lib/realloc.c

   1 /* realloc() function that is glibc compatible.
   2
   3    Copyright (C) 1997, 2003-2004, 2006-2007, 2009-2019 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 <https://www.gnu.org/licenses/>.  */
  18
  19 /* written by Jim Meyering and Bruno Haible */
  20
  21 #define _GL_USE_STDLIB_ALLOC 1
  22 #include <config.h>
  23
  24 /* Only the AC_FUNC_REALLOC macro defines 'realloc' already in config.h.  */
  25 #ifdef realloc
  26 # define NEED_REALLOC_GNU 1
  27 /* Whereas the gnulib module 'realloc-gnu' defines HAVE_REALLOC_GNU.  */
  28 #elif GNULIB_REALLOC_GNU && !HAVE_REALLOC_GNU
  29 # define NEED_REALLOC_GNU 1
  30 #endif
  31
  32 /* Infer the properties of the system's malloc function.
  33    The gnulib module 'malloc-gnu' defines HAVE_MALLOC_GNU.  */
  34 #if GNULIB_MALLOC_GNU && HAVE_MALLOC_GNU
  35 # define SYSTEM_MALLOC_GLIBC_COMPATIBLE 1
  36 #endif
  37
  38 #include <stdlib.h>
  39
  40 #include <errno.h>
  41
  42 /* Change the size of an allocated block of memory P to N bytes,
  43    with error checking.  If N is zero, change it to 1.  If P is NULL,
  44    use malloc.  */
  45
  46 void *
  47 rpl_realloc (void *p, size_t n)
  48 {
  49   void *result;
  50
  51 #if NEED_REALLOC_GNU
  52   if (n == 0)
  53     {
  54       n = 1;
  55
  56       /* In theory realloc might fail, so don't rely on it to free.  */
  57       free (p);
  58       p = NULL;
  59     }
  60 #endif
  61
  62   if (p == NULL)
  63     {
  64 #if GNULIB_REALLOC_GNU && !NEED_REALLOC_GNU && !SYSTEM_MALLOC_GLIBC_COMPATIBLE
  65       if (n == 0)
  66         n = 1;
  67 #endif
  68       result = malloc (n);
  69     }
  70   else
  71     result = realloc (p, n);
  72
  73 #if !HAVE_REALLOC_POSIX
  74   if (result == NULL)
  75     errno = ENOMEM;
  76 #endif
  77
  78   return result;
  79 }