emsdk/upstream/emscripten/system/lib/mimalloc/src/options.c

/* ----------------------------------------------------------------------------
Copyright (c) 2018-2025, Microsoft Research, Daan Leijen
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"LICENSE" at the root of this distribution.
-----------------------------------------------------------------------------*/
#include "mimalloc.h"
#include "mimalloc/internal.h"
#include "mimalloc/atomic.h"
#include "mimalloc/prim.h"  // mi_prim_out_stderr

#include <stdio.h>      // stdin/stdout
#include <stdlib.h>     // abort

static long mi_max_error_count   = 16; // stop outputting errors after this (use < 0 for no limit)
static long mi_max_warning_count = 16; // stop outputting warnings after this (use < 0 for no limit)

static void mi_add_stderr_output(void);

int mi_version(void) mi_attr_noexcept {
  return MI_MALLOC_VERSION;
}


// --------------------------------------------------------
// Options
// These can be accessed by multiple threads and may be
// concurrently initialized, but an initializing data race
// is ok since they resolve to the same value.
// --------------------------------------------------------


#define MI_OPTION(opt)                  mi_option_##opt, #opt, NULL
#define MI_OPTION_LEGACY(opt,legacy)    mi_option_##opt, #opt, #legacy

// Some options can be set at build time for statically linked libraries
// (use `-DMI_EXTRA_CPPDEFS="opt1=val1;opt2=val2"`)
//
// This is useful if we cannot pass them as environment variables
// (and setting them programmatically would be too late)

#ifndef MI_DEFAULT_VERBOSE
#define MI_DEFAULT_VERBOSE 0
#endif

#ifndef MI_DEFAULT_ARENA_EAGER_COMMIT
#define MI_DEFAULT_ARENA_EAGER_COMMIT 2
#endif

// in KiB
#ifndef MI_DEFAULT_ARENA_RESERVE
 #if (MI_INTPTR_SIZE>4)
  #define MI_DEFAULT_ARENA_RESERVE 1024L*1024L
 #else
  #define MI_DEFAULT_ARENA_RESERVE 128L*1024L
 #endif
#endif

#ifndef MI_DEFAULT_ARENA_MAX_OBJECT_SIZE
#define MI_DEFAULT_ARENA_MAX_OBJECT_SIZE   ((MI_SIZE_BITS * MI_ARENA_MAX_CHUNK_OBJ_SIZE)/MI_KiB)  /* 2 GiB (or 256 MiB on 32-bit), larger than this is alloc'd by the OS */
#endif

#ifndef MI_DEFAULT_DISALLOW_ARENA_ALLOC
#define MI_DEFAULT_DISALLOW_ARENA_ALLOC 0
#endif

#ifndef MI_DEFAULT_ALLOW_LARGE_OS_PAGES
#define MI_DEFAULT_ALLOW_LARGE_OS_PAGES 0
#endif

#ifndef MI_DEFAULT_RESERVE_HUGE_OS_PAGES
#define MI_DEFAULT_RESERVE_HUGE_OS_PAGES 0
#endif

#ifndef MI_DEFAULT_RESERVE_OS_MEMORY
#define MI_DEFAULT_RESERVE_OS_MEMORY 0
#endif

#ifndef MI_DEFAULT_GUARDED_SAMPLE_RATE
#if MI_GUARDED && !MI_DEBUG
#define MI_DEFAULT_GUARDED_SAMPLE_RATE 4000
#else
#define MI_DEFAULT_GUARDED_SAMPLE_RATE 0
#endif
#endif

#ifndef MI_DEFAULT_PAGEMAP_COMMIT
#if defined(__APPLE__)  // when overloading malloc, we still get mixed pointers sometimes on macOS; this avoids a bad access
#define MI_DEFAULT_PAGEMAP_COMMIT 1
#else
#define MI_DEFAULT_PAGEMAP_COMMIT 0
#endif
#endif

#ifndef MI_DEFAULT_PAGE_MAX_RECLAIM
#define MI_DEFAULT_PAGE_MAX_RECLAIM  (-1)               // unlimited
#endif

#ifndef MI_DEFAULT_PAGE_CROSS_THREAD_MAX_RECLAIM
#define MI_DEFAULT_PAGE_CROSS_THREAD_MAX_RECLAIM  32
#endif

#ifndef MI_DEFAULT_ALLOW_THP
#if defined(__ANDROID__)
#define MI_DEFAULT_ALLOW_THP  0
#else
#define MI_DEFAULT_ALLOW_THP  1
#endif
#endif

// Static options
static mi_option_desc_t mi_options[_mi_option_last] =
{
  // stable options
#if MI_DEBUG || defined(MI_SHOW_ERRORS)
  { 1, MI_OPTION_UNINIT, MI_OPTION(show_errors) },
#else
  { 0, MI_OPTION_UNINIT, MI_OPTION(show_errors) },
#endif
  { 0, MI_OPTION_UNINIT, MI_OPTION(show_stats) },
  { MI_DEFAULT_VERBOSE, MI_OPTION_UNINIT, MI_OPTION(verbose) },

  // some of the following options are experimental and not all combinations are allowed.
  { 1, MI_OPTION_UNINIT, MI_OPTION(deprecated_eager_commit) },  
  { MI_DEFAULT_ARENA_EAGER_COMMIT,
       MI_OPTION_UNINIT, MI_OPTION_LEGACY(arena_eager_commit,eager_region_commit) }, // eager commit arena's? 2 is used to enable this only on an OS that has overcommit (i.e. linux)
  { 1, MI_OPTION_UNINIT, MI_OPTION_LEGACY(purge_decommits,reset_decommits) },        // purge decommits memory (instead of reset) (note: on linux this uses MADV_DONTNEED for decommit)
  { MI_DEFAULT_ALLOW_LARGE_OS_PAGES,
       MI_OPTION_UNINIT, MI_OPTION_LEGACY(allow_large_os_pages,large_os_pages) },    // use large OS pages, use only with eager commit to prevent fragmentation of VMA's
  { MI_DEFAULT_RESERVE_HUGE_OS_PAGES,
       MI_OPTION_UNINIT, MI_OPTION(reserve_huge_os_pages) },      // per 1GiB huge pages
  {-1, MI_OPTION_UNINIT, MI_OPTION(reserve_huge_os_pages_at) },   // reserve huge pages at node N
  { MI_DEFAULT_RESERVE_OS_MEMORY,
       MI_OPTION_UNINIT, MI_OPTION(reserve_os_memory)     },      // reserve N KiB OS memory in advance (use `option_get_size`)
  { 0, MI_OPTION_UNINIT, MI_OPTION(deprecated_segment_cache) },   // cache N segments per thread
  { 0, MI_OPTION_UNINIT, MI_OPTION(deprecated_page_reset) },      // reset page memory on free
  { 0, MI_OPTION_UNINIT, MI_OPTION(deprecated_abandoned_page_purge) }, 
  { 0, MI_OPTION_UNINIT, MI_OPTION(deprecated_segment_reset) },   // reset segment memory on free (needs eager commit)
  { 1, MI_OPTION_UNINIT, MI_OPTION(deprecated_eager_commit_delay) },  
  { 1000,MI_OPTION_UNINIT, MI_OPTION_LEGACY(purge_delay,reset_delay) },  // purge delay in milli-seconds
  { 0,   MI_OPTION_UNINIT, MI_OPTION(use_numa_nodes) },           // 0 = use available numa nodes, otherwise use at most N nodes.
  { 0,   MI_OPTION_UNINIT, MI_OPTION_LEGACY(disallow_os_alloc,limit_os_alloc) },           // 1 = do not use OS memory for allocation (but only reserved arenas)
  { 100, MI_OPTION_UNINIT, MI_OPTION(os_tag) },                   // only apple specific for now but might serve more or less related purpose
  { 32,  MI_OPTION_UNINIT, MI_OPTION(max_errors) },               // maximum errors that are output
  { 32,  MI_OPTION_UNINIT, MI_OPTION(max_warnings) },             // maximum warnings that are output
  { 10,  MI_OPTION_UNINIT, MI_OPTION(deprecated_max_segment_reclaim)},       // max. percentage of the abandoned segments to be reclaimed per try.
  { 0,   MI_OPTION_UNINIT, MI_OPTION(destroy_on_exit)},           // release all OS memory on process exit; careful with dangling pointer or after-exit frees!
  { MI_DEFAULT_ARENA_RESERVE, MI_OPTION_UNINIT, MI_OPTION(arena_reserve) }, // reserve memory N KiB at a time (=1GiB) (use `option_get_size`)
  { 1,   MI_OPTION_UNINIT, MI_OPTION(arena_purge_mult) },         // purge delay multiplier for arena's
  { 1,   MI_OPTION_UNINIT, MI_OPTION_LEGACY(deprecated_purge_extend_delay, decommit_extend_delay) },
  { MI_DEFAULT_DISALLOW_ARENA_ALLOC,   MI_OPTION_UNINIT, MI_OPTION(disallow_arena_alloc) }, // 1 = do not use arena's for allocation (except if using specific arena id's)
  { 400, MI_OPTION_UNINIT, MI_OPTION(retry_on_oom) },             // windows only: retry on out-of-memory for N milli seconds (=400), set to 0 to disable retries.
#if defined(MI_VISIT_ABANDONED)
  { 1,   MI_OPTION_INITIALIZED, MI_OPTION(visit_abandoned) },     // allow visiting theap blocks in abandoned segments; requires taking locks during reclaim.
#else
  { 0,   MI_OPTION_UNINIT, MI_OPTION(visit_abandoned) },
#endif
  { 0,   MI_OPTION_UNINIT, MI_OPTION(guarded_min) },              // only used when building with MI_GUARDED: minimal rounded object size for guarded objects
  { MI_GiB, MI_OPTION_UNINIT, MI_OPTION(guarded_max) },           // only used when building with MI_GUARDED: maximal rounded object size for guarded objects
  { 0,   MI_OPTION_UNINIT, MI_OPTION(guarded_precise) },          // disregard minimal alignment requirement to always place guarded blocks exactly in front of a guard page (=0)
  { MI_DEFAULT_GUARDED_SAMPLE_RATE,
         MI_OPTION_UNINIT, MI_OPTION(guarded_sample_rate)},       // 1 out of N allocations in the min/max range will be guarded (=4000)
  { 0,   MI_OPTION_UNINIT, MI_OPTION(guarded_sample_seed)},
  { 10000, MI_OPTION_UNINIT, MI_OPTION(generic_collect) },        // collect theaps every N (=10000) generic allocation calls
  { 0,   MI_OPTION_UNINIT, MI_OPTION_LEGACY(page_reclaim_on_free, abandoned_reclaim_on_free) },// reclaim abandoned (small) pages on a free: -1 = disable completely, 0 = only reclaim into the originating theap, 1 = reclaim on free across theaps
  { 2,   MI_OPTION_UNINIT, MI_OPTION(page_full_retain) },         // number of (small) pages to retain in the free page queues
  { 4,   MI_OPTION_UNINIT, MI_OPTION(page_max_candidates) },      // max search to find a best page candidate
  { 0,   MI_OPTION_UNINIT, MI_OPTION(max_vabits) },               // max virtual address space bits
  { MI_DEFAULT_PAGEMAP_COMMIT,
         MI_OPTION_UNINIT, MI_OPTION(pagemap_commit) },           // commit the full pagemap upfront?
  { 0,   MI_OPTION_UNINIT, MI_OPTION(page_commit_on_demand) },    // commit pages on-demand (2 disables this only on overcommit systems (like Linux))
  { MI_DEFAULT_PAGE_MAX_RECLAIM,
         MI_OPTION_UNINIT, MI_OPTION(page_max_reclaim) },         // don't reclaim (small) pages of the same originating theap if we already own N pages in that size class
  { MI_DEFAULT_PAGE_CROSS_THREAD_MAX_RECLAIM,
         MI_OPTION_UNINIT, MI_OPTION(page_cross_thread_max_reclaim) }, // don't reclaim (small) pages across threads if we already own N pages in that size class
  { MI_DEFAULT_ALLOW_THP,
         MI_OPTION_UNINIT, MI_OPTION(allow_thp) },                // allow transparent huge pages? (=1) (on Android =0 by default). Set to 0 to disable THP for the process.
  { 0,   MI_OPTION_UNINIT, MI_OPTION(minimal_purge_size) },       // set minimal purge size (in KiB) (=0). By default set to either 64 or 2048 if THP is enabled.
  { MI_DEFAULT_ARENA_MAX_OBJECT_SIZE,   
         MI_OPTION_UNINIT, MI_OPTION(arena_max_object_size) },    // set maximal object size that can be allocated in an arena (in KiB) (=2GiB on 64-bit). 
};

static void mi_option_init(mi_option_desc_t* desc);

static bool mi_option_has_size_in_kib(mi_option_t option) {
  return (option == mi_option_reserve_os_memory || option == mi_option_arena_reserve || 
          option == mi_option_minimal_purge_size || option == mi_option_arena_max_object_size);
}

void _mi_options_init(void) {
  // called on process load
  for(int i = 0; i < _mi_option_last; i++ ) {
    mi_option_t option = (mi_option_t)i;
    long l = mi_option_get(option); MI_UNUSED(l); // initialize
  }
  mi_max_error_count = mi_option_get(mi_option_max_errors);
  mi_max_warning_count = mi_option_get(mi_option_max_warnings);
  #if MI_GUARDED
  if (mi_option_get(mi_option_guarded_sample_rate) > 0) {
    if (mi_option_is_enabled(mi_option_allow_large_os_pages)) {
      mi_option_disable(mi_option_allow_large_os_pages);
      _mi_warning_message("option 'allow_large_os_pages' is disabled to allow for guarded objects\n");
    }
  }
  #endif  
}

// called at actual process load, it should be safe to print now
void _mi_options_post_init(void) {
  mi_add_stderr_output(); // now it safe to use stderr for output
  if (mi_option_is_enabled(mi_option_verbose)) { mi_options_print(); }
}

#define mi_stringifyx(str)  #str                // and stringify
#define mi_stringify(str)   mi_stringifyx(str)  // expand

mi_decl_export void mi_options_print_out(mi_output_fun* out, void* arg) mi_attr_noexcept
{
  // show version
  const int vermajor = MI_MALLOC_VERSION/10000;
  const int verminor = (MI_MALLOC_VERSION%10000)/100;
  const int verpatch = (MI_MALLOC_VERSION%100);
  _mi_fprintf(out, arg, "v%i.%i.%i%s%s (built on %s, %s)\n", vermajor, verminor, verpatch,
      #if defined(MI_CMAKE_BUILD_TYPE)
      ", " mi_stringify(MI_CMAKE_BUILD_TYPE)
      #else
      ""
      #endif
      ,
      #if defined(MI_GIT_DESCRIBE)
      ", git " mi_stringify(MI_GIT_DESCRIBE)
      #else
      ""
      #endif
      , __DATE__, __TIME__);

  // show options
  for (int i = 0; i < _mi_option_last; i++) {
    mi_option_t option = (mi_option_t)i;
    long l = mi_option_get(option); MI_UNUSED(l); // possibly initialize
    mi_option_desc_t* desc = &mi_options[option];
    _mi_fprintf(out, arg, "option '%s': %ld %s\n", desc->name, desc->value, (mi_option_has_size_in_kib(option) ? "KiB" : ""));
  }

  // show build configuration
  _mi_fprintf(out, arg, "debug level : %d\n", MI_DEBUG );
  _mi_fprintf(out, arg, "secure level: %d\n", MI_SECURE );
  _mi_fprintf(out, arg, "mem tracking: %s\n", MI_TRACK_TOOL);
  #if MI_GUARDED
  _mi_fprintf(out, arg, "guarded build: %s\n", mi_option_get(mi_option_guarded_sample_rate) != 0 ? "enabled" : "disabled");
  #endif
  #if MI_TSAN
  _mi_fprintf(out, arg, "thread santizer enabled\n");
  #endif
}

mi_decl_export void mi_options_print(void) mi_attr_noexcept {
  mi_options_print_out(NULL, NULL);
}

long _mi_option_get_fast(mi_option_t option) {
  mi_assert(option >= 0 && option < _mi_option_last);
  mi_option_desc_t* desc = &mi_options[option];
  mi_assert(desc->option == option);  // index should match the option
  //mi_assert(desc->init != MI_OPTION_UNINIT);
  return desc->value;
}


mi_decl_nodiscard long mi_option_get(mi_option_t option) {
  mi_assert(option >= 0 && option < _mi_option_last);
  if (option < 0 || option >= _mi_option_last) return 0;
  mi_option_desc_t* desc = &mi_options[option];
  mi_assert(desc->option == option);  // index should match the option
  if mi_unlikely(desc->init == MI_OPTION_UNINIT) {
    mi_option_init(desc);
  }
  return desc->value;
}

mi_decl_nodiscard long mi_option_get_clamp(mi_option_t option, long min, long max) {
  long x = mi_option_get(option);
  return (x < min ? min : (x > max ? max : x));
}

mi_decl_nodiscard size_t mi_option_get_size(mi_option_t option) {
  const long x = mi_option_get(option);
  size_t size = (x < 0 ? 0 : (size_t)x);
  if (mi_option_has_size_in_kib(option)) {
    if (mi_mul_overflow(size, MI_KiB, &size)) {
      size = MI_MAX_ALLOC_SIZE;
    }
  }
  return size;
}

void mi_option_set(mi_option_t option, long value) {
  mi_assert(option >= 0 && option < _mi_option_last);
  if (option < 0 || option >= _mi_option_last) return;
  mi_option_desc_t* desc = &mi_options[option];
  mi_assert(desc->option == option);  // index should match the option
  desc->value = value;
  desc->init = MI_OPTION_INITIALIZED;
  // ensure min/max range; be careful to not recurse.
  if (desc->option == mi_option_guarded_min && _mi_option_get_fast(mi_option_guarded_max) < value) {
    mi_option_set(mi_option_guarded_max, value);
  }
  else if (desc->option == mi_option_guarded_max && _mi_option_get_fast(mi_option_guarded_min) > value) {
    mi_option_set(mi_option_guarded_min, value);
  }
}

void mi_option_set_default(mi_option_t option, long value) {
  mi_assert(option >= 0 && option < _mi_option_last);
  if (option < 0 || option >= _mi_option_last) return;
  mi_option_desc_t* desc = &mi_options[option];
  if (desc->init != MI_OPTION_INITIALIZED) {
    desc->value = value;
  }
}

mi_decl_nodiscard bool mi_option_is_enabled(mi_option_t option) {
  return (mi_option_get(option) != 0);
}

void mi_option_set_enabled(mi_option_t option, bool enable) {
  mi_option_set(option, (enable ? 1 : 0));
}

void mi_option_set_enabled_default(mi_option_t option, bool enable) {
  mi_option_set_default(option, (enable ? 1 : 0));
}

void mi_option_enable(mi_option_t option) {
  mi_option_set_enabled(option,true);
}

void mi_option_disable(mi_option_t option) {
  mi_option_set_enabled(option,false);
}

static void mi_cdecl mi_out_stderr(const char* msg, void* arg) {
  MI_UNUSED(arg);
  if (msg != NULL && msg[0] != 0) {
    _mi_prim_out_stderr(msg);
  }
}

// Since an output function can be registered earliest in the `main`
// function we also buffer output that happens earlier. When
// an output function is registered it is called immediately with
// the output up to that point.
#ifndef MI_MAX_DELAY_OUTPUT
#define MI_MAX_DELAY_OUTPUT ((size_t)(16*1024))
#endif
static char mi_output_buffer[MI_MAX_DELAY_OUTPUT+1];
static _Atomic(size_t) out_len;

static void mi_cdecl mi_out_buf(const char* msg, void* arg) {
  MI_UNUSED(arg);
  if (msg==NULL) return;
  if (mi_atomic_load_relaxed(&out_len)>=MI_MAX_DELAY_OUTPUT) return;
  size_t n = _mi_strlen(msg);
  if (n==0) return;
  // claim space
  size_t start = mi_atomic_add_acq_rel(&out_len, n);
  if (start >= MI_MAX_DELAY_OUTPUT) return;
  // check bound
  if (start+n >= MI_MAX_DELAY_OUTPUT) {
    n = MI_MAX_DELAY_OUTPUT-start-1;
  }
  mi_assert_internal(start + n <= MI_MAX_DELAY_OUTPUT);
  _mi_memcpy(&mi_output_buffer[start], msg, n);
}

static void mi_out_buf_flush(mi_output_fun* out, bool no_more_buf, void* arg) {
  if (out==NULL) return;
  // claim (if `no_more_buf == true`, no more output will be added after this point)
  size_t count = mi_atomic_add_acq_rel(&out_len, (no_more_buf ? MI_MAX_DELAY_OUTPUT : 1));
  // and output the current contents
  if (count>MI_MAX_DELAY_OUTPUT) count = MI_MAX_DELAY_OUTPUT;
  mi_output_buffer[count] = 0;
  out(mi_output_buffer,arg);
  if (!no_more_buf) {
    mi_output_buffer[count] = '\n'; // if continue with the buffer, insert a newline
  }
}


// Once this module is loaded, switch to this routine
// which outputs to stderr and the delayed output buffer.
static void mi_cdecl mi_out_buf_stderr(const char* msg, void* arg) {
  mi_out_stderr(msg,arg);
  mi_out_buf(msg,arg);
}



// --------------------------------------------------------
// Default output handler
// --------------------------------------------------------

// Should be atomic but gives errors on many platforms as generally we cannot cast a function pointer to a uintptr_t.
// For now, don't register output from multiple threads.
static mi_output_fun* volatile mi_out_default; // = NULL
static _Atomic(void*) mi_out_arg; // = NULL

static mi_output_fun* mi_out_get_default(void** parg) {
  if (parg != NULL) { *parg = mi_atomic_load_ptr_acquire(void,&mi_out_arg); }
  mi_output_fun* out = mi_out_default;
  return (out == NULL ? &mi_out_buf : out);
}

void mi_register_output(mi_output_fun* out, void* arg) mi_attr_noexcept {
  mi_out_default = (out == NULL ? &mi_out_stderr : out); // stop using the delayed output buffer
  mi_atomic_store_ptr_release(void,&mi_out_arg, arg);
  if (out!=NULL) mi_out_buf_flush(out,true,arg);         // output all the delayed output now
}

// add stderr to the delayed output after the module is loaded
static void mi_add_stderr_output(void) {
  mi_assert_internal(mi_out_default == NULL);
  if (mi_out_default==NULL) {
    mi_out_buf_flush(&mi_out_stderr, false, NULL); // flush current contents to stderr
    mi_out_default = &mi_out_buf_stderr;           // and add stderr to the delayed output
  }
}

// --------------------------------------------------------
// Messages, all end up calling `_mi_fputs`.
// --------------------------------------------------------
static _Atomic(size_t) error_count;   // = 0;  // when >= max_error_count stop emitting errors
static _Atomic(size_t) warning_count; // = 0;  // when >= max_warning_count stop emitting warnings

// When overriding malloc, we may recurse into mi_vfprintf if an allocation
// inside the C runtime causes another message.
// In some cases (like on macOS) the loader already allocates which
// calls into mimalloc; if we then access thread locals (like `recurse`)
// this may crash as the access may call _tlv_bootstrap that tries to
// (recursively) invoke malloc again to allocate space for the thread local
// variables on demand. This is why we use a _mi_preloading test on such
// platforms. However, C code generator may move the initial thread local address
// load before the `if` and we therefore split it out in a separate function.
static mi_decl_thread bool recurse = false;

static mi_decl_noinline bool mi_recurse_enter_prim(void) {
  if (recurse) return false;
  recurse = true;
  return true;
}

static mi_decl_noinline void mi_recurse_exit_prim(void) {
  recurse = false;
}

static bool mi_recurse_enter(void) {
  #if defined(__APPLE__) || defined(__ANDROID__) || defined(MI_TLS_RECURSE_GUARD)
  if (_mi_preloading()) return false;
  #endif
  return mi_recurse_enter_prim();
}

static void mi_recurse_exit(void) {
  #if defined(__APPLE__) || defined(__ANDROID__) || defined(MI_TLS_RECURSE_GUARD)
  if (_mi_preloading()) return;
  #endif
  mi_recurse_exit_prim();
}

void _mi_fputs(mi_output_fun* out, void* arg, const char* prefix, const char* message) {
  if (out==NULL || (void*)out==(void*)stdout || (void*)out==(void*)stderr) { // TODO: use mi_out_stderr for stderr?
    if (!mi_recurse_enter()) return;
    out = mi_out_get_default(&arg);
    if (prefix != NULL) out(prefix, arg);
    out(message, arg);
    mi_recurse_exit();
  }
  else {
    if (prefix != NULL) out(prefix, arg);
    out(message, arg);
  }
}

// Define our own limited `fprintf` that avoids memory allocation.
// We do this using `_mi_vsnprintf` with a limited buffer.
static void mi_vfprintf( mi_output_fun* out, void* arg, const char* prefix, const char* fmt, va_list args ) {
  char buf[992];
  if (fmt==NULL) return;
  if (!mi_recurse_enter()) return;
  _mi_vsnprintf(buf, sizeof(buf)-1, fmt, args);
  mi_recurse_exit();
  _mi_fputs(out,arg,prefix,buf);
}

void _mi_fprintf( mi_output_fun* out, void* arg, const char* fmt, ... ) {
  va_list args;
  va_start(args,fmt);
  mi_vfprintf(out,arg,NULL,fmt,args);
  va_end(args);
}

static void mi_vfprintf_thread(mi_output_fun* out, void* arg, const char* prefix, const char* fmt, va_list args) {
  if (prefix != NULL && _mi_strnlen(prefix,33) <= 32 && !_mi_is_main_thread()) {
    char tprefix[64];
    _mi_snprintf(tprefix, sizeof(tprefix), "%sthread 0x%tx: ", prefix, (uintptr_t)_mi_thread_id());
    mi_vfprintf(out, arg, tprefix, fmt, args);
  }
  else {
    mi_vfprintf(out, arg, prefix, fmt, args);
  }
}

void _mi_raw_message(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  mi_vfprintf(NULL, NULL, NULL, fmt, args);
  va_end(args);
}

void _mi_message(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  mi_vfprintf_thread(NULL, NULL, "mimalloc: ", fmt, args);
  va_end(args);
}

void _mi_trace_message(const char* fmt, ...) {
  if (mi_option_get(mi_option_verbose) <= 1) return;  // only with verbose level 2 or higher
  va_list args;
  va_start(args, fmt);
  mi_vfprintf_thread(NULL, NULL, "mimalloc: ", fmt, args);
  va_end(args);
}

void _mi_verbose_message(const char* fmt, ...) {
  if (!mi_option_is_enabled(mi_option_verbose)) return;
  va_list args;
  va_start(args,fmt);
  mi_vfprintf(NULL, NULL, "mimalloc: ", fmt, args);
  va_end(args);
}

static void mi_show_error_message(const char* fmt, va_list args) {
  if (!mi_option_is_enabled(mi_option_verbose)) {
    if (!mi_option_is_enabled(mi_option_show_errors)) return;
    if (mi_max_error_count >= 0 && (long)mi_atomic_increment_acq_rel(&error_count) > mi_max_error_count) return;
  }
  mi_vfprintf_thread(NULL, NULL, "mimalloc: error: ", fmt, args);
}

void _mi_warning_message(const char* fmt, ...) {
  if (!mi_option_is_enabled(mi_option_verbose)) {
    if (!mi_option_is_enabled(mi_option_show_errors)) return;
    if (mi_max_warning_count >= 0 && (long)mi_atomic_increment_acq_rel(&warning_count) > mi_max_warning_count) return;
  }
  va_list args;
  va_start(args,fmt);
  mi_vfprintf_thread(NULL, NULL, "mimalloc: warning: ", fmt, args);
  va_end(args);
}


#if MI_DEBUG
mi_decl_noreturn mi_decl_cold void _mi_assert_fail(const char* assertion, const char* fname, unsigned line, const char* func ) mi_attr_noexcept {
  _mi_fprintf(NULL, NULL, "mimalloc: assertion failed: at \"%s\":%u, %s\n  assertion: \"%s\"\n", fname, line, (func==NULL?"":func), assertion);
  abort();
}
#endif

// --------------------------------------------------------
// Errors
// --------------------------------------------------------

static mi_error_fun* volatile  mi_error_handler; // = NULL
static _Atomic(void*) mi_error_arg;     // = NULL

static void mi_error_default(int err) {
  MI_UNUSED(err);
#if (MI_DEBUG>0)
  if (err==EFAULT) {
    #ifdef _MSC_VER
    __debugbreak();
    #endif
    abort();
  }
#endif
#if (MI_SECURE>0)
  if (err==EFAULT) {  // abort on serious errors in secure mode (corrupted meta-data)
    abort();
  }
#endif
#if defined(MI_XMALLOC)
  if (err==ENOMEM || err==EOVERFLOW) { // abort on memory allocation fails in xmalloc mode
    abort();
  }
#endif
}

void mi_register_error(mi_error_fun* fun, void* arg) {
  mi_error_handler = fun;  // can be NULL
  mi_atomic_store_ptr_release(void,&mi_error_arg, arg);
}

void _mi_error_message(int err, const char* fmt, ...) {
  // show detailed error message
  va_list args;
  va_start(args, fmt);
  mi_show_error_message(fmt, args);
  va_end(args);
  // and call the error handler which may abort (or return normally)
  if (mi_error_handler != NULL) {
    mi_error_handler(err, mi_atomic_load_ptr_acquire(void,&mi_error_arg));
  }
  else {
    mi_error_default(err);
  }
}

// --------------------------------------------------------
// Initialize options by checking the environment
// --------------------------------------------------------

// TODO: implement ourselves to reduce dependencies on the C runtime
#include <stdlib.h> // strtol
#include <string.h> // strstr


static void mi_option_init(mi_option_desc_t* desc) {
  // Read option value from the environment
  char s[64 + 1];
  char buf[64+1];
  _mi_strlcpy(buf, "mimalloc_", sizeof(buf));
  _mi_strlcat(buf, desc->name, sizeof(buf));
  bool found = _mi_getenv(buf, s, sizeof(s));
  if (!found && desc->legacy_name != NULL) {
    _mi_strlcpy(buf, "mimalloc_", sizeof(buf));
    _mi_strlcat(buf, desc->legacy_name, sizeof(buf));
    found = _mi_getenv(buf, s, sizeof(s));
    if (found) {
      _mi_warning_message("environment option \"mimalloc_%s\" is deprecated -- use \"mimalloc_%s\" instead.\n", desc->legacy_name, desc->name);
    }
  }

  if (found) {
    size_t len = _mi_strnlen(s, sizeof(buf) - 1);
    for (size_t i = 0; i < len; i++) {
      buf[i] = _mi_toupper(s[i]);
    }
    buf[len] = 0;
    if (buf[0] == 0 || _mi_streq(buf,"1") || _mi_streq(buf,"TRUE") || _mi_streq(buf,"YES") || _mi_streq(buf,"ON")) {
      desc->value = 1;
      desc->init = MI_OPTION_INITIALIZED;
    }
    else if (_mi_streq(buf,"0") || _mi_streq(buf,"FALSE") || _mi_streq(buf,"NO") || _mi_streq(buf,"OFF")) {      
      desc->value = 0;
      desc->init = MI_OPTION_INITIALIZED;
    }
    else {
      char* end = buf;
      long value = strtol(buf, &end, 10);
      if (mi_option_has_size_in_kib(desc->option)) {
        // this option is interpreted in KiB to prevent overflow of `long` for large allocations
        // (long is 32-bit on 64-bit windows, which allows for 4TiB max.)
        size_t size = (value < 0 ? 0 : (size_t)value);
        bool overflow = false;
        if (*end == 'K') { end++; }
        else if (*end == 'M') { overflow = mi_mul_overflow(size,MI_KiB,&size); end++; }
        else if (*end == 'G') { overflow = mi_mul_overflow(size,MI_MiB,&size); end++; }
        else if (*end == 'T') { overflow = mi_mul_overflow(size,MI_GiB,&size); end++; }
        else { size = (size + MI_KiB - 1) / MI_KiB; }
        if (end[0] == 'I' && end[1] == 'B') { end += 2; } // KiB, MiB, GiB, TiB
        else if (*end == 'B') { end++; }                  // Kb, Mb, Gb, Tb
        if (overflow || size > (MI_MAX_ALLOC_SIZE / MI_KiB)) { size = (MI_MAX_ALLOC_SIZE / MI_KiB); }
        value = (size > LONG_MAX ? LONG_MAX : (long)size);
      }
      if (*end == 0) {
        mi_option_set(desc->option, value);
      }
      else {
        // set `init` first to avoid recursion through _mi_warning_message on mimalloc_verbose.
        desc->init = MI_OPTION_DEFAULTED;
        if (desc->option == mi_option_verbose && desc->value == 0) {
          // if the 'mimalloc_verbose' env var has a bogus value we'd never know
          // (since the value defaults to 'off') so in that case briefly enable verbose
          desc->value = 1;
          _mi_warning_message("environment option mimalloc_%s has an invalid value.\n", desc->name);
          desc->value = 0;
        }
        else {
          _mi_warning_message("environment option mimalloc_%s has an invalid value.\n", desc->name);
        }
      }
    }
    mi_assert_internal(desc->init != MI_OPTION_UNINIT);
  }
  else if (!_mi_preloading()) {
    desc->init = MI_OPTION_DEFAULTED;
  }
}