Protection for case where tcp port or unix socket is not set and plugin tries to set default socket name at startup. The tcp port or unix socket may not be set when they are not passed either on the command line or configured in my.cnf. In this case the plugin init function is called before mysql has set the default values for these.

src/audit_handler.cc

@@ -215,6 +215,16 @@ int Audit_file_handler::open(const char * io_dest, bool log_errors)
 //no locks. called by handler_start and when it is time to retry
 bool Audit_io_handler::handler_start_internal()
 {
+	if(!m_io_dest || strlen(m_io_dest) == 0)
+	{
+		if(m_log_io_errors)
+		{
+			sql_print_error(
+					"%s %s: io destination not set. Not connecting.",
+					AUDIT_LOG_PREFIX,  m_io_type);
+		}
+        return false;
+	}
 	if (open(m_io_dest, m_log_io_errors) != 0)
     {
 		//open failed        

src/audit_plugin.cc

@@ -1223,7 +1223,7 @@ static void json_socket_name_update(THD *thd, struct st_mysql_sys_var *var, void
 	{
 		strncpy( json_socket_name_buff , str, buff_len);
 	}
-	if(strlen(json_socket_name_buff) == 0) //set default
+	if(strlen(json_socket_name_buff) == 0 && (mysqld_port > 0 || mysqld_unix_port)) //set default
 	{
 		const char * name_prefix = "/tmp/mysql.audit_";