debug/snprintf_chk.c

   1 /* Copyright (C) 1991-2021 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 <stdarg.h>
  19 #include <libio/libioP.h>
  20
  21
  22 /* Write formatted output into S, according to the format
  23    string FORMAT, writing no more than MAXLEN characters.  */
  24 int
  25 ___snprintf_chk (char *s, size_t maxlen, int flag, size_t slen,
  26                  const char *format, ...)
  27 {
  28   if (__glibc_unlikely (slen < maxlen))
  29     __chk_fail ();
  30
  31   /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
  32      can only come from read-only format strings.  */
  33   unsigned int mode = (flag > 0) ? PRINTF_FORTIFY : 0;
  34   va_list ap;
  35   int ret;
  36
  37   va_start (ap, format);
  38   ret = __vsnprintf_internal (s, maxlen, format, ap, mode);
  39   va_end (ap);
  40
  41   return ret;
  42 }
  43 ldbl_strong_alias (___snprintf_chk, __snprintf_chk)