Re: [PATCH] PR libstdc++/85183 fix std::variant move-assignment

[Jonathan Wakely]

         PR libstdc++/85183
         * include/std/variant (_Move_assign_base::operator=): Fix incorrect
         value categories.
         * testsuite/20_util/variant/85183.cc: New.

Tested powerp64le-linux, committed to trunk.

commit eda33cf5c2399e0f25fae17df46efa0b534c778a
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue Apr 3 23:56:33 2018 +0100

    PR libstdc++/85183 fix std::variant move-assignment
    
            PR libstdc++/85183
            * include/std/variant (_Move_assign_base::operator=): Fix incorrect
            value categories.
            * testsuite/20_util/variant/85183.cc: New.

diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index e4ae6573ed4..028d3064272 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -605,13 +605,14 @@ namespace __variant
            if (__rhs._M_valid())
              {
                static constexpr void (*_S_vtable[])(void*, void*) =
-                 { &__erased_assign<_Types&, const _Types&>... };
-               _S_vtable[__rhs._M_index](this->_M_storage(), 
__rhs._M_storage());
+                 { &__erased_assign<_Types&, _Types&&>... };
+               _S_vtable[__rhs._M_index]
+                 (this->_M_storage(), __rhs._M_storage());
              }
          }
        else
          {
-           _Move_assign_base __tmp(__rhs);
+           _Move_assign_base __tmp(std::move(__rhs));
            this->~_Move_assign_base();
            __try
              {
diff --git a/libstdc++-v3/testsuite/20_util/variant/85183.cc 
b/libstdc++-v3/testsuite/20_util/variant/85183.cc
new file mode 100644
index 00000000000..b122c6357ad
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/variant/85183.cc
@@ -0,0 +1,35 @@
+// Copyright (C) 2018 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 copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <variant>
+
+struct moveonly {
+  moveonly() noexcept { }
+  moveonly(moveonly&&) noexcept { }
+  moveonly& operator=(moveonly&&) noexcept { return *this; }
+  ~moveonly() { }
+};
+
+void
+test01()
+{
+  std::variant<moveonly> v1, v2;
+  v1 = std::move(v2); // PR libstdc++/85183
+}