條款7 為多态基類聲明virtual析構函數

如有以下關系,不使用virtual關系會出現資源洩漏

//base class

class TimeKeeper
{
    public:
        virtual TimeKeeper* getTimeKeeper()
        {
            return NULL;
        }
};

class AtomTimeKeeper: public TimeKeeper
{
    public:
         AtomTimeKeeper(){
           pData=new char[];
         }
        TimeKeeper* getTimeKeeper()
        {
            return myAtom;
        }
    private:
        int a;
        char * pData;
        static AtomTimeKeeper* myAtom;

};
AtomTimeKeeper* AtomTimeKeeper::myAtom = new AtomTimeKeeper();

int main()
{
    AtomTimeKeeper myAtom;
    TimeKeeper* pTime=myAtom. getTimeKeeper();
    delete pTime;//這将引起部分記憶體洩漏
   return ;
}