go/build: Passes bad $GOROOT to go list subprocess

[tv42]

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

# this sdk came from `go get golang.org/dl/go1.13.3`,
# I'm fiddling with PATH to eliminate other installed Go
# versions to reproduce with a known good version,
# without parent/child version mismatch later.
$ PATH="$HOME/sdk/go1.13.3/bin:/bin:/usr/bin" go version
go version go1.13.3 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output

PATH="$HOME/sdk/go1.13.3/bin:/bin:/usr/bin" go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/tv/.cache/go-build"
GOENV="/home/tv/.config/go/env"
GOEXE=""
GOFLAGS="-trimpath"
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY="mntn.llc/go,*.mntn.llc,eagain.net/2019,eagain.net/tools"
GONOSUMDB="mntn.llc/go,*.mntn.llc,eagain.net/2019,eagain.net/tools"
GOOS="linux"
GOPATH="/home/tv/go"
GOPRIVATE="mntn.llc/go,*.mntn.llc,eagain.net/2019,eagain.net/tools"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/tv/sdk/go1.13.3"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/tv/sdk/go1.13.3/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/tv/z/go.mod"
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=/home/tv/tmp/go-build434657787=/tmp/go-build -gno-record-gcc-switches"

What did you do?

~$ mkdir z
~$ cd z
~/z$ go mod init example.com/m
go: creating new go.mod: module example.com/m
~/z$ cat >main.go
package main

import (
	"fmt"
	"go/build"
	"os"
	"runtime"
)

func main() {
	fmt.Printf("runtime.GOROOT=%v\n", runtime.GOROOT())
	_, err := build.Import("example.com/m", ".", build.ImportComment)
	if err != nil {
		fmt.Printf("error: %v", err)
		os.Exit(1)
	}
}
~/z$ PATH="$HOME/sdk/go1.13.3/bin:/bin:/usr/bin" go run .
runtime.GOROOT=go
error: go/build: importGo example.com/m: exit status 2
go: cannot find GOROOT directory: go


exit status 1

What did you expect to see?

Successful run, with ImportDir returning metadata about the package example.com/m that I just created.

What did you see instead?

The go list subprocess is spawned with a broken GOROOT=go in environment, an explicitly set $GOROOT prevents the child from deducing GOROOT from /proc/self/exe, and this causes it to fail.

Confirmation that $GOROOT is passed:

~/z$ PATH="$HOME/sdk/go1.13.3/bin:/bin:/usr/bin" sh -c 'go build && strace -f -o log -v -e execve ./m >/dev/null; grep execve log|tail -1'
1190329 execve("/home/tv/sdk/go1.13.3/bin/go", ["go", "list", "-compiler=gc", "-tags=", "-installsuffix=", "-f={{.Dir}}\n{{.ImportPath}}\n{{.R"..., "example.com/m"], [...skipped things..., "GOOS=linux", "GOARCH=amd64", "GOROOT=go", "GOPATH=/home/tv/go", "CGO_ENABLED=1"]) = 0

[tv42]

It seems golang.org/dl/go1.13.3 contains GOROOT munging logic. But that doesn't help here unless that executable is in PATH as "go" (not "go1.13.3"). This bug could be "fixed" by documenting that nobody must ever call anything under ~/sdk directly -- but that leaves people who just unpack a tarball just as broken.

[tv42]

This only triggers with modules, not with GOPATH (go/build doesn't spawn subprocesses in gopath mode).

Real world code that broke because of this: https://github.com/google/ko

[bcmills]

The fact that the

	fmt.Printf("runtime.GOROOT=%v\n", runtime.GOROOT())

line prints

runtime.GOROOT=go

suggests that this isn't actually coming from go/build at all: it's just passing on what the go command told it.

[bcmills]

I'm unable to reproduce the reported behavior.

m$ go1.13.3 mod init example.com/m
go: creating new go.mod: module example.com/m

m$ cat >main.go
package main

import (
        "fmt"
        "go/build"
        "os"
        "runtime"
)

func main() {
        fmt.Printf("runtime.GOROOT=%v\n", runtime.GOROOT())
        _, err := build.Import("example.com/m", ".", build.ImportComment)
        if err != nil {
                fmt.Printf("error: %v", err)
                os.Exit(1)
        }
}

m$ PATH="$HOME/sdk/go1.13.3/bin:/bin:/usr/bin" go run .
runtime.GOROOT=/usr/local/google/home/bcmills/sdk/go1.13.3

m$ PATH="$HOME/sdk/go1.13.3/bin" go run .
runtime.GOROOT=/usr/local/google/home/bcmills/sdk/go1.13.3

m$

Is it possible that you have a GOROOT entry in /home/tv/.config/go/env, or an explicit GOROOT environment variable set?

[tv42]

I have no GOROOT in environment, only GOFLAGS=-trimpath in ~/.config/go/env.

As far as I can understand, the problem comes from go/build using runtime.GOROOT()'s poor guess (internal/sys.DefaultGoroot as the fallback).

I'll try to make an effort to reproduce inside a reproducible container or something.

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)