1  /* strerror.c --- POSIX compatible system error routine
       2  
       3     Copyright (C) 2007-2021 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  }