Tested x86_64-linux. Pushed to trunk.
-- >8--
libstdc++-v3/ChangeLog:
PR libstdc++/98034
* include/std/atomic (__cpp_lib_atomic_lock_free_type_aliases):
Define macro.
(atomic_signed_lock_free, atomic_unsigned_lock_free): Define
aliases.
* include/std/version (__cpp_lib_atomic_lock_free_type_aliases):
Define macro.
* testsuite/29_atomics/atomic/lock_free_aliases.cc: New test.
---
libstdc++-v3/include/std/atomic | 17 ++++++++++
libstdc++-v3/include/std/version | 1 +
.../29_atomics/atomic/lock_free_aliases.cc | 34 +++++++++++++++++++
3 files changed, 52 insertions(+)
create mode 100644
libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index 356f1458f44..857f9270049 100644
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -1727,6 +1727,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __atomic_ref<_Tp>::operator=;
};
+#define __cpp_lib_atomic_lock_free_type_aliases 201907L
+#ifdef _GLIBCXX_HAVE_PLATFORM_WAIT
+ using atomic_signed_lock_free
+ = atomic<make_signed_t<__detail::__platform_wait_t>>;
+ using atomic_unsigned_lock_free
+ = atomic<make_unsigned_t<__detail::__platform_wait_t>>;
+#elif ATOMIC_INT_LOCK_FREE || !(ATOMIC_LONG_LOCK_FREE || ATOMIC_CHAR_LOCK_FREE)
+ using atomic_signed_lock_free = atomic<signed int>;
+ using atomic_unsigned_lock_free = atomic<unsigned int>;
+#elif ATOMIC_LONG_LOCK_FREE
+ using atomic_signed_lock_free = atomic<signed long>;
+ using atomic_unsigned_lock_free = atomic<unsigned long>;
+#elif ATOMIC_CHAR_LOCK_FREE
+ using atomic_signed_lock_free = atomic<signed char>;
+ using atomic_unsigned_lock_free = atomic<unsigned char>;
+#endif
+
#endif // C++2a
/// @} group atomics
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index 3c7c440bd80..61718ebad74 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -187,6 +187,7 @@
#define __cpp_lib_assume_aligned 201811L
#define __cpp_lib_atomic_flag_test 201907L
#define __cpp_lib_atomic_float 201711L
+#define __cpp_lib_atomic_lock_free_type_aliases 201907L
#define __cpp_lib_atomic_ref 201806L
#define __cpp_lib_atomic_value_initialization 201911L
#define __cpp_lib_bind_front 201907L
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
b/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
new file mode 100644
index 00000000000..02c4ccc3aa3
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
@@ -0,0 +1,34 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do compile { target c++20 } }
+
+#include <atomic>
+
+#ifndef __cpp_lib_atomic_lock_free_type_aliases
+# error "Feature test macro for lock-free type aliases is missing in <atomic>"
+#elif __cpp_lib_atomic_lock_free_type_aliases != 201907L
+# error "Feature test macro for lock-free type aliases has wrong value in
<atomic>"
+#endif
+
+template<typename T>
+constexpr bool is_atomic_specialization = false;
+template<typename T>
+constexpr bool is_atomic_specialization<std::atomic<T>> = true;
+
+// The type aliases atomic_signed_lock_free and atomic_unsigned_lock_free
+// name specializations of atomic
+static_assert( is_atomic_specialization<std::atomic_signed_lock_free> );
+static_assert( is_atomic_specialization<std::atomic_unsigned_lock_free> );
+
+#include <type_traits>
+
+// ... whose template arguments are integral types,
+static_assert( std::is_integral_v<std::atomic_signed_lock_free::value_type> );
+static_assert( std::is_integral_v<std::atomic_unsigned_lock_free::value_type>
);
+
+// ... respectively signed and unsigned,
+static_assert( std::is_signed_v<std::atomic_signed_lock_free::value_type> );
+static_assert( std::is_unsigned_v<std::atomic_unsigned_lock_free::value_type>
);
+
+// and whose is_always_lock_free property is true.
+static_assert( std::atomic_signed_lock_free::is_always_lock_free );
+static_assert( std::atomic_unsigned_lock_free::is_always_lock_free );
--
2.38.1
