What's the difference between the Derived class override the base class's virtual function with or not with a "virtual" prefix?

Question

class A
{
    virtual void funcion()
    {
        //...
    }
}
class B:public A
{
     //1:virtual void function();
     //2:void function();
}

What's the differences between the 1 and 2 ? Or it is the same?

Answer 1

They're the same. A function declared virtual in the base class is virtual all through the inheritance chain.

I find it useful to add the virtual for clarity (more often than not, the classes aren't in the same file).

Answer 2

They're exactly the same. Once a function has been declared virtual in a base class, any class that inherits from it will also have that function declared virtual by default.