In debug mode, on my Ubuntu Linux box, this fails on the last iteration:

$ ./python Lib/test/regrtest.py -R:20 test_ctypes
test_ctypes
beginning 25 repetitions
1234567890123456789012345
........................test test_ctypes failed -- Traceback (most
recent call last):
  File
"/usr/local/google/home/guido/python/py3kd/Lib/ctypes/test/test_values.py",
line 18, in test_an_integer
    self.failUnlessEqual(x*2, ctdll.get_an_integer())
AssertionError: 2818572288 != -1476395008

1 test failed:
    test_ctypes
[104230 refs]
$ 

Also, when using -R:19, I get some random leaks reported of 33 or -33
references leaked.  Does this test use threads?  It seems to have a race
condition.