cmd/go: GOOS=android requires explicitly setting CGO_ENABLED=1

[saleemrashid]

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

$ go version
go version go1.11.5 linux/amd64

Does this issue reproduce with the latest release?

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

go env Output

$ GOOS=android GOARCH=arm GOARM=7 CC=arm-linux-androideabi-gcc CXX=false go env
GOARCH="arm"
GOBIN=""
GOCACHE="/home/saleem/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="android"
GOPATH="/home/saleem/.local/lib/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/go"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
GOARM="7"
CC="arm-linux-androideabi-gcc"
CXX="false"
CGO_ENABLED="0"
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 -marm -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build669201380=/tmp/go-build -gno-record-gcc-switches"

What did you do?

package main

import (
	"fmt"
)

func main() {
	fmt.Println("Hello, World!")
}

What did you expect to see?

The command should succeed without explicitly setting CGO_ENABLED=1

What did you see instead?

Without explicitly setting CGO_ENABLED (go env shows it defaults to CGO_ENABLED=0)

$ GOOS=android GOARCH=arm GOARM=7 CC=arm-linux-androideabi-gcc CXX=false go build
/usr/lib/go/pkg/tool/linux_amd64/link: running arm-linux-androideabi-gcc failed: exit status 1
/tmp/go-link-934544495/go.o:go.go:_cgo_init: error: undefined reference to 'x_cgo_init'
/tmp/go-link-934544495/go.o:go.go:_cgo_notify_runtime_init_done: error: undefined reference to 'x_cgo_notify_runtime_init_done'
/tmp/go-link-934544495/go.o:go.go:_cgo_thread_start: error: undefined reference to 'x_cgo_thread_start'
/tmp/go-link-934544495/go.o:go.go:runtime._cgo_setenv: error: undefined reference to 'x_cgo_setenv'
/tmp/go-link-934544495/go.o:go.go:runtime._cgo_unsetenv: error: undefined reference to 'x_cgo_unsetenv'
/tmp/go-link-934544495/go.o:go.go:runtime.cgo_yield: error: undefined reference to '_cgo_yield'
collect2: error: ld returned 1 exit status

Explicitly setting CGO_ENABLED=1 leads to a successful build

$ GOOS=android GOARCH=arm GOARM=7 CC=arm-linux-androideabi-gcc CXX=false CGO_ENABLED=1 go build
$ 

[saleemrashid]

See also #25963

[bcmills]

CC @eliasnaur @ianlancetaylor

[eliasnaur]

The go tool disables CGO_ENABLED when cross-compiling:

$ go env CGO_ENABLED
1
$ GOOS=android go env CGO_ENABLED
0

I suppose we could keep CGO_ENABLED when CC or CXX is set?

[ianlancetaylor]

It would be nice to figure out when we can safely set CGO_ENABLED, but I'm not sure it should be simply because CC is set. We have a corresponding set of bug reports from people who set CC to the wrong compiler. But I don't have a better suggestion.

[eliasnaur]

How about keeping CGO_ENABLED for geese that don't support internal linking?

[rsc]

We have a very simple rule right now: cgo is disabled for all cross-compiles. We should probably keep that simple rule. People building for Android have needed to set CGO_ENABLED from the start, and they seem to be coping just fine.