the case of __del__ resurrecting an object.
This makes the apparent reference leaks in test_descr go away (which I
expected) and also kills off those in test_gc (which is more surprising
but less so once you actually think about it a bit).
subtype_dealloc(): This left the dying object exposed to gc, so that
if cyclic gc triggered during the weakref callback, gc tried to delete
the dying object a second time. That's a disaster. subtype_dealloc()
had a (I hope!) unique problem here, as every normal dealloc routine
untracks the object (from gc) before fiddling with weakrefs etc. But
subtype_dealloc has obscure technical reasons for re-registering the
dying object with gc (already explained in a large comment block at
the bottom of the function).
The fix amounts to simply refraining from reregistering the dying object
with gc until after the weakref callback (if any) has been called.
This is a critical bug (hard to predict, and causes seemingly random
memory corruption when it occurs). I'll backport it to 2.3 later.
[ 784825 ] fix obscure crash in descriptor handling
Should be applied to release23-maint and in all likelyhood
release22-maint, too.
Certainly doesn't apply to release21-maint.
Sure looks like it to me! <wink>
When I run the leak2.py script I posted to python-dev, I only see
three reference leaks in all of test_descr. When I run
test_descr.test_main, I still see 46 leaks. This clearly demands
posting a yelp to python-dev :-)
This certainly should be applied to release23-maint, and in all
likelyhood release22-maint as well.
