[bug nyacc] C99 parser crashes on #warning

Hi!

Using the file warning.c:

--8<---------------cut here---------------start------------->8---
// warning.c
#warning warn me!
#warning oops
--8<---------------cut here---------------end--------------->8---

Nyacc's c99 parser crashes on (right after) the first #warning

--8<---------------cut here---------------start------------->8---
$ guile 
GNU Guile 3.0.9
Copyright (C) 1995-2023 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> ,use (nyacc lang c99 parser)
scheme@(guile-user)> ,use (nyacc version)
scheme@(guile-user)> *nyacc-version*
$1 = "1.09.4"
scheme@(guile-user)> (with-input-from-file "warning.c" parse-c99)
warning: warn me!
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
In procedure car: Wrong type argument in position 1 (expecting pair): #<unspecified>

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,bt
In ice-9/ports.scm:
   433:17  9 (call-with-input-file _ _ #:binary _ #:encoding _ #:guess-encoding _)
    472:4  8 (_ _)
In nyacc/lang/c99/parser.scm:
    784:6  7 (parse-c99 _ #:cpp-defs _ #:inc-dirs _ #:inc-help _ #:mode _ #:xdef? _ # _ # _ …)
In ice-9/boot-9.scm:
  1747:15  6 (with-exception-handler #<procedure 7fa866593180 at ice-9/boot-9.scm:1831:7 (…> …)
  1747:15  5 (with-exception-handler #<procedure 7fa866593150 at ice-9/boot-9.scm:1831:7 (…> …)
In nyacc/lang/c99/parser.scm:
   787:33  4 (_)
In nyacc/parse.scm:
   169:37  3 (_ #<procedure 7fa8665a3ee0 at nyacc/lang/c99/parser.scm:376:8 ()> #:debug _)
In nyacc/lang/c99/parser.scm:
   697:27  2 (_)
   594:29  1 (read-token)
In ice-9/boot-9.scm:
  1685:16  0 (raise-exception _ #:continuable? _)
scheme@(guile-user) [1]> 
--8<---------------cut here---------------end--------------->8---

Greetings,
Janneke

-- 
Janneke Nieuwenhuizen <[email protected]>  | GNU LilyPond https://LilyPond.org
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