EDIT: That said, I'm on the maintainer's side here.
Is it thought? Certainly it is according the C and C++ standards, but POSIX adds:
> References to unmapped addresses shall result in a SIGSEGV signal
While time-traveling-UB is a theoretical possibility, practically POSIX compliant compilers won't reorder around potentially trapping operations (they will do the reverse, they might remove a null check if made redundant by a prior potentially trapping dereference) .
A real concern is if a null pointer is dereferenced with a large attacker-controlled offset that can avoid the trap, but that's more of an issue of failing to bound check.
But to make optimizations pretending it is an invariant, it can't happen, when the specification clearly says it could happen. That's wild, and I would argue out of specification.
I think you may be misunderstand how optimization works. It's not "AHA! Undefined Behavior, I'll poke at that!".
It's more that compilers are allowed to assume that some things just "don't happen"... and can optimize based on that. And it does make sense... if you were told to optimize a thing given certain rules, how would you do it?
