On Wed, 16 Jul 2025, 14:53 Luc Grosheintz, <luc.groshei...@gmail.com> wrote:
> The second bug report in PR121061 is that the conversion of custom
> OtherIndexType to IndexType is incorrectly not done via r-value
> references.
>
> This commit fixes the forwarding issue, adds a custom IndexType called
> RValueInt, which only allows conversion to int via r-value reference.
>
OK for trunk
> PR libstdc++/121061
>
> libstdc++-v3/ChangeLog:
>
> * include/std/mdspan (extents::extents): Perform conversion to
> index_type of an r-value reference.
> (layout_left::mapping::operator()): Ditto.
> (layout_right::mapping::operator()): Ditto.
> (layout_stride::mapping::operator()): Ditto.
> * testsuite/23_containers/mdspan/extents/custom_integer.cc: Add
> tests for RValueInt and MutatingInt.
> * testsuite/23_containers/mdspan/int_like.h (RValueInt): Add.
> * testsuite/23_containers/mdspan/layouts/mapping.cc: Test with
> RValueInt.
> * testsuite/23_containers/mdspan/mdspan.cc: Ditto.
>
> Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
> ---
> libstdc++-v3/include/std/mdspan | 8 ++++----
> .../23_containers/mdspan/extents/custom_integer.cc | 3 +++
> libstdc++-v3/testsuite/23_containers/mdspan/int_like.h | 7 +++++++
> .../testsuite/23_containers/mdspan/layouts/mapping.cc | 1 +
> libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc | 2 ++
> 5 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> index 930997e9536..271fdb5d8c7 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -285,7 +285,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> || sizeof...(_OIndexTypes) == rank_dynamic())
> constexpr explicit extents(_OIndexTypes... __exts) noexcept
> : _M_exts(span<const _IndexType, sizeof...(_OIndexTypes)>(
> - initializer_list{_S_storage::_S_int_cast(__exts)...}))
> +
> initializer_list{static_cast<_IndexType>(std::move(__exts))...}))
> { }
>
> template<typename _OIndexType, size_t _Nm>
> @@ -602,7 +602,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> operator()(_Indices... __indices) const noexcept
> {
> return __mdspan::__linear_index_left(_M_extents,
> - static_cast<index_type>(__indices)...);
> + static_cast<index_type>(std::move(__indices))...);
> }
>
> static constexpr bool
> @@ -741,7 +741,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> operator()(_Indices... __indices) const noexcept
> {
> return __mdspan::__linear_index_right(
> - _M_extents, static_cast<index_type>(__indices)...);
> + _M_extents, static_cast<index_type>(std::move(__indices))...);
> }
>
> static constexpr bool
> @@ -963,7 +963,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> operator()(_Indices... __indices) const noexcept
> {
> return __mdspan::__linear_index_strides(*this,
> - static_cast<index_type>(__indices)...);
> + static_cast<index_type>(std::move(__indices))...);
> }
>
> static constexpr bool
> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/extents/custom_integer.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/extents/custom_integer.cc
> index 92c2ebb46e1..99de4015ef3 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/extents/custom_integer.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/extents/custom_integer.cc
> @@ -85,9 +85,12 @@ main()
> test_shape_all<IntLike, true>();
> test_shape_all<ThrowingInt, false>();
> test_shape_all<MutatingInt, false>();
> + test_shape_all<RValueInt, false>();
>
> test_pack_all<int, true>();
> test_pack_all<IntLike, true>();
> test_pack_all<ThrowingInt, false>();
> + test_pack_all<MutatingInt, true>();
> + test_pack_all<RValueInt, true>();
> return 0;
> }
> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
> b/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
> index f4f4a773193..310dd8ddf20 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
> @@ -6,6 +6,7 @@ enum class CustomIndexKind
> Const,
> Throwing,
> Mutating,
> + RValue,
> };
>
> template<CustomIndexKind Kind>
> @@ -42,6 +43,11 @@ template<CustomIndexKind Kind>
> requires (Kind == CustomIndexKind::Mutating)
> { return _M_i; }
>
> + constexpr
> + operator int() && noexcept
> + requires (Kind == CustomIndexKind::RValue)
> + { return _M_i; }
> +
> private:
> int _M_i;
> };
> @@ -49,6 +55,7 @@ template<CustomIndexKind Kind>
> using IntLike = CustomIndexType<CustomIndexKind::Const>;
> using ThrowingInt = CustomIndexType<CustomIndexKind::Throwing>;
> using MutatingInt = CustomIndexType<CustomIndexKind::Mutating>;
> +using RValueInt = CustomIndexType<CustomIndexKind::RValue>;
>
> struct NotIntLike
> { };
> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> index 6742fa11a51..58bce514435 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc
> @@ -527,6 +527,7 @@ template<typename Layout>
> {
> test_linear_index_all<Layout, IntLike>();
> test_linear_index_all<Layout, MutatingInt>();
> + test_linear_index_all<Layout, RValueInt>();
> }
>
> test_required_span_size_all<Layout>();
> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> index 22ec68ea2d1..be4a1b1c17e 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/mdspan.cc
> @@ -694,6 +694,7 @@ main()
> test_from_int_like<IntLike, true, true>();
> test_from_int_like<ThrowingInt, false, false>();
> test_from_int_like<MutatingInt, true, false>();
> + test_from_int_like<RValueInt, true, false>();
>
> test_from_opaque_accessor();
> test_from_base_class_accessor();
> @@ -705,6 +706,7 @@ main()
> test_access<IntLike, true, true>();
> test_access<ThrowingInt, false, false>();
> test_access<MutatingInt, true, false>();
> + test_access<RValueInt, true, false>();
>
> test_swap();
> static_assert(test_swap());
> --
> 2.50.0
>
>
