cmd/go: still need to set GOROOT with go1.9beta2

[markus-oberhumer]

I had hoped that now that issue #18678 is resolved I never have to think about GOROOT again. That does not seem the case, though.

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

go1.9beta2.linux-amd64 running on Fedora 26

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

$ unset GOROOT
$ /opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64/bin/go env
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/mfx/go"
GORACE=""
GOROOT="/opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="/usr/bin/gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build312405700=/tmp/go-build -gno-record-gcc-switches"
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"

What did you do?

$ cat hello.go
package main

import "fmt"

func main() {
        fmt.Println("Hello go")
}

$ unset GOROOT
$ /opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64/bin/go env | grep GOROOT
GOROOT="/opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64"

As you can see GOROOT is set correctly by go env.

$ unset GOROOT
$ /opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64/bin/go build hello.go 
hello.go:3:8: cannot find package "fmt" in any of:
        /usr/local/go/src/fmt (from $GOROOT)
        /home/mfx/go/src/fmt (from $GOPATH)
package main
        imports runtime: cannot find package "runtime" in any of:
        /usr/local/go/src/runtime (from $GOROOT)
        /home/mfx/go/src/runtime (from $GOPATH)

But it seems go build has a different GOROOT /usr/local/go.

[markus-oberhumer]

Somewhat related, it seems that GOTOOLDIR is not automatically set.

$ unset GOROOT GOTOOLDIR
$ /opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64/bin/go env | egrep 'GOROOT|GOTOOLDIR'
GOROOT="/opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"

Should I file a new issue for GOTOOLDIR ?

[ianlancetaylor]

Please show us the output of go build -x.

[ianlancetaylor]

The GOTOOLDIR problem is interesting, and may be related. GOTOOLDIR is computed based on the value returned by runtime.GOROOT(), which is not the same as the GOROOT value that the go tool computes after it starts up.

[markus-oberhumer]

There's not much extra info that go build -x does provide. And as I'm just using the public version from https://storage.googleapis.com/golang/go1.9beta2.linux-amd64.tar.gz you should be able to reproduce this issue.

$ env -i /opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64/bin/go env | egrep 'GOROOT|GOTOOLDIR'                                                                 
GOROOT="/opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"

$ env -i /opt/cc-i386-linux/go/golang/go1.9beta2.linux-amd64/bin/go build -x hello.go
WORK=/tmp/go-build254896712
hello.go:3:8: cannot find package "fmt" in any of:
        /usr/local/go/src/fmt (from $GOROOT)
        ($GOPATH not set. For more details see: 'go help gopath')
package main
        imports runtime: cannot find package "runtime" in any of:
        /usr/local/go/src/runtime (from $GOROOT)
        ($GOPATH not set. For more details see: 'go help gopath')

[ianlancetaylor]

You're right, I can recreate the problem. It's easy to recreate by building Go, and then moving the entire GOROOT directory elsewhere. Our tests don't work because we don't move the GOROOT directory--we don't want to do that, because it would break any other tests running at the same time.

@bradfitz Any suggestions for how to test this? The best I can think of is to copy GOROOT, remove GOROOT/pkg, run make.bash, move the copied GOROOT elsewhere, and check that it works. But that will be very slow and I'm not even sure where to put such a test.

[gopherbot]

CL https://golang.org/cl/48550 mentions this issue.

[bradfitz]

Our tests don't work because we don't move the GOROOT directory--we don't want to do that, because it would break any other tests running at the same time.

Only one cmd/dist/test test runs at a time per builder machines. (A single build might have it tests sharded out over 6-8 machines)

And if one fails, that buildlet ("machine") is never reused. So the test can clean up after itself (rename the goroot back to its original name) and any future tests would still work.

So the src/cmd/dist/test.go test would do something like:

• rename $GOROOT to $GOROOT+"-moved"
• run the test that the go tool works
• rename $GOROOT+"-moved" back to the original $GOROOT

[bradfitz]

... and if you want to not mess with user machines, you can do it only if testenv.Builder() != ""

[bradfitz]

Oh, in dist we can't depend on testenv, but looks like it already uses os.Getenv("GO_BUILDER_NAME") in a few places.

[ianlancetaylor]

Thanks. Added a test to the CL.

[markus-oberhumer]

Thanks!