string? filename;

// this compiles just fine if it's an array of OptionEntry instead of
// OptionEntry?. However, Clutter.init_with_args() (which I use in the
// original program) expects an array of OptionEntry?.
const OptionEntry?[] entries =
{
  {
    "filename", 'f',
    0,
    OptionArg.FILENAME, ref filename,
    "The file", "FILE"
  },
  { null }
};

void main(string[] args)
{
}
