Re: [Boost-users] [signals] thread-safe default combiner

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2007-02-09 16:44:10

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On Friday 09 February 2007 16:18 pm, Doug Gregor wrote:
> > Returning an Optional if T is default constructible seems like
> > a viable refinement of that solution. I'm a little uncomfortable
> > with exceptions being thrown potentially everywhere along the
> > call chain as a default behaviour.
>
> The problem is that we don't get to return an optional, because the
> return type is specified as "T", not "optional<T>".  And,
> unfortunately, we can't rely on there always being a default
> constructor there.
>
> Right now, the implementation is allowed to crash if you call one of
> these signals and there are no slots. Throwing an exception brings
> some sane defined behavior to something that is now completely
> undefined.
>
> If we could reliably detect default-constructibility, we might be
> able to come up with something better.

We could add a little header with a definition of a "last_optional" 
combiner for people to use if they prefer.

- -- 
Frank
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