runtime: change 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.

Author: ncruces

src/runtime/signal_windows_test.go

@@ -10,7 +10,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"runtime"
-	"strconv"
 	"strings"
 	"syscall"
 	"testing"
@@ -113,18 +112,6 @@ 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 received, handled SIGTERM
 	if line, err := outReader.ReadString('\n'); err != nil {
 		t.Fatalf("could not read stdout: %v", err)

src/runtime/testdata/testwinsignal/main.go

@@ -2,16 +2,32 @@ package main
 
 import (
 	"fmt"
+	"log"
 	"os"
 	"os/signal"
+	"syscall"
 	"time"
 )
 
 func main() {
 	c := make(chan os.Signal, 1)
 	signal.Notify(c)
 
-	fmt.Println("ready")
+	kernel32 := syscall.NewLazyDLL("kernel32.dll")
+	getConsoleWindow := kernel32.NewProc("GetConsoleWindow")
+	hwnd, _, err := getConsoleWindow.Call()
+	if hwnd == 0 {
+		log.Fatal("no associated console: ", err)
+	}
+
+	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
 
 	time.Sleep(time.Second)