RE: [boost] Re: future of boost.threads

From: Darryl Green (Darryl.Green_at_[hidden])
Date: 2004-02-09 20:57:53

> -----Original Message-----
> From: Peter Dimov [mailto:pdimov_at_[hidden]] 
[snip]
> Now, in C++ functions actually can return either a value or 
> an exception.
> That is,
>     int f();
> can return an int or throw an exception. Hence, when you 
> execute that f in a
> thread, you should be able later to call
> 
>     int thread::join();
> 
> and it should return whatever f returned.

Yes. I think you mentioned this last time exception
propogation across threads was discussed,
and I agree. I seem to recall that William Kempf was keen
to shift the burden of these sorts of things to some form
of wrapper/function object
(see http://article.gmane.org/gmane.comp.lib.boost.devel/14237).

> 
> Note that you can't add exception marshalling on a higher 
> level (with the
> current interface) because you can't access a thread's state 
> (to retrieve
> its return value or exception) from another thread.

Can't some function object wrapper catch and store the exception
somewhere other than in the "thread state" for later access
from some sort of async call object regardless of the underlying
thread implementation?

The joining thread would wait on one of these async call
objects (ie join). The async call object and the wrapper
would have shared access/ownership of the result (exception
or return value) storage.

What am I missing?

Regards
Darryl Green.

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