re PR libstdc++/77727 (Unwrapping std::optional constructor is not working for non-transferable object)

PR libstdc++/77727
    * include/std/optional (optional(const optional<_Up>&)):
    Default-initialize the base and use emplace.
    (optional(optional<_Up>&&)): Likewise.
    * testsuite/20_util/optional/cons/77727.cc: New.

From-SVN: r240511

libstdc++-v3/ChangeLog

@@ -1,3 +1,11 @@
+2016-09-26  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	PR libstdc++/77727
+	* include/std/optional (optional(const optional<_Up>&)):
+	Default-initialize the base and use emplace.
+	(optional(optional<_Up>&&)): Likewise.
+	* testsuite/20_util/optional/cons/77727.cc: New.
+
 2016-09-26  François Dumont  <fdumont@gcc.gnu.org>
 
 	* include/debug/safe_base.h

libstdc++-v3/include/std/optional

@@ -502,7 +502,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 			    __not_<__converts_from_optional<_Tp, _Up>>
 			    >::value, bool> = true>
       constexpr optional(const optional<_Up>& __t)
-        : _Base(__t ? _Base(std::in_place, *__t) : _Base()) { }
+      {
+	if (__t)
+	  emplace(*__t);
+      }
 
       template <typename _Up,
                  enable_if_t<__and_<
@@ -512,7 +515,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 			       __not_<__converts_from_optional<_Tp, _Up>>
 			       >::value, bool> = false>
       explicit constexpr optional(const optional<_Up>& __t)
-        : _Base(__t ? _Base(std::in_place, *__t) : _Base()) { }
+      {
+	if (__t)
+	  emplace(*__t);
+      }
 
       template <typename _Up,
                 enable_if_t<__and_<
@@ -522,7 +528,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 			      __not_<__converts_from_optional<_Tp, _Up>>
 			      >::value, bool> = true>
       constexpr optional(optional<_Up>&& __t)
-        : _Base(__t ? _Base(std::in_place, std::move(*__t)) : _Base()) { }
+      {
+	if (__t)
+	  emplace(std::move(*__t));
+      }
 
       template <typename _Up,
                 enable_if_t<__and_<
@@ -532,7 +541,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 			    __not_<__converts_from_optional<_Tp, _Up>>
 			    >::value, bool> = false>
       explicit constexpr optional(optional<_Up>&& __t)
-        : _Base(__t ? _Base(std::in_place, std::move(*__t)) : _Base()) { }
+      {
+	if (__t)
+	  emplace(std::move(*__t));
+      }
 
       template<typename... _Args>
       explicit constexpr optional(in_place_t, _Args&&... __args)

libstdc++-v3/testsuite/20_util/optional/cons/77727.cc

@@ -0,0 +1,51 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do run }
+
+// Copyright (C) 2016 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a moved_to of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <optional>
+#include <testsuite_hooks.h>
+
+
+struct NonTransferable
+{
+  int x;
+  NonTransferable(int x) : x(x) {}
+  NonTransferable(NonTransferable&&) = delete;
+  NonTransferable& operator=(NonTransferable&&) = delete;
+  operator int() {return x;}
+};
+
+int main()
+{
+  std::optional<int> oi;
+  std::optional<NonTransferable> ot(std::move(oi));
+  VERIFY(!ot);
+
+  std::optional<int> oi2;
+  std::optional<NonTransferable> ot2(oi2);
+  VERIFY(!ot);
+
+  std::optional<int> oi3{42};
+  std::optional<NonTransferable> ot3(std::move(oi3));
+  VERIFY(ot3 && *ot3 == 42);
+
+  std::optional<int> oi4{666};
+  std::optional<NonTransferable> ot4(oi4);
+  VERIFY(ot4 && *ot4 == 666);
+}