Re: [boost] [smart_ptr] enable_shared_from_this enhancement

From: Frank Mori Hess (fmhess_at_[hidden])
Date: 2008-03-17 02:44:27

On Monday 17 March 2008 01:42, Frank Mori Hess wrote:
> On Monday 17 March 2008 01:36, Frank Mori Hess wrote:
> > The implementation I've got in mind (haven't actually tried it yet)
> > would work as follows.  I'd add two shared_ptrs to
> > enable_shared_from_this, call them "internal_shared" and
> > "external_shared".  external_shared would be assigned the external
> > shared_ptr which first takes ownership of *this. internal_shared would
> > be initialized with the "this" pointer, and a custom deleter which
> > would reset external_shared.  internal_shared would be reset right
> > after external_shared is initialized (when an external shared_ptr

Sorry for the repeated replies to myself (I probably shouldn't be posting 
past 2 AM), but I think the answer is to swap internal_shared with the 
external shared_ptr taking ownership before resetting internal_shared.  
Then everything is a copy of the original internal_shared, and 
external_shared preserves the user's deleter.

> > takes ownership of *this).  Any calls to shared_from_this() that occur
> > prior to an external shared_ptr taking ownership of *this (such as in
> > the constructor) would get a copy of internal_shared.
>
> Hmm, actually nevermind.  This scheme isn't good enough yet, as I'd also
> want a weak_ptr copy of internal_shared to recognize the case where the
> object is still being kept alive by a copy of external_shared.

-- 
Frank