That's not a hard question. If your code only works without certain optimizations, it's either not valid (as in, standards-compliant) C++ or you've found a comp

That's not a hard question. If your code only works without certain optimizations, it's either not valid (as in, standards-compliant) C++ or you've found a compiler bug. That doesn't necessarily make it bad - you may have a good reason to write non-portable code for a specific platform and a specific compiler, but it's not conformant to the language standard.