libstdc++: Export std::dextents from std.cc.in [PR121174]

r16-442 implemented both std::extents and std::dextents (and perhaps other
stuff), but exported only std::extents.
I went through https://eel.is/c++draft/mdspan.syn and I think std::dextents
is the only one implemented but not exported.

The following patch exports it, and additionally appends some further
entities to the FIXME list, those all seems to be unimplemented yet.

2025-07-20  Jakub Jelinek  <jakub@redhat.com>

	PR libstdc++/121174
	* src/c++23/std.cc.in (std::dextents): Export.  Add to FIXME comments
	other not yet implemented nor exported <mdspan> entities.

diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
index 1bd4bd58f212be34a77a099daaeb59f83b6951b4..9301ed90c00f005e88bd53790027c2e900cea0db 100644 (file)
--- a/libstdc++-v3/src/c++23/std.cc.in
+++ b/libstdc++-v3/src/c++23/std.cc.in
@@ -1850,12 +1850,15 @@ export namespace std
 export namespace std
 {
   using std::extents;
+  using std::dextents;
   using std::layout_left;
   using std::layout_right;
   using std::layout_stride;
   using std::default_accessor;
   using std::mdspan;
-  // FIXME layout_left_padded, layout_right_padded, aligned_accessor, mdsubspan
+  // FIXME layout_left_padded, layout_right_padded, aligned_accessor,
+  // strided_slice, submdspan_mapping_result, full_extent_t, full_extent,
+  // submdspan_extents, mdsubspan
 }
 #endif