* src/syntax.c (back_comment): Detect the case where a 1-char comment

starter is also the 2nd char of a 2-char comment ender.

src/ChangeLog

+2010-09-21  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+	* syntax.c (back_comment): Detect the case where a 1-char comment
+	starter is also the 2nd char of a 2-char comment ender.
+
 2010-09-17  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* gtkutil.c (xg_tool_bar_menu_proxy): Set gtk-menu-items to TRUE.

src/syntax.c

@@ -512,6 +512,7 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
     {
       int temp_byte, prev_syntax;
       int com2start, com2end;
+      int comstart;
 
       /* Move back and examine a character.  */
       DEC_BOTH (from, from_byte);
@@ -530,6 +531,7 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
 		       || SYNTAX_FLAGS_COMMENT_NESTED (syntax)) == comnested);
       com2end = (SYNTAX_FLAGS_COMEND_FIRST (syntax)
 		 && SYNTAX_FLAGS_COMEND_SECOND (prev_syntax));
+      comstart = (com2start || code == Scomment);
       
       /* Nasty cases with overlapping 2-char comment markers:
 	 - snmp-mode: -- c -- foo -- c --
@@ -541,15 +543,16 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
 		      ///   */
 
       /* If a 2-char comment sequence partly overlaps with another,
-	 we don't try to be clever.  */
-      if (from > stop && (com2end || com2start))
+	 we don't try to be clever.  E.g. |*| in C, or }% in modes that
+	 have %..\n and %{..}%.  */
+      if (from > stop && (com2end || comstart))
 	{
 	  int next = from, next_byte = from_byte, next_c, next_syntax;
 	  DEC_BOTH (next, next_byte);
 	  UPDATE_SYNTAX_TABLE_BACKWARD (next);
 	  next_c = FETCH_CHAR_AS_MULTIBYTE (next_byte);
 	  next_syntax = SYNTAX_WITH_FLAGS (next_c);
-	  if (((com2start || comnested)
+	  if (((comstart || comnested)
 	       && SYNTAX_FLAGS_COMEND_SECOND (syntax)
 	       && SYNTAX_FLAGS_COMEND_FIRST (next_syntax))
 	      || ((com2end || comnested)