20030711-1.c

来自「linux下的gcc编译器」· C语言 代码 · 共 26 行

/* Test whether strncmp has not been "optimized" into memcmp
   nor any code with memcmp semantics.  */
/* { dg-do run { target i?86-*-linux* x86_64-*-linux* ia64-*-linux* alpha*-*-linux* powerpc*-*-linux* s390*-*-linux* sparc*-*-linux* } } */
/* { dg-options "-O2" } */
#include <sys/mman.h>
#include <stdlib.h>

void __attribute__((noinline)) test (const char *p)
{
  if (__builtin_strncmp (p, "abcdefghijklmnopq", 17) == 0)
    abort ();
}

int main (void)
{
  char *p = mmap (NULL, 131072, PROT_READ | PROT_WRITE,
                  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  if (p == MAP_FAILED)
    return 0;
  if (munmap (p + 65536, 65536) < 0)
    return 0;
  __builtin_memcpy (p + 65536 - 5, "abcd", 5);
  test (p + 65536 - 5);
  return 0;
}