单件模式的析构,该如何解决

class CSingleton1{ 
private: 
    CSingleton1(){
        cout<<"CSingleton1 constructor"<<endl;
    } 
    CSingleton1& operator=(CSingleton1& o){} 
    CSingleton1& operator()(CSingleton1& o){} 
    
public: 
    virtual ~CSingleton1(){
        cout<<"CSingleton1 destructor"<<endl;
    } 
    static CSingleton1& getInstance() 
    { 
        static CSingleton1  instance; 
        return instance;     
    } 
}; 

int main()
{
    CSingleton1 a1 = CSingleton1::getInstance();
    CSingleton1 b1 = CSingleton1::getInstance();
}

class CSingleton2{ 
private: 
    CSingleton2()
         {
        cout<<"CSingleton2 constructor"<<endl;
    } 
    CSingleton2 & operator=(CSingleton2 & o){} 
    CSingleton2 & operator()(CSingleton2 & o){} 
    static  CSingleton2  *instance;
    
public: 
    virtual ~CSingleton2() 
    { 
        if(NULL!=instance) 
                  {
            cout<<"CSingleton2 destructor"<<endl;
            delete instance; 
            instance=NULL; 
                  } 
    } 
    static    CSingleton2& getInstance() 
    { 
        
                  if(NULL==instance) 
                  { 
            instance=new CSingleton2(); 
                  } 
        return *instance; 
    } 
};


int main()
{
    CSingleton2 a2 = CSingleton2::getInstance();
    CSingleton2 b2 = CSingleton2::getInstance();
    delete &a2;
}