> Undefined behavior is one of the most intelligent things the C designers did when designing the language.

I agree, actually. They just went too far. Too many things are undefined for no good reason. Even sqrt(-1) is debatable, by the way: if your platform provides an efficient way to trap, it should probably trap, and the compiler should not assume it will never happen.

And if you want crazy optimizations, consider introducing unsafe assertions into the language. That is, arbitrary boolean expressions the compiler is allowed to assume will always return true.