It's the thing that gets normal C programmers the maddest about standards nerds, too; they really, really hate that signed overflow is undefined behavior because assuming it makes modern optimizers go berzerk and do horrific things to their code
(Another fun one vaguely in this range that came up on social media recently is that while integer division by zero is going to give you a numeric trap reliably, integer division by *negative one* can too because INT_MIN / -1 is out of range.)