Re: [PATCH] libstdc++: Implement LWG 3904 change to lazy_split_view's iterator

[Jonathan Wakely <jwakely@redhat.com>]

On Tue, 11 Apr 2023 at 15:58, Patrick Palka via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk/12?

OK for all, thanks.

(This hasn't been approved by LWG yet, but it should be soon.)

>
> libstdc++-v3/ChangeLog:
>
>         * include/std/ranges (lazy_split_view::_OuterIter::_OuterIter):
>         Propagate _M_trailing_empty in the const-converting constructor
>         as per LWG 3904.
>         * testsuite/std/ranges/adaptors/adjacent/1.cc (test04): Correct
>         assertion.
>         * testsuite/std/ranges/adaptors/lazy_split.cc (test12): New test.
> ---
>  libstdc++-v3/include/std/ranges                  |  3 ++-
>  .../testsuite/std/ranges/adaptors/adjacent/1.cc  |  2 +-
>  .../testsuite/std/ranges/adaptors/lazy_split.cc  | 16 ++++++++++++++++
>  3 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index b230ebefcf5..26a9f2a6872 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -3209,7 +3209,8 @@ namespace views::__adaptor
>           _OuterIter(_OuterIter<!_Const> __i)
>             requires _Const
>               && convertible_to<iterator_t<_Vp>, iterator_t<_Base>>
> -           : _M_parent(__i._M_parent), _M_current(std::move(__i._M_current))
> +           : _M_parent(__i._M_parent), _M_current(std::move(__i._M_current)),
> +             _M_trailing_empty(__i._M_trailing_empty)
>           { }
>
>           constexpr value_type
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc
> index 443c1fbf450..19640abfe93 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc
> @@ -107,7 +107,7 @@ test04()
>    // PR libstdc++/106798
>    auto r = views::single(0) | views::lazy_split(0) | views::pairwise;
>    decltype(ranges::cend(r)) s = r.end();
> -  VERIFY( r.begin() == s );
> +  VERIFY( r.begin() != s );
>
>    return true;
>  }
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> index 9df6b3b66a6..4e5c0dc3ed5 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split.cc
> @@ -22,6 +22,7 @@
>  #include <ranges>
>  #include <string>
>  #include <string_view>
> +#include <utility>
>  #include <vector>
>  #include <testsuite_hooks.h>
>  #include <testsuite_iterators.h>
> @@ -218,6 +219,20 @@ test11()
>    static_assert(ranges::distance(views::lazy_split("text"sv, ""sv)) == 4);
>  }
>
> +constexpr bool
> +test12()
> +{
> +  // LWG 3904
> +  auto r = views::single(0) | views::lazy_split(0);
> +  auto i = r.begin();
> +  ++i;
> +  VERIFY( i != r.end() );
> +  decltype(std::as_const(r).begin()) j = i;
> +  VERIFY( j != r.end() );
> +
> +  return true;
> +}
> +
>  int
>  main()
>  {
> @@ -232,4 +247,5 @@ main()
>    test09();
>    test10();
>    test11();
> +  static_assert(test12());
>  }
> --
> 2.40.0.315.g0607f793cb
>