Neil Schemenauer added the comment:
Updated patch is attached. It appears that the extra item is only needed if
Py_TPFLAGS_TYPE_SUBCLASS set. In all other cases, it seems we don't need the
extra space for the sentinel. At least, the unit tests pass with this change.
It could be that
New submission from Neil Schemenauer :
In the process of working on some garbage collector/obmalloc experiments, I
noticed what seems to be a quirk about PyType_GenericAlloc(). It calls:
size = _PyObject_VAR_SIZE(type, nitems+1);
Note the "+1" which is documented as "for the sentinel".
