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cmd/internal/gc: add and test write barrier debug output
We can expand the test cases as we discover problems. This is some basic tests plus all the things I got wrong in some recent work. Change-Id: Id875fcfaf74eb087ae42b441fe47a34c5b8ccb39 Reviewed-on: https://go-review.googlesource.com/9158 Reviewed-by: Rick Hudson <rlh@golang.org> Reviewed-by: Austin Clements <austin@google.com>
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@ -35,6 +35,8 @@ var goarch string
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var goroot string
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var Debug_wb int
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// Debug arguments.
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// These can be specified with the -d flag, as in "-d nil"
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// to set the debug_checknil variable. In general the list passed
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@ -46,6 +48,7 @@ var debugtab = []struct {
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{"nil", &Debug_checknil}, // print information about nil checks
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{"typeassert", &Debug_typeassert}, // print information about type assertion inlining
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{"disablenil", &Disable_checknil}, // disable nil checks
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{"wb", &Debug_wb}, // print information about write barriers
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}
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// Our own isdigit, isspace, isalpha, isalnum that take care
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@ -2218,6 +2218,9 @@ func applywritebarrier(n *Node, init **NodeList) *Node {
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if Curfn != nil && Curfn.Func.Nowritebarrier {
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Yyerror("write barrier prohibited")
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}
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if Debug_wb > 0 {
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Warnl(int(n.Lineno), "write barrier")
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}
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t := n.Left.Type
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l := Nod(OADDR, n.Left, nil)
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l.Etype = 1 // addr does not escape
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110
test/writebarrier.go
Normal file
110
test/writebarrier.go
Normal file
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@ -0,0 +1,110 @@
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// 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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