bug#20498: 25.0.50; PATCH: break potential infinite loop in (line-move-to-column)

[Eli Zaretskii]

> From: Dima Kogan <dima@secretsauce.net>
> Cc: 20498@debbugs.gnu.org
> Date: Tue, 05 May 2015 01:29:14 -0700
> 
> Hi. Thank you very much for double-checking. It indeed looks like (bolp)
> should cover this case. It doesn't however. When ERC misbehaves in this
> way I observe both
> 
>  (= (line-beginning-position) (point))  --> t
>  (bolp)                                 --> nil
> 
> This sounds wrong. Looking at the buffer with my eyes, the point is not
> at the beginning of the line, so it LOOKS like the (bolp) result is
> correct.
> 
> The docs for (line-beginning-position) state that this function respects
> field boundaries. If I ignore those explicitly then I see the correct
> behavior:
> 
>  (let ((inhibit-field-text-motion t))
>        (line-beginning-position))   ---> correct start of line
> 
> So the correct patch would replace (line-beginning-position) to the
> above expression. This is trivial, and I'm not actually attaching a
> patch. If you want me to, tell me.

Thanks, I pushed such a change.

> (line-beginning-position) is used in quite a few places in emacs, and
> I'm wondering if in many of those uses the intent is to ignore fields.

I don't know, but I guess they will discover this in due time.