#include <assert.h>
#include <limits.h>

/*
* Generate mask indicating rightmost 1 in x.
* For example 0xFF00 -> 0x0100, and 0x6600 --> 0x0200.
* If x == 0, then return 0.
*/
int rightmost_one(unsigned x) {
  return x & -x;
}

int main() {
  for (unsigned x = 0; ; x++) {
    assert((x == 0 && rightmost_one(x) == 0) || (x != 0 && rightmost_one(x) == (1 << __builtin_ctz(x))));

    if (x == UINT_MAX) {
      break;
    }
  }
}