OrderedDict.move_to_end may cause crash in python 3.5

[CruiseLiu]

BPO	25406
Nosy	@rhettinger, @ericsnowcurrently, @serhiy-storchaka
Files	move_to_end_issue25406.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/serhiy-storchaka'
closed_at = <Date 2015-10-14.16:26:58.814>
created_at = <Date 2015-10-14.13:20:02.999>
labels = ['library', 'type-crash']
title = 'OrderedDict.move_to_end may cause crash in python 3.5'
updated_at = <Date 2015-10-14.16:27:21.841>
user = 'https://bugs.python.org/CruiseLiu'

bugs.python.org fields:

activity = <Date 2015-10-14.16:27:21.841>
actor = 'python-dev'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2015-10-14.16:26:58.814>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2015-10-14.13:20:02.999>
creator = 'Cruise Liu'
dependencies = []
files = ['40783']
hgrepos = []
issue_num = 25406
keywords = ['patch']
message_count = 5.0
messages = ['252991', '252996', '252999', '253004', '253005']
nosy_count = 6.0
nosy_names = ['rhettinger', 'python-dev', 'eric.snow', 'serhiy.storchaka', 'Cruise Liu', 'Snivy Pang']
pr_nums = []
priority = 'critical'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue25406'
versions = ['Python 3.5', 'Python 3.6']

[CruiseLiu]

Following code will crash python. Tested on linux and windows.

Python 3.5.0 (default, Sep 20 2015, 11:28:25) 
[GCC 5.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import collections
>>> x = collections.OrderedDict([ ('a', 1), ('b', 2), ('c', 3) ])
>>> x.move_to_end('c', last = False)
>>> x.move_to_end('a', last = False)
>>> x
Segmentation fault (core dumped)

[serhiy-storchaka]

Here is a patch that fixes the issue.

[ericsnowcurrently]

@serhiy, patch LGTM. Thanks for taking care of it.

[serhiy-storchaka]

Thank you for your review Eric.

[python-dev]

New changeset 88e6641c3dd3 by Serhiy Storchaka in branch '3.5':
Issue bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end()
https://hg.python.org/cpython/rev/88e6641c3dd3

New changeset 33d53a41daeb by Serhiy Storchaka in branch 'default':
Issue bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end()
https://hg.python.org/cpython/rev/33d53a41daeb