debug/strcat_chk.c

   1 /* Copyright (C) 1991-2015 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 <string.h>
  19 #include <memcopy.h>
  20
  21
  22 /* Append SRC on the end of DEST.  */
  23 char *
  24 __strcat_chk (dest, src, destlen)
  25      char *dest;
  26      const char *src;
  27      size_t destlen;
  28 {
  29   char *s1 = dest;
  30   const char *s2 = src;
  31   char c;
  32
  33   /* Find the end of the string.  */
  34   do
  35     {
  36       if (__glibc_unlikely (destlen-- == 0))
  37         __chk_fail ();
  38       c = *s1++;
  39     }
  40   while (c != '\0');
  41
  42   /* Make S1 point before the next character, so we can increment
  43      it while memory is read (wins on pipelined cpus).  */
  44   ++destlen;
  45   s1 -= 2;
  46
  47   do
  48     {
  49       if (__glibc_unlikely (destlen-- == 0))
  50         __chk_fail ();
  51       c = *s2++;
  52       *++s1 = c;
  53     }
  54   while (c != '\0');
  55
  56   return dest;
  57 }