On Fri, Jan 16, 2009 at 7:28 PM, Phil Christensen <p...@bubblehouse.org> wrote: > The comment was this: > > # added 2003-06-23 by Chris Armstrong. Yes, I actually have a > # use case where I need this traceback object, and I've made > # sure that it'll be cleaned up. > self.tb = tb > > presumably referring to the problem with keeping references to tracebacks > that was a potential pitfall in the Python version of that time. That's a > non-issue since Python 2.2, though, which is probably why the comment got > deleted.
Keeping references to tracebacks still has many potential pitfalls. It's a fundamental problem: tracebacks refer to all their frames, which refer to all their locals; this makes it *really* easy to create uncollectable cycles if you have any __del__ methods *anywhere*. It's just not safe to keep the traceback reference in the general case. Failure needs to work with arbitrary code. > Originally all __getstate__ did was stringify the object's state, which is > probably why cleanFailure calls it directly. It looks to me like most of the > code from __getstate__ should really be moved into a separate method, which > would be called from cleanFailure as well as __getstate__. Sure, that would be a slightly better factoring. > This assumes that __getstate__ would still set c['tb'] to None, but that > cleanFailure would not. I'm not sure what the repercussions of this would > be, though. It seems the old problem with keeping references to tracebacks > is less of an issue now, based on this from the current Python docs: > >> Note Beginning with Python 2.2, such cycles are automatically reclaimed >> when garbage collection is enabled and they become unreachable, but it >> remains more efficient to avoid creating cycles. > > I'd appreciate any feedback. > > -phil -- Christopher Armstrong http://radix.twistedmatrix.com/ http://planet-if.com/ http://canonical.com/ _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
