lib/strerror.c

   1 /* strerror.c --- POSIX compatible system error routine
   2
   3    Copyright (C) 2007-2019 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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 General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include <string.h>
  22
  23 #include <errno.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 #include "intprops.h"
  29 #include "strerror-override.h"
  30 #include "verify.h"
  31
  32 /* Use the system functions, not the gnulib overrides in this file.  */
  33 #undef sprintf
  34
  35 char *
  36 strerror (int n)
  37 #undef strerror
  38 {
  39   static char buf[STACKBUF_LEN];
  40   size_t len;
  41
  42   /* Cast away const, due to the historical signature of strerror;
  43      callers should not be modifying the string.  */
  44   const char *msg = strerror_override (n);
  45   if (msg)
  46     return (char *) msg;
  47
  48   msg = strerror (n);
  49
  50   /* Our strerror_r implementation might use the system's strerror
  51      buffer, so all other clients of strerror have to see the error
  52      copied into a buffer that we manage.  This is not thread-safe,
  53      even if the system strerror is, but portable programs shouldn't
  54      be using strerror if they care about thread-safety.  */
  55   if (!msg || !*msg)
  56     {
  57       static char const fmt[] = "Unknown error %d";
  58       verify (sizeof buf >= sizeof (fmt) + INT_STRLEN_BOUND (n));
  59       sprintf (buf, fmt, n);
  60       errno = EINVAL;
  61       return buf;
  62     }
  63
  64   /* Fix STACKBUF_LEN if this ever aborts.  */
  65   len = strlen (msg);
  66   if (sizeof buf <= len)
  67     abort ();
  68
  69   memcpy (buf, msg, len + 1);
  70   return buf;
  71 }