Re: [boost] [Signals] Named slot group usage?

From: Jody Hagins (jody-boost-011304_at_[hidden])
Date: 2005-02-11 12:26:29

On Fri, 11 Feb 2005 16:51:48 +0200
"Peter Dimov" <pdimov_at_[hidden]> wrote:

> Last time I looked, alternatives beat Boost.Signals because they don't
> 
> handle the corner cases of slot disconnection during signal
> invocation.
> 
> Example:
> 
>     R operator()(void) const
>     {
>         typename list::iterator i = list_.begin();
>         while (i != list_.end())
>         {
>             if (i->function_)
>             {
>                 (i++)->function_();
>             }
>             else
>             {
>                 i = list_.erase(i);
>             }
>         }
>     }
> 
> (from Jody Hagins's implementation)
> 
> AFAICS this doesn't work if (i++)->function_() disconnects *(i+1).
> 
> To handle disconnection correctly, one needs to invoke a temporary
> list<>. I haven't looked at what boost::signal does, but this may
> account for the dynamic allocations that have been reported.

That implementation was a very first try at something for comparison
purposes.  Because of the performance differences, I modified that code
a bit and added a few pieces of functionality, one of which is the
ability to replace a slot and/or disconnect a slot while it is being
handled.

The performance difference was measurable, but very small.  A copy of
the list is not necessary to implement this feature.