互斥锁自动解锁

以下是一个防止互斥锁忘记解锁的类

class lock
{
public:
    lock(pthread_mutex_t *m) : mutex(m) {
        pthread_mutex_lock(mutex);
    }
    ~lock() {
        pthread_mutex_unlock(mutex);
    }
private:
    lock(); // forbidden
    pthread_mutex_t *mutex;
}; // class lock