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libstdc++: Make make-unsigned-like-t<__int128> work [PR 96042]

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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  <ppalka@redhat.com>

libstdc++-v3/ChangeLog:

2020-08-19  Jonathan Wakely  <jwakely@redhat.com>
	    Patrick Palka  <ppalka@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.
This commit is contained in:
Jonathan Wakely 2020-08-19 20:36:10 +01:00
parent 23ebfda0e3
commit e6e01618e8
2 changed files with 48 additions and 4 deletions
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18
libstdc++-v3/include/bits/range_access.h
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@ -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>

34
libstdc++-v3/testsuite/std/ranges/subrange/96042.cc Normal file
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@ -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() );