// on all systems are Interrupt (send the process an interrupt) and
// Kill (force the process to exit). Interrupt is not implemented on
// Windows; using it with [os.Process.Signal] will return an error.
var (
	Interrupt Signal = syscall.Note("interrupt")
	Kill      Signal = syscall.Note("kill")
)

func startProcess(name string, argv []string, attr *ProcAttr) (p *Process, err error) {

	}

	// Check that all Process' public methods work as expected with
	// "done" Process.
	if err := proc.Kill(); err != os.ErrProcessDone {
		t.Errorf("Kill: got %v, want %v", err, os.ErrProcessDone)
	}
	if err := proc.Signal(os.Kill); err != os.ErrProcessDone {
		t.Errorf("Signal: got %v, want %v", err, os.ErrProcessDone)
	}
	if _, err := proc.Wait(); !errors.Is(err, syscall.ECHILD) {

// systems are os.Interrupt (send the process an interrupt) and os.Kill (force
// the process to exit). On Windows, sending os.Interrupt to a process with
// os.Process.Signal is not implemented; it will return an error instead of
// sending a signal.
var (
	Interrupt Signal = syscall.SIGINT
	Kill      Signal = syscall.SIGKILL
)

	testenv.MustHaveGoBuild(t)
	t.Parallel()

	p, err := StartProcess(testenv.GoToolPath(t), []string{"go"}, &ProcAttr{})
	if err != nil {
		t.Fatalf("starting test process: %v", err)
	}
	p.Wait()
	if got := p.Signal(Kill); got != ErrProcessDone {
		t.Errorf("got %v want %v", got, ErrProcessDone)
	}
}

// Lookup of a process that does not exist at time of lookup.
func TestProcessAlreadyDone(t *testing.T) {

	case statusReleased:
		return nil, syscall.EINVAL
	}

	// If we can block until Wait4 will succeed immediately, do so.
	ready, err := p.blockUntilWaitable()
	if err != nil {
		return nil, err
	}
	if ready {
		// Mark the process done now, before the call to Wait4,
		// so that Process.pidSignal will not send a signal.
		p.pidDeactivate(statusDone)
		// Acquire a write lock on sigMu to wait for any

	handle, status := p.handleTransientAcquire()
	switch status {
	case statusDone:
		return ErrProcessDone
	case statusReleased:
		return syscall.EINVAL
	}
	defer p.handleTransientRelease()

	if sig == Kill {
		var terminationHandle syscall.Handle
		e := syscall.DuplicateHandle(^syscall.Handle(0), syscall.Handle(handle), ^syscall.Handle(0), &terminationHandle, syscall.PROCESS_TERMINATE, false, 0)
		if e != nil {

	}
	return h, nil
}

// _P_PIDFD is used as idtype argument to waitid syscall.
const _P_PIDFD = 3

func (p *Process) pidfdWait() (*ProcessState, error) {
	// When pidfd is used, there is no wait/kill race (described in CL 23967)
	// because the PID recycle issue doesn't exist (IOW, pidfd, unlike PID,
	// is guaranteed to refer to one particular process). Thus, there is no

<!-- Do not add breaking changes or deprecations here! Add them to the upgrade guide instead. -->

<!--

================== TEMPLATE ==============================

<a name="FILL-IN-KEY-AREA"></a>
### FILL-IN-KEY-AREA improvements

<<<FILL IN CONTEXT FOR KEY AREA>>>
Example:
> The [configuration cache](userguide/configuration_cache.html) improves build performance by caching the result of

<!-- Do not add breaking changes or deprecations here! Add them to the upgrade guide instead. -->

<!--

================== TEMPLATE ==============================

<a name="FILL-IN-KEY-AREA"></a>
### FILL-IN-KEY-AREA improvements

<<<FILL IN CONTEXT FOR KEY AREA>>>
Example:
> The [configuration cache](userguide/configuration_cache.html) improves build performance by caching the result of

  // CHECK-NEXT: %[[FULL_0:.*]] = "tf.Fill"(%[[SHAPE_0]], %[[ELEM_0]]) {ici_weight_distribution_mlir_bridge_marker = true}
  // CHECK:      %[[ELEM_1:.*]] = "tf.Const"()
  // CHECK:      {ici_weight_distribution_mlir_bridge_marker = true}
  // CHECK-NEXT: %[[SHAPE_1:.*]] = "tf.Const"()
  // CHECK:      {ici_weight_distribution_mlir_bridge_marker = true}