* c-mode.el (c-fill-paragraph): Calculating the proper fill-prefix

	shouldn't change the buffer text.  Make it not.  If we're in the
	blank space before another comment, fill that one as a comment,
	not as normal text.

	* c-mode.el (c-fill-paragraph): When guessing the fill prefix,
	don't ever grab any actual text.

diff --git a/lisp/progmodes/c-mode.el b/lisp/progmodes/c-mode.el
index aa76614..56db49b 100644 (file)
--- a/lisp/progmodes/c-mode.el
+++ b/lisp/progmodes/c-mode.el
@@ -244,7 +244,7 @@ preserving the comment indentation or line-starting decorations."
          ;; Check for obvious entry to comment.
          (save-excursion
            (beginning-of-line)
-           (skip-chars-forward " \t")
+           (skip-chars-forward " \t\n")
            (and (looking-at comment-start-skip)
                 (setq comment-start-place (point))))))
     (if (or first-line
@@ -252,13 +252,14 @@ preserving the comment indentation or line-starting decorations."
            (eq (calculate-c-indent) t)
            ;; t if this line contains a comment starter.
            (setq first-line
-                 (save-excursion (beginning-of-line)
-                                 (prog1
-                                     (re-search-forward comment-start-skip
-                                                        (save-excursion (end-of-line)
-                                                                        (point))
-                                                        t)
-                                   (setq comment-start-place (point))))))
+                 (save-excursion
+                   (beginning-of-line)
+                   (prog1
+                       (re-search-forward comment-start-skip
+                                          (save-excursion (end-of-line)
+                                                          (point))
+                                          t)
+                     (setq comment-start-place (point))))))
        ;; Inside a comment: fill one comment paragraph.
        (let ((fill-prefix
               ;; The prefix for each line of this paragraph
@@ -270,12 +271,49 @@ preserving the comment indentation or line-starting decorations."
                     (progn (re-search-forward comment-start-skip)
                            (make-string (current-column) ?\ ))
                   (if first-line (forward-line 1))
-                  (buffer-substring (point)
-                                    (progn
-                                      (move-to-column
-                                       (calculate-c-indent-within-comment t)
-                                       t)
-                                      (point))))))
+
+                  (let ((line-width (progn (end-of-line) (current-column))))
+                    (beginning-of-line)
+                    (prog1
+                        (buffer-substring
+                         (point)
+
+                         ;; How shall we decide where the end of the
+                         ;; fill-prefix is?
+                         ;; calculate-c-indent-within-comment bases its value
+                         ;; on the indentation of previous lines; if they're
+                         ;; indented specially, it could return a column
+                         ;; that's well into the current line's text.  So
+                         ;; we'll take at most that many space, tab, or *
+                         ;; characters, and use that as our fill prefix.
+                         (let ((max-prefix-end
+                                (progn
+                                  (move-to-column
+                                   (calculate-c-indent-within-comment t)
+                                   t)
+                                  (point))))
+                           (beginning-of-line)
+                           (skip-chars-forward " \t*" max-prefix-end)
+                           (point)))
+
+                      ;; If the comment is only one line followed by a blank
+                      ;; line, calling move-to-column above may have added
+                      ;; some spaces and tabs to the end of the line; the
+                      ;; fill-paragraph function will then delete it and the
+                      ;; newline following it, so we'll lose a blank line
+                      ;; when we shouldn't.  So delete anything
+                      ;; move-to-column added to the end of the line.  We
+                      ;; record the line width instead of the position of the
+                      ;; old line end because move-to-column might break a
+                      ;; tab into spaces, and the new characters introduced
+                      ;; there shouldn't be deleted.
+
+                      ;; If you can see a better way to do this, please make
+                      ;; the change.  This seems very messy to me.
+                      (delete-region (progn (move-to-column line-width)
+                                            (point))
+                                     (progn (end-of-line) (point))))))))
+
              (paragraph-start
               ;; Lines containing just a comment start or just an end
               ;; should not be filled into paragraphs they are next to.