gh-146004: propagate all -X options to multiprocessing child processes by gpshead · Pull Request #146005 · python/cpython

gpshead · 2026-03-16T00:33:35Z

See the issue for details. Our list of -X options to opt-in was overlooking a lot. CI and buildbot tests on these may prove interesting.

Issue: recent -X options do not auto-propagate to multiprocessing processes #146004

vstinner

LGTM.

gpshead · 2026-03-28T04:39:01Z

Auto-backported test will probably fail CI as the test includes new -X options that older releases don't have. I'll clean that up in the backport PR branches.

miss-islington-app · 2026-03-28T05:03:09Z

Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

…ocesses (pythonGH-146005) Propagate all -X command line options to multiprocessing spawned child Python processes. (cherry picked from commit 1efe441) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>

miss-islington-app · 2026-03-28T05:03:28Z

Sorry, @gpshead, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 1efe441de7c448852b9ba51fb0db4d355a7157a8 3.13

bedevere-app · 2026-03-28T05:03:32Z

GH-146552 is a backport of this pull request to the 3.14 branch.

…rocesses (GH-146005) (#146552) gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) Propagate all -X command line options to multiprocessing spawned child Python processes. (cherry picked from commit 1efe441) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>

bedevere-bot · 2026-03-28T05:53:10Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows Server 2022 NoGIL 3.x (tier-1) has failed when building commit 1efe441.

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Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\test\support\os_helper.py", line 524, in temp_dir
    os.mkdir(path)
    ~~~~~~~~^^^^^^
FileExistsError: [WinError 183] Cannot create a file when that file already exists: 'C:\\bbarea\\3.x.itamaro-win64-srv-22-aws.x64.nogil\\build\\build\\test_python_13292Ã¦'
Stack (most recent call last):
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\test\libregrtest\worker.py", line 141, in <module>
    main()
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\test\libregrtest\worker.py", line 136, in main
    with os_helper.temp_cwd(work_dir, quiet=True):
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\contextlib.py", line 141, in __enter__
    return next(self.gen)
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\test\support\os_helper.py", line 597, in temp_cwd
    with temp_dir(path=name, quiet=quiet) as temp_path:

bedevere-bot · 2026-03-28T05:58:08Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows PGO Tailcall 3.x (tier-1) has failed when building commit 1efe441.

What do you need to do:

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Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
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Failed tests:

test_profiling

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "C:\bbarea\3.x.itamaro-win64-srv-22-aws.tailcall.pgo\build\Lib\test\test_profiling\test_sampling_profiler\test_advanced.py", line 169, in test_native_frames_enabled
    self.assertFalse(any(stack.endswith(";<native>") for stack in stacks))
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: True is not false

bedevere-bot · 2026-03-28T06:10:10Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows Server 2022 NoGIL 3.14 (tier-1) has failed when building commit 28d3b9b.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1717/builds/1129) and take a look at the build logs.
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You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1717/builds/1129

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 11, done.        
remote: Counting objects:  10% (1/10)        
remote: Counting objects:  20% (2/10)        
remote: Counting objects:  30% (3/10)        
remote: Counting objects:  40% (4/10)        
remote: Counting objects:  50% (5/10)        
remote: Counting objects:  60% (6/10)        
remote: Counting objects:  70% (7/10)        
remote: Counting objects:  80% (8/10)        
remote: Counting objects:  90% (9/10)        
remote: Counting objects: 100% (10/10)        
remote: Counting objects: 100% (10/10), done.        
remote: Total 11 (delta 9), reused 9 (delta 9), pack-reused 1 (from 1)        
From https://github.com/python/cpython
 * branch                    3.14       -> FETCH_HEAD
Note: switching to '28d3b9bc56df6c2da3e898a0b7a066df5761b04d'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 28d3b9bc56d [3.14] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) (#146552)
Switched to and reset branch '3.14'

Could Not Find C:\bbarea\3.14.itamaro-win64-srv-22-aws.x64.nogil\build\Lib\*.pyc
The system cannot find the file specified.
Could Not Find C:\bbarea\3.14.itamaro-win64-srv-22-aws.x64.nogil\build\PCbuild\python*.zip

Could Not Find C:\bbarea\3.14.itamaro-win64-srv-22-aws.x64.nogil\build\PCbuild\python*.zip

bedevere-bot · 2026-03-28T06:15:31Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows10 3.x (tier-1) has failed when building commit 1efe441.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/146/builds/13440) and take a look at the build logs.
Check if the failure is related to this commit (1efe441) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/146/builds/13440

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\support\os_helper.py", line 524, in temp_dir
    os.mkdir(path)
    ~~~~~~~~^^^^^^
FileExistsError: [WinError 183] Cannot create a file when that file already exists: 'D:\\buildarea\\3.x.bolen-windows10\\build\\build\\test_python_1152Ã¦'
Stack (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\libregrtest\worker.py", line 141, in <module>
    main()
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\libregrtest\worker.py", line 136, in main
    with os_helper.temp_cwd(work_dir, quiet=True):
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\contextlib.py", line 141, in __enter__
    return next(self.gen)
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\support\os_helper.py", line 597, in temp_cwd
    with temp_dir(path=name, quiet=quiet) as temp_path:


Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\support\os_helper.py", line 524, in temp_dir
    os.mkdir(path)
    ~~~~~~~~^^^^^^
FileExistsError: [WinError 183] Cannot create a file when that file already exists: 'D:\\buildarea\\3.x.bolen-windows10\\build\\build\\test_python_11832Ã¦'
Stack (most recent call last):
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\libregrtest\worker.py", line 141, in <module>
    main()
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\libregrtest\worker.py", line 136, in main
    with os_helper.temp_cwd(work_dir, quiet=True):
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\contextlib.py", line 141, in __enter__
    return next(self.gen)
  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\support\os_helper.py", line 597, in temp_cwd
    with temp_dir(path=name, quiet=quiet) as temp_path:

bedevere-bot · 2026-03-28T06:20:22Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows11 Bigmem 3.x (tier-1) has failed when building commit 1efe441.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1079/builds/8289) and take a look at the build logs.
Check if the failure is related to this commit (1efe441) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1079/builds/8289

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 11, done.        
remote: Counting objects:  10% (1/10)        
remote: Counting objects:  20% (2/10)        
remote: Counting objects:  30% (3/10)        
remote: Counting objects:  40% (4/10)        
remote: Counting objects:  50% (5/10)        
remote: Counting objects:  60% (6/10)        
remote: Counting objects:  70% (7/10)        
remote: Counting objects:  80% (8/10)        
remote: Counting objects:  90% (9/10)        
remote: Counting objects: 100% (10/10)        
remote: Counting objects: 100% (10/10), done.        
remote: Compressing objects:  25% (1/4)        
remote: Compressing objects:  50% (2/4)        
remote: Compressing objects:  75% (3/4)        
remote: Compressing objects: 100% (4/4)        
remote: Compressing objects: 100% (4/4), done.        
remote: Total 11 (delta 6), reused 6 (delta 6), pack-reused 1 (from 1)        
From https://github.com/python/cpython
 * branch                    main       -> FETCH_HEAD
Note: switching to '1efe441de7c448852b9ba51fb0db4d355a7157a8'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 1efe441de7c gh-146004: propagate all -X options to multiprocessing child processes (GH-146005)
Switched to and reset branch 'main'

Could Not Find R:\buildarea\3.x.ambv-bb-win11.bigmem\build\Lib\*.pyc
The system cannot find the file specified.
Could Not Find R:\buildarea\3.x.ambv-bb-win11.bigmem\build\PCbuild\python*.zip

Could Not Find R:\buildarea\3.x.ambv-bb-win11.bigmem\build\PCbuild\python*.zip

bedevere-bot · 2026-03-28T06:50:44Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows10 3.14 (tier-1) has failed when building commit 28d3b9b.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1711/builds/890) and take a look at the build logs.
Check if the failure is related to this commit (28d3b9b) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1711/builds/890

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 11, done.        
remote: Counting objects:  14% (1/7)        
remote: Counting objects:  28% (2/7)        
remote: Counting objects:  42% (3/7)        
remote: Counting objects:  57% (4/7)        
remote: Counting objects:  71% (5/7)        
remote: Counting objects:  85% (6/7)        
remote: Counting objects: 100% (7/7)        
remote: Counting objects: 100% (7/7), done.        
remote: Total 11 (delta 7), reused 7 (delta 7), pack-reused 4 (from 2)        
From https://github.com/python/cpython
 * branch                    3.14       -> FETCH_HEAD
Note: switching to '28d3b9bc56df6c2da3e898a0b7a066df5761b04d'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 28d3b9bc56d [3.14] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) (#146552)
Switched to and reset branch '3.14'

Could Not Find D:\buildarea\3.14.bolen-windows10\build\Lib\*.pyc
The system cannot find the file specified.
Could Not Find D:\buildarea\3.14.bolen-windows10\build\PCbuild\python*.zip

Could Not Find D:\buildarea\3.14.bolen-windows10\build\PCbuild\python*.zip

vstinner · 2026-03-28T09:03:17Z

test_support fails on Windows buildbots:

Warning -- files was modified by test_support
Warning --   Before: []
Warning --   After:  ['tmp/']

I don't see the relationship with the change.

bedevere-bot · 2026-03-28T11:58:43Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows11 Non-Debug 3.14 (tier-1) has failed when building commit 28d3b9b.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1684/builds/511) and take a look at the build logs.
Check if the failure is related to this commit (28d3b9b) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1684/builds/511

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 16, done.        
remote: Counting objects:  12% (1/8)        
remote: Counting objects:  25% (2/8)        
remote: Counting objects:  37% (3/8)        
remote: Counting objects:  50% (4/8)        
remote: Counting objects:  62% (5/8)        
remote: Counting objects:  75% (6/8)        
remote: Counting objects:  87% (7/8)        
remote: Counting objects: 100% (8/8)        
remote: Counting objects: 100% (8/8), done.        
remote: Total 16 (delta 7), reused 7 (delta 7), pack-reused 8 (from 3)        
From https://github.com/python/cpython
 * branch                    3.14       -> FETCH_HEAD
Note: switching to '28d3b9bc56df6c2da3e898a0b7a066df5761b04d'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 28d3b9bc56d [3.14] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) (#146552)
Switched to and reset branch '3.14'

Could Not Find b:\uildarea\3.14.ware-win11.nondebug\build\Lib\*.pyc
The system cannot find the file specified.
Could Not Find b:\uildarea\3.14.ware-win11.nondebug\build\PCbuild\python*.zip

Could Not Find b:\uildarea\3.14.ware-win11.nondebug\build\PCbuild\python*.zip

picnixz · 2026-03-28T12:52:41Z

I think the problem is ['-X', 'pycache_prefix=/tmp/pycache']. We should use another temporary folder here.

(The problem is likely because we are using / on Windows platforms)

chris-eibl · 2026-03-28T15:47:19Z

I suggest using tempfile.gettempdir().

picnixz · 2026-03-28T15:59:28Z

I suggest just using test.support's temporary directory instead (a fresh one). It doesn't matter that we use a real OS-tempdir

gpshead · 2026-03-28T17:04:17Z

I won't be able to get to this today. That makes sense as a fix.

picnixz · 2026-03-28T17:08:08Z

No worries! Chris handled it already: #146580

chris-eibl · 2026-03-28T18:42:09Z

Lib/test/test_support.py

            ['-X', 'dev'],
            ['-Wignore', '-X', 'dev'],
+            ['-X', 'cpu_count=4'],
+            ['-X', 'disable-remote-debug'],


This is documented as

-X disable_remote_debug

with underscores.

Furthermore, -X presite=package.module, -X gil=0,1 and some more aren't listed here.

Not a big issue IMHO, since this just tests that whatever we pass in is returned from args_from_interpreter_flags?

So an alternative fix for #146580 would be to just remove ['-X', 'pycache_prefix=/tmp/pycache'],?

Sorry, didn't realize earlier, just stumbled over it now ...

pythongh-146004: propagate all -X options to subprocesses

6a115f0

bedevere-app bot mentioned this pull request Mar 16, 2026

recent -X options do not auto-propagate to multiprocessing processes #146004

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gpshead self-assigned this Mar 16, 2026

vstinner approved these changes Mar 27, 2026

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bedevere-app bot added the awaiting merge label Mar 27, 2026

gpshead marked this pull request as ready for review March 28, 2026 04:32

bedevere-app bot added awaiting core review and removed awaiting merge labels Mar 28, 2026

Merge branch 'main' into propagate-x-options-gh146004

d203b40

gpshead enabled auto-merge (squash) March 28, 2026 04:37

gpshead added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Mar 28, 2026

gpshead merged commit 1efe441 into python:main Mar 28, 2026
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bedevere-app bot removed the awaiting core review label Mar 28, 2026

bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label Mar 28, 2026

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chris-eibl Mar 28, 2026

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gpshead commented Mar 16, 2026 •

edited by bedevere-app bot

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picnixz commented Mar 28, 2026 •

edited

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picnixz commented Mar 28, 2026 •

edited

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