[Python-Dev] [Python-checkins] cpython (2.7): Issue #10276: test_zlib checks that inputs of 2 GB are handled correctly by (original) (raw)

Nadeem Vawda nadeem.vawda at gmail.com
Tue May 3 16:22:27 CEST 2011

On Tue, May 3, 2011 at 3:19 PM, victor.stinner <python-checkins at python.org> wrote:

+# Issue #10276 - check that inputs of 2 GB are handled correctly. +# Be aware of issues #1202, #8650, #8651 and #10276 +class ChecksumBigBufferTestCase(unittest.TestCase): +    intmax = 0x7FFFFFFF + +    @unittest.skipUnless(mmap, "mmap() is not available.") +    def testbigbuffer(self): +        if sys.platform[:3] == 'win' or sys.platform == 'darwin': +            requires('largefile', +                     'test requires %s bytes and a long time to run' % +                     str(self.intmax)) +        try: +            with open(TESTFN, "wb+") as f: +                f.seek(self.intmax-4) +                f.write("asdf") +                f.flush() +                try: +                    m = mmap.mmap(f.fileno(), 0, access=mmap.ACCESSREAD) +                    self.assertEqual(zlib.crc32(m), 0x709418e7) +                    self.assertEqual(zlib.adler32(m), -2072837729) +                finally: +                    m.close() +        except (IOError, OverflowError): +            raise unittest.SkipTest("filesystem doesn't have largefile support") +        finally: +            unlink(TESTFN) + +

0x7FFFFFFF is (2G-1) bytes. For a 2GB buffer, int_max should be 0x80000000. However, if you make this change, crc32() and adler32() raise OverflowErrors (see changeset a0681e7a6ded). This makes the test to erroneously report that the filesystem doesn't support large files. The assertEqual() tests should probably be changed to assertRaises(..., OverflowError).

Also, the assignment to m needs to be moved outside of the inner try...finally block. If mmap() fails, the call to m.close() raises a new exception because m has not yet been bound. This seems to be causing failures on some of the 32-bit buildbots.

As an aside, in this sort of situation is it better to just go and commit a fix myself, or is raising it on the mailing list first the right way to do things?

Cheers, Nadeem

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