亚星游戏官网-yaxin222

周四去某企业面试，被问道C++的单例模式的实现，现场手写，我写了一个返回函数局部静态对象的例程， 然后就被鄙视了。。。 然后回家google，原来那种写法不是线程安全的，重新写了一遍，求拍砖。 C/C++ code class CSingeton { private: class CAssist { public: CAssist(void) { m_lock = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER; if (NULL == mp_inst) { pthread_mutex_lock(&m_lock); if (NULL == mp_inst) { mp_inst = new CSingeton(); } pthread_mutex_unlock(&m_lock); } } ~CAssist(void) { if (NULL != mp_inst) { delete mp_inst; mp_inst = NULL; } } CSingeton *mp_inst; pthread_mutex_t m_lock; }; public: static CSingeton &GetInst(void) { static CAssist sm_assist; return *sm_assist.mp_inst; } void PrintX(void) const { cout << m_x << endl; } private: CSingeton(void) : m_x(33) { cout << "singleton constructed" << endl; } ~CSingeton(void) { cout << "singleton destructed" << endl; } CSingeton(CSingeton const &r); CSingeton &operator =(CSingeton const &r); int m_x; };