Detailed explanation of Golang compiled into DLL file

The following column golang tutorial will introduce to you the method of compiling Golang into a DLL file. I hope it will be helpful to friends in need!

Golang requires gcc when compiling dll, so install MinGW first.

Windows 64-bit system should download the 64-bit version of MinGW: https://sourceforge.net/projects/mingw-w64/

After downloading, run mingw-w64-install.exe and complete MingGW installation.

First write the golang program exportgo.go:

package main

import "C"
import "fmt"

//export PrintBye
func PrintBye() {
    fmt.Println("From DLL: Bye!")
}

//export Sum
func Sum(a int, b int) int {
    return a + b;
}

func main() {
    // Need a main function to make CGO compile package as C shared library
}

Compile it into a DLL file:

go build -buildmode=c-shared -o exportgo.dll exportgo.go

After compilation, you get two files, exportgo.dll and exportgo.h.

Refer to the function definition in the exportgo.h file and write the C# file importgo.cs:

using System;
using System.Runtime.InteropServices;

namespace HelloWorld
{
    class Hello 
    {
        [DllImport("exportgo.dll", EntryPoint="PrintBye")]
        static extern void PrintBye();

        [DllImport("exportgo.dll", EntryPoint="Sum")]
        static extern int Sum(int a, int b);

        static void Main() 
        {
            Console.WriteLine("Hello World!");
            PrintBye();

            Console.WriteLine(Sum(33, 22));
        }

Compile the CS file to get the exe

csc importgo.cs

Put the exe and dll In the same directory, run.

>importgo.exe

Hello World!
From DLL: Bye!
55

The string parameters in golang can be referenced as follows in C#:

public struct GoString
    {
        public string Value { get; set; }
        public int Length { get; set; }

        public static implicit operator GoString(string s)
        {
            return new GoString() { Value = s, Length = s.Length };
        }

        public static implicit operator string(GoString s) => s.Value;
    }

// func.go
package main

import "C"
import "fmt"

//export Add
func Add(a C.int, b C.int) C.int {
	return a + b
}

//export Print
func Print(s *C.char) {  
/* 
函数参数可以用 string, 但是用*C.char更通用一些。
由于string的数据结构，是可以被其它go程序调用的，
但其它语言（如 python）就不行了
*/
	print("Hello ", C.GoString(s)) //这里不能用fmt包，会报错，调了很久...
}
func main() {	
}　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

Compile

go build -ldflags " -s -w" -buildmode=c-shared -o func.dll func.go
is still a bit big, 880KB. The pure C version is only 48KB. It should not contain all the dependencies. , go is all-inclusive

Go call

package main
import (
	"fmt"
	"syscall"
)

func main() {
	dll := syscall.NewLazyDLL("func.dll")
	add := dll.NewProc("Add")
	prt := dll.NewProc("Print")
	r, err, msg := add.Call(32, 44)
	fmt.Println(r)
	fmt.Println(err)
	fmt.Println(msg)
	
	name := C.CString("Andy")
	prt.Call(uintptr(unsafe.Pointer(name)))
}

out:
76
0
The operation completed successfully.
Hello Andy

Python call

from ctypes import CDLL, c_char_p
dll = CDLL("func.dll")
dll.Add(32, 33)
dll.Print(c_char_p(bytes("Andy", "utf8")))

C call

#include <iostream>
#include <windows.h>

using namespace std;
typedef int(*pAdd)(int a, int b);
typedef void(*pPrt)(char* s);

int main(int argc, char *argv[])
{
    HMODULE dll= LoadLibraryA("func.dll");
    pAdd add = (pAdd)GetProcAddress(dll, "Add");
    pPrt prt = (pPrt)GetProcAddress(dll, "Print");
    cout << add(321, 33) << endl;
    prt("Andy");
    FreeLibrary(dll);
    return 0;
}

For more related technical articles, please Visit the go language tutorial column!

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