Why program is crashing for this code?

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C++

class A
{
    int m_aptr;
public:
    A(int p):m_aptr(p){}  //constructoe
    void setvalue(int v){m_aptr=v;}
    int getvalue(){return m_aptr;}
    A( const A  &a)  //copy constructor
    {
        *this=a;
        //m_aptr=a.m_aptr;
    }
    A operator=(const  A &a) //overloading '=' operator
    {
        m_aptr=a.m_aptr;
        return *this;
    }
};




int main()
{
    A a1(10);
    A a2(a1);
    cout <<"a2= "<<a2.getvalue()<<", a1= "<<a1.getvalue();

}

Posted 3-Sep-15 0:43am

the_beginner

Updated 3-Sep-15 0:53am

Afzaal Ahmad Zeeshan

v2

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Afzaal Ahmad Zeeshan 3-Sep-15 6:54am

Error?

the_beginner 3-Sep-15 6:57am

No error , it just show stop working, also problem is due to
*this=a in copy-constructor, if I replace that line with line under it (which is commented out), program runs successfully

1 solution

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Jochen Arndt · Accepted Answer · 2015-09-03T02:08:00

Solution 1

The assignment operator must return a reference. So it must be:

A& operator=(const A &a) //overloading '=' operator
{
    m_aptr=a.m_aptr;
    return *this;
}

Posted 3-Sep-15 2:08am

Jochen Arndt

Comments

the_beginner 3-Sep-15 8:56am

thanks it worked, but i am not using '=' in main code than how its affecting, also if same code is ran with

A( const A &a) //copy constructor
{
m_aptr=a.m_aptr;
}

it wrks fine how? , it would be great if u can answer.

Jochen Arndt 3-Sep-15 9:06am

You use the copy constructor in your main code here:
A a2(a1);
And the copy constructor uses the assignment operator here:
*this = a;

Only if you replace the above by copying the member varaiable, the assignment operator is not used.

Sergey Alexandrovich Kryukov 3-Sep-15 9:31am

5ed.
—SA