From 51d8587c0f1bcc05174341d4b8e03865936b904c Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 5 May 2023 13:54:45 -0600
Subject: [PATCH] Add a test.

---
 Lib/test/test_import/__init__.py | 20 ++++++++++++++++++++
 Modules/_testmultiphase.c        | 19 ++++++++++++++++++-
 Objects/moduleobject.c           |  1 -
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_import/__init__.py b/Lib/test/test_import/__init__.py
index 773b7094c6b8ce..e2384a08ecaa90 100644
--- a/Lib/test/test_import/__init__.py
+++ b/Lib/test/test_import/__init__.py
@@ -1861,6 +1861,26 @@ def test_multi_init_extension_non_isolated_compat(self):
         with self.subTest(f'{modname}: not strict'):
             self.check_compatible_here(modname, filename, strict=False)
 
+    @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+    def test_multi_init_extension_per_interpreter_gil_compat(self):
+        modname = '_test_shared_gil_only'
+        filename = _testmultiphase.__file__
+        loader = ExtensionFileLoader(modname, filename)
+        spec = importlib.util.spec_from_loader(modname, loader)
+        module = importlib.util.module_from_spec(spec)
+        loader.exec_module(module)
+        sys.modules[modname] = module
+
+        require_extension(module)
+        with self.subTest(f'{modname}: isolated, strict'):
+            self.check_incompatible_here(modname, filename, isolated=True)
+        with self.subTest(f'{modname}: not isolated, strict'):
+            self.check_compatible_here(modname, filename,
+                                       strict=True, isolated=False)
+        with self.subTest(f'{modname}: not isolated, not strict'):
+            self.check_compatible_here(modname, filename,
+                                       strict=False, isolated=False)
+
     def test_python_compat(self):
         module = 'threading'
         require_pure_python(module)
diff --git a/Modules/_testmultiphase.c b/Modules/_testmultiphase.c
index 58b064bb17cd87..299be18545ab5b 100644
--- a/Modules/_testmultiphase.c
+++ b/Modules/_testmultiphase.c
@@ -892,7 +892,7 @@ PyInit__test_module_state_shared(void)
 }
 
 
-/* multiple interpreters supports */
+/* multiple interpreters support */
 
 static PyModuleDef_Slot non_isolated_slots[] = {
     {Py_mod_exec, execfunc},
@@ -909,3 +909,20 @@ PyInit__test_non_isolated(void)
 {
     return PyModuleDef_Init(&non_isolated_def);
 }
+
+
+static PyModuleDef_Slot shared_gil_only_slots[] = {
+    {Py_mod_exec, execfunc},
+    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED},
+    {0, NULL},
+};
+
+static PyModuleDef shared_gil_only_def = TEST_MODULE_DEF("_test_shared_gil_only",
+                                                         shared_gil_only_slots,
+                                                         testexport_methods);
+
+PyMODINIT_FUNC
+PyInit__test_shared_gil_only(void)
+{
+    return PyModuleDef_Init(&shared_gil_only_def);
+}
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 90d8f5808315a5..985be58d02c784 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -323,7 +323,6 @@ PyModule_FromDefAndSpec2(PyModuleDef* def, PyObject *spec, int module_api_versio
             goto error;
         }
     }
-    // XXX This case needs a test.
     else if (multiple_interpreters != Py_MOD_PER_INTERPRETER_GIL_SUPPORTED
              && interp->ceval.own_gil
              && !_Py_IsMainInterpreter(interp)