[boost] Re: Re: SmartPtr - Exception safety reprise

From: Fredrik Blomqvist (fredrik_blomqvist_at_[hidden])
Date: 2003-02-06 16:15:44

"Dave Abrahams" <dave_at_[hidden]> wrote in message
news:008c01c2ce1f$87ca8620$6501a8c0_at_penguin...
> On Thursday, February 06, 2003 3:13 PM [GMT+1=CET],
> David B. Held <dheld_at_[hidden]> wrote:
>
> > "David B. Held" <dheld_at_[hidden]> wrote in message
> > news:b1m57m$702$1_at_main.gmane.org...
> > > > > [...]
> > > > > I mean, the optimally_inherit eliminates the empty bases, and
> > > > > yet there is size bloat.  So VC++ makes the class bigger for
> > > > > some other reason than that it has empty bases.  I will try to
> > > > > write some tests to see why that is, or at least how.
> > > >
> > > > I repeat, I bet it's MI-related.
> > >
> > > The proof of the pudding is in the eating.
> >
> > I got a chance to taste the pudding, the the results are inconclusive.
> > The cause of the size bloat was that I had changed ref_counted to
> > inherit from noncopyable.  Seems like an innocent enough change.
> > Seems that for the single-inheritance case, we should see some
> > EBO action, right?  Well, we do, unless ref_counted is a base in
> > an MI hierarchy.  Why its place in an hierarchy should change its
> > size is a mystery to me,
>
> What do you mean that its *place* in the hierarchy affects the size? If
it's
> in the hierarchy, it's a base.
>
I bet this is the effect he observed:
http://lists.boost.org/MailArchives/boost/msg43187.php