What happens if you move an object without move constructor?

Question

What happens if std::move() is called on a user defined object, that defines no move constructor? Is it simply copied?

You mean with a deleted move constructor? Because if you don't define a move constructor yourself, and all of the objects members have a move constructor, a trivial move constructor is generated. — Cubic
– Cubic, Commented Dec 10, 2013 at 22:04
Note that std::move by itself does nothing to an object. So the answer depends on the context. For example, the moved from object could be used for a move assignment. Or something entirely different. So it is not totally dependent on the type being move constructible — juanchopanza
– juanchopanza, Commented Dec 10, 2013 at 22:04
std::move does not move, and std::forward does not forward. — Yakk - Adam Nevraumont
– Yakk - Adam Nevraumont, Commented Dec 10, 2013 at 22:08

user2428400 · Accepted Answer · 2013-12-10 22:02:22Z

5

Yes, move will fall back to copy. This is how standard containers like std::vector can implement resizing in terms of move, but remain compatible with classes which can only be copied.

However, the class may have an implicitly defined move constructor - see this guidance. http://en.cppreference.com/w/cpp/language/move_constructor#Implicitly-declared_move_constructor

answered Dec 10, 2013 at 22:02

user2428400

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