What happens to unique_ptr after std::move()?

Question

This code is what I want to do:

Tony& Movie::addTony()
{
    Tony *newTony = new Tony;
    std::unique_ptr tony(newTony);
    attachActor(std::m         


        

Answer 1

No, you cannot do that instead. Moving the unique_ptr nulls it. If it didn't, then it would not be unique. I am of course assuming that attachActor doesn't do something silly like this:

attachActor(std::unique_ptr&&) {
    // take the unique_ptr by r-value reference,
    // and then don't move from it, leaving the
    // original intact
}

Section 20.8.1 paragraph 4.

Additionally, u (the unique_ptr object) can, upon request, transfer ownership to another unique pointer u2. Upon completion of such a transfer, the following postconditions hold:
   -- u2.p is equal to the pre-transfer u.p,
   -- u.p is equal to nullptr, and
   -- if the pre-transfer u.d maintained state, such state has been transferred to u2.d.