debug/strcat_chk.c

   1 /* Copyright (C) 1991-2022 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    <https://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 (char *dest, const char *src, size_t destlen)
  25 {
  26   char *s1 = dest;
  27   const char *s2 = src;
  28   char c;
  29
  30   /* Find the end of the string.  */
  31   do
  32     {
  33       if (__glibc_unlikely (destlen-- == 0))
  34         __chk_fail ();
  35       c = *s1++;
  36     }
  37   while (c != '\0');
  38
  39   /* Make S1 point before the next character, so we can increment
  40      it while memory is read (wins on pipelined cpus).  */
  41   ++destlen;
  42   s1 -= 2;
  43
  44   do
  45     {
  46       if (__glibc_unlikely (destlen-- == 0))
  47         __chk_fail ();
  48       c = *s2++;
  49       *++s1 = c;
  50     }
  51   while (c != '\0');
  52
  53   return dest;
  54 }