auto insert for C failure / c-companion-file missing

[Paul]

Hello,

When using auto-insert and opening a new .c file I get
asked if I want auto insertion to be performed. If I
answer yes, the result is no insertion at all.
Auto insertion does work for .h files.

If I look at the responsible code I see this:
(auto-insert-alist) (emacs 21.2.1)

...
 (("\\.\\([Cc]\\|cc\\|cpp\\)\\'" . "C / C++ program")
  nil "#include \""
  (and
   (fboundp 'c-companion-file)
   (file-name-nondirectory
    (c-companion-file 'name)))
  & 34 | -10)
...

obviously this tries to execute c-companion-file
which is supposedly to supply the name of a '.h' file.

The thing is, c-companion-file isn't defined!

I looked both on google and google groups, but the
best I could find was an ignored bug report filed
by Henrik Enberg last december, in which he also
supplied a patch.

Does anybody have more information on this and how
to solve it?