Whenever we use operator+ or similar operators on random access
iterators we need to be careful to use the iterator's difference_type
rather than some other integer type. It's not guaranteed that an
expression with an arbitrary integer type, such as `it + 1u`, has the
same effects as `it + iter_difference_t<It>(1)`.

Some of our algorithms need changes to cast values to the correct type,
or to use std::next or ranges::next instead of `it + n`. Several tests
also need fixes where the arithmetic occurs directly in the test.

The __gnu_test::random_access_iterator_wrapper class template is
adjusted to have deleted operators that make programs ill-formed if the
argument to relevant operators is not the difference_type. This will
make it easier to avoid regressing in future.

libstdc++-v3/ChangeLog:

        PR libstdc++/121890
        * include/bits/ranges_algo.h (ranges::rotate, ranges::shuffle)
        (__insertion_sort, __unguarded_partition_pivot, __introselect):
        Use ranges::next to advance iterators.
        (ranges::push_heap, ranges::pop_heap, ranges::partial_sort)
        (ranges::partial_sort_copy): Use ranges::prev.
        (__final_insertion_sort): Use iter_difference_t<Iter>
        for operand of operator+ on iterator.
        * include/bits/ranges_base.h (ranges::advance): Use iterator's
        difference_type for all iterator arithmetic.
        * include/bits/stl_algo.h (__search_n_aux, __rotate)
        (__insertion_sort, __unguarded_partition_pivot, __introselect)
        (__final_insertion_sort, for_each_n, random_shuffle): Likewise.
        * include/bits/stl_algobase.h (__fill_n_a, __lc_rai::__newlast1):
        Likewise.
        * include/bits/stl_heap.h (push_heap): Likewise.
        (__is_heap_until): Add static_assert.
        (__is_heap): Convert distance to difference_type.
        * include/std/functional (boyer_moore_searcher::operator()): Use
        iterator's difference_type for iterator arithmetic.
        * testsuite/util/testsuite_iterators.h
        (random_access_iterator_wrapper): Add deleted overloads of
        operators that should be called with difference_type.
        * testsuite/24_iterators/range_operations/advance.cc: Use
        ranges::next.
        * testsuite/25_algorithms/heap/constrained.cc: Use ranges::next
        and ranges::prev.
        * testsuite/25_algorithms/nth_element/58800.cc: Use std::next.
        * testsuite/25_algorithms/nth_element/constrained.cc: Use
        ptrdiff_t for loop variable.
        * testsuite/25_algorithms/nth_element/random_test.cc: Use
        iterator's difference_type instead of int.
        * testsuite/25_algorithms/partial_sort/check_compare_by_value.cc:
        Use std::next.
        * testsuite/25_algorithms/partial_sort/constrained.cc: Use
        ptrdiff_t for loop variable.
        * testsuite/25_algorithms/partial_sort/random_test.cc: Use
        iterator's difference_type instead of int.
        * testsuite/25_algorithms/partial_sort_copy/constrained.cc:
        Use ptrdiff_t for loop variable.
        * testsuite/25_algorithms/partial_sort_copy/random_test.cc:
        Use iterator's difference_type instead of int.
        * testsuite/std/ranges/adaptors/drop.cc: Use ranges::next.
        * testsuite/25_algorithms/fill_n/diff_type.cc: New test.
        * testsuite/25_algorithms/for_each/diff_type.cc: New test.
        * testsuite/25_algorithms/lexicographical_compare/diff_type.cc:
        New test.
        * testsuite/25_algorithms/push_heap/diff_type.cc: New test.
        * testsuite/25_algorithms/nth_element/diff_type.cc: New test.
        * testsuite/25_algorithms/rotate/diff_type.cc: New test.
        * testsuite/25_algorithms/search_n/diff_type.cc: New test.
        * testsuite/25_algorithms/sort/diff_type.cc: New test.
---

Tested powerpc64le-linux.

 libstdc++-v3/include/bits/ranges_algo.h       | 56 ++++++++------
 libstdc++-v3/include/bits/ranges_base.h       |  4 +-
 libstdc++-v3/include/bits/stl_algo.h          | 76 ++++++++++++-------
 libstdc++-v3/include/bits/stl_algobase.h      | 18 +++--
 libstdc++-v3/include/bits/stl_heap.h          | 18 +++--
 libstdc++-v3/include/std/functional           |  2 +-
 .../24_iterators/range_operations/advance.cc  |  2 +-
 .../25_algorithms/fill_n/diff_type.cc         | 13 ++++
 .../25_algorithms/for_each/diff_type.cc       | 13 ++++
 .../25_algorithms/heap/constrained.cc         | 20 ++---
 .../lexicographical_compare/diff_type.cc      | 57 ++++++++++++++
 .../25_algorithms/nth_element/58800.cc        |  2 +-
 .../25_algorithms/nth_element/constrained.cc  |  2 +-
 .../25_algorithms/nth_element/diff_type.cc    | 13 ++++
 .../25_algorithms/nth_element/random_test.cc  |  4 +-
 .../partial_sort/check_compare_by_value.cc    |  4 +-
 .../25_algorithms/partial_sort/constrained.cc |  3 +-
 .../25_algorithms/partial_sort/random_test.cc |  4 +-
 .../partial_sort_copy/constrained.cc          |  4 +-
 .../partial_sort_copy/random_test.cc          |  4 +-
 .../25_algorithms/push_heap/diff_type.cc      | 13 ++++
 .../25_algorithms/rotate/diff_type.cc         | 13 ++++
 .../25_algorithms/search_n/diff_type.cc       | 13 ++++
 .../testsuite/25_algorithms/sort/diff_type.cc | 13 ++++
 .../testsuite/std/ranges/adaptors/drop.cc     |  2 +-
 .../testsuite/util/testsuite_iterators.h      | 18 +++++
 26 files changed, 301 insertions(+), 90 deletions(-)
 create mode 100644 libstdc++-v3/testsuite/25_algorithms/fill_n/diff_type.cc
 create mode 100644 libstdc++-v3/testsuite/25_algorithms/for_each/diff_type.cc
 create mode 100644 
libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/diff_type.cc
 create mode 100644 
libstdc++-v3/testsuite/25_algorithms/nth_element/diff_type.cc
 create mode 100644 libstdc++-v3/testsuite/25_algorithms/push_heap/diff_type.cc
 create mode 100644 libstdc++-v3/testsuite/25_algorithms/rotate/diff_type.cc
 create mode 100644 libstdc++-v3/testsuite/25_algorithms/search_n/diff_type.cc
 create mode 100644 libstdc++-v3/testsuite/25_algorithms/sort/diff_type.cc

diff --git a/libstdc++-v3/include/bits/ranges_algo.h 
b/libstdc++-v3/include/bits/ranges_algo.h
index 6e1e06cb2d0f..65356fd2dfd0 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -1684,8 +1684,9 @@ namespace ranges
                      if (__k == 1)
                        {
                          auto __t = std::move(*__p);
-                         ranges::move(__p + 1, __p + __n, __p);
-                         *(__p + __n - 1) = std::move(__t);
+                         ranges::move(ranges::next(__p),
+                                      ranges::next(__p, __n), __p);
+                         *ranges::next(__p, __n - 1) = std::move(__t);
                          return {std::move(__ret), std::move(__lasti)};
                        }
                    auto __q = __p + __k;
@@ -1709,8 +1710,10 @@ namespace ranges
                    if constexpr (__is_pod(iter_value_t<_Iter>))
                      if (__k == 1)
                        {
-                         auto __t = std::move(*(__p + __n - 1));
-                         ranges::move_backward(__p, __p + __n - 1, __p + __n);
+                         auto __t = std::move(*ranges::next(__p, __n - 1));
+                         ranges::move_backward(__p,
+                                               ranges::next(__p, __n - 1),
+                                               ranges::next(__p, __n));
                          *__p = std::move(__t);
                          return {std::move(__ret), std::move(__lasti)};
                        }
@@ -1970,7 +1973,7 @@ namespace ranges
        if (__urngrange / __urange >= __urange)
          // I.e. (__urngrange >= __urange * __urange) but without wrap issues.
          {
-           _Iter __i = __first + 1;
+           _Iter __i = ranges::next(__first);
 
            // Since we know the range isn't empty, an even number of elements
            // means an uneven number of elements /to swap/, in which case we
@@ -1979,7 +1982,7 @@ namespace ranges
            if ((__urange % 2) == 0)
              {
                __distr_type __d{0, 1};
-               ranges::iter_swap(__i++, __first + __d(__g));
+               ranges::iter_swap(__i++, ranges::next(__first, __d(__g)));
              }
 
            // Now we know that __last - __i is even, so we do the rest in 
pairs,
@@ -1990,11 +1993,11 @@ namespace ranges
              {
                const __uc_type __swap_range = __uc_type(__i - __first) + 1;
 
-               const pair<__uc_type, __uc_type> __pospos =
+               const pair<_DistanceType, _DistanceType> __pospos =
                  __gen_two_uniform_ints(__swap_range, __swap_range + 1, __g);
 
-               ranges::iter_swap(__i++, __first + __pospos.first);
-               ranges::iter_swap(__i++, __first + __pospos.second);
+               ranges::iter_swap(__i++, ranges::next(__first, __pospos.first));
+               ranges::iter_swap(__i++, ranges::next(__first, 
__pospos.second));
              }
 
            return __i;
@@ -2002,9 +2005,11 @@ namespace ranges
 
        __distr_type __d;
 
-       _Iter __i = __first + 1;
+       _Iter __i = ranges::next(__first);
        for (; __i != __last; ++__i)
-         ranges::iter_swap(__i, __first + __d(__g, __p_type(0, __i - 
__first)));
+         ranges::iter_swap(__i,
+                           ranges::next(__first,
+                                        __d(__g, __p_type(0, __i - __first))));
 
        return __i;
       }
@@ -2060,7 +2065,7 @@ namespace ranges
          {
            auto __comp_proj = __detail::__make_comp_proj(__comp, __proj);
            __detail::__push_heap(__first, (__last - __first) - 1,
-                                 0, ranges::iter_move(__last - 1),
+                                 0, ranges::iter_move(ranges::prev(__last)),
                                  __comp_proj);
            return __last;
          }
@@ -2137,8 +2142,9 @@ namespace ranges
          {
            if (__last - __first > 1)
              {
+               auto __back = ranges::prev(__last);
                auto __comp_proj = __detail::__make_comp_proj(__comp, __proj);
-               __detail::__pop_heap(__first, __last - 1, __last - 1, 
__comp_proj);
+               __detail::__pop_heap(__first, __back, __back, __comp_proj);
              }
            return __last;
          }
@@ -2356,12 +2362,12 @@ namespace ranges
        if (__first == __last)
          return;
 
-       for (_Iter __i = __first + 1; __i != __last; ++__i)
+       for (_Iter __i = ranges::next(__first); __i != __last; ++__i)
          {
            if (__comp(*__i, *__first))
              {
                iter_value_t<_Iter> __val = ranges::iter_move(__i);
-               ranges::move_backward(__first, __i, __i + 1);
+               ranges::move_backward(__first, __i, ranges::next(__i));
                *__first = std::move(__val);
              }
            else
@@ -2383,10 +2389,11 @@ namespace ranges
       constexpr void
       __final_insertion_sort(_Iter __first, _Iter __last, _Comp __comp)
       {
-       if (__last - __first > __sort_threshold)
+       constexpr iter_difference_t<_Iter> __threshold = __sort_threshold;
+       if (__last - __first > __threshold)
          {
-           __detail::__insertion_sort(__first, __first + __sort_threshold, 
__comp);
-           __detail::__unguarded_insertion_sort(__first + __sort_threshold, 
__last,
+           __detail::__insertion_sort(__first, __first + __threshold, __comp);
+           __detail::__unguarded_insertion_sort(__first + __threshold, __last,
                                                 __comp);
          }
        else
@@ -2416,8 +2423,10 @@ namespace ranges
       __unguarded_partition_pivot(_Iter __first, _Iter __last, _Comp __comp)
       {
        _Iter __mid = __first + (__last - __first) / 2;
-       __detail::__move_median_to_first(__first, __first + 1, __mid, __last - 
1, __comp);
-       return __detail::__unguarded_partition(__first + 1, __last, __first, 
__comp);
+       __detail::__move_median_to_first(__first, ranges::next(__first), __mid,
+                                        ranges::prev(__last), __comp);
+       return __detail::__unguarded_partition(ranges::next(__first), __last,
+                                              __first, __comp);
       }
 
     template<typename _Iter, typename _Comp>
@@ -2745,7 +2754,7 @@ namespace ranges
                            std::__invoke(__proj, *__first)))
            {
              ranges::pop_heap(__first, __middle, __comp, __proj);
-             ranges::iter_swap(__middle-1, __i);
+             ranges::iter_swap(std::prev(__middle), __i);
              ranges::push_heap(__first, __middle, __comp, __proj);
            }
        ranges::sort_heap(__first, __middle, __comp, __proj);
@@ -2812,7 +2821,7 @@ namespace ranges
            {
              ranges::pop_heap(__result_first, __result_real_last,
                               __comp, __proj2);
-             *(__result_real_last-1) = *__first;
+             *ranges::prev(__result_real_last) = *__first;
              ranges::push_heap(__result_first, __result_real_last,
                                __comp, __proj2);
            }
@@ -2924,7 +2933,8 @@ namespace ranges
          {
            if (__depth_limit == 0)
              {
-               __detail::__heap_select(__first, __nth + 1, __last, __comp);
+               __detail::__heap_select(__first, ranges::next(__nth), __last,
+                                       __comp);
                // Place the nth largest element in its final position.
                ranges::iter_swap(__first, __nth);
                return;
diff --git a/libstdc++-v3/include/bits/ranges_base.h 
b/libstdc++-v3/include/bits/ranges_base.h
index 7df638db2d6f..02e13a2027d1 100644
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -887,7 +887,7 @@ namespace ranges
                if constexpr (assignable_from<_It&, _Sent>)
                  __it = std::move(__bound);
                else if constexpr (random_access_iterator<_It>)
-                 __it += 0;
+                 __it += iter_difference_t<_It>(0);
                return __n;
              }
            else if (__diff > 0 ? __n >= __diff : __n <= __diff)
@@ -907,7 +907,7 @@ namespace ranges
              {
                // inline any possible side effects of advance(it, n)
                if constexpr (random_access_iterator<_It>)
-                 __it += 0;
+                 __it += iter_difference_t<_It>(0);
                return 0;
              }
          }
diff --git a/libstdc++-v3/include/bits/stl_algo.h 
b/libstdc++-v3/include/bits/stl_algo.h
index 81a2457ae6f2..e8a92e869619 100644
--- a/libstdc++-v3/include/bits/stl_algo.h
+++ b/libstdc++-v3/include/bits/stl_algo.h
@@ -204,7 +204,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
          while (__unary_pred(--__backTrack))
            {
              if (--__remainder == 0)
-               return (__first - __count); // Success
+               return __first - _DistanceType(__count); // Success
            }
          __remainder = __count + 1 - (__first - __backTrack);
        }
@@ -1259,8 +1259,8 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
              if (__is_pod(_ValueType) && __k == 1)
                {
                  _ValueType __t = _GLIBCXX_MOVE(*__p);
-                 _GLIBCXX_MOVE3(__p + 1, __p + __n, __p);
-                 *(__p + __n - 1) = _GLIBCXX_MOVE(__t);
+                 _GLIBCXX_MOVE3(__p + _Distance(1), __p + __n, __p);
+                 *(__p + __n - _Distance(1)) = _GLIBCXX_MOVE(__t);
                  return __ret;
                }
              _RandomAccessIterator __q = __p + __k;
@@ -1281,8 +1281,9 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
              __k = __n - __k;
              if (__is_pod(_ValueType) && __k == 1)
                {
-                 _ValueType __t = _GLIBCXX_MOVE(*(__p + __n - 1));
-                 _GLIBCXX_MOVE_BACKWARD3(__p, __p + __n - 1, __p + __n);
+                 _ValueType __t = _GLIBCXX_MOVE(*(__p + __n - _Distance(1)));
+                 _GLIBCXX_MOVE_BACKWARD3(__p, __p + __n - _Distance(1),
+                                         __p + __n);
                  *__p = _GLIBCXX_MOVE(__t);
                  return __ret;
                }
@@ -1770,15 +1771,18 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
     __insertion_sort(_RandomAccessIterator __first,
                     _RandomAccessIterator __last, _Compare __comp)
     {
-      if (__first == __last) return;
+      if (__first == __last)
+       return;
 
-      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
+      typedef iterator_traits<_RandomAccessIterator> _IterTraits;
+      typedef typename _IterTraits::difference_type _Dist;
+
+      for (_RandomAccessIterator __i = __first + _Dist(1); __i != __last; 
++__i)
        {
          if (__comp(__i, __first))
            {
-             typename iterator_traits<_RandomAccessIterator>::value_type
-               __val = _GLIBCXX_MOVE(*__i);
-             _GLIBCXX_MOVE_BACKWARD3(__first, __i, __i + 1);
+             typename _IterTraits::value_type __val = _GLIBCXX_MOVE(*__i);
+             _GLIBCXX_MOVE_BACKWARD3(__first, __i, __i + _Dist(1));
              *__first = _GLIBCXX_MOVE(__val);
            }
          else
@@ -1812,10 +1816,13 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
     __final_insertion_sort(_RandomAccessIterator __first,
                           _RandomAccessIterator __last, _Compare __comp)
     {
-      if (__last - __first > int(_S_threshold))
+      typename iterator_traits<_RandomAccessIterator>::difference_type
+       __threshold = _S_threshold;
+
+      if (__last - __first > __threshold)
        {
-         std::__insertion_sort(__first, __first + int(_S_threshold), __comp);
-         std::__unguarded_insertion_sort(__first + int(_S_threshold), __last,
+         std::__insertion_sort(__first, __first + __threshold, __comp);
+         std::__unguarded_insertion_sort(__first + __threshold, __last,
                                          __comp);
        }
       else
@@ -1851,10 +1858,14 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
     __unguarded_partition_pivot(_RandomAccessIterator __first,
                                _RandomAccessIterator __last, _Compare __comp)
     {
-      _RandomAccessIterator __mid = __first + (__last - __first) / 2;
-      std::__move_median_to_first(__first, __first + 1, __mid, __last - 1,
+      typedef iterator_traits<_RandomAccessIterator> _IterTraits;
+      typedef typename _IterTraits::difference_type _Dist;
+
+      _RandomAccessIterator __mid = __first + _Dist((__last - __first) / 2);
+      _RandomAccessIterator __second = __first + _Dist(1);
+      std::__move_median_to_first(__first, __second, __mid, __last - _Dist(1),
                                  __comp);
-      return std::__unguarded_partition(__first + 1, __last, __first, __comp);
+      return std::__unguarded_partition(__second, __last, __first, __comp);
     }
 
   template<typename _RandomAccessIterator, typename _Compare>
@@ -1916,11 +1927,14 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
                  _RandomAccessIterator __last, _Size __depth_limit,
                  _Compare __comp)
     {
+      _RandomAccessIterator __after_nth = __nth;
+      ++__after_nth;
+
       while (__last - __first > 3)
        {
          if (__depth_limit == 0)
            {
-             std::__heap_select(__first, __nth + 1, __last, __comp);
+             std::__heap_select(__first, __after_nth, __last, __comp);
              // Place the nth largest element in its final position.
              std::iter_swap(__first, __nth);
              return;
@@ -3822,7 +3836,8 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
        {
          if (__n2 <= 0)
            return __first;
-         auto __last = __first + __n2;
+         typename iterator_traits<_InputIterator>::difference_type __d = __n2;
+         auto __last = __first + __d;
          std::for_each(__first, __last, std::move(__f));
          return __last;
        }
@@ -4544,6 +4559,9 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
       if (__first == __last)
        return;
 
+      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
+       _Dist;
+
 #if RAND_MAX < __INT_MAX__
       if (__builtin_expect((__last - __first) >= RAND_MAX / 4, 0))
        {
@@ -4551,14 +4569,15 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
          // instead of using rand() for all the random numbers needed.
          unsigned __xss
            = (unsigned)std::rand() ^ ((unsigned)std::rand() << 15);
-         for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
+         for (_RandomAccessIterator __i = __first + _Dist(1); __i != __last;
+              ++__i)
            {
              __xss += !__xss;
              __xss ^= __xss << 13;
              __xss ^= __xss >> 17;
              __xss ^= __xss << 5;
-             _RandomAccessIterator __j = __first
-                                           + (__xss % ((__i - __first) + 1));
+             _RandomAccessIterator __j
+               = __first + _Dist(__xss % ((__i - __first) + 1));
              if (__i != __j)
                std::iter_swap(__i, __j);
            }
@@ -4566,11 +4585,11 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
        }
 #endif
 
-      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
+      for (_RandomAccessIterator __i = __first + _Dist(1); __i != __last; 
++__i)
        {
          // XXX rand() % N is not uniformly distributed
-         _RandomAccessIterator __j = __first
-                                       + (std::rand() % ((__i - __first) + 1));
+         _RandomAccessIterator __j
+           = __first + _Dist(std::rand() % ((__i - __first) + 1));
          if (__i != __j)
            std::iter_swap(__i, __j);
        }
@@ -4611,9 +4630,14 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
 
       if (__first == __last)
        return;
-      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
+
+      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
+       _Dist;
+
+      for (_RandomAccessIterator __i = __first + _Dist(1); __i != __last; 
++__i)
        {
-         _RandomAccessIterator __j = __first + __rand((__i - __first) + 1);
+         _RandomAccessIterator __j
+           = __first + _Dist(__rand((__i - __first) + 1));
          if (__i != __j)
            std::iter_swap(__i, __j);
        }
diff --git a/libstdc++-v3/include/bits/stl_algobase.h 
b/libstdc++-v3/include/bits/stl_algobase.h
index b104ec2536a0..820091aee2dc 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -1150,10 +1150,12 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
       if (__n <= 0)
        return __first;
 
-      __glibcxx_requires_can_increment(__first, __n);
+      typename iterator_traits<_OutputIterator>::difference_type __d = __n;
+      __glibcxx_requires_can_increment(__first, __d);
 
-      std::__fill_a(__first, __first + __n, __value);
-      return __first + __n;
+      _OutputIterator __last = __first + __d;
+      std::__fill_a(__first, __last, __value);
+      return __last;
     }
 
   /**
@@ -1310,11 +1312,11 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
        __newlast1(_RAI1 __first1, _RAI1 __last1,
                   _RAI2 __first2, _RAI2 __last2)
        {
-         const typename iterator_traits<_RAI1>::difference_type
-           __diff1 = __last1 - __first1;
-         const typename iterator_traits<_RAI2>::difference_type
-           __diff2 = __last2 - __first2;
-         return __diff2 < __diff1 ? __first1 + __diff2 : __last1;
+         typedef typename iterator_traits<_RAI1>::difference_type _Diff1;
+         typedef typename iterator_traits<_RAI2>::difference_type _Diff2;
+         const _Diff1 __diff1 = __last1 - __first1;
+         const _Diff2 __diff2 = __last2 - __first2;
+         return __diff2 < __diff1 ? __first1 + _Diff1(__diff2) : __last1;
        }
 
       template<typename _RAI>
diff --git a/libstdc++-v3/include/bits/stl_heap.h 
b/libstdc++-v3/include/bits/stl_heap.h
index 028ac83eeb70..0e9c94c6865b 100644
--- a/libstdc++-v3/include/bits/stl_heap.h
+++ b/libstdc++-v3/include/bits/stl_heap.h
@@ -76,6 +76,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     __is_heap_until(_RandomAccessIterator __first, _Distance __n,
                    _Compare& __comp)
     {
+#if __cplusplus >= 201103L
+      using _IterTraits = iterator_traits<_RandomAccessIterator>;
+      static_assert(is_same<typename _IterTraits::difference_type,
+                           _Distance>::value,
+                   "Argument 'n' must be the iterator's difference type");
+#endif
       _Distance __parent = 0;
       for (_Distance __child = 1; __child < __n; ++__child)
        {
@@ -94,8 +100,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     __is_heap(_RandomAccessIterator __first, _Distance __n)
     {
+      typename iterator_traits<_RandomAccessIterator>::difference_type 
__d(__n);
       __gnu_cxx::__ops::_Iter_less_iter __comp;
-      return std::__is_heap_until(__first, __n, __comp) == __n;
+      return std::__is_heap_until(__first, __d, __comp) == __n;
     }
 
   template<typename _RandomAccessIterator, typename _Compare,
@@ -104,9 +111,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     __is_heap(_RandomAccessIterator __first, _Compare __comp, _Distance __n)
     {
+      typename iterator_traits<_RandomAccessIterator>::difference_type 
__d(__n);
       typedef __decltype(__comp) _Cmp;
       __gnu_cxx::__ops::_Iter_comp_iter<_Cmp> __cmp(_GLIBCXX_MOVE(__comp));
-      return std::__is_heap_until(__first, __n, __cmp) == __n;
+      return std::__is_heap_until(__first, __d, __cmp) == __n;
     }
 
   template<typename _RandomAccessIterator>
@@ -175,7 +183,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       __glibcxx_requires_heap(__first, __last - 1);
 
       __gnu_cxx::__ops::_Iter_less_val __comp;
-      _ValueType __value = _GLIBCXX_MOVE(*(__last - 1));
+      _ValueType __value = _GLIBCXX_MOVE(*(__last - _DistanceType(1)));
       std::__push_heap(__first, _DistanceType((__last - __first) - 1),
                       _DistanceType(0), _GLIBCXX_MOVE(__value), __comp);
     }
@@ -208,11 +216,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            _RandomAccessIterator>)
       __glibcxx_requires_valid_range(__first, __last);
       __glibcxx_requires_irreflexive_pred(__first, __last, __comp);
-      __glibcxx_requires_heap_pred(__first, __last - 1, __comp);
+      __glibcxx_requires_heap_pred(__first, __last - _DistanceType(1), __comp);
 
       __decltype(__gnu_cxx::__ops::__iter_comp_val(_GLIBCXX_MOVE(__comp)))
        __cmp(_GLIBCXX_MOVE(__comp));
-      _ValueType __value = _GLIBCXX_MOVE(*(__last - 1));
+      _ValueType __value = _GLIBCXX_MOVE(*(__last - _DistanceType(1)));
       std::__push_heap(__first, _DistanceType((__last - __first) - 1),
                       _DistanceType(0), _GLIBCXX_MOVE(__value), __cmp);
     }
diff --git a/libstdc++-v3/include/std/functional 
b/libstdc++-v3/include/std/functional
index bf40995659d1..9d3410f3a2cd 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -1345,7 +1345,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            }
          if (__j < 0)
            {
-             const auto __match = __first + __i + 1;
+             const auto __match = __first + __i + __diff_type(1);
              return std::make_pair(__match, __match + __patlen);
            }
          __i += std::max(_M_bad_char_shift(__first[__i]),
diff --git a/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc 
b/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
index 2f48181fb675..8229b1ee6c16 100644
--- a/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
+++ b/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
@@ -42,7 +42,7 @@ test01()
   std::ranges::advance(iter, -2);
   VERIFY( iter == r.begin() );
 
-  std::ranges::advance(iter, r.begin() + 1);
+  std::ranges::advance(iter, std::ranges::next(r.begin()));
   VERIFY( iter != r.begin() );
   VERIFY( iter != r.end() );
   std::ranges::advance(iter, r.begin());
diff --git a/libstdc++-v3/testsuite/25_algorithms/fill_n/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/fill_n/diff_type.cc
new file mode 100644
index 000000000000..7265d396217d
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/fill_n/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1];
+  __gnu_test::random_access_container<int> c(a);
+  std::fill_n(c.begin(), 1U, 0);
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/for_each/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/for_each/diff_type.cc
new file mode 100644
index 000000000000..d78ba192fa8f
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/for_each/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++17 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1];
+  __gnu_test::random_access_container<int> c(a);
+  std::for_each_n(c.begin(), 1U, [](int){});
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/heap/constrained.cc 
b/libstdc++-v3/testsuite/25_algorithms/heap/constrained.cc
index 5486c8552d03..2f818e2b2870 100644
--- a/libstdc++-v3/testsuite/25_algorithms/heap/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/heap/constrained.cc
@@ -53,17 +53,17 @@ test01()
 
       iter = ranges::pop_heap(rx, pred, proj);
       VERIFY( iter == rx.end() );
-      VERIFY( *(iter-1) == 50 );
-      VERIFY( ranges::is_heap_until(rx, pred, proj) == iter-1 );
+      VERIFY( *ranges::prev(iter) == 50 );
+      VERIFY( ranges::is_heap_until(rx, pred, proj) == ranges::prev(iter) );
 
-      iter = ranges::pop_heap(rx.begin(), iter-1, pred, proj);
-      VERIFY( iter+1 == rx.end() );
-      VERIFY( *(iter-1) == 49 );
-      VERIFY( ranges::is_heap_until(rx, pred, proj) == iter-1 );
+      iter = ranges::pop_heap(rx.begin(), ranges::prev(iter), pred, proj);
+      VERIFY( ranges::next(iter) == rx.end() );
+      VERIFY( *ranges::prev(iter) == 49 );
+      VERIFY( ranges::is_heap_until(rx, pred, proj) == ranges::prev(iter) );
 
-      *(iter-1) = i;
+      *ranges::prev(iter) = i;
       iter = ranges::push_heap(rx.begin(), iter, pred, proj);
-      VERIFY( iter+1 == rx.end() );
+      VERIFY( ranges::next(iter) == rx.end() );
       VERIFY( ranges::is_heap_until(rx, pred, proj) == iter );
 
       *iter = 2*i;
@@ -71,9 +71,9 @@ test01()
       VERIFY( iter == rx.end() );
       VERIFY( ranges::is_heap_until(rx, pred, proj) == iter );
 
-      *(rx.begin()+1) *= -1;
+      *ranges::next(rx.begin()) *= -1;
       VERIFY( !ranges::is_heap(rx, pred, proj) );
-      *(rx.begin()+1) *= -1;
+      *ranges::next(rx.begin()) *= -1;
       VERIFY( ranges::is_heap(rx, pred, proj) );
 
       iter = ranges::sort_heap(rx, pred, proj);
diff --git 
a/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/diff_type.cc
new file mode 100644
index 000000000000..b790197715b6
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/diff_type.cc
@@ -0,0 +1,57 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+struct Iter
+{
+  using value_type = int;
+  using difference_type = short;
+  using iterator_category = std::random_access_iterator_tag;
+  using pointer = const value_type*;
+  using reference = const value_type&;
+
+  Iter() : p(nullptr) { }
+  explicit Iter(pointer p) : p(p) { }
+  reference operator*() const { return *p; }
+  pointer operator->() const { return p; }
+  reference operator[](difference_type n) const { return p[n]; }
+  Iter& operator++() { ++p; return *this; }
+  Iter& operator--() { --p; return *this; }
+  Iter operator++(int) { return Iter(p++); }
+  Iter operator--(int) { return Iter(p--); }
+  Iter& operator+=(difference_type n) { p += n; return *this; }
+  Iter& operator-=(difference_type n) { p -= n; return *this; }
+
+  friend Iter operator+(Iter i, difference_type n) { return i += n; }
+  friend Iter operator+(difference_type n, Iter i) { return i += n; }
+  friend Iter operator-(Iter i, difference_type n) { return i -= n; }
+  friend difference_type operator-(Iter i, Iter j) { return i.p - j.p; }
+
+  template<typename D> void operator[](D) const = delete;
+  template<typename D> void operator+=(D) = delete;
+  template<typename D> void operator-=(D) = delete;
+  template<typename D> friend void operator+(Iter, difference_type) = delete;
+  template<typename D> friend void operator+(difference_type, Iter) = delete;
+  template<typename D> friend void operator-(Iter, difference_type) = delete;
+
+  friend bool operator==(Iter i, Iter j) { return i.p == j.p; }
+  friend bool operator!=(Iter i, Iter j) { return i.p != j.p; }
+  friend bool operator<(Iter i, Iter j) { return i.p < j.p; }
+  friend bool operator<=(Iter i, Iter j) { return i.p <= j.p; }
+  friend bool operator>(Iter i, Iter j) { return i.p > j.p; }
+  friend bool operator>=(Iter i, Iter j) { return i.p >= j.p; }
+
+private:
+  pointer p;
+};
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1] = { };
+  __gnu_test::random_access_container<int> c(a);
+  (void) std::lexicographical_compare(c.begin(), c.end(), Iter(a), Iter(a+1));
+  (void) std::lexicographical_compare(Iter(a), Iter(a+1), c.begin(), c.end());
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/nth_element/58800.cc 
b/libstdc++-v3/testsuite/25_algorithms/nth_element/58800.cc
index 3989ee0bbb50..ff86c63614f5 100644
--- a/libstdc++-v3/testsuite/25_algorithms/nth_element/58800.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/nth_element/58800.cc
@@ -43,7 +43,7 @@ void test01()
 
   Container con(v.data(), v.data() + 7);
 
-  std::nth_element(con.begin(), con.begin() + 3, con.end());
+  std::nth_element(con.begin(), std::next(con.begin(), 3), con.end());
 }
 
 int main()
diff --git a/libstdc++-v3/testsuite/25_algorithms/nth_element/constrained.cc 
b/libstdc++-v3/testsuite/25_algorithms/nth_element/constrained.cc
index 8cb1625dd4d5..8d3a057e93dc 100644
--- a/libstdc++-v3/testsuite/25_algorithms/nth_element/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/nth_element/constrained.cc
@@ -38,7 +38,7 @@ test01()
 
   auto pred = std::greater{};
   auto proj = [] (int a) { return -a; };
-  for (int i = 0; i < 50; i++)
+  for (std::ptrdiff_t i = 0; i < 50; i++)
     {
       test_range<int, random_access_iterator_wrapper> rx(x);
       std::ranlux48_base g(i);
diff --git a/libstdc++-v3/testsuite/25_algorithms/nth_element/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/nth_element/diff_type.cc
new file mode 100644
index 000000000000..4cc9ca92698a
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/nth_element/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1] = { };
+  __gnu_test::random_access_container<int> c(a);
+  std::nth_element(c.begin(), c.begin(), c.end());
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/nth_element/random_test.cc 
b/libstdc++-v3/testsuite/25_algorithms/nth_element/random_test.cc
index 2e9d4b3b6e1e..9eaef61c1690 100644
--- a/libstdc++-v3/testsuite/25_algorithms/nth_element/random_test.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/nth_element/random_test.cc
@@ -37,9 +37,9 @@ struct testNthElement
   template<typename Container, typename RandomGen>
   void operator()(Container con, RandomGen& rg)
   {
-    const int size = con.end() - con.begin();
+    const auto size = con.end() - con.begin();
     auto dist = std::uniform_int_distribution<>(0, size);
-    const int element = dist(rg);
+    const decltype(size) element = dist(rg);
 
     std::nth_element(con.begin(), con.begin() + element, con.end());
 
diff --git 
a/libstdc++-v3/testsuite/25_algorithms/partial_sort/check_compare_by_value.cc 
b/libstdc++-v3/testsuite/25_algorithms/partial_sort/check_compare_by_value.cc
index 05f4f1cbdb55..e1ba840a5a3c 100644
--- 
a/libstdc++-v3/testsuite/25_algorithms/partial_sort/check_compare_by_value.cc
+++ 
b/libstdc++-v3/testsuite/25_algorithms/partial_sort/check_compare_by_value.cc
@@ -43,7 +43,7 @@ test01()
             17, 8, 18, 9, 19 };
   const int N = sizeof(s1) / sizeof(V);
   Container con(s1, s1 + N);
-  std::partial_sort(con.begin(), con.begin() + 10, con.end());
+  std::partial_sort(con.begin(), std::next(con.begin(), 10), con.end());
   VERIFY( s1[0].ok );
   for(int i = 1; i < 10; ++i)
     VERIFY( s1[i].val > s1[i - 1].val && s1[i].ok );
@@ -59,7 +59,7 @@ test02()
             17, 8, 18, 9, 19 };
   const int N = sizeof(s1) / sizeof(V);
   Container con(s1, s1 + N);
-  std::partial_sort(con.begin(), con.begin() + 10, con.end(),
+  std::partial_sort(con.begin(), std::next(con.begin(), 10), con.end(),
                    __gnu_test::order);
   VERIFY( s1[0].ok );
   for(int i = 1; i < 10; ++i)
diff --git a/libstdc++-v3/testsuite/25_algorithms/partial_sort/constrained.cc 
b/libstdc++-v3/testsuite/25_algorithms/partial_sort/constrained.cc
index 032ffe75d890..554a8d76a4b8 100644
--- a/libstdc++-v3/testsuite/25_algorithms/partial_sort/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/partial_sort/constrained.cc
@@ -47,7 +47,8 @@ test01()
       ranges::shuffle(c, g1);
       ranges::shuffle(ranges::begin(r), ranges::end(r), g2);
 
-      for (unsigned middle = 0; middle < std::min(size, 10U); ++middle)
+      for (std::ptrdiff_t middle = 0, end = std::min(size, 10U);
+          middle < end; ++middle)
        {
          auto res1 = ranges::partial_sort(c.begin(), c.begin()+middle, c.end(),
                                           {}, std::negate<>{});
diff --git a/libstdc++-v3/testsuite/25_algorithms/partial_sort/random_test.cc 
b/libstdc++-v3/testsuite/25_algorithms/partial_sort/random_test.cc
index 89eb99266608..4e690008e74a 100644
--- a/libstdc++-v3/testsuite/25_algorithms/partial_sort/random_test.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/partial_sort/random_test.cc
@@ -37,9 +37,9 @@ struct testPartialSort
   template<typename Container, typename RandomGen>
   void operator()(Container con, RandomGen& rg)
   {
-    const int size = con.end() - con.begin();
+    const auto size = con.end() - con.begin();
     auto dist = std::uniform_int_distribution<>(0, size);
-    const int element = dist(rg);
+    const decltype(size) element = dist(rg);
 
     std::partial_sort(con.begin(), con.begin() + element, con.end());
 
diff --git 
a/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/constrained.cc 
b/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/constrained.cc
index a0bd48be638b..38b2dda45199 100644
--- a/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/constrained.cc
@@ -35,7 +35,7 @@ namespace ranges = std::ranges;
 void
 test01()
 {
-  for (unsigned size = 0; size < 50; ++size)
+  for (std::ptrdiff_t size = 0; size < 50; ++size)
     {
       std::vector<int> vref(size);
       std::iota(vref.begin(), vref.end(), 0);
@@ -45,7 +45,7 @@ test01()
       ranges::shuffle(v1, g1);
       ranges::shuffle(v2, g2);
 
-      for (unsigned middle = 0; middle < 10; ++middle)
+      for (std::ptrdiff_t middle = 0; middle < 10; ++middle)
        {
          test_container<int, forward_iterator_wrapper> c
            = {v1.data(), v1.data() + size};
diff --git 
a/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/random_test.cc 
b/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/random_test.cc
index 2c0b8bca2bef..be033a240140 100644
--- a/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/random_test.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/partial_sort_copy/random_test.cc
@@ -38,9 +38,9 @@ struct testPartialSortCopy
   template<typename Container, typename RandomGen>
   void operator()(Container con, RandomGen& rg)
   {
-    const int size = con.end() - con.begin();
+    const auto size = con.end() - con.begin();
     auto dist = std::uniform_int_distribution<>(0, size);
-    const int element = dist(rg);
+    const decltype(size) element = dist(rg);
 
     std::vector<int> outvec(element + 1); // add +1 to avoid empty issues
 
diff --git a/libstdc++-v3/testsuite/25_algorithms/push_heap/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/push_heap/diff_type.cc
new file mode 100644
index 000000000000..ab4587e946d0
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/push_heap/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1] = { };
+  __gnu_test::random_access_container<int> c(a);
+  std::push_heap(c.begin(), c.end());
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/rotate/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/rotate/diff_type.cc
new file mode 100644
index 000000000000..cbf2958df0fb
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/rotate/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1] = { };
+  __gnu_test::random_access_container<int> c(a);
+  std::rotate(c.begin(), c.begin(), c.end());
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/search_n/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/search_n/diff_type.cc
new file mode 100644
index 000000000000..20253e9ca2a6
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/search_n/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1] = { };
+  __gnu_test::random_access_container<int> c(a);
+  (void) std::search_n(c.begin(), c.begin(), 1U, 0);
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/sort/diff_type.cc 
b/libstdc++-v3/testsuite/25_algorithms/sort/diff_type.cc
new file mode 100644
index 000000000000..52a83e88ff81
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/sort/diff_type.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <algorithm>
+#include <testsuite_iterators.h>
+
+void
+test_pr121890()
+{
+  // algorithms do not use iterator's difference_type for arithmetic
+  int a[1] = { };
+  __gnu_test::random_access_container<int> c(a);
+  std::sort(c.begin(), c.begin());
+}
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/drop.cc 
b/libstdc++-v3/testsuite/std/ranges/adaptors/drop.cc
index 4583fb0e7130..57db806069ed 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/drop.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/drop.cc
@@ -243,7 +243,7 @@ test08()
 
   long b[10]{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
   test_range<long, ra_test_wrapper> rb(b);
-  ranges::subrange sized = {rb.begin(), rb.begin()+6};
+  ranges::subrange sized = {rb.begin(), ranges::next(rb.begin(), 6)};
   using Sized = decltype(sized);
   static_assert( ranges::random_access_range<Sized> );
   static_assert( ranges::sized_range<Sized> );
diff --git a/libstdc++-v3/testsuite/util/testsuite_iterators.h 
b/libstdc++-v3/testsuite/util/testsuite_iterators.h
index acd412af0f22..5bf2e704e843 100644
--- a/libstdc++-v3/testsuite/util/testsuite_iterators.h
+++ b/libstdc++-v3/testsuite/util/testsuite_iterators.h
@@ -607,6 +607,16 @@ namespace __gnu_test
     T& operator[](std::ptrdiff_t n) const
     { return *(*this + n); }
 
+#if __cplusplus >= 201103L
+    // Ensure that the iterator's difference_type is always used.
+    template<typename D> void operator+=(D) = delete;
+    template<typename D> void operator-=(D) = delete;
+    template<typename D> void operator[](D) const = delete;
+    template<typename D>
+      typename std::enable_if<std::is_integral<D>::value>::type
+      operator-(D) const = delete;
+#endif
+
     _GLIBCXX14_CONSTEXPR
     bool operator<(const random_access_iterator_wrapper<T>& in) const
     {
@@ -645,6 +655,14 @@ namespace __gnu_test
     operator+(std::ptrdiff_t n, random_access_iterator_wrapper<T> it)
     { return it += n; }
 
+#if __cplusplus >= 201103L
+    // Ensure that the iterator's difference_type is always used.
+    template<typename T, typename D>
+      void operator+(random_access_iterator_wrapper<T>, D) = delete;
+    template<typename T, typename D>
+      void operator+(D, random_access_iterator_wrapper<T>) = delete;
+#endif
+
 
   /**
    * @brief A container-type class for holding iterator wrappers
-- 
2.51.0

Reply via email to