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Re: unwind-protect and inhibit-quit

From: Stefan Monnier
Subject: Re: unwind-protect and inhibit-quit
Date: Fri, 16 Jul 2021 16:06:33 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux)

>> We should devise a more reliable API, tho I'm not completely sure what
>> it should look like.  Maybe
>>     (let ((list-of-created-processes nil))
>>       (unwind-protect ...
>>         (mapc #'delete-process list-of-created-processes)))
>> Where the low-level primitives which create processes add them to
>> `list-of-created-processes`.
> But wouldn't that run into the same sort of race conditions as the
> other case? Where a process would be created, but the parent function
> would be killed before the process is added to the list?

No, because the process would (presumably) get added "atomically" to
`list-of-created-processes` as it is created (i.e. either it gets
created and gets added to the list, or it's not created), and so it doesn't
matter what the intermediate code does and returns.

> If not, why not simply add an unwind-protect as tight as possible
> around the form actually creating the process?

Because the above `unwind-protect` needs to be placed at the spot where
one does not need the process any more.


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