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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#error This header is meant to be included only once by
// Alias the internal Glibc symbols to the shim entry points.
// This file is strongly inspired by tcmalloc's libc_override_glibc.h.
// Effectively this file does two things:
// 1) Re-define the __malloc_hook & co symbols. Those symbols are defined as
// weak in glibc and are meant to be defined strongly by client processes
// to hook calls initiated from within glibc.
// 2) Re-define Glibc-specific symbols (__libc_malloc). The historical reason
// is that in the past (in RedHat 9) we had instances of libraries that were
// allocating via malloc() and freeing using __libc_free().
// See tcmalloc's libc_override_glibc.h for more context.
#include <features.h> // for __GLIBC__
#include <malloc.h>
#include <unistd.h>
#include <new>
#include "base/allocator/allocator_shim_internals.h"
#include "starboard/types.h"
// __MALLOC_HOOK_VOLATILE not defined in all Glibc headers.
#if !defined(__MALLOC_HOOK_VOLATILE)
extern "C" {
// 1) Re-define malloc_hook weak symbols.
namespace {
void* GlibcMallocHook(size_t size, const void* caller) {
return ShimMalloc(size, nullptr);
void* GlibcReallocHook(void* ptr, size_t size, const void* caller) {
return ShimRealloc(ptr, size, nullptr);
void GlibcFreeHook(void* ptr, const void* caller) {
return ShimFree(ptr, nullptr);
void* GlibcMemalignHook(size_t align, size_t size, const void* caller) {
return ShimMemalign(align, size, nullptr);
} // namespace
__attribute__((visibility("default"))) void* (
*MALLOC_HOOK_MAYBE_VOLATILE __malloc_hook)(size_t,
const void*) = &GlibcMallocHook;
__attribute__((visibility("default"))) void* (
*MALLOC_HOOK_MAYBE_VOLATILE __realloc_hook)(void*, size_t, const void*) =
__attribute__((visibility("default"))) void (
*MALLOC_HOOK_MAYBE_VOLATILE __free_hook)(void*,
const void*) = &GlibcFreeHook;
__attribute__((visibility("default"))) void* (
*MALLOC_HOOK_MAYBE_VOLATILE __memalign_hook)(size_t, size_t, const void*) =
// 2) Redefine libc symbols themselves.
SHIM_ALWAYS_EXPORT void* __libc_malloc(size_t size) {
return ShimMalloc(size, nullptr);
SHIM_ALWAYS_EXPORT void __libc_free(void* ptr) {
ShimFree(ptr, nullptr);
SHIM_ALWAYS_EXPORT void* __libc_realloc(void* ptr, size_t size) {
return ShimRealloc(ptr, size, nullptr);
SHIM_ALWAYS_EXPORT void* __libc_calloc(size_t n, size_t size) {
return ShimCalloc(n, size, nullptr);
SHIM_ALWAYS_EXPORT void __libc_cfree(void* ptr) {
return ShimFree(ptr, nullptr);
SHIM_ALWAYS_EXPORT void* __libc_memalign(size_t align, size_t s) {
return ShimMemalign(align, s, nullptr);
SHIM_ALWAYS_EXPORT void* __libc_valloc(size_t size) {
return ShimValloc(size, nullptr);
SHIM_ALWAYS_EXPORT void* __libc_pvalloc(size_t size) {
return ShimPvalloc(size);
SHIM_ALWAYS_EXPORT int __posix_memalign(void** r, size_t a, size_t s) {
return ShimPosixMemalign(r, a, s);
} // extern "C"
// Safety check.
#if !defined(__GLIBC__)
#error The target platform does not seem to use Glibc. Disable the allocator \
shim by setting use_allocator_shim=false in GN args.