On Mon, 21 Feb 2022 at 19:39, Patrick Palka via Libstdc++ <
libstd...@gcc.gnu.org> wrote:
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
>
OK, thanks.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/ranges_base.h (__detail::__is_initializer_list):
> Define.
> (viewable_range): Adjust as per P2415R2.
> * include/std/ranges (owning_view): Define as per P2415R2.
> (enable_borrowed_range<owning_view>): Likewise.
> (views::__detail::__can_subrange): Replace with ...
> (views::__detail::__can_owning_view): ... this.
> (views::_All::_S_noexcept): Sync with operator().
> (views::_All::operator()): Use owning_view instead of subrange
> as per P2415R2.
> * testsuite/std/ranges/adaptors/all.cc (test06): Adjust now that
> views::all uses owning_view instead of subrange.
> (test08): New test.
> * testsuite/std/ranges/adaptors/lazy_split.cc (test09): Adjust
> now that rvalue non-view non-borrowed ranges are viewable.
> * testsuite/std/ranges/adaptors/split.cc (test06): Likewise.
> ---
> libstdc++-v3/include/bits/ranges_base.h | 16 +++-
> libstdc++-v3/include/std/ranges | 89 ++++++++++++++++++-
> .../testsuite/std/ranges/adaptors/all.cc | 59 ++++++++----
> .../std/ranges/adaptors/lazy_split.cc | 13 ++-
> .../testsuite/std/ranges/adaptors/split.cc | 13 ++-
> 5 files changed, 157 insertions(+), 33 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/ranges_base.h
> b/libstdc++-v3/include/bits/ranges_base.h
> index 3c5f4b1790a..38db33fd2ce 100644
> --- a/libstdc++-v3/include/bits/ranges_base.h
> +++ b/libstdc++-v3/include/bits/ranges_base.h
> @@ -634,7 +634,7 @@ namespace ranges
> template<typename _Tp>
> concept __is_derived_from_view_interface
> = requires (_Tp __t) { __is_derived_from_view_interface_fn(__t,
> __t); };
> - }
> + } // namespace __detail
>
> /// [range.view] The ranges::view_base type.
> struct view_base { };
> @@ -689,11 +689,23 @@ namespace ranges
> concept common_range
> = range<_Tp> && same_as<iterator_t<_Tp>, sentinel_t<_Tp>>;
>
> + namespace __detail
> + {
> + template<typename _Tp>
> + inline constexpr bool __is_initializer_list = false;
> +
> + template<typename _Tp>
> + inline constexpr bool __is_initializer_list<initializer_list<_Tp>>
> = true;
> + } // namespace __detail
> +
> /// A range which can be safely converted to a view.
> template<typename _Tp>
> concept viewable_range = range<_Tp>
> && ((view<remove_cvref_t<_Tp>> &&
> constructible_from<remove_cvref_t<_Tp>, _Tp>)
> - || (!view<remove_cvref_t<_Tp>> && borrowed_range<_Tp>));
> + || (!view<remove_cvref_t<_Tp>>
> + && (is_lvalue_reference_v<_Tp>
> + || (movable<remove_reference_t<_Tp>>
> + &&
> !__detail::__is_initializer_list<remove_cvref_t<_Tp>>))));
>
> // [range.iter.ops] range iterator operations
>
> diff --git a/libstdc++-v3/include/std/ranges
> b/libstdc++-v3/include/std/ranges
> index ac85907f129..3e71ecb32b7 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -1144,6 +1144,87 @@ namespace views::__adaptor
> template<typename _Tp>
> inline constexpr bool enable_borrowed_range<ref_view<_Tp>> = true;
>
> + template<range _Range>
> + requires movable<_Range>
> + && (!__detail::__is_initializer_list<remove_cv_t<_Range>>)
> + class owning_view : public view_interface<owning_view<_Range>>
> + {
> + private:
> + _Range _M_r = _Range();
> +
> + public:
> + owning_view() requires default_initializable<_Range> = default;
> +
> + constexpr
> + owning_view(_Range&& __t)
> + noexcept(is_nothrow_move_constructible_v<_Range>)
> + : _M_r(std::move(__t))
> + { }
> +
> + owning_view(owning_view&&) = default;
> + owning_view& operator=(owning_view&&) = default;
> +
> + constexpr _Range&
> + base() & noexcept
> + { return _M_r; }
> +
> + constexpr const _Range&
> + base() const& noexcept
> + { return _M_r; }
> +
> + constexpr _Range&&
> + base() && noexcept
> + { return std::move(_M_r); }
> +
> + constexpr const _Range&&
> + base() const&& noexcept
> + { return std::move(_M_r); }
> +
> + constexpr iterator_t<_Range>
> + begin()
> + { return ranges::begin(_M_r); }
> +
> + constexpr sentinel_t<_Range>
> + end()
> + { return ranges::end(_M_r); }
> +
> + constexpr auto
> + begin() const requires range<const _Range>
> + { return ranges::begin(_M_r); }
> +
> + constexpr auto
> + end() const requires range<const _Range>
> + { return ranges::end(_M_r); }
> +
> + constexpr bool
> + empty() requires requires { ranges::empty(_M_r); }
> + { return ranges::empty(_M_r); }
> +
> + constexpr bool
> + empty() const requires requires { ranges::empty(_M_r); }
> + { return ranges::empty(_M_r); }
> +
> + constexpr auto
> + size() requires sized_range<_Range>
> + { return ranges::size(_M_r); }
> +
> + constexpr auto
> + size() const requires sized_range<const _Range>
> + { return ranges::size(_M_r); }
> +
> + constexpr auto
> + data() requires contiguous_range<_Range>
> + { return ranges::data(_M_r); }
> +
> + constexpr auto
> + data() const requires contiguous_range<const _Range>
> + { return ranges::data(_M_r); }
> + };
> +
> + template<typename _Tp>
> + inline constexpr bool enable_borrowed_range<owning_view<_Tp>>
> + = enable_borrowed_range<_Tp>;
> +
> namespace views
> {
> namespace __detail
> @@ -1152,7 +1233,7 @@ namespace views::__adaptor
> concept __can_ref_view = requires {
> ref_view{std::declval<_Range>()}; };
>
> template<typename _Range>
> - concept __can_subrange = requires {
> subrange{std::declval<_Range>()}; };
> + concept __can_owning_view = requires {
> owning_view{std::declval<_Range>()}; };
> } // namespace __detail
>
> struct _All : __adaptor::_RangeAdaptorClosure
> @@ -1166,13 +1247,13 @@ namespace views::__adaptor
> else if constexpr (__detail::__can_ref_view<_Range>)
> return true;
> else
> - return noexcept(subrange{std::declval<_Range>()});
> + return noexcept(owning_view{std::declval<_Range>()});
> }
>
> template<viewable_range _Range>
> requires view<decay_t<_Range>>
> || __detail::__can_ref_view<_Range>
> - || __detail::__can_subrange<_Range>
> + || __detail::__can_owning_view<_Range>
> constexpr auto
> operator() [[nodiscard]] (_Range&& __r) const
> noexcept(_S_noexcept<_Range>())
> @@ -1182,7 +1263,7 @@ namespace views::__adaptor
> else if constexpr (__detail::__can_ref_view<_Range>)
> return ref_view{std::forward<_Range>(__r)};
> else
> - return subrange{std::forward<_Range>(__r)};
> + return owning_view{std::forward<_Range>(__r)};
> }
>
> static constexpr bool _S_has_simple_call_op = true;
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
> index c25d972274f..9d4e714b3e9 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/all.cc
> @@ -19,7 +19,9 @@
> // { dg-do run { target c++2a } }
>
> #include <algorithm>
> +#include <array>
> #include <ranges>
> +#include <vector>
> #include <testsuite_hooks.h>
> #include <testsuite_iterators.h>
>
> @@ -130,20 +132,6 @@ test05()
> static_assert(!requires { 0 | all; });
> }
>
> -template<bool B1, bool B2>
> -struct BorrowedRange
> -{
> - int* ptr = nullptr;
> -
> - BorrowedRange(int (&arr)[3]) noexcept : ptr(arr) { }
> -
> - int* begin() const noexcept(B1) { return ptr; }
> - int* end() const noexcept(B2) { return ptr + 3; }
> -};
> -
> -template<bool B1, bool B2>
> -const bool std::ranges::enable_borrowed_range<BorrowedRange<B1, B2>> =
> true;
> -
> void
> test06()
> {
> @@ -152,11 +140,11 @@ test06()
> // Using ref_view:
> static_assert(noexcept(views::all(x)));
>
> - // Using subrange:
> - static_assert(noexcept(views::all(BorrowedRange<true, true>(x))));
> - static_assert(!noexcept(views::all(BorrowedRange<true, false>(x))));
> - static_assert(!noexcept(views::all(BorrowedRange<false, true>(x))));
> - static_assert(!noexcept(views::all(BorrowedRange<false, false>(x))));
> + // Using owning_view:
> + struct A { A(); A(const A&); };
> + static_assert(noexcept(views::all(std::array<int, 3>{})));
> + static_assert(!std::is_nothrow_move_constructible_v<std::array<A, 3>>);
> + static_assert(!noexcept(views::all(std::array<A, 3>{})));
> }
>
> void
> @@ -173,6 +161,38 @@ test07()
> static_assert(!ranges::viewable_range<view_t&>);
> }
>
> +constexpr bool
> +test08()
> +{
> + // Verify P2415R2 "What is a view?" changes
> + // Namely, rvalue non-view non-borrowed ranges are now viewable.
> + static_assert(ranges::viewable_range<std::vector<int>&&>);
> + static_assert(!ranges::viewable_range<const std::vector<int>&&>);
> +
> + static_assert(ranges::viewable_range<std::initializer_list<int>&>);
> + static_assert(ranges::viewable_range<const
> std::initializer_list<int>&>);
> + static_assert(!ranges::viewable_range<std::initializer_list<int>&&>);
> + static_assert(!ranges::viewable_range<const
> std::initializer_list<int>&&>);
> +
> + using type = views::all_t<std::vector<int>&&>;
> + using type = ranges::owning_view<std::vector<int>>;
> +
> + std::same_as<type> auto v = std::vector<int>{{1,2,3}} | views::all;
> +
> + VERIFY( ranges::equal(v, (int[]){1,2,3}) );
> + VERIFY( ranges::size(v) == 3 );
> + VERIFY( !ranges::empty(v) );
> + VERIFY( ranges::data(v) == &v[0] );
> +
> + const auto w = std::move(v);
> + VERIFY( ranges::equal(w, (int[]){1,2,3}) );
> + VERIFY( ranges::size(w) == 3 );
> + VERIFY( !ranges::empty(w) );
> + VERIFY( ranges::data(w) == &w[0] );
> +
> + return true;
> +}
> +
> int
> main()
> {
> @@ -183,4 +203,5 @@ main()
> test05();
> test06();
> test07();
> + static_assert(test08());
> }
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> index a7d3dd6a23e..e0279dc2a4a 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> @@ -163,10 +163,15 @@ test09()
> static_assert(!requires { lazy_split(p)(); });
> static_assert(!requires { s | lazy_split; });
>
> - static_assert(!requires { s | lazy_split(p); });
> - static_assert(!requires { lazy_split(p)(s); });
> - static_assert(!requires { s | (lazy_split(p) | views::all); });
> - static_assert(!requires { (lazy_split(p) | views::all)(s); });
> + // Test the case where the closure object is used as an rvalue and
> therefore
> + // the copy of p is forwarded as an rvalue.
> + // This used to be invalid, but is well-formed after P2415R2 relaxed the
> + // requirements of viewable_range to permit rvalue non-view non-borrowed
> + // ranges such as std::string&&.
> + static_assert(requires { s | lazy_split(p); });
> + static_assert(requires { lazy_split(p)(s); });
> + static_assert(requires { s | (lazy_split(p) | views::all); });
> + static_assert(requires { (lazy_split(p) | views::all)(s); });
>
> static_assert(requires { s | lazy_split(views::all(p)); });
> static_assert(requires { lazy_split(views::all(p))(s); });
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
> index 44245f5071a..4f8dddeb410 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
> @@ -145,10 +145,15 @@ test06()
> static_assert(!requires { split(p)(); });
> static_assert(!requires { s | split; });
>
> - static_assert(!requires { s | split(p); });
> - static_assert(!requires { split(p)(s); });
> - static_assert(!requires { s | (split(p) | views::all); });
> - static_assert(!requires { (split(p) | views::all)(s); });
> + // Test the case where the closure object is used as an rvalue and
> therefore
> + // the copy of p is forwarded as an rvalue.
> + // This used to be invalid, but is well-formed after P2415R2 relaxed the
> + // requirements of viewable_range to permit rvalue non-view non-borrowed
> + // ranges such as std::string&&.
> + static_assert(requires { s | split(p); });
> + static_assert(requires { split(p)(s); });
> + static_assert(requires { s | (split(p) | views::all); });
> + static_assert(requires { (split(p) | views::all)(s); });
>
> static_assert(requires { s | split(views::all(p)); });
> static_assert(requires { split(views::all(p))(s); });
> --
> 2.35.1.225.ge2ac9141e6
>
>
