returning initializer list mechanism

Question

What mechanism is involved, if when returning types, that are constructible from initializer lists, I don\'t specify the type I am returning, as in:

std::arr         


        

Answer 1

There are no performance penalties involved. The return value is constructed equivalent to

std::array<int, 3> x = { 1, 2, 3 };

There is not even a single copy or move of an std::array instance involved.

Answer 2

The mechanism is just a constructor:

struct X {};

struct Y {
    Y(X);
};

Y f() {
    X x;
    return x;
}