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    <blockquote> <p>does std::is_move_constructible::value == true implies that T has a usable move constructor?</p> </blockquote> <p>No. It states that you can <a href="http://en.cppreference.com/w/cpp/concept/MoveConstructible" rel="noreferrer">take an rvalue expression of the object type and construct an object from it</a>. Whether this uses the move constructor or the copy constructor is not relevant to this trait.</p> <blockquote> <p>is f2 move constructed ?</p> </blockquote> <p>Yes.</p> <blockquote> <p>if so, shouldn't the rvalue be invalidated?</p> </blockquote> <p>No. That's not how movement works.</p> <blockquote> <p>how can I know if instances of a class can be properly move-constructed(invalidate the old one)?</p> </blockquote> <p>That is not any definition of "properly move-constructed" that exists. If you want to "invalidate the old one", then you will have to do that yourself.</p> <p>Move construction generally guarantees <em>nothing</em> about the state of the old object. It will be in a valid but undefined state. Such state very much can be "the same as it was before". Move construction for a pointer is the same as copying the pointer.</p> <p>If you want to "invalidate" after a move, then you need to write your own move constructor that explicitly does that.</p> <blockquote> <p>(I'm using VS11)</p> </blockquote> <p>Then you have no compiler-generated move constructors <em>at all</em>. Not that it would matter, since the move and copy constructors for pointers both do the same thing.</p>
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    1. POWhat is the behaviour of compiler generated move constructor?
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    1. USNicol Bolas
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    1. COhow can I know if T has a customed move constructor? will (!std::is_trivially_move_constructible<T>::value && std::is_move_constructible<T>::value) do the trick?
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    2. CO@Frahm: That won't work either, as an object that has a non-trivial copy constructor will also be non-trivially moveable. There is no trait to detect the explicit provision of a user-provided move constructor. Also, why would you ever *care*? User-provided or not, just *call it*.
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    3. COI want to write a class that specialized for a trait which indicates if T can be properly moved, if not, it will fall back to detor + copy ctor, while if T(hold resources) has a customed copy ctor, and a compiler-generated move ctor, then call to that method will not behave as expected.
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