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https://github.com/golang/go
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d4663e1353
Don't write back parts of a slicing operation if they are unchanged from the source of the slice. For example: x.s = x.s[0:5] // don't write back pointer or cap x.s = x.s[:5] // don't write back pointer or cap x.s = x.s[:5:7] // don't write back pointer There is more to be done here, for example: x.s = x.s[:len(x.s):7] // don't write back ptr or len This CL can't handle that one yet. Fixes #14855 Change-Id: Id1e1a4fa7f3076dc1a76924a7f1cd791b81909bb Reviewed-on: https://go-review.googlesource.com/20954 Reviewed-by: Austin Clements <austin@google.com> Run-TryBot: Keith Randall <khr@golang.org>
185 lines
3.3 KiB
Go
185 lines
3.3 KiB
Go
// errorcheck -0 -l -d=wb
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// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Test where write barriers are and are not emitted.
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package p
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import "unsafe"
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func f(x **byte, y *byte) {
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*x = y // ERROR "write barrier"
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z := y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f1(x *[]byte, y []byte) {
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*x = y // ERROR "write barrier"
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z := y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f1a(x *[]byte, y *[]byte) {
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*x = *y // ERROR "write barrier"
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z := *y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f2(x *interface{}, y interface{}) {
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*x = y // ERROR "write barrier"
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z := y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f2a(x *interface{}, y *interface{}) {
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*x = *y // ERROR "write barrier"
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z := y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f3(x *string, y string) {
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*x = y // ERROR "write barrier"
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z := y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f3a(x *string, y *string) {
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*x = *y // ERROR "write barrier"
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z := *y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f4(x *[2]string, y [2]string) {
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*x = y // ERROR "write barrier"
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z := y // no barrier
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*x = z // ERROR "write barrier"
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}
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func f4a(x *[2]string, y *[2]string) {
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*x = *y // ERROR "write barrier"
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z := *y // no barrier
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*x = z // ERROR "write barrier"
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}
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type T struct {
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X *int
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Y int
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M map[int]int
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}
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func f5(t, u *T) {
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t.X = &u.Y // ERROR "write barrier"
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}
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func f6(t *T) {
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t.M = map[int]int{1: 2} // ERROR "write barrier"
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}
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func f7(x, y *int) []*int {
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var z [3]*int
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i := 0
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z[i] = x // ERROR "write barrier"
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i++
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z[i] = y // ERROR "write barrier"
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i++
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return z[:i]
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}
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func f9(x *interface{}, v *byte) {
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*x = v // ERROR "write barrier"
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}
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func f10(x *byte, f func(interface{})) {
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f(x)
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}
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func f11(x *unsafe.Pointer, y unsafe.Pointer) {
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*x = unsafe.Pointer(uintptr(y) + 1) // ERROR "write barrier"
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}
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func f12(x []*int, y *int) []*int {
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// write barrier for storing y in x's underlying array
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x = append(x, y) // ERROR "write barrier"
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return x
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}
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func f12a(x []int, y int) []int {
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// y not a pointer, so no write barriers in this function
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x = append(x, y)
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return x
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}
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func f13(x []int, y *[]int) {
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*y = append(x, 1) // ERROR "write barrier"
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}
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func f14(y *[]int) {
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*y = append(*y, 1) // ERROR "write barrier"
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}
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type T1 struct {
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X *int
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}
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func f15(x []T1, y T1) []T1 {
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return append(x, y) // ERROR "write barrier"
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}
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type T8 struct {
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X [8]*int
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}
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func f16(x []T8, y T8) []T8 {
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return append(x, y) // ERROR "write barrier"
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}
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func t1(i interface{}) **int {
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// From issue 14306, make sure we have write barriers in a type switch
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// where the assigned variable escapes.
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switch x := i.(type) { // ERROR "write barrier"
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case *int:
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return &x
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}
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switch y := i.(type) { // no write barrier here
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case **int:
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return y
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}
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return nil
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}
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type T17 struct {
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f func(*T17)
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}
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func f17(x *T17) {
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// See golang.org/issue/13901
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x.f = f17 // no barrier
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x.f = func(y *T17) { *y = *x } // ERROR "write barrier"
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}
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type T18 struct {
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a []int
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s string
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}
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func f18(p *T18, x *[]int) {
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p.a = p.a[:5] // no barrier
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*x = (*x)[0:5] // no barrier
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p.a = p.a[3:5] // ERROR "write barrier"
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p.a = p.a[1:2:3] // ERROR "write barrier"
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p.s = p.s[8:9] // ERROR "write barrier"
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*x = (*x)[3:5] // ERROR "write barrier"
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}
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