bug#16585: c-invalidate-state-cache fails if called when narrowed

[Daniel Colascione <dancol@dancol.org>]

c-invalidate-state-cache can fail if called in a narrowed region: we end 
up calling c-clear-char-property for bob even if that's before 
point-min, causing remote-text-properties to raise (args-out-of-range 1 2).

We get into this situation when expanding yasnippet snippets; we're 
calling c-invalidate-state-cache from c-before-change.

To repro manually, first write this to some buffer.

#include <stdio.h>

void foo() {

}


Then (this is important) run M-x c-mode. After starting the mode, move 
point to inside foo's body and eval (save-restriction (narrow-to-region 
(point-at-bol) (point-at-eol)) (c-invalidate-state-cache (point))). You 
should break into the debugger.

The patch below seems correct and fixes the problem for me, but it'd be 
nice if Alan could take a look at it before I push it to trunk. The 
version of c-invalidate-state-cache in cc-mode trunk is very different.

=== modified file 'lisp/progmodes/cc-engine.el'
--- lisp/progmodes/cc-engine.el	2014-01-19 12:32:47 +0000
+++ lisp/progmodes/cc-engine.el	2014-01-29 02:07:44 +0000
@@ -3318,15 +3318,17 @@
    ;; of all parens in preprocessor constructs, except for any such 
construct
    ;; containing point.  We can then call `c-invalidate-state-cache-1' 
without
    ;; worrying further about macros and template delimiters.
-  (c-with-<->-as-parens-suppressed
-   (if (and c-state-old-cpp-beg
-	    (< c-state-old-cpp-beg here))
-       (c-with-all-but-one-cpps-commented-out
-	c-state-old-cpp-beg
-	(min c-state-old-cpp-end here)
-	(c-invalidate-state-cache-1 here))
-     (c-with-cpps-commented-out
-      (c-invalidate-state-cache-1 here)))))
+  (save-restriction
+    (widen)
+    (c-with-<->-as-parens-suppressed
+     (if (and c-state-old-cpp-beg
+              (< c-state-old-cpp-beg here))
+         (c-with-all-but-one-cpps-commented-out
+          c-state-old-cpp-beg
+          (min c-state-old-cpp-end here)
+          (c-invalidate-state-cache-1 here))
+       (c-with-cpps-commented-out
+        (c-invalidate-state-cache-1 here))))))

  (defmacro c-state-maybe-marker (place marker)
    ;; If PLACE is non-nil, return a marker marking it, otherwise nil.