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go/test/escape2n.go
Dmitry Vyukov 0e80b2e082 cmd/gc: capture variables by value 
Language specification says that variables are captured by reference.
And that is what gc compiler does. However, in lots of cases it is
possible to capture variables by value under the hood without
affecting visible behavior of programs. For example, consider
the following typical pattern:

	func (o *Obj) requestMany(urls []string) []Result {
		wg := new(sync.WaitGroup)
		wg.Add(len(urls))
		res := make([]Result, len(urls))
		for i := range urls {
			i := i
			go func() {
				res[i] = o.requestOne(urls[i])
				wg.Done()
			}()
		}
		wg.Wait()
		return res
	}

Currently o, wg, res, and i are captured by reference causing 3+len(urls)
allocations (e.g. PPARAM o is promoted to PPARAMREF and moved to heap).
But all of them can be captured by value without changing behavior.

This change implements simple strategy for capturing by value:
if a captured variable is not addrtaken and never assigned to,
then it is captured by value (it is effectively const).
This simple strategy turned out to be very effective:
~80% of all captures in std lib are turned into value captures.
The remaining 20% are mostly in defers and non-escaping closures,
that is, they do not cause allocations anyway.

benchmark                                    old allocs     new allocs     delta
BenchmarkCompressedZipGarbage                153            126            -17.65%
BenchmarkEncodeDigitsSpeed1e4                91             69             -24.18%
BenchmarkEncodeDigitsSpeed1e5                178            129            -27.53%
BenchmarkEncodeDigitsSpeed1e6                1510           1051           -30.40%
BenchmarkEncodeDigitsDefault1e4              100            75             -25.00%
BenchmarkEncodeDigitsDefault1e5              193            139            -27.98%
BenchmarkEncodeDigitsDefault1e6              1420           985            -30.63%
BenchmarkEncodeDigitsCompress1e4             100            75             -25.00%
BenchmarkEncodeDigitsCompress1e5             193            139            -27.98%
BenchmarkEncodeDigitsCompress1e6             1420           985            -30.63%
BenchmarkEncodeTwainSpeed1e4                 109            81             -25.69%
BenchmarkEncodeTwainSpeed1e5                 211            151            -28.44%
BenchmarkEncodeTwainSpeed1e6                 1588           1097           -30.92%
BenchmarkEncodeTwainDefault1e4               103            77             -25.24%
BenchmarkEncodeTwainDefault1e5               199            143            -28.14%
BenchmarkEncodeTwainDefault1e6               1324           917            -30.74%
BenchmarkEncodeTwainCompress1e4              103            77             -25.24%
BenchmarkEncodeTwainCompress1e5              190            137            -27.89%
BenchmarkEncodeTwainCompress1e6              1327           919            -30.75%
BenchmarkConcurrentDBExec                    16223          16220          -0.02%
BenchmarkConcurrentStmtQuery                 17687          16182          -8.51%
BenchmarkConcurrentStmtExec                  5191           5186           -0.10%
BenchmarkConcurrentTxQuery                   17665          17661          -0.02%
BenchmarkConcurrentTxExec                    15154          15150          -0.03%
BenchmarkConcurrentTxStmtQuery               17661          16157          -8.52%
BenchmarkConcurrentTxStmtExec                3677           3673           -0.11%
BenchmarkConcurrentRandom                    14000          13614          -2.76%
BenchmarkManyConcurrentQueries               25             22             -12.00%
BenchmarkDecodeComplex128Slice               318            252            -20.75%
BenchmarkDecodeFloat64Slice                  318            252            -20.75%
BenchmarkDecodeInt32Slice                    318            252            -20.75%
BenchmarkDecodeStringSlice                   2318           2252           -2.85%
BenchmarkDecode                              11             8              -27.27%
BenchmarkEncodeGray                          64             56             -12.50%
BenchmarkEncodeNRGBOpaque                    64             56             -12.50%
BenchmarkEncodeNRGBA                         67             58             -13.43%
BenchmarkEncodePaletted                      68             60             -11.76%
BenchmarkEncodeRGBOpaque                     64             56             -12.50%
BenchmarkGoLookupIP                          153            139            -9.15%
BenchmarkGoLookupIPNoSuchHost                508            466            -8.27%
BenchmarkGoLookupIPWithBrokenNameServer      245            226            -7.76%
BenchmarkClientServer                        62             59             -4.84%
BenchmarkClientServerParallel4               62             59             -4.84%
BenchmarkClientServerParallel64              62             59             -4.84%
BenchmarkClientServerParallelTLS4            79             76             -3.80%
BenchmarkClientServerParallelTLS64           112            109            -2.68%
BenchmarkCreateGoroutinesCapture             10             6              -40.00%
BenchmarkAfterFunc                           1006           1005           -0.10%

Fixes #6632.

Change-Id: I0cd51e4d356331d7f3c5f447669080cd19b0d2ca
Reviewed-on: https://go-review.googlesource.com/3166
Reviewed-by: Russ Cox <rsc@golang.org>
2015-01-29 13:07:30 +00:00

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// errorcheck -0 -N -m -l
// 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.
// Test, using compiler diagnostic flags, that the escape analysis is working.
// Compiles but does not run. Inlining is disabled.
// Registerization is disabled too (-N), which should
// have no effect on escape analysis.
package foo
import (
"fmt"
"unsafe"
)
var gxx *int
func foo1(x int) { // ERROR "moved to heap: x"
gxx = &x // ERROR "&x escapes to heap"
}
func foo2(yy *int) { // ERROR "leaking param: yy"
gxx = yy
}
func foo3(x int) *int { // ERROR "moved to heap: x"
return &x // ERROR "&x escapes to heap"
}
type T *T
func foo3b(t T) { // ERROR "leaking param: t"
*t = t
}
// xx isn't going anywhere, so use of yy is ok
func foo4(xx, yy *int) { // ERROR "xx does not escape" "yy does not escape"
xx = yy
}
// xx isn't going anywhere, so taking address of yy is ok
func foo5(xx **int, yy *int) { // ERROR "xx does not escape" "yy does not escape"
xx = &yy // ERROR "&yy does not escape"
}
func foo6(xx **int, yy *int) { // ERROR "xx does not escape" "leaking param: yy"
*xx = yy
}
func foo7(xx **int, yy *int) { // ERROR "xx does not escape" "yy does not escape"
**xx = *yy
}
func foo8(xx, yy *int) int { // ERROR "xx does not escape" "yy does not escape"
xx = yy
return *xx
}
func foo9(xx, yy *int) *int { // ERROR "leaking param: xx" "leaking param: yy"
xx = yy
return xx
}
func foo10(xx, yy *int) { // ERROR "xx does not escape" "yy does not escape"
*xx = *yy
}
func foo11() int {
x, y := 0, 42
xx := &x // ERROR "&x does not escape"
yy := &y // ERROR "&y does not escape"
*xx = *yy
return x
}
var xxx **int
func foo12(yyy **int) { // ERROR "leaking param: yyy"
xxx = yyy
}
// Must treat yyy as leaking because *yyy leaks, and the escape analysis
// summaries in exported metadata do not distinguish these two cases.
func foo13(yyy **int) { // ERROR "leaking param: yyy"
*xxx = *yyy
}
func foo14(yyy **int) { // ERROR "yyy does not escape"
**xxx = **yyy
}
func foo15(yy *int) { // ERROR "moved to heap: yy"
xxx = &yy // ERROR "&yy escapes to heap"
}
func foo16(yy *int) { // ERROR "leaking param: yy"
*xxx = yy
}
func foo17(yy *int) { // ERROR "yy does not escape"
**xxx = *yy
}
func foo18(y int) { // ERROR "moved to heap: "y"
*xxx = &y // ERROR "&y escapes to heap"
}
func foo19(y int) {
**xxx = y
}
type Bar struct {
i int
ii *int
}
func NewBar() *Bar {
return &Bar{42, nil} // ERROR "&Bar literal escapes to heap"
}
func NewBarp(x *int) *Bar { // ERROR "leaking param: x"
return &Bar{42, x} // ERROR "&Bar literal escapes to heap"
}
func NewBarp2(x *int) *Bar { // ERROR "x does not escape"
return &Bar{*x, nil} // ERROR "&Bar literal escapes to heap"
}
func (b *Bar) NoLeak() int { // ERROR "b does not escape"
return *(b.ii)
}
func (b *Bar) Leak() *int { // ERROR "leaking param: b"
return &b.i // ERROR "&b.i escapes to heap"
}
func (b *Bar) AlsoNoLeak() *int { // ERROR "leaking param b content to result ~r0"
return b.ii
}
func (b Bar) AlsoLeak() *int { // ERROR "leaking param: b"
return b.ii
}
func (b Bar) LeaksToo() *int { // ERROR "leaking param: b"
v := 0 // ERROR "moved to heap: v"
b.ii = &v // ERROR "&v escapes"
return b.ii
}
func (b *Bar) LeaksABit() *int { // ERROR "leaking param b content to result ~r0"
v := 0 // ERROR "moved to heap: v"
b.ii = &v // ERROR "&v escapes"
return b.ii
}
func (b Bar) StillNoLeak() int { // ERROR "b does not escape"
v := 0
b.ii = &v // ERROR "&v does not escape"
return b.i
}
func goLeak(b *Bar) { // ERROR "leaking param: b"
go b.NoLeak()
}
type Bar2 struct {
i [12]int
ii []int
}
func NewBar2() *Bar2 {
return &Bar2{[12]int{42}, nil} // ERROR "&Bar2 literal escapes to heap"
}
func (b *Bar2) NoLeak() int { // ERROR "b does not escape"
return b.i[0]
}
func (b *Bar2) Leak() []int { // ERROR "leaking param: b"
return b.i[:] // ERROR "b.i escapes to heap"
}
func (b *Bar2) AlsoNoLeak() []int { // ERROR "leaking param b content to result ~r0"
return b.ii[0:1]
}
func (b Bar2) AgainNoLeak() [12]int { // ERROR "b does not escape"
return b.i
}
func (b *Bar2) LeakSelf() { // ERROR "leaking param: b"
b.ii = b.i[0:4] // ERROR "b.i escapes to heap"
}
func (b *Bar2) LeakSelf2() { // ERROR "leaking param: b"
var buf []int
buf = b.i[0:] // ERROR "b.i escapes to heap"
b.ii = buf
}
func foo21() func() int {
x := 42
return func() int { // ERROR "func literal escapes to heap"
return x
}
}
func foo21a() func() int {
x := 42 // ERROR "moved to heap: x"
return func() int { // ERROR "func literal escapes to heap"
x++ // ERROR "&x escapes to heap"
return x
}
}
func foo22() int {
x := 42
return func() int { // ERROR "func literal does not escape"
return x
}()
}
func foo23(x int) func() int {
return func() int { // ERROR "func literal escapes to heap"
return x
}
}
func foo23a(x int) func() int {
f := func() int { // ERROR "func literal escapes to heap"
return x
}
return f
}
func foo23b(x int) *(func() int) {
f := func() int { return x } // ERROR "moved to heap: f" "func literal escapes to heap"
return &f // ERROR "&f escapes to heap"
}
func foo23c(x int) func() int { // ERROR "moved to heap: x"
return func() int { // ERROR "func literal escapes to heap"
x++ // ERROR "&x escapes to heap"
return x
}
}
func foo24(x int) int {
return func() int { // ERROR "func literal does not escape"
return x
}()
}
var x *int
func fooleak(xx *int) int { // ERROR "leaking param: xx"
x = xx
return *x
}
func foonoleak(xx *int) int { // ERROR "xx does not escape"
return *x + *xx
}
func foo31(x int) int { // ERROR "moved to heap: x"
return fooleak(&x) // ERROR "&x escapes to heap"
}
func foo32(x int) int {
return foonoleak(&x) // ERROR "&x does not escape"
}
type Foo struct {
xx *int
x int
}
var F Foo
var pf *Foo
func (f *Foo) fooleak() { // ERROR "leaking param: f"
pf = f
}
func (f *Foo) foonoleak() { // ERROR "f does not escape"
F.x = f.x
}
func (f *Foo) Leak() { // ERROR "leaking param: f"
f.fooleak()
}
func (f *Foo) NoLeak() { // ERROR "f does not escape"
f.foonoleak()
}
func foo41(x int) { // ERROR "moved to heap: x"
F.xx = &x // ERROR "&x escapes to heap"
}
func (f *Foo) foo42(x int) { // ERROR "f does not escape" "moved to heap: x"
f.xx = &x // ERROR "&x escapes to heap"
}
func foo43(f *Foo, x int) { // ERROR "f does not escape" "moved to heap: x"
f.xx = &x // ERROR "&x escapes to heap"
}
func foo44(yy *int) { // ERROR "leaking param: yy"
F.xx = yy
}
func (f *Foo) foo45() { // ERROR "f does not escape"
F.x = f.x
}
// See foo13 above for explanation of why f leaks.
func (f *Foo) foo46() { // ERROR "leaking param: f"
F.xx = f.xx
}
func (f *Foo) foo47() { // ERROR "leaking param: f"
f.xx = &f.x // ERROR "&f.x escapes to heap"
}
var ptrSlice []*int
func foo50(i *int) { // ERROR "leaking param: i"
ptrSlice[0] = i
}
var ptrMap map[*int]*int
func foo51(i *int) { // ERROR "leaking param: i"
ptrMap[i] = i
}
func indaddr1(x int) *int { // ERROR "moved to heap: x"
return &x // ERROR "&x escapes to heap"
}
func indaddr2(x *int) *int { // ERROR "leaking param: x"
return *&x // ERROR "&x does not escape"
}
func indaddr3(x *int32) *int { // ERROR "leaking param: x"
return *(**int)(unsafe.Pointer(&x)) // ERROR "&x does not escape"
}
// From package math:
func Float32bits(f float32) uint32 {
return *(*uint32)(unsafe.Pointer(&f)) // ERROR "&f does not escape"
}
func Float32frombits(b uint32) float32 {
return *(*float32)(unsafe.Pointer(&b)) // ERROR "&b does not escape"
}
func Float64bits(f float64) uint64 {
return *(*uint64)(unsafe.Pointer(&f)) // ERROR "&f does not escape"
}
func Float64frombits(b uint64) float64 {
return *(*float64)(unsafe.Pointer(&b)) // ERROR "&b does not escape"
}
// contrast with
func float64bitsptr(f float64) *uint64 { // ERROR "moved to heap: f"
return (*uint64)(unsafe.Pointer(&f)) // ERROR "&f escapes to heap"
}
func float64ptrbitsptr(f *float64) *uint64 { // ERROR "leaking param: f"
return (*uint64)(unsafe.Pointer(f))
}
func typesw(i interface{}) *int { // ERROR "leaking param: i"
switch val := i.(type) {
case *int:
return val
case *int8:
v := int(*val) // ERROR "moved to heap: v"
return &v // ERROR "&v escapes to heap"
}
return nil
}
func exprsw(i *int) *int { // ERROR "leaking param: i"
switch j := i; *j + 110 {
case 12:
return j
case 42:
return nil
}
return nil
}
// assigning to an array element is like assigning to the array
func foo60(i *int) *int { // ERROR "leaking param: i"
var a [12]*int
a[0] = i
return a[1]
}
func foo60a(i *int) *int { // ERROR "i does not escape"
var a [12]*int
a[0] = i
return nil
}
// assigning to a struct field is like assigning to the struct
func foo61(i *int) *int { // ERROR "leaking param: i"
type S struct {
a, b *int
}
var s S
s.a = i
return s.b
}
func foo61a(i *int) *int { // ERROR "i does not escape"
type S struct {
a, b *int
}
var s S
s.a = i
return nil
}
// assigning to a struct field is like assigning to the struct but
// here this subtlety is lost, since s.a counts as an assignment to a
// track-losing dereference.
func foo62(i *int) *int { // ERROR "leaking param: i"
type S struct {
a, b *int
}
s := new(S) // ERROR "new[(]S[)] does not escape"
s.a = i
return nil // s.b
}
type M interface {
M()
}
func foo63(m M) { // ERROR "m does not escape"
}
func foo64(m M) { // ERROR "leaking param: m"
m.M()
}
func foo64b(m M) { // ERROR "leaking param: m"
defer m.M()
}
type MV int
func (MV) M() {}
func foo65() {
var mv MV
foo63(&mv) // ERROR "&mv does not escape"
}
func foo66() {
var mv MV // ERROR "moved to heap: mv"
foo64(&mv) // ERROR "&mv escapes to heap"
}
func foo67() {
var mv MV
foo63(mv)
}
func foo68() {
var mv MV
foo64(mv) // escapes but it's an int so irrelevant
}
func foo69(m M) { // ERROR "leaking param: m"
foo64(m)
}
func foo70(mv1 *MV, m M) { // ERROR "leaking param: mv1" "leaking param: m"
m = mv1
foo64(m)
}
func foo71(x *int) []*int { // ERROR "leaking param: x"
var y []*int
y = append(y, x)
return y
}
func foo71a(x int) []*int { // ERROR "moved to heap: x"
var y []*int
y = append(y, &x) // ERROR "&x escapes to heap"
return y
}
func foo72() {
var x int
var y [1]*int
y[0] = &x // ERROR "&x does not escape"
}
func foo72aa() [10]*int {
var x int // ERROR "moved to heap: x"
var y [10]*int
y[0] = &x // ERROR "&x escapes to heap"
return y
}
func foo72a() {
var y [10]*int
for i := 0; i < 10; i++ {
// escapes its scope
x := i // ERROR "moved to heap: x"
y[i] = &x // ERROR "&x escapes to heap"
}
return
}
func foo72b() [10]*int {
var y [10]*int
for i := 0; i < 10; i++ {
x := i // ERROR "moved to heap: x"
y[i] = &x // ERROR "&x escapes to heap"
}
return y
}
// issue 2145
func foo73() {
s := []int{3, 2, 1} // ERROR "\[\]int literal does not escape"
for _, v := range s {
vv := v
// actually just escapes its scope
defer func() { // ERROR "func literal escapes to heap"
println(vv)
}()
}
}
func foo731() {
s := []int{3, 2, 1} // ERROR "\[\]int literal does not escape"
for _, v := range s {
vv := v // ERROR "moved to heap: vv"
// actually just escapes its scope
defer func() { // ERROR "func literal escapes to heap"
vv = 42 // ERROR "&vv escapes to heap"
println(vv)
}()
}
}
func foo74() {
s := []int{3, 2, 1} // ERROR "\[\]int literal does not escape"
for _, v := range s {
vv := v
// actually just escapes its scope
fn := func() { // ERROR "func literal escapes to heap"
println(vv)
}
defer fn()
}
}
func foo74a() {
s := []int{3, 2, 1} // ERROR "\[\]int literal does not escape"
for _, v := range s {
vv := v // ERROR "moved to heap: vv"
// actually just escapes its scope
fn := func() { // ERROR "func literal escapes to heap"
vv += 1 // ERROR "&vv escapes to heap"
println(vv)
}
defer fn()
}
}
// issue 3975
func foo74b() {
var array [3]func()
s := []int{3, 2, 1} // ERROR "\[\]int literal does not escape"
for i, v := range s {
vv := v
// actually just escapes its scope
array[i] = func() { // ERROR "func literal escapes to heap"
println(vv)
}
}
}
func foo74c() {
var array [3]func()
s := []int{3, 2, 1} // ERROR "\[\]int literal does not escape"
for i, v := range s {
vv := v // ERROR "moved to heap: vv"
// actually just escapes its scope
array[i] = func() { // ERROR "func literal escapes to heap"
println(&vv) // ERROR "&vv escapes to heap" "&vv does not escape"
}
}
}
func myprint(y *int, x ...interface{}) *int { // ERROR "x does not escape" "leaking param: y"
return y
}
func myprint1(y *int, x ...interface{}) *interface{} { // ERROR "y does not escape" "leaking param: x"
return &x[0] // ERROR "&x.0. escapes to heap"
}
func foo75(z *int) { // ERROR "z does not escape"
myprint(z, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo75a(z *int) { // ERROR "z does not escape"
myprint1(z, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo75esc(z *int) { // ERROR "leaking param: z"
gxx = myprint(z, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo75aesc(z *int) { // ERROR "z does not escape"
var ppi **interface{} // assignments to pointer dereferences lose track
*ppi = myprint1(z, 1, 2, 3) // ERROR "[.][.][.] argument escapes to heap"
}
func foo76(z *int) { // ERROR "leaking param: z"
myprint(nil, z) // ERROR "[.][.][.] argument does not escape"
}
func foo76a(z *int) { // ERROR "leaking param: z"
myprint1(nil, z) // ERROR "[.][.][.] argument does not escape"
}
func foo76b() {
myprint(nil, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo76c() {
myprint1(nil, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo76d() {
defer myprint(nil, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo76e() {
defer myprint1(nil, 1, 2, 3) // ERROR "[.][.][.] argument does not escape"
}
func foo76f() {
for {
// TODO: This one really only escapes its scope, but we don't distinguish yet.
defer myprint(nil, 1, 2, 3) // ERROR "[.][.][.] argument escapes to heap"
}
}
func foo76g() {
for {
defer myprint1(nil, 1, 2, 3) // ERROR "[.][.][.] argument escapes to heap"
}
}
func foo77(z []interface{}) { // ERROR "z does not escape"
myprint(nil, z...) // z does not escape
}
func foo77a(z []interface{}) { // ERROR "z does not escape"
myprint1(nil, z...)
}
func foo77b(z []interface{}) { // ERROR "leaking param: z"
var ppi **interface{}
*ppi = myprint1(nil, z...)
}
func foo78(z int) *int { // ERROR "moved to heap: z"
return &z // ERROR "&z escapes to heap"
}
func foo78a(z int) *int { // ERROR "moved to heap: z"
y := &z // ERROR "&z escapes to heap"
x := &y // ERROR "&y does not escape"
return *x // really return y
}
func foo79() *int {
return new(int) // ERROR "new[(]int[)] escapes to heap"
}
func foo80() *int {
var z *int
for {
// Really just escapes its scope but we don't distinguish
z = new(int) // ERROR "new[(]int[)] escapes to heap"
}
_ = z
return nil
}
func foo81() *int {
for {
z := new(int) // ERROR "new[(]int[)] does not escape"
_ = z
}
return nil
}
func tee(p *int) (x, y *int) { return p, p } // ERROR "leaking param"
func noop(x, y *int) {} // ERROR "does not escape"
func foo82() {
var x, y, z int // ERROR "moved to heap"
go noop(tee(&z)) // ERROR "&z escapes to heap"
go noop(&x, &y) // ERROR "escapes to heap"
for {
var u, v, w int // ERROR "moved to heap"
defer noop(tee(&u)) // ERROR "&u escapes to heap"
defer noop(&v, &w) // ERROR "escapes to heap"
}
}
type Fooer interface {
Foo()
}
type LimitedFooer struct {
Fooer
N int64
}
func LimitFooer(r Fooer, n int64) Fooer { // ERROR "leaking param: r"
return &LimitedFooer{r, n} // ERROR "&LimitedFooer literal escapes to heap"
}
func foo90(x *int) map[*int]*int { // ERROR "leaking param: x"
return map[*int]*int{nil: x} // ERROR "map\[\*int\]\*int literal escapes to heap"
}
func foo91(x *int) map[*int]*int { // ERROR "leaking param: x"
return map[*int]*int{x: nil} // ERROR "map\[\*int\]\*int literal escapes to heap"
}
func foo92(x *int) [2]*int { // ERROR "leaking param: x"
return [2]*int{x, nil}
}
// does not leak c
func foo93(c chan *int) *int { // ERROR "c does not escape"
for v := range c {
return v
}
return nil
}
// does not leak m
func foo94(m map[*int]*int, b bool) *int { // ERROR "m does not escape"
for k, v := range m {
if b {
return k
}
return v
}
return nil
}
// does leak x
func foo95(m map[*int]*int, x *int) { // ERROR "m does not escape" "leaking param: x"
m[x] = x
}
// does not leak m
func foo96(m []*int) *int { // ERROR "m does not escape"
return m[0]
}
// does leak m
func foo97(m [1]*int) *int { // ERROR "leaking param: m"
return m[0]
}
// does not leak m
func foo98(m map[int]*int) *int { // ERROR "m does not escape"
return m[0]
}
// does leak m
func foo99(m *[1]*int) []*int { // ERROR "leaking param: m"
return m[:]
}
// does not leak m
func foo100(m []*int) *int { // ERROR "m does not escape"
for _, v := range m {
return v
}
return nil
}
// does leak m
func foo101(m [1]*int) *int { // ERROR "leaking param: m"
for _, v := range m {
return v
}
return nil
}
// does not leak m
func foo101a(m [1]*int) *int { // ERROR "m does not escape"
for i := range m { // ERROR "moved to heap: i"
return &i // ERROR "&i escapes to heap"
}
return nil
}
// does leak x
func foo102(m []*int, x *int) { // ERROR "m does not escape" "leaking param: x"
m[0] = x
}
// does not leak x
func foo103(m [1]*int, x *int) { // ERROR "m does not escape" "x does not escape"
m[0] = x
}
var y []*int
// does not leak x
func foo104(x []*int) { // ERROR "x does not escape"
copy(y, x)
}
// does not leak x
func foo105(x []*int) { // ERROR "x does not escape"
_ = append(y, x...)
}
// does leak x
func foo106(x *int) { // ERROR "leaking param: x"
_ = append(y, x)
}
func foo107(x *int) map[*int]*int { // ERROR "leaking param: x"
return map[*int]*int{x: nil} // ERROR "map.* literal escapes to heap"
}
func foo108(x *int) map[*int]*int { // ERROR "leaking param: x"
return map[*int]*int{nil: x} // ERROR "map.* literal escapes to heap"
}
func foo109(x *int) *int { // ERROR "leaking param: x"
m := map[*int]*int{x: nil} // ERROR "map.* literal does not escape"
for k, _ := range m {
return k
}
return nil
}
func foo110(x *int) *int { // ERROR "leaking param: x"
m := map[*int]*int{nil: x} // ERROR "map.* literal does not escape"
return m[nil]
}
func foo111(x *int) *int { // ERROR "leaking param: x"
m := []*int{x} // ERROR "\[\]\*int literal does not escape"
return m[0]
}
func foo112(x *int) *int { // ERROR "leaking param: x"
m := [1]*int{x}
return m[0]
}
func foo113(x *int) *int { // ERROR "leaking param: x"
m := Bar{ii: x}
return m.ii
}
func foo114(x *int) *int { // ERROR "leaking param: x"
m := &Bar{ii: x} // ERROR "&Bar literal does not escape"
return m.ii
}
func foo115(x *int) *int { // ERROR "leaking param: x"
return (*int)(unsafe.Pointer(uintptr(unsafe.Pointer(x)) + 1))
}
func foo116(b bool) *int {
if b {
x := 1 // ERROR "moved to heap: x"
return &x // ERROR "&x escapes to heap"
} else {
y := 1 // ERROR "moved to heap: y"
return &y // ERROR "&y escapes to heap"
}
return nil
}
func foo117(unknown func(interface{})) { // ERROR "unknown does not escape"
x := 1 // ERROR "moved to heap: x"
unknown(&x) // ERROR "&x escapes to heap"
}
func foo118(unknown func(*int)) { // ERROR "unknown does not escape"
x := 1 // ERROR "moved to heap: x"
unknown(&x) // ERROR "&x escapes to heap"
}
func external(*int)
func foo119(x *int) { // ERROR "leaking param: x"
external(x)
}
func foo120() {
// formerly exponential time analysis
L1:
L2:
L3:
L4:
L5:
L6:
L7:
L8:
L9:
L10:
L11:
L12:
L13:
L14:
L15:
L16:
L17:
L18:
L19:
L20:
L21:
L22:
L23:
L24:
L25:
L26:
L27:
L28:
L29:
L30:
L31:
L32:
L33:
L34:
L35:
L36:
L37:
L38:
L39:
L40:
L41:
L42:
L43:
L44:
L45:
L46:
L47:
L48:
L49:
L50:
L51:
L52:
L53:
L54:
L55:
L56:
L57:
L58:
L59:
L60:
L61:
L62:
L63:
L64:
L65:
L66:
L67:
L68:
L69:
L70:
L71:
L72:
L73:
L74:
L75:
L76:
L77:
L78:
L79:
L80:
L81:
L82:
L83:
L84:
L85:
L86:
L87:
L88:
L89:
L90:
L91:
L92:
L93:
L94:
L95:
L96:
L97:
L98:
L99:
L100:
// use the labels to silence compiler errors
goto L1
goto L2
goto L3
goto L4
goto L5
goto L6
goto L7
goto L8
goto L9
goto L10
goto L11
goto L12
goto L13
goto L14
goto L15
goto L16
goto L17
goto L18
goto L19
goto L20
goto L21
goto L22
goto L23
goto L24
goto L25
goto L26
goto L27
goto L28
goto L29
goto L30
goto L31
goto L32
goto L33
goto L34
goto L35
goto L36
goto L37
goto L38
goto L39
goto L40
goto L41
goto L42
goto L43
goto L44
goto L45
goto L46
goto L47
goto L48
goto L49
goto L50
goto L51
goto L52
goto L53
goto L54
goto L55
goto L56
goto L57
goto L58
goto L59
goto L60
goto L61
goto L62
goto L63
goto L64
goto L65
goto L66
goto L67
goto L68
goto L69
goto L70
goto L71
goto L72
goto L73
goto L74
goto L75
goto L76
goto L77
goto L78
goto L79
goto L80
goto L81
goto L82
goto L83
goto L84
goto L85
goto L86
goto L87
goto L88
goto L89
goto L90
goto L91
goto L92
goto L93
goto L94
goto L95
goto L96
goto L97
goto L98
goto L99
goto L100
}
func foo121() {
for i := 0; i < 10; i++ {
defer myprint(nil, i) // ERROR "[.][.][.] argument escapes to heap"
go myprint(nil, i) // ERROR "[.][.][.] argument escapes to heap"
}
}
// same as foo121 but check across import
func foo121b() {
for i := 0; i < 10; i++ {
defer fmt.Printf("%d", i) // ERROR "[.][.][.] argument escapes to heap"
go fmt.Printf("%d", i) // ERROR "[.][.][.] argument escapes to heap"
}
}
// a harmless forward jump
func foo122() {
var i *int
goto L1
L1:
i = new(int) // ERROR "new.int. does not escape"
_ = i
}
// a backward jump, increases loopdepth
func foo123() {
var i *int
L1:
i = new(int) // ERROR "new.int. escapes to heap"
goto L1
_ = i
}
func foo124(x **int) { // ERROR "x does not escape"
var i int // ERROR "moved to heap: i"
p := &i // ERROR "&i escapes"
func() { // ERROR "func literal does not escape"
*x = p // ERROR "leaking closure reference p"
}()
}
func foo125(ch chan *int) { // ERROR "does not escape"
var i int // ERROR "moved to heap"
p := &i // ERROR "&i escapes to heap"
func() { // ERROR "func literal does not escape"
ch <- p // ERROR "leaking closure reference p"
}()
}
func foo126() {
var px *int // loopdepth 0
for {
// loopdepth 1
var i int // ERROR "moved to heap"
func() { // ERROR "func literal does not escape"
px = &i // ERROR "&i escapes"
}()
}
_ = px
}
var px *int
func foo127() {
var i int // ERROR "moved to heap: i"
p := &i // ERROR "&i escapes to heap"
q := p
px = q
}
func foo128() {
var i int
p := &i // ERROR "&i does not escape"
q := p
_ = q
}
func foo129() {
var i int // ERROR "moved to heap: i"
p := &i // ERROR "&i escapes to heap"
func() { // ERROR "func literal does not escape"
q := p // ERROR "leaking closure reference p"
func() { // ERROR "func literal does not escape"
r := q // ERROR "leaking closure reference q"
px = r
}()
}()
}
func foo130() {
for {
var i int // ERROR "moved to heap"
func() { // ERROR "func literal does not escape"
px = &i // ERROR "&i escapes" "leaking closure reference i"
}()
}
}
func foo131() {
var i int // ERROR "moved to heap"
func() { // ERROR "func literal does not escape"
px = &i // ERROR "&i escapes" "leaking closure reference i"
}()
}
func foo132() {
var i int // ERROR "moved to heap"
go func() { // ERROR "func literal escapes to heap"
px = &i // ERROR "&i escapes" "leaking closure reference i"
}()
}
func foo133() {
var i int // ERROR "moved to heap"
defer func() { // ERROR "func literal does not escape"
px = &i // ERROR "&i escapes" "leaking closure reference i"
}()
}
func foo134() {
var i int
p := &i // ERROR "&i does not escape"
func() { // ERROR "func literal does not escape"
q := p
func() { // ERROR "func literal does not escape"
r := q
_ = r
}()
}()
}
func foo135() {
var i int // ERROR "moved to heap: i"
p := &i // ERROR "&i escapes to heap"
go func() { // ERROR "func literal escapes to heap"
q := p
func() { // ERROR "func literal does not escape"
r := q
_ = r
}()
}()
}
func foo136() {
var i int // ERROR "moved to heap: i"
p := &i // ERROR "&i escapes to heap"
go func() { // ERROR "func literal escapes to heap"
q := p // ERROR "leaking closure reference p"
func() { // ERROR "func literal does not escape"
r := q // ERROR "leaking closure reference q"
px = r
}()
}()
}
func foo137() {
var i int // ERROR "moved to heap: i"
p := &i // ERROR "&i escapes to heap"
func() { // ERROR "func literal does not escape"
q := p // ERROR "leaking closure reference p"
go func() { // ERROR "func literal escapes to heap"
r := q
_ = r
}()
}()
}
func foo138() *byte {
type T struct {
x [1]byte
}
t := new(T) // ERROR "new.T. escapes to heap"
return &t.x[0] // ERROR "&t.x.0. escapes to heap"
}
func foo139() *byte {
type T struct {
x struct {
y byte
}
}
t := new(T) // ERROR "new.T. escapes to heap"
return &t.x.y // ERROR "&t.x.y escapes to heap"
}
// issue 4751
func foo140() interface{} {
type T struct {
X string
}
type U struct {
X string
T *T
}
t := &T{} // ERROR "&T literal escapes to heap"
return U{
X: t.X,
T: t,
}
}
//go:noescape
func F1([]byte)
func F2([]byte)
//go:noescape
func F3(x []byte) // ERROR "F3 x does not escape"
func F4(x []byte)
func G() {
var buf1 [10]byte
F1(buf1[:]) // ERROR "buf1 does not escape"
var buf2 [10]byte // ERROR "moved to heap: buf2"
F2(buf2[:]) // ERROR "buf2 escapes to heap"
var buf3 [10]byte
F3(buf3[:]) // ERROR "buf3 does not escape"
var buf4 [10]byte // ERROR "moved to heap: buf4"
F4(buf4[:]) // ERROR "buf4 escapes to heap"
}
type Tm struct {
x int
}
func (t *Tm) M() { // ERROR "t does not escape"
}
func foo141() {
var f func()
t := new(Tm) // ERROR "escapes to heap"
f = t.M // ERROR "t.M does not escape"
_ = f
}
var gf func()
func foo142() {
t := new(Tm) // ERROR "escapes to heap"
gf = t.M // ERROR "t.M escapes to heap"
}
// issue 3888.
func foo143() {
for i := 0; i < 1000; i++ {
func() { // ERROR "func literal does not escape"
for i := 0; i < 1; i++ {
var t Tm
t.M() // ERROR "t does not escape"
}
}()
}
}
// issue 5773
// Check that annotations take effect regardless of whether they
// are before or after the use in the source code.
//go:noescape
func foo144a(*int)
func foo144() {
var x int
foo144a(&x) // ERROR "&x does not escape"
var y int
foo144b(&y) // ERROR "&y does not escape"
}
//go:noescape
func foo144b(*int)
// issue 7313: for loop init should not be treated as "in loop"
type List struct {
Next *List
}
func foo145(l List) { // ERROR "l does not escape"
var p *List
for p = &l; p.Next != nil; p = p.Next { // ERROR "&l does not escape"
}
}
func foo146(l List) { // ERROR "l does not escape"
var p *List
p = &l // ERROR "&l does not escape"
for ; p.Next != nil; p = p.Next {
}
}
func foo147(l List) { // ERROR "l does not escape"
var p *List
p = &l // ERROR "&l does not escape"
for p.Next != nil {
p = p.Next
}
}
func foo148(l List) { // ERROR " l does not escape"
for p := &l; p.Next != nil; p = p.Next { // ERROR "&l does not escape"
}
}
// related: address of variable should have depth of variable, not of loop
func foo149(l List) { // ERROR " l does not escape"
var p *List
for {
for p = &l; p.Next != nil; p = p.Next { // ERROR "&l does not escape"
}
}
}
// issue 7934: missed ... if element type had no pointers
var save150 []byte
func foo150(x ...byte) { // ERROR "leaking param: x"
save150 = x
}
func bar150() {
foo150(1, 2, 3) // ERROR "[.][.][.] argument escapes to heap"
}
// issue 7931: bad handling of slice of array
var save151 *int
func foo151(x *int) { // ERROR "leaking param: x"
save151 = x
}
func bar151() {
var a [64]int // ERROR "moved to heap: a"
a[4] = 101
foo151(&(&a)[4:8][0]) // ERROR "&\(&a\)\[4:8\]\[0\] escapes to heap" "&a escapes to heap"
}
func bar151b() {
var a [10]int // ERROR "moved to heap: a"
b := a[:] // ERROR "a escapes to heap"
foo151(&b[4:8][0]) // ERROR "&b\[4:8\]\[0\] escapes to heap"
}
func bar151c() {
var a [64]int // ERROR "moved to heap: a"
a[4] = 101
foo151(&(&a)[4:8:8][0]) // ERROR "&\(&a\)\[4:8:8\]\[0\] escapes to heap" "&a escapes to heap"
}
func bar151d() {
var a [10]int // ERROR "moved to heap: a"
b := a[:] // ERROR "a escapes to heap"
foo151(&b[4:8:8][0]) // ERROR "&b\[4:8:8\]\[0\] escapes to heap"
}
// issue 8120
type U struct {
s *string
}
func (u *U) String() *string { // ERROR "leaking param u content to result ~r0"
return u.s
}
type V struct {
s *string
}
func NewV(u U) *V { // ERROR "leaking param: u"
return &V{u.String()} // ERROR "&V literal escapes to heap" "u does not escape"
}
func foo152() {
a := "a" // ERROR "moved to heap: a"
u := U{&a} // ERROR "&a escapes to heap"
v := NewV(u)
println(v)
}
// issue 8176 - &x in type switch body not marked as escaping
func foo153(v interface{}) *int { // ERROR "leaking param: v"
switch x := v.(type) {
case int: // ERROR "moved to heap: x"
return &x // ERROR "&x escapes to heap"
}
panic(0)
}
// issue 8185 - &result escaping into result
func f() (x int, y *int) { // ERROR "moved to heap: x"
y = &x // ERROR "&x escapes to heap"
return
}
func g() (x interface{}) { // ERROR "moved to heap: x"
x = &x // ERROR "&x escapes to heap"
return
}
var sink interface{}
type Lit struct {
p *int
}
func ptrlitNoescape() {
// Both literal and element do not escape.
i := 0
x := &Lit{&i} // ERROR "&Lit literal does not escape" "&i does not escape"
_ = x
}
func ptrlitNoEscape2() {
// Literal does not escape, but element does.
i := 0 // ERROR "moved to heap: i"
x := &Lit{&i} // ERROR "&Lit literal does not escape" "&i escapes to heap"
sink = *x
}
func ptrlitEscape() {
// Both literal and element escape.
i := 0 // ERROR "moved to heap: i"
x := &Lit{&i} // ERROR "&Lit literal escapes to heap" "&i escapes to heap"
sink = x
}
// self-assignments
type Buffer struct {
arr [64]byte
buf1 []byte
buf2 []byte
str1 string
str2 string
}
func (b *Buffer) foo() { // ERROR "b does not escape"
b.buf1 = b.buf1[1:2] // ERROR "ignoring self-assignment to b.buf1"
b.buf1 = b.buf1[1:2:3] // ERROR "ignoring self-assignment to b.buf1"
b.buf1 = b.buf2[1:2] // ERROR "ignoring self-assignment to b.buf1"
b.buf1 = b.buf2[1:2:3] // ERROR "ignoring self-assignment to b.buf1"
}
func (b *Buffer) bar() { // ERROR "leaking param: b"
b.buf1 = b.arr[1:2] // ERROR "b.arr escapes to heap"
}
func (b *Buffer) baz() { // ERROR "b does not escape"
b.str1 = b.str1[1:2] // ERROR "ignoring self-assignment to b.str1"
b.str1 = b.str2[1:2] // ERROR "ignoring self-assignment to b.str1"
}
func (b *Buffer) bat() { // ERROR "leaking param: b"
o := new(Buffer) // ERROR "new\(Buffer\) escapes to heap"
o.buf1 = b.buf1[1:2]
sink = o
}
func quux(sp *string, bp *[]byte) { // ERROR "sp does not escape" "bp does not escape"
*sp = (*sp)[1:2] // ERROR "quux ignoring self-assignment to \*sp"
*bp = (*bp)[1:2] // ERROR "quux ignoring self-assignment to \*bp"
}
type StructWithString struct {
p *int
s string
}
// This is escape analysis false negative.
// We assign the pointer to x.p but leak x.s. Escape analysis coarsens flows
// to just x, and thus &i looks escaping.
func fieldFlowTracking() {
var x StructWithString
i := 0 // ERROR "moved to heap: i"
x.p = &i // ERROR "&i escapes to heap"
sink = x.s
}
// String operations.
func slicebytetostring0() {
b := make([]byte, 20) // ERROR "does not escape"
s := string(b) // ERROR "string\(b\) does not escape"
_ = s
}
func slicebytetostring1() {
b := make([]byte, 20) // ERROR "does not escape"
s := string(b) // ERROR "string\(b\) does not escape"
s1 := s[0:1]
_ = s1
}
func slicebytetostring2() {
b := make([]byte, 20) // ERROR "does not escape"
s := string(b) // ERROR "string\(b\) escapes to heap"
s1 := s[0:1] // ERROR "moved to heap: s1"
sink = &s1 // ERROR "&s1 escapes to heap"
}
func slicebytetostring3() {
b := make([]byte, 20) // ERROR "does not escape"
s := string(b) // ERROR "string\(b\) escapes to heap"
s1 := s[0:1]
sink = s1
}
func addstr0() {
s0 := "a"
s1 := "b"
s := s0 + s1 // ERROR "s0 \+ s1 does not escape"
_ = s
}
func addstr1() {
s0 := "a"
s1 := "b"
s := "c"
s += s0 + s1 // ERROR "s0 \+ s1 does not escape"
_ = s
}
func addstr2() {
b := make([]byte, 20) // ERROR "does not escape"
s0 := "a"
s := string(b) + s0 // ERROR "string\(b\) does not escape" "string\(b\) \+ s0 does not escape"
_ = s
}
func addstr3() {
s0 := "a"
s1 := "b"
s := s0 + s1 // ERROR "s0 \+ s1 escapes to heap"
s2 := s[0:1]
sink = s2
}
func intstring0() bool {
// string does not escape
x := '0'
s := string(x) // ERROR "string\(x\) does not escape"
return s == "0"
}
func intstring1() string {
// string does not escape, but the buffer does
x := '0'
s := string(x) // ERROR "string\(x\) escapes to heap"
return s
}
func intstring2() {
// string escapes to heap
x := '0'
s := string(x) // ERROR "string\(x\) escapes to heap" "moved to heap: s"
sink = &s // ERROR "&s escapes to heap"
}
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