/src/glib/glib/gmem.c

Source
/* GLIB - Library of useful routines for C programming
 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
 * file for a list of people on the GLib Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GLib at ftp://ftp.gtk.org/pub/gtk/. 
 */

/* 
 * MT safe
 */

#include "config.h"

#include "gmem.h"

#if defined(HAVE_POSIX_MEMALIGN) && !defined(_XOPEN_SOURCE)
# define _XOPEN_SOURCE 600
#endif

#if defined(HAVE_MEMALIGN) || defined(HAVE__ALIGNED_MALLOC)
/* Required for _aligned_malloc() and _aligned_free() on Windows */
#include <malloc.h>
#endif

#ifdef HAVE__ALIGNED_MALLOC
/* _aligned_malloc() takes parameters of aligned_malloc() in reverse order */
# define aligned_alloc(alignment, size) _aligned_malloc (size, alignment)

/* _aligned_malloc()'ed memory must be freed by _align_free() on MSVC */
# define aligned_free(x) _aligned_free (x)
#else
# define aligned_free(x) free (x)
#endif

#include <stdlib.h>
#include <string.h>
#include <signal.h>

#include "gslice.h"
#include "gbacktrace.h"
#include "gtestutils.h"
#include "gthread.h"
#include "glib_trace.h"

/* notes on macros:
 * having G_DISABLE_CHECKS defined disables use of glib_mem_profiler_table and
 * g_mem_profile().
 * If g_mem_gc_friendly is TRUE, freed memory should be 0-wiped.
 */

/* --- variables --- */
static GMemVTable glib_mem_vtable = {
  malloc,
  realloc,
  free,
  calloc,
  malloc,
  realloc,
};

/* --- functions --- */
/**
 * g_malloc:
 * @n_bytes: the number of bytes to allocate
 *
 * Allocates @n_bytes bytes of memory.
 * If @n_bytes is 0 it returns %NULL.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Returns: a pointer to the allocated memory
 */
gpointer
g_malloc (gsize n_bytes)
{
  if (G_LIKELY (n_bytes))
    {
      gpointer mem;

      mem = malloc (n_bytes);
      TRACE (GLIB_MEM_ALLOC((void*) mem, (unsigned int) n_bytes, 0, 0));
      if (mem)
  return mem;

      g_error ("%s: failed to allocate %"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_bytes);
    }

  TRACE(GLIB_MEM_ALLOC((void*) NULL, (int) n_bytes, 0, 0));

  return NULL;
}

/**
 * g_malloc0:
 * @n_bytes: the number of bytes to allocate
 *
 * Allocates @n_bytes bytes of memory, initialized to 0's.
 * If @n_bytes is 0 it returns %NULL.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Returns: a pointer to the allocated memory
 */
gpointer
g_malloc0 (gsize n_bytes)
{
  if (G_LIKELY (n_bytes))
    {
      gpointer mem;

      mem = calloc (1, n_bytes);
      TRACE (GLIB_MEM_ALLOC((void*) mem, (unsigned int) n_bytes, 1, 0));
      if (mem)
  return mem;

      g_error ("%s: failed to allocate %"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_bytes);
    }

  TRACE(GLIB_MEM_ALLOC((void*) NULL, (int) n_bytes, 1, 0));

  return NULL;
}

/**
 * g_realloc:
 * @mem: (nullable): the memory to reallocate
 * @n_bytes: new size of the memory in bytes
 *
 * Reallocates the memory pointed to by @mem, so that it now has space for
 * @n_bytes bytes of memory. It returns the new address of the memory, which may
 * have been moved. @mem may be %NULL, in which case it's considered to
 * have zero-length. @n_bytes may be 0, in which case %NULL will be returned
 * and @mem will be freed unless it is %NULL.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Returns: the new address of the allocated memory
 */
gpointer
g_realloc (gpointer mem,
     gsize    n_bytes)
{
  gpointer newmem;

  if (G_LIKELY (n_bytes))
    {
      newmem = realloc (mem, n_bytes);
      TRACE (GLIB_MEM_REALLOC((void*) newmem, (void*)mem, (unsigned int) n_bytes, 0));
      if (newmem)
  return newmem;

      g_error ("%s: failed to allocate %"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_bytes);
    }

  free (mem);

  TRACE (GLIB_MEM_REALLOC((void*) NULL, (void*)mem, 0, 0));

  return NULL;
}

/**
 * g_free:
 * @mem: (nullable): the memory to free
 * 
 * Frees the memory pointed to by @mem.
 *
 * If you know the allocated size of @mem, calling g_free_sized() may be faster,
 * depending on the libc implementation in use.
 *
 * Starting from GLib 2.78, this may happen automatically in case a GCC
 * compatible compiler is used with some optimization level and the allocated
 * size is known at compile time (see [documentation of
 * `__builtin_object_size()`](https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html)
 * to understand its caveats).
 *
 * If @mem is %NULL it simply returns, so there is no need to check @mem
 * against %NULL before calling this function.
 */
void
(g_free) (gpointer mem)
{
  free (mem);
  TRACE(GLIB_MEM_FREE((void*) mem));
}

/**
 * g_free_sized:
 * @mem: (nullable): the memory to free
 * @size: size of @mem, in bytes
 *
 * Frees the memory pointed to by @mem, assuming it is has the given @size.
 *
 * If @mem is %NULL this is a no-op (and @size is ignored).
 *
 * It is an error if @size doesn’t match the size passed when @mem was
 * allocated. @size is passed to this function to allow optimizations in the
 * allocator. If you don’t know the allocation size, use g_free() instead.
 *
 * In case a GCC compatible compiler is used, this function may be used
 * automatically via g_free() if the allocated size is known at compile time,
 * since GLib 2.78.
 *
 * Since: 2.76
 */
void
g_free_sized (void   *mem,
              size_t  size)
{
#ifdef HAVE_FREE_SIZED
  free_sized (mem, size);
#else
  free (mem);
#endif
  TRACE (GLIB_MEM_FREE ((void*) mem));
}

/**
 * g_clear_pointer: (skip)
 * @pp: (nullable) (not optional) (inout) (transfer full): a pointer to a
 *   variable, struct member etc. holding a pointer
 * @destroy: a function to which a gpointer can be passed, to destroy `*pp`
 *
 * Clears a reference to a variable.
 *
 * @pp must not be %NULL.
 *
 * If the reference is %NULL then this function does nothing.
 * Otherwise, the variable is destroyed using @destroy and the
 * pointer is set to %NULL.
 *
 * A macro is also included that allows this function to be used without
 * pointer casts. This will mask any warnings about incompatible function types
 * or calling conventions, so you must ensure that your @destroy function is
 * compatible with being called as [callback@GLib.DestroyNotify] using the
 * standard calling convention for the platform that GLib was compiled for;
 * otherwise the program will experience undefined behaviour.
 *
 * Examples of this kind of undefined behaviour include using many Windows Win32
 * APIs, as well as many if not all OpenGL and Vulkan calls on 32-bit Windows,
 * which typically use the `__stdcall` calling convention rather than the
 * `__cdecl` calling convention.
 *
 * The affected functions can be used by wrapping them in a
 * [callback@GLib.DestroyNotify] that is declared with the standard calling
 * convention:
 *
 * ```c
 * // Wrapper needed to avoid mismatched calling conventions on Windows
 * static void
 * destroy_sync (void *sync)
 * {
 *   glDeleteSync (sync);
 * }
 *
 * // …
 *
 * g_clear_pointer (&sync, destroy_sync);
 * ```

 *
 * Since: 2.34
 **/
#undef g_clear_pointer
void
g_clear_pointer (gpointer      *pp,
                 GDestroyNotify destroy)
{
  gpointer _p;

  _p = *pp;
  if (_p)
    {
      *pp = NULL;
      destroy (_p);
    }
}

/**
 * g_try_malloc:
 * @n_bytes: number of bytes to allocate.
 * 
 * Attempts to allocate @n_bytes, and returns %NULL on failure.
 * Contrast with g_malloc(), which aborts the program on failure.
 * 
 * Returns: the allocated memory, or %NULL.
 */
gpointer
g_try_malloc (gsize n_bytes)
{
  gpointer mem;

  if (G_LIKELY (n_bytes))
    mem = malloc (n_bytes);
  else
    mem = NULL;

  TRACE (GLIB_MEM_ALLOC((void*) mem, (unsigned int) n_bytes, 0, 1));

  return mem;
}

/**
 * g_try_malloc0:
 * @n_bytes: number of bytes to allocate
 * 
 * Attempts to allocate @n_bytes, initialized to 0's, and returns %NULL on
 * failure. Contrast with g_malloc0(), which aborts the program on failure.
 * 
 * Since: 2.8
 * Returns: the allocated memory, or %NULL
 */
gpointer
g_try_malloc0 (gsize n_bytes)
{
  gpointer mem;

  if (G_LIKELY (n_bytes))
    mem = calloc (1, n_bytes);
  else
    mem = NULL;

  return mem;
}

/**
 * g_try_realloc:
 * @mem: (nullable): previously-allocated memory, or %NULL.
 * @n_bytes: number of bytes to allocate.
 * 
 * Attempts to realloc @mem to a new size, @n_bytes, and returns %NULL
 * on failure. Contrast with g_realloc(), which aborts the program
 * on failure.
 *
 * If @mem is %NULL, behaves the same as g_try_malloc().
 * 
 * Returns: the allocated memory, or %NULL.
 */
gpointer
g_try_realloc (gpointer mem,
         gsize    n_bytes)
{
  gpointer newmem;

  if (G_LIKELY (n_bytes))
    newmem = realloc (mem, n_bytes);
  else
    {
      newmem = NULL;
      free (mem);
    }

  TRACE (GLIB_MEM_REALLOC((void*) newmem, (void*)mem, (unsigned int) n_bytes, 1));

  return newmem;
}


#define SIZE_OVERFLOWS(a,b) (G_UNLIKELY ((b) > 0 && (a) > G_MAXSIZE / (b)))

/**
 * g_malloc_n:
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 *
 * This function is similar to g_malloc(), allocating (@n_blocks * @n_block_bytes) bytes,
 * but care is taken to detect possible overflow during multiplication.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Since: 2.24
 * Returns: a pointer to the allocated memory
 */
gpointer
g_malloc_n (gsize n_blocks,
      gsize n_block_bytes)
{
  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    {
      g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_blocks, n_block_bytes);
    }

  return g_malloc (n_blocks * n_block_bytes);
}

/**
 * g_malloc0_n:
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 *
 * This function is similar to g_malloc0(), allocating (@n_blocks * @n_block_bytes) bytes,
 * but care is taken to detect possible overflow during multiplication.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Since: 2.24
 * Returns: a pointer to the allocated memory
 */
gpointer
g_malloc0_n (gsize n_blocks,
       gsize n_block_bytes)
{
  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    {
      g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_blocks, n_block_bytes);
    }

  return g_malloc0 (n_blocks * n_block_bytes);
}

/**
 * g_realloc_n:
 * @mem: (nullable): the memory to reallocate
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 *
 * This function is similar to g_realloc(), allocating (@n_blocks * @n_block_bytes) bytes,
 * but care is taken to detect possible overflow during multiplication.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Since: 2.24
 * Returns: the new address of the allocated memory
 */
gpointer
g_realloc_n (gpointer mem,
       gsize    n_blocks,
       gsize    n_block_bytes)
{
  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    {
      g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_blocks, n_block_bytes);
    }

  return g_realloc (mem, n_blocks * n_block_bytes);
}

/**
 * g_try_malloc_n:
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 * 
 * This function is similar to g_try_malloc(), allocating (@n_blocks * @n_block_bytes) bytes,
 * but care is taken to detect possible overflow during multiplication.
 * 
 * Since: 2.24
 * Returns: the allocated memory, or %NULL.
 */
gpointer
g_try_malloc_n (gsize n_blocks,
    gsize n_block_bytes)
{
  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    return NULL;

  return g_try_malloc (n_blocks * n_block_bytes);
}

/**
 * g_try_malloc0_n:
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 * 
 * This function is similar to g_try_malloc0(), allocating (@n_blocks * @n_block_bytes) bytes,
 * but care is taken to detect possible overflow during multiplication.
 * 
 * Since: 2.24
 * Returns: the allocated memory, or %NULL
 */
gpointer
g_try_malloc0_n (gsize n_blocks,
     gsize n_block_bytes)
{
  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    return NULL;

  return g_try_malloc0 (n_blocks * n_block_bytes);
}

/**
 * g_try_realloc_n:
 * @mem: (nullable): previously-allocated memory, or %NULL.
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 * 
 * This function is similar to g_try_realloc(), allocating (@n_blocks * @n_block_bytes) bytes,
 * but care is taken to detect possible overflow during multiplication.
 * 
 * Since: 2.24
 * Returns: the allocated memory, or %NULL.
 */
gpointer
g_try_realloc_n (gpointer mem,
     gsize    n_blocks,
     gsize    n_block_bytes)
{
  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    return NULL;

  return g_try_realloc (mem, n_blocks * n_block_bytes);
}

/**
 * g_mem_is_system_malloc:
 * 
 * Checks whether the allocator used by g_malloc() is the system's
 * malloc implementation. If it returns %TRUE memory allocated with
 * malloc() can be used interchangeably with memory allocated using g_malloc().
 * This function is useful for avoiding an extra copy of allocated memory returned
 * by a non-GLib-based API.
 *
 * Returns: if %TRUE, malloc() and g_malloc() can be mixed.
 *
 * Deprecated: 2.46: GLib always uses the system malloc, so this function always
 * returns %TRUE.
 **/
gboolean
g_mem_is_system_malloc (void)
{
  return TRUE;
}

/**
 * g_mem_set_vtable:
 * @vtable: table of memory allocation routines.
 * 
 * This function used to let you override the memory allocation function.
 * However, its use was incompatible with the use of global constructors
 * in GLib and GIO, because those use the GLib allocators before main is
 * reached. Therefore this function is now deprecated and is just a stub.
 *
 * Deprecated: 2.46: This function now does nothing. Use other memory
 * profiling tools instead
 */
void
g_mem_set_vtable (GMemVTable *vtable)
{
  g_warning (G_STRLOC ": custom memory allocation vtable not supported");
}


/**
 * glib_mem_profiler_table:
 *
 * Used to be a #GMemVTable containing profiling variants of the memory
 * allocation functions, but this variable shouldn't be modified anymore.
 *
 * Deprecated: 2.46: Use other memory profiling tools instead
 */
GMemVTable *glib_mem_profiler_table = &glib_mem_vtable;

/**
 * g_mem_profile:
 *
 * GLib used to support some tools for memory profiling, but this
 * no longer works. There are many other useful tools for memory
 * profiling these days which can be used instead.
 *
 * Deprecated: 2.46: Use other memory profiling tools instead
 */
void
g_mem_profile (void)
{
  g_warning (G_STRLOC ": memory profiling not supported");
}

/**
 * g_aligned_alloc:
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 * @alignment: the alignment to be enforced, which must be a positive power of 2
 *   and a multiple of `sizeof(void*)`
 *
 * This function is similar to g_malloc(), allocating (@n_blocks * @n_block_bytes)
 * bytes, but care is taken to align the allocated memory to with the given
 * alignment value. Additionally, it will detect possible overflow during
 * multiplication.
 *
 * If the allocation fails (because the system is out of memory),
 * the program is terminated.
 *
 * Aligned memory allocations returned by this function can only be
 * freed using g_aligned_free_sized() or g_aligned_free().
 *
 * Returns: (transfer full): the allocated memory
 *
 * Since: 2.72
 */
gpointer
g_aligned_alloc (gsize n_blocks,
                 gsize n_block_bytes,
                 gsize alignment)
{
  gpointer res = NULL;
  gsize real_size;

  if (G_UNLIKELY ((alignment == 0) || (alignment & (alignment - 1)) != 0))
    {
      g_error ("%s: alignment %"G_GSIZE_FORMAT" must be a positive power of two",
               G_STRLOC, alignment);
    }

  if (G_UNLIKELY ((alignment % sizeof (void *)) != 0))
    {
      g_error ("%s: alignment %"G_GSIZE_FORMAT" must be a multiple of %"G_GSIZE_FORMAT,
               G_STRLOC, alignment, sizeof (void *));
    }

  if (SIZE_OVERFLOWS (n_blocks, n_block_bytes))
    {
      g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
               G_STRLOC, n_blocks, n_block_bytes);
    }

  real_size = n_blocks * n_block_bytes;

  if (G_UNLIKELY (real_size == 0))
    {
      TRACE(GLIB_MEM_ALLOC((void*) NULL, (int) real_size, 0, 0));
      return NULL;
    }

  /* We need to clear errno because posix_memalign() will use its return
   * value in the same way memalign() and aligned_alloc() will set errno.
   * Additionally, posix_memalign() will warn if its return value is left
   * unassigned.
   *
   * We handle all possible return values (ENOMEM and EINVAL) with either
   * precondition or postcondition checking.
   */
  errno = 0;

#if defined(HAVE_POSIX_MEMALIGN)
  errno = posix_memalign (&res, alignment, real_size);
#elif defined(HAVE_ALIGNED_ALLOC) || defined(HAVE__ALIGNED_MALLOC)
  /* real_size must be a multiple of alignment */
  if (real_size % alignment != 0)
    {
      gsize offset = real_size % alignment;

      if (G_MAXSIZE - real_size < (alignment - offset))
        {
          g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"+%"G_GSIZE_FORMAT" bytes",
                   G_STRLOC, real_size, (alignment - offset));
        }

      real_size += (alignment - offset);
    }

  res = aligned_alloc (alignment, real_size);
#elif defined(HAVE_MEMALIGN)
  res = memalign (alignment, real_size);
#else
# error "This platform does not have an aligned memory allocator."
#endif

  TRACE (GLIB_MEM_ALLOC((void*) res, (unsigned int) real_size, 0, 0));
  if (res)
    return res;

  g_error ("%s: failed to allocate %"G_GSIZE_FORMAT" bytes",
           G_STRLOC, real_size);

  return NULL;
}

/**
 * g_aligned_alloc0:
 * @n_blocks: the number of blocks to allocate
 * @n_block_bytes: the size of each block in bytes
 * @alignment: the alignment to be enforced, which must be a positive power of 2
 *   and a multiple of `sizeof(void*)`
 *
 * This function is similar to g_aligned_alloc(), but it will
 * also clear the allocated memory before returning it.
 *
 * Returns: (transfer full): the allocated, cleared memory
 *
 * Since: 2.72
 */
gpointer
g_aligned_alloc0 (gsize n_blocks,
                  gsize n_block_bytes,
                  gsize alignment)
{
  gpointer res = g_aligned_alloc (n_blocks, n_block_bytes, alignment);

  if (G_LIKELY (res != NULL))
    memset (res, 0, n_blocks * n_block_bytes);

  return res;
}

/**
 * g_aligned_free:
 * @mem: (nullable): the memory to deallocate
 *
 * Frees the memory allocated by g_aligned_alloc().
 *
 * Since: 2.72
 */
void
g_aligned_free (gpointer mem)
{
  aligned_free (mem);
}

/**
 * g_aligned_free_sized:
 * @mem: (nullable): the memory to free
 * @alignment: alignment of @mem
 * @size: size of @mem, in bytes
 *
 * Frees the memory pointed to by @mem, assuming it is has the given @size and
 * @alignment.
 *
 * If @mem is %NULL this is a no-op (and @size is ignored).
 *
 * It is an error if @size doesn’t match the size, or @alignment doesn’t match
 * the alignment, passed when @mem was allocated. @size and @alignment are
 * passed to this function to allow optimizations in the allocator. If you
 * don’t know either of them, use g_aligned_free() instead.
 *
 * Since: 2.76
 */
void
g_aligned_free_sized (void   *mem,
                      size_t  alignment,
                      size_t  size)
{
#ifdef HAVE_FREE_ALIGNED_SIZED
  free_aligned_sized (mem, alignment, size);
#else
  aligned_free (mem);
#endif
}

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Created: 2026-05-16 06:18