gh-110014: Fix inconsistent struct definition in pycore_semaphore.h

[colesbury]

The pycore_semaphore.h header is included by Python/lock.c and Python/parking_lot.c. The macro _POSIX_SEMAPHORES was not consistently defined across the two files (due to a missing include of <unistd.h>) leading to different struct definitions. The RHEL8 ppc64le LTO buildbot correctly warned due to this issue.

• Issue: GCC warnings on pycore_semaphore.h and Python/parking_lot.c #110014

[colesbury]

!buildbot ppc64le

[bedevere-bot]

The regex 'ppc64le' did not match any buildbot builder.Is the requested builder in the list of stable builders?

[colesbury]

!buildbot lto

[bedevere-bot]

The regex 'lto' did not match any buildbot builder.Is the requested builder in the list of stable builders?

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @colesbury for commit 6e0228b 🤖

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[colesbury]

1. I verified locally that pycore_semaphore.h now consistently defines _PySemaphore (by temporarily added #warning)
2. https://buildbot.python.org/all/#/builders/256/builds/1238 (ppc64, lto) does not have any warnings related to pycore_semaphore.h. It's not identical to the buildbot running on the main branch, but it's the closest configuration I could find for PRs.

[vstinner]

The regex 'ppc64le' did not match any buildbot builder.Is the requested builder in the list of stable builders?

Oh, maybe the search is case sensitive and you should use PPC64LE or PPC64LE RHEL8.

[colesbury]

!buildbot PPC64LE

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @colesbury for commit 6e0228b 🤖

The command will test the builders whose names match following regular expression: PPC64LE

The builders matched are:

• PPC64LE Fedora Stable LTO + PGO PR
• PPC64LE RHEL8 PR
• PPC64LE RHEL7 Refleaks PR
• PPC64LE RHEL7 LTO + PGO PR
• PPC64LE RHEL8 LTO + PGO PR
• PPC64LE Fedora Stable Clang Installed PR
• PPC64LE Fedora Stable LTO PR
• PPC64LE RHEL7 PR
• PPC64LE Fedora Stable PR
• PPC64LE Fedora Stable Refleaks PR
• PPC64LE RHEL7 LTO PR
• PPC64LE RHEL8 Refleaks PR
• PPC64LE Fedora Stable Clang PR
• PPC64LE RHEL8 LTO PR

[vstinner]

Oh, maybe the search is case sensitive and you should use PPC64LE or PPC64LE RHEL8.

I wrote python/buildmaster-config#409 to make the search ignores the case.

I got bitten multiple times by the !buildbot command which said nothing. So I added the "The regex 'lto' did not match any buildbot builder.Is the requested builder in the list of stable builders?" message (I just added the missing space ;-)).

[colesbury]

Thanks!

[colesbury]

@vstinner, would you please review this when you get a chance?

[vstinner]

Oh wait. The problem is way wider than pycore_semaphore.h! _POSIX_THREADS and _POSIX_SEMAPHORES macros are checked in Python/pthread_thread.h, pycore_condvar.h. and pycore_pythread.h without explicitly including <unistd.h>.

I wrote a wider change to attempt to fix all cases: PR gh-110139.

[vstinner]

I wrote a more complete fix: PR #110139. Thanks for working on fixing these warnings!