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[3.13] GH-134453: Fix subprocess memoryview input handling on POSIX (GH-134949)#142063

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Merged

gpshead merged 1 commit intopython:3.13frommiss-islington:backport-cc6bc4c-3.13

Nov 29, 2025

Merged

[3.13] GH-134453: Fix subprocess memoryview input handling on POSIX (GH-134949)#142063

gpshead merged 1 commit intopython:3.13frommiss-islington:backport-cc6bc4c-3.13

Nov 29, 2025

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miss-islington commentedNov 29, 2025•
edited by bedevere-appbot
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Fix inconsistent subprocess.Popen.communicate() behavior between Windows
and POSIX when using memoryview objects with non-byte elements as input.

On POSIX systems, the code was incorrectly comparing bytes written against
element count instead of byte count, causing data truncation for large
inputs with non-byte element types.

Changes:

Cast memoryview inputs to byte view when input is already a memoryview
Fix progress tracking to use len(input_view) instead of len(self._input)
Add comprehensive test coverage for memoryview inputs

🤖 Generated withClaude Code

Co-Authored-By: Claudenoreply@anthropic.com

old-man-yells-at-ReST
Update 2025-05-30-18-37-44.gh-issue-134453.kxkA-o.rst
assertIsNone review feedback
fix memoryview_nonbytes test to fail without our fix on main, and have a nicer error.

Thanks to Peter Bierma@ZeroIntensity for the code review.
(cherry picked from commitcc6bc4c)

Co-authored-by: Gregory P. Smith68491+gpshead@users.noreply.github.com

Issue:Inconsistentsubprocess.Popen.communicate() behavior between Windows and Posix on non-byte memoryview input #134453

pythonGH-134453: Fix subprocess memoryview input handling on POSIX (p…

c9538b7

…ythonGH-134949)Fix inconsistent subprocess.Popen.communicate() behavior between Windowsand POSIX when using memoryview objects with non-byte elements as input.On POSIX systems, the code was incorrectly comparing bytes written againstelement count instead of byte count, causing data truncation for largeinputs with non-byte element types.Changes:- Cast memoryview inputs to byte view when input is already a memoryview- Fix progress tracking to use len(input_view) instead of len(self._input)- Add comprehensive test coverage for memoryview inputs🤖 Generated with [Claude Code](https://claude.ai/code)Co-Authored-By: Claude <noreply@anthropic.com>* old-man-yells-at-ReST* Update 2025-05-30-18-37-44.gh-issue-134453.kxkA-o.rst* assertIsNone review feedback* fix memoryview_nonbytes test to fail without our fix on main, and have a nicer error.Thanks to Peter Bierma@ZeroIntensity for the code review.(cherry picked from commit cc6bc4c97f7be5b401a91119ba603e6c1a07c99b)Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>