(indent-for-comment): Check for null `comment-start-skip'.

1 files changed, 41 insertions, 38 deletions

diff --git a/lisp/simple.el b/lisp/simple.el
index 5e0687ca364..db3340e956f 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -2392,44 +2392,47 @@ If nil, use `comment-end' instead."
                                 (looking-at "[ \t]*$")))
          (starter (or (and empty block-comment-start) comment-start))
          (ender (or (and empty block-comment-end) comment-end)))
-    (if (null starter)
-        (error "No comment syntax defined")
-      (let* ((eolpos (save-excursion (end-of-line) (point)))
-             cpos indent begpos)
-        (beginning-of-line)
-        (if (re-search-forward comment-start-skip eolpos 'move)
-            (progn (setq cpos (point-marker))
-                   ;; Find the start of the comment delimiter.
-                   ;; If there were paren-pairs in comment-start-skip,
-                   ;; position at the end of the first pair.
-                   (if (match-end 1)
-                       (goto-char (match-end 1))
-                     ;; If comment-start-skip matched a string with
-                     ;; internal whitespace (not final whitespace) then
-                     ;; the delimiter start at the end of that
-                     ;; whitespace.  Otherwise, it starts at the
-                     ;; beginning of what was matched.
-                     (skip-syntax-backward " " (match-beginning 0))
-                     (skip-syntax-backward "^ " (match-beginning 0)))))
-        (setq begpos (point))
-        ;; Compute desired indent.
-        (if (= (current-column)
-               (setq indent (if comment-indent-hook
-                                (funcall comment-indent-hook)
-                              (funcall comment-indent-function))))
-            (goto-char begpos)
-          ;; If that's different from current, change it.
-          (skip-chars-backward " \t")
-          (delete-region (point) begpos)
-          (indent-to indent))
-        ;; An existing comment?
-        (if cpos 
-            (progn (goto-char cpos)
-                   (set-marker cpos nil))
-          ;; No, insert one.
-          (insert starter)
-          (save-excursion
-            (insert ender)))))))
+    (cond
+     ((null starter)
+      (error "No comment syntax defined"))
+     ((null comment-start-skip)
+      (error "This mode doesn't define `comment-start-skip'"))
+     (t (let* ((eolpos (save-excursion (end-of-line) (point)))
+               cpos indent begpos)
+          (beginning-of-line)
+          (if (re-search-forward comment-start-skip eolpos 'move)
+              (progn (setq cpos (point-marker))
+                     ;; Find the start of the comment delimiter.
+                     ;; If there were paren-pairs in comment-start-skip,
+                     ;; position at the end of the first pair.
+                     (if (match-end 1)
+                         (goto-char (match-end 1))
+                       ;; If comment-start-skip matched a string with
+                       ;; internal whitespace (not final whitespace) then
+                       ;; the delimiter start at the end of that
+                       ;; whitespace.  Otherwise, it starts at the
+                       ;; beginning of what was matched.
+                       (skip-syntax-backward " " (match-beginning 0))
+                       (skip-syntax-backward "^ " (match-beginning 0)))))
+          (setq begpos (point))
+          ;; Compute desired indent.
+          (if (= (current-column)
+                 (setq indent (if comment-indent-hook
+                                  (funcall comment-indent-hook)
+                                (funcall comment-indent-function))))
+              (goto-char begpos)
+            ;; If that's different from current, change it.
+            (skip-chars-backward " \t")
+            (delete-region (point) begpos)
+            (indent-to indent))
+          ;; An existing comment?
+          (if cpos 
+              (progn (goto-char cpos)
+                     (set-marker cpos nil))
+            ;; No, insert one.
+            (insert starter)
+            (save-excursion
+              (insert ender))))))))
 
 (defun set-comment-column (arg)
   "Set the comment column based on point.