bug#56841: Emacs-28 C Mode: Fontification errors when arglist closing ) is on next line

[Alan Mackenzie]

Hello, Eli.

On Sat, Jul 30, 2022 at 17:14:43 +0300, Eli Zaretskii wrote:
> > Cc: Bill Sacks <sacks@ucar.edu>
> > Date: Sat, 30 Jul 2022 13:05:24 +0000
> > From: Alan Mackenzie <acm@muc.de>

> > 1. Start emacs -Q.
> > 2. Insert the following file in C Mode:

> > void myfunc(

> >   ) {

> > }

> > 3. In line 2 (the first blank line) type "<TAB>int somevar".
> > 4. Note that somevar is not fontified.  This is a bug, given that the
> >   arglist to myfunc is terminated with a ) on line 3.
> > 5. Do something (e.g. typing M-x) to cause a redisplay.  somevar gets
> >   its correct face.
> > 6. Note that any insertion or deletion in L2 causes somevar to lose its
> >   fontification.  This is a bug.
> > 7. (After 6).  Move point onto somevar and do C-u C-x =.  This shows
> >   that the face text property is set on the character despite the face
> >   not appearing on the screen.

> Are you saying this is not a bug in CC mode but somewhere else?  Or
> are you saying that you don't yet know what is the culprit and will
> investigate?

It is most definitely a bug in CC Mode, and I'm looking at it at the
moment.

My feeling right now is that the fix will be too involved to go into the
release branch.

-- 
Alan Mackenzie (Nuremberg, Germany).