[IronPython] blocker: objects deleted when they shouldn't be

[William Reade]

Great -- thank you very much.

Dino Viehland wrote:
> It might be this week, it might be next week - I'm currently doing some perf tuning for the DLR team and am queueing up a bunch of bugs to fix in a single day or two.
>
> -----Original Message-----
> From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of William Reade
> Sent: Monday, September 29, 2008 10:50 AM
> To: Discussion of IronPython
> Subject: Re: [IronPython] blocker: objects deleted when they shouldn't be
>
> Thanks Dino :)
>
> Can you suggest an approximate ETA for a fix? I don't want to hassle
> you, but I'm very keen to get numpy matrices working and would really
> appreciate a guess -- even if it's wildly wrong, it still gives me a
> framework to work within ;).
>
> Cheers
> William
>
> Dino Viehland wrote:
>   
>> Very cool bug and great analysis - thanks for reporting this.  BTW That code lives in MetaPythonType.Calls now.
>>
>> It seems like this logic needs to be moved into PythonType.CreateInstance instead instead of in the generated rule code.
>>
>> -----Original Message-----
>> From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of William Reade
>> Sent: Monday, September 29, 2008 7:11 AM
>> To: users at lists.ironpython.com
>> Subject: [IronPython] blocker: objects deleted when they shouldn't be
>>
>> Hi all
>>
>> I'm about to file this on Codeplex, but I think I've tracked down a
>> subtle and nasty bug, which is blocking Ironclad with numpy (it fatally
>> breaks matrices and masked arrays), and I feel compelled to shout loudly
>> about it to ensure it doesn't get lost in the noise of the impending 2.0
>> release.
>>
>> In short, the following code:
>> -------------------------------------------------------------
>> from System import GC
>>
>> class C(object):
>>     _instance = None
>>     def __new__(cls):
>>         if C._instance is None:
>>             C._instance = object.__new__(cls)
>>         return C._instance
>>
>>     def __del__(self):
>>         print 'deleting object with id', id(self)
>>
>> c = C()
>> print 'created a C with id', id(c)
>> d = C()
>> print 'created another C with id', id(d)
>>
>> for _ in range(3):
>>     GC.Collect()
>>     GC.WaitForPendingFinalizers()
>>
>> print id(c), id(d)
>> print c
>> print d
>> -------------------------------------------------------------
>>
>> ...produces the following output:
>> -------------------------------------------------------------
>> C:\dev\ironclad\build>ipy deltest.py
>> created a C with id 43
>> created another C with id 43
>> deleting object with id 43
>> 43 43
>> <C object at 0x000000000000002B>
>> <C object at 0x000000000000002B>
>> -------------------------------------------------------------
>>
>> ...and I don't think that the 'deleting...' message should be printed at
>> that point.
>>
>> My suspicion is that c's 'magic_finalization_wossname'* slot is being
>> overwritten with a new instance after __new__ returns, leaving the
>> original 'magic_finalization_wossname' unreferenced; in the fullness of
>> time, that gets finalized and calls c.__del__, even though c itself
>> still exists.
>>
>> Cheers
>> William
>>
>> * This is probably not the actual member name, but I couldn't find the
>> relevant code today, even though I remember reading it in the past...
>> hopefully the implementers know what I'm trying to refer to, even if
>> nobody else does.
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>>
>>     
>
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