A copy constructor is the constructor called when an instance is copied.

A copy constructor is a constructor in which the first argument is a reference to an object that has the same type as the object to be initialized.


#include <cassert>

#include <cstdlib>



struct MyClass

{

  //MyClass construtor

  MyClass(const int x = 0) : m_x(x) {}

  //MyClass copy constructor

  MyClass(const MyClass& other) : m_x(other.m_x) {}

  //MyClass copy asignment constructor

  MyClass& operator=(const MyClass& rhs)

  {

    //Identity test, advised by Scott Meyers. Effective C++ (3rd edition). Item 11.

    if (this == &rhs) return *this;



    const_cast<int&>(m_x) = rhs.m_x;

    return *this;

  }

  //MyClass data member

  const int m_x;

};



int main()

{

  const int x = std::rand();

  MyClass a(x) ;     //Call of constructor

  MyClass b(a) ;     //Call of copy constructor

  MyClass c = b;     //Converted to call of copy constructor

  MyClass d = c = b; //Call of copy assignment operator

  assert(a.m_x == b.m_x);

  assert(a.m_x == c.m_x);

  assert(a.m_x == d.m_x);

}

References

Joint Strike Fighter Air Vehicle C++ Coding Standards for the System Development and Demonstration Program. Document Number 2RDU00001 Rev C. December 2005. 4.3.11: 'A copy constructor is a constructor in which the first argument is a reference to an object that has the same type as the object to be initialized.'

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(C++) copy constructor

References