Put them into main mdspan commit. No harm in having them.
On Tue, Jul 1, 2025 at 3:21 PM Luc Grosheintz <luc.groshei...@gmail.com>
wrote:
> You're right, I remember checking this; but it appears I conned
> myself. I've reverted the change to <mdspan>, do you want to keep
> the tests?
>
> On 7/1/25 12:35, Tomasz Kaminski wrote:
> > Hi,
> >
> > I do not think that the change is necessary, as for the functions default
> > on the first declaration
> > (as in the case for the constructors/assigments for mdpsan) have noexcept
> > specifier deduced
> > from it body. In other words, I think the test should pass, without
> adding
> > the complicated noexcept
> > conditions.
> >
> > Regards,
> > Tomasz
> >
> > On Fri, Jun 27, 2025 at 11:19 AM Luc Grosheintz <
> luc.groshei...@gmail.com>
> > wrote:
> >
> >> If all members of mdspan are nothrow movable, then mdspan can also
> >> be nothrow movable. The standard doesn't specify that mdspan must be
> >> nothrow movable (when possible). Nothrow movable enables containers
> >> to use move operations even if they have a strong exception guarantee.
> >>
> >> This commit strenghtens the exception guarantees for mdspan, making
> >> it nothrow movable if all it's members are nothrow movable.
> >>
> >> libstdc++-v3/ChangeLog:
> >>
> >> * include/std/mdspan (mdspan): Make nothrow movable, if all
> >> members are nothrow movable.
> >> * testsuite/23_containers/mdspan/mdspan.cc: Test nothrow
> movable
> >> property.
> >>
> >> Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
> >> ---
> >> libstdc++-v3/include/std/mdspan | 10 +++-
> >> .../testsuite/23_containers/mdspan/mdspan.cc | 53 ++++++++++++++++++-
> >> 2 files changed, 60 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/libstdc++-v3/include/std/mdspan
> >> b/libstdc++-v3/include/std/mdspan
> >> index 852f881971e..563aa312f8a 100644
> >> --- a/libstdc++-v3/include/std/mdspan
> >> +++ b/libstdc++-v3/include/std/mdspan
> >> @@ -1119,7 +1119,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >> mdspan(const mdspan& __other) = default;
> >>
> >> constexpr
> >> - mdspan(mdspan&& __other) = default;
> >> + mdspan(mdspan&& __other)
> >> + noexcept(is_nothrow_move_constructible_v<accessor_type>
> >> + && is_nothrow_move_constructible_v<mapping_type>
> >> + && is_nothrow_move_constructible_v<data_handle_type>) =
> default;
> >>
> >> template<__mdspan::__valid_index_type<index_type>...
> _OIndexTypes>
> >> requires ((sizeof...(_OIndexTypes) == rank()
> >> @@ -1197,7 +1200,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >> operator=(const mdspan& __other) = default;
> >>
> >> constexpr mdspan&
> >> - operator=(mdspan&& __other) = default;
> >> + operator=(mdspan&& __other)
> >> + noexcept(is_nothrow_move_assignable_v<accessor_type>
> >> + && is_nothrow_move_assignable_v<mapping_type>
> >> + && is_nothrow_move_assignable_v<data_handle_type>) = default;
> >>
> >> template<__mdspan::__valid_index_type<index_type>...
> _OIndexTypes>
> >> requires (sizeof...(_OIndexTypes) == rank())
> >> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> >> b/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> >> index d2672878d69..6d8f32ff103 100644
> >> --- a/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> >> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> >> @@ -310,11 +310,29 @@ test_from_int_like()
> >> verify(std::mdspan(storage.data(), shape_view));
> >> }
> >>
> >> -template<typename T>
> >> +template<typename T, bool NothrowConstructible = true,
> >> + bool NothrowAssignable = true>
> >> class OpaqueAccessor
> >> {
> >> struct Handle
> >> {
> >> + constexpr
> >> + Handle(T * other)
> >> + : ptr(other)
> >> + { }
> >> +
> >> + constexpr
> >> + Handle(const Handle&) noexcept(NothrowConstructible) = default;
> >> +
> >> + constexpr
> >> + Handle(Handle&&) noexcept(NothrowConstructible) = default;
> >> +
> >> + constexpr Handle&
> >> + operator=(const Handle&) noexcept(NothrowAssignable) = default;
> >> +
> >> + constexpr Handle&
> >> + operator=(Handle&&) noexcept(NothrowAssignable) = default;
> >> +
> >> T * ptr;
> >> };
> >>
> >> @@ -489,6 +507,37 @@ test_swap()
> >> return true;
> >> }
> >>
> >> +template<bool Constructible, bool Assignable>
> >> +constexpr void
> >> +test_nothrow_movable()
> >> +{
> >> + using Layout = std::layout_left;
> >> + using Extents = std::dextents<int, 3>;
> >> + using Accessor = OpaqueAccessor<int, Constructible, Assignable>;
> >> + using Handle = Accessor::data_handle_type;
> >> + static_assert(std::is_nothrow_move_assignable_v<Accessor>);
> >> + static_assert(std::is_nothrow_move_constructible_v<Accessor>);
> >> + static_assert(std::is_nothrow_move_assignable_v<Handle> ==
> Assignable);
> >> + static_assert(std::is_nothrow_move_constructible_v<Handle> ==
> >> Constructible);
> >> +
> >> + using MDSpan = std::mdspan<int, Extents, Layout, Accessor>;
> >> + static_assert(std::is_nothrow_move_assignable_v<MDSpan> ==
> Assignable);
> >> + static_assert(std::is_nothrow_move_constructible_v<MDSpan> ==
> >> Constructible);
> >> +}
> >> +
> >> +constexpr void
> >> +test_nothrow_movable_all()
> >> +{
> >> + using MDSpan = std::mdspan<double, std::dextents<int, 3>>;
> >> + static_assert(std::is_nothrow_move_assignable_v<MDSpan>);
> >> + static_assert(std::is_nothrow_move_constructible_v<MDSpan>);
> >> +
> >> + test_nothrow_movable<true, true>();
> >> + test_nothrow_movable<true, false>();
> >> + test_nothrow_movable<false, true>();
> >> + test_nothrow_movable<false, false>();
> >> +}
> >> +
> >> int
> >> main()
> >> {
> >> @@ -536,5 +585,7 @@ main()
> >>
> >> test_swap();
> >> static_assert(test_swap());
> >> +
> >> + test_nothrow_movable_all();
> >> return 0;
> >> }
> >> --
> >> 2.49.0
> >>
> >>
> >
>
>
