Implementaion of ThreadSafe Singleton class in C++?

Can any one suggest how can we implement threadsafe singleton class, What are the createria' that needs to be satified ?

What if we inherit from such class, derived just get the singleton nature ?

 

The question is not entirely clear but if your intention is to protect access to a resource, e.g. a member variable, by mutliple threads, you could look at using the C++ Mutex class.

 

class Singleton {
    Singleton();
    ~Singleton();
    static Singleton *s_singleton;
    static void init();
  public:
    static Singleton& instance();
};
Singleton *Singleton::s_singleton = 0;
void Singleton::init() {
    static Singleton singleton;
    s_singleton = &singleton;
}
Singleton& Singleton::instance() {
    lock(&mutex);
    if (!s_singleton) {
        init();
    }
    unlock(&mutex);
    return *s_singleton;
}

Code (markup):

(From Dr. Dobb's article, but could not post the link)

I would also highly recommend taking a look at the boost library for a platform independent solution.

You don't want to write something Windows specific and then have to port it to Linux/Mac, etc.
(or vice versa)

Hope that helps.