From 088db0103f8fba9c54928ce1fdab61ce44c3bcd1 Mon Sep 17 00:00:00 2001
From: Shauren <shauren.trinity@gmail.com>
Date: Wed, 11 May 2022 13:59:41 +0200
Subject: Core/Misc: Remove uses of std::aligned_storage (deprecated in future
 c++ standard)

---
 src/common/Threading/MPSCQueue.h | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

(limited to 'src/common/Threading')

diff --git a/src/common/Threading/MPSCQueue.h b/src/common/Threading/MPSCQueue.h
index 91654546298..ee58eb96b29 100644
--- a/src/common/Threading/MPSCQueue.h
+++ b/src/common/Threading/MPSCQueue.h
@@ -18,8 +18,9 @@
 #ifndef MPSCQueue_h__
 #define MPSCQueue_h__
 
+#include <array>
 #include <atomic>
-#include <type_traits>
+#include <new>
 
 namespace Trinity
 {
@@ -92,12 +93,14 @@ private:
 template<typename T, std::atomic<T*> T::* IntrusiveLink>
 class MPSCQueueIntrusive
 {
+    using Atomic = std::atomic<T*>;
+
 public:
-    MPSCQueueIntrusive() : _dummyPtr(reinterpret_cast<T*>(std::addressof(_dummy))), _head(_dummyPtr), _tail(_dummyPtr)
+    MPSCQueueIntrusive() : _dummyPtr(reinterpret_cast<T*>(_dummy.data())), _head(_dummyPtr), _tail(_dummyPtr)
     {
-        // _dummy is constructed from aligned_storage and is intentionally left uninitialized (it might not be default constructible)
+        // _dummy is constructed from raw byte array and is intentionally left uninitialized (it might not be default constructible)
         // so we init only its IntrusiveLink here
-        std::atomic<T*>* dummyNext = new (&(_dummyPtr->*IntrusiveLink)) std::atomic<T*>();
+        Atomic* dummyNext = new (&(_dummyPtr->*IntrusiveLink)) Atomic();
         dummyNext->store(nullptr, std::memory_order_relaxed);
     }
 
@@ -106,6 +109,9 @@ public:
         T* output;
         while (Dequeue(output))
             delete output;
+
+        // destruct our dummy atomic
+        (_dummyPtr->*IntrusiveLink).~Atomic();
     }
 
     void Enqueue(T* input)
@@ -152,10 +158,10 @@ public:
     }
 
 private:
-    std::aligned_storage_t<sizeof(T), alignof(T)> _dummy;
+    alignas(T) std::array<std::byte, sizeof(T)> _dummy;
     T* _dummyPtr;
-    std::atomic<T*> _head;
-    std::atomic<T*> _tail;
+    Atomic _head;
+    Atomic _tail;
 
     MPSCQueueIntrusive(MPSCQueueIntrusive const&) = delete;
     MPSCQueueIntrusive& operator=(MPSCQueueIntrusive const&) = delete;
-- 
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