Re: Cannot interrupt async shell command

[Juri Linkov]

> * Start an async shell command: M-! sleep 100 & RET
> * Switch to the buffer *Async Shell Command*
> * Type C-c C-c
>
> I got the error: Marker does not point anywhere
>
> Backtrace looks as follows:
>
> Debugger entered--Lisp error: (error "Marker does not point anywhere")
>   shell-filter-ctrl-a-ctrl-b("")
>   run-hook-with-args(shell-filter-ctrl-a-ctrl-b "")
>   comint-send-input(t t)
>   comint-skip-input()
>   comint-interrupt-subjob()
>   call-interactively(comint-interrupt-subjob)

Another commands unusable in *Async Shell Command* are `comint-quit-subjob',
`comint-stop-subjob' and `comint-kill-subjob'.  All they don't work here
due to the call to `comint-skip-input' and `shell-filter-ctrl-a-ctrl-b'
which fails in *Async Shell Command* because the marker
`comint-last-output-start' has no position.

One way to fix this bug is to replace the following line in
`shell-filter-ctrl-a-ctrl-b':

      (goto-char (or comint-last-output-start (point-min)))

with

      (goto-char (or (and (marker-position comint-last-output-start)
                          comint-last-output-start)
                     (point-min)))

i.e. to check if there is a buffer position recorded in
comint-last-output-start instead of checking the marker
(always created in `comint-mode') for nil.

-- 
Juri Linkov
http://www.jurta.org/emacs/