bug#59233: CC Mode 5.35.2 (C/*l); (A different type of) incorrect fontification of variables as types while typing

Hello, Po.

Thanks for the most recent two bug reports!

On Sun, Nov 13, 2022 at 09:24:28 +0800, Po Lu via CC-Mode-help wrote:
> Package: cc-mode

> Hello.  If you put the following in a C mode buffer:

> foo (void)
> {
>   Window root;
>   xcb_randr_get_providers_cookie_t cookie;
>   xcb_randr_get_providers_reply_t *reply;
>   xcb_randr_provider_t *providers;
>   int nproviders;
>   xcb_dri3_open_cookie_t *open_cookies;
>   xcb_dri3_open_reply_t *open_replies;
>   int ndevices;

>   root = DefaultRootWindow (compositor.display);

>   /* Get a list of all providers on the default screen.  */
>   cookie = xcb_randr_get_providers (compositor.conn,
> 				    root,
> 				    XCB_CURRENT_TIME);
>   reply = xcb_randr_get_providers_reply (compositor.conn,
> 					 cookie, NULL);

>   if (!reply)
>     return NULL;

>   providers = xcb_randr_get_providers_providers (reply);
>   nproviders = xcb_randr_get_providers_providers_length (reply);

>   /* Now, open each and every provider.  */
>   open_cookies = alloca (nproviders * sizeof *open_cookies);
>   open_replies = alloca (nproviders )
> }

> place point after the last "nproviders", and type:

>     SPC * SPC s i z e o f SPC * o p e n _ r e p l i e s

> nproviders will be mistakenly recognized as a type.  I guess because it
> looks like a pointer to nproviders to CC Mode.

It looks like a function declaration int foo (nproviders *), declaring a
function taking one argument, with type a pointer to nproviders.

This is very similar to a previous bug, hence easy to correct.  Would
you please do the usual with the attached patch.  Thanks!

> Thanks.

> Emacs  : GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu)
>  of 2022-11-12
> Package: CC Mode 5.35.2 (C/*l)
> Buffer Style: gnu
> c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)

[ .... ]

-- 
Alan Mackenzie (Nuremberg, Germany).

diff -r d83cff83c20e cc-engine.el
--- a/cc-engine.el	Thu Nov 10 09:56:38 2022 +0000
+++ b/cc-engine.el	Sun Nov 13 13:28:20 2022 +0000
@@ -11099,6 +11099,11 @@
 	     ;; `got-parens' or `got-suffix' is set it's "a()", "a[]", "a()[]",
 	     ;; or similar, which we accept only if the context rules out
 	     ;; expressions.
+	     ;;
+	     ;; If we've got at-type 'maybe, we cannot confidently promote the
+	     ;; possible type to a found type.
+	     (when (and (eq at-type 'maybe))
+	       (setq unsafe-maybe t))
 	     (throw 'at-decl-or-cast t)))
 
 	 ;; If we had a complete symbol table here (which rules out