bug#17893: 24.4.50; (error "Marker does not point anywhere")

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: charles@aurox.ch,  17893@debbugs.gnu.org
> Date: Mon, 20 Nov 2017 13:59:12 -0500
> 
> >  M-n
> >  M-: Info-tag-table-marker RET
> >   => #<marker in no buffer>
> 
> Maybe there's a bug, indeed.  Does the above lead to undesired behavior?

I didn't dig deep enough to find out.  But it's clear that such a
marker is useless at best.

> No.  It just assumes that whichever package owns a marker that needs
> special treatment should register itself on that hook.  Maybe that's too
> much to ask, but it's definitely not "impossible".

Registering a hook is easy, the problem is doing everything that's
needed in the hook.  Especially given that clone-buffer is not
documented, and therefore all these caveats are nowhere to be learned.

> > As another data point, there are 6 users of clone-buffer in Emacs
> > core, and only one of them bothers to set up a clone-buffer-hook.
> 
> Do these suffer from problems?

I don't know.  But markers are quite common, so I'd be surprised if
they didn't.