+    EXPECT_EQ(resize_default_init_call_count, 1);
+    EXPECT_EQ(append_default_init_call_count, 1);
+  }
+}
+
+TEST(ResizeUninit, Amortized) {
+  std::string str;
+  size_t prev_cap = str.capacity();
+  int cap_increase_count = 0;
+  for (int i = 0; i < 1000; ++i) {
+    absl::strings_internal::STLStringResizeUninitializedAmortized(&str, i);
+    size_t new_cap = str.capacity();
+    if (new_cap > prev_cap) ++cap_increase_count;
+    prev_cap = new_cap;
+  }
+  EXPECT_LT(cap_increase_count, 50);
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/str_format/output.h b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/output.h
new file mode 100644
index 0000000000000000000000000000000000000000..15e751ab6f0c2603cd2b9b07d12656536ddcf51d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/output.h
@@ -0,0 +1,97 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Output extension hooks for the Format library.
+// `internal::InvokeFlush` calls the appropriate flush function for the
+// specified output argument.
+// `BufferRawSink` is a simple output sink for a char buffer. Used by SnprintF.
+// `FILERawSink` is a std::FILE* based sink. Used by PrintF and FprintF.
+
+#ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
+#define ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
+
+#include <cstdio>
+#include <ios>
+#include <ostream>
+#include <string>
+
+#include "absl/base/port.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace str_format_internal {
+
+// RawSink implementation that writes into a char* buffer.
+// It will not overflow the buffer, but will keep the total count of chars
+// that would have been written.
+class BufferRawSink {
+ public:
+  BufferRawSink(char* buffer, size_t size) : buffer_(buffer), size_(size) {}
+
+  size_t total_written() const { return total_written_; }
+  void Write(string_view v);
+
+ private:
+  char* buffer_;
+  size_t size_;
+  size_t total_written_ = 0;
+};
+
+// RawSink implementation that writes into a FILE*.
+// It keeps track of the total number of bytes written and any error encountered
+// during the writes.
+class FILERawSink {
+ public:
+  explicit FILERawSink(std::FILE* output) : output_(output) {}
+
+  void Write(string_view v);
+
+  size_t count() const { return count_; }
+  int error() const { return error_; }
+
+ private:
+  std::FILE* output_;
+  int error_ = 0;
+  size_t count_ = 0;
+};
+
+// Provide RawSink integration with common types from the STL.
+inline void AbslFormatFlush(std::string* out, string_view s) {
+  out->append(s.data(), s.size());
+}
+inline void AbslFormatFlush(std::ostream* out, string_view s) {
+  out->write(s.data(), static_cast<std::streamsize>(s.size()));
+}
+
+inline void AbslFormatFlush(FILERawSink* sink, string_view v) {
+  sink->Write(v);
+}
+
+inline void AbslFormatFlush(BufferRawSink* sink, string_view v) {
+  sink->Write(v);
+}
+
+// This is a SFINAE to get a better compiler error message when the type
+// is not supported.
+template <typename T>
+auto InvokeFlush(T* out, string_view s) -> decltype(AbslFormatFlush(out, s)) {
+  AbslFormatFlush(out, s);
+}
+
+}  // namespace str_format_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/str_format/output_test.cc b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/output_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ce2e91a0bbe8975ab0703e19f9c4479c82d6080a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/output_test.cc
@@ -0,0 +1,79 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/str_format/output.h"
+
+#include <sstream>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/cord.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace {
+
+TEST(InvokeFlush, String) {
+  std::string str = "ABC";
+  str_format_internal::InvokeFlush(&str, "DEF");
+  EXPECT_EQ(str, "ABCDEF");
+}
+
+TEST(InvokeFlush, Stream) {
+  std::stringstream str;
+  str << "ABC";
+  str_format_internal::InvokeFlush(&str, "DEF");
+  EXPECT_EQ(str.str(), "ABCDEF");
+}
+
+TEST(InvokeFlush, Cord) {
+  absl::Cord str("ABC");
+  str_format_internal::InvokeFlush(&str, "DEF");
+  EXPECT_EQ(str, "ABCDEF");
+}
+
+TEST(BufferRawSink, Limits) {
+  char buf[16];
+  {
+    std::fill(std::begin(buf), std::end(buf), 'x');
+    str_format_internal::BufferRawSink bufsink(buf, sizeof(buf) - 1);
+    str_format_internal::InvokeFlush(&bufsink, "Hello World237");
+    EXPECT_EQ(std::string(buf, sizeof(buf)), "Hello World237xx");
+  }
+  {
+    std::fill(std::begin(buf), std::end(buf), 'x');
+    str_format_internal::BufferRawSink bufsink(buf, sizeof(buf) - 1);
+    str_format_internal::InvokeFlush(&bufsink, "Hello World237237");
+    EXPECT_EQ(std::string(buf, sizeof(buf)), "Hello World2372x");
+  }
+  {
+    std::fill(std::begin(buf), std::end(buf), 'x');
+    str_format_internal::BufferRawSink bufsink(buf, sizeof(buf) - 1);
+    str_format_internal::InvokeFlush(&bufsink, "Hello World");
+    str_format_internal::InvokeFlush(&bufsink, "237");
+    EXPECT_EQ(std::string(buf, sizeof(buf)), "Hello World237xx");
+  }
+  {
+    std::fill(std::begin(buf), std::end(buf), 'x');
+    str_format_internal::BufferRawSink bufsink(buf, sizeof(buf) - 1);
+    str_format_internal::InvokeFlush(&bufsink, "Hello World");
+    str_format_internal::InvokeFlush(&bufsink, "237237");
+    EXPECT_EQ(std::string(buf, sizeof(buf)), "Hello World2372x");
+  }
+}
+
+}  // namespace
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/str_format/parser.h b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/parser.h
new file mode 100644
index 0000000000000000000000000000000000000000..b1d6d5fd0e8fefb67e9b6e335f045067942e3143
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/parser.h
@@ -0,0 +1,269 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
+#define ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
+
+#include <stddef.h>
+#include <stdlib.h>
+
+#include <cassert>
+#include <cstring>
+#include <initializer_list>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/base/config.h"
+#include "absl/base/optimization.h"
+#include "absl/strings/internal/str_format/checker.h"
+#include "absl/strings/internal/str_format/constexpr_parser.h"
+#include "absl/strings/internal/str_format/extension.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace str_format_internal {
+
+std::string LengthModToString(LengthMod v);
+
+const char* ConsumeUnboundConversionNoInline(const char* p, const char* end,
+                                             UnboundConversion* conv,
+                                             int* next_arg);
+
+// Parse the format string provided in 'src' and pass the identified items into
+// 'consumer'.
+// Text runs will be passed by calling
+//   Consumer::Append(string_view);
+// ConversionItems will be passed by calling
+//   Consumer::ConvertOne(UnboundConversion, string_view);
+// In the case of ConvertOne, the string_view that is passed is the
+// portion of the format string corresponding to the conversion, not including
+// the leading %. On success, it returns true. On failure, it stops and returns
+// false.
+template <typename Consumer>
+bool ParseFormatString(string_view src, Consumer consumer) {
+  int next_arg = 0;
+  const char* p = src.data();
+  const char* const end = p + src.size();
+  while (p != end) {
+    const char* percent =
+        static_cast<const char*>(memchr(p, '%', static_cast<size_t>(end - p)));
+    if (!percent) {
+      // We found the last substring.
+      return consumer.Append(string_view(p, static_cast<size_t>(end - p)));
+    }
+    // We found a percent, so push the text run then process the percent.
+    if (ABSL_PREDICT_FALSE(!consumer.Append(
+            string_view(p, static_cast<size_t>(percent - p))))) {
+      return false;
+    }
+    if (ABSL_PREDICT_FALSE(percent + 1 >= end)) return false;
+
+    auto tag = GetTagForChar(percent[1]);
+    if (tag.is_conv()) {
+      if (ABSL_PREDICT_FALSE(next_arg < 0)) {
+        // This indicates an error in the format string.
+        // The only way to get `next_arg < 0` here is to have a positional
+        // argument first which sets next_arg to -1 and then a non-positional
+        // argument.
+        return false;
+      }
+      p = percent + 2;
+
+      // Keep this case separate from the one below.
+      // ConvertOne is more efficient when the compiler can see that the `basic`
+      // flag is set.
+      UnboundConversion conv;
+      conv.conv = tag.as_conv();
+      conv.arg_position = ++next_arg;
+      if (ABSL_PREDICT_FALSE(
+              !consumer.ConvertOne(conv, string_view(percent + 1, 1)))) {
+        return false;
+      }
+    } else if (percent[1] != '%') {
+      UnboundConversion conv;
+      p = ConsumeUnboundConversionNoInline(percent + 1, end, &conv, &next_arg);
+      if (ABSL_PREDICT_FALSE(p == nullptr)) return false;
+      if (ABSL_PREDICT_FALSE(!consumer.ConvertOne(
+              conv, string_view(percent + 1,
+                                static_cast<size_t>(p - (percent + 1)))))) {
+        return false;
+      }
+    } else {
+      if (ABSL_PREDICT_FALSE(!consumer.Append("%"))) return false;
+      p = percent + 2;
+      continue;
+    }
+  }
+  return true;
+}
+
+// Always returns true, or fails to compile in a constexpr context if s does not
+// point to a constexpr char array.
+constexpr bool EnsureConstexpr(string_view s) {
+  return s.empty() || s[0] == s[0];
+}
+
+class ParsedFormatBase {
+ public:
+  explicit ParsedFormatBase(
+      string_view format, bool allow_ignored,
+      std::initializer_list<FormatConversionCharSet> convs);
+
+  ParsedFormatBase(const ParsedFormatBase& other) { *this = other; }
+
+  ParsedFormatBase(ParsedFormatBase&& other) { *this = std::move(other); }
+
+  ParsedFormatBase& operator=(const ParsedFormatBase& other) {
+    if (this == &other) return *this;
+    has_error_ = other.has_error_;
+    items_ = other.items_;
+    size_t text_size = items_.empty() ? 0 : items_.back().text_end;
+    data_.reset(new char[text_size]);
+    memcpy(data_.get(), other.data_.get(), text_size);
+    return *this;
+  }
+
+  ParsedFormatBase& operator=(ParsedFormatBase&& other) {
+    if (this == &other) return *this;
+    has_error_ = other.has_error_;
+    data_ = std::move(other.data_);
+    items_ = std::move(other.items_);
+    // Reset the vector to make sure the invariants hold.
+    other.items_.clear();
+    return *this;
+  }
+
+  template <typename Consumer>
+  bool ProcessFormat(Consumer consumer) const {
+    const char* const base = data_.get();
+    string_view text(base, 0);
+    for (const auto& item : items_) {
+      const char* const end = text.data() + text.size();
+      text =
+          string_view(end, static_cast<size_t>((base + item.text_end) - end));
+      if (item.is_conversion) {
+        if (!consumer.ConvertOne(item.conv, text)) return false;
+      } else {
+        if (!consumer.Append(text)) return false;
+      }
+    }
+    return !has_error_;
+  }
+
+  bool has_error() const { return has_error_; }
+
+ private:
+  // Returns whether the conversions match and if !allow_ignored it verifies
+  // that all conversions are used by the format.
+  bool MatchesConversions(
+      bool allow_ignored,
+      std::initializer_list<FormatConversionCharSet> convs) const;
+
+  struct ParsedFormatConsumer;
+
+  struct ConversionItem {
+    bool is_conversion;
+    // Points to the past-the-end location of this element in the data_ array.
+    size_t text_end;
+    UnboundConversion conv;
+  };
+
+  bool has_error_;
+  std::unique_ptr<char[]> data_;
+  std::vector<ConversionItem> items_;
+};
+
+
+// A value type representing a preparsed format.  These can be created, copied
+// around, and reused to speed up formatting loops.
+// The user must specify through the template arguments the conversion
+// characters used in the format. This will be checked at compile time.
+//
+// This class uses Conv enum values to specify each argument.
+// This allows for more flexibility as you can specify multiple possible
+// conversion characters for each argument.
+// ParsedFormat<char...> is a simplified alias for when the user only
+// needs to specify a single conversion character for each argument.
+//
+// Example:
+//   // Extended format supports multiple characters per argument:
+//   using MyFormat = ExtendedParsedFormat<Conv::d | Conv::x>;
+//   MyFormat GetFormat(bool use_hex) {
+//     if (use_hex) return MyFormat("foo %x bar");
+//     return MyFormat("foo %d bar");
+//   }
+//   // 'format' can be used with any value that supports 'd' and 'x',
+//   // like `int`.
+//   auto format = GetFormat(use_hex);
+//   value = StringF(format, i);
+//
+// This class also supports runtime format checking with the ::New() and
+// ::NewAllowIgnored() factory functions.
+// This is the only API that allows the user to pass a runtime specified format
+// string. These factory functions will return NULL if the format does not match
+// the conversions requested by the user.
+template <FormatConversionCharSet... C>
+class ExtendedParsedFormat : public str_format_internal::ParsedFormatBase {
+ public:
+  explicit ExtendedParsedFormat(string_view format)
+#ifdef ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
+      __attribute__((
+          enable_if(str_format_internal::EnsureConstexpr(format),
+                    "Format string is not constexpr."),
+          enable_if(str_format_internal::ValidFormatImpl<C...>(format),
+                    "Format specified does not match the template arguments.")))
+#endif  // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
+      : ExtendedParsedFormat(format, false) {
+  }
+
+  // ExtendedParsedFormat factory function.
+  // The user still has to specify the conversion characters, but they will not
+  // be checked at compile time. Instead, it will be checked at runtime.
+  // This delays the checking to runtime, but allows the user to pass
+  // dynamically sourced formats.
+  // It returns NULL if the format does not match the conversion characters.
+  // The user is responsible for checking the return value before using it.
+  //
+  // The 'New' variant will check that all the specified arguments are being
+  // consumed by the format and return NULL if any argument is being ignored.
+  // The 'NewAllowIgnored' variant will not verify this and will allow formats
+  // that ignore arguments.
+  static std::unique_ptr<ExtendedParsedFormat> New(string_view format) {
+    return New(format, false);
+  }
+  static std::unique_ptr<ExtendedParsedFormat> NewAllowIgnored(
+      string_view format) {
+    return New(format, true);
+  }
+
+ private:
+  static std::unique_ptr<ExtendedParsedFormat> New(string_view format,
+                                                   bool allow_ignored) {
+    std::unique_ptr<ExtendedParsedFormat> conv(
+        new ExtendedParsedFormat(format, allow_ignored));
+    if (conv->has_error()) return nullptr;
+    return conv;
+  }
+
+  ExtendedParsedFormat(string_view s, bool allow_ignored)
+      : ParsedFormatBase(s, allow_ignored, {C...}) {}
+};
+}  // namespace str_format_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/str_format/parser_test.cc b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/parser_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e2225c6018343447ae86e24d2915da76d9e0d300
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/str_format/parser_test.cc
@@ -0,0 +1,446 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/str_format/parser.h"
+
+#include <string.h>
+#include <algorithm>
+#include <initializer_list>
+#include <string>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+#include "absl/strings/internal/str_format/constexpr_parser.h"
+#include "absl/strings/internal/str_format/extension.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace str_format_internal {
+
+namespace {
+
+using testing::Pair;
+
+TEST(LengthModTest, Names) {
+  struct Expectation {
+    int line;
+    LengthMod mod;
+    const char *name;
+  };
+  const Expectation kExpect[] = {
+    {__LINE__, LengthMod::none, ""  },
+    {__LINE__, LengthMod::h,    "h" },
+    {__LINE__, LengthMod::hh,   "hh"},
+    {__LINE__, LengthMod::l,    "l" },
+    {__LINE__, LengthMod::ll,   "ll"},
+    {__LINE__, LengthMod::L,    "L" },
+    {__LINE__, LengthMod::j,    "j" },
+    {__LINE__, LengthMod::z,    "z" },
+    {__LINE__, LengthMod::t,    "t" },
+    {__LINE__, LengthMod::q,    "q" },
+  };
+  EXPECT_EQ(ABSL_ARRAYSIZE(kExpect), 10);
+  for (auto e : kExpect) {
+    SCOPED_TRACE(e.line);
+    EXPECT_EQ(e.name, LengthModToString(e.mod));
+  }
+}
+
+TEST(ConversionCharTest, Names) {
+  struct Expectation {
+    FormatConversionChar id;
+    char name;
+  };
+  // clang-format off
+  const Expectation kExpect[] = {
+#define X(c) {FormatConversionCharInternal::c, #c[0]}
+    X(c), X(s),                                      // text
+    X(d), X(i), X(o), X(u), X(x), X(X),              // int
+    X(f), X(F), X(e), X(E), X(g), X(G), X(a), X(A),  // float
+    X(n), X(p),                                      // misc
+#undef X
+    {FormatConversionCharInternal::kNone, '\0'},
+  };
+  // clang-format on
+  for (auto e : kExpect) {
+    SCOPED_TRACE(e.name);
+    FormatConversionChar v = e.id;
+    EXPECT_EQ(e.name, FormatConversionCharToChar(v));
+  }
+}
+
+class ConsumeUnboundConversionTest : public ::testing::Test {
+ public:
+  std::pair<string_view, string_view> Consume(string_view src) {
+    int next = 0;
+    o = UnboundConversion();  // refresh
+    const char* p = ConsumeUnboundConversion(
+        src.data(), src.data() + src.size(), &o, &next);
+    if (!p) return {{}, src};
+    return {string_view(src.data(), p - src.data()),
+            string_view(p, src.data() + src.size() - p)};
+  }
+
+  bool Run(const char *fmt, bool force_positional = false) {
+    int next = force_positional ? -1 : 0;
+    o = UnboundConversion();  // refresh
+    return ConsumeUnboundConversion(fmt, fmt + strlen(fmt), &o, &next) ==
+           fmt + strlen(fmt);
+  }
+  UnboundConversion o;
+};
+
+TEST_F(ConsumeUnboundConversionTest, ConsumeSpecification) {
+  struct Expectation {
+    int line;
+    string_view src;
+    string_view out;
+    string_view src_post;
+  };
+  const Expectation kExpect[] = {
+    {__LINE__, "",     "",     ""  },
+    {__LINE__, "b",    "",     "b" },  // 'b' is invalid
+    {__LINE__, "ba",   "",     "ba"},  // 'b' is invalid
+    {__LINE__, "l",    "",     "l" },  // just length mod isn't okay
+    {__LINE__, "d",    "d",    ""  },  // basic
+    {__LINE__, "v",    "v",    ""  },  // basic
+    {__LINE__, "d ",   "d",    " " },  // leave suffix
+    {__LINE__, "dd",   "d",    "d" },  // don't be greedy
+    {__LINE__, "d9",   "d",    "9" },  // leave non-space suffix
+    {__LINE__, "dzz",  "d",    "zz"},  // length mod as suffix
+    {__LINE__, "3v",   "",     "3v"},  // 'v' cannot have modifiers
+    {__LINE__, "hv",   "",     "hv"},  // 'v' cannot have modifiers
+    {__LINE__, "1$v",   "1$v",     ""},  // 'v' can have use posix syntax
+    {__LINE__, "1$*2$d", "1$*2$d", ""  },  // arg indexing and * allowed.
+    {__LINE__, "0-14.3hhd", "0-14.3hhd", ""},  // precision, width
+    {__LINE__, " 0-+#14.3hhd", " 0-+#14.3hhd", ""},  // flags
+  };
+  for (const auto& e : kExpect) {
+    SCOPED_TRACE(e.line);
+    EXPECT_THAT(Consume(e.src), Pair(e.out, e.src_post));
+  }
+}
+
+TEST_F(ConsumeUnboundConversionTest, BasicConversion) {
+  EXPECT_FALSE(Run(""));
+  EXPECT_FALSE(Run("z"));
+
+  EXPECT_FALSE(Run("dd"));  // no excess allowed
+
+  EXPECT_TRUE(Run("d"));
+  EXPECT_EQ('d', FormatConversionCharToChar(o.conv));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_LT(o.width.value(), 0);
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_LT(o.precision.value(), 0);
+  EXPECT_EQ(1, o.arg_position);
+}
+
+TEST_F(ConsumeUnboundConversionTest, ArgPosition) {
+  EXPECT_TRUE(Run("d"));
+  EXPECT_EQ(1, o.arg_position);
+  EXPECT_TRUE(Run("3$d"));
+  EXPECT_EQ(3, o.arg_position);
+  EXPECT_TRUE(Run("1$d"));
+  EXPECT_EQ(1, o.arg_position);
+  EXPECT_TRUE(Run("1$d", true));
+  EXPECT_EQ(1, o.arg_position);
+  EXPECT_TRUE(Run("123$d"));
+  EXPECT_EQ(123, o.arg_position);
+  EXPECT_TRUE(Run("123$d", true));
+  EXPECT_EQ(123, o.arg_position);
+  EXPECT_TRUE(Run("10$d"));
+  EXPECT_EQ(10, o.arg_position);
+  EXPECT_TRUE(Run("10$d", true));
+  EXPECT_EQ(10, o.arg_position);
+
+  // Position can't be zero.
+  EXPECT_FALSE(Run("0$d"));
+  EXPECT_FALSE(Run("0$d", true));
+  EXPECT_FALSE(Run("1$*0$d"));
+  EXPECT_FALSE(Run("1$.*0$d"));
+
+  // Position can't start with a zero digit at all. That is not a 'decimal'.
+  EXPECT_FALSE(Run("01$p"));
+  EXPECT_FALSE(Run("01$p", true));
+  EXPECT_FALSE(Run("1$*01$p"));
+  EXPECT_FALSE(Run("1$.*01$p"));
+}
+
+TEST_F(ConsumeUnboundConversionTest, WidthAndPrecision) {
+  EXPECT_TRUE(Run("14d"));
+  EXPECT_EQ('d', FormatConversionCharToChar(o.conv));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_EQ(14, o.width.value());
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_LT(o.precision.value(), 0);
+
+  EXPECT_TRUE(Run("14.d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_EQ(14, o.width.value());
+  EXPECT_EQ(0, o.precision.value());
+
+  EXPECT_TRUE(Run(".d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_LT(o.width.value(), 0);
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_EQ(0, o.precision.value());
+
+  EXPECT_TRUE(Run(".5d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_LT(o.width.value(), 0);
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_EQ(5, o.precision.value());
+
+  EXPECT_TRUE(Run(".0d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_LT(o.width.value(), 0);
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_EQ(0, o.precision.value());
+
+  EXPECT_TRUE(Run("14.5d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_EQ(14, o.width.value());
+  EXPECT_EQ(5, o.precision.value());
+
+  EXPECT_TRUE(Run("*.*d"));
+  EXPECT_TRUE(o.width.is_from_arg());
+  EXPECT_EQ(1, o.width.get_from_arg());
+  EXPECT_TRUE(o.precision.is_from_arg());
+  EXPECT_EQ(2, o.precision.get_from_arg());
+  EXPECT_EQ(3, o.arg_position);
+
+  EXPECT_TRUE(Run("*d"));
+  EXPECT_TRUE(o.width.is_from_arg());
+  EXPECT_EQ(1, o.width.get_from_arg());
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_LT(o.precision.value(), 0);
+  EXPECT_EQ(2, o.arg_position);
+
+  EXPECT_TRUE(Run(".*d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_LT(o.width.value(), 0);
+  EXPECT_TRUE(o.precision.is_from_arg());
+  EXPECT_EQ(1, o.precision.get_from_arg());
+  EXPECT_EQ(2, o.arg_position);
+
+  // mixed implicit and explicit: didn't specify arg position.
+  EXPECT_FALSE(Run("*23$.*34$d"));
+
+  EXPECT_TRUE(Run("12$*23$.*34$d"));
+  EXPECT_EQ(12, o.arg_position);
+  EXPECT_TRUE(o.width.is_from_arg());
+  EXPECT_EQ(23, o.width.get_from_arg());
+  EXPECT_TRUE(o.precision.is_from_arg());
+  EXPECT_EQ(34, o.precision.get_from_arg());
+
+  EXPECT_TRUE(Run("2$*5$.*9$d"));
+  EXPECT_EQ(2, o.arg_position);
+  EXPECT_TRUE(o.width.is_from_arg());
+  EXPECT_EQ(5, o.width.get_from_arg());
+  EXPECT_TRUE(o.precision.is_from_arg());
+  EXPECT_EQ(9, o.precision.get_from_arg());
+
+  EXPECT_FALSE(Run(".*0$d")) << "no arg 0";
+
+  // Large values
+  EXPECT_TRUE(Run("999999999.999999999d"));
+  EXPECT_FALSE(o.width.is_from_arg());
+  EXPECT_EQ(999999999, o.width.value());
+  EXPECT_FALSE(o.precision.is_from_arg());
+  EXPECT_EQ(999999999, o.precision.value());
+
+  EXPECT_FALSE(Run("1000000000.999999999d"));
+  EXPECT_FALSE(Run("999999999.1000000000d"));
+  EXPECT_FALSE(Run("9999999999d"));
+  EXPECT_FALSE(Run(".9999999999d"));
+}
+
+TEST_F(ConsumeUnboundConversionTest, Flags) {
+  static const char kAllFlags[] = "-+ #0";
+  static const int kNumFlags = ABSL_ARRAYSIZE(kAllFlags) - 1;
+  for (int rev = 0; rev < 2; ++rev) {
+    for (int i = 0; i < 1 << kNumFlags; ++i) {
+      std::string fmt;
+      for (int k = 0; k < kNumFlags; ++k)
+        if ((i >> k) & 1) fmt += kAllFlags[k];
+      // flag order shouldn't matter
+      if (rev == 1) {
+        std::reverse(fmt.begin(), fmt.end());
+      }
+      fmt += 'd';
+      SCOPED_TRACE(fmt);
+      EXPECT_TRUE(Run(fmt.c_str()));
+      EXPECT_EQ(fmt.find('-') == std::string::npos,
+                !FlagsContains(o.flags, Flags::kLeft));
+      EXPECT_EQ(fmt.find('+') == std::string::npos,
+                !FlagsContains(o.flags, Flags::kShowPos));
+      EXPECT_EQ(fmt.find(' ') == std::string::npos,
+                !FlagsContains(o.flags, Flags::kSignCol));
+      EXPECT_EQ(fmt.find('#') == std::string::npos,
+                !FlagsContains(o.flags, Flags::kAlt));
+      EXPECT_EQ(fmt.find('0') == std::string::npos,
+                !FlagsContains(o.flags, Flags::kZero));
+    }
+  }
+}
+
+TEST_F(ConsumeUnboundConversionTest, BasicFlag) {
+  // Flag is on
+  for (const char* fmt : {"d", "llx", "G", "1$X"}) {
+    SCOPED_TRACE(fmt);
+    EXPECT_TRUE(Run(fmt));
+    EXPECT_EQ(o.flags, Flags::kBasic);
+  }
+
+  // Flag is off
+  for (const char* fmt : {"3d", ".llx", "-G", "1$#X", "lc"}) {
+    SCOPED_TRACE(fmt);
+    EXPECT_TRUE(Run(fmt));
+    EXPECT_NE(o.flags, Flags::kBasic);
+  }
+}
+
+TEST_F(ConsumeUnboundConversionTest, LengthMod) {
+  EXPECT_TRUE(Run("d"));
+  EXPECT_EQ(LengthMod::none, o.length_mod);
+  EXPECT_TRUE(Run("hd"));
+  EXPECT_EQ(LengthMod::h, o.length_mod);
+  EXPECT_TRUE(Run("hhd"));
+  EXPECT_EQ(LengthMod::hh, o.length_mod);
+  EXPECT_TRUE(Run("ld"));
+  EXPECT_EQ(LengthMod::l, o.length_mod);
+  EXPECT_TRUE(Run("lld"));
+  EXPECT_EQ(LengthMod::ll, o.length_mod);
+  EXPECT_TRUE(Run("Lf"));
+  EXPECT_EQ(LengthMod::L, o.length_mod);
+  EXPECT_TRUE(Run("qf"));
+  EXPECT_EQ(LengthMod::q, o.length_mod);
+  EXPECT_TRUE(Run("jd"));
+  EXPECT_EQ(LengthMod::j, o.length_mod);
+  EXPECT_TRUE(Run("zd"));
+  EXPECT_EQ(LengthMod::z, o.length_mod);
+  EXPECT_TRUE(Run("td"));
+  EXPECT_EQ(LengthMod::t, o.length_mod);
+}
+
+struct SummarizeConsumer {
+  std::string* out;
+  explicit SummarizeConsumer(std::string* out) : out(out) {}
+
+  bool Append(string_view s) {
+    *out += "[" + std::string(s) + "]";
+    return true;
+  }
+
+  bool ConvertOne(const UnboundConversion& conv, string_view s) {
+    *out += "{";
+    *out += std::string(s);
+    *out += ":";
+    *out += std::to_string(conv.arg_position) + "$";
+    if (conv.width.is_from_arg()) {
+      *out += std::to_string(conv.width.get_from_arg()) + "$*";
+    }
+    if (conv.precision.is_from_arg()) {
+      *out += "." + std::to_string(conv.precision.get_from_arg()) + "$*";
+    }
+    *out += FormatConversionCharToChar(conv.conv);
+    *out += "}";
+    return true;
+  }
+};
+
+std::string SummarizeParsedFormat(const ParsedFormatBase& pc) {
+  std::string out;
+  if (!pc.ProcessFormat(SummarizeConsumer(&out))) out += "!";
+  return out;
+}
+
+class ParsedFormatTest : public testing::Test {};
+
+TEST_F(ParsedFormatTest, ValueSemantics) {
+  ParsedFormatBase p1({}, true, {});  // empty format
+  EXPECT_EQ("", SummarizeParsedFormat(p1));
+
+  ParsedFormatBase p2 = p1;  // copy construct (empty)
+  EXPECT_EQ(SummarizeParsedFormat(p1), SummarizeParsedFormat(p2));
+
+  p1 = ParsedFormatBase("hello%s", true,
+                        {FormatConversionCharSetInternal::s});  // move assign
+  EXPECT_EQ("[hello]{s:1$s}", SummarizeParsedFormat(p1));
+
+  ParsedFormatBase p3 = p1;  // copy construct (nonempty)
+  EXPECT_EQ(SummarizeParsedFormat(p1), SummarizeParsedFormat(p3));
+
+  using std::swap;
+  swap(p1, p2);
+  EXPECT_EQ("", SummarizeParsedFormat(p1));
+  EXPECT_EQ("[hello]{s:1$s}", SummarizeParsedFormat(p2));
+  swap(p1, p2);  // undo
+
+  p2 = p1;  // copy assign
+  EXPECT_EQ(SummarizeParsedFormat(p1), SummarizeParsedFormat(p2));
+}
+
+struct ExpectParse {
+  const char* in;
+  std::initializer_list<FormatConversionCharSet> conv_set;
+  const char* out;
+};
+
+TEST_F(ParsedFormatTest, Parsing) {
+  // Parse should be equivalent to that obtained by ConversionParseIterator.
+  // No need to retest the parsing edge cases here.
+  const ExpectParse kExpect[] = {
+      {"", {}, ""},
+      {"ab", {}, "[ab]"},
+      {"a%d", {FormatConversionCharSetInternal::d}, "[a]{d:1$d}"},
+      {"a%+d", {FormatConversionCharSetInternal::d}, "[a]{+d:1$d}"},
+      {"a% d", {FormatConversionCharSetInternal::d}, "[a]{ d:1$d}"},
+      {"a%b %d", {}, "[a]!"},  // stop after error
+  };
+  for (const auto& e : kExpect) {
+    SCOPED_TRACE(e.in);
+    EXPECT_EQ(e.out,
+              SummarizeParsedFormat(ParsedFormatBase(e.in, false, e.conv_set)));
+  }
+}
+
+TEST_F(ParsedFormatTest, ParsingFlagOrder) {
+  const ExpectParse kExpect[] = {
+      {"a%+ 0d", {FormatConversionCharSetInternal::d}, "[a]{+ 0d:1$d}"},
+      {"a%+0 d", {FormatConversionCharSetInternal::d}, "[a]{+0 d:1$d}"},
+      {"a%0+ d", {FormatConversionCharSetInternal::d}, "[a]{0+ d:1$d}"},
+      {"a% +0d", {FormatConversionCharSetInternal::d}, "[a]{ +0d:1$d}"},
+      {"a%0 +d", {FormatConversionCharSetInternal::d}, "[a]{0 +d:1$d}"},
+      {"a% 0+d", {FormatConversionCharSetInternal::d}, "[a]{ 0+d:1$d}"},
+      {"a%+   0+d", {FormatConversionCharSetInternal::d}, "[a]{+   0+d:1$d}"},
+  };
+  for (const auto& e : kExpect) {
+    SCOPED_TRACE(e.in);
+    EXPECT_EQ(e.out,
+              SummarizeParsedFormat(ParsedFormatBase(e.in, false, e.conv_set)));
+  }
+}
+
+}  // namespace
+}  // namespace str_format_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/str_join_internal.h b/weight/_dep/abseil-cpp/absl/strings/internal/str_join_internal.h
new file mode 100644
index 0000000000000000000000000000000000000000..d97d5033d8ee108035452531b3088dae0e4bd2a9
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/str_join_internal.h
@@ -0,0 +1,317 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// This file declares INTERNAL parts of the Join API that are inlined/templated
+// or otherwise need to be available at compile time. The main abstractions
+// defined in this file are:
+//
+//   - A handful of default Formatters
+//   - JoinAlgorithm() overloads
+//   - JoinRange() overloads
+//   - JoinTuple()
+//
+// DO NOT INCLUDE THIS FILE DIRECTLY. Use this file by including
+// absl/strings/str_join.h
+//
+// IWYU pragma: private, include "absl/strings/str_join.h"
+
+#ifndef ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
+#define ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
+
+#include <cstring>
+#include <iterator>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include <utility>
+
+#include "absl/strings/internal/ostringstream.h"
+#include "absl/strings/internal/resize_uninitialized.h"
+#include "absl/strings/str_cat.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace strings_internal {
+
+//
+// Formatter objects
+//
+// The following are implementation classes for standard Formatter objects. The
+// factory functions that users will call to create and use these formatters are
+// defined and documented in strings/join.h.
+//
+
+// The default formatter. Converts alpha-numeric types to strings.
+struct AlphaNumFormatterImpl {
+  // This template is needed in order to support passing in a dereferenced
+  // vector<bool>::iterator
+  template <typename T>
+  void operator()(std::string* out, const T& t) const {
+    StrAppend(out, AlphaNum(t));
+  }
+
+  void operator()(std::string* out, const AlphaNum& t) const {
+    StrAppend(out, t);
+  }
+};
+
+// A type that's used to overload the JoinAlgorithm() function (defined below)
+// for ranges that do not require additional formatting (e.g., a range of
+// strings).
+
+struct NoFormatter : public AlphaNumFormatterImpl {};
+
+// Formats types to strings using the << operator.
+class StreamFormatterImpl {
+ public:
+  // The method isn't const because it mutates state. Making it const will
+  // render StreamFormatterImpl thread-hostile.
+  template <typename T>
+  void operator()(std::string* out, const T& t) {
+    // The stream is created lazily to avoid paying the relatively high cost
+    // of its construction when joining an empty range.
+    if (strm_) {
+      strm_->clear();  // clear the bad, fail and eof bits in case they were set
+      strm_->str(out);
+    } else {
+      strm_.reset(new strings_internal::OStringStream(out));
+    }
+    *strm_ << t;
+  }
+
+ private:
+  std::unique_ptr<strings_internal::OStringStream> strm_;
+};
+
+// Formats a std::pair<>. The 'first' member is formatted using f1_ and the
+// 'second' member is formatted using f2_. sep_ is the separator.
+template <typename F1, typename F2>
+class PairFormatterImpl {
+ public:
+  PairFormatterImpl(F1 f1, absl::string_view sep, F2 f2)
+      : f1_(std::move(f1)), sep_(sep), f2_(std::move(f2)) {}
+
+  template <typename T>
+  void operator()(std::string* out, const T& p) {
+    f1_(out, p.first);
+    out->append(sep_);
+    f2_(out, p.second);
+  }
+
+  template <typename T>
+  void operator()(std::string* out, const T& p) const {
+    f1_(out, p.first);
+    out->append(sep_);
+    f2_(out, p.second);
+  }
+
+ private:
+  F1 f1_;
+  std::string sep_;
+  F2 f2_;
+};
+
+// Wraps another formatter and dereferences the argument to operator() then
+// passes the dereferenced argument to the wrapped formatter. This can be
+// useful, for example, to join a std::vector<int*>.
+template <typename Formatter>
+class DereferenceFormatterImpl {
+ public:
+  DereferenceFormatterImpl() : f_() {}
+  explicit DereferenceFormatterImpl(Formatter&& f)
+      : f_(std::forward<Formatter>(f)) {}
+
+  template <typename T>
+  void operator()(std::string* out, const T& t) {
+    f_(out, *t);
+  }
+
+  template <typename T>
+  void operator()(std::string* out, const T& t) const {
+    f_(out, *t);
+  }
+
+ private:
+  Formatter f_;
+};
+
+// DefaultFormatter<T> is a traits class that selects a default Formatter to use
+// for the given type T. The ::Type member names the Formatter to use. This is
+// used by the strings::Join() functions that do NOT take a Formatter argument,
+// in which case a default Formatter must be chosen.
+//
+// AlphaNumFormatterImpl is the default in the base template, followed by
+// specializations for other types.
+template <typename ValueType>
+struct DefaultFormatter {
+  typedef AlphaNumFormatterImpl Type;
+};
+template <>
+struct DefaultFormatter<const char*> {
+  typedef AlphaNumFormatterImpl Type;
+};
+template <>
+struct DefaultFormatter<char*> {
+  typedef AlphaNumFormatterImpl Type;
+};
+template <>
+struct DefaultFormatter<std::string> {
+  typedef NoFormatter Type;
+};
+template <>
+struct DefaultFormatter<absl::string_view> {
+  typedef NoFormatter Type;
+};
+template <typename ValueType>
+struct DefaultFormatter<ValueType*> {
+  typedef DereferenceFormatterImpl<typename DefaultFormatter<ValueType>::Type>
+      Type;
+};
+
+template <typename ValueType>
+struct DefaultFormatter<std::unique_ptr<ValueType>>
+    : public DefaultFormatter<ValueType*> {};
+
+//
+// JoinAlgorithm() functions
+//
+
+// The main joining algorithm. This simply joins the elements in the given
+// iterator range, each separated by the given separator, into an output string,
+// and formats each element using the provided Formatter object.
+template <typename Iterator, typename Formatter>
+std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
+                          Formatter&& f) {
+  std::string result;
+  absl::string_view sep("");
+  for (Iterator it = start; it != end; ++it) {
+    result.append(sep.data(), sep.size());
+    f(&result, *it);
+    sep = s;
+  }
+  return result;
+}
+
+// A joining algorithm that's optimized for a forward iterator range of
+// string-like objects that do not need any additional formatting. This is to
+// optimize the common case of joining, say, a std::vector<string> or a
+// std::vector<absl::string_view>.
+//
+// This is an overload of the previous JoinAlgorithm() function. Here the
+// Formatter argument is of type NoFormatter. Since NoFormatter is an internal
+// type, this overload is only invoked when strings::Join() is called with a
+// range of string-like objects (e.g., std::string, absl::string_view), and an
+// explicit Formatter argument was NOT specified.
+//
+// The optimization is that the needed space will be reserved in the output
+// string to avoid the need to resize while appending. To do this, the iterator
+// range will be traversed twice: once to calculate the total needed size, and
+// then again to copy the elements and delimiters to the output string.
+template <typename Iterator,
+          typename = typename std::enable_if<std::is_convertible<
+              typename std::iterator_traits<Iterator>::iterator_category,
+              std::forward_iterator_tag>::value>::type>
+std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
+                          NoFormatter) {
+  std::string result;
+  if (start != end) {
+    // Sums size
+    auto&& start_value = *start;
+    size_t result_size = start_value.size();
+    for (Iterator it = start; ++it != end;) {
+      result_size += s.size();
+      result_size += (*it).size();
+    }
+
+    if (result_size > 0) {
+      STLStringResizeUninitialized(&result, result_size);
+
+      // Joins strings
+      char* result_buf = &*result.begin();
+
+      memcpy(result_buf, start_value.data(), start_value.size());
+      result_buf += start_value.size();
+      for (Iterator it = start; ++it != end;) {
+        memcpy(result_buf, s.data(), s.size());
+        result_buf += s.size();
+        auto&& value = *it;
+        memcpy(result_buf, value.data(), value.size());
+        result_buf += value.size();
+      }
+    }
+  }
+
+  return result;
+}
+
+// JoinTupleLoop implements a loop over the elements of a std::tuple, which
+// are heterogeneous. The primary template matches the tuple interior case. It
+// continues the iteration after appending a separator (for nonzero indices)
+// and formatting an element of the tuple. The specialization for the I=N case
+// matches the end-of-tuple, and terminates the iteration.
+template <size_t I, size_t N>
+struct JoinTupleLoop {
+  template <typename Tup, typename Formatter>
+  void operator()(std::string* out, const Tup& tup, absl::string_view sep,
+                  Formatter&& fmt) {
+    if (I > 0) out->append(sep.data(), sep.size());
+    fmt(out, std::get<I>(tup));
+    JoinTupleLoop<I + 1, N>()(out, tup, sep, fmt);
+  }
+};
+template <size_t N>
+struct JoinTupleLoop<N, N> {
+  template <typename Tup, typename Formatter>
+  void operator()(std::string*, const Tup&, absl::string_view, Formatter&&) {}
+};
+
+template <typename... T, typename Formatter>
+std::string JoinAlgorithm(const std::tuple<T...>& tup, absl::string_view sep,
+                          Formatter&& fmt) {
+  std::string result;
+  JoinTupleLoop<0, sizeof...(T)>()(&result, tup, sep, fmt);
+  return result;
+}
+
+template <typename Iterator>
+std::string JoinRange(Iterator first, Iterator last,
+                      absl::string_view separator) {
+  // No formatter was explicitly given, so a default must be chosen.
+  typedef typename std::iterator_traits<Iterator>::value_type ValueType;
+  typedef typename DefaultFormatter<ValueType>::Type Formatter;
+  return JoinAlgorithm(first, last, separator, Formatter());
+}
+
+template <typename Range, typename Formatter>
+std::string JoinRange(const Range& range, absl::string_view separator,
+                      Formatter&& fmt) {
+  using std::begin;
+  using std::end;
+  return JoinAlgorithm(begin(range), end(range), separator, fmt);
+}
+
+template <typename Range>
+std::string JoinRange(const Range& range, absl::string_view separator) {
+  using std::begin;
+  using std::end;
+  return JoinRange(begin(range), end(range), separator);
+}
+
+}  // namespace strings_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/string_constant.h b/weight/_dep/abseil-cpp/absl/strings/internal/string_constant.h
new file mode 100644
index 0000000000000000000000000000000000000000..f68b17d75e84fd469c96cfe028bd4dbac9e05ea7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/string_constant.h
@@ -0,0 +1,72 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_STRING_CONSTANT_H_
+#define ABSL_STRINGS_INTERNAL_STRING_CONSTANT_H_
+
+#include "absl/meta/type_traits.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace strings_internal {
+
+// StringConstant<T> represents a compile time string constant.
+// It can be accessed via its `absl::string_view value` static member.
+// It is guaranteed that the `string_view` returned has constant `.data()`,
+// constant `.size()` and constant `value[i]` for all `0 <= i < .size()`
+//
+// The `T` is an opaque type. It is guaranteed that different string constants
+// will have different values of `T`. This allows users to associate the string
+// constant with other static state at compile time.
+//
+// Instances should be made using the `MakeStringConstant()` factory function
+// below.
+template <typename T>
+struct StringConstant {
+ private:
+  static constexpr bool TryConstexprEval(absl::string_view view) {
+    return view.empty() || 2 * view[0] != 1;
+  }
+
+ public:
+  static constexpr absl::string_view value = T{}();
+  constexpr absl::string_view operator()() const { return value; }
+
+  // Check to be sure `view` points to constant data.
+  // Otherwise, it can't be constant evaluated.
+  static_assert(TryConstexprEval(value),
+                "The input string_view must point to constant data.");
+};
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+template <typename T>
+constexpr absl::string_view StringConstant<T>::value;
+#endif
+
+// Factory function for `StringConstant` instances.
+// It supports callables that have a constexpr default constructor and a
+// constexpr operator().
+// It must return an `absl::string_view` or `const char*` pointing to constant
+// data. This is validated at compile time.
+template <typename T>
+constexpr StringConstant<T> MakeStringConstant(T) {
+  return {};
+}
+
+}  // namespace strings_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_STRING_CONSTANT_H_
diff --git a/weight/_dep/abseil-cpp/absl/strings/internal/string_constant_test.cc b/weight/_dep/abseil-cpp/absl/strings/internal/string_constant_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..392833cf1592dc6636516baa78069993bbc4f2c8
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/internal/string_constant_test.cc
@@ -0,0 +1,60 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/string_constant.h"
+
+#include "absl/meta/type_traits.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+using absl::strings_internal::MakeStringConstant;
+
+struct Callable {
+  constexpr absl::string_view operator()() const {
+    return absl::string_view("Callable", 8);
+  }
+};
+
+TEST(StringConstant, Traits) {
+  constexpr auto str = MakeStringConstant(Callable{});
+  using T = decltype(str);
+
+  EXPECT_TRUE(std::is_empty<T>::value);
+  EXPECT_TRUE(std::is_trivial<T>::value);
+  EXPECT_TRUE(absl::is_trivially_default_constructible<T>::value);
+  EXPECT_TRUE(absl::is_trivially_copy_constructible<T>::value);
+  EXPECT_TRUE(absl::is_trivially_move_constructible<T>::value);
+  EXPECT_TRUE(absl::is_trivially_destructible<T>::value);
+}
+
+TEST(StringConstant, MakeFromCallable) {
+  constexpr auto str = MakeStringConstant(Callable{});
+  using T = decltype(str);
+  EXPECT_EQ(Callable{}(), T::value);
+  EXPECT_EQ(Callable{}(), str());
+}
+
+TEST(StringConstant, MakeFromStringConstant) {
+  // We want to make sure the StringConstant itself is a valid input to the
+  // factory function.
+  constexpr auto str = MakeStringConstant(Callable{});
+  constexpr auto str2 = MakeStringConstant(str);
+  using T = decltype(str2);
+  EXPECT_EQ(Callable{}(), T::value);
+  EXPECT_EQ(Callable{}(), str2());
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/strings/string_view.h b/weight/_dep/abseil-cpp/absl/strings/string_view.h
new file mode 100644
index 0000000000000000000000000000000000000000..04ca0a38ae7a2c65b35e036a21823bfe3f9d0491
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/strings/string_view.h
@@ -0,0 +1,769 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: string_view.h
+// -----------------------------------------------------------------------------
+//
+// This file contains the definition of the `absl::string_view` class. A
+// `string_view` points to a contiguous span of characters, often part or all of
+// another `std::string`, double-quoted string literal, character array, or even
+// another `string_view`.
+//
+// This `absl::string_view` abstraction is designed to be a drop-in
+// replacement for the C++17 `std::string_view` abstraction.
+#ifndef ABSL_STRINGS_STRING_VIEW_H_
+#define ABSL_STRINGS_STRING_VIEW_H_
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstring>
+#include <iosfwd>
+#include <iterator>
+#include <limits>
+#include <string>
+
+#include "absl/base/attributes.h"
+#include "absl/base/nullability.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/throw_delegate.h"
+#include "absl/base/macros.h"
+#include "absl/base/optimization.h"
+#include "absl/base/port.h"
+
+#ifdef ABSL_USES_STD_STRING_VIEW
+
+#include <string_view>  // IWYU pragma: export
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+using string_view = std::string_view;
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#else  // ABSL_USES_STD_STRING_VIEW
+
+#if ABSL_HAVE_BUILTIN(__builtin_memcmp) ||        \
+    (defined(__GNUC__) && !defined(__clang__)) || \
+    (defined(_MSC_VER) && _MSC_VER >= 1928)
+#define ABSL_INTERNAL_STRING_VIEW_MEMCMP __builtin_memcmp
+#else  // ABSL_HAVE_BUILTIN(__builtin_memcmp)
+#define ABSL_INTERNAL_STRING_VIEW_MEMCMP memcmp
+#endif  // ABSL_HAVE_BUILTIN(__builtin_memcmp)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// absl::string_view
+//
+// A `string_view` provides a lightweight view into the string data provided by
+// a `std::string`, double-quoted string literal, character array, or even
+// another `string_view`. A `string_view` does *not* own the string to which it
+// points, and that data cannot be modified through the view.
+//
+// You can use `string_view` as a function or method parameter anywhere a
+// parameter can receive a double-quoted string literal, `const char*`,
+// `std::string`, or another `absl::string_view` argument with no need to copy
+// the string data. Systematic use of `string_view` within function arguments
+// reduces data copies and `strlen()` calls.
+//
+// Because of its small size, prefer passing `string_view` by value:
+//
+//   void MyFunction(absl::string_view arg);
+//
+// If circumstances require, you may also pass one by const reference:
+//
+//   void MyFunction(const absl::string_view& arg);  // not preferred
+//
+// Passing by value generates slightly smaller code for many architectures.
+//
+// In either case, the source data of the `string_view` must outlive the
+// `string_view` itself.
+//
+// A `string_view` is also suitable for local variables if you know that the
+// lifetime of the underlying object is longer than the lifetime of your
+// `string_view` variable. However, beware of binding a `string_view` to a
+// temporary value:
+//
+//   // BAD use of string_view: lifetime problem
+//   absl::string_view sv = obj.ReturnAString();
+//
+//   // GOOD use of string_view: str outlives sv
+//   std::string str = obj.ReturnAString();
+//   absl::string_view sv = str;
+//
+// Due to lifetime issues, a `string_view` is sometimes a poor choice for a
+// return value and usually a poor choice for a data member. If you do use a
+// `string_view` this way, it is your responsibility to ensure that the object
+// pointed to by the `string_view` outlives the `string_view`.
+//
+// A `string_view` may represent a whole string or just part of a string. For
+// example, when splitting a string, `std::vector<absl::string_view>` is a
+// natural data type for the output.
+//
+// For another example, a Cord is a non-contiguous, potentially very
+// long string-like object.  The Cord class has an interface that iteratively
+// provides string_view objects that point to the successive pieces of a Cord
+// object.
+//
+// When constructed from a source which is NUL-terminated, the `string_view`
+// itself will not include the NUL-terminator unless a specific size (including
+// the NUL) is passed to the constructor. As a result, common idioms that work
+// on NUL-terminated strings do not work on `string_view` objects. If you write
+// code that scans a `string_view`, you must check its length rather than test
+// for nul, for example. Note, however, that nuls may still be embedded within
+// a `string_view` explicitly.
+//
+// You may create a null `string_view` in two ways:
+//
+//   absl::string_view sv;
+//   absl::string_view sv(nullptr, 0);
+//
+// For the above, `sv.data() == nullptr`, `sv.length() == 0`, and
+// `sv.empty() == true`. Also, if you create a `string_view` with a non-null
+// pointer then `sv.data() != nullptr`. Thus, you can use `string_view()` to
+// signal an undefined value that is different from other `string_view` values
+// in a similar fashion to how `const char* p1 = nullptr;` is different from
+// `const char* p2 = "";`. However, in practice, it is not recommended to rely
+// on this behavior.
+//
+// Be careful not to confuse a null `string_view` with an empty one. A null
+// `string_view` is an empty `string_view`, but some empty `string_view`s are
+// not null. Prefer checking for emptiness over checking for null.
+//
+// There are many ways to create an empty string_view:
+//
+//   const char* nullcp = nullptr;
+//   // string_view.size() will return 0 in all cases.
+//   absl::string_view();
+//   absl::string_view(nullcp, 0);
+//   absl::string_view("");
+//   absl::string_view("", 0);
+//   absl::string_view("abcdef", 0);
+//   absl::string_view("abcdef" + 6, 0);
+//
+// All empty `string_view` objects whether null or not, are equal:
+//
+//   absl::string_view() == absl::string_view("", 0)
+//   absl::string_view(nullptr, 0) == absl::string_view("abcdef"+6, 0)
+class string_view {
+ public:
+  using traits_type = std::char_traits<char>;
+  using value_type = char;
+  using pointer = absl::Nullable<char*>;
+  using const_pointer = absl::Nullable<const char*>;
+  using reference = char&;
+  using const_reference = const char&;
+  using const_iterator = absl::Nullable<const char*>;
+  using iterator = const_iterator;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+  using reverse_iterator = const_reverse_iterator;
+  using size_type = size_t;
+  using difference_type = std::ptrdiff_t;
+
+  static constexpr size_type npos = static_cast<size_type>(-1);
+
+  // Null `string_view` constructor
+  constexpr string_view() noexcept : ptr_(nullptr), length_(0) {}
+
+  // Implicit constructors
+
+  template <typename Allocator>
+  string_view(  // NOLINT(runtime/explicit)
+      const std::basic_string<char, std::char_traits<char>, Allocator>& str
+          ABSL_ATTRIBUTE_LIFETIME_BOUND) noexcept
+      // This is implemented in terms of `string_view(p, n)` so `str.size()`
+      // doesn't need to be reevaluated after `ptr_` is set.
+      // The length check is also skipped since it is unnecessary and causes
+      // code bloat.
+      : string_view(str.data(), str.size(), SkipCheckLengthTag{}) {}
+
+  // Implicit constructor of a `string_view` from NUL-terminated `str`. When
+  // accepting possibly null strings, use `absl::NullSafeStringView(str)`
+  // instead (see below).
+  // The length check is skipped since it is unnecessary and causes code bloat.
+  constexpr string_view(  // NOLINT(runtime/explicit)
+      absl::Nonnull<const char*> str)
+      : ptr_(str), length_(str ? StrlenInternal(str) : 0) {}
+
+  // Implicit constructor of a `string_view` from a `const char*` and length.
+  constexpr string_view(absl::Nullable<const char*> data, size_type len)
+      : ptr_(data), length_(CheckLengthInternal(len)) {}
+
+  // NOTE: Harmlessly omitted to work around gdb bug.
+  //   constexpr string_view(const string_view&) noexcept = default;
+  //   string_view& operator=(const string_view&) noexcept = default;
+
+  // Iterators
+
+  // string_view::begin()
+  //
+  // Returns an iterator pointing to the first character at the beginning of the
+  // `string_view`, or `end()` if the `string_view` is empty.
+  constexpr const_iterator begin() const noexcept { return ptr_; }
+
+  // string_view::end()
+  //
+  // Returns an iterator pointing just beyond the last character at the end of
+  // the `string_view`. This iterator acts as a placeholder; attempting to
+  // access it results in undefined behavior.
+  constexpr const_iterator end() const noexcept { return ptr_ + length_; }
+
+  // string_view::cbegin()
+  //
+  // Returns a const iterator pointing to the first character at the beginning
+  // of the `string_view`, or `end()` if the `string_view` is empty.
+  constexpr const_iterator cbegin() const noexcept { return begin(); }
+
+  // string_view::cend()
+  //
+  // Returns a const iterator pointing just beyond the last character at the end
+  // of the `string_view`. This pointer acts as a placeholder; attempting to
+  // access its element results in undefined behavior.
+  constexpr const_iterator cend() const noexcept { return end(); }
+
+  // string_view::rbegin()
+  //
+  // Returns a reverse iterator pointing to the last character at the end of the
+  // `string_view`, or `rend()` if the `string_view` is empty.
+  const_reverse_iterator rbegin() const noexcept {
+    return const_reverse_iterator(end());
+  }
+
+  // string_view::rend()
+  //
+  // Returns a reverse iterator pointing just before the first character at the
+  // beginning of the `string_view`. This pointer acts as a placeholder;
+  // attempting to access its element results in undefined behavior.
+  const_reverse_iterator rend() const noexcept {
+    return const_reverse_iterator(begin());
+  }
+
+  // string_view::crbegin()
+  //
+  // Returns a const reverse iterator pointing to the last character at the end
+  // of the `string_view`, or `crend()` if the `string_view` is empty.
+  const_reverse_iterator crbegin() const noexcept { return rbegin(); }
+
+  // string_view::crend()
+  //
+  // Returns a const reverse iterator pointing just before the first character
+  // at the beginning of the `string_view`. This pointer acts as a placeholder;
+  // attempting to access its element results in undefined behavior.
+  const_reverse_iterator crend() const noexcept { return rend(); }
+
+  // Capacity Utilities
+
+  // string_view::size()
+  //
+  // Returns the number of characters in the `string_view`.
+  constexpr size_type size() const noexcept { return length_; }
+
+  // string_view::length()
+  //
+  // Returns the number of characters in the `string_view`. Alias for `size()`.
+  constexpr size_type length() const noexcept { return size(); }
+
+  // string_view::max_size()
+  //
+  // Returns the maximum number of characters the `string_view` can hold.
+  constexpr size_type max_size() const noexcept { return kMaxSize; }
+
+  // string_view::empty()
+  //
+  // Checks if the `string_view` is empty (refers to no characters).
+  constexpr bool empty() const noexcept { return length_ == 0; }
+
+  // string_view::operator[]
+  //
+  // Returns the ith element of the `string_view` using the array operator.
+  // Note that this operator does not perform any bounds checking.
+  constexpr const_reference operator[](size_type i) const {
+    return ABSL_HARDENING_ASSERT(i < size()), ptr_[i];
+  }
+
+  // string_view::at()
+  //
+  // Returns the ith element of the `string_view`. Bounds checking is performed,
+  // and an exception of type `std::out_of_range` will be thrown on invalid
+  // access.
+  constexpr const_reference at(size_type i) const {
+    return ABSL_PREDICT_TRUE(i < size())
+               ? ptr_[i]
+               : ((void)base_internal::ThrowStdOutOfRange(
+                      "absl::string_view::at"),
+                  ptr_[i]);
+  }
+
+  // string_view::front()
+  //
+  // Returns the first element of a `string_view`.
+  constexpr const_reference front() const {
+    return ABSL_HARDENING_ASSERT(!empty()), ptr_[0];
+  }
+
+  // string_view::back()
+  //
+  // Returns the last element of a `string_view`.
+  constexpr const_reference back() const {
+    return ABSL_HARDENING_ASSERT(!empty()), ptr_[size() - 1];
+  }
+
+  // string_view::data()
+  //
+  // Returns a pointer to the underlying character array (which is of course
+  // stored elsewhere). Note that `string_view::data()` may contain embedded nul
+  // characters, but the returned buffer may or may not be NUL-terminated;
+  // therefore, do not pass `data()` to a routine that expects a NUL-terminated
+  // string.
+  constexpr const_pointer data() const noexcept { return ptr_; }
+
+  // Modifiers
+
+  // string_view::remove_prefix()
+  //
+  // Removes the first `n` characters from the `string_view`. Note that the
+  // underlying string is not changed, only the view.
+  constexpr void remove_prefix(size_type n) {
+    ABSL_HARDENING_ASSERT(n <= length_);
+    ptr_ += n;
+    length_ -= n;
+  }
+
+  // string_view::remove_suffix()
+  //
+  // Removes the last `n` characters from the `string_view`. Note that the
+  // underlying string is not changed, only the view.
+  constexpr void remove_suffix(size_type n) {
+    ABSL_HARDENING_ASSERT(n <= length_);
+    length_ -= n;
+  }
+
+  // string_view::swap()
+  //
+  // Swaps this `string_view` with another `string_view`.
+  constexpr void swap(string_view& s) noexcept {
+    auto t = *this;
+    *this = s;
+    s = t;
+  }
+
+  // Explicit conversion operators
+
+  // Converts to `std::basic_string`.
+  template <typename A>
+  explicit operator std::basic_string<char, traits_type, A>() const {
+    if (!data()) return {};
+    return std::basic_string<char, traits_type, A>(data(), size());
+  }
+
+  // string_view::copy()
+  //
+  // Copies the contents of the `string_view` at offset `pos` and length `n`
+  // into `buf`.
+  size_type copy(char* buf, size_type n, size_type pos = 0) const {
+    if (ABSL_PREDICT_FALSE(pos > length_)) {
+      base_internal::ThrowStdOutOfRange("absl::string_view::copy");
+    }
+    size_type rlen = (std::min)(length_ - pos, n);
+    if (rlen > 0) {
+      const char* start = ptr_ + pos;
+      traits_type::copy(buf, start, rlen);
+    }
+    return rlen;
+  }
+
+  // string_view::substr()
+  //
+  // Returns a "substring" of the `string_view` (at offset `pos` and length
+  // `n`) as another string_view. This function throws `std::out_of_bounds` if
+  // `pos > size`.
+  // Use absl::ClippedSubstr if you need a truncating substr operation.
+  constexpr string_view substr(size_type pos = 0, size_type n = npos) const {
+    return ABSL_PREDICT_FALSE(pos > length_)
+               ? (base_internal::ThrowStdOutOfRange(
+                      "absl::string_view::substr"),
+                  string_view())
+               : string_view(ptr_ + pos, Min(n, length_ - pos));
+  }
+
+  // string_view::compare()
+  //
+  // Performs a lexicographical comparison between this `string_view` and
+  // another `string_view` `x`, returning a negative value if `*this` is less
+  // than `x`, 0 if `*this` is equal to `x`, and a positive value if `*this`
+  // is greater than `x`.
+  constexpr int compare(string_view x) const noexcept {
+    return CompareImpl(length_, x.length_,
+                       Min(length_, x.length_) == 0
+                           ? 0
+                           : ABSL_INTERNAL_STRING_VIEW_MEMCMP(
+                                 ptr_, x.ptr_, Min(length_, x.length_)));
+  }
+
+  // Overload of `string_view::compare()` for comparing a substring of the
+  // 'string_view` and another `absl::string_view`.
+  constexpr int compare(size_type pos1, size_type count1, string_view v) const {
+    return substr(pos1, count1).compare(v);
+  }
+
+  // Overload of `string_view::compare()` for comparing a substring of the
+  // `string_view` and a substring of another `absl::string_view`.
+  constexpr int compare(size_type pos1, size_type count1, string_view v,
+                        size_type pos2, size_type count2) const {
+    return substr(pos1, count1).compare(v.substr(pos2, count2));
+  }
+
+  // Overload of `string_view::compare()` for comparing a `string_view` and a
+  // a different C-style string `s`.
+  constexpr int compare(absl::Nonnull<const char*> s) const {
+    return compare(string_view(s));
+  }
+
+  // Overload of `string_view::compare()` for comparing a substring of the
+  // `string_view` and a different string C-style string `s`.
+  constexpr int compare(size_type pos1, size_type count1,
+                        absl::Nonnull<const char*> s) const {
+    return substr(pos1, count1).compare(string_view(s));
+  }
+
+  // Overload of `string_view::compare()` for comparing a substring of the
+  // `string_view` and a substring of a different C-style string `s`.
+  constexpr int compare(size_type pos1, size_type count1,
+                        absl::Nonnull<const char*> s, size_type count2) const {
+    return substr(pos1, count1).compare(string_view(s, count2));
+  }
+
+  // Find Utilities
+
+  // string_view::find()
+  //
+  // Finds the first occurrence of the substring `s` within the `string_view`,
+  // returning the position of the first character's match, or `npos` if no
+  // match was found.
+  size_type find(string_view s, size_type pos = 0) const noexcept;
+
+  // Overload of `string_view::find()` for finding the given character `c`
+  // within the `string_view`.
+  size_type find(char c, size_type pos = 0) const noexcept;
+
+  // Overload of `string_view::find()` for finding a substring of a different
+  // C-style string `s` within the `string_view`.
+  size_type find(absl::Nonnull<const char*> s, size_type pos,
+                 size_type count) const {
+    return find(string_view(s, count), pos);
+  }
+
+  // Overload of `string_view::find()` for finding a different C-style string
+  // `s` within the `string_view`.
+  size_type find(absl::Nonnull<const char *> s, size_type pos = 0) const {
+    return find(string_view(s), pos);
+  }
+
+  // string_view::rfind()
+  //
+  // Finds the last occurrence of a substring `s` within the `string_view`,
+  // returning the position of the first character's match, or `npos` if no
+  // match was found.
+  size_type rfind(string_view s, size_type pos = npos) const noexcept;
+
+  // Overload of `string_view::rfind()` for finding the last given character `c`
+  // within the `string_view`.
+  size_type rfind(char c, size_type pos = npos) const noexcept;
+
+  // Overload of `string_view::rfind()` for finding a substring of a different
+  // C-style string `s` within the `string_view`.
+  size_type rfind(absl::Nonnull<const char*> s, size_type pos,
+                  size_type count) const {
+    return rfind(string_view(s, count), pos);
+  }
+
+  // Overload of `string_view::rfind()` for finding a different C-style string
+  // `s` within the `string_view`.
+  size_type rfind(absl::Nonnull<const char*> s, size_type pos = npos) const {
+    return rfind(string_view(s), pos);
+  }
+
+  // string_view::find_first_of()
+  //
+  // Finds the first occurrence of any of the characters in `s` within the
+  // `string_view`, returning the start position of the match, or `npos` if no
+  // match was found.
+  size_type find_first_of(string_view s, size_type pos = 0) const noexcept;
+
+  // Overload of `string_view::find_first_of()` for finding a character `c`
+  // within the `string_view`.
+  size_type find_first_of(char c, size_type pos = 0) const noexcept {
+    return find(c, pos);
+  }
+
+  // Overload of `string_view::find_first_of()` for finding a substring of a
+  // different C-style string `s` within the `string_view`.
+  size_type find_first_of(absl::Nonnull<const char*> s, size_type pos,
+                          size_type count) const {
+    return find_first_of(string_view(s, count), pos);
+  }
+
+  // Overload of `string_view::find_first_of()` for finding a different C-style
+  // string `s` within the `string_view`.
+  size_type find_first_of(absl::Nonnull<const char*> s,
+                          size_type pos = 0) const {
+    return find_first_of(string_view(s), pos);
+  }
+
+  // string_view::find_last_of()
+  //
+  // Finds the last occurrence of any of the characters in `s` within the
+  // `string_view`, returning the start position of the match, or `npos` if no
+  // match was found.
+  size_type find_last_of(string_view s, size_type pos = npos) const noexcept;
+
+  // Overload of `string_view::find_last_of()` for finding a character `c`
+  // within the `string_view`.
+  size_type find_last_of(char c, size_type pos = npos) const noexcept {
+    return rfind(c, pos);
+  }
+
+  // Overload of `string_view::find_last_of()` for finding a substring of a
+  // different C-style string `s` within the `string_view`.
+  size_type find_last_of(absl::Nonnull<const char*> s, size_type pos,
+                         size_type count) const {
+    return find_last_of(string_view(s, count), pos);
+  }
+
+  // Overload of `string_view::find_last_of()` for finding a different C-style
+  // string `s` within the `string_view`.
+  size_type find_last_of(absl::Nonnull<const char*> s,
+                         size_type pos = npos) const {
+    return find_last_of(string_view(s), pos);
+  }
+
+  // string_view::find_first_not_of()
+  //
+  // Finds the first occurrence of any of the characters not in `s` within the
+  // `string_view`, returning the start position of the first non-match, or
+  // `npos` if no non-match was found.
+  size_type find_first_not_of(string_view s, size_type pos = 0) const noexcept;
+
+  // Overload of `string_view::find_first_not_of()` for finding a character
+  // that is not `c` within the `string_view`.
+  size_type find_first_not_of(char c, size_type pos = 0) const noexcept;
+
+  // Overload of `string_view::find_first_not_of()` for finding a substring of a
+  // different C-style string `s` within the `string_view`.
+  size_type find_first_not_of(absl::Nonnull<const char*> s, size_type pos,
+                              size_type count) const {
+    return find_first_not_of(string_view(s, count), pos);
+  }
+
+  // Overload of `string_view::find_first_not_of()` for finding a different
+  // C-style string `s` within the `string_view`.
+  size_type find_first_not_of(absl::Nonnull<const char*> s,
+                              size_type pos = 0) const {
+    return find_first_not_of(string_view(s), pos);
+  }
+
+  // string_view::find_last_not_of()
+  //
+  // Finds the last occurrence of any of the characters not in `s` within the
+  // `string_view`, returning the start position of the last non-match, or
+  // `npos` if no non-match was found.
+  size_type find_last_not_of(string_view s,
+                             size_type pos = npos) const noexcept;
+
+  // Overload of `string_view::find_last_not_of()` for finding a character
+  // that is not `c` within the `string_view`.
+  size_type find_last_not_of(char c, size_type pos = npos) const noexcept;
+
+  // Overload of `string_view::find_last_not_of()` for finding a substring of a
+  // different C-style string `s` within the `string_view`.
+  size_type find_last_not_of(absl::Nonnull<const char*> s, size_type pos,
+                             size_type count) const {
+    return find_last_not_of(string_view(s, count), pos);
+  }
+
+  // Overload of `string_view::find_last_not_of()` for finding a different
+  // C-style string `s` within the `string_view`.
+  size_type find_last_not_of(absl::Nonnull<const char*> s,
+                             size_type pos = npos) const {
+    return find_last_not_of(string_view(s), pos);
+  }
+
+#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 202002L
+  // string_view::starts_with()
+  //
+  // Returns true if the `string_view` starts with the prefix `s`.
+  //
+  // This method only exists when targeting at least C++20.
+  // If support for C++ prior to C++20 is required, use `absl::StartsWith()`
+  // from `//absl/strings/match.h` for compatibility.
+  constexpr bool starts_with(string_view s) const noexcept {
+    return s.empty() ||
+           (size() >= s.size() &&
+            ABSL_INTERNAL_STRING_VIEW_MEMCMP(data(), s.data(), s.size()) == 0);
+  }
+
+  // Overload of `string_view::starts_with()` that returns true if `c` is the
+  // first character of the `string_view`.
+  constexpr bool starts_with(char c) const noexcept {
+    return !empty() && front() == c;
+  }
+
+  // Overload of `string_view::starts_with()` that returns true if the
+  // `string_view` starts with the C-style prefix `s`.
+  constexpr bool starts_with(const char* s) const {
+    return starts_with(string_view(s));
+  }
+
+  // string_view::ends_with()
+  //
+  // Returns true if the `string_view` ends with the suffix `s`.
+  //
+  // This method only exists when targeting at least C++20.
+  // If support for C++ prior to C++20 is required, use `absl::EndsWith()`
+  // from `//absl/strings/match.h` for compatibility.
+  constexpr bool ends_with(string_view s) const noexcept {
+    return s.empty() || (size() >= s.size() && ABSL_INTERNAL_STRING_VIEW_MEMCMP(
+                                                   data() + (size() - s.size()),
+                                                   s.data(), s.size()) == 0);
+  }
+
+  // Overload of `string_view::ends_with()` that returns true if `c` is the
+  // last character of the `string_view`.
+  constexpr bool ends_with(char c) const noexcept {
+    return !empty() && back() == c;
+  }
+
+  // Overload of `string_view::ends_with()` that returns true if the
+  // `string_view` ends with the C-style suffix `s`.
+  constexpr bool ends_with(const char* s) const {
+    return ends_with(string_view(s));
+  }
+#endif  // ABSL_INTERNAL_CPLUSPLUS_LANG >= 202002L
+
+ private:
+  // The constructor from std::string delegates to this constructor.
+  // See the comment on that constructor for the rationale.
+  struct SkipCheckLengthTag {};
+  string_view(absl::Nullable<const char*> data, size_type len,
+              SkipCheckLengthTag) noexcept
+      : ptr_(data), length_(len) {}
+
+  static constexpr size_type kMaxSize =
+      (std::numeric_limits<difference_type>::max)();
+
+  static constexpr size_type CheckLengthInternal(size_type len) {
+    return ABSL_HARDENING_ASSERT(len <= kMaxSize), len;
+  }
+
+  static constexpr size_type StrlenInternal(absl::Nonnull<const char*> str) {
+#if defined(_MSC_VER) && _MSC_VER >= 1910 && !defined(__clang__)
+    // MSVC 2017+ can evaluate this at compile-time.
+    const char* begin = str;
+    while (*str != '\0') ++str;
+    return str - begin;
+#elif ABSL_HAVE_BUILTIN(__builtin_strlen) || \
+    (defined(__GNUC__) && !defined(__clang__))
+    // GCC has __builtin_strlen according to
+    // https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Other-Builtins.html, but
+    // ABSL_HAVE_BUILTIN doesn't detect that, so we use the extra checks above.
+    // __builtin_strlen is constexpr.
+    return __builtin_strlen(str);
+#else
+    return str ? strlen(str) : 0;
+#endif
+  }
+
+  static constexpr size_t Min(size_type length_a, size_type length_b) {
+    return length_a < length_b ? length_a : length_b;
+  }
+
+  static constexpr int CompareImpl(size_type length_a, size_type length_b,
+                                   int compare_result) {
+    return compare_result == 0 ? static_cast<int>(length_a > length_b) -
+                                     static_cast<int>(length_a < length_b)
+                               : (compare_result < 0 ? -1 : 1);
+  }
+
+  absl::Nullable<const char*> ptr_;
+  size_type length_;
+};
+
+// This large function is defined inline so that in a fairly common case where
+// one of the arguments is a literal, the compiler can elide a lot of the
+// following comparisons.
+constexpr bool operator==(string_view x, string_view y) noexcept {
+  return x.size() == y.size() &&
+         (x.empty() ||
+          ABSL_INTERNAL_STRING_VIEW_MEMCMP(x.data(), y.data(), x.size()) == 0);
+}
+
+constexpr bool operator!=(string_view x, string_view y) noexcept {
+  return !(x == y);
+}
+
+constexpr bool operator<(string_view x, string_view y) noexcept {
+  return x.compare(y) < 0;
+}
+
+constexpr bool operator>(string_view x, string_view y) noexcept {
+  return y < x;
+}
+
+constexpr bool operator<=(string_view x, string_view y) noexcept {
+  return !(y < x);
+}
+
+constexpr bool operator>=(string_view x, string_view y) noexcept {
+  return !(x < y);
+}
+
+// IO Insertion Operator
+std::ostream& operator<<(std::ostream& o, string_view piece);
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#undef ABSL_INTERNAL_STRING_VIEW_MEMCMP
+
+#endif  // ABSL_USES_STD_STRING_VIEW
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// ClippedSubstr()
+//
+// Like `s.substr(pos, n)`, but clips `pos` to an upper bound of `s.size()`.
+// Provided because std::string_view::substr throws if `pos > size()`
+inline string_view ClippedSubstr(string_view s, size_t pos,
+                                 size_t n = string_view::npos) {
+  pos = (std::min)(pos, static_cast<size_t>(s.size()));
+  return s.substr(pos, n);
+}
+
+// NullSafeStringView()
+//
+// Creates an `absl::string_view` from a pointer `p` even if it's null-valued.
+// This function should be used where an `absl::string_view` can be created from
+// a possibly-null pointer.
+constexpr string_view NullSafeStringView(absl::Nullable<const char*> p) {
+  return p ? string_view(p) : string_view();
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_STRING_VIEW_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/graphcycles_benchmark.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/graphcycles_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..54823e0ba51a3815daddb6a8047001b7052b281f
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/graphcycles_benchmark.cc
@@ -0,0 +1,44 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/graphcycles.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "absl/base/internal/raw_logging.h"
+
+namespace {
+
+void BM_StressTest(benchmark::State& state) {
+  const int num_nodes = state.range(0);
+  while (state.KeepRunningBatch(num_nodes)) {
+    absl::synchronization_internal::GraphCycles g;
+    std::vector<absl::synchronization_internal::GraphId> nodes(num_nodes);
+    for (int i = 0; i < num_nodes; i++) {
+      nodes[i] = g.GetId(reinterpret_cast<void*>(static_cast<uintptr_t>(i)));
+    }
+    for (int i = 0; i < num_nodes; i++) {
+      int end = std::min(num_nodes, i + 5);
+      for (int j = i + 1; j < end; j++) {
+        ABSL_RAW_CHECK(g.InsertEdge(nodes[i], nodes[j]), "");
+      }
+    }
+  }
+}
+BENCHMARK(BM_StressTest)->Range(2048, 1048576);
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/graphcycles_test.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/graphcycles_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3c6ef7985c1b8eb966909967e6eba77827f0b489
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/graphcycles_test.cc
@@ -0,0 +1,463 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/graphcycles.h"
+
+#include <map>
+#include <random>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+#include "absl/log/check.h"
+#include "absl/log/log.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+// We emulate a GraphCycles object with a node vector and an edge vector.
+// We then compare the two implementations.
+
+using Nodes = std::vector<int>;
+struct Edge {
+  int from;
+  int to;
+};
+using Edges = std::vector<Edge>;
+using RandomEngine = std::mt19937_64;
+
+// Mapping from integer index to GraphId.
+typedef std::map<int, GraphId> IdMap;
+static GraphId Get(const IdMap& id, int num) {
+  auto iter = id.find(num);
+  return (iter == id.end()) ? InvalidGraphId() : iter->second;
+}
+
+// Return whether "to" is reachable from "from".
+static bool IsReachable(Edges *edges, int from, int to,
+                        std::unordered_set<int> *seen) {
+  seen->insert(from);     // we are investigating "from"; don't do it again
+  if (from == to) return true;
+  for (const auto &edge : *edges) {
+    if (edge.from == from) {
+      if (edge.to == to) {  // success via edge directly
+        return true;
+      } else if (seen->find(edge.to) == seen->end() &&  // success via edge
+                 IsReachable(edges, edge.to, to, seen)) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+static void PrintEdges(Edges *edges) {
+  LOG(INFO) << "EDGES (" << edges->size() << ")";
+  for (const auto &edge : *edges) {
+    int a = edge.from;
+    int b = edge.to;
+    LOG(INFO) << a << " " << b;
+  }
+  LOG(INFO) << "---";
+}
+
+static void PrintGCEdges(Nodes *nodes, const IdMap &id, GraphCycles *gc) {
+  LOG(INFO) << "GC EDGES";
+  for (int a : *nodes) {
+    for (int b : *nodes) {
+      if (gc->HasEdge(Get(id, a), Get(id, b))) {
+        LOG(INFO) << a << " " << b;
+      }
+    }
+  }
+  LOG(INFO) << "---";
+}
+
+static void PrintTransitiveClosure(Nodes *nodes, Edges *edges) {
+  LOG(INFO) << "Transitive closure";
+  for (int a : *nodes) {
+    for (int b : *nodes) {
+      std::unordered_set<int> seen;
+      if (IsReachable(edges, a, b, &seen)) {
+        LOG(INFO) << a << " " << b;
+      }
+    }
+  }
+  LOG(INFO) << "---";
+}
+
+static void PrintGCTransitiveClosure(Nodes *nodes, const IdMap &id,
+                                     GraphCycles *gc) {
+  LOG(INFO) << "GC Transitive closure";
+  for (int a : *nodes) {
+    for (int b : *nodes) {
+      if (gc->IsReachable(Get(id, a), Get(id, b))) {
+        LOG(INFO) << a << " " << b;
+      }
+    }
+  }
+  LOG(INFO) << "---";
+}
+
+static void CheckTransitiveClosure(Nodes *nodes, Edges *edges, const IdMap &id,
+                                   GraphCycles *gc) {
+  std::unordered_set<int> seen;
+  for (const auto &a : *nodes) {
+    for (const auto &b : *nodes) {
+      seen.clear();
+      bool gc_reachable = gc->IsReachable(Get(id, a), Get(id, b));
+      bool reachable = IsReachable(edges, a, b, &seen);
+      if (gc_reachable != reachable) {
+        PrintEdges(edges);
+        PrintGCEdges(nodes, id, gc);
+        PrintTransitiveClosure(nodes, edges);
+        PrintGCTransitiveClosure(nodes, id, gc);
+        LOG(FATAL) << "gc_reachable " << gc_reachable << " reachable "
+                   << reachable << " a " << a << " b " << b;
+      }
+    }
+  }
+}
+
+static void CheckEdges(Nodes *nodes, Edges *edges, const IdMap &id,
+                       GraphCycles *gc) {
+  int count = 0;
+  for (const auto &edge : *edges) {
+    int a = edge.from;
+    int b = edge.to;
+    if (!gc->HasEdge(Get(id, a), Get(id, b))) {
+      PrintEdges(edges);
+      PrintGCEdges(nodes, id, gc);
+      LOG(FATAL) << "!gc->HasEdge(" << a << ", " << b << ")";
+    }
+  }
+  for (const auto &a : *nodes) {
+    for (const auto &b : *nodes) {
+      if (gc->HasEdge(Get(id, a), Get(id, b))) {
+        count++;
+      }
+    }
+  }
+  if (count != edges->size()) {
+    PrintEdges(edges);
+    PrintGCEdges(nodes, id, gc);
+    LOG(FATAL) << "edges->size() " << edges->size() << "  count " << count;
+  }
+}
+
+static void CheckInvariants(const GraphCycles &gc) {
+  CHECK(gc.CheckInvariants()) << "CheckInvariants";
+}
+
+// Returns the index of a randomly chosen node in *nodes.
+// Requires *nodes be non-empty.
+static int RandomNode(RandomEngine* rng, Nodes *nodes) {
+  std::uniform_int_distribution<int> uniform(0, nodes->size()-1);
+  return uniform(*rng);
+}
+
+// Returns the index of a randomly chosen edge in *edges.
+// Requires *edges be non-empty.
+static int RandomEdge(RandomEngine* rng, Edges *edges) {
+  std::uniform_int_distribution<int> uniform(0, edges->size()-1);
+  return uniform(*rng);
+}
+
+// Returns the index of edge (from, to) in *edges or -1 if it is not in *edges.
+static int EdgeIndex(Edges *edges, int from, int to) {
+  int i = 0;
+  while (i != edges->size() &&
+         ((*edges)[i].from != from || (*edges)[i].to != to)) {
+    i++;
+  }
+  return i == edges->size()? -1 : i;
+}
+
+TEST(GraphCycles, RandomizedTest) {
+  int next_node = 0;
+  Nodes nodes;
+  Edges edges;   // from, to
+  IdMap id;
+  GraphCycles graph_cycles;
+  static const int kMaxNodes = 7;  // use <= 7 nodes to keep test short
+  static const int kDataOffset = 17;  // an offset to the node-specific data
+  int n = 100000;
+  int op = 0;
+  RandomEngine rng(testing::UnitTest::GetInstance()->random_seed());
+  std::uniform_int_distribution<int> uniform(0, 5);
+
+  auto ptr = [](intptr_t i) {
+    return reinterpret_cast<void*>(i + kDataOffset);
+  };
+
+  for (int iter = 0; iter != n; iter++) {
+    for (const auto &node : nodes) {
+      ASSERT_EQ(graph_cycles.Ptr(Get(id, node)), ptr(node)) << " node " << node;
+    }
+    CheckEdges(&nodes, &edges, id, &graph_cycles);
+    CheckTransitiveClosure(&nodes, &edges, id, &graph_cycles);
+    op = uniform(rng);
+    switch (op) {
+    case 0:     // Add a node
+      if (nodes.size() < kMaxNodes) {
+        int new_node = next_node++;
+        GraphId new_gnode = graph_cycles.GetId(ptr(new_node));
+        ASSERT_NE(new_gnode, InvalidGraphId());
+        id[new_node] = new_gnode;
+        ASSERT_EQ(ptr(new_node), graph_cycles.Ptr(new_gnode));
+        nodes.push_back(new_node);
+      }
+      break;
+
+    case 1:    // Remove a node
+      if (nodes.size() > 0) {
+        int node_index = RandomNode(&rng, &nodes);
+        int node = nodes[node_index];
+        nodes[node_index] = nodes.back();
+        nodes.pop_back();
+        graph_cycles.RemoveNode(ptr(node));
+        ASSERT_EQ(graph_cycles.Ptr(Get(id, node)), nullptr);
+        id.erase(node);
+        int i = 0;
+        while (i != edges.size()) {
+          if (edges[i].from == node || edges[i].to == node) {
+            edges[i] = edges.back();
+            edges.pop_back();
+          } else {
+            i++;
+          }
+        }
+      }
+      break;
+
+    case 2:   // Add an edge
+      if (nodes.size() > 0) {
+        int from = RandomNode(&rng, &nodes);
+        int to = RandomNode(&rng, &nodes);
+        if (EdgeIndex(&edges, nodes[from], nodes[to]) == -1) {
+          if (graph_cycles.InsertEdge(id[nodes[from]], id[nodes[to]])) {
+            Edge new_edge;
+            new_edge.from = nodes[from];
+            new_edge.to = nodes[to];
+            edges.push_back(new_edge);
+          } else {
+            std::unordered_set<int> seen;
+            ASSERT_TRUE(IsReachable(&edges, nodes[to], nodes[from], &seen))
+                << "Edge " << nodes[to] << "->" << nodes[from];
+          }
+        }
+      }
+      break;
+
+    case 3:    // Remove an edge
+      if (edges.size() > 0) {
+        int i = RandomEdge(&rng, &edges);
+        int from = edges[i].from;
+        int to = edges[i].to;
+        ASSERT_EQ(i, EdgeIndex(&edges, from, to));
+        edges[i] = edges.back();
+        edges.pop_back();
+        ASSERT_EQ(-1, EdgeIndex(&edges, from, to));
+        graph_cycles.RemoveEdge(id[from], id[to]);
+      }
+      break;
+
+    case 4:   // Check a path
+      if (nodes.size() > 0) {
+        int from = RandomNode(&rng, &nodes);
+        int to = RandomNode(&rng, &nodes);
+        GraphId path[2*kMaxNodes];
+        int path_len = graph_cycles.FindPath(id[nodes[from]], id[nodes[to]],
+                                             ABSL_ARRAYSIZE(path), path);
+        std::unordered_set<int> seen;
+        bool reachable = IsReachable(&edges, nodes[from], nodes[to], &seen);
+        bool gc_reachable =
+            graph_cycles.IsReachable(Get(id, nodes[from]), Get(id, nodes[to]));
+        ASSERT_EQ(path_len != 0, reachable);
+        ASSERT_EQ(path_len != 0, gc_reachable);
+        // In the following line, we add one because a node can appear
+        // twice, if the path is from that node to itself, perhaps via
+        // every other node.
+        ASSERT_LE(path_len, kMaxNodes + 1);
+        if (path_len != 0) {
+          ASSERT_EQ(id[nodes[from]], path[0]);
+          ASSERT_EQ(id[nodes[to]], path[path_len-1]);
+          for (int i = 1; i < path_len; i++) {
+            ASSERT_TRUE(graph_cycles.HasEdge(path[i-1], path[i]));
+          }
+        }
+      }
+      break;
+
+    case 5:  // Check invariants
+      CheckInvariants(graph_cycles);
+      break;
+
+    default:
+      LOG(FATAL) << "op " << op;
+    }
+
+    // Very rarely, test graph expansion by adding then removing many nodes.
+    std::bernoulli_distribution one_in_1024(1.0 / 1024);
+    if (one_in_1024(rng)) {
+      CheckEdges(&nodes, &edges, id, &graph_cycles);
+      CheckTransitiveClosure(&nodes, &edges, id, &graph_cycles);
+      for (int i = 0; i != 256; i++) {
+        int new_node = next_node++;
+        GraphId new_gnode = graph_cycles.GetId(ptr(new_node));
+        ASSERT_NE(InvalidGraphId(), new_gnode);
+        id[new_node] = new_gnode;
+        ASSERT_EQ(ptr(new_node), graph_cycles.Ptr(new_gnode));
+        for (const auto &node : nodes) {
+          ASSERT_NE(node, new_node);
+        }
+        nodes.push_back(new_node);
+      }
+      for (int i = 0; i != 256; i++) {
+        ASSERT_GT(nodes.size(), 0);
+        int node_index = RandomNode(&rng, &nodes);
+        int node = nodes[node_index];
+        nodes[node_index] = nodes.back();
+        nodes.pop_back();
+        graph_cycles.RemoveNode(ptr(node));
+        id.erase(node);
+        int j = 0;
+        while (j != edges.size()) {
+          if (edges[j].from == node || edges[j].to == node) {
+            edges[j] = edges.back();
+            edges.pop_back();
+          } else {
+            j++;
+          }
+        }
+      }
+      CheckInvariants(graph_cycles);
+    }
+  }
+}
+
+class GraphCyclesTest : public ::testing::Test {
+ public:
+  IdMap id_;
+  GraphCycles g_;
+
+  static void* Ptr(int i) {
+    return reinterpret_cast<void*>(static_cast<uintptr_t>(i));
+  }
+
+  static int Num(void* ptr) {
+    return static_cast<int>(reinterpret_cast<uintptr_t>(ptr));
+  }
+
+  // Test relies on ith NewNode() call returning Node numbered i
+  GraphCyclesTest() {
+    for (int i = 0; i < 100; i++) {
+      id_[i] = g_.GetId(Ptr(i));
+    }
+    CheckInvariants(g_);
+  }
+
+  bool AddEdge(int x, int y) {
+    return g_.InsertEdge(Get(id_, x), Get(id_, y));
+  }
+
+  void AddMultiples() {
+    // For every node x > 0: add edge to 2*x, 3*x
+    for (int x = 1; x < 25; x++) {
+      EXPECT_TRUE(AddEdge(x, 2*x)) << x;
+      EXPECT_TRUE(AddEdge(x, 3*x)) << x;
+    }
+    CheckInvariants(g_);
+  }
+
+  std::string Path(int x, int y) {
+    GraphId path[5];
+    int np = g_.FindPath(Get(id_, x), Get(id_, y), ABSL_ARRAYSIZE(path), path);
+    std::string result;
+    for (int i = 0; i < np; i++) {
+      if (i >= ABSL_ARRAYSIZE(path)) {
+        result += " ...";
+        break;
+      }
+      if (!result.empty()) result.push_back(' ');
+      char buf[20];
+      snprintf(buf, sizeof(buf), "%d", Num(g_.Ptr(path[i])));
+      result += buf;
+    }
+    return result;
+  }
+};
+
+TEST_F(GraphCyclesTest, NoCycle) {
+  AddMultiples();
+  CheckInvariants(g_);
+}
+
+TEST_F(GraphCyclesTest, SimpleCycle) {
+  AddMultiples();
+  EXPECT_FALSE(AddEdge(8, 4));
+  EXPECT_EQ("4 8", Path(4, 8));
+  CheckInvariants(g_);
+}
+
+TEST_F(GraphCyclesTest, IndirectCycle) {
+  AddMultiples();
+  EXPECT_TRUE(AddEdge(16, 9));
+  CheckInvariants(g_);
+  EXPECT_FALSE(AddEdge(9, 2));
+  EXPECT_EQ("2 4 8 16 9", Path(2, 9));
+  CheckInvariants(g_);
+}
+
+TEST_F(GraphCyclesTest, LongPath) {
+  ASSERT_TRUE(AddEdge(2, 4));
+  ASSERT_TRUE(AddEdge(4, 6));
+  ASSERT_TRUE(AddEdge(6, 8));
+  ASSERT_TRUE(AddEdge(8, 10));
+  ASSERT_TRUE(AddEdge(10, 12));
+  ASSERT_FALSE(AddEdge(12, 2));
+  EXPECT_EQ("2 4 6 8 10 ...", Path(2, 12));
+  CheckInvariants(g_);
+}
+
+TEST_F(GraphCyclesTest, RemoveNode) {
+  ASSERT_TRUE(AddEdge(1, 2));
+  ASSERT_TRUE(AddEdge(2, 3));
+  ASSERT_TRUE(AddEdge(3, 4));
+  ASSERT_TRUE(AddEdge(4, 5));
+  g_.RemoveNode(g_.Ptr(id_[3]));
+  id_.erase(3);
+  ASSERT_TRUE(AddEdge(5, 1));
+}
+
+TEST_F(GraphCyclesTest, ManyEdges) {
+  const int N = 50;
+  for (int i = 0; i < N; i++) {
+    for (int j = 1; j < N; j++) {
+      ASSERT_TRUE(AddEdge(i, i+j));
+    }
+  }
+  CheckInvariants(g_);
+  ASSERT_TRUE(AddEdge(2*N-1, 0));
+  CheckInvariants(g_);
+  ASSERT_FALSE(AddEdge(10, 9));
+  CheckInvariants(g_);
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout.cc
new file mode 100644
index 0000000000000000000000000000000000000000..48ea6287b7b18774789aa4aba9d669cd0e76b3a8
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout.cc
@@ -0,0 +1,225 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+#ifndef _WIN32
+#include <sys/types.h>
+#endif
+
+#include <algorithm>
+#include <chrono>  // NOLINT(build/c++11)
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <limits>
+
+#include "absl/base/attributes.h"
+#include "absl/base/call_once.h"
+#include "absl/base/config.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr uint64_t KernelTimeout::kNoTimeout;
+constexpr int64_t KernelTimeout::kMaxNanos;
+#endif
+
+int64_t KernelTimeout::SteadyClockNow() {
+  if (!SupportsSteadyClock()) {
+    return absl::GetCurrentTimeNanos();
+  }
+  return std::chrono::duration_cast<std::chrono::nanoseconds>(
+             std::chrono::steady_clock::now().time_since_epoch())
+      .count();
+}
+
+KernelTimeout::KernelTimeout(absl::Time t) {
+  // `absl::InfiniteFuture()` is a common "no timeout" value and cheaper to
+  // compare than convert.
+  if (t == absl::InfiniteFuture()) {
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  int64_t unix_nanos = absl::ToUnixNanos(t);
+
+  // A timeout that lands before the unix epoch is converted to 0.
+  // In theory implementations should expire these timeouts immediately.
+  if (unix_nanos < 0) {
+    unix_nanos = 0;
+  }
+
+  // Values greater than or equal to kMaxNanos are converted to infinite.
+  if (unix_nanos >= kMaxNanos) {
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  rep_ = static_cast<uint64_t>(unix_nanos) << 1;
+}
+
+KernelTimeout::KernelTimeout(absl::Duration d) {
+  // `absl::InfiniteDuration()` is a common "no timeout" value and cheaper to
+  // compare than convert.
+  if (d == absl::InfiniteDuration()) {
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  int64_t nanos = absl::ToInt64Nanoseconds(d);
+
+  // Negative durations are normalized to 0.
+  // In theory implementations should expire these timeouts immediately.
+  if (nanos < 0) {
+    nanos = 0;
+  }
+
+  int64_t now = SteadyClockNow();
+  if (nanos > kMaxNanos - now) {
+    // Durations that would be greater than kMaxNanos are converted to infinite.
+    rep_ = kNoTimeout;
+    return;
+  }
+
+  nanos += now;
+  rep_ = (static_cast<uint64_t>(nanos) << 1) | uint64_t{1};
+}
+
+int64_t KernelTimeout::MakeAbsNanos() const {
+  if (!has_timeout()) {
+    return kMaxNanos;
+  }
+
+  int64_t nanos = RawAbsNanos();
+
+  if (is_relative_timeout()) {
+    // We need to change epochs, because the relative timeout might be
+    // represented by an absolute timestamp from another clock.
+    nanos = std::max<int64_t>(nanos - SteadyClockNow(), 0);
+    int64_t now = absl::GetCurrentTimeNanos();
+    if (nanos > kMaxNanos - now) {
+      // Overflow.
+      nanos = kMaxNanos;
+    } else {
+      nanos += now;
+    }
+  } else if (nanos == 0) {
+    // Some callers have assumed that 0 means no timeout, so instead we return a
+    // time of 1 nanosecond after the epoch.
+    nanos = 1;
+  }
+
+  return nanos;
+}
+
+int64_t KernelTimeout::InNanosecondsFromNow() const {
+  if (!has_timeout()) {
+    return kMaxNanos;
+  }
+
+  int64_t nanos = RawAbsNanos();
+  if (is_absolute_timeout()) {
+    return std::max<int64_t>(nanos - absl::GetCurrentTimeNanos(), 0);
+  }
+  return std::max<int64_t>(nanos - SteadyClockNow(), 0);
+}
+
+struct timespec KernelTimeout::MakeAbsTimespec() const {
+  return absl::ToTimespec(absl::Nanoseconds(MakeAbsNanos()));
+}
+
+struct timespec KernelTimeout::MakeRelativeTimespec() const {
+  return absl::ToTimespec(absl::Nanoseconds(InNanosecondsFromNow()));
+}
+
+#ifndef _WIN32
+struct timespec KernelTimeout::MakeClockAbsoluteTimespec(clockid_t c) const {
+  if (!has_timeout()) {
+    return absl::ToTimespec(absl::Nanoseconds(kMaxNanos));
+  }
+
+  int64_t nanos = RawAbsNanos();
+  if (is_absolute_timeout()) {
+    nanos -= absl::GetCurrentTimeNanos();
+  } else {
+    nanos -= SteadyClockNow();
+  }
+
+  struct timespec now;
+  ABSL_RAW_CHECK(clock_gettime(c, &now) == 0, "clock_gettime() failed");
+  absl::Duration from_clock_epoch =
+      absl::DurationFromTimespec(now) + absl::Nanoseconds(nanos);
+  if (from_clock_epoch <= absl::ZeroDuration()) {
+    // Some callers have assumed that 0 means no timeout, so instead we return a
+    // time of 1 nanosecond after the epoch. For safety we also do not return
+    // negative values.
+    return absl::ToTimespec(absl::Nanoseconds(1));
+  }
+  return absl::ToTimespec(from_clock_epoch);
+}
+#endif
+
+KernelTimeout::DWord KernelTimeout::InMillisecondsFromNow() const {
+  constexpr DWord kInfinite = std::numeric_limits<DWord>::max();
+
+  if (!has_timeout()) {
+    return kInfinite;
+  }
+
+  constexpr uint64_t kNanosInMillis = uint64_t{1'000'000};
+  constexpr uint64_t kMaxValueNanos =
+      std::numeric_limits<int64_t>::max() - kNanosInMillis + 1;
+
+  uint64_t ns_from_now = static_cast<uint64_t>(InNanosecondsFromNow());
+  if (ns_from_now >= kMaxValueNanos) {
+    // Rounding up would overflow.
+    return kInfinite;
+  }
+  // Convert to milliseconds, always rounding up.
+  uint64_t ms_from_now = (ns_from_now + kNanosInMillis - 1) / kNanosInMillis;
+  if (ms_from_now > kInfinite) {
+    return kInfinite;
+  }
+  return static_cast<DWord>(ms_from_now);
+}
+
+std::chrono::time_point<std::chrono::system_clock>
+KernelTimeout::ToChronoTimePoint() const {
+  if (!has_timeout()) {
+    return std::chrono::time_point<std::chrono::system_clock>::max();
+  }
+
+  // The cast to std::microseconds is because (on some platforms) the
+  // std::ratio used by std::chrono::steady_clock doesn't convert to
+  // std::nanoseconds, so it doesn't compile.
+  auto micros = std::chrono::duration_cast<std::chrono::microseconds>(
+      std::chrono::nanoseconds(MakeAbsNanos()));
+  return std::chrono::system_clock::from_time_t(0) + micros;
+}
+
+std::chrono::nanoseconds KernelTimeout::ToChronoDuration() const {
+  if (!has_timeout()) {
+    return std::chrono::nanoseconds::max();
+  }
+  return std::chrono::nanoseconds(InNanosecondsFromNow());
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout.h
new file mode 100644
index 0000000000000000000000000000000000000000..06404a7566bbca30fbff3ab12eb9291f02ace1ca
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout.h
@@ -0,0 +1,178 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_
+
+#ifndef _WIN32
+#include <sys/types.h>
+#endif
+
+#include <algorithm>
+#include <chrono>  // NOLINT(build/c++11)
+#include <cstdint>
+#include <ctime>
+#include <limits>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+// An optional timeout, with nanosecond granularity.
+//
+// This is a private low-level API for use by a handful of low-level
+// components. Higher-level components should build APIs based on
+// absl::Time and absl::Duration.
+class KernelTimeout {
+ public:
+  // Construct an absolute timeout that should expire at `t`.
+  explicit KernelTimeout(absl::Time t);
+
+  // Construct a relative timeout that should expire after `d`.
+  explicit KernelTimeout(absl::Duration d);
+
+  // Infinite timeout.
+  constexpr KernelTimeout() : rep_(kNoTimeout) {}
+
+  // A more explicit factory for those who prefer it.
+  // Equivalent to `KernelTimeout()`.
+  static constexpr KernelTimeout Never() { return KernelTimeout(); }
+
+  // Returns true if there is a timeout that will eventually expire.
+  // Returns false if the timeout is infinite.
+  bool has_timeout() const { return rep_ != kNoTimeout; }
+
+  // If `has_timeout()` is true, returns true if the timeout was provided as an
+  // `absl::Time`. The return value is undefined if `has_timeout()` is false
+  // because all indefinite timeouts are equivalent.
+  bool is_absolute_timeout() const { return (rep_ & 1) == 0; }
+
+  // If `has_timeout()` is true, returns true if the timeout was provided as an
+  // `absl::Duration`. The return value is undefined if `has_timeout()` is false
+  // because all indefinite timeouts are equivalent.
+  bool is_relative_timeout() const { return (rep_ & 1) == 1; }
+
+  // Convert to `struct timespec` for interfaces that expect an absolute
+  // timeout. If !has_timeout() or is_relative_timeout(), attempts to convert to
+  // a reasonable absolute timeout, but callers should to test has_timeout() and
+  // is_relative_timeout() and prefer to use a more appropriate interface.
+  struct timespec MakeAbsTimespec() const;
+
+  // Convert to `struct timespec` for interfaces that expect a relative
+  // timeout. If !has_timeout() or is_absolute_timeout(), attempts to convert to
+  // a reasonable relative timeout, but callers should to test has_timeout() and
+  // is_absolute_timeout() and prefer to use a more appropriate interface. Since
+  // the return value is a relative duration, it should be recomputed by calling
+  // this method in the case of a spurious wakeup.
+  struct timespec MakeRelativeTimespec() const;
+
+#ifndef _WIN32
+  // Convert to `struct timespec` for interfaces that expect an absolute timeout
+  // on a specific clock `c`. This is similar to `MakeAbsTimespec()`, but
+  // callers usually want to use this method with `CLOCK_MONOTONIC` when
+  // relative timeouts are requested, and when the appropriate interface expects
+  // an absolute timeout relative to a specific clock (for example,
+  // pthread_cond_clockwait() or sem_clockwait()). If !has_timeout(), attempts
+  // to convert to a reasonable absolute timeout, but callers should to test
+  // has_timeout() prefer to use a more appropriate interface.
+  struct timespec MakeClockAbsoluteTimespec(clockid_t c) const;
+#endif
+
+  // Convert to unix epoch nanos for interfaces that expect an absolute timeout
+  // in nanoseconds. If !has_timeout() or is_relative_timeout(), attempts to
+  // convert to a reasonable absolute timeout, but callers should to test
+  // has_timeout() and is_relative_timeout() and prefer to use a more
+  // appropriate interface.
+  int64_t MakeAbsNanos() const;
+
+  // Converts to milliseconds from now, or INFINITE when
+  // !has_timeout(). For use by SleepConditionVariableSRW on
+  // Windows. Callers should recognize that the return value is a
+  // relative duration (it should be recomputed by calling this method
+  // in the case of a spurious wakeup).
+  // This header file may be included transitively by public header files,
+  // so we define our own DWORD and INFINITE instead of getting them from
+  // <intsafe.h> and <WinBase.h>.
+  typedef unsigned long DWord;  // NOLINT
+  DWord InMillisecondsFromNow() const;
+
+  // Convert to std::chrono::time_point for interfaces that expect an absolute
+  // timeout, like std::condition_variable::wait_until(). If !has_timeout() or
+  // is_relative_timeout(), attempts to convert to a reasonable absolute
+  // timeout, but callers should test has_timeout() and is_relative_timeout()
+  // and prefer to use a more appropriate interface.
+  std::chrono::time_point<std::chrono::system_clock> ToChronoTimePoint() const;
+
+  // Convert to std::chrono::time_point for interfaces that expect a relative
+  // timeout, like std::condition_variable::wait_for(). If !has_timeout() or
+  // is_absolute_timeout(), attempts to convert to a reasonable relative
+  // timeout, but callers should test has_timeout() and is_absolute_timeout()
+  // and prefer to use a more appropriate interface. Since the return value is a
+  // relative duration, it should be recomputed by calling this method in the
+  // case of a spurious wakeup.
+  std::chrono::nanoseconds ToChronoDuration() const;
+
+  // Returns true if steady (aka monotonic) clocks are supported by the system.
+  // This method exists because go/btm requires synchronized clocks, and
+  // thus requires we use the system (aka walltime) clock.
+  static constexpr bool SupportsSteadyClock() { return true; }
+
+ private:
+  // Returns the current time, expressed as a count of nanoseconds since the
+  // epoch used by an arbitrary clock. The implementation tries to use a steady
+  // (monotonic) clock if one is available.
+  static int64_t SteadyClockNow();
+
+  // Internal representation.
+  //   - If the value is kNoTimeout, then the timeout is infinite, and
+  //     has_timeout() will return true.
+  //   - If the low bit is 0, then the high 63 bits is the number of nanoseconds
+  //     after the unix epoch.
+  //   - If the low bit is 1, then the high 63 bits is the number of nanoseconds
+  //     after the epoch used by SteadyClockNow().
+  //
+  // In all cases the time is stored as an absolute time, the only difference is
+  // the clock epoch. The use of absolute times is important since in the case
+  // of a relative timeout with a spurious wakeup, the program would have to
+  // restart the wait, and thus needs a way of recomputing the remaining time.
+  uint64_t rep_;
+
+  // Returns the number of nanoseconds stored in the internal representation.
+  // When combined with the clock epoch indicated by the low bit (which is
+  // accessed through is_absolute_timeout() and is_relative_timeout()), the
+  // return value is used to compute when the timeout should occur.
+  int64_t RawAbsNanos() const { return static_cast<int64_t>(rep_ >> 1); }
+
+  // Converts to nanoseconds from now. Since the return value is a relative
+  // duration, it should be recomputed by calling this method in the case of a
+  // spurious wakeup.
+  int64_t InNanosecondsFromNow() const;
+
+  // A value that represents no timeout (or an infinite timeout).
+  static constexpr uint64_t kNoTimeout = (std::numeric_limits<uint64_t>::max)();
+
+  // The maximum value that can be stored in the high 63 bits.
+  static constexpr int64_t kMaxNanos = (std::numeric_limits<int64_t>::max)();
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout_test.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bc546719b8b0af0abe1bf2386679118632bec8f6
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/kernel_timeout_test.cc
@@ -0,0 +1,393 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+#include <ctime>
+#include <chrono>  // NOLINT(build/c++11)
+#include <limits>
+
+#include "absl/base/config.h"
+#include "absl/random/random.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "gtest/gtest.h"
+
+// Test go/btm support by randomizing the value of clock_gettime() for
+// CLOCK_MONOTONIC. This works by overriding a weak symbol in glibc.
+// We should be resistant to this randomization when !SupportsSteadyClock().
+#if defined(__GOOGLE_GRTE_VERSION__) &&      \
+    !defined(ABSL_HAVE_ADDRESS_SANITIZER) && \
+    !defined(ABSL_HAVE_MEMORY_SANITIZER) &&  \
+    !defined(ABSL_HAVE_THREAD_SANITIZER)
+extern "C" int __clock_gettime(clockid_t c, struct timespec* ts);
+
+extern "C" int clock_gettime(clockid_t c, struct timespec* ts) {
+  if (c == CLOCK_MONOTONIC &&
+      !absl::synchronization_internal::KernelTimeout::SupportsSteadyClock()) {
+    absl::SharedBitGen gen;
+    ts->tv_sec = absl::Uniform(gen, 0, 1'000'000'000);
+    ts->tv_nsec = absl::Uniform(gen, 0, 1'000'000'000);
+    return 0;
+  }
+  return __clock_gettime(c, ts);
+}
+#endif
+
+namespace {
+
+#if defined(ABSL_HAVE_ADDRESS_SANITIZER) ||                        \
+    defined(ABSL_HAVE_MEMORY_SANITIZER) ||                         \
+    defined(ABSL_HAVE_THREAD_SANITIZER) || defined(__ANDROID__) || \
+    defined(__APPLE__) || defined(_WIN32) || defined(_WIN64)
+constexpr absl::Duration kTimingBound = absl::Milliseconds(5);
+#else
+constexpr absl::Duration kTimingBound = absl::Microseconds(250);
+#endif
+
+using absl::synchronization_internal::KernelTimeout;
+
+TEST(KernelTimeout, FiniteTimes) {
+  constexpr absl::Duration kDurationsToTest[] = {
+    absl::ZeroDuration(),
+    absl::Nanoseconds(1),
+    absl::Microseconds(1),
+    absl::Milliseconds(1),
+    absl::Seconds(1),
+    absl::Minutes(1),
+    absl::Hours(1),
+    absl::Hours(1000),
+    -absl::Nanoseconds(1),
+    -absl::Microseconds(1),
+    -absl::Milliseconds(1),
+    -absl::Seconds(1),
+    -absl::Minutes(1),
+    -absl::Hours(1),
+    -absl::Hours(1000),
+  };
+
+  for (auto duration : kDurationsToTest) {
+    const absl::Time now = absl::Now();
+    const absl::Time when = now + duration;
+    SCOPED_TRACE(duration);
+    KernelTimeout t(when);
+    EXPECT_TRUE(t.has_timeout());
+    EXPECT_TRUE(t.is_absolute_timeout());
+    EXPECT_FALSE(t.is_relative_timeout());
+    EXPECT_EQ(absl::TimeFromTimespec(t.MakeAbsTimespec()), when);
+#ifndef _WIN32
+    EXPECT_LE(
+        absl::AbsDuration(absl::Now() + duration -
+                          absl::TimeFromTimespec(
+                              t.MakeClockAbsoluteTimespec(CLOCK_REALTIME))),
+        absl::Milliseconds(10));
+#endif
+    EXPECT_LE(
+        absl::AbsDuration(absl::DurationFromTimespec(t.MakeRelativeTimespec()) -
+                          std::max(duration, absl::ZeroDuration())),
+        kTimingBound);
+    EXPECT_EQ(absl::FromUnixNanos(t.MakeAbsNanos()), when);
+    EXPECT_LE(absl::AbsDuration(absl::Milliseconds(t.InMillisecondsFromNow()) -
+                                std::max(duration, absl::ZeroDuration())),
+              absl::Milliseconds(5));
+    EXPECT_LE(absl::AbsDuration(absl::FromChrono(t.ToChronoTimePoint()) - when),
+              absl::Microseconds(1));
+    EXPECT_LE(absl::AbsDuration(absl::FromChrono(t.ToChronoDuration()) -
+                                std::max(duration, absl::ZeroDuration())),
+              kTimingBound);
+  }
+}
+
+TEST(KernelTimeout, InfiniteFuture) {
+  KernelTimeout t(absl::InfiniteFuture());
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, DefaultConstructor) {
+  // The default constructor is equivalent to absl::InfiniteFuture().
+  KernelTimeout t;
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, TimeMaxNanos) {
+  // Time >= kMaxNanos should behave as no timeout.
+  KernelTimeout t(absl::FromUnixNanos(std::numeric_limits<int64_t>::max()));
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, Never) {
+  // KernelTimeout::Never() is equivalent to absl::InfiniteFuture().
+  KernelTimeout t = KernelTimeout::Never();
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, InfinitePast) {
+  KernelTimeout t(absl::InfinitePast());
+  EXPECT_TRUE(t.has_timeout());
+  EXPECT_TRUE(t.is_absolute_timeout());
+  EXPECT_FALSE(t.is_relative_timeout());
+  EXPECT_LE(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::FromUnixNanos(1));
+#ifndef _WIN32
+  EXPECT_LE(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::FromUnixSeconds(1));
+#endif
+  EXPECT_EQ(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::ZeroDuration());
+  EXPECT_LE(absl::FromUnixNanos(t.MakeAbsNanos()), absl::FromUnixNanos(1));
+  EXPECT_EQ(t.InMillisecondsFromNow(), KernelTimeout::DWord{0});
+  EXPECT_LT(t.ToChronoTimePoint(), std::chrono::system_clock::from_time_t(0) +
+                                       std::chrono::seconds(1));
+  EXPECT_EQ(t.ToChronoDuration(), std::chrono::nanoseconds(0));
+}
+
+TEST(KernelTimeout, FiniteDurations) {
+  constexpr absl::Duration kDurationsToTest[] = {
+    absl::ZeroDuration(),
+    absl::Nanoseconds(1),
+    absl::Microseconds(1),
+    absl::Milliseconds(1),
+    absl::Seconds(1),
+    absl::Minutes(1),
+    absl::Hours(1),
+    absl::Hours(1000),
+  };
+
+  for (auto duration : kDurationsToTest) {
+    SCOPED_TRACE(duration);
+    KernelTimeout t(duration);
+    EXPECT_TRUE(t.has_timeout());
+    EXPECT_FALSE(t.is_absolute_timeout());
+    EXPECT_TRUE(t.is_relative_timeout());
+    EXPECT_LE(absl::AbsDuration(absl::Now() + duration -
+                                absl::TimeFromTimespec(t.MakeAbsTimespec())),
+              absl::Milliseconds(5));
+#ifndef _WIN32
+    EXPECT_LE(
+        absl::AbsDuration(absl::Now() + duration -
+                          absl::TimeFromTimespec(
+                              t.MakeClockAbsoluteTimespec(CLOCK_REALTIME))),
+        absl::Milliseconds(5));
+#endif
+    EXPECT_LE(
+        absl::AbsDuration(absl::DurationFromTimespec(t.MakeRelativeTimespec()) -
+                          duration),
+        kTimingBound);
+    EXPECT_LE(absl::AbsDuration(absl::Now() + duration -
+                                absl::FromUnixNanos(t.MakeAbsNanos())),
+              absl::Milliseconds(5));
+    EXPECT_LE(absl::Milliseconds(t.InMillisecondsFromNow()) - duration,
+              absl::Milliseconds(5));
+    EXPECT_LE(absl::AbsDuration(absl::Now() + duration -
+                                absl::FromChrono(t.ToChronoTimePoint())),
+              kTimingBound);
+    EXPECT_LE(
+        absl::AbsDuration(absl::FromChrono(t.ToChronoDuration()) - duration),
+        kTimingBound);
+  }
+}
+
+TEST(KernelTimeout, NegativeDurations) {
+  constexpr absl::Duration kDurationsToTest[] = {
+    -absl::ZeroDuration(),
+    -absl::Nanoseconds(1),
+    -absl::Microseconds(1),
+    -absl::Milliseconds(1),
+    -absl::Seconds(1),
+    -absl::Minutes(1),
+    -absl::Hours(1),
+    -absl::Hours(1000),
+    -absl::InfiniteDuration(),
+  };
+
+  for (auto duration : kDurationsToTest) {
+    // Negative durations should all be converted to zero durations or "now".
+    SCOPED_TRACE(duration);
+    KernelTimeout t(duration);
+    EXPECT_TRUE(t.has_timeout());
+    EXPECT_FALSE(t.is_absolute_timeout());
+    EXPECT_TRUE(t.is_relative_timeout());
+    EXPECT_LE(absl::AbsDuration(absl::Now() -
+                                absl::TimeFromTimespec(t.MakeAbsTimespec())),
+              absl::Milliseconds(5));
+#ifndef _WIN32
+    EXPECT_LE(absl::AbsDuration(absl::Now() - absl::TimeFromTimespec(
+                                                  t.MakeClockAbsoluteTimespec(
+                                                      CLOCK_REALTIME))),
+              absl::Milliseconds(5));
+#endif
+    EXPECT_EQ(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+              absl::ZeroDuration());
+    EXPECT_LE(
+        absl::AbsDuration(absl::Now() - absl::FromUnixNanos(t.MakeAbsNanos())),
+        absl::Milliseconds(5));
+    EXPECT_EQ(t.InMillisecondsFromNow(), KernelTimeout::DWord{0});
+    EXPECT_LE(absl::AbsDuration(absl::Now() -
+                                absl::FromChrono(t.ToChronoTimePoint())),
+              absl::Milliseconds(5));
+    EXPECT_EQ(t.ToChronoDuration(), std::chrono::nanoseconds(0));
+  }
+}
+
+TEST(KernelTimeout, InfiniteDuration) {
+  KernelTimeout t(absl::InfiniteDuration());
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, DurationMaxNanos) {
+  // Duration >= kMaxNanos should behave as no timeout.
+  KernelTimeout t(absl::Nanoseconds(std::numeric_limits<int64_t>::max()));
+  EXPECT_FALSE(t.has_timeout());
+  // Callers are expected to check has_timeout() instead of using the methods
+  // below, but we do try to do something reasonable if they don't. We may not
+  // be able to round-trip back to absl::InfiniteDuration() or
+  // absl::InfiniteFuture(), but we should return a very large value.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_EQ(t.InMillisecondsFromNow(),
+            std::numeric_limits<KernelTimeout::DWord>::max());
+  EXPECT_EQ(t.ToChronoTimePoint(),
+            std::chrono::time_point<std::chrono::system_clock>::max());
+  EXPECT_GE(t.ToChronoDuration(), std::chrono::nanoseconds::max());
+}
+
+TEST(KernelTimeout, OverflowNanos) {
+  // Test what happens when KernelTimeout is constructed with an absl::Duration
+  // that would overflow now_nanos + duration.
+  int64_t now_nanos = absl::ToUnixNanos(absl::Now());
+  int64_t limit = std::numeric_limits<int64_t>::max() - now_nanos;
+  absl::Duration duration = absl::Nanoseconds(limit) + absl::Seconds(1);
+  KernelTimeout t(duration);
+  // Timeouts should still be far in the future.
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeAbsTimespec()),
+            absl::Now() + absl::Hours(100000));
+#ifndef _WIN32
+  EXPECT_GT(absl::TimeFromTimespec(t.MakeClockAbsoluteTimespec(CLOCK_REALTIME)),
+            absl::Now() + absl::Hours(100000));
+#endif
+  EXPECT_GT(absl::DurationFromTimespec(t.MakeRelativeTimespec()),
+            absl::Hours(100000));
+  EXPECT_GT(absl::FromUnixNanos(t.MakeAbsNanos()),
+            absl::Now() + absl::Hours(100000));
+  EXPECT_LE(absl::Milliseconds(t.InMillisecondsFromNow()) - duration,
+            absl::Milliseconds(5));
+  EXPECT_GT(t.ToChronoTimePoint(),
+            std::chrono::system_clock::now() + std::chrono::hours(100000));
+  EXPECT_GT(t.ToChronoDuration(), std::chrono::hours(100000));
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/per_thread_sem.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/per_thread_sem.h
new file mode 100644
index 0000000000000000000000000000000000000000..144ab3cdd8c073b21931a13ad4ee1223867fe03d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/per_thread_sem.h
@@ -0,0 +1,119 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// PerThreadSem is a low-level synchronization primitive controlling the
+// runnability of a single thread, used internally by Mutex and CondVar.
+//
+// This is NOT a general-purpose synchronization mechanism, and should not be
+// used directly by applications.  Applications should use Mutex and CondVar.
+//
+// The semantics of PerThreadSem are the same as that of a counting semaphore.
+// Each thread maintains an abstract "count" value associated with its identity.
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_PER_THREAD_SEM_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_PER_THREAD_SEM_H_
+
+#include <atomic>
+
+#include "absl/base/internal/thread_identity.h"
+#include "absl/synchronization/internal/create_thread_identity.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+class Mutex;
+
+namespace synchronization_internal {
+
+class PerThreadSem {
+ public:
+  PerThreadSem() = delete;
+  PerThreadSem(const PerThreadSem&) = delete;
+  PerThreadSem& operator=(const PerThreadSem&) = delete;
+
+  // Routine invoked periodically (once a second) by a background thread.
+  // Has no effect on user-visible state.
+  static void Tick(base_internal::ThreadIdentity* identity);
+
+  // ---------------------------------------------------------------------------
+  // Routines used by autosizing threadpools to detect when threads are
+  // blocked.  Each thread has a counter pointer, initially zero.  If non-zero,
+  // the implementation atomically increments the counter when it blocks on a
+  // semaphore, a decrements it again when it wakes.  This allows a threadpool
+  // to keep track of how many of its threads are blocked.
+  // SetThreadBlockedCounter() should be used only by threadpool
+  // implementations.  GetThreadBlockedCounter() should be used by modules that
+  // block threads; if the pointer returned is non-zero, the location should be
+  // incremented before the thread blocks, and decremented after it wakes.
+  static void SetThreadBlockedCounter(std::atomic<int> *counter);
+  static std::atomic<int> *GetThreadBlockedCounter();
+
+ private:
+  // Create the PerThreadSem associated with "identity".  Initializes count=0.
+  // REQUIRES: May only be called by ThreadIdentity.
+  static inline void Init(base_internal::ThreadIdentity* identity);
+
+  // Increments "identity"'s count.
+  static inline void Post(base_internal::ThreadIdentity* identity);
+
+  // Waits until either our count > 0 or t has expired.
+  // If count > 0, decrements count and returns true.  Otherwise returns false.
+  // !t.has_timeout() => Wait(t) will return true.
+  static inline bool Wait(KernelTimeout t);
+
+  // Permitted callers.
+  friend class PerThreadSemTest;
+  friend class absl::Mutex;
+  friend void OneTimeInitThreadIdentity(absl::base_internal::ThreadIdentity*);
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// In some build configurations we pass --detect-odr-violations to the
+// gold linker.  This causes it to flag weak symbol overrides as ODR
+// violations.  Because ODR only applies to C++ and not C,
+// --detect-odr-violations ignores symbols not mangled with C++ names.
+// By changing our extension points to be extern "C", we dodge this
+// check.
+extern "C" {
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)(
+    absl::base_internal::ThreadIdentity* identity);
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)(
+    absl::base_internal::ThreadIdentity* identity);
+bool ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemWait)(
+    absl::synchronization_internal::KernelTimeout t);
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(
+    absl::base_internal::ThreadIdentity* identity);
+}  // extern "C"
+
+void absl::synchronization_internal::PerThreadSem::Init(
+    absl::base_internal::ThreadIdentity* identity) {
+  ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)(identity);
+}
+
+void absl::synchronization_internal::PerThreadSem::Post(
+    absl::base_internal::ThreadIdentity* identity) {
+  ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)(identity);
+}
+
+bool absl::synchronization_internal::PerThreadSem::Wait(
+    absl::synchronization_internal::KernelTimeout t) {
+  return ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemWait)(t);
+}
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_PER_THREAD_SEM_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/pthread_waiter.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/pthread_waiter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bf700e95528c7245e7a5ff9f93f22e003596bce7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/pthread_waiter.cc
@@ -0,0 +1,167 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/pthread_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_PTHREAD_WAITER
+
+#include <pthread.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include <cassert>
+#include <cerrno>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+namespace {
+class PthreadMutexHolder {
+ public:
+  explicit PthreadMutexHolder(pthread_mutex_t *mu) : mu_(mu) {
+    const int err = pthread_mutex_lock(mu_);
+    if (err != 0) {
+      ABSL_RAW_LOG(FATAL, "pthread_mutex_lock failed: %d", err);
+    }
+  }
+
+  PthreadMutexHolder(const PthreadMutexHolder &rhs) = delete;
+  PthreadMutexHolder &operator=(const PthreadMutexHolder &rhs) = delete;
+
+  ~PthreadMutexHolder() {
+    const int err = pthread_mutex_unlock(mu_);
+    if (err != 0) {
+      ABSL_RAW_LOG(FATAL, "pthread_mutex_unlock failed: %d", err);
+    }
+  }
+
+ private:
+  pthread_mutex_t *mu_;
+};
+}  // namespace
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char PthreadWaiter::kName[];
+#endif
+
+PthreadWaiter::PthreadWaiter() : waiter_count_(0), wakeup_count_(0) {
+  const int err = pthread_mutex_init(&mu_, 0);
+  if (err != 0) {
+    ABSL_RAW_LOG(FATAL, "pthread_mutex_init failed: %d", err);
+  }
+
+  const int err2 = pthread_cond_init(&cv_, 0);
+  if (err2 != 0) {
+    ABSL_RAW_LOG(FATAL, "pthread_cond_init failed: %d", err2);
+  }
+}
+
+#ifdef __APPLE__
+#define ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP 1
+#endif
+
+#if defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
+#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
+#elif defined(__ANDROID_API__) && __ANDROID_API__ >= 30
+#define ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT 1
+#endif
+
+// Calls pthread_cond_timedwait() or possibly something else like
+// pthread_cond_timedwait_relative_np() depending on the platform and
+// KernelTimeout requested. The return value is the same as the return
+// value of pthread_cond_timedwait().
+int PthreadWaiter::TimedWait(KernelTimeout t) {
+  assert(t.has_timeout());
+  if (KernelTimeout::SupportsSteadyClock() && t.is_relative_timeout()) {
+#ifdef ABSL_INTERNAL_HAS_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
+    const auto rel_timeout = t.MakeRelativeTimespec();
+    return pthread_cond_timedwait_relative_np(&cv_, &mu_, &rel_timeout);
+#elif defined(ABSL_INTERNAL_HAVE_PTHREAD_COND_CLOCKWAIT) && \
+    defined(CLOCK_MONOTONIC)
+    const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
+    return pthread_cond_clockwait(&cv_, &mu_, CLOCK_MONOTONIC,
+                                  &abs_clock_timeout);
+#endif
+  }
+
+  const auto abs_timeout = t.MakeAbsTimespec();
+  return pthread_cond_timedwait(&cv_, &mu_, &abs_timeout);
+}
+
+bool PthreadWaiter::Wait(KernelTimeout t) {
+  PthreadMutexHolder h(&mu_);
+  ++waiter_count_;
+  // Loop until we find a wakeup to consume or timeout.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (wakeup_count_ == 0) {
+    if (!first_pass) MaybeBecomeIdle();
+    // No wakeups available, time to wait.
+    if (!t.has_timeout()) {
+      const int err = pthread_cond_wait(&cv_, &mu_);
+      if (err != 0) {
+        ABSL_RAW_LOG(FATAL, "pthread_cond_wait failed: %d", err);
+      }
+    } else {
+      const int err = TimedWait(t);
+      if (err == ETIMEDOUT) {
+        --waiter_count_;
+        return false;
+      }
+      if (err != 0) {
+        ABSL_RAW_LOG(FATAL, "PthreadWaiter::TimedWait() failed: %d", err);
+      }
+    }
+    first_pass = false;
+  }
+  // Consume a wakeup and we're done.
+  --wakeup_count_;
+  --waiter_count_;
+  return true;
+}
+
+void PthreadWaiter::Post() {
+  PthreadMutexHolder h(&mu_);
+  ++wakeup_count_;
+  InternalCondVarPoke();
+}
+
+void PthreadWaiter::Poke() {
+  PthreadMutexHolder h(&mu_);
+  InternalCondVarPoke();
+}
+
+void PthreadWaiter::InternalCondVarPoke() {
+  if (waiter_count_ != 0) {
+    const int err = pthread_cond_signal(&cv_);
+    if (ABSL_PREDICT_FALSE(err != 0)) {
+      ABSL_RAW_LOG(FATAL, "pthread_cond_signal failed: %d", err);
+    }
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_PTHREAD_WAITER
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/pthread_waiter.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/pthread_waiter.h
new file mode 100644
index 0000000000000000000000000000000000000000..23db76ad442e656b9c98af29ed9964e989ba38cf
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/pthread_waiter.h
@@ -0,0 +1,60 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
+
+#if !defined(_WIN32) && !defined(__MINGW32__)
+#include <pthread.h>
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_PTHREAD_WAITER 1
+
+class PthreadWaiter : public WaiterCrtp<PthreadWaiter> {
+ public:
+  PthreadWaiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "PthreadWaiter";
+
+ private:
+  int TimedWait(KernelTimeout t);
+
+  // REQUIRES: mu_ must be held.
+  void InternalCondVarPoke();
+
+  pthread_mutex_t mu_;
+  pthread_cond_t cv_;
+  int waiter_count_;
+  int wakeup_count_;  // Unclaimed wakeups.
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // !defined(_WIN32) && !defined(__MINGW32__)
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/sem_waiter.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/sem_waiter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d62dbdc70d1a8fd38c7a7de2ffb4b0a62cb3896a
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/sem_waiter.cc
@@ -0,0 +1,122 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/sem_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_SEM_WAITER
+
+#include <semaphore.h>
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <cerrno>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char SemWaiter::kName[];
+#endif
+
+SemWaiter::SemWaiter() : wakeups_(0) {
+  if (sem_init(&sem_, 0, 0) != 0) {
+    ABSL_RAW_LOG(FATAL, "sem_init failed with errno %d\n", errno);
+  }
+}
+
+#if defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
+#define ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT 1
+#elif defined(__ANDROID_API__) && __ANDROID_API__ >= 30
+#define ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT 1
+#endif
+
+// Calls sem_timedwait() or possibly something else like
+// sem_clockwait() depending on the platform and
+// KernelTimeout requested. The return value is the same as a call to the return
+// value to a call to sem_timedwait().
+int SemWaiter::TimedWait(KernelTimeout t) {
+  if (KernelTimeout::SupportsSteadyClock() && t.is_relative_timeout()) {
+#if defined(ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT) && defined(CLOCK_MONOTONIC)
+    const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
+    return sem_clockwait(&sem_, CLOCK_MONOTONIC, &abs_clock_timeout);
+#endif
+  }
+
+  const auto abs_timeout = t.MakeAbsTimespec();
+  return sem_timedwait(&sem_, &abs_timeout);
+}
+
+bool SemWaiter::Wait(KernelTimeout t) {
+  // Loop until we timeout or consume a wakeup.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (true) {
+    int x = wakeups_.load(std::memory_order_relaxed);
+    while (x != 0) {
+      if (!wakeups_.compare_exchange_weak(x, x - 1,
+                                          std::memory_order_acquire,
+                                          std::memory_order_relaxed)) {
+        continue;  // Raced with someone, retry.
+      }
+      // Successfully consumed a wakeup, we're done.
+      return true;
+    }
+
+    if (!first_pass) MaybeBecomeIdle();
+    // Nothing to consume, wait (looping on EINTR).
+    while (true) {
+      if (!t.has_timeout()) {
+        if (sem_wait(&sem_) == 0) break;
+        if (errno == EINTR) continue;
+        ABSL_RAW_LOG(FATAL, "sem_wait failed: %d", errno);
+      } else {
+        if (TimedWait(t) == 0) break;
+        if (errno == EINTR) continue;
+        if (errno == ETIMEDOUT) return false;
+        ABSL_RAW_LOG(FATAL, "SemWaiter::TimedWait() failed: %d", errno);
+      }
+    }
+    first_pass = false;
+  }
+}
+
+void SemWaiter::Post() {
+  // Post a wakeup.
+  if (wakeups_.fetch_add(1, std::memory_order_release) == 0) {
+    // We incremented from 0, need to wake a potential waiter.
+    Poke();
+  }
+}
+
+void SemWaiter::Poke() {
+  if (sem_post(&sem_) != 0) {  // Wake any semaphore waiter.
+    ABSL_RAW_LOG(FATAL, "sem_post failed with errno %d\n", errno);
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_SEM_WAITER
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/sem_waiter.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/sem_waiter.h
new file mode 100644
index 0000000000000000000000000000000000000000..c22746f903f1e69646959710007ffde4bdb1b16d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/sem_waiter.h
@@ -0,0 +1,65 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_SEM_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_SEM_WAITER_H_
+
+#include "absl/base/config.h"
+
+#ifdef ABSL_HAVE_SEMAPHORE_H
+#include <semaphore.h>
+
+#include <atomic>
+#include <cstdint>
+
+#include "absl/base/internal/thread_identity.h"
+#include "absl/synchronization/internal/futex.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_SEM_WAITER 1
+
+class SemWaiter : public WaiterCrtp<SemWaiter> {
+ public:
+  SemWaiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "SemWaiter";
+
+ private:
+  int TimedWait(KernelTimeout t);
+
+  sem_t sem_;
+
+  // This seems superfluous, but for Poke() we need to cause spurious
+  // wakeups on the semaphore. Hence we can't actually use the
+  // semaphore's count.
+  std::atomic<int> wakeups_;
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_HAVE_SEMAPHORE_H
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_SEM_WAITER_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/stdcpp_waiter.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/stdcpp_waiter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..355718a792b9c3f100dec5abdbbf76be57a1b81d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/stdcpp_waiter.cc
@@ -0,0 +1,91 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/stdcpp_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_STDCPP_WAITER
+
+#include <chrono>  // NOLINT(build/c++11)
+#include <condition_variable>  // NOLINT(build/c++11)
+#include <mutex>  // NOLINT(build/c++11)
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char StdcppWaiter::kName[];
+#endif
+
+StdcppWaiter::StdcppWaiter() : waiter_count_(0), wakeup_count_(0) {}
+
+bool StdcppWaiter::Wait(KernelTimeout t) {
+  std::unique_lock<std::mutex> lock(mu_);
+  ++waiter_count_;
+
+  // Loop until we find a wakeup to consume or timeout.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (wakeup_count_ == 0) {
+    if (!first_pass) MaybeBecomeIdle();
+    // No wakeups available, time to wait.
+    if (!t.has_timeout()) {
+      cv_.wait(lock);
+    } else {
+      auto wait_result = t.SupportsSteadyClock() && t.is_relative_timeout()
+                             ? cv_.wait_for(lock, t.ToChronoDuration())
+                             : cv_.wait_until(lock, t.ToChronoTimePoint());
+      if (wait_result == std::cv_status::timeout) {
+        --waiter_count_;
+        return false;
+      }
+    }
+    first_pass = false;
+  }
+
+  // Consume a wakeup and we're done.
+  --wakeup_count_;
+  --waiter_count_;
+  return true;
+}
+
+void StdcppWaiter::Post() {
+  std::lock_guard<std::mutex> lock(mu_);
+  ++wakeup_count_;
+  InternalCondVarPoke();
+}
+
+void StdcppWaiter::Poke() {
+  std::lock_guard<std::mutex> lock(mu_);
+  InternalCondVarPoke();
+}
+
+void StdcppWaiter::InternalCondVarPoke() {
+  if (waiter_count_ != 0) {
+    cv_.notify_one();
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_STDCPP_WAITER
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/stdcpp_waiter.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/stdcpp_waiter.h
new file mode 100644
index 0000000000000000000000000000000000000000..e592a27bd553ad8e8bd56a32b48ee427d8548c79
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/stdcpp_waiter.h
@@ -0,0 +1,56 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_STDCPP_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_STDCPP_WAITER_H_
+
+#include <condition_variable>  // NOLINT(build/c++11)
+#include <mutex>  // NOLINT(build/c++11)
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_STDCPP_WAITER 1
+
+class StdcppWaiter : public WaiterCrtp<StdcppWaiter> {
+ public:
+  StdcppWaiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "StdcppWaiter";
+
+ private:
+  // REQUIRES: mu_ must be held.
+  void InternalCondVarPoke();
+
+  std::mutex mu_;
+  std::condition_variable cv_;
+  int waiter_count_;
+  int wakeup_count_;  // Unclaimed wakeups.
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_STDCPP_WAITER_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/thread_pool.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/thread_pool.h
new file mode 100644
index 0000000000000000000000000000000000000000..5eb0bb605e4762c82afb857719cb03d8a5cf2626
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/thread_pool.h
@@ -0,0 +1,96 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
+
+#include <cassert>
+#include <cstddef>
+#include <functional>
+#include <queue>
+#include <thread>  // NOLINT(build/c++11)
+#include <utility>
+#include <vector>
+
+#include "absl/base/thread_annotations.h"
+#include "absl/functional/any_invocable.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+// A simple ThreadPool implementation for tests.
+class ThreadPool {
+ public:
+  explicit ThreadPool(int num_threads) {
+    threads_.reserve(num_threads);
+    for (int i = 0; i < num_threads; ++i) {
+      threads_.push_back(std::thread(&ThreadPool::WorkLoop, this));
+    }
+  }
+
+  ThreadPool(const ThreadPool &) = delete;
+  ThreadPool &operator=(const ThreadPool &) = delete;
+
+  ~ThreadPool() {
+    {
+      absl::MutexLock l(&mu_);
+      for (size_t i = 0; i < threads_.size(); i++) {
+        queue_.push(nullptr);  // Shutdown signal.
+      }
+    }
+    for (auto &t : threads_) {
+      t.join();
+    }
+  }
+
+  // Schedule a function to be run on a ThreadPool thread immediately.
+  void Schedule(absl::AnyInvocable<void()> func) {
+    assert(func != nullptr);
+    absl::MutexLock l(&mu_);
+    queue_.push(std::move(func));
+  }
+
+ private:
+  bool WorkAvailable() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
+    return !queue_.empty();
+  }
+
+  void WorkLoop() {
+    while (true) {
+      absl::AnyInvocable<void()> func;
+      {
+        absl::MutexLock l(&mu_);
+        mu_.Await(absl::Condition(this, &ThreadPool::WorkAvailable));
+        func = std::move(queue_.front());
+        queue_.pop();
+      }
+      if (func == nullptr) {  // Shutdown signal.
+        break;
+      }
+      func();
+    }
+  }
+
+  absl::Mutex mu_;
+  std::queue<absl::AnyInvocable<void()>> queue_ ABSL_GUARDED_BY(mu_);
+  std::vector<std::thread> threads_;
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter.h
new file mode 100644
index 0000000000000000000000000000000000000000..6ba204bea0a82208001f5658a9e0592fc67dc2b7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter.h
@@ -0,0 +1,69 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_WAITER_H_
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/futex_waiter.h"
+#include "absl/synchronization/internal/pthread_waiter.h"
+#include "absl/synchronization/internal/sem_waiter.h"
+#include "absl/synchronization/internal/stdcpp_waiter.h"
+#include "absl/synchronization/internal/win32_waiter.h"
+
+// May be chosen at compile time via -DABSL_FORCE_WAITER_MODE=<index>
+#define ABSL_WAITER_MODE_FUTEX 0
+#define ABSL_WAITER_MODE_SEM 1
+#define ABSL_WAITER_MODE_CONDVAR 2
+#define ABSL_WAITER_MODE_WIN32 3
+#define ABSL_WAITER_MODE_STDCPP 4
+
+#if defined(ABSL_FORCE_WAITER_MODE)
+#define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE
+#elif defined(ABSL_INTERNAL_HAVE_WIN32_WAITER)
+#define ABSL_WAITER_MODE ABSL_WAITER_MODE_WIN32
+#elif defined(ABSL_INTERNAL_HAVE_FUTEX_WAITER)
+#define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX
+#elif defined(ABSL_INTERNAL_HAVE_SEM_WAITER)
+#define ABSL_WAITER_MODE ABSL_WAITER_MODE_SEM
+#elif defined(ABSL_INTERNAL_HAVE_PTHREAD_WAITER)
+#define ABSL_WAITER_MODE ABSL_WAITER_MODE_CONDVAR
+#elif defined(ABSL_INTERNAL_HAVE_STDCPP_WAITER)
+#define ABSL_WAITER_MODE ABSL_WAITER_MODE_STDCPP
+#else
+#error ABSL_WAITER_MODE is undefined
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
+using Waiter = FutexWaiter;
+#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_SEM
+using Waiter = SemWaiter;
+#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_CONDVAR
+using Waiter = PthreadWaiter;
+#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_WIN32
+using Waiter = Win32Waiter;
+#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_STDCPP
+using Waiter = StdcppWaiter;
+#endif
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_WAITER_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_base.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_base.cc
new file mode 100644
index 0000000000000000000000000000000000000000..46928b404e093e8de4cdbf487b446f608f2a6a95
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_base.cc
@@ -0,0 +1,42 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/waiter_base.h"
+
+#include "absl/base/config.h"
+#include "absl/base/internal/thread_identity.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr int WaiterBase::kIdlePeriods;
+#endif
+
+void WaiterBase::MaybeBecomeIdle() {
+  base_internal::ThreadIdentity *identity =
+      base_internal::CurrentThreadIdentityIfPresent();
+  assert(identity != nullptr);
+  const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);
+  const int ticker = identity->ticker.load(std::memory_order_relaxed);
+  const int wait_start = identity->wait_start.load(std::memory_order_relaxed);
+  if (!is_idle && ticker - wait_start > kIdlePeriods) {
+    identity->is_idle.store(true, std::memory_order_relaxed);
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_base.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_base.h
new file mode 100644
index 0000000000000000000000000000000000000000..cf17548193789bf36dfc8e492eed89b455855712
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_base.h
@@ -0,0 +1,90 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_WAITER_BASE_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_WAITER_BASE_H_
+
+#include "absl/base/config.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+// `Waiter` is a platform specific semaphore implementation that `PerThreadSem`
+// waits on to implement blocking in `absl::Mutex`.  Implementations should
+// inherit from `WaiterCrtp` and must implement `Wait()`, `Post()`, and `Poke()`
+// as described in `WaiterBase`.  `waiter.h` selects the implementation and uses
+// static-dispatch for performance.
+class WaiterBase {
+ public:
+  WaiterBase() = default;
+
+  // Not copyable or movable
+  WaiterBase(const WaiterBase&) = delete;
+  WaiterBase& operator=(const WaiterBase&) = delete;
+
+  // Blocks the calling thread until a matching call to `Post()` or
+  // `t` has passed. Returns `true` if woken (`Post()` called),
+  // `false` on timeout.
+  //
+  // bool Wait(KernelTimeout t);
+
+  // Restart the caller of `Wait()` as with a normal semaphore.
+  //
+  // void Post();
+
+  // If anyone is waiting, wake them up temporarily and cause them to
+  // call `MaybeBecomeIdle()`. They will then return to waiting for a
+  // `Post()` or timeout.
+  //
+  // void Poke();
+
+  // Returns the name of this implementation. Used only for debugging.
+  //
+  // static constexpr char kName[];
+
+  // How many periods to remain idle before releasing resources
+#ifndef ABSL_HAVE_THREAD_SANITIZER
+  static constexpr int kIdlePeriods = 60;
+#else
+  // Memory consumption under ThreadSanitizer is a serious concern,
+  // so we release resources sooner. The value of 1 leads to 1 to 2 second
+  // delay before marking a thread as idle.
+  static constexpr int kIdlePeriods = 1;
+#endif
+
+ protected:
+  static void MaybeBecomeIdle();
+};
+
+template <typename T>
+class WaiterCrtp : public WaiterBase {
+ public:
+  // Returns the Waiter associated with the identity.
+  static T* GetWaiter(base_internal::ThreadIdentity* identity) {
+    static_assert(
+        sizeof(T) <= sizeof(base_internal::ThreadIdentity::WaiterState),
+        "Insufficient space for Waiter");
+    return reinterpret_cast<T*>(identity->waiter_state.data);
+  }
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_WAITER_BASE_H_
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_test.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..992db29be84452b9dcf9c4f11944a4a39cbaa3ae
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/waiter_test.cc
@@ -0,0 +1,180 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/waiter.h"
+
+#include <ctime>
+#include <iostream>
+#include <ostream>
+
+#include "absl/base/config.h"
+#include "absl/random/random.h"
+#include "absl/synchronization/internal/create_thread_identity.h"
+#include "absl/synchronization/internal/futex_waiter.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/pthread_waiter.h"
+#include "absl/synchronization/internal/sem_waiter.h"
+#include "absl/synchronization/internal/stdcpp_waiter.h"
+#include "absl/synchronization/internal/thread_pool.h"
+#include "absl/synchronization/internal/win32_waiter.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "gtest/gtest.h"
+
+// Test go/btm support by randomizing the value of clock_gettime() for
+// CLOCK_MONOTONIC. This works by overriding a weak symbol in glibc.
+// We should be resistant to this randomization when !SupportsSteadyClock().
+#if defined(__GOOGLE_GRTE_VERSION__) &&      \
+    !defined(ABSL_HAVE_ADDRESS_SANITIZER) && \
+    !defined(ABSL_HAVE_MEMORY_SANITIZER) &&  \
+    !defined(ABSL_HAVE_THREAD_SANITIZER)
+extern "C" int __clock_gettime(clockid_t c, struct timespec* ts);
+
+extern "C" int clock_gettime(clockid_t c, struct timespec* ts) {
+  if (c == CLOCK_MONOTONIC &&
+      !absl::synchronization_internal::KernelTimeout::SupportsSteadyClock()) {
+    absl::SharedBitGen gen;
+    ts->tv_sec = absl::Uniform(gen, 0, 1'000'000'000);
+    ts->tv_nsec = absl::Uniform(gen, 0, 1'000'000'000);
+    return 0;
+  }
+  return __clock_gettime(c, ts);
+}
+#endif
+
+namespace {
+
+TEST(Waiter, PrintPlatformImplementation) {
+  // Allows us to verify that the platform is using the expected implementation.
+  std::cout << absl::synchronization_internal::Waiter::kName << std::endl;
+}
+
+template <typename T>
+class WaiterTest : public ::testing::Test {
+ public:
+  // Waiter implementations assume that a ThreadIdentity has already been
+  // created.
+  WaiterTest() {
+    absl::synchronization_internal::GetOrCreateCurrentThreadIdentity();
+  }
+};
+
+TYPED_TEST_SUITE_P(WaiterTest);
+
+absl::Duration WithTolerance(absl::Duration d) { return d * 0.95; }
+
+TYPED_TEST_P(WaiterTest, WaitNoTimeout) {
+  absl::synchronization_internal::ThreadPool tp(1);
+  TypeParam waiter;
+  tp.Schedule([&]() {
+    // Include some `Poke()` calls to ensure they don't cause `waiter` to return
+    // from `Wait()`.
+    waiter.Poke();
+    absl::SleepFor(absl::Seconds(1));
+    waiter.Poke();
+    absl::SleepFor(absl::Seconds(1));
+    waiter.Post();
+  });
+  absl::Time start = absl::Now();
+  EXPECT_TRUE(
+      waiter.Wait(absl::synchronization_internal::KernelTimeout::Never()));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Seconds(2)));
+}
+
+TYPED_TEST_P(WaiterTest, WaitDurationWoken) {
+  absl::synchronization_internal::ThreadPool tp(1);
+  TypeParam waiter;
+  tp.Schedule([&]() {
+    // Include some `Poke()` calls to ensure they don't cause `waiter` to return
+    // from `Wait()`.
+    waiter.Poke();
+    absl::SleepFor(absl::Milliseconds(500));
+    waiter.Post();
+  });
+  absl::Time start = absl::Now();
+  EXPECT_TRUE(waiter.Wait(
+      absl::synchronization_internal::KernelTimeout(absl::Seconds(10))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(2));
+}
+
+TYPED_TEST_P(WaiterTest, WaitTimeWoken) {
+  absl::synchronization_internal::ThreadPool tp(1);
+  TypeParam waiter;
+  tp.Schedule([&]() {
+    // Include some `Poke()` calls to ensure they don't cause `waiter` to return
+    // from `Wait()`.
+    waiter.Poke();
+    absl::SleepFor(absl::Milliseconds(500));
+    waiter.Post();
+  });
+  absl::Time start = absl::Now();
+  EXPECT_TRUE(waiter.Wait(absl::synchronization_internal::KernelTimeout(
+      start + absl::Seconds(10))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(2));
+}
+
+TYPED_TEST_P(WaiterTest, WaitDurationReached) {
+  TypeParam waiter;
+  absl::Time start = absl::Now();
+  EXPECT_FALSE(waiter.Wait(
+      absl::synchronization_internal::KernelTimeout(absl::Milliseconds(500))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(1));
+}
+
+TYPED_TEST_P(WaiterTest, WaitTimeReached) {
+  TypeParam waiter;
+  absl::Time start = absl::Now();
+  EXPECT_FALSE(waiter.Wait(absl::synchronization_internal::KernelTimeout(
+      start + absl::Milliseconds(500))));
+  absl::Duration waited = absl::Now() - start;
+  EXPECT_GE(waited, WithTolerance(absl::Milliseconds(500)));
+  EXPECT_LT(waited, absl::Seconds(1));
+}
+
+REGISTER_TYPED_TEST_SUITE_P(WaiterTest,
+                            WaitNoTimeout,
+                            WaitDurationWoken,
+                            WaitTimeWoken,
+                            WaitDurationReached,
+                            WaitTimeReached);
+
+#ifdef ABSL_INTERNAL_HAVE_FUTEX_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Futex, WaiterTest,
+                               absl::synchronization_internal::FutexWaiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_PTHREAD_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Pthread, WaiterTest,
+                               absl::synchronization_internal::PthreadWaiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_SEM_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Sem, WaiterTest,
+                               absl::synchronization_internal::SemWaiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_WIN32_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Win32, WaiterTest,
+                               absl::synchronization_internal::Win32Waiter);
+#endif
+#ifdef ABSL_INTERNAL_HAVE_STDCPP_WAITER
+INSTANTIATE_TYPED_TEST_SUITE_P(Stdcpp, WaiterTest,
+                               absl::synchronization_internal::StdcppWaiter);
+#endif
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/win32_waiter.cc b/weight/_dep/abseil-cpp/absl/synchronization/internal/win32_waiter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bd95ff080099fc0cfa3ae38f3204fc0d42039c99
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/win32_waiter.cc
@@ -0,0 +1,151 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/win32_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_WIN32_WAITER
+
+#include <windows.h>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char Win32Waiter::kName[];
+#endif
+
+class Win32Waiter::WinHelper {
+ public:
+  static SRWLOCK *GetLock(Win32Waiter *w) {
+    return reinterpret_cast<SRWLOCK *>(&w->mu_storage_);
+  }
+
+  static CONDITION_VARIABLE *GetCond(Win32Waiter *w) {
+    return reinterpret_cast<CONDITION_VARIABLE *>(&w->cv_storage_);
+  }
+
+  static_assert(sizeof(SRWLOCK) == sizeof(void *),
+                "`mu_storage_` does not have the same size as SRWLOCK");
+  static_assert(alignof(SRWLOCK) == alignof(void *),
+                "`mu_storage_` does not have the same alignment as SRWLOCK");
+
+  static_assert(sizeof(CONDITION_VARIABLE) == sizeof(void *),
+                "`ABSL_CONDITION_VARIABLE_STORAGE` does not have the same size "
+                "as `CONDITION_VARIABLE`");
+  static_assert(
+      alignof(CONDITION_VARIABLE) == alignof(void *),
+      "`cv_storage_` does not have the same alignment as `CONDITION_VARIABLE`");
+
+  // The SRWLOCK and CONDITION_VARIABLE types must be trivially constructible
+  // and destructible because we never call their constructors or destructors.
+  static_assert(std::is_trivially_constructible<SRWLOCK>::value,
+                "The `SRWLOCK` type must be trivially constructible");
+  static_assert(
+      std::is_trivially_constructible<CONDITION_VARIABLE>::value,
+      "The `CONDITION_VARIABLE` type must be trivially constructible");
+  static_assert(std::is_trivially_destructible<SRWLOCK>::value,
+                "The `SRWLOCK` type must be trivially destructible");
+  static_assert(std::is_trivially_destructible<CONDITION_VARIABLE>::value,
+                "The `CONDITION_VARIABLE` type must be trivially destructible");
+};
+
+class LockHolder {
+ public:
+  explicit LockHolder(SRWLOCK* mu) : mu_(mu) {
+    AcquireSRWLockExclusive(mu_);
+  }
+
+  LockHolder(const LockHolder&) = delete;
+  LockHolder& operator=(const LockHolder&) = delete;
+
+  ~LockHolder() {
+    ReleaseSRWLockExclusive(mu_);
+  }
+
+ private:
+  SRWLOCK* mu_;
+};
+
+Win32Waiter::Win32Waiter() {
+  auto *mu = ::new (static_cast<void *>(&mu_storage_)) SRWLOCK;
+  auto *cv = ::new (static_cast<void *>(&cv_storage_)) CONDITION_VARIABLE;
+  InitializeSRWLock(mu);
+  InitializeConditionVariable(cv);
+  waiter_count_ = 0;
+  wakeup_count_ = 0;
+}
+
+bool Win32Waiter::Wait(KernelTimeout t) {
+  SRWLOCK *mu = WinHelper::GetLock(this);
+  CONDITION_VARIABLE *cv = WinHelper::GetCond(this);
+
+  LockHolder h(mu);
+  ++waiter_count_;
+
+  // Loop until we find a wakeup to consume or timeout.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (wakeup_count_ == 0) {
+    if (!first_pass) MaybeBecomeIdle();
+    // No wakeups available, time to wait.
+    if (!SleepConditionVariableSRW(cv, mu, t.InMillisecondsFromNow(), 0)) {
+      // GetLastError() returns a Win32 DWORD, but we assign to
+      // unsigned long to simplify the ABSL_RAW_LOG case below.  The uniform
+      // initialization guarantees this is not a narrowing conversion.
+      const unsigned long err{GetLastError()};  // NOLINT(runtime/int)
+      if (err == ERROR_TIMEOUT) {
+        --waiter_count_;
+        return false;
+      } else {
+        ABSL_RAW_LOG(FATAL, "SleepConditionVariableSRW failed: %lu", err);
+      }
+    }
+    first_pass = false;
+  }
+  // Consume a wakeup and we're done.
+  --wakeup_count_;
+  --waiter_count_;
+  return true;
+}
+
+void Win32Waiter::Post() {
+  LockHolder h(WinHelper::GetLock(this));
+  ++wakeup_count_;
+  InternalCondVarPoke();
+}
+
+void Win32Waiter::Poke() {
+  LockHolder h(WinHelper::GetLock(this));
+  InternalCondVarPoke();
+}
+
+void Win32Waiter::InternalCondVarPoke() {
+  if (waiter_count_ != 0) {
+    WakeConditionVariable(WinHelper::GetCond(this));
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_WIN32_WAITER
diff --git a/weight/_dep/abseil-cpp/absl/synchronization/internal/win32_waiter.h b/weight/_dep/abseil-cpp/absl/synchronization/internal/win32_waiter.h
new file mode 100644
index 0000000000000000000000000000000000000000..fdab264e8cb742f61fdcf4148e06322e54673baf
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/synchronization/internal/win32_waiter.h
@@ -0,0 +1,72 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_
+#define ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_
+
+#ifdef _WIN32
+#include <sdkddkver.h>
+#endif
+
+#if defined(_WIN32) && !defined(__MINGW32__) && \
+    _WIN32_WINNT >= _WIN32_WINNT_VISTA
+
+#include "absl/base/config.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+#include "absl/synchronization/internal/waiter_base.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#define ABSL_INTERNAL_HAVE_WIN32_WAITER 1
+
+class Win32Waiter : public WaiterCrtp<Win32Waiter> {
+ public:
+  Win32Waiter();
+
+  bool Wait(KernelTimeout t);
+  void Post();
+  void Poke();
+
+  static constexpr char kName[] = "Win32Waiter";
+
+ private:
+  // WinHelper - Used to define utilities for accessing the lock and
+  // condition variable storage once the types are complete.
+  class WinHelper;
+
+  // REQUIRES: WinHelper::GetLock(this) must be held.
+  void InternalCondVarPoke();
+
+  // We can't include Windows.h in our headers, so we use aligned character
+  // buffers to define the storage of SRWLOCK and CONDITION_VARIABLE.
+  // SRW locks and condition variables do not need to be explicitly destroyed.
+  // https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-initializesrwlock
+  // https://stackoverflow.com/questions/28975958/why-does-windows-have-no-deleteconditionvariable-function-to-go-together-with
+  alignas(void*) unsigned char mu_storage_[sizeof(void*)];
+  alignas(void*) unsigned char cv_storage_[sizeof(void*)];
+  int waiter_count_;
+  int wakeup_count_;
+};
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // defined(_WIN32) && !defined(__MINGW32__) &&
+        // _WIN32_WINNT >= _WIN32_WINNT_VISTA
+
+#endif  // ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_
diff --git a/weight/_dep/abseil-cpp/absl/time/BUILD.bazel b/weight/_dep/abseil-cpp/absl/time/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..e3fe705b33a787fad39e1c78479f7c4934b314a0
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/BUILD.bazel
@@ -0,0 +1,158 @@
+#
+# Copyright 2017 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+load(
+    "//absl:copts/configure_copts.bzl",
+    "ABSL_DEFAULT_COPTS",
+    "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
+)
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "header_modules",
+        "layering_check",
+        "parse_headers",
+    ],
+)
+
+licenses(["notice"])
+
+cc_library(
+    name = "time",
+    srcs = [
+        "civil_time.cc",
+        "clock.cc",
+        "duration.cc",
+        "format.cc",
+        "internal/get_current_time_chrono.inc",
+        "internal/get_current_time_posix.inc",
+        "time.cc",
+    ],
+    hdrs = [
+        "civil_time.h",
+        "clock.h",
+        "time.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:raw_logging_internal",
+        "//absl/numeric:int128",
+        "//absl/strings",
+        "//absl/time/internal/cctz:civil_time",
+        "//absl/time/internal/cctz:time_zone",
+        "//absl/types:optional",
+    ],
+)
+
+cc_library(
+    name = "test_util",
+    testonly = 1,
+    srcs = ["internal/test_util.cc"],
+    hdrs = ["internal/test_util.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":time",
+        "//absl/base:config",
+        "//absl/base:raw_logging_internal",
+    ],
+)
+
+cc_test(
+    name = "time_test",
+    srcs = [
+        "civil_time_test.cc",
+        "clock_test.cc",
+        "duration_test.cc",
+        "format_test.cc",
+        "time_test.cc",
+        "time_zone_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    data = ["//absl/time/internal/cctz:zoneinfo"],
+    env = {"TZDIR": "absl/time/internal/cctz/testdata/zoneinfo"},
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":test_util",
+        ":time",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/numeric:int128",
+        "//absl/strings:str_format",
+        "//absl/time/internal/cctz:time_zone",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "flag_test",
+    srcs = [
+        "flag_test.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "no_test_android_arm",
+        "no_test_android_arm64",
+        "no_test_android_x86",
+        "no_test_ios_x86_64",
+        "no_test_lexan",
+        "no_test_loonix",
+        "no_test_wasm",
+    ],
+    deps = [
+        ":time",
+        "//absl/flags:flag",
+        "//absl/flags:reflection",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "time_benchmark",
+    srcs = [
+        "civil_time_benchmark.cc",
+        "clock_benchmark.cc",
+        "duration_benchmark.cc",
+        "format_benchmark.cc",
+        "time_benchmark.cc",
+    ],
+    copts = ABSL_TEST_COPTS,
+    data = ["//absl/time/internal/cctz:zoneinfo"],
+    env = {"TZDIR": "absl/time/internal/cctz/testdata/zoneinfo"},
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = [
+        "benchmark",
+    ],
+    deps = [
+        ":test_util",
+        ":time",
+        "//absl/base",
+        "//absl/base:core_headers",
+        "//absl/flags:flag",
+        "//absl/hash",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
diff --git a/weight/_dep/abseil-cpp/absl/time/CMakeLists.txt b/weight/_dep/abseil-cpp/absl/time/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..e1ade7a31a8cbaa7a15d56450332b0353e7b2df2
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/CMakeLists.txt
@@ -0,0 +1,141 @@
+#
+# Copyright 2017 The Abseil Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+absl_cc_library(
+  NAME
+    time
+  HDRS
+    "civil_time.h"
+    "clock.h"
+    "time.h"
+  SRCS
+    "civil_time.cc"
+    "clock.cc"
+    "duration.cc"
+    "format.cc"
+    "internal/get_current_time_chrono.inc"
+    "internal/get_current_time_posix.inc"
+    "time.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::civil_time
+    absl::core_headers
+    absl::int128
+    absl::raw_logging_internal
+    absl::strings
+    absl::time_zone
+  PUBLIC
+)
+
+absl_cc_library(
+  NAME
+    civil_time
+  HDRS
+    "internal/cctz/include/cctz/civil_time.h"
+    "internal/cctz/include/cctz/civil_time_detail.h"
+  SRCS
+  "internal/cctz/src/civil_time_detail.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+)
+
+absl_cc_library(
+  NAME
+    time_zone
+  HDRS
+    "internal/cctz/include/cctz/time_zone.h"
+    "internal/cctz/include/cctz/zone_info_source.h"
+  SRCS
+    "internal/cctz/src/time_zone_fixed.cc"
+    "internal/cctz/src/time_zone_fixed.h"
+    "internal/cctz/src/time_zone_format.cc"
+    "internal/cctz/src/time_zone_if.cc"
+    "internal/cctz/src/time_zone_if.h"
+    "internal/cctz/src/time_zone_impl.cc"
+    "internal/cctz/src/time_zone_impl.h"
+    "internal/cctz/src/time_zone_info.cc"
+    "internal/cctz/src/time_zone_info.h"
+    "internal/cctz/src/time_zone_libc.cc"
+    "internal/cctz/src/time_zone_libc.h"
+    "internal/cctz/src/time_zone_lookup.cc"
+    "internal/cctz/src/time_zone_posix.cc"
+    "internal/cctz/src/time_zone_posix.h"
+    "internal/cctz/src/tzfile.h"
+    "internal/cctz/src/zone_info_source.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    Threads::Threads
+    # TODO(#1495): Use $<LINK_LIBRARY:FRAMEWORK,CoreFoundation> once our
+    # minimum CMake version >= 3.24
+    $<$<PLATFORM_ID:Darwin>:-Wl,-framework,CoreFoundation>
+)
+
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    time_internal_test_util
+  HDRS
+    "internal/test_util.h"
+  SRCS
+    "internal/test_util.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::time
+    absl::config
+    absl::raw_logging_internal
+    absl::time_zone
+  TESTONLY
+)
+
+absl_cc_test(
+  NAME
+    time_test
+  SRCS
+    "civil_time_test.cc"
+    "clock_test.cc"
+    "duration_test.cc"
+    "format_test.cc"
+    "time_test.cc"
+    "time_zone_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::time_internal_test_util
+    absl::time
+    absl::config
+    absl::core_headers
+    absl::strings
+    absl::str_format
+    absl::time_zone
+    GTest::gmock_main
+)
+
+absl_cc_test(
+  NAME
+    flag_test
+  SRCS
+    "flag_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::flags
+    absl::flags_reflection
+    GTest::gmock_main
+)
diff --git a/weight/_dep/abseil-cpp/absl/time/civil_time.h b/weight/_dep/abseil-cpp/absl/time/civil_time.h
new file mode 100644
index 0000000000000000000000000000000000000000..3e904a113d88a42584da721432fa5a729c0aa4c6
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/civil_time.h
@@ -0,0 +1,589 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: civil_time.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines abstractions for computing with "civil time".
+// The term "civil time" refers to the legally recognized human-scale time
+// that is represented by the six fields `YYYY-MM-DD hh:mm:ss`. A "date"
+// is perhaps the most common example of a civil time (represented here as
+// an `absl::CivilDay`).
+//
+// Modern-day civil time follows the Gregorian Calendar and is a
+// time-zone-independent concept: a civil time of "2015-06-01 12:00:00", for
+// example, is not tied to a time zone. Put another way, a civil time does not
+// map to a unique point in time; a civil time must be mapped to an absolute
+// time *through* a time zone.
+//
+// Because a civil time is what most people think of as "time," it is common to
+// map absolute times to civil times to present to users.
+//
+// Time zones define the relationship between absolute and civil times. Given an
+// absolute or civil time and a time zone, you can compute the other time:
+//
+//   Civil Time = F(Absolute Time, Time Zone)
+//   Absolute Time = G(Civil Time, Time Zone)
+//
+// The Abseil time library allows you to construct such civil times from
+// absolute times; consult time.h for such functionality.
+//
+// This library provides six classes for constructing civil-time objects, and
+// provides several helper functions for rounding, iterating, and performing
+// arithmetic on civil-time objects, while avoiding complications like
+// daylight-saving time (DST):
+//
+//   * `absl::CivilSecond`
+//   * `absl::CivilMinute`
+//   * `absl::CivilHour`
+//   * `absl::CivilDay`
+//   * `absl::CivilMonth`
+//   * `absl::CivilYear`
+//
+// Example:
+//
+//   // Construct a civil-time object for a specific day
+//   const absl::CivilDay cd(1969, 07, 20);
+//
+//   // Construct a civil-time object for a specific second
+//   const absl::CivilSecond cd(2018, 8, 1, 12, 0, 1);
+//
+// Note: In C++14 and later, this library is usable in a constexpr context.
+//
+// Example:
+//
+//   // Valid in C++14
+//   constexpr absl::CivilDay cd(1969, 07, 20);
+
+#ifndef ABSL_TIME_CIVIL_TIME_H_
+#define ABSL_TIME_CIVIL_TIME_H_
+
+#include <iosfwd>
+#include <string>
+
+#include "absl/base/config.h"
+#include "absl/strings/string_view.h"
+#include "absl/time/internal/cctz/include/cctz/civil_time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace time_internal {
+struct second_tag : cctz::detail::second_tag {};
+struct minute_tag : second_tag, cctz::detail::minute_tag {};
+struct hour_tag : minute_tag, cctz::detail::hour_tag {};
+struct day_tag : hour_tag, cctz::detail::day_tag {};
+struct month_tag : day_tag, cctz::detail::month_tag {};
+struct year_tag : month_tag, cctz::detail::year_tag {};
+}  // namespace time_internal
+
+// -----------------------------------------------------------------------------
+// CivilSecond, CivilMinute, CivilHour, CivilDay, CivilMonth, CivilYear
+// -----------------------------------------------------------------------------
+//
+// Each of these civil-time types is a simple value type with the same
+// interface for construction and the same six accessors for each of the civil
+// time fields (year, month, day, hour, minute, and second, aka YMDHMS). These
+// classes differ only in their alignment, which is indicated by the type name
+// and specifies the field on which arithmetic operates.
+//
+// CONSTRUCTION
+//
+// Each of the civil-time types can be constructed in two ways: by directly
+// passing to the constructor up to six integers representing the YMDHMS fields,
+// or by copying the YMDHMS fields from a differently aligned civil-time type.
+// Omitted fields are assigned their minimum valid value. Hours, minutes, and
+// seconds will be set to 0, month and day will be set to 1. Since there is no
+// minimum year, the default is 1970.
+//
+// Examples:
+//
+//   absl::CivilDay default_value;               // 1970-01-01 00:00:00
+//
+//   absl::CivilDay a(2015, 2, 3);               // 2015-02-03 00:00:00
+//   absl::CivilDay b(2015, 2, 3, 4, 5, 6);      // 2015-02-03 00:00:00
+//   absl::CivilDay c(2015);                     // 2015-01-01 00:00:00
+//
+//   absl::CivilSecond ss(2015, 2, 3, 4, 5, 6);  // 2015-02-03 04:05:06
+//   absl::CivilMinute mm(ss);                   // 2015-02-03 04:05:00
+//   absl::CivilHour hh(mm);                     // 2015-02-03 04:00:00
+//   absl::CivilDay d(hh);                       // 2015-02-03 00:00:00
+//   absl::CivilMonth m(d);                      // 2015-02-01 00:00:00
+//   absl::CivilYear y(m);                       // 2015-01-01 00:00:00
+//
+//   m = absl::CivilMonth(y);                    // 2015-01-01 00:00:00
+//   d = absl::CivilDay(m);                      // 2015-01-01 00:00:00
+//   hh = absl::CivilHour(d);                    // 2015-01-01 00:00:00
+//   mm = absl::CivilMinute(hh);                 // 2015-01-01 00:00:00
+//   ss = absl::CivilSecond(mm);                 // 2015-01-01 00:00:00
+//
+// Each civil-time class is aligned to the civil-time field indicated in the
+// class's name after normalization. Alignment is performed by setting all the
+// inferior fields to their minimum valid value (as described above). The
+// following are examples of how each of the six types would align the fields
+// representing November 22, 2015 at 12:34:56 in the afternoon. (Note: the
+// string format used here is not important; it's just a shorthand way of
+// showing the six YMDHMS fields.)
+//
+//   absl::CivilSecond   : 2015-11-22 12:34:56
+//   absl::CivilMinute   : 2015-11-22 12:34:00
+//   absl::CivilHour     : 2015-11-22 12:00:00
+//   absl::CivilDay      : 2015-11-22 00:00:00
+//   absl::CivilMonth    : 2015-11-01 00:00:00
+//   absl::CivilYear     : 2015-01-01 00:00:00
+//
+// Each civil-time type performs arithmetic on the field to which it is
+// aligned. This means that adding 1 to an absl::CivilDay increments the day
+// field (normalizing as necessary), and subtracting 7 from an absl::CivilMonth
+// operates on the month field (normalizing as necessary). All arithmetic
+// produces a valid civil time. Difference requires two similarly aligned
+// civil-time objects and returns the scalar answer in units of the objects'
+// alignment. For example, the difference between two absl::CivilHour objects
+// will give an answer in units of civil hours.
+//
+// ALIGNMENT CONVERSION
+//
+// The alignment of a civil-time object cannot change, but the object may be
+// used to construct a new object with a different alignment. This is referred
+// to as "realigning". When realigning to a type with the same or more
+// precision (e.g., absl::CivilDay -> absl::CivilSecond), the conversion may be
+// performed implicitly since no information is lost. However, if information
+// could be discarded (e.g., CivilSecond -> CivilDay), the conversion must
+// be explicit at the call site.
+//
+// Examples:
+//
+//   void UseDay(absl::CivilDay day);
+//
+//   absl::CivilSecond cs;
+//   UseDay(cs);                  // Won't compile because data may be discarded
+//   UseDay(absl::CivilDay(cs));  // OK: explicit conversion
+//
+//   absl::CivilDay cd;
+//   UseDay(cd);                  // OK: no conversion needed
+//
+//   absl::CivilMonth cm;
+//   UseDay(cm);                  // OK: implicit conversion to absl::CivilDay
+//
+// NORMALIZATION
+//
+// Normalization takes invalid values and adjusts them to produce valid values.
+// Within the civil-time library, integer arguments passed to the Civil*
+// constructors may be out-of-range, in which case they are normalized by
+// carrying overflow into a field of courser granularity to produce valid
+// civil-time objects. This normalization enables natural arithmetic on
+// constructor arguments without worrying about the field's range.
+//
+// Examples:
+//
+//   // Out-of-range; normalized to 2016-11-01
+//   absl::CivilDay d(2016, 10, 32);
+//   // Out-of-range, negative: normalized to 2016-10-30T23
+//   absl::CivilHour h1(2016, 10, 31, -1);
+//   // Normalization is cumulative: normalized to 2016-10-30T23
+//   absl::CivilHour h2(2016, 10, 32, -25);
+//
+// Note: If normalization is undesired, you can signal an error by comparing
+// the constructor arguments to the normalized values returned by the YMDHMS
+// properties.
+//
+// COMPARISON
+//
+// Comparison between civil-time objects considers all six YMDHMS fields,
+// regardless of the type's alignment. Comparison between differently aligned
+// civil-time types is allowed.
+//
+// Examples:
+//
+//   absl::CivilDay feb_3(2015, 2, 3);  // 2015-02-03 00:00:00
+//   absl::CivilDay mar_4(2015, 3, 4);  // 2015-03-04 00:00:00
+//   // feb_3 < mar_4
+//   // absl::CivilYear(feb_3) == absl::CivilYear(mar_4)
+//
+//   absl::CivilSecond feb_3_noon(2015, 2, 3, 12, 0, 0);  // 2015-02-03 12:00:00
+//   // feb_3 < feb_3_noon
+//   // feb_3 == absl::CivilDay(feb_3_noon)
+//
+//   // Iterates all the days of February 2015.
+//   for (absl::CivilDay d(2015, 2, 1); d < absl::CivilMonth(2015, 3); ++d) {
+//     // ...
+//   }
+//
+// ARITHMETIC
+//
+// Civil-time types support natural arithmetic operators such as addition,
+// subtraction, and difference. Arithmetic operates on the civil-time field
+// indicated in the type's name. Difference operators require arguments with
+// the same alignment and return the answer in units of the alignment.
+//
+// Example:
+//
+//   absl::CivilDay a(2015, 2, 3);
+//   ++a;                              // 2015-02-04 00:00:00
+//   --a;                              // 2015-02-03 00:00:00
+//   absl::CivilDay b = a + 1;         // 2015-02-04 00:00:00
+//   absl::CivilDay c = 1 + b;         // 2015-02-05 00:00:00
+//   int n = c - a;                    // n = 2 (civil days)
+//   int m = c - absl::CivilMonth(c);  // Won't compile: different types.
+//
+// ACCESSORS
+//
+// Each civil-time type has accessors for all six of the civil-time fields:
+// year, month, day, hour, minute, and second.
+//
+// civil_year_t year()
+// int          month()
+// int          day()
+// int          hour()
+// int          minute()
+// int          second()
+//
+// Recall that fields inferior to the type's alignment will be set to their
+// minimum valid value.
+//
+// Example:
+//
+//   absl::CivilDay d(2015, 6, 28);
+//   // d.year() == 2015
+//   // d.month() == 6
+//   // d.day() == 28
+//   // d.hour() == 0
+//   // d.minute() == 0
+//   // d.second() == 0
+//
+// CASE STUDY: Adding a month to January 31.
+//
+// One of the classic questions that arises when considering a civil time
+// library (or a date library or a date/time library) is this:
+//   "What is the result of adding a month to January 31?"
+// This is an interesting question because it is unclear what is meant by a
+// "month", and several different answers are possible, depending on context:
+//
+//   1. March 3 (or 2 if a leap year), if "add a month" means to add a month to
+//      the current month, and adjust the date to overflow the extra days into
+//      March. In this case the result of "February 31" would be normalized as
+//      within the civil-time library.
+//   2. February 28 (or 29 if a leap year), if "add a month" means to add a
+//      month, and adjust the date while holding the resulting month constant.
+//      In this case, the result of "February 31" would be truncated to the last
+//      day in February.
+//   3. An error. The caller may get some error, an exception, an invalid date
+//      object, or perhaps return `false`. This may make sense because there is
+//      no single unambiguously correct answer to the question.
+//
+// Practically speaking, any answer that is not what the programmer intended
+// is the wrong answer.
+//
+// The Abseil time library avoids this problem by making it impossible to
+// ask ambiguous questions. All civil-time objects are aligned to a particular
+// civil-field boundary (such as aligned to a year, month, day, hour, minute,
+// or second), and arithmetic operates on the field to which the object is
+// aligned. This means that in order to "add a month" the object must first be
+// aligned to a month boundary, which is equivalent to the first day of that
+// month.
+//
+// Of course, there are ways to compute an answer the question at hand using
+// this Abseil time library, but they require the programmer to be explicit
+// about the answer they expect. To illustrate, let's see how to compute all
+// three of the above possible answers to the question of "Jan 31 plus 1
+// month":
+//
+// Example:
+//
+//   const absl::CivilDay d(2015, 1, 31);
+//
+//   // Answer 1:
+//   // Add 1 to the month field in the constructor, and rely on normalization.
+//   const auto normalized = absl::CivilDay(d.year(), d.month() + 1, d.day());
+//   // normalized == 2015-03-03 (aka Feb 31)
+//
+//   // Answer 2:
+//   // Add 1 to month field, capping to the end of next month.
+//   const auto next_month = absl::CivilMonth(d) + 1;
+//   const auto last_day_of_next_month = absl::CivilDay(next_month + 1) - 1;
+//   const auto capped = std::min(normalized, last_day_of_next_month);
+//   // capped == 2015-02-28
+//
+//   // Answer 3:
+//   // Signal an error if the normalized answer is not in next month.
+//   if (absl::CivilMonth(normalized) != next_month) {
+//     // error, month overflow
+//   }
+//
+using CivilSecond =
+    time_internal::cctz::detail::civil_time<time_internal::second_tag>;
+using CivilMinute =
+    time_internal::cctz::detail::civil_time<time_internal::minute_tag>;
+using CivilHour =
+    time_internal::cctz::detail::civil_time<time_internal::hour_tag>;
+using CivilDay =
+    time_internal::cctz::detail::civil_time<time_internal::day_tag>;
+using CivilMonth =
+    time_internal::cctz::detail::civil_time<time_internal::month_tag>;
+using CivilYear =
+    time_internal::cctz::detail::civil_time<time_internal::year_tag>;
+
+// civil_year_t
+//
+// Type alias of a civil-time year value. This type is guaranteed to (at least)
+// support any year value supported by `time_t`.
+//
+// Example:
+//
+//   absl::CivilSecond cs = ...;
+//   absl::civil_year_t y = cs.year();
+//   cs = absl::CivilSecond(y, 1, 1, 0, 0, 0);  // CivilSecond(CivilYear(cs))
+//
+using civil_year_t = time_internal::cctz::year_t;
+
+// civil_diff_t
+//
+// Type alias of the difference between two civil-time values.
+// This type is used to indicate arguments that are not
+// normalized (such as parameters to the civil-time constructors), the results
+// of civil-time subtraction, or the operand to civil-time addition.
+//
+// Example:
+//
+//   absl::civil_diff_t n_sec = cs1 - cs2;             // cs1 == cs2 + n_sec;
+//
+using civil_diff_t = time_internal::cctz::diff_t;
+
+// Weekday::monday, Weekday::tuesday, Weekday::wednesday, Weekday::thursday,
+// Weekday::friday, Weekday::saturday, Weekday::sunday
+//
+// The Weekday enum class represents the civil-time concept of a "weekday" with
+// members for all days of the week.
+//
+//   absl::Weekday wd = absl::Weekday::thursday;
+//
+using Weekday = time_internal::cctz::weekday;
+
+// GetWeekday()
+//
+// Returns the absl::Weekday for the given (realigned) civil-time value.
+//
+// Example:
+//
+//   absl::CivilDay a(2015, 8, 13);
+//   absl::Weekday wd = absl::GetWeekday(a);  // wd == absl::Weekday::thursday
+//
+inline Weekday GetWeekday(CivilSecond cs) {
+  return time_internal::cctz::get_weekday(cs);
+}
+
+// NextWeekday()
+// PrevWeekday()
+//
+// Returns the absl::CivilDay that strictly follows or precedes a given
+// absl::CivilDay, and that falls on the given absl::Weekday.
+//
+// Example, given the following month:
+//
+//       August 2015
+//   Su Mo Tu We Th Fr Sa
+//                      1
+//    2  3  4  5  6  7  8
+//    9 10 11 12 13 14 15
+//   16 17 18 19 20 21 22
+//   23 24 25 26 27 28 29
+//   30 31
+//
+//   absl::CivilDay a(2015, 8, 13);
+//   // absl::GetWeekday(a) == absl::Weekday::thursday
+//   absl::CivilDay b = absl::NextWeekday(a, absl::Weekday::thursday);
+//   // b = 2015-08-20
+//   absl::CivilDay c = absl::PrevWeekday(a, absl::Weekday::thursday);
+//   // c = 2015-08-06
+//
+//   absl::CivilDay d = ...
+//   // Gets the following Thursday if d is not already Thursday
+//   absl::CivilDay thurs1 = absl::NextWeekday(d - 1, absl::Weekday::thursday);
+//   // Gets the previous Thursday if d is not already Thursday
+//   absl::CivilDay thurs2 = absl::PrevWeekday(d + 1, absl::Weekday::thursday);
+//
+inline CivilDay NextWeekday(CivilDay cd, Weekday wd) {
+  return CivilDay(time_internal::cctz::next_weekday(cd, wd));
+}
+inline CivilDay PrevWeekday(CivilDay cd, Weekday wd) {
+  return CivilDay(time_internal::cctz::prev_weekday(cd, wd));
+}
+
+// GetYearDay()
+//
+// Returns the day-of-year for the given (realigned) civil-time value.
+//
+// Example:
+//
+//   absl::CivilDay a(2015, 1, 1);
+//   int yd_jan_1 = absl::GetYearDay(a);   // yd_jan_1 = 1
+//   absl::CivilDay b(2015, 12, 31);
+//   int yd_dec_31 = absl::GetYearDay(b);  // yd_dec_31 = 365
+//
+inline int GetYearDay(CivilSecond cs) {
+  return time_internal::cctz::get_yearday(cs);
+}
+
+// FormatCivilTime()
+//
+// Formats the given civil-time value into a string value of the following
+// format:
+//
+//  Type        | Format
+//  ---------------------------------
+//  CivilSecond | YYYY-MM-DDTHH:MM:SS
+//  CivilMinute | YYYY-MM-DDTHH:MM
+//  CivilHour   | YYYY-MM-DDTHH
+//  CivilDay    | YYYY-MM-DD
+//  CivilMonth  | YYYY-MM
+//  CivilYear   | YYYY
+//
+// Example:
+//
+//   absl::CivilDay d = absl::CivilDay(1969, 7, 20);
+//   std::string day_string = absl::FormatCivilTime(d);  // "1969-07-20"
+//
+std::string FormatCivilTime(CivilSecond c);
+std::string FormatCivilTime(CivilMinute c);
+std::string FormatCivilTime(CivilHour c);
+std::string FormatCivilTime(CivilDay c);
+std::string FormatCivilTime(CivilMonth c);
+std::string FormatCivilTime(CivilYear c);
+
+// Support for StrFormat(), StrCat(), etc
+template <typename Sink>
+void AbslStringify(Sink& sink, CivilSecond c) {
+  sink.Append(FormatCivilTime(c));
+}
+template <typename Sink>
+void AbslStringify(Sink& sink, CivilMinute c) {
+  sink.Append(FormatCivilTime(c));
+}
+template <typename Sink>
+void AbslStringify(Sink& sink, CivilHour c) {
+  sink.Append(FormatCivilTime(c));
+}
+template <typename Sink>
+void AbslStringify(Sink& sink, CivilDay c) {
+  sink.Append(FormatCivilTime(c));
+}
+template <typename Sink>
+void AbslStringify(Sink& sink, CivilMonth c) {
+  sink.Append(FormatCivilTime(c));
+}
+template <typename Sink>
+void AbslStringify(Sink& sink, CivilYear c) {
+  sink.Append(FormatCivilTime(c));
+}
+
+// absl::ParseCivilTime()
+//
+// Parses a civil-time value from the specified `absl::string_view` into the
+// passed output parameter. Returns `true` upon successful parsing.
+//
+// The expected form of the input string is as follows:
+//
+//  Type        | Format
+//  ---------------------------------
+//  CivilSecond | YYYY-MM-DDTHH:MM:SS
+//  CivilMinute | YYYY-MM-DDTHH:MM
+//  CivilHour   | YYYY-MM-DDTHH
+//  CivilDay    | YYYY-MM-DD
+//  CivilMonth  | YYYY-MM
+//  CivilYear   | YYYY
+//
+// Example:
+//
+//   absl::CivilDay d;
+//   bool ok = absl::ParseCivilTime("2018-01-02", &d); // OK
+//
+// Note that parsing will fail if the string's format does not match the
+// expected type exactly. `ParseLenientCivilTime()` below is more lenient.
+//
+bool ParseCivilTime(absl::string_view s, CivilSecond* c);
+bool ParseCivilTime(absl::string_view s, CivilMinute* c);
+bool ParseCivilTime(absl::string_view s, CivilHour* c);
+bool ParseCivilTime(absl::string_view s, CivilDay* c);
+bool ParseCivilTime(absl::string_view s, CivilMonth* c);
+bool ParseCivilTime(absl::string_view s, CivilYear* c);
+
+// ParseLenientCivilTime()
+//
+// Parses any of the formats accepted by `absl::ParseCivilTime()`, but is more
+// lenient if the format of the string does not exactly match the associated
+// type.
+//
+// Example:
+//
+//   absl::CivilDay d;
+//   bool ok = absl::ParseLenientCivilTime("1969-07-20", &d); // OK
+//   ok = absl::ParseLenientCivilTime("1969-07-20T10", &d);   // OK: T10 floored
+//   ok = absl::ParseLenientCivilTime("1969-07", &d);   // OK: day defaults to 1
+//
+bool ParseLenientCivilTime(absl::string_view s, CivilSecond* c);
+bool ParseLenientCivilTime(absl::string_view s, CivilMinute* c);
+bool ParseLenientCivilTime(absl::string_view s, CivilHour* c);
+bool ParseLenientCivilTime(absl::string_view s, CivilDay* c);
+bool ParseLenientCivilTime(absl::string_view s, CivilMonth* c);
+bool ParseLenientCivilTime(absl::string_view s, CivilYear* c);
+
+namespace time_internal {  // For functions found via ADL on civil-time tags.
+
+// Streaming Operators
+//
+// Each civil-time type may be sent to an output stream using operator<<().
+// The result matches the string produced by `FormatCivilTime()`.
+//
+// Example:
+//
+//   absl::CivilDay d = absl::CivilDay(1969, 7, 20);
+//   std::cout << "Date is: " << d << "\n";
+//
+std::ostream& operator<<(std::ostream& os, CivilYear y);
+std::ostream& operator<<(std::ostream& os, CivilMonth m);
+std::ostream& operator<<(std::ostream& os, CivilDay d);
+std::ostream& operator<<(std::ostream& os, CivilHour h);
+std::ostream& operator<<(std::ostream& os, CivilMinute m);
+std::ostream& operator<<(std::ostream& os, CivilSecond s);
+
+// AbslParseFlag()
+//
+// Parses the command-line flag string representation `s` into a civil-time
+// value. Flags must be specified in a format that is valid for
+// `absl::ParseLenientCivilTime()`.
+bool AbslParseFlag(absl::string_view s, CivilSecond* c, std::string* error);
+bool AbslParseFlag(absl::string_view s, CivilMinute* c, std::string* error);
+bool AbslParseFlag(absl::string_view s, CivilHour* c, std::string* error);
+bool AbslParseFlag(absl::string_view s, CivilDay* c, std::string* error);
+bool AbslParseFlag(absl::string_view s, CivilMonth* c, std::string* error);
+bool AbslParseFlag(absl::string_view s, CivilYear* c, std::string* error);
+
+// AbslUnparseFlag()
+//
+// Unparses a civil-time value into a command-line string representation using
+// the format specified by `absl::ParseCivilTime()`.
+std::string AbslUnparseFlag(CivilSecond c);
+std::string AbslUnparseFlag(CivilMinute c);
+std::string AbslUnparseFlag(CivilHour c);
+std::string AbslUnparseFlag(CivilDay c);
+std::string AbslUnparseFlag(CivilMonth c);
+std::string AbslUnparseFlag(CivilYear c);
+
+}  // namespace time_internal
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_TIME_CIVIL_TIME_H_
diff --git a/weight/_dep/abseil-cpp/absl/time/civil_time_benchmark.cc b/weight/_dep/abseil-cpp/absl/time/civil_time_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2de0233dc4ff0605e3d6aea40c23a21b5571d825
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/civil_time_benchmark.cc
@@ -0,0 +1,130 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/time/civil_time.h"
+
+#include <cstddef>
+#include <numeric>
+#include <string>
+#include <vector>
+
+#include "absl/hash/hash.h"
+#include "benchmark/benchmark.h"
+
+namespace {
+
+// Run on (12 X 3492 MHz CPUs); 2018-11-05T13:44:29.814239103-08:00
+// CPU: Intel Haswell with HyperThreading (6 cores) dL1:32KB dL2:256KB dL3:15MB
+// Benchmark                 Time(ns)        CPU(ns)     Iterations
+// ----------------------------------------------------------------
+// BM_Difference_Days              14.5           14.5     48531105
+// BM_Step_Days                    12.6           12.6     54876006
+// BM_Format                      587            587        1000000
+// BM_Parse                       692            692        1000000
+// BM_RoundTripFormatParse       1309           1309         532075
+// BM_CivilYearAbslHash             0.710          0.710  976400000
+// BM_CivilMonthAbslHash            1.13           1.13   619500000
+// BM_CivilDayAbslHash              1.70           1.70   426000000
+// BM_CivilHourAbslHash             2.45           2.45   287600000
+// BM_CivilMinuteAbslHash           3.21           3.21   226200000
+// BM_CivilSecondAbslHash           4.10           4.10   171800000
+
+void BM_Difference_Days(benchmark::State& state) {
+  const absl::CivilDay c(2014, 8, 22);
+  const absl::CivilDay epoch(1970, 1, 1);
+  while (state.KeepRunning()) {
+    absl::civil_diff_t n = c - epoch;
+    benchmark::DoNotOptimize(n);
+  }
+}
+BENCHMARK(BM_Difference_Days);
+
+void BM_Step_Days(benchmark::State& state) {
+  const absl::CivilDay kStart(2014, 8, 22);
+  absl::CivilDay c = kStart;
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(++c);
+  }
+}
+BENCHMARK(BM_Step_Days);
+
+void BM_Format(benchmark::State& state) {
+  const absl::CivilSecond c(2014, 1, 2, 3, 4, 5);
+  while (state.KeepRunning()) {
+    std::string s = absl::FormatCivilTime(c);
+    benchmark::DoNotOptimize(s);
+  }
+}
+BENCHMARK(BM_Format);
+
+void BM_Parse(benchmark::State& state) {
+  const std::string f = "2014-01-02T03:04:05";
+  absl::CivilSecond c;
+  while (state.KeepRunning()) {
+    bool b = absl::ParseCivilTime(f, &c);
+    benchmark::DoNotOptimize(b);
+  }
+}
+BENCHMARK(BM_Parse);
+
+void BM_RoundTripFormatParse(benchmark::State& state) {
+  const absl::CivilSecond c(2014, 1, 2, 3, 4, 5);
+  absl::CivilSecond out;
+  while (state.KeepRunning()) {
+    bool b = absl::ParseCivilTime(absl::FormatCivilTime(c), &out);
+    benchmark::DoNotOptimize(b);
+  }
+}
+BENCHMARK(BM_RoundTripFormatParse);
+
+template <typename T>
+void BM_CivilTimeAbslHash(benchmark::State& state) {
+  const int kSize = 100000;
+  std::vector<T> civil_times(kSize);
+  std::iota(civil_times.begin(), civil_times.end(), T(2018));
+
+  absl::Hash<T> absl_hasher;
+  while (state.KeepRunningBatch(kSize)) {
+    for (const T civil_time : civil_times) {
+      size_t hash = absl_hasher(civil_time);
+      benchmark::DoNotOptimize(hash);
+    }
+  }
+}
+void BM_CivilYearAbslHash(benchmark::State& state) {
+  BM_CivilTimeAbslHash<absl::CivilYear>(state);
+}
+void BM_CivilMonthAbslHash(benchmark::State& state) {
+  BM_CivilTimeAbslHash<absl::CivilMonth>(state);
+}
+void BM_CivilDayAbslHash(benchmark::State& state) {
+  BM_CivilTimeAbslHash<absl::CivilDay>(state);
+}
+void BM_CivilHourAbslHash(benchmark::State& state) {
+  BM_CivilTimeAbslHash<absl::CivilHour>(state);
+}
+void BM_CivilMinuteAbslHash(benchmark::State& state) {
+  BM_CivilTimeAbslHash<absl::CivilMinute>(state);
+}
+void BM_CivilSecondAbslHash(benchmark::State& state) {
+  BM_CivilTimeAbslHash<absl::CivilSecond>(state);
+}
+BENCHMARK(BM_CivilYearAbslHash);
+BENCHMARK(BM_CivilMonthAbslHash);
+BENCHMARK(BM_CivilDayAbslHash);
+BENCHMARK(BM_CivilHourAbslHash);
+BENCHMARK(BM_CivilMinuteAbslHash);
+BENCHMARK(BM_CivilSecondAbslHash);
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/time/civil_time_test.cc b/weight/_dep/abseil-cpp/absl/time/civil_time_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..19292a9c66593af7a976e1cf0c51e04268191241
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/civil_time_test.cc
@@ -0,0 +1,1262 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/time/civil_time.h"
+
+#include <iomanip>
+#include <limits>
+#include <sstream>
+#include <type_traits>
+
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+#include "absl/strings/str_format.h"
+
+namespace {
+
+TEST(CivilTime, DefaultConstruction) {
+  absl::CivilSecond ss;
+  EXPECT_EQ("1970-01-01T00:00:00", absl::FormatCivilTime(ss));
+
+  absl::CivilMinute mm;
+  EXPECT_EQ("1970-01-01T00:00", absl::FormatCivilTime(mm));
+
+  absl::CivilHour hh;
+  EXPECT_EQ("1970-01-01T00", absl::FormatCivilTime(hh));
+
+  absl::CivilDay d;
+  EXPECT_EQ("1970-01-01", absl::FormatCivilTime(d));
+
+  absl::CivilMonth m;
+  EXPECT_EQ("1970-01", absl::FormatCivilTime(m));
+
+  absl::CivilYear y;
+  EXPECT_EQ("1970", absl::FormatCivilTime(y));
+}
+
+TEST(CivilTime, StructMember) {
+  struct S {
+    absl::CivilDay day;
+  };
+  S s = {};
+  EXPECT_EQ(absl::CivilDay{}, s.day);
+}
+
+TEST(CivilTime, FieldsConstruction) {
+  EXPECT_EQ("2015-01-02T03:04:05",
+            absl::FormatCivilTime(absl::CivilSecond(2015, 1, 2, 3, 4, 5)));
+  EXPECT_EQ("2015-01-02T03:04:00",
+            absl::FormatCivilTime(absl::CivilSecond(2015, 1, 2, 3, 4)));
+  EXPECT_EQ("2015-01-02T03:00:00",
+            absl::FormatCivilTime(absl::CivilSecond(2015, 1, 2, 3)));
+  EXPECT_EQ("2015-01-02T00:00:00",
+            absl::FormatCivilTime(absl::CivilSecond(2015, 1, 2)));
+  EXPECT_EQ("2015-01-01T00:00:00",
+            absl::FormatCivilTime(absl::CivilSecond(2015, 1)));
+  EXPECT_EQ("2015-01-01T00:00:00",
+            absl::FormatCivilTime(absl::CivilSecond(2015)));
+
+  EXPECT_EQ("2015-01-02T03:04",
+            absl::FormatCivilTime(absl::CivilMinute(2015, 1, 2, 3, 4, 5)));
+  EXPECT_EQ("2015-01-02T03:04",
+            absl::FormatCivilTime(absl::CivilMinute(2015, 1, 2, 3, 4)));
+  EXPECT_EQ("2015-01-02T03:00",
+            absl::FormatCivilTime(absl::CivilMinute(2015, 1, 2, 3)));
+  EXPECT_EQ("2015-01-02T00:00",
+            absl::FormatCivilTime(absl::CivilMinute(2015, 1, 2)));
+  EXPECT_EQ("2015-01-01T00:00",
+            absl::FormatCivilTime(absl::CivilMinute(2015, 1)));
+  EXPECT_EQ("2015-01-01T00:00",
+            absl::FormatCivilTime(absl::CivilMinute(2015)));
+
+  EXPECT_EQ("2015-01-02T03",
+            absl::FormatCivilTime(absl::CivilHour(2015, 1, 2, 3, 4, 5)));
+  EXPECT_EQ("2015-01-02T03",
+            absl::FormatCivilTime(absl::CivilHour(2015, 1, 2, 3, 4)));
+  EXPECT_EQ("2015-01-02T03",
+            absl::FormatCivilTime(absl::CivilHour(2015, 1, 2, 3)));
+  EXPECT_EQ("2015-01-02T00",
+            absl::FormatCivilTime(absl::CivilHour(2015, 1, 2)));
+  EXPECT_EQ("2015-01-01T00",
+            absl::FormatCivilTime(absl::CivilHour(2015, 1)));
+  EXPECT_EQ("2015-01-01T00",
+            absl::FormatCivilTime(absl::CivilHour(2015)));
+
+  EXPECT_EQ("2015-01-02",
+            absl::FormatCivilTime(absl::CivilDay(2015, 1, 2, 3, 4, 5)));
+  EXPECT_EQ("2015-01-02",
+            absl::FormatCivilTime(absl::CivilDay(2015, 1, 2, 3, 4)));
+  EXPECT_EQ("2015-01-02",
+            absl::FormatCivilTime(absl::CivilDay(2015, 1, 2, 3)));
+  EXPECT_EQ("2015-01-02",
+            absl::FormatCivilTime(absl::CivilDay(2015, 1, 2)));
+  EXPECT_EQ("2015-01-01",
+            absl::FormatCivilTime(absl::CivilDay(2015, 1)));
+  EXPECT_EQ("2015-01-01",
+            absl::FormatCivilTime(absl::CivilDay(2015)));
+
+  EXPECT_EQ("2015-01",
+            absl::FormatCivilTime(absl::CivilMonth(2015, 1, 2, 3, 4, 5)));
+  EXPECT_EQ("2015-01",
+            absl::FormatCivilTime(absl::CivilMonth(2015, 1, 2, 3, 4)));
+  EXPECT_EQ("2015-01",
+            absl::FormatCivilTime(absl::CivilMonth(2015, 1, 2, 3)));
+  EXPECT_EQ("2015-01",
+            absl::FormatCivilTime(absl::CivilMonth(2015, 1, 2)));
+  EXPECT_EQ("2015-01",
+            absl::FormatCivilTime(absl::CivilMonth(2015, 1)));
+  EXPECT_EQ("2015-01",
+            absl::FormatCivilTime(absl::CivilMonth(2015)));
+
+  EXPECT_EQ("2015",
+            absl::FormatCivilTime(absl::CivilYear(2015, 1, 2, 3, 4, 5)));
+  EXPECT_EQ("2015",
+            absl::FormatCivilTime(absl::CivilYear(2015, 1, 2, 3, 4)));
+  EXPECT_EQ("2015",
+            absl::FormatCivilTime(absl::CivilYear(2015, 1, 2, 3)));
+  EXPECT_EQ("2015",
+            absl::FormatCivilTime(absl::CivilYear(2015, 1, 2)));
+  EXPECT_EQ("2015",
+            absl::FormatCivilTime(absl::CivilYear(2015, 1)));
+  EXPECT_EQ("2015",
+            absl::FormatCivilTime(absl::CivilYear(2015)));
+}
+
+TEST(CivilTime, FieldsConstructionLimits) {
+  const int kIntMax = std::numeric_limits<int>::max();
+  EXPECT_EQ("2038-01-19T03:14:07",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, 1, 0, 0, kIntMax)));
+  EXPECT_EQ("6121-02-11T05:21:07",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, 1, 0, kIntMax, kIntMax)));
+  EXPECT_EQ("251104-11-20T12:21:07",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, 1, kIntMax, kIntMax, kIntMax)));
+  EXPECT_EQ("6130715-05-30T12:21:07",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, kIntMax, kIntMax, kIntMax, kIntMax)));
+  EXPECT_EQ("185087685-11-26T12:21:07",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, kIntMax, kIntMax, kIntMax, kIntMax, kIntMax)));
+
+  const int kIntMin = std::numeric_limits<int>::min();
+  EXPECT_EQ("1901-12-13T20:45:52",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, 1, 0, 0, kIntMin)));
+  EXPECT_EQ("-2182-11-20T18:37:52",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, 1, 0, kIntMin, kIntMin)));
+  EXPECT_EQ("-247165-02-11T10:37:52",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, 1, kIntMin, kIntMin, kIntMin)));
+  EXPECT_EQ("-6126776-08-01T10:37:52",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, 1, kIntMin, kIntMin, kIntMin, kIntMin)));
+  EXPECT_EQ("-185083747-10-31T10:37:52",
+            absl::FormatCivilTime(absl::CivilSecond(
+                1970, kIntMin, kIntMin, kIntMin, kIntMin, kIntMin)));
+}
+
+TEST(CivilTime, RangeLimits) {
+  const absl::civil_year_t kYearMax =
+      std::numeric_limits<absl::civil_year_t>::max();
+  EXPECT_EQ(absl::CivilYear(kYearMax),
+            absl::CivilYear::max());
+  EXPECT_EQ(absl::CivilMonth(kYearMax, 12),
+            absl::CivilMonth::max());
+  EXPECT_EQ(absl::CivilDay(kYearMax, 12, 31),
+            absl::CivilDay::max());
+  EXPECT_EQ(absl::CivilHour(kYearMax, 12, 31, 23),
+            absl::CivilHour::max());
+  EXPECT_EQ(absl::CivilMinute(kYearMax, 12, 31, 23, 59),
+            absl::CivilMinute::max());
+  EXPECT_EQ(absl::CivilSecond(kYearMax, 12, 31, 23, 59, 59),
+            absl::CivilSecond::max());
+
+  const absl::civil_year_t kYearMin =
+      std::numeric_limits<absl::civil_year_t>::min();
+  EXPECT_EQ(absl::CivilYear(kYearMin),
+            absl::CivilYear::min());
+  EXPECT_EQ(absl::CivilMonth(kYearMin, 1),
+            absl::CivilMonth::min());
+  EXPECT_EQ(absl::CivilDay(kYearMin, 1, 1),
+            absl::CivilDay::min());
+  EXPECT_EQ(absl::CivilHour(kYearMin, 1, 1, 0),
+            absl::CivilHour::min());
+  EXPECT_EQ(absl::CivilMinute(kYearMin, 1, 1, 0, 0),
+            absl::CivilMinute::min());
+  EXPECT_EQ(absl::CivilSecond(kYearMin, 1, 1, 0, 0, 0),
+            absl::CivilSecond::min());
+}
+
+TEST(CivilTime, ImplicitCrossAlignment) {
+  absl::CivilYear year(2015);
+  absl::CivilMonth month = year;
+  absl::CivilDay day = month;
+  absl::CivilHour hour = day;
+  absl::CivilMinute minute = hour;
+  absl::CivilSecond second = minute;
+
+  second = year;
+  EXPECT_EQ(second, year);
+  second = month;
+  EXPECT_EQ(second, month);
+  second = day;
+  EXPECT_EQ(second, day);
+  second = hour;
+  EXPECT_EQ(second, hour);
+  second = minute;
+  EXPECT_EQ(second, minute);
+
+  minute = year;
+  EXPECT_EQ(minute, year);
+  minute = month;
+  EXPECT_EQ(minute, month);
+  minute = day;
+  EXPECT_EQ(minute, day);
+  minute = hour;
+  EXPECT_EQ(minute, hour);
+
+  hour = year;
+  EXPECT_EQ(hour, year);
+  hour = month;
+  EXPECT_EQ(hour, month);
+  hour = day;
+  EXPECT_EQ(hour, day);
+
+  day = year;
+  EXPECT_EQ(day, year);
+  day = month;
+  EXPECT_EQ(day, month);
+
+  month = year;
+  EXPECT_EQ(month, year);
+
+  // Ensures unsafe conversions are not allowed.
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilSecond, absl::CivilMinute>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilSecond, absl::CivilHour>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilSecond, absl::CivilDay>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilSecond, absl::CivilMonth>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilSecond, absl::CivilYear>::value));
+
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilMinute, absl::CivilHour>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilMinute, absl::CivilDay>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilMinute, absl::CivilMonth>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilMinute, absl::CivilYear>::value));
+
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilHour, absl::CivilDay>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilHour, absl::CivilMonth>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilHour, absl::CivilYear>::value));
+
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilDay, absl::CivilMonth>::value));
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilDay, absl::CivilYear>::value));
+
+  EXPECT_FALSE(
+      (std::is_convertible<absl::CivilMonth, absl::CivilYear>::value));
+}
+
+TEST(CivilTime, ExplicitCrossAlignment) {
+  //
+  // Assign from smaller units -> larger units
+  //
+
+  absl::CivilSecond second(2015, 1, 2, 3, 4, 5);
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(second));
+
+  absl::CivilMinute minute(second);
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(minute));
+
+  absl::CivilHour hour(minute);
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(hour));
+
+  absl::CivilDay day(hour);
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(day));
+
+  absl::CivilMonth month(day);
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(month));
+
+  absl::CivilYear year(month);
+  EXPECT_EQ("2015", absl::FormatCivilTime(year));
+
+  //
+  // Now assign from larger units -> smaller units
+  //
+
+  month = absl::CivilMonth(year);
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(month));
+
+  day = absl::CivilDay(month);
+  EXPECT_EQ("2015-01-01", absl::FormatCivilTime(day));
+
+  hour = absl::CivilHour(day);
+  EXPECT_EQ("2015-01-01T00", absl::FormatCivilTime(hour));
+
+  minute = absl::CivilMinute(hour);
+  EXPECT_EQ("2015-01-01T00:00", absl::FormatCivilTime(minute));
+
+  second = absl::CivilSecond(minute);
+  EXPECT_EQ("2015-01-01T00:00:00", absl::FormatCivilTime(second));
+}
+
+// Metafunction to test whether difference is allowed between two types.
+template <typename T1, typename T2>
+struct HasDiff {
+  template <typename U1, typename U2>
+  static std::false_type test(...);
+  template <typename U1, typename U2>
+  static std::true_type test(decltype(std::declval<U1>() - std::declval<U2>()));
+  static constexpr bool value = decltype(test<T1, T2>(0))::value;
+};
+
+TEST(CivilTime, DisallowCrossAlignedDifference) {
+  // Difference is allowed between types with the same alignment.
+  static_assert(HasDiff<absl::CivilSecond, absl::CivilSecond>::value, "");
+  static_assert(HasDiff<absl::CivilMinute, absl::CivilMinute>::value, "");
+  static_assert(HasDiff<absl::CivilHour, absl::CivilHour>::value, "");
+  static_assert(HasDiff<absl::CivilDay, absl::CivilDay>::value, "");
+  static_assert(HasDiff<absl::CivilMonth, absl::CivilMonth>::value, "");
+  static_assert(HasDiff<absl::CivilYear, absl::CivilYear>::value, "");
+
+  // Difference is disallowed between types with different alignments.
+  static_assert(!HasDiff<absl::CivilSecond, absl::CivilMinute>::value, "");
+  static_assert(!HasDiff<absl::CivilSecond, absl::CivilHour>::value, "");
+  static_assert(!HasDiff<absl::CivilSecond, absl::CivilDay>::value, "");
+  static_assert(!HasDiff<absl::CivilSecond, absl::CivilMonth>::value, "");
+  static_assert(!HasDiff<absl::CivilSecond, absl::CivilYear>::value, "");
+
+  static_assert(!HasDiff<absl::CivilMinute, absl::CivilHour>::value, "");
+  static_assert(!HasDiff<absl::CivilMinute, absl::CivilDay>::value, "");
+  static_assert(!HasDiff<absl::CivilMinute, absl::CivilMonth>::value, "");
+  static_assert(!HasDiff<absl::CivilMinute, absl::CivilYear>::value, "");
+
+  static_assert(!HasDiff<absl::CivilHour, absl::CivilDay>::value, "");
+  static_assert(!HasDiff<absl::CivilHour, absl::CivilMonth>::value, "");
+  static_assert(!HasDiff<absl::CivilHour, absl::CivilYear>::value, "");
+
+  static_assert(!HasDiff<absl::CivilDay, absl::CivilMonth>::value, "");
+  static_assert(!HasDiff<absl::CivilDay, absl::CivilYear>::value, "");
+
+  static_assert(!HasDiff<absl::CivilMonth, absl::CivilYear>::value, "");
+}
+
+TEST(CivilTime, ValueSemantics) {
+  const absl::CivilHour a(2015, 1, 2, 3);
+  const absl::CivilHour b = a;
+  const absl::CivilHour c(b);
+  absl::CivilHour d;
+  d = c;
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(d));
+}
+
+TEST(CivilTime, Relational) {
+  // Tests that the alignment unit is ignored in comparison.
+  const absl::CivilYear year(2014);
+  const absl::CivilMonth month(year);
+  EXPECT_EQ(year, month);
+
+#define TEST_RELATIONAL(OLDER, YOUNGER) \
+  do {                                  \
+    EXPECT_FALSE(OLDER < OLDER);        \
+    EXPECT_FALSE(OLDER > OLDER);        \
+    EXPECT_TRUE(OLDER >= OLDER);        \
+    EXPECT_TRUE(OLDER <= OLDER);        \
+    EXPECT_FALSE(YOUNGER < YOUNGER);    \
+    EXPECT_FALSE(YOUNGER > YOUNGER);    \
+    EXPECT_TRUE(YOUNGER >= YOUNGER);    \
+    EXPECT_TRUE(YOUNGER <= YOUNGER);    \
+    EXPECT_EQ(OLDER, OLDER);            \
+    EXPECT_NE(OLDER, YOUNGER);          \
+    EXPECT_LT(OLDER, YOUNGER);          \
+    EXPECT_LE(OLDER, YOUNGER);          \
+    EXPECT_GT(YOUNGER, OLDER);          \
+    EXPECT_GE(YOUNGER, OLDER);          \
+  } while (0)
+
+  // Alignment is ignored in comparison (verified above), so CivilSecond is
+  // used to test comparison in all field positions.
+  TEST_RELATIONAL(absl::CivilSecond(2014, 1, 1, 0, 0, 0),
+                  absl::CivilSecond(2015, 1, 1, 0, 0, 0));
+  TEST_RELATIONAL(absl::CivilSecond(2014, 1, 1, 0, 0, 0),
+                  absl::CivilSecond(2014, 2, 1, 0, 0, 0));
+  TEST_RELATIONAL(absl::CivilSecond(2014, 1, 1, 0, 0, 0),
+                  absl::CivilSecond(2014, 1, 2, 0, 0, 0));
+  TEST_RELATIONAL(absl::CivilSecond(2014, 1, 1, 0, 0, 0),
+                  absl::CivilSecond(2014, 1, 1, 1, 0, 0));
+  TEST_RELATIONAL(absl::CivilSecond(2014, 1, 1, 1, 0, 0),
+                  absl::CivilSecond(2014, 1, 1, 1, 1, 0));
+  TEST_RELATIONAL(absl::CivilSecond(2014, 1, 1, 1, 1, 0),
+                  absl::CivilSecond(2014, 1, 1, 1, 1, 1));
+
+  // Tests the relational operators of two different civil-time types.
+  TEST_RELATIONAL(absl::CivilDay(2014, 1, 1),
+                  absl::CivilMinute(2014, 1, 1, 1, 1));
+  TEST_RELATIONAL(absl::CivilDay(2014, 1, 1),
+                  absl::CivilMonth(2014, 2));
+
+#undef TEST_RELATIONAL
+}
+
+TEST(CivilTime, Arithmetic) {
+  absl::CivilSecond second(2015, 1, 2, 3, 4, 5);
+  EXPECT_EQ("2015-01-02T03:04:06", absl::FormatCivilTime(second += 1));
+  EXPECT_EQ("2015-01-02T03:04:07", absl::FormatCivilTime(second + 1));
+  EXPECT_EQ("2015-01-02T03:04:08", absl::FormatCivilTime(2 + second));
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(second - 1));
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(second -= 1));
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(second++));
+  EXPECT_EQ("2015-01-02T03:04:07", absl::FormatCivilTime(++second));
+  EXPECT_EQ("2015-01-02T03:04:07", absl::FormatCivilTime(second--));
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(--second));
+
+  absl::CivilMinute minute(2015, 1, 2, 3, 4);
+  EXPECT_EQ("2015-01-02T03:05", absl::FormatCivilTime(minute += 1));
+  EXPECT_EQ("2015-01-02T03:06", absl::FormatCivilTime(minute + 1));
+  EXPECT_EQ("2015-01-02T03:07", absl::FormatCivilTime(2 + minute));
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(minute - 1));
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(minute -= 1));
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(minute++));
+  EXPECT_EQ("2015-01-02T03:06", absl::FormatCivilTime(++minute));
+  EXPECT_EQ("2015-01-02T03:06", absl::FormatCivilTime(minute--));
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(--minute));
+
+  absl::CivilHour hour(2015, 1, 2, 3);
+  EXPECT_EQ("2015-01-02T04", absl::FormatCivilTime(hour += 1));
+  EXPECT_EQ("2015-01-02T05", absl::FormatCivilTime(hour + 1));
+  EXPECT_EQ("2015-01-02T06", absl::FormatCivilTime(2 + hour));
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(hour - 1));
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(hour -= 1));
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(hour++));
+  EXPECT_EQ("2015-01-02T05", absl::FormatCivilTime(++hour));
+  EXPECT_EQ("2015-01-02T05", absl::FormatCivilTime(hour--));
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(--hour));
+
+  absl::CivilDay day(2015, 1, 2);
+  EXPECT_EQ("2015-01-03", absl::FormatCivilTime(day += 1));
+  EXPECT_EQ("2015-01-04", absl::FormatCivilTime(day + 1));
+  EXPECT_EQ("2015-01-05", absl::FormatCivilTime(2 + day));
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(day - 1));
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(day -= 1));
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(day++));
+  EXPECT_EQ("2015-01-04", absl::FormatCivilTime(++day));
+  EXPECT_EQ("2015-01-04", absl::FormatCivilTime(day--));
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(--day));
+
+  absl::CivilMonth month(2015, 1);
+  EXPECT_EQ("2015-02", absl::FormatCivilTime(month += 1));
+  EXPECT_EQ("2015-03", absl::FormatCivilTime(month + 1));
+  EXPECT_EQ("2015-04", absl::FormatCivilTime(2 + month));
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(month - 1));
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(month -= 1));
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(month++));
+  EXPECT_EQ("2015-03", absl::FormatCivilTime(++month));
+  EXPECT_EQ("2015-03", absl::FormatCivilTime(month--));
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(--month));
+
+  absl::CivilYear year(2015);
+  EXPECT_EQ("2016", absl::FormatCivilTime(year += 1));
+  EXPECT_EQ("2017", absl::FormatCivilTime(year + 1));
+  EXPECT_EQ("2018", absl::FormatCivilTime(2 + year));
+  EXPECT_EQ("2015", absl::FormatCivilTime(year - 1));
+  EXPECT_EQ("2015", absl::FormatCivilTime(year -= 1));
+  EXPECT_EQ("2015", absl::FormatCivilTime(year++));
+  EXPECT_EQ("2017", absl::FormatCivilTime(++year));
+  EXPECT_EQ("2017", absl::FormatCivilTime(year--));
+  EXPECT_EQ("2015", absl::FormatCivilTime(--year));
+}
+
+TEST(CivilTime, ArithmeticLimits) {
+  const int kIntMax = std::numeric_limits<int>::max();
+  const int kIntMin = std::numeric_limits<int>::min();
+
+  absl::CivilSecond second(1970, 1, 1, 0, 0, 0);
+  second += kIntMax;
+  EXPECT_EQ("2038-01-19T03:14:07", absl::FormatCivilTime(second));
+  second -= kIntMax;
+  EXPECT_EQ("1970-01-01T00:00:00", absl::FormatCivilTime(second));
+  second += kIntMin;
+  EXPECT_EQ("1901-12-13T20:45:52", absl::FormatCivilTime(second));
+  second -= kIntMin;
+  EXPECT_EQ("1970-01-01T00:00:00", absl::FormatCivilTime(second));
+
+  absl::CivilMinute minute(1970, 1, 1, 0, 0);
+  minute += kIntMax;
+  EXPECT_EQ("6053-01-23T02:07", absl::FormatCivilTime(minute));
+  minute -= kIntMax;
+  EXPECT_EQ("1970-01-01T00:00", absl::FormatCivilTime(minute));
+  minute += kIntMin;
+  EXPECT_EQ("-2114-12-08T21:52", absl::FormatCivilTime(minute));
+  minute -= kIntMin;
+  EXPECT_EQ("1970-01-01T00:00", absl::FormatCivilTime(minute));
+
+  absl::CivilHour hour(1970, 1, 1, 0);
+  hour += kIntMax;
+  EXPECT_EQ("246953-10-09T07", absl::FormatCivilTime(hour));
+  hour -= kIntMax;
+  EXPECT_EQ("1970-01-01T00", absl::FormatCivilTime(hour));
+  hour += kIntMin;
+  EXPECT_EQ("-243014-03-24T16", absl::FormatCivilTime(hour));
+  hour -= kIntMin;
+  EXPECT_EQ("1970-01-01T00", absl::FormatCivilTime(hour));
+
+  absl::CivilDay day(1970, 1, 1);
+  day += kIntMax;
+  EXPECT_EQ("5881580-07-11", absl::FormatCivilTime(day));
+  day -= kIntMax;
+  EXPECT_EQ("1970-01-01", absl::FormatCivilTime(day));
+  day += kIntMin;
+  EXPECT_EQ("-5877641-06-23", absl::FormatCivilTime(day));
+  day -= kIntMin;
+  EXPECT_EQ("1970-01-01", absl::FormatCivilTime(day));
+
+  absl::CivilMonth month(1970, 1);
+  month += kIntMax;
+  EXPECT_EQ("178958940-08", absl::FormatCivilTime(month));
+  month -= kIntMax;
+  EXPECT_EQ("1970-01", absl::FormatCivilTime(month));
+  month += kIntMin;
+  EXPECT_EQ("-178955001-05", absl::FormatCivilTime(month));
+  month -= kIntMin;
+  EXPECT_EQ("1970-01", absl::FormatCivilTime(month));
+
+  absl::CivilYear year(0);
+  year += kIntMax;
+  EXPECT_EQ("2147483647", absl::FormatCivilTime(year));
+  year -= kIntMax;
+  EXPECT_EQ("0", absl::FormatCivilTime(year));
+  year += kIntMin;
+  EXPECT_EQ("-2147483648", absl::FormatCivilTime(year));
+  year -= kIntMin;
+  EXPECT_EQ("0", absl::FormatCivilTime(year));
+}
+
+TEST(CivilTime, Difference) {
+  absl::CivilSecond second(2015, 1, 2, 3, 4, 5);
+  EXPECT_EQ(0, second - second);
+  EXPECT_EQ(10, (second + 10) - second);
+  EXPECT_EQ(-10, (second - 10) - second);
+
+  absl::CivilMinute minute(2015, 1, 2, 3, 4);
+  EXPECT_EQ(0, minute - minute);
+  EXPECT_EQ(10, (minute + 10) - minute);
+  EXPECT_EQ(-10, (minute - 10) - minute);
+
+  absl::CivilHour hour(2015, 1, 2, 3);
+  EXPECT_EQ(0, hour - hour);
+  EXPECT_EQ(10, (hour + 10) - hour);
+  EXPECT_EQ(-10, (hour - 10) - hour);
+
+  absl::CivilDay day(2015, 1, 2);
+  EXPECT_EQ(0, day - day);
+  EXPECT_EQ(10, (day + 10) - day);
+  EXPECT_EQ(-10, (day - 10) - day);
+
+  absl::CivilMonth month(2015, 1);
+  EXPECT_EQ(0, month - month);
+  EXPECT_EQ(10, (month + 10) - month);
+  EXPECT_EQ(-10, (month - 10) - month);
+
+  absl::CivilYear year(2015);
+  EXPECT_EQ(0, year - year);
+  EXPECT_EQ(10, (year + 10) - year);
+  EXPECT_EQ(-10, (year - 10) - year);
+}
+
+TEST(CivilTime, DifferenceLimits) {
+  const absl::civil_diff_t kDiffMax =
+      std::numeric_limits<absl::civil_diff_t>::max();
+  const absl::civil_diff_t kDiffMin =
+      std::numeric_limits<absl::civil_diff_t>::min();
+
+  // Check day arithmetic at the end of the year range.
+  const absl::CivilDay max_day(kDiffMax, 12, 31);
+  EXPECT_EQ(1, max_day - (max_day - 1));
+  EXPECT_EQ(-1, (max_day - 1) - max_day);
+
+  // Check day arithmetic at the start of the year range.
+  const absl::CivilDay min_day(kDiffMin, 1, 1);
+  EXPECT_EQ(1, (min_day + 1) - min_day);
+  EXPECT_EQ(-1, min_day - (min_day + 1));
+
+  // Check the limits of the return value.
+  const absl::CivilDay d1(1970, 1, 1);
+  const absl::CivilDay d2(25252734927768524, 7, 27);
+  EXPECT_EQ(kDiffMax, d2 - d1);
+  EXPECT_EQ(kDiffMin, d1 - (d2 + 1));
+}
+
+TEST(CivilTime, Properties) {
+  absl::CivilSecond ss(2015, 2, 3, 4, 5, 6);
+  EXPECT_EQ(2015, ss.year());
+  EXPECT_EQ(2, ss.month());
+  EXPECT_EQ(3, ss.day());
+  EXPECT_EQ(4, ss.hour());
+  EXPECT_EQ(5, ss.minute());
+  EXPECT_EQ(6, ss.second());
+  EXPECT_EQ(absl::Weekday::tuesday, absl::GetWeekday(ss));
+  EXPECT_EQ(34, absl::GetYearDay(ss));
+
+  absl::CivilMinute mm(2015, 2, 3, 4, 5, 6);
+  EXPECT_EQ(2015, mm.year());
+  EXPECT_EQ(2, mm.month());
+  EXPECT_EQ(3, mm.day());
+  EXPECT_EQ(4, mm.hour());
+  EXPECT_EQ(5, mm.minute());
+  EXPECT_EQ(0, mm.second());
+  EXPECT_EQ(absl::Weekday::tuesday, absl::GetWeekday(mm));
+  EXPECT_EQ(34, absl::GetYearDay(mm));
+
+  absl::CivilHour hh(2015, 2, 3, 4, 5, 6);
+  EXPECT_EQ(2015, hh.year());
+  EXPECT_EQ(2, hh.month());
+  EXPECT_EQ(3, hh.day());
+  EXPECT_EQ(4, hh.hour());
+  EXPECT_EQ(0, hh.minute());
+  EXPECT_EQ(0, hh.second());
+  EXPECT_EQ(absl::Weekday::tuesday, absl::GetWeekday(hh));
+  EXPECT_EQ(34, absl::GetYearDay(hh));
+
+  absl::CivilDay d(2015, 2, 3, 4, 5, 6);
+  EXPECT_EQ(2015, d.year());
+  EXPECT_EQ(2, d.month());
+  EXPECT_EQ(3, d.day());
+  EXPECT_EQ(0, d.hour());
+  EXPECT_EQ(0, d.minute());
+  EXPECT_EQ(0, d.second());
+  EXPECT_EQ(absl::Weekday::tuesday, absl::GetWeekday(d));
+  EXPECT_EQ(34, absl::GetYearDay(d));
+
+  absl::CivilMonth m(2015, 2, 3, 4, 5, 6);
+  EXPECT_EQ(2015, m.year());
+  EXPECT_EQ(2, m.month());
+  EXPECT_EQ(1, m.day());
+  EXPECT_EQ(0, m.hour());
+  EXPECT_EQ(0, m.minute());
+  EXPECT_EQ(0, m.second());
+  EXPECT_EQ(absl::Weekday::sunday, absl::GetWeekday(m));
+  EXPECT_EQ(32, absl::GetYearDay(m));
+
+  absl::CivilYear y(2015, 2, 3, 4, 5, 6);
+  EXPECT_EQ(2015, y.year());
+  EXPECT_EQ(1, y.month());
+  EXPECT_EQ(1, y.day());
+  EXPECT_EQ(0, y.hour());
+  EXPECT_EQ(0, y.minute());
+  EXPECT_EQ(0, y.second());
+  EXPECT_EQ(absl::Weekday::thursday, absl::GetWeekday(y));
+  EXPECT_EQ(1, absl::GetYearDay(y));
+}
+
+TEST(CivilTime, Format) {
+  absl::CivilSecond ss;
+  EXPECT_EQ("1970-01-01T00:00:00", absl::FormatCivilTime(ss));
+
+  absl::CivilMinute mm;
+  EXPECT_EQ("1970-01-01T00:00", absl::FormatCivilTime(mm));
+
+  absl::CivilHour hh;
+  EXPECT_EQ("1970-01-01T00", absl::FormatCivilTime(hh));
+
+  absl::CivilDay d;
+  EXPECT_EQ("1970-01-01", absl::FormatCivilTime(d));
+
+  absl::CivilMonth m;
+  EXPECT_EQ("1970-01", absl::FormatCivilTime(m));
+
+  absl::CivilYear y;
+  EXPECT_EQ("1970", absl::FormatCivilTime(y));
+}
+
+TEST(CivilTime, Parse) {
+  absl::CivilSecond ss;
+  absl::CivilMinute mm;
+  absl::CivilHour hh;
+  absl::CivilDay d;
+  absl::CivilMonth m;
+  absl::CivilYear y;
+
+  // CivilSecond OK; others fail
+  EXPECT_TRUE(absl::ParseCivilTime("2015-01-02T03:04:05", &ss));
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(ss));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04:05", &mm));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04:05", &hh));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04:05", &d));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04:05", &m));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04:05", &y));
+
+  // CivilMinute OK; others fail
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04", &ss));
+  EXPECT_TRUE(absl::ParseCivilTime("2015-01-02T03:04", &mm));
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(mm));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04", &hh));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04", &d));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04", &m));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03:04", &y));
+
+  // CivilHour OK; others fail
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03", &ss));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03", &mm));
+  EXPECT_TRUE(absl::ParseCivilTime("2015-01-02T03", &hh));
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(hh));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03", &d));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03", &m));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02T03", &y));
+
+  // CivilDay OK; others fail
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02", &ss));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02", &mm));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02", &hh));
+  EXPECT_TRUE(absl::ParseCivilTime("2015-01-02", &d));
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(d));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02", &m));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01-02", &y));
+
+  // CivilMonth OK; others fail
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01", &ss));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01", &mm));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01", &hh));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01", &d));
+  EXPECT_TRUE(absl::ParseCivilTime("2015-01", &m));
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(m));
+  EXPECT_FALSE(absl::ParseCivilTime("2015-01", &y));
+
+  // CivilYear OK; others fail
+  EXPECT_FALSE(absl::ParseCivilTime("2015", &ss));
+  EXPECT_FALSE(absl::ParseCivilTime("2015", &mm));
+  EXPECT_FALSE(absl::ParseCivilTime("2015", &hh));
+  EXPECT_FALSE(absl::ParseCivilTime("2015", &d));
+  EXPECT_FALSE(absl::ParseCivilTime("2015", &m));
+  EXPECT_TRUE(absl::ParseCivilTime("2015", &y));
+  EXPECT_EQ("2015", absl::FormatCivilTime(y));
+}
+
+TEST(CivilTime, FormatAndParseLenient) {
+  absl::CivilSecond ss;
+  EXPECT_EQ("1970-01-01T00:00:00", absl::FormatCivilTime(ss));
+
+  absl::CivilMinute mm;
+  EXPECT_EQ("1970-01-01T00:00", absl::FormatCivilTime(mm));
+
+  absl::CivilHour hh;
+  EXPECT_EQ("1970-01-01T00", absl::FormatCivilTime(hh));
+
+  absl::CivilDay d;
+  EXPECT_EQ("1970-01-01", absl::FormatCivilTime(d));
+
+  absl::CivilMonth m;
+  EXPECT_EQ("1970-01", absl::FormatCivilTime(m));
+
+  absl::CivilYear y;
+  EXPECT_EQ("1970", absl::FormatCivilTime(y));
+
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-01-02T03:04:05", &ss));
+  EXPECT_EQ("2015-01-02T03:04:05", absl::FormatCivilTime(ss));
+
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-01-02T03:04:05", &mm));
+  EXPECT_EQ("2015-01-02T03:04", absl::FormatCivilTime(mm));
+
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-01-02T03:04:05", &hh));
+  EXPECT_EQ("2015-01-02T03", absl::FormatCivilTime(hh));
+
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-01-02T03:04:05", &d));
+  EXPECT_EQ("2015-01-02", absl::FormatCivilTime(d));
+
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-01-02T03:04:05", &m));
+  EXPECT_EQ("2015-01", absl::FormatCivilTime(m));
+
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-01-02T03:04:05", &y));
+  EXPECT_EQ("2015", absl::FormatCivilTime(y));
+}
+
+TEST(CivilTime, ParseEdgeCases) {
+  absl::CivilSecond ss;
+  EXPECT_TRUE(
+      absl::ParseLenientCivilTime("9223372036854775807-12-31T23:59:59", &ss));
+  EXPECT_EQ("9223372036854775807-12-31T23:59:59", absl::FormatCivilTime(ss));
+  EXPECT_TRUE(
+      absl::ParseLenientCivilTime("-9223372036854775808-01-01T00:00:00", &ss));
+  EXPECT_EQ("-9223372036854775808-01-01T00:00:00", absl::FormatCivilTime(ss));
+
+  absl::CivilMinute mm;
+  EXPECT_TRUE(
+      absl::ParseLenientCivilTime("9223372036854775807-12-31T23:59", &mm));
+  EXPECT_EQ("9223372036854775807-12-31T23:59", absl::FormatCivilTime(mm));
+  EXPECT_TRUE(
+      absl::ParseLenientCivilTime("-9223372036854775808-01-01T00:00", &mm));
+  EXPECT_EQ("-9223372036854775808-01-01T00:00", absl::FormatCivilTime(mm));
+
+  absl::CivilHour hh;
+  EXPECT_TRUE(
+      absl::ParseLenientCivilTime("9223372036854775807-12-31T23", &hh));
+  EXPECT_EQ("9223372036854775807-12-31T23", absl::FormatCivilTime(hh));
+  EXPECT_TRUE(
+      absl::ParseLenientCivilTime("-9223372036854775808-01-01T00", &hh));
+  EXPECT_EQ("-9223372036854775808-01-01T00", absl::FormatCivilTime(hh));
+
+  absl::CivilDay d;
+  EXPECT_TRUE(absl::ParseLenientCivilTime("9223372036854775807-12-31", &d));
+  EXPECT_EQ("9223372036854775807-12-31", absl::FormatCivilTime(d));
+  EXPECT_TRUE(absl::ParseLenientCivilTime("-9223372036854775808-01-01", &d));
+  EXPECT_EQ("-9223372036854775808-01-01", absl::FormatCivilTime(d));
+
+  absl::CivilMonth m;
+  EXPECT_TRUE(absl::ParseLenientCivilTime("9223372036854775807-12", &m));
+  EXPECT_EQ("9223372036854775807-12", absl::FormatCivilTime(m));
+  EXPECT_TRUE(absl::ParseLenientCivilTime("-9223372036854775808-01", &m));
+  EXPECT_EQ("-9223372036854775808-01", absl::FormatCivilTime(m));
+
+  absl::CivilYear y;
+  EXPECT_TRUE(absl::ParseLenientCivilTime("9223372036854775807", &y));
+  EXPECT_EQ("9223372036854775807", absl::FormatCivilTime(y));
+  EXPECT_TRUE(absl::ParseLenientCivilTime("-9223372036854775808", &y));
+  EXPECT_EQ("-9223372036854775808", absl::FormatCivilTime(y));
+
+  // Tests some valid, but interesting, cases
+  EXPECT_TRUE(absl::ParseLenientCivilTime("0", &ss)) << ss;
+  EXPECT_EQ(absl::CivilYear(0), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime("0-1", &ss)) << ss;
+  EXPECT_EQ(absl::CivilMonth(0, 1), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime(" 2015 ", &ss)) << ss;
+  EXPECT_EQ(absl::CivilYear(2015), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime(" 2015-6 ", &ss)) << ss;
+  EXPECT_EQ(absl::CivilMonth(2015, 6), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-6-7", &ss)) << ss;
+  EXPECT_EQ(absl::CivilDay(2015, 6, 7), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime(" 2015-6-7 ", &ss)) << ss;
+  EXPECT_EQ(absl::CivilDay(2015, 6, 7), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime("2015-06-07T10:11:12 ", &ss)) << ss;
+  EXPECT_EQ(absl::CivilSecond(2015, 6, 7, 10, 11, 12), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime(" 2015-06-07T10:11:12 ", &ss)) << ss;
+  EXPECT_EQ(absl::CivilSecond(2015, 6, 7, 10, 11, 12), ss);
+  EXPECT_TRUE(absl::ParseLenientCivilTime("-01-01", &ss)) << ss;
+  EXPECT_EQ(absl::CivilMonth(-1, 1), ss);
+
+  // Tests some invalid cases
+  EXPECT_FALSE(absl::ParseLenientCivilTime("01-01-2015", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015-", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("0xff-01", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015-02-30T04:05:06", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015-02-03T04:05:96", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("X2015-02-03T04:05:06", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015-02-03T04:05:003", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015 -02-03T04:05:06", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015-02-03-04:05:06", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("2015:02:03T04-05-06", &ss)) << ss;
+  EXPECT_FALSE(absl::ParseLenientCivilTime("9223372036854775808", &y)) << y;
+}
+
+TEST(CivilTime, AbslStringify) {
+  EXPECT_EQ("2015-01-02T03:04:05",
+            absl::StrFormat("%v", absl::CivilSecond(2015, 1, 2, 3, 4, 5)));
+
+  EXPECT_EQ("2015-01-02T03:04",
+            absl::StrFormat("%v", absl::CivilMinute(2015, 1, 2, 3, 4)));
+
+  EXPECT_EQ("2015-01-02T03",
+            absl::StrFormat("%v", absl::CivilHour(2015, 1, 2, 3)));
+
+  EXPECT_EQ("2015-01-02", absl::StrFormat("%v", absl::CivilDay(2015, 1, 2)));
+
+  EXPECT_EQ("2015-01", absl::StrFormat("%v", absl::CivilMonth(2015, 1)));
+
+  EXPECT_EQ("2015", absl::StrFormat("%v", absl::CivilYear(2015)));
+}
+
+TEST(CivilTime, OutputStream) {
+  absl::CivilSecond cs(2016, 2, 3, 4, 5, 6);
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::CivilYear(cs);
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..2016.................X..", ss.str());
+  }
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::CivilMonth(cs);
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..2016-02..............X..", ss.str());
+  }
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::CivilDay(cs);
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..2016-02-03...........X..", ss.str());
+  }
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::CivilHour(cs);
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..2016-02-03T04........X..", ss.str());
+  }
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::CivilMinute(cs);
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..2016-02-03T04:05.....X..", ss.str());
+  }
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::CivilSecond(cs);
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..2016-02-03T04:05:06..X..", ss.str());
+  }
+  {
+    std::stringstream ss;
+    ss << std::left << std::setfill('.');
+    ss << std::setw(3) << 'X';
+    ss << std::setw(21) << absl::Weekday::wednesday;
+    ss << std::setw(3) << 'X';
+    EXPECT_EQ("X..Wednesday............X..", ss.str());
+  }
+}
+
+TEST(CivilTime, Weekday) {
+  absl::CivilDay d(1970, 1, 1);
+  EXPECT_EQ(absl::Weekday::thursday, absl::GetWeekday(d)) << d;
+
+  // We used to get this wrong for years < -30.
+  d = absl::CivilDay(-31, 12, 24);
+  EXPECT_EQ(absl::Weekday::wednesday, absl::GetWeekday(d)) << d;
+}
+
+TEST(CivilTime, NextPrevWeekday) {
+  // Jan 1, 1970 was a Thursday.
+  const absl::CivilDay thursday(1970, 1, 1);
+
+  // Thursday -> Thursday
+  absl::CivilDay d = absl::NextWeekday(thursday, absl::Weekday::thursday);
+  EXPECT_EQ(7, d - thursday) << d;
+  EXPECT_EQ(d - 14, absl::PrevWeekday(thursday, absl::Weekday::thursday));
+
+  // Thursday -> Friday
+  d = absl::NextWeekday(thursday, absl::Weekday::friday);
+  EXPECT_EQ(1, d - thursday) << d;
+  EXPECT_EQ(d - 7, absl::PrevWeekday(thursday, absl::Weekday::friday));
+
+  // Thursday -> Saturday
+  d = absl::NextWeekday(thursday, absl::Weekday::saturday);
+  EXPECT_EQ(2, d - thursday) << d;
+  EXPECT_EQ(d - 7, absl::PrevWeekday(thursday, absl::Weekday::saturday));
+
+  // Thursday -> Sunday
+  d = absl::NextWeekday(thursday, absl::Weekday::sunday);
+  EXPECT_EQ(3, d - thursday) << d;
+  EXPECT_EQ(d - 7, absl::PrevWeekday(thursday, absl::Weekday::sunday));
+
+  // Thursday -> Monday
+  d = absl::NextWeekday(thursday, absl::Weekday::monday);
+  EXPECT_EQ(4, d - thursday) << d;
+  EXPECT_EQ(d - 7, absl::PrevWeekday(thursday, absl::Weekday::monday));
+
+  // Thursday -> Tuesday
+  d = absl::NextWeekday(thursday, absl::Weekday::tuesday);
+  EXPECT_EQ(5, d - thursday) << d;
+  EXPECT_EQ(d - 7, absl::PrevWeekday(thursday, absl::Weekday::tuesday));
+
+  // Thursday -> Wednesday
+  d = absl::NextWeekday(thursday, absl::Weekday::wednesday);
+  EXPECT_EQ(6, d - thursday) << d;
+  EXPECT_EQ(d - 7, absl::PrevWeekday(thursday, absl::Weekday::wednesday));
+}
+
+// NOTE: Run this with --copt=-ftrapv to detect overflow problems.
+TEST(CivilTime, DifferenceWithHugeYear) {
+  absl::CivilDay d1(9223372036854775807, 1, 1);
+  absl::CivilDay d2(9223372036854775807, 12, 31);
+  EXPECT_EQ(364, d2 - d1);
+
+  d1 = absl::CivilDay(-9223372036854775807 - 1, 1, 1);
+  d2 = absl::CivilDay(-9223372036854775807 - 1, 12, 31);
+  EXPECT_EQ(365, d2 - d1);
+
+  // Check the limits of the return value at the end of the year range.
+  d1 = absl::CivilDay(9223372036854775807, 1, 1);
+  d2 = absl::CivilDay(9198119301927009252, 6, 6);
+  EXPECT_EQ(9223372036854775807, d1 - d2);
+  d2 = d2 - 1;
+  EXPECT_EQ(-9223372036854775807 - 1, d2 - d1);
+
+  // Check the limits of the return value at the start of the year range.
+  d1 = absl::CivilDay(-9223372036854775807 - 1, 1, 1);
+  d2 = absl::CivilDay(-9198119301927009254, 7, 28);
+  EXPECT_EQ(9223372036854775807, d2 - d1);
+  d2 = d2 + 1;
+  EXPECT_EQ(-9223372036854775807 - 1, d1 - d2);
+
+  // Check the limits of the return value from either side of year 0.
+  d1 = absl::CivilDay(-12626367463883278, 9, 3);
+  d2 = absl::CivilDay(12626367463883277, 3, 28);
+  EXPECT_EQ(9223372036854775807, d2 - d1);
+  d2 = d2 + 1;
+  EXPECT_EQ(-9223372036854775807 - 1, d1 - d2);
+}
+
+// NOTE: Run this with --copt=-ftrapv to detect overflow problems.
+TEST(CivilTime, DifferenceNoIntermediateOverflow) {
+  // The difference up to the minute field would be below the minimum
+  // int64_t, but the 52 extra seconds brings us back to the minimum.
+  absl::CivilSecond s1(-292277022657, 1, 27, 8, 29 - 1, 52);
+  absl::CivilSecond s2(1970, 1, 1, 0, 0 - 1, 0);
+  EXPECT_EQ(-9223372036854775807 - 1, s1 - s2);
+
+  // The difference up to the minute field would be above the maximum
+  // int64_t, but the -53 extra seconds brings us back to the maximum.
+  s1 = absl::CivilSecond(292277026596, 12, 4, 15, 30, 7 - 7);
+  s2 = absl::CivilSecond(1970, 1, 1, 0, 0, 0 - 7);
+  EXPECT_EQ(9223372036854775807, s1 - s2);
+}
+
+TEST(CivilTime, NormalizeSimpleOverflow) {
+  absl::CivilSecond cs;
+  cs = absl::CivilSecond(2013, 11, 15, 16, 32, 59 + 1);
+  EXPECT_EQ("2013-11-15T16:33:00", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16, 59 + 1, 14);
+  EXPECT_EQ("2013-11-15T17:00:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 23 + 1, 32, 14);
+  EXPECT_EQ("2013-11-16T00:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 30 + 1, 16, 32, 14);
+  EXPECT_EQ("2013-12-01T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 12 + 1, 15, 16, 32, 14);
+  EXPECT_EQ("2014-01-15T16:32:14", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeSimpleUnderflow) {
+  absl::CivilSecond cs;
+  cs = absl::CivilSecond(2013, 11, 15, 16, 32, 0 - 1);
+  EXPECT_EQ("2013-11-15T16:31:59", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16, 0 - 1, 14);
+  EXPECT_EQ("2013-11-15T15:59:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 0 - 1, 32, 14);
+  EXPECT_EQ("2013-11-14T23:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 1 - 1, 16, 32, 14);
+  EXPECT_EQ("2013-10-31T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 1 - 1, 15, 16, 32, 14);
+  EXPECT_EQ("2012-12-15T16:32:14", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeMultipleOverflow) {
+  absl::CivilSecond cs(2013, 12, 31, 23, 59, 59 + 1);
+  EXPECT_EQ("2014-01-01T00:00:00", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeMultipleUnderflow) {
+  absl::CivilSecond cs(2014, 1, 1, 0, 0, 0 - 1);
+  EXPECT_EQ("2013-12-31T23:59:59", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeOverflowLimits) {
+  absl::CivilSecond cs;
+
+  const int kintmax = std::numeric_limits<int>::max();
+  cs = absl::CivilSecond(0, kintmax, kintmax, kintmax, kintmax, kintmax);
+  EXPECT_EQ("185085715-11-27T12:21:07", absl::FormatCivilTime(cs));
+
+  const int kintmin = std::numeric_limits<int>::min();
+  cs = absl::CivilSecond(0, kintmin, kintmin, kintmin, kintmin, kintmin);
+  EXPECT_EQ("-185085717-10-31T10:37:52", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeComplexOverflow) {
+  absl::CivilSecond cs;
+  cs = absl::CivilSecond(2013, 11, 15, 16, 32, 14 + 123456789);
+  EXPECT_EQ("2017-10-14T14:05:23", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16, 32 + 1234567, 14);
+  EXPECT_EQ("2016-03-22T00:39:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16 + 123456, 32, 14);
+  EXPECT_EQ("2027-12-16T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15 + 1234, 16, 32, 14);
+  EXPECT_EQ("2017-04-02T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11 + 123, 15, 16, 32, 14);
+  EXPECT_EQ("2024-02-15T16:32:14", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeComplexUnderflow) {
+  absl::CivilSecond cs;
+  cs = absl::CivilSecond(1999, 3, 0, 0, 0, 0);  // year 400
+  EXPECT_EQ("1999-02-28T00:00:00", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16, 32, 14 - 123456789);
+  EXPECT_EQ("2009-12-17T18:59:05", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16, 32 - 1234567, 14);
+  EXPECT_EQ("2011-07-12T08:25:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15, 16 - 123456, 32, 14);
+  EXPECT_EQ("1999-10-16T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11, 15 - 1234, 16, 32, 14);
+  EXPECT_EQ("2010-06-30T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11 - 123, 15, 16, 32, 14);
+  EXPECT_EQ("2003-08-15T16:32:14", absl::FormatCivilTime(cs));
+}
+
+TEST(CivilTime, NormalizeMishmash) {
+  absl::CivilSecond cs;
+  cs = absl::CivilSecond(2013, 11 - 123, 15 + 1234, 16 - 123456, 32 + 1234567,
+                         14 - 123456789);
+  EXPECT_EQ("1991-05-09T03:06:05", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11 + 123, 15 - 1234, 16 + 123456, 32 - 1234567,
+                         14 + 123456789);
+  EXPECT_EQ("2036-05-24T05:58:23", absl::FormatCivilTime(cs));
+
+  cs = absl::CivilSecond(2013, 11, -146097 + 1, 16, 32, 14);
+  EXPECT_EQ("1613-11-01T16:32:14", absl::FormatCivilTime(cs));
+  cs = absl::CivilSecond(2013, 11 + 400 * 12, -146097 + 1, 16, 32, 14);
+  EXPECT_EQ("2013-11-01T16:32:14", absl::FormatCivilTime(cs));
+}
+
+// Convert all the days from 1970-1-1 to 1970-1-146097 (aka 2369-12-31)
+// and check that they normalize to the expected time.  146097 days span
+// the 400-year Gregorian cycle used during normalization.
+TEST(CivilTime, NormalizeAllTheDays) {
+  absl::CivilDay expected(1970, 1, 1);
+  for (int day = 1; day <= 146097; ++day) {
+    absl::CivilSecond cs(1970, 1, day, 0, 0, 0);
+    EXPECT_EQ(expected, cs);
+    ++expected;
+  }
+}
+
+TEST(CivilTime, NormalizeWithHugeYear) {
+  absl::CivilMonth c(9223372036854775807, 1);
+  EXPECT_EQ("9223372036854775807-01", absl::FormatCivilTime(c));
+  c = c - 1;  // Causes normalization
+  EXPECT_EQ("9223372036854775806-12", absl::FormatCivilTime(c));
+
+  c = absl::CivilMonth(-9223372036854775807 - 1, 1);
+  EXPECT_EQ("-9223372036854775808-01", absl::FormatCivilTime(c));
+  c = c + 12;  // Causes normalization
+  EXPECT_EQ("-9223372036854775807-01", absl::FormatCivilTime(c));
+}
+
+TEST(CivilTime, LeapYears) {
+  const absl::CivilSecond s1(2013, 2, 28 + 1, 0, 0, 0);
+  EXPECT_EQ("2013-03-01T00:00:00", absl::FormatCivilTime(s1));
+
+  const absl::CivilSecond s2(2012, 2, 28 + 1, 0, 0, 0);
+  EXPECT_EQ("2012-02-29T00:00:00", absl::FormatCivilTime(s2));
+
+  const absl::CivilSecond s3(1900, 2, 28 + 1, 0, 0, 0);
+  EXPECT_EQ("1900-03-01T00:00:00", absl::FormatCivilTime(s3));
+
+  const struct {
+    int year;
+    int days;
+    struct {
+      int month;
+      int day;
+    } leap_day;  // The date of the day after Feb 28.
+  } kLeapYearTable[]{
+      {1900, 365, {3, 1}},
+      {1999, 365, {3, 1}},
+      {2000, 366, {2, 29}},  // leap year
+      {2001, 365, {3, 1}},
+      {2002, 365, {3, 1}},
+      {2003, 365, {3, 1}},
+      {2004, 366, {2, 29}},  // leap year
+      {2005, 365, {3, 1}},
+      {2006, 365, {3, 1}},
+      {2007, 365, {3, 1}},
+      {2008, 366, {2, 29}},  // leap year
+      {2009, 365, {3, 1}},
+      {2100, 365, {3, 1}},
+  };
+
+  for (int i = 0; i < ABSL_ARRAYSIZE(kLeapYearTable); ++i) {
+    const int y = kLeapYearTable[i].year;
+    const int m = kLeapYearTable[i].leap_day.month;
+    const int d = kLeapYearTable[i].leap_day.day;
+    const int n = kLeapYearTable[i].days;
+
+    // Tests incrementing through the leap day.
+    const absl::CivilDay feb28(y, 2, 28);
+    const absl::CivilDay next_day = feb28 + 1;
+    EXPECT_EQ(m, next_day.month());
+    EXPECT_EQ(d, next_day.day());
+
+    // Tests difference in days of leap years.
+    const absl::CivilYear year(feb28);
+    const absl::CivilYear next_year = year + 1;
+    EXPECT_EQ(n, absl::CivilDay(next_year) - absl::CivilDay(year));
+  }
+}
+
+TEST(CivilTime, FirstThursdayInMonth) {
+  const absl::CivilDay nov1(2014, 11, 1);
+  const absl::CivilDay thursday =
+      absl::NextWeekday(nov1 - 1, absl::Weekday::thursday);
+  EXPECT_EQ("2014-11-06", absl::FormatCivilTime(thursday));
+
+  // Bonus: Date of Thanksgiving in the United States
+  // Rule: Fourth Thursday of November
+  const absl::CivilDay thanksgiving = thursday +  7 * 3;
+  EXPECT_EQ("2014-11-27", absl::FormatCivilTime(thanksgiving));
+}
+
+TEST(CivilTime, DocumentationExample) {
+  absl::CivilSecond second(2015, 6, 28, 1, 2, 3);  // 2015-06-28 01:02:03
+  absl::CivilMinute minute(second);                // 2015-06-28 01:02:00
+  absl::CivilDay day(minute);                      // 2015-06-28 00:00:00
+
+  second -= 1;                    // 2015-06-28 01:02:02
+  --second;                       // 2015-06-28 01:02:01
+  EXPECT_EQ(minute, second - 1);  // Comparison between types
+  EXPECT_LT(minute, second);
+
+  // int diff = second - minute;  // ERROR: Mixed types, won't compile
+
+  absl::CivilDay june_1(2015, 6, 1);  // Pass fields to c'tor.
+  int diff = day - june_1;            // Num days between 'day' and June 1
+  EXPECT_EQ(27, diff);
+
+  // Fields smaller than alignment are floored to their minimum value.
+  absl::CivilDay day_floor(2015, 1, 2, 9, 9, 9);
+  EXPECT_EQ(0, day_floor.hour());  // 09:09:09 is floored
+  EXPECT_EQ(absl::CivilDay(2015, 1, 2), day_floor);
+
+  // Unspecified fields default to their minimum value
+  absl::CivilDay day_default(2015);  // Defaults to Jan 1
+  EXPECT_EQ(absl::CivilDay(2015, 1, 1), day_default);
+
+  // Iterates all the days of June.
+  absl::CivilMonth june(day);  // CivilDay -> CivilMonth
+  absl::CivilMonth july = june + 1;
+  for (absl::CivilDay day = june_1; day < july; ++day) {
+    // ...
+  }
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/time/clock.cc b/weight/_dep/abseil-cpp/absl/time/clock.cc
new file mode 100644
index 0000000000000000000000000000000000000000..aa74367b8a77eca041f705b46cf5cbfb39dbab8d
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/clock.cc
@@ -0,0 +1,590 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/time/clock.h"
+
+#include "absl/base/attributes.h"
+#include "absl/base/optimization.h"
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+#include <algorithm>
+#include <atomic>
+#include <cerrno>
+#include <cstdint>
+#include <ctime>
+#include <limits>
+
+#include "absl/base/internal/spinlock.h"
+#include "absl/base/internal/unscaledcycleclock.h"
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+#include "absl/base/thread_annotations.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+Time Now() {
+  // TODO(bww): Get a timespec instead so we don't have to divide.
+  int64_t n = absl::GetCurrentTimeNanos();
+  if (n >= 0) {
+    return time_internal::FromUnixDuration(
+        time_internal::MakeDuration(n / 1000000000, n % 1000000000 * 4));
+  }
+  return time_internal::FromUnixDuration(absl::Nanoseconds(n));
+}
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// Decide if we should use the fast GetCurrentTimeNanos() algorithm based on the
+// cyclecounter, otherwise just get the time directly from the OS on every call.
+// By default, the fast algorithm based on the cyclecount is disabled because in
+// certain situations, for example, if the OS enters a "sleep" mode, it may
+// produce incorrect values immediately upon waking.
+// This can be chosen at compile-time via
+// -DABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS=[0|1]
+#ifndef ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
+#define ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS 0
+#endif
+
+#if defined(__APPLE__) || defined(_WIN32)
+#include "absl/time/internal/get_current_time_chrono.inc"
+#else
+#include "absl/time/internal/get_current_time_posix.inc"
+#endif
+
+// Allows override by test.
+#ifndef GET_CURRENT_TIME_NANOS_FROM_SYSTEM
+#define GET_CURRENT_TIME_NANOS_FROM_SYSTEM() \
+  ::absl::time_internal::GetCurrentTimeNanosFromSystem()
+#endif
+
+#if !ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+int64_t GetCurrentTimeNanos() { return GET_CURRENT_TIME_NANOS_FROM_SYSTEM(); }
+ABSL_NAMESPACE_END
+}  // namespace absl
+#else  // Use the cyclecounter-based implementation below.
+
+// Allows override by test.
+#ifndef GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW
+#define GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW() \
+  ::absl::time_internal::UnscaledCycleClockWrapperForGetCurrentTime::Now()
+#endif
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+// This is a friend wrapper around UnscaledCycleClock::Now()
+// (needed to access UnscaledCycleClock).
+class UnscaledCycleClockWrapperForGetCurrentTime {
+ public:
+  static int64_t Now() { return base_internal::UnscaledCycleClock::Now(); }
+};
+}  // namespace time_internal
+
+// uint64_t is used in this module to provide an extra bit in multiplications
+
+// ---------------------------------------------------------------------
+// An implementation of reader-write locks that use no atomic ops in the read
+// case.  This is a generalization of Lamport's method for reading a multiword
+// clock.  Increment a word on each write acquisition, using the low-order bit
+// as a spinlock; the word is the high word of the "clock".  Readers read the
+// high word, then all other data, then the high word again, and repeat the
+// read if the reads of the high words yields different answers, or an odd
+// value (either case suggests possible interference from a writer).
+// Here we use a spinlock to ensure only one writer at a time, rather than
+// spinning on the bottom bit of the word to benefit from SpinLock
+// spin-delay tuning.
+
+// Acquire seqlock (*seq) and return the value to be written to unlock.
+static inline uint64_t SeqAcquire(std::atomic<uint64_t> *seq) {
+  uint64_t x = seq->fetch_add(1, std::memory_order_relaxed);
+
+  // We put a release fence between update to *seq and writes to shared data.
+  // Thus all stores to shared data are effectively release operations and
+  // update to *seq above cannot be re-ordered past any of them.  Note that
+  // this barrier is not for the fetch_add above.  A release barrier for the
+  // fetch_add would be before it, not after.
+  std::atomic_thread_fence(std::memory_order_release);
+
+  return x + 2;   // original word plus 2
+}
+
+// Release seqlock (*seq) by writing x to it---a value previously returned by
+// SeqAcquire.
+static inline void SeqRelease(std::atomic<uint64_t> *seq, uint64_t x) {
+  // The unlock store to *seq must have release ordering so that all
+  // updates to shared data must finish before this store.
+  seq->store(x, std::memory_order_release);  // release lock for readers
+}
+
+// ---------------------------------------------------------------------
+
+// "nsscaled" is unit of time equal to a (2**kScale)th of a nanosecond.
+enum { kScale = 30 };
+
+// The minimum interval between samples of the time base.
+// We pick enough time to amortize the cost of the sample,
+// to get a reasonably accurate cycle counter rate reading,
+// and not so much that calculations will overflow 64-bits.
+static const uint64_t kMinNSBetweenSamples = 2000 << 20;
+
+// We require that kMinNSBetweenSamples shifted by kScale
+// have at least a bit left over for 64-bit calculations.
+static_assert(((kMinNSBetweenSamples << (kScale + 1)) >> (kScale + 1)) ==
+               kMinNSBetweenSamples,
+               "cannot represent kMaxBetweenSamplesNSScaled");
+
+// data from a sample of the kernel's time value
+struct TimeSampleAtomic {
+  std::atomic<uint64_t> raw_ns{0};              // raw kernel time
+  std::atomic<uint64_t> base_ns{0};             // our estimate of time
+  std::atomic<uint64_t> base_cycles{0};         // cycle counter reading
+  std::atomic<uint64_t> nsscaled_per_cycle{0};  // cycle period
+  // cycles before we'll sample again (a scaled reciprocal of the period,
+  // to avoid a division on the fast path).
+  std::atomic<uint64_t> min_cycles_per_sample{0};
+};
+// Same again, but with non-atomic types
+struct TimeSample {
+  uint64_t raw_ns = 0;                 // raw kernel time
+  uint64_t base_ns = 0;                // our estimate of time
+  uint64_t base_cycles = 0;            // cycle counter reading
+  uint64_t nsscaled_per_cycle = 0;     // cycle period
+  uint64_t min_cycles_per_sample = 0;  // approx cycles before next sample
+};
+
+struct ABSL_CACHELINE_ALIGNED TimeState {
+  std::atomic<uint64_t> seq{0};
+  TimeSampleAtomic last_sample;  // the last sample; under seq
+
+  // The following counters are used only by the test code.
+  int64_t stats_initializations{0};
+  int64_t stats_reinitializations{0};
+  int64_t stats_calibrations{0};
+  int64_t stats_slow_paths{0};
+  int64_t stats_fast_slow_paths{0};
+
+  uint64_t last_now_cycles ABSL_GUARDED_BY(lock){0};
+
+  // Used by GetCurrentTimeNanosFromKernel().
+  // We try to read clock values at about the same time as the kernel clock.
+  // This value gets adjusted up or down as estimate of how long that should
+  // take, so we can reject attempts that take unusually long.
+  std::atomic<uint64_t> approx_syscall_time_in_cycles{10 * 1000};
+  // Number of times in a row we've seen a kernel time call take substantially
+  // less than approx_syscall_time_in_cycles.
+  std::atomic<uint32_t> kernel_time_seen_smaller{0};
+
+  // A reader-writer lock protecting the static locations below.
+  // See SeqAcquire() and SeqRelease() above.
+  absl::base_internal::SpinLock lock{absl::kConstInit,
+                                     base_internal::SCHEDULE_KERNEL_ONLY};
+};
+ABSL_CONST_INIT static TimeState time_state;
+
+// Return the time in ns as told by the kernel interface.  Place in *cycleclock
+// the value of the cycleclock at about the time of the syscall.
+// This call represents the time base that this module synchronizes to.
+// Ensures that *cycleclock does not step back by up to (1 << 16) from
+// last_cycleclock, to discard small backward counter steps.  (Larger steps are
+// assumed to be complete resyncs, which shouldn't happen.  If they do, a full
+// reinitialization of the outer algorithm should occur.)
+static int64_t GetCurrentTimeNanosFromKernel(uint64_t last_cycleclock,
+                                             uint64_t *cycleclock)
+    ABSL_EXCLUSIVE_LOCKS_REQUIRED(time_state.lock) {
+  uint64_t local_approx_syscall_time_in_cycles =  // local copy
+      time_state.approx_syscall_time_in_cycles.load(std::memory_order_relaxed);
+
+  int64_t current_time_nanos_from_system;
+  uint64_t before_cycles;
+  uint64_t after_cycles;
+  uint64_t elapsed_cycles;
+  int loops = 0;
+  do {
+    before_cycles =
+        static_cast<uint64_t>(GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW());
+    current_time_nanos_from_system = GET_CURRENT_TIME_NANOS_FROM_SYSTEM();
+    after_cycles =
+        static_cast<uint64_t>(GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW());
+    // elapsed_cycles is unsigned, so is large on overflow
+    elapsed_cycles = after_cycles - before_cycles;
+    if (elapsed_cycles >= local_approx_syscall_time_in_cycles &&
+        ++loops == 20) {  // clock changed frequencies?  Back off.
+      loops = 0;
+      if (local_approx_syscall_time_in_cycles < 1000 * 1000) {
+        local_approx_syscall_time_in_cycles =
+            (local_approx_syscall_time_in_cycles + 1) << 1;
+      }
+      time_state.approx_syscall_time_in_cycles.store(
+          local_approx_syscall_time_in_cycles, std::memory_order_relaxed);
+    }
+  } while (elapsed_cycles >= local_approx_syscall_time_in_cycles ||
+           last_cycleclock - after_cycles < (static_cast<uint64_t>(1) << 16));
+
+  // Adjust approx_syscall_time_in_cycles to be within a factor of 2
+  // of the typical time to execute one iteration of the loop above.
+  if ((local_approx_syscall_time_in_cycles >> 1) < elapsed_cycles) {
+    // measured time is no smaller than half current approximation
+    time_state.kernel_time_seen_smaller.store(0, std::memory_order_relaxed);
+  } else if (time_state.kernel_time_seen_smaller.fetch_add(
+                 1, std::memory_order_relaxed) >= 3) {
+    // smaller delays several times in a row; reduce approximation by 12.5%
+    const uint64_t new_approximation =
+        local_approx_syscall_time_in_cycles -
+        (local_approx_syscall_time_in_cycles >> 3);
+    time_state.approx_syscall_time_in_cycles.store(new_approximation,
+                                                   std::memory_order_relaxed);
+    time_state.kernel_time_seen_smaller.store(0, std::memory_order_relaxed);
+  }
+
+  *cycleclock = after_cycles;
+  return current_time_nanos_from_system;
+}
+
+static int64_t GetCurrentTimeNanosSlowPath() ABSL_ATTRIBUTE_COLD;
+
+// Read the contents of *atomic into *sample.
+// Each field is read atomically, but to maintain atomicity between fields,
+// the access must be done under a lock.
+static void ReadTimeSampleAtomic(const struct TimeSampleAtomic *atomic,
+                                 struct TimeSample *sample) {
+  sample->base_ns = atomic->base_ns.load(std::memory_order_relaxed);
+  sample->base_cycles = atomic->base_cycles.load(std::memory_order_relaxed);
+  sample->nsscaled_per_cycle =
+      atomic->nsscaled_per_cycle.load(std::memory_order_relaxed);
+  sample->min_cycles_per_sample =
+      atomic->min_cycles_per_sample.load(std::memory_order_relaxed);
+  sample->raw_ns = atomic->raw_ns.load(std::memory_order_relaxed);
+}
+
+// Public routine.
+// Algorithm:  We wish to compute real time from a cycle counter.  In normal
+// operation, we construct a piecewise linear approximation to the kernel time
+// source, using the cycle counter value.  The start of each line segment is at
+// the same point as the end of the last, but may have a different slope (that
+// is, a different idea of the cycle counter frequency).  Every couple of
+// seconds, the kernel time source is sampled and compared with the current
+// approximation.  A new slope is chosen that, if followed for another couple
+// of seconds, will correct the error at the current position.  The information
+// for a sample is in the "last_sample" struct.  The linear approximation is
+//   estimated_time = last_sample.base_ns +
+//     last_sample.ns_per_cycle * (counter_reading - last_sample.base_cycles)
+// (ns_per_cycle is actually stored in different units and scaled, to avoid
+// overflow).  The base_ns of the next linear approximation is the
+// estimated_time using the last approximation; the base_cycles is the cycle
+// counter value at that time; the ns_per_cycle is the number of ns per cycle
+// measured since the last sample, but adjusted so that most of the difference
+// between the estimated_time and the kernel time will be corrected by the
+// estimated time to the next sample.  In normal operation, this algorithm
+// relies on:
+// - the cycle counter and kernel time rates not changing a lot in a few
+//   seconds.
+// - the client calling into the code often compared to a couple of seconds, so
+//   the time to the next correction can be estimated.
+// Any time ns_per_cycle is not known, a major error is detected, or the
+// assumption about frequent calls is violated, the implementation returns the
+// kernel time.  It records sufficient data that a linear approximation can
+// resume a little later.
+
+int64_t GetCurrentTimeNanos() {
+  // read the data from the "last_sample" struct (but don't need raw_ns yet)
+  // The reads of "seq" and test of the values emulate a reader lock.
+  uint64_t base_ns;
+  uint64_t base_cycles;
+  uint64_t nsscaled_per_cycle;
+  uint64_t min_cycles_per_sample;
+  uint64_t seq_read0;
+  uint64_t seq_read1;
+
+  // If we have enough information to interpolate, the value returned will be
+  // derived from this cycleclock-derived time estimate.  On some platforms
+  // (POWER) the function to retrieve this value has enough complexity to
+  // contribute to register pressure - reading it early before initializing
+  // the other pieces of the calculation minimizes spill/restore instructions,
+  // minimizing icache cost.
+  uint64_t now_cycles =
+      static_cast<uint64_t>(GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW());
+
+  // Acquire pairs with the barrier in SeqRelease - if this load sees that
+  // store, the shared-data reads necessarily see that SeqRelease's updates
+  // to the same shared data.
+  seq_read0 = time_state.seq.load(std::memory_order_acquire);
+
+  base_ns = time_state.last_sample.base_ns.load(std::memory_order_relaxed);
+  base_cycles =
+      time_state.last_sample.base_cycles.load(std::memory_order_relaxed);
+  nsscaled_per_cycle =
+      time_state.last_sample.nsscaled_per_cycle.load(std::memory_order_relaxed);
+  min_cycles_per_sample = time_state.last_sample.min_cycles_per_sample.load(
+      std::memory_order_relaxed);
+
+  // This acquire fence pairs with the release fence in SeqAcquire.  Since it
+  // is sequenced between reads of shared data and seq_read1, the reads of
+  // shared data are effectively acquiring.
+  std::atomic_thread_fence(std::memory_order_acquire);
+
+  // The shared-data reads are effectively acquire ordered, and the
+  // shared-data writes are effectively release ordered. Therefore if our
+  // shared-data reads see any of a particular update's shared-data writes,
+  // seq_read1 is guaranteed to see that update's SeqAcquire.
+  seq_read1 = time_state.seq.load(std::memory_order_relaxed);
+
+  // Fast path.  Return if min_cycles_per_sample has not yet elapsed since the
+  // last sample, and we read a consistent sample.  The fast path activates
+  // only when min_cycles_per_sample is non-zero, which happens when we get an
+  // estimate for the cycle time.  The predicate will fail if now_cycles <
+  // base_cycles, or if some other thread is in the slow path.
+  //
+  // Since we now read now_cycles before base_ns, it is possible for now_cycles
+  // to be less than base_cycles (if we were interrupted between those loads and
+  // last_sample was updated). This is harmless, because delta_cycles will wrap
+  // and report a time much much bigger than min_cycles_per_sample. In that case
+  // we will take the slow path.
+  uint64_t delta_cycles;
+  if (seq_read0 == seq_read1 && (seq_read0 & 1) == 0 &&
+      (delta_cycles = now_cycles - base_cycles) < min_cycles_per_sample) {
+    return static_cast<int64_t>(
+        base_ns + ((delta_cycles * nsscaled_per_cycle) >> kScale));
+  }
+  return GetCurrentTimeNanosSlowPath();
+}
+
+// Return (a << kScale)/b.
+// Zero is returned if b==0.   Scaling is performed internally to
+// preserve precision without overflow.
+static uint64_t SafeDivideAndScale(uint64_t a, uint64_t b) {
+  // Find maximum safe_shift so that
+  //  0 <= safe_shift <= kScale  and  (a << safe_shift) does not overflow.
+  int safe_shift = kScale;
+  while (((a << safe_shift) >> safe_shift) != a) {
+    safe_shift--;
+  }
+  uint64_t scaled_b = b >> (kScale - safe_shift);
+  uint64_t quotient = 0;
+  if (scaled_b != 0) {
+    quotient = (a << safe_shift) / scaled_b;
+  }
+  return quotient;
+}
+
+static uint64_t UpdateLastSample(
+    uint64_t now_cycles, uint64_t now_ns, uint64_t delta_cycles,
+    const struct TimeSample *sample) ABSL_ATTRIBUTE_COLD;
+
+// The slow path of GetCurrentTimeNanos().  This is taken while gathering
+// initial samples, when enough time has elapsed since the last sample, and if
+// any other thread is writing to last_sample.
+//
+// Manually mark this 'noinline' to minimize stack frame size of the fast
+// path.  Without this, sometimes a compiler may inline this big block of code
+// into the fast path.  That causes lots of register spills and reloads that
+// are unnecessary unless the slow path is taken.
+//
+// TODO(absl-team): Remove this attribute when our compiler is smart enough
+// to do the right thing.
+ABSL_ATTRIBUTE_NOINLINE
+static int64_t GetCurrentTimeNanosSlowPath()
+    ABSL_LOCKS_EXCLUDED(time_state.lock) {
+  // Serialize access to slow-path.  Fast-path readers are not blocked yet, and
+  // code below must not modify last_sample until the seqlock is acquired.
+  time_state.lock.Lock();
+
+  // Sample the kernel time base.  This is the definition of
+  // "now" if we take the slow path.
+  uint64_t now_cycles;
+  uint64_t now_ns = static_cast<uint64_t>(
+      GetCurrentTimeNanosFromKernel(time_state.last_now_cycles, &now_cycles));
+  time_state.last_now_cycles = now_cycles;
+
+  uint64_t estimated_base_ns;
+
+  // ----------
+  // Read the "last_sample" values again; this time holding the write lock.
+  struct TimeSample sample;
+  ReadTimeSampleAtomic(&time_state.last_sample, &sample);
+
+  // ----------
+  // Try running the fast path again; another thread may have updated the
+  // sample between our run of the fast path and the sample we just read.
+  uint64_t delta_cycles = now_cycles - sample.base_cycles;
+  if (delta_cycles < sample.min_cycles_per_sample) {
+    // Another thread updated the sample.  This path does not take the seqlock
+    // so that blocked readers can make progress without blocking new readers.
+    estimated_base_ns = sample.base_ns +
+        ((delta_cycles * sample.nsscaled_per_cycle) >> kScale);
+    time_state.stats_fast_slow_paths++;
+  } else {
+    estimated_base_ns =
+        UpdateLastSample(now_cycles, now_ns, delta_cycles, &sample);
+  }
+
+  time_state.lock.Unlock();
+
+  return static_cast<int64_t>(estimated_base_ns);
+}
+
+// Main part of the algorithm.  Locks out readers, updates the approximation
+// using the new sample from the kernel, and stores the result in last_sample
+// for readers.  Returns the new estimated time.
+static uint64_t UpdateLastSample(uint64_t now_cycles, uint64_t now_ns,
+                                 uint64_t delta_cycles,
+                                 const struct TimeSample *sample)
+    ABSL_EXCLUSIVE_LOCKS_REQUIRED(time_state.lock) {
+  uint64_t estimated_base_ns = now_ns;
+  uint64_t lock_value =
+      SeqAcquire(&time_state.seq);  // acquire seqlock to block readers
+
+  // The 5s in the next if-statement limits the time for which we will trust
+  // the cycle counter and our last sample to give a reasonable result.
+  // Errors in the rate of the source clock can be multiplied by the ratio
+  // between this limit and kMinNSBetweenSamples.
+  if (sample->raw_ns == 0 ||  // no recent sample, or clock went backwards
+      sample->raw_ns + static_cast<uint64_t>(5) * 1000 * 1000 * 1000 < now_ns ||
+      now_ns < sample->raw_ns || now_cycles < sample->base_cycles) {
+    // record this sample, and forget any previously known slope.
+    time_state.last_sample.raw_ns.store(now_ns, std::memory_order_relaxed);
+    time_state.last_sample.base_ns.store(estimated_base_ns,
+                                         std::memory_order_relaxed);
+    time_state.last_sample.base_cycles.store(now_cycles,
+                                             std::memory_order_relaxed);
+    time_state.last_sample.nsscaled_per_cycle.store(0,
+                                                    std::memory_order_relaxed);
+    time_state.last_sample.min_cycles_per_sample.store(
+        0, std::memory_order_relaxed);
+    time_state.stats_initializations++;
+  } else if (sample->raw_ns + 500 * 1000 * 1000 < now_ns &&
+             sample->base_cycles + 50 < now_cycles) {
+    // Enough time has passed to compute the cycle time.
+    if (sample->nsscaled_per_cycle != 0) {  // Have a cycle time estimate.
+      // Compute time from counter reading, but avoiding overflow
+      // delta_cycles may be larger than on the fast path.
+      uint64_t estimated_scaled_ns;
+      int s = -1;
+      do {
+        s++;
+        estimated_scaled_ns = (delta_cycles >> s) * sample->nsscaled_per_cycle;
+      } while (estimated_scaled_ns / sample->nsscaled_per_cycle !=
+               (delta_cycles >> s));
+      estimated_base_ns = sample->base_ns +
+                          (estimated_scaled_ns >> (kScale - s));
+    }
+
+    // Compute the assumed cycle time kMinNSBetweenSamples ns into the future
+    // assuming the cycle counter rate stays the same as the last interval.
+    uint64_t ns = now_ns - sample->raw_ns;
+    uint64_t measured_nsscaled_per_cycle = SafeDivideAndScale(ns, delta_cycles);
+
+    uint64_t assumed_next_sample_delta_cycles =
+        SafeDivideAndScale(kMinNSBetweenSamples, measured_nsscaled_per_cycle);
+
+    // Estimate low by this much.
+    int64_t diff_ns = static_cast<int64_t>(now_ns - estimated_base_ns);
+
+    // We want to set nsscaled_per_cycle so that our estimate of the ns time
+    // at the assumed cycle time is the assumed ns time.
+    // That is, we want to set nsscaled_per_cycle so:
+    //  kMinNSBetweenSamples + diff_ns  ==
+    //  (assumed_next_sample_delta_cycles * nsscaled_per_cycle) >> kScale
+    // But we wish to damp oscillations, so instead correct only most
+    // of our current error, by solving:
+    //  kMinNSBetweenSamples + diff_ns - (diff_ns / 16) ==
+    //  (assumed_next_sample_delta_cycles * nsscaled_per_cycle) >> kScale
+    ns = static_cast<uint64_t>(static_cast<int64_t>(kMinNSBetweenSamples) +
+                               diff_ns - (diff_ns / 16));
+    uint64_t new_nsscaled_per_cycle =
+        SafeDivideAndScale(ns, assumed_next_sample_delta_cycles);
+    if (new_nsscaled_per_cycle != 0 &&
+        diff_ns < 100 * 1000 * 1000 && -diff_ns < 100 * 1000 * 1000) {
+      // record the cycle time measurement
+      time_state.last_sample.nsscaled_per_cycle.store(
+          new_nsscaled_per_cycle, std::memory_order_relaxed);
+      uint64_t new_min_cycles_per_sample =
+          SafeDivideAndScale(kMinNSBetweenSamples, new_nsscaled_per_cycle);
+      time_state.last_sample.min_cycles_per_sample.store(
+          new_min_cycles_per_sample, std::memory_order_relaxed);
+      time_state.stats_calibrations++;
+    } else {  // something went wrong; forget the slope
+      time_state.last_sample.nsscaled_per_cycle.store(
+          0, std::memory_order_relaxed);
+      time_state.last_sample.min_cycles_per_sample.store(
+          0, std::memory_order_relaxed);
+      estimated_base_ns = now_ns;
+      time_state.stats_reinitializations++;
+    }
+    time_state.last_sample.raw_ns.store(now_ns, std::memory_order_relaxed);
+    time_state.last_sample.base_ns.store(estimated_base_ns,
+                                         std::memory_order_relaxed);
+    time_state.last_sample.base_cycles.store(now_cycles,
+                                             std::memory_order_relaxed);
+  } else {
+    // have a sample, but no slope; waiting for enough time for a calibration
+    time_state.stats_slow_paths++;
+  }
+
+  SeqRelease(&time_state.seq, lock_value);  // release the readers
+
+  return estimated_base_ns;
+}
+ABSL_NAMESPACE_END
+}  // namespace absl
+#endif  // ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace {
+
+// Returns the maximum duration that SleepOnce() can sleep for.
+constexpr absl::Duration MaxSleep() {
+#ifdef _WIN32
+  // Windows Sleep() takes unsigned long argument in milliseconds.
+  return absl::Milliseconds(
+      std::numeric_limits<unsigned long>::max());  // NOLINT(runtime/int)
+#else
+  return absl::Seconds(std::numeric_limits<time_t>::max());
+#endif
+}
+
+// Sleeps for the given duration.
+// REQUIRES: to_sleep <= MaxSleep().
+void SleepOnce(absl::Duration to_sleep) {
+#ifdef _WIN32
+  Sleep(static_cast<DWORD>(to_sleep / absl::Milliseconds(1)));
+#else
+  struct timespec sleep_time = absl::ToTimespec(to_sleep);
+  while (nanosleep(&sleep_time, &sleep_time) != 0 && errno == EINTR) {
+    // Ignore signals and wait for the full interval to elapse.
+  }
+#endif
+}
+
+}  // namespace
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+extern "C" {
+
+ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(
+    absl::Duration duration) {
+  while (duration > absl::ZeroDuration()) {
+    absl::Duration to_sleep = std::min(duration, absl::MaxSleep());
+    absl::SleepOnce(to_sleep);
+    duration -= to_sleep;
+  }
+}
+
+}  // extern "C"
diff --git a/weight/_dep/abseil-cpp/absl/time/clock.h b/weight/_dep/abseil-cpp/absl/time/clock.h
new file mode 100644
index 0000000000000000000000000000000000000000..41d2cf27700824260e190ce303538cfbc48f2231
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/clock.h
@@ -0,0 +1,78 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: clock.h
+// -----------------------------------------------------------------------------
+//
+// This header file contains utility functions for working with the system-wide
+// realtime clock. For descriptions of the main time abstractions used within
+// this header file, consult the time.h header file.
+#ifndef ABSL_TIME_CLOCK_H_
+#define ABSL_TIME_CLOCK_H_
+
+#include <cstdint>
+
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Now()
+//
+// Returns the current time, expressed as an `absl::Time` absolute time value.
+absl::Time Now();
+
+// GetCurrentTimeNanos()
+//
+// Returns the current time, expressed as a count of nanoseconds since the Unix
+// Epoch (https://en.wikipedia.org/wiki/Unix_time). Prefer `absl::Now()` instead
+// for all but the most performance-sensitive cases (i.e. when you are calling
+// this function hundreds of thousands of times per second).
+int64_t GetCurrentTimeNanos();
+
+// SleepFor()
+//
+// Sleeps for the specified duration, expressed as an `absl::Duration`.
+//
+// Notes:
+// * Signal interruptions will not reduce the sleep duration.
+// * Returns immediately when passed a nonpositive duration.
+void SleepFor(absl::Duration duration);
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+// -----------------------------------------------------------------------------
+// Implementation Details
+// -----------------------------------------------------------------------------
+
+// In some build configurations we pass --detect-odr-violations to the
+// gold linker.  This causes it to flag weak symbol overrides as ODR
+// violations.  Because ODR only applies to C++ and not C,
+// --detect-odr-violations ignores symbols not mangled with C++ names.
+// By changing our extension points to be extern "C", we dodge this
+// check.
+extern "C" {
+ABSL_DLL void ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(
+    absl::Duration duration);
+}  // extern "C"
+
+inline void absl::SleepFor(absl::Duration duration) {
+  ABSL_INTERNAL_C_SYMBOL(AbslInternalSleepFor)(duration);
+}
+
+#endif  // ABSL_TIME_CLOCK_H_
diff --git a/weight/_dep/abseil-cpp/absl/time/duration_test.cc b/weight/_dep/abseil-cpp/absl/time/duration_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..dcf7aad6f7cd275e06556fc8bcacd20856bcd9a5
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/duration_test.cc
@@ -0,0 +1,1837 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#if defined(_MSC_VER)
+#include <winsock2.h>  // for timeval
+#endif
+
+#include <array>
+#include <cfloat>
+#include <chrono>  // NOLINT(build/c++11)
+#include <cmath>
+#include <cstdint>
+#include <ctime>
+#include <iomanip>
+#include <limits>
+#include <random>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/str_format.h"
+#include "absl/time/time.h"
+
+namespace {
+
+constexpr int64_t kint64max = std::numeric_limits<int64_t>::max();
+constexpr int64_t kint64min = std::numeric_limits<int64_t>::min();
+
+// Approximates the given number of years. This is only used to make some test
+// code more readable.
+absl::Duration ApproxYears(int64_t n) { return absl::Hours(n) * 365 * 24; }
+
+// A gMock matcher to match timespec values. Use this matcher like:
+// timespec ts1, ts2;
+// EXPECT_THAT(ts1, TimespecMatcher(ts2));
+MATCHER_P(TimespecMatcher, ts, "") {
+  if (ts.tv_sec == arg.tv_sec && ts.tv_nsec == arg.tv_nsec)
+    return true;
+  *result_listener << "expected: {" << ts.tv_sec << ", " << ts.tv_nsec << "} ";
+  *result_listener << "actual: {" << arg.tv_sec << ", " << arg.tv_nsec << "}";
+  return false;
+}
+
+// A gMock matcher to match timeval values. Use this matcher like:
+// timeval tv1, tv2;
+// EXPECT_THAT(tv1, TimevalMatcher(tv2));
+MATCHER_P(TimevalMatcher, tv, "") {
+  if (tv.tv_sec == arg.tv_sec && tv.tv_usec == arg.tv_usec)
+    return true;
+  *result_listener << "expected: {" << tv.tv_sec << ", " << tv.tv_usec << "} ";
+  *result_listener << "actual: {" << arg.tv_sec << ", " << arg.tv_usec << "}";
+  return false;
+}
+
+TEST(Duration, ConstExpr) {
+  constexpr absl::Duration d0 = absl::ZeroDuration();
+  static_assert(d0 == absl::ZeroDuration(), "ZeroDuration()");
+  constexpr absl::Duration d1 = absl::Seconds(1);
+  static_assert(d1 == absl::Seconds(1), "Seconds(1)");
+  static_assert(d1 != absl::ZeroDuration(), "Seconds(1)");
+  constexpr absl::Duration d2 = absl::InfiniteDuration();
+  static_assert(d2 == absl::InfiniteDuration(), "InfiniteDuration()");
+  static_assert(d2 != absl::ZeroDuration(), "InfiniteDuration()");
+}
+
+TEST(Duration, ValueSemantics) {
+  // If this compiles, the test passes.
+  constexpr absl::Duration a;      // Default construction
+  constexpr absl::Duration b = a;  // Copy construction
+  constexpr absl::Duration c(b);   // Copy construction (again)
+
+  absl::Duration d;
+  d = c;  // Assignment
+}
+
+TEST(Duration, Factories) {
+  constexpr absl::Duration zero = absl::ZeroDuration();
+  constexpr absl::Duration nano = absl::Nanoseconds(1);
+  constexpr absl::Duration micro = absl::Microseconds(1);
+  constexpr absl::Duration milli = absl::Milliseconds(1);
+  constexpr absl::Duration sec = absl::Seconds(1);
+  constexpr absl::Duration min = absl::Minutes(1);
+  constexpr absl::Duration hour = absl::Hours(1);
+
+  EXPECT_EQ(zero, absl::Duration());
+  EXPECT_EQ(zero, absl::Seconds(0));
+  EXPECT_EQ(nano, absl::Nanoseconds(1));
+  EXPECT_EQ(micro, absl::Nanoseconds(1000));
+  EXPECT_EQ(milli, absl::Microseconds(1000));
+  EXPECT_EQ(sec, absl::Milliseconds(1000));
+  EXPECT_EQ(min, absl::Seconds(60));
+  EXPECT_EQ(hour, absl::Minutes(60));
+
+  // Tests factory limits
+  const absl::Duration inf = absl::InfiniteDuration();
+
+  EXPECT_GT(inf, absl::Seconds(kint64max));
+  EXPECT_LT(-inf, absl::Seconds(kint64min));
+  EXPECT_LT(-inf, absl::Seconds(-kint64max));
+
+  EXPECT_EQ(inf, absl::Minutes(kint64max));
+  EXPECT_EQ(-inf, absl::Minutes(kint64min));
+  EXPECT_EQ(-inf, absl::Minutes(-kint64max));
+  EXPECT_GT(inf, absl::Minutes(kint64max / 60));
+  EXPECT_LT(-inf, absl::Minutes(kint64min / 60));
+  EXPECT_LT(-inf, absl::Minutes(-kint64max / 60));
+
+  EXPECT_EQ(inf, absl::Hours(kint64max));
+  EXPECT_EQ(-inf, absl::Hours(kint64min));
+  EXPECT_EQ(-inf, absl::Hours(-kint64max));
+  EXPECT_GT(inf, absl::Hours(kint64max / 3600));
+  EXPECT_LT(-inf, absl::Hours(kint64min / 3600));
+  EXPECT_LT(-inf, absl::Hours(-kint64max / 3600));
+}
+
+TEST(Duration, ToConversion) {
+#define TEST_DURATION_CONVERSION(UNIT)                                  \
+  do {                                                                  \
+    const absl::Duration d = absl::UNIT(1.5);                           \
+    constexpr absl::Duration z = absl::ZeroDuration();                  \
+    constexpr absl::Duration inf = absl::InfiniteDuration();            \
+    constexpr double dbl_inf = std::numeric_limits<double>::infinity(); \
+    EXPECT_EQ(kint64min, absl::ToInt64##UNIT(-inf));                    \
+    EXPECT_EQ(-1, absl::ToInt64##UNIT(-d));                             \
+    EXPECT_EQ(0, absl::ToInt64##UNIT(z));                               \
+    EXPECT_EQ(1, absl::ToInt64##UNIT(d));                               \
+    EXPECT_EQ(kint64max, absl::ToInt64##UNIT(inf));                     \
+    EXPECT_EQ(-dbl_inf, absl::ToDouble##UNIT(-inf));                    \
+    EXPECT_EQ(-1.5, absl::ToDouble##UNIT(-d));                          \
+    EXPECT_EQ(0, absl::ToDouble##UNIT(z));                              \
+    EXPECT_EQ(1.5, absl::ToDouble##UNIT(d));                            \
+    EXPECT_EQ(dbl_inf, absl::ToDouble##UNIT(inf));                      \
+  } while (0)
+
+  TEST_DURATION_CONVERSION(Nanoseconds);
+  TEST_DURATION_CONVERSION(Microseconds);
+  TEST_DURATION_CONVERSION(Milliseconds);
+  TEST_DURATION_CONVERSION(Seconds);
+  TEST_DURATION_CONVERSION(Minutes);
+  TEST_DURATION_CONVERSION(Hours);
+
+#undef TEST_DURATION_CONVERSION
+}
+
+template <int64_t N>
+void TestToConversion() {
+  constexpr absl::Duration nano = absl::Nanoseconds(N);
+  EXPECT_EQ(N, absl::ToInt64Nanoseconds(nano));
+  EXPECT_EQ(0, absl::ToInt64Microseconds(nano));
+  EXPECT_EQ(0, absl::ToInt64Milliseconds(nano));
+  EXPECT_EQ(0, absl::ToInt64Seconds(nano));
+  EXPECT_EQ(0, absl::ToInt64Minutes(nano));
+  EXPECT_EQ(0, absl::ToInt64Hours(nano));
+  const absl::Duration micro = absl::Microseconds(N);
+  EXPECT_EQ(N * 1000, absl::ToInt64Nanoseconds(micro));
+  EXPECT_EQ(N, absl::ToInt64Microseconds(micro));
+  EXPECT_EQ(0, absl::ToInt64Milliseconds(micro));
+  EXPECT_EQ(0, absl::ToInt64Seconds(micro));
+  EXPECT_EQ(0, absl::ToInt64Minutes(micro));
+  EXPECT_EQ(0, absl::ToInt64Hours(micro));
+  const absl::Duration milli = absl::Milliseconds(N);
+  EXPECT_EQ(N * 1000 * 1000, absl::ToInt64Nanoseconds(milli));
+  EXPECT_EQ(N * 1000, absl::ToInt64Microseconds(milli));
+  EXPECT_EQ(N, absl::ToInt64Milliseconds(milli));
+  EXPECT_EQ(0, absl::ToInt64Seconds(milli));
+  EXPECT_EQ(0, absl::ToInt64Minutes(milli));
+  EXPECT_EQ(0, absl::ToInt64Hours(milli));
+  const absl::Duration sec = absl::Seconds(N);
+  EXPECT_EQ(N * 1000 * 1000 * 1000, absl::ToInt64Nanoseconds(sec));
+  EXPECT_EQ(N * 1000 * 1000, absl::ToInt64Microseconds(sec));
+  EXPECT_EQ(N * 1000, absl::ToInt64Milliseconds(sec));
+  EXPECT_EQ(N, absl::ToInt64Seconds(sec));
+  EXPECT_EQ(0, absl::ToInt64Minutes(sec));
+  EXPECT_EQ(0, absl::ToInt64Hours(sec));
+  const absl::Duration min = absl::Minutes(N);
+  EXPECT_EQ(N * 60 * 1000 * 1000 * 1000, absl::ToInt64Nanoseconds(min));
+  EXPECT_EQ(N * 60 * 1000 * 1000, absl::ToInt64Microseconds(min));
+  EXPECT_EQ(N * 60 * 1000, absl::ToInt64Milliseconds(min));
+  EXPECT_EQ(N * 60, absl::ToInt64Seconds(min));
+  EXPECT_EQ(N, absl::ToInt64Minutes(min));
+  EXPECT_EQ(0, absl::ToInt64Hours(min));
+  const absl::Duration hour = absl::Hours(N);
+  EXPECT_EQ(N * 60 * 60 * 1000 * 1000 * 1000, absl::ToInt64Nanoseconds(hour));
+  EXPECT_EQ(N * 60 * 60 * 1000 * 1000, absl::ToInt64Microseconds(hour));
+  EXPECT_EQ(N * 60 * 60 * 1000, absl::ToInt64Milliseconds(hour));
+  EXPECT_EQ(N * 60 * 60, absl::ToInt64Seconds(hour));
+  EXPECT_EQ(N * 60, absl::ToInt64Minutes(hour));
+  EXPECT_EQ(N, absl::ToInt64Hours(hour));
+}
+
+TEST(Duration, ToConversionDeprecated) {
+  TestToConversion<43>();
+  TestToConversion<1>();
+  TestToConversion<0>();
+  TestToConversion<-1>();
+  TestToConversion<-43>();
+}
+
+template <int64_t N>
+void TestFromChronoBasicEquality() {
+  using std::chrono::nanoseconds;
+  using std::chrono::microseconds;
+  using std::chrono::milliseconds;
+  using std::chrono::seconds;
+  using std::chrono::minutes;
+  using std::chrono::hours;
+
+  static_assert(absl::Nanoseconds(N) == absl::FromChrono(nanoseconds(N)), "");
+  static_assert(absl::Microseconds(N) == absl::FromChrono(microseconds(N)), "");
+  static_assert(absl::Milliseconds(N) == absl::FromChrono(milliseconds(N)), "");
+  static_assert(absl::Seconds(N) == absl::FromChrono(seconds(N)), "");
+  static_assert(absl::Minutes(N) == absl::FromChrono(minutes(N)), "");
+  static_assert(absl::Hours(N) == absl::FromChrono(hours(N)), "");
+}
+
+TEST(Duration, FromChrono) {
+  TestFromChronoBasicEquality<-123>();
+  TestFromChronoBasicEquality<-1>();
+  TestFromChronoBasicEquality<0>();
+  TestFromChronoBasicEquality<1>();
+  TestFromChronoBasicEquality<123>();
+
+  // Minutes (might, depending on the platform) saturate at +inf.
+  const auto chrono_minutes_max = std::chrono::minutes::max();
+  const auto minutes_max = absl::FromChrono(chrono_minutes_max);
+  const int64_t minutes_max_count = chrono_minutes_max.count();
+  if (minutes_max_count > kint64max / 60) {
+    EXPECT_EQ(absl::InfiniteDuration(), minutes_max);
+  } else {
+    EXPECT_EQ(absl::Minutes(minutes_max_count), minutes_max);
+  }
+
+  // Minutes (might, depending on the platform) saturate at -inf.
+  const auto chrono_minutes_min = std::chrono::minutes::min();
+  const auto minutes_min = absl::FromChrono(chrono_minutes_min);
+  const int64_t minutes_min_count = chrono_minutes_min.count();
+  if (minutes_min_count < kint64min / 60) {
+    EXPECT_EQ(-absl::InfiniteDuration(), minutes_min);
+  } else {
+    EXPECT_EQ(absl::Minutes(minutes_min_count), minutes_min);
+  }
+
+  // Hours (might, depending on the platform) saturate at +inf.
+  const auto chrono_hours_max = std::chrono::hours::max();
+  const auto hours_max = absl::FromChrono(chrono_hours_max);
+  const int64_t hours_max_count = chrono_hours_max.count();
+  if (hours_max_count > kint64max / 3600) {
+    EXPECT_EQ(absl::InfiniteDuration(), hours_max);
+  } else {
+    EXPECT_EQ(absl::Hours(hours_max_count), hours_max);
+  }
+
+  // Hours (might, depending on the platform) saturate at -inf.
+  const auto chrono_hours_min = std::chrono::hours::min();
+  const auto hours_min = absl::FromChrono(chrono_hours_min);
+  const int64_t hours_min_count = chrono_hours_min.count();
+  if (hours_min_count < kint64min / 3600) {
+    EXPECT_EQ(-absl::InfiniteDuration(), hours_min);
+  } else {
+    EXPECT_EQ(absl::Hours(hours_min_count), hours_min);
+  }
+}
+
+template <int64_t N>
+void TestToChrono() {
+  using std::chrono::nanoseconds;
+  using std::chrono::microseconds;
+  using std::chrono::milliseconds;
+  using std::chrono::seconds;
+  using std::chrono::minutes;
+  using std::chrono::hours;
+
+  EXPECT_EQ(nanoseconds(N), absl::ToChronoNanoseconds(absl::Nanoseconds(N)));
+  EXPECT_EQ(microseconds(N), absl::ToChronoMicroseconds(absl::Microseconds(N)));
+  EXPECT_EQ(milliseconds(N), absl::ToChronoMilliseconds(absl::Milliseconds(N)));
+  EXPECT_EQ(seconds(N), absl::ToChronoSeconds(absl::Seconds(N)));
+
+  constexpr auto absl_minutes = absl::Minutes(N);
+  auto chrono_minutes = minutes(N);
+  if (absl_minutes == -absl::InfiniteDuration()) {
+    chrono_minutes = minutes::min();
+  } else if (absl_minutes == absl::InfiniteDuration()) {
+    chrono_minutes = minutes::max();
+  }
+  EXPECT_EQ(chrono_minutes, absl::ToChronoMinutes(absl_minutes));
+
+  constexpr auto absl_hours = absl::Hours(N);
+  auto chrono_hours = hours(N);
+  if (absl_hours == -absl::InfiniteDuration()) {
+    chrono_hours = hours::min();
+  } else if (absl_hours == absl::InfiniteDuration()) {
+    chrono_hours = hours::max();
+  }
+  EXPECT_EQ(chrono_hours, absl::ToChronoHours(absl_hours));
+}
+
+TEST(Duration, ToChrono) {
+  using std::chrono::nanoseconds;
+  using std::chrono::microseconds;
+  using std::chrono::milliseconds;
+  using std::chrono::seconds;
+  using std::chrono::minutes;
+  using std::chrono::hours;
+
+  TestToChrono<kint64min>();
+  TestToChrono<-1>();
+  TestToChrono<0>();
+  TestToChrono<1>();
+  TestToChrono<kint64max>();
+
+  // Verify truncation toward zero.
+  const auto tick = absl::Nanoseconds(1) / 4;
+  EXPECT_EQ(nanoseconds(0), absl::ToChronoNanoseconds(tick));
+  EXPECT_EQ(nanoseconds(0), absl::ToChronoNanoseconds(-tick));
+  EXPECT_EQ(microseconds(0), absl::ToChronoMicroseconds(tick));
+  EXPECT_EQ(microseconds(0), absl::ToChronoMicroseconds(-tick));
+  EXPECT_EQ(milliseconds(0), absl::ToChronoMilliseconds(tick));
+  EXPECT_EQ(milliseconds(0), absl::ToChronoMilliseconds(-tick));
+  EXPECT_EQ(seconds(0), absl::ToChronoSeconds(tick));
+  EXPECT_EQ(seconds(0), absl::ToChronoSeconds(-tick));
+  EXPECT_EQ(minutes(0), absl::ToChronoMinutes(tick));
+  EXPECT_EQ(minutes(0), absl::ToChronoMinutes(-tick));
+  EXPECT_EQ(hours(0), absl::ToChronoHours(tick));
+  EXPECT_EQ(hours(0), absl::ToChronoHours(-tick));
+
+  // Verifies +/- infinity saturation at max/min.
+  constexpr auto inf = absl::InfiniteDuration();
+  EXPECT_EQ(nanoseconds::min(), absl::ToChronoNanoseconds(-inf));
+  EXPECT_EQ(nanoseconds::max(), absl::ToChronoNanoseconds(inf));
+  EXPECT_EQ(microseconds::min(), absl::ToChronoMicroseconds(-inf));
+  EXPECT_EQ(microseconds::max(), absl::ToChronoMicroseconds(inf));
+  EXPECT_EQ(milliseconds::min(), absl::ToChronoMilliseconds(-inf));
+  EXPECT_EQ(milliseconds::max(), absl::ToChronoMilliseconds(inf));
+  EXPECT_EQ(seconds::min(), absl::ToChronoSeconds(-inf));
+  EXPECT_EQ(seconds::max(), absl::ToChronoSeconds(inf));
+  EXPECT_EQ(minutes::min(), absl::ToChronoMinutes(-inf));
+  EXPECT_EQ(minutes::max(), absl::ToChronoMinutes(inf));
+  EXPECT_EQ(hours::min(), absl::ToChronoHours(-inf));
+  EXPECT_EQ(hours::max(), absl::ToChronoHours(inf));
+}
+
+TEST(Duration, FactoryOverloads) {
+  enum E { kOne = 1 };
+#define TEST_FACTORY_OVERLOADS(NAME)                                          \
+  EXPECT_EQ(1, NAME(kOne) / NAME(kOne));                                      \
+  EXPECT_EQ(1, NAME(static_cast<int8_t>(1)) / NAME(1));                       \
+  EXPECT_EQ(1, NAME(static_cast<int16_t>(1)) / NAME(1));                      \
+  EXPECT_EQ(1, NAME(static_cast<int32_t>(1)) / NAME(1));                      \
+  EXPECT_EQ(1, NAME(static_cast<int64_t>(1)) / NAME(1));                      \
+  EXPECT_EQ(1, NAME(static_cast<uint8_t>(1)) / NAME(1));                      \
+  EXPECT_EQ(1, NAME(static_cast<uint16_t>(1)) / NAME(1));                     \
+  EXPECT_EQ(1, NAME(static_cast<uint32_t>(1)) / NAME(1));                     \
+  EXPECT_EQ(1, NAME(static_cast<uint64_t>(1)) / NAME(1));                     \
+  EXPECT_EQ(NAME(1) / 2, NAME(static_cast<float>(0.5)));                      \
+  EXPECT_EQ(NAME(1) / 2, NAME(static_cast<double>(0.5)));                     \
+  EXPECT_EQ(1.5, absl::FDivDuration(NAME(static_cast<float>(1.5)), NAME(1))); \
+  EXPECT_EQ(1.5, absl::FDivDuration(NAME(static_cast<double>(1.5)), NAME(1)));
+
+  TEST_FACTORY_OVERLOADS(absl::Nanoseconds);
+  TEST_FACTORY_OVERLOADS(absl::Microseconds);
+  TEST_FACTORY_OVERLOADS(absl::Milliseconds);
+  TEST_FACTORY_OVERLOADS(absl::Seconds);
+  TEST_FACTORY_OVERLOADS(absl::Minutes);
+  TEST_FACTORY_OVERLOADS(absl::Hours);
+
+#undef TEST_FACTORY_OVERLOADS
+
+  EXPECT_EQ(absl::Milliseconds(1500), absl::Seconds(1.5));
+  EXPECT_LT(absl::Nanoseconds(1), absl::Nanoseconds(1.5));
+  EXPECT_GT(absl::Nanoseconds(2), absl::Nanoseconds(1.5));
+
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+  EXPECT_EQ(absl::InfiniteDuration(), absl::Nanoseconds(dbl_inf));
+  EXPECT_EQ(absl::InfiniteDuration(), absl::Microseconds(dbl_inf));
+  EXPECT_EQ(absl::InfiniteDuration(), absl::Milliseconds(dbl_inf));
+  EXPECT_EQ(absl::InfiniteDuration(), absl::Seconds(dbl_inf));
+  EXPECT_EQ(absl::InfiniteDuration(), absl::Minutes(dbl_inf));
+  EXPECT_EQ(absl::InfiniteDuration(), absl::Hours(dbl_inf));
+  EXPECT_EQ(-absl::InfiniteDuration(), absl::Nanoseconds(-dbl_inf));
+  EXPECT_EQ(-absl::InfiniteDuration(), absl::Microseconds(-dbl_inf));
+  EXPECT_EQ(-absl::InfiniteDuration(), absl::Milliseconds(-dbl_inf));
+  EXPECT_EQ(-absl::InfiniteDuration(), absl::Seconds(-dbl_inf));
+  EXPECT_EQ(-absl::InfiniteDuration(), absl::Minutes(-dbl_inf));
+  EXPECT_EQ(-absl::InfiniteDuration(), absl::Hours(-dbl_inf));
+}
+
+TEST(Duration, InfinityExamples) {
+  // These examples are used in the documentation in time.h. They are
+  // written so that they can be copy-n-pasted easily.
+
+  constexpr absl::Duration inf = absl::InfiniteDuration();
+  constexpr absl::Duration d = absl::Seconds(1);  // Any finite duration
+
+  EXPECT_TRUE(inf == inf + inf);
+  EXPECT_TRUE(inf == inf + d);
+  EXPECT_TRUE(inf == inf - inf);
+  EXPECT_TRUE(-inf == d - inf);
+
+  EXPECT_TRUE(inf == d * 1e100);
+  EXPECT_TRUE(0 == d / inf);  // NOLINT(readability/check)
+
+  // Division by zero returns infinity, or kint64min/MAX where necessary.
+  EXPECT_TRUE(inf == d / 0);
+  EXPECT_TRUE(kint64max == d / absl::ZeroDuration());
+}
+
+TEST(Duration, InfinityComparison) {
+  const absl::Duration inf = absl::InfiniteDuration();
+  const absl::Duration any_dur = absl::Seconds(1);
+
+  // Equality
+  EXPECT_EQ(inf, inf);
+  EXPECT_EQ(-inf, -inf);
+  EXPECT_NE(inf, -inf);
+  EXPECT_NE(any_dur, inf);
+  EXPECT_NE(any_dur, -inf);
+
+  // Relational
+  EXPECT_GT(inf, any_dur);
+  EXPECT_LT(-inf, any_dur);
+  EXPECT_LT(-inf, inf);
+  EXPECT_GT(inf, -inf);
+}
+
+TEST(Duration, InfinityAddition) {
+  const absl::Duration sec_max = absl::Seconds(kint64max);
+  const absl::Duration sec_min = absl::Seconds(kint64min);
+  const absl::Duration any_dur = absl::Seconds(1);
+  const absl::Duration inf = absl::InfiniteDuration();
+
+  // Addition
+  EXPECT_EQ(inf, inf + inf);
+  EXPECT_EQ(inf, inf + -inf);
+  EXPECT_EQ(-inf, -inf + inf);
+  EXPECT_EQ(-inf, -inf + -inf);
+
+  EXPECT_EQ(inf, inf + any_dur);
+  EXPECT_EQ(inf, any_dur + inf);
+  EXPECT_EQ(-inf, -inf + any_dur);
+  EXPECT_EQ(-inf, any_dur + -inf);
+
+  // Interesting case
+  absl::Duration almost_inf = sec_max + absl::Nanoseconds(999999999);
+  EXPECT_GT(inf, almost_inf);
+  almost_inf += -absl::Nanoseconds(999999999);
+  EXPECT_GT(inf, almost_inf);
+
+  // Addition overflow/underflow
+  EXPECT_EQ(inf, sec_max + absl::Seconds(1));
+  EXPECT_EQ(inf, sec_max + sec_max);
+  EXPECT_EQ(-inf, sec_min + -absl::Seconds(1));
+  EXPECT_EQ(-inf, sec_min + -sec_max);
+
+  // For reference: IEEE 754 behavior
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+  EXPECT_TRUE(std::isinf(dbl_inf + dbl_inf));
+  EXPECT_TRUE(std::isnan(dbl_inf + -dbl_inf));  // We return inf
+  EXPECT_TRUE(std::isnan(-dbl_inf + dbl_inf));  // We return inf
+  EXPECT_TRUE(std::isinf(-dbl_inf + -dbl_inf));
+}
+
+TEST(Duration, InfinitySubtraction) {
+  const absl::Duration sec_max = absl::Seconds(kint64max);
+  const absl::Duration sec_min = absl::Seconds(kint64min);
+  const absl::Duration any_dur = absl::Seconds(1);
+  const absl::Duration inf = absl::InfiniteDuration();
+
+  // Subtraction
+  EXPECT_EQ(inf, inf - inf);
+  EXPECT_EQ(inf, inf - -inf);
+  EXPECT_EQ(-inf, -inf - inf);
+  EXPECT_EQ(-inf, -inf - -inf);
+
+  EXPECT_EQ(inf, inf - any_dur);
+  EXPECT_EQ(-inf, any_dur - inf);
+  EXPECT_EQ(-inf, -inf - any_dur);
+  EXPECT_EQ(inf, any_dur - -inf);
+
+  // Subtraction overflow/underflow
+  EXPECT_EQ(inf, sec_max - -absl::Seconds(1));
+  EXPECT_EQ(inf, sec_max - -sec_max);
+  EXPECT_EQ(-inf, sec_min - absl::Seconds(1));
+  EXPECT_EQ(-inf, sec_min - sec_max);
+
+  // Interesting case
+  absl::Duration almost_neg_inf = sec_min;
+  EXPECT_LT(-inf, almost_neg_inf);
+  almost_neg_inf -= -absl::Nanoseconds(1);
+  EXPECT_LT(-inf, almost_neg_inf);
+
+  // For reference: IEEE 754 behavior
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+  EXPECT_TRUE(std::isnan(dbl_inf - dbl_inf));  // We return inf
+  EXPECT_TRUE(std::isinf(dbl_inf - -dbl_inf));
+  EXPECT_TRUE(std::isinf(-dbl_inf - dbl_inf));
+  EXPECT_TRUE(std::isnan(-dbl_inf - -dbl_inf));  // We return inf
+}
+
+TEST(Duration, InfinityMultiplication) {
+  const absl::Duration sec_max = absl::Seconds(kint64max);
+  const absl::Duration sec_min = absl::Seconds(kint64min);
+  const absl::Duration inf = absl::InfiniteDuration();
+
+#define TEST_INF_MUL_WITH_TYPE(T)                                     \
+  EXPECT_EQ(inf, inf * static_cast<T>(2));                            \
+  EXPECT_EQ(-inf, inf * static_cast<T>(-2));                          \
+  EXPECT_EQ(-inf, -inf * static_cast<T>(2));                          \
+  EXPECT_EQ(inf, -inf * static_cast<T>(-2));                          \
+  EXPECT_EQ(inf, inf * static_cast<T>(0));                            \
+  EXPECT_EQ(-inf, -inf * static_cast<T>(0));                          \
+  EXPECT_EQ(inf, sec_max * static_cast<T>(2));                        \
+  EXPECT_EQ(inf, sec_min * static_cast<T>(-2));                       \
+  EXPECT_EQ(inf, (sec_max / static_cast<T>(2)) * static_cast<T>(3));  \
+  EXPECT_EQ(-inf, sec_max * static_cast<T>(-2));                      \
+  EXPECT_EQ(-inf, sec_min * static_cast<T>(2));                       \
+  EXPECT_EQ(-inf, (sec_min / static_cast<T>(2)) * static_cast<T>(3));
+
+  TEST_INF_MUL_WITH_TYPE(int64_t);  // NOLINT(readability/function)
+  TEST_INF_MUL_WITH_TYPE(double);   // NOLINT(readability/function)
+
+#undef TEST_INF_MUL_WITH_TYPE
+
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+  EXPECT_EQ(inf, inf * dbl_inf);
+  EXPECT_EQ(-inf, -inf * dbl_inf);
+  EXPECT_EQ(-inf, inf * -dbl_inf);
+  EXPECT_EQ(inf, -inf * -dbl_inf);
+
+  const absl::Duration any_dur = absl::Seconds(1);
+  EXPECT_EQ(inf, any_dur * dbl_inf);
+  EXPECT_EQ(-inf, -any_dur * dbl_inf);
+  EXPECT_EQ(-inf, any_dur * -dbl_inf);
+  EXPECT_EQ(inf, -any_dur * -dbl_inf);
+
+  // Fixed-point multiplication will produce a finite value, whereas floating
+  // point fuzziness will overflow to inf.
+  EXPECT_NE(absl::InfiniteDuration(), absl::Seconds(1) * kint64max);
+  EXPECT_EQ(inf, absl::Seconds(1) * static_cast<double>(kint64max));
+  EXPECT_NE(-absl::InfiniteDuration(), absl::Seconds(1) * kint64min);
+  EXPECT_EQ(-inf, absl::Seconds(1) * static_cast<double>(kint64min));
+
+  // Note that sec_max * or / by 1.0 overflows to inf due to the 53-bit
+  // limitations of double.
+  EXPECT_NE(inf, sec_max);
+  EXPECT_NE(inf, sec_max / 1);
+  EXPECT_EQ(inf, sec_max / 1.0);
+  EXPECT_NE(inf, sec_max * 1);
+  EXPECT_EQ(inf, sec_max * 1.0);
+}
+
+TEST(Duration, InfinityDivision) {
+  const absl::Duration sec_max = absl::Seconds(kint64max);
+  const absl::Duration sec_min = absl::Seconds(kint64min);
+  const absl::Duration inf = absl::InfiniteDuration();
+
+  // Division of Duration by a double
+#define TEST_INF_DIV_WITH_TYPE(T)            \
+  EXPECT_EQ(inf, inf / static_cast<T>(2));   \
+  EXPECT_EQ(-inf, inf / static_cast<T>(-2)); \
+  EXPECT_EQ(-inf, -inf / static_cast<T>(2)); \
+  EXPECT_EQ(inf, -inf / static_cast<T>(-2));
+
+  TEST_INF_DIV_WITH_TYPE(int64_t);  // NOLINT(readability/function)
+  TEST_INF_DIV_WITH_TYPE(double);   // NOLINT(readability/function)
+
+#undef TEST_INF_DIV_WITH_TYPE
+
+  // Division of Duration by a double overflow/underflow
+  EXPECT_EQ(inf, sec_max / 0.5);
+  EXPECT_EQ(inf, sec_min / -0.5);
+  EXPECT_EQ(inf, ((sec_max / 0.5) + absl::Seconds(1)) / 0.5);
+  EXPECT_EQ(-inf, sec_max / -0.5);
+  EXPECT_EQ(-inf, sec_min / 0.5);
+  EXPECT_EQ(-inf, ((sec_min / 0.5) - absl::Seconds(1)) / 0.5);
+
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+  EXPECT_EQ(inf, inf / dbl_inf);
+  EXPECT_EQ(-inf, inf / -dbl_inf);
+  EXPECT_EQ(-inf, -inf / dbl_inf);
+  EXPECT_EQ(inf, -inf / -dbl_inf);
+
+  const absl::Duration any_dur = absl::Seconds(1);
+  EXPECT_EQ(absl::ZeroDuration(), any_dur / dbl_inf);
+  EXPECT_EQ(absl::ZeroDuration(), any_dur / -dbl_inf);
+  EXPECT_EQ(absl::ZeroDuration(), -any_dur / dbl_inf);
+  EXPECT_EQ(absl::ZeroDuration(), -any_dur / -dbl_inf);
+}
+
+TEST(Duration, InfinityModulus) {
+  const absl::Duration sec_max = absl::Seconds(kint64max);
+  const absl::Duration any_dur = absl::Seconds(1);
+  const absl::Duration inf = absl::InfiniteDuration();
+
+  EXPECT_EQ(inf, inf % inf);
+  EXPECT_EQ(inf, inf % -inf);
+  EXPECT_EQ(-inf, -inf % -inf);
+  EXPECT_EQ(-inf, -inf % inf);
+
+  EXPECT_EQ(any_dur, any_dur % inf);
+  EXPECT_EQ(any_dur, any_dur % -inf);
+  EXPECT_EQ(-any_dur, -any_dur % inf);
+  EXPECT_EQ(-any_dur, -any_dur % -inf);
+
+  EXPECT_EQ(inf, inf % -any_dur);
+  EXPECT_EQ(inf, inf % any_dur);
+  EXPECT_EQ(-inf, -inf % -any_dur);
+  EXPECT_EQ(-inf, -inf % any_dur);
+
+  // Remainder isn't affected by overflow.
+  EXPECT_EQ(absl::ZeroDuration(), sec_max % absl::Seconds(1));
+  EXPECT_EQ(absl::ZeroDuration(), sec_max % absl::Milliseconds(1));
+  EXPECT_EQ(absl::ZeroDuration(), sec_max % absl::Microseconds(1));
+  EXPECT_EQ(absl::ZeroDuration(), sec_max % absl::Nanoseconds(1));
+  EXPECT_EQ(absl::ZeroDuration(), sec_max % absl::Nanoseconds(1) / 4);
+}
+
+TEST(Duration, InfinityIDiv) {
+  const absl::Duration sec_max = absl::Seconds(kint64max);
+  const absl::Duration any_dur = absl::Seconds(1);
+  const absl::Duration inf = absl::InfiniteDuration();
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+
+  // IDivDuration (int64_t return value + a remainer)
+  absl::Duration rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64max, absl::IDivDuration(inf, inf, &rem));
+  EXPECT_EQ(inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64max, absl::IDivDuration(-inf, -inf, &rem));
+  EXPECT_EQ(-inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64max, absl::IDivDuration(inf, any_dur, &rem));
+  EXPECT_EQ(inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(0, absl::IDivDuration(any_dur, inf, &rem));
+  EXPECT_EQ(any_dur, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64max, absl::IDivDuration(-inf, -any_dur, &rem));
+  EXPECT_EQ(-inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(0, absl::IDivDuration(-any_dur, -inf, &rem));
+  EXPECT_EQ(-any_dur, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64min, absl::IDivDuration(-inf, inf, &rem));
+  EXPECT_EQ(-inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64min, absl::IDivDuration(inf, -inf, &rem));
+  EXPECT_EQ(inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64min, absl::IDivDuration(-inf, any_dur, &rem));
+  EXPECT_EQ(-inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(0, absl::IDivDuration(-any_dur, inf, &rem));
+  EXPECT_EQ(-any_dur, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(kint64min, absl::IDivDuration(inf, -any_dur, &rem));
+  EXPECT_EQ(inf, rem);
+
+  rem = absl::ZeroDuration();
+  EXPECT_EQ(0, absl::IDivDuration(any_dur, -inf, &rem));
+  EXPECT_EQ(any_dur, rem);
+
+  // IDivDuration overflow/underflow
+  rem = any_dur;
+  EXPECT_EQ(kint64max,
+            absl::IDivDuration(sec_max, absl::Nanoseconds(1) / 4, &rem));
+  EXPECT_EQ(sec_max - absl::Nanoseconds(kint64max) / 4, rem);
+
+  rem = any_dur;
+  EXPECT_EQ(kint64max,
+            absl::IDivDuration(sec_max, absl::Milliseconds(1), &rem));
+  EXPECT_EQ(sec_max - absl::Milliseconds(kint64max), rem);
+
+  rem = any_dur;
+  EXPECT_EQ(kint64max,
+            absl::IDivDuration(-sec_max, -absl::Milliseconds(1), &rem));
+  EXPECT_EQ(-sec_max + absl::Milliseconds(kint64max), rem);
+
+  rem = any_dur;
+  EXPECT_EQ(kint64min,
+            absl::IDivDuration(-sec_max, absl::Milliseconds(1), &rem));
+  EXPECT_EQ(-sec_max - absl::Milliseconds(kint64min), rem);
+
+  rem = any_dur;
+  EXPECT_EQ(kint64min,
+            absl::IDivDuration(sec_max, -absl::Milliseconds(1), &rem));
+  EXPECT_EQ(sec_max + absl::Milliseconds(kint64min), rem);
+
+  //
+  // operator/(Duration, Duration) is a wrapper for IDivDuration().
+  //
+
+  // IEEE 754 says inf / inf should be nan, but int64_t doesn't have
+  // nan so we'll return kint64max/kint64min instead.
+  EXPECT_TRUE(std::isnan(dbl_inf / dbl_inf));
+  EXPECT_EQ(kint64max, inf / inf);
+  EXPECT_EQ(kint64max, -inf / -inf);
+  EXPECT_EQ(kint64min, -inf / inf);
+  EXPECT_EQ(kint64min, inf / -inf);
+
+  EXPECT_TRUE(std::isinf(dbl_inf / 2.0));
+  EXPECT_EQ(kint64max, inf / any_dur);
+  EXPECT_EQ(kint64max, -inf / -any_dur);
+  EXPECT_EQ(kint64min, -inf / any_dur);
+  EXPECT_EQ(kint64min, inf / -any_dur);
+
+  EXPECT_EQ(0.0, 2.0 / dbl_inf);
+  EXPECT_EQ(0, any_dur / inf);
+  EXPECT_EQ(0, any_dur / -inf);
+  EXPECT_EQ(0, -any_dur / inf);
+  EXPECT_EQ(0, -any_dur / -inf);
+  EXPECT_EQ(0, absl::ZeroDuration() / inf);
+
+  // Division of Duration by a Duration overflow/underflow
+  EXPECT_EQ(kint64max, sec_max / absl::Milliseconds(1));
+  EXPECT_EQ(kint64max, -sec_max / -absl::Milliseconds(1));
+  EXPECT_EQ(kint64min, -sec_max / absl::Milliseconds(1));
+  EXPECT_EQ(kint64min, sec_max / -absl::Milliseconds(1));
+}
+
+TEST(Duration, InfinityFDiv) {
+  const absl::Duration any_dur = absl::Seconds(1);
+  const absl::Duration inf = absl::InfiniteDuration();
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+
+  EXPECT_EQ(dbl_inf, absl::FDivDuration(inf, inf));
+  EXPECT_EQ(dbl_inf, absl::FDivDuration(-inf, -inf));
+  EXPECT_EQ(dbl_inf, absl::FDivDuration(inf, any_dur));
+  EXPECT_EQ(0.0, absl::FDivDuration(any_dur, inf));
+  EXPECT_EQ(dbl_inf, absl::FDivDuration(-inf, -any_dur));
+  EXPECT_EQ(0.0, absl::FDivDuration(-any_dur, -inf));
+
+  EXPECT_EQ(-dbl_inf, absl::FDivDuration(-inf, inf));
+  EXPECT_EQ(-dbl_inf, absl::FDivDuration(inf, -inf));
+  EXPECT_EQ(-dbl_inf, absl::FDivDuration(-inf, any_dur));
+  EXPECT_EQ(0.0, absl::FDivDuration(-any_dur, inf));
+  EXPECT_EQ(-dbl_inf, absl::FDivDuration(inf, -any_dur));
+  EXPECT_EQ(0.0, absl::FDivDuration(any_dur, -inf));
+}
+
+TEST(Duration, DivisionByZero) {
+  const absl::Duration zero = absl::ZeroDuration();
+  const absl::Duration inf = absl::InfiniteDuration();
+  const absl::Duration any_dur = absl::Seconds(1);
+  const double dbl_inf = std::numeric_limits<double>::infinity();
+  const double dbl_denorm = std::numeric_limits<double>::denorm_min();
+
+  // Operator/(Duration, double)
+  EXPECT_EQ(inf, zero / 0.0);
+  EXPECT_EQ(-inf, zero / -0.0);
+  EXPECT_EQ(inf, any_dur / 0.0);
+  EXPECT_EQ(-inf, any_dur / -0.0);
+  EXPECT_EQ(-inf, -any_dur / 0.0);
+  EXPECT_EQ(inf, -any_dur / -0.0);
+
+  // Tests dividing by a number very close to, but not quite zero.
+  EXPECT_EQ(zero, zero / dbl_denorm);
+  EXPECT_EQ(zero, zero / -dbl_denorm);
+  EXPECT_EQ(inf, any_dur / dbl_denorm);
+  EXPECT_EQ(-inf, any_dur / -dbl_denorm);
+  EXPECT_EQ(-inf, -any_dur / dbl_denorm);
+  EXPECT_EQ(inf, -any_dur / -dbl_denorm);
+
+  // IDiv
+  absl::Duration rem = zero;
+  EXPECT_EQ(kint64max, absl::IDivDuration(zero, zero, &rem));
+  EXPECT_EQ(inf, rem);
+
+  rem = zero;
+  EXPECT_EQ(kint64max, absl::IDivDuration(any_dur, zero, &rem));
+  EXPECT_EQ(inf, rem);
+
+  rem = zero;
+  EXPECT_EQ(kint64min, absl::IDivDuration(-any_dur, zero, &rem));
+  EXPECT_EQ(-inf, rem);
+
+  // Operator/(Duration, Duration)
+  EXPECT_EQ(kint64max, zero / zero);
+  EXPECT_EQ(kint64max, any_dur / zero);
+  EXPECT_EQ(kint64min, -any_dur / zero);
+
+  // FDiv
+  EXPECT_EQ(dbl_inf, absl::FDivDuration(zero, zero));
+  EXPECT_EQ(dbl_inf, absl::FDivDuration(any_dur, zero));
+  EXPECT_EQ(-dbl_inf, absl::FDivDuration(-any_dur, zero));
+}
+
+TEST(Duration, NaN) {
+  // Note that IEEE 754 does not define the behavior of a nan's sign when it is
+  // copied, so the code below allows for either + or - InfiniteDuration.
+#define TEST_NAN_HANDLING(NAME, NAN)           \
+  do {                                         \
+    const auto inf = absl::InfiniteDuration(); \
+    auto x = NAME(NAN);                        \
+    EXPECT_TRUE(x == inf || x == -inf);        \
+    auto y = NAME(42);                         \
+    y *= NAN;                                  \
+    EXPECT_TRUE(y == inf || y == -inf);        \
+    auto z = NAME(42);                         \
+    z /= NAN;                                  \
+    EXPECT_TRUE(z == inf || z == -inf);        \
+  } while (0)
+
+  const double nan = std::numeric_limits<double>::quiet_NaN();
+  TEST_NAN_HANDLING(absl::Nanoseconds, nan);
+  TEST_NAN_HANDLING(absl::Microseconds, nan);
+  TEST_NAN_HANDLING(absl::Milliseconds, nan);
+  TEST_NAN_HANDLING(absl::Seconds, nan);
+  TEST_NAN_HANDLING(absl::Minutes, nan);
+  TEST_NAN_HANDLING(absl::Hours, nan);
+
+  TEST_NAN_HANDLING(absl::Nanoseconds, -nan);
+  TEST_NAN_HANDLING(absl::Microseconds, -nan);
+  TEST_NAN_HANDLING(absl::Milliseconds, -nan);
+  TEST_NAN_HANDLING(absl::Seconds, -nan);
+  TEST_NAN_HANDLING(absl::Minutes, -nan);
+  TEST_NAN_HANDLING(absl::Hours, -nan);
+
+#undef TEST_NAN_HANDLING
+}
+
+TEST(Duration, Range) {
+  const absl::Duration range = ApproxYears(100 * 1e9);
+  const absl::Duration range_future = range;
+  const absl::Duration range_past = -range;
+
+  EXPECT_LT(range_future, absl::InfiniteDuration());
+  EXPECT_GT(range_past, -absl::InfiniteDuration());
+
+  const absl::Duration full_range = range_future - range_past;
+  EXPECT_GT(full_range, absl::ZeroDuration());
+  EXPECT_LT(full_range, absl::InfiniteDuration());
+
+  const absl::Duration neg_full_range = range_past - range_future;
+  EXPECT_LT(neg_full_range, absl::ZeroDuration());
+  EXPECT_GT(neg_full_range, -absl::InfiniteDuration());
+
+  EXPECT_LT(neg_full_range, full_range);
+  EXPECT_EQ(neg_full_range, -full_range);
+}
+
+TEST(Duration, RelationalOperators) {
+#define TEST_REL_OPS(UNIT)               \
+  static_assert(UNIT(2) == UNIT(2), ""); \
+  static_assert(UNIT(1) != UNIT(2), ""); \
+  static_assert(UNIT(1) < UNIT(2), "");  \
+  static_assert(UNIT(3) > UNIT(2), "");  \
+  static_assert(UNIT(1) <= UNIT(2), ""); \
+  static_assert(UNIT(2) <= UNIT(2), ""); \
+  static_assert(UNIT(3) >= UNIT(2), ""); \
+  static_assert(UNIT(2) >= UNIT(2), "");
+
+  TEST_REL_OPS(absl::Nanoseconds);
+  TEST_REL_OPS(absl::Microseconds);
+  TEST_REL_OPS(absl::Milliseconds);
+  TEST_REL_OPS(absl::Seconds);
+  TEST_REL_OPS(absl::Minutes);
+  TEST_REL_OPS(absl::Hours);
+
+#undef TEST_REL_OPS
+}
+
+TEST(Duration, Addition) {
+#define TEST_ADD_OPS(UNIT)                  \
+  do {                                      \
+    EXPECT_EQ(UNIT(2), UNIT(1) + UNIT(1));  \
+    EXPECT_EQ(UNIT(1), UNIT(2) - UNIT(1));  \
+    EXPECT_EQ(UNIT(0), UNIT(2) - UNIT(2));  \
+    EXPECT_EQ(UNIT(-1), UNIT(1) - UNIT(2)); \
+    EXPECT_EQ(UNIT(-2), UNIT(0) - UNIT(2)); \
+    EXPECT_EQ(UNIT(-2), UNIT(1) - UNIT(3)); \
+    absl::Duration a = UNIT(1);             \
+    a += UNIT(1);                           \
+    EXPECT_EQ(UNIT(2), a);                  \
+    a -= UNIT(1);                           \
+    EXPECT_EQ(UNIT(1), a);                  \
+  } while (0)
+
+  TEST_ADD_OPS(absl::Nanoseconds);
+  TEST_ADD_OPS(absl::Microseconds);
+  TEST_ADD_OPS(absl::Milliseconds);
+  TEST_ADD_OPS(absl::Seconds);
+  TEST_ADD_OPS(absl::Minutes);
+  TEST_ADD_OPS(absl::Hours);
+
+#undef TEST_ADD_OPS
+
+  EXPECT_EQ(absl::Seconds(2), absl::Seconds(3) - 2 * absl::Milliseconds(500));
+  EXPECT_EQ(absl::Seconds(2) + absl::Milliseconds(500),
+            absl::Seconds(3) - absl::Milliseconds(500));
+
+  EXPECT_EQ(absl::Seconds(1) + absl::Milliseconds(998),
+            absl::Milliseconds(999) + absl::Milliseconds(999));
+
+  EXPECT_EQ(absl::Milliseconds(-1),
+            absl::Milliseconds(998) - absl::Milliseconds(999));
+
+  // Tests fractions of a nanoseconds. These are implementation details only.
+  EXPECT_GT(absl::Nanoseconds(1), absl::Nanoseconds(1) / 2);
+  EXPECT_EQ(absl::Nanoseconds(1),
+            absl::Nanoseconds(1) / 2 + absl::Nanoseconds(1) / 2);
+  EXPECT_GT(absl::Nanoseconds(1) / 4, absl::Nanoseconds(0));
+  EXPECT_EQ(absl::Nanoseconds(1) / 8, absl::Nanoseconds(0));
+
+  // Tests subtraction that will cause wrap around of the rep_lo_ bits.
+  absl::Duration d_7_5 = absl::Seconds(7) + absl::Milliseconds(500);
+  absl::Duration d_3_7 = absl::Seconds(3) + absl::Milliseconds(700);
+  absl::Duration ans_3_8 = absl::Seconds(3) + absl::Milliseconds(800);
+  EXPECT_EQ(ans_3_8, d_7_5 - d_3_7);
+
+  // Subtracting min_duration
+  absl::Duration min_dur = absl::Seconds(kint64min);
+  EXPECT_EQ(absl::Seconds(0), min_dur - min_dur);
+  EXPECT_EQ(absl::Seconds(kint64max), absl::Seconds(-1) - min_dur);
+}
+
+TEST(Duration, Negation) {
+  // By storing negations of various values in constexpr variables we
+  // verify that the initializers are constant expressions.
+  constexpr absl::Duration negated_zero_duration = -absl::ZeroDuration();
+  EXPECT_EQ(negated_zero_duration, absl::ZeroDuration());
+
+  constexpr absl::Duration negated_infinite_duration =
+      -absl::InfiniteDuration();
+  EXPECT_NE(negated_infinite_duration, absl::InfiniteDuration());
+  EXPECT_EQ(-negated_infinite_duration, absl::InfiniteDuration());
+
+  // The public APIs to check if a duration is infinite depend on using
+  // -InfiniteDuration(), but we're trying to test operator- here, so we
+  // need to use the lower-level internal query IsInfiniteDuration.
+  EXPECT_TRUE(
+      absl::time_internal::IsInfiniteDuration(negated_infinite_duration));
+
+  // The largest Duration is kint64max seconds and kTicksPerSecond - 1 ticks.
+  // Using the absl::time_internal::MakeDuration API is the cleanest way to
+  // construct that Duration.
+  constexpr absl::Duration max_duration = absl::time_internal::MakeDuration(
+      kint64max, absl::time_internal::kTicksPerSecond - 1);
+  constexpr absl::Duration negated_max_duration = -max_duration;
+  // The largest negatable value is one tick above the minimum representable;
+  // it's the negation of max_duration.
+  constexpr absl::Duration nearly_min_duration =
+      absl::time_internal::MakeDuration(kint64min, int64_t{1});
+  constexpr absl::Duration negated_nearly_min_duration = -nearly_min_duration;
+
+  EXPECT_EQ(negated_max_duration, nearly_min_duration);
+  EXPECT_EQ(negated_nearly_min_duration, max_duration);
+  EXPECT_EQ(-(-max_duration), max_duration);
+
+  constexpr absl::Duration min_duration =
+      absl::time_internal::MakeDuration(kint64min);
+  constexpr absl::Duration negated_min_duration = -min_duration;
+  EXPECT_EQ(negated_min_duration, absl::InfiniteDuration());
+}
+
+TEST(Duration, AbsoluteValue) {
+  EXPECT_EQ(absl::ZeroDuration(), AbsDuration(absl::ZeroDuration()));
+  EXPECT_EQ(absl::Seconds(1), AbsDuration(absl::Seconds(1)));
+  EXPECT_EQ(absl::Seconds(1), AbsDuration(absl::Seconds(-1)));
+
+  EXPECT_EQ(absl::InfiniteDuration(), AbsDuration(absl::InfiniteDuration()));
+  EXPECT_EQ(absl::InfiniteDuration(), AbsDuration(-absl::InfiniteDuration()));
+
+  absl::Duration max_dur =
+      absl::Seconds(kint64max) + (absl::Seconds(1) - absl::Nanoseconds(1) / 4);
+  EXPECT_EQ(max_dur, AbsDuration(max_dur));
+
+  absl::Duration min_dur = absl::Seconds(kint64min);
+  EXPECT_EQ(absl::InfiniteDuration(), AbsDuration(min_dur));
+  EXPECT_EQ(max_dur, AbsDuration(min_dur + absl::Nanoseconds(1) / 4));
+}
+
+TEST(Duration, Multiplication) {
+#define TEST_MUL_OPS(UNIT)                                    \
+  do {                                                        \
+    EXPECT_EQ(UNIT(5), UNIT(2) * 2.5);                        \
+    EXPECT_EQ(UNIT(2), UNIT(5) / 2.5);                        \
+    EXPECT_EQ(UNIT(-5), UNIT(-2) * 2.5);                      \
+    EXPECT_EQ(UNIT(-5), -UNIT(2) * 2.5);                      \
+    EXPECT_EQ(UNIT(-5), UNIT(2) * -2.5);                      \
+    EXPECT_EQ(UNIT(-2), UNIT(-5) / 2.5);                      \
+    EXPECT_EQ(UNIT(-2), -UNIT(5) / 2.5);                      \
+    EXPECT_EQ(UNIT(-2), UNIT(5) / -2.5);                      \
+    EXPECT_EQ(UNIT(2), UNIT(11) % UNIT(3));                   \
+    absl::Duration a = UNIT(2);                               \
+    a *= 2.5;                                                 \
+    EXPECT_EQ(UNIT(5), a);                                    \
+    a /= 2.5;                                                 \
+    EXPECT_EQ(UNIT(2), a);                                    \
+    a %= UNIT(1);                                             \
+    EXPECT_EQ(UNIT(0), a);                                    \
+    absl::Duration big = UNIT(1000000000);                    \
+    big *= 3;                                                 \
+    big /= 3;                                                 \
+    EXPECT_EQ(UNIT(1000000000), big);                         \
+    EXPECT_EQ(-UNIT(2), -UNIT(2));                            \
+    EXPECT_EQ(-UNIT(2), UNIT(2) * -1);                        \
+    EXPECT_EQ(-UNIT(2), -1 * UNIT(2));                        \
+    EXPECT_EQ(-UNIT(-2), UNIT(2));                            \
+    EXPECT_EQ(2, UNIT(2) / UNIT(1));                          \
+    absl::Duration rem;                                       \
+    EXPECT_EQ(2, absl::IDivDuration(UNIT(2), UNIT(1), &rem)); \
+    EXPECT_EQ(2.0, absl::FDivDuration(UNIT(2), UNIT(1)));     \
+  } while (0)
+
+  TEST_MUL_OPS(absl::Nanoseconds);
+  TEST_MUL_OPS(absl::Microseconds);
+  TEST_MUL_OPS(absl::Milliseconds);
+  TEST_MUL_OPS(absl::Seconds);
+  TEST_MUL_OPS(absl::Minutes);
+  TEST_MUL_OPS(absl::Hours);
+
+#undef TEST_MUL_OPS
+
+  // Ensures that multiplication and division by 1 with a maxed-out durations
+  // doesn't lose precision.
+  absl::Duration max_dur =
+      absl::Seconds(kint64max) + (absl::Seconds(1) - absl::Nanoseconds(1) / 4);
+  absl::Duration min_dur = absl::Seconds(kint64min);
+  EXPECT_EQ(max_dur, max_dur * 1);
+  EXPECT_EQ(max_dur, max_dur / 1);
+  EXPECT_EQ(min_dur, min_dur * 1);
+  EXPECT_EQ(min_dur, min_dur / 1);
+
+  // Tests division on a Duration with a large number of significant digits.
+  // Tests when the digits span hi and lo as well as only in hi.
+  absl::Duration sigfigs = absl::Seconds(2000000000) + absl::Nanoseconds(3);
+  EXPECT_EQ(absl::Seconds(666666666) + absl::Nanoseconds(666666667) +
+                absl::Nanoseconds(1) / 2,
+            sigfigs / 3);
+  sigfigs = absl::Seconds(int64_t{7000000000});
+  EXPECT_EQ(absl::Seconds(2333333333) + absl::Nanoseconds(333333333) +
+                absl::Nanoseconds(1) / 4,
+            sigfigs / 3);
+
+  EXPECT_EQ(absl::Seconds(7) + absl::Milliseconds(500), absl::Seconds(3) * 2.5);
+  EXPECT_EQ(absl::Seconds(8) * -1 + absl::Milliseconds(300),
+            (absl::Seconds(2) + absl::Milliseconds(200)) * -3.5);
+  EXPECT_EQ(-absl::Seconds(8) + absl::Milliseconds(300),
+            (absl::Seconds(2) + absl::Milliseconds(200)) * -3.5);
+  EXPECT_EQ(absl::Seconds(1) + absl::Milliseconds(875),
+            (absl::Seconds(7) + absl::Milliseconds(500)) / 4);
+  EXPECT_EQ(absl::Seconds(30),
+            (absl::Seconds(7) + absl::Milliseconds(500)) / 0.25);
+  EXPECT_EQ(absl::Seconds(3),
+            (absl::Seconds(7) + absl::Milliseconds(500)) / 2.5);
+
+  // Tests division remainder.
+  EXPECT_EQ(absl::Nanoseconds(0), absl::Nanoseconds(7) % absl::Nanoseconds(1));
+  EXPECT_EQ(absl::Nanoseconds(0), absl::Nanoseconds(0) % absl::Nanoseconds(10));
+  EXPECT_EQ(absl::Nanoseconds(2), absl::Nanoseconds(7) % absl::Nanoseconds(5));
+  EXPECT_EQ(absl::Nanoseconds(2), absl::Nanoseconds(2) % absl::Nanoseconds(5));
+
+  EXPECT_EQ(absl::Nanoseconds(1), absl::Nanoseconds(10) % absl::Nanoseconds(3));
+  EXPECT_EQ(absl::Nanoseconds(1),
+            absl::Nanoseconds(10) % absl::Nanoseconds(-3));
+  EXPECT_EQ(absl::Nanoseconds(-1),
+            absl::Nanoseconds(-10) % absl::Nanoseconds(3));
+  EXPECT_EQ(absl::Nanoseconds(-1),
+            absl::Nanoseconds(-10) % absl::Nanoseconds(-3));
+
+  EXPECT_EQ(absl::Milliseconds(100),
+            absl::Seconds(1) % absl::Milliseconds(300));
+  EXPECT_EQ(
+      absl::Milliseconds(300),
+      (absl::Seconds(3) + absl::Milliseconds(800)) % absl::Milliseconds(500));
+
+  EXPECT_EQ(absl::Nanoseconds(1), absl::Nanoseconds(1) % absl::Seconds(1));
+  EXPECT_EQ(absl::Nanoseconds(-1), absl::Nanoseconds(-1) % absl::Seconds(1));
+  EXPECT_EQ(0, absl::Nanoseconds(-1) / absl::Seconds(1));  // Actual -1e-9
+
+  // Tests identity a = (a/b)*b + a%b
+#define TEST_MOD_IDENTITY(a, b) \
+  EXPECT_EQ((a), ((a) / (b))*(b) + ((a)%(b)))
+
+  TEST_MOD_IDENTITY(absl::Seconds(0), absl::Seconds(2));
+  TEST_MOD_IDENTITY(absl::Seconds(1), absl::Seconds(1));
+  TEST_MOD_IDENTITY(absl::Seconds(1), absl::Seconds(2));
+  TEST_MOD_IDENTITY(absl::Seconds(2), absl::Seconds(1));
+
+  TEST_MOD_IDENTITY(absl::Seconds(-2), absl::Seconds(1));
+  TEST_MOD_IDENTITY(absl::Seconds(2), absl::Seconds(-1));
+  TEST_MOD_IDENTITY(absl::Seconds(-2), absl::Seconds(-1));
+
+  TEST_MOD_IDENTITY(absl::Nanoseconds(0), absl::Nanoseconds(2));
+  TEST_MOD_IDENTITY(absl::Nanoseconds(1), absl::Nanoseconds(1));
+  TEST_MOD_IDENTITY(absl::Nanoseconds(1), absl::Nanoseconds(2));
+  TEST_MOD_IDENTITY(absl::Nanoseconds(2), absl::Nanoseconds(1));
+
+  TEST_MOD_IDENTITY(absl::Nanoseconds(-2), absl::Nanoseconds(1));
+  TEST_MOD_IDENTITY(absl::Nanoseconds(2), absl::Nanoseconds(-1));
+  TEST_MOD_IDENTITY(absl::Nanoseconds(-2), absl::Nanoseconds(-1));
+
+  // Mixed seconds + subseconds
+  absl::Duration mixed_a = absl::Seconds(1) + absl::Nanoseconds(2);
+  absl::Duration mixed_b = absl::Seconds(1) + absl::Nanoseconds(3);
+
+  TEST_MOD_IDENTITY(absl::Seconds(0), mixed_a);
+  TEST_MOD_IDENTITY(mixed_a, mixed_a);
+  TEST_MOD_IDENTITY(mixed_a, mixed_b);
+  TEST_MOD_IDENTITY(mixed_b, mixed_a);
+
+  TEST_MOD_IDENTITY(-mixed_a, mixed_b);
+  TEST_MOD_IDENTITY(mixed_a, -mixed_b);
+  TEST_MOD_IDENTITY(-mixed_a, -mixed_b);
+
+#undef TEST_MOD_IDENTITY
+}
+
+TEST(Duration, Truncation) {
+  const absl::Duration d = absl::Nanoseconds(1234567890);
+  const absl::Duration inf = absl::InfiniteDuration();
+  for (int unit_sign : {1, -1}) {  // sign shouldn't matter
+    EXPECT_EQ(absl::Nanoseconds(1234567890),
+              Trunc(d, unit_sign * absl::Nanoseconds(1)));
+    EXPECT_EQ(absl::Microseconds(1234567),
+              Trunc(d, unit_sign * absl::Microseconds(1)));
+    EXPECT_EQ(absl::Milliseconds(1234),
+              Trunc(d, unit_sign * absl::Milliseconds(1)));
+    EXPECT_EQ(absl::Seconds(1), Trunc(d, unit_sign * absl::Seconds(1)));
+    EXPECT_EQ(inf, Trunc(inf, unit_sign * absl::Seconds(1)));
+
+    EXPECT_EQ(absl::Nanoseconds(-1234567890),
+              Trunc(-d, unit_sign * absl::Nanoseconds(1)));
+    EXPECT_EQ(absl::Microseconds(-1234567),
+              Trunc(-d, unit_sign * absl::Microseconds(1)));
+    EXPECT_EQ(absl::Milliseconds(-1234),
+              Trunc(-d, unit_sign * absl::Milliseconds(1)));
+    EXPECT_EQ(absl::Seconds(-1), Trunc(-d, unit_sign * absl::Seconds(1)));
+    EXPECT_EQ(-inf, Trunc(-inf, unit_sign * absl::Seconds(1)));
+  }
+}
+
+TEST(Duration, Flooring) {
+  const absl::Duration d = absl::Nanoseconds(1234567890);
+  const absl::Duration inf = absl::InfiniteDuration();
+  for (int unit_sign : {1, -1}) {  // sign shouldn't matter
+    EXPECT_EQ(absl::Nanoseconds(1234567890),
+              absl::Floor(d, unit_sign * absl::Nanoseconds(1)));
+    EXPECT_EQ(absl::Microseconds(1234567),
+              absl::Floor(d, unit_sign * absl::Microseconds(1)));
+    EXPECT_EQ(absl::Milliseconds(1234),
+              absl::Floor(d, unit_sign * absl::Milliseconds(1)));
+    EXPECT_EQ(absl::Seconds(1), absl::Floor(d, unit_sign * absl::Seconds(1)));
+    EXPECT_EQ(inf, absl::Floor(inf, unit_sign * absl::Seconds(1)));
+
+    EXPECT_EQ(absl::Nanoseconds(-1234567890),
+              absl::Floor(-d, unit_sign * absl::Nanoseconds(1)));
+    EXPECT_EQ(absl::Microseconds(-1234568),
+              absl::Floor(-d, unit_sign * absl::Microseconds(1)));
+    EXPECT_EQ(absl::Milliseconds(-1235),
+              absl::Floor(-d, unit_sign * absl::Milliseconds(1)));
+    EXPECT_EQ(absl::Seconds(-2), absl::Floor(-d, unit_sign * absl::Seconds(1)));
+    EXPECT_EQ(-inf, absl::Floor(-inf, unit_sign * absl::Seconds(1)));
+  }
+}
+
+TEST(Duration, Ceiling) {
+  const absl::Duration d = absl::Nanoseconds(1234567890);
+  const absl::Duration inf = absl::InfiniteDuration();
+  for (int unit_sign : {1, -1}) {  // // sign shouldn't matter
+    EXPECT_EQ(absl::Nanoseconds(1234567890),
+              absl::Ceil(d, unit_sign * absl::Nanoseconds(1)));
+    EXPECT_EQ(absl::Microseconds(1234568),
+              absl::Ceil(d, unit_sign * absl::Microseconds(1)));
+    EXPECT_EQ(absl::Milliseconds(1235),
+              absl::Ceil(d, unit_sign * absl::Milliseconds(1)));
+    EXPECT_EQ(absl::Seconds(2), absl::Ceil(d, unit_sign * absl::Seconds(1)));
+    EXPECT_EQ(inf, absl::Ceil(inf, unit_sign * absl::Seconds(1)));
+
+    EXPECT_EQ(absl::Nanoseconds(-1234567890),
+              absl::Ceil(-d, unit_sign * absl::Nanoseconds(1)));
+    EXPECT_EQ(absl::Microseconds(-1234567),
+              absl::Ceil(-d, unit_sign * absl::Microseconds(1)));
+    EXPECT_EQ(absl::Milliseconds(-1234),
+              absl::Ceil(-d, unit_sign * absl::Milliseconds(1)));
+    EXPECT_EQ(absl::Seconds(-1), absl::Ceil(-d, unit_sign * absl::Seconds(1)));
+    EXPECT_EQ(-inf, absl::Ceil(-inf, unit_sign * absl::Seconds(1)));
+  }
+}
+
+TEST(Duration, RoundTripUnits) {
+  const int kRange = 100000;
+
+#define ROUND_TRIP_UNIT(U, LOW, HIGH)          \
+  do {                                         \
+    for (int64_t i = LOW; i < HIGH; ++i) {     \
+      absl::Duration d = absl::U(i);           \
+      if (d == absl::InfiniteDuration())       \
+        EXPECT_EQ(kint64max, d / absl::U(1));  \
+      else if (d == -absl::InfiniteDuration()) \
+        EXPECT_EQ(kint64min, d / absl::U(1));  \
+      else                                     \
+        EXPECT_EQ(i, absl::U(i) / absl::U(1)); \
+    }                                          \
+  } while (0)
+
+  ROUND_TRIP_UNIT(Nanoseconds, kint64min, kint64min + kRange);
+  ROUND_TRIP_UNIT(Nanoseconds, -kRange, kRange);
+  ROUND_TRIP_UNIT(Nanoseconds, kint64max - kRange, kint64max);
+
+  ROUND_TRIP_UNIT(Microseconds, kint64min, kint64min + kRange);
+  ROUND_TRIP_UNIT(Microseconds, -kRange, kRange);
+  ROUND_TRIP_UNIT(Microseconds, kint64max - kRange, kint64max);
+
+  ROUND_TRIP_UNIT(Milliseconds, kint64min, kint64min + kRange);
+  ROUND_TRIP_UNIT(Milliseconds, -kRange, kRange);
+  ROUND_TRIP_UNIT(Milliseconds, kint64max - kRange, kint64max);
+
+  ROUND_TRIP_UNIT(Seconds, kint64min, kint64min + kRange);
+  ROUND_TRIP_UNIT(Seconds, -kRange, kRange);
+  ROUND_TRIP_UNIT(Seconds, kint64max - kRange, kint64max);
+
+  ROUND_TRIP_UNIT(Minutes, kint64min / 60, kint64min / 60 + kRange);
+  ROUND_TRIP_UNIT(Minutes, -kRange, kRange);
+  ROUND_TRIP_UNIT(Minutes, kint64max / 60 - kRange, kint64max / 60);
+
+  ROUND_TRIP_UNIT(Hours, kint64min / 3600, kint64min / 3600 + kRange);
+  ROUND_TRIP_UNIT(Hours, -kRange, kRange);
+  ROUND_TRIP_UNIT(Hours, kint64max / 3600 - kRange, kint64max / 3600);
+
+#undef ROUND_TRIP_UNIT
+}
+
+TEST(Duration, TruncConversions) {
+  // Tests ToTimespec()/DurationFromTimespec()
+  const struct {
+    absl::Duration d;
+    timespec ts;
+  } to_ts[] = {
+      {absl::Seconds(1) + absl::Nanoseconds(1), {1, 1}},
+      {absl::Seconds(1) + absl::Nanoseconds(1) / 2, {1, 0}},
+      {absl::Seconds(1) + absl::Nanoseconds(0), {1, 0}},
+      {absl::Seconds(0) + absl::Nanoseconds(0), {0, 0}},
+      {absl::Seconds(0) - absl::Nanoseconds(1) / 2, {0, 0}},
+      {absl::Seconds(0) - absl::Nanoseconds(1), {-1, 999999999}},
+      {absl::Seconds(-1) + absl::Nanoseconds(1), {-1, 1}},
+      {absl::Seconds(-1) + absl::Nanoseconds(1) / 2, {-1, 1}},
+      {absl::Seconds(-1) + absl::Nanoseconds(0), {-1, 0}},
+      {absl::Seconds(-1) - absl::Nanoseconds(1) / 2, {-1, 0}},
+  };
+  for (const auto& test : to_ts) {
+    EXPECT_THAT(absl::ToTimespec(test.d), TimespecMatcher(test.ts));
+  }
+  const struct {
+    timespec ts;
+    absl::Duration d;
+  } from_ts[] = {
+      {{1, 1}, absl::Seconds(1) + absl::Nanoseconds(1)},
+      {{1, 0}, absl::Seconds(1) + absl::Nanoseconds(0)},
+      {{0, 0}, absl::Seconds(0) + absl::Nanoseconds(0)},
+      {{0, -1}, absl::Seconds(0) - absl::Nanoseconds(1)},
+      {{-1, 999999999}, absl::Seconds(0) - absl::Nanoseconds(1)},
+      {{-1, 1}, absl::Seconds(-1) + absl::Nanoseconds(1)},
+      {{-1, 0}, absl::Seconds(-1) + absl::Nanoseconds(0)},
+      {{-1, -1}, absl::Seconds(-1) - absl::Nanoseconds(1)},
+      {{-2, 999999999}, absl::Seconds(-1) - absl::Nanoseconds(1)},
+  };
+  for (const auto& test : from_ts) {
+    EXPECT_EQ(test.d, absl::DurationFromTimespec(test.ts));
+  }
+
+  // Tests ToTimeval()/DurationFromTimeval() (same as timespec above)
+  const struct {
+    absl::Duration d;
+    timeval tv;
+  } to_tv[] = {
+      {absl::Seconds(1) + absl::Microseconds(1), {1, 1}},
+      {absl::Seconds(1) + absl::Microseconds(1) / 2, {1, 0}},
+      {absl::Seconds(1) + absl::Microseconds(0), {1, 0}},
+      {absl::Seconds(0) + absl::Microseconds(0), {0, 0}},
+      {absl::Seconds(0) - absl::Microseconds(1) / 2, {0, 0}},
+      {absl::Seconds(0) - absl::Microseconds(1), {-1, 999999}},
+      {absl::Seconds(-1) + absl::Microseconds(1), {-1, 1}},
+      {absl::Seconds(-1) + absl::Microseconds(1) / 2, {-1, 1}},
+      {absl::Seconds(-1) + absl::Microseconds(0), {-1, 0}},
+      {absl::Seconds(-1) - absl::Microseconds(1) / 2, {-1, 0}},
+  };
+  for (const auto& test : to_tv) {
+    EXPECT_THAT(absl::ToTimeval(test.d), TimevalMatcher(test.tv));
+  }
+  const struct {
+    timeval tv;
+    absl::Duration d;
+  } from_tv[] = {
+      {{1, 1}, absl::Seconds(1) + absl::Microseconds(1)},
+      {{1, 0}, absl::Seconds(1) + absl::Microseconds(0)},
+      {{0, 0}, absl::Seconds(0) + absl::Microseconds(0)},
+      {{0, -1}, absl::Seconds(0) - absl::Microseconds(1)},
+      {{-1, 999999}, absl::Seconds(0) - absl::Microseconds(1)},
+      {{-1, 1}, absl::Seconds(-1) + absl::Microseconds(1)},
+      {{-1, 0}, absl::Seconds(-1) + absl::Microseconds(0)},
+      {{-1, -1}, absl::Seconds(-1) - absl::Microseconds(1)},
+      {{-2, 999999}, absl::Seconds(-1) - absl::Microseconds(1)},
+  };
+  for (const auto& test : from_tv) {
+    EXPECT_EQ(test.d, absl::DurationFromTimeval(test.tv));
+  }
+}
+
+TEST(Duration, SmallConversions) {
+  // Special tests for conversions of small durations.
+
+  EXPECT_EQ(absl::ZeroDuration(), absl::Seconds(0));
+  // TODO(bww): Is the next one OK?
+  EXPECT_EQ(absl::ZeroDuration(), absl::Seconds(std::nextafter(0.125e-9, 0)));
+  EXPECT_EQ(absl::Nanoseconds(1) / 4, absl::Seconds(0.125e-9));
+  EXPECT_EQ(absl::Nanoseconds(1) / 4, absl::Seconds(0.250e-9));
+  EXPECT_EQ(absl::Nanoseconds(1) / 2, absl::Seconds(0.375e-9));
+  EXPECT_EQ(absl::Nanoseconds(1) / 2, absl::Seconds(0.500e-9));
+  EXPECT_EQ(absl::Nanoseconds(3) / 4, absl::Seconds(0.625e-9));
+  EXPECT_EQ(absl::Nanoseconds(3) / 4, absl::Seconds(0.750e-9));
+  EXPECT_EQ(absl::Nanoseconds(1), absl::Seconds(0.875e-9));
+  EXPECT_EQ(absl::Nanoseconds(1), absl::Seconds(1.000e-9));
+
+  EXPECT_EQ(absl::ZeroDuration(), absl::Seconds(std::nextafter(-0.125e-9, 0)));
+  EXPECT_EQ(-absl::Nanoseconds(1) / 4, absl::Seconds(-0.125e-9));
+  EXPECT_EQ(-absl::Nanoseconds(1) / 4, absl::Seconds(-0.250e-9));
+  EXPECT_EQ(-absl::Nanoseconds(1) / 2, absl::Seconds(-0.375e-9));
+  EXPECT_EQ(-absl::Nanoseconds(1) / 2, absl::Seconds(-0.500e-9));
+  EXPECT_EQ(-absl::Nanoseconds(3) / 4, absl::Seconds(-0.625e-9));
+  EXPECT_EQ(-absl::Nanoseconds(3) / 4, absl::Seconds(-0.750e-9));
+  EXPECT_EQ(-absl::Nanoseconds(1), absl::Seconds(-0.875e-9));
+  EXPECT_EQ(-absl::Nanoseconds(1), absl::Seconds(-1.000e-9));
+
+  timespec ts;
+  ts.tv_sec = 0;
+  ts.tv_nsec = 0;
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(0)), TimespecMatcher(ts));
+  // TODO(bww): Are the next three OK?
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(1) / 4), TimespecMatcher(ts));
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(2) / 4), TimespecMatcher(ts));
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(3) / 4), TimespecMatcher(ts));
+  ts.tv_nsec = 1;
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(4) / 4), TimespecMatcher(ts));
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(5) / 4), TimespecMatcher(ts));
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(6) / 4), TimespecMatcher(ts));
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(7) / 4), TimespecMatcher(ts));
+  ts.tv_nsec = 2;
+  EXPECT_THAT(ToTimespec(absl::Nanoseconds(8) / 4), TimespecMatcher(ts));
+
+  timeval tv;
+  tv.tv_sec = 0;
+  tv.tv_usec = 0;
+  EXPECT_THAT(ToTimeval(absl::Nanoseconds(0)), TimevalMatcher(tv));
+  // TODO(bww): Is the next one OK?
+  EXPECT_THAT(ToTimeval(absl::Nanoseconds(999)), TimevalMatcher(tv));
+  tv.tv_usec = 1;
+  EXPECT_THAT(ToTimeval(absl::Nanoseconds(1000)), TimevalMatcher(tv));
+  EXPECT_THAT(ToTimeval(absl::Nanoseconds(1999)), TimevalMatcher(tv));
+  tv.tv_usec = 2;
+  EXPECT_THAT(ToTimeval(absl::Nanoseconds(2000)), TimevalMatcher(tv));
+}
+
+void VerifyApproxSameAsMul(double time_as_seconds, int* const misses) {
+  auto direct_seconds = absl::Seconds(time_as_seconds);
+  auto mul_by_one_second = time_as_seconds * absl::Seconds(1);
+  // These are expected to differ by up to one tick due to fused multiply/add
+  // contraction.
+  if (absl::AbsDuration(direct_seconds - mul_by_one_second) >
+      absl::time_internal::MakeDuration(0, 1u)) {
+    if (*misses > 10) return;
+    ASSERT_LE(++(*misses), 10) << "Too many errors, not reporting more.";
+    EXPECT_EQ(direct_seconds, mul_by_one_second)
+        << "given double time_as_seconds = " << std::setprecision(17)
+        << time_as_seconds;
+  }
+}
+
+// For a variety of interesting durations, we find the exact point
+// where one double converts to that duration, and the very next double
+// converts to the next duration.  For both of those points, verify that
+// Seconds(point) returns a duration near point * Seconds(1.0). (They may
+// not be exactly equal due to fused multiply/add contraction.)
+TEST(Duration, ToDoubleSecondsCheckEdgeCases) {
+#if (defined(__i386__) || defined(_M_IX86)) && FLT_EVAL_METHOD != 0
+  // We're using an x87-compatible FPU, and intermediate operations can be
+  // performed with 80-bit floats. This means the edge cases are different than
+  // what we expect here, so just skip this test.
+  GTEST_SKIP()
+      << "Skipping the test because we detected x87 floating-point semantics";
+#endif
+
+  constexpr uint32_t kTicksPerSecond = absl::time_internal::kTicksPerSecond;
+  constexpr auto duration_tick = absl::time_internal::MakeDuration(0, 1u);
+  int misses = 0;
+  for (int64_t seconds = 0; seconds < 99; ++seconds) {
+    uint32_t tick_vals[] = {0, +999, +999999, +999999999, kTicksPerSecond - 1,
+                            0, 1000, 1000000, 1000000000, kTicksPerSecond,
+                            1, 1001, 1000001, 1000000001, kTicksPerSecond + 1,
+                            2, 1002, 1000002, 1000000002, kTicksPerSecond + 2,
+                            3, 1003, 1000003, 1000000003, kTicksPerSecond + 3,
+                            4, 1004, 1000004, 1000000004, kTicksPerSecond + 4,
+                            5, 6,    7,       8,          9};
+    for (uint32_t ticks : tick_vals) {
+      absl::Duration s_plus_t = absl::Seconds(seconds) + ticks * duration_tick;
+      for (absl::Duration d : {s_plus_t, -s_plus_t}) {
+        absl::Duration after_d = d + duration_tick;
+        EXPECT_NE(d, after_d);
+        EXPECT_EQ(after_d - d, duration_tick);
+
+        double low_edge = ToDoubleSeconds(d);
+        EXPECT_EQ(d, absl::Seconds(low_edge));
+
+        double high_edge = ToDoubleSeconds(after_d);
+        EXPECT_EQ(after_d, absl::Seconds(high_edge));
+
+        for (;;) {
+          double midpoint = low_edge + (high_edge - low_edge) / 2;
+          if (midpoint == low_edge || midpoint == high_edge) break;
+          absl::Duration mid_duration = absl::Seconds(midpoint);
+          if (mid_duration == d) {
+            low_edge = midpoint;
+          } else {
+            EXPECT_EQ(mid_duration, after_d);
+            high_edge = midpoint;
+          }
+        }
+        // Now low_edge is the highest double that converts to Duration d,
+        // and high_edge is the lowest double that converts to Duration after_d.
+        VerifyApproxSameAsMul(low_edge, &misses);
+        VerifyApproxSameAsMul(high_edge, &misses);
+      }
+    }
+  }
+}
+
+TEST(Duration, ToDoubleSecondsCheckRandom) {
+  std::random_device rd;
+  std::seed_seq seed({rd(), rd(), rd(), rd(), rd(), rd(), rd(), rd()});
+  std::mt19937_64 gen(seed);
+  // We want doubles distributed from 1/8ns up to 2^63, where
+  // as many values are tested from 1ns to 2ns as from 1sec to 2sec,
+  // so even distribute along a log-scale of those values, and
+  // exponentiate before using them.  (9.223377e+18 is just slightly
+  // out of bounds for absl::Duration.)
+  std::uniform_real_distribution<double> uniform(std::log(0.125e-9),
+                                                 std::log(9.223377e+18));
+  int misses = 0;
+  for (int i = 0; i < 1000000; ++i) {
+    double d = std::exp(uniform(gen));
+    VerifyApproxSameAsMul(d, &misses);
+    VerifyApproxSameAsMul(-d, &misses);
+  }
+}
+
+TEST(Duration, ConversionSaturation) {
+  absl::Duration d;
+
+  const auto max_timeval_sec =
+      std::numeric_limits<decltype(timeval::tv_sec)>::max();
+  const auto min_timeval_sec =
+      std::numeric_limits<decltype(timeval::tv_sec)>::min();
+  timeval tv;
+  tv.tv_sec = max_timeval_sec;
+  tv.tv_usec = 999998;
+  d = absl::DurationFromTimeval(tv);
+  tv = ToTimeval(d);
+  EXPECT_EQ(max_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(999998, tv.tv_usec);
+  d += absl::Microseconds(1);
+  tv = ToTimeval(d);
+  EXPECT_EQ(max_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(999999, tv.tv_usec);
+  d += absl::Microseconds(1);  // no effect
+  tv = ToTimeval(d);
+  EXPECT_EQ(max_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(999999, tv.tv_usec);
+
+  tv.tv_sec = min_timeval_sec;
+  tv.tv_usec = 1;
+  d = absl::DurationFromTimeval(tv);
+  tv = ToTimeval(d);
+  EXPECT_EQ(min_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(1, tv.tv_usec);
+  d -= absl::Microseconds(1);
+  tv = ToTimeval(d);
+  EXPECT_EQ(min_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(0, tv.tv_usec);
+  d -= absl::Microseconds(1);  // no effect
+  tv = ToTimeval(d);
+  EXPECT_EQ(min_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(0, tv.tv_usec);
+
+  const auto max_timespec_sec =
+      std::numeric_limits<decltype(timespec::tv_sec)>::max();
+  const auto min_timespec_sec =
+      std::numeric_limits<decltype(timespec::tv_sec)>::min();
+  timespec ts;
+  ts.tv_sec = max_timespec_sec;
+  ts.tv_nsec = 999999998;
+  d = absl::DurationFromTimespec(ts);
+  ts = absl::ToTimespec(d);
+  EXPECT_EQ(max_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(999999998, ts.tv_nsec);
+  d += absl::Nanoseconds(1);
+  ts = absl::ToTimespec(d);
+  EXPECT_EQ(max_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(999999999, ts.tv_nsec);
+  d += absl::Nanoseconds(1);  // no effect
+  ts = absl::ToTimespec(d);
+  EXPECT_EQ(max_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(999999999, ts.tv_nsec);
+
+  ts.tv_sec = min_timespec_sec;
+  ts.tv_nsec = 1;
+  d = absl::DurationFromTimespec(ts);
+  ts = absl::ToTimespec(d);
+  EXPECT_EQ(min_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(1, ts.tv_nsec);
+  d -= absl::Nanoseconds(1);
+  ts = absl::ToTimespec(d);
+  EXPECT_EQ(min_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(0, ts.tv_nsec);
+  d -= absl::Nanoseconds(1);  // no effect
+  ts = absl::ToTimespec(d);
+  EXPECT_EQ(min_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(0, ts.tv_nsec);
+}
+
+TEST(Duration, FormatDuration) {
+  // Example from Go's docs.
+  EXPECT_EQ("72h3m0.5s",
+            absl::FormatDuration(absl::Hours(72) + absl::Minutes(3) +
+                                 absl::Milliseconds(500)));
+  // Go's largest time: 2540400h10m10.000000000s
+  EXPECT_EQ("2540400h10m10s",
+            absl::FormatDuration(absl::Hours(2540400) + absl::Minutes(10) +
+                                 absl::Seconds(10)));
+
+  EXPECT_EQ("0", absl::FormatDuration(absl::ZeroDuration()));
+  EXPECT_EQ("0", absl::FormatDuration(absl::Seconds(0)));
+  EXPECT_EQ("0", absl::FormatDuration(absl::Nanoseconds(0)));
+
+  EXPECT_EQ("1ns", absl::FormatDuration(absl::Nanoseconds(1)));
+  EXPECT_EQ("1us", absl::FormatDuration(absl::Microseconds(1)));
+  EXPECT_EQ("1ms", absl::FormatDuration(absl::Milliseconds(1)));
+  EXPECT_EQ("1s", absl::FormatDuration(absl::Seconds(1)));
+  EXPECT_EQ("1m", absl::FormatDuration(absl::Minutes(1)));
+  EXPECT_EQ("1h", absl::FormatDuration(absl::Hours(1)));
+
+  EXPECT_EQ("1h1m", absl::FormatDuration(absl::Hours(1) + absl::Minutes(1)));
+  EXPECT_EQ("1h1s", absl::FormatDuration(absl::Hours(1) + absl::Seconds(1)));
+  EXPECT_EQ("1m1s", absl::FormatDuration(absl::Minutes(1) + absl::Seconds(1)));
+
+  EXPECT_EQ("1h0.25s",
+            absl::FormatDuration(absl::Hours(1) + absl::Milliseconds(250)));
+  EXPECT_EQ("1m0.25s",
+            absl::FormatDuration(absl::Minutes(1) + absl::Milliseconds(250)));
+  EXPECT_EQ("1h1m0.25s",
+            absl::FormatDuration(absl::Hours(1) + absl::Minutes(1) +
+                                 absl::Milliseconds(250)));
+  EXPECT_EQ("1h0.0005s",
+            absl::FormatDuration(absl::Hours(1) + absl::Microseconds(500)));
+  EXPECT_EQ("1h0.0000005s",
+            absl::FormatDuration(absl::Hours(1) + absl::Nanoseconds(500)));
+
+  // Subsecond special case.
+  EXPECT_EQ("1.5ns", absl::FormatDuration(absl::Nanoseconds(1) +
+                                          absl::Nanoseconds(1) / 2));
+  EXPECT_EQ("1.25ns", absl::FormatDuration(absl::Nanoseconds(1) +
+                                           absl::Nanoseconds(1) / 4));
+  EXPECT_EQ("1ns", absl::FormatDuration(absl::Nanoseconds(1) +
+                                        absl::Nanoseconds(1) / 9));
+  EXPECT_EQ("1.2us", absl::FormatDuration(absl::Microseconds(1) +
+                                          absl::Nanoseconds(200)));
+  EXPECT_EQ("1.2ms", absl::FormatDuration(absl::Milliseconds(1) +
+                                          absl::Microseconds(200)));
+  EXPECT_EQ("1.0002ms", absl::FormatDuration(absl::Milliseconds(1) +
+                                             absl::Nanoseconds(200)));
+  EXPECT_EQ("1.00001ms", absl::FormatDuration(absl::Milliseconds(1) +
+                                              absl::Nanoseconds(10)));
+  EXPECT_EQ("1.000001ms",
+            absl::FormatDuration(absl::Milliseconds(1) + absl::Nanoseconds(1)));
+
+  // Negative durations.
+  EXPECT_EQ("-1ns", absl::FormatDuration(absl::Nanoseconds(-1)));
+  EXPECT_EQ("-1us", absl::FormatDuration(absl::Microseconds(-1)));
+  EXPECT_EQ("-1ms", absl::FormatDuration(absl::Milliseconds(-1)));
+  EXPECT_EQ("-1s", absl::FormatDuration(absl::Seconds(-1)));
+  EXPECT_EQ("-1m", absl::FormatDuration(absl::Minutes(-1)));
+  EXPECT_EQ("-1h", absl::FormatDuration(absl::Hours(-1)));
+
+  EXPECT_EQ("-1h1m",
+            absl::FormatDuration(-(absl::Hours(1) + absl::Minutes(1))));
+  EXPECT_EQ("-1h1s",
+            absl::FormatDuration(-(absl::Hours(1) + absl::Seconds(1))));
+  EXPECT_EQ("-1m1s",
+            absl::FormatDuration(-(absl::Minutes(1) + absl::Seconds(1))));
+
+  EXPECT_EQ("-1ns", absl::FormatDuration(absl::Nanoseconds(-1)));
+  EXPECT_EQ("-1.2us", absl::FormatDuration(
+                          -(absl::Microseconds(1) + absl::Nanoseconds(200))));
+  EXPECT_EQ("-1.2ms", absl::FormatDuration(
+                          -(absl::Milliseconds(1) + absl::Microseconds(200))));
+  EXPECT_EQ("-1.0002ms", absl::FormatDuration(-(absl::Milliseconds(1) +
+                                                absl::Nanoseconds(200))));
+  EXPECT_EQ("-1.00001ms", absl::FormatDuration(-(absl::Milliseconds(1) +
+                                                 absl::Nanoseconds(10))));
+  EXPECT_EQ("-1.000001ms", absl::FormatDuration(-(absl::Milliseconds(1) +
+                                                  absl::Nanoseconds(1))));
+
+  //
+  // Interesting corner cases.
+  //
+
+  const absl::Duration qns = absl::Nanoseconds(1) / 4;
+  const absl::Duration max_dur =
+      absl::Seconds(kint64max) + (absl::Seconds(1) - qns);
+  const absl::Duration min_dur = absl::Seconds(kint64min);
+
+  EXPECT_EQ("0.25ns", absl::FormatDuration(qns));
+  EXPECT_EQ("-0.25ns", absl::FormatDuration(-qns));
+  EXPECT_EQ("2562047788015215h30m7.99999999975s",
+            absl::FormatDuration(max_dur));
+  EXPECT_EQ("-2562047788015215h30m8s", absl::FormatDuration(min_dur));
+
+  // Tests printing full precision from units that print using FDivDuration
+  EXPECT_EQ("55.00000000025s", absl::FormatDuration(absl::Seconds(55) + qns));
+  EXPECT_EQ("55.00000025ms",
+            absl::FormatDuration(absl::Milliseconds(55) + qns));
+  EXPECT_EQ("55.00025us", absl::FormatDuration(absl::Microseconds(55) + qns));
+  EXPECT_EQ("55.25ns", absl::FormatDuration(absl::Nanoseconds(55) + qns));
+
+  // Formatting infinity
+  EXPECT_EQ("inf", absl::FormatDuration(absl::InfiniteDuration()));
+  EXPECT_EQ("-inf", absl::FormatDuration(-absl::InfiniteDuration()));
+
+  // Formatting approximately +/- 100 billion years
+  const absl::Duration huge_range = ApproxYears(100000000000);
+  EXPECT_EQ("876000000000000h", absl::FormatDuration(huge_range));
+  EXPECT_EQ("-876000000000000h", absl::FormatDuration(-huge_range));
+
+  EXPECT_EQ("876000000000000h0.999999999s",
+            absl::FormatDuration(huge_range +
+                                 (absl::Seconds(1) - absl::Nanoseconds(1))));
+  EXPECT_EQ("876000000000000h0.9999999995s",
+            absl::FormatDuration(
+                huge_range + (absl::Seconds(1) - absl::Nanoseconds(1) / 2)));
+  EXPECT_EQ("876000000000000h0.99999999975s",
+            absl::FormatDuration(
+                huge_range + (absl::Seconds(1) - absl::Nanoseconds(1) / 4)));
+
+  EXPECT_EQ("-876000000000000h0.999999999s",
+            absl::FormatDuration(-huge_range -
+                                 (absl::Seconds(1) - absl::Nanoseconds(1))));
+  EXPECT_EQ("-876000000000000h0.9999999995s",
+            absl::FormatDuration(
+                -huge_range - (absl::Seconds(1) - absl::Nanoseconds(1) / 2)));
+  EXPECT_EQ("-876000000000000h0.99999999975s",
+            absl::FormatDuration(
+                -huge_range - (absl::Seconds(1) - absl::Nanoseconds(1) / 4)));
+}
+
+TEST(Duration, ParseDuration) {
+  absl::Duration d;
+
+  // No specified unit. Should only work for zero and infinity.
+  EXPECT_TRUE(absl::ParseDuration("0", &d));
+  EXPECT_EQ(absl::ZeroDuration(), d);
+  EXPECT_TRUE(absl::ParseDuration("+0", &d));
+  EXPECT_EQ(absl::ZeroDuration(), d);
+  EXPECT_TRUE(absl::ParseDuration("-0", &d));
+  EXPECT_EQ(absl::ZeroDuration(), d);
+
+  EXPECT_TRUE(absl::ParseDuration("inf", &d));
+  EXPECT_EQ(absl::InfiniteDuration(), d);
+  EXPECT_TRUE(absl::ParseDuration("+inf", &d));
+  EXPECT_EQ(absl::InfiniteDuration(), d);
+  EXPECT_TRUE(absl::ParseDuration("-inf", &d));
+  EXPECT_EQ(-absl::InfiniteDuration(), d);
+  EXPECT_FALSE(absl::ParseDuration("infBlah", &d));
+
+  // Illegal input forms.
+  EXPECT_FALSE(absl::ParseDuration("", &d));
+  EXPECT_FALSE(absl::ParseDuration("0.0", &d));
+  EXPECT_FALSE(absl::ParseDuration(".0", &d));
+  EXPECT_FALSE(absl::ParseDuration(".", &d));
+  EXPECT_FALSE(absl::ParseDuration("01", &d));
+  EXPECT_FALSE(absl::ParseDuration("1", &d));
+  EXPECT_FALSE(absl::ParseDuration("-1", &d));
+  EXPECT_FALSE(absl::ParseDuration("2", &d));
+  EXPECT_FALSE(absl::ParseDuration("2 s", &d));
+  EXPECT_FALSE(absl::ParseDuration(".s", &d));
+  EXPECT_FALSE(absl::ParseDuration("-.s", &d));
+  EXPECT_FALSE(absl::ParseDuration("s", &d));
+  EXPECT_FALSE(absl::ParseDuration(" 2s", &d));
+  EXPECT_FALSE(absl::ParseDuration("2s ", &d));
+  EXPECT_FALSE(absl::ParseDuration(" 2s ", &d));
+  EXPECT_FALSE(absl::ParseDuration("2mt", &d));
+  EXPECT_FALSE(absl::ParseDuration("1e3s", &d));
+
+  // One unit type.
+  EXPECT_TRUE(absl::ParseDuration("1ns", &d));
+  EXPECT_EQ(absl::Nanoseconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1us", &d));
+  EXPECT_EQ(absl::Microseconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1ms", &d));
+  EXPECT_EQ(absl::Milliseconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1s", &d));
+  EXPECT_EQ(absl::Seconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("2m", &d));
+  EXPECT_EQ(absl::Minutes(2), d);
+  EXPECT_TRUE(absl::ParseDuration("2h", &d));
+  EXPECT_EQ(absl::Hours(2), d);
+
+  // Huge counts of a unit.
+  EXPECT_TRUE(absl::ParseDuration("9223372036854775807us", &d));
+  EXPECT_EQ(absl::Microseconds(9223372036854775807), d);
+  EXPECT_TRUE(absl::ParseDuration("-9223372036854775807us", &d));
+  EXPECT_EQ(absl::Microseconds(-9223372036854775807), d);
+
+  // Multiple units.
+  EXPECT_TRUE(absl::ParseDuration("2h3m4s", &d));
+  EXPECT_EQ(absl::Hours(2) + absl::Minutes(3) + absl::Seconds(4), d);
+  EXPECT_TRUE(absl::ParseDuration("3m4s5us", &d));
+  EXPECT_EQ(absl::Minutes(3) + absl::Seconds(4) + absl::Microseconds(5), d);
+  EXPECT_TRUE(absl::ParseDuration("2h3m4s5ms6us7ns", &d));
+  EXPECT_EQ(absl::Hours(2) + absl::Minutes(3) + absl::Seconds(4) +
+                absl::Milliseconds(5) + absl::Microseconds(6) +
+                absl::Nanoseconds(7),
+            d);
+
+  // Multiple units out of order.
+  EXPECT_TRUE(absl::ParseDuration("2us3m4s5h", &d));
+  EXPECT_EQ(absl::Hours(5) + absl::Minutes(3) + absl::Seconds(4) +
+                absl::Microseconds(2),
+            d);
+
+  // Fractional values of units.
+  EXPECT_TRUE(absl::ParseDuration("1.5ns", &d));
+  EXPECT_EQ(1.5 * absl::Nanoseconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1.5us", &d));
+  EXPECT_EQ(1.5 * absl::Microseconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1.5ms", &d));
+  EXPECT_EQ(1.5 * absl::Milliseconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1.5s", &d));
+  EXPECT_EQ(1.5 * absl::Seconds(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1.5m", &d));
+  EXPECT_EQ(1.5 * absl::Minutes(1), d);
+  EXPECT_TRUE(absl::ParseDuration("1.5h", &d));
+  EXPECT_EQ(1.5 * absl::Hours(1), d);
+
+  // Huge fractional counts of a unit.
+  EXPECT_TRUE(absl::ParseDuration("0.4294967295s", &d));
+  EXPECT_EQ(absl::Nanoseconds(429496729) + absl::Nanoseconds(1) / 2, d);
+  EXPECT_TRUE(absl::ParseDuration("0.429496729501234567890123456789s", &d));
+  EXPECT_EQ(absl::Nanoseconds(429496729) + absl::Nanoseconds(1) / 2, d);
+
+  // Negative durations.
+  EXPECT_TRUE(absl::ParseDuration("-1s", &d));
+  EXPECT_EQ(absl::Seconds(-1), d);
+  EXPECT_TRUE(absl::ParseDuration("-1m", &d));
+  EXPECT_EQ(absl::Minutes(-1), d);
+  EXPECT_TRUE(absl::ParseDuration("-1h", &d));
+  EXPECT_EQ(absl::Hours(-1), d);
+
+  EXPECT_TRUE(absl::ParseDuration("-1h2s", &d));
+  EXPECT_EQ(-(absl::Hours(1) + absl::Seconds(2)), d);
+  EXPECT_FALSE(absl::ParseDuration("1h-2s", &d));
+  EXPECT_FALSE(absl::ParseDuration("-1h-2s", &d));
+  EXPECT_FALSE(absl::ParseDuration("-1h -2s", &d));
+}
+
+TEST(Duration, FormatParseRoundTrip) {
+#define TEST_PARSE_ROUNDTRIP(d)                \
+  do {                                         \
+    std::string s = absl::FormatDuration(d);   \
+    absl::Duration dur;                        \
+    EXPECT_TRUE(absl::ParseDuration(s, &dur)); \
+    EXPECT_EQ(d, dur);                         \
+  } while (0)
+
+  TEST_PARSE_ROUNDTRIP(absl::Nanoseconds(1));
+  TEST_PARSE_ROUNDTRIP(absl::Microseconds(1));
+  TEST_PARSE_ROUNDTRIP(absl::Milliseconds(1));
+  TEST_PARSE_ROUNDTRIP(absl::Seconds(1));
+  TEST_PARSE_ROUNDTRIP(absl::Minutes(1));
+  TEST_PARSE_ROUNDTRIP(absl::Hours(1));
+  TEST_PARSE_ROUNDTRIP(absl::Hours(1) + absl::Nanoseconds(2));
+
+  TEST_PARSE_ROUNDTRIP(absl::Nanoseconds(-1));
+  TEST_PARSE_ROUNDTRIP(absl::Microseconds(-1));
+  TEST_PARSE_ROUNDTRIP(absl::Milliseconds(-1));
+  TEST_PARSE_ROUNDTRIP(absl::Seconds(-1));
+  TEST_PARSE_ROUNDTRIP(absl::Minutes(-1));
+  TEST_PARSE_ROUNDTRIP(absl::Hours(-1));
+
+  TEST_PARSE_ROUNDTRIP(absl::Hours(-1) + absl::Nanoseconds(2));
+  TEST_PARSE_ROUNDTRIP(absl::Hours(1) + absl::Nanoseconds(-2));
+  TEST_PARSE_ROUNDTRIP(absl::Hours(-1) + absl::Nanoseconds(-2));
+
+  TEST_PARSE_ROUNDTRIP(absl::Nanoseconds(1) +
+                       absl::Nanoseconds(1) / 4);  // 1.25ns
+
+  const absl::Duration huge_range = ApproxYears(100000000000);
+  TEST_PARSE_ROUNDTRIP(huge_range);
+  TEST_PARSE_ROUNDTRIP(huge_range + (absl::Seconds(1) - absl::Nanoseconds(1)));
+
+#undef TEST_PARSE_ROUNDTRIP
+}
+
+TEST(Duration, AbslStringify) {
+  // FormatDuration is already well tested, so just use one test case here to
+  // verify that StrFormat("%v", d) works as expected.
+  absl::Duration d = absl::Seconds(1);
+  EXPECT_EQ(absl::StrFormat("%v", d), absl::FormatDuration(d));
+}
+
+TEST(Duration, NoPadding) {
+  // Should match the size of a struct with uint32_t alignment and no padding.
+  using NoPadding = std::array<uint32_t, 3>;
+  EXPECT_EQ(sizeof(NoPadding), sizeof(absl::Duration));
+  EXPECT_EQ(alignof(NoPadding), alignof(absl::Duration));
+}
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/time/format_benchmark.cc b/weight/_dep/abseil-cpp/absl/time/format_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..19e481dbd1a5cc6ffec796fdd4686bb5c94dd346
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/format_benchmark.cc
@@ -0,0 +1,64 @@
+// Copyright 2018 The Abseil Authors.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstddef>
+#include <string>
+
+#include "absl/time/internal/test_util.h"
+#include "absl/time/time.h"
+#include "benchmark/benchmark.h"
+
+namespace {
+
+namespace {
+const char* const kFormats[] = {
+    absl::RFC1123_full,     // 0
+    absl::RFC1123_no_wday,  // 1
+    absl::RFC3339_full,     // 2
+    absl::RFC3339_sec,      // 3
+    "%Y-%m-%d%ET%H:%M:%S",  // 4
+    "%Y-%m-%d",             // 5
+};
+const int kNumFormats = sizeof(kFormats) / sizeof(kFormats[0]);
+}  // namespace
+
+void BM_Format_FormatTime(benchmark::State& state) {
+  const std::string fmt = kFormats[state.range(0)];
+  state.SetLabel(fmt);
+  const absl::TimeZone lax =
+      absl::time_internal::LoadTimeZone("America/Los_Angeles");
+  const absl::Time t =
+      absl::FromCivil(absl::CivilSecond(1977, 6, 28, 9, 8, 7), lax) +
+      absl::Nanoseconds(1);
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(absl::FormatTime(fmt, t, lax).length());
+  }
+}
+BENCHMARK(BM_Format_FormatTime)->DenseRange(0, kNumFormats - 1);
+
+void BM_Format_ParseTime(benchmark::State& state) {
+  const std::string fmt = kFormats[state.range(0)];
+  state.SetLabel(fmt);
+  const absl::TimeZone lax =
+      absl::time_internal::LoadTimeZone("America/Los_Angeles");
+  absl::Time t = absl::FromCivil(absl::CivilSecond(1977, 6, 28, 9, 8, 7), lax) +
+                 absl::Nanoseconds(1);
+  const std::string when = absl::FormatTime(fmt, t, lax);
+  std::string err;
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(absl::ParseTime(fmt, when, lax, &t, &err));
+  }
+}
+BENCHMARK(BM_Format_ParseTime)->DenseRange(0, kNumFormats - 1);
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/time/internal/cctz/BUILD.bazel b/weight/_dep/abseil-cpp/absl/time/internal/cctz/BUILD.bazel
new file mode 100644
index 0000000000000000000000000000000000000000..0b43bb128fc50f636304e649283f4b7a0bce54e7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/internal/cctz/BUILD.bazel
@@ -0,0 +1,167 @@
+# Copyright 2016 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+package(features = [
+    "header_modules",
+    "layering_check",
+    "parse_headers",
+])
+
+licenses(["notice"])
+
+### libraries
+
+cc_library(
+    name = "civil_time",
+    srcs = ["src/civil_time_detail.cc"],
+    hdrs = [
+        "include/cctz/civil_time.h",
+    ],
+    textual_hdrs = ["include/cctz/civil_time_detail.h"],
+    visibility = ["//visibility:public"],
+    deps = ["//absl/base:config"],
+)
+
+cc_library(
+    name = "time_zone",
+    srcs = [
+        "src/time_zone_fixed.cc",
+        "src/time_zone_fixed.h",
+        "src/time_zone_format.cc",
+        "src/time_zone_if.cc",
+        "src/time_zone_if.h",
+        "src/time_zone_impl.cc",
+        "src/time_zone_impl.h",
+        "src/time_zone_info.cc",
+        "src/time_zone_info.h",
+        "src/time_zone_libc.cc",
+        "src/time_zone_libc.h",
+        "src/time_zone_lookup.cc",
+        "src/time_zone_posix.cc",
+        "src/time_zone_posix.h",
+        "src/tzfile.h",
+        "src/zone_info_source.cc",
+    ],
+    hdrs = [
+        "include/cctz/time_zone.h",
+        "include/cctz/zone_info_source.h",
+    ],
+    linkopts = select({
+        "@platforms//os:osx": ["-Wl,-framework,CoreFoundation"],
+        "@platforms//os:ios": ["-Wl,-framework,CoreFoundation"],
+        "//conditions:default": [],
+    }),
+    visibility = ["//visibility:public"],
+    deps = [
+        ":civil_time",
+        "//absl/base:config",
+    ] + select(
+        {
+            "//conditions:default": [],
+        },
+    ),
+)
+
+### tests
+
+test_suite(
+    name = "all_tests",
+    visibility = ["//visibility:public"],
+)
+
+cc_test(
+    name = "civil_time_test",
+    size = "small",
+    srcs = ["src/civil_time_test.cc"],
+    deps = [
+        ":civil_time",
+        "//absl/base:config",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "time_zone_format_test",
+    size = "small",
+    srcs = ["src/time_zone_format_test.cc"],
+    data = [":zoneinfo"],
+    env = {"TZDIR": "absl/time/internal/cctz/testdata/zoneinfo"},
+    tags = [
+        "no_test_android_arm",
+        "no_test_android_arm64",
+        "no_test_android_x86",
+        "no_test_wasm",
+    ],
+    deps = [
+        ":civil_time",
+        ":time_zone",
+        "//absl/base:config",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "time_zone_lookup_test",
+    size = "small",
+    timeout = "moderate",
+    srcs = ["src/time_zone_lookup_test.cc"],
+    data = [":zoneinfo"],
+    env = {"TZDIR": "absl/time/internal/cctz/testdata/zoneinfo"},
+    tags = [
+        "no_test_android_arm",
+        "no_test_android_arm64",
+        "no_test_android_x86",
+        "no_test_wasm",
+    ],
+    deps = [
+        ":civil_time",
+        ":time_zone",
+        "//absl/base:config",
+        "@com_google_googletest//:gtest",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+### benchmarks
+
+cc_test(
+    name = "cctz_benchmark",
+    srcs = [
+        "src/cctz_benchmark.cc",
+        "src/time_zone_if.h",
+        "src/time_zone_impl.h",
+        "src/time_zone_info.h",
+        "src/tzfile.h",
+    ],
+    linkstatic = 1,
+    tags = ["benchmark"],
+    deps = [
+        ":civil_time",
+        ":time_zone",
+        "//absl/base:config",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
+
+filegroup(
+    name = "zoneinfo",
+    srcs = glob(["testdata/zoneinfo/**"]),
+    visibility = ["//absl/time:__subpackages__"],
+)
+
+### examples
+
+### binaries
diff --git a/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/cctz_benchmark.cc b/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/cctz_benchmark.cc
new file mode 100644
index 0000000000000000000000000000000000000000..11f9ba6c65ea63574cdc37be15cd8b21df59dec7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/cctz_benchmark.cc
@@ -0,0 +1,922 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+#include <algorithm>
+#include <cassert>
+#include <chrono>
+#include <ctime>
+#include <random>
+#include <string>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "absl/time/internal/cctz/include/cctz/civil_time.h"
+#include "absl/time/internal/cctz/include/cctz/time_zone.h"
+#include "time_zone_impl.h"
+
+namespace {
+
+namespace cctz = absl::time_internal::cctz;
+
+void BM_Difference_Days(benchmark::State& state) {
+  const cctz::civil_day c(2014, 8, 22);
+  const cctz::civil_day epoch(1970, 1, 1);
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(c - epoch);
+  }
+}
+BENCHMARK(BM_Difference_Days);
+
+void BM_Step_Days(benchmark::State& state) {
+  const cctz::civil_day kStart(2014, 8, 22);
+  cctz::civil_day c = kStart;
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(++c);
+  }
+}
+BENCHMARK(BM_Step_Days);
+
+void BM_GetWeekday(benchmark::State& state) {
+  const cctz::civil_day c(2014, 8, 22);
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::get_weekday(c));
+  }
+}
+BENCHMARK(BM_GetWeekday);
+
+void BM_NextWeekday(benchmark::State& state) {
+  const cctz::civil_day kStart(2014, 8, 22);
+  const cctz::civil_day kDays[7] = {
+      kStart + 0, kStart + 1, kStart + 2, kStart + 3,
+      kStart + 4, kStart + 5, kStart + 6,
+  };
+  const cctz::weekday kWeekdays[7] = {
+      cctz::weekday::monday,   cctz::weekday::tuesday, cctz::weekday::wednesday,
+      cctz::weekday::thursday, cctz::weekday::friday,  cctz::weekday::saturday,
+      cctz::weekday::sunday,
+  };
+  while (state.KeepRunningBatch(7 * 7)) {
+    for (const auto from : kDays) {
+      for (const auto to : kWeekdays) {
+        benchmark::DoNotOptimize(cctz::next_weekday(from, to));
+      }
+    }
+  }
+}
+BENCHMARK(BM_NextWeekday);
+
+void BM_PrevWeekday(benchmark::State& state) {
+  const cctz::civil_day kStart(2014, 8, 22);
+  const cctz::civil_day kDays[7] = {
+      kStart + 0, kStart + 1, kStart + 2, kStart + 3,
+      kStart + 4, kStart + 5, kStart + 6,
+  };
+  const cctz::weekday kWeekdays[7] = {
+      cctz::weekday::monday,   cctz::weekday::tuesday, cctz::weekday::wednesday,
+      cctz::weekday::thursday, cctz::weekday::friday,  cctz::weekday::saturday,
+      cctz::weekday::sunday,
+  };
+  while (state.KeepRunningBatch(7 * 7)) {
+    for (const auto from : kDays) {
+      for (const auto to : kWeekdays) {
+        benchmark::DoNotOptimize(cctz::prev_weekday(from, to));
+      }
+    }
+  }
+}
+BENCHMARK(BM_PrevWeekday);
+
+const char RFC3339_full[] = "%Y-%m-%d%ET%H:%M:%E*S%Ez";
+const char RFC3339_sec[] = "%Y-%m-%d%ET%H:%M:%S%Ez";
+
+const char RFC1123_full[] = "%a, %d %b %Y %H:%M:%S %z";
+const char RFC1123_no_wday[] = "%d %b %Y %H:%M:%S %z";
+
+// A list of known time-zone names.
+// TODO: Refactor with src/time_zone_lookup_test.cc.
+const char* const kTimeZoneNames[] = {"Africa/Abidjan",
+                                      "Africa/Accra",
+                                      "Africa/Addis_Ababa",
+                                      "Africa/Algiers",
+                                      "Africa/Asmara",
+                                      "Africa/Bamako",
+                                      "Africa/Bangui",
+                                      "Africa/Banjul",
+                                      "Africa/Bissau",
+                                      "Africa/Blantyre",
+                                      "Africa/Brazzaville",
+                                      "Africa/Bujumbura",
+                                      "Africa/Cairo",
+                                      "Africa/Casablanca",
+                                      "Africa/Ceuta",
+                                      "Africa/Conakry",
+                                      "Africa/Dakar",
+                                      "Africa/Dar_es_Salaam",
+                                      "Africa/Djibouti",
+                                      "Africa/Douala",
+                                      "Africa/El_Aaiun",
+                                      "Africa/Freetown",
+                                      "Africa/Gaborone",
+                                      "Africa/Harare",
+                                      "Africa/Johannesburg",
+                                      "Africa/Juba",
+                                      "Africa/Kampala",
+                                      "Africa/Khartoum",
+                                      "Africa/Kigali",
+                                      "Africa/Kinshasa",
+                                      "Africa/Lagos",
+                                      "Africa/Libreville",
+                                      "Africa/Lome",
+                                      "Africa/Luanda",
+                                      "Africa/Lubumbashi",
+                                      "Africa/Lusaka",
+                                      "Africa/Malabo",
+                                      "Africa/Maputo",
+                                      "Africa/Maseru",
+                                      "Africa/Mbabane",
+                                      "Africa/Mogadishu",
+                                      "Africa/Monrovia",
+                                      "Africa/Nairobi",
+                                      "Africa/Ndjamena",
+                                      "Africa/Niamey",
+                                      "Africa/Nouakchott",
+                                      "Africa/Ouagadougou",
+                                      "Africa/Porto-Novo",
+                                      "Africa/Sao_Tome",
+                                      "Africa/Timbuktu",
+                                      "Africa/Tripoli",
+                                      "Africa/Tunis",
+                                      "Africa/Windhoek",
+                                      "America/Adak",
+                                      "America/Anchorage",
+                                      "America/Anguilla",
+                                      "America/Antigua",
+                                      "America/Araguaina",
+                                      "America/Argentina/Buenos_Aires",
+                                      "America/Argentina/Catamarca",
+                                      "America/Argentina/Cordoba",
+                                      "America/Argentina/Jujuy",
+                                      "America/Argentina/La_Rioja",
+                                      "America/Argentina/Mendoza",
+                                      "America/Argentina/Rio_Gallegos",
+                                      "America/Argentina/Salta",
+                                      "America/Argentina/San_Juan",
+                                      "America/Argentina/San_Luis",
+                                      "America/Argentina/Tucuman",
+                                      "America/Argentina/Ushuaia",
+                                      "America/Aruba",
+                                      "America/Asuncion",
+                                      "America/Atikokan",
+                                      "America/Atka",
+                                      "America/Bahia",
+                                      "America/Bahia_Banderas",
+                                      "America/Barbados",
+                                      "America/Belem",
+                                      "America/Belize",
+                                      "America/Blanc-Sablon",
+                                      "America/Boa_Vista",
+                                      "America/Bogota",
+                                      "America/Boise",
+                                      "America/Cambridge_Bay",
+                                      "America/Campo_Grande",
+                                      "America/Cancun",
+                                      "America/Caracas",
+                                      "America/Cayenne",
+                                      "America/Cayman",
+                                      "America/Chicago",
+                                      "America/Chihuahua",
+                                      "America/Ciudad_Juarez",
+                                      "America/Coral_Harbour",
+                                      "America/Costa_Rica",
+                                      "America/Creston",
+                                      "America/Cuiaba",
+                                      "America/Curacao",
+                                      "America/Danmarkshavn",
+                                      "America/Dawson",
+                                      "America/Dawson_Creek",
+                                      "America/Denver",
+                                      "America/Detroit",
+                                      "America/Dominica",
+                                      "America/Edmonton",
+                                      "America/Eirunepe",
+                                      "America/El_Salvador",
+                                      "America/Ensenada",
+                                      "America/Fort_Nelson",
+                                      "America/Fortaleza",
+                                      "America/Glace_Bay",
+                                      "America/Godthab",
+                                      "America/Goose_Bay",
+                                      "America/Grand_Turk",
+                                      "America/Grenada",
+                                      "America/Guadeloupe",
+                                      "America/Guatemala",
+                                      "America/Guayaquil",
+                                      "America/Guyana",
+                                      "America/Halifax",
+                                      "America/Havana",
+                                      "America/Hermosillo",
+                                      "America/Indiana/Indianapolis",
+                                      "America/Indiana/Knox",
+                                      "America/Indiana/Marengo",
+                                      "America/Indiana/Petersburg",
+                                      "America/Indiana/Tell_City",
+                                      "America/Indiana/Vevay",
+                                      "America/Indiana/Vincennes",
+                                      "America/Indiana/Winamac",
+                                      "America/Inuvik",
+                                      "America/Iqaluit",
+                                      "America/Jamaica",
+                                      "America/Juneau",
+                                      "America/Kentucky/Louisville",
+                                      "America/Kentucky/Monticello",
+                                      "America/Kralendijk",
+                                      "America/La_Paz",
+                                      "America/Lima",
+                                      "America/Los_Angeles",
+                                      "America/Lower_Princes",
+                                      "America/Maceio",
+                                      "America/Managua",
+                                      "America/Manaus",
+                                      "America/Marigot",
+                                      "America/Martinique",
+                                      "America/Matamoros",
+                                      "America/Mazatlan",
+                                      "America/Menominee",
+                                      "America/Merida",
+                                      "America/Metlakatla",
+                                      "America/Mexico_City",
+                                      "America/Miquelon",
+                                      "America/Moncton",
+                                      "America/Monterrey",
+                                      "America/Montevideo",
+                                      "America/Montreal",
+                                      "America/Montserrat",
+                                      "America/Nassau",
+                                      "America/New_York",
+                                      "America/Nipigon",
+                                      "America/Nome",
+                                      "America/Noronha",
+                                      "America/North_Dakota/Beulah",
+                                      "America/North_Dakota/Center",
+                                      "America/North_Dakota/New_Salem",
+                                      "America/Nuuk",
+                                      "America/Ojinaga",
+                                      "America/Panama",
+                                      "America/Pangnirtung",
+                                      "America/Paramaribo",
+                                      "America/Phoenix",
+                                      "America/Port-au-Prince",
+                                      "America/Port_of_Spain",
+                                      "America/Porto_Acre",
+                                      "America/Porto_Velho",
+                                      "America/Puerto_Rico",
+                                      "America/Punta_Arenas",
+                                      "America/Rainy_River",
+                                      "America/Rankin_Inlet",
+                                      "America/Recife",
+                                      "America/Regina",
+                                      "America/Resolute",
+                                      "America/Rio_Branco",
+                                      "America/Santa_Isabel",
+                                      "America/Santarem",
+                                      "America/Santiago",
+                                      "America/Santo_Domingo",
+                                      "America/Sao_Paulo",
+                                      "America/Scoresbysund",
+                                      "America/Shiprock",
+                                      "America/Sitka",
+                                      "America/St_Barthelemy",
+                                      "America/St_Johns",
+                                      "America/St_Kitts",
+                                      "America/St_Lucia",
+                                      "America/St_Thomas",
+                                      "America/St_Vincent",
+                                      "America/Swift_Current",
+                                      "America/Tegucigalpa",
+                                      "America/Thule",
+                                      "America/Thunder_Bay",
+                                      "America/Tijuana",
+                                      "America/Toronto",
+                                      "America/Tortola",
+                                      "America/Vancouver",
+                                      "America/Virgin",
+                                      "America/Whitehorse",
+                                      "America/Winnipeg",
+                                      "America/Yakutat",
+                                      "America/Yellowknife",
+                                      "Antarctica/Casey",
+                                      "Antarctica/Davis",
+                                      "Antarctica/DumontDUrville",
+                                      "Antarctica/Macquarie",
+                                      "Antarctica/Mawson",
+                                      "Antarctica/McMurdo",
+                                      "Antarctica/Palmer",
+                                      "Antarctica/Rothera",
+                                      "Antarctica/Syowa",
+                                      "Antarctica/Troll",
+                                      "Antarctica/Vostok",
+                                      "Arctic/Longyearbyen",
+                                      "Asia/Aden",
+                                      "Asia/Almaty",
+                                      "Asia/Amman",
+                                      "Asia/Anadyr",
+                                      "Asia/Aqtau",
+                                      "Asia/Aqtobe",
+                                      "Asia/Ashgabat",
+                                      "Asia/Atyrau",
+                                      "Asia/Baghdad",
+                                      "Asia/Bahrain",
+                                      "Asia/Baku",
+                                      "Asia/Bangkok",
+                                      "Asia/Barnaul",
+                                      "Asia/Beirut",
+                                      "Asia/Bishkek",
+                                      "Asia/Brunei",
+                                      "Asia/Chita",
+                                      "Asia/Choibalsan",
+                                      "Asia/Chongqing",
+                                      "Asia/Colombo",
+                                      "Asia/Damascus",
+                                      "Asia/Dhaka",
+                                      "Asia/Dili",
+                                      "Asia/Dubai",
+                                      "Asia/Dushanbe",
+                                      "Asia/Famagusta",
+                                      "Asia/Gaza",
+                                      "Asia/Harbin",
+                                      "Asia/Hebron",
+                                      "Asia/Ho_Chi_Minh",
+                                      "Asia/Hong_Kong",
+                                      "Asia/Hovd",
+                                      "Asia/Irkutsk",
+                                      "Asia/Istanbul",
+                                      "Asia/Jakarta",
+                                      "Asia/Jayapura",
+                                      "Asia/Jerusalem",
+                                      "Asia/Kabul",
+                                      "Asia/Kamchatka",
+                                      "Asia/Karachi",
+                                      "Asia/Kashgar",
+                                      "Asia/Kathmandu",
+                                      "Asia/Khandyga",
+                                      "Asia/Kolkata",
+                                      "Asia/Krasnoyarsk",
+                                      "Asia/Kuala_Lumpur",
+                                      "Asia/Kuching",
+                                      "Asia/Kuwait",
+                                      "Asia/Macau",
+                                      "Asia/Magadan",
+                                      "Asia/Makassar",
+                                      "Asia/Manila",
+                                      "Asia/Muscat",
+                                      "Asia/Nicosia",
+                                      "Asia/Novokuznetsk",
+                                      "Asia/Novosibirsk",
+                                      "Asia/Omsk",
+                                      "Asia/Oral",
+                                      "Asia/Phnom_Penh",
+                                      "Asia/Pontianak",
+                                      "Asia/Pyongyang",
+                                      "Asia/Qatar",
+                                      "Asia/Qostanay",
+                                      "Asia/Qyzylorda",
+                                      "Asia/Riyadh",
+                                      "Asia/Sakhalin",
+                                      "Asia/Samarkand",
+                                      "Asia/Seoul",
+                                      "Asia/Shanghai",
+                                      "Asia/Singapore",
+                                      "Asia/Srednekolymsk",
+                                      "Asia/Taipei",
+                                      "Asia/Tashkent",
+                                      "Asia/Tbilisi",
+                                      "Asia/Tehran",
+                                      "Asia/Tel_Aviv",
+                                      "Asia/Thimphu",
+                                      "Asia/Tokyo",
+                                      "Asia/Tomsk",
+                                      "Asia/Ulaanbaatar",
+                                      "Asia/Urumqi",
+                                      "Asia/Ust-Nera",
+                                      "Asia/Vientiane",
+                                      "Asia/Vladivostok",
+                                      "Asia/Yakutsk",
+                                      "Asia/Yangon",
+                                      "Asia/Yekaterinburg",
+                                      "Asia/Yerevan",
+                                      "Atlantic/Azores",
+                                      "Atlantic/Bermuda",
+                                      "Atlantic/Canary",
+                                      "Atlantic/Cape_Verde",
+                                      "Atlantic/Faroe",
+                                      "Atlantic/Jan_Mayen",
+                                      "Atlantic/Madeira",
+                                      "Atlantic/Reykjavik",
+                                      "Atlantic/South_Georgia",
+                                      "Atlantic/St_Helena",
+                                      "Atlantic/Stanley",
+                                      "Australia/Adelaide",
+                                      "Australia/Brisbane",
+                                      "Australia/Broken_Hill",
+                                      "Australia/Canberra",
+                                      "Australia/Currie",
+                                      "Australia/Darwin",
+                                      "Australia/Eucla",
+                                      "Australia/Hobart",
+                                      "Australia/Lindeman",
+                                      "Australia/Lord_Howe",
+                                      "Australia/Melbourne",
+                                      "Australia/Perth",
+                                      "Australia/Sydney",
+                                      "Australia/Yancowinna",
+                                      "Etc/GMT",
+                                      "Etc/GMT+0",
+                                      "Etc/GMT+1",
+                                      "Etc/GMT+10",
+                                      "Etc/GMT+11",
+                                      "Etc/GMT+12",
+                                      "Etc/GMT+2",
+                                      "Etc/GMT+3",
+                                      "Etc/GMT+4",
+                                      "Etc/GMT+5",
+                                      "Etc/GMT+6",
+                                      "Etc/GMT+7",
+                                      "Etc/GMT+8",
+                                      "Etc/GMT+9",
+                                      "Etc/GMT-0",
+                                      "Etc/GMT-1",
+                                      "Etc/GMT-10",
+                                      "Etc/GMT-11",
+                                      "Etc/GMT-12",
+                                      "Etc/GMT-13",
+                                      "Etc/GMT-14",
+                                      "Etc/GMT-2",
+                                      "Etc/GMT-3",
+                                      "Etc/GMT-4",
+                                      "Etc/GMT-5",
+                                      "Etc/GMT-6",
+                                      "Etc/GMT-7",
+                                      "Etc/GMT-8",
+                                      "Etc/GMT-9",
+                                      "Etc/GMT0",
+                                      "Etc/Greenwich",
+                                      "Etc/UCT",
+                                      "Etc/UTC",
+                                      "Etc/Universal",
+                                      "Etc/Zulu",
+                                      "Europe/Amsterdam",
+                                      "Europe/Andorra",
+                                      "Europe/Astrakhan",
+                                      "Europe/Athens",
+                                      "Europe/Belfast",
+                                      "Europe/Belgrade",
+                                      "Europe/Berlin",
+                                      "Europe/Bratislava",
+                                      "Europe/Brussels",
+                                      "Europe/Bucharest",
+                                      "Europe/Budapest",
+                                      "Europe/Busingen",
+                                      "Europe/Chisinau",
+                                      "Europe/Copenhagen",
+                                      "Europe/Dublin",
+                                      "Europe/Gibraltar",
+                                      "Europe/Guernsey",
+                                      "Europe/Helsinki",
+                                      "Europe/Isle_of_Man",
+                                      "Europe/Istanbul",
+                                      "Europe/Jersey",
+                                      "Europe/Kaliningrad",
+                                      "Europe/Kirov",
+                                      "Europe/Kyiv",
+                                      "Europe/Lisbon",
+                                      "Europe/Ljubljana",
+                                      "Europe/London",
+                                      "Europe/Luxembourg",
+                                      "Europe/Madrid",
+                                      "Europe/Malta",
+                                      "Europe/Mariehamn",
+                                      "Europe/Minsk",
+                                      "Europe/Monaco",
+                                      "Europe/Moscow",
+                                      "Europe/Nicosia",
+                                      "Europe/Oslo",
+                                      "Europe/Paris",
+                                      "Europe/Podgorica",
+                                      "Europe/Prague",
+                                      "Europe/Riga",
+                                      "Europe/Rome",
+                                      "Europe/Samara",
+                                      "Europe/San_Marino",
+                                      "Europe/Sarajevo",
+                                      "Europe/Saratov",
+                                      "Europe/Simferopol",
+                                      "Europe/Skopje",
+                                      "Europe/Sofia",
+                                      "Europe/Stockholm",
+                                      "Europe/Tallinn",
+                                      "Europe/Tirane",
+                                      "Europe/Tiraspol",
+                                      "Europe/Ulyanovsk",
+                                      "Europe/Vaduz",
+                                      "Europe/Vatican",
+                                      "Europe/Vienna",
+                                      "Europe/Vilnius",
+                                      "Europe/Volgograd",
+                                      "Europe/Warsaw",
+                                      "Europe/Zagreb",
+                                      "Europe/Zurich",
+                                      "Factory",
+                                      "Indian/Antananarivo",
+                                      "Indian/Chagos",
+                                      "Indian/Christmas",
+                                      "Indian/Cocos",
+                                      "Indian/Comoro",
+                                      "Indian/Kerguelen",
+                                      "Indian/Mahe",
+                                      "Indian/Maldives",
+                                      "Indian/Mauritius",
+                                      "Indian/Mayotte",
+                                      "Indian/Reunion",
+                                      "Pacific/Apia",
+                                      "Pacific/Auckland",
+                                      "Pacific/Bougainville",
+                                      "Pacific/Chatham",
+                                      "Pacific/Chuuk",
+                                      "Pacific/Easter",
+                                      "Pacific/Efate",
+                                      "Pacific/Fakaofo",
+                                      "Pacific/Fiji",
+                                      "Pacific/Funafuti",
+                                      "Pacific/Galapagos",
+                                      "Pacific/Gambier",
+                                      "Pacific/Guadalcanal",
+                                      "Pacific/Guam",
+                                      "Pacific/Honolulu",
+                                      "Pacific/Johnston",
+                                      "Pacific/Kanton",
+                                      "Pacific/Kiritimati",
+                                      "Pacific/Kosrae",
+                                      "Pacific/Kwajalein",
+                                      "Pacific/Majuro",
+                                      "Pacific/Marquesas",
+                                      "Pacific/Midway",
+                                      "Pacific/Nauru",
+                                      "Pacific/Niue",
+                                      "Pacific/Norfolk",
+                                      "Pacific/Noumea",
+                                      "Pacific/Pago_Pago",
+                                      "Pacific/Palau",
+                                      "Pacific/Pitcairn",
+                                      "Pacific/Pohnpei",
+                                      "Pacific/Port_Moresby",
+                                      "Pacific/Rarotonga",
+                                      "Pacific/Saipan",
+                                      "Pacific/Samoa",
+                                      "Pacific/Tahiti",
+                                      "Pacific/Tarawa",
+                                      "Pacific/Tongatapu",
+                                      "Pacific/Wake",
+                                      "Pacific/Wallis",
+                                      "Pacific/Yap",
+                                      "UTC",
+                                      nullptr};
+
+std::vector<std::string> AllTimeZoneNames() {
+  std::vector<std::string> names;
+  for (const char* const* namep = kTimeZoneNames; *namep != nullptr; ++namep) {
+    names.push_back(std::string("file:") + *namep);
+  }
+  assert(!names.empty());
+
+  std::mt19937 urbg(42);  // a UniformRandomBitGenerator with fixed seed
+  std::shuffle(names.begin(), names.end(), urbg);
+  return names;
+}
+
+cctz::time_zone TestTimeZone() {
+  cctz::time_zone tz;
+  cctz::load_time_zone("America/Los_Angeles", &tz);
+  return tz;
+}
+
+void BM_Zone_LoadUTCTimeZoneFirst(benchmark::State& state) {
+  cctz::time_zone tz;
+  cctz::load_time_zone("UTC", &tz);  // in case we're first
+  cctz::time_zone::Impl::ClearTimeZoneMapTestOnly();
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::load_time_zone("UTC", &tz));
+  }
+}
+BENCHMARK(BM_Zone_LoadUTCTimeZoneFirst);
+
+void BM_Zone_LoadUTCTimeZoneLast(benchmark::State& state) {
+  cctz::time_zone tz;
+  for (const auto& name : AllTimeZoneNames()) {
+    cctz::load_time_zone(name, &tz);  // prime cache
+  }
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::load_time_zone("UTC", &tz));
+  }
+}
+BENCHMARK(BM_Zone_LoadUTCTimeZoneLast);
+
+void BM_Zone_LoadTimeZoneFirst(benchmark::State& state) {
+  cctz::time_zone tz = cctz::utc_time_zone();  // in case we're first
+  const std::string name = "file:America/Los_Angeles";
+  while (state.KeepRunning()) {
+    state.PauseTiming();
+    cctz::time_zone::Impl::ClearTimeZoneMapTestOnly();
+    state.ResumeTiming();
+    benchmark::DoNotOptimize(cctz::load_time_zone(name, &tz));
+  }
+}
+BENCHMARK(BM_Zone_LoadTimeZoneFirst);
+
+void BM_Zone_LoadTimeZoneCached(benchmark::State& state) {
+  cctz::time_zone tz = cctz::utc_time_zone();  // in case we're first
+  cctz::time_zone::Impl::ClearTimeZoneMapTestOnly();
+  const std::string name = "file:America/Los_Angeles";
+  cctz::load_time_zone(name, &tz);  // prime cache
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::load_time_zone(name, &tz));
+  }
+}
+BENCHMARK(BM_Zone_LoadTimeZoneCached);
+
+void BM_Zone_LoadLocalTimeZoneCached(benchmark::State& state) {
+  cctz::utc_time_zone();  // in case we're first
+  cctz::time_zone::Impl::ClearTimeZoneMapTestOnly();
+  cctz::local_time_zone();  // prime cache
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::local_time_zone());
+  }
+}
+BENCHMARK(BM_Zone_LoadLocalTimeZoneCached);
+
+void BM_Zone_LoadAllTimeZonesFirst(benchmark::State& state) {
+  cctz::time_zone tz;
+  const std::vector<std::string> names = AllTimeZoneNames();
+  for (auto index = names.size(); state.KeepRunning(); ++index) {
+    if (index == names.size()) {
+      index = 0;
+    }
+    if (index == 0) {
+      state.PauseTiming();
+      cctz::time_zone::Impl::ClearTimeZoneMapTestOnly();
+      state.ResumeTiming();
+    }
+    benchmark::DoNotOptimize(cctz::load_time_zone(names[index], &tz));
+  }
+}
+BENCHMARK(BM_Zone_LoadAllTimeZonesFirst);
+
+void BM_Zone_LoadAllTimeZonesCached(benchmark::State& state) {
+  cctz::time_zone tz;
+  const std::vector<std::string> names = AllTimeZoneNames();
+  for (const auto& name : names) {
+    cctz::load_time_zone(name, &tz);  // prime cache
+  }
+  for (auto index = names.size(); state.KeepRunning(); ++index) {
+    if (index == names.size()) {
+      index = 0;
+    }
+    benchmark::DoNotOptimize(cctz::load_time_zone(names[index], &tz));
+  }
+}
+BENCHMARK(BM_Zone_LoadAllTimeZonesCached);
+
+void BM_Zone_TimeZoneEqualityImplicit(benchmark::State& state) {
+  cctz::time_zone tz;  // implicit UTC
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(tz == tz);
+  }
+}
+BENCHMARK(BM_Zone_TimeZoneEqualityImplicit);
+
+void BM_Zone_TimeZoneEqualityExplicit(benchmark::State& state) {
+  cctz::time_zone tz = cctz::utc_time_zone();  // explicit UTC
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(tz == tz);
+  }
+}
+BENCHMARK(BM_Zone_TimeZoneEqualityExplicit);
+
+void BM_Zone_UTCTimeZone(benchmark::State& state) {
+  cctz::time_zone tz;
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::utc_time_zone());
+  }
+}
+BENCHMARK(BM_Zone_UTCTimeZone);
+
+// In each "ToCivil" benchmark we switch between two instants separated
+// by at least one transition in order to defeat any internal caching of
+// previous results (e.g., see local_time_hint_).
+//
+// The "UTC" variants use UTC instead of the Google/local time zone.
+
+void BM_Time_ToCivil_CCTZ(benchmark::State& state) {
+  const cctz::time_zone tz = TestTimeZone();
+  std::chrono::system_clock::time_point tp =
+      std::chrono::system_clock::from_time_t(1384569027);
+  std::chrono::system_clock::time_point tp2 =
+      std::chrono::system_clock::from_time_t(1418962578);
+  while (state.KeepRunning()) {
+    std::swap(tp, tp2);
+    tp += std::chrono::seconds(1);
+    benchmark::DoNotOptimize(cctz::convert(tp, tz));
+  }
+}
+BENCHMARK(BM_Time_ToCivil_CCTZ);
+
+void BM_Time_ToCivil_Libc(benchmark::State& state) {
+  // No timezone support, so just use localtime.
+  time_t t = 1384569027;
+  time_t t2 = 1418962578;
+  struct tm tm;
+  while (state.KeepRunning()) {
+    std::swap(t, t2);
+    t += 1;
+#if defined(_WIN32) || defined(_WIN64)
+    benchmark::DoNotOptimize(localtime_s(&tm, &t));
+#else
+    benchmark::DoNotOptimize(localtime_r(&t, &tm));
+#endif
+  }
+}
+BENCHMARK(BM_Time_ToCivil_Libc);
+
+void BM_Time_ToCivilUTC_CCTZ(benchmark::State& state) {
+  const cctz::time_zone tz = cctz::utc_time_zone();
+  std::chrono::system_clock::time_point tp =
+      std::chrono::system_clock::from_time_t(1384569027);
+  while (state.KeepRunning()) {
+    tp += std::chrono::seconds(1);
+    benchmark::DoNotOptimize(cctz::convert(tp, tz));
+  }
+}
+BENCHMARK(BM_Time_ToCivilUTC_CCTZ);
+
+void BM_Time_ToCivilUTC_Libc(benchmark::State& state) {
+  time_t t = 1384569027;
+  struct tm tm;
+  while (state.KeepRunning()) {
+    t += 1;
+#if defined(_WIN32) || defined(_WIN64)
+    benchmark::DoNotOptimize(gmtime_s(&tm, &t));
+#else
+    benchmark::DoNotOptimize(gmtime_r(&t, &tm));
+#endif
+  }
+}
+BENCHMARK(BM_Time_ToCivilUTC_Libc);
+
+// In each "FromCivil" benchmark we switch between two YMDhms values
+// separated by at least one transition in order to defeat any internal
+// caching of previous results (e.g., see time_local_hint_).
+//
+// The "UTC" variants use UTC instead of the Google/local time zone.
+// The "Day0" variants require normalization of the day of month.
+
+void BM_Time_FromCivil_CCTZ(benchmark::State& state) {
+  const cctz::time_zone tz = TestTimeZone();
+  int i = 0;
+  while (state.KeepRunning()) {
+    if ((i++ & 1) == 0) {
+      benchmark::DoNotOptimize(
+          cctz::convert(cctz::civil_second(2014, 12, 18, 20, 16, 18), tz));
+    } else {
+      benchmark::DoNotOptimize(
+          cctz::convert(cctz::civil_second(2013, 11, 15, 18, 30, 27), tz));
+    }
+  }
+}
+BENCHMARK(BM_Time_FromCivil_CCTZ);
+
+void BM_Time_FromCivil_Libc(benchmark::State& state) {
+  // No timezone support, so just use localtime.
+  int i = 0;
+  while (state.KeepRunning()) {
+    struct tm tm;
+    if ((i++ & 1) == 0) {
+      tm.tm_year = 2014 - 1900;
+      tm.tm_mon = 12 - 1;
+      tm.tm_mday = 18;
+      tm.tm_hour = 20;
+      tm.tm_min = 16;
+      tm.tm_sec = 18;
+    } else {
+      tm.tm_year = 2013 - 1900;
+      tm.tm_mon = 11 - 1;
+      tm.tm_mday = 15;
+      tm.tm_hour = 18;
+      tm.tm_min = 30;
+      tm.tm_sec = 27;
+    }
+    tm.tm_isdst = -1;
+    benchmark::DoNotOptimize(mktime(&tm));
+  }
+}
+BENCHMARK(BM_Time_FromCivil_Libc);
+
+void BM_Time_FromCivilUTC_CCTZ(benchmark::State& state) {
+  const cctz::time_zone tz = cctz::utc_time_zone();
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(
+        cctz::convert(cctz::civil_second(2014, 12, 18, 20, 16, 18), tz));
+  }
+}
+BENCHMARK(BM_Time_FromCivilUTC_CCTZ);
+
+// There is no BM_Time_FromCivilUTC_Libc.
+
+void BM_Time_FromCivilDay0_CCTZ(benchmark::State& state) {
+  const cctz::time_zone tz = TestTimeZone();
+  int i = 0;
+  while (state.KeepRunning()) {
+    if ((i++ & 1) == 0) {
+      benchmark::DoNotOptimize(
+          cctz::convert(cctz::civil_second(2014, 12, 0, 20, 16, 18), tz));
+    } else {
+      benchmark::DoNotOptimize(
+          cctz::convert(cctz::civil_second(2013, 11, 0, 18, 30, 27), tz));
+    }
+  }
+}
+BENCHMARK(BM_Time_FromCivilDay0_CCTZ);
+
+void BM_Time_FromCivilDay0_Libc(benchmark::State& state) {
+  // No timezone support, so just use localtime.
+  int i = 0;
+  while (state.KeepRunning()) {
+    struct tm tm;
+    if ((i++ & 1) == 0) {
+      tm.tm_year = 2014 - 1900;
+      tm.tm_mon = 12 - 1;
+      tm.tm_mday = 0;
+      tm.tm_hour = 20;
+      tm.tm_min = 16;
+      tm.tm_sec = 18;
+    } else {
+      tm.tm_year = 2013 - 1900;
+      tm.tm_mon = 11 - 1;
+      tm.tm_mday = 0;
+      tm.tm_hour = 18;
+      tm.tm_min = 30;
+      tm.tm_sec = 27;
+    }
+    tm.tm_isdst = -1;
+    benchmark::DoNotOptimize(mktime(&tm));
+  }
+}
+BENCHMARK(BM_Time_FromCivilDay0_Libc);
+
+const char* const kFormats[] = {
+    RFC1123_full,           // 0
+    RFC1123_no_wday,        // 1
+    RFC3339_full,           // 2
+    RFC3339_sec,            // 3
+    "%Y-%m-%d%ET%H:%M:%S",  // 4
+    "%Y-%m-%d",             // 5
+};
+const int kNumFormats = sizeof(kFormats) / sizeof(kFormats[0]);
+
+void BM_Format_FormatTime(benchmark::State& state) {
+  const std::string fmt = kFormats[state.range(0)];
+  state.SetLabel(fmt);
+  const cctz::time_zone tz = TestTimeZone();
+  const std::chrono::system_clock::time_point tp =
+      cctz::convert(cctz::civil_second(1977, 6, 28, 9, 8, 7), tz) +
+      std::chrono::microseconds(1);
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::format(fmt, tp, tz));
+  }
+}
+BENCHMARK(BM_Format_FormatTime)->DenseRange(0, kNumFormats - 1);
+
+void BM_Format_ParseTime(benchmark::State& state) {
+  const std::string fmt = kFormats[state.range(0)];
+  state.SetLabel(fmt);
+  const cctz::time_zone tz = TestTimeZone();
+  std::chrono::system_clock::time_point tp =
+      cctz::convert(cctz::civil_second(1977, 6, 28, 9, 8, 7), tz) +
+      std::chrono::microseconds(1);
+  const std::string when = cctz::format(fmt, tp, tz);
+  while (state.KeepRunning()) {
+    benchmark::DoNotOptimize(cctz::parse(fmt, when, tz, &tp));
+  }
+}
+BENCHMARK(BM_Format_ParseTime)->DenseRange(0, kNumFormats - 1);
+
+}  // namespace
diff --git a/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/time_zone_format.cc b/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/time_zone_format.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e7e30a2fb780aba1d23afa0095f8e386b9ca6592
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/time_zone_format.cc
@@ -0,0 +1,1029 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+#if !defined(HAS_STRPTIME)
+#if !defined(_MSC_VER) && !defined(__MINGW32__) && !defined(__VXWORKS__)
+#define HAS_STRPTIME 1  // Assume everyone else has strptime().
+#endif
+#endif
+
+#if defined(HAS_STRPTIME) && HAS_STRPTIME
+#if !defined(_XOPEN_SOURCE) && !defined(__FreeBSD__) && !defined(__OpenBSD__)
+#define _XOPEN_SOURCE 500  // Exposes definitions for SUSv2 (UNIX 98).
+#endif
+#endif
+
+#include "absl/base/config.h"
+#include "absl/time/internal/cctz/include/cctz/time_zone.h"
+
+// Include time.h directly since, by C++ standards, ctime doesn't have to
+// declare strptime.
+#include <time.h>
+
+#include <cctype>
+#include <chrono>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <ctime>
+#include <limits>
+#include <string>
+#include <vector>
+#if !HAS_STRPTIME
+#include <iomanip>
+#include <sstream>
+#endif
+
+#include "absl/time/internal/cctz/include/cctz/civil_time.h"
+#include "time_zone_if.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+namespace cctz {
+namespace detail {
+
+namespace {
+
+#if !HAS_STRPTIME
+// Build a strptime() using C++11's std::get_time().
+char* strptime(const char* s, const char* fmt, std::tm* tm) {
+  std::istringstream input(s);
+  input >> std::get_time(tm, fmt);
+  if (input.fail()) return nullptr;
+  return const_cast<char*>(s) +
+         (input.eof() ? strlen(s) : static_cast<std::size_t>(input.tellg()));
+}
+#endif
+
+// Convert a cctz::weekday to a tm_wday value (0-6, Sunday = 0).
+int ToTmWday(weekday wd) {
+  switch (wd) {
+    case weekday::sunday:
+      return 0;
+    case weekday::monday:
+      return 1;
+    case weekday::tuesday:
+      return 2;
+    case weekday::wednesday:
+      return 3;
+    case weekday::thursday:
+      return 4;
+    case weekday::friday:
+      return 5;
+    case weekday::saturday:
+      return 6;
+  }
+  return 0; /*NOTREACHED*/
+}
+
+// Convert a tm_wday value (0-6, Sunday = 0) to a cctz::weekday.
+weekday FromTmWday(int tm_wday) {
+  switch (tm_wday) {
+    case 0:
+      return weekday::sunday;
+    case 1:
+      return weekday::monday;
+    case 2:
+      return weekday::tuesday;
+    case 3:
+      return weekday::wednesday;
+    case 4:
+      return weekday::thursday;
+    case 5:
+      return weekday::friday;
+    case 6:
+      return weekday::saturday;
+  }
+  return weekday::sunday; /*NOTREACHED*/
+}
+
+std::tm ToTM(const time_zone::absolute_lookup& al) {
+  std::tm tm{};
+  tm.tm_sec = al.cs.second();
+  tm.tm_min = al.cs.minute();
+  tm.tm_hour = al.cs.hour();
+  tm.tm_mday = al.cs.day();
+  tm.tm_mon = al.cs.month() - 1;
+
+  // Saturate tm.tm_year is cases of over/underflow.
+  if (al.cs.year() < std::numeric_limits<int>::min() + 1900) {
+    tm.tm_year = std::numeric_limits<int>::min();
+  } else if (al.cs.year() - 1900 > std::numeric_limits<int>::max()) {
+    tm.tm_year = std::numeric_limits<int>::max();
+  } else {
+    tm.tm_year = static_cast<int>(al.cs.year() - 1900);
+  }
+
+  tm.tm_wday = ToTmWday(get_weekday(al.cs));
+  tm.tm_yday = get_yearday(al.cs) - 1;
+  tm.tm_isdst = al.is_dst ? 1 : 0;
+  return tm;
+}
+
+// Returns the week of the year [0:53] given a civil day and the day on
+// which weeks are defined to start.
+int ToWeek(const civil_day& cd, weekday week_start) {
+  const civil_day d(cd.year() % 400, cd.month(), cd.day());
+  return static_cast<int>((d - prev_weekday(civil_year(d), week_start)) / 7);
+}
+
+const char kDigits[] = "0123456789";
+
+// Formats a 64-bit integer in the given field width.  Note that it is up
+// to the caller of Format64() [and Format02d()/FormatOffset()] to ensure
+// that there is sufficient space before ep to hold the conversion.
+char* Format64(char* ep, int width, std::int_fast64_t v) {
+  bool neg = false;
+  if (v < 0) {
+    --width;
+    neg = true;
+    if (v == std::numeric_limits<std::int_fast64_t>::min()) {
+      // Avoid negating minimum value.
+      std::int_fast64_t last_digit = -(v % 10);
+      v /= 10;
+      if (last_digit < 0) {
+        ++v;
+        last_digit += 10;
+      }
+      --width;
+      *--ep = kDigits[last_digit];
+    }
+    v = -v;
+  }
+  do {
+    --width;
+    *--ep = kDigits[v % 10];
+  } while (v /= 10);
+  while (--width >= 0) *--ep = '0';  // zero pad
+  if (neg) *--ep = '-';
+  return ep;
+}
+
+// Formats [0 .. 99] as %02d.
+char* Format02d(char* ep, int v) {
+  *--ep = kDigits[v % 10];
+  *--ep = kDigits[(v / 10) % 10];
+  return ep;
+}
+
+// Formats a UTC offset, like +00:00.
+char* FormatOffset(char* ep, int offset, const char* mode) {
+  // TODO: Follow the RFC3339 "Unknown Local Offset Convention" and
+  // generate a "negative zero" when we're formatting a zero offset
+  // as the result of a failed load_time_zone().
+  char sign = '+';
+  if (offset < 0) {
+    offset = -offset;  // bounded by 24h so no overflow
+    sign = '-';
+  }
+  const int seconds = offset % 60;
+  const int minutes = (offset /= 60) % 60;
+  const int hours = offset /= 60;
+  const char sep = mode[0];
+  const bool ext = (sep != '\0' && mode[1] == '*');
+  const bool ccc = (ext && mode[2] == ':');
+  if (ext && (!ccc || seconds != 0)) {
+    ep = Format02d(ep, seconds);
+    *--ep = sep;
+  } else {
+    // If we're not rendering seconds, sub-minute negative offsets
+    // should get a positive sign (e.g., offset=-10s => "+00:00").
+    if (hours == 0 && minutes == 0) sign = '+';
+  }
+  if (!ccc || minutes != 0 || seconds != 0) {
+    ep = Format02d(ep, minutes);
+    if (sep != '\0') *--ep = sep;
+  }
+  ep = Format02d(ep, hours);
+  *--ep = sign;
+  return ep;
+}
+
+// Formats a std::tm using strftime(3).
+void FormatTM(std::string* out, const std::string& fmt, const std::tm& tm) {
+  // strftime(3) returns the number of characters placed in the output
+  // array (which may be 0 characters).  It also returns 0 to indicate
+  // an error, like the array wasn't large enough.  To accommodate this,
+  // the following code grows the buffer size from 2x the format string
+  // length up to 32x.
+  for (std::size_t i = 2; i != 32; i *= 2) {
+    std::size_t buf_size = fmt.size() * i;
+    std::vector<char> buf(buf_size);
+    if (std::size_t len = strftime(&buf[0], buf_size, fmt.c_str(), &tm)) {
+      out->append(&buf[0], len);
+      return;
+    }
+  }
+}
+
+// Used for %E#S/%E#f specifiers and for data values in parse().
+template <typename T>
+const char* ParseInt(const char* dp, int width, T min, T max, T* vp) {
+  if (dp != nullptr) {
+    const T kmin = std::numeric_limits<T>::min();
+    bool erange = false;
+    bool neg = false;
+    T value = 0;
+    if (*dp == '-') {
+      neg = true;
+      if (width <= 0 || --width != 0) {
+        ++dp;
+      } else {
+        dp = nullptr;  // width was 1
+      }
+    }
+    if (const char* const bp = dp) {
+      while (const char* cp = strchr(kDigits, *dp)) {
+        int d = static_cast<int>(cp - kDigits);
+        if (d >= 10) break;
+        if (value < kmin / 10) {
+          erange = true;
+          break;
+        }
+        value *= 10;
+        if (value < kmin + d) {
+          erange = true;
+          break;
+        }
+        value -= d;
+        dp += 1;
+        if (width > 0 && --width == 0) break;
+      }
+      if (dp != bp && !erange && (neg || value != kmin)) {
+        if (!neg || value != 0) {
+          if (!neg) value = -value;  // make positive
+          if (min <= value && value <= max) {
+            *vp = value;
+          } else {
+            dp = nullptr;
+          }
+        } else {
+          dp = nullptr;
+        }
+      } else {
+        dp = nullptr;
+      }
+    }
+  }
+  return dp;
+}
+
+// The number of base-10 digits that can be represented by a signed 64-bit
+// integer.  That is, 10^kDigits10_64 <= 2^63 - 1 < 10^(kDigits10_64 + 1).
+const int kDigits10_64 = 18;
+
+// 10^n for everything that can be represented by a signed 64-bit integer.
+const std::int_fast64_t kExp10[kDigits10_64 + 1] = {
+    1,
+    10,
+    100,
+    1000,
+    10000,
+    100000,
+    1000000,
+    10000000,
+    100000000,
+    1000000000,
+    10000000000,
+    100000000000,
+    1000000000000,
+    10000000000000,
+    100000000000000,
+    1000000000000000,
+    10000000000000000,
+    100000000000000000,
+    1000000000000000000,
+};
+
+}  // namespace
+
+// Uses strftime(3) to format the given Time.  The following extended format
+// specifiers are also supported:
+//
+//   - %Ez  - RFC3339-compatible numeric UTC offset (+hh:mm or -hh:mm)
+//   - %E*z - Full-resolution numeric UTC offset (+hh:mm:ss or -hh:mm:ss)
+//   - %E#S - Seconds with # digits of fractional precision
+//   - %E*S - Seconds with full fractional precision (a literal '*')
+//   - %E4Y - Four-character years (-999 ... -001, 0000, 0001 ... 9999)
+//   - %ET  - The RFC3339 "date-time" separator "T"
+//
+// The standard specifiers from RFC3339_* (%Y, %m, %d, %H, %M, and %S) are
+// handled internally for performance reasons.  strftime(3) is slow due to
+// a POSIX requirement to respect changes to ${TZ}.
+//
+// The TZ/GNU %s extension is handled internally because strftime() has
+// to use mktime() to generate it, and that assumes the local time zone.
+//
+// We also handle the %z and %Z specifiers to accommodate platforms that do
+// not support the tm_gmtoff and tm_zone extensions to std::tm.
+//
+// Requires that zero() <= fs < seconds(1).
+std::string format(const std::string& format, const time_point<seconds>& tp,
+                   const detail::femtoseconds& fs, const time_zone& tz) {
+  std::string result;
+  result.reserve(format.size());  // A reasonable guess for the result size.
+  const time_zone::absolute_lookup al = tz.lookup(tp);
+  const std::tm tm = ToTM(al);
+
+  // Scratch buffer for internal conversions.
+  char buf[3 + kDigits10_64];  // enough for longest conversion
+  char* const ep = buf + sizeof(buf);
+  char* bp;  // works back from ep
+
+  // Maintain three, disjoint subsequences that span format.
+  //   [format.begin() ... pending) : already formatted into result
+  //   [pending ... cur) : formatting pending, but no special cases
+  //   [cur ... format.end()) : unexamined
+  // Initially, everything is in the unexamined part.
+  const char* pending = format.c_str();  // NUL terminated
+  const char* cur = pending;
+  const char* end = pending + format.length();
+
+  while (cur != end) {  // while something is unexamined
+    // Moves cur to the next percent sign.
+    const char* start = cur;
+    while (cur != end && *cur != '%') ++cur;
+
+    // If the new pending text is all ordinary, copy it out.
+    if (cur != start && pending == start) {
+      result.append(pending, static_cast<std::size_t>(cur - pending));
+      pending = start = cur;
+    }
+
+    // Span the sequential percent signs.
+    const char* percent = cur;
+    while (cur != end && *cur == '%') ++cur;
+
+    // If the new pending text is all percents, copy out one
+    // percent for every matched pair, then skip those pairs.
+    if (cur != start && pending == start) {
+      std::size_t escaped = static_cast<std::size_t>(cur - pending) / 2;
+      result.append(pending, escaped);
+      pending += escaped * 2;
+      // Also copy out a single trailing percent.
+      if (pending != cur && cur == end) {
+        result.push_back(*pending++);
+      }
+    }
+
+    // Loop unless we have an unescaped percent.
+    if (cur == end || (cur - percent) % 2 == 0) continue;
+
+    // Simple specifiers that we handle ourselves.
+    if (strchr("YmdeUuWwHMSzZs%", *cur)) {
+      if (cur - 1 != pending) {
+        FormatTM(&result, std::string(pending, cur - 1), tm);
+      }
+      switch (*cur) {
+        case 'Y':
+          // This avoids the tm.tm_year overflow problem for %Y, however
+          // tm.tm_year will still be used by other specifiers like %D.
+          bp = Format64(ep, 0, al.cs.year());
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'm':
+          bp = Format02d(ep, al.cs.month());
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'd':
+        case 'e':
+          bp = Format02d(ep, al.cs.day());
+          if (*cur == 'e' && *bp == '0') *bp = ' ';  // for Windows
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'U':
+          bp = Format02d(ep, ToWeek(civil_day(al.cs), weekday::sunday));
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'u':
+          bp = Format64(ep, 0, tm.tm_wday ? tm.tm_wday : 7);
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'W':
+          bp = Format02d(ep, ToWeek(civil_day(al.cs), weekday::monday));
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'w':
+          bp = Format64(ep, 0, tm.tm_wday);
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'H':
+          bp = Format02d(ep, al.cs.hour());
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'M':
+          bp = Format02d(ep, al.cs.minute());
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'S':
+          bp = Format02d(ep, al.cs.second());
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'z':
+          bp = FormatOffset(ep, al.offset, "");
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'Z':
+          result.append(al.abbr);
+          break;
+        case 's':
+          bp = Format64(ep, 0, ToUnixSeconds(tp));
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case '%':
+          result.push_back('%');
+          break;
+      }
+      pending = ++cur;
+      continue;
+    }
+
+    // More complex specifiers that we handle ourselves.
+    if (*cur == ':' && cur + 1 != end) {
+      if (*(cur + 1) == 'z') {
+        // Formats %:z.
+        if (cur - 1 != pending) {
+          FormatTM(&result, std::string(pending, cur - 1), tm);
+        }
+        bp = FormatOffset(ep, al.offset, ":");
+        result.append(bp, static_cast<std::size_t>(ep - bp));
+        pending = cur += 2;
+        continue;
+      }
+      if (*(cur + 1) == ':' && cur + 2 != end) {
+        if (*(cur + 2) == 'z') {
+          // Formats %::z.
+          if (cur - 1 != pending) {
+            FormatTM(&result, std::string(pending, cur - 1), tm);
+          }
+          bp = FormatOffset(ep, al.offset, ":*");
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          pending = cur += 3;
+          continue;
+        }
+        if (*(cur + 2) == ':' && cur + 3 != end) {
+          if (*(cur + 3) == 'z') {
+            // Formats %:::z.
+            if (cur - 1 != pending) {
+              FormatTM(&result, std::string(pending, cur - 1), tm);
+            }
+            bp = FormatOffset(ep, al.offset, ":*:");
+            result.append(bp, static_cast<std::size_t>(ep - bp));
+            pending = cur += 4;
+            continue;
+          }
+        }
+      }
+    }
+
+    // Loop if there is no E modifier.
+    if (*cur != 'E' || ++cur == end) continue;
+
+    // Format our extensions.
+    if (*cur == 'T') {
+      // Formats %ET.
+      if (cur - 2 != pending) {
+        FormatTM(&result, std::string(pending, cur - 2), tm);
+      }
+      result.append("T");
+      pending = ++cur;
+    } else if (*cur == 'z') {
+      // Formats %Ez.
+      if (cur - 2 != pending) {
+        FormatTM(&result, std::string(pending, cur - 2), tm);
+      }
+      bp = FormatOffset(ep, al.offset, ":");
+      result.append(bp, static_cast<std::size_t>(ep - bp));
+      pending = ++cur;
+    } else if (*cur == '*' && cur + 1 != end && *(cur + 1) == 'z') {
+      // Formats %E*z.
+      if (cur - 2 != pending) {
+        FormatTM(&result, std::string(pending, cur - 2), tm);
+      }
+      bp = FormatOffset(ep, al.offset, ":*");
+      result.append(bp, static_cast<std::size_t>(ep - bp));
+      pending = cur += 2;
+    } else if (*cur == '*' && cur + 1 != end &&
+               (*(cur + 1) == 'S' || *(cur + 1) == 'f')) {
+      // Formats %E*S or %E*F.
+      if (cur - 2 != pending) {
+        FormatTM(&result, std::string(pending, cur - 2), tm);
+      }
+      char* cp = ep;
+      bp = Format64(cp, 15, fs.count());
+      while (cp != bp && cp[-1] == '0') --cp;
+      switch (*(cur + 1)) {
+        case 'S':
+          if (cp != bp) *--bp = '.';
+          bp = Format02d(bp, al.cs.second());
+          break;
+        case 'f':
+          if (cp == bp) *--bp = '0';
+          break;
+      }
+      result.append(bp, static_cast<std::size_t>(cp - bp));
+      pending = cur += 2;
+    } else if (*cur == '4' && cur + 1 != end && *(cur + 1) == 'Y') {
+      // Formats %E4Y.
+      if (cur - 2 != pending) {
+        FormatTM(&result, std::string(pending, cur - 2), tm);
+      }
+      bp = Format64(ep, 4, al.cs.year());
+      result.append(bp, static_cast<std::size_t>(ep - bp));
+      pending = cur += 2;
+    } else if (std::isdigit(*cur)) {
+      // Possibly found %E#S or %E#f.
+      int n = 0;
+      if (const char* np = ParseInt(cur, 0, 0, 1024, &n)) {
+        if (*np == 'S' || *np == 'f') {
+          // Formats %E#S or %E#f.
+          if (cur - 2 != pending) {
+            FormatTM(&result, std::string(pending, cur - 2), tm);
+          }
+          bp = ep;
+          if (n > 0) {
+            if (n > kDigits10_64) n = kDigits10_64;
+            bp = Format64(bp, n,
+                          (n > 15) ? fs.count() * kExp10[n - 15]
+                                   : fs.count() / kExp10[15 - n]);
+            if (*np == 'S') *--bp = '.';
+          }
+          if (*np == 'S') bp = Format02d(bp, al.cs.second());
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          pending = cur = ++np;
+        }
+      }
+    }
+  }
+
+  // Formats any remaining data.
+  if (end != pending) {
+    FormatTM(&result, std::string(pending, end), tm);
+  }
+
+  return result;
+}
+
+namespace {
+
+const char* ParseOffset(const char* dp, const char* mode, int* offset) {
+  if (dp != nullptr) {
+    const char first = *dp++;
+    if (first == '+' || first == '-') {
+      char sep = mode[0];
+      int hours = 0;
+      int minutes = 0;
+      int seconds = 0;
+      const char* ap = ParseInt(dp, 2, 0, 23, &hours);
+      if (ap != nullptr && ap - dp == 2) {
+        dp = ap;
+        if (sep != '\0' && *ap == sep) ++ap;
+        const char* bp = ParseInt(ap, 2, 0, 59, &minutes);
+        if (bp != nullptr && bp - ap == 2) {
+          dp = bp;
+          if (sep != '\0' && *bp == sep) ++bp;
+          const char* cp = ParseInt(bp, 2, 0, 59, &seconds);
+          if (cp != nullptr && cp - bp == 2) dp = cp;
+        }
+        *offset = ((hours * 60 + minutes) * 60) + seconds;
+        if (first == '-') *offset = -*offset;
+      } else {
+        dp = nullptr;
+      }
+    } else if (first == 'Z' || first == 'z') {  // Zulu
+      *offset = 0;
+    } else {
+      dp = nullptr;
+    }
+  }
+  return dp;
+}
+
+const char* ParseZone(const char* dp, std::string* zone) {
+  zone->clear();
+  if (dp != nullptr) {
+    while (*dp != '\0' && !std::isspace(*dp)) zone->push_back(*dp++);
+    if (zone->empty()) dp = nullptr;
+  }
+  return dp;
+}
+
+const char* ParseSubSeconds(const char* dp, detail::femtoseconds* subseconds) {
+  if (dp != nullptr) {
+    std::int_fast64_t v = 0;
+    std::int_fast64_t exp = 0;
+    const char* const bp = dp;
+    while (const char* cp = strchr(kDigits, *dp)) {
+      int d = static_cast<int>(cp - kDigits);
+      if (d >= 10) break;
+      if (exp < 15) {
+        exp += 1;
+        v *= 10;
+        v += d;
+      }
+      ++dp;
+    }
+    if (dp != bp) {
+      v *= kExp10[15 - exp];
+      *subseconds = detail::femtoseconds(v);
+    } else {
+      dp = nullptr;
+    }
+  }
+  return dp;
+}
+
+// Parses a string into a std::tm using strptime(3).
+const char* ParseTM(const char* dp, const char* fmt, std::tm* tm) {
+  if (dp != nullptr) {
+    dp = strptime(dp, fmt, tm);
+  }
+  return dp;
+}
+
+// Sets year, tm_mon and tm_mday given the year, week_num, and tm_wday,
+// and the day on which weeks are defined to start.  Returns false if year
+// would need to move outside its bounds.
+bool FromWeek(int week_num, weekday week_start, year_t* year, std::tm* tm) {
+  const civil_year y(*year % 400);
+  civil_day cd = prev_weekday(y, week_start);  // week 0
+  cd = next_weekday(cd - 1, FromTmWday(tm->tm_wday)) + (week_num * 7);
+  if (const year_t shift = cd.year() - y.year()) {
+    if (shift > 0) {
+      if (*year > std::numeric_limits<year_t>::max() - shift) return false;
+    } else {
+      if (*year < std::numeric_limits<year_t>::min() - shift) return false;
+    }
+    *year += shift;
+  }
+  tm->tm_mon = cd.month() - 1;
+  tm->tm_mday = cd.day();
+  return true;
+}
+
+}  // namespace
+
+// Uses strptime(3) to parse the given input.  Supports the same extended
+// format specifiers as format(), although %E#S and %E*S are treated
+// identically (and similarly for %E#f and %E*f).  %Ez and %E*z also accept
+// the same inputs. %ET accepts either 'T' or 't'.
+//
+// The standard specifiers from RFC3339_* (%Y, %m, %d, %H, %M, and %S) are
+// handled internally so that we can normally avoid strptime() altogether
+// (which is particularly helpful when the native implementation is broken).
+//
+// The TZ/GNU %s extension is handled internally because strptime() has to
+// use localtime_r() to generate it, and that assumes the local time zone.
+//
+// We also handle the %z specifier to accommodate platforms that do not
+// support the tm_gmtoff extension to std::tm.  %Z is parsed but ignored.
+bool parse(const std::string& format, const std::string& input,
+           const time_zone& tz, time_point<seconds>* sec,
+           detail::femtoseconds* fs, std::string* err) {
+  // The unparsed input.
+  const char* data = input.c_str();  // NUL terminated
+
+  // Skips leading whitespace.
+  while (std::isspace(*data)) ++data;
+
+  const year_t kyearmax = std::numeric_limits<year_t>::max();
+  const year_t kyearmin = std::numeric_limits<year_t>::min();
+
+  // Sets default values for unspecified fields.
+  bool saw_year = false;
+  year_t year = 1970;
+  std::tm tm{};
+  tm.tm_year = 1970 - 1900;
+  tm.tm_mon = 1 - 1;  // Jan
+  tm.tm_mday = 1;
+  tm.tm_hour = 0;
+  tm.tm_min = 0;
+  tm.tm_sec = 0;
+  tm.tm_wday = 4;  // Thu
+  tm.tm_yday = 0;
+  tm.tm_isdst = 0;
+  auto subseconds = detail::femtoseconds::zero();
+  bool saw_offset = false;
+  int offset = 0;  // No offset from passed tz.
+  std::string zone = "UTC";
+
+  const char* fmt = format.c_str();  // NUL terminated
+  bool twelve_hour = false;
+  bool afternoon = false;
+  int week_num = -1;
+  weekday week_start = weekday::sunday;
+
+  bool saw_percent_s = false;
+  std::int_fast64_t percent_s = 0;
+
+  // Steps through format, one specifier at a time.
+  while (data != nullptr && *fmt != '\0') {
+    if (std::isspace(*fmt)) {
+      while (std::isspace(*data)) ++data;
+      while (std::isspace(*++fmt)) continue;
+      continue;
+    }
+
+    if (*fmt != '%') {
+      if (*data == *fmt) {
+        ++data;
+        ++fmt;
+      } else {
+        data = nullptr;
+      }
+      continue;
+    }
+
+    const char* percent = fmt;
+    if (*++fmt == '\0') {
+      data = nullptr;
+      continue;
+    }
+    switch (*fmt++) {
+      case 'Y':
+        // Symmetrically with FormatTime(), directly handing %Y avoids the
+        // tm.tm_year overflow problem.  However, tm.tm_year will still be
+        // used by other specifiers like %D.
+        data = ParseInt(data, 0, kyearmin, kyearmax, &year);
+        if (data != nullptr) saw_year = true;
+        continue;
+      case 'm':
+        data = ParseInt(data, 2, 1, 12, &tm.tm_mon);
+        if (data != nullptr) tm.tm_mon -= 1;
+        week_num = -1;
+        continue;
+      case 'd':
+      case 'e':
+        data = ParseInt(data, 2, 1, 31, &tm.tm_mday);
+        week_num = -1;
+        continue;
+      case 'U':
+        data = ParseInt(data, 0, 0, 53, &week_num);
+        week_start = weekday::sunday;
+        continue;
+      case 'W':
+        data = ParseInt(data, 0, 0, 53, &week_num);
+        week_start = weekday::monday;
+        continue;
+      case 'u':
+        data = ParseInt(data, 0, 1, 7, &tm.tm_wday);
+        if (data != nullptr) tm.tm_wday %= 7;
+        continue;
+      case 'w':
+        data = ParseInt(data, 0, 0, 6, &tm.tm_wday);
+        continue;
+      case 'H':
+        data = ParseInt(data, 2, 0, 23, &tm.tm_hour);
+        twelve_hour = false;
+        continue;
+      case 'M':
+        data = ParseInt(data, 2, 0, 59, &tm.tm_min);
+        continue;
+      case 'S':
+        data = ParseInt(data, 2, 0, 60, &tm.tm_sec);
+        continue;
+      case 'I':
+      case 'l':
+      case 'r':  // probably uses %I
+        twelve_hour = true;
+        break;
+      case 'R':  // uses %H
+      case 'T':  // uses %H
+      case 'c':  // probably uses %H
+      case 'X':  // probably uses %H
+        twelve_hour = false;
+        break;
+      case 'z':
+        data = ParseOffset(data, "", &offset);
+        if (data != nullptr) saw_offset = true;
+        continue;
+      case 'Z':  // ignored; zone abbreviations are ambiguous
+        data = ParseZone(data, &zone);
+        continue;
+      case 's':
+        data =
+            ParseInt(data, 0, std::numeric_limits<std::int_fast64_t>::min(),
+                     std::numeric_limits<std::int_fast64_t>::max(), &percent_s);
+        if (data != nullptr) saw_percent_s = true;
+        continue;
+      case ':':
+        if (fmt[0] == 'z' ||
+            (fmt[0] == ':' &&
+             (fmt[1] == 'z' || (fmt[1] == ':' && fmt[2] == 'z')))) {
+          data = ParseOffset(data, ":", &offset);
+          if (data != nullptr) saw_offset = true;
+          fmt += (fmt[0] == 'z') ? 1 : (fmt[1] == 'z') ? 2 : 3;
+          continue;
+        }
+        break;
+      case '%':
+        data = (*data == '%' ? data + 1 : nullptr);
+        continue;
+      case 'E':
+        if (fmt[0] == 'T') {
+          if (*data == 'T' || *data == 't') {
+            ++data;
+            ++fmt;
+          } else {
+            data = nullptr;
+          }
+          continue;
+        }
+        if (fmt[0] == 'z' || (fmt[0] == '*' && fmt[1] == 'z')) {
+          data = ParseOffset(data, ":", &offset);
+          if (data != nullptr) saw_offset = true;
+          fmt += (fmt[0] == 'z') ? 1 : 2;
+          continue;
+        }
+        if (fmt[0] == '*' && fmt[1] == 'S') {
+          data = ParseInt(data, 2, 0, 60, &tm.tm_sec);
+          if (data != nullptr && *data == '.') {
+            data = ParseSubSeconds(data + 1, &subseconds);
+          }
+          fmt += 2;
+          continue;
+        }
+        if (fmt[0] == '*' && fmt[1] == 'f') {
+          if (data != nullptr && std::isdigit(*data)) {
+            data = ParseSubSeconds(data, &subseconds);
+          }
+          fmt += 2;
+          continue;
+        }
+        if (fmt[0] == '4' && fmt[1] == 'Y') {
+          const char* bp = data;
+          data = ParseInt(data, 4, year_t{-999}, year_t{9999}, &year);
+          if (data != nullptr) {
+            if (data - bp == 4) {
+              saw_year = true;
+            } else {
+              data = nullptr;  // stopped too soon
+            }
+          }
+          fmt += 2;
+          continue;
+        }
+        if (std::isdigit(*fmt)) {
+          int n = 0;  // value ignored
+          if (const char* np = ParseInt(fmt, 0, 0, 1024, &n)) {
+            if (*np == 'S') {
+              data = ParseInt(data, 2, 0, 60, &tm.tm_sec);
+              if (data != nullptr && *data == '.') {
+                data = ParseSubSeconds(data + 1, &subseconds);
+              }
+              fmt = ++np;
+              continue;
+            }
+            if (*np == 'f') {
+              if (data != nullptr && std::isdigit(*data)) {
+                data = ParseSubSeconds(data, &subseconds);
+              }
+              fmt = ++np;
+              continue;
+            }
+          }
+        }
+        if (*fmt == 'c') twelve_hour = false;  // probably uses %H
+        if (*fmt == 'X') twelve_hour = false;  // probably uses %H
+        if (*fmt != '\0') ++fmt;
+        break;
+      case 'O':
+        if (*fmt == 'H') twelve_hour = false;
+        if (*fmt == 'I') twelve_hour = true;
+        if (*fmt != '\0') ++fmt;
+        break;
+    }
+
+    // Parses the current specifier.
+    const char* orig_data = data;
+    std::string spec(percent, static_cast<std::size_t>(fmt - percent));
+    data = ParseTM(data, spec.c_str(), &tm);
+
+    // If we successfully parsed %p we need to remember whether the result
+    // was AM or PM so that we can adjust tm_hour before time_zone::lookup().
+    // So reparse the input with a known AM hour, and check if it is shifted
+    // to a PM hour.
+    if (spec == "%p" && data != nullptr) {
+      std::string test_input = "1";
+      test_input.append(orig_data, static_cast<std::size_t>(data - orig_data));
+      const char* test_data = test_input.c_str();
+      std::tm tmp{};
+      ParseTM(test_data, "%I%p", &tmp);
+      afternoon = (tmp.tm_hour == 13);
+    }
+  }
+
+  // Adjust a 12-hour tm_hour value if it should be in the afternoon.
+  if (twelve_hour && afternoon && tm.tm_hour < 12) {
+    tm.tm_hour += 12;
+  }
+
+  if (data == nullptr) {
+    if (err != nullptr) *err = "Failed to parse input";
+    return false;
+  }
+
+  // Skip any remaining whitespace.
+  while (std::isspace(*data)) ++data;
+
+  // parse() must consume the entire input string.
+  if (*data != '\0') {
+    if (err != nullptr) *err = "Illegal trailing data in input string";
+    return false;
+  }
+
+  // If we saw %s then we ignore anything else and return that time.
+  if (saw_percent_s) {
+    *sec = FromUnixSeconds(percent_s);
+    *fs = detail::femtoseconds::zero();
+    return true;
+  }
+
+  // If we saw %z, %Ez, or %E*z then we want to interpret the parsed fields
+  // in UTC and then shift by that offset.  Otherwise we want to interpret
+  // the fields directly in the passed time_zone.
+  time_zone ptz = saw_offset ? utc_time_zone() : tz;
+
+  // Allows a leap second of 60 to normalize forward to the following ":00".
+  if (tm.tm_sec == 60) {
+    tm.tm_sec -= 1;
+    offset -= 1;
+    subseconds = detail::femtoseconds::zero();
+  }
+
+  if (!saw_year) {
+    year = year_t{tm.tm_year};
+    if (year > kyearmax - 1900) {
+      // Platform-dependent, maybe unreachable.
+      if (err != nullptr) *err = "Out-of-range year";
+      return false;
+    }
+    year += 1900;
+  }
+
+  // Compute year, tm.tm_mon and tm.tm_mday if we parsed a week number.
+  if (week_num != -1) {
+    if (!FromWeek(week_num, week_start, &year, &tm)) {
+      if (err != nullptr) *err = "Out-of-range field";
+      return false;
+    }
+  }
+
+  const int month = tm.tm_mon + 1;
+  civil_second cs(year, month, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+  // parse() should not allow normalization. Due to the restricted field
+  // ranges above (see ParseInt()), the only possibility is for days to roll
+  // into months. That is, parsing "Sep 31" should not produce "Oct 1".
+  if (cs.month() != month || cs.day() != tm.tm_mday) {
+    if (err != nullptr) *err = "Out-of-range field";
+    return false;
+  }
+
+  // Accounts for the offset adjustment before converting to absolute time.
+  if ((offset < 0 && cs > civil_second::max() + offset) ||
+      (offset > 0 && cs < civil_second::min() + offset)) {
+    if (err != nullptr) *err = "Out-of-range field";
+    return false;
+  }
+  cs -= offset;
+
+  const auto tp = ptz.lookup(cs).pre;
+  // Checks for overflow/underflow and returns an error as necessary.
+  if (tp == time_point<seconds>::max()) {
+    const auto al = ptz.lookup(time_point<seconds>::max());
+    if (cs > al.cs) {
+      if (err != nullptr) *err = "Out-of-range field";
+      return false;
+    }
+  }
+  if (tp == time_point<seconds>::min()) {
+    const auto al = ptz.lookup(time_point<seconds>::min());
+    if (cs < al.cs) {
+      if (err != nullptr) *err = "Out-of-range field";
+      return false;
+    }
+  }
+
+  *sec = tp;
+  *fs = subseconds;
+  return true;
+}
+
+}  // namespace detail
+}  // namespace cctz
+}  // namespace time_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/time_zone_if.cc b/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/time_zone_if.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0e65cd9e73a045881ad786d9b23b358ee7b66e13
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/internal/cctz/src/time_zone_if.cc
@@ -0,0 +1,47 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+#include "time_zone_if.h"
+
+#include "absl/base/config.h"
+#include "time_zone_info.h"
+#include "time_zone_libc.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+namespace cctz {
+
+std::unique_ptr<TimeZoneIf> TimeZoneIf::UTC() { return TimeZoneInfo::UTC(); }
+
+std::unique_ptr<TimeZoneIf> TimeZoneIf::Make(const std::string& name) {
+  // Support "libc:localtime" and "libc:*" to access the legacy
+  // localtime and UTC support respectively from the C library.
+  // NOTE: The "libc:*" zones are internal, test-only interfaces, and
+  // are subject to change/removal without notice. Do not use them.
+  if (name.compare(0, 5, "libc:") == 0) {
+    return TimeZoneLibC::Make(name.substr(5));
+  }
+
+  // Otherwise use the "zoneinfo" implementation.
+  return TimeZoneInfo::Make(name);
+}
+
+// Defined out-of-line to avoid emitting a weak vtable in all TUs.
+TimeZoneIf::~TimeZoneIf() {}
+
+}  // namespace cctz
+}  // namespace time_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/time/internal/get_current_time_posix.inc b/weight/_dep/abseil-cpp/absl/time/internal/get_current_time_posix.inc
new file mode 100644
index 0000000000000000000000000000000000000000..42072000ae3c1c0c17ba0aebb05b05f537e1b47b
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/internal/get_current_time_posix.inc
@@ -0,0 +1,24 @@
+#include "absl/time/clock.h"
+
+#include <sys/time.h>
+#include <ctime>
+#include <cstdint>
+
+#include "absl/base/internal/raw_logging.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+
+static int64_t GetCurrentTimeNanosFromSystem() {
+  const int64_t kNanosPerSecond = 1000 * 1000 * 1000;
+  struct timespec ts;
+  ABSL_RAW_CHECK(clock_gettime(CLOCK_REALTIME, &ts) == 0,
+                 "Failed to read real-time clock.");
+  return (int64_t{ts.tv_sec} * kNanosPerSecond +
+          int64_t{ts.tv_nsec});
+}
+
+}  // namespace time_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/time/internal/test_util.cc b/weight/_dep/abseil-cpp/absl/time/internal/test_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3e2452e9c33dcca69be97ddd49166b41f5918f87
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/internal/test_util.cc
@@ -0,0 +1,32 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/time/internal/test_util.h"
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+
+TimeZone LoadTimeZone(const std::string& name) {
+  TimeZone tz;
+  ABSL_RAW_CHECK(LoadTimeZone(name, &tz), name.c_str());
+  return tz;
+}
+
+}  // namespace time_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/time/time.cc b/weight/_dep/abseil-cpp/absl/time/time.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d983c12bb55979a3d6d4d3f9c9c9d0054b539dea
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/time.cc
@@ -0,0 +1,507 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// The implementation of the absl::Time class, which is declared in
+// //absl/time.h.
+//
+// The representation for an absl::Time is an absl::Duration offset from the
+// epoch.  We use the traditional Unix epoch (1970-01-01 00:00:00 +0000)
+// for convenience, but this is not exposed in the API and could be changed.
+//
+// NOTE: To keep type verbosity to a minimum, the following variable naming
+// conventions are used throughout this file.
+//
+// tz: An absl::TimeZone
+// ci: An absl::TimeZone::CivilInfo
+// ti: An absl::TimeZone::TimeInfo
+// cd: An absl::CivilDay or a cctz::civil_day
+// cs: An absl::CivilSecond or a cctz::civil_second
+// bd: An absl::Time::Breakdown
+// cl: A cctz::time_zone::civil_lookup
+// al: A cctz::time_zone::absolute_lookup
+
+#include "absl/time/time.h"
+
+#if defined(_MSC_VER)
+#include <winsock2.h>  // for timeval
+#endif
+
+#include <cstring>
+#include <ctime>
+#include <limits>
+
+#include "absl/time/internal/cctz/include/cctz/civil_time.h"
+#include "absl/time/internal/cctz/include/cctz/time_zone.h"
+
+namespace cctz = absl::time_internal::cctz;
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace {
+
+inline cctz::time_point<cctz::seconds> unix_epoch() {
+  return std::chrono::time_point_cast<cctz::seconds>(
+      std::chrono::system_clock::from_time_t(0));
+}
+
+// Floors d to the next unit boundary closer to negative infinity.
+inline int64_t FloorToUnit(absl::Duration d, absl::Duration unit) {
+  absl::Duration rem;
+  int64_t q = absl::IDivDuration(d, unit, &rem);
+  return (q > 0 || rem >= ZeroDuration() ||
+          q == std::numeric_limits<int64_t>::min())
+             ? q
+             : q - 1;
+}
+
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+inline absl::Time::Breakdown InfiniteFutureBreakdown() {
+  absl::Time::Breakdown bd;
+  bd.year = std::numeric_limits<int64_t>::max();
+  bd.month = 12;
+  bd.day = 31;
+  bd.hour = 23;
+  bd.minute = 59;
+  bd.second = 59;
+  bd.subsecond = absl::InfiniteDuration();
+  bd.weekday = 4;
+  bd.yearday = 365;
+  bd.offset = 0;
+  bd.is_dst = false;
+  bd.zone_abbr = "-00";
+  return bd;
+}
+
+inline absl::Time::Breakdown InfinitePastBreakdown() {
+  Time::Breakdown bd;
+  bd.year = std::numeric_limits<int64_t>::min();
+  bd.month = 1;
+  bd.day = 1;
+  bd.hour = 0;
+  bd.minute = 0;
+  bd.second = 0;
+  bd.subsecond = -absl::InfiniteDuration();
+  bd.weekday = 7;
+  bd.yearday = 1;
+  bd.offset = 0;
+  bd.is_dst = false;
+  bd.zone_abbr = "-00";
+  return bd;
+}
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+
+inline absl::TimeZone::CivilInfo InfiniteFutureCivilInfo() {
+  TimeZone::CivilInfo ci;
+  ci.cs = CivilSecond::max();
+  ci.subsecond = InfiniteDuration();
+  ci.offset = 0;
+  ci.is_dst = false;
+  ci.zone_abbr = "-00";
+  return ci;
+}
+
+inline absl::TimeZone::CivilInfo InfinitePastCivilInfo() {
+  TimeZone::CivilInfo ci;
+  ci.cs = CivilSecond::min();
+  ci.subsecond = -InfiniteDuration();
+  ci.offset = 0;
+  ci.is_dst = false;
+  ci.zone_abbr = "-00";
+  return ci;
+}
+
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+inline absl::TimeConversion InfiniteFutureTimeConversion() {
+  absl::TimeConversion tc;
+  tc.pre = tc.trans = tc.post = absl::InfiniteFuture();
+  tc.kind = absl::TimeConversion::UNIQUE;
+  tc.normalized = true;
+  return tc;
+}
+
+inline TimeConversion InfinitePastTimeConversion() {
+  absl::TimeConversion tc;
+  tc.pre = tc.trans = tc.post = absl::InfinitePast();
+  tc.kind = absl::TimeConversion::UNIQUE;
+  tc.normalized = true;
+  return tc;
+}
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+
+// Makes a Time from sec, overflowing to InfiniteFuture/InfinitePast as
+// necessary. If sec is min/max, then consult cs+tz to check for overflow.
+Time MakeTimeWithOverflow(const cctz::time_point<cctz::seconds>& sec,
+                          const cctz::civil_second& cs,
+                          const cctz::time_zone& tz,
+                          bool* normalized = nullptr) {
+  const auto max = cctz::time_point<cctz::seconds>::max();
+  const auto min = cctz::time_point<cctz::seconds>::min();
+  if (sec == max) {
+    const auto al = tz.lookup(max);
+    if (cs > al.cs) {
+      if (normalized) *normalized = true;
+      return absl::InfiniteFuture();
+    }
+  }
+  if (sec == min) {
+    const auto al = tz.lookup(min);
+    if (cs < al.cs) {
+      if (normalized) *normalized = true;
+      return absl::InfinitePast();
+    }
+  }
+  const auto hi = (sec - unix_epoch()).count();
+  return time_internal::FromUnixDuration(time_internal::MakeDuration(hi));
+}
+
+// Returns Mon=1..Sun=7.
+inline int MapWeekday(const cctz::weekday& wd) {
+  switch (wd) {
+    case cctz::weekday::monday:
+      return 1;
+    case cctz::weekday::tuesday:
+      return 2;
+    case cctz::weekday::wednesday:
+      return 3;
+    case cctz::weekday::thursday:
+      return 4;
+    case cctz::weekday::friday:
+      return 5;
+    case cctz::weekday::saturday:
+      return 6;
+    case cctz::weekday::sunday:
+      return 7;
+  }
+  return 1;
+}
+
+bool FindTransition(const cctz::time_zone& tz,
+                    bool (cctz::time_zone::*find_transition)(
+                        const cctz::time_point<cctz::seconds>& tp,
+                        cctz::time_zone::civil_transition* trans) const,
+                    Time t, TimeZone::CivilTransition* trans) {
+  // Transitions are second-aligned, so we can discard any fractional part.
+  const auto tp = unix_epoch() + cctz::seconds(ToUnixSeconds(t));
+  cctz::time_zone::civil_transition tr;
+  if (!(tz.*find_transition)(tp, &tr)) return false;
+  trans->from = CivilSecond(tr.from);
+  trans->to = CivilSecond(tr.to);
+  return true;
+}
+
+}  // namespace
+
+//
+// Time
+//
+
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+absl::Time::Breakdown Time::In(absl::TimeZone tz) const {
+  if (*this == absl::InfiniteFuture()) return InfiniteFutureBreakdown();
+  if (*this == absl::InfinitePast()) return InfinitePastBreakdown();
+
+  const auto tp = unix_epoch() + cctz::seconds(time_internal::GetRepHi(rep_));
+  const auto al = cctz::time_zone(tz).lookup(tp);
+  const auto cs = al.cs;
+  const auto cd = cctz::civil_day(cs);
+
+  absl::Time::Breakdown bd;
+  bd.year = cs.year();
+  bd.month = cs.month();
+  bd.day = cs.day();
+  bd.hour = cs.hour();
+  bd.minute = cs.minute();
+  bd.second = cs.second();
+  bd.subsecond = time_internal::MakeDuration(0, time_internal::GetRepLo(rep_));
+  bd.weekday = MapWeekday(cctz::get_weekday(cd));
+  bd.yearday = cctz::get_yearday(cd);
+  bd.offset = al.offset;
+  bd.is_dst = al.is_dst;
+  bd.zone_abbr = al.abbr;
+  return bd;
+}
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+
+//
+// Conversions from/to other time types.
+//
+
+absl::Time FromUDate(double udate) {
+  return time_internal::FromUnixDuration(absl::Milliseconds(udate));
+}
+
+absl::Time FromUniversal(int64_t universal) {
+  return absl::UniversalEpoch() + 100 * absl::Nanoseconds(universal);
+}
+
+int64_t ToUnixNanos(Time t) {
+  if (time_internal::GetRepHi(time_internal::ToUnixDuration(t)) >= 0 &&
+      time_internal::GetRepHi(time_internal::ToUnixDuration(t)) >> 33 == 0) {
+    return (time_internal::GetRepHi(time_internal::ToUnixDuration(t)) *
+            1000 * 1000 * 1000) +
+           (time_internal::GetRepLo(time_internal::ToUnixDuration(t)) / 4);
+  }
+  return FloorToUnit(time_internal::ToUnixDuration(t), absl::Nanoseconds(1));
+}
+
+int64_t ToUnixMicros(Time t) {
+  if (time_internal::GetRepHi(time_internal::ToUnixDuration(t)) >= 0 &&
+      time_internal::GetRepHi(time_internal::ToUnixDuration(t)) >> 43 == 0) {
+    return (time_internal::GetRepHi(time_internal::ToUnixDuration(t)) *
+            1000 * 1000) +
+           (time_internal::GetRepLo(time_internal::ToUnixDuration(t)) / 4000);
+  }
+  return FloorToUnit(time_internal::ToUnixDuration(t), absl::Microseconds(1));
+}
+
+int64_t ToUnixMillis(Time t) {
+  if (time_internal::GetRepHi(time_internal::ToUnixDuration(t)) >= 0 &&
+      time_internal::GetRepHi(time_internal::ToUnixDuration(t)) >> 53 == 0) {
+    return (time_internal::GetRepHi(time_internal::ToUnixDuration(t)) * 1000) +
+           (time_internal::GetRepLo(time_internal::ToUnixDuration(t)) /
+            (4000 * 1000));
+  }
+  return FloorToUnit(time_internal::ToUnixDuration(t), absl::Milliseconds(1));
+}
+
+int64_t ToUnixSeconds(Time t) {
+  return time_internal::GetRepHi(time_internal::ToUnixDuration(t));
+}
+
+time_t ToTimeT(Time t) { return absl::ToTimespec(t).tv_sec; }
+
+double ToUDate(Time t) {
+  return absl::FDivDuration(time_internal::ToUnixDuration(t),
+                            absl::Milliseconds(1));
+}
+
+int64_t ToUniversal(absl::Time t) {
+  return absl::FloorToUnit(t - absl::UniversalEpoch(), absl::Nanoseconds(100));
+}
+
+absl::Time TimeFromTimespec(timespec ts) {
+  return time_internal::FromUnixDuration(absl::DurationFromTimespec(ts));
+}
+
+absl::Time TimeFromTimeval(timeval tv) {
+  return time_internal::FromUnixDuration(absl::DurationFromTimeval(tv));
+}
+
+timespec ToTimespec(Time t) {
+  timespec ts;
+  absl::Duration d = time_internal::ToUnixDuration(t);
+  if (!time_internal::IsInfiniteDuration(d)) {
+    ts.tv_sec = static_cast<decltype(ts.tv_sec)>(time_internal::GetRepHi(d));
+    if (ts.tv_sec == time_internal::GetRepHi(d)) {  // no time_t narrowing
+      ts.tv_nsec = time_internal::GetRepLo(d) / 4;  // floor
+      return ts;
+    }
+  }
+  if (d >= absl::ZeroDuration()) {
+    ts.tv_sec = std::numeric_limits<time_t>::max();
+    ts.tv_nsec = 1000 * 1000 * 1000 - 1;
+  } else {
+    ts.tv_sec = std::numeric_limits<time_t>::min();
+    ts.tv_nsec = 0;
+  }
+  return ts;
+}
+
+timeval ToTimeval(Time t) {
+  timeval tv;
+  timespec ts = absl::ToTimespec(t);
+  tv.tv_sec = static_cast<decltype(tv.tv_sec)>(ts.tv_sec);
+  if (tv.tv_sec != ts.tv_sec) {  // narrowing
+    if (ts.tv_sec < 0) {
+      tv.tv_sec = std::numeric_limits<decltype(tv.tv_sec)>::min();
+      tv.tv_usec = 0;
+    } else {
+      tv.tv_sec = std::numeric_limits<decltype(tv.tv_sec)>::max();
+      tv.tv_usec = 1000 * 1000 - 1;
+    }
+    return tv;
+  }
+  tv.tv_usec = static_cast<int>(ts.tv_nsec / 1000);  // suseconds_t
+  return tv;
+}
+
+Time FromChrono(const std::chrono::system_clock::time_point& tp) {
+  return time_internal::FromUnixDuration(time_internal::FromChrono(
+      tp - std::chrono::system_clock::from_time_t(0)));
+}
+
+std::chrono::system_clock::time_point ToChronoTime(absl::Time t) {
+  using D = std::chrono::system_clock::duration;
+  auto d = time_internal::ToUnixDuration(t);
+  if (d < ZeroDuration()) d = Floor(d, FromChrono(D{1}));
+  return std::chrono::system_clock::from_time_t(0) +
+         time_internal::ToChronoDuration<D>(d);
+}
+
+//
+// TimeZone
+//
+
+absl::TimeZone::CivilInfo TimeZone::At(Time t) const {
+  if (t == absl::InfiniteFuture()) return InfiniteFutureCivilInfo();
+  if (t == absl::InfinitePast()) return InfinitePastCivilInfo();
+
+  const auto ud = time_internal::ToUnixDuration(t);
+  const auto tp = unix_epoch() + cctz::seconds(time_internal::GetRepHi(ud));
+  const auto al = cz_.lookup(tp);
+
+  TimeZone::CivilInfo ci;
+  ci.cs = CivilSecond(al.cs);
+  ci.subsecond = time_internal::MakeDuration(0, time_internal::GetRepLo(ud));
+  ci.offset = al.offset;
+  ci.is_dst = al.is_dst;
+  ci.zone_abbr = al.abbr;
+  return ci;
+}
+
+absl::TimeZone::TimeInfo TimeZone::At(CivilSecond ct) const {
+  const cctz::civil_second cs(ct);
+  const auto cl = cz_.lookup(cs);
+
+  TimeZone::TimeInfo ti;
+  switch (cl.kind) {
+    case cctz::time_zone::civil_lookup::UNIQUE:
+      ti.kind = TimeZone::TimeInfo::UNIQUE;
+      break;
+    case cctz::time_zone::civil_lookup::SKIPPED:
+      ti.kind = TimeZone::TimeInfo::SKIPPED;
+      break;
+    case cctz::time_zone::civil_lookup::REPEATED:
+      ti.kind = TimeZone::TimeInfo::REPEATED;
+      break;
+  }
+  ti.pre = MakeTimeWithOverflow(cl.pre, cs, cz_);
+  ti.trans = MakeTimeWithOverflow(cl.trans, cs, cz_);
+  ti.post = MakeTimeWithOverflow(cl.post, cs, cz_);
+  return ti;
+}
+
+bool TimeZone::NextTransition(Time t, CivilTransition* trans) const {
+  return FindTransition(cz_, &cctz::time_zone::next_transition, t, trans);
+}
+
+bool TimeZone::PrevTransition(Time t, CivilTransition* trans) const {
+  return FindTransition(cz_, &cctz::time_zone::prev_transition, t, trans);
+}
+
+//
+// Conversions involving time zones.
+//
+ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
+absl::TimeConversion ConvertDateTime(int64_t year, int mon, int day, int hour,
+                                     int min, int sec, TimeZone tz) {
+  // Avoids years that are too extreme for CivilSecond to normalize.
+  if (year > 300000000000) return InfiniteFutureTimeConversion();
+  if (year < -300000000000) return InfinitePastTimeConversion();
+
+  const CivilSecond cs(year, mon, day, hour, min, sec);
+  const auto ti = tz.At(cs);
+
+  TimeConversion tc;
+  tc.pre = ti.pre;
+  tc.trans = ti.trans;
+  tc.post = ti.post;
+  switch (ti.kind) {
+    case TimeZone::TimeInfo::UNIQUE:
+      tc.kind = TimeConversion::UNIQUE;
+      break;
+    case TimeZone::TimeInfo::SKIPPED:
+      tc.kind = TimeConversion::SKIPPED;
+      break;
+    case TimeZone::TimeInfo::REPEATED:
+      tc.kind = TimeConversion::REPEATED;
+      break;
+  }
+  tc.normalized = false;
+  if (year != cs.year() || mon != cs.month() || day != cs.day() ||
+      hour != cs.hour() || min != cs.minute() || sec != cs.second()) {
+    tc.normalized = true;
+  }
+  return tc;
+}
+ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
+
+absl::Time FromTM(const struct tm& tm, absl::TimeZone tz) {
+  civil_year_t tm_year = tm.tm_year;
+  // Avoids years that are too extreme for CivilSecond to normalize.
+  if (tm_year > 300000000000ll) return InfiniteFuture();
+  if (tm_year < -300000000000ll) return InfinitePast();
+  int tm_mon = tm.tm_mon;
+  if (tm_mon == std::numeric_limits<int>::max()) {
+    tm_mon -= 12;
+    tm_year += 1;
+  }
+  const auto ti = tz.At(CivilSecond(tm_year + 1900, tm_mon + 1, tm.tm_mday,
+                                    tm.tm_hour, tm.tm_min, tm.tm_sec));
+  return tm.tm_isdst == 0 ? ti.post : ti.pre;
+}
+
+struct tm ToTM(absl::Time t, absl::TimeZone tz) {
+  struct tm tm = {};
+
+  const auto ci = tz.At(t);
+  const auto& cs = ci.cs;
+  tm.tm_sec = cs.second();
+  tm.tm_min = cs.minute();
+  tm.tm_hour = cs.hour();
+  tm.tm_mday = cs.day();
+  tm.tm_mon = cs.month() - 1;
+
+  // Saturates tm.tm_year in cases of over/underflow, accounting for the fact
+  // that tm.tm_year is years since 1900.
+  if (cs.year() < std::numeric_limits<int>::min() + 1900) {
+    tm.tm_year = std::numeric_limits<int>::min();
+  } else if (cs.year() > std::numeric_limits<int>::max()) {
+    tm.tm_year = std::numeric_limits<int>::max() - 1900;
+  } else {
+    tm.tm_year = static_cast<int>(cs.year() - 1900);
+  }
+
+  switch (GetWeekday(cs)) {
+    case Weekday::sunday:
+      tm.tm_wday = 0;
+      break;
+    case Weekday::monday:
+      tm.tm_wday = 1;
+      break;
+    case Weekday::tuesday:
+      tm.tm_wday = 2;
+      break;
+    case Weekday::wednesday:
+      tm.tm_wday = 3;
+      break;
+    case Weekday::thursday:
+      tm.tm_wday = 4;
+      break;
+    case Weekday::friday:
+      tm.tm_wday = 5;
+      break;
+    case Weekday::saturday:
+      tm.tm_wday = 6;
+      break;
+  }
+  tm.tm_yday = GetYearDay(cs) - 1;
+  tm.tm_isdst = ci.is_dst ? 1 : 0;
+
+  return tm;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/weight/_dep/abseil-cpp/absl/time/time_test.cc b/weight/_dep/abseil-cpp/absl/time/time_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bcf4f2adfead8cd24ffd8db8e04c79a41be6f9a7
--- /dev/null
+++ b/weight/_dep/abseil-cpp/absl/time/time_test.cc
@@ -0,0 +1,1288 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/time/time.h"
+
+#if defined(_MSC_VER)
+#include <winsock2.h>  // for timeval
+#endif
+
+#include <chrono>  // NOLINT(build/c++11)
+#include <cstring>
+#include <ctime>
+#include <iomanip>
+#include <limits>
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/numeric/int128.h"
+#include "absl/strings/str_format.h"
+#include "absl/time/clock.h"
+#include "absl/time/internal/test_util.h"
+
+namespace {
+
+#if defined(GTEST_USES_SIMPLE_RE) && GTEST_USES_SIMPLE_RE
+const char kZoneAbbrRE[] = ".*";  // just punt
+#else
+const char kZoneAbbrRE[] = "[A-Za-z]{3,4}|[-+][0-9]{2}([0-9]{2})?";
+#endif
+
+// This helper is a macro so that failed expectations show up with the
+// correct line numbers.
+#define EXPECT_CIVIL_INFO(ci, y, m, d, h, min, s, off, isdst)      \
+  do {                                                             \
+    EXPECT_EQ(y, ci.cs.year());                                    \
+    EXPECT_EQ(m, ci.cs.month());                                   \
+    EXPECT_EQ(d, ci.cs.day());                                     \
+    EXPECT_EQ(h, ci.cs.hour());                                    \
+    EXPECT_EQ(min, ci.cs.minute());                                \
+    EXPECT_EQ(s, ci.cs.second());                                  \
+    EXPECT_EQ(off, ci.offset);                                     \
+    EXPECT_EQ(isdst, ci.is_dst);                                   \
+    EXPECT_THAT(ci.zone_abbr, testing::MatchesRegex(kZoneAbbrRE)); \
+  } while (0)
+
+// A gMock matcher to match timespec values. Use this matcher like:
+// timespec ts1, ts2;
+// EXPECT_THAT(ts1, TimespecMatcher(ts2));
+MATCHER_P(TimespecMatcher, ts, "") {
+  if (ts.tv_sec == arg.tv_sec && ts.tv_nsec == arg.tv_nsec) return true;
+  *result_listener << "expected: {" << ts.tv_sec << ", " << ts.tv_nsec << "} ";
+  *result_listener << "actual: {" << arg.tv_sec << ", " << arg.tv_nsec << "}";
+  return false;
+}
+
+// A gMock matcher to match timeval values. Use this matcher like:
+// timeval tv1, tv2;
+// EXPECT_THAT(tv1, TimevalMatcher(tv2));
+MATCHER_P(TimevalMatcher, tv, "") {
+  if (tv.tv_sec == arg.tv_sec && tv.tv_usec == arg.tv_usec) return true;
+  *result_listener << "expected: {" << tv.tv_sec << ", " << tv.tv_usec << "} ";
+  *result_listener << "actual: {" << arg.tv_sec << ", " << arg.tv_usec << "}";
+  return false;
+}
+
+TEST(Time, ConstExpr) {
+  constexpr absl::Time t0 = absl::UnixEpoch();
+  static_assert(t0 == absl::Time(), "UnixEpoch");
+  constexpr absl::Time t1 = absl::InfiniteFuture();
+  static_assert(t1 != absl::Time(), "InfiniteFuture");
+  constexpr absl::Time t2 = absl::InfinitePast();
+  static_assert(t2 != absl::Time(), "InfinitePast");
+  constexpr absl::Time t3 = absl::FromUnixNanos(0);
+  static_assert(t3 == absl::Time(), "FromUnixNanos");
+  constexpr absl::Time t4 = absl::FromUnixMicros(0);
+  static_assert(t4 == absl::Time(), "FromUnixMicros");
+  constexpr absl::Time t5 = absl::FromUnixMillis(0);
+  static_assert(t5 == absl::Time(), "FromUnixMillis");
+  constexpr absl::Time t6 = absl::FromUnixSeconds(0);
+  static_assert(t6 == absl::Time(), "FromUnixSeconds");
+  constexpr absl::Time t7 = absl::FromTimeT(0);
+  static_assert(t7 == absl::Time(), "FromTimeT");
+}
+
+TEST(Time, ValueSemantics) {
+  absl::Time a;      // Default construction
+  absl::Time b = a;  // Copy construction
+  EXPECT_EQ(a, b);
+  absl::Time c(a);  // Copy construction (again)
+  EXPECT_EQ(a, b);
+  EXPECT_EQ(a, c);
+  EXPECT_EQ(b, c);
+  b = c;  // Assignment
+  EXPECT_EQ(a, b);
+  EXPECT_EQ(a, c);
+  EXPECT_EQ(b, c);
+}
+
+TEST(Time, UnixEpoch) {
+  const auto ci = absl::UTCTimeZone().At(absl::UnixEpoch());
+  EXPECT_EQ(absl::CivilSecond(1970, 1, 1, 0, 0, 0), ci.cs);
+  EXPECT_EQ(absl::ZeroDuration(), ci.subsecond);
+  EXPECT_EQ(absl::Weekday::thursday, absl::GetWeekday(ci.cs));
+}
+
+TEST(Time, Breakdown) {
+  absl::TimeZone tz = absl::time_internal::LoadTimeZone("America/New_York");
+  absl::Time t = absl::UnixEpoch();
+
+  // The Unix epoch as seen in NYC.
+  auto ci = tz.At(t);
+  EXPECT_CIVIL_INFO(ci, 1969, 12, 31, 19, 0, 0, -18000, false);
+  EXPECT_EQ(absl::ZeroDuration(), ci.subsecond);
+  EXPECT_EQ(absl::Weekday::wednesday, absl::GetWeekday(ci.cs));
+
+  // Just before the epoch.
+  t -= absl::Nanoseconds(1);
+  ci = tz.At(t);
+  EXPECT_CIVIL_INFO(ci, 1969, 12, 31, 18, 59, 59, -18000, false);
+  EXPECT_EQ(absl::Nanoseconds(999999999), ci.subsecond);
+  EXPECT_EQ(absl::Weekday::wednesday, absl::GetWeekday(ci.cs));
+
+  // Some time later.
+  t += absl::Hours(24) * 2735;
+  t += absl::Hours(18) + absl::Minutes(30) + absl::Seconds(15) +
+       absl::Nanoseconds(9);
+  ci = tz.At(t);
+  EXPECT_CIVIL_INFO(ci, 1977, 6, 28, 14, 30, 15, -14400, true);
+  EXPECT_EQ(8, ci.subsecond / absl::Nanoseconds(1));
+  EXPECT_EQ(absl::Weekday::tuesday, absl::GetWeekday(ci.cs));
+}
+
+TEST(Time, AdditiveOperators) {
+  const absl::Duration d = absl::Nanoseconds(1);
+  const absl::Time t0;
+  const absl::Time t1 = t0 + d;
+
+  EXPECT_EQ(d, t1 - t0);
+  EXPECT_EQ(-d, t0 - t1);
+  EXPECT_EQ(t0, t1 - d);
+
+  absl::Time t(t0);
+  EXPECT_EQ(t0, t);
+  t += d;
+  EXPECT_EQ(t0 + d, t);
+  EXPECT_EQ(d, t - t0);
+  t -= d;
+  EXPECT_EQ(t0, t);
+
+  // Tests overflow between subseconds and seconds.
+  t = absl::UnixEpoch();
+  t += absl::Milliseconds(500);
+  EXPECT_EQ(absl::UnixEpoch() + absl::Milliseconds(500), t);
+  t += absl::Milliseconds(600);
+  EXPECT_EQ(absl::UnixEpoch() + absl::Milliseconds(1100), t);
+  t -= absl::Milliseconds(600);
+  EXPECT_EQ(absl::UnixEpoch() + absl::Milliseconds(500), t);
+  t -= absl::Milliseconds(500);
+  EXPECT_EQ(absl::UnixEpoch(), t);
+}
+
+TEST(Time, RelationalOperators) {
+  constexpr absl::Time t1 = absl::FromUnixNanos(0);
+  constexpr absl::Time t2 = absl::FromUnixNanos(1);
+  constexpr absl::Time t3 = absl::FromUnixNanos(2);
+
+  static_assert(absl::Time() == t1, "");
+  static_assert(t1 == t1, "");
+  static_assert(t2 == t2, "");
+  static_assert(t3 == t3, "");
+
+  static_assert(t1 < t2, "");
+  static_assert(t2 < t3, "");
+  static_assert(t1 < t3, "");
+
+  static_assert(t1 <= t1, "");
+  static_assert(t1 <= t2, "");
+  static_assert(t2 <= t2, "");
+  static_assert(t2 <= t3, "");
+  static_assert(t3 <= t3, "");
+  static_assert(t1 <= t3, "");
+
+  static_assert(t2 > t1, "");
+  static_assert(t3 > t2, "");
+  static_assert(t3 > t1, "");
+
+  static_assert(t2 >= t2, "");
+  static_assert(t2 >= t1, "");
+  static_assert(t3 >= t3, "");
+  static_assert(t3 >= t2, "");
+  static_assert(t1 >= t1, "");
+  static_assert(t3 >= t1, "");
+}
+
+TEST(Time, Infinity) {
+  constexpr absl::Time ifuture = absl::InfiniteFuture();
+  constexpr absl::Time ipast = absl::InfinitePast();
+
+  static_assert(ifuture == ifuture, "");
+  static_assert(ipast == ipast, "");
+  static_assert(ipast < ifuture, "");
+  static_assert(ifuture > ipast, "");
+
+  // Arithmetic saturates
+  EXPECT_EQ(ifuture, ifuture + absl::Seconds(1));
+  EXPECT_EQ(ifuture, ifuture - absl::Seconds(1));
+  EXPECT_EQ(ipast, ipast + absl::Seconds(1));
+  EXPECT_EQ(ipast, ipast - absl::Seconds(1));
+
+  EXPECT_EQ(absl::InfiniteDuration(), ifuture - ifuture);
+  EXPECT_EQ(absl::InfiniteDuration(), ifuture - ipast);
+  EXPECT_EQ(-absl::InfiniteDuration(), ipast - ifuture);
+  EXPECT_EQ(-absl::InfiniteDuration(), ipast - ipast);
+
+  constexpr absl::Time t = absl::UnixEpoch();  // Any finite time.
+  static_assert(t < ifuture, "");
+  static_assert(t > ipast, "");
+
+  EXPECT_EQ(ifuture, t + absl::InfiniteDuration());
+  EXPECT_EQ(ipast, t - absl::InfiniteDuration());
+}
+
+TEST(Time, FloorConversion) {
+#define TEST_FLOOR_CONVERSION(TO, FROM) \
+  EXPECT_EQ(1, TO(FROM(1001)));         \
+  EXPECT_EQ(1, TO(FROM(1000)));         \
+  EXPECT_EQ(0, TO(FROM(999)));          \
+  EXPECT_EQ(0, TO(FROM(1)));            \
+  EXPECT_EQ(0, TO(FROM(0)));            \
+  EXPECT_EQ(-1, TO(FROM(-1)));          \
+  EXPECT_EQ(-1, TO(FROM(-999)));        \
+  EXPECT_EQ(-1, TO(FROM(-1000)));       \
+  EXPECT_EQ(-2, TO(FROM(-1001)));
+
+  TEST_FLOOR_CONVERSION(absl::ToUnixMicros, absl::FromUnixNanos);
+  TEST_FLOOR_CONVERSION(absl::ToUnixMillis, absl::FromUnixMicros);
+  TEST_FLOOR_CONVERSION(absl::ToUnixSeconds, absl::FromUnixMillis);
+  TEST_FLOOR_CONVERSION(absl::ToTimeT, absl::FromUnixMillis);
+
+#undef TEST_FLOOR_CONVERSION
+
+  // Tests ToUnixNanos.
+  EXPECT_EQ(1, absl::ToUnixNanos(absl::UnixEpoch() + absl::Nanoseconds(3) / 2));
+  EXPECT_EQ(1, absl::ToUnixNanos(absl::UnixEpoch() + absl::Nanoseconds(1)));
+  EXPECT_EQ(0, absl::ToUnixNanos(absl::UnixEpoch() + absl::Nanoseconds(1) / 2));
+  EXPECT_EQ(0, absl::ToUnixNanos(absl::UnixEpoch() + absl::Nanoseconds(0)));
+  EXPECT_EQ(-1,
+            absl::ToUnixNanos(absl::UnixEpoch() - absl::Nanoseconds(1) / 2));
+  EXPECT_EQ(-1, absl::ToUnixNanos(absl::UnixEpoch() - absl::Nanoseconds(1)));
+  EXPECT_EQ(-2,
+            absl::ToUnixNanos(absl::UnixEpoch() - absl::Nanoseconds(3) / 2));
+
+  // Tests ToUniversal, which uses a different epoch than the tests above.
+  EXPECT_EQ(1,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(101)));
+  EXPECT_EQ(1,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(100)));
+  EXPECT_EQ(0,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(99)));
+  EXPECT_EQ(0,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(1)));
+  EXPECT_EQ(0,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(0)));
+  EXPECT_EQ(-1,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(-1)));
+  EXPECT_EQ(-1,
+            absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(-99)));
+  EXPECT_EQ(
+      -1, absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(-100)));
+  EXPECT_EQ(
+      -2, absl::ToUniversal(absl::UniversalEpoch() + absl::Nanoseconds(-101)));
+
+  // Tests ToTimespec()/TimeFromTimespec()
+  const struct {
+    absl::Time t;
+    timespec ts;
+  } to_ts[] = {
+      {absl::FromUnixSeconds(1) + absl::Nanoseconds(1), {1, 1}},
+      {absl::FromUnixSeconds(1) + absl::Nanoseconds(1) / 2, {1, 0}},
+      {absl::FromUnixSeconds(1) + absl::Nanoseconds(0), {1, 0}},
+      {absl::FromUnixSeconds(0) + absl::Nanoseconds(0), {0, 0}},
+      {absl::FromUnixSeconds(0) - absl::Nanoseconds(1) / 2, {-1, 999999999}},
+      {absl::FromUnixSeconds(0) - absl::Nanoseconds(1), {-1, 999999999}},
+      {absl::FromUnixSeconds(-1) + absl::Nanoseconds(1), {-1, 1}},
+      {absl::FromUnixSeconds(-1) + absl::Nanoseconds(1) / 2, {-1, 0}},
+      {absl::FromUnixSeconds(-1) + absl::Nanoseconds(0), {-1, 0}},
+      {absl::FromUnixSeconds(-1) - absl::Nanoseconds(1) / 2, {-2, 999999999}},
+  };
+  for (const auto& test : to_ts) {
+    EXPECT_THAT(absl::ToTimespec(test.t), TimespecMatcher(test.ts));
+  }
+  const struct {
+    timespec ts;
+    absl::Time t;
+  } from_ts[] = {
+      {{1, 1}, absl::FromUnixSeconds(1) + absl::Nanoseconds(1)},
+      {{1, 0}, absl::FromUnixSeconds(1) + absl::Nanoseconds(0)},
+      {{0, 0}, absl::FromUnixSeconds(0) + absl::Nanoseconds(0)},
+      {{0, -1}, absl::FromUnixSeconds(0) - absl::Nanoseconds(1)},
+      {{-1, 999999999}, absl::FromUnixSeconds(0) - absl::Nanoseconds(1)},
+      {{-1, 1}, absl::FromUnixSeconds(-1) + absl::Nanoseconds(1)},
+      {{-1, 0}, absl::FromUnixSeconds(-1) + absl::Nanoseconds(0)},
+      {{-1, -1}, absl::FromUnixSeconds(-1) - absl::Nanoseconds(1)},
+      {{-2, 999999999}, absl::FromUnixSeconds(-1) - absl::Nanoseconds(1)},
+  };
+  for (const auto& test : from_ts) {
+    EXPECT_EQ(test.t, absl::TimeFromTimespec(test.ts));
+  }
+
+  // Tests ToTimeval()/TimeFromTimeval() (same as timespec above)
+  const struct {
+    absl::Time t;
+    timeval tv;
+  } to_tv[] = {
+      {absl::FromUnixSeconds(1) + absl::Microseconds(1), {1, 1}},
+      {absl::FromUnixSeconds(1) + absl::Microseconds(1) / 2, {1, 0}},
+      {absl::FromUnixSeconds(1) + absl::Microseconds(0), {1, 0}},
+      {absl::FromUnixSeconds(0) + absl::Microseconds(0), {0, 0}},
+      {absl::FromUnixSeconds(0) - absl::Microseconds(1) / 2, {-1, 999999}},
+      {absl::FromUnixSeconds(0) - absl::Microseconds(1), {-1, 999999}},
+      {absl::FromUnixSeconds(-1) + absl::Microseconds(1), {-1, 1}},
+      {absl::FromUnixSeconds(-1) + absl::Microseconds(1) / 2, {-1, 0}},
+      {absl::FromUnixSeconds(-1) + absl::Microseconds(0), {-1, 0}},
+      {absl::FromUnixSeconds(-1) - absl::Microseconds(1) / 2, {-2, 999999}},
+  };
+  for (const auto& test : to_tv) {
+    EXPECT_THAT(ToTimeval(test.t), TimevalMatcher(test.tv));
+  }
+  const struct {
+    timeval tv;
+    absl::Time t;
+  } from_tv[] = {
+      {{1, 1}, absl::FromUnixSeconds(1) + absl::Microseconds(1)},
+      {{1, 0}, absl::FromUnixSeconds(1) + absl::Microseconds(0)},
+      {{0, 0}, absl::FromUnixSeconds(0) + absl::Microseconds(0)},
+      {{0, -1}, absl::FromUnixSeconds(0) - absl::Microseconds(1)},
+      {{-1, 999999}, absl::FromUnixSeconds(0) - absl::Microseconds(1)},
+      {{-1, 1}, absl::FromUnixSeconds(-1) + absl::Microseconds(1)},
+      {{-1, 0}, absl::FromUnixSeconds(-1) + absl::Microseconds(0)},
+      {{-1, -1}, absl::FromUnixSeconds(-1) - absl::Microseconds(1)},
+      {{-2, 999999}, absl::FromUnixSeconds(-1) - absl::Microseconds(1)},
+  };
+  for (const auto& test : from_tv) {
+    EXPECT_EQ(test.t, absl::TimeFromTimeval(test.tv));
+  }
+
+  // Tests flooring near negative infinity.
+  const int64_t min_plus_1 = std::numeric_limits<int64_t>::min() + 1;
+  EXPECT_EQ(min_plus_1, absl::ToUnixSeconds(absl::FromUnixSeconds(min_plus_1)));
+  EXPECT_EQ(std::numeric_limits<int64_t>::min(),
+            absl::ToUnixSeconds(absl::FromUnixSeconds(min_plus_1) -
+                                absl::Nanoseconds(1) / 2));
+
+  // Tests flooring near positive infinity.
+  EXPECT_EQ(std::numeric_limits<int64_t>::max(),
+            absl::ToUnixSeconds(
+                absl::FromUnixSeconds(std::numeric_limits<int64_t>::max()) +
+                absl::Nanoseconds(1) / 2));
+  EXPECT_EQ(std::numeric_limits<int64_t>::max(),
+            absl::ToUnixSeconds(
+                absl::FromUnixSeconds(std::numeric_limits<int64_t>::max())));
+  EXPECT_EQ(std::numeric_limits<int64_t>::max() - 1,
+            absl::ToUnixSeconds(
+                absl::FromUnixSeconds(std::numeric_limits<int64_t>::max()) -
+                absl::Nanoseconds(1) / 2));
+}
+
+TEST(Time, RoundtripConversion) {
+#define TEST_CONVERSION_ROUND_TRIP(SOURCE, FROM, TO, MATCHER) \
+  EXPECT_THAT(TO(FROM(SOURCE)), MATCHER(SOURCE))
+
+  // FromUnixNanos() and ToUnixNanos()
+  int64_t now_ns = absl::GetCurrentTimeNanos();
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromUnixNanos, absl::ToUnixNanos,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromUnixNanos, absl::ToUnixNanos,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromUnixNanos, absl::ToUnixNanos,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(now_ns, absl::FromUnixNanos, absl::ToUnixNanos,
+                             testing::Eq)
+      << now_ns;
+
+  // FromUnixMicros() and ToUnixMicros()
+  int64_t now_us = absl::GetCurrentTimeNanos() / 1000;
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromUnixMicros, absl::ToUnixMicros,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromUnixMicros, absl::ToUnixMicros,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromUnixMicros, absl::ToUnixMicros,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(now_us, absl::FromUnixMicros, absl::ToUnixMicros,
+                             testing::Eq)
+      << now_us;
+
+  // FromUnixMillis() and ToUnixMillis()
+  int64_t now_ms = absl::GetCurrentTimeNanos() / 1000000;
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromUnixMillis, absl::ToUnixMillis,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromUnixMillis, absl::ToUnixMillis,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromUnixMillis, absl::ToUnixMillis,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(now_ms, absl::FromUnixMillis, absl::ToUnixMillis,
+                             testing::Eq)
+      << now_ms;
+
+  // FromUnixSeconds() and ToUnixSeconds()
+  int64_t now_s = std::time(nullptr);
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromUnixSeconds, absl::ToUnixSeconds,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromUnixSeconds, absl::ToUnixSeconds,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromUnixSeconds, absl::ToUnixSeconds,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(now_s, absl::FromUnixSeconds, absl::ToUnixSeconds,
+                             testing::Eq)
+      << now_s;
+
+  // FromTimeT() and ToTimeT()
+  time_t now_time_t = std::time(nullptr);
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromTimeT, absl::ToTimeT, testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromTimeT, absl::ToTimeT, testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromTimeT, absl::ToTimeT, testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(now_time_t, absl::FromTimeT, absl::ToTimeT,
+                             testing::Eq)
+      << now_time_t;
+
+  // TimeFromTimeval() and ToTimeval()
+  timeval tv;
+  tv.tv_sec = -1;
+  tv.tv_usec = 0;
+  TEST_CONVERSION_ROUND_TRIP(tv, absl::TimeFromTimeval, absl::ToTimeval,
+                             TimevalMatcher);
+  tv.tv_sec = -1;
+  tv.tv_usec = 999999;
+  TEST_CONVERSION_ROUND_TRIP(tv, absl::TimeFromTimeval, absl::ToTimeval,
+                             TimevalMatcher);
+  tv.tv_sec = 0;
+  tv.tv_usec = 0;
+  TEST_CONVERSION_ROUND_TRIP(tv, absl::TimeFromTimeval, absl::ToTimeval,
+                             TimevalMatcher);
+  tv.tv_sec = 0;
+  tv.tv_usec = 1;
+  TEST_CONVERSION_ROUND_TRIP(tv, absl::TimeFromTimeval, absl::ToTimeval,
+                             TimevalMatcher);
+  tv.tv_sec = 1;
+  tv.tv_usec = 0;
+  TEST_CONVERSION_ROUND_TRIP(tv, absl::TimeFromTimeval, absl::ToTimeval,
+                             TimevalMatcher);
+
+  // TimeFromTimespec() and ToTimespec()
+  timespec ts;
+  ts.tv_sec = -1;
+  ts.tv_nsec = 0;
+  TEST_CONVERSION_ROUND_TRIP(ts, absl::TimeFromTimespec, absl::ToTimespec,
+                             TimespecMatcher);
+  ts.tv_sec = -1;
+  ts.tv_nsec = 999999999;
+  TEST_CONVERSION_ROUND_TRIP(ts, absl::TimeFromTimespec, absl::ToTimespec,
+                             TimespecMatcher);
+  ts.tv_sec = 0;
+  ts.tv_nsec = 0;
+  TEST_CONVERSION_ROUND_TRIP(ts, absl::TimeFromTimespec, absl::ToTimespec,
+                             TimespecMatcher);
+  ts.tv_sec = 0;
+  ts.tv_nsec = 1;
+  TEST_CONVERSION_ROUND_TRIP(ts, absl::TimeFromTimespec, absl::ToTimespec,
+                             TimespecMatcher);
+  ts.tv_sec = 1;
+  ts.tv_nsec = 0;
+  TEST_CONVERSION_ROUND_TRIP(ts, absl::TimeFromTimespec, absl::ToTimespec,
+                             TimespecMatcher);
+
+  // FromUDate() and ToUDate()
+  double now_ud = absl::GetCurrentTimeNanos() / 1000000;
+  TEST_CONVERSION_ROUND_TRIP(-1.5, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(-0.5, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(0.5, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(1.5, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq);
+  TEST_CONVERSION_ROUND_TRIP(now_ud, absl::FromUDate, absl::ToUDate,
+                             testing::DoubleEq)
+      << std::fixed << std::setprecision(17) << now_ud;
+
+  // FromUniversal() and ToUniversal()
+  int64_t now_uni = ((719162LL * (24 * 60 * 60)) * (1000 * 1000 * 10)) +
+                    (absl::GetCurrentTimeNanos() / 100);
+  TEST_CONVERSION_ROUND_TRIP(-1, absl::FromUniversal, absl::ToUniversal,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(0, absl::FromUniversal, absl::ToUniversal,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(1, absl::FromUniversal, absl::ToUniversal,
+                             testing::Eq);
+  TEST_CONVERSION_ROUND_TRIP(now_uni, absl::FromUniversal, absl::ToUniversal,
+                             testing::Eq)
+      << now_uni;
+
+#undef TEST_CONVERSION_ROUND_TRIP
+}
+
+template <typename Duration>
+std::chrono::system_clock::time_point MakeChronoUnixTime(const Duration& d) {
+  return std::chrono::system_clock::from_time_t(0) + d;
+}
+
+TEST(Time, FromChrono) {
+  EXPECT_EQ(absl::FromTimeT(-1),
+            absl::FromChrono(std::chrono::system_clock::from_time_t(-1)));
+  EXPECT_EQ(absl::FromTimeT(0),
+            absl::FromChrono(std::chrono::system_clock::from_time_t(0)));
+  EXPECT_EQ(absl::FromTimeT(1),
+            absl::FromChrono(std::chrono::system_clock::from_time_t(1)));
+
+  EXPECT_EQ(
+      absl::FromUnixMillis(-1),
+      absl::FromChrono(MakeChronoUnixTime(std::chrono::milliseconds(-1))));
+  EXPECT_EQ(absl::FromUnixMillis(0),
+            absl::FromChrono(MakeChronoUnixTime(std::chrono::milliseconds(0))));
+  EXPECT_EQ(absl::FromUnixMillis(1),
+            absl::FromChrono(MakeChronoUnixTime(std::chrono::milliseconds(1))));
+
+  // Chrono doesn't define exactly its range and precision (neither does
+  // absl::Time), so let's simply test +/- ~100 years to make sure things work.
+  const auto century_sec = 60 * 60 * 24 * 365 * int64_t{100};
+  const auto century = std::chrono::seconds(century_sec);
+  const auto chrono_future = MakeChronoUnixTime(century);
+  const auto chrono_past = MakeChronoUnixTime(-century);
+  EXPECT_EQ(absl::FromUnixSeconds(century_sec),
+            absl::FromChrono(chrono_future));
+  EXPECT_EQ(absl::FromUnixSeconds(-century_sec), absl::FromChrono(chrono_past));
+
+  // Roundtrip them both back to chrono.
+  EXPECT_EQ(chrono_future,
+            absl::ToChronoTime(absl::FromUnixSeconds(century_sec)));
+  EXPECT_EQ(chrono_past,
+            absl::ToChronoTime(absl::FromUnixSeconds(-century_sec)));
+}
+
+TEST(Time, ToChronoTime) {
+  EXPECT_EQ(std::chrono::system_clock::from_time_t(-1),
+            absl::ToChronoTime(absl::FromTimeT(-1)));
+  EXPECT_EQ(std::chrono::system_clock::from_time_t(0),
+            absl::ToChronoTime(absl::FromTimeT(0)));
+  EXPECT_EQ(std::chrono::system_clock::from_time_t(1),
+            absl::ToChronoTime(absl::FromTimeT(1)));
+
+  EXPECT_EQ(MakeChronoUnixTime(std::chrono::milliseconds(-1)),
+            absl::ToChronoTime(absl::FromUnixMillis(-1)));
+  EXPECT_EQ(MakeChronoUnixTime(std::chrono::milliseconds(0)),
+            absl::ToChronoTime(absl::FromUnixMillis(0)));
+  EXPECT_EQ(MakeChronoUnixTime(std::chrono::milliseconds(1)),
+            absl::ToChronoTime(absl::FromUnixMillis(1)));
+
+  // Time before the Unix epoch should floor, not trunc.
+  const auto tick = absl::Nanoseconds(1) / 4;
+  EXPECT_EQ(std::chrono::system_clock::from_time_t(0) -
+                std::chrono::system_clock::duration(1),
+            absl::ToChronoTime(absl::UnixEpoch() - tick));
+}
+
+// Check that absl::int128 works as a std::chrono::duration representation.
+TEST(Time, Chrono128) {
+  // Define a std::chrono::time_point type whose time[sic]_since_epoch() is
+  // a signed 128-bit count of attoseconds. This has a range and resolution
+  // (currently) beyond those of absl::Time, and undoubtedly also beyond those
+  // of std::chrono::system_clock::time_point.
+  //
+  // Note: The to/from-chrono support should probably be updated to handle
+  // such wide representations.
+  using Timestamp =
+      std::chrono::time_point<std::chrono::system_clock,
+                              std::chrono::duration<absl::int128, std::atto>>;
+
+  // Expect that we can round-trip the std::chrono::system_clock::time_point
+  // extremes through both absl::Time and Timestamp, and that Timestamp can
+  // handle the (current) absl::Time extremes.
+  //
+  // Note: We should use std::chrono::floor() instead of time_point_cast(),
+  // but floor() is only available since c++17.
+  for (const auto tp : {std::chrono::system_clock::time_point::min(),
+                        std::chrono::system_clock::time_point::max()}) {
+    EXPECT_EQ(tp, absl::ToChronoTime(absl::FromChrono(tp)));
+    EXPECT_EQ(tp, std::chrono::time_point_cast<
+                      std::chrono::system_clock::time_point::duration>(
+                      std::chrono::time_point_cast<Timestamp::duration>(tp)));
+  }
+  Timestamp::duration::rep v = std::numeric_limits<int64_t>::min();
+  v *= Timestamp::duration::period::den;
+  auto ts = Timestamp(Timestamp::duration(v));
+  ts += std::chrono::duration<int64_t, std::atto>(0);
+  EXPECT_EQ(std::numeric_limits<int64_t>::min(),
+            ts.time_since_epoch().count() / Timestamp::duration::period::den);
+  EXPECT_EQ(0,
+            ts.time_since_epoch().count() % Timestamp::duration::period::den);
+  v = std::numeric_limits<int64_t>::max();
+  v *= Timestamp::duration::period::den;
+  ts = Timestamp(Timestamp::duration(v));
+  ts += std::chrono::duration<int64_t, std::atto>(999999999750000000);
+  EXPECT_EQ(std::numeric_limits<int64_t>::max(),
+            ts.time_since_epoch().count() / Timestamp::duration::period::den);
+  EXPECT_EQ(999999999750000000,
+            ts.time_since_epoch().count() % Timestamp::duration::period::den);
+}
+
+TEST(Time, TimeZoneAt) {
+  const absl::TimeZone nyc =
+      absl::time_internal::LoadTimeZone("America/New_York");
+  const std::string fmt = "%a, %e %b %Y %H:%M:%S %z (%Z)";
+
+  // A non-transition where the civil time is unique.
+  absl::CivilSecond nov01(2013, 11, 1, 8, 30, 0);
+  const auto nov01_ci = nyc.At(nov01);
+  EXPECT_EQ(absl::TimeZone::TimeInfo::UNIQUE, nov01_ci.kind);
+  EXPECT_EQ("Fri,  1 Nov 2013 08:30:00 -0400 (EDT)",
+            absl::FormatTime(fmt, nov01_ci.pre, nyc));
+  EXPECT_EQ(nov01_ci.pre, nov01_ci.trans);
+  EXPECT_EQ(nov01_ci.pre, nov01_ci.post);
+  EXPECT_EQ(nov01_ci.pre, absl::FromCivil(nov01, nyc));
+
+  // A Spring DST transition, when there is a gap in civil time
+  // and we prefer the later of the possible interpretations of a
+  // non-existent time.
+  absl::CivilSecond mar13(2011, 3, 13, 2, 15, 0);
+  const auto mar_ci = nyc.At(mar13);
+  EXPECT_EQ(absl::TimeZone::TimeInfo::SKIPPED, mar_ci.kind);
+  EXPECT_EQ("Sun, 13 Mar 2011 03:15:00 -0400 (EDT)",
+            absl::FormatTime(fmt, mar_ci.pre, nyc));
+  EXPECT_EQ("Sun, 13 Mar 2011 03:00:00 -0400 (EDT)",
+            absl::FormatTime(fmt, mar_ci.trans, nyc));
+  EXPECT_EQ("Sun, 13 Mar 2011 01:15:00 -0500 (EST)",
+            absl::FormatTime(fmt, mar_ci.post, nyc));
+  EXPECT_EQ(mar_ci.trans, absl::FromCivil(mar13, nyc));
+
+  // A Fall DST transition, when civil times are repeated and
+  // we prefer the earlier of the possible interpretations of an
+  // ambiguous time.
+  absl::CivilSecond nov06(2011, 11, 6, 1, 15, 0);
+  const auto nov06_ci = nyc.At(nov06);
+  EXPECT_EQ(absl::TimeZone::TimeInfo::REPEATED, nov06_ci.kind);
+  EXPECT_EQ("Sun,  6 Nov 2011 01:15:00 -0400 (EDT)",
+            absl::FormatTime(fmt, nov06_ci.pre, nyc));
+  EXPECT_EQ("Sun,  6 Nov 2011 01:00:00 -0500 (EST)",
+            absl::FormatTime(fmt, nov06_ci.trans, nyc));
+  EXPECT_EQ("Sun,  6 Nov 2011 01:15:00 -0500 (EST)",
+            absl::FormatTime(fmt, nov06_ci.post, nyc));
+  EXPECT_EQ(nov06_ci.pre, absl::FromCivil(nov06, nyc));
+
+  // Check that (time_t) -1 is handled correctly.
+  absl::CivilSecond minus1(1969, 12, 31, 18, 59, 59);
+  const auto minus1_cl = nyc.At(minus1);
+  EXPECT_EQ(absl::TimeZone::TimeInfo::UNIQUE, minus1_cl.kind);
+  EXPECT_EQ(-1, absl::ToTimeT(minus1_cl.pre));
+  EXPECT_EQ("Wed, 31 Dec 1969 18:59:59 -0500 (EST)",
+            absl::FormatTime(fmt, minus1_cl.pre, nyc));
+  EXPECT_EQ("Wed, 31 Dec 1969 23:59:59 +0000 (UTC)",
+            absl::FormatTime(fmt, minus1_cl.pre, absl::UTCTimeZone()));
+}
+
+// FromCivil(CivilSecond(year, mon, day, hour, min, sec), UTCTimeZone())
+// has a specialized fastpath implementation, which we exercise here.
+TEST(Time, FromCivilUTC) {
+  const absl::TimeZone utc = absl::UTCTimeZone();
+  const std::string fmt = "%a, %e %b %Y %H:%M:%S %z (%Z)";
+  const int kMax = std::numeric_limits<int>::max();
+  const int kMin = std::numeric_limits<int>::min();
+  absl::Time t;
+
+  // 292091940881 is the last positive year to use the fastpath.
+  t = absl::FromCivil(
+      absl::CivilSecond(292091940881, kMax, kMax, kMax, kMax, kMax), utc);
+  EXPECT_EQ("Fri, 25 Nov 292277026596 12:21:07 +0000 (UTC)",
+            absl::FormatTime(fmt, t, utc));
+  t = absl::FromCivil(
+      absl::CivilSecond(292091940882, kMax, kMax, kMax, kMax, kMax), utc);
+  EXPECT_EQ("infinite-future", absl::FormatTime(fmt, t, utc));  // no overflow
+
+  // -292091936940 is the last negative year to use the fastpath.
+  t = absl::FromCivil(
+      absl::CivilSecond(-292091936940, kMin, kMin, kMin, kMin, kMin), utc);
+  EXPECT_EQ("Fri,  1 Nov -292277022657 10:37:52 +0000 (UTC)",
+            absl::FormatTime(fmt, t, utc));
+  t = absl::FromCivil(
+      absl::CivilSecond(-292091936941, kMin, kMin, kMin, kMin, kMin), utc);
+  EXPECT_EQ("infinite-past", absl::FormatTime(fmt, t, utc));  // no underflow
+
+  // Check that we're counting leap years correctly.
+  t = absl::FromCivil(absl::CivilSecond(1900, 2, 28, 23, 59, 59), utc);
+  EXPECT_EQ("Wed, 28 Feb 1900 23:59:59 +0000 (UTC)",
+            absl::FormatTime(fmt, t, utc));
+  t = absl::FromCivil(absl::CivilSecond(1900, 3, 1, 0, 0, 0), utc);
+  EXPECT_EQ("Thu,  1 Mar 1900 00:00:00 +0000 (UTC)",
+            absl::FormatTime(fmt, t, utc));
+  t = absl::FromCivil(absl::CivilSecond(2000, 2, 29, 23, 59, 59), utc);
+  EXPECT_EQ("Tue, 29 Feb 2000 23:59:59 +0000 (UTC)",
+            absl::FormatTime(fmt, t, utc));
+  t = absl::FromCivil(absl::CivilSecond(2000, 3, 1, 0, 0, 0), utc);
+  EXPECT_EQ("Wed,  1 Mar 2000 00:00:00 +0000 (UTC)",
+            absl::FormatTime(fmt, t, utc));
+}
+
+TEST(Time, ToTM) {
+  const absl::TimeZone utc = absl::UTCTimeZone();
+
+  // Compares the results of ToTM() to gmtime_r() for lots of times over the
+  // course of a few days.
+  const absl::Time start =
+      absl::FromCivil(absl::CivilSecond(2014, 1, 2, 3, 4, 5), utc);
+  const absl::Time end =
+      absl::FromCivil(absl::CivilSecond(2014, 1, 5, 3, 4, 5), utc);
+  for (absl::Time t = start; t < end; t += absl::Seconds(30)) {
+    const struct tm tm_bt = ToTM(t, utc);
+    const time_t tt = absl::ToTimeT(t);
+    struct tm tm_lc;
+#ifdef _WIN32
+    gmtime_s(&tm_lc, &tt);
+#else
+    gmtime_r(&tt, &tm_lc);
+#endif
+    EXPECT_EQ(tm_lc.tm_year, tm_bt.tm_year);
+    EXPECT_EQ(tm_lc.tm_mon, tm_bt.tm_mon);
+    EXPECT_EQ(tm_lc.tm_mday, tm_bt.tm_mday);
+    EXPECT_EQ(tm_lc.tm_hour, tm_bt.tm_hour);
+    EXPECT_EQ(tm_lc.tm_min, tm_bt.tm_min);
+    EXPECT_EQ(tm_lc.tm_sec, tm_bt.tm_sec);
+    EXPECT_EQ(tm_lc.tm_wday, tm_bt.tm_wday);
+    EXPECT_EQ(tm_lc.tm_yday, tm_bt.tm_yday);
+    EXPECT_EQ(tm_lc.tm_isdst, tm_bt.tm_isdst);
+
+    ASSERT_FALSE(HasFailure());
+  }
+
+  // Checks that the tm_isdst field is correct when in standard time.
+  const absl::TimeZone nyc =
+      absl::time_internal::LoadTimeZone("America/New_York");
+  absl::Time t = absl::FromCivil(absl::CivilSecond(2014, 3, 1, 0, 0, 0), nyc);
+  struct tm tm = ToTM(t, nyc);
+  EXPECT_FALSE(tm.tm_isdst);
+
+  // Checks that the tm_isdst field is correct when in daylight time.
+  t = absl::FromCivil(absl::CivilSecond(2014, 4, 1, 0, 0, 0), nyc);
+  tm = ToTM(t, nyc);
+  EXPECT_TRUE(tm.tm_isdst);
+
+  // Checks overflow.
+  tm = ToTM(absl::InfiniteFuture(), nyc);
+  EXPECT_EQ(std::numeric_limits<int>::max() - 1900, tm.tm_year);
+  EXPECT_EQ(11, tm.tm_mon);
+  EXPECT_EQ(31, tm.tm_mday);
+  EXPECT_EQ(23, tm.tm_hour);
+  EXPECT_EQ(59, tm.tm_min);
+  EXPECT_EQ(59, tm.tm_sec);
+  EXPECT_EQ(4, tm.tm_wday);
+  EXPECT_EQ(364, tm.tm_yday);
+  EXPECT_FALSE(tm.tm_isdst);
+
+  // Checks underflow.
+  tm = ToTM(absl::InfinitePast(), nyc);
+  EXPECT_EQ(std::numeric_limits<int>::min(), tm.tm_year);
+  EXPECT_EQ(0, tm.tm_mon);
+  EXPECT_EQ(1, tm.tm_mday);
+  EXPECT_EQ(0, tm.tm_hour);
+  EXPECT_EQ(0, tm.tm_min);
+  EXPECT_EQ(0, tm.tm_sec);
+  EXPECT_EQ(0, tm.tm_wday);
+  EXPECT_EQ(0, tm.tm_yday);
+  EXPECT_FALSE(tm.tm_isdst);
+}
+
+TEST(Time, FromTM) {
+  const absl::TimeZone nyc =
+      absl::time_internal::LoadTimeZone("America/New_York");
+
+  // Verifies that tm_isdst doesn't affect anything when the time is unique.
+  struct tm tm;
+  std::memset(&tm, 0, sizeof(tm));
+  tm.tm_year = 2014 - 1900;
+  tm.tm_mon = 6 - 1;
+  tm.tm_mday = 28;
+  tm.tm_hour = 1;
+  tm.tm_min = 2;
+  tm.tm_sec = 3;
+  tm.tm_isdst = -1;
+  absl::Time t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-06-28T01:02:03-04:00", absl::FormatTime(t, nyc));  // DST
+  tm.tm_isdst = 0;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-06-28T01:02:03-04:00", absl::FormatTime(t, nyc));  // DST
+  tm.tm_isdst = 1;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-06-28T01:02:03-04:00", absl::FormatTime(t, nyc));  // DST
+
+  // Adjusts tm to refer to an ambiguous time.
+  tm.tm_year = 2014 - 1900;
+  tm.tm_mon = 11 - 1;
+  tm.tm_mday = 2;
+  tm.tm_hour = 1;
+  tm.tm_min = 30;
+  tm.tm_sec = 42;
+  tm.tm_isdst = -1;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-11-02T01:30:42-04:00", absl::FormatTime(t, nyc));  // DST
+  tm.tm_isdst = 0;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-11-02T01:30:42-05:00", absl::FormatTime(t, nyc));  // STD
+  tm.tm_isdst = 1;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-11-02T01:30:42-04:00", absl::FormatTime(t, nyc));  // DST
+
+  // Adjusts tm to refer to a skipped time.
+  tm.tm_year = 2014 - 1900;
+  tm.tm_mon = 3 - 1;
+  tm.tm_mday = 9;
+  tm.tm_hour = 2;
+  tm.tm_min = 30;
+  tm.tm_sec = 42;
+  tm.tm_isdst = -1;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-03-09T03:30:42-04:00", absl::FormatTime(t, nyc));  // DST
+  tm.tm_isdst = 0;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-03-09T01:30:42-05:00", absl::FormatTime(t, nyc));  // STD
+  tm.tm_isdst = 1;
+  t = FromTM(tm, nyc);
+  EXPECT_EQ("2014-03-09T03:30:42-04:00", absl::FormatTime(t, nyc));  // DST
+
+  // Adjusts tm to refer to a time with a year larger than 2147483647.
+  tm.tm_year = 2147483647 - 1900 + 1;
+  tm.tm_mon = 6 - 1;
+  tm.tm_mday = 28;
+  tm.tm_hour = 1;
+  tm.tm_min = 2;
+  tm.tm_sec = 3;
+  tm.tm_isdst = -1;
+  t = FromTM(tm, absl::UTCTimeZone());
+  EXPECT_EQ("2147483648-06-28T01:02:03+00:00",
+            absl::FormatTime(t, absl::UTCTimeZone()));
+
+  // Adjusts tm to refer to a time with a very large month.
+  tm.tm_year = 2019 - 1900;
+  tm.tm_mon = 2147483647;
+  tm.tm_mday = 28;
+  tm.tm_hour = 1;
+  tm.tm_min = 2;
+  tm.tm_sec = 3;
+  tm.tm_isdst = -1;
+  t = FromTM(tm, absl::UTCTimeZone());
+  EXPECT_EQ("178958989-08-28T01:02:03+00:00",
+            absl::FormatTime(t, absl::UTCTimeZone()));
+}
+
+TEST(Time, TMRoundTrip) {
+  const absl::TimeZone nyc =
+      absl::time_internal::LoadTimeZone("America/New_York");
+
+  // Test round-tripping across a skipped transition
+  absl::Time start = absl::FromCivil(absl::CivilHour(2014, 3, 9, 0), nyc);
+  absl::Time end = absl::FromCivil(absl::CivilHour(2014, 3, 9, 4), nyc);
+  for (absl::Time t = start; t < end; t += absl::Minutes(1)) {
+    struct tm tm = ToTM(t, nyc);
+    absl::Time rt = FromTM(tm, nyc);
+    EXPECT_EQ(rt, t);
+  }
+
+  // Test round-tripping across an ambiguous transition
+  start = absl::FromCivil(absl::CivilHour(2014, 11, 2, 0), nyc);
+  end = absl::FromCivil(absl::CivilHour(2014, 11, 2, 4), nyc);
+  for (absl::Time t = start; t < end; t += absl::Minutes(1)) {
+    struct tm tm = ToTM(t, nyc);
+    absl::Time rt = FromTM(tm, nyc);
+    EXPECT_EQ(rt, t);
+  }
+
+  // Test round-tripping of unique instants crossing a day boundary
+  start = absl::FromCivil(absl::CivilHour(2014, 6, 27, 22), nyc);
+  end = absl::FromCivil(absl::CivilHour(2014, 6, 28, 4), nyc);
+  for (absl::Time t = start; t < end; t += absl::Minutes(1)) {
+    struct tm tm = ToTM(t, nyc);
+    absl::Time rt = FromTM(tm, nyc);
+    EXPECT_EQ(rt, t);
+  }
+}
+
+TEST(Time, Range) {
+  // The API's documented range is +/- 100 billion years.
+  const absl::Duration range = absl::Hours(24) * 365.2425 * 100000000000;
+
+  // Arithmetic and comparison still works at +/-range around base values.
+  absl::Time bases[2] = {absl::UnixEpoch(), absl::Now()};
+  for (const auto base : bases) {
+    absl::Time bottom = base - range;
+    EXPECT_GT(bottom, bottom - absl::Nanoseconds(1));
+    EXPECT_LT(bottom, bottom + absl::Nanoseconds(1));
+    absl::Time top = base + range;
+    EXPECT_GT(top, top - absl::Nanoseconds(1));
+    EXPECT_LT(top, top + absl::Nanoseconds(1));
+    absl::Duration full_range = 2 * range;
+    EXPECT_EQ(full_range, top - bottom);
+    EXPECT_EQ(-full_range, bottom - top);
+  }
+}
+
+TEST(Time, Limits) {
+  // It is an implementation detail that Time().rep_ == ZeroDuration(),
+  // and that the resolution of a Duration is 1/4 of a nanosecond.
+  const absl::Time zero;
+  const absl::Time max =
+      zero + absl::Seconds(std::numeric_limits<int64_t>::max()) +
+      absl::Nanoseconds(999999999) + absl::Nanoseconds(3) / 4;
+  const absl::Time min =
+      zero + absl::Seconds(std::numeric_limits<int64_t>::min());
+
+  // Some simple max/min bounds checks.
+  EXPECT_LT(max, absl::InfiniteFuture());
+  EXPECT_GT(min, absl::InfinitePast());
+  EXPECT_LT(zero, max);
+  EXPECT_GT(zero, min);
+  EXPECT_GE(absl::UnixEpoch(), min);
+  EXPECT_LT(absl::UnixEpoch(), max);
+
+  // Check sign of Time differences.
+  EXPECT_LT(absl::ZeroDuration(), max - zero);
+  EXPECT_LT(absl::ZeroDuration(),
+            zero - absl::Nanoseconds(1) / 4 - min);  // avoid zero - min
+
+  // Arithmetic works at max - 0.25ns and min + 0.25ns.
+  EXPECT_GT(max, max - absl::Nanoseconds(1) / 4);
+  EXPECT_LT(min, min + absl::Nanoseconds(1) / 4);
+}
+
+TEST(Time, ConversionSaturation) {
+  const absl::TimeZone utc = absl::UTCTimeZone();
+  absl::Time t;
+
+  const auto max_time_t = std::numeric_limits<time_t>::max();
+  const auto min_time_t = std::numeric_limits<time_t>::min();
+  time_t tt = max_time_t - 1;
+  t = absl::FromTimeT(tt);
+  tt = absl::ToTimeT(t);
+  EXPECT_EQ(max_time_t - 1, tt);
+  t += absl::Seconds(1);
+  tt = absl::ToTimeT(t);
+  EXPECT_EQ(max_time_t, tt);
+  t += absl::Seconds(1);  // no effect
+  tt = absl::ToTimeT(t);
+  EXPECT_EQ(max_time_t, tt);
+
+  tt = min_time_t + 1;
+  t = absl::FromTimeT(tt);
+  tt = absl::ToTimeT(t);
+  EXPECT_EQ(min_time_t + 1, tt);
+  t -= absl::Seconds(1);
+  tt = absl::ToTimeT(t);
+  EXPECT_EQ(min_time_t, tt);
+  t -= absl::Seconds(1);  // no effect
+  tt = absl::ToTimeT(t);
+  EXPECT_EQ(min_time_t, tt);
+
+  const auto max_timeval_sec =
+      std::numeric_limits<decltype(timeval::tv_sec)>::max();
+  const auto min_timeval_sec =
+      std::numeric_limits<decltype(timeval::tv_sec)>::min();
+  timeval tv;
+  tv.tv_sec = max_timeval_sec;
+  tv.tv_usec = 999998;
+  t = absl::TimeFromTimeval(tv);
+  tv = ToTimeval(t);
+  EXPECT_EQ(max_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(999998, tv.tv_usec);
+  t += absl::Microseconds(1);
+  tv = ToTimeval(t);
+  EXPECT_EQ(max_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(999999, tv.tv_usec);
+  t += absl::Microseconds(1);  // no effect
+  tv = ToTimeval(t);
+  EXPECT_EQ(max_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(999999, tv.tv_usec);
+
+  tv.tv_sec = min_timeval_sec;
+  tv.tv_usec = 1;
+  t = absl::TimeFromTimeval(tv);
+  tv = ToTimeval(t);
+  EXPECT_EQ(min_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(1, tv.tv_usec);
+  t -= absl::Microseconds(1);
+  tv = ToTimeval(t);
+  EXPECT_EQ(min_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(0, tv.tv_usec);
+  t -= absl::Microseconds(1);  // no effect
+  tv = ToTimeval(t);
+  EXPECT_EQ(min_timeval_sec, tv.tv_sec);
+  EXPECT_EQ(0, tv.tv_usec);
+
+  const auto max_timespec_sec =
+      std::numeric_limits<decltype(timespec::tv_sec)>::max();
+  const auto min_timespec_sec =
+      std::numeric_limits<decltype(timespec::tv_sec)>::min();
+  timespec ts;
+  ts.tv_sec = max_timespec_sec;
+  ts.tv_nsec = 999999998;
+  t = absl::TimeFromTimespec(ts);
+  ts = absl::ToTimespec(t);
+  EXPECT_EQ(max_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(999999998, ts.tv_nsec);
+  t += absl::Nanoseconds(1);
+  ts = absl::ToTimespec(t);
+  EXPECT_EQ(max_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(999999999, ts.tv_nsec);
+  t += absl::Nanoseconds(1);  // no effect
+  ts = absl::ToTimespec(t);
+  EXPECT_EQ(max_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(999999999, ts.tv_nsec);
+
+  ts.tv_sec = min_timespec_sec;
+  ts.tv_nsec = 1;
+  t = absl::TimeFromTimespec(ts);
+  ts = absl::ToTimespec(t);
+  EXPECT_EQ(min_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(1, ts.tv_nsec);
+  t -= absl::Nanoseconds(1);
+  ts = absl::ToTimespec(t);
+  EXPECT_EQ(min_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(0, ts.tv_nsec);
+  t -= absl::Nanoseconds(1);  // no effect
+  ts = absl::ToTimespec(t);
+  EXPECT_EQ(min_timespec_sec, ts.tv_sec);
+  EXPECT_EQ(0, ts.tv_nsec);
+
+  // Checks how TimeZone::At() saturates on infinities.
+  auto ci = utc.At(absl::InfiniteFuture());
+  EXPECT_CIVIL_INFO(ci, std::numeric_limits<int64_t>::max(), 12, 31, 23, 59, 59,
+                    0, false);
+  EXPECT_EQ(absl::InfiniteDuration(), ci.subsecond);
+  EXPECT_EQ(absl::Weekday::thursday, absl::GetWeekday(ci.cs));
+  EXPECT_EQ(365, absl::GetYearDay(ci.cs));
+  EXPECT_STREQ("-00", ci.zone_abbr);  // artifact of TimeZone::At()
+  ci = utc.At(absl::InfinitePast());
+  EXPECT_CIVIL_INFO(ci, std::numeric_limits<int64_t>::min(), 1, 1, 0, 0, 0, 0,
+                    false);
+  EXPECT_EQ(-absl::InfiniteDuration(), ci.subsecond);
+  EXPECT_EQ(absl::Weekday::sunday, absl::GetWeekday(ci.cs));
+  EXPECT_EQ(1, absl::GetYearDay(ci.cs));
+  EXPECT_STREQ("-00", ci.zone_abbr);  // artifact of TimeZone::At()
+
+  // Approach the maximal Time value from below.
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 4, 15, 30, 6), utc);
+  EXPECT_EQ("292277026596-12-04T15:30:06+00:00",
+            absl::FormatTime(absl::RFC3339_full, t, utc));
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 4, 15, 30, 7), utc);
+  EXPECT_EQ("292277026596-12-04T15:30:07+00:00",
+            absl::FormatTime(absl::RFC3339_full, t, utc));
+  EXPECT_EQ(
+      absl::UnixEpoch() + absl::Seconds(std::numeric_limits<int64_t>::max()),
+      t);
+
+  // Checks that we can also get the maximal Time value for a far-east zone.
+  const absl::TimeZone plus14 = absl::FixedTimeZone(14 * 60 * 60);
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 5, 5, 30, 7), plus14);
+  EXPECT_EQ("292277026596-12-05T05:30:07+14:00",
+            absl::FormatTime(absl::RFC3339_full, t, plus14));
+  EXPECT_EQ(
+      absl::UnixEpoch() + absl::Seconds(std::numeric_limits<int64_t>::max()),
+      t);
+
+  // One second later should push us to infinity.
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 4, 15, 30, 8), utc);
+  EXPECT_EQ("infinite-future", absl::FormatTime(absl::RFC3339_full, t, utc));
+
+  // Approach the minimal Time value from above.
+  t = absl::FromCivil(absl::CivilSecond(-292277022657, 1, 27, 8, 29, 53), utc);
+  EXPECT_EQ("-292277022657-01-27T08:29:53+00:00",
+            absl::FormatTime(absl::RFC3339_full, t, utc));
+  t = absl::FromCivil(absl::CivilSecond(-292277022657, 1, 27, 8, 29, 52), utc);
+  EXPECT_EQ("-292277022657-01-27T08:29:52+00:00",
+            absl::FormatTime(absl::RFC3339_full, t, utc));
+  EXPECT_EQ(
+      absl::UnixEpoch() + absl::Seconds(std::numeric_limits<int64_t>::min()),
+      t);
+
+  // Checks that we can also get the minimal Time value for a far-west zone.
+  const absl::TimeZone minus12 = absl::FixedTimeZone(-12 * 60 * 60);
+  t = absl::FromCivil(absl::CivilSecond(-292277022657, 1, 26, 20, 29, 52),
+                      minus12);
+  EXPECT_EQ("-292277022657-01-26T20:29:52-12:00",
+            absl::FormatTime(absl::RFC3339_full, t, minus12));
+  EXPECT_EQ(
+      absl::UnixEpoch() + absl::Seconds(std::numeric_limits<int64_t>::min()),
+      t);
+
+  // One second before should push us to -infinity.
+  t = absl::FromCivil(absl::CivilSecond(-292277022657, 1, 27, 8, 29, 51), utc);
+  EXPECT_EQ("infinite-past", absl::FormatTime(absl::RFC3339_full, t, utc));
+}
+
+// In zones with POSIX-style recurring rules we use special logic to
+// handle conversions in the distant future.  Here we check the limits
+// of those conversions, particularly with respect to integer overflow.
+TEST(Time, ExtendedConversionSaturation) {
+  const absl::TimeZone syd =
+      absl::time_internal::LoadTimeZone("Australia/Sydney");
+  const absl::TimeZone nyc =
+      absl::time_internal::LoadTimeZone("America/New_York");
+  const absl::Time max =
+      absl::FromUnixSeconds(std::numeric_limits<int64_t>::max());
+  absl::TimeZone::CivilInfo ci;
+  absl::Time t;
+
+  // The maximal time converted in each zone.
+  ci = syd.At(max);
+  EXPECT_CIVIL_INFO(ci, 292277026596, 12, 5, 2, 30, 7, 39600, true);
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 5, 2, 30, 7), syd);
+  EXPECT_EQ(max, t);
+  ci = nyc.At(max);
+  EXPECT_CIVIL_INFO(ci, 292277026596, 12, 4, 10, 30, 7, -18000, false);
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 4, 10, 30, 7), nyc);
+  EXPECT_EQ(max, t);
+
+  // One second later should push us to infinity.
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 5, 2, 30, 8), syd);
+  EXPECT_EQ(absl::InfiniteFuture(), t);
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 4, 10, 30, 8), nyc);
+  EXPECT_EQ(absl::InfiniteFuture(), t);
+
+  // And we should stick there.
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 5, 2, 30, 9), syd);
+  EXPECT_EQ(absl::InfiniteFuture(), t);
+  t = absl::FromCivil(absl::CivilSecond(292277026596, 12, 4, 10, 30, 9), nyc);
+  EXPECT_EQ(absl::InfiniteFuture(), t);
+
+  // All the way up to a saturated date/time, without overflow.
+  t = absl::FromCivil(absl::CivilSecond::max(), syd);
+  EXPECT_EQ(absl::InfiniteFuture(), t);
+  t = absl::FromCivil(absl::CivilSecond::max(), nyc);
+  EXPECT_EQ(absl::InfiniteFuture(), t);
+}
+
+TEST(Time, FromCivilAlignment) {
+  const absl::TimeZone utc = absl::UTCTimeZone();
+  const absl::CivilSecond cs(2015, 2, 3, 4, 5, 6);
+  absl::Time t = absl::FromCivil(cs, utc);
+  EXPECT_EQ("2015-02-03T04:05:06+00:00", absl::FormatTime(t, utc));
+  t = absl::FromCivil(absl::CivilMinute(cs), utc);
+  EXPECT_EQ("2015-02-03T04:05:00+00:00", absl::FormatTime(t, utc));
+  t = absl::FromCivil(absl::CivilHour(cs), utc);
+  EXPECT_EQ("2015-02-03T04:00:00+00:00", absl::FormatTime(t, utc));
+  t = absl::FromCivil(absl::CivilDay(cs), utc);
+  EXPECT_EQ("2015-02-03T00:00:00+00:00", absl::FormatTime(t, utc));
+  t = absl::FromCivil(absl::CivilMonth(cs), utc);
+  EXPECT_EQ("2015-02-01T00:00:00+00:00", absl::FormatTime(t, utc));
+  t = absl::FromCivil(absl::CivilYear(cs), utc);
+  EXPECT_EQ("2015-01-01T00:00:00+00:00", absl::FormatTime(t, utc));
+}
+
+TEST(Time, LegacyDateTime) {
+  const absl::TimeZone utc = absl::UTCTimeZone();
+  const std::string ymdhms = "%Y-%m-%d %H:%M:%S";
+  const int kMax = std::numeric_limits<int>::max();
+  const int kMin = std::numeric_limits<int>::min();
+  absl::Time t;
+
+  t = absl::FromDateTime(std::numeric_limits<absl::civil_year_t>::max(), kMax,
+                         kMax, kMax, kMax, kMax, utc);
+  EXPECT_EQ("infinite-future",
+            absl::FormatTime(ymdhms, t, utc));  // no overflow
+  t = absl::FromDateTime(std::numeric_limits<absl::civil_year_t>::min(), kMin,
+                         kMin, kMin, kMin, kMin, utc);
+  EXPECT_EQ("infinite-past", absl::FormatTime(ymdhms, t, utc));  // no overflow
+
+  // Check normalization.
+  EXPECT_TRUE(absl::ConvertDateTime(2013, 10, 32, 8, 30, 0, utc).normalized);
+  t = absl::FromDateTime(2015, 1, 1, 0, 0, 60, utc);
+  EXPECT_EQ("2015-01-01 00:01:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, 1, 0, 60, 0, utc);
+  EXPECT_EQ("2015-01-01 01:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, 1, 24, 0, 0, utc);
+  EXPECT_EQ("2015-01-02 00:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, 32, 0, 0, 0, utc);
+  EXPECT_EQ("2015-02-01 00:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 13, 1, 0, 0, 0, utc);
+  EXPECT_EQ("2016-01-01 00:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 13, 32, 60, 60, 60, utc);
+  EXPECT_EQ("2016-02-03 13:01:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, 1, 0, 0, -1, utc);
+  EXPECT_EQ("2014-12-31 23:59:59", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, 1, 0, -1, 0, utc);
+  EXPECT_EQ("2014-12-31 23:59:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, 1, -1, 0, 0, utc);
+  EXPECT_EQ("2014-12-31 23:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, 1, -1, 0, 0, 0, utc);
+  EXPECT_EQ("2014-12-30 00:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, -1, 1, 0, 0, 0, utc);
+  EXPECT_EQ("2014-11-01 00:00:00", absl::FormatTime(ymdhms, t, utc));
+  t = absl::FromDateTime(2015, -1, -1, -1, -1, -1, utc);
+  EXPECT_EQ("2014-10-29 22:58:59", absl::FormatTime(ymdhms, t, utc));
+}
+
+TEST(Time, NextTransitionUTC) {
+  const auto tz = absl::UTCTimeZone();
+  absl::TimeZone::CivilTransition trans;
+
+  auto t = absl::InfinitePast();
+  EXPECT_FALSE(tz.NextTransition(t, &trans));
+
+  t = absl::InfiniteFuture();
+  EXPECT_FALSE(tz.NextTransition(t, &trans));
+}
+
+TEST(Time, PrevTransitionUTC) {
+  const auto tz = absl::UTCTimeZone();
+  absl::TimeZone::CivilTransition trans;
+
+  auto t = absl::InfiniteFuture();
+  EXPECT_FALSE(tz.PrevTransition(t, &trans));
+
+  t = absl::InfinitePast();
+  EXPECT_FALSE(tz.PrevTransition(t, &trans));
+}
+
+TEST(Time, NextTransitionNYC) {
+  const auto tz = absl::time_internal::LoadTimeZone("America/New_York");
+  absl::TimeZone::CivilTransition trans;
+
+  auto t = absl::FromCivil(absl::CivilSecond(2018, 6, 30, 0, 0, 0), tz);
+  EXPECT_TRUE(tz.NextTransition(t, &trans));
+  EXPECT_EQ(absl::CivilSecond(2018, 11, 4, 2, 0, 0), trans.from);
+  EXPECT_EQ(absl::CivilSecond(2018, 11, 4, 1, 0, 0), trans.to);
+
+  t = absl::InfiniteFuture();
+  EXPECT_FALSE(tz.NextTransition(t, &trans));
+
+  t = absl::InfinitePast();
+  EXPECT_TRUE(tz.NextTransition(t, &trans));
+  if (trans.from == absl::CivilSecond(1918, 03, 31, 2, 0, 0)) {
+    // It looks like the tzdata is only 32 bit (probably macOS),
+    // which bottoms out at 1901-12-13T20:45:52+00:00.
+    EXPECT_EQ(absl::CivilSecond(1918, 3, 31, 3, 0, 0), trans.to);
+  } else {
+    EXPECT_EQ(absl::CivilSecond(1883, 11, 18, 12, 3, 58), trans.from);
+    EXPECT_EQ(absl::CivilSecond(1883, 11, 18, 12, 0, 0), trans.to);
+  }
+}
+
+TEST(Time, PrevTransitionNYC) {
+  const auto tz = absl::time_internal::LoadTimeZone("America/New_York");
+  absl::TimeZone::CivilTransition trans;
+
+  auto t = absl::FromCivil(absl::CivilSecond(2018, 6, 30, 0, 0, 0), tz);
+  EXPECT_TRUE(tz.PrevTransition(t, &trans));
+  EXPECT_EQ(absl::CivilSecond(2018, 3, 11, 2, 0, 0), trans.from);
+  EXPECT_EQ(absl::CivilSecond(2018, 3, 11, 3, 0, 0), trans.to);
+
+  t = absl::InfinitePast();
+  EXPECT_FALSE(tz.PrevTransition(t, &trans));
+
+  t = absl::InfiniteFuture();
+  EXPECT_TRUE(tz.PrevTransition(t, &trans));
+  // We have a transition but we don't know which one.
+}
+
+TEST(Time, AbslStringify) {
+  // FormatTime is already well tested, so just use one test case here to
+  // verify that StrFormat("%v", t) works as expected.
+  absl::Time t = absl::Now();
+  EXPECT_EQ(absl::StrFormat("%v", t), absl::FormatTime(t));
+}
+
+}  // namespace