On Mon, Jun 30, 2025 at 4:27 PM Jonathan Wakely <jwak...@redhat.com> wrote:
> On Mon, 30 Jun 2025 at 11:48, Tomasz Kaminski <tkami...@redhat.com> wrote:
> >
> >
> >
> > On Mon, Jun 30, 2025 at 9:58 AM Tomasz Kaminski <tkami...@redhat.com>
> wrote:
> >>
> >>
> >>
> >> On Mon, Jun 30, 2025 at 9:25 AM Luc Grosheintz <
> luc.groshei...@gmail.com> wrote:
> >>>
> >>> libstdc++-v3/ChangeLog:
> >>>
> >>> * include/std/mdspan (default_accessor): New class.
> >>> * src/c++23/std.cc.in: Register default_accessor.
> >>> * testsuite/23_containers/mdspan/accessors/default.cc: New
> test.
> >>> * testsuite/23_containers/mdspan/accessors/default_neg.cc: New
> test.
> >>>
> >>> Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
> >>> ---
> >>>
> >>> Version of v5 with all local changes included.
> >>
> >> LGTM, tested locally and now running a full test suite.
> >> Once it will get approval from Jonathan, I will handle merging it.
> >
> > All test passed.
>
> OK for trunk, thank you both.
>
Patch now merged to trunk. I hope to review mdspan itself this week.
>
> >>
> >>
> >>>
> >>>
> >>> libstdc++-v3/include/std/mdspan | 31 ++++++
> >>> libstdc++-v3/src/c++23/std.cc.in | 3 +-
> >>> .../23_containers/mdspan/accessors/default.cc | 99 +++++++++++++++++++
> >>> .../mdspan/accessors/default_neg.cc | 23 +++++
> >>> 4 files changed, 155 insertions(+), 1 deletion(-)
> >>> create mode 100644
> libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc
> >>> create mode 100644
> libstdc++-v3/testsuite/23_containers/mdspan/accessors/default_neg.cc
> >>>
> >>> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> >>> index 6dc2441f80b..c72a64094b7 100644
> >>> --- a/libstdc++-v3/include/std/mdspan
> >>> +++ b/libstdc++-v3/include/std/mdspan
> >>> @@ -1004,6 +1004,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >>> [[no_unique_address]] _S_strides_t _M_strides;
> >>> };
> >>>
> >>> + template<typename _ElementType>
> >>> + struct default_accessor
> >>> + {
> >>> + static_assert(!is_array_v<_ElementType>,
> >>> + "ElementType must not be an array type");
> >>> + static_assert(!is_abstract_v<_ElementType>,
> >>> + "ElementType must not be an abstract class type");
> >>> +
> >>> + using offset_policy = default_accessor;
> >>> + using element_type = _ElementType;
> >>> + using reference = element_type&;
> >>> + using data_handle_type = element_type*;
> >>> +
> >>> + constexpr
> >>> + default_accessor() noexcept = default;
> >>> +
> >>> + template<typename _OElementType>
> >>> + requires is_convertible_v<_OElementType(*)[],
> element_type(*)[]>
> >>> + constexpr
> >>> + default_accessor(default_accessor<_OElementType>) noexcept
> >>> + { }
> >>> +
> >>> + constexpr reference
> >>> + access(data_handle_type __p, size_t __i) const noexcept
> >>> + { return __p[__i]; }
> >>> +
> >>> + constexpr data_handle_type
> >>> + offset(data_handle_type __p, size_t __i) const noexcept
> >>> + { return __p + __i; }
> >>> + };
> >>> +
> >>> _GLIBCXX_END_NAMESPACE_VERSION
> >>> }
> >>> #endif
> >>> diff --git a/libstdc++-v3/src/c++23/std.cc.in
> b/libstdc++-v3/src/c++23/std.cc.in
> >>> index 9336118f5d9..e692caaa5f9 100644
> >>> --- a/libstdc++-v3/src/c++23/std.cc.in
> >>> +++ b/libstdc++-v3/src/c++23/std.cc.in
> >>> @@ -1850,7 +1850,8 @@ export namespace std
> >>> using std::layout_left;
> >>> using std::layout_right;
> >>> using std::layout_stride;
> >>> - // FIXME layout_left_padded, layout_right_padded, default_accessor
> and mdspan
> >>> + using std::default_accessor;
> >>> + // FIXME layout_left_padded, layout_right_padded, aligned_accessor
> and mdspan
> >>> }
> >>> #endif
> >>>
> >>> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc
> >>> new file mode 100644
> >>> index 00000000000..c036f8ad10f
> >>> --- /dev/null
> >>> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc
> >>> @@ -0,0 +1,99 @@
> >>> +// { dg-do run { target c++23 } }
> >>> +#include <mdspan>
> >>> +
> >>> +#include <testsuite_hooks.h>
> >>> +
> >>> +constexpr size_t dyn = std::dynamic_extent;
> >>> +
> >>> +template<typename Accessor>
> >>> + constexpr void
> >>> + test_accessor_policy()
> >>> + {
> >>> + static_assert(std::copyable<Accessor>);
> >>> + static_assert(std::is_nothrow_move_constructible_v<Accessor>);
> >>> + static_assert(std::is_nothrow_move_assignable_v<Accessor>);
> >>> + static_assert(std::is_nothrow_swappable_v<Accessor>);
> >>> + }
> >>> +
> >>> +constexpr bool
> >>> +test_access()
> >>> +{
> >>> + std::default_accessor<double> accessor;
> >>> + std::array<double, 5> a{10, 11, 12, 13, 14};
> >>> + VERIFY(accessor.access(a.data(), 0) == 10);
> >>> + VERIFY(accessor.access(a.data(), 4) == 14);
> >>> + return true;
> >>> +}
> >>> +
> >>> +constexpr bool
> >>> +test_offset()
> >>> +{
> >>> + std::default_accessor<double> accessor;
> >>> + std::array<double, 5> a{10, 11, 12, 13, 14};
> >>> + VERIFY(accessor.offset(a.data(), 0) == a.data());
> >>> + VERIFY(accessor.offset(a.data(), 4) == a.data() + 4);
> >>> + return true;
> >>> +}
> >>> +
> >>> +class Base
> >>> +{ };
> >>> +
> >>> +class Derived : public Base
> >>> +{ };
> >>> +
> >>> +constexpr void
> >>> +test_ctor()
> >>> +{
> >>> + // T -> T
> >>> +
> static_assert(std::is_nothrow_constructible_v<std::default_accessor<double>,
> >>> +
> std::default_accessor<double>>);
> >>> + static_assert(std::is_convertible_v<std::default_accessor<double>,
> >>> + std::default_accessor<double>>);
> >>> +
> >>> + // T -> const T
> >>> + static_assert(std::is_convertible_v<std::default_accessor<double>,
> >>> + std::default_accessor<const
> double>>);
> >>> + static_assert(std::is_convertible_v<std::default_accessor<Derived>,
> >>> + std::default_accessor<const
> Derived>>);
> >>> +
> >>> + // const T -> T
> >>> +
> static_assert(!std::is_constructible_v<std::default_accessor<double>,
> >>> + std::default_accessor<const
> double>>);
> >>> +
> static_assert(!std::is_constructible_v<std::default_accessor<Derived>,
> >>> + std::default_accessor<const
> Derived>>);
> >>> +
> >>> + // T <-> volatile T
> >>> + static_assert(std::is_convertible_v<std::default_accessor<int>,
> >>> + std::default_accessor<volatile
> int>>);
> >>> + static_assert(!std::is_constructible_v<std::default_accessor<int>,
> >>> +
> std::default_accessor<volatile int>>);
> >>> +
> >>> + // size difference
> >>> + static_assert(!std::is_constructible_v<std::default_accessor<char>,
> >>> + std::default_accessor<int>>);
> >>> +
> >>> + // signedness
> >>> + static_assert(!std::is_constructible_v<std::default_accessor<int>,
> >>> +
> std::default_accessor<unsigned int>>);
> >>> +
> static_assert(!std::is_constructible_v<std::default_accessor<unsigned int>,
> >>> + std::default_accessor<int>>);
> >>> +
> >>> + // Derived <-> Base
> >>> + static_assert(!std::is_constructible_v<std::default_accessor<Base>,
> >>> +
> std::default_accessor<Derived>>);
> >>> +
> static_assert(!std::is_constructible_v<std::default_accessor<Derived>,
> >>> + std::default_accessor<Base>>);
> >>> +
> >>> +}
> >>> +
> >>> +int
> >>> +main()
> >>> +{
> >>> + test_accessor_policy<std::default_accessor<double>>();
> >>> + test_access();
> >>> + static_assert(test_access());
> >>> + test_offset();
> >>> + static_assert(test_offset());
> >>> + test_ctor();
> >>> + return 0;
> >>> +}
> >>> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default_neg.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default_neg.cc
> >>> new file mode 100644
> >>> index 00000000000..f8da2b569ca
> >>> --- /dev/null
> >>> +++
> b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default_neg.cc
> >>> @@ -0,0 +1,23 @@
> >>> +// { dg-do compile { target c++23 } }
> >>> +#include<mdspan>
> >>> +
> >>> +std::default_accessor<int[3]> a; // { dg-error "required from here" }
> >>> +
> >>> +class AbstractBase
> >>> +{
> >>> + virtual void
> >>> + foo() const = 0;
> >>> +};
> >>> +
> >>> +class Derived : public AbstractBase
> >>> +{
> >>> + void
> >>> + foo() const override
> >>> + { }
> >>> +};
> >>> +
> >>> +std::default_accessor<Derived> b_ok;
> >>> +std::default_accessor<AbstractBase> b_err; // { dg-error "required
> from here"}
> >>> +
> >>> +// { dg-prune-output "ElementType must not be an array type" }
> >>> +// { dg-prune-output "ElementType must not be an abstract" }
> >>> --
> >>> 2.49.0
> >>>
>
>
