From e269268e45ba0befabdfc8a8c2f04dcbb44ccdf4 Mon Sep 17 00:00:00 2001
From: Luc Grosheintz <luc.grosheintz@gmail.com>
Date: Thu, 2 Oct 2025 11:27:16 +0200
Subject: [PATCH] libstdc++: Implement submdspan_mapping_result. [PR110352]
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Implement the class submdspan_mapping_result and add it to the std
module.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/std/mdspan (submdspan_mapping_result): New class.
	* src/c++23/std.cc.in (submdspan_mapping_result): Add.

Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
---
 libstdc++-v3/include/std/mdspan  | 7 +++++++
 libstdc++-v3/src/c++23/std.cc.in | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 7f69626e4e8..d555b7f2580 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -361,6 +361,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       [[no_unique_address]] extent_type extent{};
       [[no_unique_address]] stride_type stride{};
     };
+
+  template<typename _Mapping>
+    struct submdspan_mapping_result
+    {
+      [[no_unique_address]] _Mapping mapping = _Mapping();
+      size_t offset{};
+    };
 #endif
 
   template<typename _IndexType, size_t... _Extents>
diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
index bfccf3cec95..9cf5fa7dcb6 100644
--- a/libstdc++-v3/src/c++23/std.cc.in
+++ b/libstdc++-v3/src/c++23/std.cc.in
@@ -1875,8 +1875,9 @@ export namespace std
   using strided_slice;
   using full_extent_t;
   using full_extent;
+  using submdspan_mapping_result;
 #endif
-  // FIXME submdspan_mapping_result, submdspan_extents, mdsubspan
+  // FIXME submdspan_extents, mdsubspan
 }
 #endif
 
-- 
2.47.3