class CSingleton{

public:
    static CSingleton* GetInstance(){
        if(m_pInstance==NULL){              //m_pInstance==nullptr
            m_pInstance=new CSingleton();
        }
        return m_pInstance;
    }

private:
    CSingleton(){}
    ~CSingleton(){
        if(Singleton::local_instance!=nullptr){
            delete Singleton::local_instance;
        }
    }
    static CSingleton* m_pInstance;

};

CSingleton* CSingleton::m_pInstance=NULL;


//或者
class CSingleton{

public:
    static CSingleton* GetInstance(){
        return m_pInstance;
    }

private:
    CSingleton(){}
    ~CSingleton(){
        if(Singleton::local_instance!=nullptr){
            delete Singleton::local_instance;
        }
    }
    static CSingleton* m_pInstance;

};

 CSingleton* CSingleton::m_pInstance=new CSingleton();;

//调用
CSingleton* p1=CSingleton::GetInstance();
CSingleton* p2=CSingleton::GetInstance();
//p1和p2地址一样

class Singleton{

private:
    static Singleton* local_instance;

    Singleton(){}
    ~Singleton(){}

public:
    static Singleton* getInstance(){
        static Singleton local;
        return &local;
    }

        //或者
        static Singleton& getInstance(){
                static Singleton local;
                return local;
        }

};

//调用
Singleton* p1=Singleton::getInstance();
Singleton* p2=Singleton::getInstance();
//p1和p2地址一样