bug#60996: 29.0.60; Native compile fails to remove temp file for trampoline

[Andrea Corallo <akrl@sdf.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Andrea Corallo <akrl@sdf.org>
>> Cc: andrewjmoreton@gmail.com, 60996@debbugs.gnu.org
>> Date: Thu, 26 Jan 2023 16:50:59 +0000
>> 
>> What I've understood from the trace is that `comp--native-compile' is
>> trying to delete the trampoline that was just compiled.
>> 
>> This is not expected in normal conditions so we have to understand why.
>> 
>> The only case where we might do that AFAIR is when
>> `inhibit-automatic-native-compilation' is used.  This was the infamous
>> mechanism that was installed by Lars where, if I'm not wrong, we are
>> supposed to compile a trampoline, load it, and remove it to pretend we
>> didn't compiled anything :x
>
> OK, this seems to be what is happening here, because we compile the
> trampoline to a temporary directory.  Otherwise, I don't see why we
> would do that, and why we would delete a trampoline we just compiled.

Agree, or at least I hope (otherwise we have two problems in place of
one :).

>> If (as I understand) in Windows we can't delete a mapped file we have a
>> problem more to solve.
>
> Yes.  If this is what happens, then I think we will have to maintain a
> list of such trampolines, and delete them just before exiting, after
> calling dynlib_close for them.

Mmmhh, and what if another Emacs tries to delete or overwrite the same
file?

But my question is: is this mechanism _really_ necessary?

From my POV it's just a kludge that was, is and will be source of
problems.  Was never clear to me for which specific reason this was
implemented as, at the time, I had the impression that all Debian
requirements could be handled with what we already offered.

At the time I firmly opposed to this change, but I was told by Lars it
went into master "for discussion" (!?), indeed the review discussion
never happened...  and now we are left with this present.

Unless we have a very strong reason to keep it, I believe we should just
get rid of this mechanism, otherwise it will be source of pain for us
again and again in the future.

Best Regards

  Andrea