Comment by TuxSH

So do signed types (guaranteed to be 2's complement since C23, though all sane targets have been using that representation for a long time).

Two's complement encodes -x as ~x + 1 = 2^n - x = -x (mod 2^n) and can therefore be mixed with unsigned for (+, -, *, &, |, ^, ~, <<).

> I think they should be used exclusively when this is needed

The opposite: signed type usage should be kept to a minimum because signed type (and pointer) overflow is UB and will get optimized as such.