I tried various things including upgrading the guest Linux to Debian 12,
and trying master vs 29 branches. Still seeing crashes.

Today I tried configure emacs 29 without "--with-native-compilation". It
appears that core dump is no longer happening. Now when I copy on the host,
I see the following message in Emacs:

dbus-check-event: D-Bus error: "Not a valid D-Bus event", (dbus-event 10 14)

Backtrace buffer shows the following:

Debugger entered--Lisp error: (dbus-error "Not a valid D-Bus event"
(dbus-event 10 14))
  signal(dbus-error ("Not a valid D-Bus event" (dbus-event 10 14)))
  dbus-check-event((dbus-event 10 14))
  dbus-event-bus-name((dbus-event 10 14))
  dbus-notice-synchronous-call-errors((dbus-event 10 14) (dbus-error "Not a
valid D-Bus event" (dbus-event 10 14)))
  run-hook-with-args(dbus-notice-synchronous-call-errors (dbus-event 10 14)
(dbus-error "Not a valid D-Bus event" (dbus-event 10 14)))
  dbus-handle-event((dbus-event 10 14))
  funcall-interactively(dbus-handle-event (dbus-event 10 14))
  call-interactively(dbus-handle-event nil [(dbus-event 10 14)])
  command-execute(dbus-handle-event nil [(dbus-event 10 14)] t)

On Sun, May 5, 2024 at 10:34 AM Michael Albinus <michael.albinus@gmx.de>
wrote:

> Eli Zaretskii <eliz@gnu.org> writes:
>
> Hi Eli,
>
> >> I did (setq debug-on-error t), went to
> https://en.wikipedia.org/wiki/Emacs, randomly selected a fragment
> >> "Emacs has over", then did a ctrll+c.
> >>
> >> Emacs in VirtualBox immediately showed the following:
> >>
> >> Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p
> nil)
> >>   dbus-handle-event((dbus-event "[ \11]*$"))
> >>   funcall-interactively(dbus-handle-event (dbus-event "[ \11]*$"))
> >>   call-interactively(dbus-handle-event nil [(dbus-event "[ \11]*$")])
> >>   command-execute(dbus-handle-event nil [(dbus-event "[ \11]*$")] t)
> >
> > Does VirtualBox have anything in its documentation that suggests that
> > Ctrl-C on the Windows side will cause a D-Bus event on the VM side?
> >
> > Michael, any idea what is this D-Bus event, and what does it have to
> > do with copying into the Windows clipboard?
>
> `dbus-handle-event' is the handler for D-Bus events (sic!). It is
> invoked, when a D-Bus event arrives in the keyboard buffer, see
> `special-event-map'.
>
> It isn't called explicitly anywhere in Emacs. So I assume that the
> "D-Bus" event is pushed to the keyboard buffer by accident, when
> communicating with the VirtualBox.
>
> > Thanks.
>
> Best regards, Michael.
>