Attempt at using shared objects with Go

loader.go

package main

import (
	// this package reqiures libffi-dev (ubuntu)
	"bitbucket.org/binet/go-ffi/pkg/ffi"
	"fmt"
	"unsafe"
)

import "C"

func main() {
	// this would be an actual Test package if Cgo was supported in tests
	lib, err := ffi.NewLibrary("./libshared.so")

	if err != nil {
		panic(err)
	}

	// first test, proof of concept
	{
		hello, err := lib.Fct("main.Test1", ffi.Pointer, []ffi.Type{})
		if err != nil {
			panic(err)
		}

		res := (uintptr)(hello().Uint())
		str := C.GoString((*C.char)(unsafe.Pointer(res)))
		if str != "hello dlopen()" {
			fmt.Printf("First test failed, got back: %v = %v\n", string(str), []byte(str))
			return
		} else {
			fmt.Printf("First test passed\n")
		}
	}

	// second test, multiple returns
	{
		hello, err := lib.Fct("main.Test2", ffi.Pointer, []ffi.Type{ffi.Int, ffi.Int})
		if err != nil {
			panic(err)
		}

		res := hello(2, 1);
		addr := unsafe.Pointer(uintptr(res.UnsafeAddr()));
		int_size := C.int(unsafe.Sizeof(C.int(0)));
		return_val_1 := C.GoBytes(addr, int_size);
		return_val_2 := C.GoBytes(unsafe.Pointer(uintptr(addr)+uintptr(int_size)), int_size);
		if return_val_1[0] != 3 || return_val_2[0] != 1 {
			fmt.Printf("Second test failed, got values:\n");
			fmt.Printf("\t1) %v\n\t2) %v\n", return_val_1, return_val_2);
			return
		} else {
			fmt.Printf("Second test passed\n");
		}
		/*
		addr2 := unsafe.Pointer(uintptr(addr) + unsafe.Sizeof(addr))
		fmt.Printf("Addr2: %v\n", addr2);
		str := C.GoBytes(addr, C.int(unsafe.Sizeof(C.int));
		fmt.Printf("Str: %v\n", str);
		str2 := C.GoBytes(), C.int(unsafe.Sizeof(C.int)));
		fmt.Printf("Str2: %v\n", str2);
		*/

		/*
		res := (uintptr)(hello(12, 13).Uint())
		fmt.Printf("Res: %v\n", res);
		str := C.GoBytes(unsafe.Pointer(res), C.int(8));
		fmt.Printf("GoString: %v\n", str);
		*/
	}

	// third test, one argument

	// fourth test, multiple arguments
}

Makefile

default:
	gccgo -g -O0 -fPIC -shared shared.go -o libshared.so -lgcc
	go build loader.go

shared.go

package main

func main() {} // skeleton

func Test1() string {
	return "hello dlopen()";
}

func Test2(i, j int) (int, int) {
	return i+j, i-j
}