The object returned by tp_new() may not have a tp_init.
If the object is an ExtensionClass, for example, the slot is not even
defined. So we must check that the type has the slot (implied by
HAVE_CLASS) before calling tp_init().
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index a7263d8..31a7c3d 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -199,7 +199,8 @@
if (!PyType_IsSubtype(obj->ob_type, type))
return obj;
type = obj->ob_type;
- if (type->tp_init != NULL &&
+ if (PyType_HasFeature(type, Py_TPFLAGS_HAVE_CLASS) &&
+ type->tp_init != NULL &&
type->tp_init(obj, args, kwds) < 0) {
Py_DECREF(obj);
obj = NULL;