lib/strerror.c

   1 /* strerror.c --- POSIX compatible system error routine
   2
   3    Copyright (C) 2007-2025 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 #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
  31 /* Use the system functions, not the gnulib overrides in this file.  */
  32 #undef sprintf
  33
  34 /* macOS 12's "warning: 'sprintf' is deprecated" is pointless,
  35    as sprintf is used safely here.  */
  36 #if defined __APPLE__ && defined __MACH__ && _GL_GNUC_PREREQ (4, 2)
  37 # pragma GCC diagnostic ignored "-Wdeprecated-declarations"
  38 #endif
  39
  40 char *
  41 strerror (int n)
  42 #undef strerror
  43 {
  44   static char buf[STACKBUF_LEN];
  45   size_t len;
  46
  47   /* Cast away const, due to the historical signature of strerror;
  48      callers should not be modifying the string.  */
  49   const char *msg = strerror_override (n);
  50   if (msg)
  51     return (char *) msg;
  52
  53   msg = strerror (n);
  54
  55   /* Our strerror_r implementation might use the system's strerror
  56      buffer, so all other clients of strerror have to see the error
  57      copied into a buffer that we manage.  This is not thread-safe,
  58      even if the system strerror is, but portable programs shouldn't
  59      be using strerror if they care about thread-safety.  */
  60   if (!msg || !*msg)
  61     {
  62       static char const fmt[] = "Unknown error %d";
  63       static_assert (sizeof buf >= sizeof (fmt) + INT_STRLEN_BOUND (n));
  64       sprintf (buf, fmt, n);
  65       errno = EINVAL;
  66       return buf;
  67     }
  68
  69   /* Fix STACKBUF_LEN if this ever aborts.  */
  70   len = strlen (msg);
  71   if (sizeof buf <= len)
  72     abort ();
  73
  74   memcpy (buf, msg, len + 1);
  75   return buf;
  76 }