cmd/go: panic: runtime error: slice bounds out of range

[jbuberel]

Does not appear to be a dup of #11414

Problem is reproducible on tip +e8c4a5b as well as go1.5rc1 tag. Added a few printfs just before line 453:

jbuberel@ubuntu:~/vtest/src$ go run p/command.go 
parent.ImportPath: [p]
len(parent.ImportPath)-chopped: [-5]
vpath: [vendor/github.com/gorilla/mux]
panic: runtime error: slice bounds out of range

Full output:

$ go run p/cmd.go 
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
main.vendoredImportPath(0xc82010bc00, 0xc8201114c1, 0x16, 0x0, 0x0, 0x0, 0x0, 0x0)
        /home/jbuberel/go15/src/cmd/go/pkg.go:453 +0x540
main.loadImport(0xc8201114c1, 0x16, 0xc820110fa0, 0x1a, 0xc82010bc00, 0xc8201078c0, 0xc8200efa70, 0x1, 0x1, 0x1, ...)
        /home/jbuberel/go15/src/cmd/go/pkg.go:317 +0x138e
main.(*Package).load(0xc82010bc00, 0xc8201078c0, 0xc8200d2900, 0x0, 0x0, 0x0)
        /home/jbuberel/go15/src/cmd/go/pkg.go:899 +0x42e1
main.goFilesPackage(0xc82000a350, 0x1, 0x1, 0x8)
        /home/jbuberel/go15/src/cmd/go/build.go:750 +0x836
main.runRun(0xba6020, 0xc82000a350, 0x1, 0x1)
        /home/jbuberel/go15/src/cmd/go/run.go:87 +0x479
main.main()
        /home/jbuberel/go15/src/cmd/go/main.go:181 +0x782

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
        /home/jbuberel/go15/src/runtime/asm_amd64.s:1696 +0x1

goroutine 5 [syscall]:
os/signal.loop()
        /home/jbuberel/go15/src/os/signal/signal_unix.go:22 +0x18
created by os/signal.init.1
        /home/jbuberel/go15/src/os/signal/signal_unix.go:28 +0x37
jbuberel@ubuntu:~/vtest/src$ mv ../vendor/ ../v
jbuberel@ubuntu:~/vtest/src$ go run p/cmd.go   
p/cmd.go:4:2: cannot find package "github.com/gorilla/mux" in any of:
        /home/jbuberel/go15/src/github.com/gorilla/mux (from $GOROOT)
        /home/jbuberel/vtest/src/github.com/gorilla/mux (from $GOPATH)
jbuberel@ubuntu:~/vtest/src$ mv p/cmd.go p/command.go
jbuberel@ubuntu:~/vtest/src$ go run p/command.go 
p/command.go:4:2: cannot find package "github.com/gorilla/mux" in any of:
        /home/jbuberel/go15/src/github.com/gorilla/mux (from $GOROOT)
        /home/jbuberel/vtest/src/github.com/gorilla/mux (from $GOPATH)

Version, build and directory configuration:

$ go version
go version devel +e8c4a5b Sat Aug 15 17:38:56 2015 +0000 linux/amd64
jbuberel@ubuntu:~/vtest/src$ go env
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/jbuberel/vtest"
GORACE=""
GOROOT="/home/jbuberel/go15"
GOTOOLDIR="/home/jbuberel/go15/pkg/tool/linux_amd64"
GO15VENDOREXPERIMENT="1"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0"
CXX="g++"
CGO_ENABLED="1"
jbuberel@ubuntu:~/vtest/src$ cd ../
jbuberel@ubuntu:~/vtest$ cd ../
jbuberel@ubuntu:~$ tree vtest/
vtest/
|-- src
|   `-- p
|       `-- command.go
`-- vendor
    `-- github.com
        `-- gorilla
            |-- context
            |   |-- context.go
            |   |-- context_test.go
            |   |-- doc.go
            |   |-- LICENSE
            |   `-- README.md
            `-- mux
                |-- bench_test.go
                |-- doc.go
                |-- LICENSE
                |-- mux.go
                |-- mux_test.go
                |-- old_test.go
                |-- README.md
                |-- regexp.go
                `-- route.go

Contents of command.go:

package main

import (
        "fmt"
        "github.com/gorilla/mux"
)

func main() {
        m := mux.NewRouter()
        fmt.Println(m)
}

[jbuberel]

Moving the vendor directory out of the root of $GOPATH and the problem goes away:

vendor in $GOPATH root causes panic:

$ tree ~/vtest
/home/jbuberel/vtest
|-- src
|   `-- package
|       `-- command.go
`-- vendor
    `-- github.com
        `-- gorilla
            |-- context
            |   |-- context.go
            |   |-- context_test.go
            |   |-- doc.go
            |   |-- LICENSE
            |   `-- README.md
            `-- mux
                |-- bench_test.go
                |-- doc.go
                |-- LICENSE
                |-- mux.go
                |-- mux_test.go
                |-- old_test.go
                |-- README.md
                |-- regexp.go
                `-- route.go
$ go run command.go 
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
main.vendoredImportPath(0xc82010bc00, 0xc82010f421, 0x16, 0x0, 0x0, 0x0, 0x0, 0x0)
        /home/jbuberel/go15/src/cmd/go/pkg.go:453 +0x540
main.loadImport(0xc82010f421, 0x16, 0xc8200ef920, 0x20, 0xc82010bc00, 0xc8201078c0, 0xc8200efbc0, 0x1, 0x1, 0x1, ...)
        /home/jbuberel/go15/src/cmd/go/pkg.go:317 +0x138e
main.(*Package).load(0xc82010bc00, 0xc8201078c0, 0xc8200d2900, 0x0, 0x0, 0x0)
        /home/jbuberel/go15/src/cmd/go/pkg.go:899 +0x42e1
main.goFilesPackage(0xc82000a350, 0x1, 0x1, 0x8)
        /home/jbuberel/go15/src/cmd/go/build.go:750 +0x836
main.runRun(0xba4fe0, 0xc82000a350, 0x1, 0x1)
        /home/jbuberel/go15/src/cmd/go/run.go:87 +0x479
main.main()
        /home/jbuberel/go15/src/cmd/go/main.go:181 +0x782

vendor in $GOPATH/src works correctly:

$ tree ~/vtest
/home/jbuberel/vtest
`-- src
    |-- package
    |   `-- command.go
    `-- vendor
        `-- github.com
            `-- gorilla
                |-- context
                |   |-- context.go
                |   |-- context_test.go
                |   |-- doc.go
                |   |-- LICENSE
                |   `-- README.md
                `-- mux
                    |-- bench_test.go
                    |-- doc.go
                    |-- LICENSE
                    |-- mux.go
                    |-- mux_test.go
                    |-- old_test.go
                    |-- README.md
                    |-- regexp.go
                    `-- route.go

7 directories, 15 files
jbuberel@ubuntu:~/vtest/src/package$ go run command.go 
&{<nil> <nil> [] map[] false false}

[rsc]

Nice, thanks.

[gopherbot]

CL https://golang.org/cl/13674 mentions this issue.