Re: [boost] [smart_ptr] optimize current enable_shared_from_this with100% compatibility

From: Daniel Frey (d.frey_at_[hidden])
Date: 2008-04-22 04:43:07

On Tue, 2008-04-22 at 01:54 +0300, Peter Dimov wrote:
> Your patch (still) contains a number of changes, some of which are unrelated 
> to its purpose (to save one pointer in esft). To break it down:

OK, so let's separate them. For now, I'll skip 1 and 2.

> 4. Adds if( tmp != pi_ ) optimizations. OK, but a separate issue.

Committed to svn.

> 5. Adds shared_ptr(shared_count, p). OK, essential. The && overload is not 
> guarded, BTW.

I assume by "guarded" you mean "protected by #ifdef
BOOST_HAS_RVALUE_REFS"? It actually is guarded then, although it might
not be visible from looking at the patch itself, since I added it to the
section with the other move semantic ctors.

> 6. Adds _internal_shared_count. OK, essential. Should probably be called 
> get_shared_count.

Do you suggest to make it a part of the public interface?

This would allow another, very explicit approach to have an aliasing
ctor:

shared_ptr<T> t = ...;
U* pu = ...;

shared_ptr<U> u( t.get_shared_count(), pu ); // aliasing

Which /could/ replace the existing aliasing ctor - except that this is
again a breaking change. But OK, that's independent of renaming it to
get_shared_count.

> You may commit #4 right away; as for the rest, I'd really like to see the 
> patch without #1 and #2.

OK, I'll prepare it after work.

Regards, Daniel