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

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From: Pip Cet <pipcet <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 46256 <at> debbugs.gnu.org, andrewjmoreton <at> gmail.com, Andrea Corallo <akrl <at> sdf.org>
Subject: bug#46256: [feature/native-comp] AOT eln files ignored if run from build tree
Date: Mon, 8 Mar 2021 06:48:40 +0000

[Message part 1 (text/plain, inline)]

On Mon, Mar 8, 2021 at 5:54 AM Pip Cet <pipcet <at> gmail.com> wrote:
> Note that this might not always work because of conservative GC.

If it doesn't work, can you simply retry a few times? Eventually there
shouldn't be references to the stale native_comp_unit on the stack.

However, I think I've worked out why dynlib_close doesn't do its job:

Fnative_elisp_load creates a comp unit, but, if the shared library has
already been initialized, it doesn't set that comp unit's comp_unit
variable to point to the new comp unit; instead, it will continue
pointing to the first comp unit which still has it open.

Then, the original comp unit is unloaded but not the new one created
by Fnative_elisp_load. We call dynlib_close() once, but we called it
twice before, leaving the shared library open and initialized.

Then, we try to load the comp unit again, and follow the stale
comp_unit variable pointing to the original comp unit.

Fix should be as attached. Note the fix is, at worst, harmless (unless
I messed up), so we should apply it anyway just because it's good not
to leave stale pointers lying around even if we hope that the OS
unmaps them at some point.

Pip

[0001-Fix-stale-pointers-in-comp-units-causing-crashes-bug.patch (text/x-patch, attachment)]

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