At 10:48 AM 5/19/2005 -0700, Guido van Rossum wrote:
Hm. The way I see it, as soon as a generator raises an exception, its frame is part of a cycle: the frame's f_exc_traceback points to the traceback object, and the traceback object's tb_frame points back to the frame. So that's a cycle right there.
But that cycle doesn't include the generator-iterator object, and it's not a collectable cycle while the iterator still lives. Once the iterator itself goes away, that frame cycle is collectable. However, Tim's new post brings up a different issue: if the collector can't tell the difference between a cycle participant and an object that's only reachable from a cycle, then the mere existence of a generator __del__ will prevent the cycle collection of the entire traceback/frame system that includes a generator-iterator reference anywhere! And that's a pretty serious problem.