bug#46908: 28.0.50; Dozens of spurious markers in buffer-undo-list

[martin rudalics]

>> When I read the discussion on emacs-help I tried with `buffer-undo-list'
>> nil and doing some window modifications but didn't find a smoking gun.
>
> AFAIK window modifications are not necessary to reproduce the issue,
> probably they are completely unrelated.

Maybe.  But I don't know of any packages that are much interested in
reading or manipulating `window-point'.  So if `window-point' is
involved in at least one scenario that reproduces the problem, it might
help to trace that occurrence back to its origins.

> Did you try to reproduce the issue with the recipe?  It is complete.

I did not because I just believe you that your recipe is valid.  The
problem is that you have to trace back those marker entries back to
where they have been created in such abundance.  And I have no idea
how to do that.

> Sorry for the confusion:

You did not confuse me.

> We did not turn winner-mode on in the recipe,
> please just ignore that part of the discussion, that was a false lead.

If turning on `winner-mode' _can_ create many `window-point' marker
entries, it's not necessarily a false lead.  It might help to locate the
real culprit with one important restriction: You'd have to look into
clients that either deal with `window-point' directly or call something
that does deal with `window-point' only.

> You just need insert and undo to reproduce.  Please try.  emacs -Q, just
> editing commands plus undo produce the zombi markers.

I tried it now.  The only thing I can say is that with Emacs 27 it
usually returns 0 or 1 here while with master it returns 10.  So maybe
you should try (after verifying what I found out) to trace the recent
changes in master.

martin