go/build: defaultGOPATH cannot handle the confiliction correctly

[hirochachacha]

Please answer these questions before submitting your issue. Thanks!

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

package main

import (
	"fmt"
	"go/build"
)

func main() {
	fmt.Println(build.Default.GOPATH)
}

then,
$GOROOT="$HOME/go" GOPATH="" go run c.go:

$GOROOT="$HOME/go/" GOPATH="" go run c.go:

/Users/hiro/go

What did you expect to see?

same outputs

What did you see instead?

different outputs

Does this issue reproduce with the latest release (go1.7.5)?

IIUC, default go path is introduced in go1.8.

System details

go version devel +3e55059 Mon Jan 30 20:38:03 2017 +0000 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/hiro/.go"
GORACE=""
GOROOT="/Users/hiro/go"
GOTOOLDIR="/Users/hiro/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/wq/dwn8hs0x7njbzty9f68y61700000gn/T/go-build575104841=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
GOROOT/bin/go version: go version devel +3e55059 Mon Jan 30 20:38:03 2017 +0000 darwin/amd64
GOROOT/bin/go tool compile -V: compile version devel +3e55059 Mon Jan 30 20:38:03 2017 +0000 X:framepointer
uname -v: Darwin Kernel Version 16.3.0: Thu Nov 17 20:23:58 PST 2016; root:xnu-3789.31.2~1/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.12.2
BuildVersion:	16C67
lldb --version: lldb-360.1.70
gdb --version: GNU gdb (GDB) 7.12

[gopherbot]

CL https://golang.org/cl/36073 mentions this issue.

[rakyll]

If GOROOT is being corrupted due to the mishandling, we should consider fixing this in 1.8.

/cc @bradfitz

[bradfitz]

That one-line change might be okay. I'd prefer to see a test, though, at which point it's more than one line.

I'll let @rsc decide.

[davecheney]

Assigning "" to an environment variable does not unset it.

package main

import (
        "fmt"
        "os"
)

func main() {
        fmt.Println(os.LookupEnv("GOPATH"))
}

deadwood(~/src) % go run printenv.go
/home/dfc true
deadwood(~/src) % unset GOPATH
deadwood(~/src) % go run printenv.go
 false
deadwood(~/src) % env GOPATH="" go run printenv.go                                                                             
 true

[hirochachacha]

@davecheney

go/build/build.go uses:

func envOr(name, def string) string {
	s := os.Getenv(name)
	if s == "" {
		return def
	}
	return s
}

I cannot judge this is WAI or an another subtle bug, though.

[davecheney]

I'm not sure this is a bug

…

On Wed, 1 Feb 2017, 10:27 hirochachacha ***@***.***> wrote: @davecheney <https://github.com/davecheney> go/build/build.go uses: func envOr(name, def string) string { s := os.Getenv(name) if s == "" { return def } return s } I cannot judge this is WAI or an another subtle bug, though. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#18863 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcA-2wq94CuSkV8eINLFbSVrgPHBTMks5rX8NUgaJpZM4LytPI> .

[gopherbot]

CL https://golang.org/cl/36427 mentions this issue.

[rsc]

Cherry-pick to release branch pending.

[gopherbot]

CL https://golang.org/cl/36536 mentions this issue.