C++ Inheritance: Derived class pointer to a Base class invokes Derived class method

Question

I am learning C++ inheritance, so I tried this code by creating a Base class dynamically and made a downcast to its Derived class (obviously its not valid to downcast) in order

Answer 1

What you are seeing is Undefined Behavior at work.

Your functions are non-virtual, they are simply member functions of the type you've told the compiler the pointer points to.

child *c = (child*)new parent;

This is a c-style cast that strong-arms the compiler into the belief that the pointer c definitely points to something that is a child.

Thus, when you call c->who(), you are specifically calling child::who, because the pointer is a pointer-to-child.

The reason nothing terrible happens and you see "I am child" is because you don't try to dereference that pointer or make use of any of the child-specific fields that your pointed-to-instance doesn't actually have. So you get away with it.