[PATCH v1 3/4] libstdc++: Implement submdspan_mapping_result. [PR110352]

[Jonathan Wakely]

On Thu, 2 Oct 2025 at 10:32, Luc Grosheintz <luc.grosheintz@gmail.com> wrote:
>
> Implement the class submdspan_mapping_result and add it to the std
> module.
>
>         PR libstdc++/110352
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/mdspan (submdspan_mapping_result): New class.
>         * src/c++23/std.cc.in (submdspan_mapping_result): Add.

OK for trunk, thanks.

>
> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
> ---
>  libstdc++-v3/include/std/mdspan  | 7 +++++++
>  libstdc++-v3/src/c++23/std.cc.in | 3 ++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
> index 00bb9716a9d..cef6d625982 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -361,6 +361,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        [[no_unique_address]] extent_type extent{};
>        [[no_unique_address]] stride_type stride{};
>      };
> +
> +  template<typename _Mapping>
> +    struct submdspan_mapping_result
> +    {
> +      [[no_unique_address]] _Mapping mapping = _Mapping();
> +      size_t offset{};
> +    };
>  #endif
>
>    template<typename _IndexType, size_t... _Extents>
> diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
> index bfccf3cec95..9cf5fa7dcb6 100644
> --- a/libstdc++-v3/src/c++23/std.cc.in
> +++ b/libstdc++-v3/src/c++23/std.cc.in
> @@ -1875,8 +1875,9 @@ export namespace std
>    using strided_slice;
>    using full_extent_t;
>    using full_extent;
> +  using submdspan_mapping_result;
>  #endif
> -  // FIXME submdspan_mapping_result, submdspan_extents, mdsubspan
> +  // FIXME submdspan_extents, mdsubspan
>  }
>  #endif
>
> --
> 2.50.1
>