[patch] LWG DR 2285: std::make_reverse_iterator

[Jonathan Wakely]

This is a trivial addition, implementing
http://cplusplus.github.io/LWG/lwg-defects.html#2285

I've also added the __cpp_lib_tuple_element_t macro missing from the
commit that implemented that.

Tested x86_64-linux, committed to trunk.

commit 363e23c37b089661c7533476cc7b3e5b05f20f9f
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Fri Dec 12 13:12:23 2014 +0000

    	* include/bits/stl_iterator.h (make_reverse_iterator): LWG DR 2285.
    	* include/std/tuple: Add feature-test macro.
    	* testsuite/24_iterators/reverse_iterator/make.cc: New.

diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index f4522a4..15014d5 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -388,6 +388,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __y.base() - __x.base(); }
   //@}
 
+#if __cplusplus > 201103L
+#define __cpp_lib_make_reverse_iterator 201402
+
+  // _GLIBCXX_RESOLVE_LIB_DEFECTS
+  // DR 2285. make_reverse_iterator
+  /// Generator function for reverse_iterator.
+  template<typename _Iterator>
+    inline reverse_iterator<_Iterator>
+    make_reverse_iterator(_Iterator __i)
+    { return reverse_iterator<_Iterator>(__i); }
+#endif
+
   // 24.4.2.2.1 back_insert_iterator
   /**
    *  @brief  Turns assignment into insertion.
diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 6be7f23..01ab5fe 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -687,6 +687,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     };
 
 #if __cplusplus > 201103L
+#define __cpp_lib_tuple_element_t 201402
+
   template<std::size_t __i, typename _Tp>
     using tuple_element_t = typename tuple_element<__i, _Tp>::type;
 #endif
diff --git a/libstdc++-v3/testsuite/24_iterators/reverse_iterator/make.cc b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/make.cc
new file mode 100644
index 0000000..a0f70de
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/make.cc
@@ -0,0 +1,35 @@
+// 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/>.
+
+// { dg-options "-std=gnu++14" }
+
+#include <iterator>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  int a[2]{ 1, 2 };
+  auto b = std::make_reverse_iterator(a);
+  VERIFY( b == std::reverse_iterator<int*>(a) );
+}
+
+int
+main()
+{
+  test01();
+}