}

	// The "pre" output should all have been flushed already.
	if want, got := pre, out.String(); want != got {
		t.Errorf("filter should have already flushed %q, but flushed %q", want, got)
	}

	code, err := f.Finish()
	if err != nil {
		t.Fatal(err)
	}

	// Nothing more should have been written to out.
	if want, got := pre, out.String(); want != got {
		t.Errorf("want output %q, got %q", want, got)
	}

	// along stderr from adb.
	cmd.Stderr = struct{ io.Writer }{os.Stderr}
	err := cmd.Run()

	// Before we process err, flush any further output and get the exit code.
	exitCode, err2 := filter.Finish()

	if err != nil {
		return 0, fmt.Errorf("adb exec-out %s: %v", args, err)
	}
	return exitCode, err2
}

func adb(args ...string) error {
	if out, err := adbCmd(args...).CombinedOutput(); err != nil {

Worse, there is no guarantee that the write to <code>done</code> will ever
be observed by <code>main</code>, since there are no synchronization
events between the two threads.  The loop in <code>main</code> is not
guaranteed to finish.
</p>

<p>
There are subtler variants on this theme, such as this program.
</p>

<pre>
type T struct {
	msg string
}

var g *T

func setup() {
	t := new(T)