On Fri, Jun 27, 2025 at 11:29 AM Luc Grosheintz <luc.groshei...@gmail.com>
wrote:
> Previously the prerequite of the extents ctors that
>
> static_extent(i) == dynamic_extent || extent(i) == other.extent(i).
>
> was not checked. This commit add the __glibcxx_assert and test it.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/mdspan (extents): Check prerequite of the ctor that
> static_extent(i) == dynamic_extent || extent(i) == other.extent(i).
> * testsuite/23_containers/mdspan/extents/class_mandates_neg.cc:
> Test the implemented prerequite.
>
> Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
> ---
>
LGTM. As in case of mdspan, I would put the constexpr _neg test in other
file.
> libstdc++-v3/include/std/mdspan | 13 ++++++++
> .../mdspan/extents/class_mandates_neg.cc | 31 +++++++++++++++++++
> 2 files changed, 44 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> index 39d02ac08df..e198d65bba3 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -110,10 +110,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> return __se;
> }
>
> + template<size_t _OtherRank, typename _GetOtherExtent>
> + constexpr bool
> + _S_is_compatible_extents(_GetOtherExtent __get_extent) noexcept
> + {
> + if constexpr (_OtherRank == _S_rank)
> + for (size_t __i = 0; __i < _S_rank; ++__i)
> + if (_Extents[__i] != dynamic_extent
> + && !cmp_equal(_Extents[__i],
> _S_int_cast(__get_extent(__i))))
> + return false;
> + return true;
> + }
> +
> template<size_t _OtherRank, typename _GetOtherExtent>
> constexpr void
> _M_init_dynamic_extents(_GetOtherExtent __get_extent) noexcept
> {
> +
> __glibcxx_assert(_S_is_compatible_extents<_OtherRank>(__get_extent));
> for (size_t __i = 0; __i < _S_rank_dynamic; ++__i)
> {
> size_t __di = __i;
> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/extents/class_mandates_neg.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/extents/class_mandates_neg.cc
> index f9c1c019666..8179ff39962 100644
> ---
> a/libstdc++-v3/testsuite/23_containers/mdspan/extents/class_mandates_neg.cc
> +++
> b/libstdc++-v3/testsuite/23_containers/mdspan/extents/class_mandates_neg.cc
> @@ -3,10 +3,41 @@
>
> #include <cstdint>
>
> +constexpr size_t dyn = std::dynamic_extent;
> +
> std::extents<uint8_t, size_t(1) << 9> e1; // { dg-error "from here" }
> std::extents<char, 1> e2; // { dg-error "from here" }
> std::extents<bool, 1> e3; // { dg-error "from here" }
> std::extents<double, 1> e4; // { dg-error "from here" }
> +
> +constexpr bool
> +test_dyn2sta_extents_mismatch_00()
> +{
> + auto e0 = std::extents<int, dyn>{1};
> + [[maybe_unused]] auto e1 = std::extents<int, 2>{e0}; // {
> dg-error "expansion of" }
> + return true;
> +}
> +static_assert(test_dyn2sta_extents_mismatch_00()); // {
> dg-error "expansion of" }
> +
> +constexpr bool
> +test_dyn2sta_extents_mismatch_01()
> +{
> + [[maybe_unused]] auto e = std::extents<int, 1, dyn>{2, 2}; // {
> dg-error "expansion of" }
> + return true;
> +}
> +static_assert(test_dyn2sta_extents_mismatch_01()); // {
> dg-error "expansion of" }
> +
> +constexpr bool
> +test_dyn2sta_extents_mismatch_02()
> +{
> + std::array<int, 2> exts{2, 2};
> + [[maybe_unused]] auto e = std::extents<int, 1, dyn>{exts}; // {
> dg-error "expansion of" }
> + return true;
> +}
> +static_assert(test_dyn2sta_extents_mismatch_02()); // {
> dg-error "expansion of" }
> +
> // { dg-prune-output "dynamic or representable as IndexType" }
> // { dg-prune-output "signed or unsigned integer" }
> // { dg-prune-output "invalid use of incomplete type" }
> +// { dg-prune-output "non-constant condition for static assertion" }
> +// { dg-prune-output "__glibcxx_assert" }
> --
> 2.49.0
>
>
