[gcc r16-3566] libstdc++: Add _GLIBCXX_RESOLVE_LIB_DEFECTS for 4314 in <mdspan>.

[Tomasz Kaminski]

https://gcc.gnu.org/g:43a8c0f8e67f282823a3af1df4cd77dd86981b9c

commit r16-3566-g43a8c0f8e67f282823a3af1df4cd77dd86981b9c
Author: Luc Grosheintz <luc.grosheintz@gmail.com>
Date:   Wed Sep 3 17:28:27 2025 +0200

    libstdc++: Add _GLIBCXX_RESOLVE_LIB_DEFECTS for 4314 in <mdspan>.
    
    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.
    
    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.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>

Diff:
---
 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 6c7469cd2d80..678b2619ebe4 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>)