Add garbage collection for module objects. Closes patch #102939 and

fixes bug #126345.

Objects/moduleobject.c

@@ -18,6 +18,7 @@ PyModule_New(char *name)
 		return NULL;
 	nameobj = PyString_FromString(name);
 	m->md_dict = PyDict_New();
+	PyObject_GC_Init(m);
 	if (m->md_dict == NULL || nameobj == NULL)
 		goto fail;
 	if (PyDict_SetItemString(m->md_dict, "__name__", nameobj) != 0)
@@ -130,11 +131,12 @@ _PyModule_Clear(PyObject *m)
 static void
 module_dealloc(PyModuleObject *m)
 {
+	PyObject_GC_Fini(m);
 	if (m->md_dict != NULL) {
 		_PyModule_Clear((PyObject *)m);
 		Py_DECREF(m->md_dict);
 	}
-	PyObject_DEL(m);
+	PyObject_DEL(PyObject_AS_GC(m));
 }
 
 static PyObject *
@@ -211,16 +213,39 @@ module_setattr(PyModuleObject *m, char *name, PyObject *v)
 		return PyDict_SetItemString(m->md_dict, name, v);
 }
 
+/* We only need a traverse function, no clear function: If the module
+   is in a cycle, md_dict will be cleared as well, which will break
+   the cycle. */
+static int
+module_traverse(PyModuleObject *m, visitproc visit, void *arg)
+{
+	if (m->md_dict != NULL)
+		return visit(m->md_dict, arg);
+	return 0;
+}
+
 PyTypeObject PyModule_Type = {
 	PyObject_HEAD_INIT(&PyType_Type)
 	0,			/*ob_size*/
 	"module",		/*tp_name*/
-	sizeof(PyModuleObject),	/*tp_size*/
+	sizeof(PyModuleObject) + PyGC_HEAD_SIZE,	/*tp_size*/
 	0,			/*tp_itemsize*/
 	(destructor)module_dealloc, /*tp_dealloc*/
 	0,			/*tp_print*/
 	(getattrfunc)module_getattr, /*tp_getattr*/
 	(setattrfunc)module_setattr, /*tp_setattr*/
 	0,			/*tp_compare*/
 	(reprfunc)module_repr, /*tp_repr*/
+	0,			/*tp_as_number*/
+	0,			/*tp_as_sequence*/
+	0,		/*tp_as_mapping*/
+	0,		/* tp_hash */
+	0,		/* tp_call */
+	0,		/* tp_str */
+	0,		/* tp_getattro */
+	0,		/* tp_setattro */
+	0,		/* tp_as_buffer */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_GC, /*tp_flags*/
+	0,		/* tp_doc */
+	(traverseproc)module_traverse,	/* tp_traverse */
 };