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bpo-38030: Fix os.stat failures on block devices on Windows #15681

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Merged
zooba merged 1 commit into from
Sep 4, 2019
Merged

bpo-38030: Fix os.stat failures on block devices on Windows #15681

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8 changes: 8 additions & 0 deletions Lib/test/test_os.py
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Original file line number Diff line number Diff line change
Expand Up @@ -591,6 +591,14 @@ def test_access_denied(self):
result = os.stat(fname)
self.assertNotEqual(result.st_size, 0)

@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
def test_stat_block_device(self):
# bpo-38030: os.stat fails for block devices
# Test a filename like "//./C:"
fname = "//./" + os.path.splitdrive(os.getcwd())[0]
result = os.stat(fname)
self.assertEqual(result.st_mode, stat.S_IFBLK)


class UtimeTests(unittest.TestCase):
def setUp(self):
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Windows/2019-09-04-14-01-08.bpo-38030._USdtk.rst
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@@ -0,0 +1 @@
Fixes :func:`os.stat` failing for block devices on Windows
19 changes: 13 additions & 6 deletions Modules/posixmodule.c
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Expand Up @@ -1794,13 +1794,13 @@ win32_xstat_impl(const wchar_t *path, struct _Py_stat_struct *result,
case ERROR_INVALID_PARAMETER:
case ERROR_INVALID_FUNCTION:
case ERROR_NOT_SUPPORTED:
retval = -1;
/* Volumes and physical disks are block devices, e.g.
\\.\C: and \\.\PhysicalDrive0. */
memset(result, 0, sizeof(*result));
result->st_mode = 0x6000; /* S_IFBLK */
goto cleanup;
}
/* Volumes and physical disks are block devices, e.g.
\\.\C: and \\.\PhysicalDrive0. */
memset(result, 0, sizeof(*result));
result->st_mode = 0x6000; /* S_IFBLK */
retval = -1;
goto cleanup;
}
}
Expand All @@ -1827,7 +1827,14 @@ win32_xstat_impl(const wchar_t *path, struct _Py_stat_struct *result,

cleanup:
if (hFile != INVALID_HANDLE_VALUE) {
CloseHandle(hFile);
/* Preserve last error if we are failing */
error = retval ? GetLastError() : 0;
if (!CloseHandle(hFile)) {
retval = -1;
} else if (retval) {

@eryksun eryksun Sep 4, 2019 •
edited
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Have you had a problem with this? The normal path for the internal implementation of CloseHandle is to call status = NtClose(handle). If the return status is successful, it just returns TRUE. Otherwise Windows sets the last error from the status code (i.e. RtlNtStatusToDosError, etc) and returns FALSE. It's not going to modify our thread's last error value if it succeeds.

@zooba zooba Sep 4, 2019

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No, just being overly defensive. There are other functions that (incorrectly) change the last error, and it's easier to be consistent about preserving it than to rely on a not-strictly-followed convention.

@zooba zooba Sep 4, 2019

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In particular, for others who come in and copy my code without necessarily checking severe edge cases like this :)

/* Restore last error */
SetLastError(error);
}
}

return retval;
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