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gh-146196: Fix potential Undefined Behavior in _PyUnicodeWriter_WriteASCIIString#146201

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vstinner merged 2 commits into
python:mainfrom
ashm-dev:ub
Mar 20, 2026
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gh-146196: Fix potential Undefined Behavior in _PyUnicodeWriter_WriteASCIIString#146201
vstinner merged 2 commits into
python:mainfrom
ashm-dev:ub

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@ashm-dev

@ashm-dev ashm-dev commented Mar 20, 2026 •
edited by bedevere-app Bot
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@bedevere-app bedevere-app Bot mentioned this pull request Mar 20, 2026
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@ashm-dev ashm-dev requested a review from AA-Turner as a code owner March 20, 2026 15:06
@vstinner vstinner added the needs backport to 3.14 bugs and security fixes label Mar 20, 2026
@vstinner vstinner enabled auto-merge (squash) March 20, 2026 15:34
Hide details View details @vstinner vstinner merged commit cd10a2e into python:main Mar 20, 2026
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@miss-islington-app

miss-islington-app Bot commented Mar 20, 2026

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Thanks @ashm-dev for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

@miss-islington-app

miss-islington-app Bot commented Mar 20, 2026

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Sorry, @ashm-dev and @vstinner, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker cd10a2e65c25682095f6ee4a9b9a181938a50d2e 3.14

vstinner added a commit to vstinner/cpython that referenced this pull request Mar 20, 2026
@ashm-dev @vstinner
pythongh-146196: Fix Undefined Behavior in _PyUnicodeWriter_WriteASCI… …
ca11535 
…IString() (python#146201)

Avoid calling memcpy(data + writer->pos, NULL, 0)
which has an undefined behavior.

Co-authored-by: Victor Stinner <vstinner@python.org>
(cherry picked from commit cd10a2e)
@bedevere-app

bedevere-app Bot commented Mar 20, 2026

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GH-146220 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Mar 20, 2026
@ashm-dev ashm-dev deleted the ub branch March 20, 2026 16:02
vstinner added a commit that referenced this pull request Mar 20, 2026
@vstinner @ashm-dev
[3.14] gh-146196: Fix Undefined Behavior in _PyUnicodeWriter_WriteASC… …
6e73225 
…IIString() (#146201) (#146220)

gh-146196: Fix Undefined Behavior in _PyUnicodeWriter_WriteASCIIString() (#146201)

Avoid calling memcpy(data + writer->pos, NULL, 0)
which has an undefined behavior.


(cherry picked from commit cd10a2e)

Co-authored-by: Shamil <ashm.tech@proton.me>
@serhiy-storchaka serhiy-storchaka mentioned this pull request Mar 20, 2026
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@pablogsal pablogsal mentioned this pull request Apr 4, 2026
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ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
@ashm-dev @vstinner @ljfp
pythongh-146196: Fix Undefined Behavior in _PyUnicodeWriter_WriteASCI… …
be90080 
…IString() (python#146201)

Avoid calling memcpy(data + writer->pos, NULL, 0)
which has an undefined behavior.

Co-authored-by: Victor Stinner <vstinner@python.org>
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