On 19/08/20 17:00 +0100, Jonathan Wakely wrote:
Because __int128 can be used as the difference type for iota_view, we
need to ensure that it meets the requirements of an integer-class type.
The requirements in [iterator.concept.winc] p10 include numeric_limits
being specialized and giving meaningful answers. Currently we only
specialize numeric_limits for non-standard integer types in non-strict
modes. However, nothing prevents us from defining an explicit
specialization for any implementation-defined type, so it doesn't matter
whether std::is_integral<__int128> is true or not.
This patch ensures that the numeric_limits specializations for signed
and unsigned __int128 are defined whenever __int128 is available. It
also makes the __numeric_traits and __int_limits helpers work for
__int128, via a new __gnu_cxx::__is_integer_nonstrict trait.
libstdc++-v3/ChangeLog:
PR libstdc++/96042
* include/ext/numeric_traits.h (__is_integer_nonstrict): New
trait which is true for 128-bit integers even in strict modes.
(__numeric_traits_integer, __numeric_traits): Use
__is_integer_nonstrict instead of __is_integer.
* include/std/limits [__STRICT_ANSI__ && __SIZEOF_INT128__]
(numeric_limits<__int128>, (numeric_limits<unsigned __int128>):
Define.
* testsuite/std/ranges/iota/96042.cc: New test.
The attached patch is another change needed to support __int128 as an
integer-like type in strict mode.
Tested x86_64-linux, -m32 and -m64. Committed to trunk.
I'll backport this to gcc-10 too.
commit e6e01618e83bcd9eb3a2b27df30ed87106a748b4
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Aug 19 20:36:10 2020
libstdc++: Make make-unsigned-like-t<__int128> work [PR 96042]
As well as ensuring that numeric_limits<__int128> is defined, we need to
ensure that make-unsigned-like-t and to-unsigned-like work correctly for
128-bit integers in strict mode. This ensures that a subrange created
from an iota_view's iterator and sentinel can represent its size.
Co-authored-by: Patrick Palka <ppa...@redhat.com>
libstdc++-v3/ChangeLog:
2020-08-19 Jonathan Wakely <jwak...@redhat.com>
Patrick Palka <ppa...@redhat.com>
PR libstdc++/96042
* include/bits/range_access.h (__detail::__to_unsigned_like):
Do not use make_unsigned_t<T> in the return type, as it can
result in an error before the integral<T> constraint is checked.
[__STRICT_ANSI__]: Add overloads for 128-bit integer types.
(__detail::__make_unsigned_like_t): Define as the return type
of __to_unsigned_like.
* testsuite/std/ranges/subrange/96042.cc: New test.
diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h
index 3eb1f2fd272..bafced31ea8 100644
--- a/libstdc++-v3/include/bits/range_access.h
+++ b/libstdc++-v3/include/bits/range_access.h
@@ -364,13 +364,23 @@ namespace ranges
{ return __max_size_type(__t); }
template<integral _Tp>
- constexpr make_unsigned_t<_Tp>
+ constexpr auto
__to_unsigned_like(_Tp __t) noexcept
- { return __t; }
+ { return static_cast<make_unsigned_t<_Tp>>(__t); }
- template<typename _Tp, bool _MaxDiff = same_as<_Tp, __max_diff_type>>
+#if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__
+ constexpr unsigned __int128
+ __to_unsigned_like(__int128 __t) noexcept
+ { return __t; }
+
+ constexpr unsigned __int128
+ __to_unsigned_like(unsigned __int128 __t) noexcept
+ { return __t; }
+#endif
+
+ template<typename _Tp>
using __make_unsigned_like_t
- = conditional_t<_MaxDiff, __max_size_type, make_unsigned_t<_Tp>>;
+ = decltype(__detail::__to_unsigned_like(std::declval<_Tp>()));
// Part of the constraints of ranges::borrowed_range
template<typename _Tp>
diff --git a/libstdc++-v3/testsuite/std/ranges/subrange/96042.cc b/libstdc++-v3/testsuite/std/ranges/subrange/96042.cc
new file mode 100644
index 00000000000..5826203f03c
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/subrange/96042.cc
@@ -0,0 +1,34 @@
+// 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++20" }
+// { dg-do compile { target c++2a } }
+
+#include <ranges>
+
+constexpr bool
+test01()
+{
+ using I = unsigned long long;
+ // view with a difference type that doesn't fit in long long:
+ std::ranges::iota_view<I, I> v(0, std::numeric_limits<I>::max());
+ // view with a size type that doesn't fit in unsigned long long:
+ std::ranges::subrange sr{v.begin(), v.end()};
+ auto sz = std::ranges::size(sr);
+ return sz == std::numeric_limits<I>::max();
+}
+static_assert( test01() );
