re PR c++/59012 (alignas does not support parameter pack expansions)

PR c++/59012
	* parser.c (cp_parser_std_attribute_list): Handle attribute expansion.
	(cp_parser_std_attribute_spec): Handle alignas pack expansion.
	* decl2.c (is_late_template_attribute): An attribute exp is dependent.
	* pt.c (make_pack_expansion): Allow TREE_LIST for attribute expansion.
	(apply_late_template_attributes): Handle attribute pack expansion.

From-SVN: r222902

gcc/cp/ChangeLog

@@ -1,3 +1,12 @@
+2015-05-07  Jason Merrill  <jason@redhat.com>
+
+	PR c++/59012
+	* parser.c (cp_parser_std_attribute_list): Handle attribute expansion.
+	(cp_parser_std_attribute_spec): Handle alignas pack expansion.
+	* decl2.c (is_late_template_attribute): An attribute exp is dependent.
+	* pt.c (make_pack_expansion): Allow TREE_LIST for attribute expansion.
+	(apply_late_template_attributes): Handle attribute pack expansion.
+
 2015-05-07  Marek Polacek  <polacek@redhat.com>
 
 	PR c/65179

gcc/cp/decl2.c

@@ -1175,6 +1175,10 @@ is_late_template_attribute (tree attr, tree decl)
       && is_attribute_p ("omp declare simd", name))
     return true;
 
+  /* An attribute pack is clearly dependent.  */
+  if (args && PACK_EXPANSION_P (args))
+    return true;
+
   /* If any of the arguments are dependent expressions, we can't evaluate
      the attribute until instantiation time.  */
   for (arg = args; arg; arg = TREE_CHAIN (arg))

gcc/cp/parser.c

@@ -22486,6 +22486,13 @@ cp_parser_std_attribute_list (cp_parser *parser)
 	  attributes = attribute;
 	}
       token = cp_lexer_peek_token (parser->lexer);
+      if (token->type == CPP_ELLIPSIS)
+	{
+	  cp_lexer_consume_token (parser->lexer);
+	  TREE_VALUE (attribute)
+	    = make_pack_expansion (TREE_VALUE (attribute));
+	  token = cp_lexer_peek_token (parser->lexer);
+	}
       if (token->type != CPP_COMMA)
 	break;
       cp_lexer_consume_token (parser->lexer);
@@ -22564,20 +22571,27 @@ cp_parser_std_attribute_spec (cp_parser *parser)
 	    return alignas_expr;
 	}
 
+      alignas_expr = cxx_alignas_expr (alignas_expr);
+      alignas_expr = build_tree_list (NULL_TREE, alignas_expr);
+
+      if (cp_lexer_next_token_is (parser->lexer, CPP_ELLIPSIS))
+	{
+	  cp_lexer_consume_token (parser->lexer);
+	  alignas_expr = make_pack_expansion (alignas_expr);
+	}
+
       if (cp_parser_require (parser, CPP_CLOSE_PAREN, RT_CLOSE_PAREN) == NULL)
 	{
 	  cp_parser_error (parser, "expected %<)%>");
 	  return error_mark_node;
 	}
 
-      alignas_expr = cxx_alignas_expr (alignas_expr);
-
       /* Build the C++-11 representation of an 'aligned'
 	 attribute.  */
       attributes =
 	build_tree_list (build_tree_list (get_identifier ("gnu"),
 					  get_identifier ("aligned")),
-			 build_tree_list (NULL_TREE, alignas_expr));
+			 alignas_expr);
     }
 
   return attributes;

gcc/cp/pt.c

@@ -3338,9 +3338,9 @@ make_pack_expansion (tree arg)
   if (!arg || arg == error_mark_node)
     return arg;
 
-  if (TREE_CODE (arg) == TREE_LIST)
+  if (TREE_CODE (arg) == TREE_LIST && TREE_PURPOSE (arg))
     {
-      /* The only time we will see a TREE_LIST here is for a base
+      /* A TREE_LIST with a non-null TREE_PURPOSE is for a base
          class initializer.  In this case, the TREE_PURPOSE will be a
          _TYPE node (representing the base class expansion we're
          initializing) and the TREE_VALUE will be a TREE_LIST
@@ -9012,6 +9012,21 @@ apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
 		      = tree_cons (NULL_TREE, TREE_VALUE (TREE_VALUE (t)),
 				   chain);
 		}
+	      else if (TREE_VALUE (t) && PACK_EXPANSION_P (TREE_VALUE (t)))
+		{
+		  /* An attribute pack expansion.  */
+		  tree purp = TREE_PURPOSE (t);
+		  tree pack = (tsubst_pack_expansion
+			       (TREE_VALUE (t), args, complain, in_decl));
+		  int len = TREE_VEC_LENGTH (pack);
+		  for (int i = 0; i < len; ++i)
+		    {
+		      tree elt = TREE_VEC_ELT (pack, i);
+		      *q = build_tree_list (purp, elt);
+		      q = &TREE_CHAIN (*q);
+		    }
+		  continue;
+		}
 	      else
 		TREE_VALUE (t)
 		  = tsubst_expr (TREE_VALUE (t), args, complain, in_decl,

gcc/testsuite/g++.dg/cpp0x/alignas4.C

@@ -0,0 +1,19 @@
+// PR c++/59012
+// { dg-do compile { target c++11 } }
+// { dg-final { scan-assembler "align 8" { target x86_64-*-*-gnu } } }
+
+template <class... T>
+struct A
+{
+  alignas(T...) char t;
+};
+
+A<int,double> a;
+
+template <class... T>
+struct A2
+{
+  [[gnu::aligned (alignof (T))...]] char t;
+};
+
+A2<int,double> a2;