[ python-Bugs-840829 ] weakref callbacks and gc corrupt memory

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Bugs item #840829, was opened at 2003-11-12 12:05
Message generated for change (Comment added) made by tim_one
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Category: Python Interpreter Core
Group: Python 2.3
Status: Open
Resolution: None
Priority: 9
Submitted By: Thomas Heller (theller)
>Assigned to: Thomas Heller (theller)
Summary: weakref callbacks and gc corrupt memory

Initial Comment:
This program crashes the Python interpreter in a debug
build, and probably corrupts memory in release build
(on Windows, at least):

"""
import weakref
import gc

_boundMethods = weakref.WeakKeyDictionary()

def safeRef(object):
    selfkey = object.im_self
    funckey = object.im_func
    _boundMethods[selfkey] = weakref.WeakKeyDictionary()
    _boundMethods[selfkey][funckey] =
BoundMethodWeakref(object)

class BoundMethodWeakref:
    def __init__(self, boundMethod):
        def remove(object):
            gc.collect()
        self.weakSelf =
weakref.ref(boundMethod.im_self, remove)

class X(object):
    def test(self):
        pass

def test():
    print "A"
    safeRef(X().test)
    print "B"

if __name__ == "__main__":
    test()
"""

See also these messages:

http://mail.python.org/pipermail/python-dev/2003-November/040189.html

http://mail.python.org/pipermail/python-dev/2003-November/040191.html


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>Comment By: Tim Peters (tim_one)
Date: 2003-11-12 15:47

Message:
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Back to you, Thomas!  Please check your real app against 
current CVS Python.  I checked in a putative fix as

Lib/test/test_weakref.py; new revision: 1.29
Misc/NEWS; new revision: 1.890
Objects/typeobject.c; new revision: 2.251

The new test case in test_weakref.py is very much simpler 
than what you've been running, so I want confirmation that 
the real problem is fixed too before closing this.

Please record what happens here, then assign back to me.

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Comment By: Tim Peters (tim_one)
Date: 2003-11-12 14:54

Message:
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user_id=31435

I agree this is a critical bug; assigned to me.

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Comment By: Thomas Heller (theller)
Date: 2003-11-12 12:08

Message:
Logged In: YES 
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Attached the script triggering the error.

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Comment By: Thomas Heller (theller)
Date: 2003-11-12 12:07

Message:
Logged In: YES 
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IMO this is a serious problem because it renders weakref
callbacks basically unusable - gc can occur at any time.
So I raised the priority to 9.

----------------------------------------------------------------------

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