Checking for safe font-lock keywords and hi-lock mode.

[David Koppelman]

Is there any way to check whether font-lock keywords are safe? For
example, such a function might be named font-lock-pattern-safe and
used in the code below, where patterns might contain malicious code:

(font-lock-add-keywords nil
  (apply 'append
   (mapcar 
    (lambda (p) (if (font-lock-pattern-safe-p p) (list p) nil)) 
    patterns))) )

A return of true would mean safe, nil would mean maybe dangerous.

My immediate concern is hi-lock and I would use such a function in
hi-lock-find-patterns. (This automatically grabs font lock patterns
from a file.) If no such function is available right now then
hi-lock-find-patterns should be off by default and if on should ask. I
can have a patch ready by Friday either safe checking (if possible) or
else using some mixture of configuration setting, user input and
whitelisting.