/usr/share/go-1.6/test/writebarrier.go is in golang-1.6-src 1.6.1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// 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 // ERROR "write barrier"
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f1(x *[]byte, y []byte) {
*x = y // ERROR "write barrier"
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 // ERROR "write barrier"
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f2a(x *interface{}, y *interface{}) {
*x = *y // ERROR "write barrier"
z := y // no barrier
*x = z // ERROR "write barrier"
}
func f3(x *string, y string) {
*x = y // ERROR "write barrier"
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) { // ERROR "write barrier"
case *int:
return &x
}
switch y := i.(type) { // no write barrier here
case **int:
return y
}
return nil
}
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