main: Check for error in msgrcv

src/app/main.cpp

@@ -162,7 +162,9 @@ static void msg_read_thread(){
     while (1){
         // make sure that the message recieved is compatible
         // and that we're not trying to use variables that don't exist (yet)
-        size_t msg_size = msgrcv(msgid, (void *) raw_msg, sizeof(raw_msg), 1, 0) + sizeof(long);
+        size_t msg_size = msgrcv(msgid, (void *) raw_msg, sizeof(raw_msg), 1, 0);
+        if (msg_size != -1)
+        {
             if (hdr->version == 1){
                 if (msg_size > offsetof(struct mangoapp_msg_v1, visible_frametime_ns)){
                     bool should_new_frame = false;
@@ -214,6 +216,11 @@ static void msg_read_thread(){
                 exit(1);
             }
         }
+        else
+        {
+            printf("mangoapp: msgrcv returned -1 with error %d - %s\n", errno, strerror(errno));
+        }
+    }
 }
 
 static const char *GamescopeOverlayProperty = "GAMESCOPE_EXTERNAL_OVERLAY";