bug#18749: 24.3.94; CC Mode 5.32.5 (C/l); cc-mode state cache failure leading to bad indentation

[Alan Mackenzie]

Hello, Michael.

On Fri, Oct 17, 2014 at 06:19:50PM -0000, Alan Mackenzie wrote:

> > A consistent c-mode indentation error that causes bad indentation, much
> > cursing, and gnashing of teeth.  This occurs in the latest emacs-24
> > branch (and trunk).

[ .... ]

> >     M-x c-toggle-parse-state-debug
> >     C-x C-f rwuniqsetup.c.before.2
> >     C-s ipaddr_rec_to_bin RET
> >     C-v

> > At this point, indentation is having problems.  Try hitting TAB on line
> > 1371, for example.  Or line 1374 for a complete failure to indent at
> > all.

[ .... ]

> Look forward to a patch soon!

OK, Could you try this, please, and get back to me ASAP.  Thanks!



diff -r a785658eaedb cc-engine.el
--- a/cc-engine.el      Thu Oct 02 20:17:43 2014 +0000
+++ b/cc-engine.el      Fri Oct 17 19:58:19 2014 +0000
@@ -254,6 +254,24 @@
     (setq c-macro-cache-start-pos beg
          c-macro-cache-syntactic nil))))
 
+(defun c-macro-is-genuine-p ()
+  ;; Check that the ostensible CPP construct at point is a real one.  In
+  ;; particular, if point is on the first line of a narrowed buffer, make sure
+  ;; that the "#" isn't, say, the second character of a "##" operator.  Return
+  ;; t when the macro is real, nil otherwise.
+  (let ((here (point)))
+    (beginning-of-line)
+    (prog1
+       (if (and (eq (point) (point-min))
+                (/= (point) 1))
+           (save-restriction
+             (widen)
+             (beginning-of-line)
+             (and (looking-at c-anchored-cpp-prefix)
+                  (eq (match-beginning 1) here)))
+         t)
+      (goto-char here))))
+
 (defun c-beginning-of-macro (&optional lim)
   "Go to the beginning of a preprocessor directive.
 Leave point at the beginning of the directive and return t if in one,
@@ -284,7 +302,8 @@
            (forward-line -1))
          (back-to-indentation)
          (if (and (<= (point) here)
-                  (looking-at c-opt-cpp-start))
+                  (looking-at c-opt-cpp-start)
+                  (c-macro-is-genuine-p))
              (progn
                (setq c-macro-cache (cons (point) nil)
                      c-macro-cache-start-pos here)


> > -- 
> > Michael Welsh Duggan
> > (md5i@md5i.com)

-- 
Alan Mackenzie (Nuremberg, Germany).