1  extern void abort(void);
       2  extern void exit(int);
       3  
       4  void
       5  foo (char *bp, unsigned n)
       6  {
       7    register char c;
       8    register char *ep = bp + n;
       9    register char *sp;
      10  
      11    while (bp < ep)
      12      {
      13        sp = bp + 3;
      14        c = *sp;
      15        *sp = *bp;
      16        *bp++ = c;
      17        sp = bp + 1;
      18        c = *sp;
      19        *sp = *bp;
      20        *bp++ = c;
      21        bp += 2;
      22      }
      23  }
      24  
      25  int main(void)
      26  {
      27    int one = 1;
      28  
      29    if (sizeof(int) != 4 * sizeof(char))
      30      exit(0);
      31  
      32    foo((char *)&one, sizeof(one));
      33    foo((char *)&one, sizeof(one));
      34  
      35    if (one != 1)
      36      abort();
      37  
      38    exit(0);
      39  }