bug#36484: c-mode hangs on macro with comment

[Alan Mackenzie <acm@muc.de>]

Hello again, Nicholas.

In article <mailman.43.1562114299.2688.bug-gnu-emacs@gnu.org> you wrote:
> Here's a simple C program:

> #define x /***/5
> int main(void) {
>     return x;
> }

> `gcc -Wall` compiles it without any warnings, but opening it causes
> Emacs to hang, and sometimes even to freeze hard.

> It has something to do with the macro, but I haven't been able to
> figure out exactly what's going on.

There was an infinite loop in c-end-of-macro, now fixed.

[ .... ]

> Running that function under the profiler suggests that the problem is
> in `c-end-of-macro`:

Indeed, so.

[ .... ]

I've committed a patch to the Emacs repository master branch.  Would you
please update your copy of master, and confirm the bug is indeed fixed
(or else, tell me what's still wrong).

> GNU Emacs 27.0.50 (build 6, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
> of 2019-06-30

Thanks for taking the trouble to report this bug, and thanks even more
for making it such an easy to follow report, and doing so much diagnosis
on it.

-- 
Alan Mackenzie (Nuremberg, Germany).