三種常見的線程安全單例模式

//懶漢式 1  
class CSingleton    
{    
private:    
//構造 拷貝 賦值均是私有或關閉   
    CSingleton();    
    static pthread_t mutex_;     
public:    
    CSingleton(const Singleton&)=delete;  
    CSingleton& operator=(const Singleton&)=delete;  
    static Singleton *Getinstance()  
    {    
        if(m_Instance == NULL)    
        {   //double check    
            pthread_mutex_lock(mutex_);           //用lock實現線程安全   
            if(m_Instance == NULL)    
            {    
                m_Instance = new Singleton();    
            }   
            pthread_mutex_unlock(mutex_)   
        }    
        return m_Instance;    
    }  
    static Singleton *m_Instance;    
    
};    
Singleton* CSingleton::m_Instance = 0;    
  
  
//懶漢式 2  
class CSingleton  
{  
private:  
    CSingleton();  
public:  
    CSingleton(const Singleton&)=delete;  
    CSingleton& operator=(const Singleton&)=delete;  
      
    static Singleton* get_instance(){  
        static Singleton* m_instance = new Singleton();  
        return instance;  
    }  
  
};  
  
//餓漢式  
class CSingleton {  
private:  
    CSingleton();  
public:  
    CSingleton(const Singleton&)=delete;  
    CSingleton& operator=(const Singleton&)=delete;  
    static Singleton* m_instance = new Singleton();  
      
    Singleton* getInstance()   
    {  
        return m_instance;  
    }  
}