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gh-132070: Use _PyObject_IsUniquelyReferenced in unicodeobject #133039

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merged 4 commits into from
Apr 29, 2025
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gh-132070: Use _PyObject_IsUniquelyReferenced in unicodeobject #133039

merged 4 commits into from
Apr 29, 2025

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@corona10 corona10 commented Apr 27, 2025 •
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@corona10 corona10 changed the title Kumar test gh-132070: use _PyObject_IsUniquelyReferenced in unicodeobject Apr 27, 2025
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corona10 commented Apr 27, 2025 •
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@kumaraditya303 @colesbury
I continued working on Kumar's PR #132091. In the new change, more states of unicode_modifiable are observed in free-threading builds. So I added a fallback to use resize_copy when unicode_modifiable fails, but I'm not sure if this is the right approach.
But the test failure issues are resolved.

@corona10 corona10 marked this pull request as ready for review April 27, 2025 10:12
@corona10 corona10 changed the title gh-132070: use _PyObject_IsUniquelyReferenced in unicodeobject gh-132070: Use _PyObject_IsUniquelyReferenced in unicodeobject Apr 27, 2025
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Update Objects/unicodeobject.c
2750016 
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
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LGTM.

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I looked into the case that requires resize_copy: We have an io.StringIO, which is used first by one thread and then by a second thread. (It's not used by two threads simultaneously). The io.StringIO has the only reference to a PyUnicodeWriter, which in turn has the only reference to unicode object that is treated as a buffer.

The _PyObject_IsUniquelyReferenced() check is too conservative in this case because the unicode object is owned by a different thread. The unicode object is actually safe to modify, we just can't tell that from _PyObject_IsUniquelyReferenced().

@corona10 corona10 merged commit 75cbb8d into python:main Apr 29, 2025
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Thanks @corona10 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 Apr 29, 2025
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pythongh-132070: Use _PyObject_IsUniquelyReferenced in unicodeobject (p…
4f40bf2 
…ythongh-133039)

---------
(cherry picked from commit 75cbb8d)

Co-authored-by: Donghee Na <donghee.na@python.org>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
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bedevere-app bot commented Apr 29, 2025

GH-133121 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.13 bugs and security fixes label Apr 29, 2025
@corona10 corona10 deleted the kumar-test branch April 29, 2025 02:07
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bedevere-app bot commented Apr 29, 2025

GH-133126 is a backport of this pull request to the 3.13 branch.

corona10 added a commit that referenced this pull request Apr 29, 2025
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[3.13] gh-132070: Use _PyObject_IsUniquelyReferenced in unicodeobject (…
7ffef8d 
…gh-133039) (gh-133126)

* gh-132070: Use _PyObject_IsUniquelyReferenced in unicodeobject (gh-133039)

---------
(cherry picked from commit 75cbb8d)

Co-authored-by: Donghee Na <donghee.na@python.org>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

* Add _PyObject_IsUniquelyReferenced

---------

Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
@corona10 corona10 mentioned this pull request Apr 29, 2025
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@colesbury colesbury colesbury approved these changes

@serhiy-storchaka serhiy-storchaka serhiy-storchaka approved these changes

@kumaraditya303 kumaraditya303 Awaiting requested review from kumaraditya303

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