Ejemplo

class Base {
public:
void fnc();
};

class Derived: public Base {
public:
void fnc(){}
};

int main(){
Derived d;

Base *basePtr = &d;
Derived *derivedPtr = &d;

basePtr->fnc();//calls Base::fnc()
derivedPtr->fnc();  //calls Derived::fnc()

return 0;
}

Solución
No altere temporalmente las funciones no virtuales. Cambie el diseño para no utilizar la clase  básica, o convierta la función de clase básica en virtual para garantizar un comportamiento polimórfico.


class Base {
public:
virtual void fnc();
};

class Derived: public Base {
public:
void fnc(){}
};

int main(){
Derived d;

Base *basePtr = &d;
Derived *derivedPtr = &d;

basePtr->fnc();//calls 
Derived::fnc()
derivedPtr->fnc();  //calls Derived::fnc()

return 0;
}