Re: libstdc++: Make atomic<T*>::wait() const [PR102994]

[Thomas Rodgers <trodgers@redhat.com>]

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const qualification was also missing in the free functions for
wait/wait_explicit/notify_one/notify_all. Revised patch attached.

On Tue, Nov 9, 2021 at 11:40 AM Jonathan Wakely <jwakely@redhat.com> wrote:

> On Tue, 9 Nov 2021 at 18:09, Thomas Rodgers wrote:
>
>> Revised patch attached.
>>
>
> OK for trunk and gcc-11, thanks.
>
>
>
>> On Fri, Nov 5, 2021 at 4:46 PM Jonathan Wakely <jwakely.gcc@gmail.com>
>> wrote:
>>
>>> On Fri, 5 Nov 2021 at 21:51, Jonathan Wakely via Libstdc++
>>> <libstdc++@gcc.gnu.org> wrote:
>>> >
>>> > OK, thanks.
>>>
>>> Actually, we should really have a test to verify it can be called on a
>>> const object. Please add something when you commit, it can be dumb and
>>> simple, it just needs to verify that it can be called.
>>>
>>>
>>> >
>>> >
>>> > On Fri, 5 Nov 2021 at 21:46, Thomas Rodgers via Libstdc++ <
>>> > libstdc++@gcc.gnu.org> wrote:
>>> >
>>> > >
>>> > >
>>>
>>>

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From 337c147b5bb0265522d5aac4beefb3dec1ebe026 Mon Sep 17 00:00:00 2001
From: Thomas Rodgers <rodgert@twrodgers.com>
Date: Tue, 9 Nov 2021 09:42:49 -0800
Subject: [PATCH] libstdc++: Make atomic<T*>::wait() const [PR102994]

This was an oversight in the original commit adding wait/notify
to atomic<T>.

libstdc++-v3/ChangeLog:

	PR libstdc++/102994
	* include/bits/atomic_base.h (__atomic_base<_PTp*>::wait()):
	Add const qualifier.
	* include/std/atomic (atomic<_Tp*>::wait(), atomic_wait(),
	atomic_wait_explicit(), atomic_notify_one(), atomic_notify_all()):
	Likewise.
	* testsuite/29_atomics/atomic/wait_notify/102994.cc:
	New test.
---
 libstdc++-v3/include/bits/atomic_base.h       |  2 +-
 libstdc++-v3/include/std/atomic               |  8 ++++----
 .../29_atomics/atomic/wait_notify/102994.cc   | 19 +++++++++++++++++++
 3 files changed, 24 insertions(+), 5 deletions(-)
 create mode 100644 libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/102994.cc

diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h
index 9e18aadadaf..a104adc1a10 100644
--- a/libstdc++-v3/include/bits/atomic_base.h
+++ b/libstdc++-v3/include/bits/atomic_base.h
@@ -893,7 +893,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #if __cpp_lib_atomic_wait
       _GLIBCXX_ALWAYS_INLINE void
       wait(__pointer_type __old,
-	   memory_order __m = memory_order_seq_cst) noexcept
+	   memory_order __m = memory_order_seq_cst) const noexcept
       {
 	std::__atomic_wait_address_v(&_M_p, __old,
 				     [__m, this]
diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index 936dd50ba1c..9b827b425dc 100644
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -646,9 +646,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 					    __cmpexch_failure_order(__m));
       }
 
-#if __cpp_lib_atomic_wait 
+#if __cpp_lib_atomic_wait
     void
-    wait(__pointer_type __old, memory_order __m = memory_order_seq_cst) noexcept
+    wait(__pointer_type __old, memory_order __m = memory_order_seq_cst) const noexcept
     { _M_b.wait(__old, __m); }
 
     // TODO add const volatile overload
@@ -1434,12 +1434,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   template<typename _Tp>
     inline void
-    atomic_notify_one(atomic<_Tp>* __a) noexcept
+    atomic_notify_one(const atomic<_Tp>* __a) noexcept
     { __a->notify_one(); }
 
   template<typename _Tp>
     inline void
-    atomic_notify_all(atomic<_Tp>* __a) noexcept
+    atomic_notify_all(const atomic<_Tp>* __a) noexcept
     { __a->notify_all(); }
 #endif // __cpp_lib_atomic_wait
 
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/102994.cc b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/102994.cc
new file mode 100644
index 00000000000..28c3d66f451
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/wait_notify/102994.cc
@@ -0,0 +1,19 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do compile { target c++20 } }
+// { dg-require-gthreads "" }
+
+#include <atomic>
+
+void
+test1(const std::atomic<char*> &a, char*p)
+{
+  a.wait(p);
+}
+
+void
+test2(const std::atomic<int>* a, int v)
+{
+  std::atomic_wait(a, v);
+  std::atomic_notify_one(a);
+  std::atomic_notify_all(a);
+}
-- 
2.31.1