[gcc r16-2445] libstdc++: Prepare test code for default_accessor for reuse.

[Tomasz Kaminski]

https://gcc.gnu.org/g:9acdbf81eef6db74502a9b704ba08e5a84dfb5fa

commit r16-2445-g9acdbf81eef6db74502a9b704ba08e5a84dfb5fa
Author: Luc Grosheintz <luc.grosheintz@gmail.com>
Date:   Wed Jul 23 11:25:52 2025 +0200

    libstdc++: Prepare test code for default_accessor for reuse.
    
    All test code of default_accessor can be reused. This commit moves
    the reuseable code into a file generic.cc and prepares the tests for
    reuse with aligned_accessor.
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/23_containers/mdspan/accessors/default.cc: Delete.
            * testsuite/23_containers/mdspan/accessors/generic.cc: Slightly
            generalize the test code previously in default.cc.
    
    Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
    Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>

Diff:
---
 .../23_containers/mdspan/accessors/default.cc      |  99 ----------------
 .../23_containers/mdspan/accessors/generic.cc      | 125 +++++++++++++++++++++
 2 files changed, 125 insertions(+), 99 deletions(-)

diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc
deleted file mode 100644
index c036f8ad10ff..000000000000
--- a/libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc
+++ /dev/null
@@ -1,99 +0,0 @@
-// { dg-do run { target c++23 } }
-#include <mdspan>
-
-#include <testsuite_hooks.h>
-
-constexpr size_t dyn = std::dynamic_extent;
-
-template<typename Accessor>
-  constexpr void
-  test_accessor_policy()
-  {
-    static_assert(std::copyable<Accessor>);
-    static_assert(std::is_nothrow_move_constructible_v<Accessor>);
-    static_assert(std::is_nothrow_move_assignable_v<Accessor>);
-    static_assert(std::is_nothrow_swappable_v<Accessor>);
-  }
-
-constexpr bool
-test_access()
-{
-  std::default_accessor<double> accessor;
-  std::array<double, 5> a{10, 11, 12, 13, 14};
-  VERIFY(accessor.access(a.data(), 0) == 10);
-  VERIFY(accessor.access(a.data(), 4) == 14);
-  return true;
-}
-
-constexpr bool
-test_offset()
-{
-  std::default_accessor<double> accessor;
-  std::array<double, 5> a{10, 11, 12, 13, 14};
-  VERIFY(accessor.offset(a.data(), 0) == a.data());
-  VERIFY(accessor.offset(a.data(), 4) == a.data() + 4);
-  return true;
-}
-
-class Base
-{ };
-
-class Derived : public Base
-{ };
-
-constexpr void
-test_ctor()
-{
-  // T -> T
-  static_assert(std::is_nothrow_constructible_v<std::default_accessor<double>,
-						std::default_accessor<double>>);
-  static_assert(std::is_convertible_v<std::default_accessor<double>,
-				      std::default_accessor<double>>);
-
-  // T -> const T
-  static_assert(std::is_convertible_v<std::default_accessor<double>,
-				      std::default_accessor<const double>>);
-  static_assert(std::is_convertible_v<std::default_accessor<Derived>,
-				      std::default_accessor<const Derived>>);
-
-  // const T -> T
-  static_assert(!std::is_constructible_v<std::default_accessor<double>,
-					 std::default_accessor<const double>>);
-  static_assert(!std::is_constructible_v<std::default_accessor<Derived>,
-					 std::default_accessor<const Derived>>);
-
-  // T <-> volatile T
-  static_assert(std::is_convertible_v<std::default_accessor<int>,
-				      std::default_accessor<volatile int>>);
-  static_assert(!std::is_constructible_v<std::default_accessor<int>,
-					 std::default_accessor<volatile int>>);
-
-  // size difference
-  static_assert(!std::is_constructible_v<std::default_accessor<char>,
-					 std::default_accessor<int>>);
-
-  // signedness
-  static_assert(!std::is_constructible_v<std::default_accessor<int>,
-					 std::default_accessor<unsigned int>>);
-  static_assert(!std::is_constructible_v<std::default_accessor<unsigned int>,
-					 std::default_accessor<int>>);
-
-  // Derived <-> Base
-  static_assert(!std::is_constructible_v<std::default_accessor<Base>,
-					 std::default_accessor<Derived>>);
-  static_assert(!std::is_constructible_v<std::default_accessor<Derived>,
-					 std::default_accessor<Base>>);
-
-}
-
-int
-main()
-{
-  test_accessor_policy<std::default_accessor<double>>();
-  test_access();
-  static_assert(test_access());
-  test_offset();
-  static_assert(test_offset());
-  test_ctor();
-  return 0;
-}
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/accessors/generic.cc b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/generic.cc
new file mode 100644
index 000000000000..c3350353aae9
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/accessors/generic.cc
@@ -0,0 +1,125 @@
+// { dg-do run { target c++23 } }
+#include <mdspan>
+
+#include <testsuite_hooks.h>
+
+template<typename Accessor>
+  constexpr bool
+  test_class_properties()
+  {
+    static_assert(std::is_trivially_copyable_v<Accessor>);
+    static_assert(std::semiregular<Accessor>);
+    return true;
+  }
+
+template<typename Accessor>
+  constexpr bool
+  test_accessor_policy()
+  {
+    static_assert(std::copyable<Accessor>);
+    static_assert(std::is_nothrow_move_constructible_v<Accessor>);
+    static_assert(std::is_nothrow_move_assignable_v<Accessor>);
+    static_assert(std::is_nothrow_swappable_v<Accessor>);
+    return true;
+  }
+
+class Base
+{ };
+
+class Derived : public Base
+{ };
+
+template<template<typename T> typename Accessor>
+  constexpr bool
+  test_ctor()
+  {
+    // T -> T
+    static_assert(std::is_nothrow_constructible_v<Accessor<double>,
+						  Accessor<double>>);
+    static_assert(std::is_convertible_v<Accessor<double>, Accessor<double>>);
+
+    // T -> const T
+    static_assert(std::is_convertible_v<Accessor<double>,
+					Accessor<const double>>);
+    static_assert(std::is_convertible_v<Accessor<Derived>,
+					Accessor<const Derived>>);
+
+    // const T -> T
+    static_assert(!std::is_constructible_v<Accessor<double>,
+					   Accessor<const double>>);
+    static_assert(!std::is_constructible_v<Accessor<Derived>,
+					   Accessor<const Derived>>);
+
+    // T <-> volatile T
+    static_assert(std::is_convertible_v<Accessor<int>, Accessor<volatile int>>);
+    static_assert(!std::is_constructible_v<Accessor<int>,
+					   Accessor<volatile int>>);
+
+    // size difference
+    static_assert(!std::is_constructible_v<Accessor<char>, Accessor<int>>);
+
+    // signedness
+    static_assert(!std::is_constructible_v<Accessor<int>,
+					   Accessor<unsigned int>>);
+    static_assert(!std::is_constructible_v<Accessor<unsigned int>,
+					   Accessor<int>>);
+
+    // Derived <-> Base
+    static_assert(!std::is_constructible_v<Accessor<Base>, Accessor<Derived>>);
+    static_assert(!std::is_constructible_v<Accessor<Derived>, Accessor<Base>>);
+    return true;
+  }
+
+template<template<typename T> typename Accessor>
+  constexpr bool
+  test_properties()
+  {
+    test_class_properties<Accessor<double>>();
+    test_accessor_policy<Accessor<double>>();
+    test_ctor<Accessor>();
+    return true;
+  }
+
+static_assert(test_properties<std::default_accessor>());
+
+template<typename A>
+  constexpr size_t
+  accessor_alignment = alignof(typename A::element_type);
+
+template<typename Accessor>
+  constexpr void
+  test_access(Accessor accessor)
+  {
+    constexpr size_t N = accessor_alignment<Accessor>;
+    alignas(N) std::array<double, 5> a{10, 11, 12, 13, 14};
+    for (size_t i = 0; i < a.size(); ++i)
+      VERIFY(accessor.access(a.data(), i) == 10 + i);
+  }
+
+template<typename Accessor>
+  constexpr void
+  test_offset(Accessor accessor)
+  {
+    constexpr size_t N = accessor_alignment<Accessor>;
+    alignas(N) std::array<double, 5> a{10, 11, 12, 13, 14};
+    for (size_t i = 0; i < a.size(); ++i)
+      VERIFY(accessor.offset(a.data(), i) == a.data() + i);
+  }
+
+template<typename Accessor>
+  constexpr bool
+  test_all()
+  {
+    auto accessor = Accessor{};
+    test_offset(accessor);
+    test_access(accessor);
+    return true;
+  }
+
+int
+main()
+{
+  test_all<std::default_accessor<double>>();
+  static_assert(test_all<std::default_accessor<double>>());
+  return 0;
+}