fix compatibility problem for gcc 4.8+.

README.md

@@ -37,7 +37,7 @@ cmake
 1. Install boost, see [Boost setup](#boost_setup) section.
 2. Use `git clone --recurse-submodules https://github.com/socketio/socket.io-client-cpp.git` to clone your local repo.
 3. Add `<your boost install folder>/include`,`./lib/websocketpp` and `./lib/rapidjson/include` to headers search path.
-4. Include all files under `./src` in your project, add `sio_packet.cpp`,`sio_socket.cpp`,`internal/sio_client_impl.cpp` to source list.
+4. Include all files under `./src` in your project, add `sio_client.cpp`,`sio_socket.cpp`,`internal/sio_client_impl.cpp`, `internal/sio_packet.cpp` to source list.
 5. Add `<your boost install folder>/lib` to library search path, add `boost.lib`(Win32) or `-lboost`(Other) link option.
 6. Include `sio_client.h` in your client code where you want to use it.
 

src/internal/sio_packet.cpp

@@ -303,7 +303,7 @@ namespace sio
         }
         if (_frame == frame_message && (_type == type_binary_event || _type == type_binary_ack)) {
             //parse later when all buffers are arrived.
-            _buffers.push_back(make_shared<const string>(payload_ptr.data() + json_pos, payload_ptr.length() - json_pos));
+            _buffers.push_back(make_shared<string>(payload_ptr.data() + json_pos, payload_ptr.length() - json_pos));
             return true;
         }
         else

src/sio_message.h

@@ -27,6 +27,8 @@ namespace sio
             flag_array,
             flag_object
         };
+
+        virtual ~message() = default;
         
         class list;