move constructor and copy constructor in C++

Question

My understanding is that a move constructor is called if it exists when we return a local object from a function. However, I ran into a situation where the copy constructor

Answer 1

The following code does not implicitly move the constructed object:

tNode foo2()
{
    std::unique_ptr up = std::make_unique(20);
    return *up;
}

This is because, however obvious/intuitive it might seem to us, the compiler cannot prove that it is safe to move-from the object contained by up. It's forced to return by copy.

You could force it to return by R-value by explicitly casting the object as such:

tNode foo2()
{
    std::unique_ptr up = std::make_unique(20);
    return std::move(*up);
}