view(move): fixing move semantics

core/src/impl/Kokkos_ViewMapping.hpp

@@ -3131,8 +3131,8 @@ class ViewMapping<
 
   using handle_type = typename ViewDataHandle<Traits>::handle_type;
 
-  handle_type m_impl_handle;
-  offset_type m_impl_offset;
+  handle_type m_impl_handle = nullptr;
+  offset_type m_impl_offset {};
 
  private:
   template <class, class...>
@@ -3348,14 +3348,25 @@ class ViewMapping<
   //----------------------------------------
 
   KOKKOS_DEFAULTED_FUNCTION ~ViewMapping() = default;
-  KOKKOS_INLINE_FUNCTION ViewMapping() : m_impl_handle(), m_impl_offset() {}
+  KOKKOS_DEFAULTED_FUNCTION ViewMapping()  = default;
 
   KOKKOS_DEFAULTED_FUNCTION ViewMapping(const ViewMapping&) = default;
   KOKKOS_DEFAULTED_FUNCTION ViewMapping& operator=(const ViewMapping&) =
       default;
 
-  KOKKOS_DEFAULTED_FUNCTION ViewMapping(ViewMapping&&) = default;
-  KOKKOS_DEFAULTED_FUNCTION ViewMapping& operator=(ViewMapping&&) = default;
+  //! Move constructor. Leaves @p other in an empty state.
+  KOKKOS_INLINE_FUNCTION
+  ViewMapping(ViewMapping&& other)
+      : m_impl_handle(std::exchange(other.m_impl_handle, nullptr)),
+        m_impl_offset(std::move(other.m_impl_offset)) {}
+
+  //! Move assignment. Leaves @p other in an empty state.
+  KOKKOS_INLINE_FUNCTION
+  ViewMapping& operator=(ViewMapping&& other) {
+    m_impl_handle = std::exchange(other.m_impl_handle, nullptr);
+    m_impl_offset = std::move(other.m_impl_offset);
+    return *this;
+  }
 
   //----------------------------------------
 

core/src/impl/Kokkos_ViewTracker.hpp

@@ -42,9 +42,10 @@ struct ViewTracker {
 
   track_type m_tracker;
 
-  KOKKOS_INLINE_FUNCTION
-  ViewTracker() : m_tracker() {}
+  KOKKOS_DEFAULTED_FUNCTION
+  ViewTracker() = default;
 
+  //! Copy constructor.
   KOKKOS_INLINE_FUNCTION
   ViewTracker(const ViewTracker& vt) noexcept
       : m_tracker(vt.m_tracker, view_traits::is_managed) {}
@@ -73,6 +74,7 @@ struct ViewTracker {
     KOKKOS_IF_ON_DEVICE((m_tracker.assign_force_disable(vt.m_track.m_tracker);))
   }
 
+  //! Copy assignment.
   KOKKOS_INLINE_FUNCTION ViewTracker& operator=(
       const ViewTracker& rhs) noexcept {
     if (this == &rhs) return *this;
@@ -89,6 +91,14 @@ struct ViewTracker {
   KOKKOS_INLINE_FUNCTION
   explicit ViewTracker(const track_type& tt) noexcept
       : m_tracker(tt, view_traits::is_managed) {}
+
+  //! Move constructor.
+  KOKKOS_DEFAULTED_FUNCTION
+  ViewTracker(ViewTracker&&) = default;
+
+  //! Move assignment.
+  KOKKOS_DEFAULTED_FUNCTION
+  ViewTracker& operator=(ViewTracker&& other) = default;
 };
 
 }  // namespace Impl

core/unit_test/CMakeLists.txt

@@ -240,6 +240,7 @@ foreach(Tag Threads;Serial;OpenMP;Cuda;HPX;OpenMPTarget;OpenACC;HIP;SYCL)
       ViewMapping_b
       ViewMapping_subview
       ViewMemoryAccessViolation
+      ViewMove
       ViewOfClass
       ViewResize
       WorkGraph

core/unit_test/TestViewMove.hpp

@@ -0,0 +1,59 @@
+//@HEADER
+// ************************************************************************
+//
+//                        Kokkos v. 4.0
+//       Copyright (2022) National Technology & Engineering
+//               Solutions of Sandia, LLC (NTESS).
+//
+// Under the terms of Contract DE-NA0003525 with NTESS,
+// the U.S. Government retains certain rights in this software.
+//
+// Part of Kokkos, under the Apache License v2.0 with LLVM Exceptions.
+// See https://kokkos.org/LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//@HEADER
+#ifndef TESTVIEWMOVE_HPP_
+#define TESTVIEWMOVE_HPP_
+
+#include <gtest/gtest.h>
+#include <Kokkos_Core.hpp>
+
+namespace Test {
+
+template <typename view_t>
+struct TestViewMove {
+  template <typename T, typename = std::enable_if_t<
+                            std::is_same_v<std::decay_t<T>, view_t>>>
+  TestViewMove(T&& view_) : view(std::forward<T>(view_)) {}
+
+  view_t view;
+};
+
+/**
+ * @test Ensure that @ref Kokkos::View and its members have proper move
+ *       semantics.
+ */
+TEST(TEST_CATEGORY, view_move) {
+  using execution_space = TEST_EXECSPACE;
+  using view_t          = Kokkos::View<double*, execution_space>;
+  using tester_t        = TestViewMove<view_t>;
+
+  view_t view("view move test", 5);
+
+  EXPECT_EQ(view.use_count(), 1);
+  EXPECT_TRUE(view.is_allocated());
+
+  tester_t tester{std::move(view)};
+
+  //! As the view was moved, it's left in a pristine (a.k.a. *empty*) state.
+  EXPECT_EQ(view.use_count(), 0);
+  EXPECT_FALSE(view.is_allocated());
+
+  EXPECT_EQ(tester.view.use_count(), 1);
+  EXPECT_TRUE(tester.view.is_allocated());
+}
+
+}  // namespace Test
+
+#endif  // TESTVIEWMOVE_HPP_