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c++classconstructorclass-design

What does a compiler add to an empty class declaration?

Suppose, I write

class A { };

The compiler should provide (as and when needed)

  1. a constructor
  2. a destructor
  3. a copy constructor
  4. = operator

Is this all the compiler provides? Are there any additions or deletions to this list?

Solution

  • It's complete. But there are two points you should note:

    1. It's the copy =operator. Just like there is a copy constructor, there is a copy assignment operator.
    2. They are only provided if actually used.

    Some explanation for 2:

    struct A { private: A(); };
struct B : A { };

    That's fine! Providing a default constructor would be ill-formed for "B", because it would not be able to call the base-class' constructor. But the default constructor (and the other special functions) is only provided (we say it's implicitly defined) if it's actually needed.