On Sun, May 17, 2026 at 9:29 PM Jonathan Wakely <[email protected]> wrote:
> This is specified as const in the standard.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/mdspan (mdspan::is_exhaustive): Add const keyword.
> * testsuite/23_containers/mdspan/mdspan.cc: Check that
> is_unique, is_exhaustive, and is_strided can be called on a
> const object.
> ---
>
> Tested x86_64-linux.
>
>
> libstdc++-v3/include/std/mdspan | 2 +-
> libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> index 5938bf09a940..27d15df12944 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -2621,7 +2621,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> { return _PaddedStorage::_M_is_always_exhaustive(); }
>
> constexpr bool
> - is_exhaustive() noexcept
> + is_exhaustive() const noexcept
> { return _M_storage._M_is_exhaustive(); }
>
This is not mdspan, but `layout_left_padded`, and the problem seems to be
repeated in more mappings, and we should fix all of them. Do you want me
to create a follow-up patch with that? I would also backport it to 16.
>
> static constexpr bool
> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> index 62ff7201cce9..99205142579a 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> @@ -715,7 +715,7 @@ template<typename Layout, bool Expected>
> test_nothrow_is_methods()
> {
> using Extents = std::extents<int, dyn>;
> - using MDSpan = std::mdspan<double, Extents, Layout>;
> + using MDSpan = const std::mdspan<double, Extents, Layout>;
> static_assert(noexcept(MDSpan::is_always_unique()) == Expected);
> static_assert(noexcept(MDSpan::is_always_exhaustive()) == Expected);
> static_assert(noexcept(MDSpan::is_always_strided()) == Expected);
> --
> 2.54.0
>
>
