runtime: allow TestCtrlHandler to run in ConPTY

Fixes #51602. Previous test would not run in a pseudo-console (ConPTY).

New test avoids taskkill entirely by having the child request its own
console window be closed.

Verified that this runs locally (within a real console), over SSH
(within a pseudo-console), and that it breaks if #41884 were reverted.

Change-Id: If868b92ec36647e5d0e4107e29a2a6e048d35ced
GitHub-Last-Rev: b1421e4
GitHub-Pull-Request: #51681
Reviewed-on: https://go-review.googlesource.com/c/go/+/392874
Reviewed-by: Bryan Mills <[email protected]>
Trust: Bryan Mills <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Alex Brainman <[email protected]>
Trust: Alex Brainman <[email protected]>

src/runtime/signal_windows_test.go

@@ -10,7 +10,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"runtime"
-	"strconv"
 	"strings"
 	"syscall"
 	"testing"
@@ -92,13 +91,16 @@ func TestCtrlHandler(t *testing.T) {
 
 	// run test program
 	cmd = exec.Command(exe)
+	var stdout bytes.Buffer
 	var stderr bytes.Buffer
+	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
-	outPipe, err := cmd.StdoutPipe()
+	inPipe, err := cmd.StdinPipe()
 	if err != nil {
-		t.Fatalf("Failed to create stdout pipe: %v", err)
+		t.Fatalf("Failed to create stdin pipe: %v", err)
 	}
-	outReader := bufio.NewReader(outPipe)
+	// keep inPipe alive until the end of the test
+	defer inPipe.Close()
 
 	// in a new command window
 	const _CREATE_NEW_CONSOLE = 0x00000010
@@ -114,29 +116,15 @@ func TestCtrlHandler(t *testing.T) {
 		cmd.Wait()
 	}()
 
-	// wait for child to be ready to receive signals
-	if line, err := outReader.ReadString('\n'); err != nil {
-		t.Fatalf("could not read stdout: %v", err)
-	} else if strings.TrimSpace(line) != "ready" {
-		t.Fatalf("unexpected message: %s", line)
-	}
-
-	// gracefully kill pid, this closes the command window
-	if err := exec.Command("taskkill.exe", "/pid", strconv.Itoa(cmd.Process.Pid)).Run(); err != nil {
-		t.Fatalf("failed to kill: %v", err)
+	// check child exited gracefully, did not timeout
+	if err := cmd.Wait(); err != nil {
+		t.Fatalf("Program exited with error: %v\n%s", err, &stderr)
 	}
 
 	// check child received, handled SIGTERM
-	if line, err := outReader.ReadString('\n'); err != nil {
-		t.Fatalf("could not read stdout: %v", err)
-	} else if expected, got := syscall.SIGTERM.String(), strings.TrimSpace(line); expected != got {
+	if expected, got := syscall.SIGTERM.String(), strings.TrimSpace(stdout.String()); expected != got {
 		t.Fatalf("Expected '%s' got: %s", expected, got)
 	}
-
-	// check child exited gracefully, did not timeout
-	if err := cmd.Wait(); err != nil {
-		t.Fatalf("Program exited with error: %v\n%s", err, &stderr)
-	}
 }
 
 // TestLibraryCtrlHandler tests that Go DLL allows calling program to handle console control events.

src/runtime/testdata/testwinsignal/main.go

@@ -2,18 +2,52 @@ package main
 
 import (
 	"fmt"
+	"io"
+	"log"
 	"os"
 	"os/signal"
+	"syscall"
 	"time"
 )
 
 func main() {
+	// Ensure that this process terminates when the test times out,
+	// even if the expected signal never arrives.
+	go func() {
+		io.Copy(io.Discard, os.Stdin)
+		log.Fatal("stdin is closed; terminating")
+	}()
+
+	// Register to receive all signals.
 	c := make(chan os.Signal, 1)
 	signal.Notify(c)
 
-	fmt.Println("ready")
+	// Get console window handle.
+	kernel32 := syscall.NewLazyDLL("kernel32.dll")
+	getConsoleWindow := kernel32.NewProc("GetConsoleWindow")
+	hwnd, _, err := getConsoleWindow.Call()
+	if hwnd == 0 {
+		log.Fatal("no associated console: ", err)
+	}
+
+	// Send message to close the console window.
+	const _WM_CLOSE = 0x0010
+	user32 := syscall.NewLazyDLL("user32.dll")
+	postMessage := user32.NewProc("PostMessageW")
+	ok, _, err := postMessage.Call(hwnd, _WM_CLOSE, 0, 0)
+	if ok == 0 {
+		log.Fatal("post message failed: ", err)
+	}
+
 	sig := <-c
 
+	// Allow some time for the handler to complete if it's going to.
+	//
+	// (In https://go.dev/issue/41884 the handler returned immediately,
+	// which caused Windows to terminate the program before the goroutine
+	// that received the SIGTERM had a chance to actually clean up.)
 	time.Sleep(time.Second)
+
+	// Print the signal's name: "terminated" makes the test succeed.
 	fmt.Println(sig)
 }