CC Mode. Adding a ) can hide the resulting (..) from searches. Fix it.

2 files changed, 41 insertions, 9 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 2ffd9ce77a8..d5576370727 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2012-04-22  Alan Mackenzie  <acm@muc.de>
+
+        * progmodes/cc-engine.el (c-append-lower-brace-pair-to-state-cache):
+        Adding a ) can hide the resulting (..) from searches.  Fix it.
+        Bound the backward search to the position of the existing (.
+
 2012-04-21  Juanma Barranquero  <lekktu@gmail.com>
 
         * progmodes/verilog-mode.el (verilog-mode): Check whether
diff --git a/lisp/progmodes/cc-engine.el b/lisp/progmodes/cc-engine.el
index 65e28c11e21..82aee7bdbb9 100644
--- a/lisp/progmodes/cc-engine.el
+++ b/lisp/progmodes/cc-engine.el
@@ -2612,13 +2612,24 @@ comment at the start of cc-engine.el for more info."
   (setq c-state-point-min (point-min)))
 
 (defun c-append-lower-brace-pair-to-state-cache (from &optional upper-lim)
-  ;; If there is a brace pair preceding FROM in the buffer (not necessarily
-  ;; immediately preceding), push a cons onto `c-state-cache' to represent it.
-  ;; FROM must not be inside a literal.  If UPPER-LIM is non-nil, we append
-  ;; the highest brace pair whose "}" is below UPPER-LIM.
+  ;; If there is a brace pair preceding FROM in the buffer, at the same level
+  ;; of nesting (not necessarily immediately preceding), push a cons onto
+  ;; `c-state-cache' to represent it.  FROM must not be inside a literal.  If
+  ;; UPPER-LIM is non-nil, we append the highest brace pair whose "}" is below
+  ;; UPPER-LIM.
   ;;
   ;; Return non-nil when this has been done.
   ;;
+  ;; The situation it copes with is this transformation:
+  ;;
+  ;; OLD:   {                       (.)    {...........}
+  ;;                                       ^             ^
+  ;;                                     FROM          HERE
+  ;;                                     
+  ;; NEW:   {             {....}    (.)    {.........
+  ;;                         ^           ^           ^
+  ;;                LOWER BRACE PAIR   HERE   or   HERE
+  ;;                                       
   ;; This routine should be fast.  Since it can get called a LOT, we maintain
   ;; `c-state-brace-pair-desert', a small cache of "failures", such that we
   ;; reduce the time wasted in repeated fruitless searches in brace deserts.
@@ -2637,10 +2648,25 @@ comment at the start of cc-engine.el for more info."
         (unless (and c-state-brace-pair-desert
                      (eq cache-pos (car c-state-brace-pair-desert))
                      (<= from (cdr c-state-brace-pair-desert)))
-          ;; Only search what we absolutely need to:
-          (if (and c-state-brace-pair-desert
-                   (eq cache-pos (car c-state-brace-pair-desert)))
-              (narrow-to-region (cdr c-state-brace-pair-desert) (point-max)))
+          ;; DESERT-LIM.  Only search what we absolutely need to,
+          (let ((desert-lim
+                 (and c-state-brace-pair-desert
+                      (eq cache-pos (car c-state-brace-pair-desert))
+                      (cdr c-state-brace-pair-desert)))
+                ;; CACHE-LIM.  This limit will be necessary when an opening
+                ;; paren at `cache-pos' has just had its matching close paren
+                ;; inserted.  `cache-pos' continues to be a search bound, even
+                ;; though the algorithm below would skip over the new paren
+                ;; pair.
+                (cache-lim (and cache-pos (< cache-pos from) cache-pos)))
+            (narrow-to-region
+                (cond
+                 ((and desert-lim cache-lim)
+                  (max desert-lim cache-lim))
+                 (desert-lim)
+                 (cache-lim)
+                 ((point-min)))
+                (point-max)))
 
           ;; In the next pair of nested loops, the inner one moves back past a
           ;; pair of (mis-)matching parens or brackets; the outer one moves
@@ -2674,7 +2700,7 @@ comment at the start of cc-engine.el for more info."
                           (cons new-cons (cdr c-state-cache))))
                  (t (setq c-state-cache (cons new-cons c-state-cache)))))
 
-            ;; We haven't found a brace pair.  Record this.
+            ;; We haven't found a brace pair.  Record this in the cache.
             (setq c-state-brace-pair-desert (cons cache-pos from))))))))
 
 (defsubst c-state-push-any-brace-pair (bra+1 macro-start-or-here)