Tested x86_64-pc-linux-gnu, committed to trunk.
Jonathan Wakely writes:
> On 30/11/20 10:17 -0800, Thomas Rodgers wrote:
>>From: Thomas Rodgers <trodg...@redhat.com>
>>
>>Adds __cpp_lib_atomic_wait feature test macro which was overlooked in
>>the initial commit of this feature. Replaces uses of
>>_GLIBCXX_HAVE_ATOMIC_WAIT.
>>
>>libstdc++-v3/ChangeLog:
>>
>> * include/bits/atomic_base.h: Replace usage of
>> _GLIBCXX_HAVE_ATOMIC_WAIT with __cpp_lib_atomic_wait.
>> * include/bits/atomic_timed_wait.h: Likewise.
>> * include/bits/atomic_wait.h: Define __cpp_lib_atomic_wait
>> feature test macro.
>> * include/bits/semaphore_base: Replace usage of
>> _GLIBCXX_HAVE_ATOMIC_WAIT with __cpp_lib_atomic_wait.
>> * include/std/atomic: Likewise.
>> * include/std/latch: Likewise.
>> * include/std/semaphore: Likewise.
>> * include/std/version: Define __cpp_lib_atomic wait
>> feature test macro and replace usage of
>> _GLIBCXX_HAVE_ATOMIC_WAIT.
>> * testsuite/29_atomics/atomic/wait_notify/1.cc: New test.
>> * testsuite/29_atomics/atomic/wait_notify/2.cc: Likewise.
>>
>>---
>> libstdc++-v3/include/bits/atomic_base.h | 36 +++++++++----------
>> libstdc++-v3/include/bits/atomic_timed_wait.h | 5 +--
>> libstdc++-v3/include/bits/atomic_wait.h | 3 +-
>> libstdc++-v3/include/bits/semaphore_base.h | 4 +--
>> libstdc++-v3/include/std/atomic | 16 ++++-----
>> libstdc++-v3/include/std/latch | 4 +--
>> libstdc++-v3/include/std/semaphore | 4 +--
>> libstdc++-v3/include/std/version | 7 ++--
>> .../29_atomics/atomic/wait_notify/1.cc | 28 +++++++++++++++
>> .../29_atomics/atomic/wait_notify/2.cc | 29 +++++++++++++++
>> 10 files changed, 98 insertions(+), 38 deletions(-)
>> create mode 100644 libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/1.cc
>> create mode 100644 libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/2.cc
>>
>>diff --git a/libstdc++-v3/include/bits/atomic_base.h
>>b/libstdc++-v3/include/bits/atomic_base.h
>>index d0d962d3047..ad4e24b4d20 100644
>>--- a/libstdc++-v3/include/bits/atomic_base.h
>>+++ b/libstdc++-v3/include/bits/atomic_base.h
>>@@ -230,7 +230,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> return __v == __GCC_ATOMIC_TEST_AND_SET_TRUEVAL;
>> }
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>
> I've not always been consistent about using #if or #ifdef for
> __cpp_lib macros, but let's not make that worse in a single patch. I
> think we should just use #if for __cpp_lib macros. That affects
> several places in the patch.
>
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(bool __old,
>> memory_order __m = memory_order_seq_cst) const noexcept
>>@@ -253,7 +253,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { std::__atomic_notify(&_M_i, true); }
>>
>> // TODO add const volatile overload
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> #endif // C++20
>>
>> _GLIBCXX_ALWAYS_INLINE void
>>@@ -604,7 +604,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__m));
>> }
>>
>>-#if __cplusplus > 201703L && defined _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(__int_type __old,
>> memory_order __m = memory_order_seq_cst) const noexcept
>>@@ -627,7 +627,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { std::__atomic_notify(&_M_i, true); }
>>
>> // TODO add const volatile overload
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> _GLIBCXX_ALWAYS_INLINE __int_type
>> fetch_add(__int_type __i,
>>@@ -898,7 +898,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> int(__m1), int(__m2));
>> }
>>
>>-#if __cplusplus > 201703L && defined _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(__pointer_type __old,
>> memory_order __m = memory_order_seq_cst) noexcept
>>@@ -921,7 +921,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { std::__atomic_notify(&_M_p, true); }
>>
>> // TODO add const volatile overload
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> _GLIBCXX_ALWAYS_INLINE __pointer_type
>> fetch_add(ptrdiff_t __d,
>>@@ -1011,7 +1011,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> int(__success), int(__failure));
>> }
>>
>>-#if __cplusplus > 201703L && defined _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> template<typename _Tp>
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(const _Tp* __ptr, _Val<_Tp> __old,
>>@@ -1036,7 +1036,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { std::__atomic_notify(__ptr, true); }
>>
>> // TODO add const volatile overload
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> template<typename _Tp>
>> _GLIBCXX_ALWAYS_INLINE _Tp
>>@@ -1291,7 +1291,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__order));
>> }
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(_Fp __old, memory_order __m = memory_order_seq_cst) const noexcept
>> { __atomic_impl::wait(&_M_fp, __old, __m); }
>>@@ -1309,7 +1309,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { __atomic_impl::notify_all(&_M_fp); }
>>
>> // TODO add const volatile overload
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> value_type
>> fetch_add(value_type __i,
>>@@ -1448,7 +1448,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__order));
>> }
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(_Tp __old, memory_order __m = memory_order_seq_cst) const noexcept
>> { __atomic_impl::wait(_M_ptr, __old, __m); }
>>@@ -1466,7 +1466,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { __atomic_impl::notify_all(_M_ptr); }
>>
>> // TODO add const volatile overload
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> private:
>> _Tp* _M_ptr;
>>@@ -1563,7 +1563,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__order));
>> }
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(_Tp __old, memory_order __m = memory_order_seq_cst) const noexcept
>> { __atomic_impl::wait(_M_ptr, __old, __m); }
>>@@ -1581,7 +1581,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { __atomic_impl::notify_all(_M_ptr); }
>>
>> // TODO add const volatile overload
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> value_type
>> fetch_add(value_type __i,
>>@@ -1738,7 +1738,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__order));
>> }
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(_Fp __old, memory_order __m = memory_order_seq_cst) const noexcept
>> { __atomic_impl::wait(_M_ptr, __old, __m); }
>>@@ -1756,7 +1756,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { __atomic_impl::notify_all(_M_ptr); }
>>
>> // TODO add const volatile overload
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> value_type
>> fetch_add(value_type __i,
>>@@ -1867,7 +1867,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__order));
>> }
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>> _GLIBCXX_ALWAYS_INLINE void
>> wait(_Tp __old, memory_order __m = memory_order_seq_cst) const noexcept
>> { __atomic_impl::wait(_M_ptr, __old, __m); }
>>@@ -1885,7 +1885,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { __atomic_impl::notify_all(_M_ptr); }
>>
>> // TODO add const volatile overload
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> _GLIBCXX_ALWAYS_INLINE value_type
>> fetch_add(difference_type __d,
>>diff --git a/libstdc++-v3/include/bits/atomic_timed_wait.h
>>b/libstdc++-v3/include/bits/atomic_timed_wait.h
>>index f3a07a36722..6dd1a145e69 100644
>>--- a/libstdc++-v3/include/bits/atomic_timed_wait.h
>>+++ b/libstdc++-v3/include/bits/atomic_timed_wait.h
>>@@ -33,7 +33,8 @@
>> #pragma GCC system_header
>>
>> #include <bits/atomic_wait.h>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+
>>+#ifdef __cpp_lib_atomic_wait
>> #include <bits/functional_hash.h>
>>
>> #include <chrono>
>>@@ -292,5 +293,5 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> }
>> _GLIBCXX_END_NAMESPACE_VERSION
>> } // namespace std
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> #endif // _GLIBCXX_ATOMIC_TIMED_WAIT_H
>>diff --git a/libstdc++-v3/include/bits/atomic_wait.h
>>b/libstdc++-v3/include/bits/atomic_wait.h
>>index a59ed8cb418..5efd96d22a1 100644
>>--- a/libstdc++-v3/include/bits/atomic_wait.h
>>+++ b/libstdc++-v3/include/bits/atomic_wait.h
>>@@ -50,8 +50,7 @@
>> # include <bits/std_mutex.h> // std::mutex, std::__condvar
>> #endif
>>
>>-// Other headers use this to check for the facilities defined in this header.
>>-#define _GLIBCXX_HAVE_ATOMIC_WAIT 1
>>+#define __cpp_lib_atomic_wait 201907L
>>
>> namespace std _GLIBCXX_VISIBILITY(default)
>> {
>>diff --git a/libstdc++-v3/include/bits/semaphore_base.h
>>b/libstdc++-v3/include/bits/semaphore_base.h
>>index f2984236e03..0ed1f5895af 100644
>>--- a/libstdc++-v3/include/bits/semaphore_base.h
>>+++ b/libstdc++-v3/include/bits/semaphore_base.h
>>@@ -33,7 +33,7 @@
>> #pragma GCC system_header
>>
>> #include <bits/atomic_base.h>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>> #include <bits/atomic_timed_wait.h>
>>
>> #include <ext/numeric_traits.h>
>>@@ -297,5 +297,5 @@ template<ptrdiff_t __least_max_value>
>> _GLIBCXX_END_NAMESPACE_VERSION
>> } // namespace std
>>
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> #endif // _GLIBCXX_SEMAPHORE_BASE_H
>>diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
>>index 664af023d77..4a9b00182a3 100644
>>--- a/libstdc++-v3/include/std/atomic
>>+++ b/libstdc++-v3/include/std/atomic
>>@@ -164,7 +164,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> memory_order __m = memory_order_seq_cst) volatile noexcept
>> { return _M_base.compare_exchange_strong(__i1, __i2, __m); }
>>
>>-#if __cplusplus > 201703L && defined _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> void
>> wait(bool __old, memory_order __m = memory_order_seq_cst) const noexcept
>> { _M_base.wait(__old, __m); }
>>@@ -178,7 +178,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> void
>> notify_all() const noexcept
>> { _M_base.notify_all(); }
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> };
>>
>> #if __cplusplus <= 201703L
>>@@ -380,7 +380,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> { return compare_exchange_strong(__e, __i, __m,
>> __cmpexch_failure_order(__m)); }
>>
>>-#if __cplusplus > 201703L && defined _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> void
>> wait(_Tp __old, memory_order __m = memory_order_seq_cst) const noexcept
>> {
>>@@ -404,7 +404,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> void
>> notify_all() const noexcept
>> { std::__atomic_notify(&_M_i, true); }
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> };
>> #undef _GLIBCXX20_INIT
>>@@ -644,7 +644,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> __cmpexch_failure_order(__m));
>> }
>>
>>-#if __cplusplus > 201703L && _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> void
>> wait(__pointer_type __old, memory_order __m = memory_order_seq_cst)
>> noexcept
>> { _M_b.wait(__old, __m); }
>>@@ -658,7 +658,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> void
>> notify_all() const noexcept
>> { _M_b.notify_all(); }
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> __pointer_type
>> fetch_add(ptrdiff_t __d,
>> memory_order __m = memory_order_seq_cst) noexcept
>>@@ -1412,7 +1412,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> }
>>
>>
>>-#if __cplusplus > 201703L && _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#if __cpp_lib_atomic_wait
>> template<typename _Tp>
>> inline void
>> atomic_wait(const atomic<_Tp>* __a,
>>@@ -1435,7 +1435,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> inline void
>> atomic_notify_all(atomic<_Tp>* __a) noexcept
>> { __a->notify_all(); }
>>-#endif // C++20 && HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>>
>> // Function templates for atomic_integral and atomic_pointer operations
>> only.
>> // Some operations (and, or, xor) are only available for atomic integrals,
>>diff --git a/libstdc++-v3/include/std/latch b/libstdc++-v3/include/std/latch
>>index 2684b72288f..3ae77cb1cd2 100644
>>--- a/libstdc++-v3/include/std/latch
>>+++ b/libstdc++-v3/include/std/latch
>>@@ -36,7 +36,7 @@
>> #include <bits/atomic_base.h>
>> #include <ext/numeric_traits.h>
>>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>
> Just #if not #ifdef
>
>> namespace std _GLIBCXX_VISIBILITY(default)
>> {
>> _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>@@ -89,6 +89,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> };
>> _GLIBCXX_END_NAMESPACE_VERSION
>> } // namespace
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> #endif // __cplusplus > 201703L
>> #endif // _GLIBCXX_LATCH
>>diff --git a/libstdc++-v3/include/std/semaphore
>>b/libstdc++-v3/include/std/semaphore
>>index 184c7c2867c..0ecf3bf2fa0 100644
>>--- a/libstdc++-v3/include/std/semaphore
>>+++ b/libstdc++-v3/include/std/semaphore
>>@@ -33,7 +33,7 @@
>>
>> #if __cplusplus > 201703L
>> #include <bits/semaphore_base.h>
>>-#ifdef _GLIBCXX_HAVE_ATOMIC_WAIT
>>+#ifdef __cpp_lib_atomic_wait
>
> #if
>
>> #include <ext/numeric_traits.h>
>>
>> namespace std _GLIBCXX_VISIBILITY(default)
>>@@ -90,6 +90,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> using binary_semaphore = std::counting_semaphore<1>;
>> _GLIBCXX_END_NAMESPACE_VERSION
>> } // namespace
>>-#endif // HAVE_ATOMIC_WAIT
>>+#endif // __cpp_lib_atomic_wait
>> #endif // C++20
>> #endif // _GLIBCXX_SEMAPHORE
>>diff --git a/libstdc++-v3/include/std/version
>>b/libstdc++-v3/include/std/version
>>index 0f2da8a5ddd..e5502c9e84b 100644
>>--- a/libstdc++-v3/include/std/version
>>+++ b/libstdc++-v3/include/std/version
>>@@ -197,6 +197,9 @@
>> #if _GLIBCXX_HOSTED
>> #define __cpp_lib_array_constexpr 201811L
>> #define __cpp_lib_assume_aligned 201811L
>>+#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
>>+#define __cpp_lib_atomic_wait 201907L
>
> A single space after the # please.
>
>>+#endif
>> #define __cpp_lib_bind_front 201907L
>> // FIXME: #define __cpp_lib_execution 201902L
>> #define __cpp_lib_integer_comparison_functions 202002L
>>@@ -216,7 +219,7 @@
>> #ifdef _GLIBCXX_HAS_GTHREADS
>> # define __cpp_lib_jthread 201911L
>> #endif
>>-#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
>>+#if defined __cpp_lib_atomic_wait
>
> Remove the "defined".
>
>> # define __cpp_lib_latch 201907L
>> #endif
>> #define __cpp_lib_list_remove_return_type 201806L
>>@@ -228,7 +231,7 @@
>> #if __cpp_lib_concepts
>> # define __cpp_lib_ranges 201911L
>> #endif
>>-#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
>>+#if defined __cpp_lib_atomic_wait
>
> Remove the "defined".
>
>> # define __cpp_lib_semaphore 201907L
>> #endif
>> #define __cpp_lib_shift 201806L
>>diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/1.cc
>>b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/1.cc
>>new file mode 100644
>>index 00000000000..5a08d64c1f0
>>--- /dev/null
>>+++ b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/1.cc
>>@@ -0,0 +1,28 @@
>>+// Copyright (C) 2020 Free Software Foundation, Inc.
>>+//
>>+// This file is part of the GNU ISO C++ Library. This library is free
>>+// software; you can redistribute it and/or modify it under the
>>+// terms of the GNU General Public License as published by the
>>+// Free Software Foundation; either version 3, or (at your option)
>>+// any later version.
>>+
>>+// This library is distributed in the hope that it will be useful,
>>+// but WITHOUT ANY WARRANTY; without even the implied warranty of
>>+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>+// GNU General Public License for more details.
>>+
>>+// You should have received a copy of the GNU General Public License along
>>+// with this library; see the file COPYING3. If not see
>>+// <http://www.gnu.org/licenses/>.
>>+
>>+// { dg-options "-std=gnu++2a" }
>>+// { dg-do compile { target c++2a } }
>
> This will fail on targets that don't support the feature.
>
> It needs to be:
>
> // { dg-options "-std=gnu++2a" }
> // { dg-do compile { target c++2a } }
> // { dg-require-effective-target gthreads }
>
> The last line there works since last week when I added "gthreads" as
> an effective target keyword, which replaces:
>
> // { dg-require-gthreads "" }
>
> If we wanted to be really correct it would be:
>
> // { dg-require-effective-target gthreads { target { ! futex } } }
>
> Which requires gthreads only for target { ! futex } i.e. if futexes
> are supported, then gthreads is not needed (which exactly matches the
> code). But it's good enough to just require gthreads, since in
> practice the combination of futex && ! gthreads is probably
> non-existent. Keeping the directive more readable is more important
> than verifying the feature test macro is defined on non-existent
> targets.
>
>>+#include <atomic>
>>+
>>+#ifndef __cpp_lib_atomic_wait
>>+# error "Feature-test macro for atomic wait missing in <atomic>"
>>+#elif __cpp_lib_atomic_wait != 201907L
>>+# error "Feature-test macro for atomic wait has wrong value in <atomic>"
>>+#endif
>>+
>>diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/2.cc
>>b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/2.cc
>>new file mode 100644
>>index 00000000000..5031a369e79
>>--- /dev/null
>>+++ b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/2.cc
>>@@ -0,0 +1,29 @@
>>+// Copyright (C) 2020 Free Software Foundation, Inc.
>>+//
>>+// This file is part of the GNU ISO C++ Library. This library is free
>>+// software; you can redistribute it and/or modify it under the
>>+// terms of the GNU General Public License as published by the
>>+// Free Software Foundation; either version 3, or (at your option)
>>+// any later version.
>>+
>>+// This library is distributed in the hope that it will be useful,
>>+// but WITHOUT ANY WARRANTY; without even the implied warranty of
>>+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>+// GNU General Public License for more details.
>>+
>>+// You should have received a copy of the GNU General Public License along
>>+// with this library; see the file COPYING3. If not see
>>+// <http://www.gnu.org/licenses/>.
>>+
>>+// { dg-options "-std=gnu++2a" }
>>+// { dg-do compile { target c++2a } }
>
> This will fail on non-gthreads targets too. As above.
>
>>+#include <version>
>>+
>>+#ifndef __cpp_lib_atomic_wait
>>+# error "Feature-test macro for atomic wait missing in <version>"
>>+#elif __cpp_lib_atomic_wait != 201907L
>>+# error "Feature-test macro for atomic wait has wrong value in <version>"
>>+#endif
>
>
> OK with those changes, thanks.
