Target Stable ABI on free-threaded Python 3.15+

.github/workflows/python.yml

@@ -135,9 +135,10 @@ jobs:
         fi
         mkdir -p "artifacts/whl/${{ needs.pre-commit.outputs.dist-base }}"
         mv dist/* "artifacts/whl/${{ needs.pre-commit.outputs.dist-base }}"
-        # from system builds, save version-specific wheels and oldest abi3 wheel
+        # from system builds, save version-specific wheels, oldest abi3 wheel,
+        # and oldest abi3.abi3t wheel
         python -c 'import sys, sysconfig
-        if "${{ matrix.openslide }}" == "system" and (sys.version_info < (3, 12) or sysconfig.get_config_var("Py_GIL_DISABLED")):
+        if "${{ matrix.openslide }}" == "system" and (sys.version_info < (3, 12) or (sys.version_info < (3, 16) and sysconfig.get_config_var("Py_GIL_DISABLED"))):
             print("archive_wheel=1")' >> $GITHUB_ENV
     - name: Install
       run: pip install artifacts/whl/${{ needs.pre-commit.outputs.dist-base }}/*.whl
@@ -210,9 +211,10 @@ jobs:
         python -m build -w
         mkdir -p "artifacts/whl/${{ needs.pre-commit.outputs.dist-base }}"
         mv dist/*.whl "artifacts/whl/${{ needs.pre-commit.outputs.dist-base }}"
-        # from zip builds, save version-specific wheels and oldest abi3 wheel
+        # from zip builds, save version-specific wheels, oldest abi3 wheel,
+        # and oldest abi3.abi3t wheel
         python -c 'import sys, sysconfig
-        if "${{ matrix.openslide }}" == "zip" and (sys.version_info < (3, 12) or sysconfig.get_config_var("Py_GIL_DISABLED")):
+        if "${{ matrix.openslide }}" == "zip" and (sys.version_info < (3, 12) or (sys.version_info < (3, 16) and sysconfig.get_config_var("Py_GIL_DISABLED"))):
             print("archive_wheel=1")' >> $GITHUB_ENV
     - name: Install
       run: pip install artifacts/whl/${{ needs.pre-commit.outputs.dist-base }}/*.whl

openslide/_convert.c

@@ -102,9 +102,44 @@ static PyMethodDef _convert_methods[] = {
     {NULL, NULL, 0, NULL}
 };
 
+#ifdef Py_TARGET_ABI3T
+PyABIInfo_VAR(abi_info);
+
+static PySlot _convert_slot_array[] = {
+    PySlot_STATIC_DATA(Py_mod_abi, &abi_info),
+    PySlot_STATIC_DATA(Py_mod_name, "_convert"),
+    PySlot_STATIC_DATA(Py_mod_methods, _convert_methods),
+    PySlot_DATA(Py_mod_gil, Py_MOD_GIL_NOT_USED),
+    PySlot_DATA(Py_mod_multiple_interpreters,
+                Py_MOD_PER_INTERPRETER_GIL_SUPPORTED),
+    PySlot_END
+};
+
+PyMODEXPORT_FUNC
+PyModExport__convert(void)
+{
+    return _convert_slot_array;
+}
+
+#ifdef _WIN32
+// distutils insists on exporting a PyInit_ function on Windows
+// https://github.com/pypa/distutils/issues/387
+// https://github.com/python/cpython/issues/158098
+PyMODINIT_FUNC
+PyInit__convert(void)
+{
+    PyErr_SetString(PyExc_SystemError,
+                    "PyInit_* called for module with PyModExport_*");
+    return NULL;
+}
+#endif
+
+#else
+
 static PyModuleDef_Slot _convert_slots[] = {
 #if PY_VERSION_HEX >= 0x030D0000 && !defined(Py_LIMITED_API)
     {Py_mod_gil, Py_MOD_GIL_NOT_USED},
+    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
 #endif
     {0, NULL}
 };
@@ -123,3 +158,4 @@ PyInit__convert(void)
 {
     return PyModuleDef_Init(&_convert_module);
 }
+#endif

setup.py

@@ -3,29 +3,47 @@
 import sysconfig
 
 from setuptools import Extension, setup
+from setuptools import __version__ as _setuptools_ver
 
 # Load version string
 with open(Path(__file__).parent / 'openslide/_version.py') as _fh:
     exec(_fh.read())  # instantiates __version__  # noqa: S102
 
-# use the Limited API on Python 3.11+ on GIL builds; build release-specific
-# wheels on older or free-threaded Python
-_abi3 = sys.version_info >= (3, 11) and not sysconfig.get_config_var('Py_GIL_DISABLED')
+# Use the free-threaded Stable ABI (abi3t) only on free-threaded Python
+# 3.15+ with setuptools 84.2+; Python supports building abi3t from
+# GIL-enabled interpreters but setuptools doesn't yet.  Use the
+# non-free-threaded Stable API (abi3) on Python 3.11+ with GIL enabled, and
+# release-specific wheels in all other cases.
+_freethread = sysconfig.get_config_var('Py_GIL_DISABLED')
+_abi3t = (
+    sys.version_info >= (3, 15)
+    and _freethread
+    and tuple(int(c) for c in _setuptools_ver.split('.')) >= (84, 2)
+)
+_abi3 = sys.version_info >= (3, 11) and not _freethread
 
 setup(
     ext_modules=[
         Extension(
             'openslide._convert',
             ['openslide/_convert.c'],
             # hide symbols that aren't in the Limited API
-            define_macros=[('Py_LIMITED_API', '0x030b0000')] if _abi3 else [],
-            # tag extension module for Limited API
-            py_limited_api=_abi3,
+            define_macros=[('Py_TARGET_ABI3T', '0x030f0000')]
+            if _abi3t
+            else [('Py_LIMITED_API', '0x030b0000')]
+            if _abi3
+            else [],
+            # tag extension module for Stable ABI
+            py_limited_api=_abi3 or _abi3t,
         ),
     ],
     options={
-        # tag wheel for Limited API
-        'bdist_wheel': {'py_limited_api': 'cp311'} if _abi3 else {},
+        # tag wheel for Stable ABI
+        'bdist_wheel': {'py_limited_api': 'cp315'}
+        if _abi3t
+        else {'py_limited_api': 'cp311'}
+        if _abi3
+        else {},
     },
     #
     # setuptools < 61 compatibility for distro packages building from source