[m-rev.] for review: Add interface for joinable threads.

[Julien Fischer]

Hi Peter,

On Thu, 22 Feb 2024, Peter Wang wrote:

> It is often necessary to be certain that a thread has terminated before
> the rest of the program can continue. In some cases, signalling that a
> thread is ABOUT to terminate (using any synchronisation device)
> is insufficient: even after the last piece of Mercury code has run,
> the thread still has additional cleanup code to run, which might include
> arbitrary code in thread-specific data destructors, etc.
>
> Introduce a predicate to create a joinable native thread,
> and a predicate to wait for that thread to terminate (joining).
>
> Joinable threads are only implemented for C backends for now.

I assume you have at given some consideration that the API proposed for
joinable threads is implementable for Java and C#?

> library/thread.m:
>    Add new predicates spawn_native_joinable and join_thread.
>
>    Add a internal type thread_handle.
>
>    Rename the internal type thread_id type to thread_desc,
>    as thread_id is too similar to thread_handle.
>
> tests/hard_coded/Mmakefile:
> tests/hard_coded/spawn_native_joinable.exp:
> tests/hard_coded/spawn_native_joinable.exp2:
> tests/hard_coded/spawn_native_joinable.m:
>    Add test case.
>
> NEWS.md:
>    Announce changes.

The diff looks fine.

Julien.