Fixed compilation warning

src/description.cpp

@@ -214,7 +214,7 @@ string Description::generateSdp(const string &eol) const {
 	// see Negotiating Media Multiplexing Using the Session Description Protocol
 	// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-54
 	sdp << "a=group:BUNDLE";
-	for (int i = 0; i < mMedia.size() + 1; ++i)
+	for (int i = 0; i < int(mMedia.size() + 1); ++i)
 		if (auto it = mMedia.find(i); it != mMedia.end())
 			sdp << ' ' << it->second.mid;
 		else
@@ -233,7 +233,7 @@ string Description::generateSdp(const string &eol) const {
 	}
 
 	// Descriptions and attributes
-	for (int i = 0; i < mMedia.size() + 1; ++i) {
+	for (int i = 0; i < int(mMedia.size() + 1); ++i) {
 		if (auto it = mMedia.find(i); it != mMedia.end()) {
 			// Non-data media
 			const auto &media = it->second;

src/rtc.cpp

@@ -487,7 +487,7 @@ int rtcSetMessageCallback(int id, rtcMessageCallbackFunc cb) {
 			    },
 			    [id, cb](const string &s) {
 				    if (auto ptr = getUserPointer(id))
-					    cb(s.c_str(), -(s.size() + 1), *ptr);
+					    cb(s.c_str(), -int(s.size() + 1), *ptr);
 			    });
 		else
 			channel->onMessage(nullptr);