I think the general problem is that if so much is going to hinge on this, it should be much easier to tell whether or not you know what you're doing. Undefined

I think the general problem is that if so much is going to hinge on this, it should be much easier to tell whether or not you know what you're doing. Undefined behavior really wouldn't be a problem if you could spot it reliably (possibly using tools, like the compiler toolchain itself). This loose mapping between four optimization levels and a variety of obscure language situations is invisible and situated only in a handful of top engineers' memories. That's not a great way to run a language if you actually care about the correctness of programs written in that language.