what happens to std::vector storage after std::move()

Question

I am calling std::vector.reserve() then I call std::move() on that vector object. Do I need to allocate space again? Does move changes the capacity of the vector?

`std::move` is just a cast. It does nothing to the object. It onky changes the type of the reference. You are interested in the subsequent move constructor/move assignment. — n. m. could be an AI, Nov 20 '18 at 17:46
The content of a vector which was the source of a move assignment or moved copy constructor can be guessed from the [allocator requirements](http://eel.is/c++draft/allocator.requirements). All implementation do their best to avoid unnecessary memory allocation, so in practice, if the allocator allowes it, the moved from object has a null capacity. — Oliv, Nov 20 '18 at 19:38

score 2 · Accepted Answer · answered Nov 20 '18 at 17:47

2

The move constructor for vector[6] only guarantees that other.empty() == true (other being the moved-from object) after the move happens, it doesn't guarantee anything about the capacity() of the moved-from vector. So you can't be sure if it does or doesn't change the capacity.

So, to answer your question:

Does move changes the capacity of the vector?

This is unspecified.

answered Nov 20 '18 at 17:47

Hatted Rooster

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not specified, though would be rather strange if a vector does not steal the actual memory when move constructed or if the moved from would allocate new memory – 463035818_is_not_an_ai Nov 20 '18 at 17:50
@user463035818 Well that's true but can't make guarantees on it ^^ – Hatted Rooster Nov 20 '18 at 17:52

what happens to std::vector storage after std::move()

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