C to Go

greeter.c

#include "greeter.h"
#include <stdio.h>

int greet(const char *name, int year, char *out) {
    int n;
    
    n = sprintf(out, "Greetings, %s from %d! We come in peace :)", name, year);

    return n;
}

greeter.h

#ifndef _GREETER_H
#define _GREETER_H

int greet(const char *name, int year, char *out);

#endif

main.go

package main

// #cgo CFLAGS: -g -Wall
// #include <stdlib.h>
// #include "greeter.h"
import "C"
import (
	"fmt"
	"unsafe"
)

func main() {
	name := C.CString("Gopher")
	defer C.free(unsafe.Pointer(name))

	year := C.int(2018)

	ptr := C.malloc(C.sizeof_char * 1024)
	defer C.free(unsafe.Pointer(ptr))

	size := C.greet(name, year, (*C.char)(ptr))

	b := C.GoBytes(ptr, size)
	fmt.Println(string(b))
}