check_integer(leftmost_bit(0), -1);
check_integer(leftmost_bit(0x80000000), 31);
check_integer(leftmost_bit(0xffffffff), 31);
check_integer(leftmost_bit(0), -1);
check_integer(leftmost_bit(0x80000000), 31);
check_integer(leftmost_bit(0xffffffff), 31);