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A* a =new A();//default constructor
foo(*a); //copy constr
A b=*a; //copy constr
b=*a; //assignment constr

My answer is 2. But I have tested it, the actual number should be 3. I understand it called copy ctor for foo(*a) and A b=*a;
But why does it call copy ctor after assignment operator of b=*a; Can some one explain plz?

You are right. It's two.

b=*a should be assignment operator.

Not sure how you thought it could be 3?

foo(*a);
calling this function causes actual argument *a assigned to formal argument of foo().
2 you got + this =3

Because you are returning by value in assignment operator tahn by reference

Ur assignment operator shud be like this

A& A::operator =(const A &a){
i=a.i;
cout<<"Assignment Operator"<<endl;
return *this;
}

The code should only call 2 copy ctors once ur assignment operator is fixed

Always a temporary object is created when not returned by reference then later it is copied to caller object using copy constructor.

so the final output should be 2.

So the answer is: It depends on the implementation of the copy constructor. Copy Constructor is definitely called twice, for lines 2 (when foo is called) and 3, but a poorly implemented assignment operator might call the copy constructor when when returning or being called.

Sorry, I meant ". . . on the implementation Assignment Operator . . ."

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