Internal change

PiperOrigin-RevId: 606672326

src/google/protobuf/message.cc

@@ -11,6 +11,7 @@
 
 #include "google/protobuf/message.h"
 
+#include <atomic>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
@@ -257,7 +258,7 @@ class GeneratedMessageFactory final : public MessageFactory {
   {
     auto it = type_map_.find(type);
     if (it == type_map_.end()) return absl::nullopt;
-    return it->second;
+    return it->second.get();
   }
 
   const google::protobuf::internal::DescriptorTable* FindInFileMap(
@@ -303,7 +304,17 @@ class GeneratedMessageFactory final : public MessageFactory {
   DynamicMessageFactory dropped_defaults_factory_;
 
   absl::Mutex mutex_;
-  absl::flat_hash_map<const Descriptor*, const Message*> type_map_
+  class MessagePtr {
+   public:
+    MessagePtr() : value_() {}
+    explicit MessagePtr(const Message* msg) : value_(msg) {}
+    const Message* get() const { return value_; }
+    void set(const Message* msg) { value_ = msg; }
+
+   private:
+    const Message* value_;
+  };
+  absl::flat_hash_map<const Descriptor*, MessagePtr> type_map_
       ABSL_GUARDED_BY(mutex_);
 };
 
@@ -352,7 +363,7 @@ const Message* GeneratedMessageFactory::GetPrototype(const Descriptor* type) {
       // And update the main map to make the next lookup faster.
       // We don't need to recheck here. Even if someone raced us here the result
       // is the same, so we can just write it.
-      type_map_[type] = result;
+      type_map_[type].set(result);
     }
   }