pointers c++

#include <iostream>

using namespace std;

class Car {
    public:
     virtual ~Car() { cout << "we delete Car"; };

    public:
        virtual double speed() { return 14; };
};


class Dacia : public Car {
    public:
        ~Dacia() { cout << "we delete Dacia"; };

    public:
        double speed() { return 15; };

};

class StackOverflowException : exception {
};

class StackUnderflowException : exception {
};

template <class T>
    struct StackBox{
        StackBox *mNextOnStack;
        T mValue;
    };

template <class T>
    class MyStack{
        public:
            MyStack(): mStackTop(NULL){};
        public:
            void push(T);
            T pop(void);

        private:
            StackBox<T> *mStackTop;
    };


template <class T>
void MyStack<T>::push(T value){
    StackBox<T> *sb = new StackBox<T>();
    if(sb == NULL)
        throw new StackOverflowException();

    sb->mValue = value;
    sb->mNextOnStack = mStackTop;
    mStackTop = sb;
}

template <class T>
T MyStack<T>::pop(){
    if(mStackTop!=NULL){
        T v = mStackTop->mValue;
        StackBox<T> *nos = mStackTop->mNextOnStack;
        delete mStackTop;
        mStackTop = nos;
        return v;
    }
    else {
        throw new StackUnderflowException();
    }
}

int main()
{
    cout<<"Hello World"<<" ";
    double a=45, b=78.67, c=90;
    MyStack<double> numere;

    numere.push(a);
    numere.push(b);
    numere.push(c);

    cout<<numere.pop()<<" ";
    cout<<numere.pop();

    Dacia *myDacia = new Dacia();

    Car *pMyCar;
    pMyCar = myDacia;


    cout << "speed " << pMyCar->speed();

    delete pMyCar;

    return 0;
}