I know now that Shared_ptr is thread-safe enougth for my needs and often the best solution but sometimes one wants a more lightweight alternative and I've been using Intrusive_ptr. To make it easier to use I've stolen this class from Beyond the C++ Standard Library by B. Karlsson, If a class inherits it publicly it becomes "intrusive enabled".

class IntrusiveCount { // base class to enable derived class for use with the Boost intrusive smart pointer
public:
   virtual ~IntrusiveCount(){}
   friend void intrusive_ptr_add_ref(IntrusiveCount* p) {
      ++p->ref_count;
   }
   friend void intrusive_ptr_release(IntrusiveCount* p) {
      if (--p->ref_count == 0) delete p;
   }
protected:
   IntrusiveCount() : ref_count(0) {}
   IntrusiveCount& operator=(const IntrusiveCount&) {
      return *this;
   }
private:
   IntrusiveCount(const IntrusiveCount&);
   short ref_count;
};

The problem with the above class is that its not thread-safe so I've tried to modified it using TBB. I would appreciate if someone could have a look at it and tell me if there's something wrong with my approach.

class IntrusiveCount { // thread-safe base class to enable derived class for use with the Boost intrusive smart pointer
public:
   virtual ~IntrusiveCount(){}
   friend void intrusive_ptr_add_ref(IntrusiveCount* p) {
      p->ref_count.fetch_and_add(1); // increment counter atomically
   }
   friend void intrusive_ptr_release(IntrusiveCount* p) {
      if (p->ref_count.fetch_and_add(-1) == 1) delete p; // decrement counter. If it was 1 before it's 0 now so delete
   }
protected:
   IntrusiveCount() {ref_count=0;}
   IntrusiveCount& operator=(const IntrusiveCount&) {
      return *this;
   }
private:
   IntrusiveCount(const IntrusiveCount&);
   tbb::atomic<int> ref_count;
};
 
I had to change the counter to an int (from short) otherwise I get this level 2 warning on VS2008 standard,
 
C:UsersadminDocumentsMint	bbsrcinclude	bbatomic.h(157) : warning C4244: 'argument' : 
conversion from 'tbb::internal::atomic_traits<Size,M>::word' to 'short', possible loss of data