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

[Eli Zaretskii]

> 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?