bpo-39824: module_traverse() don't call m_traverse if md_state=NULL (GH-18738)

Extension modules: m_traverse, m_clear and m_free functions of
PyModuleDef are no longer called if the module state was requested
but is not allocated yet. This is the case immediately after the
module is created and before the module is executed (Py_mod_exec
function). More precisely, these functions are not called if m_size is
greater than 0 and the module state (as returned by
PyModule_GetState()) is NULL.

Extension modules without module state (m_size <= 0) are not affected.

Co-Authored-By: Petr Viktorin <encukou@gmail.com>

Lib/test/test_importlib/extension/test_loader.py

@@ -267,29 +267,6 @@ class MultiPhaseExtensionModuleTests(abc.LoaderTests):
                 self.assertEqual(module.__name__, name)
                 self.assertEqual(module.__doc__, "Module named in %s" % lang)
 
-    @unittest.skipIf(not hasattr(sys, 'gettotalrefcount'),
-            '--with-pydebug has to be enabled for this test')
-    def test_bad_traverse(self):
-        ''' Issue #32374: Test that traverse fails when accessing per-module
-            state before Py_mod_exec was executed.
-            (Multiphase initialization modules only)
-        '''
-        script = """if True:
-                try:
-                    from test import support
-                    import importlib.util as util
-                    spec = util.find_spec('_testmultiphase')
-                    spec.name = '_testmultiphase_with_bad_traverse'
-
-                    with support.SuppressCrashReport():
-                        m = spec.loader.create_module(spec)
-                except:
-                    # Prevent Python-level exceptions from
-                    # ending the process with non-zero status
-                    # (We are testing for a crash in C-code)
-                    pass"""
-        assert_python_failure("-c", script)
-
 
 (Frozen_MultiPhaseExtensionModuleTests,
  Source_MultiPhaseExtensionModuleTests