1  /* Test whether strncmp has not been "optimized" into memcmp
       2     nor any code with memcmp semantics.  */
       3  /* { dg-do run { target mmap } } */
       4  /* { dg-options "-O2" } */
       5  #include <stddef.h>
       6  #include <stdio.h>
       7  #include <sys/mman.h>
       8  #ifndef MAP_ANONYMOUS
       9  #define MAP_ANONYMOUS MAP_ANON
      10  #endif
      11  #ifndef MAP_ANON
      12  #define MAP_ANON 0
      13  #endif
      14  #ifndef MAP_FAILED
      15  #define MAP_FAILED ((void *)-1)
      16  #endif
      17  #include <stdlib.h>
      18  
      19  void __attribute__((noinline)) test (const char *p)
      20  {
      21    if (__builtin_strncmp (p, "abcdefghijklmnopq", 17) == 0)
      22      abort ();
      23  }
      24  
      25  int main (void)
      26  {
      27    char *p = mmap (NULL, 131072, PROT_READ | PROT_WRITE,
      28                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
      29    if (p == MAP_FAILED)
      30      return 0;
      31    if (munmap (p + 65536, 65536) < 0)
      32      return 0;
      33    __builtin_memcpy (p + 65536 - 5, "abcd", 5);
      34    test (p + 65536 - 5);
      35    return 0;
      36  }