[PATCH v1] libstdc++: Add _GLIBCXX_RESOLVE_LIB_DEFECTS for 4314 in <mdspan>.

[Tomasz Kaminski]

On Wed, Sep 3, 2025 at 6:03 PM Jonathan Wakely <jwakely@redhat.com> wrote:

> On Wed, 3 Sept 2025 at 16:30, Luc Grosheintz <luc.grosheintz@gmail.com>
> wrote:
> >
> > In r16-2328-g29d53f6213e0a1 we fixed a bug related to user-defined
> > objects that can convert to an integers only via an rvalue reference.
> > The same commit also implemented LWG 4314 [1], but didn't mark it with
> > _GLIBCXX_RESOLVE_LIB_DEFECTS. This commit adds the missing markers.
> >
> > [1]: https://cplusplus.github.io/LWG/issue4314
> >
> > It also fixes one cases of trailing white-space near a ctor for
> > aligned_accessor.
>
> OK, thanks.
>
Pushed to the trunk.

>
>
> >
> > libstdc++-v3/ChangeLog:
> >
> >         * include/std/mdspan (layout_left::mapping::operator()): Add
> >         _GLIBCXX_RESOLVE_LIB_DEFECTS marker for 4314.
> >         (layout_left::mapping::operator()): Ditto.
> >         (layout_stride::mapping::operator()): Ditto.
> >
> > Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
> > ---
> >  libstdc++-v3/include/std/mdspan | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> > index 6c7469cd2d8..678b2619ebe 100644
> > --- a/libstdc++-v3/include/std/mdspan
> > +++ b/libstdc++-v3/include/std/mdspan
> > @@ -727,6 +727,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >        required_span_size() const noexcept
> >        { return __mdspan::__size(_M_extents); }
> >
> > +      // _GLIBCXX_RESOLVE_LIB_DEFECTS
> > +      // 4314. Missing move in mdspan layout mapping::operator()
> >        template<__mdspan::__valid_index_type<index_type>... _Indices>
> >         requires (sizeof...(_Indices) == extents_type::rank())
> >         constexpr index_type
> > @@ -866,6 +868,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >        required_span_size() const noexcept
> >        { return __mdspan::__size(_M_extents); }
> >
> > +      // _GLIBCXX_RESOLVE_LIB_DEFECTS
> > +      // 4314. Missing move in mdspan layout mapping::operator()
> >        template<__mdspan::__valid_index_type<index_type>... _Indices>
> >         requires (sizeof...(_Indices) == extents_type::rank())
> >         constexpr index_type
> > @@ -1089,6 +1093,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >         return __ret;
> >        }
> >
> > +      // _GLIBCXX_RESOLVE_LIB_DEFECTS
> > +      // 4314. Missing move in mdspan layout mapping::operator()
> >        template<__mdspan::__valid_index_type<index_type>... _Indices>
> >         requires (sizeof...(_Indices) == extents_type::rank())
> >         constexpr index_type
> > @@ -1208,7 +1214,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >        aligned_accessor() noexcept = default;
> >
> >        template<typename _OElementType, size_t _OByteAlignment>
> > -       requires (_OByteAlignment >= byte_alignment)
> > +       requires (_OByteAlignment >= byte_alignment)
> >             && is_convertible_v<_OElementType(*)[], element_type(*)[]>
> >         constexpr
> >         aligned_accessor(aligned_accessor<_OElementType,
> _OByteAlignment>)
> > --
> > 2.51.0
> >
>
>
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