src/runtime/gc_test.go - go - Git at Google

 // Copyright 2011 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 (
 	"io"
 	"os"
 	"reflect"
 	"runtime"
 	"runtime/debug"
 	"testing"
 	"time"
 	"unsafe"
 )

 func TestGcSys(t *testing.T) {
 	if os.Getenv("GOGC") == "off" {
 		t.Skip("skipping test; GOGC=off in environment")
 	}
 	got := runTestProg(t, "testprog", "GCSys")
 	want := "OK\n"
 	if got != want {
 		t.Fatalf("expected %q, but got %q", want, got)
 	}
 }

 func TestGcDeepNesting(t *testing.T) {
 	type T [2][2][2][2][2][2][2][2][2][2]*int
 	a := new(T)

 	// Prevent the compiler from applying escape analysis.
 	// This makes sure new(T) is allocated on heap, not on the stack.
 	t.Logf("%p", a)

 	a[0][0][0][0][0][0][0][0][0][0] = new(int)
 	*a[0][0][0][0][0][0][0][0][0][0] = 13
 	runtime.GC()
 	if *a[0][0][0][0][0][0][0][0][0][0] != 13 {
 		t.Fail()
 	}
 }

 func TestGcHashmapIndirection(t *testing.T) {
 	defer debug.SetGCPercent(debug.SetGCPercent(1))
 	runtime.GC()
 	type T struct {
 		a [256]int
 	}
 	m := make(map[T]T)
 	for i := 0; i < 2000; i++ {
 		var a T
 		a.a[0] = i
 		m[a] = T{}
 	}
 }

 func TestGcArraySlice(t *testing.T) {
 	type X struct {
 		buf     [1]byte
 		nextbuf []byte
 		next    *X
 	}
 	var head *X
 	for i := 0; i < 10; i++ {
 		p := &X{}
 		p.buf[0] = 42
 		p.next = head
 		if head != nil {
 			p.nextbuf = head.buf[:]
 		}
 		head = p
 		runtime.GC()
 	}
 	for p := head; p != nil; p = p.next {
 		if p.buf[0] != 42 {
 			t.Fatal("corrupted heap")
 		}
 	}
 }

 func TestGcRescan(t *testing.T) {
 	type X struct {
 		c     chan error
 		nextx *X
 	}
 	type Y struct {
 		X
 		nexty *Y
 		p     *int
 	}
 	var head *Y
 	for i := 0; i < 10; i++ {
 		p := &Y{}
 		p.c = make(chan error)
 		if head != nil {
 			p.nextx = &head.X
 		}
 		p.nexty = head
 		p.p = new(int)
 		*p.p = 42
 		head = p
 		runtime.GC()
 	}
 	for p := head; p != nil; p = p.nexty {
 		if *p.p != 42 {
 			t.Fatal("corrupted heap")
 		}
 	}
 }

 func TestGcLastTime(t *testing.T) {
 	ms := new(runtime.MemStats)
 	t0 := time.Now().UnixNano()
 	runtime.GC()
 	t1 := time.Now().UnixNano()
 	runtime.ReadMemStats(ms)
 	last := int64(ms.LastGC)
 	if t0 > last || last > t1 {
 		t.Fatalf("bad last GC time: got %v, want [%v, %v]", last, t0, t1)
 	}
 	pause := ms.PauseNs[(ms.NumGC+255)%256]
 	// Due to timer granularity, pause can actually be 0 on windows
 	// or on virtualized environments.
 	if pause == 0 {
 		t.Logf("last GC pause was 0")
 	} else if pause > 10e9 {
 		t.Logf("bad last GC pause: got %v, want [0, 10e9]", pause)
 	}
 }

 var hugeSink interface{}

 func TestHugeGCInfo(t *testing.T) {
 	// The test ensures that compiler can chew these huge types even on weakest machines.
 	// The types are not allocated at runtime.
 	if hugeSink != nil {
 		// 400MB on 32 bots, 4TB on 64-bits.
 		const n = (400 << 20) + (unsafe.Sizeof(uintptr(0))-4)<<40
 		hugeSink = new([n]*byte)
 		hugeSink = new([n]uintptr)
 		hugeSink = new(struct {
 			x float64
 			y [n]*byte
 			z []string
 		})
 		hugeSink = new(struct {
 			x float64
 			y [n]uintptr
 			z []string
 		})
 	}
 }

 func TestPeriodicGC(t *testing.T) {
 	// Make sure we're not in the middle of a GC.
 	runtime.GC()

 	var ms1, ms2 runtime.MemStats
 	runtime.ReadMemStats(&ms1)

 	// Make periodic GC run continuously.
 	orig := *runtime.ForceGCPeriod
 	*runtime.ForceGCPeriod = 0

 	// Let some periodic GCs happen. In a heavily loaded system,
 	// it's possible these will be delayed, so this is designed to
 	// succeed quickly if things are working, but to give it some
 	// slack if things are slow.
 	var numGCs uint32
 	const want = 2
 	for i := 0; i < 20 && numGCs < want; i++ {
 		time.Sleep(5 * time.Millisecond)

 		// Test that periodic GC actually happened.
 		runtime.ReadMemStats(&ms2)
 		numGCs = ms2.NumGC - ms1.NumGC
 	}
 	*runtime.ForceGCPeriod = orig

 	if numGCs < want {
 		t.Fatalf("no periodic GC: got %v GCs, want >= 2", numGCs)
 	}
 }

 func BenchmarkSetTypePtr(b *testing.B) {
 	benchSetType(b, new(*byte))
 }

 func BenchmarkSetTypePtr8(b *testing.B) {
 	benchSetType(b, new([8]*byte))
 }

 func BenchmarkSetTypePtr16(b *testing.B) {
 	benchSetType(b, new([16]*byte))
 }

 func BenchmarkSetTypePtr32(b *testing.B) {
 	benchSetType(b, new([32]*byte))
 }

 func BenchmarkSetTypePtr64(b *testing.B) {
 	benchSetType(b, new([64]*byte))
 }

 func BenchmarkSetTypePtr126(b *testing.B) {
 	benchSetType(b, new([126]*byte))
 }

 func BenchmarkSetTypePtr128(b *testing.B) {
 	benchSetType(b, new([128]*byte))
 }

 func BenchmarkSetTypePtrSlice(b *testing.B) {
 	benchSetType(b, make([]*byte, 1<<10))
 }

 type Node1 struct {
 	Value       [1]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode1(b *testing.B) {
 	benchSetType(b, new(Node1))
 }

 func BenchmarkSetTypeNode1Slice(b *testing.B) {
 	benchSetType(b, make([]Node1, 32))
 }

 type Node8 struct {
 	Value       [8]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode8(b *testing.B) {
 	benchSetType(b, new(Node8))
 }

 func BenchmarkSetTypeNode8Slice(b *testing.B) {
 	benchSetType(b, make([]Node8, 32))
 }

 type Node64 struct {
 	Value       [64]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode64(b *testing.B) {
 	benchSetType(b, new(Node64))
 }

 func BenchmarkSetTypeNode64Slice(b *testing.B) {
 	benchSetType(b, make([]Node64, 32))
 }

 type Node64Dead struct {
 	Left, Right *byte
 	Value       [64]uintptr
 }

 func BenchmarkSetTypeNode64Dead(b *testing.B) {
 	benchSetType(b, new(Node64Dead))
 }

 func BenchmarkSetTypeNode64DeadSlice(b *testing.B) {
 	benchSetType(b, make([]Node64Dead, 32))
 }

 type Node124 struct {
 	Value       [124]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode124(b *testing.B) {
 	benchSetType(b, new(Node124))
 }

 func BenchmarkSetTypeNode124Slice(b *testing.B) {
 	benchSetType(b, make([]Node124, 32))
 }

 type Node126 struct {
 	Value       [126]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode126(b *testing.B) {
 	benchSetType(b, new(Node126))
 }

 func BenchmarkSetTypeNode126Slice(b *testing.B) {
 	benchSetType(b, make([]Node126, 32))
 }

 type Node128 struct {
 	Value       [128]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode128(b *testing.B) {
 	benchSetType(b, new(Node128))
 }

 func BenchmarkSetTypeNode128Slice(b *testing.B) {
 	benchSetType(b, make([]Node128, 32))
 }

 type Node130 struct {
 	Value       [130]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode130(b *testing.B) {
 	benchSetType(b, new(Node130))
 }

 func BenchmarkSetTypeNode130Slice(b *testing.B) {
 	benchSetType(b, make([]Node130, 32))
 }

 type Node1024 struct {
 	Value       [1024]uintptr
 	Left, Right *byte
 }

 func BenchmarkSetTypeNode1024(b *testing.B) {
 	benchSetType(b, new(Node1024))
 }

 func BenchmarkSetTypeNode1024Slice(b *testing.B) {
 	benchSetType(b, make([]Node1024, 32))
 }

 func benchSetType(b *testing.B, x interface{}) {
 	v := reflect.ValueOf(x)
 	t := v.Type()
 	switch t.Kind() {
 	case reflect.Ptr:
 		b.SetBytes(int64(t.Elem().Size()))
 	case reflect.Slice:
 		b.SetBytes(int64(t.Elem().Size()) * int64(v.Len()))
 	}
 	b.ResetTimer()
 	runtime.BenchSetType(b.N, x)
 }

 func BenchmarkAllocation(b *testing.B) {
 	type T struct {
 		x, y *byte
 	}
 	ngo := runtime.GOMAXPROCS(0)
 	work := make(chan bool, b.N+ngo)
 	result := make(chan *T)
 	for i := 0; i < b.N; i++ {
 		work <- true
 	}
 	for i := 0; i < ngo; i++ {
 		work <- false
 	}
 	for i := 0; i < ngo; i++ {
 		go func() {
 			var x *T
 			for <-work {
 				for i := 0; i < 1000; i++ {
 					x = &T{}
 				}
 			}
 			result <- x
 		}()
 	}
 	for i := 0; i < ngo; i++ {
 		<-result
 	}
 }

 func TestPrintGC(t *testing.T) {
 	if testing.Short() {
 		t.Skip("Skipping in short mode")
 	}
 	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
 	done := make(chan bool)
 	go func() {
 		for {
 			select {
 			case <-done:
 				return
 			default:
 				runtime.GC()
 			}
 		}
 	}()
 	for i := 0; i < 1e4; i++ {
 		func() {
 			defer print("")
 		}()
 	}
 	close(done)
 }

 // The implicit y, ok := x.(error) for the case error
 // in testTypeSwitch used to not initialize the result y
 // before passing &y to assertE2I2GC.
 // Catch this by making assertE2I2 call runtime.GC,
 // which will force a stack scan and failure if there are
 // bad pointers, and then fill the stack with bad pointers
 // and run the type switch.
 func TestAssertE2I2Liveness(t *testing.T) {
 	// Note that this flag is defined in export_test.go
 	// and is not available to ordinary imports of runtime.
 	*runtime.TestingAssertE2I2GC = true
 	defer func() {
 		*runtime.TestingAssertE2I2GC = false
 	}()

 	poisonStack()
 	testTypeSwitch(io.EOF)
 	poisonStack()
 	testAssert(io.EOF)
 	poisonStack()
 	testAssertVar(io.EOF)
 }

 func poisonStack() uintptr {
 	var x [1000]uintptr
 	for i := range x {
 		x[i] = 0xff
 	}
 	return x[123]
 }

 func testTypeSwitch(x interface{}) error {
 	switch y := x.(type) {
 	case nil:
 		// ok
 	case error:
 		return y
 	}
 	return nil
 }

 func testAssert(x interface{}) error {
 	if y, ok := x.(error); ok {
 		return y
 	}
 	return nil
 }

 func testAssertVar(x interface{}) error {
 	var y, ok = x.(error)
 	if ok {
 		return y
 	}
 	return nil
 }

 func TestAssertE2T2Liveness(t *testing.T) {
 	*runtime.TestingAssertE2T2GC = true
 	defer func() {
 		*runtime.TestingAssertE2T2GC = false
 	}()

 	poisonStack()
 	testIfaceEqual(io.EOF)
 }

 var a bool

 //go:noinline
 func testIfaceEqual(x interface{}) {
 	if x == "abc" {
 		a = true
 	}
 }

 func TestPageAccounting(t *testing.T) {
 	// Grow the heap in small increments. This used to drop the
 	// pages-in-use count below zero because of a rounding
 	// mismatch (golang.org/issue/15022).
 	const blockSize = 64 << 10
 	blocks := make([]*[blockSize]byte, (64<<20)/blockSize)
 	for i := range blocks {
 		blocks[i] = new([blockSize]byte)
 	}

 	// Check that the running page count matches reality.
 	pagesInUse, counted := runtime.CountPagesInUse()
 	if pagesInUse != counted {
 		t.Fatalf("mheap_.pagesInUse is %d, but direct count is %d", pagesInUse, counted)
 	}
 }
	// Copyright 2011 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 (
	"io"
	"os"
	"reflect"
	"runtime"
	"runtime/debug"
	"testing"
	"time"
	"unsafe"
	)

	func TestGcSys(t *testing.T) {
	if os.Getenv("GOGC") == "off" {
	t.Skip("skipping test; GOGC=off in environment")
	}
	got := runTestProg(t, "testprog", "GCSys")
	want := "OK\n"
	if got != want {
	t.Fatalf("expected %q, but got %q", want, got)
	}
	}

	func TestGcDeepNesting(t *testing.T) {
	type T [2][2][2][2][2][2][2][2][2][2]*int
	a := new(T)

	// Prevent the compiler from applying escape analysis.
	// This makes sure new(T) is allocated on heap, not on the stack.
	t.Logf("%p", a)

	a[0][0][0][0][0][0][0][0][0][0] = new(int)
	*a[0][0][0][0][0][0][0][0][0][0] = 13
	runtime.GC()
	if *a[0][0][0][0][0][0][0][0][0][0] != 13 {
	t.Fail()
	}
	}

	func TestGcHashmapIndirection(t *testing.T) {
	defer debug.SetGCPercent(debug.SetGCPercent(1))
	runtime.GC()
	type T struct {
	a [256]int
	}
	m := make(map[T]T)
	for i := 0; i < 2000; i++ {
	var a T
	a.a[0] = i
	m[a] = T{}
	}
	}

	func TestGcArraySlice(t *testing.T) {
	type X struct {
	buf [1]byte
	nextbuf []byte
	next *X
	}
	var head *X
	for i := 0; i < 10; i++ {
	p := &X{}
	p.buf[0] = 42
	p.next = head
	if head != nil {
	p.nextbuf = head.buf[:]
	}
	head = p
	runtime.GC()
	}
	for p := head; p != nil; p = p.next {
	if p.buf[0] != 42 {
	t.Fatal("corrupted heap")
	}
	}
	}

	func TestGcRescan(t *testing.T) {
	type X struct {
	c chan error
	nextx *X
	}
	type Y struct {
	X
	nexty *Y
	p *int
	}
	var head *Y
	for i := 0; i < 10; i++ {
	p := &Y{}
	p.c = make(chan error)
	if head != nil {
	p.nextx = &head.X
	}
	p.nexty = head
	p.p = new(int)
	*p.p = 42
	head = p
	runtime.GC()
	}
	for p := head; p != nil; p = p.nexty {
	if *p.p != 42 {
	t.Fatal("corrupted heap")
	}
	}
	}

	func TestGcLastTime(t *testing.T) {
	ms := new(runtime.MemStats)
	t0 := time.Now().UnixNano()
	runtime.GC()
	t1 := time.Now().UnixNano()
	runtime.ReadMemStats(ms)
	last := int64(ms.LastGC)
	if t0 > last \|\| last > t1 {
	t.Fatalf("bad last GC time: got %v, want [%v, %v]", last, t0, t1)
	}
	pause := ms.PauseNs[(ms.NumGC+255)%256]
	// Due to timer granularity, pause can actually be 0 on windows
	// or on virtualized environments.
	if pause == 0 {
	t.Logf("last GC pause was 0")
	} else if pause > 10e9 {
	t.Logf("bad last GC pause: got %v, want [0, 10e9]", pause)
	}
	}

	var hugeSink interface{}

	func TestHugeGCInfo(t *testing.T) {
	// The test ensures that compiler can chew these huge types even on weakest machines.
	// The types are not allocated at runtime.
	if hugeSink != nil {
	// 400MB on 32 bots, 4TB on 64-bits.
	const n = (400 << 20) + (unsafe.Sizeof(uintptr(0))-4)<<40
	hugeSink = new([n]*byte)
	hugeSink = new([n]uintptr)
	hugeSink = new(struct {
	x float64
	y [n]*byte
	z []string
	})
	hugeSink = new(struct {
	x float64
	y [n]uintptr
	z []string
	})
	}
	}

	func TestPeriodicGC(t *testing.T) {
	// Make sure we're not in the middle of a GC.
	runtime.GC()

	var ms1, ms2 runtime.MemStats
	runtime.ReadMemStats(&ms1)

	// Make periodic GC run continuously.
	orig := *runtime.ForceGCPeriod
	*runtime.ForceGCPeriod = 0

	// Let some periodic GCs happen. In a heavily loaded system,
	// it's possible these will be delayed, so this is designed to
	// succeed quickly if things are working, but to give it some
	// slack if things are slow.
	var numGCs uint32
	const want = 2
	for i := 0; i < 20 && numGCs < want; i++ {
	time.Sleep(5 * time.Millisecond)

	// Test that periodic GC actually happened.
	runtime.ReadMemStats(&ms2)
	numGCs = ms2.NumGC - ms1.NumGC
	}
	*runtime.ForceGCPeriod = orig

	if numGCs < want {
	t.Fatalf("no periodic GC: got %v GCs, want >= 2", numGCs)
	}
	}

	func BenchmarkSetTypePtr(b *testing.B) {
	benchSetType(b, new(*byte))
	}

	func BenchmarkSetTypePtr8(b *testing.B) {
	benchSetType(b, new([8]*byte))
	}

	func BenchmarkSetTypePtr16(b *testing.B) {
	benchSetType(b, new([16]*byte))
	}

	func BenchmarkSetTypePtr32(b *testing.B) {
	benchSetType(b, new([32]*byte))
	}

	func BenchmarkSetTypePtr64(b *testing.B) {
	benchSetType(b, new([64]*byte))
	}

	func BenchmarkSetTypePtr126(b *testing.B) {
	benchSetType(b, new([126]*byte))
	}

	func BenchmarkSetTypePtr128(b *testing.B) {
	benchSetType(b, new([128]*byte))
	}

	func BenchmarkSetTypePtrSlice(b *testing.B) {
	benchSetType(b, make([]*byte, 1<<10))
	}

	type Node1 struct {
	Value [1]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode1(b *testing.B) {
	benchSetType(b, new(Node1))
	}

	func BenchmarkSetTypeNode1Slice(b *testing.B) {
	benchSetType(b, make([]Node1, 32))
	}

	type Node8 struct {
	Value [8]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode8(b *testing.B) {
	benchSetType(b, new(Node8))
	}

	func BenchmarkSetTypeNode8Slice(b *testing.B) {
	benchSetType(b, make([]Node8, 32))
	}

	type Node64 struct {
	Value [64]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode64(b *testing.B) {
	benchSetType(b, new(Node64))
	}

	func BenchmarkSetTypeNode64Slice(b *testing.B) {
	benchSetType(b, make([]Node64, 32))
	}

	type Node64Dead struct {
	Left, Right *byte
	Value [64]uintptr
	}

	func BenchmarkSetTypeNode64Dead(b *testing.B) {
	benchSetType(b, new(Node64Dead))
	}

	func BenchmarkSetTypeNode64DeadSlice(b *testing.B) {
	benchSetType(b, make([]Node64Dead, 32))
	}

	type Node124 struct {
	Value [124]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode124(b *testing.B) {
	benchSetType(b, new(Node124))
	}

	func BenchmarkSetTypeNode124Slice(b *testing.B) {
	benchSetType(b, make([]Node124, 32))
	}

	type Node126 struct {
	Value [126]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode126(b *testing.B) {
	benchSetType(b, new(Node126))
	}

	func BenchmarkSetTypeNode126Slice(b *testing.B) {
	benchSetType(b, make([]Node126, 32))
	}

	type Node128 struct {
	Value [128]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode128(b *testing.B) {
	benchSetType(b, new(Node128))
	}

	func BenchmarkSetTypeNode128Slice(b *testing.B) {
	benchSetType(b, make([]Node128, 32))
	}

	type Node130 struct {
	Value [130]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode130(b *testing.B) {
	benchSetType(b, new(Node130))
	}

	func BenchmarkSetTypeNode130Slice(b *testing.B) {
	benchSetType(b, make([]Node130, 32))
	}

	type Node1024 struct {
	Value [1024]uintptr
	Left, Right *byte
	}

	func BenchmarkSetTypeNode1024(b *testing.B) {
	benchSetType(b, new(Node1024))
	}

	func BenchmarkSetTypeNode1024Slice(b *testing.B) {
	benchSetType(b, make([]Node1024, 32))
	}

	func benchSetType(b *testing.B, x interface{}) {
	v := reflect.ValueOf(x)
	t := v.Type()
	switch t.Kind() {
	case reflect.Ptr:
	b.SetBytes(int64(t.Elem().Size()))
	case reflect.Slice:
	b.SetBytes(int64(t.Elem().Size()) * int64(v.Len()))
	}
	b.ResetTimer()
	runtime.BenchSetType(b.N, x)
	}

	func BenchmarkAllocation(b *testing.B) {
	type T struct {
	x, y *byte
	}
	ngo := runtime.GOMAXPROCS(0)
	work := make(chan bool, b.N+ngo)
	result := make(chan *T)
	for i := 0; i < b.N; i++ {
	work <- true
	}
	for i := 0; i < ngo; i++ {
	work <- false
	}
	for i := 0; i < ngo; i++ {
	go func() {
	var x *T
	for <-work {
	for i := 0; i < 1000; i++ {
	x = &T{}
	}
	}
	result <- x
	}()
	}
	for i := 0; i < ngo; i++ {
	<-result
	}
	}

	func TestPrintGC(t *testing.T) {
	if testing.Short() {
	t.Skip("Skipping in short mode")
	}
	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
	done := make(chan bool)
	go func() {
	for {
	select {
	case <-done:
	return
	default:
	runtime.GC()
	}
	}
	}()
	for i := 0; i < 1e4; i++ {
	func() {
	defer print("")
	}()
	}
	close(done)
	}

	// The implicit y, ok := x.(error) for the case error
	// in testTypeSwitch used to not initialize the result y
	// before passing &y to assertE2I2GC.
	// Catch this by making assertE2I2 call runtime.GC,
	// which will force a stack scan and failure if there are
	// bad pointers, and then fill the stack with bad pointers
	// and run the type switch.
	func TestAssertE2I2Liveness(t *testing.T) {
	// Note that this flag is defined in export_test.go
	// and is not available to ordinary imports of runtime.
	*runtime.TestingAssertE2I2GC = true
	defer func() {
	*runtime.TestingAssertE2I2GC = false
	}()

	poisonStack()
	testTypeSwitch(io.EOF)
	poisonStack()
	testAssert(io.EOF)
	poisonStack()
	testAssertVar(io.EOF)
	}

	func poisonStack() uintptr {
	var x [1000]uintptr
	for i := range x {
	x[i] = 0xff
	}
	return x[123]
	}

	func testTypeSwitch(x interface{}) error {
	switch y := x.(type) {
	case nil:
	// ok
	case error:
	return y
	}
	return nil
	}

	func testAssert(x interface{}) error {
	if y, ok := x.(error); ok {
	return y
	}
	return nil
	}

	func testAssertVar(x interface{}) error {
	var y, ok = x.(error)
	if ok {
	return y
	}
	return nil
	}

	func TestAssertE2T2Liveness(t *testing.T) {
	*runtime.TestingAssertE2T2GC = true
	defer func() {
	*runtime.TestingAssertE2T2GC = false
	}()

	poisonStack()
	testIfaceEqual(io.EOF)
	}

	var a bool

	//go:noinline
	func testIfaceEqual(x interface{}) {
	if x == "abc" {
	a = true
	}
	}

	func TestPageAccounting(t *testing.T) {
	// Grow the heap in small increments. This used to drop the
	// pages-in-use count below zero because of a rounding
	// mismatch (golang.org/issue/15022).
	const blockSize = 64 << 10
	blocks := make([]*[blockSize]byte, (64<<20)/blockSize)
	for i := range blocks {
	blocks[i] = new([blockSize]byte)
	}

	// Check that the running page count matches reality.
	pagesInUse, counted := runtime.CountPagesInUse()
	if pagesInUse != counted {
	t.Fatalf("mheap_.pagesInUse is %d, but direct count is %d", pagesInUse, counted)
	}
	}