Re: problems with c-fill-paragraph, c++ comments in c modules

[Alan Mackenzie]

Hi, Ragweed,

Ragweed <jeffrey.magill@gmail.com> wrote:
> I've recently built Emacs 23.2.1 on a linux box and it doesn't behave
> the same as the Emacs 21.4.1 on the same host with respect to c++
> comments in a c file.  I can't figure out how to get Emacs 23.2.1 to
> run c-fill-paragraph properly for c++-style comments when they're in a
> c file.

> Consider the following long c++ style comment in a file named test.c:
>>// The quick brown fox jumps over the lazy dog. The quick brown fox jumps 
>>over the lazy dog. The quick brown fox jumps over the lazy dog.

> If I run c-fill-paragraph with the cursor  on that line, Emacs 21.4.1
> converts it to what I want:
>>// The quick brown fox jumps over the lazy dog. The quick brown fox jumps over
>>// the lazy dog. The quick brown fox jumps over the lazy dog.

> If I run c-fill-paragraph in 23.2.1, I get:
> // The quick brown fox jumps over the lazy dog. The quick brown fox
> jumps over
> the lazy dog. The quick brown fox jumps over the lazy dog.

> That is, it wraps the comment to the next line but doesn't prefix the
> next line with the comment prefix.

> If I rename the file to test.cpp, then emacs 23.2.1 DOES prefix the
> line.

> I renamed my .emacs file so that both versions of Emacs use their
> default settings and ignore my normal customizations.

Thanks for taking the trouble to report this bug.  It was actually
reported a couple of months ago and fixed in the repository.

Would you please try applying the following patch (in directory
..../lisp/progmodes), compile the changed file (or just rebuild Emacs
again), and report whether or not the patch does fix the problem.

Thanks!

Here is the patch:

*** orig/cc-cmds.el     2010-07-05 20:17:46.000000000 +0000
--- cc-cmds.el  2010-07-11 18:46:13.066679040 +0000
***************
*** 3975,3980 ****
--- 3975,3988 ----
                                       (goto-char ender-start)
                                       (current-column)))
                       (point-rel (- ender-start here))
+                      (sentence-ends-comment
+                       (save-excursion
+                         (goto-char ender-start)
+                         (and (search-backward-regexp
+                               (c-sentence-end) (c-point 'bol) t)
+                              (goto-char (match-end 0))
+                         (looking-at "[ \t]*")
+                         (= (match-end 0) ender-start))))
                       spaces)
  
                  (save-excursion
***************
*** 4017,4023 ****
                              (setq spaces
                                    (max
                                     (min spaces
!                                         (if sentence-end-double-space 2 1))
                                     1)))
                          ;; Insert the filler first to keep marks right.
                          (insert-char ?x spaces t)
--- 4025,4033 ----
                              (setq spaces
                                    (max
                                     (min spaces
!                                         (if (and sentence-ends-comment
!                                                  sentence-end-double-space)
!                                             2 1))
                                     1)))
                          ;; Insert the filler first to keep marks right.
                          (insert-char ?x spaces t)
***************
*** 4229,4236 ****
    (let ((fill-paragraph-function
         ;; Avoid infinite recursion.
         (if (not (eq fill-paragraph-function 'c-fill-paragraph))
!            fill-paragraph-function)))
!     (c-mask-paragraph t nil 'fill-paragraph arg))
    ;; Always return t.  This has the effect that if filling isn't done
    ;; above, it isn't done at all, and it's therefore effectively
    ;; disabled in normal code.
--- 4239,4249 ----
    (let ((fill-paragraph-function
         ;; Avoid infinite recursion.
         (if (not (eq fill-paragraph-function 'c-fill-paragraph))
!            fill-paragraph-function))
!       (start-point (point-marker)))
!     (c-mask-paragraph
!      t nil (lambda () (fill-region-as-paragraph (point-min) (point-max) arg)))
!     (goto-char start-point))
    ;; Always return t.  This has the effect that if filling isn't done
    ;; above, it isn't done at all, and it's therefore effectively
    ;; disabled in normal code.



-- 
Alan Mackenzie (Nuremberg, Germany).