[boost] Re: intrusive_ptr: proposal for common base class

26 Jun 2004


      Stefan Slapeta wrote:
...
class intrusive_ptr_base
{
    friend void intrusive_ptr_add_ref(intrusive_ptr_base*);
    friend void intrusive_ptr_release(intrusive_ptr_base*);
int ref_count__;
protected:
    intrusive_ptr_base() : ref_count__(0) {}
virtual ~intrusive_ptr_base() {}
I don't necessarily think this is a good idea, but I will only comment
on the code. You can use CRTP here instead, to avoid the virtual
destructor. Something like:

   template<class Derived>
   class intrusive_ptr_base
   {
       friend void intrusive_ptr_add_ref(intrusive_ptr_base* o)
       {
           ++o->ref_count__;
       }

       friend void intrusive_ptr_release(intrusive_ptr_base* o)
       {
           if (--o->ref_count__ == 0) {
               delete static_cast<Derived*>(o);
           }
       }

       int ref_count__;

   protected:
       intrusive_ptr_base() : ref_count__(0) {}
   };

-- 
Daniel Wallin