This happens for `/0` subnet masks. In practice, it's not an issue because if `bytes` is 0, then so are `netbits`, `bits` and `mask`. So the two incorrectly addressed array elements are not actually modified. The first operation is a `&= 0xff` and the second a `|= 0`, so nothing changes. But some tools might not consider the values and report this as undefined behavior, which it technically is.