Use GetArena() instead of GetOwningArena() #5.

PiperOrigin-RevId: 573864426

src/google/protobuf/arena.h

@@ -261,7 +261,7 @@ class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
   // again.
   template <typename T>
   PROTOBUF_ALWAYS_INLINE static void Destroy(T* obj) {
-    if (InternalGetOwningArena(obj) == nullptr) delete obj;
+    if (InternalGetArena(obj) == nullptr) delete obj;
   }
 
   // Allocates memory with the specific size and alignment.
@@ -389,7 +389,8 @@ class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
     // mutually exclusive fashion, we use implicit conversions to base classes
     // to force an explicit ranking for our preferences.  The lowest ranked
     // version that compiles will be accepted.
-    struct Rank1 {};
+    struct Rank2 {};
+    struct Rank1 : Rank2 {};
     struct Rank0 : Rank1 {};
 
     static Arena* GetOwningArena(const T* p) {
@@ -403,7 +404,13 @@ class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
     }
 
     template <typename U>
-    static Arena* GetOwningArena(Rank1, const U*) {
+    static auto GetOwningArena(Rank1, const U* p)
+        -> EnableIfArena<decltype(p->GetArena())> {
+      return p->GetArena();
+    }
+
+    template <typename U>
+    static Arena* GetOwningArena(Rank2, const U*) {
       return nullptr;
     }
 

src/google/protobuf/arena_unittest.cc

@@ -561,16 +561,6 @@ TEST(ArenaTest, UnsafeArenaSwap) {
   TestUtil::ExpectAllFieldsSet(*message2);
 }
 
-TEST(ArenaTest, GetOwningArena) {
-  Arena arena;
-  auto* m1 = Arena::CreateMessage<TestAllTypes>(&arena);
-  EXPECT_EQ(Arena::InternalGetOwningArena(m1), &arena);
-  EXPECT_EQ(&arena, Arena::InternalGetOwningArena(
-                        m1->mutable_repeated_foreign_message()));
-  EXPECT_EQ(&arena,
-            Arena::InternalGetOwningArena(m1->mutable_repeated_int32()));
-}
-
 TEST(ArenaTest, SwapBetweenArenasUsingReflection) {
   Arena arena1;
   TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);

src/google/protobuf/compiler/cpp/field_generators/message_field.cc

@@ -55,9 +55,9 @@ std::vector<Sub> Vars(const FieldDescriptor* field, const Options& opts,
                           ? default_ptr
                           : absl::Substitute("reinterpret_cast<const $0*>($1)",
                                              base, default_ptr)},
-      {"base_cast",
-       absl::Substitute("reinterpret_cast<$0*>",
-                        !is_foreign && !weak ? qualified_type : base)},
+      {"base_cast", !is_foreign && !weak
+                        ? ""
+                        : absl::Substitute("reinterpret_cast<$0*>", base)},
       Sub{"weak_cast",
           !weak ? "" : absl::Substitute("reinterpret_cast<$0*>", base)}
           .ConditionalFunctionCall(),
@@ -431,19 +431,15 @@ void SingularMessage::GenerateSwappingCode(io::Printer* p) const {
 }
 
 void SingularMessage::GenerateDestructorCode(io::Printer* p) const {
-  if (opts_->opensource_runtime) {
-    // TODO Remove this when we don't need to destruct default
-    // instances.  In google3 a default instance will never get deleted so we
-    // don't need to worry about that but in opensource protobuf default
-    // instances are deleted in shutdown process and we need to take special
-    // care when handling them.
-    p->Emit("if (this != internal_default_instance()) ");
-  }
   if (should_split()) {
-    p->Emit("delete $cached_split_ptr$->$name$_;\n");
-    return;
+    p->Emit(R"cc(
+      delete $cached_split_ptr$->$name$_;
+    )cc");
+  } else {
+    p->Emit(R"cc(
+      delete $field_$;
+    )cc");
   }
-  p->Emit("delete $field_$;\n");
 }
 
 using internal::cpp::HasHasbit;