gl/realloc.c

   1 /* realloc() function that is glibc compatible.
   2
   3    Copyright (C) 1997, 2003-2004, 2006-2007, 2009-2010 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* written by Jim Meyering and Bruno Haible */
  20
  21 #include <config.h>
  22
  23 /* Only the AC_FUNC_REALLOC macro defines 'realloc' already in config.h.  */
  24 #ifdef realloc
  25 # define NEED_REALLOC_GNU 1
  26 /* Whereas the gnulib module 'realloc-gnu' defines HAVE_REALLOC_GNU.  */
  27 #elif GNULIB_REALLOC_GNU && !HAVE_REALLOC_GNU
  28 # define NEED_REALLOC_GNU 1
  29 #endif
  30
  31 /* Infer the properties of the system's malloc function.
  32    The gnulib module 'malloc-gnu' defines HAVE_MALLOC_GNU.  */
  33 #if GNULIB_MALLOC_GNU && HAVE_MALLOC_GNU
  34 # define SYSTEM_MALLOC_GLIBC_COMPATIBLE 1
  35 #endif
  36
  37 /* Below we want to call the system's malloc and realloc.
  38    Undefine the symbols here so that including <stdlib.h> provides a
  39    declaration of malloc(), not of rpl_malloc(), and likewise for realloc.  */
  40 #undef malloc
  41 #undef realloc
  42
  43 /* Specification.  */
  44 #include <stdlib.h>
  45
  46 #include <errno.h>
  47
  48 /* Below we want to call the system's malloc and realloc.
  49    Undefine the symbols, if they were defined by gnulib's <stdlib.h>
  50    replacement.  */
  51 #undef malloc
  52 #undef realloc
  53
  54 /* Change the size of an allocated block of memory P to N bytes,
  55    with error checking.  If N is zero, change it to 1.  If P is NULL,
  56    use malloc.  */
  57
  58 void *
  59 rpl_realloc (void *p, size_t n)
  60 {
  61   void *result;
  62
  63 #if NEED_REALLOC_GNU
  64   if (n == 0)
  65     {
  66       n = 1;
  67
  68       /* In theory realloc might fail, so don't rely on it to free.  */
  69       free (p);
  70       p = NULL;
  71     }
  72 #endif
  73
  74   if (p == NULL)
  75     {
  76 #if GNULIB_REALLOC_GNU && !NEED_REALLOC_GNU && !SYSTEM_MALLOC_GLIBC_COMPATIBLE
  77       if (n == 0)
  78         n = 1;
  79 #endif
  80       result = malloc (n);
  81     }
  82   else
  83     result = realloc (p, n);
  84
  85 #if !HAVE_REALLOC_POSIX
  86   if (result == NULL)
  87     errno = ENOMEM;
  88 #endif
  89
  90   return result;
  91 }