Is incrementing a null pointer well-defined?

Question

There are lots of examples of undefined/unspecified behavior when doing pointer arithmetics - pointers have to point inside the same array (or one past the end), or inside t

Answer 1

It turns out it's actually undefined. There are systems for which this is true

int *p = NULL;
if (*(int *)&p == 0xFFFF)

Therefore, ++p would trip the undefined overflow rule (turns out that sizeof(int *) == 2)). Pointers aren't guaranteed to be unsigned integers so the unsigned wrap rule doesn't apply.