bug#23999: 25.0.95; Emacs hangs in rectangle-mark-mode with numeric prefix argument to `C-f'

[Stephen Berman]

On Fri, 22 Jul 2016 13:19:14 +0200 Stephen Berman <stephen.berman@gmx.net> 
wrote:

> On Fri, 22 Jul 2016 12:31:33 +0300 Eli Zaretskii <eliz@gnu.org> wrote:
>
>>> > I'm fine with pushing to master if no one objects to this particular
>>> > solution.
>>> 
>>> Why not emacs-25, given that the behavior is a regression from 24.5 (and
>>> of course assuming the fix doesn't break anything else)?
>>
>> Because a workaround exists, 
>
> You mean just repeating a motion command instead of using a numeric
> prefix?
>
>>                              and because we cannot assume it doesn't
>> break anything else without prolonging the pretest.
>
> Thanks for your healthy scepticism here; I checked again and indeed the
> patch changes the behavior in rectangle-mark-mode when attempting to
> move past bol or eol.  The patch tries to rectify this and according to
                                  ^
Sorry:                           below

> my tests, it works with a numeric prefix argument but behaves the same
> as the current version when attempting to move past bol or eol.
>
> If you think this corrected patch should still not go into emacs-25,
> perhaps there should be a note in PROBLEMS, since motion commands in
> general accept a numeric prefix and someone who successfully used
> rectangle-mark-mode that way in 24.5 will naturally assume it works in
> 25.1 and be surprised when Emacs hangs.
>
> Steve Berman
>
> diff --git a/lisp/rect.el b/lisp/rect.el
> index fb85b18..bb01b98 100644
> --- a/lisp/rect.el
> +++ b/lisp/rect.el
> @@ -653,6 +653,12 @@ rectangle--*-char
>                    (end-of-buffer (+ col (1+ n)))
>                    (beginning-of-buffer (- curcol 1))))
>                 (diff (abs (- nextcol col))))
> +       ;; Move to the correct column when selecting a rectangular
> +       ;; region by passing a numeric prefix argument to a motion
> +       ;; command, but stop at bol in any case.
> +       (if (wholenump nextcol)
> +           (move-to-column nextcol)
> +         (goto-char bol))
>            (cond
>             ((and (< nextcol curcol) (< curcol col))
>              (let ((curdiff (- col curcol)))