lib/free.c

   1 /* Make free() preserve errno.
   2
   3    Copyright (C) 2003, 2006, 2009-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* written by Paul Eggert */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <stdlib.h>
  24
  25 /* A function definition is only needed if HAVE_FREE_POSIX is not defined.  */
  26 #if !HAVE_FREE_POSIX
  27
  28 # include <errno.h>
  29
  30 void
  31 rpl_free (void *p)
  32 # undef free
  33 {
  34 # if defined __GNUC__ && !defined __clang__
  35   /* An invalid GCC optimization
  36      <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98396>
  37      would optimize away the assignments in the code below, when link-time
  38      optimization (LTO) is enabled.  Make the code more complicated, so that
  39      GCC does not grok how to optimize it.  */
  40   int err[2];
  41   err[0] = errno;
  42   err[1] = errno;
  43   errno = 0;
  44   free (p);
  45   errno = err[errno == 0];
  46 # else
  47   int err = errno;
  48   free (p);
  49   errno = err;
  50 # endif
  51 }
  52
  53 #endif