bug#7918: [PATCH] cc-mode: only the first clause of a for-loop should be checked for declarations

[Lars Ingebrigtsen]

Daniel Colascione <dan.colascione@gmail.com> writes:

> // This code has no variable declarations
>
> void foo() {
>     for (; (DWORD) a * b ;)
>         ;
>
>     for (; a * b ;)
>         ;
> }
>

I can confirm that the Emacs trunk still highlights the "a" in these
examples wrong, and that Daniel's patch seems to fix the issue.
However, I'm totally unfamiliar with the cc-mode code, so it would be
nice if somebody could look at it before it's applied.

=== modified file 'lisp/progmodes/cc-fonts.el'
--- lisp/progmodes/cc-fonts.el  2010-12-07 12:15:28 +0000
+++ lisp/progmodes/cc-fonts.el  2011-01-25 11:10:00 +0000
@@ -1080,7 +1080,8 @@
          ;; o - '<> if the arglist is of angle bracket type;
          ;; o - 'arglist if it's some other arglist;
          ;; o - nil, if not in an arglist at all.  This includes the
-         ;;   parenthesised condition which follows "if", "while", etc.
+         ;;   parenthesised condition which follows "if", "while", etc.,
+         ;;   but not "for", which is 'arglist after `;'.
          context
          ;; The position of the next token after the closing paren of
          ;; the last detected cast.
@@ -1109,7 +1110,7 @@
          ;; `c-forward-decl-or-cast-1' and `c-forward-label' for
          ;; later fontification.
          (c-record-type-identifiers t)
-         label-type
+         label-type paren-state most-enclosing-brace
          c-record-ref-identifiers
          ;; Make `c-forward-type' calls mark up template arglists if
          ;; it finds any.  That's necessary so that we later will
@@ -1171,7 +1172,6 @@
                                 'font-lock-function-name-face))))
          (c-font-lock-function-postfix limit))
 
-        
         (setq start-pos (point))
         (when
             ;; The result of the `if' condition below is true when we don't 
recognize a
@@ -1189,7 +1189,31 @@
            ;; (e.g. "for (").
            (let ((type (and (> match-pos (point-min))
                             (c-get-char-property (1- match-pos) 'c-type))))
-             (cond ((not (memq (char-before match-pos) '(?\( ?, ?\[ ?<)))
+             (cond
+               (;; Try to not fontify the second and third clauses of
+               ;; `for' statements as declarations.
+               (and (or (eq (char-before match-pos) ?\;)
+                        (save-excursion
+                          ;; Catch things like for(; (DWORD)(int) x &
+                          ;; y; ) without invoking the full might of
+                          ;; c-beginning-of-statement-1.
+                          (goto-char match-pos)
+                          (while (eq (char-before) ?\))
+                            (c-go-list-backward)
+                            (c-backward-syntactic-ws))
+                          (eq (char-before) ?\;)))
+                    
+                     (setq paren-state (c-parse-state))
+                     (setq most-enclosing-brace
+                           (c-most-enclosing-brace paren-state))
+                    (eq (char-after most-enclosing-brace) ?\())
+               
+                ;; After a ";" in a for-block. A declaration can never
+                ;; begin after a `;' if the most enclosing paren is a
+                ;; `('.
+               (setq context 'arglist
+                      c-restricted-<>-arglists t))
+               ((not (memq (char-before match-pos) '(?\( ?, ?\[ ?<)))
                     (setq context nil
                           c-restricted-<>-arglists nil))
                    ;; A control flow expression
@@ -1252,7 +1276,7 @@
                ;; Are we at a declarator?  Try to go back to the declaration
                ;; to check this.  Note that `c-beginning-of-decl-1' is slow,
                ;; so we cache its result between calls.
-               (let (paren-state bod-res encl-pos is-typedef)
+               (let (bod-res encl-pos is-typedef)
                  (goto-char start-pos)
                  (save-excursion
                    (unless (and decl-search-lim
@@ -1318,20 +1342,7 @@
                ;; Back up to the type to fontify the declarator(s).
                (goto-char (car decl-or-cast))
 
-               (let ((decl-list
-                      (if context
-                          ;; Should normally not fontify a list of
-                          ;; declarators inside an arglist, but the first
-                          ;; argument in the ';' separated list of a "for"
-                          ;; statement is an exception.
-                          (when (eq (char-before match-pos) ?\()
-                            (save-excursion
-                              (goto-char (1- match-pos))
-                              (c-backward-syntactic-ws)
-                              (and (c-simple-skip-symbol-backward)
-                                   (looking-at c-paren-stmt-key))))
-                        t)))
-
+                (let ((decl-list (not context)))
                  ;; Fix the `c-decl-id-start' or `c-decl-type-start' property
                  ;; before the first declarator if it's a list.
                  ;; `c-font-lock-declarators' handles the rest.



-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no