cmd.Stderr = new(bytes.Buffer)
	out, err := cmd.Output()
	t.Logf("%v:\n%s", cmd, out)
	t.Logf("stderr:\n%s", cmd.Stderr)
	if err == nil {
		t.Errorf("unexpected success; want failure due to newline in file path")
	}

through the fmt package.  For example, if a String method
calls panic("bad"), the resulting formatted message will look
like

	%!s(PANIC=bad)

The %!s just shows the print verb in use when the failure
occurred. If the panic is caused by a nil receiver to an Error
or String method, however, the output is the undecorated
string, "<nil>".

# Scanning

An analogous set of functions scans formatted text to yield

	{26, "SIGVTALRM", "virtual timer expired"},
	{27, "SIGPROF", "profiling timer expired"},
	{28, "SIGWINCH", "window changed"},
	{29, "SIGIO", "I/O possible"},
	{30, "SIGPWR", "power failure"},
	{31, "SIGSYS", "bad system call"},

	fatal(s)
}

// throw triggers a fatal error that dumps a stack trace and exits.
//
// throw should be used for runtime-internal fatal errors where Go itself,
// rather than user code, may be at fault for the failure.
//
// NOTE: temporarily marked "go:noinline" pending investigation/fix of
// issue #67274, so as to fix longtest builders.
//
// throw should be an internal detail,

	{14, "SIGALRM", "alarm clock"},
	{15, "SIGTERM", "terminated"},
	{16, "SIGUSR1", "user defined signal 1"},
	{17, "SIGUSR2", "user defined signal 2"},
	{18, "SIGCHLD", "child exited"},
	{19, "SIGPWR", "power failure"},
	{20, "SIGWINCH", "window changed"},
	{21, "SIGURG", "urgent I/O condition"},
	{22, "SIGIO", "I/O possible"},
	{23, "SIGSTOP", "stopped (signal)"},
	{24, "SIGTSTP", "stopped"},
	{25, "SIGCONT", "continued"},

		// skip unnamed functions (func _())
		if fromType.HasShape() {
			// Unified IR uses OCONVIFACE for converting all derived types
			// to interface type. Avoid assertion failure in
			// MarkTypeUsedInInterface, because we've marked used types
			// separately anyway.
		} else {
			reflectdata.MarkTypeUsedInInterface(fromType, ir.CurFunc.LSym)
		}
	}

	if !fromType.IsInterface() {

	RET

TEXT runtime·madvise_trampoline(SB), NOSPLIT, $0
	MOVQ	8(DI), SI	// arg 2 len
	MOVL	16(DI), DX	// arg 3 advice
	MOVQ	0(DI), DI	// arg 1 addr
	CALL	libc_madvise(SB)
	// ignore failure - maybe pages are locked
	RET

TEXT runtime·open_trampoline(SB),NOSPLIT,$0
	MOVL	8(DI), SI		// arg 2 - flags
	MOVL	12(DI), DX		// arg 3 - mode
	MOVQ	0(DI), DI		// arg 1 - path

		if cls := runtime.GCTestPointerClass(unsafe.Pointer(new)); cls != "stack" {
			t.Fatalf("test bug: new (%#x) should be a stack pointer, not %s", new2, cls)
		}
		// This was a real failure.
		return false
	}
	return true
}

func TestGCTestMoveStackRepeatedly(t *testing.T) {
	// Move the stack repeatedly to make sure we're not doubling
	// it each time.
	for i := 0; i < 100; i++ {

	lineNum  int // current line number.
	env      []string
}

// run runs the generators in the current file.
func (g *Generator) run() (ok bool) {
	// Processing below here calls g.errorf on failure, which does panic(stop).
	// If we encounter an error, we abort the package.
	defer func() {
		e := recover()
		if e != nil {
			ok = false
			if e != stop {
				panic(e)
			}
			base.SetExitStatus(1)

			}
		} else if err := syscall.SetNonblock(fd, true); err == nil {
			f.nonblock = true
			clearNonBlock = true
		} else {
			pollable = false
		}
	}

	// An error here indicates a failure to register
	// with the netpoll system. That can happen for
	// a file descriptor that is not supported by
	// epoll/kqueue; for example, disk files on
	// Linux systems. We assume that any real error