extern void abort(void);extern void exit(int);voidfoo (char *bp, unsigned n){  register char c;  register char *ep = bp + n;  register char *sp;  while (bp < ep)    {      sp = bp + 3;      c = *sp;      *sp = *bp;      *bp++ = c;      sp = bp + 1;      c = *sp;      *sp = *bp;      *bp++ = c;      bp += 2;    }}int main(void){  int one = 1;  if (sizeof(int) != 4 * sizeof(char))    exit(0);  foo((char *)&one, sizeof(one));  foo((char *)&one, sizeof(one));  if (one != 1)    abort();  exit(0);}