[cpp-threads] Asynchronous Execution Issues

[Lawrence Crowl]

On 4/27/09, Anthony Williams <anthony at justsoftwaresolutions.co.uk> wrote:
> I agree that it's an issue, but I think "doesn't ever work"
> is an exaggeration.

Me too.

> I see several options:
>
> 1) Make it undefined behaviour for a thread_local destructor to
> access any objects of static storage duration.
>
> 2) Provide a function which a thread can call that says
> "destroy thread locals NOW", and make it undefined to access any
> thread_local after that function returns.
>
> 3) Provide a means for a thread to register a single function
> to be called after thread_local objects have been destroyed. It
> is undefined behaviour for that function to access thread_local
> objects, but it may call library functions. This function could
> then set the "done" flag.

How about a fourth option?

    Add a three more "set" functions to std::promise (or an
    additional parameter) that provide the additional semantics
    that is_ready on the corresponding future will not be true
    until the thread calling the promise has terminated.

Practically, this means that the promise::set... will need to
save the thread handle within the shared storage so that the
...future::wait... can join with the thread?

I was planning to put something in the mid-term mailing on this
issue, but I'm not doing so now.  :-)

-- 
Lawrence Crowl