[v3] LWG 2106: move_iterator::reference

[Marc Glisse <marc dot glisse at inria dot fr>]

Hello,

this issue got delayed in LWG, apparently because of a failed 
"improvement" to the wording along the way (happens, that's ok), but there 
seems to be a consensus on the resolution and I don't really see the point 
of waiting (it changes code that currently returns a reference to a 
temporary).

Tested on x86_64-linux-gnu. Stage 1?

2014-04-01  Marc Glisse  <marc.glisse@inria.fr>

	PR libstdc++/59434
	* include/bits/stl_iterator.h (move_iterator::reference,
	move_iterator::operator*): Implement LWG 2106.
	* testsuite/24_iterators/move_iterator/dr2106.cc: New file.

--
Marc Glisse

Index: libstdc++-v3/include/bits/stl_iterator.h
===================================================================
--- libstdc++-v3/include/bits/stl_iterator.h	(revision 208349)
+++ libstdc++-v3/include/bits/stl_iterator.h	(working copy)
@@ -958,48 +958,52 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  generic algorithms can be called with move iterators to replace
    *  copying with moving.
    */
   template<typename _Iterator>
     class move_iterator
     {
     protected:
       _Iterator _M_current;
 
       typedef iterator_traits<_Iterator>		__traits_type;
+      typedef typename __traits_type::reference		__base_ref;
 
     public:
       typedef _Iterator					iterator_type;
       typedef typename __traits_type::iterator_category iterator_category;
       typedef typename __traits_type::value_type  	value_type;
       typedef typename __traits_type::difference_type	difference_type;
       // NB: DR 680.
       typedef _Iterator					pointer;
-      typedef value_type&&				reference;
+      // DR 2106.
+      typedef typename conditional<is_reference<__base_ref>::value,
+			 typename remove_reference<__base_ref>::type&&,
+			 __base_ref>::type		reference;
 
       move_iterator()
       : _M_current() { }
 
       explicit
       move_iterator(iterator_type __i)
       : _M_current(__i) { }
 
       template<typename _Iter>
 	move_iterator(const move_iterator<_Iter>& __i)
 	: _M_current(__i.base()) { }
 
       iterator_type
       base() const
       { return _M_current; }
 
       reference
       operator*() const
-      { return std::move(*_M_current); }
+      { return static_cast<reference>(*_M_current); }
 
       pointer
       operator->() const
       { return _M_current; }
 
       move_iterator&
       operator++()
       {
 	++_M_current;
 	return *this;
Index: libstdc++-v3/testsuite/24_iterators/move_iterator/dr2106.cc
===================================================================
--- libstdc++-v3/testsuite/24_iterators/move_iterator/dr2106.cc	(revision 0)
+++ libstdc++-v3/testsuite/24_iterators/move_iterator/dr2106.cc	(working copy)
@@ -0,0 +1,33 @@
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
+
+// Copyright (C) 2014 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 <iterator>
+#include <type_traits>
+#include <vector>
+
+typedef std::vector<bool>	Vec;
+typedef Vec::reference		Ref;
+typedef Vec::const_reference	CRef;
+typedef Vec::iterator		It;
+typedef Vec::const_iterator	CIt;
+typedef std::move_iterator<It>	MIt;
+typedef std::move_iterator<CIt>	MCIt;
+static_assert(std::is_same<MIt::reference, Ref>::value,"");
+static_assert(std::is_same<MCIt::reference, CRef>::value,"");

Property changes on: libstdc++-v3/testsuite/24_iterators/move_iterator/dr2106.cc
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Added: svn:keywords
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+Author Date Id Revision URL
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Added: svn:eol-style
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+native
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