| // Protocol Buffers - Google's data interchange format | |
| // Copyright 2008 Google Inc. All rights reserved. | |
| // https://developers.google.com/protocol-buffers/ | |
| // | |
| // Redistribution and use in source and binary forms, with or without | |
| // modification, are permitted provided that the following conditions are | |
| // met: | |
| // | |
| // * Redistributions of source code must retain the above copyright | |
| // notice, this list of conditions and the following disclaimer. | |
| // * Redistributions in binary form must reproduce the above | |
| // copyright notice, this list of conditions and the following disclaimer | |
| // in the documentation and/or other materials provided with the | |
| // distribution. | |
| // * Neither the name of Google Inc. nor the names of its | |
| // contributors may be used to endorse or promote products derived from | |
| // this software without specific prior written permission. | |
| // | |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| namespace google { | |
| namespace protobuf { | |
| TypeName(const TypeName&); \ | |
| void operator=(const TypeName&) | |
| TypeName(); \ | |
| TypeName(const TypeName&); \ | |
| void operator=(const TypeName&) | |
| // =================================================================== | |
| // from google3/base/basictypes.h | |
| // The GOOGLE_ARRAYSIZE(arr) macro returns the # of elements in an array arr. | |
| // The expression is a compile-time constant, and therefore can be | |
| // used in defining new arrays, for example. | |
| // | |
| // GOOGLE_ARRAYSIZE catches a few type errors. If you see a compiler error | |
| // | |
| // "warning: division by zero in ..." | |
| // | |
| // when using GOOGLE_ARRAYSIZE, you are (wrongfully) giving it a pointer. | |
| // You should only use GOOGLE_ARRAYSIZE on statically allocated arrays. | |
| // | |
| // The following comments are on the implementation details, and can | |
| // be ignored by the users. | |
| // | |
| // ARRAYSIZE(arr) works by inspecting sizeof(arr) (the # of bytes in | |
| // the array) and sizeof(*(arr)) (the # of bytes in one array | |
| // element). If the former is divisible by the latter, perhaps arr is | |
| // indeed an array, in which case the division result is the # of | |
| // elements in the array. Otherwise, arr cannot possibly be an array, | |
| // and we generate a compiler error to prevent the code from | |
| // compiling. | |
| // | |
| // Since the size of bool is implementation-defined, we need to cast | |
| // !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final | |
| // result has type size_t. | |
| // | |
| // This macro is not perfect as it wrongfully accepts certain | |
| // pointers, namely where the pointer size is divisible by the pointee | |
| // size. Since all our code has to go through a 32-bit compiler, | |
| // where a pointer is 4 bytes, this means all pointers to a type whose | |
| // size is 3 or greater than 4 will be (righteously) rejected. | |
| // | |
| // Kudos to Jorg Brown for this simple and elegant implementation. | |
| ((sizeof(a) / sizeof(*(a))) / \ | |
| static_cast<size_t>(!(sizeof(a) % sizeof(*(a))))) | |
| // The COMPILE_ASSERT macro can be used to verify that a compile time | |
| // expression is true. For example, you could use it to verify the | |
| // size of a static array: | |
| // | |
| // COMPILE_ASSERT(ARRAYSIZE(content_type_names) == CONTENT_NUM_TYPES, | |
| // content_type_names_incorrect_size); | |
| // | |
| // or to make sure a struct is smaller than a certain size: | |
| // | |
| // COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); | |
| // | |
| // The second argument to the macro is the name of the variable. If | |
| // the expression is false, most compilers will issue a warning/error | |
| // containing the name of the variable. | |
| namespace internal { | |
| template <bool> | |
| struct CompileAssert { | |
| }; | |
| } // namespace internal | |
| ::google::protobuf::internal::CompileAssert<(bool(expr))> \ | |
| msg[bool(expr) ? 1 : -1]; \ | |
| (void)msg | |
| // Implementation details of COMPILE_ASSERT: | |
| // | |
| // - COMPILE_ASSERT works by defining an array type that has -1 | |
| // elements (and thus is invalid) when the expression is false. | |
| // | |
| // - The simpler definition | |
| // | |
| // #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1] | |
| // | |
| // does not work, as gcc supports variable-length arrays whose sizes | |
| // are determined at run-time (this is gcc's extension and not part | |
| // of the C++ standard). As a result, gcc fails to reject the | |
| // following code with the simple definition: | |
| // | |
| // int foo; | |
| // COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is | |
| // // not a compile-time constant. | |
| // | |
| // - By using the type CompileAssert<(bool(expr))>, we ensures that | |
| // expr is a compile-time constant. (Template arguments must be | |
| // determined at compile-time.) | |
| // | |
| // - The outter parentheses in CompileAssert<(bool(expr))> are necessary | |
| // to work around a bug in gcc 3.4.4 and 4.0.1. If we had written | |
| // | |
| // CompileAssert<bool(expr)> | |
| // | |
| // instead, these compilers will refuse to compile | |
| // | |
| // COMPILE_ASSERT(5 > 0, some_message); | |
| // | |
| // (They seem to think the ">" in "5 > 0" marks the end of the | |
| // template argument list.) | |
| // | |
| // - The array size is (bool(expr) ? 1 : -1), instead of simply | |
| // | |
| // ((expr) ? 1 : -1). | |
| // | |
| // This is to avoid running into a bug in MS VC 7.1, which | |
| // causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1. | |
| } // namespace protobuf | |
| } // namespace google | |