[souprock]

Uh, so what?

Letting the compiler assume that a "switch" without a default will never go there is a great optimization too. Why not put that in the standard?

Actually, this is worse. Letting the loop be UB is like letting a true "if" be UB. Just never mind the code actually written; surely it doesn't mean what it says.

[gpderetta]

> Letting the compiler assume that a "switch" without a default will never go there is a great optimization too. Why not put that in the standard?

that's actually the case already. A missing default is UB if the switch condition does not match any of the cases. And C compilers already optimize accordingly.