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

[Stefan Monnier <monnier@iro.umontreal.ca>]

> No idea what caused this error (I have no code that calls
> `clear-transient-map', and here it seems to have been called somehow at
> top level (?)), but here is the backtrace, FWIW:

> Debugger entered--Lisp error: (error "Marker does not point anywhere")
>   pop-mark()
>   #[...]()
>   #[...]()
>   funcall(#[...])
>   clear-transient-map()

That's probably the pop-mark that's in mouse-drag-track.  It has
a `push-mark' before, so naively it seems like the mark should be set.

> I was in Info at the time.

I think we need more data to figure out why the mark isn't set and hence
what to do about it.  A reproducible test case would obviously be best,
but otherwise maybe some indication of what kind of mouse gesture you
did, or what kind of customizations you might have that could interact
with that code and could unset the mark (maybe from
a pre/post-command-hook?).


        Stefan