winreg.EnumValue does not truncate strings correctly

[anshul6]

BPO	25778
Nosy	@pfmoore, @tjguk, @bitdancer, @zware, @eryksun, @zooba
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	nullcheck.py nullcheck2.py issue25778_py3_1.patch issue25778_py27_1.patch issue25778_py36_2.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 = 'https://github.com/zooba'
closed_at = <Date 2016-12-28.23:22:00.636>
created_at = <Date 2015-12-02.13:55:25.549>
labels = ['easy', 'deferred-blocker', 'type-bug', 'extension-modules', '3.7', 'library', 'OS-windows']
title = 'winreg.EnumValue does not truncate strings correctly'
updated_at = <Date 2017-03-31.16:36:14.672>
user = 'https://bugs.python.org/anshul6'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:14.672>
actor = 'dstufft'
assignee = 'steve.dower'
closed = True
closed_date = <Date 2016-12-28.23:22:00.636>
closer = 'steve.dower'
components = ['Extension Modules', 'Library (Lib)', 'Windows']
creation = <Date 2015-12-02.13:55:25.549>
creator = 'anshul6'
dependencies = []
files = ['41208', '41213', '41220', '41469', '41470']
hgrepos = []
issue_num = 25778
keywords = ['patch', 'easy']
message_count = 39.0
messages = ['255715', '255717', '255718', '255720', '255736', '255738', '255742', '255745', '255751', '255755', '255800', '255801', '255803', '255804', '255805', '255806', '255807', '255808', '255809', '255810', '255816', '255820', '255823', '255825', '255828', '255829', '255830', '257291', '257316', '257324', '258414', '258436', '282280', '282285', '282296', '282300', '283518', '283520', '284238']
nosy_count = 12.0
nosy_names = ['paul.moore', 'tim.golden', 'stutzbach', 'r.david.murray', 'SilentGhost', 'python-dev', 'zach.ware', 'eryksun', 'steve.dower', 'Edward.K..Ream', 'random832', 'anshul6']
pr_nums = ['552']
priority = 'deferred blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25778'
versions = ['Python 3.6', 'Python 3.7']

[anshul6]

I have described the error message I got when I recently installed Python 3.5.0 (via Anaconda3) and then subsequently tried to import mathplotlib.pyplot and seaborn packages at this StackOverflow post (http://stackoverflow.com/questions/34004063/error-on-import-matplotlib-pyplot-on-anaconda3-for-windows-10-home-64-bit-pc)

Another person responded to the above post with a simple 1-line patch to the file "fontList.py3k.cache" (please see the above post for details).

This does appear to be a purely Python 3 issue on some Windows platforms. It would be nice if Python 3 developers could check the patch out for any possible side-effects, and incorporate a permanent fix in future versions. Thanks.

[bitdancer]

The stackoverflow comment is this:

"The issue is that winreg.EnumValue is not cutting string values at their length properly for some reason, and strings will include null characters which os.path.abspath is not able to process."

The "one line patch" in the stackoverflow comment is against matplotlib, not python, so it doesn't help toward fixing this.

What would be most useful toward fixing this is a reproducer, but since that will depend on data in the registry whoever creates the reproducer may as well do it as a unit test.

I'm adding 2.7 to versions since it seems unlikely the code is different there, but I haven't checked. Anshul, if you have tested this on python2.7 and not seen the problem there, please update the issue with that info.

[anshul6]

Before I got the "one line patch" on stackoverflow, I tried creating a new environment with Python 2.7.10 and did *not* get the error message I got with Python 3.5.0. Here's an outline of what I did:

1. Created a new environment to use Python 2.7.10: conda create --name python2.7.10 python=2.7.10
2. Installed matplotlib package within it: conda install --name python2.7.10 matplotlib
3. Installed seaborn package within it: conda install --name python2.7.10 seaborn

When I started Python within this environment (verified it was version 2.7.10 with "print(sys.version)"), and did "import matplotlib.pyplot" and "import seaborn", the FileNotFoundError message did not appear. So the problem appears to be associated with Python3, not Python2.

Hope this helps.

[eryksun]

Based on matplotlib's win32InstalledFonts function 1, I created a small test to check the data strings returned by winreg.EnumValue for the presence of null characters. I tested on Windows 7 and 10 but couldn't reproduce the problem. Please run nullcheck.py to check the results on your system.

[anshul6]

Please tell me where I can find nullcheck.py and how I should run it (I assume something like "python nullcheck.py" in the Windows Command Prompt?) I'm relatively new to Python, so explicit instructions would be appreciated. Thanks!

[SilentGhost]

Anshul, it's attached to this issue, before messages start under Files heading. Here is the direct link https://bugs.python.org/file41208/nullcheck.py

[eryksun]

You should be able to run nullcheck.py in the command prompt by changing to the directory where it's saved and entering nullcheck.py. For example, if you saved it in your Downloads folder:

>cd /d C:\Users\Anshul\Downloads
>nullcheck.py

If that fails because the .py file association isn't set up properly, instead try

>py nullcheck.py

[anshul6]

Ok thanks. Here's what I got:

C:\Users\Anshul\Downloads\Python>conda info --envs
# conda environments:

python2.7.10 C:\Anaconda3\envs\python2.7.10
root * C:\Anaconda3

C:\Users\Anshul\Downloads\Python>python -V
Python 3.5.0 :: Anaconda 2.4.0 (64-bit)

C:\Users\Anshul\Downloads\Python>python nullcheck.py
Checking: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts
('tahoma.ttf\x000\x000\x00\x00\x00', 1) Tahoma (TrueType)
('verdref.ttf\x000\x000\x00PA\x00\x00\x00\x00', 1) Verdana Ref (TrueType)
('grgaref.ttf\x000\x000\x00PA\x00\x00\x00\x00', 1) Georgia Ref (TrueType)
('refspec.ttf\x000\x000\x00PA\x10\x00%APP', 1) RefSpecialty (TrueType)
Cannot open: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Fonts
done

C:\Users\Anshul\Downloads\Python>activate python2.7.10
Activating environment "C:\Anaconda3\envs\python2.7.10"...

[python2.7] C:\Users\Anshul\Downloads\Python>python -V
Python 2.7.10 :: Continuum Analytics, Inc.

[python2.7] C:\Users\Anshul\Downloads\Python>python nullcheck.py
Traceback (most recent call last):
  File "nullcheck.py", line 3, in <module>
    import winreg
ImportError: No module named winreg

[python2.7] C:\Users\Anshul\Downloads\Python>

[eryksun]

I only wrote it for Python 3, but it would be interesting to see what you get with Python 2. Please try nullcheck2.py.