实现了一个多线程安全的单例模式：

以下的单例模式，如果想要成为一个基础的基类，可以将private设为protect,将instance类型写成模版形式，那么想要实现新的单例，直接继承此单例模式就好了。

Singleton* Singleton::instance = NULL;pthread_mutex_t Singleton::mutex = PTHREAD_MUTEX_INITIALIZER;Singleton* Singleton::GetInstance() {    if(NULL == instance) {        pthread_mutex_lock(&mutex);        instance = new Singleton();        pthread_mutex_unlock(&mutex);    }    return instance;}class Singleton {    public:        static Singleton* GetInstance();        void PrintTest() {           printf("hello world\n");       }    private:         Singleton(){};            private:        class CGarbo {            public:                ~CGarbo() {                    if(NULL != Singleton::instance)                        delete Singleton::instance;                    pthread_mutex_destroy(&mutex);                }        };        static CGarbo Garbo;        static Singleton* instance ;        static pthread_mutex_t mutex;};