At 03:00 AM 4/12/2006 -0400, Tim Peters wrote:
>Phillip, when eyeballing gen_dealloc(), I didn't understand two things:
>
>1. Why doesn't
>
> if (gen->gi_frame->f_stacktop!=NULL) {
>
> check first to be sure that gen->gi_frame != Py_None?
Apparently, it's because I'm an idiot, and because nobody else realized
this during the initial review of the patch. :)
>Is that impossible here for some reason?
No, I goofed. It's amazing that this doesn't dump core whenever a
generator exits. :(
>2. It _looks_ like "gi_frame != NULL" is an (undocumented) invariant.
>Right? If so,
>
> Py_XDECREF(gen->gi_frame);
>
> sends a confusing message (because of the "X", implying that NULL is OK).
> Regardless, it would be good to add comments to genobject.h explaining
> the possible values gi_frame can hold. For example, what does it mean
> when gi_frame is Py_None? Can it ever be NULL?
I think what happened is that at one point I thought I was going to set
gi_frame=NULL when there's no active frame, in order to speed up
reclamation of the frame. However, I think I then thought that it would
break the operation of the generator's 'gi_frame' attribute, which is
defined as T_OBJECT. Or else I thought that the tp_visit was screwed up in
that case.
So, it looks to me like what this *should* do is simply allow gi_frame to
be NULL instead of Py_None, which would get rid of all the silly casting,
and retroactively make the XDECREF correct. :)
Does gen_traverse() need to do anything special to visit a null
pointer? Should it only conditionally visit it?
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
