Unformatted “Windows Error 0x%X” exception message on Wine

[vadmium]

BPO	22977
Nosy	@vstinner, @tjguk, @vadmium, @zware, @serhiy-storchaka, @eryksun, @zooba
Files	win-error-format.patch win-error-format-v2.patch win-error-format-v3.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2015-04-06.17:40:25.386>
created_at = <Date 2014-12-02.11:19:44.468>
labels = ['easy', 'type-bug', 'OS-windows']
title = 'Unformatted \xe2\x80\x9cWindows Error 0x%X\xe2\x80\x9d exception message on Wine'
updated_at = <Date 2015-04-06.17:40:25.385>
user = 'https://github.com/vadmium'

bugs.python.org fields:

activity = <Date 2015-04-06.17:40:25.385>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2015-04-06.17:40:25.386>
closer = 'serhiy.storchaka'
components = ['Windows']
creation = <Date 2014-12-02.11:19:44.468>
creator = 'martin.panter'
dependencies = []
files = ['37678', '37686', '38641']
hgrepos = []
issue_num = 22977
keywords = ['patch', 'easy']
message_count = 21.0
messages = ['231987', '232046', '233873', '233876', '233899', '238978', '238986', '238989', '239875', '239877', '239878', '239882', '239885', '239888', '239891', '239892', '239910', '239949', '240164', '240166', '240168']
nosy_count = 9.0
nosy_names = ['vstinner', 'tim.golden', 'Arfrever', 'python-dev', 'martin.panter', 'zach.ware', 'serhiy.storchaka', 'eryksun', 'steve.dower']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue22977'
versions = ['Python 3.4', 'Python 3.5']

[vadmium]

The following code generates a connection reset error on Wine (Windows emulator, because I don’t have actual Windows to test on). Probably only a minor issue, but the error message isn’t quite right:

>>> s = create_connection(("localhost", 8181))
>>> # Server end accepts connection and then closes it
>>> s.sendall(b"3" * 3000000)                 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ConnectionResetError: [WinError 10054] Windows Error 0x%X

I’m just guessing, but looking at Python/errors.c, there are two PyUnicode_FromFormat("Windows Error 0x%X", ...) calls. The documentation for that function says only a lower-case %x is supported, so that would explain the behaviour I am seeing.

[eryksun]

This also affects SEH-related exceptions raised by ctypes. For example, VC++ uses exception code 0xE06D7363 (i.e. b'\xe0msc'), so unhandled VC++ exceptions leak into Python like this:

    >>> ctypes.windll.kernel32.RaiseException(0xe06d7363, 0, 0, None)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    OSError: [WinError -529697949] Windows Error 0x%X

The ctypes SEH handler defaults to calling PyErr_SetFromWindowsErr(code). Since this isn't actually a Windows error code, Win32 FormatMessageW fails. Then Python uses the following default: PyUnicode_FromFormat("Windows Error 0x%X", err).

Normally (i.e. not under Wine) the OP's error number formats correctly:

    >>> ctypes.windll.kernel32.RaiseException(10054, 0, 0, None)     
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host

PyErr_SetExcFromWindowsErrWithFilenameObjects
https://hg.python.org/cpython/file/ab2c023a9432/Python/errors.c#l553

PyErr_SetFromErrnoWithFilenameObjects
https://hg.python.org/cpython/file/ab2c023a9432/Python/errors.c#l416

[vadmium]

Here’s a simple patch which should fix it, although I have not verified this because I don’t have a Windows compiler (and MINGW cross compiling sounds too tricky)

[vstinner]

The attached patch lacks an unit test. When I will be able to build CPython again, I will try the patch.

[vadmium]

This patch includes a test case, based on Eryksun’s exception code

[vadmium]

V3 patch with suggested changes to the test case, though still completely untested by me.

[serhiy-storchaka]

LGTM.

[serhiy-storchaka]

There are other occurrences of %X in the code. Do you want provide a patch for them Martin?

[vadmium]

All the other occurrences of capitalized %X that I can find are not using Python’s string formatting functions. Please point them out if you can, but all I can see are some using a Microsoft vfwprintf_s() API, some calling standard C sprintf(), sscanf(), fprintf(), strftime() and strptime() APIs, and of course native Python 2-style string formatting, which I assume should all support %X.

[serhiy-storchaka]

Yes, you are right.