Cross compile shared libraries

Question

I'd like to know if it is possible (and if yes: how) to cross compile shared libraries with Go. Say I have this code:

package main

import "C"

//export DoubleIt
func DoubleIt(x int) int {
    return x * 2
}

func main() {}

in src/doubler/main.go. On Mac I can run

go build -o libdoubler.dylib -buildmode=c-shared doubler

to get a shared library called libdoubler.dylib. Similar on linux, just with the extension .so.

Now I'd like to use Linux as the main platform to build my libraries (for Mac and Windows). What are my options?

Setting GOOS to darwin and running the above on linux, I get

can't load package: package doubler: no buildable Go source files in /home/patrick/Desktop/go/src/doubler

Any ideas?

Answer 1

The problem you face is not actually about compiling shared libraries or executables, but about using cgo and trying to cross-compile. (Still, if you want a library, not an executable, package name shouldn't be main.)

When cross-compiling, cgo is disabled by default. If you add the environment variable CGO_ENABLED=1, then your example will work:

CGO_ENABLED=1 GOOS=darwin go build -o libdoubler.dylib -buildmode=c-shared doubler

Keep in mind that using cgo while cross-compiling will be cumbersome. You will need to make sure that C libraries for the target platform are ready on your host machine. If it is not really necessary, stay away from cgo. If you have to, then you may consider compiling on the target machine instead of dealing with the maintenance of cross-compiling with cgo.