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

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vstinner merged 2 commits intopython: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 intopython:mainfrom
ashm-dev:ub

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@ashm-dev ashm-dev commented Mar 20, 2026

@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
@vstinner vstinner merged commit cd10a2e into python:main Mar 20, 2026
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@miss-islington-app
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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!

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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
…IString() (python#146201)

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

Co-authored-by: Victor Stinner <[email protected]>
(cherry picked from commit cd10a2e)
@bedevere-app
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bedevere-app bot commented Mar 20, 2026

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
…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 <[email protected]>
CuriousLearner added a commit to CuriousLearner/cpython that referenced this pull request Mar 22, 2026
* upstream/main: (1475 commits)
  Docs: replace all `datetime` imports with `import datetime as dt` (python#145640)
  pythongh-146153: Use `frozendict` in pure python fallback for `curses.has_key` (python#146154)
  pythongh-138234: clarify returncode behavior for subprocesses created with `shell=True` (python#138536)
  pythongh-140947: fix contextvars handling for server tasks in asyncio  (python#141158)
  pythonGH-100108: Add async generators best practices section (python#141885)
  pythonGH-145667: Merge `GET_ITER` and `GET_YIELD_FROM_ITER` (pythonGH-146120)
  pythongh-146228: Better fork support in cached FastPath (python#146231)
  pythongh-146227: Fix wrong type in _Py_atomic_load_uint16 in pyatomic_std.h (pythongh-146229)
  pythongh-145980: Fix copy/paste mistake in binascii.c (python#146230)
  pythongh-146092: Raise MemoryError on allocation failure in _zoneinfo (python#146165)
  pythongh-91279: Note `SOURCE_DATE_EPOCH` support in `ZipFile.writestr()` doc (python#139396)
  pythongh-146196: Fix Undefined Behavior in _PyUnicodeWriter_WriteASCIIString() (python#146201)
  pythongh-143930: Reject leading dashes in webbrowser URLs
  pythongh-145916: Soft-deprecate ctypes.util.find_library (pythonGH-145919)
  pythongh-146205: Check the errno with != 0 in close impls in select module (python#146206)
  pythongh-146171: Fix nested AttributeError suggestions (python#146188)
  pythongh-146099: Optimize _GUARD_CODE_VERSION+IP via function version symbols (pythonGH-146101)
  pythongh-145980: Add support for alternative alphabets in the binascii module (pythonGH-145981)
  pythongh-145754: Update signature retrieval in unittest.mock to use forwardref annotation format (python#145756)
  pythongh-145177: Add emscripten run --test, uses test args from config.toml (python#146160)
  ...
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2 participants