Update: I don't think the fact that this class could be misused with Multiple Inheritance is reason enough. Any class which derives from multiple base classes with their own reference count would have the same issue. Whether these refcounts are implemented via a base class or not makes no difference.
I don't think there's any issue with multithreading;
Boost provides a facility for that. It can be configured for either thread-safe or thread-unsafe refcounting:
#include <boost/intrusive_ptr.hpp> #include <boost/smart_ptr/intrusive_ref_counter.hpp> class CMyClass : public boost::intrusive_ref_counter< CMyClass, boost::thread_unsafe_counter> ... boost::intrusive_ptr<CMyClass> myPtr;