Is it possible to std::move objects out of functions? (C++11)

Question

This program tries to move a string out of a function and use it for the construction of another string:

#include 
#include 
#i         


        

Answer 1

That Get_String function binds an rvalue reference to a function-local object. Rvalue references are useful for things that are about to be destroyed, but just as bad as lvalue references for things that have already been destroyed.

To move a local object out of a function, you just return by class type:

std::string Get_String(void) {
    std::string str{"hello world"};
    return str;
}

If the compiler doesn't manage to eliminate the copy/move entirely, then the return value that the caller gets will be constructed using a move constructor, not a copy constructor, as long as the return expression is:

• a temporary, or
• a single identifier naming something with automatic storage duration (like str above), or
• std::move(something)

(So you could still have return std::move(str); to be explicit, but it's not necessary here.)