GH-121832: Assert that the version number of static builtin types is not changed by PyType_Modified. (GH-122182)

Update datetime module and test_type_cache.py to not call PyType_Modified.

Lib/test/test_type_cache.py

@@ -161,8 +161,8 @@ class TypeCacheWithSpecializationTests(unittest.TestCase):
         self._check_specialization(load_foo_2, A, "LOAD_ATTR", should_specialize=False)
 
     def test_class_load_attr_specialization_static_type(self):
-        self._assign_valid_version_or_skip(str)
+        self.assertNotEqual(type_get_version(str), 0)
-        self._assign_valid_version_or_skip(bytes)
+        self.assertNotEqual(type_get_version(bytes), 0)
 
         def get_capitalize_1(type_):
             return type_.capitalize
@@ -170,25 +170,6 @@ class TypeCacheWithSpecializationTests(unittest.TestCase):
         self._check_specialization(get_capitalize_1, str, "LOAD_ATTR", should_specialize=True)
         self.assertEqual(get_capitalize_1(str)('hello'), 'Hello')
         self.assertEqual(get_capitalize_1(bytes)(b'hello'), b'Hello')
-        del get_capitalize_1
-
-        # Permanently overflow the static type version counter, and force str and bytes
-        # to have tp_version_tag == 0
-        for _ in range(2**16):
-            type_modified(str)
-            type_assign_version(str)
-            type_modified(bytes)
-            type_assign_version(bytes)
-
-        self.assertEqual(type_get_version(str), 0)
-        self.assertEqual(type_get_version(bytes), 0)
-
-        def get_capitalize_2(type_):
-            return type_.capitalize
-
-        self._check_specialization(get_capitalize_2, str, "LOAD_ATTR", should_specialize=False)
-        self.assertEqual(get_capitalize_2(str)('hello'), 'Hello')
-        self.assertEqual(get_capitalize_2(bytes)(b'hello'), b'Hello')
 
     def test_property_load_attr_specialization_user_type(self):
         class G:

Modules/_datetimemodule.c

@@ -7256,6 +7256,7 @@ _datetime_exec(PyObject *module)
         Py_DECREF(value);                               \
     } while(0)
 
+    if (!reloading) {
         /* timedelta values */
         PyObject *d = _PyType_GetDict(&PyDateTime_DeltaType);
         DATETIME_ADD_MACRO(d, "resolution", new_delta(0, 0, 1, 0));
@@ -7299,6 +7300,7 @@ _datetime_exec(PyObject *module)
         /* +23:59 */
         DATETIME_ADD_MACRO(
                 d, "max", create_timezone_from_delta(0, (23 * 60 + 59) * 60, 0, 0));
+    }
 
 #undef DATETIME_ADD_MACRO
 
@@ -7342,12 +7344,6 @@ _datetime_exec(PyObject *module)
     static_assert(DI100Y == 25 * DI4Y - 1, "DI100Y");
     assert(DI100Y == days_before_year(100+1));
 
-    if (reloading) {
-        for (size_t i = 0; i < Py_ARRAY_LENGTH(capi_types); i++) {
-            PyType_Modified(capi_types[i]);
-        }
-    }
-
     if (set_current_module(interp, module) < 0) {
         goto error;
     }

Objects/typeobject.c

@@ -1026,6 +1026,8 @@ type_modified_unlocked(PyTypeObject *type)
     if (type->tp_version_tag == 0) {
         return;
     }
+    // Cannot modify static builtin types.
+    assert((type->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN) == 0);
 
     PyObject *subclasses = lookup_tp_subclasses(type);
     if (subclasses != NULL) {