#include <iostream>

class NotVirtual {
};

class Virtual {
  public:
    virtual void foo() {
    }
};

template <typename VBase>
class Base : private VBase {
  public:
    // the virtuality of foo() depends on its declaration
    // (if any) in the base class VBase
    void foo() {
       std::cout << "Base::foo()" << '\n';
    }
};

template <typename V>
class Derived : public Base<V> {
  public:
    void foo() {
       std::cout << "Derived::foo()" << '\n';
    }
};

int main()
{
    Base<NotVirtual>* p1 = new Derived<NotVirtual>;
    p1->foo();  // calls Base::foo()

    Base<Virtual>* p2 = new Derived<Virtual>;
    p2->foo();  // calls Derived::foo()
}