[PATCH v2 1/5] libstdc++: Refactor layout mapping tests to use a concept.

[Tomasz Kaminski]

On Thu, Sep 11, 2025 at 1:47 PM Luc Grosheintz <luc.grosheintz@gmail.com>
wrote:

> The layout mapping test include a check that applies if is_exhaustive is
> static. This commit introduces a concept to check if is_exhaustive is a
> static member function that's compatible with the upcoming
> layout_left_padded.
>
> libstdc++-v3/ChangeLog:
>
>         * testsuite/23_containers/mdspan/layouts/mapping.cc
>         (has_static_is_exhaustive): New concept.
>         (test_mapping_properties): Update test.
>
> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
> ---
>
LGTM.

>  .../testsuite/23_containers/mdspan/layouts/mapping.cc | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> index 58bce514435..ee902a3cc05 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> @@ -7,6 +7,15 @@
>
>  constexpr size_t dyn = std::dynamic_extent;
>
> +template<typename Mapping>
> +  concept has_static_is_exhaustive = requires
> +  {
> +    { Mapping::is_exhaustive() } -> std::same_as<bool>;
> +  };
> +
>
> +static_assert(has_static_is_exhaustive<std::layout_right::mapping<std::extents<int>>>);
>
> +static_assert(!has_static_is_exhaustive<std::layout_stride::mapping<std::extents<int>>>);
> +
>  template<typename Layout, typename Extents>
>    constexpr bool
>    test_mapping_properties()
> @@ -32,7 +41,7 @@ template<typename Layout, typename Extents>
>
>      static_assert(M::is_always_unique() && M::is_unique());
>      static_assert(M::is_always_strided() && M::is_strided());
> -    if constexpr (!std::is_same_v<Layout, std::layout_stride>)
> +    if constexpr (has_static_is_exhaustive<M>)
>        static_assert(M::is_always_exhaustive() && M::is_exhaustive());
>      return true;
>    }
> --
> 2.50.1
>
>
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