func: static int add_old_style_options(const char *fmt, QemuOpts *opts,
  
                                   const char *base_filename,
  
                                   const char *base_fmt)
  
  {
  
      if (base_filename) {
  
          if (qemu_opt_set(opts, BLOCK_OPT_BACKING_FILE, base_filename)) {
  
              error_report("Backing file not supported for file format '%s'",
  
                           fmt);
  
              return -1;
  
          }
  
      }
  
      if (base_fmt) {
  
          if (qemu_opt_set(opts, BLOCK_OPT_BACKING_FMT, base_fmt)) {
  
              error_report("Backing file format not supported for file "
  
                           "format '%s'", fmt);
  
              return -1;
  
          }
  
      }
  
      return 0;
  
  }
  