[boost] Re: Smart Pointers - (many) thanks and (some)questions

From: Dave Abrahams (abrahams_at_[hidden])
Date: 1999-12-30 19:41:41

> I am thinking that some details of the shared_ptr implementation,
> such as the deallocation function, should be abstracted into a
> class with virtual functions, an instance of which can be passed
> into the shared_ptr constructor, and the rest handled either by
> derivation from shared_ptr (for adding or hiding operations) or
> conditional compilation (for thread safety on various systems).

Oh, I have always assumed something more like this:

namespace boost {

template<class T> struct deallocator
{
};

template<class T> class deallocator<T*>
{
    void deallocate()(T p) { delete p; }
};

}

The user then specializes boost::deallocator<T> for her own type when it
needs special treatment (yes, this means you need to wrap ints and other
basic types in a struct unless you'll have only one way to deallocate ints.
so what?)

Then you get fancy with the empty base optimization to store a deallocator
object somewhere in the smart pointer. This avoids all virtual function
overhead.

If you don't wnat to get all fancy-like, you can construct the deallocator
on-the-fly at deallocation time, or you can just use a template function for
that matter.

-Dave