go_module_jitting.go

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"plugin"

	"github.com/pkg/errors"
)

var contents = `
package main

func AddTwo(i int) int {
	return i + 2
}
`

var compileTmpDir = "./jit_tmp"

func jitCompile(name, goCode string) (string, error) {
	tmpFile := filepath.Join(compileTmpDir, name+".go")
	pluginFile := filepath.Join(compileTmpDir, name+".go.so")

	err := ioutil.WriteFile(tmpFile, []byte(goCode), 0644)
	if err != nil {
		return "", errors.Wrap(err, "could not create tmpfile")
	}
	defer os.Remove(tmpFile)

	cmd := exec.Command("go", "build", "-o", pluginFile, "-buildmode=plugin", tmpFile)
	err = cmd.Start()
	if err != nil {
		return "", errors.Wrap(err, "go build could not be started")
	}

	err = cmd.Wait()
	if err != nil {
		return "", errors.Wrap(err, "go build failed")
	}

	return pluginFile, nil
}

func main() {
	pluginPath, err := jitCompile("add_two", contents)
	if err != nil {
		fmt.Printf("jit compilation failed: %s\n", err)
		os.Exit(1)
	}
	defer os.Remove(pluginPath)

	plug, err := plugin.Open(pluginPath)
	if err != nil {
		fmt.Println(err)
		return
	}

	addTwoSymbol, err := plug.Lookup("AddTwo")
	if err != nil {
		fmt.Println(err)
		return
	}

	jittedAddTwo, ok := addTwoSymbol.(func(int) int)
	if !ok {
		fmt.Println("addTwoSymbol has wrong type")
		return
	}

	result := jittedAddTwo(2)
	fmt.Printf("result=%d\n", result)
}