[SYCL] Fixes circular reference between events and queues

Signed-off-by: Steffen Larsen <[email protected]>

Author: Steffen Larsen

sycl/source/detail/event_impl.cpp

@@ -114,8 +114,9 @@ void event_impl::wait_and_throw(
     if (Cmd)
       Cmd->getQueue()->throw_asynchronous();
   }
-  if (MQueue)
-    MQueue->throw_asynchronous();
+  QueueImplPtr Queue = MQueue.lock();
+  if (Queue)
+    Queue->throw_asynchronous();
 }
 
 template <>

sycl/source/detail/event_impl.hpp

@@ -25,6 +25,7 @@ class context_impl;
 using ContextImplPtr = std::shared_ptr<cl::sycl::detail::context_impl>;
 class queue_impl;
 using QueueImplPtr = std::shared_ptr<cl::sycl::detail::queue_impl>;
+using QueueImplWPtr = std::weak_ptr<cl::sycl::detail::queue_impl>;
 
 class event_impl {
 public:
@@ -147,7 +148,7 @@ class event_impl {
 private:
   RT::PiEvent MEvent = nullptr;
   ContextImplPtr MContext;
-  QueueImplPtr MQueue;
+  QueueImplWPtr MQueue;
   bool MOpenCLInterop = false;
   bool MHostEvent = true;
   std::unique_ptr<HostProfilingInfo> MHostProfilingInfo;