Re: cannot activate font-lock-mode

[Stefan Monnier]

>> Now, when desktop.el loads it, it asks if I want to apply the
>> font-lock-keywords customisation, because it is risky (is it?).

> Font-lock can modify arbitrary text properties, such as display
> strings, and not just faces.

And it can also directly run any code, which is even more immediately scary.
We should probably write a font-lock-keywords-safe-p.  Something like the
one below, maybe.


        Stefan


--- orig/lisp/font-lock.el
+++ mod/lisp/font-lock.el
@@ -454,6 +454,23 @@
 user-level keywords, but normally their values have been
 optimized.")
 
+(defun font-lock-keywords-safe-p (val)
+  (catch 'unsafe
+    (while (consp val)
+      (let ((kw (pop val)))
+        (unless (stringp (pop kw)) (throw 'unsafe nil))
+        (while (consp kw)
+          (let ((hl (pop kw)))
+            (unless (natnump (pop hl)) (throw 'unsafe nil))
+            (unless (or (symbolp (car hl))
+                        (and (eq 'quote (safe-car (car hl)))
+                             (symbolp (safe-car (cdar hl)))))
+              (throw 'unsafe nil))))
+        (when kw (throw 'unsafe nil))))
+    (when val (throw 'unsafe nil))
+    t))
+(put 'font-lock-keywords 'safe-local-variable 'font-lock-keywords-safe-p)
+
 (defvar font-lock-keywords-alist nil
   "Alist of additional `font-lock-keywords' elements for major modes.