[benj111]

Slightly off topic, but why did 1 become the truthy value and not -1?

Logical nots would then work.

And youre still an inc/Dec away from the opposite.

[never_inline]

That depends on

a) Two's complement representation

and

b) Wraparound on arithmetic, which is still UB in low-level languages.

[benj111]

Ok. I used -1 as a short hand for 0b11111111(11111111(1111111111111111(11111111111111111111111111111111))))

Not doesn't rely on wrap around arithmetic.

Wrap around arithmetic is only undefined for signed values.

What platform doesn't wrap around signed integers?

Just because c has some undefined behaviour, doesn't make it some natural law of the universe.