* lisp/newcomment.el (comment-use-global-state): Change default value

to t, mark obsolete.
(comment-beginning): In addition to `comment-to-syntax', check the
value of `comment-use-global-state'.

Fixes: debbugs:15251

etc/NEWS

@@ -157,6 +157,9 @@ some enhancements, like the ability to restore deleted frames.  Command
 ** The command `quail-help' is deleted.  Use `C-h C-\'
 (`describe-input-method') instead.
 
+** The default value of `comment-use-global-state' is changed to t,
+and this variable has been marked obsolete.
+
 
 * Editing Changes in Emacs 24.4
 
@@ -214,7 +217,7 @@ You can use the new function `remember-store-in-files' within the
 See `remember-data-directory' and `remember-directory-file-name-format'
 for new options related to this function.
 
-** More packages look for ~/.emacs.d/<foo> additionally to ~/.<foo>.
+* More packages look for ~/.emacs.d/<foo> additionally to ~/.<foo>.
 Affected files:
 ~/.emacs.d/timelog	replaces  ~/.timelog
 ~/.emacs.d/vip		replaces  ~/.vip

lisp/ChangeLog

+2013-10-05  Dmitry Gutov  <dgutov@yandex.ru>
+
+	* newcomment.el (comment-use-global-state): Change default value
+	to t, mark obsolete (Bug#15251).
+	(comment-beginning): In addition to `comment-to-syntax', check the
+	value of `comment-use-global-state'.
+
 2013-10-05  Stefan Monnier  <monnier@iro.umontreal.ca>
 
 	* progmodes/ruby-mode.el (ruby-use-smie): Change default.

lisp/newcomment.el

@@ -435,12 +435,15 @@ If UNP is non-nil, unquote nested comment markers."
 ;;;; Navigation
 ;;;;
 
-(defvar comment-use-global-state nil
+(defvar comment-use-global-state t
   "Non-nil means that the global syntactic context is used.
 More specifically, it means that `syntax-ppss' is used to find out whether
-point is within a string or not.  Major modes whose syntax is faithfully
-described by the syntax-tables can set this to non-nil so comment markers
-in strings will not confuse Emacs.")
+point is within a string or not.  Major modes whose syntax is not faithfully
+described by the syntax-tables (or where `font-lock-syntax-table' is radically
+different from the main syntax table) can set this to nil,
+then `syntax-ppss' cache won't be used in comment-related routines.")
+
+(make-obsolete-variable 'comment-use-global-state 'comment-use-syntax "24.4")
 
 (defun comment-search-forward (limit &optional noerror)
   "Find a comment start between point and LIMIT.
@@ -515,7 +518,7 @@ Ensure that `comment-normalize-vars' has been called before you use this."
   "Find the beginning of the enclosing comment.
 Returns nil if not inside a comment, else moves point and returns
 the same as `comment-search-backward'."
-  (if comment-use-syntax
+  (if (and comment-use-syntax comment-use-global-state)
       (let ((state (syntax-ppss)))
         (when (nth 4 state)
           (goto-char (nth 8 state))