GNU bug report logs - #41357
28.0.50; GC may miss to mark calle safe register content

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From: Pip Cet <pipcet <at> gmail.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 41357 <at> debbugs.gnu.org, Andrea Corallo <akrl <at> sdf.org>
Subject: bug#41357: 28.0.50; GC may miss to mark calle safe register content
Date: Sun, 17 May 2020 17:00:38 +0000

On Sun, May 17, 2020 at 4:47 PM Paul Eggert <eggert <at> cs.ucla.edu> wrote:
> On 5/17/20 9:40 AM, Andrea Corallo wrote:
> > I think this is a real bug that we have in the codebase (emacs-27
> > included).
> Thanks for all the detective work! Your analysis is correct and your patch looks
> good.

That's my impression as well.

> The only question in my mind is whether to install the patch into the emacs-27
> branch or the master branch. Given Eli's problems with stability in emacs-27
> (see Bug#41321), I'm inclined to think the former, as the bug could explain the
> problems Eli is observing.

I don't think that platform even has callee-saved registers? But I
think the fix should go on the emacs-27 branch. It's a bad bug and
sheer luck that Fgarbage_collect on my platform (using this specific
compiler, etc.) pushes all callee-saved registers. We shouldn't rely
on such lucks on all platforms.

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