Add test

Author: fmeum

src/os/signal/signal_test.go

@@ -217,9 +217,7 @@ func testCancel(t *testing.T, ignore bool) {
 	// Either way, this should undo both calls to Notify above.
 	if ignore {
 		Ignore(syscall.SIGWINCH, syscall.SIGHUP)
-		// Don't bother deferring a call to Reset: it is documented to undo Notify,
-		// but its documentation says nothing about Ignore, and (as of the time of
-		// writing) it empirically does not undo an Ignore.
+		defer Reset(syscall.SIGWINCH, syscall.SIGHUP)
 	} else {
 		Reset(syscall.SIGWINCH, syscall.SIGHUP)
 	}
@@ -913,3 +911,61 @@ func TestSignalTrace(t *testing.T) {
 	close(quit)
 	<-done
 }
+
+// #46321 test Reset actually undoes the effect of Ignore.
+func TestResetIgnore(t *testing.T) {
+	if os.Getenv("GO_TEST_RESET_IGNORE") != "" {
+		s, err := strconv.Atoi(os.Getenv("GO_TEST_RESET_IGNORE"))
+		if err != nil {
+			t.Fatalf("failed to parse signal: %v", err)
+		}
+		resetIgnoreTestProgram(t, syscall.Signal(s))
+	}
+
+	sigs := []syscall.Signal{
+		syscall.SIGINT,
+		syscall.SIGHUP,
+		syscall.SIGUSR1,
+		syscall.SIGTERM,
+		syscall.SIGCHLD,
+		syscall.SIGWINCH,
+	}
+
+	for _, notify := range []bool{false, true} {
+		for _, sig := range sigs {
+			t.Run(fmt.Sprintf("%s[notify=%t]", sig, notify), func(t *testing.T) {
+				Ignore(sig)
+				if notify {
+					c := make(chan os.Signal, 1)
+					Notify(c, sig)
+					defer Stop(c)
+				}
+				Reset(sig)
+
+				if Ignored(sig) {
+					t.Fatalf("expected %q to not be ignored", sig)
+				}
+
+				// Child processes inherit the ignored status of signals, so verify that it
+				// is indeed not ignored.
+				testenv.MustHaveExec(t)
+
+				cmd := testenv.Command(t, os.Args[0], "-test.run=^TestResetIgnore$")
+				cmd.Env = append(os.Environ(), "GO_TEST_RESET_IGNORE="+strconv.Itoa(int(sig)))
+				err := cmd.Run()
+				if _, ok := err.(*exec.ExitError); ok {
+					t.Fatalf("expected %q to not be ignored in child process", sig)
+				} else if err != nil {
+					t.Fatalf("child process failed to launch: %v", err)
+				}
+			})
+		}
+	}
+}
+
+func resetIgnoreTestProgram(t *testing.T, sig os.Signal) {
+	if Ignored(sig) {
+		os.Exit(1)
+	}
+	os.Exit(0)
+}