gh-117649: Raise ImportError for unsupported modules in free-threaded build

The free-threaded build does not currently support the combination of
single-phase init modules and legacy, non-isolated subinterpreters. Note
that with isolated interpreters, single-phase init modules already
trigger `ImportError`.

Author: colesbury

Lib/test/test_capi/test_misc.py

@@ -26,6 +26,7 @@
 from test.support import threading_helper
 from test.support import warnings_helper
 from test.support import requires_limited_api
+from test.support import requires_gil_enabled
 from test.support.script_helper import assert_python_failure, assert_python_ok, run_python_until_end
 try:
     import _posixsubprocess
@@ -2070,6 +2071,7 @@ def test_configured_settings(self):
 
     @unittest.skipIf(_testsinglephase is None, "test requires _testsinglephase module")
     @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    @requires_gil_enabled("gh-117649: test does not work in free-threaded build")
     def test_overridden_setting_extensions_subinterp_check(self):
         """
         PyInterpreterConfig.check_multi_interp_extensions can be overridden
@@ -2165,6 +2167,7 @@ def test_mutate_exception(self):
         self.assertFalse(hasattr(binascii.Error, "foobar"))
 
     @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+    @requires_gil_enabled("gh-117649: test does not work in free-threaded build")
     def test_module_state_shared_in_global(self):
         """
         bpo-44050: Extension module state should be shared between interpreters

Lib/test/test_import/__init__.py

@@ -30,7 +30,8 @@
 from test.support import os_helper
 from test.support import (
     STDLIB_DIR, swap_attr, swap_item, cpython_only, is_apple_mobile, is_emscripten,
-    is_wasi, run_in_subinterp, run_in_subinterp_with_config, Py_TRACE_REFS)
+    is_wasi, run_in_subinterp, run_in_subinterp_with_config, Py_TRACE_REFS,
+    requires_gil_enabled)
 from test.support.import_helper import (
     forget, make_legacy_pyc, unlink, unload, ready_to_import,
     DirsOnSysPath, CleanImport, import_module)
@@ -158,6 +159,9 @@ def meth(self, _meth=meth):
             finally:
                 restore__testsinglephase()
     meth = cpython_only(meth)
+    # gh-117649: free-threaded build does not currently support single-phase
+    # init modules in subinterpreters.
+    meth = requires_gil_enabled(meth)
     return unittest.skipIf(_testsinglephase is None,
                            'test requires _testsinglephase module')(meth)
 

Lib/test/test_importlib/test_util.py

@@ -11,6 +11,7 @@
 import re
 import string
 import sys
+import sysconfig
 from test import support
 import textwrap
 import types
@@ -688,10 +689,20 @@ def test_single_phase_init_module(self):
             with _incompatible_extension_module_restrictions(disable_check=True):
                 import _testsinglephase
             ''')
-        with self.subTest('check disabled, shared GIL'):
-            self.run_with_shared_gil(script)
-        with self.subTest('check disabled, per-interpreter GIL'):
-            self.run_with_own_gil(script)
+        if not sysconfig.get_config_var('Py_GIL_DISABLED'):
+            with self.subTest('check disabled, shared GIL'):
+                self.run_with_shared_gil(script)
+            with self.subTest('check disabled, per-interpreter GIL'):
+                self.run_with_own_gil(script)
+        else:
+            # gh-117649: Py_GIL_DISABLED builds do not support legacy
+            # single-phase init extensions within subinterpreters.
+            with self.subTest('check disabled, shared GIL'):
+                with self.assertRaises(ImportError):
+                    self.run_with_shared_gil(script)
+            with self.subTest('check disabled, per-interpreter GIL'):
+                with self.assertRaises(ImportError):
+                    self.run_with_own_gil(script)
 
         script = textwrap.dedent(f'''
             from importlib.util import _incompatible_extension_module_restrictions

Python/import.c

@@ -1244,6 +1244,19 @@ import_find_extension(PyThreadState *tstate, PyObject *name,
         return NULL;
     }
 
+    /* gh-117649: The free-threaded build does not currently support
+       single-phase init modules in subinterpreters. */
+#ifdef Py_GIL_DISABLED
+    if (def->m_size == -1 && !_Py_IsMainInterpreter(tstate->interp)) {
+        return PyErr_Format(
+            PyExc_ImportError,
+            "module %s does not support the combination of free-threading "
+            "and subinterpreters",
+             name_buf);
+        return NULL;
+    }
+#endif
+
     PyObject *mod, *mdict;
     PyObject *modules = MODULES(tstate->interp);