[IronPython] Possible bug in Ipy 2.6.1 WeakDictionary

Idan Zaltzberg idan at cloudshare.com
Tue Oct 5 11:46:12 CEST 2010

I want to try to build from source.

We are using the 2.6.1 release from April on .Net 2.0, so I guess I need to


After that, can you tell which configuration to use in Visual Studio in
order to get the same result as d/ling the binaries directly from site?

*From:* users-bounces at lists.ironpython.com [mailto:
users-bounces at lists.ironpython.com] *On Behalf Of *Dino Viehland
*Sent:* Monday, October 04, 2010 7:22 PM
*To:* Discussion of IronPython
*Subject:* Re: [IronPython] Possible bug in Ipy 2.6.1 WeakDictionary

Nope, you have it right – this is fixed in the Main branch and internally
it’s fixed in the 2.6 branch as well (There was a report about this from
some internal uses of IronPython).    Unfortunately it looks like the fix
hasn’t propagated out to the 2.6 branch on CodePlex for some reason.  I’ll
try and figure out what’s going on there but either way it’ll be fixed in
the next set of releases.  If you want to build from source you can just add
a call to CheckCleanup(); in there before the dict[new WeakObject(…)] = …

*From:* users-bounces at lists.ironpython.com [mailto:
users-bounces at lists.ironpython.com] *On Behalf Of *Idan Zaltzberg
*Sent:* Monday, October 04, 2010 9:02 AM
*To:* Discussion of IronPython
*Subject:* [IronPython] Possible bug in Ipy 2.6.1 WeakDictionary


I'm investigating memory leakage in a Ipy 2.6.1 application.

Using WinDbg I found a WeakDictionary that is only increasing in size,
though most of the instances are already collected.

This WeakDicitionary is used by a DelegationInfo object.

Looking at the code, I think I found the problem:

The method CheckCleanup is called the method "public void Add(TKey key,
TValue value)"

*But it NOT called* from the indexer:

public TValue this[TKey key] {

            get {

                return dict[key];


            set {

                // If the WeakHash already holds this value as a key, it
will lead to a circular-reference and result

                // in the objects being kept alive forever. The caller needs
to ensure that this cannot happen.


                dict[new WeakObject(key)] = value;



Since the dictionary is populated using the indexer in DelegateInfo:

_constantMap[target] = new WeakReference(clone = (object

This means that the "version" field is never updated, and the dictionary
never gets cleaned up.

Have I got something wrong here?

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