Allow arithmetic operators inside C++ template constructs.

Fixes debbugs #22486.  This corrects the previous patch with this message
which was empty.

* lisp/progmodes/cc-langs.el (c-multichar->-op-not->>-regexp): New language
variable.
(c-<>-notable-chars-re): New language variable.

* lisp/progmodes/cc-engine.el (c-forward-<>-arglist-recur): User
c-<>-notable-chars-re in place of the former fixed string in searching for
places to stop and examine.
Use c-multichar->-op-not->>-regexp to check that a found ">" is not part of a
multichar operator in place of the former c->-op-without->-cont-regexp.
Add code to skip forwards over a balanced parenthesized expression.

lisp/progmodes/cc-engine.el

@@ -6056,7 +6056,10 @@ comment at the start of cc-engine.el for more info."
 		   ;; Stop on ',', '|', '&', '+' and '-' to catch
 		   ;; common binary operators that could be between
 		   ;; two comparison expressions "a<b" and "c>d".
-		   "[<;{},|+&-]\\|[>)]"
+		   ;; 2016-02-11: C++11 templates can now contain arithmetic
+		   ;; expressions, so template detection in C++ is now less
+		   ;; robust than it was.
+		   c-<>-notable-chars-re
 		   nil t t))
 
 		(cond
@@ -6064,7 +6067,9 @@ comment at the start of cc-engine.el for more info."
 		  ;; Either an operator starting with '>' or the end of
 		  ;; the angle bracket arglist.
 
-		  (if (looking-at c->-op-without->-cont-regexp)
+		  (if (save-excursion
+			(c-backward-token-2)
+			(looking-at c-multichar->-op-not->>-regexp))
 		      (progn
 			(goto-char (match-end 0))
 			t)		; Continue the loop.
@@ -6134,6 +6139,11 @@ comment at the start of cc-engine.el for more info."
 		      )))
 		  t)			; carry on looping.
 
+		 ((and
+		   (eq (char-before) ?\()
+		   (c-go-up-list-forward)
+		   (eq (char-before) ?\))))
+
 		 ((and (not c-restricted-<>-arglists)
 		       (or (and (eq (char-before) ?&)
 				(not (eq (char-after) ?&)))

lisp/progmodes/cc-langs.el

@@ -228,6 +228,12 @@ the evaluated constant value at compile time."
     ;; with the group symbol for each group and should return non-nil
     ;; if that group is to be included.
     ;;
+    ;; OP-FILTER selects the operators.  It is either t to select all
+    ;; operators, a string to select all operators for which `string-match'
+    ;; matches the operator with the string, or a function which will be
+    ;; called with the operator and should return non-nil when the operator
+    ;; is to be selected.
+    ;;
     ;; If XLATE is given, it's a function which is called for each
     ;; matching operator and its return value is collected instead.
     ;; If it returns a list, the elements are spliced directly into
@@ -1245,7 +1251,6 @@ operators."
 		    t
 		    "\\`<."
 		    (lambda (op) (substring op 1)))))
-
 (c-lang-defvar c-<-op-cont-regexp (c-lang-const c-<-op-cont-regexp))
 
 (c-lang-defconst c->-op-cont-tokens
@@ -1264,7 +1269,6 @@ operators."
   ;; Regexp matching the second and subsequent characters of all
   ;; multicharacter tokens that begin with ">".
   t (c-make-keywords-re nil (c-lang-const c->-op-cont-tokens)))
-
 (c-lang-defvar c->-op-cont-regexp (c-lang-const c->-op-cont-regexp))
 
 (c-lang-defconst c->-op-without->-cont-regexp
@@ -1279,10 +1283,19 @@ operators."
 		     "\\`>>"
 		     (lambda (op) (substring op 1)))
        :test 'string-equal)))
-
 (c-lang-defvar c->-op-without->-cont-regexp
   (c-lang-const c->-op-without->-cont-regexp))
 
+(c-lang-defconst c-multichar->-op-not->>-regexp
+  ;; Regexp matching multichar tokens containing ">", except ">>"
+  t (c-make-keywords-re nil
+      (delete ">>"
+	      (c-filter-ops (c-lang-const c-all-op-syntax-tokens)
+			    t
+			    "\\(.>\\|>.\\)"))))
+(c-lang-defvar c-multichar->-op-not->>-regexp
+  (c-lang-const c-multichar->-op-not->>-regexp))
+
 (c-lang-defconst c-stmt-delim-chars
   ;; The characters that should be considered to bound statements.  To
   ;; optimize `c-crosses-statement-barrier-p' somewhat, it's assumed to
@@ -3087,6 +3100,20 @@ expression is considered to be a type."
 		    ; generics is not yet coded in CC Mode.
 (c-lang-defvar c-recognize-<>-arglists (c-lang-const c-recognize-<>-arglists))
 
+(c-lang-defconst c-<>-notable-chars-re
+  "A regexp matching any single character notable inside a <...> construct.
+This must include \"<\" and \">\", and should include \",\", and
+any character which cannot be valid inside such a construct.
+This is used in `c-forward-<>-arglist-recur' to try to detect
+sequences of tokens which cannot be a template/generic construct.
+When \"(\" is present, that defun will attempt to parse a
+parenthesized expression inside the template.  When \")\" is
+present it will treat an unbalanced closing paren as a sign of
+the invalidity of the putative template construct."
+  t "[<;{},|+&->)]"
+  c++ "[<;{},>()]")
+(c-lang-defvar c-<>-notable-chars-re (c-lang-const c-<>-notable-chars-re))
+
 (c-lang-defconst c-enums-contain-decls
   "Non-nil means that an enum structure can contain declarations."
   t nil