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GeezerVison is showing github.com — gh-155561: Use multi-phase init for Modules/_testlimitedcapi.c by encukou · Pull Request #156052 · python/cpython

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encukou commented Aug 19, 2026 •

edited by bedevere-app Bot

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This is a continuation of #155693

We can't use PyModExport for modules that might be in inittab, but we can move to multi-phase init.

Issue: C API: Enable limited C API tests on Free Threading #155561

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vstinner and others added 5 commits

August 13, 2026 12:36


          pythongh-155561: Use PySlot API in Modules/_testlimitedcapi.c

a11419e


          Merge branch 'main' into limited_pyslot

37a19de


          Add missing _PyTestLimitedCAPI_Init_Type() call

27c121d


          Use multi-phase init, but still with a PyModuleDef

bca539b


          Merge in the main branch

08e4a85

encukou requested a review from vstinner

August 19, 2026 12:39

bedevere-app Bot added tests

Tests in the Lib/test dir

awaiting core review labels

Aug 19, 2026

bedevere-app Bot mentioned this pull request

Aug 19, 2026

C API: Enable limited C API tests on Free Threading #155561

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vstinner commented Aug 31, 2026

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According to CIs, building _testlimitedcapi fails on Free Threading:

./Modules/_testlimitedcapi.c:103:5: error: use of undeclared identifier 'PyModuleDef_HEAD_INIT'
  103 |     PyModuleDef_HEAD_INIT,
      |     ^~~~~~~~~~~~~~~~~~~~~
./Modules/_testlimitedcapi.c:102:27: error: variable has incomplete type 'struct PyModuleDef'
  102 | static struct PyModuleDef _testlimitedcapimodule_def = {
      |                           ^
./Include/pytypedefs.h:12:16: note: forward declaration of 'struct PyModuleDef'
   12 | typedef struct PyModuleDef PyModuleDef;
      |                ^
2 errors generated.

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vstinner reviewed

Aug 31, 2026

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Modules/_testlimitedcapi.c Outdated

		// Use the oldest limited C API version
		# define Py_LIMITED_API 0x03020000
		#endif
		// Need limited C API version 3.15 for PySlot

vstinner Aug 31, 2026

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PySlot is not used. I suppose that this comment is outdated.

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encukou added 3 commits

September 3, 2026 13:06


          Restore the Py_GIL_DISABLED check


          Remove the #ifdef in .c file; rely on the one in parts.h

241876f


          Merge in the main branch

05ace4c

encukou added the skip news label

Sep 3, 2026


          Add Py_MOD_GIL_NOT_USED for noGIL

009ce74

encukou added the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label

Sep 3, 2026

bedevere-bot commented Sep 3, 2026

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🤖 New build scheduled with the buildbot fleet by @encukou for commit 009ce74 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F156052%2Fmerge

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

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bedevere-bot removed the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label

Sep 3, 2026

vstinner commented Sep 3, 2026

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The Alpine Linux buildbot failure looks like a legit bug, but it's unrelated to this change:

  /usr/lib/ccache/bin/g++ -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fno-strict-overflow -Wsign-compare -g -Og -Wall -fPIC -I/buildbot/buildarea/pull_request.ware-alpine.nogil/build/build/test_python_92877æ/tempcwd/env/include -I/buildbot/buildarea/pull_request.ware-alpine.nogil/build/Include -I/buildbot/buildarea/pull_request.ware-alpine.nogil/build -c extension.cpp -o build/temp.linux-x86_64-cpython-316t-pydebug/extension.o -Werror -DMODULE_NAME=_testcppext_internal -DTEST_INTERNAL_C_API=1
  In file included from /buildbot/buildarea/pull_request.ware-alpine.nogil/build/Include/internal/pycore_object.h:13,
                   from /buildbot/buildarea/pull_request.ware-alpine.nogil/build/Include/internal/pycore_cell.h:5,
                   from extension.cpp:29:
  /buildbot/buildarea/pull_request.ware-alpine.nogil/build/Include/internal/pycore_interpframe.h: In function 'PyFrameObject* _PyFrame_GetFrameObject(_PyInterpreterFrame*)':
  /buildbot/buildarea/pull_request.ware-alpine.nogil/build/Include/internal/pycore_pyatomic_ft_wrappers.h:33:32: error: invalid conversion from 'void*' to 'PyFrameObject*' {aka '_frame*'} [-fpermissive]
     33 |     _Py_atomic_load_ptr_acquire(&value)
        |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
        |                                |
        |                                void*
  /buildbot/buildarea/pull_request.ware-alpine.nogil/build/Include/internal/pycore_interpframe.h:348:26: note: in expansion of macro 'FT_ATOMIC_LOAD_PTR_ACQUIRE'
    348 |     PyFrameObject *res = FT_ATOMIC_LOAD_PTR_ACQUIRE(frame->frame_obj);
        |                          ^~~~~~~~~~~~~~~~~~~~~~~~~~
  error: command '/usr/lib/ccache/bin/g++' failed with exit code 1

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vstinner commented Sep 3, 2026

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The Alpine Linux buildbot failure looks like a legit bug, but it's unrelated to this change:

Ah, in fact the AMD64 Alpine Linux NoGIL 3.x buildbot already fails on the main branch: I wrote PR gh-156893 to fix the issue.

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vstinner commented Sep 3, 2026

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The "buildbot/AMD64 CentOS9 NoGIL PR" failure is the same as the Alpine Linux issue: test_cppext fails, so PR #156893 will fix it.

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vstinner approved these changes

Sep 3, 2026

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LGTM.

This change doesn't build Modules/_testlimitedcapi.c with the limited C API on Free Threading yet, but it converts the module to multi-phase init which is already a good step forwards!

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bedevere-app Bot added awaiting merge and removed awaiting core review labels

Sep 3, 2026

encukou merged commit 112560e into python:main

Sep 4, 2026

132 of 136 checks passed

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bedevere-app Bot removed the awaiting merge label

Sep 4, 2026

encukou deleted the limited_pyslot branch

September 4, 2026 10:35

encukou mentioned this pull request

Sep 4, 2026

gh-155561: Use PySlot API in Modules/_testlimitedcapi.c #155693

Closed

clin1234 pushed a commit to clin1234/cpython that referenced this pull request

Sep 12, 2026


          pythongh-155561: Use multi-phase init for Modules/_testlimitedcapi.c (p…

e58d344

…ythonGH-156052)

Co-authored-by: Victor Stinner <[email protected]>

vstinner added a commit that referenced this pull request

Oct 10, 2026


          [3.15] gh-155561: Build most _testlimitedcapi files with Py_TARGET_AB…

72d25d5

…I3T (#155570) (#159144)

* gh-155561: Build most _testlimitedcapi files with Py_TARGET_ABI3T (#155570)

The following files are not build with Py_TARGET_ABI3T:

* Modules/_testlimitedcapi.c
* Modules/_testlimitedcapi/heaptype_relative.c
* Modules/_testlimitedcapi/vectorcall_limited.c

(cherry picked from commit 5dfa606)

* gh-155561: Use multi-phase init for Modules/_testlimitedcapi.c (GH-156052)

Co-authored-by: Victor Stinner <[email protected]>
(cherry picked from commit 112560e)

---------

Co-authored-by: Petr Viktorin <[email protected]>

vstinner added the needs backport to 3.15 bugs and security fixes label

Oct 13, 2026

miss-islington-app Bot commented Oct 13, 2026

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Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

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miss-islington-app Bot commented Oct 13, 2026

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Sorry, @encukou, I could not cleanly backport this to 3.15 due to a conflict.

Please backport manually with cherry_picker, see the devguide for more information.

cherry_picker 112560ee34a70c02baebdc11519d1f77e90ecab8 3.15

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miss-islington-app Bot assigned encukou

Oct 13, 2026

vstinner removed the needs backport to 3.15 bugs and security fixes label

Oct 13, 2026

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encukou commented Aug 19, 2026 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

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encukou commented Aug 19, 2026 •

edited by bedevere-app Bot

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