ctype Structure keeps reference to function pointers

[vpelletier]

BPO	15240
Nosy	@jcea, @vpelletier
Files	reproduce.py: Test case (needs objgraph)

^{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 2012-07-02.19:40:37.553>
created_at = <Date 2012-07-02.19:29:42.167>
labels = ['ctypes', 'type-bug', 'invalid']
title = 'ctype Structure keeps reference to function pointers'
updated_at = <Date 2012-07-02.19:51:59.156>
user = 'https://github.com/vpelletier'

bugs.python.org fields:

activity = <Date 2012-07-02.19:51:59.156>
actor = 'jcea'
assignee = 'none'
closed = True
closed_date = <Date 2012-07-02.19:40:37.553>
closer = 'vpelletier'
components = ['ctypes']
creation = <Date 2012-07-02.19:29:42.167>
creator = 'vpelletier'
dependencies = []
files = ['26234']
hgrepos = []
issue_num = 15240
keywords = []
message_count = 2.0
messages = ['164534', '164535']
nosy_count = 2.0
nosy_names = ['jcea', 'vpelletier']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue15240'
versions = ['Python 2.6', 'Python 2.7', 'Python 3.2']

[vpelletier]

When storing a ctype function pointer in a ctype structure field, a reference remains even when that field is overwritten with some values:

• None
• None cast into a function pointer
  But the reference is somehow removed when overwriting the field with a "real" function pointer (a lambda in attached test case).

This causes problem when the structure is a class property and function pointer is created out of a method of the same class: a circular reference is created, which is not garbage-collected.

To run the attached test case, you need objgraph[1], and to uncomment one (or none) of the commented-out lines in "close" method.

[1] http://mg.pov.lt/objgraph/

[vpelletier]

Trying to generate a graph on several python and several uncommented lines, I see that my test case is incomplete. Time to review my copy.