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encoding/gob: Slice encoding is not symmetric #24495

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rvolosatovs opened this issue Mar 22, 2018 · 2 comments
Closed

encoding/gob: Slice encoding is not symmetric #24495

rvolosatovs opened this issue Mar 22, 2018 · 2 comments

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@rvolosatovs
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@rvolosatovs rvolosatovs commented Mar 22, 2018

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

go version go1.10 linux/amd64

Does this issue reproduce with the latest release?

yes

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

GOARCH="amd64"
GOBIN="/home/rvolosatovs/.local/bin.go"
GOCACHE="/home/rvolosatovs/.local/cache/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/rvolosatovs"
GORACE=""
GOROOT="/nix/store/r7p21cmhq0jimq2f8c8y5sm2vqg2ap99-go-1.10/share/go"
GOTMPDIR=""
GOTOOLDIR="/nix/store/r7p21cmhq0jimq2f8c8y5sm2vqg2ap99-go-1.10/share/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build642040554=/tmp/go-build -gno-record-gcc-switches"

What did you do?

https://play.golang.org/p/ycEF5lDyE1p

Relevant part of the code:

for _, a := range [][]byte{
		nil,
		[]byte{},
		[]byte{42},
	} {
		var buf bytes.Buffer
		gob.NewEncoder(&buf).Encode(a)

		var b []byte
		gob.NewDecoder(&buf).Decode(&b)

		fmt.Println(reflect.DeepEqual(b, a))
	}

What did you expect to see?

true
true
true

What did you see instead?

true
false
true

Hence, zero-length slices are encoded in the same way as nil slices, which makes encoding non-symmetric.

@robpike
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@robpike robpike commented Mar 22, 2018

Gob does not have a concept of nil in its data format, so this is working as designed.

@robpike robpike closed this Mar 22, 2018
@rvolosatovs
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@rvolosatovs rvolosatovs commented Mar 22, 2018

But zero-length slice is not nil, right?
https://play.golang.org/p/aBW1WGw8RlV

@golang golang locked and limited conversation to collaborators Mar 22, 2019
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