What does a compiler add to an empty class declaration?

问题

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?

回答1:

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.

回答2:

Your list is complete. This is all it is adding.

回答3:

The list is not completed............ In addition with the above mention FOUR properties , there is an address operator ( & ) overloaded method , that return the address of the invoking object , is also provided automatically by the compiler.

回答4:

There are five properties:

constructor

copy constructor

destructor

assignment operator

the reference operator(&) - the address

来源：https://stackoverflow.com/questions/2659895/what-does-a-compiler-add-to-an-empty-class-declaration