Re: [boost] [smart_ptr] shared_ptr template type

Subject: Re: [boost] [smart_ptr] shared_ptr template type
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2009-07-15 09:54:23

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On Tuesday 14 July 2009, Zachary Turner wrote:
> If traits are going
> to be supported at all, I think they should be supported first-class,
> and allow one to just parameterize the class with a traits class to
> begin with.

> template<class T, class Traits=default_smart_pointer_traits<T> > class
> generic_shared
> {
> };

I don't intend to add additional template parameters to generic_shared.  I 
like shared_ptr, and plan to stay as close to the shared_ptr design as 
possible.  If you want to go the route of high configurability and multiple 
template parameters, it would probably be better to start from the design of 
Loki::SmartPtr than boost::shared_ptr.

My only goal is to make an incremental deviation that adds support for more 
than just plain old pointers as the wrapped pointer type.  Incidental to that 
is defining some concepts that will allow conforming smart pointer classes to 
use each other as their underlying pointer type.  Other than that, I plan to 
ape the shared_ptr interface as closely as possible.  It may be that I just 
alienate both camps, with the "simplicity" people ignoring it as too complex 
and the "configurability" people wanting more, but that's the road I'm on.

The traits stuff in generic_shared is only intended to communicate the 
necessary information about a pointer-like class to generic_shared, not to 
provide a customization point for the wrapped type.  Such customization would 
belong in the template parameter list of the wrapped class (the T in 
generic_shared<T>) anyways, not the class wrapping it.  And if it were really 
absolutely necessary, the customization could be inserted as a wrapper class 
in between generic_shared and T, like 

generic_shared<my_customization_wrapper<T, mypolicy> >
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