bug#46256: [feature/native-comp] AOT eln files ignored if run from build tree

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Mon, 8 Mar 2021 13:52:49 +0000
> Cc: Andrea Corallo <akrl@sdf.org>, 46256@debbugs.gnu.org, 
> andrewjmoreton@gmail.com
> 
> > > Wait, I thought this was on Windows?
> >
> > Yes, and...?
> 
> No dlclose() on Windows.

Why does this matter in this case?  (And I do have dlclose in a
standard library that comes with MinGW, btw.  Not that it's relevant.)

> FreeLibrary() is documented to behave differently from dlclose()

It is?  In what way?

> and I don't have a Windows system to test whether it's actually
> different in practice.

Well, how about explaining the details in terms that are simple enough
that I could understand and do the testing?  Until now, you and Andrea
have been talking Chinese as far as I'm concerned.  Please be aware
that I don't know half the details you two do about native-comp
internals, and will never be able to know that: too many other things
on my plate and too little time.  Can you perhaps explain the issue
without alluding to CU_1, CU_2, Fnative_elisp_load etc., and without
assuming that their interactions are common knowledge?

> > Why would any of the above assumptions be violated?
> 
> I have several suspicions, including "because the second compilation
> unit referring to the same handle hasn't been collected". Because that
> is definitely a bug, and one we should fix, and then we can debug this
> issue more if and when it reappears.

More Chinese.