[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Mike Place]

Mike Place added the comment:

+1 to getting this patch in. The fact that this raises a ValueError and not an 
ImportError is really annoying and we definitely see it as a bug.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Jason R. Coombs]

Jason R. Coombs added the comment:

The first thing it helps is that it eliminates a ValueError on import. Without 
it, code must catch both ValueError and ImportError to run portably:

import ctypes

try:
  import ctypes.wintypes
except ImportError, ValueError:
  # catch ImportError and ValueError due to issue16396
  pass

...

def code_that_runs_only_on_win():
  ctypes.wintypes.foo

One _could_ cause ctypes.wintypes to always raise an ImportError on non-Windows 
systems, allowing the import routine to be simpler:

try:
  import ctypes.wintypes
except ImportError:
  pass

But it would be even nicer if ctypes.wintypes always imported on any platform, 
such that the statement could be simply:

import ctypes.wintypes

But it's conceivable that certain functionality in wintypes might be useful on 
other systems. Consider, for example, a routine that works with pickles 
produced on a Windows system, or simply a comparison of some object in 
ctypes.wintypes against a value produced on a Windows system.

The argument for that need (esp. on Python 2.7) is not strong, but since the 
patch to address the ValueError is simple, straightforward, and perhaps even 
simpler than something that would address the ValueError specifically, it seems 
worthwhile to accept the patch.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Meador Inge]

Meador Inge added the comment:

Using 'ctypes.wintypes' on non-Windows systems is most likely a bad idea.  Most 
of the types are defined in terms of the types for the target that the 
interpreter is built for.  Comparing serializations thereof in a cross platform 
manner doesn't make sense for a lot of cases.  

I really think it is only useful for Windows platforms and allowing it to 
silently import is misleading.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Benjamin Peterson]

Benjamin Peterson added the comment:

This is not a regression, though, so most people wouldn't be able to simplify 
their code because they have to support older Python versions.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Benjamin Peterson]

Benjamin Peterson added the comment:

We can argue about whether it's a bugfix or not. But I don't see how having 
this patch in 2.7 helps anyone, since ctypes.wintypes is useless on non-Windows 
platforms.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Amaury Forgeot d'Arc]

Amaury Forgeot d'Arc added the comment:

I think it's the opposite: when Unix support was added to ctypes, 'import 
ctypes.wintypes' was not considered. By that logic, the patch is a new feature.
IMO historical arguments are moot :-)

I agree with the conclusion tough: the patch will not break code that carefully 
catches ValueError, and so it suitable for 2.7.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Meador Inge]

Meador Inge added the comment:

On Mon, Aug 12, 2013 at 7:11 AM, Ezio Melotti rep...@bugs.python.orgwrote:

 Even if the patch is applied only on 3.4, I would still like to see the
 ValueError turned into ImportError for 2.7/3.3.


Why not raise an ImportError for all versions?  I don't see how
'ctypes.wintypes' is ever actually useful on anything but Windows.
 Allowing it to successfully import on non-Windows systems seems misleading.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Ezio Melotti]

Ezio Melotti added the comment:

Even if the patch is applied only on 3.4, I would still like to see the 
ValueError turned into ImportError for 2.7/3.3.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Jason R. Coombs]

Jason R. Coombs added the comment:

My sense on the issue is that wintypes was added to the library and was never 
intended to raise a ValueError on import. By that logic, the behavior is a bug, 
not a new feature. I agree with Ezio that raising a ValueError on import is a 
bug. And since the patch not only addresses the ValueError on import, but 
simply addresses the underlying cause, it seems to me the most obvious solution.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Benjamin Peterson]

Benjamin Peterson added the comment:

Smells like a new feature to me.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Christian Heimes]

Christian Heimes added the comment:

RM, please decide. :)

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assignee:  - benjamin.peterson
stage: needs patch - patch review

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Jason R. Coombs]

Changes by Jason R. Coombs jar...@jaraco.com:


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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Christian Heimes]

Christian Heimes added the comment:

The fix is trivial: 

- define VARIANT_FALSE and VARIANT_BOOL according to specs
- enable 'v' on non-Windows systems
- enable tests for vbool

Done

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Added file: http://bugs.python.org/file30684/16396_vbool.patch

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Jason R. Coombs]

Jason R. Coombs added the comment:

Looks good to me. Ben, any objections to applying this to 2.7?

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Ezio Melotti]

Ezio Melotti added the comment:

That patch is more a workaround than an actual fix.  Lib/ctypes/wintypes.py 
should either fail with an ImportError or be importable.  For the former it's 
possible to catch the ValueError and turn it into an ImportError, or perhaps 
raise it if some precondition is missing; for the latter, either the creation 
of that signle class is skipped if _type_ 'v' is not supported, or a way to 
define it that works on other platforms too should be found instead.

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Ezio Melotti]

Changes by Ezio Melotti ezio.melo...@gmail.com:


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stage:  - needs patch
type:  - behavior
versions: +Python 3.4 -Python 3.2

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Dmi Baranov]

Dmi Baranov added the comment:

Found only this patch [1] :) I think is possible to change 
VARIANT_BOOL._type_ to any of short types [2] for non-nt platforms?

[1] 
https://code.launchpad.net/~mandel/python-distutils-extra/import_issues/+merge/53519
[2] http://msdn.microsoft.com/en-us/library/cc237864.aspx

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[Terry J. Reedy]

Changes by Terry J. Reedy tjre...@udel.edu:


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versions:  -Python 3.1

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[anatoly techtonik]

New submission from anatoly techtonik:

 import ctypes.wintypes
Traceback (most recent call last):
  File stdin, line 1, in module
  File /usr/lib/python3.2/ctypes/wintypes.py, line 20, in module
class VARIANT_BOOL(ctypes._SimpleCData):
ValueError: _type_ 'v' not supported
 


Shouldn't it just import silently without failing? Or if it's destined to fail, 
explain how to make a cross-platform import?

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components: ctypes
messages: 174634
nosy: techtonik
priority: normal
severity: normal
status: open
title: Importing ctypes.wintypes on Linux gives a traceback
versions: Python 2.7, Python 3.1, Python 3.2, Python 3.3

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[issue16396] Importing ctypes.wintypes on Linux gives a traceback

[anatoly techtonik]

anatoly techtonik added the comment:

Perhaps the patch already there - see http://www.themacaque.com/?p=826

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