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gh-156062: Fix SynchronizedBase instantiation without a lock or a ctx #156063

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gh-156062: Fix SynchronizedBase instantiation without a lock or a ctx #156063

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2 changes: 1 addition & 1 deletion Lib/multiprocessing/sharedctypes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,7 @@ def __init__(self, obj, lock=None, ctx=None):
if lock:
self._lock = lock
else:
ctx = ctx or get_context(force=True)
ctx = ctx or get_context()
self._lock = ctx.RLock()
self.acquire = self._lock.acquire
self.release = self._lock.release
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19 changes: 19 additions & 0 deletions Lib/test/_test_multiprocessing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4628,6 +4628,25 @@ def test_sharedctypes(self, lock=False):
def test_synchronize(self):
self.test_sharedctypes(lock=True)

def test_synchronized_wrapper_default_context(self):
# gh-156062: SynchronizedBase used to call get_context() with an
# unexpected argument when neither a lock nor a context was given,
# so the wrapper classes could not be instantiated directly.
from multiprocessing.sharedctypes import (
RawValue, RawArray,
Synchronized, SynchronizedArray, SynchronizedString,
)
for wrapper, obj in [
(Synchronized, RawValue('i', 7)),
(SynchronizedArray, RawArray('d', [1.0, 2.0])),
(SynchronizedString, RawArray('c', 8)),
]:
with self.subTest(wrapper=wrapper.__name__):
wrapped = wrapper(obj)
self.assertIs(wrapped.get_obj(), obj)
with wrapped:
pass

def test_copy(self):
foo = _Foo(2, 5.0, 2 ** 33)
bar = copy(foo)
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-08-19-17-31-12.gh-issue-156062.-nTriK.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix :class:`!multiprocessing.sharedctypes.SynchronizedBase` and its subclasses
raising :exc:`TypeError` when instantiated without a *lock* or a *ctx*
argument: they called :func:`multiprocessing.get_context` with an
unsupported ``force`` argument.
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