src/libc_override_glibc.h

// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
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// ---
// Author: Craig Silverstein <opensource@google.com>
//
// Used to override malloc routines on systems that are using glibc.

#ifndef TCMALLOC_LIBC_OVERRIDE_GLIBC_INL_H_
#define TCMALLOC_LIBC_OVERRIDE_GLIBC_INL_H_

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

#ifndef __GLIBC__
# error libc_override_glibc.h is for glibc distributions only.
#endif

// In glibc, the memory-allocation methods are weak symbols, so we can
// just override them with our own.  If we're using gcc, we can use
// __attribute__((alias)) to do the overriding easily (exception:
// Mach-O, which doesn't support aliases).  Otherwise we have to use a
// function call.
#if !defined(__GNUC__) || defined(__MACH__)

// This also defines ReplaceSystemAlloc().
# include "libc_override_redefine.h"  // defines functions malloc()/etc

#else  // #if !defined(__GNUC__) || defined(__MACH__)

// If we get here, we're a gcc system, so do all the overriding we do
// with gcc.  This does the overriding of all the 'normal' memory
// allocation.  This also defines ReplaceSystemAlloc().
# include "libc_override_gcc_and_weak.h"

// We also have to do some glibc-specific overriding.  Some library
// routines on RedHat 9 allocate memory using malloc() and free it
// using __libc_free() (or vice-versa).  Since we provide our own
// implementations of malloc/free, we need to make sure that the
// __libc_XXX variants (defined as part of glibc) also point to the
// same implementations.  Since it only matters for redhat, we
// do it inside the gcc #ifdef, since redhat uses gcc.
// TODO(csilvers): only do this if we detect we're an old enough glibc?

#define ALIAS(tc_fn)   __attribute__ ((alias (#tc_fn)))
extern "C" {
  void* __libc_malloc(size_t size)                ALIAS(tc_malloc);
  void __libc_free(void* ptr)                     ALIAS(tc_free);
  void* __libc_realloc(void* ptr, size_t size)    ALIAS(tc_realloc);
  void* __libc_calloc(size_t n, size_t size)      ALIAS(tc_calloc);
  void __libc_cfree(void* ptr)                    ALIAS(tc_cfree);
  void* __libc_memalign(size_t align, size_t s)   ALIAS(tc_memalign);
  void* __libc_valloc(size_t size)                ALIAS(tc_valloc);
  void* __libc_pvalloc(size_t size)               ALIAS(tc_pvalloc);
  int __posix_memalign(void** r, size_t a, size_t s)  ALIAS(tc_posix_memalign);
}   // extern "C"
#undef ALIAS

#endif  // #if defined(__GNUC__) && !defined(__MACH__)

// No need to write ReplaceSystemAlloc(); one of the #includes above
// did it for us.

#endif  // TCMALLOC_LIBC_OVERRIDE_GLIBC_INL_H_