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[3.14] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) #146552

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Merged
gpshead merged 1 commit into from
Mar 28, 2026
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[3.14] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) #146552

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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>
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@gpshead @miss-islington
gpshead authored and miss-islington committed Mar 28, 2026
commit 6919dddb2d5c09ee3698b645653302d62a9bcef8
19 changes: 10 additions & 9 deletions Lib/subprocess.py
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Original file line number Diff line number Diff line change
Expand Up @@ -351,15 +351,16 @@ def _args_from_interpreter_flags():
# -X options
if dev_mode:
args.extend(('-X', 'dev'))
for opt in ('faulthandler', 'tracemalloc', 'importtime',
'frozen_modules', 'showrefcount', 'utf8', 'gil'):
if opt in xoptions:
value = xoptions[opt]
if value is True:
arg = opt
else:
arg = '%s=%s' % (opt, value)
args.extend(('-X', arg))
for opt in sorted(xoptions):
if opt == 'dev':
# handled above via sys.flags.dev_mode
continue
value = xoptions[opt]
if value is True:
arg = opt
else:
arg = '%s=%s' % (opt, value)
args.extend(('-X', arg))

return args

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7 changes: 7 additions & 0 deletions Lib/test/test_support.py
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Expand Up @@ -559,12 +559,19 @@ def test_args_from_interpreter_flags(self):
# -X options
['-X', 'dev'],
['-Wignore', '-X', 'dev'],
['-X', 'cpu_count=4'],
['-X', 'disable-remote-debug'],
['-X', 'faulthandler'],
['-X', 'importtime'],
['-X', 'importtime=2'],
['-X', 'int_max_str_digits=1000'],
['-X', 'lazy_imports=all'],
['-X', 'no_debug_ranges'],
['-X', 'pycache_prefix=/tmp/pycache'],
['-X', 'showrefcount'],
['-X', 'tracemalloc'],
['-X', 'tracemalloc=3'],
['-X', 'warn_default_encoding'],
):
with self.subTest(opts=opts):
self.check_options(opts, 'args_from_interpreter_flags')
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9 changes: 9 additions & 0 deletions Misc/NEWS.d/next/Library/2026-03-16-00-00-00.gh-issue-146004.xOptProp.rst
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@@ -0,0 +1,9 @@
All :option:`-X` options from the Python command line are now propagated to
child processes spawned by :mod:`multiprocessing`, not just a hard-coded
subset. This makes the behavior consistent between default "spawn" and
"forkserver" start methods and the old "fork" start method. The options
that were previously not propagated are: ``context_aware_warnings``,
``cpu_count``, ``disable-remote-debug``, ``int_max_str_digits``,
``lazy_imports``, ``no_debug_ranges``, ``pathconfig_warnings``, ``perf``,
``perf_jit``, ``presite``, ``pycache_prefix``, ``thread_inherit_context``,
and ``warn_default_encoding``.
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