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Should not appear slice bounds out of range #29833

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kexirong opened this issue Jan 19, 2019 · 7 comments
Closed

Should not appear slice bounds out of range #29833

kexirong opened this issue Jan 19, 2019 · 7 comments
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@kexirong
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kexirong commented Jan 19, 2019 •
edited

What version of Go are you using (go version)?

$ go version
go version go1.11.4 linux/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/kk/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/data/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build753918768=/tmp/go-build -gno-record-gcc-switches"

What did you do?

run the code will recurrent

package main

import (
	"errors"
	"fmt"
)

func test() (*byte, error) {
	bs := []*byte{}
	b := byte('a')
	bs = append(bs, &b)
	if len(bs) != 1 {
		return nil, errors.New("")
	}
	r := bs[len(bs)-1]
	bs = bs[0 : len(bs)-1]
	return r, nil
}
func main() {
	_, err := test()
	if err != nil {
		fmt.Println(err)
	}
}

code link://https://play.golang.org/p/-vi8ee_6RWF

What did you expect to see?

Comment out return nil, errors.New("") will to run without error

func test() (*byte, error) {
	bs := []*byte{}
	b := byte('a')
	bs = append(bs, &b)
	if len(bs) != 1 {
		//	return nil, errors.New("")
	}
	r := bs[len(bs)-1]
	bs = bs[0 : len(bs)-1]
	return r, nil
}

What did you see instead?

panic: runtime error: slice bounds out of range

goroutine 1 [running]:
main.test(...)
       main.go:16
main.main()
       main.go:20 +0x120

I can't understand why this is
@mvdan
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mvdan commented Jan 19, 2019

Commenting out the line doesn't make the program panic: https://play.golang.org/p/VrcWRTHJh2m

Please note that the issue tracker is for bugs in Go. If you have a question about your code, see https://golang.org/wiki/Questions.

@mvdan mvdan closed this as completed Jan 19, 2019
@kexirong
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kexirong commented Jan 19, 2019 •
edited

Commenting out the line doesn't make the program panic: https://play.golang.org/p/VrcWRTHJh2m

Please note that the issue tracker is for bugs in Go. If you have a question about your code, see https://golang.org/wiki/Questions.

did you sure the playground is go1.11.4 @mvdan

@mvdan
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mvdan commented Jan 19, 2019

Yes. I even tried it locally with both go version go1.11.4 linux/amd64 and go version devel +c077c74312 Fri Jan 18 03:50:05 2019 +0000 linux/amd64.

@kexirong
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are you didn't Commenting out the linereturn nil, errors.New("") when run the code @mvdan

@mvdan
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mvdan commented Jan 19, 2019

I am commenting it out - see the playground link I pasted earlier.

@kexirong
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kexirong commented Jan 19, 2019 •
edited

Thank you , My English is poor，What I want to express is why panic when didn't commenting out the line @mvdan

@mvdan
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mvdan commented Jan 19, 2019

Ok, now I understand what you meant. The good news is that this is already being tracked in #29503; it will be fixed in the upcoming 1.11.5.

@mvdan mvdan mentioned this issue Jan 19, 2019
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@mvdan @gopherbot @kexirong