bug#21615: 24.5; font-lock-extend-region-wholelines' infinite loop

[Eli Zaretskii <eliz@gnu.org>]

> From: brubar.cs@gmail.com
> Date: Sun, 04 Oct 2015 19:34:07 +0200
> 
> 
> The function `font-lock-extend-region-wholelines' uses `bolp' to check
> if point is at the beginning of the line, and, if not, it calls
> `line-beginning-position' to move to the beginning of the line.
> 
> Here is the code from `font-lock-extend-region-wholelines':
> 
> ,----
> | (goto-char font-lock-beg)
> | (unless (bolp)
> |   (setq changed t font-lock-beg (line-beginning-position)))
> `----
> 
> 
> But, `line-beginning-position' moves to the beginning of the line *OR*
> to the beginning of a *field*. Thus, if point is at the beginning of a
> field that is not at the beginning of a line, `changed' is set to t but
> the region is not changed. As `font-lock-extend-region-wholelines' is
> called again until it doesn't signal a change, we end up in an infinite
> loop.
> 
> 
> 
> To reproduce, use the attached file and run it like that:
> 
> 
> ,----
> | emacs -Q --file test-font-lock-infloop.el --eval '(progn (eval-buffer) (DO-NOT-EVAL-ME))'
> `----

Thanks, I fixed that in the development sources.