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gh-74929: Fix an extra DECREF for PEP 667 implementation by gaogaotiantian · Pull Request #118583 · python/cpython · GitHub
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gh-74929: Fix an extra DECREF for PEP 667 implementation#118583

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gvanrossum merged 2 commits into
python:mainfrom
gaogaotiantian:fix-framelocalsproxy-setitem
May 5, 2024
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gh-74929: Fix an extra DECREF for PEP 667 implementation#118583
gvanrossum merged 2 commits into
python:mainfrom
gaogaotiantian:fix-framelocalsproxy-setitem

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gaogaotiantian commented May 5, 2024 •
edited by bedevere-app Bot
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In the PEP 667 implementation, when I copied the code from _PyFrame_LocalsToFast, I did not realize the value is a new reference so it was decrefed in the original code. This resulted in an extra DECREF in __setitem__. Unfortunately I did not catch it because the test cases used were all immortals.

Two test cases were added:

  • local object variable - this will trigger an assertion failure in debug mode
  • f_locals updating itself multiple times - this will crash the interpreter without the fix

bedevere-app Bot mentioned this pull request May 5, 2024
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gaogaotiantian requested a review from gvanrossum May 5, 2024 00:05
gaogaotiantian mentioned this pull request May 5, 2024
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gvanrossum approved these changes May 5, 2024
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Maybe you want to delete or update the comment in the test?

Comment thread Lib/test/test_frame.py Outdated
self.assertEqual(o, 'a.b.c')

def test_update_with_self(self):
# Make sure reference is not leaking here

gvanrossum May 5, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

The problem was not a leak though -- it was a free-after-use (the opposite of a leak, really :-).

gaogaotiantian May 5, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Right. I was imaging a pool of reference and a hole that's leaking the reference without people knowing it so the pool is drained, but yeah leak is not a good word choice here. I just deleted it, the test itself makes sense without any comments.

gvanrossum May 5, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Ooh, that's actually a nice image. :-) I will merge now.

gaogaotiantian May 5, 2024

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Thanks for the quick review!

gvanrossum enabled auto-merge (squash) May 5, 2024 02:53
gvanrossum merged commit 5dd3673 into python:main May 5, 2024
gaogaotiantian deleted the fix-framelocalsproxy-setitem branch May 5, 2024 03:36
SonicField pushed a commit to SonicField/cpython that referenced this pull request May 8, 2024
pythongh-74929: Remove undesirable DECREF in PEP 667 implementation (p… …
b98b3de
…ython#118583) With tests.
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gvanrossum gvanrossum approved these changes
markshannon Awaiting requested review from markshannon markshannon is a code owner

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