How to use both default and custom copy constructor in C++?

Question

I have a long class with a lot of data members. I want to write a copy constructor for it. But, if I write my own copy constructor, I lose access to the default copy constructor.

I just want to repair a few pointers in my own copy constructor. So I want to have a shallow copy of the object which can be done by the default copy constructor.

Is there a possibility to access the default copy constructor when I have my own copy constructor?

Answer 1

Wrap the things you don't want to change in a struct, and derive (privately) from it. In your copy constructor, simply invoke the copy constructor of your base class.

Answer 2

No you cannot have both default and your own copy c-tor.

But there are two workarounds with this problem:

---

1 Enclose your pointers in some class with defined copy semantics

Example:

class A {
public:
private:
   int trivial1;
   int trivial2;
   ...
   SomePointer  nontrivialMember;
};

class SomePointer {
public:
  SomePointer(const SomePointer&); // here the non trivial part of A copy semantics
  int* nonTrivialMember;
};

---

2 Enclose the trivial parameters in some trivial structure

Example:

class A {
public:
   A(const A& o) : data(o.data) {
     // non trivial part
   }
private:
   struct Data {
     int trivial1;
     int trivial2;
     ...
   } data;
   int* nontrivialMember;
};

---

I would always select the first solution.

[UPDATE]

There is also 3rd solution, very similar to my second, enclose your trivial part in privately inherited base class. I'd still prefer the 1st solution.