x/mobile: gomobile bind does not work with cgo and android

[anjmao]

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

go version go1.13.4 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/anjmao/Library/Caches/go-build"
GOENV="/Users/anjmao/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/anjmao/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
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 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/p8/5ggx21z124n8kxx2wfv674380000gp/T/go-build165303278=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I have this simple test package with cgo and I'm building it for android with android-ndk-r20.

package test

// #include <stdlib.h>
import "C"

type cCharPointer struct {
	Ptr *C.char
}

func Hello() string {
	return "hi"
}

Build:

gomobile bind -o App.aar -target=android $GOPATH/mobile/test

What did you expect to see?

No error. Note that:

1. It works if I specify ios target.
2. It works for both android and ios if cgo is not used.
3. It works with cgo for older gomobile version. Tested with this commit

What did you see instead?

Error:

gomobile: /Users/anjmao/go/bin/gobind -lang=go,java -outdir=/var/folders/p8/5ggx21z124n8kxx2wfv674380000gp/T/gomobile-work-476890504 github.com/mobile/test failed: exit status 1
[/Users/anjmao/go/src/github.com/mobile/test/test.go:4:8: could not import C (no metadata for C)]

[bcmills]

CC @steeve @hyangah

[anjmao]

Specifically inner gobind command fails to run gobind with these environment variables

GOOS=android CGO_ENABLED=1 gobind -lang=go,java -outdir=./build/bind $GOPATH/mobile/test

I installed go std library for cgo with

TOOLCHAIN=/usr/local/android-ndk-r20/toolchains/llvm/prebuilt/linux-x86_64
ARCH=armv7a
export AR=$TOOLCHAIN/bin/$ARCH-linux-android-ar
export AS=$TOOLCHAIN/bin/$ARCH-linux-android-as
export CC=$TOOLCHAIN/bin/$ARCH-linux-androideabi28-clang
export CXX=$TOOLCHAIN/bin/$ARCH-linux-androideabi28-clang++
export LD=$TOOLCHAIN/bin/$ARCH-linux-android-ld
export RANLIB=$TOOLCHAIN/bin/$ARCH-linux-android-ranlib
export STRIP=$TOOLCHAIN/bin/$ARCH-linux-android-strip

GOOS=android GOARCH=arm CGO_ENABLED=1 go install std

It would be awesome if some of you @steeve @hyangah could check if gomobile + latest android ndk + clang + cgo works for you.

[anjmao]

I found the problem. My command was missing GOARCH env variable. Full command should be

GOOS=android GOARCH=arm CGO_ENABLED=1 gomobile bind ...

[anjmao]

One thing I don't like is that I get this error could not import C (no metadata for C) even If I provide wrong CC env variable, for example setting it to CC=no-such-binary. Maybe it make sense to create separate issue for improvements validating passed env variables when using cgo as it can get really annoying then dealing with these issues.

/CC @bcmills

[zongquan]

My build environment has encountered the same problem, and trying to change the any version of Go can't be solved.

[JasonHonor]

Me too, anyone can help me ?

[bbadbeef]

Me too, anyone can help me ?

me too. have you solve it yet?

[steeve]

Don't forget to set CGO_ENABLED=1

[bbadbeef]

Don't forget to set CGO_ENABLED=1

I set CGO_ENABLED=1 and still get this error.
use this command on mac:
GOOS=android GOARCH=arm CGO_ENABLED=1 gomobile bind -target=android .
when remove cgo's part , it works ok

[bbadbeef]

i use an older version of gomobile and it works ok with cgo

[bestbug456]

@bbadbeef which version did you use?

[bbadbeef]

@bbadbeef which version did you use?

92f3b9c works ok, the newer versions are not

finally i found it's not ok, just not output error message when compiling

[cswxzx]

Me too, anyone can help me ?

me too. have you solve it yet?

[bestbug456]

Guys for you information for android I've start using this docker images which works fine: openpriv/android-go-mobile at the moment is updated at 10 Jul 2018.

[bbadbeef]

my go function have c type param and return value, can it be supported with gomobile?
in header files it shows
" // skipped function xxxx with unsupported parameter or return types"