There's still no time travel in any of those posts; some may require an explanation of "the compiler replaced the UB division with a call to 'bar'" or something

There's still no time travel in any of those posts; some may require an explanation of "the compiler replaced the UB division with a call to 'bar'" or something, but "calling 'bar'" is still a subset of the "anything" that UB can result in. If there's a specific example you think doesn't follow that, I'd appreciate a specific reference. (and singron's mention of SIGSEGV handling is entirely irrelevant; the C standard only cares about the abstract machine; in general real memory state can temporarily appear in arbitrarily weird states in practice if interrupted by a signal even without UB, e.g. https://godbolt.org/z/91ModhbEY https://godbolt.org/z/91ModhbEY will have all a[0..15] written even if there's a handled trap on the write to b[0] (or otherwise an interrupt between the two SIMD writes) (using restrict for simplicity, but taking an 'int n' argument and using that for the loop bound will result in ~the same thing without restrict, just with less direct assembly); the same applies even to Rust, though of course with Rust you shouldn't be able to have a situation where you trap on a safe write; could still have a random interrupt happen in the middle though)