[SYCL] Fix dangling pointer in device_event (#5137)

Fixes #4959
This should not break SYCL library ABI but can affect device-code ABI.

Author: steffenlarsen

sycl/include/CL/sycl/device_event.hpp

@@ -21,19 +21,17 @@ namespace sycl {
 /// \ingroup sycl_api
 class device_event {
 private:
-  __ocl_event_t *m_Event;
+  __ocl_event_t m_Event;
 
 public:
   device_event(const device_event &rhs) = default;
   device_event(device_event &&rhs) = default;
   device_event &operator=(const device_event &rhs) = default;
   device_event &operator=(device_event &&rhs) = default;
 
-  device_event(__ocl_event_t *Event) : m_Event(Event) {}
+  device_event(__ocl_event_t Event) : m_Event(Event) {}
 
-  void wait() {
-    __spirv_GroupWaitEvents(__spv::Scope::Workgroup, 1, m_Event);
-  }
+  void wait() { __spirv_GroupWaitEvents(__spv::Scope::Workgroup, 1, &m_Event); }
 };
 
 } // namespace sycl

sycl/include/CL/sycl/group.hpp

@@ -294,7 +294,7 @@ template <int Dimensions = 1> class group {
     __ocl_event_t E = __SYCL_OpGroupAsyncCopyGlobalToLocal(
         __spv::Scope::Workgroup, DestT(dest.get()), SrcT(src.get()),
         numElements, srcStride, 0);
-    return device_event(&E);
+    return device_event(E);
   }
 
   /// Asynchronously copies a number of elements specified by \p numElements
@@ -312,7 +312,7 @@ template <int Dimensions = 1> class group {
     __ocl_event_t E = __SYCL_OpGroupAsyncCopyLocalToGlobal(
         __spv::Scope::Workgroup, DestT(dest.get()), SrcT(src.get()),
         numElements, destStride, 0);
-    return device_event(&E);
+    return device_event(E);
   }
 
   /// Specialization for scalar bool type.