src/libc_override.h

// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
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// ---
// Author: Craig Silverstein <opensource@google.com>
//
// This .h file imports the code that causes tcmalloc to override libc
// versions of malloc/free/new/delete/etc.  That is, it provides the
// logic that makes it so calls to malloc(10) go through tcmalloc,
// rather than the default (libc) malloc.
//
// This file also provides a method: ReplaceSystemAlloc(), that every
// libc_override_*.h file it #includes is required to provide.  This
// is called when first setting up tcmalloc -- that is, when a global
// constructor in tcmalloc.cc is executed -- to do any initialization
// work that may be required for this OS.  (Note we cannot entirely
// control when tcmalloc is initialized, and the system may do some
// mallocs and frees before this routine is called.)  It may be a
// noop.
//
// Every libc has its own way of doing this, and sometimes the compiler
// matters too, so we have a different file for each libc, and often
// for different compilers and OS's.

#ifndef TCMALLOC_LIBC_OVERRIDE_INL_H_
#define TCMALLOC_LIBC_OVERRIDE_INL_H_

#include <config.h>
#ifdef HAVE_FEATURES_H
#include <features.h>   // for __GLIBC__
#endif
#include <gperftools/tcmalloc.h>

#if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1900)
#define CPP_NOTHROW noexcept
#define CPP_BADALLOC
#else
#define CPP_NOTHROW throw()
#define CPP_BADALLOC throw(std::bad_alloc)
#endif

static void ReplaceSystemAlloc();  // defined in the .h files below

#if defined(TCMALLOC_DONT_REPLACE_SYSTEM_ALLOC)
// TCMALLOC_DONT_REPLACE_SYSTEM_ALLOC has the following semantic:
//  - tcmalloc with all its tc_* (tc_malloc, tc_free) symbols is being built
//    and linked as usual.
//  - the default system allocator symbols (malloc, free, operator new) are NOT
//    overridden. The embedded must take care of routing them to tc_* symbols.
// This no-op #if block effectively prevents the inclusion of the
// libc_override_* headers below.
static void ReplaceSystemAlloc() {}

// For windows, there are two ways to get tcmalloc.  If we're
// patching, then src/windows/patch_function.cc will do the necessary
// overriding here.  Otherwise, we doing the 'redefine' trick, where
// we remove malloc/new/etc from mscvcrt.dll, and just need to define
// them now.
#elif defined(_WIN32) && defined(WIN32_DO_PATCHING)
void PatchWindowsFunctions();   // in src/windows/patch_function.cc
static void ReplaceSystemAlloc() { PatchWindowsFunctions(); }

#elif defined(_WIN32) && !defined(WIN32_DO_PATCHING)
// "libc_override_redefine.h" is included in the original gperftools.  But,
// we define allocator functions in Chromium's base/allocator/allocator_shim.cc
// on Windows.  We don't include libc_override_redefine.h here.
// ReplaceSystemAlloc() is defined here instead.
static void ReplaceSystemAlloc() {}

#elif defined(__APPLE__)
#include "libc_override_osx.h"

#elif defined(__GLIBC__)
#include "libc_override_glibc.h"

// Not all gcc systems necessarily support weak symbols, but all the
// ones I know of do, so for now just assume they all do.
#elif defined(__GNUC__)
#include "libc_override_gcc_and_weak.h"

#else
#error Need to add support for your libc/OS here

#endif

#endif  // TCMALLOC_LIBC_OVERRIDE_INL_H_