string/strerror.c

   1 /* Copyright (C) 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <libintl.h>
  19 #include <stdio.h>
  20 #include <string.h>
  21 #include <errno.h>
  22
  23 /* Return a string describing the errno code in ERRNUM.
  24    The storage is good only until the next call to strerror.
  25    Writing to the storage causes undefined behavior.  */
  26 libc_freeres_ptr (static char *buf);
  27
  28 char *
  29 strerror (int errnum)
  30 {
  31   char *ret = __strerror_r (errnum, NULL, 0);
  32   int saved_errno;
  33
  34   if (__glibc_likely (ret != NULL))
  35     return ret;
  36   saved_errno = errno;
  37   if (buf == NULL)
  38     buf = malloc (1024);
  39   __set_errno (saved_errno);
  40   if (buf == NULL)
  41     return _("Unknown error");
  42   return __strerror_r (errnum, buf, 1024);
  43 }