all: support native build on Android

[NatoBoram]

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

$ go version
go version go1.16.7 android/arm64

Does this issue reproduce with the latest release?

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

go env Output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/data/data/com.termux/files/home/.cache/go-build"
GOENV="/data/data/com.termux/files/home/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="android"
GOINSECURE=""
GOMODCACHE="/data/data/com.termux/files/home/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="android"
GOPATH="/data/data/com.termux/files/home/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/data/data/com.termux/files/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/data/data/com.termux/files/usr/lib/go/pkg/tool/android_arm64"
GOVCS=""
GOVERSION="go1.16.7"
GCCGO="gccgo"
AR="ar"
CC="aarch64-linux-android-clang"
CXX="aarch64-linux-android-clang++"
CGO_ENABLED="1"
GOMOD="/data/data/com.termux/files/home/Applications/go/src/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 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/data/data/com.termux/files/usr/tmp/go-build2204854682=/tmp/go-build -gno-record-gcc-switches"

What did you do?

./make.bash

What did you expect to see?

Installed Go for android/arm64 in /data/data/com.termux/files/home/Applications/go
Installed commands in /data/data/com.termux/files/home/Applications/go/bin

What did you see instead?

Building Go cmd/dist using /data/data/com.termux/files/usr/lib/go. (go1.16.7 android/arm64)
Building Go toolchain1 using /data/data/com.termux/files/usr/lib/go.
Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
Building Go toolchain2 using go_bootstrap and Go toolchain1.
Building Go toolchain3 using go_bootstrap and Go toolchain2.
Building packages and commands for android/arm64.
# runtime/cgo
/data/data/com.termux/files/usr/bin/ld: /system/lib64/liblog.so: unknown type [0x13] section `.relr.dyn'
/data/data/com.termux/files/usr/bin/ld: skipping incompatible /system/lib64/liblog.so when searching for -llog
/data/data/com.termux/files/usr/bin/ld: /system/lib64/liblog.so: unknown type [0x13] section `.relr.dyn'
/data/data/com.termux/files/usr/bin/ld: skipping incompatible /system/lib64/liblog.so when searching for -llog
/data/data/com.termux/files/usr/bin/ld: cannot find -llog
/data/data/com.termux/files/usr/bin/ld: /system/lib64/liblog.so: unknown type [0x13] section `.relr.dyn'
/data/data/com.termux/files/usr/bin/ld: skipping incompatible /system/lib64/liblog.so when searching for -llog
/data/data/com.termux/files/usr/bin/ld: /system/lib64/liblog.so: unknown type [0x13] section `.relr.dyn'
/data/data/com.termux/files/usr/bin/ld: skipping incompatible /system/lib64/liblog.so when searching for -llog
clang-12: error: linker command failed with exit code 1 (use -v to see invocation)
go tool dist: FAILED: /data/data/com.termux/files/home/Applications/go/pkg/tool/android_arm64/go_bootstrap install -gcflags=all= -ldflags=all= std cmd: exit status 2

[ianlancetaylor]

This looks like a problem with the Android linker /data/data/com.termux/files/usr/bin/ld reading the Android library /system/lib64/liblog.so. I don't know what Termux is, but if the problem is the Android linker being unable to read an Android library, I don't think that we can fix that problem in Go.

Does Go 1.16 work? It has the same use of -llog in the runtime/cgo package. That use was added in Go 1.4.

[NatoBoram]

Oh my god. You're right. This is a regression in Android 12 Developer Preview 4. Here's a neofetch.

OS: Android 12 aarch64
Host: google Pixel 3
Kernel: 4.9.270-gc51c7b10ee52-ab7522847
Uptime: 5 days, 1 hour, 38 mins
Packages: 109 (dpkg), 1 (pkg)
Shell: bash 5.1.8
CPU: Qualcomm SDM845 (8) @ 1.766GHz
Memory: 2690MiB / 3579MiB

Termux is a terminal emulator for Android : https://github.com/termux/termux-app

Google has been trying to forbid executing arbitrary code for a long time now, looks like they finally flipped the switch. Here's the latest updates from Termux

• Play Store now forbids downloading executable code termux/termux-app#655
• No more exec from data folder on targetAPI >= Android Q termux/termux-app#1072
• Revisit the Android W^X problem termux/termux-app#2155

Since it will be no longer possible to build Go on Android, is it going to be dropped from Go's support or will Go continue to support up to Android 11?

[ianlancetaylor]

CC @hyangah to take a look

[cherrymui]

Go supports and will probably continue to support Android as a target.

As far as I can tell, Android is mostly not a developer platform and most Android developers don't build on Android. And I'm not sure there is a "standard" development environment. As far as I can tell, building on Android is not really officially supported and tested.

[hyangah]

As seen in

go/src/internal/testenv/testenv.go

Lines 37 to 49 in df9c5d8

	func HasGoBuild() bool {
	if os.Getenv("GO_GCFLAGS") != "" {
	// It's too much work to require every caller of the go command
	// to pass along "-gcflags="+os.Getenv("GO_GCFLAGS").
	// For now, if $GO_GCFLAGS is set, report that we simply can't
	// run go build.
	return false
	}
	switch runtime.GOOS {
	case "android", "js", "ios":
	return false
	}
	return true

, we even disabled many tests that require go toolchains. This mode of android support was never intended.

[Grimler91]

The -llog flag has been removed from the golang that is cross-compiled for termux. If you want to compile golang in termux and be able to use it successfully you probably need to apply all three patches that termux applies.

Since it will be no longer possible to build Go on Android, is it going to be dropped from Go's support or will Go continue to support up to Android 11?

The potential issues/drawbacks only happen for apps targeting android 11 or newer. As of now (and probably for the foreseeable future) termux targets android 10. This works fine for now except for that the app is not allowed to be updated through playstore (and will be removed at some points).

There's nothing golang itself can do to be compatible with android >= 11, as the issue is when an app (like termux) runs ("exec()s") golang, and not with golang itself. In theory it should be possible to create an android app that still allows you to use golang to compile code on android >= 11, but you would not be able to run any of the resulting binaries.

[NatoBoram]

Only src-runtime-cgo-cgo.go.patch and src-runtime-cgo-gcc_android.c.patch worked for me, but I was able to build go1.17.

$ go version
go version go1.17 android/arm64

go env Output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/data/data/com.termux/files/home/.cache/go-build"
GOENV="/data/data/com.termux/files/home/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="android"
GOINSECURE=""
GOMODCACHE="/data/data/com.termux/files/home/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="android"
GOPATH="/data/data/com.termux/files/home/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/data/data/com.termux/files/home/Applications/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/data/data/com.termux/files/home/Applications/go/pkg/tool/android_arm64"
GOVCS=""
GOVERSION="go1.17"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/data/data/com.termux/files/usr/tmp/go-build2291608239=/tmp/go-build -gno-record-gcc-switches"

git diff Output

diff --git a/src/runtime/cgo/cgo.go b/src/runtime/cgo/cgo.go
index 4d2caf6c4f..e2cece097a 100644
--- a/src/runtime/cgo/cgo.go
+++ b/src/runtime/cgo/cgo.go
@@ -15,7 +15,6 @@ package cgo
 #cgo darwin,arm64 LDFLAGS: -framework CoreFoundation
 #cgo dragonfly LDFLAGS: -lpthread
 #cgo freebsd LDFLAGS: -lpthread
-#cgo android LDFLAGS: -llog
 #cgo !android,linux LDFLAGS: -lpthread
 #cgo netbsd LDFLAGS: -lpthread
 #cgo openbsd LDFLAGS: -lpthread
diff --git a/src/runtime/cgo/gcc_android.c b/src/runtime/cgo/gcc_android.c
index 7ea213599d..3e6afc5b79 100644
--- a/src/runtime/cgo/gcc_android.c
+++ b/src/runtime/cgo/gcc_android.c
@@ -13,22 +13,12 @@ fatalf(const char* format, ...)
 {
 	va_list ap;
 
-	// Write to both stderr and logcat.
-	//
-	// When running from an .apk, /dev/stderr and /dev/stdout
-	// redirect to /dev/null. And when running a test binary
-	// via adb shell, it's easy to miss logcat.
-
 	fprintf(stderr, "runtime/cgo: ");
 	va_start(ap, format);
 	vfprintf(stderr, format, ap);
 	va_end(ap);
 	fprintf(stderr, "\n");
 
-	va_start(ap, format);
-	__android_log_vprint(ANDROID_LOG_FATAL, "runtime/cgo", format, ap);
-	va_end(ap);
-
 	abort();
 }