It doesn't make sense to define what happens when you e.g. read from NULL because it's hardware specific - if you have virtual memory of some sort, you'd probably get a page mapping error. If you don't (embedded, WASM), you'd read back whatever value is at that address.
Does Rust define what I get when I dereference NULL in unsafe code? I doubt it, since it would require a NULL check before every pointer dereference.
The only insane thing about UB is that compiler writers took what everyone understand meant "the compiler emits what it emits and you get what you get" and turned it into "since it's undefined it means it can never happen so we can delete your null check".
Does Rust define what I get when I dereference NULL in unsafe code? I doubt it, since it would require a NULL check before every pointer dereference.
The only insane thing about UB is that compiler writers took what everyone understand meant "the compiler emits what it emits and you get what you get" and turned it into "since it's undefined it means it can never happen so we can delete your null check".