On Tue, 23 Sept 2025 at 14:40, Luc Grosheintz <[email protected]> wrote:
>
> For padded layouts we want to check that the product of the
> padded stride with the remaining extents is representable.
>
> Creating a second overload, allows passing in subspans of the
> static extents and retains the ergonomics for the common case
> of passing in all static extents.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/mdspan (__static_quotient): New overload.
>
> Signed-off-by: Luc Grosheintz <[email protected]>
> ---
> libstdc++-v3/include/std/mdspan | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
> index 01d3b2cb6b1..9dd0c85f5b0 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -597,13 +597,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> return __res;
> }
>
> - template<typename _Extents,
> - typename _IndexType = typename _Extents::index_type>
> + template<typename _IndexType>
> consteval _IndexType
> - __static_quotient(_IndexType __nom =
> __gnu_cxx::__int_traits<_IndexType>
> - ::__max)
> + __static_quotient(std::span<const size_t> __sta_exts,
> + _IndexType __nom = __gnu_cxx::__int_traits<_IndexType>::__max)
> {
> - std::span<const size_t> __sta_exts = __static_extents<_Extents>();
> for (auto __factor : __sta_exts)
> {
> if (__factor != dynamic_extent)
> @@ -614,6 +612,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> return __nom;
> }
>
> + template<typename _Extents,
> + typename _IndexType = typename _Extents::index_type>
> + requires __is_extents<_Extents>
> + consteval _IndexType
> + __static_quotient(_IndexType __nom =
> __gnu_cxx::__int_traits<_IndexType>
> + ::__max)
I would break the line before the '=' token, but that's pre-existing
on trunk, so is fine like this.
OK for trunk, thanks.
> + {
> + std::span<const size_t> __sta_exts = __static_extents<_Extents>();
> + return __static_quotient<_IndexType>(__sta_exts, __nom);
> + }
> +
> template<typename _Extents>
> constexpr bool
> __is_representable_extents(const _Extents& __exts) noexcept
> --
> 2.50.1
>
