expand_path

static VALUE
path_expand_path(int argc, VALUE *argv, VALUE self)
{
    VALUE str = get_strpath(self);
    VALUE dname;
    if (rb_scan_args(argc, argv, "01", &dname) == 0)
        str = rb_funcall(rb_cFile, id_expand_path, 1, str);
    else
        str = rb_funcall(rb_cFile, id_expand_path, 2, str, dname);
    return rb_class_new_instance(1, &str, rb_obj_class(self));
}