long f (long x) { return x / (-0x7fffffffL - 1L); } long r (long x) { return x % (-0x7fffffffL - 1L); } /* Since we have a negative divisor, this equation must hold for the results of / and %; no specific results are guaranteed. */ long std_eqn (long num, long denom, long quot, long rem) { /* For completeness, a check for "ABS (rem) < ABS (denom)" belongs here, but causes trouble on 32-bit machines and isn't worthwhile. */ return quot * (-0x7fffffffL - 1L) + rem == num; } long nums[] = { -1L, 0x7fffffffL, -0x7fffffffL - 1L }; main () { int i; for (i = 0; i < sizeof (nums) / sizeof (nums[0]); i++) if (std_eqn (nums[i], -0x7fffffffL - 1L, f (nums[i]), r (nums[i])) == 0) abort (); exit (0); }