_readme.md

How to cross compile Go with CGO programs for a different OS/Arch

It is possible to compile Go programs for a different OS, even though go build says otherwise.

You'll need:

• a valid toolchain for the platform/os you're targetting
• Go Tip (works on 1.1 and 1.2rc1 but you might as well be on tip)
• golang-crosscompile helper script https://github.com/davecheney/golang-crosscompile
• the patch provided

First of all, clone the Go repo and switch to tip:

$ hg clone -u release https://code.google.com/p/go
$ cd go
go$ hg update default

Apply the patch:

go$ curl https://gist.github.com/steeve/6905542/raw/cross_compile_goos.patch | patch -p1
patching file src/cmd/go/build.go

Build Go:

go$ cd src
go/src$ bash all.bash

Now use golang-crosscompiler to build all the toolchains

go$ git clone https://github.com/davecheney/golang-crosscompile.git
go$ source golang-crosscompile/crosscompile.bash
go$ go-crosscompile-build-all
go-crosscompile-build darwin/386
# Building C bootstrap tool.
....
---
Installed Go for windows/amd64 in /usr/local/go
Installed commands in /usr/local/go/bin

Almost there, now a little cmd-fu and you're done. Just set the CC env var to your toolchain's gcc, set the proper GOOS, GOARCH, GOARM (if needed) and finally the proper -extld ldflag.

Cross compiling from darwin/amd64 to windows/386:

$ CC=i586-mingw32-gcc GOOS=windows GOARCH=386 CGO_ENABLED=1 go build -v -o myprogram.exe -ldflags="-extld=$CC"

Cross compiling from darwin/amd64 to linux/amd64:

$ CC=x86_64-pc-linux-gcc GOOS=linux GOARCH=amd64 CGO_ENABLED=1 go build -v -o myprogram -ldflags="-extld=$CC"

Cross compiling from linux/amd64 to linux/arm (in that case a Raspberry Pi):

$ CC=arm-linux-gnueabihf-gcc GOOS=linux GOARCH=arm GOARM=6 CGO_ENABLED=1 go build -v -o myprogram -ldflags="-extld=$CC"

cross_compile_goos.patch

diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go.patched
index 2ce968a..a90044f 100644
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go.patched
@@ -1921,9 +1921,9 @@ var (
 )
 
 func (b *builder) cgo(p *Package, cgoExe, obj string, gccfiles []string, gxxfiles []string) (outGo, outObj []string, err error) {
-  if goos != toolGOOS {
-		return nil, nil, errors.New("cannot use cgo when compiling for a different operating system")
-	}
+	// if goos != toolGOOS {
+	// 	return nil, nil, errors.New("cannot use cgo when compiling for a different operating system")
+	// }
 
 	cgoCPPFLAGS := stringList(envList("CGO_CPPFLAGS"), p.CgoCPPFLAGS)
 	cgoCFLAGS := stringList(envList("CGO_CFLAGS"), p.CgoCFLAGS)