Allocator shim skeleton + Linux impl behind a build flag

base/allocator/allocator_shim_override_glibc_weak_symbols.h

+// 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.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_GLIBC_WEAK_SYMBOLS_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_GLIBC_WEAK_SYMBOLS_H_
+
+// 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"
+
+// __MALLOC_HOOK_VOLATILE not defined in all Glibc headers.
+#if !defined(__MALLOC_HOOK_VOLATILE)
+#define MALLOC_HOOK_MAYBE_VOLATILE /**/
+#else
+#define MALLOC_HOOK_MAYBE_VOLATILE __MALLOC_HOOK_VOLATILE
+#endif
+
+extern "C" {
+
+// 1) Re-define malloc_hook weak symbols.
+namespace {
+
+void* GlibcMallocHook(size_t size, const void* caller) {
+  return ShimMalloc(size);
+}
+
+void* GlibcReallocHook(void* ptr, size_t size, const void* caller) {
+  return ShimRealloc(ptr, size);
+}
+
+void GlibcFreeHook(void* ptr, const void* caller) {
+  return ShimFree(ptr);
+}
+
+void* GlibcMemalignHook(size_t align, size_t size, const void* caller) {
+  return ShimMemalign(align, size);
+}
+
+}  // namespace
+
+SHIM_ALWAYS_EXPORT void* (*MALLOC_HOOK_MAYBE_VOLATILE __malloc_hook)(
+    size_t,
+    const void*) = &GlibcMallocHook;
+
+SHIM_ALWAYS_EXPORT void* (*MALLOC_HOOK_MAYBE_VOLATILE __realloc_hook)(
+    void*,
+    size_t,
+    const void*) = &GlibcReallocHook;
+
+SHIM_ALWAYS_EXPORT void (*MALLOC_HOOK_MAYBE_VOLATILE __free_hook)(void*,
+                                                                  const void*) =
+    &GlibcFreeHook;
+
+SHIM_ALWAYS_EXPORT void* (*MALLOC_HOOK_MAYBE_VOLATILE __memalign_hook)(
+    size_t,
+    size_t,
+    const void*) = &GlibcMemalignHook;
+
+// 2) Redefine libc symbols themselves.
+
+SHIM_ALWAYS_EXPORT void* __libc_malloc(size_t size)
+    SHIM_ALIAS_SYMBOL(ShimMalloc);
+
+SHIM_ALWAYS_EXPORT void __libc_free(void* ptr) SHIM_ALIAS_SYMBOL(ShimFree);
+
+SHIM_ALWAYS_EXPORT void* __libc_realloc(void* ptr, size_t size)
+    SHIM_ALIAS_SYMBOL(ShimRealloc);
+
+SHIM_ALWAYS_EXPORT void* __libc_calloc(size_t n, size_t size)
+    SHIM_ALIAS_SYMBOL(ShimCalloc);
+
+SHIM_ALWAYS_EXPORT void __libc_cfree(void* ptr) SHIM_ALIAS_SYMBOL(ShimFree);
+
+SHIM_ALWAYS_EXPORT void* __libc_memalign(size_t align, size_t s)
+    SHIM_ALIAS_SYMBOL(ShimMemalign);
+
+SHIM_ALWAYS_EXPORT void* __libc_valloc(size_t size)
+    SHIM_ALIAS_SYMBOL(ShimValloc);
+
+SHIM_ALWAYS_EXPORT void* __libc_pvalloc(size_t size)
+    SHIM_ALIAS_SYMBOL(ShimPvalloc);
+
+SHIM_ALWAYS_EXPORT int __posix_memalign(void** r, size_t a, size_t s)
+    SHIM_ALIAS_SYMBOL(ShimPosixMemalign);
+
+}  // extern "C"
+
+// Safety check.
+#if !defined(__GLIBC__)
+#error The current platform does not seem to use Glibc.
+#endif