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gh-141671: PyMODINIT_FUNC: apply`__declspec(dllexport)` on Windows#141672

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encukou merged 11 commits intopython:mainfromencukou:pymodexport-always-export

Jan 7, 2026

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gh-141671: PyMODINIT_FUNC: apply`__declspec(dllexport)` on Windows#141672

encukou merged 11 commits intopython:mainfromencukou:pymodexport-always-export

Jan 7, 2026

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encukou commentedNov 17, 2025•
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Issue:PyMODINIT_FUNC does not apply__declspec(dllexport) on Windows #141671

encukou added2 commits

November 17, 2025 17:42

pythongh-141671: Use __declspec(dllexport) when not building core

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encukou requested a review fromzooba

November 17, 2025 16:48

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Nov 17, 2025

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Nov 17, 2025

PyMODINIT_FUNC does not apply__declspec(dllexport) on Windows#141671

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encukou mentioned this pull request

Nov 17, 2025

Implement PEP 793 – PyModExport#140550

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encukou commentedNov 17, 2025•
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cc@jaraco /@pfmoore: what are your thoughts on removing/EXPORT from setuptools/distutils on Python 3.15+?

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Nov 17, 2025

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Include/exports.h Outdated


		#if defined(_WIN32) \|\| defined(__CYGWIN__)
		#if defined(Py_ENABLE_SHARED)
		#if!defined(Py_BUILD_CORE) \|\|defined(Py_ENABLE_SHARED)

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I'm not 100% sure about this... don't we need it for our own exports?

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Only forPy_ENABLE_SHARED -- see#99888 that added the#else.

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Ah, I see we do these checks again everywhere else we use the macros. No problem them.

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pfmoore commentedNov 17, 2025

TBH, I have no view. My knowledge of C is very out of date, so I wouldn't trust anything I might say anyway...

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da-woods commentedNov 18, 2025•
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The/EXPORT from setuptools has definitely caused Cython an amount of pain before (although some of that was self-inflicted....). It'd be nice not to have to definePyInit_ just to to make the name exist. Although I suspect we can't really avoid it in a realistic timeline.

(Edit: admittedly we also aren't the people that it's designed to help either)

encukou added8 commits

November 18, 2025 11:07

Use _PyINIT_EXPORTED_SYMBOL

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Use__declspec(dllexport) outside core

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Allow embedders to customize

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Remove duplication with defaults

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Remove duplication with default

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Reduce diff

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Merge in the main branch

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Link macro that's now documented

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encukou commentedDec 16, 2025

Here's a version that removes some redundant defines (setting things to defaults).

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Dec 17, 2025

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LGTM. This change mostly moves code around, and just add__declspec(dllexport) on Windows.

Include/exports.h


		#define PyMODINIT_FUNC _PyINIT_FUNC_DECLSPEC PyObject*
		#define PyMODEXPORT_FUNC _PyINIT_FUNC_DECLSPEC PyModuleDef_Slot*
		#ifndef PyMODINIT_FUNC

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vstinnerDec 17, 2025

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Supporting an already defined PyMODINIT_FUNC/PyMODEXPORT_FUNC is a new feature. Is it really worth it? I'm not against it, just curious.

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encukouDec 17, 2025

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It's an escape hatch: if there's an unexpected problem with this PR, this can allow people to hotfix it without patching or waiting for a new release.

bedevere-appbot added awaiting merge and removed awaiting core review labels

Dec 17, 2025

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

Dec 19, 2025

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bedevere-bot commentedDec 19, 2025

🤖 New build scheduled with the buildbot fleet by@encukou for commit5091b79 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F141672%2Fmerge

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AraHaan reviewed

Dec 29, 2025

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Include/exports.h

		#if defined(Py_BUILD_CORE)
		#define _PyINIT_EXPORTED_SYMBOL Py_EXPORTED_SYMBOL
		#else
		#define _PyINIT_EXPORTED_SYMBOL __declspec(dllexport)

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AraHaanDec 29, 2025

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I think a better option instead is to definePy_EXPORTED_SYMBOL here and then use that.

Also I feel like an escape hatch likePy_EMBED_MODULE where it basically usesPy_LOCAL_SYMBOL instead could be an option as well for when one does not want the module init function exported due to intending to usePyImport_AppendInitTab within the exe that they directly build the module into.