Re: [Boost-users] [signals2] tracking intrusively ref-counted object

Subject: Re: [Boost-users] [signals2] tracking intrusively ref-counted object
From: Frank Mori Hess (fmhess_at_[hidden])
Date: 2009-09-05 19:35:09

On Saturday 05 September 2009, Igor R wrote:
> Hello,
>
> In my project I've got intrusively ref.counted objects (particularly,
> ATL COM-objects), which listen to signals of some asynchronous
> subsystem. Currently, when these objects connect to the signals, they
> bind their own intrusive smart-ptrs to the slot functor, like this:
> // pseudo code
> Object::init()
> {
>   asyncSubsystem_.onSignal_.connect(bind(&Object::handleSignal,
> intrusive_from_this...)); // ensure the slot wouldn't bound to a dead
> object
> }
>
> Of course, this implies that the object cannot "die" until it's
> explicitly disconnected from the signal, so when the user of my
> library wants to get rid of such an object, he must call one more
> function (say, obj->close()) before resetting his smart-ptr to the
> object -- which is not just inconvenient, but also threatens the
> exception safety of user's code.

If you can access the value of the reference count, you could have your 
slot check to see if the reference count has dropped to 1 (assuming the 
slot takes the reference-counted pointer by reference).  If the use count 
is one, the slot could disconnect itself.