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Copy constructor

wer (1)



Integer I1(I2); // copy constructor called

I1 = I2; // Values assigned member by member

why we have to use copy constructor? Instead of using second one.
Catfish3 (666)
Sometimes the copy constructor is automatically used.

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#include <iostream>

class Whine {
public:
    int i;

    Whine()
    {
        std::clog << this << " : Regular constructor\n";
    }

    Whine(const Whine &w)
    {
        std::clog << this << " : Copy constructor from " << &w << '\n';
    }

    Whine & operator = (const Whine &w)
    {
        std::clog << this << " : Copy assignment from " << &w << '\n';
        return *this;
    }

    ~Whine()
    {
        std::clog << this << " : Destructor\n";
    }

    // C++11 only:
    /*

    Whine(Whine &&w)
    {
        std::clog << this << " : Move constructor from " << &w << '\n';
    }

    Whine & operator = (Whine &&w)
    {
        std::clog << this << " : Move assignment from " << &w << '\n';
        return *this;
    }

    */
};

void function(Whine w)
{
    w.i = 0;
}

int main()
{
    Whine w;

    function(w);
}
 
0x22ff38 : Regular constructor
0x22ff3c : Copy constructor from 0x22ff38
0x22ff3c : Destructor
0x22ff38 : Destructor

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