if (filename == 0)
if (filename == 0 || *filename == '\0')
rl_read_init_file (filename)     char *filename;{  /* Default the filename. */  if (filename == 0)    {      filename = last_readline_init_file;      if (filename == 0)        filename = get_env_value ("INPUTRC");      if (filename == 0)	filename = DEFAULT_INPUTRC;    }  if (*filename == 0)    filename = DEFAULT_INPUTRC;#if defined (__MSDOS__)  if (_rl_read_init_file (filename, 0) == 0)    return 0;  filename = "~/_inputrc";#endif  return (_rl_read_init_file (filename, 0));}