First, I get the following compilation warnings under Linux:
/home/antoine/cpython/26/Modules/_fileio.c: In function ‘fileio_truncate’:
/home/antoine/cpython/26/Modules/_fileio.c:651: attention : unused variable ‘tempposobj’
/home/antoine/cpython/26/Modules/_fileio.c:650: attention : unused variable ‘oldposobj’

The two variables should be declared at the beginning of the Windows-specific block instead.

Second, there's a test failure in test_io:

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FAIL: test_large_file_ops (test.test_io.IOTest)
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Traceback (most recent call last):
  File "/home/antoine/cpython/26/Lib/test/test_io.py", line 221, in test_large_file_ops
    self.large_file_ops(f)
  File "/home/antoine/cpython/26/Lib/test/test_io.py", line 154, in large_file_ops
    self.assertEqual(f.tell(), self.LARGE + 1)
AssertionError: 2147483650L != 2147483649

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