How can a unique_ptr be returned by value without std::move? [duplicate]

Answer 1

Because return of certain expressions, such as local automatic variables, are explicitly defined to return a moved object, if the moving operator is available.

So:

return p;

is more or less similar to:

return std::move(p);

But note that this will not work for example with a global variable.

std::unique_ptr g(new int(3));
std::unique_ptr ptr() {
    return g;  //  error!!!
}