From 639475f047006ae1008d6dedaabdb56aba03a731 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 3 Mar 2016 17:43:03 -0500
Subject: [PATCH] re PR c++/67364 ("accessing uninitialized member" error in
 constexpr context)

	PR c++/67364

	* constexpr.c (cxx_eval_component_reference): Just return an empty
	CONSTRUCTOR for an empty class.

From-SVN: r233945
---
 gcc/cp/ChangeLog                               |  6 ++++++
 gcc/cp/constexpr.c                             |  5 +++--
 gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C | 17 +++++++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index f1d51cfa481..f2c9cd25c1b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2016-03-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/67364
+	* constexpr.c (cxx_eval_component_reference): Just return an empty
+	CONSTRUCTOR for an empty class.
+
 2016-03-01  Jason Merrill  <jason@redhat.com>
 
 	PR c++/70036
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index bcb129f22c4..5a81469b8ad 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1988,11 +1988,12 @@ cxx_eval_component_reference (const constexpr_ctx *ctx, tree t,
     }
 
   if (CONSTRUCTOR_NO_IMPLICIT_ZERO (whole)
-      && !is_empty_class (TREE_TYPE (part)))
+      && !is_really_empty_class (TREE_TYPE (t)))
     {
       /* 'whole' is part of the aggregate initializer we're currently
 	 building; if there's no initializer for this member yet, that's an
-	 error. */
+	 error.  But expand_aggr_init_1 doesn't bother to initialize really
+	 empty classes, so ignore them here, too.  */
       if (!ctx->quiet)
 	error ("accessing uninitialized member %qD", part);
       *non_constant_p = true;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C
new file mode 100644
index 00000000000..7437367d6af
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-empty11.C
@@ -0,0 +1,17 @@
+// PR c++/67364
+// { dg-do compile { target c++11 } }
+
+template <typename Xn>
+struct element : Xn {
+  constexpr element() : Xn() { }
+};
+
+template <typename Xn>
+struct closure {
+  element<Xn> member;
+  constexpr closure() { }
+};
+
+struct empty { struct {} s; };
+constexpr closure<empty> tup{};
+constexpr empty first = tup.member;