Go: x/text: panic in language.ParseAcceptLanguage while processing bcp47 tag

[ph1048]

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

$ go version
go version go1.15.4 linux/amd64

Does this issue reproduce with the latest release?

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

go env Output

$ go env

GO111MODULE=""

GOARCH="amd64"

GOBIN=""

GOCACHE="/home/sasha/.cache/go-build"

GOENV="/home/sasha/.config/go/env"

GOEXE=""

GOFLAGS=""

GOHOSTARCH="amd64"

GOHOSTOS="linux"

GOINSECURE=""

GOMODCACHE="/home/sasha/goenv/pkg/mod"

GONOPROXY=""

GONOSUMDB=""

GOOS="linux"

GOPATH="/home/sasha/goenv"

GOPRIVATE=""

GOPROXY="https://proxy.golang.org,direct"

GOROOT="/usr/local/go"

GOSUMDB="sum.golang.org"

GOTMPDIR=""

GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"

GCCGO="gccgo"

AR="ar"

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-build111267796=/tmp/go-build -gno-record-gcc-switches"

GOROOT/bin/go version: go version go1.15.4 linux/amd64

GOROOT/bin/go tool compile -V: compile version go1.15.4

uname -sr: Linux 4.19.128-microsoft-standard

Distributor ID: Kali

Description:    Kali GNU/Linux Rolling

Release:    2020.2

Codename:   kali-rolling

/lib/x86_64-linux-gnu/libc.so.6: GNU C Library (Debian GLIBC 2.31-3) stable release version 2.31.

gdb --version: GNU gdb (Debian 9.2-1) 9.2

What did you do?

https://play.golang.org/p/SwAU9tKYRsj

What did you expect to see?

Error via return value

What did you see instead?

panic: runtime error: slice bounds out of range [9:8]

goroutine 1 [running]:
golang.org/x/text/internal/language.(*scanner).resizeRange(0xc000068d08, 0x6, 0x8, 0x3)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:142 +0x2e7
golang.org/x/text/internal/language.(*scanner).replace(...)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:151
golang.org/x/text/internal/language.parseTag(0xc000068d08, 0x0, 0x0, 0x0, 0xc00007e0a3)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:296 +0x13b
golang.org/x/text/internal/language.parseExtension(0xc000068d08, 0x8)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:552 +0xe74
golang.org/x/text/internal/language.parseExtensions(0xc000068d08, 0x3030000000000)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:451 +0xa5
golang.org/x/text/internal/language.parse(0xc000068d08, 0x4d9210, 0x7, 0x3030000000000, 0x0, 0x0, 0x0, 0x0)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:268 +0x2bc
golang.org/x/text/internal/language.Parse(0x4d9210, 0x7, 0x0, 0x0, 0x0, 0x4b1185, 0x4d9210)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/internal/language/parse.go:250 +0x1c7
golang.org/x/text/language.CanonType.Parse(0x17, 0x4d9210, 0x7, 0x4d9210, 0x7, 0x0, 0x0, 0x3fc0389239a6386c)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/language/parse.go:46 +0x3f
golang.org/x/text/language.Parse(...)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/language/parse.go:34
golang.org/x/text/language.ParseAcceptLanguage(0x4d9210, 0x7, 0xc000068f48, 0x442bca, 0x56ed40, 0xc000032778, 0xc000068f78, 0x405e25, 0xc00005e058, 0x0)
    /tmp/gopath300097471/pkg/mod/golang.org/x/[email protected]/language/parse.go:154 +0x165
main.main()
    /tmp/sandbox168582112/prog.go:10   ##+0x3a

[odeke-em]

Thank you for this report @ph1048! Kindly paging @mpvl

[mengzhuo]

Hmm...Gobot not working

https://go-review.googlesource.com/c/text/+/270697

[odeke-em]

@mengzhuo thanks for mailing the fix! To get gobot to attach to the proper issue, for any repo that isn’t the main Go repository, please use this format:
Fixes golang/go#NNNN

[gopherbot]

Change https://golang.org/cl/270697 mentions this issue: internal/language: fix resizeRange index wrong way

[mengzhuo]

@odeke-em it works, thanks for the info.