[fsckboy]

>The compiler leverages undefined behavior by allowing optimizations to not have to care about code that exhibits such undefined behavior.

that's pure maliciousness. if the programmer has written code that exhibits undefined behavior, it should be flagged as an error so it can be changed to code that does not exhibit undefined behavior.

programs need to have one unambiguous meaning, and it should be the meaning intended by the programmer. if meanings can be detected as ambiguous or as not what the programmer intended, that should be flagged, not magically swept under the carpet because it's "faster".

[anyfoo]

The compiler generally cannot know when the program runs into undefined behavior, because of the halting problem. For detecting undefined behavior at runtime, there’s UBSan. It’s good, but it makes things slower.

[fsckboy]

or to put it another way, divide by zero is undefined behavior. do you think it should be trapped? or just optimized away so the program can get more quickly back to defined behavior...

[anyfoo]

Nobody declared divide by zero as undefined behavior for any optimization benefit.