Ezio Melotti wrote on Fri, Jan 11, 2013 at 08:44:43 +0000:
> >>> ### one ref leaked for every child in __setstate__:
> >>> e2.__setstate__(p2)
> [76810 refs]
> >>> e2.__setstate__(p2)
> [76813 refs]
> >>> e2.__setstate__(p2)
> [76816 refs]
> 
> I'm not working on this anymore now, so someone more familiar with the
> code can take a look, see if my patch is correct, and fix the
> remaining leaks.
> 

Thank for narrowing it down so much.  Attached patch incorporates your
getstate fix and a fix for setstate.  It passes the -R 3:2 tests.