Ctypes C-level infinite recursion

[fijal]

BPO	1838
Nosy	@gvanrossum, @arigo, @theller, @amauryfa, @devdanzin, @alex
Files	crash.py python_recursive_as_parameter.diff python_recursive_as_parameter.diff

^{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/theller'
closed_at = <Date 2011-03-26.23:16:49.143>
created_at = <Date 2008-01-16.09:38:43.242>
labels = ['ctypes', 'type-crash']
title = 'Ctypes C-level infinite recursion'
updated_at = <Date 2011-03-26.23:16:49.141>
user = 'https://bugs.python.org/fijal'

bugs.python.org fields:

activity = <Date 2011-03-26.23:16:49.141>
actor = 'python-dev'
assignee = 'theller'
closed = True
closed_date = <Date 2011-03-26.23:16:49.143>
closer = 'python-dev'
components = ['ctypes']
creation = <Date 2008-01-16.09:38:43.242>
creator = 'fijal'
dependencies = []
files = ['9183', '18933', '18936']
hgrepos = []
issue_num = 1838
keywords = ['patch']
message_count = 10.0
messages = ['59993', '59996', '87911', '116867', '116874', '116890', '116898', '116914', '116934', '132281']
nosy_count = 9.0
nosy_names = ['gvanrossum', 'arigo', 'theller', 'amaury.forgeotdarc', 'fijal', 'ajaksu2', 'alex', 'BreamoreBoy', 'python-dev']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue1838'
versions = ['Python 2.6', 'Python 3.1']

[fijal]

Code in example abuses the fact that _as_parameter_ is passed
recursively. Not sure if this is for fixing or not.

[gvanrossum]

I've got a hunch that any crashes you cause with ctypes are your own
fault. :-)

[devdanzin]

Confirmed in trunk and py3k. Maybe we should treat ctypes segfaults that
don't involve external C code more strictly as bugs?

[BreamoreBoy]

I'm not convinced that this needs doing, so I'll close in a couple of weeks unless anyone objects.

[alex]

I concur with Daniel, this strikes me as a legitimate bug. Crashing is obviously possibly by calling into arbitrary C code, but in this case control never leaves the runtime.

[gvanrossum]

So has anyone got an idea on how to fix this without solving the halting problem?

[alex]

No need to solve the halting problem, just to detect a cycle in data. I've got a patch, however it requires objects to be hashable. Another case for identity dict I suppose :) Not sure if that's a reasonable requirement, in any event, proof of concept patch, against trunk.

[amauryfa]

This function is called quite often. Building a set each time will be expensive.
What about a simpler recursion check with Py_EnterRecursiveCall()?

[alex]

Good idea Amaury, seems to work just fine.

[python-dev]

New changeset 4945a45b8be4 by Benjamin Peterson in branch '3.1':
check possible recursive _as_parameter_ to prevent segfault (closes bpo-1838)
http://hg.python.org/cpython/rev/4945a45b8be4

New changeset 4bd06503eaca by Benjamin Peterson in branch '2.7':
check possible recursive _as_parameter_ to prevent segfault (closes bpo-1838)
http://hg.python.org/cpython/rev/4bd06503eaca