internal/poll: add tests for Windows file and serial ports

I also wanted to test net sockets, but I do not know how to
access their file handles. So I did not implement socket tests.

Updates #21172

Change-Id: I5062c0e65a817571d755397d60762c175f9791ce
Reviewed-on: https://go-review.googlesource.com/53530Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/internal/poll/export_windows_test.go

+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Export guts for testing on windows.
+// Since testing imports os and os imports internal/poll,
+// the internal/poll tests can not be in package poll.
+
+package poll
+
+var (
+	LogInitFD = &logInitFD
+)
+
+func (fd *FD) IsPartOfNetpoll() bool {
+	return fd.pd.runtimeCtx != 0
+}

src/internal/poll/fd_windows.go

@@ -295,6 +295,9 @@ type FD struct {
 	isDir bool
 }
 
+// logInitFD is set by tests to enable file descriptor initialization logging.
+var logInitFD func(net string, fd *FD, err error)
+
 // Init initializes the FD. The Sysfd field should already be set.
 // This can be called multiple times on a single FD.
 // The net argument is a network name from the net package (e.g., "tcp"),
@@ -319,6 +322,7 @@ func (fd *FD) Init(net string) (string, error) {
 		return "", errors.New("internal error: unknown network type " + net)
 	}
 
+	var err error
 	if !fd.isFile && !fd.isConsole && !fd.isDir {
 		// Only call init for a network socket.
 		// This means that we don't add files to the runtime poller.
@@ -331,9 +335,13 @@ func (fd *FD) Init(net string) (string, error) {
 		// somehow call ExecIO, then ExecIO, and therefore the
 		// calling method, will return an error, because
 		// fd.pd.runtimeCtx will be 0.
-		if err := fd.pd.init(fd); err != nil {
-			return "", err
-		}
+		err = fd.pd.init(fd)
+	}
+	if logInitFD != nil {
+		logInitFD(net, fd, err)
+	}
+	if err != nil {
+		return "", err
 	}
 	if hasLoadSetFileCompletionNotificationModes {
 		// We do not use events, so we can skip them always.

src/internal/poll/fd_windows_test.go

+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package poll_test
+
+import (
+	"fmt"
+	"internal/poll"
+	"os"
+	"sync"
+	"syscall"
+	"testing"
+)
+
+type loggedFD struct {
+	Net string
+	FD  *poll.FD
+	Err error
+}
+
+var (
+	logMu     sync.Mutex
+	loggedFDs map[syscall.Handle]*loggedFD
+)
+
+func logFD(net string, fd *poll.FD, err error) {
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	loggedFDs[fd.Sysfd] = &loggedFD{
+		Net: net,
+		FD:  fd,
+		Err: err,
+	}
+}
+
+func init() {
+	loggedFDs = make(map[syscall.Handle]*loggedFD)
+	*poll.LogInitFD = logFD
+}
+
+func findLoggedFD(h syscall.Handle) (lfd *loggedFD, found bool) {
+	logMu.Lock()
+	defer logMu.Unlock()
+
+	lfd, found = loggedFDs[h]
+	return lfd, found
+}
+
+// checkFileIsNotPartOfNetpoll verifies that f is not managed by netpoll.
+// It returns error, if check fails.
+func checkFileIsNotPartOfNetpoll(f *os.File) error {
+	lfd, found := findLoggedFD(syscall.Handle(f.Fd()))
+	if !found {
+		return fmt.Errorf("%v fd=%v: is not found in the log", f.Name(), f.Fd())
+	}
+	if lfd.FD.IsPartOfNetpoll() {
+		return fmt.Errorf("%v fd=%v: is part of netpoll, but should not be (logged: net=%v err=%v)", f.Name(), f.Fd(), lfd.Net, lfd.Err)
+	}
+	return nil
+}
+
+func TestFileFdsAreInitialised(t *testing.T) {
+	exe, err := os.Executable()
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, err := os.Open(exe)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	err = checkFileIsNotPartOfNetpoll(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestSerialFdsAreInitialised(t *testing.T) {
+	for _, name := range []string{"COM1", "COM2", "COM3", "COM4"} {
+		t.Run(name, func(t *testing.T) {
+			h, err := syscall.CreateFile(syscall.StringToUTF16Ptr(name),
+				syscall.GENERIC_READ|syscall.GENERIC_WRITE,
+				0,
+				nil,
+				syscall.OPEN_EXISTING,
+				syscall.FILE_ATTRIBUTE_NORMAL|syscall.FILE_FLAG_OVERLAPPED,
+				0)
+			if err != nil {
+				if errno, ok := err.(syscall.Errno); ok {
+					switch errno {
+					case syscall.ERROR_FILE_NOT_FOUND,
+						syscall.ERROR_ACCESS_DENIED:
+						t.Log("Skipping: ", err)
+						return
+					}
+				}
+				t.Fatal(err)
+			}
+			f := os.NewFile(uintptr(h), name)
+			defer f.Close()
+
+			err = checkFileIsNotPartOfNetpoll(f)
+			if err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}