go writebarrier 源码
golang writebarrier 代码
文件路径：/test/writebarrier.go
// errorcheck -0 -l -d=wb
// Copyright 2015 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 where write barriers are and are not emitted.
package p
import "unsafe"
func f(x **byte, y *byte) {
*x = y // no barrier (dead store)
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f1(x *[]byte, y []byte) {
*x = y // no barrier (dead store)
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f1a(x *[]byte, y *[]byte) {
*x = *y // ERROR "write barrier"
z := *y // no barrier
*x = z // ERROR "write barrier"
}
func f2(x *interface{}, y interface{}) {
*x = y // no barrier (dead store)
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f2a(x *interface{}, y *interface{}) {
*x = *y // no barrier (dead store)
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f3(x *string, y string) {
*x = y // no barrier (dead store)
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f3a(x *string, y *string) {
*x = *y // ERROR "write barrier"
z := *y // no barrier
*x = z // ERROR "write barrier"
}
func f4(x *[2]string, y [2]string) {
*x = y // ERROR "write barrier"
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f4a(x *[2]string, y *[2]string) {
*x = *y // ERROR "write barrier"
z := *y // no barrier
*x = z // ERROR "write barrier"
}
type T struct {
X *int
Y int
M map[int]int
}
func f5(t, u *T) {
t.X = &u.Y // ERROR "write barrier"
}
func f6(t *T) {
t.M = map[int]int{1: 2} // ERROR "write barrier"
}
func f7(x, y *int) []*int {
var z [3]*int
i := 0
z[i] = x // ERROR "write barrier"
i++
z[i] = y // ERROR "write barrier"
i++
return z[:i]
}
func f9(x *interface{}, v *byte) {
*x = v // ERROR "write barrier"
}
func f10(x *byte, f func(interface{})) {
f(x)
}
func f11(x *unsafe.Pointer, y unsafe.Pointer) {
*x = unsafe.Pointer(uintptr(y) + 1) // ERROR "write barrier"
}
func f12(x []*int, y *int) []*int {
// write barrier for storing y in x's underlying array
x = append(x, y) // ERROR "write barrier"
return x
}
func f12a(x []int, y int) []int {
// y not a pointer, so no write barriers in this function
x = append(x, y)
return x
}
func f13(x []int, y *[]int) {
*y = append(x, 1) // ERROR "write barrier"
}
func f14(y *[]int) {
*y = append(*y, 1) // ERROR "write barrier"
}
type T1 struct {
X *int
}
func f15(x []T1, y T1) []T1 {
return append(x, y) // ERROR "write barrier"
}
type T8 struct {
X [8]*int
}
func f16(x []T8, y T8) []T8 {
return append(x, y) // ERROR "write barrier"
}
func t1(i interface{}) **int {
// From issue 14306, make sure we have write barriers in a type switch
// where the assigned variable escapes.
switch x := i.(type) {
case *int: // ERROR "write barrier"
return &x
}
switch y := i.(type) {
case **int: // no write barrier here
return y
}
return nil
}
type T17 struct {
f func(*T17)
}
func f17(x *T17) {
// Originally from golang.org/issue/13901, but the hybrid
// barrier requires both to have barriers.
x.f = f17 // ERROR "write barrier"
x.f = func(y *T17) { *y = *x } // ERROR "write barrier"
}
type T18 struct {
a []int
s string
}
func f18(p *T18, x *[]int) {
p.a = p.a[:5] // no barrier
*x = (*x)[0:5] // no barrier
p.a = p.a[3:5] // ERROR "write barrier"
p.a = p.a[1:2:3] // ERROR "write barrier"
p.s = p.s[8:9] // ERROR "write barrier"
*x = (*x)[3:5] // ERROR "write barrier"
}
func f19(x, y *int, i int) int {
// Constructing a temporary slice on the stack should not
// require any write barriers. See issue 14263.
a := []*int{x, y} // no barrier
return *a[i]
}
func f20(x, y *int, i int) []*int {
// ... but if that temporary slice escapes, then the
// write barriers are necessary.
a := []*int{x, y} // ERROR "write barrier"
return a
}
var x21 *int
var y21 struct {
x *int
}
var z21 int
// f21x: Global -> heap pointer updates must have write barriers.
func f21a(x *int) {
x21 = x // ERROR "write barrier"
y21.x = x // ERROR "write barrier"
}
func f21b(x *int) {
x21 = &z21 // ERROR "write barrier"
y21.x = &z21 // ERROR "write barrier"
}
func f21c(x *int) {
y21 = struct{ x *int }{x} // ERROR "write barrier"
}
func f22(x *int) (y *int) {
// pointer write on stack should have no write barrier.
// this is a case that the frontend failed to eliminate.
p := &y
*p = x // no barrier
return
}
type T23 struct {
p *int
a int
}
var t23 T23
var i23 int
// f23x: zeroing global needs write barrier for the hybrid barrier.
func f23a() {
t23 = T23{} // ERROR "write barrier"
}
func f23b() {
// also test partial assignments
t23 = T23{a: 1} // ERROR "write barrier"
}
func f23c() {
t23 = T23{} // no barrier (dead store)
// also test partial assignments
t23 = T23{p: &i23} // ERROR "write barrier"
}
var g int
func f24() **int {
p := new(*int)
*p = &g // no write barrier here
return p
}
func f25() []string {
return []string{"abc", "def", "ghi"} // no write barrier here
}
type T26 struct {
a, b, c int
d, e, f *int
}
var g26 int
func f26(p *int) *T26 { // see issue 29573
return &T26{
a: 5,
b: 6,
c: 7,
d: &g26, // no write barrier: global ptr
e: nil, // no write barrier: nil ptr
f: p, // ERROR "write barrier"
}
}
func f27(p *int) []interface{} {
return []interface{}{
nil, // no write barrier: zeroed memory, nil ptr
(*T26)(nil), // no write barrier: zeroed memory, type ptr & nil ptr
&g26, // no write barrier: zeroed memory, type ptr & global ptr
7, // no write barrier: zeroed memory, type ptr & global ptr
p, // ERROR "write barrier"
}
}
var g28 [256]uint64
func f28() []interface{} {
return []interface{}{
false, // no write barrier
true, // no write barrier
0, // no write barrier
1, // no write barrier
uint8(127), // no write barrier
int8(-4), // no write barrier
&g28[5], // no write barrier
}
}
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