rem: static char * get_stack_driver_path() {
add: static char * get_stack_driver_path(void) {
context: static char * get_stack_driver_path() {  char * path;  // user-defined stack driver path?  path = getenv("NET_STACK_DRIVER_PATH");  if (path)    return path;  // use the default stack driver path  return NET_STACK_DRIVER_PATH;}