Re: [boost] [smart_ptr] optimize current enable_shared_from_this with 100% compatibility

From: Daniel Frey (d.frey_at_[hidden])
Date: 2008-04-23 14:33:56

On Wed, 2008-04-23 at 08:45 -0400, Frank Mori Hess wrote:
> The comment is obsolete, now that the pointer value is calculated in the 
> shared_from_this() calls.  Yes, the deleter_wrapper only needs a 
> shared_count.  

The comment suggest that the lazy initialization is just a work-around
for the more desirable initialization during the ctor. Is this no longer
true?

> And what I was getting at before, _internal_shared_count could be made a local 
> variable in init_internal_shared_once(), if you add a line where you stuff it 
> inside its own deleter_wrapper.  Anywhere else it is used, it can be obtained 
> from _internal_weak_count.

I think we should pick the low-hanging fruits first. If it's OK for you
I'll apply the attached patch.

Next thing I'd like to address is getting rid of the _owner flag, I
think it should be possible. We are then left with an overhead of the
vtable and two plain pointers (inside of shared_count and weak_count).

For the vtable, we could remove it by switching shared_from_this from a
member function to a free function that takes T* as a parameter, but
that's of course a breaking change...

Regards, Daniel