bug#41809: c-context-line-break incorrect after comments: cache issue?

[Alan Mackenzie]

Hello, Daniel.

On Thu, Jun 11, 2020 at 18:38:29 -0000, Alan Mackenzie wrote:
> In article <mailman.1663.1591891807.2541.bug-gnu-emacs@gnu.org> you wrote:
> > c-context-line-break sometimes incorrectly extends a comment when invoked
> > immediately after the end of a comment. To repro:

> > emacs -Q --eval '(progn (c-mode) (insert "/*foo*/") (backward-char)
> > (c-context-line-break) (delete-char -2) (end-of-line)
> > (c-context-line-break))'

> > The second c-context-line-break occurs when point is *after* the comment,
> > so the /*foo*/ comment shouldn't be extended --- yet it is. The problem
> > appears to be some kind of cc-mode cache corruption. This recipe behaves
> > correctly:

> > $ emacs -Q --eval '(progn (c-mode) (insert "/*foo*/") (backward-char)
> > (c-context-line-break) (delete-char -2) (end-of-line) (c-before-change
> > (point-min) (point-max)) (c-after-change (point-min) (point-max) (1-
> > (point-max))) (c-context-line-break))'

> Thanks for the report.

> After a quick bit of edebugging, it seems to be an off-by-one error in
> some cache handling.  It shouldn't be too difficult to sort out.

It wasn't.  I've committed a simple patch for this, and I'm closing the
bug.

> -- 
> Alan Mackenzie (Nuremberg, Germany).