Implement resolution of LWG DR 685 precisely

	PR libstdc++/71771
	* include/bits/stl_iterator.h
	(operator-(reverse_iterator<Iter>, reverse_iterator<Iter>): Only
	define for C++98 mode.
	(operator-(move_iterator<Iter>, move_iterator<Iter>): Don't define.
	* testsuite/24_iterators/headers/iterator/synopsis.cc: Use
	-std=gnu++98.
	* testsuite/24_iterators/headers/iterator/synopsis_c++11.cc: New test.
	* testsuite/24_iterators/headers/iterator/synopsis_c++14.cc: New test.
	* testsuite/24_iterators/headers/iterator/synopsis_c++17.cc: New test.
	* testsuite/24_iterators/move_iterator/greedy_ops.cc: Don't test
	difference operator.
	* testsuite/24_iterators/reverse_iterator/greedy_ops.cc: Only test
	difference operator for C++98.
	* testsuite/24_iterators/reverse_iterator/71771.cc: New test.

From-SVN: r239691

9 files changed, 462 insertions, 29 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index ab0c91b..dc42ee4 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,21 @@
 2016-08-23  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/71771
+	* include/bits/stl_iterator.h
+	(operator-(reverse_iterator<Iter>, reverse_iterator<Iter>): Only
+	define for C++98 mode.
+	(operator-(move_iterator<Iter>, move_iterator<Iter>): Don't define.
+	* testsuite/24_iterators/headers/iterator/synopsis.cc: Use
+	-std=gnu++98.
+	* testsuite/24_iterators/headers/iterator/synopsis_c++11.cc: New test.
+	* testsuite/24_iterators/headers/iterator/synopsis_c++14.cc: New test.
+	* testsuite/24_iterators/headers/iterator/synopsis_c++17.cc: New test.
+	* testsuite/24_iterators/move_iterator/greedy_ops.cc: Don't test
+	difference operator.
+	* testsuite/24_iterators/reverse_iterator/greedy_ops.cc: Only test
+	difference operator for C++98.
+	* testsuite/24_iterators/reverse_iterator/71771.cc: New test.
+
 	* include/bits/c++config (_GLIBCXX17_CONSTEXPR): Define.
 	* include/bits/range_access.h (begin, end, rbegin, rend, crbegin)
 	(crend): Add _GLIBCXX17_CONSTEXPR as per P0031R0.
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 037e966..a98fff1 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -330,19 +330,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	       const reverse_iterator<_Iterator>& __y)
     { return !(__x < __y); }
 
-  template<typename _Iterator>
-    inline _GLIBCXX17_CONSTEXPR
-    typename reverse_iterator<_Iterator>::difference_type
-    operator-(const reverse_iterator<_Iterator>& __x,
-	      const reverse_iterator<_Iterator>& __y)
-    { return __y.base() - __x.base(); }
-
-  template<typename _Iterator>
-    inline _GLIBCXX17_CONSTEXPR reverse_iterator<_Iterator>
-    operator+(typename reverse_iterator<_Iterator>::difference_type __n,
-	      const reverse_iterator<_Iterator>& __x)
-    { return reverse_iterator<_Iterator>(__x.base() - __n); }
-
   // _GLIBCXX_RESOLVE_LIB_DEFECTS
   // DR 280. Comparison of reverse_iterator to const reverse_iterator.
   template<typename _IteratorL, typename _IteratorR>
@@ -380,21 +367,36 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     operator>=(const reverse_iterator<_IteratorL>& __x,
 	       const reverse_iterator<_IteratorR>& __y)
     { return !(__x < __y); }
+  //@}
+
+#if __cplusplus < 201103L
+  template<typename _Iterator>
+    inline typename reverse_iterator<_Iterator>::difference_type
+    operator-(const reverse_iterator<_Iterator>& __x,
+	      const reverse_iterator<_Iterator>& __y)
+    { return __y.base() - __x.base(); }
 
   template<typename _IteratorL, typename _IteratorR>
-#if __cplusplus >= 201103L
-    // DR 685.
-    inline _GLIBCXX17_CONSTEXPR auto
+    inline typename reverse_iterator<_IteratorL>::difference_type
     operator-(const reverse_iterator<_IteratorL>& __x,
 	      const reverse_iterator<_IteratorR>& __y)
-    -> decltype(__y.base() - __x.base())
+    { return __y.base() - __x.base(); }
 #else
-    inline typename reverse_iterator<_IteratorL>::difference_type
+  // _GLIBCXX_RESOLVE_LIB_DEFECTS
+  // DR 685. reverse_iterator/move_iterator difference has invalid signatures
+  template<typename _IteratorL, typename _IteratorR>
+    inline _GLIBCXX17_CONSTEXPR auto
     operator-(const reverse_iterator<_IteratorL>& __x,
 	      const reverse_iterator<_IteratorR>& __y)
-#endif
+    -> decltype(__y.base() - __x.base())
     { return __y.base() - __x.base(); }
-  //@}
+#endif
+
+  template<typename _Iterator>
+    inline _GLIBCXX17_CONSTEXPR reverse_iterator<_Iterator>
+    operator+(typename reverse_iterator<_Iterator>::difference_type __n,
+	      const reverse_iterator<_Iterator>& __x)
+    { return reverse_iterator<_Iterator>(__x.base() - __n); }
 
 #if __cplusplus >= 201103L
   // Same as C++14 make_reverse_iterator but used in C++03 mode too.
@@ -1192,13 +1194,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __x.base() - __y.base(); }
 
   template<typename _Iterator>
-    inline _GLIBCXX17_CONSTEXPR auto
-    operator-(const move_iterator<_Iterator>& __x,
-	      const move_iterator<_Iterator>& __y)
-    -> decltype(__x.base() - __y.base())
-    { return __x.base() - __y.base(); }
-
-  template<typename _Iterator>
     inline _GLIBCXX17_CONSTEXPR move_iterator<_Iterator>
     operator+(typename move_iterator<_Iterator>::difference_type __n,
 	      const move_iterator<_Iterator>& __x)
diff --git a/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis.cc b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis.cc
index ed01258..35284d0 100644
--- a/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis.cc
+++ b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis.cc
@@ -1,3 +1,4 @@
+// { dg-options "-std=gnu++98" }
 // { dg-do compile }
 
 // Copyright (C) 2007-2016 Free Software Foundation, Inc.
diff --git a/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++11.cc b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++11.cc
new file mode 100644
index 0000000..f0b620f
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++11.cc
@@ -0,0 +1,165 @@
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
+
+// 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 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>
+
+namespace std {
+
+  // C++11 24.4.4, iterator operations:
+  template <class InputIterator, class Distance>
+    void
+    advance(InputIterator& i, Distance n);
+
+  template <class InputIterator>
+    typename iterator_traits<InputIterator>::difference_type
+    distance(InputIterator first, InputIterator last);
+
+  template<class ForwardIterator>
+    ForwardIterator
+    next(ForwardIterator x,
+	 typename iterator_traits<ForwardIterator>::difference_type);
+
+  template<class BidirectionalIterator>
+    BidirectionalIterator
+    prev(BidirectionalIterator x,
+	 typename iterator_traits<BidirectionalIterator>::difference_type);
+
+  // C++11 24.5, Iterator adaptors:
+  template <class Iterator> class reverse_iterator;
+
+  template <class Iterator1, class Iterator2>
+  bool operator==(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator<(const reverse_iterator<Iterator1>& x,
+		 const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator!=(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator>(const reverse_iterator<Iterator1>& x,
+		 const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator>=(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator<=(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  auto
+  operator-(const reverse_iterator<Iterator1>& x,
+	    const reverse_iterator<Iterator2>& y)
+  -> decltype(x.base() - y.base());
+
+  template <class Iterator>
+  reverse_iterator<Iterator>
+  operator+(typename reverse_iterator<Iterator>::difference_type n,
+	    const reverse_iterator<Iterator>& x);
+
+  template <class Container> class back_insert_iterator;
+
+  template <class Container>
+  back_insert_iterator<Container> back_inserter(Container& x);
+
+  template <class Container> class front_insert_iterator;
+
+  template <class Container>
+  front_insert_iterator<Container> front_inserter(Container& x);
+
+  template <class Container> class insert_iterator;
+
+  template <class Container, class Iterator>
+  insert_iterator<Container> inserter(Container& x, Iterator i);
+
+  template <class Iterator> class move_iterator;
+
+  template <class Iterator1, class Iterator2>
+  bool operator==(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator!=(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator<(const move_iterator<Iterator1>& x,
+		 const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator<=(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator>(const move_iterator<Iterator1>& x,
+		 const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  bool operator>=(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  auto operator-(const move_iterator<Iterator1>& x,
+		 const move_iterator<Iterator2>& y)
+  -> decltype(x.base() - y.base());
+
+  template <class Iterator>
+  move_iterator<Iterator>
+  operator+(typename move_iterator<Iterator>::difference_type,
+	    const move_iterator<Iterator>&);
+
+  template <class Iterator>
+  move_iterator<Iterator> make_move_iterator(const Iterator&);
+
+  // 24.6, stream iterators:
+  template <class T, class charT, class traits, class Distance>
+  class istream_iterator;
+
+  template <class T, class charT, class traits, class Distance>
+  bool operator==(const istream_iterator<T,charT,traits,Distance>& x,
+		  const istream_iterator<T,charT,traits,Distance>& y);
+
+  template <class T, class charT, class traits, class Distance>
+  bool operator!=(const istream_iterator<T,charT,traits,Distance>& x,
+		  const istream_iterator<T,charT,traits,Distance>& y);
+
+  template <class T, class charT, class traits>
+  class ostream_iterator;
+
+  template<class charT, class traits>
+  class istreambuf_iterator;
+
+  template <class charT, class traits>
+  bool
+  operator==(const istreambuf_iterator<charT,traits>&,
+	     const istreambuf_iterator<charT,traits>&);
+
+  template <class charT, class traits>
+    bool operator!=(const istreambuf_iterator<charT,traits>&,
+                    const istreambuf_iterator<charT,traits>&);
+
+  template <class charT, class traits>
+    class ostreambuf_iterator;
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++14.cc b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++14.cc
new file mode 100644
index 0000000..7f6063f
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++14.cc
@@ -0,0 +1,28 @@
+// { dg-options "-std=gnu++14" }
+// { dg-do compile }
+
+// 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 copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "./synopsis_c++11.cc"
+
+namespace std {
+
+  // C++14 24.5, iterator adaptors:
+  template <class Iterator>
+  reverse_iterator<Iterator> make_reverse_iterator(const Iterator&);
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++17.cc b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++17.cc
new file mode 100644
index 0000000..c2adc40
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/headers/iterator/synopsis_c++17.cc
@@ -0,0 +1,181 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do compile }
+
+// 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 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>
+
+namespace std {
+
+  // C++17 24.4.3, iterator operations:
+  template <class InputIterator, class Distance>
+    constexpr void
+    advance(InputIterator& i, Distance n);
+
+  template <class InputIterator>
+    constexpr typename iterator_traits<InputIterator>::difference_type
+    distance(InputIterator first, InputIterator last);
+
+  template <class ForwardIterator>
+    constexpr ForwardIterator
+    next(ForwardIterator x,
+	 typename iterator_traits<ForwardIterator>::difference_type);
+
+  template <class BidirectionalIterator>
+    constexpr BidirectionalIterator
+    prev(BidirectionalIterator x,
+	 typename iterator_traits<BidirectionalIterator>::difference_type);
+
+  // C++17 24.5, iterator adaptors:
+  template <class Iterator> class reverse_iterator;
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator==(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator<(const reverse_iterator<Iterator1>& x,
+		 const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator!=(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator>(const reverse_iterator<Iterator1>& x,
+		 const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator>=(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator<=(const reverse_iterator<Iterator1>& x,
+		  const reverse_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr auto
+  operator-(const reverse_iterator<Iterator1>& x,
+	    const reverse_iterator<Iterator2>& y)
+  -> decltype(x.base() - y.base());
+
+  template <class Iterator>
+  constexpr reverse_iterator<Iterator>
+  operator+(typename reverse_iterator<Iterator>::difference_type n,
+	    const reverse_iterator<Iterator>& x);
+
+  template <class Iterator>
+  constexpr reverse_iterator<Iterator> make_reverse_iterator(const Iterator&);
+
+  template <class Container> class back_insert_iterator;
+
+  template <class Container>
+  back_insert_iterator<Container> back_inserter(Container& x);
+
+  template <class Container> class front_insert_iterator;
+
+  template <class Container>
+  front_insert_iterator<Container> front_inserter(Container& x);
+
+  template <class Container> class insert_iterator;
+
+  template <class Container, class Iterator>
+  insert_iterator<Container> inserter(Container& x, Iterator i);
+
+  template <class Iterator> class move_iterator;
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator==(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator!=(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator<(const move_iterator<Iterator1>& x,
+		 const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator<=(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator>(const move_iterator<Iterator1>& x,
+		 const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  bool operator>=(const move_iterator<Iterator1>& x,
+		  const move_iterator<Iterator2>& y);
+
+  template <class Iterator1, class Iterator2>
+  constexpr
+  auto operator-(const move_iterator<Iterator1>& x,
+		 const move_iterator<Iterator2>& y)
+  -> decltype(x.base() - y.base());
+
+  template <class Iterator>
+  constexpr move_iterator<Iterator>
+  operator+(typename move_iterator<Iterator>::difference_type,
+	    const move_iterator<Iterator>&);
+
+  template <class Iterator>
+  constexpr move_iterator<Iterator> make_move_iterator(const Iterator&);
+
+  // 24.6, stream iterators:
+  template <class T, class charT, class traits, class Distance>
+  class istream_iterator;
+
+  template <class T, class charT, class traits, class Distance>
+  bool operator==(const istream_iterator<T,charT,traits,Distance>& x,
+		  const istream_iterator<T,charT,traits,Distance>& y);
+
+  template <class T, class charT, class traits, class Distance>
+  bool operator!=(const istream_iterator<T,charT,traits,Distance>& x,
+		  const istream_iterator<T,charT,traits,Distance>& y);
+
+  template <class T, class charT, class traits>
+  class ostream_iterator;
+
+  template<class charT, class traits>
+  class istreambuf_iterator;
+
+  template <class charT, class traits>
+  bool
+  operator==(const istreambuf_iterator<charT,traits>&,
+	     const istreambuf_iterator<charT,traits>&);
+
+  template <class charT, class traits>
+    bool operator!=(const istreambuf_iterator<charT,traits>&,
+                    const istreambuf_iterator<charT,traits>&);
+
+  template <class charT, class traits>
+    class ostreambuf_iterator;
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/move_iterator/greedy_ops.cc b/libstdc++-v3/testsuite/24_iterators/move_iterator/greedy_ops.cc
index 655313a..e546e19 100644
--- a/libstdc++-v3/testsuite/24_iterators/move_iterator/greedy_ops.cc
+++ b/libstdc++-v3/testsuite/24_iterators/move_iterator/greedy_ops.cc
@@ -32,7 +32,7 @@ void test01()
   it <= it;
   it > it;
   it >= it;
-  it - it;
+  // it - it;  // See PR libstdc++/71771
   1 + it;
   it + 1;
 }
diff --git a/libstdc++-v3/testsuite/24_iterators/reverse_iterator/71771.cc b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/71771.cc
new file mode 100644
index 0000000..41b5086
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/71771.cc
@@ -0,0 +1,45 @@
+// 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 copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do compile { target c++11 } }
+
+#include <iterator>
+#include <testsuite_iterators.h>
+
+// PR libstdc++/71771
+
+template<typename Iter>
+auto
+diff2(std::reverse_iterator<Iter> it1, std::reverse_iterator<Iter> it2)
+-> decltype(it1 - it2)
+{ return it1 - it2; }
+
+template<typename Iter>
+void
+diff2(Iter, Iter)
+{ }
+
+void
+test01()
+{
+  int i[2];
+  __gnu_test::test_container<int, __gnu_test::bidirectional_iterator_wrapper>
+    c(i);
+  using reverse_iterator
+    = std::reverse_iterator<__gnu_test::bidirectional_iterator_wrapper<int>>;
+  diff2(reverse_iterator(c.end()), reverse_iterator(c.begin()));
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/reverse_iterator/greedy_ops.cc b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/greedy_ops.cc
index 05aa340..1360029 100644
--- a/libstdc++-v3/testsuite/24_iterators/reverse_iterator/greedy_ops.cc
+++ b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/greedy_ops.cc
@@ -31,7 +31,9 @@ void test01()
   it <= it;
   it > it;
   it >= it;
-  it - it;
+#if __cplusplus < 201103L
+  it - it; // See PR libstdc++/71771
+#endif
   1 + it;
   it + 1;
 }