My code needs to be compatible with a platform that doesn't have rvalue references available, for the time being. I've avoided explicit uses of move and made my && arguments fall back to const&. But I'm not sure about returning a unique_future. I see that unique_future<T> has a special move-the-guts type, with an implicit conversion operator and a constructor. But do I need to do anything special to declare a function returning one, and likewise the return statement itself? The code in packaged_task ( unique_future<R> packaged_task<R>::get_future() ) is not conditionally compiled based on BOOST_NO_RVALUE_REFERENCES, so I'm supposing that it just works by itself. Is that correct? But maybe it only works by itself in some cases? In that code, the return statement names a constructor directly. return unique_future<R>(task); In my code, I'm returning a unique_future that I already made somewhere else (actually, the result of another function call) so it would be wanting to call the copy constructor, I would think. So if I write unique_future<int> foo(); unique_future<int> bar() { return foo(); } what _should_ happen is that the existing value uses a user-defined conversion to construct the "copy", right? So I should expect this to work correctly if the thing I'm returning is already exactly the right type, as well as when naming the constructor directly. —John