object.__basicsize__ is erroneously 0 on big-endian 64-bit machines (int vs Py_ssize_t)

[davidmalcolm]

BPO	9688
Nosy	@benjaminp, @davidmalcolm
Files	fix-typeobject-T_INT-usage.patch: Patch against 2.7 branch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2010-08-25.23:13:27.378>
created_at = <Date 2010-08-25.22:44:35.116>
labels = ['type-bug']
title = 'object.__basicsize__ is erroneously 0 on big-endian 64-bit machines (int vs Py_ssize_t)'
updated_at = <Date 2010-08-25.23:13:27.376>
user = 'https://github.com/davidmalcolm'

bugs.python.org fields:

activity = <Date 2010-08-25.23:13:27.376>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2010-08-25.23:13:27.378>
closer = 'benjamin.peterson'
components = []
creation = <Date 2010-08-25.22:44:35.116>
creator = 'dmalcolm'
dependencies = []
files = ['18646']
hgrepos = []
issue_num = 9688
keywords = ['patch']
message_count = 2.0
messages = ['114942', '114947']
nosy_count = 2.0
nosy_names = ['benjamin.peterson', 'dmalcolm']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'patch review'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue9688'
versions = ['Python 2.7']

[davidmalcolm]

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.

[benjaminp]

r84320.