`scad-mode` (derived from CC Mode) hangs Emacs. How to debug/fix?

Question

I have found that scad-mode.el, a derived mode from CC Mode, which can be found here:

https://github.com/openscad/openscad/blob/master/contrib/scad-mode.el

hangs emacs if I type

#(

into the window, or indeed any line containing a # and also one of ()[]{}. I have to kill Emacs completely and restart it after this crash.

I'm not familiar with how one write a derived mode and have not been able to figure out why this happens. I deleted almost all of scad-mode.el and I still get the hang. (This makes me suspect that the hang is caused by something missing rather than something in the code.) Furthermore, I can't find a coherent explanation of how one writes derived modes. The example derived mode,

http://cc-mode.sourceforge.net/derived-mode-ex.el

doesn't look much like scad-mode.el. I wonder if perhaps things have changed since 2002, when the example was written. The documentation text for c-basic-common-init says I need to call c-init-language-vars first, which scad-mode does not. But if I add a call to this

(c-init-language-vars scad-mode)

I get the message:

File mode specification error: (void-function c-init-language-vars)

Can anybody tell me what's wrong with scad-mode.el that it causes Emacs to hang? Or how to go about debugging it?

Note: I reduced scad-mode.el to this:

(add-to-list 'auto-mode-alist '("\\.scad$" . scad-mode))
(require 'cc-mode)
(define-derived-mode scad-mode prog-mode "SCAD"
  "Major mode for editing OpenSCAD code."
  (c-initialize-cc-mode)
  (c-basic-common-init 'scad-mode "k&r")
)
(provide 'scad-mode)

and it still hangs the same way. It's not clear to me how to truly disentangle the question of how to write a mode from the question of why this is hanging. It has been suggested to me that it's an emacs bug.