libssp/strncat-chk.c

   1 /* Checking strncat.
   2    Copyright (C) 1991, 1997, 2003, 2004, 2005 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 2, or (at your option) any later
   9 version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file into combinations with other programs,
  14 and to distribute those combinations without any restriction coming
  15 from the use of this file.  (The General Public License restrictions
  16 do apply in other respects; for example, they cover modification of
  17 the file, and distribution when not linked into a combine
  18 executable.)
  19
  20 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  21 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  22 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  23 for more details.
  24
  25 You should have received a copy of the GNU General Public License
  26 along with GCC; see the file COPYING.  If not, write to the Free
  27 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  28 02110-1301, USA.  */
  29
  30 /* As a special exception, if you link this library with files compiled with
  31    GCC to produce an executable, this does not cause the resulting executable
  32    to be covered by the GNU General Public License. This exception does not
  33    however invalidate any other reasons why the executable file might be
  34    covered by the GNU General Public License.  */
  35
  36 #include "config.h"
  37 #include <ssp/ssp.h>
  38 #ifdef HAVE_STRING_H
  39 # include <string.h>
  40 #endif
  41
  42 extern void __chk_fail (void) __attribute__((__noreturn__));
  43
  44 char *
  45 __strncat_chk (char *__restrict__ dest, const char *__restrict__ src,
  46                size_t n, size_t slen)
  47 {
  48   char c;
  49   char *s = dest;
  50
  51   do
  52     {
  53       if (slen-- == 0)
  54         __chk_fail ();
  55       c = *dest++;
  56     }
  57   while (c != '\0');
  58
  59   ++slen;
  60   dest -= 2;
  61
  62   if (n >= 4)
  63     {
  64       size_t n4 = n >> 2;
  65       do
  66         {
  67           if (slen-- == 0)
  68             __chk_fail ();
  69           c = *src++;
  70           *++dest = c;
  71           if (c == '\0')
  72             return s;
  73           if (slen-- == 0)
  74             __chk_fail ();
  75           c = *src++;
  76           *++dest = c;
  77           if (c == '\0')
  78             return s;
  79           if (slen-- == 0)
  80             __chk_fail ();
  81           c = *src++;
  82           *++dest = c;
  83           if (c == '\0')
  84             return s;
  85           if (slen-- == 0)
  86             __chk_fail ();
  87           c = *src++;
  88           *++dest = c;
  89           if (c == '\0')
  90             return s;
  91           if (slen-- == 0)
  92             __chk_fail ();
  93           c = *src++;
  94           *++dest = c;
  95           if (c == '\0')
  96             return s;
  97         } while (--n4 > 0);
  98       n &= 3;
  99     }
 100
 101   while (n > 0)
 102     {
 103       if (slen-- == 0)
 104         __chk_fail ();
 105       c = *src++;
 106       *++dest = c;
 107       if (c == '\0')
 108         return s;
 109       n--;
 110     }
 111
 112   if (c != '\0')
 113     {
 114       if (slen-- == 0)
 115         __chk_fail ();
 116       *++dest = '\0';
 117     }
 118
 119   return s;
 120 }