On Thu, Jul 17, 2025 at 9:09 AM Luc Grosheintz <luc.groshei...@gmail.com>
wrote:
This commit implements the C++26 feature std::dims, sets the feature
> testing macro to 202403 and adds tests.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/version.def (mdspan): Set value for C++26.
> * include/bits/version.h: Regenerate.
> * include/std/mdspan (dims): Add.
> * testsuite/23_containers/mdspan/extents/misc.cc: Add tests.
> * testsuite/23_containers/mdspan/version.cc: Update test.
>
The update to the std module is missing.
Outside of that this LGTM.
>
> Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
> ---
> libstdc++-v3/include/bits/version.def | 4 ++++
> libstdc++-v3/include/bits/version.h | 7 ++++++-
> libstdc++-v3/include/std/mdspan | 5 +++++
> .../testsuite/23_containers/mdspan/extents/misc.cc | 7 +++++++
> libstdc++-v3/testsuite/23_containers/mdspan/version.cc | 6 ++++--
> 5 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/version.def
> b/libstdc++-v3/include/bits/version.def
> index cf0672b4822..f645bb3ed3b 100644
> --- a/libstdc++-v3/include/bits/version.def
> +++ b/libstdc++-v3/include/bits/version.def
> @@ -1007,6 +1007,10 @@ ftms = {
>
> ftms = {
> name = mdspan;
> + values = {
> + v = 202403;
> + cxxmin = 26;
> + };
> values = {
> v = 202207;
> cxxmin = 23;
> diff --git a/libstdc++-v3/include/bits/version.h
> b/libstdc++-v3/include/bits/version.h
> index c01ddf14dd5..fbdc9b65acf 100644
> --- a/libstdc++-v3/include/bits/version.h
> +++ b/libstdc++-v3/include/bits/version.h
> @@ -1125,7 +1125,12 @@
> #undef __glibcxx_want_span
>
> #if !defined(__cpp_lib_mdspan)
> -# if (__cplusplus >= 202100L)
> +# if (__cplusplus > 202302L)
> +# define __glibcxx_mdspan 202403L
> +# if defined(__glibcxx_want_all) || defined(__glibcxx_want_mdspan)
> +# define __cpp_lib_mdspan 202403L
> +# endif
> +# elif (__cplusplus >= 202100L)
> # define __glibcxx_mdspan 202207L
> # if defined(__glibcxx_want_all) || defined(__glibcxx_want_mdspan)
> # define __cpp_lib_mdspan 202207L
> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> index b34116a85e6..ffbd1d9d542 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -412,6 +412,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> using dextents = decltype(__mdspan::__build_dextents_type<_IndexType>(
> make_index_sequence<_Rank>()));
>
> +#if __glibcxx_mdspan >= 202403L
> + template<size_t _Rank, typename _IndexType = size_t>
> + using dims = dextents<_IndexType, _Rank>;
> +#endif
> +
> template<typename... _Integrals>
> requires (is_convertible_v<_Integrals, size_t> && ...)
> explicit extents(_Integrals...) ->
> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
> index bca8901685d..933a77aab79 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
> @@ -159,6 +159,13 @@ static_assert(std::extents<int, 1,
> dyn>::static_extent(1) == dyn);
> static_assert(std::extents<int, dyn, dyn>::static_extent(0) == dyn);
> static_assert(std::extents<int, dyn, dyn>::static_extent(1) == dyn);
>
> +// dims
> +#if __glibcxx_mdspan >= 202403L
> +static_assert(std::is_same_v<std::dims<0>, std::dextents<size_t, 0>>);
> +static_assert(std::is_same_v<std::dims<3>, std::dextents<size_t, 3>>);
> +static_assert(std::is_same_v<std::dims<3, int>, std::dextents<int, 3>>);
> +#endif
> +
> // extent
> template<typename Extent>
> constexpr void
> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
> index 106ee4010ee..aa3767bd2c5 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
> @@ -3,7 +3,9 @@
>
> #ifndef __cpp_lib_mdspan
> #error "Feature test macro __cpp_lib_mdspan is missing for <mdspan>"
> -#if __cpp_lib_mdspan < 202207
> -#error "Feature test macro __cpp_lib_mdspan has the wrong value"
> +#if __cplusplus <= 202302L && __cpp_lib_mdspan != 202207L
> +#error "Feature test macro __cpp_lib_mdspan has the wrong value for C++23"
> +#elif __cplusplus > 202302L && __cpp_lib_mdspan != 202403L
> +#error "Feature test macro __cpp_lib_mdspan has the wrong value for C++26"
> #endif
> #endif
> --
> 2.50.0
>
>
