On 64-bit bigendian machines (ppc64 and s390x), I'm seeing:
>>> print object.__basicsize__
0

(Discovered via a segfault in Jinja2 tries to use ctypes to manipulate ob_refcnt of variables, and gets the wrong location, corrupting the objects instead; see https://bugzilla.redhat.com/show_bug.cgi?id=627347 )

struct _typeobject declares tp_basicsize and tp_itemsize as Py_ssize_t:
{
...
  Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
...
}

but type_members defines them as T_INT:
 {"__basicsize__", T_INT, offsetof(PyTypeObject,tp_basicsize),READONLY},
 {"__itemsize__", T_INT, offsetof(PyTypeObject, tp_itemsize), READONLY},

Hence when accessing "object.__basicsize__", PyMember_GetOne reads it as a
T_INT, which gets it as 0 (incorrect).  Accessing it as Py_ssize_t reads it as
16 (correct)
(gdb) p *(Py_ssize_t*)addr
$9 = 16
(gdb) p *(int*)addr
$10 = 0

I'm attaching a patch which changes them to use T_PYSSIZE_T and adds a selftest.