From 0592708f6bf7ae736b7f2b11ef94f3596ccd30b9 Mon Sep 17 00:00:00 2001
From: jason <jason@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 3 Apr 2012 23:37:11 +0000
Subject: [PATCH] 	PR c++/52796 	* pt.c (tsubst_initializer_list): A
 pack expansion with no elements 	means value-initialization.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@186121 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/cp/ChangeLog                             |  6 ++++++
 gcc/cp/pt.c                                  |  8 ++++++++
 gcc/testsuite/ChangeLog                      |  5 +++++
 gcc/testsuite/g++.dg/cpp0x/variadic-value1.C | 24 ++++++++++++++++++++++++
 4 files changed, 43 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-value1.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b8451f12857..0de8e3a56f9 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2012-04-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/52796
+	* pt.c (tsubst_initializer_list): A pack expansion with no elements
+	means value-initialization.
+
 2012-03-29  Meador Inge  <meadori@codesourcery.com>
 
 	PR c++/52672
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 56e4a9cfdf0..9834c64216e 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -18983,6 +18983,7 @@ tsubst_initializer_list (tree t, tree argvec)
             }
           else
             {
+	      tree tmp;
               decl = tsubst_copy (TREE_PURPOSE (t), argvec, 
                                   tf_warning_or_error, NULL_TREE);
 
@@ -18991,10 +18992,17 @@ tsubst_initializer_list (tree t, tree argvec)
                 in_base_initializer = 1;
 
 	      init = TREE_VALUE (t);
+	      tmp = init;
 	      if (init != void_type_node)
 		init = tsubst_expr (init, argvec,
 				    tf_warning_or_error, NULL_TREE,
 				    /*integral_constant_expression_p=*/false);
+	      if (init == NULL_TREE && tmp != NULL_TREE)
+		/* If we had an initializer but it instantiated to nothing,
+		   value-initialize the object.  This will only occur when
+		   the initializer was a pack expansion where the parameter
+		   packs used in that expansion were of length zero.  */
+		init = void_type_node;
               in_base_initializer = 0;
             }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d594c862656..58c01575b96 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2012-04-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/52796
+	* g++.dg/cpp0x/variadic-value1.C: New.
+
 2012-04-03  Richard Guenther  <rguenther@suse.de>
 
 	Backport from mainline
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-value1.C b/gcc/testsuite/g++.dg/cpp0x/variadic-value1.C
new file mode 100644
index 00000000000..179919a5bc7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic-value1.C
@@ -0,0 +1,24 @@
+// PR c++/52796
+// { dg-do run { target c++11 } }
+
+inline void *operator new(__SIZE_TYPE__ s, void *p) { return p; }
+
+struct A
+{
+  int i;
+  template<class... Ts>
+  A(Ts&&... ts): i(ts...) { }
+};
+
+static union {
+  unsigned char c[sizeof(A)];
+  int i;
+};
+
+int main()
+{
+  i = 0xdeadbeef;
+  new(c) A;
+  if (i != 0)
+    __builtin_abort();
+}
-- 
2.11.0