Pedwarn on a non-standard position of a C++ attribute.

From-SVN: r260682

gcc/cp/ChangeLog

+2018-05-24  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	Pedwarn on a non-standard position of a C++ attribute.
+	* parser.c (cp_parser_namespace_definition): Pedwarn about attributes
+	after the namespace name.
+
 2018-05-24  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* cp-tree.h (INDIRECT_TYPE_P): New.

gcc/cp/parser.c

@@ -18656,6 +18656,11 @@ cp_parser_namespace_definition (cp_parser* parser)
 	{
 	  identifier = cp_parser_identifier (parser);
 
+	  if (cp_next_tokens_can_be_std_attribute_p (parser))
+	    pedwarn (input_location, OPT_Wpedantic,
+		     "standard attributes on namespaces must precede "
+		     "the namespace name");
+
 	  /* Parse any attributes specified after the identifier.  */
 	  attribs = attr_chainon (attribs, cp_parser_attributes_opt (parser));
 	}

gcc/testsuite/g++.dg/cpp0x/gen-attrs-56.C

@@ -2,4 +2,4 @@
 // { dg-do compile { target c++11 } }
 
 namespace foo __attribute__((visibility("default"))) {}
-namespace bar [[gnu::visibility("default")]] {}
+namespace [[gnu::visibility("default")]] bar {}

gcc/testsuite/g++.dg/cpp0x/gen-attrs-64.C

 // PR c++/85140
 // { dg-do compile { target c++11 } }
 
-namespace N alignas() {}	// { dg-error "expected" }
+namespace alignas() N  {}	// { dg-error "expected" }

gcc/testsuite/g++.dg/cpp1z/namespace-attribs2.C

+// { dg-options "-std=c++17" }
+// { dg-additional-options "-pedantic" }
+
+namespace B [[deprecated]] {} // { dg-warning "ignored|must precede" }
+
+namespace [[deprecated]] D {} // { dg-warning "ignored" }
+