Re: [Boost-users] Boost.Signals2 - tracking an object managed with tr1::shared_ptr

Subject: Re: [Boost-users] Boost.Signals2 - tracking an object managed with tr1::shared_ptr
From: Monteleone, Nathan (nathan.monteleone_at_[hidden])
Date: 2009-09-14 11:54:29

> On Friday 11 September 2009, Frank Mori Hess wrote:
> > On Thursday 10 September 2009, Monteleone, Nathan wrote:
> > > Is it possible to use slot::track with a tr1::shared_ptr instead of
> a
> > > boost::shared_ptr?
> >
> > Sorry, not at present.  I've thought about it a bit, especially with
> > respect to std::shared_ptr, but haven't gotten around to doing
> anything
> > about it.  It wouldn't be too hard to support some fixed set of
> shared_ptr
> > types using boost::variant.  Maybe an additional slow path that uses
> heap
> > allocation and some type traits could support unforeseen shared_ptr
> types.
> >
> 
> Oh, and the other solution would be to add yet more template parameters
> to the
> signal class (like the SlotFunction = boost::function) to permit the
> shared_ptr/weak_ptr types to be specified per-signal.

Frank,

First of all, thanks for your work on the signals2 library.

Ideally I'd like to be able to provide extensions to support more than just the boost/tr1 smart pointer types.  OpenThreads/OSG's ref_ptr would be one example.  A template parameter couldn't give me that power unless it was a policy, right?  For that reason I like your traits idea better.  I sympathize with your reluctance to add "yet more" template parameters :)

Any idea how other libraries dealing with the whole boost vs. std::tr1 namespace issue?  Seems unfortunate to have to add template parameters all over the place for that, but I don't see any other way.  Am I making a mistake by using tr1 for the stuff that is in tr1 and boost for everything else?

This is also interesting, although it doesn't help with the tr1 namespace woes: http://boost.org/libs/smart_ptr/sp_techniques.html#weak_without_shared
The gist of it is that you can make any object support weak_ptr with an internal shared_ptr to itself, with a null_deleter.  Might be of interest for people wanting to track a wider variety of objects.

-Nathan