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GeezerVison is showing github.com — gh-149879: Fix multiprocessing tests on Cygwin by vstinner · Pull Request #149999 · python/cpython

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@vstinner

@vstinner vstinner commented May 18, 2026 •
edited by bedevere-app Bot
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  • Disable fork and forkserver start methods on Cygwin
  • Disable AF_UNIX connection family on Cygwin
  • Issue: Enhance Cygwin support #149879

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@vstinner
pythongh-149879: Fix multiprocessing tests on Cygwin
8ba561c
* Disable fork and forkserver start methods on Cygwin
* Disable AF_UNIX connection family on Cygwin
@vstinner vstinner added the skip news label May 18, 2026
@bedevere-app bedevere-app Bot mentioned this pull request May 18, 2026
Enhance Cygwin support #149879
Closed
@vstinner

vstinner commented May 18, 2026

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Two test_multiprocessing_spawn.test_misc tests are still failing and requires more investigation:

  • FAIL: test_resource_tracker_sigterm (test.test_multiprocessing_spawn.test_misc.TestResourceTracker.test_resource_tracker_sigterm)
    test.test_multiprocessing_spawn.test_processes
  • FAIL: test_wait_result (test.test_multiprocessing_spawn.test_processes.WithProcessesTestCondition.test_wait_result)
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@vstinner
Enable more more tests on Cygwin
a451d96
@vstinner
vstinner marked this pull request as ready for review May 18, 2026 20:37
@vstinner
vstinner requested review from gpshead and vsajip as code owners May 18, 2026 20:37
@bedevere-app bedevere-app Bot added the awaiting core review label May 18, 2026
@vstinner

vstinner commented May 18, 2026

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The forkserver start method requires multiprocessing.reduction.HAVE_SEND_HANDLE which is False on Cygwin:

HAVE_SEND_HANDLE = (sys.platform == 'win32' or
                    (hasattr(socket, 'CMSG_LEN') and
                     hasattr(socket, 'SCM_RIGHTS') and
                     hasattr(socket.socket, 'sendmsg')))

I disabled SCM_RIGHTS and sendmsg() in the socket module on Cygwn.

The "win32" implementation uses the _winapi extension which is not available on Cygwin.

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@vstinner

vstinner commented May 18, 2026

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Disable fork and forkserver start methods on Cygwin

I tested again and in fact, it's possible to support the fork start method on Cygwin. I close this PR and I wrote PR gh-150031 instead.

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@vstinner vstinner closed this May 18, 2026
@vstinner
vstinner deleted the mp_cygwin branch May 18, 2026 22:02
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@gpshead gpshead Awaiting requested review from gpshead gpshead is a code owner
@vsajip vsajip Awaiting requested review from vsajip vsajip is a code owner

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@vstinner
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