android versus linux for GOOS

[jonathan...@gmail.com]

If statically compiling all the way down, is there any reason to use GOOS as android and not linux?

[Frits van Bommel]

In the Go 1.6.1 tree:

$ find -name '*_android.go'
./runtime/write_err_android.go
./runtime/stubs_android.go
./runtime/internal/sys/zgoos_android.go
./runtime/os_android.go
./net/cgo_android.go
$ egrep '\+build.*\bandroid\b' -rn .
./os/user/lookup_unix.go:5:// +build darwin dragonfly freebsd !android,linux netbsd openbsd solaris
./os/user/lookup_stubs.go:5:// +build !cgo,!windows,!plan9 android
./runtime/write_err.go:5:// +build !android
./runtime/cgo/gcc_fatalf.c:7:// +build !android,linux
./runtime/internal/sys/zgoos_linux.go:3:// +build !android
./runtime/internal/sys/gengoos.go:50:            fmt.Fprintf(&buf, "// +build !android\n\n") // must explicitly exclude android for linux
./net/cgo_socknew.go:6:// +build android linux solaris
./net/cgo_resnew.go:6:// +build darwin linux,!android netbsd solaris
./net/cgo_resold.go:6:// +build android freebsd dragonfly openbsd
./net/cgo_linux.go:5:// +build !android,cgo,!netgo
$ egrep '//build.*\bandroid\b|runtime\.GOOS == "android"' -rn .
./os/os_test.go:589:    if runtime.GOOS == "android" {
./os/file_unix.go:349:        if runtime.GOOS == "android" {
./os/exec/exec_test.go:251:    if runtime.GOOS == "android" {
./runtime/pprof/pprof_test.go:261:    if runtime.GOOS == "android" {

[Dave Cheney]

It depends on what you want to do. The differences between Linux and android are mainly to do with libc vs bionic and the different ways of handling tls and threading on those platforms.

What is the problem you are trying to solve?

[jonathan...@gmail.com]

Just wanted to know where to expect issues in terms of compatibility, whether the two are actual compatible or not when fully statically linked. Initial test showed some kind of dns lookup issue when using GOOS linux instead of android which points inline with Frits reply? I remember hearing something of some compile flag that uses a golang dns bit?

[jonathan...@gmail.com]

Even when using netgo build tag I still get:

dial tcp: lookup XXX on [::1]:53: read udp [::1]:53137-\u003e[::1]:53: read: connection refused

We have a fair amount of linux C dependencies we want to use, some not supporting android so was hoping a full static binary built for linux would still function, appears not?

[Dave Cheney]

I doubt that will just work (tm). Android is not Linux when it comes to C code because the latter uses libc where Android uses its own implementation called bionic. In Go, we can mostly gloss over the details, but if it's honest to god C code, it'll trip over them straight away. 

[jonathan...@gmail.com]

That is involved if static linking all the way?

[Dave Cheney]

Yes, if you statically link a libc binary and run it on a platform that expects bionic, or vice versa, it's unlikely that will work.