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[var-template] Accept variable template declaration

This patch lets us accept declarations of constexpr variable templates.
Actual semantics processing of specialization is subject of follow up

The patch represents a variable template as a variable temploid whose
scope is a namespace, or member template that generates a static data member.

Applied to var-template branch.

-- Gaby

2013-03-29  Gabriel Dos Reis  <>
	* cp-tree.h (variable_template_p): New.
	* pt.c (check_template_variable): Accept variable temploids at
	non-class scope.
	(push_template_decl_real): The current instantiation of a template
	can be a VAR_DECL.

Index: gcc/cp/cp-tree.h
--- gcc/cp/cp-tree.h	(revision 197248)
+++ gcc/cp/cp-tree.h	(working copy)
@@ -4926,6 +4926,18 @@
   return TREE_TYPE (type_of_this_parm (fntype));
+/* True if T designates a variable template declaration.  */
+inline bool
+variable_template_p (tree t)
+    return false;
+  if (tree r = DECL_TEMPLATE_RESULT (t))
+    return VAR_P (r);
+  return false;
 /* A parameter list indicating for a function with no parameters,
    e.g  "int f(void)".  */
 extern cp_parameter_declarator *no_parameters;
Index: gcc/cp/pt.c
--- gcc/cp/pt.c	(revision 197248)
+++ gcc/cp/pt.c	(working copy)
@@ -2270,9 +2270,11 @@
   tree ctx = CP_DECL_CONTEXT (decl);
   int wanted = num_template_headers_for_class (ctx);
-  if (!TYPE_P (ctx) || !CLASSTYPE_TEMPLATE_INFO (ctx))
-    permerror (DECL_SOURCE_LOCATION (decl),
-	       "%qD is not a static data member of a class template", decl);
+  if (!TYPE_P (ctx) || !CLASSTYPE_TEMPLATE_INFO (ctx)) {
+    if (cxx_dialect < cxx1y)
+      permerror (DECL_SOURCE_LOCATION (decl),
+                 "%qD is not a static data member of a class template", decl);
+  }
   else if (template_header_count > wanted)
       pedwarn (DECL_SOURCE_LOCATION (decl), 0,
@@ -4616,6 +4618,10 @@
 	       && TYPE_DECL_ALIAS_P (decl))
 	/* alias-declaration */
 	gcc_assert (!DECL_ARTIFICIAL (decl));
+      else if (VAR_P (decl)) {
+        if (!DECL_DECLARED_CONSTEXPR_P (decl))
+          error ("template declaration of non-constexpr variable %qD", decl);
+      }
 	  error ("template declaration of %q#D", decl);

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