put disabled copy constructor in private

Question

To disable copy constructor and assignment operator, it is clear that we could do either, since c++11:

class A {
 public:
  A(const A&) = delete;
  A& operator=(const A&) = delete;
} 

or for c++03:

class A {
 private:
  A(const A&);
  A& operator=(const A&);
}

however, what happens with this:

class A {
 private:
  A(const A&) = delete;
  A& operator=(const A&) = delete;
}

i guess this also leads to the same result. Is there any side effect?

Answer 1

It doesn't matter what access you give a deleted function - it simply doesn't exist(¹), so it is inaccessible whatever the caller.

The error messages may be slightly more confusing. See for example http:://cpp.sh/9hv7y where the first error is about "private" rather than "deleted".

---

¹ "it doesn't exist" is a simplification. It exists in the sense that it participates in overload resolution, but it is an error if it is the selected function. Thus

struct only_double {
    only_double(intmax_t) = delete;
    only_double(double arg);
};
only_double zero(0); // Error - deleted constructor called