// Normal execution.
	for {
		r1, _, err := r.ReadRune()
		if err != nil {
			if err != io.EOF {
				t.Error("unexpected error on ReadRune:", err)
			}
			break
		}
		got += string(r1)
		// Put it back and read it again.
		if err = r.UnreadRune(); err != nil {
			t.Fatal("unexpected error on UnreadRune:", err)
		}
		r2, _, err := r.ReadRune()
		if err != nil {

// details about what was run and exits.
// Otherwise runGcc returns the data written to standard output and standard error.
// Note that for some of the uses we expect useful data back
// on standard error, but for those uses gcc must still exit 0.
func runGcc(stdin []byte, args []string) (string, string) {
	if *debugGcc {
		fmt.Fprintf(os.Stderr, "$ %s <<EOF\n", strings.Join(args, " "))