On Mon, 12 Sept 2022 at 17:46, Patrick Palka via Libstdc++
<libstd...@gcc.gnu.org> wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk only?
I briefly wondered whether we could just use a union there and provide
the special members to init/copy/destroy it properly, but we already
use <optional> in <ranges> so it's probably not worth it.
OK for trunk.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/ranges (join_view::_Iterator::_M_satisfy):
> Adjust resetting _M_inner as per LWG 3569.
> (join_view::_Iterator::_M_inner): Wrap in std::optional
> as per LWG 3569.
> (join_view::_Iterator::_Iterator): Relax constraints as
> per LWG 3569.
> (join_view::_Iterator::operator*): Adjust as per LWG 3569.
> (join_view::_Iterator::operator->): Likewise.
> (join_view::_Iterator::operator++): Likewise.
> (join_view::_Iterator::operator--): Likewise.
> (join_view::_Iterator::iter_move): Likewise.
> (join_view::_Iterator::iter_swap): Likewise.
> * testsuite/std/ranges/adaptor/join.cc (test14): New test.
> ---
> libstdc++-v3/include/std/ranges | 28 +++++++++----------
> .../testsuite/std/ranges/adaptors/join.cc | 17 +++++++++++
> 2 files changed, 30 insertions(+), 15 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index 20eb4e82ac8..6297ce7cee3 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -2746,7 +2746,7 @@ namespace views::__adaptor
> }
>
> if constexpr (_S_ref_is_glvalue)
> - _M_inner = _Inner_iter();
> + _M_inner.reset();
> }
>
> static constexpr auto
> @@ -2769,7 +2769,7 @@ namespace views::__adaptor
> using _Inner_iter = join_view::_Inner_iter<_Const>;
>
> _Outer_iter _M_outer = _Outer_iter();
> - _Inner_iter _M_inner = _Inner_iter();
> + optional<_Inner_iter> _M_inner;
> _Parent* _M_parent = nullptr;
>
> public:
> @@ -2780,9 +2780,7 @@ namespace views::__adaptor
> = common_type_t<range_difference_t<_Base>,
> range_difference_t<range_reference_t<_Base>>>;
>
> - _Iterator() requires (default_initializable<_Outer_iter>
> - && default_initializable<_Inner_iter>)
> - = default;
> + _Iterator() requires default_initializable<_Outer_iter> = default;
>
> constexpr
> _Iterator(_Parent* __parent, _Outer_iter __outer)
> @@ -2801,7 +2799,7 @@ namespace views::__adaptor
>
> constexpr decltype(auto)
> operator*() const
> - { return *_M_inner; }
> + { return **_M_inner; }
>
> // _GLIBCXX_RESOLVE_LIB_DEFECTS
> // 3500. join_view::iterator::operator->() is bogus
> @@ -2809,7 +2807,7 @@ namespace views::__adaptor
> operator->() const
> requires __detail::__has_arrow<_Inner_iter>
> && copyable<_Inner_iter>
> - { return _M_inner; }
> + { return *_M_inner; }
>
> constexpr _Iterator&
> operator++()
> @@ -2820,7 +2818,7 @@ namespace views::__adaptor
> else
> return *_M_parent->_M_inner;
> }();
> - if (++_M_inner == ranges::end(__inner_range))
> + if (++*_M_inner == ranges::end(__inner_range))
> {
> ++_M_outer;
> _M_satisfy();
> @@ -2850,9 +2848,9 @@ namespace views::__adaptor
> {
> if (_M_outer == ranges::end(_M_parent->_M_base))
> _M_inner = ranges::end(*--_M_outer);
> - while (_M_inner == ranges::begin(*_M_outer))
> - _M_inner = ranges::end(*--_M_outer);
> - --_M_inner;
> + while (*_M_inner == ranges::begin(*_M_outer))
> + *_M_inner = ranges::end(*--_M_outer);
> + --*_M_inner;
> return *this;
> }
>
> @@ -2879,14 +2877,14 @@ namespace views::__adaptor
>
> friend constexpr decltype(auto)
> iter_move(const _Iterator& __i)
> - noexcept(noexcept(ranges::iter_move(__i._M_inner)))
> - { return ranges::iter_move(__i._M_inner); }
> + noexcept(noexcept(ranges::iter_move(*__i._M_inner)))
> + { return ranges::iter_move(*__i._M_inner); }
>
> friend constexpr void
> iter_swap(const _Iterator& __x, const _Iterator& __y)
> - noexcept(noexcept(ranges::iter_swap(__x._M_inner, __y._M_inner)))
> + noexcept(noexcept(ranges::iter_swap(*__x._M_inner,
> *__y._M_inner)))
> requires indirectly_swappable<_Inner_iter>
> - { return ranges::iter_swap(__x._M_inner, __y._M_inner); }
> + { return ranges::iter_swap(*__x._M_inner, *__y._M_inner); }
>
> friend _Iterator<!_Const>;
> template<bool> friend struct _Sentinel;
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc
> index 530ab6663b5..afc11d4bd7a 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/join.cc
> @@ -21,6 +21,7 @@
> #include <algorithm>
> #include <array>
> #include <ranges>
> +#include <sstream>
> #include <string>
> #include <string_view>
> #include <vector>
> @@ -217,6 +218,21 @@ test13()
> std::vector<std::vector<int>> v{{5, 6, 7}};
> v | l | std::views::join;
> }
> +
> +void
> +test14()
> +{
> + // LWG 3569: join_view fails to support ranges of ranges with
> + // non-default_initializable iterators
> + auto ss = std::istringstream{"1 2 3"};
> + auto v = views::single(views::istream<int>(ss));
> + using inner = ranges::range_reference_t<decltype(v)>;
> + static_assert(ranges::input_range<inner>
> + && !ranges::forward_range<inner>
> + && !std::default_initializable<ranges::iterator_t<inner>>);
> + VERIFY( ranges::equal(v | views::join, (int[]){1, 2, 3}) );
> +}
> +
> int
> main()
> {
> @@ -233,4 +249,5 @@ main()
> test11();
> test12();
> test13();
> + test14();
> }
> --
> 2.37.3.542.gdd3f6c4cae
>
