gcc/testsuite/gcc.dg/memset-1.c

/* { dg-do compile } */
/* { dg-options "-O2" } */

typedef __SIZE_TYPE__ size_t;

extern void warn_memset_zero_len (void)
__attribute__((__warning__ ("memset used with constant zero length parameter;"
			    " this could be due to transposed parameters")));

extern inline __attribute__((gnu_inline, always_inline, artificial)) void *
memset (void *dest, int ch, size_t len)
{
  if (__builtin_constant_p (len) && len == 0)
    {
      warn_memset_zero_len ();	/* { dg-warning "memset used with constant zero" } */
      return dest;
    }
  return __builtin_memset (dest, ch, len);
}

char buf[10];

int
main (void)
{
  memset (buf, sizeof (buf), 0);
  return 0;
}