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 <stdbool.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/param.h>
  24 #include <_itoa.h>
  25
  26 /* It is critical here that we always use the `dcgettext' function for
  27    the message translation.  Since <libintl.h> only defines the macro
  28    `dgettext' to use `dcgettext' for optimizing programs this is not
  29    always guaranteed.  */
  30 #ifndef dgettext
  31 # include <locale.h>            /* We need LC_MESSAGES.  */
  32 # define dgettext(domainname, msgid) dcgettext (domainname, msgid, LC_MESSAGES)
  33 #endif
  34
  35 /* Return a string describing the errno code in ERRNUM.  */
  36 char *
  37 __strerror_r (int errnum, char *buf, size_t buflen)
  38 {
  39   if (__builtin_expect (errnum < 0 || errnum >= _sys_nerr_internal
  40                         || _sys_errlist_internal[errnum] == NULL, 0))
  41     {
  42       /* Buffer we use to print the number in.  For a maximum size for
  43          `int' of 8 bytes we never need more than 20 digits.  */
  44       char numbuf[21];
  45       const char *unk = _("Unknown error ");
  46       size_t unklen = strlen (unk);
  47       char *p, *q;
  48       bool negative = errnum < 0;
  49
  50       numbuf[20] = '\0';
  51       p = _itoa_word (abs (errnum), &numbuf[20], 10, 0);
  52
  53       /* Now construct the result while taking care for the destination
  54          buffer size.  */
  55       q = __mempcpy (buf, unk, MIN (unklen, buflen));
  56       if (negative && unklen < buflen)
  57         {
  58           *q++ = '-';
  59           ++unklen;
  60         }
  61       if (unklen < buflen)
  62         memcpy (q, p, MIN ((size_t) (&numbuf[21] - p), buflen - unklen));
  63
  64       /* Terminate the string in any case.  */
  65       if (buflen > 0)
  66         buf[buflen - 1] = '\0';
  67
  68       return buf;
  69     }
  70
  71   return (char *) _(_sys_errlist_internal[errnum]);
  72 }
  73 weak_alias (__strerror_r, strerror_r)
  74 libc_hidden_def (__strerror_r)