template<class T>
class Singleton {
   private:
      static T* m_instance;
      
      Singleton() { }
      ~Singleton() { }
  public:
      static T* Instance() {
         if(m_instance == NULL)
            m_instance = new T();
         return m_instance;
};

template<class T> T *Singleton::m_instance = NULL;

class A : public Singleton<A> {
};