Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 817 insertions, 0 deletions

diff --git a/src/runtime/crash_test.go b/src/runtime/crash_test.go
new file mode 100644
index 0000000..e5bd797
--- /dev/null
+++ b/src/runtime/crash_test.go
@@ -0,0 +1,817 @@
+// Copyright 2012 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 runtime_test
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"internal/testenv"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+var toRemove []string
+
+func TestMain(m *testing.M) {
+	status := m.Run()
+	for _, file := range toRemove {
+		os.RemoveAll(file)
+	}
+	os.Exit(status)
+}
+
+var testprog struct {
+	sync.Mutex
+	dir    string
+	target map[string]buildexe
+}
+
+type buildexe struct {
+	exe string
+	err error
+}
+
+func runTestProg(t *testing.T, binary, name string, env ...string) string {
+	if *flagQuick {
+		t.Skip("-quick")
+	}
+
+	testenv.MustHaveGoBuild(t)
+
+	exe, err := buildTestProg(t, binary)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return runBuiltTestProg(t, exe, name, env...)
+}
+
+func runBuiltTestProg(t *testing.T, exe, name string, env ...string) string {
+	if *flagQuick {
+		t.Skip("-quick")
+	}
+
+	testenv.MustHaveGoBuild(t)
+
+	cmd := testenv.CleanCmdEnv(exec.Command(exe, name))
+	cmd.Env = append(cmd.Env, env...)
+	if testing.Short() {
+		cmd.Env = append(cmd.Env, "RUNTIME_TEST_SHORT=1")
+	}
+	var b bytes.Buffer
+	cmd.Stdout = &b
+	cmd.Stderr = &b
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("starting %s %s: %v", exe, name, err)
+	}
+
+	// If the process doesn't complete within 1 minute,
+	// assume it is hanging and kill it to get a stack trace.
+	p := cmd.Process
+	done := make(chan bool)
+	go func() {
+		scale := 1
+		// This GOARCH/GOOS test is copied from cmd/dist/test.go.
+		// TODO(iant): Have cmd/dist update the environment variable.
+		if runtime.GOARCH == "arm" || runtime.GOOS == "windows" {
+			scale = 2
+		}
+		if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
+			if sc, err := strconv.Atoi(s); err == nil {
+				scale = sc
+			}
+		}
+
+		select {
+		case <-done:
+		case <-time.After(time.Duration(scale) * time.Minute):
+			p.Signal(sigquit)
+		}
+	}()
+
+	if err := cmd.Wait(); err != nil {
+		t.Logf("%s %s exit status: %v", exe, name, err)
+	}
+	close(done)
+
+	return b.String()
+}
+
+func buildTestProg(t *testing.T, binary string, flags ...string) (string, error) {
+	if *flagQuick {
+		t.Skip("-quick")
+	}
+
+	testprog.Lock()
+	defer testprog.Unlock()
+	if testprog.dir == "" {
+		dir, err := os.MkdirTemp("", "go-build")
+		if err != nil {
+			t.Fatalf("failed to create temp directory: %v", err)
+		}
+		testprog.dir = dir
+		toRemove = append(toRemove, dir)
+	}
+
+	if testprog.target == nil {
+		testprog.target = make(map[string]buildexe)
+	}
+	name := binary
+	if len(flags) > 0 {
+		name += "_" + strings.Join(flags, "_")
+	}
+	target, ok := testprog.target[name]
+	if ok {
+		return target.exe, target.err
+	}
+
+	exe := filepath.Join(testprog.dir, name+".exe")
+	cmd := exec.Command(testenv.GoToolPath(t), append([]string{"build", "-o", exe}, flags...)...)
+	cmd.Dir = "testdata/" + binary
+	out, err := testenv.CleanCmdEnv(cmd).CombinedOutput()
+	if err != nil {
+		target.err = fmt.Errorf("building %s %v: %v\n%s", binary, flags, err, out)
+		testprog.target[name] = target
+		return "", target.err
+	}
+	target.exe = exe
+	testprog.target[name] = target
+	return exe, nil
+}
+
+func TestVDSO(t *testing.T) {
+	t.Parallel()
+	output := runTestProg(t, "testprog", "SignalInVDSO")
+	want := "success\n"
+	if output != want {
+		t.Fatalf("output:\n%s\n\nwanted:\n%s", output, want)
+	}
+}
+
+func testCrashHandler(t *testing.T, cgo bool) {
+	type crashTest struct {
+		Cgo bool
+	}
+	var output string
+	if cgo {
+		output = runTestProg(t, "testprogcgo", "Crash")
+	} else {
+		output = runTestProg(t, "testprog", "Crash")
+	}
+	want := "main: recovered done\nnew-thread: recovered done\nsecond-new-thread: recovered done\nmain-again: recovered done\n"
+	if output != want {
+		t.Fatalf("output:\n%s\n\nwanted:\n%s", output, want)
+	}
+}
+
+func TestCrashHandler(t *testing.T) {
+	testCrashHandler(t, false)
+}
+
+func testDeadlock(t *testing.T, name string) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	output := runTestProg(t, "testprog", name)
+	want := "fatal error: all goroutines are asleep - deadlock!\n"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestSimpleDeadlock(t *testing.T) {
+	testDeadlock(t, "SimpleDeadlock")
+}
+
+func TestInitDeadlock(t *testing.T) {
+	testDeadlock(t, "InitDeadlock")
+}
+
+func TestLockedDeadlock(t *testing.T) {
+	testDeadlock(t, "LockedDeadlock")
+}
+
+func TestLockedDeadlock2(t *testing.T) {
+	testDeadlock(t, "LockedDeadlock2")
+}
+
+func TestGoexitDeadlock(t *testing.T) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	output := runTestProg(t, "testprog", "GoexitDeadlock")
+	want := "no goroutines (main called runtime.Goexit) - deadlock!"
+	if !strings.Contains(output, want) {
+		t.Fatalf("output:\n%s\n\nwant output containing: %s", output, want)
+	}
+}
+
+func TestStackOverflow(t *testing.T) {
+	output := runTestProg(t, "testprog", "StackOverflow")
+	want := []string{
+		"runtime: goroutine stack exceeds 1474560-byte limit\n",
+		"fatal error: stack overflow",
+		// information about the current SP and stack bounds
+		"runtime: sp=",
+		"stack=[",
+	}
+	if !strings.HasPrefix(output, want[0]) {
+		t.Errorf("output does not start with %q", want[0])
+	}
+	for _, s := range want[1:] {
+		if !strings.Contains(output, s) {
+			t.Errorf("output does not contain %q", s)
+		}
+	}
+	if t.Failed() {
+		t.Logf("output:\n%s", output)
+	}
+}
+
+func TestThreadExhaustion(t *testing.T) {
+	output := runTestProg(t, "testprog", "ThreadExhaustion")
+	want := "runtime: program exceeds 10-thread limit\nfatal error: thread exhaustion"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestRecursivePanic(t *testing.T) {
+	output := runTestProg(t, "testprog", "RecursivePanic")
+	want := `wrap: bad
+panic: again
+
+`
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+}
+
+func TestRecursivePanic2(t *testing.T) {
+	output := runTestProg(t, "testprog", "RecursivePanic2")
+	want := `first panic
+second panic
+panic: third panic
+
+`
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+}
+
+func TestRecursivePanic3(t *testing.T) {
+	output := runTestProg(t, "testprog", "RecursivePanic3")
+	want := `panic: first panic
+
+`
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+}
+
+func TestRecursivePanic4(t *testing.T) {
+	output := runTestProg(t, "testprog", "RecursivePanic4")
+	want := `panic: first panic [recovered]
+	panic: second panic
+`
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+}
+
+func TestRecursivePanic5(t *testing.T) {
+	output := runTestProg(t, "testprog", "RecursivePanic5")
+	want := `first panic
+second panic
+panic: third panic
+`
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+}
+
+func TestGoexitCrash(t *testing.T) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	output := runTestProg(t, "testprog", "GoexitExit")
+	want := "no goroutines (main called runtime.Goexit) - deadlock!"
+	if !strings.Contains(output, want) {
+		t.Fatalf("output:\n%s\n\nwant output containing: %s", output, want)
+	}
+}
+
+func TestGoexitDefer(t *testing.T) {
+	c := make(chan struct{})
+	go func() {
+		defer func() {
+			r := recover()
+			if r != nil {
+				t.Errorf("non-nil recover during Goexit")
+			}
+			c <- struct{}{}
+		}()
+		runtime.Goexit()
+	}()
+	// Note: if the defer fails to run, we will get a deadlock here
+	<-c
+}
+
+func TestGoNil(t *testing.T) {
+	output := runTestProg(t, "testprog", "GoNil")
+	want := "go of nil func value"
+	if !strings.Contains(output, want) {
+		t.Fatalf("output:\n%s\n\nwant output containing: %s", output, want)
+	}
+}
+
+func TestMainGoroutineID(t *testing.T) {
+	output := runTestProg(t, "testprog", "MainGoroutineID")
+	want := "panic: test\n\ngoroutine 1 [running]:\n"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestNoHelperGoroutines(t *testing.T) {
+	output := runTestProg(t, "testprog", "NoHelperGoroutines")
+	matches := regexp.MustCompile(`goroutine [0-9]+ \[`).FindAllStringSubmatch(output, -1)
+	if len(matches) != 1 || matches[0][0] != "goroutine 1 [" {
+		t.Fatalf("want to see only goroutine 1, see:\n%s", output)
+	}
+}
+
+func TestBreakpoint(t *testing.T) {
+	output := runTestProg(t, "testprog", "Breakpoint")
+	// If runtime.Breakpoint() is inlined, then the stack trace prints
+	// "runtime.Breakpoint(...)" instead of "runtime.Breakpoint()".
+	want := "runtime.Breakpoint("
+	if !strings.Contains(output, want) {
+		t.Fatalf("output:\n%s\n\nwant output containing: %s", output, want)
+	}
+}
+
+func TestGoexitInPanic(t *testing.T) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	// see issue 8774: this code used to trigger an infinite recursion
+	output := runTestProg(t, "testprog", "GoexitInPanic")
+	want := "fatal error: no goroutines (main called runtime.Goexit) - deadlock!"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+// Issue 14965: Runtime panics should be of type runtime.Error
+func TestRuntimePanicWithRuntimeError(t *testing.T) {
+	testCases := [...]func(){
+		0: func() {
+			var m map[uint64]bool
+			m[1234] = true
+		},
+		1: func() {
+			ch := make(chan struct{})
+			close(ch)
+			close(ch)
+		},
+		2: func() {
+			var ch = make(chan struct{})
+			close(ch)
+			ch <- struct{}{}
+		},
+		3: func() {
+			var s = make([]int, 2)
+			_ = s[2]
+		},
+		4: func() {
+			n := -1
+			_ = make(chan bool, n)
+		},
+		5: func() {
+			close((chan bool)(nil))
+		},
+	}
+
+	for i, fn := range testCases {
+		got := panicValue(fn)
+		if _, ok := got.(runtime.Error); !ok {
+			t.Errorf("test #%d: recovered value %v(type %T) does not implement runtime.Error", i, got, got)
+		}
+	}
+}
+
+func panicValue(fn func()) (recovered interface{}) {
+	defer func() {
+		recovered = recover()
+	}()
+	fn()
+	return
+}
+
+func TestPanicAfterGoexit(t *testing.T) {
+	// an uncaught panic should still work after goexit
+	output := runTestProg(t, "testprog", "PanicAfterGoexit")
+	want := "panic: hello"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestRecoveredPanicAfterGoexit(t *testing.T) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	output := runTestProg(t, "testprog", "RecoveredPanicAfterGoexit")
+	want := "fatal error: no goroutines (main called runtime.Goexit) - deadlock!"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestRecoverBeforePanicAfterGoexit(t *testing.T) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	t.Parallel()
+	output := runTestProg(t, "testprog", "RecoverBeforePanicAfterGoexit")
+	want := "fatal error: no goroutines (main called runtime.Goexit) - deadlock!"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestRecoverBeforePanicAfterGoexit2(t *testing.T) {
+	// External linking brings in cgo, causing deadlock detection not working.
+	testenv.MustInternalLink(t)
+
+	t.Parallel()
+	output := runTestProg(t, "testprog", "RecoverBeforePanicAfterGoexit2")
+	want := "fatal error: no goroutines (main called runtime.Goexit) - deadlock!"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestNetpollDeadlock(t *testing.T) {
+	if os.Getenv("GO_BUILDER_NAME") == "darwin-amd64-10_12" {
+		// A suspected kernel bug in macOS 10.12 occasionally results in
+		// an apparent deadlock when dialing localhost. The errors have not
+		// been observed on newer versions of the OS, so we don't plan to work
+		// around them. See https://golang.org/issue/22019.
+		testenv.SkipFlaky(t, 22019)
+	}
+
+	t.Parallel()
+	output := runTestProg(t, "testprognet", "NetpollDeadlock")
+	want := "done\n"
+	if !strings.HasSuffix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestPanicTraceback(t *testing.T) {
+	t.Parallel()
+	output := runTestProg(t, "testprog", "PanicTraceback")
+	want := "panic: hello\n\tpanic: panic pt2\n\tpanic: panic pt1\n"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+	// Check functions in the traceback.
+	fns := []string{"main.pt1.func1", "panic", "main.pt2.func1", "panic", "main.pt2", "main.pt1"}
+	for _, fn := range fns {
+		re := regexp.MustCompile(`(?m)^` + regexp.QuoteMeta(fn) + `\(.*\n`)
+		idx := re.FindStringIndex(output)
+		if idx == nil {
+			t.Fatalf("expected %q function in traceback:\n%s", fn, output)
+		}
+		output = output[idx[1]:]
+	}
+}
+
+func testPanicDeadlock(t *testing.T, name string, want string) {
+	// test issue 14432
+	output := runTestProg(t, "testprog", name)
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+func TestPanicDeadlockGosched(t *testing.T) {
+	testPanicDeadlock(t, "GoschedInPanic", "panic: errorThatGosched\n\n")
+}
+
+func TestPanicDeadlockSyscall(t *testing.T) {
+	testPanicDeadlock(t, "SyscallInPanic", "1\n2\npanic: 3\n\n")
+}
+
+func TestPanicLoop(t *testing.T) {
+	output := runTestProg(t, "testprog", "PanicLoop")
+	if want := "panic while printing panic value"; !strings.Contains(output, want) {
+		t.Errorf("output does not contain %q:\n%s", want, output)
+	}
+}
+
+func TestMemPprof(t *testing.T) {
+	testenv.MustHaveGoRun(t)
+
+	exe, err := buildTestProg(t, "testprog")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := testenv.CleanCmdEnv(exec.Command(exe, "MemProf")).CombinedOutput()
+	if err != nil {
+		t.Fatal(err)
+	}
+	fn := strings.TrimSpace(string(got))
+	defer os.Remove(fn)
+
+	for try := 0; try < 2; try++ {
+		cmd := testenv.CleanCmdEnv(exec.Command(testenv.GoToolPath(t), "tool", "pprof", "-alloc_space", "-top"))
+		// Check that pprof works both with and without explicit executable on command line.
+		if try == 0 {
+			cmd.Args = append(cmd.Args, exe, fn)
+		} else {
+			cmd.Args = append(cmd.Args, fn)
+		}
+		found := false
+		for i, e := range cmd.Env {
+			if strings.HasPrefix(e, "PPROF_TMPDIR=") {
+				cmd.Env[i] = "PPROF_TMPDIR=" + os.TempDir()
+				found = true
+				break
+			}
+		}
+		if !found {
+			cmd.Env = append(cmd.Env, "PPROF_TMPDIR="+os.TempDir())
+		}
+
+		top, err := cmd.CombinedOutput()
+		t.Logf("%s:\n%s", cmd.Args, top)
+		if err != nil {
+			t.Error(err)
+		} else if !bytes.Contains(top, []byte("MemProf")) {
+			t.Error("missing MemProf in pprof output")
+		}
+	}
+}
+
+var concurrentMapTest = flag.Bool("run_concurrent_map_tests", false, "also run flaky concurrent map tests")
+
+func TestConcurrentMapWrites(t *testing.T) {
+	if !*concurrentMapTest {
+		t.Skip("skipping without -run_concurrent_map_tests")
+	}
+	testenv.MustHaveGoRun(t)
+	output := runTestProg(t, "testprog", "concurrentMapWrites")
+	want := "fatal error: concurrent map writes"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+func TestConcurrentMapReadWrite(t *testing.T) {
+	if !*concurrentMapTest {
+		t.Skip("skipping without -run_concurrent_map_tests")
+	}
+	testenv.MustHaveGoRun(t)
+	output := runTestProg(t, "testprog", "concurrentMapReadWrite")
+	want := "fatal error: concurrent map read and map write"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+func TestConcurrentMapIterateWrite(t *testing.T) {
+	if !*concurrentMapTest {
+		t.Skip("skipping without -run_concurrent_map_tests")
+	}
+	testenv.MustHaveGoRun(t)
+	output := runTestProg(t, "testprog", "concurrentMapIterateWrite")
+	want := "fatal error: concurrent map iteration and map write"
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+}
+
+type point struct {
+	x, y *int
+}
+
+func (p *point) negate() {
+	*p.x = *p.x * -1
+	*p.y = *p.y * -1
+}
+
+// Test for issue #10152.
+func TestPanicInlined(t *testing.T) {
+	defer func() {
+		r := recover()
+		if r == nil {
+			t.Fatalf("recover failed")
+		}
+		buf := make([]byte, 2048)
+		n := runtime.Stack(buf, false)
+		buf = buf[:n]
+		if !bytes.Contains(buf, []byte("(*point).negate(")) {
+			t.Fatalf("expecting stack trace to contain call to (*point).negate()")
+		}
+	}()
+
+	pt := new(point)
+	pt.negate()
+}
+
+// Test for issues #3934 and #20018.
+// We want to delay exiting until a panic print is complete.
+func TestPanicRace(t *testing.T) {
+	testenv.MustHaveGoRun(t)
+
+	exe, err := buildTestProg(t, "testprog")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// The test is intentionally racy, and in my testing does not
+	// produce the expected output about 0.05% of the time.
+	// So run the program in a loop and only fail the test if we
+	// get the wrong output ten times in a row.
+	const tries = 10
+retry:
+	for i := 0; i < tries; i++ {
+		got, err := testenv.CleanCmdEnv(exec.Command(exe, "PanicRace")).CombinedOutput()
+		if err == nil {
+			t.Logf("try %d: program exited successfully, should have failed", i+1)
+			continue
+		}
+
+		if i > 0 {
+			t.Logf("try %d:\n", i+1)
+		}
+		t.Logf("%s\n", got)
+
+		wants := []string{
+			"panic: crash",
+			"PanicRace",
+			"created by ",
+		}
+		for _, want := range wants {
+			if !bytes.Contains(got, []byte(want)) {
+				t.Logf("did not find expected string %q", want)
+				continue retry
+			}
+		}
+
+		// Test generated expected output.
+		return
+	}
+	t.Errorf("test ran %d times without producing expected output", tries)
+}
+
+func TestBadTraceback(t *testing.T) {
+	output := runTestProg(t, "testprog", "BadTraceback")
+	for _, want := range []string{
+		"runtime: unexpected return pc",
+		"called from 0xbad",
+		"00000bad",    // Smashed LR in hex dump
+		"<main.badLR", // Symbolization in hex dump (badLR1 or badLR2)
+	} {
+		if !strings.Contains(output, want) {
+			t.Errorf("output does not contain %q:\n%s", want, output)
+		}
+	}
+}
+
+func TestTimePprof(t *testing.T) {
+	// Pass GOTRACEBACK for issue #41120 to try to get more
+	// information on timeout.
+	fn := runTestProg(t, "testprog", "TimeProf", "GOTRACEBACK=crash")
+	fn = strings.TrimSpace(fn)
+	defer os.Remove(fn)
+
+	cmd := testenv.CleanCmdEnv(exec.Command(testenv.GoToolPath(t), "tool", "pprof", "-top", "-nodecount=1", fn))
+	cmd.Env = append(cmd.Env, "PPROF_TMPDIR="+os.TempDir())
+	top, err := cmd.CombinedOutput()
+	t.Logf("%s", top)
+	if err != nil {
+		t.Error(err)
+	} else if bytes.Contains(top, []byte("ExternalCode")) {
+		t.Error("profiler refers to ExternalCode")
+	}
+}
+
+// Test that runtime.abort does so.
+func TestAbort(t *testing.T) {
+	// Pass GOTRACEBACK to ensure we get runtime frames.
+	output := runTestProg(t, "testprog", "Abort", "GOTRACEBACK=system")
+	if want := "runtime.abort"; !strings.Contains(output, want) {
+		t.Errorf("output does not contain %q:\n%s", want, output)
+	}
+	if strings.Contains(output, "BAD") {
+		t.Errorf("output contains BAD:\n%s", output)
+	}
+	// Check that it's a signal traceback.
+	want := "PC="
+	// For systems that use a breakpoint, check specifically for that.
+	switch runtime.GOARCH {
+	case "386", "amd64":
+		switch runtime.GOOS {
+		case "plan9":
+			want = "sys: breakpoint"
+		case "windows":
+			want = "Exception 0x80000003"
+		default:
+			want = "SIGTRAP"
+		}
+	}
+	if !strings.Contains(output, want) {
+		t.Errorf("output does not contain %q:\n%s", want, output)
+	}
+}
+
+// For TestRuntimePanic: test a panic in the runtime package without
+// involving the testing harness.
+func init() {
+	if os.Getenv("GO_TEST_RUNTIME_PANIC") == "1" {
+		defer func() {
+			if r := recover(); r != nil {
+				// We expect to crash, so exit 0
+				// to indicate failure.
+				os.Exit(0)
+			}
+		}()
+		runtime.PanicForTesting(nil, 1)
+		// We expect to crash, so exit 0 to indicate failure.
+		os.Exit(0)
+	}
+}
+
+func TestRuntimePanic(t *testing.T) {
+	testenv.MustHaveExec(t)
+	cmd := testenv.CleanCmdEnv(exec.Command(os.Args[0], "-test.run=TestRuntimePanic"))
+	cmd.Env = append(cmd.Env, "GO_TEST_RUNTIME_PANIC=1")
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+	if err == nil {
+		t.Error("child process did not fail")
+	} else if want := "runtime.unexportedPanicForTesting"; !bytes.Contains(out, []byte(want)) {
+		t.Errorf("output did not contain expected string %q", want)
+	}
+}
+
+// Test that g0 stack overflows are handled gracefully.
+func TestG0StackOverflow(t *testing.T) {
+	testenv.MustHaveExec(t)
+
+	switch runtime.GOOS {
+	case "darwin", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "android":
+		t.Skipf("g0 stack is wrong on pthread platforms (see golang.org/issue/26061)")
+	}
+
+	if os.Getenv("TEST_G0_STACK_OVERFLOW") != "1" {
+		cmd := testenv.CleanCmdEnv(exec.Command(os.Args[0], "-test.run=TestG0StackOverflow", "-test.v"))
+		cmd.Env = append(cmd.Env, "TEST_G0_STACK_OVERFLOW=1")
+		out, err := cmd.CombinedOutput()
+		// Don't check err since it's expected to crash.
+		if n := strings.Count(string(out), "morestack on g0\n"); n != 1 {
+			t.Fatalf("%s\n(exit status %v)", out, err)
+		}
+		// Check that it's a signal-style traceback.
+		if runtime.GOOS != "windows" {
+			if want := "PC="; !strings.Contains(string(out), want) {
+				t.Errorf("output does not contain %q:\n%s", want, out)
+			}
+		}
+		return
+	}
+
+	runtime.G0StackOverflow()
+}
+
+// Test that panic message is not clobbered.
+// See issue 30150.
+func TestDoublePanic(t *testing.T) {
+	output := runTestProg(t, "testprog", "DoublePanic", "GODEBUG=clobberfree=1")
+	wants := []string{"panic: XXX", "panic: YYY"}
+	for _, want := range wants {
+		if !strings.Contains(output, want) {
+			t.Errorf("output:\n%s\n\nwant output containing: %s", output, want)
+		}
+	}
+}