c++ - Isn't return value optimization (RVO) a bug?

Question

I maybe asking a dumb question, but I looked at the wikipedia page for RVO here and could not stop wondering if that behavior is wrong. I tried it in my machine and RVO is fully kicked in despite optimization level. What if there was actually something BIG happenning in a constructor? I know it shouldn't, but what if? I can't understand why RVO would still happen when there are side effects in the constructor.

EDIT: -fno-elide-constructors seems to stop RVO. But the question remains.

EDIT2: On a more serious note, how many people know about something like this? It maybe in the standard, but it is still a really ugly feature as I see it. At least compilers should disable it by default and provide a switch for people who know about this. :)

EDIT 3: I still insist that this is really bad. :). I don't think I know of any other language constraint like this that goes directly against the syntax of language. Everything else throws either compiler or linker errors right?

Answer 1

The standard mandates that operations with concern a program's observable state must not be optimized away, except for copy construction in certain circumstances. You must not rely on copy constructors to be executed, even if they have side effects you expect to see (e.g., console output).