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

It's a fact of life that not all syntactic forms will have meaning. What's sqrt(-1)? Trick question, There's no meaningful answer (in terms of real numbers alone)! Why should anyone specify if it crashes the program, returns 0, throws an exception, etc.? Who cares? garbage in, garbage out.

Another example, "the floor had a pretty day with his melted spaceship" that is a grammatically well formed sentence but what does it mean? Don't answer that!