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gh-140729: profiling or tracing multiprocessing can cause error #141874

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4250035
fix: profiling or tracing multiprocessing can cause error
yihong0618 Nov 23, 2025
c217303
fix: add news
yihong0618 Nov 23, 2025
d4f4615
fix: news format
yihong0618 Nov 23, 2025
50dec2f
fix: skip these tests on windows
yihong0618 Nov 23, 2025
a8a26da
fix: only fix cProfile
yihong0618 Dec 3, 2025
dbf6e55
fix: forget to delete lines
yihong0618 Dec 3, 2025
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2 changes: 1 addition & 1 deletion Lib/profiling/tracing/__init__.py
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Expand Up@@ -197,7 +197,7 @@ def main():
# in the module's namespace.
globs = module.__dict__
globs.update({
'__spec__': spec,
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@YvesDupYvesDupDec 1, 2025•
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By removing spec value to the __spec__key, does the comment above still apppropriate ?
Should not we replace it here with a reference to the issue and @gaogaotiantian original fix ?

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@gaogaotiantiangaogaotiantianDec 3, 2025

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So my original "source" is https://docs.python.org/3/reference/import.html#module-specs - where it says the __main__ module normally sets __spec__ to None. But it's for my individual project so as long as it works it's fine. Not sure about the very accurate and official answer.

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@yihong0618yihong0618Dec 3, 2025

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By removing spec value to the __spec__key, does the comment above still apppropriate ? Should not we replace it here with a reference to the issue and @gaogaotiantian original fix ?

remove is not right still fail...we the right is set it to None

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@YvesDupYvesDupDec 3, 2025•
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remove is not right still fail...we the right is set it to None

You are right.

How about adding a comment such as:
See gh-140729: set None to __spec__ according to the documentation (https://docs.python.org/3/reference/import.html#module-specs)

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@yihong0618yihong0618Dec 3, 2025

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the original fixed from gaotian do not add it, I follow it style~

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@YvesDupYvesDupDec 5, 2025

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Such a shame, add a comment might be helpful.

'__spec__': None,
'__file__': spec.origin,
'__name__': spec.name,
'__package__': None,
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37 changes: 37 additions & 0 deletions Lib/test/test_profiling/test_tracing_profiler.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,12 +2,14 @@

import sys
import unittest
import subprocess

# rip off all interesting stuff from test_profile
import profiling.tracing as cProfile
import tempfile
import textwrap
from test.test_profile import ProfileTest, regenerate_expected_output
from test.support import script_helper, os_helper, SHORT_TIMEOUT
from test.support.script_helper import assert_python_failure, assert_python_ok
from test import support

Expand DownExpand Up@@ -170,6 +172,41 @@ class Foo:
f.close()
assert_python_ok('-m', "cProfile", f.name)

@unittest.skipIf(sys.platform == 'win32',
'Profiler with multiprocessing can not run on win32')
def test_profile_multiprocessing(self):
test_script = '''
import multiprocessing

def worker_proc(x):
return x * 42

def main_proc():
p = multiprocessing.Process(target=worker_proc, args=(10,))
p.start()
p.join()
print("SUCCESS")

if __name__ == "__main__":
main_proc()
'''
with os_helper.temp_dir() as temp_dir:
script = script_helper.make_script(
temp_dir, 'test_cprofile_multiprocessing', test_script
)
with script_helper.spawn_python(
"-m", "cProfile",
script,
stderr=subprocess.PIPE,
text=True
) as proc:
proc.wait(timeout=SHORT_TIMEOUT)
stdout = proc.stdout.read()
stderr = proc.stderr.read()

self.assertIn("SUCCESS", stdout)
self.assertNotIn("has no attribute \'worker_proc\'", stderr)


def main():
if '-r' not in sys.argv:
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2025-11-23-19-06-41.gh-issue-140729.bk_HDs.rst
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
Set ``__main__.__spec__`` to ``None`` when running a script with :mod:`cProfile`
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