Re: Registry save: apparently circular structure being printed

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Bob Newell <bobnewell@bobnewell.net> writes:

> I came across something that undoubtedly will be hard to reproduce ---
> until some ultimately inconvenient moment. I had just set up a half
> dozen or so RSS feeds for gnus (using the simple G R method). Now, the
> RSS part may or may not be relevant, but I did load a lot of articles
> and make a lot of changes to the feeds, killing some, adding some,
> etc., for quite a while.
>
> I have code that ensures gnus is properly closed out on exiting Emacs,
> and that includes saving the registry (gnus takes care of it on its
> own exit, it seems).
>
> At the point of saving the registry, I started getting the message
> "Apparently circular structure being printed". This persisted until I
> killed emacs directly and deleted the gnus registry. Not exactly an
> optimal solution!
>
> I realize this is obscure, and my report is necessarily bare-bones,
> but has anyone ever seen anything like this?

Unfortunately, yes, I think Uwe Brauer reported something similar a
while ago. Can you tell me what version of emacs you're using?

I'm 80% confident that this has to do with something that changed in
Emacs 26 about the way objects are represented: it used to be that the
registry could simply write all its contents to disk, but now it needs
special processing. A while ago I provided a naive fix that ended up
causing further bugs, which I'm not yet done stamping out. I don't know
where the "circular structure" error is coming from, actually, but it
seems very likely that it's related.

Tell me your emacs version, and if you can, please provide a backtrace
that I can compare to Uwe's, and see if I can figure this out.

Yours,
Eric