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gh-143304: Fix ctypes.CDLL to honor handle parameter on POSIX systems #143318

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Merged
encukou merged 7 commits into from
Feb 24, 2026
Merged

gh-143304: Fix ctypes.CDLL to honor handle parameter on POSIX systems #143318

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8634db5
Fix ctypes.CDLL to honor handle parameter on POSIX systems
Koolvansh07 Dec 31, 2025
bb4c92e
Add NEWS entry for gh-143304
Koolvansh07 Dec 31, 2025
d8b9ed3
Address review feedback
Koolvansh07 Jan 1, 2026
32eb34d
Move handle check to beginning to avoid unnecessary computation
Koolvansh07 Jan 1, 2026
6d95eff
Remove debug files that were accidentally committed
Koolvansh07 Jan 1, 2026
d3f65b6
Move handle check to end of function as suggested by reviewer
Koolvansh07 Jan 1, 2026
cdb8f6e
Update test assertion to match (actual, expected) convention
Koolvansh07 Jan 1, 2026
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Fix ctypes.CDLL to honor handle parameter on POSIX systems 
The handle parameter was being ignored in the POSIX implementation
of CDLL._load_library(), causing it to always call _dlopen() even
when a valid handle was provided. This was a regression introduced
in recent refactoring.

This commit adds the missing handle check to match the Windows
implementation behavior, and includes a regression test.

Fixes gh-143304
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@Koolvansh07
Koolvansh07 committed Dec 31, 2025
commit 8634db59e345563daa3566ab72bb0dbcd61724d9
2 changes: 2 additions & 0 deletions Lib/ctypes/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -458,6 +458,8 @@ def _load_library(self, name, mode, handle, winmode):
if name and name.endswith(")") and ".a(" in name:
mode |= _os.RTLD_MEMBER | _os.RTLD_NOW
self._name = name
if handle is not None:
return handle
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return _dlopen(name, mode)

def __repr__(self):
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14 changes: 14 additions & 0 deletions Lib/test/test_ctypes/test_loading.py
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Expand Up @@ -106,6 +106,20 @@ def test_load_without_name_and_with_handle(self):
lib = ctypes.WinDLL(name=None, handle=handle)
self.assertIs(handle, lib._handle)

@unittest.skipIf(os.name == "nt", 'POSIX-specific test')
def test_load_without_name_and_with_handle_posix(self):
# Test that CDLL honors the handle parameter on POSIX systems
# This is a regression test for gh-143304
if libc_name is None:
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self.skipTest('could not find libc')
# First load a library normally to get a handle
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lib1 = CDLL(libc_name)
handle = lib1._handle
# Now create a new CDLL instance with the same handle
lib2 = CDLL(name=None, handle=handle)
# The handle should be used directly, not ignored
self.assertIs(handle, lib2._handle)
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@picnixz picnixz Jan 1, 2026

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Suggested change
self.assertIs(handle, lib2._handle)
self.assertIs(lib2._handle, handle)

Can you check whether there were tests for Python 3.12 where we had this handle? or if the tests were rewritten as well (see the PRs mentioned on the issue).

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@Koolvansh07 Koolvansh07 Jan 1, 2026

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I checked the 3.12 branch source code:

  1. Lib/ctypes/__init__.py in 3.12 DID support the handle parameter (it checked if handle is None:).
    1. Lib/test/test_ctypes/test_loading.py in 3.12 DID NOT have any test using CDLL(..., handle=...) on POSIX.

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Ok thx!


@unittest.skipUnless(os.name == "nt", 'Windows-specific test')
def test_1703286_A(self):
# On winXP 64-bit, advapi32 loads at an address that does
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