From b90fa7f01ec2ae227b9675535b969cf571eea3d9 Mon Sep 17 00:00:00 2001
From: Protobuf Team Bot <protobuf-github-bot@google.com>
Date: Tue, 3 Sep 2024 13:41:47 -0700
Subject: [PATCH] Streamline creation of new elements in `RepeatedPtrField`

The logic to create new elements in `RepeatedPtrField` was spread across an inconsistent patchwork of specializations of individual `GenericTypeHandler` static functions as well as external member and non-member functions, all living in multiple sources. Now all that logic is concentrated in three `GenericTypeHandler` full class specializations.

One change that to carefully verify in postsubmit is the now-removed old workaround for an MSVC bug #254 (MSVC compatibility is not checked in presubmit).

PiperOrigin-RevId: 670689695
---
 src/google/protobuf/arena.h                   |  11 +
 src/google/protobuf/arenastring.h             |  28 +--
 src/google/protobuf/compiler/cpp/message.cc   |   6 +-
 .../protobuf/compiler/java/java_features.pb.h |   6 +-
 src/google/protobuf/compiler/plugin.pb.h      |  24 +-
 src/google/protobuf/cpp_features.pb.h         |   6 +-
 src/google/protobuf/descriptor.pb.h           | 198 +++------------
 src/google/protobuf/extension_set.cc          |  10 +-
 .../protobuf/generated_message_reflection.cc  |  24 +-
 src/google/protobuf/lazy_repeated_field.cc    |  21 +-
 src/google/protobuf/lazy_repeated_field.h     |   3 +-
 src/google/protobuf/message.cc                |  22 --
 src/google/protobuf/message_lite.cc           |  10 -
 src/google/protobuf/message_lite.h            |   5 -
 src/google/protobuf/port.h                    |   4 +
 src/google/protobuf/port_def.inc              |   4 -
 src/google/protobuf/port_undef.inc            |   1 -
 src/google/protobuf/reflection_ops.cc         |  22 +-
 src/google/protobuf/repeated_field.h          |  13 +-
 .../protobuf/repeated_field_unittest.cc       |   2 -
 src/google/protobuf/repeated_ptr_field.cc     |  19 +-
 src/google/protobuf/repeated_ptr_field.h      | 228 +++++++++---------
 22 files changed, 218 insertions(+), 449 deletions(-)

diff --git a/src/google/protobuf/arena.h b/src/google/protobuf/arena.h
index a853034140dac..6b6ff37d72148 100644
--- a/src/google/protobuf/arena.h
+++ b/src/google/protobuf/arena.h
@@ -87,6 +87,17 @@ template <typename T>
 void arena_delete_object(void* object) {
   delete reinterpret_cast<T*>(object);
 }
+
+inline bool CanUseInternalSwap(Arena* lhs, Arena* rhs) {
+  if (DebugHardenForceCopyInSwap()) {
+    // We force copy in swap when we are not using an arena.
+    // If we did with an arena we would grow arena usage too much.
+    return lhs != nullptr && lhs == rhs;
+  } else {
+    return lhs == rhs;
+  }
+}
+
 }  // namespace internal
 
 // ArenaOptions provides optional additional parameters to arena construction
diff --git a/src/google/protobuf/arenastring.h b/src/google/protobuf/arenastring.h
index 0c1c4e271dd7a..1267b4cfb8050 100644
--- a/src/google/protobuf/arenastring.h
+++ b/src/google/protobuf/arenastring.h
@@ -503,22 +503,22 @@ inline PROTOBUF_NDEBUG_INLINE void ArenaStringPtr::InternalSwap(
   // Silence unused variable warnings in release buildls.
   (void)arena;
   std::swap(lhs->tagged_ptr_, rhs->tagged_ptr_);
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-  for (auto* p : {lhs, rhs}) {
-    if (p->IsDefault()) continue;
-    std::string* old_value = p->tagged_ptr_.Get();
-    std::string* new_value =
-        p->IsFixedSizeArena()
-            ? Arena::Create<std::string>(arena, *old_value)
-            : Arena::Create<std::string>(arena, std::move(*old_value));
-    if (arena == nullptr) {
-      delete old_value;
-      p->tagged_ptr_.SetAllocated(new_value);
-    } else {
-      p->tagged_ptr_.SetMutableArena(new_value);
+  if (internal::DebugHardenForceCopyInSwap()) {
+    for (auto* p : {lhs, rhs}) {
+      if (p->IsDefault()) continue;
+      std::string* old_value = p->tagged_ptr_.Get();
+      std::string* new_value =
+          p->IsFixedSizeArena()
+              ? Arena::Create<std::string>(arena, *old_value)
+              : Arena::Create<std::string>(arena, std::move(*old_value));
+      if (arena == nullptr) {
+        delete old_value;
+        p->tagged_ptr_.SetAllocated(new_value);
+      } else {
+        p->tagged_ptr_.SetMutableArena(new_value);
+      }
     }
   }
-#endif  // PROTOBUF_FORCE_COPY_IN_SWAP
 }
 
 inline void ArenaStringPtr::ClearNonDefaultToEmpty() {
diff --git a/src/google/protobuf/compiler/cpp/message.cc b/src/google/protobuf/compiler/cpp/message.cc
index 0901ac55b9ccf..547b5a6154266 100644
--- a/src/google/protobuf/compiler/cpp/message.cc
+++ b/src/google/protobuf/compiler/cpp/message.cc
@@ -2126,11 +2126,7 @@ void MessageGenerator::GenerateClassDefinition(io::Printer* p) {
           friend void swap($classname$& a, $classname$& b) { a.Swap(&b); }
           inline void Swap($classname$* other) {
             if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-            if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-            if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+            if ($pbi$::CanUseInternalSwap(GetArena(), other->GetArena())) {
               InternalSwap(other);
             } else {
               $pbi$::GenericSwap(this, other);
diff --git a/src/google/protobuf/compiler/java/java_features.pb.h b/src/google/protobuf/compiler/java/java_features.pb.h
index 707a65f692b44..87d53bca49a56 100644
--- a/src/google/protobuf/compiler/java/java_features.pb.h
+++ b/src/google/protobuf/compiler/java/java_features.pb.h
@@ -159,11 +159,7 @@ class PROTOC_EXPORT JavaFeatures final
   friend void swap(JavaFeatures& a, JavaFeatures& b) { a.Swap(&b); }
   inline void Swap(JavaFeatures* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
diff --git a/src/google/protobuf/compiler/plugin.pb.h b/src/google/protobuf/compiler/plugin.pb.h
index b6ab93d9bbe77..f47ee739a66b3 100644
--- a/src/google/protobuf/compiler/plugin.pb.h
+++ b/src/google/protobuf/compiler/plugin.pb.h
@@ -176,11 +176,7 @@ class PROTOC_EXPORT Version final
   friend void swap(Version& a, Version& b) { a.Swap(&b); }
   inline void Swap(Version* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -415,11 +411,7 @@ class PROTOC_EXPORT CodeGeneratorResponse_File final
   friend void swap(CodeGeneratorResponse_File& a, CodeGeneratorResponse_File& b) { a.Swap(&b); }
   inline void Swap(CodeGeneratorResponse_File* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -670,11 +662,7 @@ class PROTOC_EXPORT CodeGeneratorResponse final
   friend void swap(CodeGeneratorResponse& a, CodeGeneratorResponse& b) { a.Swap(&b); }
   inline void Swap(CodeGeneratorResponse* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -949,11 +937,7 @@ class PROTOC_EXPORT CodeGeneratorRequest final
   friend void swap(CodeGeneratorRequest& a, CodeGeneratorRequest& b) { a.Swap(&b); }
   inline void Swap(CodeGeneratorRequest* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
diff --git a/src/google/protobuf/cpp_features.pb.h b/src/google/protobuf/cpp_features.pb.h
index de4cc6be4772c..86812176c2abf 100644
--- a/src/google/protobuf/cpp_features.pb.h
+++ b/src/google/protobuf/cpp_features.pb.h
@@ -160,11 +160,7 @@ class PROTOBUF_EXPORT CppFeatures final
   friend void swap(CppFeatures& a, CppFeatures& b) { a.Swap(&b); }
   inline void Swap(CppFeatures* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index 723f20db29d4f..a33bf456b7ce8 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -762,11 +762,7 @@ class PROTOBUF_EXPORT UninterpretedOption_NamePart final
   friend void swap(UninterpretedOption_NamePart& a, UninterpretedOption_NamePart& b) { a.Swap(&b); }
   inline void Swap(UninterpretedOption_NamePart* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -980,11 +976,7 @@ class PROTOBUF_EXPORT SourceCodeInfo_Location final
   friend void swap(SourceCodeInfo_Location& a, SourceCodeInfo_Location& b) { a.Swap(&b); }
   inline void Swap(SourceCodeInfo_Location* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -1265,11 +1257,7 @@ class PROTOBUF_EXPORT GeneratedCodeInfo_Annotation final
   friend void swap(GeneratedCodeInfo_Annotation& a, GeneratedCodeInfo_Annotation& b) { a.Swap(&b); }
   inline void Swap(GeneratedCodeInfo_Annotation* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -1545,11 +1533,7 @@ class PROTOBUF_EXPORT FieldOptions_FeatureSupport final
   friend void swap(FieldOptions_FeatureSupport& a, FieldOptions_FeatureSupport& b) { a.Swap(&b); }
   inline void Swap(FieldOptions_FeatureSupport* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -1784,11 +1768,7 @@ class PROTOBUF_EXPORT FieldOptions_EditionDefault final
   friend void swap(FieldOptions_EditionDefault& a, FieldOptions_EditionDefault& b) { a.Swap(&b); }
   inline void Swap(FieldOptions_EditionDefault* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -1997,11 +1977,7 @@ class PROTOBUF_EXPORT FeatureSet final
   friend void swap(FeatureSet& a, FeatureSet& b) { a.Swap(&b); }
   inline void Swap(FeatureSet* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -2562,11 +2538,7 @@ class PROTOBUF_EXPORT ExtensionRangeOptions_Declaration final
   friend void swap(ExtensionRangeOptions_Declaration& a, ExtensionRangeOptions_Declaration& b) { a.Swap(&b); }
   inline void Swap(ExtensionRangeOptions_Declaration* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -2820,11 +2792,7 @@ class PROTOBUF_EXPORT EnumDescriptorProto_EnumReservedRange final
   friend void swap(EnumDescriptorProto_EnumReservedRange& a, EnumDescriptorProto_EnumReservedRange& b) { a.Swap(&b); }
   inline void Swap(EnumDescriptorProto_EnumReservedRange* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -3027,11 +2995,7 @@ class PROTOBUF_EXPORT DescriptorProto_ReservedRange final
   friend void swap(DescriptorProto_ReservedRange& a, DescriptorProto_ReservedRange& b) { a.Swap(&b); }
   inline void Swap(DescriptorProto_ReservedRange* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -3234,11 +3198,7 @@ class PROTOBUF_EXPORT UninterpretedOption final
   friend void swap(UninterpretedOption& a, UninterpretedOption& b) { a.Swap(&b); }
   inline void Swap(UninterpretedOption* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -3536,11 +3496,7 @@ class PROTOBUF_EXPORT SourceCodeInfo final
   friend void swap(SourceCodeInfo& a, SourceCodeInfo& b) { a.Swap(&b); }
   inline void Swap(SourceCodeInfo* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -3736,11 +3692,7 @@ class PROTOBUF_EXPORT GeneratedCodeInfo final
   friend void swap(GeneratedCodeInfo& a, GeneratedCodeInfo& b) { a.Swap(&b); }
   inline void Swap(GeneratedCodeInfo* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -3936,11 +3888,7 @@ class PROTOBUF_EXPORT FeatureSetDefaults_FeatureSetEditionDefault final
   friend void swap(FeatureSetDefaults_FeatureSetEditionDefault& a, FeatureSetDefaults_FeatureSetEditionDefault& b) { a.Swap(&b); }
   inline void Swap(FeatureSetDefaults_FeatureSetEditionDefault* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -4169,11 +4117,7 @@ class PROTOBUF_EXPORT ServiceOptions final
   friend void swap(ServiceOptions& a, ServiceOptions& b) { a.Swap(&b); }
   inline void Swap(ServiceOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -4584,11 +4528,7 @@ class PROTOBUF_EXPORT OneofOptions final
   friend void swap(OneofOptions& a, OneofOptions& b) { a.Swap(&b); }
   inline void Swap(OneofOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -4986,11 +4926,7 @@ class PROTOBUF_EXPORT MethodOptions final
   friend void swap(MethodOptions& a, MethodOptions& b) { a.Swap(&b); }
   inline void Swap(MethodOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -5434,11 +5370,7 @@ class PROTOBUF_EXPORT MessageOptions final
   friend void swap(MessageOptions& a, MessageOptions& b) { a.Swap(&b); }
   inline void Swap(MessageOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -5901,11 +5833,7 @@ class PROTOBUF_EXPORT FileOptions final
   friend void swap(FileOptions& a, FileOptions& b) { a.Swap(&b); }
   inline void Swap(FileOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -6630,11 +6558,7 @@ class PROTOBUF_EXPORT FieldOptions final
   friend void swap(FieldOptions& a, FieldOptions& b) { a.Swap(&b); }
   inline void Swap(FieldOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -7295,11 +7219,7 @@ class PROTOBUF_EXPORT FeatureSetDefaults final
   friend void swap(FeatureSetDefaults& a, FeatureSetDefaults& b) { a.Swap(&b); }
   inline void Swap(FeatureSetDefaults* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -7527,11 +7447,7 @@ class PROTOBUF_EXPORT ExtensionRangeOptions final
   friend void swap(ExtensionRangeOptions& a, ExtensionRangeOptions& b) { a.Swap(&b); }
   inline void Swap(ExtensionRangeOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -7981,11 +7897,7 @@ class PROTOBUF_EXPORT EnumValueOptions final
   friend void swap(EnumValueOptions& a, EnumValueOptions& b) { a.Swap(&b); }
   inline void Swap(EnumValueOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -8426,11 +8338,7 @@ class PROTOBUF_EXPORT EnumOptions final
   friend void swap(EnumOptions& a, EnumOptions& b) { a.Swap(&b); }
   inline void Swap(EnumOptions* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -8867,11 +8775,7 @@ class PROTOBUF_EXPORT OneofDescriptorProto final
   friend void swap(OneofDescriptorProto& a, OneofDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(OneofDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -9089,11 +8993,7 @@ class PROTOBUF_EXPORT MethodDescriptorProto final
   friend void swap(MethodDescriptorProto& a, MethodDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(MethodDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -9375,11 +9275,7 @@ class PROTOBUF_EXPORT FieldDescriptorProto final
   friend void swap(FieldDescriptorProto& a, FieldDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(FieldDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -9793,11 +9689,7 @@ class PROTOBUF_EXPORT EnumValueDescriptorProto final
   friend void swap(EnumValueDescriptorProto& a, EnumValueDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(EnumValueDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -10028,11 +9920,7 @@ class PROTOBUF_EXPORT DescriptorProto_ExtensionRange final
   friend void swap(DescriptorProto_ExtensionRange& a, DescriptorProto_ExtensionRange& b) { a.Swap(&b); }
   inline void Swap(DescriptorProto_ExtensionRange* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -10257,11 +10145,7 @@ class PROTOBUF_EXPORT ServiceDescriptorProto final
   friend void swap(ServiceDescriptorProto& a, ServiceDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(ServiceDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -10498,11 +10382,7 @@ class PROTOBUF_EXPORT EnumDescriptorProto final
   friend void swap(EnumDescriptorProto& a, EnumDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(EnumDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -10783,11 +10663,7 @@ class PROTOBUF_EXPORT DescriptorProto final
   friend void swap(DescriptorProto& a, DescriptorProto& b) { a.Swap(&b); }
   inline void Swap(DescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -11164,11 +11040,7 @@ class PROTOBUF_EXPORT FileDescriptorProto final
   friend void swap(FileDescriptorProto& a, FileDescriptorProto& b) { a.Swap(&b); }
   inline void Swap(FileDescriptorProto* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
@@ -11594,11 +11466,7 @@ class PROTOBUF_EXPORT FileDescriptorSet final
   friend void swap(FileDescriptorSet& a, FileDescriptorSet& b) { a.Swap(&b); }
   inline void Swap(FileDescriptorSet* other) {
     if (other == this) return;
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena()) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena()) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (::google::protobuf::internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       ::google::protobuf::internal::GenericSwap(this, other);
diff --git a/src/google/protobuf/extension_set.cc b/src/google/protobuf/extension_set.cc
index a673e0bf4e8e4..3665660e4e2a8 100644
--- a/src/google/protobuf/extension_set.cc
+++ b/src/google/protobuf/extension_set.cc
@@ -811,9 +811,7 @@ MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
     ABSL_DCHECK_TYPE(*extension, REPEATED_FIELD, MESSAGE);
   }
 
-  return reinterpret_cast<internal::RepeatedPtrFieldBase*>(
-             extension->ptr.repeated_message_value)
-      ->AddMessage(&prototype);
+  return extension->ptr.repeated_message_value->AddFromPrototype(&prototype);
 }
 
 // Defined in extension_set_heavy.cc.
@@ -1097,11 +1095,7 @@ void ExtensionSet::InternalExtensionMergeFrom(const MessageLite* extendee,
 }
 
 void ExtensionSet::Swap(const MessageLite* extendee, ExtensionSet* other) {
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-  if (arena_ != nullptr && arena_ == other->arena_) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-  if (arena_ == other->arena_) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+  if (internal::CanUseInternalSwap(arena_, other->arena_)) {
     InternalSwap(other);
   } else {
     // TODO: We maybe able to optimize a case where we are
diff --git a/src/google/protobuf/generated_message_reflection.cc b/src/google/protobuf/generated_message_reflection.cc
index 5c7a86d4ac92f..c657c189f6eb9 100644
--- a/src/google/protobuf/generated_message_reflection.cc
+++ b/src/google/protobuf/generated_message_reflection.cc
@@ -779,11 +779,7 @@ void SwapFieldHelper::SwapMessage(const Reflection* r, Message* lhs,
 
   if (*lhs_sub == *rhs_sub) return;
 
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-  if (lhs_arena != nullptr && lhs_arena == rhs_arena) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-  if (lhs_arena == rhs_arena) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+  if (internal::CanUseInternalSwap(lhs_arena, rhs_arena)) {
     std::swap(*lhs_sub, *rhs_sub);
     return;
   }
@@ -1084,11 +1080,7 @@ void Reflection::Swap(Message* lhs, Message* rhs) const {
 
   // Check that both messages are in the same arena (or both on the heap). We
   // need to copy all data if not, due to ownership semantics.
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-  if (lhs_arena == nullptr || lhs_arena != rhs_arena) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-  if (lhs_arena != rhs_arena) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+  if (!internal::CanUseInternalSwap(lhs_arena, rhs_arena)) {
     // One of the two is guaranteed to have an arena.  Switch things around
     // to guarantee that lhs has an arena.
     Arena* arena = lhs_arena;
@@ -1100,12 +1092,12 @@ void Reflection::Swap(Message* lhs, Message* rhs) const {
     Message* temp = lhs->New(arena);
     temp->MergeFrom(*rhs);
     rhs->CopyFrom(*lhs);
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    lhs->CopyFrom(*temp);
-    if (arena == nullptr) delete temp;
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    Swap(lhs, temp);
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    if (internal::DebugHardenForceCopyInSwap()) {
+      lhs->CopyFrom(*temp);
+      if (arena == nullptr) delete temp;
+    } else {
+      Swap(lhs, temp);
+    }
     return;
   }
 
diff --git a/src/google/protobuf/lazy_repeated_field.cc b/src/google/protobuf/lazy_repeated_field.cc
index e3b83ad04dcb5..4ea2a504cf549 100644
--- a/src/google/protobuf/lazy_repeated_field.cc
+++ b/src/google/protobuf/lazy_repeated_field.cc
@@ -27,11 +27,12 @@
 #include "google/protobuf/io/zero_copy_stream_impl_lite.h"
 #include "google/protobuf/message_lite.h"
 #include "google/protobuf/parse_context.h"
+#include "google/protobuf/port.h"
+#include "google/protobuf/repeated_ptr_field.h"
 
 // Must be included last.
 // clang-format off
 #include "google/protobuf/port_def.inc"
-#include "google/protobuf/repeated_ptr_field.h"
 // clang-format on
 
 namespace google {
@@ -222,13 +223,13 @@ void LazyRepeatedPtrField::Swap(LazyRepeatedPtrField* lhs, Arena* lhs_arena,
     if (cleanup_old) old_unparsed.Destroy();
   };
   static auto take_ownership = [](LazyRepeatedPtrField* f, Arena* arena) {
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    reallocate(f, arena, true);
-#else
-    arena->Own(reinterpret_cast<RepeatedPtrField<MessageLite>*>(
-        f->raw_.load(std::memory_order_relaxed).mutable_value()));
-    f->unparsed_.TransferHeapOwnershipToArena(arena);
-#endif
+    if (internal::DebugHardenForceCopyInSwap()) {
+      reallocate(f, arena, true);
+    } else {
+      arena->Own(reinterpret_cast<RepeatedPtrField<MessageLite>*>(
+          f->raw_.load(std::memory_order_relaxed).mutable_value()));
+      f->unparsed_.TransferHeapOwnershipToArena(arena);
+    }
   };
 
   using std::swap;  // Enable ADL with fallback
@@ -239,12 +240,10 @@ void LazyRepeatedPtrField::Swap(LazyRepeatedPtrField* lhs, Arena* lhs_arena,
   // arena is actually on the opposite message.  Now we straighten out our
   // ownership by forcing reallocations/ownership changes as needed.
   if (lhs_arena == rhs_arena) {
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (lhs_arena == nullptr) {
+    if (internal::DebugHardenForceCopyInSwap() && lhs_arena == nullptr) {
       reallocate(lhs, lhs_arena, true);
       reallocate(rhs, rhs_arena, true);
     }
-#endif
   } else {
     if (lhs_arena == nullptr) {
       take_ownership(rhs, rhs_arena);
diff --git a/src/google/protobuf/lazy_repeated_field.h b/src/google/protobuf/lazy_repeated_field.h
index ab573e58c0810..40ec02e771aa4 100644
--- a/src/google/protobuf/lazy_repeated_field.h
+++ b/src/google/protobuf/lazy_repeated_field.h
@@ -328,7 +328,8 @@ class LazyRepeatedPtrField {
     const char* ptr2 = ptr;
     TagType next_tag;
     do {
-      MessageLite* submsg = value->AddMessage(prototype);
+      MessageLite* submsg =
+          value->AddFromPrototype<GenericTypeHandler<MessageLite>>(prototype);
       // ptr2 points to the start of the element's encoded length.
       ptr = ctx->ParseMessage(submsg, ptr2);
       if (PROTOBUF_PREDICT_FALSE(ptr == nullptr)) return nullptr;
diff --git a/src/google/protobuf/message.cc b/src/google/protobuf/message.cc
index f60818f424b11..40afaa6e63c1d 100644
--- a/src/google/protobuf/message.cc
+++ b/src/google/protobuf/message.cc
@@ -495,28 +495,6 @@ const internal::RepeatedFieldAccessor* Reflection::RepeatedFieldAccessor(
 }
 
 namespace internal {
-template <>
-#if defined(_MSC_VER) && (_MSC_VER >= 1800)
-// Note: force noinline to workaround MSVC compiler bug with /Zc:inline, issue
-// #240
-PROTOBUF_NOINLINE
-#endif
-    Message*
-    GenericTypeHandler<Message>::NewFromPrototype(const Message* prototype,
-                                                  Arena* arena) {
-  return prototype->New(arena);
-}
-template <>
-#if defined(_MSC_VER) && (_MSC_VER >= 1800)
-// Note: force noinline to workaround MSVC compiler bug with /Zc:inline, issue
-// #240
-PROTOBUF_NOINLINE
-#endif
-    Arena*
-    GenericTypeHandler<Message>::GetArena(Message* value) {
-  return value->GetArena();
-}
-
 template void InternalMetadata::DoClear<UnknownFieldSet>();
 template void InternalMetadata::DoMergeFrom<UnknownFieldSet>(
     const UnknownFieldSet& other);
diff --git a/src/google/protobuf/message_lite.cc b/src/google/protobuf/message_lite.cc
index 9b3debf11e850..acc9859130930 100644
--- a/src/google/protobuf/message_lite.cc
+++ b/src/google/protobuf/message_lite.cc
@@ -703,16 +703,6 @@ absl::Cord MessageLite::SerializePartialAsCord() const {
 
 namespace internal {
 
-MessageLite* NewFromPrototypeHelper(const MessageLite* prototype,
-                                    Arena* arena) {
-  return prototype->New(arena);
-}
-template <>
-void GenericTypeHandler<MessageLite>::Merge(const MessageLite& from,
-                                            MessageLite* to) {
-  to->CheckTypeAndMergeFrom(from);
-}
-
 // Non-inline variants of std::string specializations for
 // various InternalMetadata routines.
 template <>
diff --git a/src/google/protobuf/message_lite.h b/src/google/protobuf/message_lite.h
index c3ae2039b3d63..571e2f535bd9f 100644
--- a/src/google/protobuf/message_lite.h
+++ b/src/google/protobuf/message_lite.h
@@ -225,9 +225,6 @@ class WireFormatLite;
 class WeakFieldMap;
 class RustMapHelper;
 
-template <typename Type>
-class GenericTypeHandler;  // defined in repeated_field.h
-
 // We compute sizes as size_t but cache them as int.  This function converts a
 // computed size to a cached size.  Since we don't proceed with serialization
 // if the total size was > INT_MAX, it is not important what this function
@@ -963,8 +960,6 @@ class PROTOBUF_EXPORT MessageLite {
 
   template <typename Type>
   friend class Arena::InternalHelper;
-  template <typename Type>
-  friend class internal::GenericTypeHandler;
 
   friend auto internal::GetClassData(const MessageLite& msg);
 
diff --git a/src/google/protobuf/port.h b/src/google/protobuf/port.h
index 9cfc2806e8802..a011b7383ff82 100644
--- a/src/google/protobuf/port.h
+++ b/src/google/protobuf/port.h
@@ -276,6 +276,10 @@ constexpr bool DebugHardenForceCopyInRelease() {
   return false;
 }
 
+constexpr bool DebugHardenForceCopyInSwap() {
+  return false;
+}
+
 // Returns true if pointers are 8B aligned, leaving least significant 3 bits
 // available.
 inline constexpr bool PtrIsAtLeast8BAligned() { return alignof(void*) >= 8; }
diff --git a/src/google/protobuf/port_def.inc b/src/google/protobuf/port_def.inc
index 78ba5d5e51d23..eb0e0f7b077be 100644
--- a/src/google/protobuf/port_def.inc
+++ b/src/google/protobuf/port_def.inc
@@ -398,10 +398,6 @@ static_assert(PROTOBUF_ABSL_MIN(20230125, 3),
 #define PROTOBUF_RESTRICT
 #endif
 
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-#error PROTOBUF_FORCE_COPY_IN_SWAP was previously defined
-#endif
-
 #ifdef PROTOBUF_FORCE_COPY_IN_MOVE
 #error PROTOBUF_FORCE_COPY_IN_MOVE was previously defined
 #endif
diff --git a/src/google/protobuf/port_undef.inc b/src/google/protobuf/port_undef.inc
index 381e85ed3c923..8ed957d5857dc 100644
--- a/src/google/protobuf/port_undef.inc
+++ b/src/google/protobuf/port_undef.inc
@@ -41,7 +41,6 @@
 #undef PROTOC_EXPORT
 #undef PROTOBUF_NODISCARD
 #undef PROTOBUF_RESTRICT
-#undef PROTOBUF_FORCE_COPY_IN_SWAP
 #undef PROTOBUF_FORCE_COPY_IN_MOVE
 #undef PROTOBUF_FUZZ_MESSAGE_SPACE_USED_LONG
 #undef PROTOBUF_FORCE_COPY_DEFAULT_STRING
diff --git a/src/google/protobuf/reflection_ops.cc b/src/google/protobuf/reflection_ops.cc
index 3b77cf41e0ec9..6d6811becf5c5 100644
--- a/src/google/protobuf/reflection_ops.cc
+++ b/src/google/protobuf/reflection_ops.cc
@@ -419,10 +419,10 @@ void ReflectionOps::FindInitializationErrors(const Message& message,
 }
 
 void GenericSwap(Message* lhs, Message* rhs) {
-#ifndef PROTOBUF_FORCE_COPY_IN_SWAP
-  ABSL_DCHECK(lhs->GetArena() != rhs->GetArena());
-  ABSL_DCHECK(lhs->GetArena() != nullptr || rhs->GetArena() != nullptr);
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+  if (!internal::DebugHardenForceCopyInSwap()) {
+    ABSL_DCHECK(lhs->GetArena() != rhs->GetArena());
+    ABSL_DCHECK(lhs->GetArena() != nullptr || rhs->GetArena() != nullptr);
+  }
   // At least one of these must have an arena, so make `rhs` point to it.
   Arena* arena = rhs->GetArena();
   if (arena == nullptr) {
@@ -436,13 +436,13 @@ void GenericSwap(Message* lhs, Message* rhs) {
   tmp->CheckTypeAndMergeFrom(*lhs);
   lhs->Clear();
   lhs->CheckTypeAndMergeFrom(*rhs);
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-  rhs->Clear();
-  rhs->CheckTypeAndMergeFrom(*tmp);
-  if (arena == nullptr) delete tmp;
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-  rhs->GetReflection()->Swap(tmp, rhs);
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+  if (internal::DebugHardenForceCopyInSwap()) {
+    rhs->Clear();
+    rhs->CheckTypeAndMergeFrom(*tmp);
+    if (arena == nullptr) delete tmp;
+  } else {
+    rhs->GetReflection()->Swap(tmp, rhs);
+  }
 }
 
 }  // namespace internal
diff --git a/src/google/protobuf/repeated_field.h b/src/google/protobuf/repeated_field.h
index 5d13a3f676cdc..f885f49d594bf 100644
--- a/src/google/protobuf/repeated_field.h
+++ b/src/google/protobuf/repeated_field.h
@@ -28,7 +28,6 @@
 #include <iterator>
 #include <limits>
 #include <memory>
-#include <string>
 #include <type_traits>
 #include <utility>
 
@@ -36,7 +35,6 @@
 #include "absl/base/dynamic_annotations.h"
 #include "absl/base/optimization.h"
 #include "absl/log/absl_check.h"
-#include "absl/log/absl_log.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/cord.h"
 #include "google/protobuf/arena.h"
@@ -46,7 +44,6 @@
 #include "google/protobuf/port.h"
 #include "google/protobuf/repeated_ptr_field.h"
 
-
 // Must be included last.
 #include "google/protobuf/port_def.inc"
 
@@ -79,7 +76,11 @@ constexpr int RepeatedFieldLowerClampLimit() {
 // overflows when multiplied by 2 (which is undefined behavior). Sizes above
 // this will clamp to the maximum int value instead of following exponential
 // growth when growing a repeated field.
+#if defined(__cpp_inline_variables)
+inline constexpr int kRepeatedFieldUpperClampLimit =
+#else
 constexpr int kRepeatedFieldUpperClampLimit =
+#endif
     (std::numeric_limits<int>::max() / 2) + 1;
 
 template <typename Element>
@@ -1074,11 +1075,7 @@ void RepeatedField<Element>::Swap(RepeatedField* other) {
   if (this == other) return;
   Arena* arena = GetArena();
   Arena* other_arena = other->GetArena();
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-  if (arena != nullptr && arena == other_arena) {
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-  if (arena == other_arena) {
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+  if (internal::CanUseInternalSwap(arena, other_arena)) {
     InternalSwap(other);
   } else {
     RepeatedField<Element> temp(other_arena);
diff --git a/src/google/protobuf/repeated_field_unittest.cc b/src/google/protobuf/repeated_field_unittest.cc
index 551b135811f74..e7b4e4b9318e7 100644
--- a/src/google/protobuf/repeated_field_unittest.cc
+++ b/src/google/protobuf/repeated_field_unittest.cc
@@ -19,7 +19,6 @@
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
-#include <functional>
 #include <iterator>
 #include <limits>
 #include <list>
@@ -34,7 +33,6 @@
 #include <gtest/gtest.h>
 #include "absl/log/absl_check.h"
 #include "absl/numeric/bits.h"
-#include "absl/random/random.h"
 #include "absl/strings/cord.h"
 #include "absl/strings/str_cat.h"
 #include "absl/types/span.h"
diff --git a/src/google/protobuf/repeated_ptr_field.cc b/src/google/protobuf/repeated_ptr_field.cc
index 891439c14d257..6c95d427d502f 100644
--- a/src/google/protobuf/repeated_ptr_field.cc
+++ b/src/google/protobuf/repeated_ptr_field.cc
@@ -16,9 +16,9 @@
 #include <cstdint>
 #include <cstring>
 #include <limits>
+#include <new>
 #include <string>
 
-#include "absl/base/prefetch.h"
 #include "absl/log/absl_check.h"
 #include "google/protobuf/arena.h"
 #include "google/protobuf/message_lite.h"
@@ -93,14 +93,6 @@ void RepeatedPtrFieldBase::DestroyProtos() {
   tagged_rep_or_elem_ = nullptr;
 }
 
-void* RepeatedPtrFieldBase::AddMessageLite(ElementFactory factory) {
-  return AddInternal(factory);
-}
-
-void* RepeatedPtrFieldBase::AddString() {
-  return AddInternal([](Arena* arena) { return NewStringElement(arena); });
-}
-
 void RepeatedPtrFieldBase::CloseGap(int start, int num) {
   if (using_sso()) {
     if (start == 0 && num == 1) {
@@ -116,11 +108,6 @@ void RepeatedPtrFieldBase::CloseGap(int start, int num) {
   ExchangeCurrentSize(current_size_ - num);
 }
 
-MessageLite* RepeatedPtrFieldBase::AddMessage(const MessageLite* prototype) {
-  return static_cast<MessageLite*>(
-      AddInternal([prototype](Arena* a) { return prototype->New(a); }));
-}
-
 void InternalOutOfLineDeleteMessageLite(MessageLite* message) {
   delete message;
 }
@@ -223,10 +210,6 @@ void RepeatedPtrFieldBase::MergeFrom<MessageLite>(
   }
 }
 
-void* NewStringElement(Arena* arena) {
-  return Arena::Create<std::string>(arena);
-}
-
 }  // namespace internal
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/repeated_ptr_field.h b/src/google/protobuf/repeated_ptr_field.h
index 9659da94e0ef0..b2178c6bf1f3f 100644
--- a/src/google/protobuf/repeated_ptr_field.h
+++ b/src/google/protobuf/repeated_ptr_field.h
@@ -26,8 +26,8 @@
 #include <cstdint>
 #include <iterator>
 #include <limits>
+#include <new>
 #include <string>
-#include <tuple>
 #include <type_traits>
 #include <utility>
 
@@ -40,7 +40,6 @@
 #include "google/protobuf/message_lite.h"
 #include "google/protobuf/port.h"
 
-
 // Must be included last.
 #include "google/protobuf/port_def.inc"
 
@@ -92,9 +91,13 @@ struct IsMovable
 // Do not use this struct - it exists for internal use only.
 template <typename T>
 struct ArenaOffsetHelper {
-  constexpr static size_t value = offsetof(T, arena_);
+  static constexpr size_t value = offsetof(T, arena_);
 };
 
+// Defined further below.
+template <typename Type>
+class GenericTypeHandler;
+
 // This is the common base class for RepeatedPtrFields.  It deals only in void*
 // pointers.  Users should not use this interface directly.
 //
@@ -102,11 +105,17 @@ struct ArenaOffsetHelper {
 // but may have a template argument called TypeHandler.  Its signature is:
 //   class TypeHandler {
 //    public:
-//     typedef MyType Type;
-//     static Type* New();
-//     static Type* NewFromPrototype(const Type* prototype,
-//                                       Arena* arena);
-//     static void Delete(Type*);
+//     using Type = MyType;
+//     using Movable = ...;
+//
+//     static ElementFactory GetNewFunc();
+//     static ElementFactory GetNewFromPrototypeFunc(const Type* prototype);
+//     static void GetArena(Type* value);
+//
+//     static Type* New(Arena* arena);
+//     static Type* New(Arena* arena, Type&& value);
+//     static Type* NewFromPrototype(const Type* prototype, Arena* arena);
+//     static void Delete(Type*, Arena* arena);
 //     static void Clear(Type*);
 //     static void Merge(const Type& from, Type* to);
 //
@@ -114,20 +123,18 @@ struct ArenaOffsetHelper {
 //     static int SpaceUsedLong(const Type&);
 //   };
 class PROTOBUF_EXPORT RepeatedPtrFieldBase {
-  template <typename Handler>
-  using Value = typename Handler::Type;
+  template <typename TypeHandler>
+  using Value = typename TypeHandler::Type;
 
   static constexpr int kSSOCapacity = 1;
 
-  using ElementFactory = void* (*)(Arena*);
-
  protected:
-  // We use the same Handler for all Message types to deduplicate generated
+  // We use the same TypeHandler for all Message types to deduplicate generated
   // code.
-  template <typename Handler>
+  template <typename TypeHandler>
   using CommonHandler = typename std::conditional<
-      std::is_base_of<MessageLite, Value<Handler>>::value,
-      internal::GenericTypeHandler<MessageLite>, Handler>::type;
+      std::is_base_of<MessageLite, Value<TypeHandler>>::value,
+      GenericTypeHandler<MessageLite>, TypeHandler>::type;
 
   constexpr RepeatedPtrFieldBase()
       : tagged_rep_or_elem_(nullptr),
@@ -145,7 +152,7 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
 
   ~RepeatedPtrFieldBase() {
 #ifndef NDEBUG
-    // Try to trigger segfault / asan failure in non-opt builds. If arena_
+    // Try to trigger segfault / asan failure in non-opt builds if arena_
     // lifetime has ended before the destructor.
     if (arena_) (void)arena_->SpaceAllocated();
 #endif
@@ -182,14 +189,18 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
     return cast<TypeHandler>(element_at(index));
   }
 
-  template <typename Handler>
-  Value<Handler>* Add() {
-    if (std::is_same<Value<Handler>, std::string>{}) {
-      return cast<Handler>(AddString());
-    }
-    return cast<Handler>(AddMessageLite(Handler::GetNewFunc()));
+  template <typename TypeHandler>
+  Value<TypeHandler>* Add() {
+    return cast<TypeHandler>(AddInternal(TypeHandler::GetNewFunc()));
   }
 
+  template <typename TypeHandler>
+  Value<TypeHandler>* AddFromPrototype(const Value<TypeHandler>* prototype) {
+    return cast<TypeHandler>(
+        AddInternal(TypeHandler::GetNewFromPrototypeFunc(prototype)));
+  }
+
+  // TODO: Rework in terms of `AddInternal()`.
   template <
       typename TypeHandler,
       typename std::enable_if<TypeHandler::Movable::value>::type* = nullptr>
@@ -247,12 +258,6 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
     return *cast<TypeHandler>(element_at(index));
   }
 
-  // Creates and adds an element using the given prototype, without introducing
-  // a link-time dependency on the concrete message type.
-  //
-  // Pre-condition: prototype must not be nullptr.
-  MessageLite* AddMessage(const MessageLite* prototype);
-
   template <typename TypeHandler>
   void Clear() {
     const int n = current_size_;
@@ -318,9 +323,9 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
   template <typename TypeHandler>
   void CopyFrom(const RepeatedPtrFieldBase& other) {
     if (&other == this) return;
-    RepeatedPtrFieldBase::Clear<TypeHandler>();
+    Clear<TypeHandler>();
     if (other.empty()) return;
-    RepeatedPtrFieldBase::MergeFrom<typename TypeHandler::Type>(other);
+    MergeFrom<typename TypeHandler::Type>(other);
   }
 
   void CloseGap(int start, int num);
@@ -355,12 +360,7 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
 
   template <typename TypeHandler>
   PROTOBUF_NDEBUG_INLINE void Swap(RepeatedPtrFieldBase* other) {
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() != nullptr && GetArena() == other->GetArena())
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    if (GetArena() == other->GetArena())
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
-    {
+    if (internal::CanUseInternalSwap(GetArena(), other->GetArena())) {
       InternalSwap(other);
     } else {
       SwapFallback<TypeHandler>(other);
@@ -512,11 +512,7 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
 
   template <typename TypeHandler>
   PROTOBUF_NOINLINE void SwapFallback(RepeatedPtrFieldBase* other) {
-#ifdef PROTOBUF_FORCE_COPY_IN_SWAP
-    ABSL_DCHECK(GetArena() == nullptr || other->GetArena() != GetArena());
-#else   // PROTOBUF_FORCE_COPY_IN_SWAP
-    ABSL_DCHECK(other->GetArena() != GetArena());
-#endif  // !PROTOBUF_FORCE_COPY_IN_SWAP
+    ABSL_DCHECK(!internal::CanUseInternalSwap(GetArena(), other->GetArena()));
 
     // Copy semantics in this case. We try to improve efficiency by placing the
     // temporary on |other|'s arena so that messages are copied twice rather
@@ -726,10 +722,6 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
     return InternalExtend(n - Capacity());
   }
 
-  // Internal helpers for Add that keep definition out-of-line.
-  void* AddMessageLite(ElementFactory factory);
-  void* AddString();
-
   // Common implementation used by various Add* methods. `factory` is an object
   // used to construct a new element unless there are spare cleared elements
   // ready for reuse. Returns pointer to the new element.
@@ -776,8 +768,8 @@ void RepeatedPtrFieldBase::MergeFrom<std::string>(
     const RepeatedPtrFieldBase& from);
 
 
-template <typename F>
-void* RepeatedPtrFieldBase::AddInternal(F factory) {
+template <typename Factory>
+void* RepeatedPtrFieldBase::AddInternal(Factory factory) {
   Arena* const arena = GetArena();
   if (tagged_rep_or_elem_ == nullptr) {
     ExchangeCurrentSize(1);
@@ -817,27 +809,45 @@ PROTOBUF_EXPORT void InternalOutOfLineDeleteMessageLite(MessageLite* message);
 template <typename GenericType>
 class GenericTypeHandler {
  public:
-  typedef GenericType Type;
-  using Movable = IsMovable<GenericType>;
+  using Type = GenericType;
+  using Movable = IsMovable<Type>;
 
   static constexpr auto GetNewFunc() { return Arena::DefaultConstruct<Type>; }
+  static constexpr auto GetNewFromPrototypeFunc(const Type* prototype) {
+    return [prototype](Arena* arena) {
+      ABSL_DCHECK(prototype != nullptr);
+      return prototype->New(arena);
+    };
+  }
+  static inline Arena* GetArena(Type* value) {
+    return Arena::InternalGetArena(value);
+  }
 
-  static inline GenericType* New(Arena* arena) {
-    return static_cast<GenericType*>(Arena::DefaultConstruct<Type>(arena));
+  static inline Type* New(Arena* arena) {
+    return static_cast<Type*>(Arena::DefaultConstruct<Type>(arena));
   }
-  static inline GenericType* New(Arena* arena, GenericType&& value) {
-    return Arena::Create<GenericType>(arena, std::move(value));
+  static inline Type* New(Arena* arena, Type&& value) {
+    return Arena::Create<Type>(arena, std::move(value));
   }
-  static inline GenericType* NewFromPrototype(const GenericType* /*prototype*/,
-                                              Arena* arena = nullptr) {
-    return New(arena);
+  static inline Type* NewFromPrototype(const Type* prototype,
+                                       Arena* arena = nullptr) {
+#if __cpp_if_constexpr
+    if constexpr (std::is_base_of<MessageLite, Type>::value) {
+#else
+    if (std::is_base_of<MessageLite, Type>::value) {
+#endif
+      ABSL_DCHECK(prototype != nullptr);
+      return prototype->New(arena);
+    } else {
+      return New(arena);
+    }
   }
-  static inline void Delete(GenericType* value, Arena* arena) {
+  static inline void Delete(Type* value, Arena* arena) {
     if (arena != nullptr) return;
 #ifdef __cpp_if_constexpr
-    if constexpr (std::is_base_of<MessageLite, GenericType>::value) {
+    if constexpr (std::is_base_of<MessageLite, Type>::value) {
       // Using virtual destructor to reduce generated code size that would have
-      // happened otherwise due to inlined `~GenericType`.
+      // happened otherwise due to inlined `~Type()`.
       InternalOutOfLineDeleteMessageLite(value);
     } else {
       delete value;
@@ -846,86 +856,56 @@ class GenericTypeHandler {
     delete value;
 #endif
   }
-  static inline Arena* GetArena(GenericType* value) {
-    return Arena::InternalGetArena(value);
+  static inline void Clear(Type* value) { value->Clear(); }
+  static inline void Merge(const Type& from, Type* to) {
+#if __cpp_if_constexpr
+    if constexpr (std::is_base_of<MessageLite, Type>::value) {
+#else
+    if (std::is_base_of<MessageLite, Type>::value) {
+#endif
+      to->CheckTypeAndMergeFrom(from);
+    } else {
+      to->MergeFrom(from);
+    }
   }
-
-  static inline void Clear(GenericType* value) { value->Clear(); }
-  static void Merge(const GenericType& from, GenericType* to);
-  static inline size_t SpaceUsedLong(const GenericType& value) {
+  static inline size_t SpaceUsedLong(const Type& value) {
     return value.SpaceUsedLong();
   }
 };
 
-// NewFromPrototypeHelper() is not defined inline here, as we will need to do a
-// virtual function dispatch anyways to go from Message* to call New/Merge. (The
-// additional helper is needed as a workaround for MSVC.)
-PROTOBUF_EXPORT MessageLite* NewFromPrototypeHelper(
-    const MessageLite* prototype, Arena* arena);
-
-template <>
-inline MessageLite* GenericTypeHandler<MessageLite>::NewFromPrototype(
-    const MessageLite* prototype, Arena* arena) {
-  return NewFromPrototypeHelper(prototype, arena);
-}
-template <>
-inline Arena* GenericTypeHandler<MessageLite>::GetArena(MessageLite* value) {
-  return value->GetArena();
-}
-
-template <typename GenericType>
-PROTOBUF_NOINLINE inline void GenericTypeHandler<GenericType>::Merge(
-    const GenericType& from, GenericType* to) {
-  to->MergeFrom(from);
-}
-template <>
-PROTOBUF_EXPORT void GenericTypeHandler<MessageLite>::Merge(
-    const MessageLite& from, MessageLite* to);
-
-// Message specialization bodies defined in message.cc. This split is necessary
-// to allow proto2-lite (which includes this header) to be independent of
-// Message.
-template <>
-PROTOBUF_EXPORT Message* GenericTypeHandler<Message>::NewFromPrototype(
-    const Message* prototype, Arena* arena);
-template <>
-PROTOBUF_EXPORT Arena* GenericTypeHandler<Message>::GetArena(Message* value);
-
-PROTOBUF_EXPORT void* NewStringElement(Arena* arena);
-
 template <>
 class GenericTypeHandler<std::string> {
  public:
-  typedef std::string Type;
+  using Type = std::string;
   using Movable = IsMovable<Type>;
 
-  static constexpr auto GetNewFunc() { return NewStringElement; }
-
-  static PROTOBUF_NOINLINE std::string* New(Arena* arena) {
-    return Arena::Create<std::string>(arena);
+  static constexpr auto* GetNewFunc() { return Arena::Create<Type>; }
+  static constexpr auto GetNewFromPrototypeFunc(const Type* prototype) {
+    return GetNewFunc();
   }
-  static PROTOBUF_NOINLINE std::string* New(Arena* arena, std::string&& value) {
-    return Arena::Create<std::string>(arena, std::move(value));
+  static PROTOBUF_NOINLINE Type* New(Arena* arena) {
+    return Arena::Create<Type>(arena);
   }
-  static inline std::string* NewFromPrototype(const std::string*,
-                                              Arena* arena) {
+  static PROTOBUF_NOINLINE Type* New(Arena* arena, Type&& value) {
+    return Arena::Create<Type>(arena, std::move(value));
+  }
+  static inline Type* NewFromPrototype(const Type*, Arena* arena) {
     return New(arena);
   }
-  static inline Arena* GetArena(std::string*) { return nullptr; }
-  static inline void Delete(std::string* value, Arena* arena) {
+  static inline void Delete(Type* value, Arena* arena) {
     if (arena == nullptr) {
       delete value;
     }
   }
-  static inline void Clear(std::string* value) { value->clear(); }
-  static inline void Merge(const std::string& from, std::string* to) {
-    *to = from;
-  }
-  static size_t SpaceUsedLong(const std::string& value) {
+  static inline Arena* GetArena(Type*) { return nullptr; }
+  static inline void Clear(Type* value) { value->clear(); }
+  static inline void Merge(const Type& from, Type* to) { *to = from; }
+  static inline size_t SpaceUsedLong(const Type& value) {
     return sizeof(value) + StringSpaceUsedExcludingSelfLong(value);
   }
 };
 
+
 }  // namespace internal
 
 // RepeatedPtrField is like RepeatedField, but used for repeated strings or
@@ -1009,6 +989,12 @@ class RepeatedPtrField final : private internal::RepeatedPtrFieldBase {
   // fastest API for adding a new element.
   pointer Add() ABSL_ATTRIBUTE_LIFETIME_BOUND;
 
+  // Like `Add()`, but creates a new element from a provided prototype. For
+  // strings, this is equivalent to `Add()`. For messages, this is equivalent
+  // to `AddAllocated(new T(prototype))`.
+  pointer AddFromPrototype(const_pointer prototype)
+      ABSL_ATTRIBUTE_LIFETIME_BOUND;
+
   // `Add(std::move(value));` is equivalent to `*Add() = std::move(value);`
   // It will either move-construct to the end of this field, or swap value
   // with the new-or-recycled element at the end of this field.  Note that
@@ -1384,6 +1370,12 @@ inline Element* RepeatedPtrField<Element>::Add() ABSL_ATTRIBUTE_LIFETIME_BOUND {
   return RepeatedPtrFieldBase::Add<TypeHandler>();
 }
 
+template <typename Element>
+Element* RepeatedPtrField<Element>::AddFromPrototype(const Element* prototype)
+    ABSL_ATTRIBUTE_LIFETIME_BOUND {
+  return RepeatedPtrFieldBase::AddFromPrototype<TypeHandler>(prototype);
+}
+
 template <typename Element>
 inline void RepeatedPtrField<Element>::Add(Element&& value) {
   RepeatedPtrFieldBase::Add<TypeHandler>(std::move(value));