string/xpg-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 <assert.h>
  19 #include <errno.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <sys/param.h>
  23
  24
  25 /* Fill buf with a string describing the errno code in ERRNUM.  */
  26 int
  27 __xpg_strerror_r (int errnum, char *buf, size_t buflen)
  28 {
  29   const char *estr = __strerror_r (errnum, buf, buflen);
  30
  31   /* We know that __strerror_r returns buf (with a dynamically computed
  32      string) if errnum is invalid, otherwise it returns a string whose
  33      storage has indefinite extent.  */
  34   if (estr == buf)
  35     {
  36       assert (errnum < 0 || errnum >= _sys_nerr_internal
  37               || _sys_errlist_internal[errnum] == NULL);
  38       return EINVAL;
  39     }
  40   else
  41     {
  42       assert (errnum >= 0 && errnum < _sys_nerr_internal
  43               && _sys_errlist_internal[errnum] != NULL);
  44
  45       size_t estrlen = strlen (estr);
  46
  47       /* Terminate the string in any case.  */
  48       if (buflen > 0)
  49         *((char *) __mempcpy (buf, estr, MIN (buflen - 1, estrlen))) = '\0';
  50
  51       return buflen <= estrlen ? ERANGE : 0;
  52     }
  53 }