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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Messing with the GC
Date: Sun, 20 Jan 2013 17:14:43 -0500
References: <alvpvkFthuoU1@mid.uni-berlin.de> <am317sFljunU1@mid.uni-berlin.de>
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On 1/20/2013 3:09 PM, Jens Thoms Toerring wrote:

>      thank you for the explanations. I had overlooked the
> cyclic nature of what I had produced here and, of course,
> the GC can't be blamed for not collecting objects that are
> part of a cycle. The other question about the last refe-
> rence to an object vanishing within a method call (which,
> as I now clearly understand, can't happen and wouldn't make
> much sense) was triggered by a segmentation fault I get
> when I do something similar in PySide, so I was getting
> worried if it might be due to a GC issue. Now I know its
> got to be something different;-)

Perhaps the hardest part of writing C extensions to CPython directly in 
C (versus something like Cython) is properly balancing increfs and 
decrefs. An incref without a later decref can lead to a memory leak. A 
decref without a preceding incref (so CPython thinks the object can be 
deleted, when it should not be) can lead to segfaults. So I would report 
PySide code leading to segfaults to the PySide people.

-- 
Terry Jan Reedy