- PyType_Ready(): Initialize the ob_type field to &PyType_Type if it's

  NULL, so that you can call PyType_Ready() to initialize a type that
  is to be separately compiled with C on Windows.

inherit_special():  Add a long comment explaining that you have to set
tp_new if your base class is PyBaseObject_Type.

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index ba3006389f2b9d2845b446cbcf2b8d70c7e2d8b4..b8a33c89074eb133550cfe53251fde1fe027d1b5 100644 (file)
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1747,6 +1747,16 @@ inherit_special(PyTypeObject *type, PyTypeObject *base)
                        type->tp_clear = base->tp_clear;
        }
        if (type->tp_flags & base->tp_flags & Py_TPFLAGS_HAVE_CLASS) {
+               /* The condition below could use some explanation.
+                  It appears that tp_new is not inherited for static types
+                  whose base class is 'object'; this seems to be a precaution
+                  so that old extension types don't suddenly become
+                  callable (object.__new__ wouldn't insure the invariants
+                  that the extension type's own factory function ensures).
+                  Heap types, of course, are under our control, so they do
+                  inherit tp_new; static extension types that specify some
+                  other built-in type as the default are considered
+                  new-style-aware so they also inherit object.__new__. */
                if (base != &PyBaseObject_Type ||
                    (type->tp_flags & Py_TPFLAGS_HEAPTYPE)) {
                        if (type->tp_new == NULL)
@@ -1940,6 +1950,12 @@ PyType_Ready(PyTypeObject *type)
 
        type->tp_flags |= Py_TPFLAGS_READYING;
 
+       /* Initialize ob_type if NULL.  This means extensions that want to be
+          compilable separately on Windows can call PyType_Ready() instead of
+          initializing the ob_type field of their type objects. */
+       if (type->ob_type == NULL)
+               type->ob_type = &PyType_Type;
+
        /* Initialize tp_base (defaults to BaseObject unless that's us) */
        base = type->tp_base;
        if (base == NULL && type != &PyBaseObject_Type)