-

#include <stdio.h>
#include <stdlib.h>

int main(int argc, const char *argv[])
{
    int i = atoi(argv[1]);
    int idx;

    for (idx = __builtin_ffs(i) - 1;
         idx >= 0;
         i ^= (1U << idx), idx = __builtin_ffs(i) - 1) {
        printf("bit %d\n", idx);
    }

    return 0;
}