Re: [boost] Re: Deadline for the Standard Library Technical Report

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-01-27 22:04:09

At 05:47 PM 1/27/2003, Andrei Alexandrescu wrote:

 >Q. Why doesn't shared_ptr provide (your pet feature here)?
 >A. Because (your pet feature here) would mandate a reference counted
 >implementation or a linked list implementation, or some other specific
 >implementation. This is not the intent.
 >
 >This is a presupposition. Someone wants to mandate lazy
 >initialization/specific dereference testing/specific initialization
 >testing/tons others. Would any of these require a refcounted/reflinked
 >implementation?

That particular FAQ item was written quite a while ago, before weak_ptr 
support, before custom deleter support, etc. We had gotten several requests 
for features that seemed to tilt the spec strongly toward one or the other 
of the implementation techniques.

The question of whether "any of these require a refcounted/reflinked
implementation?" is a good one.

The question came up with use_count(), and was handled by not requiring 
use_count() be constant complexity.

For a shared-ownership smart pointer with weak_ptr support, I expect some 
people will say that mandates a refcounted rather than reflinked 
implementation. I don't think that is true, but it may make a reflinked 
implementation less attractive. What's your opinion on that?

--Beman