libstdc++: Fix bug in default ctor of extents.

The array that stores the dynamic extents used to be default
initialized. The standard requires value intialization. This
commit fixes the bug and adds a test.

libstdc++-v3/ChangeLog:

	* include/std/mdspan: Value initialize the array storing the
	dynamic extents.
	* testsuite/23_containers/mdspan/extents/ctor_default.cc: New
	test.

Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>

diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 47cfa405e442008b1a7707c0a3f870e7f49ee5ca..bcf2fa60feabd0e3be47fc354bfe7bf0c8e96298 100644 (file)
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -146,7 +146,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       private:
        using _S_storage = __array_traits<_IndexType, _S_rank_dynamic>::_Type;
-       [[no_unique_address]] _S_storage _M_dynamic_extents;
+       [[no_unique_address]] _S_storage _M_dynamic_extents{};
       };
 
     template<typename _OIndexType, typename _SIndexType>

diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_default.cc b/libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_default.cc
new file mode 100644 (file)
index 0000000..eec300f
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_default.cc
@@ -0,0 +1,41 @@
+// { dg-do run { target c++23 } }
+#include <mdspan>
+
+#include <cstdint>
+#include <testsuite_hooks.h>
+
+constexpr auto dyn = std::dynamic_extent;
+
+template<typename Extents>
+  constexpr void
+  test_default_ctor()
+  {
+    Extents exts;
+    for(size_t i = 0; i < Extents::rank(); ++i)
+      if(exts.static_extent(i) == std::dynamic_extent)
+       VERIFY(exts.extent(i) == 0);
+      else
+       VERIFY(exts.extent(i) == Extents::static_extent(i));
+  }
+
+constexpr bool
+test_default_ctor_all()
+{
+  test_default_ctor<std::extents<int, 1>>();
+  test_default_ctor<std::extents<int, dyn>>();
+  test_default_ctor<std::extents<int, 1, 2>>();
+  test_default_ctor<std::extents<int, dyn, 2>>();
+  test_default_ctor<std::extents<int, dyn, dyn>>();
+  test_default_ctor<std::extents<int, 1, 2, 3>>();
+  test_default_ctor<std::extents<int, dyn, 2, dyn>>();
+  test_default_ctor<std::extents<int, dyn, dyn, dyn>>();
+  return true;
+}
+
+int
+main()
+{
+  test_default_ctor_all();
+  static_assert(test_default_ctor_all());
+  return 0;
+}