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> From: Frank Li <frankqunli@gmail.com>
> Date: Wed, 1 Sep 2021 18:15:15 -0400
>
> Hi Eli,
>
> It is very easy to reproduce. It happens in C++ mode or C mode and when it happens, Syntax highlighting
> disappears.

Well, I tried just now with Emacs 26.1, and I couldn't reproduce
this.  So please show one sample C/C++ file where you see this, and
please verify that it happens in "emacs -Q".  If it doesn't happen in
"emacs -Q", there's some customization of yours that triggers the
problem, and I would ask you to try to figure out which customization
is that.

Thanks.