Fix issues involving const_cast and repeated fields in reflection.

The motivation is to fix correctness issues seen in split repeated fields.

PiperOrigin-RevId: 543779129

src/google/protobuf/generated_message_reflection.cc

@@ -59,6 +59,7 @@
 #include "google/protobuf/inlined_string_field.h"
 #include "google/protobuf/map_field.h"
 #include "google/protobuf/map_field_inl.h"
+#include "google/protobuf/raw_ptr.h"
 #include "google/protobuf/repeated_field.h"
 #include "google/protobuf/unknown_field_set.h"
 
@@ -2561,7 +2562,9 @@ const void* Reflection::GetRawRepeatedField(const Message& message,
                                             int ctype,
                                             const Descriptor* desc) const {
   USAGE_CHECK_REPEATED("GetRawRepeatedField");
-  if (field->cpp_type() != cpptype)
+  if (field->cpp_type() != cpptype &&
+      (field->cpp_type() != FieldDescriptor::CPPTYPE_ENUM ||
+       cpptype != FieldDescriptor::CPPTYPE_INT32))
     ReportReflectionUsageTypeError(descriptor_, field, "GetRawRepeatedField",
                                    cpptype);
   if (ctype >= 0)
@@ -2569,13 +2572,8 @@ const void* Reflection::GetRawRepeatedField(const Message& message,
   if (desc != nullptr)
     ABSL_CHECK_EQ(field->message_type(), desc) << "wrong submessage type";
   if (field->is_extension()) {
-    // Should use extension_set::GetRawRepeatedField. However, the required
-    // parameter "default repeated value" is not very easy to get here.
-    // Map is not supported in extensions, it is acceptable to use
-    // extension_set::MutableRawRepeatedField which does not change the message.
-    return MutableExtensionSet(const_cast<Message*>(&message))
-        ->MutableRawRepeatedField(field->number(), field->type(),
-                                  field->is_packed(), field);
+    return GetExtensionSet(message).GetRawRepeatedField(
+        field->number(), internal::DefaultRawPtr());
   } else {
     // Trigger transform for MapField
     if (IsMapFieldInApi(field)) {
@@ -3007,8 +3005,8 @@ void Reflection::ClearOneof(Message* message,
   template <>                                                              \
   const RepeatedField<TYPE>& Reflection::GetRepeatedFieldInternal<TYPE>(   \
       const Message& message, const FieldDescriptor* field) const {        \
-    return *static_cast<RepeatedField<TYPE>*>(MutableRawRepeatedField(     \
-        const_cast<Message*>(&message), field, CPPTYPE, CTYPE, nullptr));  \
+    return *static_cast<const RepeatedField<TYPE>*>(                       \
+        GetRawRepeatedField(message, field, CPPTYPE, CTYPE, nullptr));     \
   }                                                                        \
                                                                            \
   template <>                                                              \
@@ -3029,6 +3027,14 @@ HANDLE_TYPE(bool, FieldDescriptor::CPPTYPE_BOOL, -1);
 
 #undef HANDLE_TYPE
 
+const void* Reflection::GetRawRepeatedString(const Message& message,
+                                             const FieldDescriptor* field,
+                                             bool is_string) const {
+  (void)is_string;  // Parameter is used by Google-internal code.
+  return GetRawRepeatedField(message, field, FieldDescriptor::CPPTYPE_STRING,
+                             FieldOptions::STRING, nullptr);
+}
+
 void* Reflection::MutableRawRepeatedString(Message* message,
                                            const FieldDescriptor* field,
                                            bool is_string) const {
@@ -3114,6 +3120,27 @@ MessageFactory* Reflection::GetMessageFactory() const {
   return message_factory_;
 }
 
+const void* Reflection::RepeatedFieldData(
+    const Message& message, const FieldDescriptor* field,
+    FieldDescriptor::CppType cpp_type, const Descriptor* message_type) const {
+  ABSL_CHECK(field->is_repeated());
+  ABSL_CHECK(field->cpp_type() == cpp_type ||
+             (field->cpp_type() == FieldDescriptor::CPPTYPE_ENUM &&
+              cpp_type == FieldDescriptor::CPPTYPE_INT32))
+      << "The type parameter T in RepeatedFieldRef<T> API doesn't match "
+      << "the actual field type (for enums T should be the generated enum "
+      << "type or int32_t).";
+  if (message_type != nullptr) {
+    ABSL_CHECK_EQ(message_type, field->message_type());
+  }
+  if (field->is_extension()) {
+    return GetExtensionSet(message).GetRawRepeatedField(
+        field->number(), internal::DefaultRawPtr());
+  } else {
+    return &GetRawNonOneof<char>(message, field);
+  }
+}
+
 void* Reflection::RepeatedFieldData(Message* message,
                                     const FieldDescriptor* field,
                                     FieldDescriptor::CppType cpp_type,

src/google/protobuf/message.h

@@ -1031,8 +1031,11 @@ class PROTOBUF_EXPORT Reflection final {
   // "message_type" should be set to its descriptor. Otherwise "message_type"
   // should be set to nullptr. Implementations of this method should check
   // whether "cpp_type"/"message_type" is consistent with the actual type of the
-  // field. We use 1 routine rather than 2 (const vs mutable) because it is
-  // protected and it doesn't change the message.
+  // field.
+  const void* RepeatedFieldData(const Message& message,
+                                const FieldDescriptor* field,
+                                FieldDescriptor::CppType cpp_type,
+                                const Descriptor* message_type) const;
   void* RepeatedFieldData(Message* message, const FieldDescriptor* field,
                           FieldDescriptor::CppType cpp_type,
                           const Descriptor* message_type) const;
@@ -1136,8 +1139,9 @@ class PROTOBUF_EXPORT Reflection final {
   // call MutableRawRepeatedField directly here because we don't have access to
   // FieldOptions::* which are defined in descriptor.pb.h.  Including that
   // file here is not possible because it would cause a circular include cycle.
-  // We use 1 routine rather than 2 (const vs mutable) because it is private
-  // and mutable a repeated string field doesn't change the message.
+  const void* GetRawRepeatedString(const Message& message,
+                                   const FieldDescriptor* field,
+                                   bool is_string) const;
   void* MutableRawRepeatedString(Message* message, const FieldDescriptor* field,
                                  bool is_string) const;
 
@@ -1493,8 +1497,8 @@ template <>
 inline const RepeatedPtrField<std::string>&
 Reflection::GetRepeatedPtrFieldInternal<std::string>(
     const Message& message, const FieldDescriptor* field) const {
-  return *static_cast<RepeatedPtrField<std::string>*>(
-      MutableRawRepeatedString(const_cast<Message*>(&message), field, true));
+  return *static_cast<const RepeatedPtrField<std::string>*>(
+      GetRawRepeatedString(message, field, true));
 }
 
 template <>

src/google/protobuf/reflection.h

@@ -91,9 +91,8 @@ class RepeatedFieldRef<
   friend class Reflection;
   RepeatedFieldRef(const Message& message, const FieldDescriptor* field) {
     const Reflection* reflection = message.GetReflection();
-    data_ = reflection->RepeatedFieldData(const_cast<Message*>(&message), field,
-                                          internal::RefTypeTraits<T>::cpp_type,
-                                          nullptr);
+    data_ = reflection->RepeatedFieldData(
+        message, field, internal::RefTypeTraits<T>::cpp_type, nullptr);
     accessor_ = reflection->RepeatedFieldAccessor(field);
   }
 
@@ -200,8 +199,7 @@ class RepeatedFieldRef<
   RepeatedFieldRef(const Message& message, const FieldDescriptor* field) {
     const Reflection* reflection = message.GetReflection();
     data_ = reflection->RepeatedFieldData(
-        const_cast<Message*>(&message), field,
-        internal::RefTypeTraits<T>::cpp_type,
+        message, field, internal::RefTypeTraits<T>::cpp_type,
         internal::RefTypeTraits<T>::GetMessageFieldDescriptor());
     accessor_ = reflection->RepeatedFieldAccessor(field);
     default_instance_ =