1  struct
       2    {
       3      int input;
       4      int output;
       5    }
       6  ffstesttab[] =
       7    {
       8  #if __INT_MAX__ >= 2147483647
       9      /* at least 32-bit integers */
      10      { 0x80000000, 32 },
      11      { 0xa5a5a5a5, 1 },
      12      { 0x5a5a5a5a, 2 },
      13      { 0xcafe0000, 18 },
      14  #endif
      15  #if __INT_MAX__ >= 32767
      16      /* at least 16-bit integers */
      17      { 0x8000, 16 },
      18      { 0xa5a5, 1 },
      19      { 0x5a5a, 2 },
      20      { 0x0ca0, 6 },
      21  #endif
      22  #if __INT_MAX__ < 32767
      23  #error integers are too small
      24  #endif
      25    };
      26  
      27  #define NFFSTESTS (sizeof (ffstesttab) / sizeof (ffstesttab[0]))
      28  
      29  extern void abort (void);
      30  extern void exit (int);
      31  
      32  int
      33  main (void)
      34  {
      35    int i;
      36  
      37    for (i = 0; i < NFFSTESTS; i++)
      38      {
      39        if (__builtin_ffs (ffstesttab[i].input) != ffstesttab[i].output)
      40  	abort ();
      41      }
      42  
      43    exit (0);
      44  }