Hum, I used "+ 8" to add the new 64-bit version tag of dictionaries. But I didn't use struct.calcsize() to compute it, so there is maybe an aliasing/padding issue.

http://buildbot.python.org/all/builders/ARMv7%20Ubuntu%203.x/builds/4815/steps/test/logs/stdio

======================================================================
FAIL: test_objecttypes (test.test_sys.SizeofTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/ssd/buildbot/buildarea/3.x.gps-ubuntu-exynos5-armv7l/build/Lib/test/test_sys.py", line 940, in test_objecttypes
    check({}, size('n2P') + 8 + calcsize('2nP2n') + 8 + (8*2//3)*calcsize('n2P'))
  File "/ssd/buildbot/buildarea/3.x.gps-ubuntu-exynos5-armv7l/build/Lib/test/support/__init__.py", line 1510, in check_sizeof
    test.assertEqual(result, size, msg)
AssertionError: 144 != 140 : wrong size for <class 'dict'>: got 144, expected 140

======================================================================
FAIL: test_sizeof_exact (test.test_ordered_dict.CPythonOrderedDictSubclassTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/ssd/buildbot/buildarea/3.x.gps-ubuntu-exynos5-armv7l/build/Lib/test/test_ordered_dict.py", line 677, in test_sizeof_exact
    check(od, basicsize + 8*p + 8 + 5*entrysize)  # 8byte indicies + 8*2//3 * entry table
  File "/ssd/buildbot/buildarea/3.x.gps-ubuntu-exynos5-armv7l/build/Lib/test/support/__init__.py", line 1510, in check_sizeof
    test.assertEqual(result, size, msg)
AssertionError: 208 != 204 : wrong size for <class 'test.test_ordered_dict.CPythonOrderedDictSubclassTests.OrderedDict'>: got 208, expected 204

======================================================================
FAIL: test_sizeof_exact (test.test_ordered_dict.CPythonOrderedDictTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/ssd/buildbot/buildarea/3.x.gps-ubuntu-exynos5-armv7l/build/Lib/test/test_ordered_dict.py", line 677, in test_sizeof_exact
    check(od, basicsize + 8*p + 8 + 5*entrysize)  # 8byte indicies + 8*2//3 * entry table
  File "/ssd/buildbot/buildarea/3.x.gps-ubuntu-exynos5-armv7l/build/Lib/test/support/__init__.py", line 1510, in check_sizeof
    test.assertEqual(result, size, msg)
AssertionError: 208 != 204 : wrong size for <class 'collections.OrderedDict'>: got 208, expected 204

New changeset c3776dd858f0 by Victor Stinner in branch 'default':
Try to fix sizeof unit tests on dict
https://hg.python.org/cpython/rev/c3776dd858f0

According to buildbots, the issue seems to be fixed.