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

/* Return 1 when x contains an odd number of 1s; 0 otherwise.
   Assume w=32 */
int odd_ones(unsigned x) {
  x ^= x >> 16;
  x ^= x >> 8;
  x ^= x >> 4;
  x ^= x >> 2;
  x ^= x >> 1;
  return x & 1;
}

int main() {
  for (unsigned x = 0; ; x++) {
    assert(odd_ones(x) == __builtin_parity(x));

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