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libstdc++: Implement P2367 changes to avoid some list-initialization

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This implements the wording changes of P2367R0 "Remove misuses of
list-initialization from Clause 24", modulo the parts that depend
on P1739R4 which we don't yet implement (due to LWG 3407).

libstdc++-v3/ChangeLog:

	* include/bits/ranges_util.h (subrange::subrange): Avoid
	list-initialization in delegating constructor.
	* include/std/ranges (single_view): Replace implicit guide
	with explicit deduction guide that decays its argument.
	(_Single::operator()): Avoid CTAD when constructing the
	single_view object.
	(_Iota::operator()): Avoid list-initialization.
	(__detail::__can_filter_view, _Filter::operator()): Likewise.
	(__detail::__can_transform_view, _Transform::operator()): Likewise.
	(take_view::begin): Likewise.
	(__detail::__can_take_view, _Take::operator()): Likewise.
	(__detail::__can_take_while_view, _TakeWhile::operator()): Likewise.
	(__detail::__can_drop_view, _Drop::operator()): Likewise.
	(__detail::__can_drop_while_view, _DropWhile::operator()): Likewise.
	(split_view::split_view): Use views::single when initializing
	_M_pattern.
	(__detail::__can_split_view, _Split::operator()): Avoid
	list-initialization.
	(_Counted::operator()): Likewise.
	* testsuite/std/ranges/p2367.cc: New test.
This commit is contained in:
Patrick Palka 2021-04-30 10:59:20 -04:00
parent 47915ef847
commit 6e00d9bb11
3 changed files with 78 additions and 27 deletions
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2
libstdc++-v3/include/bits/ranges_util.h
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@ -251,7 +251,7 @@ namespace ranges
&& convertible_to<sentinel_t<_Rng>, _Sent>
constexpr
subrange(_Rng&& __r) requires (!_S_store_size)
: subrange{ranges::begin(__r), ranges::end(__r)}
: subrange(ranges::begin(__r), ranges::end(__r))
{ }
template<borrowed_range _Rng>

55
libstdc++-v3/include/std/ranges
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@ -246,6 +246,9 @@ namespace ranges
[[no_unique_address]] __detail::__box<_Tp> _M_value;
};
template<typename _Tp>
single_view(_Tp) -> single_view<_Tp>;
namespace __detail
{
template<typename _Wp>
@ -597,7 +600,7 @@ namespace views
template<typename _Tp>
constexpr auto
operator()(_Tp&& __e) const
{ return single_view{std::forward<_Tp>(__e)}; }
{ return single_view<decay_t<_Tp>>(std::forward<_Tp>(__e)); }
};
inline constexpr _Single single{};
@ -607,12 +610,12 @@ namespace views
template<typename _Tp>
constexpr auto
operator()(_Tp&& __e) const
{ return iota_view{std::forward<_Tp>(__e)}; }
{ return iota_view(std::forward<_Tp>(__e)); }
template<typename _Tp, typename _Up>
constexpr auto
operator()(_Tp&& __e, _Up&& __f) const
{ return iota_view{std::forward<_Tp>(__e), std::forward<_Up>(__f)}; }
{ return iota_view(std::forward<_Tp>(__e), std::forward<_Up>(__f)); }
};
inline constexpr _Iota iota{};
@ -1336,7 +1339,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Pred>
concept __can_filter_view
= requires { filter_view{std::declval<_Range>(), std::declval<_Pred>()}; };
= requires { filter_view(std::declval<_Range>(), std::declval<_Pred>()); };
} // namespace __detail
struct _Filter : __adaptor::_RangeAdaptor<_Filter>
@ -1346,7 +1349,7 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Pred&& __p) const
{
return filter_view{std::forward<_Range>(__r), std::forward<_Pred>(__p)};
return filter_view(std::forward<_Range>(__r), std::forward<_Pred>(__p));
}
using _RangeAdaptor<_Filter>::operator();
@ -1717,7 +1720,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Fp>
concept __can_transform_view
= requires { transform_view{std::declval<_Range>(), std::declval<_Fp>()}; };
= requires { transform_view(std::declval<_Range>(), std::declval<_Fp>()); };
} // namespace __detail
struct _Transform : __adaptor::_RangeAdaptor<_Transform>
@ -1727,7 +1730,7 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Fp&& __f) const
{
return transform_view{std::forward<_Range>(__r), std::forward<_Fp>(__f)};
return transform_view(std::forward<_Range>(__r), std::forward<_Fp>(__f));
}
using _RangeAdaptor<_Transform>::operator();
@ -1813,11 +1816,11 @@ namespace views::__adaptor
else
{
auto __sz = size();
return counted_iterator{ranges::begin(_M_base), __sz};
return counted_iterator(ranges::begin(_M_base), __sz);
}
}
else
return counted_iterator{ranges::begin(_M_base), _M_count};
return counted_iterator(ranges::begin(_M_base), _M_count);
}
constexpr auto
@ -1830,11 +1833,11 @@ namespace views::__adaptor
else
{
auto __sz = size();
return counted_iterator{ranges::begin(_M_base), __sz};
return counted_iterator(ranges::begin(_M_base), __sz);
}
}
else
return counted_iterator{ranges::begin(_M_base), _M_count};
return counted_iterator(ranges::begin(_M_base), _M_count);
}
constexpr auto
@ -1897,7 +1900,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Tp>
concept __can_take_view
= requires { take_view{std::declval<_Range>(), std::declval<_Tp>()}; };
= requires { take_view(std::declval<_Range>(), std::declval<_Tp>()); };
} // namespace __detail
struct _Take : __adaptor::_RangeAdaptor<_Take>
@ -1907,7 +1910,7 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Tp&& __n) const
{
return take_view{std::forward<_Range>(__r), std::forward<_Tp>(__n)};
return take_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
}
using _RangeAdaptor<_Take>::operator();
@ -2016,7 +2019,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Pred>
concept __can_take_while_view
= requires { take_while_view{std::declval<_Range>(), std::declval<_Pred>()}; };
= requires { take_while_view(std::declval<_Range>(), std::declval<_Pred>()); };
} // namespace __detail
struct _TakeWhile : __adaptor::_RangeAdaptor<_TakeWhile>
@ -2026,7 +2029,7 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Pred&& __p) const
{
return take_while_view{std::forward<_Range>(__r), std::forward<_Pred>(__p)};
return take_while_view(std::forward<_Range>(__r), std::forward<_Pred>(__p));
}
using _RangeAdaptor<_TakeWhile>::operator();
@ -2135,7 +2138,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Tp>
concept __can_drop_view
= requires { drop_view{std::declval<_Range>(), std::declval<_Tp>()}; };
= requires { drop_view(std::declval<_Range>(), std::declval<_Tp>()); };
} // namespace __detail
struct _Drop : __adaptor::_RangeAdaptor<_Drop>
@ -2145,7 +2148,7 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Tp&& __n) const
{
return drop_view{std::forward<_Range>(__r), std::forward<_Tp>(__n)};
return drop_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
}
using _RangeAdaptor<_Drop>::operator();
@ -2217,7 +2220,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Pred>
concept __can_drop_while_view
= requires { drop_while_view{std::declval<_Range>(), std::declval<_Pred>()}; };
= requires { drop_while_view(std::declval<_Range>(), std::declval<_Pred>()); };
} // namespace __detail
struct _DropWhile : __adaptor::_RangeAdaptor<_DropWhile>
@ -2227,8 +2230,8 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Pred&& __p) const
{
return drop_while_view{std::forward<_Range>(__r),
std::forward<_Pred>(__p)};
return drop_while_view(std::forward<_Range>(__r),
std::forward<_Pred>(__p));
}
using _RangeAdaptor<_DropWhile>::operator();
@ -2948,7 +2951,7 @@ namespace views::__adaptor
&& constructible_from<_Pattern, single_view<range_value_t<_Range>>>
constexpr
split_view(_Range&& __r, range_value_t<_Range> __e)
: _M_pattern(std::move(__e)),
: _M_pattern(views::single(std::move(__e))),
_M_base(views::all(std::forward<_Range>(__r)))
{ }
@ -3012,7 +3015,7 @@ namespace views::__adaptor
{
template<typename _Range, typename _Pattern>
concept __can_split_view
= requires { split_view{std::declval<_Range>(), std::declval<_Pattern>()}; };
= requires { split_view(std::declval<_Range>(), std::declval<_Pattern>()); };
} // namespace __detail
struct _Split : __adaptor::_RangeAdaptor<_Split>
@ -3022,7 +3025,7 @@ namespace views::__adaptor
constexpr auto
operator()(_Range&& __r, _Pattern&& __f) const
{
return split_view{std::forward<_Range>(__r), std::forward<_Pattern>(__f)};
return split_view(std::forward<_Range>(__r), std::forward<_Pattern>(__f));
}
using _RangeAdaptor<_Split>::operator();
@ -3041,10 +3044,10 @@ namespace views::__adaptor
operator()(_Iter __i, iter_difference_t<_Iter> __n) const
{
if constexpr (random_access_iterator<_Iter>)
return subrange{__i, __i + __n};
return subrange(__i, __i + __n);
else
return subrange{counted_iterator{std::move(__i), __n},
default_sentinel};
return subrange(counted_iterator(std::move(__i), __n),
default_sentinel);
}
};

48
libstdc++-v3/testsuite/std/ranges/p2367.cc Normal file
View File

@ -0,0 +1,48 @@
// Copyright (C) 2021 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=gnu++2a" }
// { dg-do compile { target c++2a } }
// Verify P2367 changes.
#include <ranges>
namespace ranges = std::ranges;
namespace views = std::views;
void
test01()
{
extern int (&x)[5];
// Verify changes to views::single.
using ranges::single_view;
using std::same_as;
same_as<single_view<int*>> auto v1 = views::single(x);
same_as<single_view<int>> auto v2 = views::single((const int)5);
same_as<single_view<single_view<int>>> auto v3 = views::single(v2);
// Verify changes to views::take.
auto v4 = views::take(x, 0ull);
// Verify changes to views::drop.
auto v5 = views::drop(x, 0ull);
// Verify changes to views::split.
auto v6 = views::split(x, 5u);
}