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nascheme merged 2 commits into from
Jul 8, 2025
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GH-91636: Clear weakrefs created by finalizers. #136401

nascheme merged 2 commits into from
Jul 8, 2025
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@naschemenascheme commented Jul 8, 2025•
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Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have tp_clear called on them to Python-level code.

Note that this is part of the GH-136189 change, split out to make it easier for back-porting. This change is conceptually quite simple and is a candidate to backport to all older Python versions (this bug existed for a long time, perhaps in version 2.3). There is some duplicated code between handle_finalizers and clear_finalizers but I think it's simpler just to leave that duplication. In the "main" branch I'll clean that up.

@nascheme
Clear weakrefs created by finalizers.
6a1b24b
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code.
@bedevere-appbedevere-appbot mentioned this pull request Jul 8, 2025
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@naschemenascheme added 3.13 bugs and security fixes 3.14 bugs and security fixes 3.15 new features, bugs and security fixes labels Jul 8, 2025
@naschemenascheme marked this pull request as ready for review July 8, 2025 01:15
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nascheme commented Jul 8, 2025

@colesbury In case you want to look at the free_threading_gc changes.

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sergey-miryanov commented Jul 8, 2025

Looks good to me.

colesbury
colesbury reviewed Jul 8, 2025
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@nascheme
Reduce code duplication.
412bc2a
Add a boolean flag to indicate that callbacks should be enabled. This allows the same function to be used before and after finalizer execution.
sergey-miryanov
sergey-miryanov reviewed Jul 8, 2025
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Python/gc.c
if (!allow_callbacks){
return0;
}

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Similar question: The old and allow_callbacks arguments are orthogonal even in older versions?

@naschemenascheme merged commit b6b99bf into python:mainJul 8, 2025
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@naschemenascheme mentioned this pull request Jul 8, 2025
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AndPuQing pushed a commit to AndPuQing/cpython that referenced this pull request Jul 11, 2025
@nascheme@AndPuQing
pythonGH-91636: Clear weakrefs created by finalizers. (pythonGH-136401)
403847c
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code.
Pranjal095 pushed a commit to Pranjal095/cpython that referenced this pull request Jul 12, 2025
@nascheme@Pranjal095
pythonGH-91636: Clear weakrefs created by finalizers. (pythonGH-136401)
47ecfed
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code.
picnixz pushed a commit to picnixz/cpython that referenced this pull request Jul 13, 2025
@nascheme@picnixz
pythonGH-91636: Clear weakrefs created by finalizers. (pythonGH-136401)
9ae4af5
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code.
taegyunkim pushed a commit to taegyunkim/cpython that referenced this pull request Aug 4, 2025
@nascheme@taegyunkim
pythonGH-91636: Clear weakrefs created by finalizers. (pythonGH-136401)
c923ad6
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code.
Agent-Hellboy pushed a commit to Agent-Hellboy/cpython that referenced this pull request Aug 19, 2025
@nascheme@Agent-Hellboy
pythonGH-91636: Clear weakrefs created by finalizers. (pythonGH-136401)
5b60a46
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code.
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sergey-miryanov commented Sep 3, 2025

It seems that this is not backported to 3.14 and 3.13. Do we still a plan to backport it?
cc @nascheme, @Yhg1s, @hugovk

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nascheme commented Sep 4, 2025

Yeah, you are right. I think it would be good to backport this one.

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hugovk commented Sep 11, 2025

This bug had been around for a while, let's wait for 3.14.1 for the backport rather than do it during RC.

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sergey-miryanov commented Nov 25, 2025

@hugovk It's about 3.14.1 here. Should we backport this PR? I'm not sure about the process. Is it enough to add backport labels?

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hugovk commented Nov 26, 2025

@sergey-miryanov Yeah, please add the labels and Miss Islington will attempt backports. And then we can carefully review the backport PRs.

@sergey-miryanovsergey-miryanov added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Nov 26, 2025
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miss-islington-appbot commented Nov 26, 2025

Thanks @nascheme for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

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miss-islington-appbot commented Nov 26, 2025

Thanks @nascheme for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Nov 26, 2025
@nascheme@miss-islington
pythonGH-91636: Clear weakrefs created by finalizers. (pythonGH-136401)
e5595d5
Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code. (cherry picked from commit b6b99bf) Co-authored-by: Neil Schemenauer <nas-github@arctrix.com>
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miss-islington-appbot commented Nov 26, 2025

Sorry, @nascheme, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker b6b99bf7f1edab77c485faf4e23da868f3a7b68c 3.13

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bedevere-appbot commented Nov 26, 2025

GH-141993 is a backport of this pull request to the 3.14 branch.

@bedevere-appbedevere-appbot removed the needs backport to 3.14 bugs and security fixes label Nov 26, 2025
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sergey-miryanov commented Nov 26, 2025

I will look into manually backport this to 3.13
cc @Yhg1s@nascheme

gpshead pushed a commit that referenced this pull request Nov 29, 2025
@miss-islington@nascheme
[3.14]GH-91636: Clear weakrefs created by finalizers. (GH-136401) (#…
fed2af6
…141993) GH-91636: Clear weakrefs created by finalizers. (GH-136401) Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code. (cherry picked from commit b6b99bf) Co-authored-by: Neil Schemenauer <nas-github@arctrix.com>
hugovk added a commit to hugovk/cpython that referenced this pull request Dec 1, 2025
@hugovk
Revert "[3.14]pythonGH-91636: Clear weakrefs created by finalizers. (p…
87b3635
…ythonGH-136401) (python#141993)" This reverts commit fed2af6.
hugovk added a commit that referenced this pull request Dec 1, 2025
@hugovk
[3.14] Revert "GH-91636: Clear weakrefs created by finalizers. (GH-13…
7642070
…6401) (#141993)" (#142152)
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serhiy-storchaka commented Dec 26, 2025

Reminder about backporting to 3.13.

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sergey-miryanov commented Jan 23, 2026

Thanks for reminder. Sorry for the delay. Will work on backporting this weekends.

sergey-miryanov added a commit to sergey-miryanov/cpython that referenced this pull request Jan 24, 2026
@sergey-miryanov@nascheme
[3.13]pythonGH-91636: Clear weakrefs created by finalizers. (pythonG…
41fd1aa
…H-136401) Weakrefs to unreachable garbage that are created during running of finalizers need to be cleared. This avoids exposing objects that have `tp_clear` called on them to Python-level code. (cherry picked from commit b6b99bf) Co-authored-by: Neil Schemenauer <nas-github@arctrix.com>
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bedevere-appbot commented Jan 24, 2026

GH-144214 is a backport of this pull request to the 3.13 branch.

@bedevere-appbedevere-appbot removed the needs backport to 3.13 bugs and security fixes label Jan 24, 2026
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