mingw-w64-crt/ssp/strncat_chk.c

/**
 * This file has no copyright assigned and is placed in the Public Domain.
 * This file is part of the mingw-w64 runtime package.
 * No warranty is given; refer to the file DISCLAIMER.PD within this package.
 */

#include <string.h>

void __cdecl __chk_fail(void) __attribute__((__noreturn__));

char *__cdecl __strncat_chk(char *dst, const char *src, size_t n, size_t bufsize);

char *__cdecl __strncat_chk(char *dst, const char *src, size_t n, size_t bufsize)
{
  size_t cur_len = strlen(dst);
  char *orig_dst = dst;
  char c;

  if (cur_len > bufsize)
    __chk_fail();

  dst += cur_len;
  bufsize -= cur_len;

  while (n > 0) {
    if (bufsize == 0)
      __chk_fail();
    c = *src++;
    *dst++ = c;
    n--;
    bufsize--;
    if (c == '\0')
      return orig_dst;
  }

  if (bufsize == 0)
    __chk_fail();
  *dst++ = '\0';

  return orig_dst;
}