[do not merge] Implement P1144 trivially-relocatable for indirect and polymorphic

indirect.h

@@ -44,6 +44,16 @@ namespace xyz {
 }
 #endif  // XYZ_UNREACHABLE_DEFINED
 
+#ifndef XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+#define XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+#if defined(__cpp_impl_trivially_relocatable) && \
+    defined(__cpp_lib_trivially_relocatable)
+#define XYZ_TRIVIALLY_RELOCATABLE_IF(x) [[trivially_relocatable(x)]]
+#else
+#define XYZ_TRIVIALLY_RELOCATABLE_IF(x)
+#endif
+#endif  // XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+
 template <class T, class A>
 class indirect;
 
@@ -53,8 +63,25 @@ inline constexpr bool is_indirect_v = false;
 template <class T, class A>
 inline constexpr bool is_indirect_v<indirect<T, A>> = true;
 
+#if defined(__cpp_lib_trivially_relocatable)
+template <class A>
+inline constexpr bool indirect_allocator_pocma_models_relocatable_v =
+    std::allocator_traits<A>::is_always_equal::value ||
+    (std::allocator_traits<A>::propagate_on_container_copy_assignment::value &&
+     std::allocator_traits<A>::propagate_on_container_move_assignment::value &&
+     std::allocator_traits<A>::propagate_on_container_swap::value);
+
+template <class A>
+inline constexpr bool indirect_be_trivially_relocatable_v =
+    std::is_trivially_relocatable_v<A> &&
+    std::is_trivially_relocatable_v<
+        typename std::allocator_traits<A>::pointer> &&
+    indirect_allocator_pocma_models_relocatable_v<A>;
+#endif
+
 template <class T, class A = std::allocator<T>>
-class indirect {
+class XYZ_TRIVIALLY_RELOCATABLE_IF(
+    indirect_be_trivially_relocatable_v<A>) indirect {
   using allocator_traits = std::allocator_traits<A>;
 
  public:

indirect_test.cc

@@ -42,6 +42,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <optional>
 #endif  // XYZ_HAS_STD_OPTIONAL
 #include <tuple>
+#include <type_traits>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -54,6 +55,17 @@ using std::in_place_t;
 
 namespace {
 
+TEST(IndirectTest, TriviallyRelocatable) {
+#if defined(__cpp_impl_trivially_relocatable) && \
+    defined(__cpp_lib_trivially_relocatable)
+  static_assert(std::is_trivially_relocatable_v<xyz::indirect<int>>);
+#ifdef XYZ_HAS_STD_MEMORY_RESOURCE
+  static_assert(!std::is_trivially_relocatable_v<
+                xyz::indirect<int, std::pmr::polymorphic_allocator<int>>>);
+#endif
+#endif  // defined(__cpp_impl_trivially_relocatable) && ...
+}
+
 TEST(IndirectTest, DefaultConstructor) {
   xyz::indirect<int> i;
   EXPECT_EQ(*i, 0);

polymorphic.h

@@ -46,6 +46,16 @@ namespace xyz {
 }
 #endif  // XYZ_UNREACHABLE_DEFINED
 
+#ifndef XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+#define XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+#if defined(__cpp_impl_trivially_relocatable) && \
+    defined(__cpp_lib_trivially_relocatable)
+#define XYZ_TRIVIALLY_RELOCATABLE_IF(x) [[trivially_relocatable(x)]]
+#else
+#define XYZ_TRIVIALLY_RELOCATABLE_IF(x)
+#endif
+#endif  // XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+
 namespace detail {
 template <class T, class A>
 struct control_block {
@@ -117,8 +127,24 @@ class direct_control_block final : public control_block<T, A> {
 
 }  // namespace detail
 
+#if defined(__cpp_lib_trivially_relocatable)
+template <class A>
+inline constexpr bool polymorphic_allocator_pocma_models_relocatable_v =
+    std::allocator_traits<A>::is_always_equal::value ||
+    (std::allocator_traits<A>::propagate_on_container_copy_assignment::value &&
+     std::allocator_traits<A>::propagate_on_container_move_assignment::value &&
+     std::allocator_traits<A>::propagate_on_container_swap::value);
+
+template <class T, class A>
+inline constexpr bool polymorphic_be_trivially_relocatable_v =
+    std::is_trivially_relocatable_v<A> &&
+    std::is_trivially_relocatable_v<detail::control_block<T, A>*> &&
+    polymorphic_allocator_pocma_models_relocatable_v<A>;
+#endif
+
 template <class T, class A = std::allocator<T>>
-class polymorphic {
+class XYZ_TRIVIALLY_RELOCATABLE_IF(
+    (polymorphic_be_trivially_relocatable_v<T, A>)) polymorphic {
   using cblock_t = detail::control_block<T, A>;
   cblock_t* cb_;
 

polymorphic_cxx14.h

@@ -54,6 +54,16 @@ namespace xyz {
 }  // namespace xyz
 #endif  // XYZ_UNREACHABLE_DEFINED
 
+#ifndef XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+#define XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+#if defined(__cpp_impl_trivially_relocatable) && \
+    defined(__cpp_lib_trivially_relocatable)
+#define XYZ_TRIVIALLY_RELOCATABLE_IF(x) [[trivially_relocatable(x)]]
+#else
+#define XYZ_TRIVIALLY_RELOCATABLE_IF(x)
+#endif
+#endif  // XYZ_TRIVIALLY_RELOCATABLE_IF_DEFINED
+
 #ifndef XYZ_EMPTY_BASE_DEFINED
 #define XYZ_EMPTY_BASE_DEFINED
 // This is a helper class to allow empty base class optimization.
@@ -157,8 +167,33 @@ class direct_control_block final : public control_block<T, A> {
 
 }  // namespace detail
 
+#if defined(__cpp_lib_trivially_relocatable)
+template <class A>
+struct polymorphic_allocator_pocma_models_relocatable
+    : std::integral_constant<
+          bool,
+          std::allocator_traits<A>::is_always_equal::value ||
+              (std::allocator_traits<
+                   A>::propagate_on_container_copy_assignment::value &&
+               std::allocator_traits<
+                   A>::propagate_on_container_move_assignment::value &&
+               std::allocator_traits<A>::propagate_on_container_swap::value)> {
+};
+
+template <class T, class A>
+struct polymorphic_be_trivially_relocatable
+    : std::integral_constant<
+          bool, std::is_trivially_relocatable<A>::value &&
+                    std::is_trivially_relocatable<
+                        detail::control_block<T, A>*>::value &&
+                    polymorphic_allocator_pocma_models_relocatable<A>::value> {
+};
+#endif
+
 template <class T, class A = std::allocator<T>>
-class polymorphic : private detail::empty_base_optimization<A> {
+class XYZ_TRIVIALLY_RELOCATABLE_IF(
+    (polymorphic_be_trivially_relocatable<T, A>::value)) polymorphic
+    : private detail::empty_base_optimization<A> {
   using cblock_t = detail::control_block<T, A>;
   cblock_t* cb_;
 

polymorphic_test.cc

@@ -56,6 +56,7 @@ using std::in_place_type_t;
 #ifdef XYZ_HAS_STD_OPTIONAL
 #include <optional>
 #endif  // XYZ_HAS_STD_OPTIONAL
+#include <type_traits>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -216,6 +217,18 @@ TEST(PolymorphicTest, SwapWithNoSBOAndSBO) {
   EXPECT_EQ(b->value(), 42);
 }
 
+TEST(PolymorphicTest, TriviallyRelocatable) {
+#if defined(__cpp_impl_trivially_relocatable) && \
+    defined(__cpp_lib_trivially_relocatable)
+  static_assert(std::is_trivially_relocatable<xyz::polymorphic<int>>::value,
+                "");
+#ifdef XYZ_HAS_STD_MEMORY_RESOURCE
+  static_assert(!std::is_trivially_relocatable_v<
+                xyz::polymorphic<int, std::pmr::polymorphic_allocator<int>>>);
+#endif
+#endif  // defined(__cpp_impl_trivially_relocatable) && ...
+}
+
 TEST(PolymorphicTest, AccessDerivedObject) {
   xyz::polymorphic<Base> a(xyz::in_place_type_t<Derived>{}, 42);
   EXPECT_EQ(a->value(), 42);