Add ovrride keyword for overriden functions

src/google/protobuf/util/internal/default_value_objectwriter.h

@@ -117,7 +117,7 @@ class PROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
   DefaultValueObjectWriter* RenderBytes(StringPiece name,
                                         StringPiece value) override;
 
-  virtual DefaultValueObjectWriter* RenderNull(StringPiece name);
+  DefaultValueObjectWriter* RenderNull(StringPiece name) override;
 
   // Register the callback for scrubbing of fields.
   void RegisterFieldScrubCallBack(FieldScrubCallBack field_scrub_callback);

src/google/protobuf/util/internal/json_objectwriter.h

@@ -96,21 +96,21 @@ class PROTOBUF_EXPORT JsonObjectWriter : public StructuredObjectWriter {
   virtual ~JsonObjectWriter();
 
   // ObjectWriter methods.
-  virtual JsonObjectWriter* StartObject(StringPiece name);
-  virtual JsonObjectWriter* EndObject();
-  virtual JsonObjectWriter* StartList(StringPiece name);
-  virtual JsonObjectWriter* EndList();
-  virtual JsonObjectWriter* RenderBool(StringPiece name, bool value);
-  virtual JsonObjectWriter* RenderInt32(StringPiece name, int32 value);
-  virtual JsonObjectWriter* RenderUint32(StringPiece name, uint32 value);
-  virtual JsonObjectWriter* RenderInt64(StringPiece name, int64 value);
-  virtual JsonObjectWriter* RenderUint64(StringPiece name, uint64 value);
-  virtual JsonObjectWriter* RenderDouble(StringPiece name, double value);
-  virtual JsonObjectWriter* RenderFloat(StringPiece name, float value);
-  virtual JsonObjectWriter* RenderString(StringPiece name,
-                                         StringPiece value);
-  virtual JsonObjectWriter* RenderBytes(StringPiece name, StringPiece value);
-  virtual JsonObjectWriter* RenderNull(StringPiece name);
+  JsonObjectWriter* StartObject(StringPiece name) override;
+  JsonObjectWriter* EndObject() override;
+  JsonObjectWriter* StartList(StringPiece name) override;
+  JsonObjectWriter* EndList() override;
+  JsonObjectWriter* RenderBool(StringPiece name, bool value) override;
+  JsonObjectWriter* RenderInt32(StringPiece name, int32 value) override;
+  JsonObjectWriter* RenderUint32(StringPiece name, uint32 value) override;
+  JsonObjectWriter* RenderInt64(StringPiece name, int64 value) override;
+  JsonObjectWriter* RenderUint64(StringPiece name, uint64 value) override;
+  JsonObjectWriter* RenderDouble(StringPiece name, double value) override;
+  JsonObjectWriter* RenderFloat(StringPiece name, float value) override;
+  JsonObjectWriter* RenderString(StringPiece name,
+                                 StringPiece value) override;
+  JsonObjectWriter* RenderBytes(StringPiece name, StringPiece value) override;
+  JsonObjectWriter* RenderNull(StringPiece name) override;
   virtual JsonObjectWriter* RenderNullAsEmpty(StringPiece name);
 
   void set_use_websafe_base64_for_bytes(bool value) {