regarding copy constructor

[vishnu123]

why there is need of copy constructor..actually what was the problem before that raise to the solution like "copy constructors".

dont mind please explain me with some examples too ..

with regards,
vishnu k.

[MiiNiPaa]

why there is need of copy constructor

Because often, compiler generated one is not sufficient.

what was the problem before that raise to the solution like "copy constructors".

To create a copy of the object?

with some examples

struct foo
{
    foo(int i)
    {
        arr = new int[i];
    }
    int* arr;
};

int main()
{
    foo x(10); //Create foo object containing array of 10 ints
    x.arr[5] = 42; //Modify said array
    foo y = x; //Creating a copy of x. Using compiler generated CC which does only shallow copy
    y.arr[5] = 9000; //Modifying y array
    std::cout << x.arr[5]; //Woops. Totally unexpected. Why does it outputs 9000?
}

[vishnu123]

HI MiiNipaa,


can we overload the = operator to do the same functionality of copying objects instead of copy constructors.? if no,
why cant we do it?


thanx in advance.

[MiiNiPaa]

We need to have both copy constructor and assigment operator.
When object is initialized, only constructor can be called:
foo y = x; //calls copy constructor, not assigment operator  
This is because only constructors can initialize object.

Assigment operators work on already initialized objects.