I just saw a patch by Jakub Jelinek that fixed the omission of
exporting std::dextents also addressed by this patch.
Since this is also mentioned in the commit message, I think it's
least work if I immediately create v3.
On 7/21/25 09:43, Luc Grosheintz wrote:
This commit implements the C++26 feature std::dims described in P2389R2.
It sets the feature testing macro to 202406 and adds tests.
Also adds dextents to the module, and fixes the test mdspan/version.cc
libstdc++-v3/ChangeLog:
* include/bits/version.def (mdspan): Set value for C++26.
* include/bits/version.h: Regenerate.
* include/std/mdspan (dims): Add.
* src/c++23/std.cc.in (dims): Add.
(dextents): Add.
* testsuite/23_containers/mdspan/extents/misc.cc: Add tests.
* testsuite/23_containers/mdspan/version.cc: Update test.
Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
libstdc++-v3/include/bits/version.def | 4 ++++
libstdc++-v3/include/bits/version.h | 7 ++++++-
libstdc++-v3/include/std/mdspan | 5 +++++
libstdc++-v3/src/c++23/std.cc.in | 4 ++++
.../testsuite/23_containers/mdspan/extents/misc.cc | 7 +++++++
.../testsuite/23_containers/mdspan/version.cc | 11 +++++++----
6 files changed, 33 insertions(+), 5 deletions(-)
diff --git a/libstdc++-v3/include/bits/version.def
b/libstdc++-v3/include/bits/version.def
index dbe2cb8f175..e9830d9d685 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -1007,6 +1007,10 @@ ftms = {
ftms = {
name = mdspan;
+ values = {
+ v = 202406;
+ cxxmin = 26;
+ };
values = {
v = 202207;
cxxmin = 23;
diff --git a/libstdc++-v3/include/bits/version.h
b/libstdc++-v3/include/bits/version.h
index 7bb6016df68..59b0cfa1f92 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -1125,7 +1125,12 @@
#undef __glibcxx_want_span
#if !defined(__cpp_lib_mdspan)
-# if (__cplusplus >= 202100L)
+# if (__cplusplus > 202302L)
+# define __glibcxx_mdspan 202406L
+# if defined(__glibcxx_want_all) || defined(__glibcxx_want_mdspan)
+# define __cpp_lib_mdspan 202406L
+# endif
+# elif (__cplusplus >= 202100L)
# define __glibcxx_mdspan 202207L
# if defined(__glibcxx_want_all) || defined(__glibcxx_want_mdspan)
# define __cpp_lib_mdspan 202207L
diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 271fdb5d8c7..9afb9304fb5 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -414,6 +414,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using dextents = decltype(__mdspan::__build_dextents_type<_IndexType>(
make_index_sequence<_Rank>()));
+#if __glibcxx_mdspan >= 202406L
+ template<size_t _Rank, typename _IndexType = size_t>
+ using dims = dextents<_IndexType, _Rank>;
+#endif
+
template<typename... _Integrals>
requires (is_convertible_v<_Integrals, size_t> && ...)
explicit extents(_Integrals...) ->
diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
index 1bd4bd58f21..569b6aae9a1 100644
--- a/libstdc++-v3/src/c++23/std.cc.in
+++ b/libstdc++-v3/src/c++23/std.cc.in
@@ -1850,6 +1850,10 @@ export namespace std
export namespace std
{
using std::extents;
+ using std::dextents;
+#if __glibcxx_mdspan >= 202406L
+ using std::dims;
+#endif
using std::layout_left;
using std::layout_right;
using std::layout_stride;
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
b/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
index bca8901685d..8a43a682004 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/extents/misc.cc
@@ -159,6 +159,13 @@ static_assert(std::extents<int, 1, dyn>::static_extent(1)
== dyn);
static_assert(std::extents<int, dyn, dyn>::static_extent(0) == dyn);
static_assert(std::extents<int, dyn, dyn>::static_extent(1) == dyn);
+// dims
+#if __glibcxx_mdspan >= 202406L
+static_assert(std::is_same_v<std::dims<0>, std::dextents<size_t, 0>>);
+static_assert(std::is_same_v<std::dims<3>, std::dextents<size_t, 3>>);
+static_assert(std::is_same_v<std::dims<3, int>, std::dextents<int, 3>>);
+#endif
+
// extent
template<typename Extent>
constexpr void
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
b/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
index 106ee4010ee..752060262a0 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/version.cc
@@ -1,9 +1,12 @@
-// { dg-do compile { target c++23 } }
+// { dg-do preprocess { target c++23 } }
+// { dg-add-options no_pch }
+
#include <mdspan>
#ifndef __cpp_lib_mdspan
#error "Feature test macro __cpp_lib_mdspan is missing for <mdspan>"
-#if __cpp_lib_mdspan < 202207
-#error "Feature test macro __cpp_lib_mdspan has the wrong value"
-#endif
+#elif __cplusplus <= 202302L && __cpp_lib_mdspan != 202207L
+#error "Feature test macro __cpp_lib_mdspan has the wrong value for C++23"
+#elif __cplusplus > 202302L && __cpp_lib_mdspan != 202406L
+#error "Feature test macro __cpp_lib_mdspan has the wrong value for C++26"
#endif
