When will a C++11 compiler make RVO and NRVO outperform move semantics and const reference binding?

Question

Consider the case when \"whole\" objects with move semantics enabled are returned from functions, as with std::basic_string<>:

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Answer 1

I'm not sure if this is standardized (as Nicol says, all optimizations are up to the compiler), but I heard STL talk about this and (at least in MSVC), RVO happens before anything else. So if there's a chance to apply RVO, then that'll happen without any action on your part. Second, when you return a temporary, you don't have to write std::move (I think this is actually in the standard), since the return value will implicitly be treated as an rvalue.

The upshot is: Don't second-guess the compiler, just write the most natural-looking code and it'll give you the best-possible result.