Once in a while C++ code will not work when compiled with some level of optimization. It may be compiler doing optimization that breaks the code or it may be code containing undefined behavior which allows the compiler to do whatever it feels.
Suppose I have some piece of code that breaks when compiled with higher optimizations level only. How do i know if it's the code or the compiler and what do I do if it's the compiler?
Best Answer
I would say it is a safe bet that, in the vast majority of the cases, it is your code, not the compiler, that is broken. And even in the extraordinary case when it is the compiler, you are probably using some obscure language feature in an unusual way, for which the specific compiler is not prepared; in other words, you could most likely change your code to be more idiomatic and avoid the weak spot of the compiler.
At any rate, if you can prove that you found a compiler bug (based on the language spec), report it the compiler developers, so that they may get it fixed some time.