Patchwork partial fix for libstdc++/51365

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Submitter Jonathan Wakely
Date Dec. 20, 2011, 9:10 a.m.
Message ID <CAH6eHdQL3TE-4N=gfWPCyfmk-tZdbBF1R00ZW-M8GvUJ2ja=oQ@mail.gmail.com>
Download mbox | patch
Permalink /patch/132375/
State New
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Jonathan Wakely - Dec. 20, 2011, 9:10 a.m.
PR libstdc++/51365
        * include/std/tuple (_Tuple_impl): Check __is_final as well as
        is_empty.
        * testsuite/20_util/tuple/51365.cc: New.

This uses __is_final for std::tuple, it still needs to be used for
containers, shared_ptr and futures.

Tested x86_64-linux, committed to trunk.

Patch

Index: include/std/tuple
===================================================================
--- include/std/tuple	(revision 182460)
+++ include/std/tuple	(working copy)
@@ -69,7 +69,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __add_r_ref<_Tp&>
     { typedef _Tp& type; };
 
-  template<std::size_t _Idx, typename _Head, bool _IsEmpty>
+  template<std::size_t _Idx, typename _Head, bool _IsEmptyNotFinal>
     struct _Head_base;
 
   template<std::size_t _Idx, typename _Head>
@@ -201,6 +201,11 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       void _M_swap(_Tuple_impl&) noexcept { /* no-op */ }
     };
 
+  // Use the Empty Base-class Optimization for empty, non-final types.
+  template<typename _Tp>
+    using __empty_not_final
+      = typename conditional<__is_final(_Tp), false_type, is_empty<_Tp>>::type;
+
   /**
    * Recursive tuple implementation. Here we store the @c Head element
    * and derive from a @c Tuple_impl containing the remaining elements
@@ -209,12 +214,12 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<std::size_t _Idx, typename _Head, typename... _Tail>
     struct _Tuple_impl<_Idx, _Head, _Tail...>
     : public _Tuple_impl<_Idx + 1, _Tail...>,
-      private _Head_base<_Idx, _Head, std::is_empty<_Head>::value>
+      private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
     {
       template<std::size_t, typename...> friend class _Tuple_impl;
 
       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
-      typedef _Head_base<_Idx, _Head, std::is_empty<_Head>::value> _Base;
+      typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
 
       static constexpr _Head&  
       _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
Index: testsuite/20_util/tuple/51365.cc
===================================================================
--- testsuite/20_util/tuple/51365.cc	(revision 0)
+++ testsuite/20_util/tuple/51365.cc	(revision 0)
@@ -0,0 +1,27 @@ 
+// { dg-options "-std=gnu++0x" }
+// { dg-do compile }
+
+// Copyright (C) 2011 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/>.
+
+#include <tuple>
+
+// libstdc++/51365
+
+struct F final { };
+std::tuple<F> t;
+