libstdc++: Fix weakly_incrementable to allow __int128 (PR 93267)

The __iota_diff_t alias can be the type __int128, but that does not
satisfy the signed_integral and __is_signed_integer_like concepts when
__STRICT_ANSI__ is defined (which is true for -std=c++2a).

Because weakly_incrementable is defined in terms of signed_integral, it
is not satisfied by __int128, which means iota_view's iterator doesn't
always satisfy input_or_output_iterator and so iota_view is not always a
range.

The solution is to define __max_size_type and __max_diff_type using
__int128, so that __is_signed_integer_like allows __int128, and then
make weakly_incrementable use __is_signed_integer_like instead of
signed_integral.

	PR libstdc++/93267
	* include/bits/iterator_concepts.h (__max_diff_type, __max_size_type):
	Move here from <bits/range_access.h> and define using __int128 when
	available.
	(__is_integer_like, __is_signed_integer_like): Move here from
	<bits/range_access.h>.
	(weakly_incrementable): Use __is_signed_integer_like.
	* include/bits/range_access.h (__max_diff_type, __max_size_type)
	(__is_integer_like, __is_signed_integer_like): Move to
	<bits/iterator_concepts.h>.
	(__make_unsigned_like_t): Move here from <ranges>.
	* include/std/ranges (__make_unsigned_like_t): Move to
	<bits/range_access.h>.
	(iota_view): Replace using-directive with using-declarations.
	* testsuite/std/ranges/iota/93267.cc: New test.
	* testsuite/std/ranges/iota_view.cc: Move to new 'iota' sub-directory.

6 files changed, 84 insertions, 20 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 626f59c..2941482 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,22 @@
+2020-01-15  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/93267
+	* include/bits/iterator_concepts.h (__max_diff_type, __max_size_type):
+	Move here from <bits/range_access.h> and define using __int128 when
+	available.
+	(__is_integer_like, __is_signed_integer_like): Move here from
+	<bits/range_access.h>.
+	(weakly_incrementable): Use __is_signed_integer_like.
+	* include/bits/range_access.h (__max_diff_type, __max_size_type)
+	(__is_integer_like, __is_signed_integer_like): Move to
+	<bits/iterator_concepts.h>.
+	(__make_unsigned_like_t): Move here from <ranges>.
+	* include/std/ranges (__make_unsigned_like_t): Move to
+	<bits/range_access.h>.
+	(iota_view): Replace using-directive with using-declarations.
+	* testsuite/std/ranges/iota/93267.cc: New test.
+	* testsuite/std/ranges/iota_view.cc: Move to new 'iota' sub-directory.
+
 2020-01-13  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/93244
diff --git a/libstdc++-v3/include/bits/iterator_concepts.h b/libstdc++-v3/include/bits/iterator_concepts.h
index 4ba32a0..bf58159 100644
--- a/libstdc++-v3/include/bits/iterator_concepts.h
+++ b/libstdc++-v3/include/bits/iterator_concepts.h
@@ -492,6 +492,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  = std::forward<_Tp>(__t);
       };
 
+  namespace ranges::__detail
+  {
+#if __SIZEOF_INT128__
+    using __max_diff_type = __int128;
+    using __max_size_type = unsigned __int128;
+#else
+    using __max_diff_type = long long;
+    using __max_size_type = unsigned long long;
+#endif
+
+    template<typename _Tp>
+      concept __is_integer_like = integral<_Tp>
+	|| same_as<_Tp, __max_diff_type> || same_as<_Tp, __max_size_type>;
+
+    template<typename _Tp>
+      concept __is_signed_integer_like = signed_integral<_Tp>
+	|| same_as<_Tp, __max_diff_type>;
+
+  } // namespace ranges::__detail
+
+  namespace __detail { using ranges::__detail::__is_signed_integer_like; }
+
   /// Requirements on types that can be incremented with ++.
   template<typename _Iter>
     concept weakly_incrementable = default_initializable<_Iter>
@@ -499,7 +521,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       && requires(_Iter __i)
       {
 	typename iter_difference_t<_Iter>;
-	requires signed_integral<iter_difference_t<_Iter>>;
+	requires __detail::__is_signed_integer_like<iter_difference_t<_Iter>>;
 	{ ++__i } -> same_as<_Iter&>;
 	__i++;
       };
diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h
index 721c755..8b546a5 100644
--- a/libstdc++-v3/include/bits/range_access.h
+++ b/libstdc++-v3/include/bits/range_access.h
@@ -347,22 +347,15 @@ namespace ranges
 
   namespace __detail
   {
-    using __max_diff_type = long long;
-    using __max_size_type = unsigned long long;
-
-    template<typename _Tp>
-      concept __is_integer_like = integral<_Tp>
-	|| same_as<_Tp, __max_diff_type> || same_as<_Tp, __max_size_type>;
-
-    template<typename _Tp>
-      concept __is_signed_integer_like = signed_integral<_Tp>
-	|| same_as<_Tp, __max_diff_type>;
-
     template<integral _Tp>
       constexpr make_unsigned_t<_Tp>
       __to_unsigned_like(_Tp __t) noexcept
       { return __t; }
 
+    template<typename _Tp, bool _MaxDiff = same_as<_Tp, __max_diff_type>>
+      using __make_unsigned_like_t
+	= conditional_t<_MaxDiff, __max_size_type, make_unsigned_t<_Tp>>;
+
     // Part of the constraints of ranges::safe_range
     template<typename _Tp>
       concept __maybe_safe_range
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 888414a..ea558c7 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -244,10 +244,6 @@ namespace ranges
 	= !range<_Tp> && __pair_like<_Tp>
 	&& sentinel_for<tuple_element_t<1, _Tp>, tuple_element_t<0, _Tp>>;
 
-    template<typename _Tp, bool _MaxDiff = same_as<_Tp, __max_diff_type>>
-      using __make_unsigned_like_t
-	= conditional_t<_MaxDiff, __max_size_type, make_unsigned_t<_Tp>>;
-
   } // namespace __detail
 
   enum class subrange_kind : bool { unsized, sized };
@@ -717,7 +713,8 @@ namespace ranges
 	constexpr _Iterator&
 	operator+=(difference_type __n) requires __detail::__advanceable<_Winc>
 	{
-	  using namespace __detail;
+	  using __detail::__is_integer_like;
+	  using __detail::__is_signed_integer_like;
 	  if constexpr (__is_integer_like<_Winc>
 	      && !__is_signed_integer_like<_Winc>)
 	    {
@@ -734,7 +731,8 @@ namespace ranges
 	constexpr _Iterator&
 	operator-=(difference_type __n) requires __detail::__advanceable<_Winc>
 	{
-	  using namespace __detail;
+	  using __detail::__is_integer_like;
+	  using __detail::__is_signed_integer_like;
 	  if constexpr (__is_integer_like<_Winc>
 	      && !__is_signed_integer_like<_Winc>)
 	    {
@@ -804,7 +802,8 @@ namespace ranges
 	operator-(const _Iterator& __x, const _Iterator& __y)
 	  requires __detail::__advanceable<_Winc>
 	{
-	  using namespace __detail;
+	  using __detail::__is_integer_like;
+	  using __detail::__is_signed_integer_like;
 	  using _Dt = difference_type;
 	  if constexpr (__is_integer_like<_Winc>)
 	    {
@@ -892,7 +891,8 @@ namespace ranges
       || (integral<_Winc> && integral<_Bound>)
       || sized_sentinel_for<_Bound, _Winc>
       {
-	using namespace __detail;
+	using __detail::__is_integer_like;
+	using __detail::__to_unsigned_like;
 	if constexpr (__is_integer_like<_Winc> && __is_integer_like<_Bound>)
 	  return (_M_value < 0)
 	    ? ((_M_bound < 0)
diff --git a/libstdc++-v3/testsuite/std/ranges/iota/93267.cc b/libstdc++-v3/testsuite/std/ranges/iota/93267.cc
new file mode 100644
index 0000000..39b3c77
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/iota/93267.cc
@@ -0,0 +1,30 @@
+// Copyright (C) 2020 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=c++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <ranges>
+
+void
+test01()
+{
+  // PR libstdc++/93267
+  std::ranges::iota_view<long long, int> i(0, 3);
+  static_assert( std::weakly_incrementable<decltype(i.begin())> );
+  (void) std::ranges::begin(i);
+}
diff --git a/libstdc++-v3/testsuite/std/ranges/iota_view.cc b/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
index 798e745..798e745 100644
--- a/libstdc++-v3/testsuite/std/ranges/iota_view.cc
+++ b/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc