用scopeguard库来保证Exception-Safe Code

 int clientfd= socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);    
        if(clientfd < 0){
           syslog(LOG_LOCAL0|LOG_ERR,"can not create BroadcastMessage  socket");
        return;
        }
        ON_BLOCK_EXIT(close, clientfd);

  
        MYSQL *mysql = getConnectDb();
        if (mysql == NULL){
            syslog(LOG_LOCAL0|LOG_ERR,"can not connect mysql database /n");
        return ;
        }   
        ON_BLOCK_EXIT(putConnectDb, mysql);