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

 // Copyright 2010 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.

 // Export guts for testing.

 package runtime

 import (
 	"runtime/internal/atomic"
 	"runtime/internal/sys"
 	"unsafe"
 )

 var Fadd64 = fadd64
 var Fsub64 = fsub64
 var Fmul64 = fmul64
 var Fdiv64 = fdiv64
 var F64to32 = f64to32
 var F32to64 = f32to64
 var Fcmp64 = fcmp64
 var Fintto64 = fintto64
 var F64toint = f64toint

 var Entersyscall = entersyscall
 var Exitsyscall = exitsyscall
 var LockedOSThread = lockedOSThread
 var Xadduintptr = atomic.Xadduintptr

 var FuncPC = funcPC

 var Fastlog2 = fastlog2

 var Atoi = atoi
 var Atoi32 = atoi32

 type LFNode struct {
 	Next    uint64
 	Pushcnt uintptr
 }

 func LFStackPush(head *uint64, node *LFNode) {
 	(*lfstack)(head).push((*lfnode)(unsafe.Pointer(node)))
 }

 func LFStackPop(head *uint64) *LFNode {
 	return (*LFNode)(unsafe.Pointer((*lfstack)(head).pop()))
 }

 func GCMask(x interface{}) (ret []byte) {
 	systemstack(func() {
 		ret = getgcmask(x)
 	})
 	return
 }

 func RunSchedLocalQueueTest() {
 	_p_ := new(p)
 	gs := make([]g, len(_p_.runq))
 	for i := 0; i < len(_p_.runq); i++ {
 		if g, _ := runqget(_p_); g != nil {
 			throw("runq is not empty initially")
 		}
 		for j := 0; j < i; j++ {
 			runqput(_p_, &gs[i], false)
 		}
 		for j := 0; j < i; j++ {
 			if g, _ := runqget(_p_); g != &gs[i] {
 				print("bad element at iter ", i, "/", j, "\n")
 				throw("bad element")
 			}
 		}
 		if g, _ := runqget(_p_); g != nil {
 			throw("runq is not empty afterwards")
 		}
 	}
 }

 func RunSchedLocalQueueStealTest() {
 	p1 := new(p)
 	p2 := new(p)
 	gs := make([]g, len(p1.runq))
 	for i := 0; i < len(p1.runq); i++ {
 		for j := 0; j < i; j++ {
 			gs[j].sig = 0
 			runqput(p1, &gs[j], false)
 		}
 		gp := runqsteal(p2, p1, true)
 		s := 0
 		if gp != nil {
 			s++
 			gp.sig++
 		}
 		for {
 			gp, _ = runqget(p2)
 			if gp == nil {
 				break
 			}
 			s++
 			gp.sig++
 		}
 		for {
 			gp, _ = runqget(p1)
 			if gp == nil {
 				break
 			}
 			gp.sig++
 		}
 		for j := 0; j < i; j++ {
 			if gs[j].sig != 1 {
 				print("bad element ", j, "(", gs[j].sig, ") at iter ", i, "\n")
 				throw("bad element")
 			}
 		}
 		if s != i/2 && s != i/2+1 {
 			print("bad steal ", s, ", want ", i/2, " or ", i/2+1, ", iter ", i, "\n")
 			throw("bad steal")
 		}
 	}
 }

 func RunSchedLocalQueueEmptyTest(iters int) {
 	// Test that runq is not spuriously reported as empty.
 	// Runq emptiness affects scheduling decisions and spurious emptiness
 	// can lead to underutilization (both runnable Gs and idle Ps coexist
 	// for arbitrary long time).
 	done := make(chan bool, 1)
 	p := new(p)
 	gs := make([]g, 2)
 	ready := new(uint32)
 	for i := 0; i < iters; i++ {
 		*ready = 0
 		next0 := (i & 1) == 0
 		next1 := (i & 2) == 0
 		runqput(p, &gs[0], next0)
 		go func() {
 			for atomic.Xadd(ready, 1); atomic.Load(ready) != 2; {
 			}
 			if runqempty(p) {
 				println("next:", next0, next1)
 				throw("queue is empty")
 			}
 			done <- true
 		}()
 		for atomic.Xadd(ready, 1); atomic.Load(ready) != 2; {
 		}
 		runqput(p, &gs[1], next1)
 		runqget(p)
 		<-done
 		runqget(p)
 	}
 }

 var (
 	StringHash = stringHash
 	BytesHash  = bytesHash
 	Int32Hash  = int32Hash
 	Int64Hash  = int64Hash
 	MemHash    = memhash
 	MemHash32  = memhash32
 	MemHash64  = memhash64
 	EfaceHash  = efaceHash
 	IfaceHash  = ifaceHash
 )

 var UseAeshash = &useAeshash

 func MemclrBytes(b []byte) {
 	s := (*slice)(unsafe.Pointer(&b))
 	memclrNoHeapPointers(s.array, uintptr(s.len))
 }

 var HashLoad = &hashLoad

 // entry point for testing
 func GostringW(w []uint16) (s string) {
 	systemstack(func() {
 		s = gostringw(&w[0])
 	})
 	return
 }

 type Uintreg sys.Uintreg

 var Open = open
 var Close = closefd
 var Read = read
 var Write = write

 func Envs() []string     { return envs }
 func SetEnvs(e []string) { envs = e }

 var BigEndian = sys.BigEndian

 // For benchmarking.

 func BenchSetType(n int, x interface{}) {
 	e := *efaceOf(&x)
 	t := e._type
 	var size uintptr
 	var p unsafe.Pointer
 	switch t.kind & kindMask {
 	case kindPtr:
 		t = (*ptrtype)(unsafe.Pointer(t)).elem
 		size = t.size
 		p = e.data
 	case kindSlice:
 		slice := *(*struct {
 			ptr      unsafe.Pointer
 			len, cap uintptr
 		})(e.data)
 		t = (*slicetype)(unsafe.Pointer(t)).elem
 		size = t.size * slice.len
 		p = slice.ptr
 	}
 	allocSize := roundupsize(size)
 	systemstack(func() {
 		for i := 0; i < n; i++ {
 			heapBitsSetType(uintptr(p), allocSize, size, t)
 		}
 	})
 }

 const PtrSize = sys.PtrSize

 var ForceGCPeriod = &forcegcperiod

 // SetTracebackEnv is like runtime/debug.SetTraceback, but it raises
 // the "environment" traceback level, so later calls to
 // debug.SetTraceback (e.g., from testing timeouts) can't lower it.
 func SetTracebackEnv(level string) {
 	setTraceback(level)
 	traceback_env = traceback_cache
 }

 var ReadUnaligned32 = readUnaligned32
 var ReadUnaligned64 = readUnaligned64

 func CountPagesInUse() (pagesInUse, counted uintptr) {
 	stopTheWorld("CountPagesInUse")

 	pagesInUse = uintptr(mheap_.pagesInUse)

 	for _, s := range mheap_.allspans {
 		if s.state == mSpanInUse {
 			counted += s.npages
 		}
 	}

 	startTheWorld()

 	return
 }

 func Fastrand() uint32          { return fastrand() }
 func Fastrandn(n uint32) uint32 { return fastrandn(n) }

 type ProfBuf profBuf

 func NewProfBuf(hdrsize, bufwords, tags int) *ProfBuf {
 	return (*ProfBuf)(newProfBuf(hdrsize, bufwords, tags))
 }

 func (p *ProfBuf) Write(tag *unsafe.Pointer, now int64, hdr []uint64, stk []uintptr) {
 	(*profBuf)(p).write(tag, now, hdr, stk)
 }

 const (
 	ProfBufBlocking    = profBufBlocking
 	ProfBufNonBlocking = profBufNonBlocking
 )

 func (p *ProfBuf) Read(mode profBufReadMode) ([]uint64, []unsafe.Pointer, bool) {
 	return (*profBuf)(p).read(profBufReadMode(mode))
 }

 func (p *ProfBuf) Close() {
 	(*profBuf)(p).close()
 }

 // ReadMemStatsSlow returns both the runtime-computed MemStats and
 // MemStats accumulated by scanning the heap.
 func ReadMemStatsSlow() (base, slow MemStats) {
 	stopTheWorld("ReadMemStatsSlow")

 	// Run on the system stack to avoid stack growth allocation.
 	systemstack(func() {
 		// Make sure stats don't change.
 		getg().m.mallocing++

 		readmemstats_m(&base)

 		// Initialize slow from base and zero the fields we're
 		// recomputing.
 		slow = base
 		slow.Alloc = 0
 		slow.TotalAlloc = 0
 		slow.Mallocs = 0
 		slow.Frees = 0
 		var bySize [_NumSizeClasses]struct {
 			Mallocs, Frees uint64
 		}

 		// Add up current allocations in spans.
 		for _, s := range mheap_.allspans {
 			if s.state != mSpanInUse {
 				continue
 			}
 			if sizeclass := s.spanclass.sizeclass(); sizeclass == 0 {
 				slow.Mallocs++
 				slow.Alloc += uint64(s.elemsize)
 			} else {
 				slow.Mallocs += uint64(s.allocCount)
 				slow.Alloc += uint64(s.allocCount) * uint64(s.elemsize)
 				bySize[sizeclass].Mallocs += uint64(s.allocCount)
 			}
 		}

 		// Add in frees. readmemstats_m flushed the cached stats, so
 		// these are up-to-date.
 		var smallFree uint64
 		slow.Frees = mheap_.nlargefree
 		for i := range mheap_.nsmallfree {
 			slow.Frees += mheap_.nsmallfree[i]
 			bySize[i].Frees = mheap_.nsmallfree[i]
 			bySize[i].Mallocs += mheap_.nsmallfree[i]
 			smallFree += mheap_.nsmallfree[i] * uint64(class_to_size[i])
 		}
 		slow.Frees += memstats.tinyallocs
 		slow.Mallocs += slow.Frees

 		slow.TotalAlloc = slow.Alloc + mheap_.largefree + smallFree

 		for i := range slow.BySize {
 			slow.BySize[i].Mallocs = bySize[i].Mallocs
 			slow.BySize[i].Frees = bySize[i].Frees
 		}

 		getg().m.mallocing--
 	})

 	startTheWorld()
 	return
 }

 // BlockOnSystemStack switches to the system stack, prints "x\n" to
 // stderr, and blocks in a stack containing
 // "runtime.blockOnSystemStackInternal".
 func BlockOnSystemStack() {
 	systemstack(blockOnSystemStackInternal)
 }

 func blockOnSystemStackInternal() {
 	print("x\n")
 	lock(&deadlock)
 	lock(&deadlock)
 }

 type RWMutex struct {
 	rw rwmutex
 }

 func (rw *RWMutex) RLock() {
 	rw.rw.rlock()
 }

 func (rw *RWMutex) RUnlock() {
 	rw.rw.runlock()
 }

 func (rw *RWMutex) Lock() {
 	rw.rw.lock()
 }

 func (rw *RWMutex) Unlock() {
 	rw.rw.unlock()
 }

 const RuntimeHmapSize = unsafe.Sizeof(hmap{})

 func MapBucketsCount(m map[int]int) int {
 	h := *(**hmap)(unsafe.Pointer(&m))
 	return 1 << h.B
 }

 func MapBucketsPointerIsNil(m map[int]int) bool {
 	h := *(**hmap)(unsafe.Pointer(&m))
 	return h.buckets == nil
 }

 func LockOSCounts() (external, internal uint32) {
 	g := getg()
 	if g.m.lockedExt+g.m.lockedInt == 0 {
 		if g.lockedm != 0 {
 			panic("lockedm on non-locked goroutine")
 		}
 	} else {
 		if g.lockedm == 0 {
 			panic("nil lockedm on locked goroutine")
 		}
 	}
 	return g.m.lockedExt, g.m.lockedInt
 }

 //go:noinline
 func TracebackSystemstack(stk []uintptr, i int) int {
 	if i == 0 {
 		pc, sp := getcallerpc(), getcallersp()
 		return gentraceback(pc, sp, 0, getg(), 0, &stk[0], len(stk), nil, nil, _TraceJumpStack)
 	}
 	n := 0
 	systemstack(func() {
 		n = TracebackSystemstack(stk, i-1)
 	})
 	return n
 }

 func KeepNArenaHints(n int) {
 	hint := mheap_.arenaHints
 	for i := 1; i < n; i++ {
 		hint = hint.next
 		if hint == nil {
 			return
 		}
 	}
 	hint.next = nil
 }

 // MapNextArenaHint reserves a page at the next arena growth hint,
 // preventing the arena from growing there, and returns the range of
 // addresses that are no longer viable.
 func MapNextArenaHint() (start, end uintptr) {
 	hint := mheap_.arenaHints
 	addr := hint.addr
 	if hint.down {
 		start, end = addr-heapArenaBytes, addr
 		addr -= physPageSize
 	} else {
 		start, end = addr, addr+heapArenaBytes
 	}
 	sysReserve(unsafe.Pointer(addr), physPageSize)
 	return
 }

 func GetNextArenaHint() uintptr {
 	return mheap_.arenaHints.addr
 }

 type G = g

 func Getg() *G {
 	return getg()
 }

 //go:noinline
 func PanicForTesting(b []byte, i int) byte {
 	return unexportedPanicForTesting(b, i)
 }

 //go:noinline
 func unexportedPanicForTesting(b []byte, i int) byte {
 	return b[i]
 }

 func G0StackOverflow() {
 	systemstack(func() {
 		stackOverflow(nil)
 	})
 }

 func stackOverflow(x *byte) {
 	var buf [256]byte
 	stackOverflow(&buf[0])
 }
	// Copyright 2010 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.

	// Export guts for testing.

	package runtime

	import (
	"runtime/internal/atomic"
	"runtime/internal/sys"
	"unsafe"
	)

	var Fadd64 = fadd64
	var Fsub64 = fsub64
	var Fmul64 = fmul64
	var Fdiv64 = fdiv64
	var F64to32 = f64to32
	var F32to64 = f32to64
	var Fcmp64 = fcmp64
	var Fintto64 = fintto64
	var F64toint = f64toint

	var Entersyscall = entersyscall
	var Exitsyscall = exitsyscall
	var LockedOSThread = lockedOSThread
	var Xadduintptr = atomic.Xadduintptr

	var FuncPC = funcPC

	var Fastlog2 = fastlog2

	var Atoi = atoi
	var Atoi32 = atoi32

	type LFNode struct {
	Next uint64
	Pushcnt uintptr
	}

	func LFStackPush(head uint64, node LFNode) {
	(lfstack)(head).push((lfnode)(unsafe.Pointer(node)))
	}

	func LFStackPop(head uint64) LFNode {
	return (LFNode)(unsafe.Pointer((lfstack)(head).pop()))
	}

	func GCMask(x interface{}) (ret []byte) {
	systemstack(func() {
	ret = getgcmask(x)
	})
	return
	}

	func RunSchedLocalQueueTest() {
	_p_ := new(p)
	gs := make([]g, len(_p_.runq))
	for i := 0; i < len(_p_.runq); i++ {
	if g, _ := runqget(_p_); g != nil {
	throw("runq is not empty initially")
	}
	for j := 0; j < i; j++ {
	runqput(_p_, &gs[i], false)
	}
	for j := 0; j < i; j++ {
	if g, _ := runqget(_p_); g != &gs[i] {
	print("bad element at iter ", i, "/", j, "\n")
	throw("bad element")
	}
	}
	if g, _ := runqget(_p_); g != nil {
	throw("runq is not empty afterwards")
	}
	}
	}

	func RunSchedLocalQueueStealTest() {
	p1 := new(p)
	p2 := new(p)
	gs := make([]g, len(p1.runq))
	for i := 0; i < len(p1.runq); i++ {
	for j := 0; j < i; j++ {
	gs[j].sig = 0
	runqput(p1, &gs[j], false)
	}
	gp := runqsteal(p2, p1, true)
	s := 0
	if gp != nil {
	s++
	gp.sig++
	}
	for {
	gp, _ = runqget(p2)
	if gp == nil {
	break
	}
	s++
	gp.sig++
	}
	for {
	gp, _ = runqget(p1)
	if gp == nil {
	break
	}
	gp.sig++
	}
	for j := 0; j < i; j++ {
	if gs[j].sig != 1 {
	print("bad element ", j, "(", gs[j].sig, ") at iter ", i, "\n")
	throw("bad element")
	}
	}
	if s != i/2 && s != i/2+1 {
	print("bad steal ", s, ", want ", i/2, " or ", i/2+1, ", iter ", i, "\n")
	throw("bad steal")
	}
	}
	}

	func RunSchedLocalQueueEmptyTest(iters int) {
	// Test that runq is not spuriously reported as empty.
	// Runq emptiness affects scheduling decisions and spurious emptiness
	// can lead to underutilization (both runnable Gs and idle Ps coexist
	// for arbitrary long time).
	done := make(chan bool, 1)
	p := new(p)
	gs := make([]g, 2)
	ready := new(uint32)
	for i := 0; i < iters; i++ {
	*ready = 0
	next0 := (i & 1) == 0
	next1 := (i & 2) == 0
	runqput(p, &gs[0], next0)
	go func() {
	for atomic.Xadd(ready, 1); atomic.Load(ready) != 2; {
	}
	if runqempty(p) {
	println("next:", next0, next1)
	throw("queue is empty")
	}
	done <- true
	}()
	for atomic.Xadd(ready, 1); atomic.Load(ready) != 2; {
	}
	runqput(p, &gs[1], next1)
	runqget(p)
	<-done
	runqget(p)
	}
	}

	var (
	StringHash = stringHash
	BytesHash = bytesHash
	Int32Hash = int32Hash
	Int64Hash = int64Hash
	MemHash = memhash
	MemHash32 = memhash32
	MemHash64 = memhash64
	EfaceHash = efaceHash
	IfaceHash = ifaceHash
	)

	var UseAeshash = &useAeshash

	func MemclrBytes(b []byte) {
	s := (*slice)(unsafe.Pointer(&b))
	memclrNoHeapPointers(s.array, uintptr(s.len))
	}

	var HashLoad = &hashLoad

	// entry point for testing
	func GostringW(w []uint16) (s string) {
	systemstack(func() {
	s = gostringw(&w[0])
	})
	return
	}

	type Uintreg sys.Uintreg

	var Open = open
	var Close = closefd
	var Read = read
	var Write = write

	func Envs() []string { return envs }
	func SetEnvs(e []string) { envs = e }

	var BigEndian = sys.BigEndian

	// For benchmarking.

	func BenchSetType(n int, x interface{}) {
	e := *efaceOf(&x)
	t := e._type
	var size uintptr
	var p unsafe.Pointer
	switch t.kind & kindMask {
	case kindPtr:
	t = (*ptrtype)(unsafe.Pointer(t)).elem
	size = t.size
	p = e.data
	case kindSlice:
	slice := (struct {
	ptr unsafe.Pointer
	len, cap uintptr
	})(e.data)
	t = (*slicetype)(unsafe.Pointer(t)).elem
	size = t.size * slice.len
	p = slice.ptr
	}
	allocSize := roundupsize(size)
	systemstack(func() {
	for i := 0; i < n; i++ {
	heapBitsSetType(uintptr(p), allocSize, size, t)
	}
	})
	}

	const PtrSize = sys.PtrSize

	var ForceGCPeriod = &forcegcperiod

	// SetTracebackEnv is like runtime/debug.SetTraceback, but it raises
	// the "environment" traceback level, so later calls to
	// debug.SetTraceback (e.g., from testing timeouts) can't lower it.
	func SetTracebackEnv(level string) {
	setTraceback(level)
	traceback_env = traceback_cache
	}

	var ReadUnaligned32 = readUnaligned32
	var ReadUnaligned64 = readUnaligned64

	func CountPagesInUse() (pagesInUse, counted uintptr) {
	stopTheWorld("CountPagesInUse")

	pagesInUse = uintptr(mheap_.pagesInUse)

	for _, s := range mheap_.allspans {
	if s.state == mSpanInUse {
	counted += s.npages
	}
	}

	startTheWorld()

	return
	}

	func Fastrand() uint32 { return fastrand() }
	func Fastrandn(n uint32) uint32 { return fastrandn(n) }

	type ProfBuf profBuf

	func NewProfBuf(hdrsize, bufwords, tags int) *ProfBuf {
	return (*ProfBuf)(newProfBuf(hdrsize, bufwords, tags))
	}

	func (p ProfBuf) Write(tag unsafe.Pointer, now int64, hdr []uint64, stk []uintptr) {
	(*profBuf)(p).write(tag, now, hdr, stk)
	}

	const (
	ProfBufBlocking = profBufBlocking
	ProfBufNonBlocking = profBufNonBlocking
	)

	func (p *ProfBuf) Read(mode profBufReadMode) ([]uint64, []unsafe.Pointer, bool) {
	return (*profBuf)(p).read(profBufReadMode(mode))
	}

	func (p *ProfBuf) Close() {
	(*profBuf)(p).close()
	}

	// ReadMemStatsSlow returns both the runtime-computed MemStats and
	// MemStats accumulated by scanning the heap.
	func ReadMemStatsSlow() (base, slow MemStats) {
	stopTheWorld("ReadMemStatsSlow")

	// Run on the system stack to avoid stack growth allocation.
	systemstack(func() {
	// Make sure stats don't change.
	getg().m.mallocing++

	readmemstats_m(&base)

	// Initialize slow from base and zero the fields we're
	// recomputing.
	slow = base
	slow.Alloc = 0
	slow.TotalAlloc = 0
	slow.Mallocs = 0
	slow.Frees = 0
	var bySize [_NumSizeClasses]struct {
	Mallocs, Frees uint64
	}

	// Add up current allocations in spans.
	for _, s := range mheap_.allspans {
	if s.state != mSpanInUse {
	continue
	}
	if sizeclass := s.spanclass.sizeclass(); sizeclass == 0 {
	slow.Mallocs++
	slow.Alloc += uint64(s.elemsize)
	} else {
	slow.Mallocs += uint64(s.allocCount)
	slow.Alloc += uint64(s.allocCount) * uint64(s.elemsize)
	bySize[sizeclass].Mallocs += uint64(s.allocCount)
	}
	}

	// Add in frees. readmemstats_m flushed the cached stats, so
	// these are up-to-date.
	var smallFree uint64
	slow.Frees = mheap_.nlargefree
	for i := range mheap_.nsmallfree {
	slow.Frees += mheap_.nsmallfree[i]
	bySize[i].Frees = mheap_.nsmallfree[i]
	bySize[i].Mallocs += mheap_.nsmallfree[i]
	smallFree += mheap_.nsmallfree[i] * uint64(class_to_size[i])
	}
	slow.Frees += memstats.tinyallocs
	slow.Mallocs += slow.Frees

	slow.TotalAlloc = slow.Alloc + mheap_.largefree + smallFree

	for i := range slow.BySize {
	slow.BySize[i].Mallocs = bySize[i].Mallocs
	slow.BySize[i].Frees = bySize[i].Frees
	}

	getg().m.mallocing--
	})

	startTheWorld()
	return
	}

	// BlockOnSystemStack switches to the system stack, prints "x\n" to
	// stderr, and blocks in a stack containing
	// "runtime.blockOnSystemStackInternal".
	func BlockOnSystemStack() {
	systemstack(blockOnSystemStackInternal)
	}

	func blockOnSystemStackInternal() {
	print("x\n")
	lock(&deadlock)
	lock(&deadlock)
	}

	type RWMutex struct {
	rw rwmutex
	}

	func (rw *RWMutex) RLock() {
	rw.rw.rlock()
	}

	func (rw *RWMutex) RUnlock() {
	rw.rw.runlock()
	}

	func (rw *RWMutex) Lock() {
	rw.rw.lock()
	}

	func (rw *RWMutex) Unlock() {
	rw.rw.unlock()
	}

	const RuntimeHmapSize = unsafe.Sizeof(hmap{})

	func MapBucketsCount(m map[int]int) int {
	h := (*hmap)(unsafe.Pointer(&m))
	return 1 << h.B
	}

	func MapBucketsPointerIsNil(m map[int]int) bool {
	h := (*hmap)(unsafe.Pointer(&m))
	return h.buckets == nil
	}

	func LockOSCounts() (external, internal uint32) {
	g := getg()
	if g.m.lockedExt+g.m.lockedInt == 0 {
	if g.lockedm != 0 {
	panic("lockedm on non-locked goroutine")
	}
	} else {
	if g.lockedm == 0 {
	panic("nil lockedm on locked goroutine")
	}
	}
	return g.m.lockedExt, g.m.lockedInt
	}

	//go:noinline
	func TracebackSystemstack(stk []uintptr, i int) int {
	if i == 0 {
	pc, sp := getcallerpc(), getcallersp()
	return gentraceback(pc, sp, 0, getg(), 0, &stk[0], len(stk), nil, nil, _TraceJumpStack)
	}
	n := 0
	systemstack(func() {
	n = TracebackSystemstack(stk, i-1)
	})
	return n
	}

	func KeepNArenaHints(n int) {
	hint := mheap_.arenaHints
	for i := 1; i < n; i++ {
	hint = hint.next
	if hint == nil {
	return
	}
	}
	hint.next = nil
	}

	// MapNextArenaHint reserves a page at the next arena growth hint,
	// preventing the arena from growing there, and returns the range of
	// addresses that are no longer viable.
	func MapNextArenaHint() (start, end uintptr) {
	hint := mheap_.arenaHints
	addr := hint.addr
	if hint.down {
	start, end = addr-heapArenaBytes, addr
	addr -= physPageSize
	} else {
	start, end = addr, addr+heapArenaBytes
	}
	sysReserve(unsafe.Pointer(addr), physPageSize)
	return
	}

	func GetNextArenaHint() uintptr {
	return mheap_.arenaHints.addr
	}

	type G = g

	func Getg() *G {
	return getg()
	}

	//go:noinline
	func PanicForTesting(b []byte, i int) byte {
	return unexportedPanicForTesting(b, i)
	}

	//go:noinline
	func unexportedPanicForTesting(b []byte, i int) byte {
	return b[i]
	}

	func G0StackOverflow() {
	systemstack(func() {
	stackOverflow(nil)
	})
	}

	func stackOverflow(x *byte) {
	var buf [256]byte
	stackOverflow(&buf[0])
	}