examples/cxx: add explicit-declared copy constructor

examples/cxx/experimental/experimental_cpp_component/include/esp_event_cxx.hpp

@@ -1,16 +1,8 @@
-// Copyright 2019 Espressif Systems (Shanghai) PTE LTD
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//         http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+/*
+ * SPDX-FileCopyrightText: 2019-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 #ifndef ESP_EVENT_CXX_H_
 #define ESP_EVENT_CXX_H_
@@ -69,6 +61,7 @@ class ESPEventID {
 public:
     ESPEventID() : id(0) { }
     explicit ESPEventID(int32_t event_id) : id(event_id) { }
+    ESPEventID(const ESPEventID &rhs) : id(rhs.id) { }
 
     inline bool operator==(const ESPEventID &rhs) const {
         return id == rhs.get_id();