are copy and move constructors automatic friends?

Question

We can access private variables of another class when we define copy or move constructors. Does C++ make them friend to each other automatically?

For example:

my_str::my_str(my_str&& m) 
{
    size_ = m.size_; //accessing private variable another my_str class
    buff_ = m.buff_; //accessing private variable another my_str class
    m.buff_ = nullptr;
    m.size_ = 0;
}

Answer 1

It is not considered friend, but yes, any member function of class my_str can access private members of all instances of type my_str, not just the this instance:

class my_str {
    void foo(my_str& other) {
        // can access private members of both this-> and other.
    }

    static void bar(my_str& other) {
        // can access private members of other.
    }
};

The general idea behind it is to allow 2 or more objects of the same type to interact without having to expose their private members.