Re: [Boost-users] Using boost.signals with boost.bind

Subject: Re: [Boost-users] Using boost.signals with boost.bind
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-10-14 09:37:23

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On Monday 13 October 2008 08:25 am, Sergey Kishchenko wrote:
>     boost::shared_ptr<signal_type> apSig(new signal_type());
>     apSig->connect(binded_func);
>     (*apSig)();
>
>     apSig.reset(new signal_type());
>     boost::signals::connection con = apSig->connect(binded_func);
>     std::cout<<"Connected: "<<con.connected()<<" Blocked:
> "<<con.blocked()<<"\n"; }
>
>
> Program output:
>
> Func::operator(42)
> Connected: 0 Blocked: 1
>
> Ie, if i create new signal and then try to connect to the same slot, it
> fails. If I use not boost::bind object but only boost::function as slot,
> all works ok. I can not understand, why? I used Boost 1.34.1, gcc 4.1.2

It looks like a bug to me.  In boost.signals, the slot has a shared_ptr to its 
signal/slot connection, which I think it uses for automatic connection 
management.  So it looks like it was coded under the assumption a slot object 
(or any of its copies) would not be re-used with more than 1 signal.  The 
slot is probably (permanently) auto-disconnecting when the first signal it 
was connected to is destroyed.  The signals2 lib, which might get reviewed 
soon if there are enough reviewers, doesn't show this problem.
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