Dir.mkdir

static VALUE
dir_s_mkdir(int argc, VALUE *argv, VALUE obj)
{
    struct mkdir_arg m;
    VALUE path, vmode;
    int r;

    if (rb_scan_args(argc, argv, "11", &path, &vmode) == 2) {
        m.mode = NUM2MODET(vmode);
    }
    else {
        m.mode = 0777;
    }

    path = check_dirname(path);
    m.path = RSTRING_PTR(path);
    r = (int)(VALUE)rb_thread_call_without_gvl(nogvl_mkdir, &m, RUBY_UBF_IO, 0);
    if (r < 0)
        rb_sys_fail_path(path);

    return INT2FIX(0);
}