If that was true then the optimizers wouldn't need to exist in the first place.
Compared to the alternatives.
It gets very frustrating to communicate at this level.
I don't think compilers allowing trash through is a good thing.
That's an opinion, another one would be that the flexibility allowed by undefined behavior is one of C's strengths at the same time. Strength/weakness are often two sides of the same coin. Which is why these discussions get a bit circular.
Have you ever seen the error steamroller? https://github.com/mattdiamond/fuckitjs