How does std::move determine which class members need to be transferred with ownership?

std::move itself does not determine which class members should be transferred with ownership. It is simply a cast to an rvalue reference, which allows the use of move semantics.

The actual move occurs in the move constructor or move assignment operator, which you need to implement in your class. In these methods, you explicitly specify which members should be "moved" (usually resources like pointers, buffers, etc.) and which should be copied or left unchanged.

Example:

class MyClass {
    std::string data;
public:
    MyClass(MyClass&& other) noexcept : data(std::move(other.data)) {
        // other.data is now in a valid but unspecified state
    }
};

Here, std::move inside the move constructor indicates that the data member should be moved, not copied. Thus, it is in the implementation of the move constructor that you decide which members to transfer with ownership.