3.1 No virtual constructor

As it turns out, a polymorphic class must have a non-virtual constructor, just like everyone else.

Why can’t a constructor be virtual?

Let us consider some of the syntax alternatives to construct an object. For our discussion, let us consider A to be a class, myA and myOtherA be variables of class A type, and pA be a pointer to a class A object.

• A myA; This constructor creates a class A object because the type A is compile-time determined. As a result, there is no benefit from making a constructor virtual.
• pA = new A; Even though the allocation of the new object is dynamic, the type is determined at compile time because of the mentioning of A.
• A myOtherA(myA); The constructor clones the variable myA as myOtherA. The type is determined by A at compile time.

Because whenever a constructor is used, the type must be explicitly stated, the constructor can always be determined at compile time. As a result, there is no benefit in making the constructor virtual.