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GeezerVison is showing github.com — gh-129204: Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment knob by vfazio · Pull Request #132184 · python/cpython

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@vfazio

@vfazio vfazio commented Apr 7, 2025 •
edited by bedevere-app Bot
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Add support for disabling the use of posix_spawn via a variable in the process environment.

While it was previously possible to toggle this by modifying the value of subprocess._USE_POSIX_SPAWN, this required either patching CPython or modifying it within the interpreter instance which is not always possible, such as when running applications or scripts not under a user's control.

  • Issue: Doc: mention a minimal version of QEMU user emulation necessary for 3.13+? #129204

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@vfazio
Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment knob
10029dd 
Add support for disabling the use of `posix_spawn` via a variable in
the process environment.

While it was previously possible to toggle this by modifying the value
of `subprocess._USE_POSIX_SPAWN`, this required either patching CPython
or modifying it within the interpreter instance which is not always
possible, such as when running applications or scripts not under a
user's control.

Signed-off-by: Vincent Fazio <[email protected]>
@vfazio
vfazio requested a review from gpshead as a code owner April 7, 2025 01:10
@bedevere-app bedevere-app Bot added the awaiting review label Apr 7, 2025
@bedevere-app bedevere-app Bot mentioned this pull request Apr 7, 2025
Doc: mention a minimal version of QEMU user emulation necessary for 3.13+? #129204
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@vfazio
fixup NEWS entry
e08d8dd
@vfazio

vfazio commented Apr 7, 2025

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vfazio@Zephyrus:~/development/cpython$ _PYTHON_SUBPROCESS_USE_POSIX_SPAWN="0" ./python -c "import subprocess; print(subprocess._USE_POSIX_SPAWN)"
False
vfazio@Zephyrus:~/development/cpython$ _PYTHON_SUBPROCESS_USE_POSIX_SPAWN=0 ./python -c "import subprocess; print(subprocess._USE_POSIX_SPAWN)"
False
vfazio@Zephyrus:~/development/cpython$ _PYTHON_SUBPROCESS_USE_POSIX_SPAWN=1 ./python -c "import subprocess; print(subprocess._USE_POSIX_SPAWN)"
True
vfazio@Zephyrus:~/development/cpython$ _PYTHON_SUBPROCESS_USE_POSIX_SPAWN="" ./python -c "import subprocess; print(subprocess._USE_POSIX_SPAWN)"
True

@gpshead per our discussion in #129204 (comment)
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gpshead
gpshead approved these changes Apr 7, 2025
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Apr 7, 2025
@gpshead
gpshead merged commit 4c5dcc6 into python:main Apr 7, 2025
@bedevere-app bedevere-app Bot removed the awaiting merge label Apr 7, 2025
@gpshead gpshead added the needs backport to 3.13 only security fixes label Apr 7, 2025
@miss-islington-app

miss-islington-app Bot commented Apr 7, 2025

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Thanks @vfazio for the PR, and @gpshead for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖
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miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Apr 7, 2025
@vfazio @miss-islington
pythongh-129204: Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment k…
458033a 
…nob (pythonGH-132184)

* Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment knob

Add support for disabling the use of `posix_spawn` via a variable in
the process environment.

While it was previously possible to toggle this by modifying the value
of `subprocess._USE_POSIX_SPAWN`, this required either patching CPython
or modifying it within the interpreter instance which is not always
possible, such as when running applications or scripts not under a
user's control.

Signed-off-by: Vincent Fazio <[email protected]>

* fixup NEWS entry

---------
(cherry picked from commit 4c5dcc6)

Co-authored-by: Vincent Fazio <[email protected]>
Signed-off-by: Vincent Fazio <[email protected]>
@bedevere-app

bedevere-app Bot commented Apr 7, 2025

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GH-132191 is a backport of this pull request to the 3.13 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.13 only security fixes label Apr 7, 2025
gpshead pushed a commit that referenced this pull request Apr 7, 2025
@miss-islington @vfazio
[3.13] gh-129204: Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment …
68bbdd9 
…knob (GH-132184) (#132191)

gh-129204: Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment knob (GH-132184)

* Add _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment knob

Add support for disabling the use of `posix_spawn` via a variable in
the process environment.

While it was previously possible to toggle this by modifying the value
of `subprocess._USE_POSIX_SPAWN`, this required either patching CPython
or modifying it within the interpreter instance which is not always
possible, such as when running applications or scripts not under a
user's control.



* fixup NEWS entry

---------
(cherry picked from commit 4c5dcc6)

Signed-off-by: Vincent Fazio <[email protected]>
Co-authored-by: Vincent Fazio <[email protected]>
@vfazio vfazio mentioned this pull request Apr 7, 2025
Detect QEMU linux-user emulation in subprocess._use_posix_spawn() #131398
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@vfazio @gpshead
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