Question

How can the compiler determine if a constructor is a copy constructor?

Answer 1

Answer)

Whenever you initialize an object, C++ will make the copy by invoking the class's copy constructor, a constructor that accepts another object of the same type as a parameter.

Copy constructors in the compiler are invoked whenever:

1. A newly-created object is initialized to the value of an existing object.

Example :-

MyClass1 apple;

MyClass1 orange = apple;

MyClass1 banana = orange;

Here, since orange and banana are being initialized to the values of apple and orange, respectively, C++ will invoke the copy constructors to initialize their values. Although it looks like you're assigning values to two and three using the = operator, since they're newly-created objects, the = indicates initialization, not assignment.

In fact, the above code is equivalent to the more explicit initialization code below:

MyClass1 apple;

MyClass1 orange(apple); // Equivalent to the above code.

MyClass1 banana(orange); // Same here

2. An object is passed to a function as a non-reference parameter.

consider the following function:

void myFunction1 (MyClass1 parameter1)

{ // ... Work with parameter1 ... }

If we write MyClass1 ob1;

myFunction1(ob1);

Then the variable parameter1 inside of myFunction1 will be initialized to a copy of ob1 using the copy constructor.

3. An object is returned from a function.

MyClass1 myFunction1()

{

MyClass1 ob1;

return ob1;

}

If we call myFunction1, then C++ will create a new myClass1 object that's initialized to ob1 when myFunction1 returns. Thus while your code might act like it's transparently moving the object from inside of myFunction1 to the rest of your code, it's actually making a temporary copy.