https://github.com/python/cpython/commit/f610e8cc7f0c9687d01592a08c78326351c6264d
commit: f610e8cc7f0c9687d01592a08c78326351c6264d
branch: main
author: Petr Viktorin <[email protected]>
committer: encukou <[email protected]>
date: 2026-10-02T15:34:44+02:00
summary:
gh-158098: Add Setuptools workaround to abi3t migration guide (#158405)
files:
M Doc/howto/abi3t-migration.rst
diff --git a/Doc/howto/abi3t-migration.rst b/Doc/howto/abi3t-migration.rst
index ec78a33ed25820e..501106679b02bd9 100644
--- a/Doc/howto/abi3t-migration.rst
+++ b/Doc/howto/abi3t-migration.rst
@@ -217,9 +217,9 @@ Module export hook
Unless you've done this step already, your extension module defines a
:ref:`module initialization function <extension-pyinit>`
-named :samp:`PyInit_{<module_name>}`.
+named :samp:`PyInit_{<modname>}` (where ``modname`` is the name of your
module).
You will need to port it to a :ref:`module export hook
<extension-export-hook>`,
-:samp:`PyModExport_{<module name>}`, a feature added in CPython 3.15 in
+:samp:`PyModExport_{<modname>}`, a feature added in CPython 3.15 in
:pep:`793`.
Your existing init function should look like this (with your own names
@@ -297,6 +297,34 @@ pointer to static data.
If you cannot avoid additional code, refer to the
:ref:`caveats in PyModExport documentation <pymodexport-api-caveats>`.
+.. note::
+
+ When building for Windows using the Setuptools_ build tool,
+ removing the :samp:`PyInit_{<modname>}` function may result in the linker
error
+ :samp:`LINK : error LNK2001: unresolved external symbol PyInit_{<modname>}`.
+ This is caused by Setuptools passing an ``/EXPORT`` linker flag, which
+ is redundant since Python 3.15 (see :gh:`141671`).
+ A workaround is to add a dummy :samp:`PyInit_{<modname>}` function
+ to your code.
+ Python 3.15+ will never call this function if
+ :samp:`PyModExport_{<modname>}` is present, so it can always fail:
+
+ .. code-block:: c
+
+ // Workaround for https://github.com/pypa/distutils/issues/387
+ PyMODINIT_FUNC
+ PyInit_<modname>(void)
+ {
+ PyErr_SetString(PyExc_SystemError,
+ "PyInit_* called for module with PyModExport_*");
+ return NULL;
+ }
+
+ (This issue is present in Setuptools 84.0.0; it might be fixed in newer
+ versions.)
+
+.. _Setuptools: https://setuptools.pypa.io/
+
Existing slots
--------------
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