debug/wcscat_chk.c

   1 /* Copyright (C) 1995-2024 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 <wchar.h>
  19
  20
  21 /* Append SRC on the end of DEST.  Check for overflows.  */
  22 wchar_t *
  23 __wcscat_chk (wchar_t *dest, const wchar_t *src, size_t destlen)
  24 {
  25   wchar_t *s1 = dest;
  26   const wchar_t *s2 = src;
  27   wchar_t c;
  28
  29   /* Find the end of the string.  */
  30   do
  31     {
  32       if (__glibc_unlikely (destlen-- == 0))
  33         __chk_fail ();
  34       c = *s1++;
  35     }
  36   while (c != L'\0');
  37
  38   /* Make S1 point before the next character, so we can increment
  39      it while memory is read (wins on pipelined cpus).  */
  40   s1 -= 2;
  41   ++destlen;
  42
  43   do
  44     {
  45       if (__glibc_unlikely (destlen-- == 0))
  46         __chk_fail ();
  47       c = *s2++;
  48       *++s1 = c;
  49     }
  50   while (c != L'\0');
  51
  52   return dest;
  53 }