Crash if using import "C" in main file

[palindrom228]

i'm trying to use your library in my project, and want to wrap it for my project with go layer that exports dll file, and in this case im getting null pointer in runtime

step to reproduce:

1. use Windows arm64
2. import "C" in main file
3. start sing-box instance
4. runtime crashes with no error

sing-box config: { "log": { "level": "warning", "timestamp": true }, "dns": { "servers": [ { "tag": "remote", "address": "8.8.8.8", "detour": "proxy" } ], "final": "remote" }, "inbounds": [ { "type": "tun", "tag": "tun-in", "interface_name": "singbox_tun", "address": [ "172.19.0.1/30" ], "mtu": 9000, "auto_route": true, "strict_route": false, "stack": "gvisor", "sniff": true } ], "outbounds": [ { "type": "socks", "tag": "proxy", "server": "127.0.0.1", "server_port": 10808, "version": "5" }, { "type": "direct", "tag": "direct" }, { "type": "dns", "tag": "dns_out" } ], "route": { "auto_detect_interface": true, "rules": [ { "outbound": "direct", "ip_is_private": true }, { "outbound": "dns_out", "port": [ 53 ], "process_name": [ "xray.exe", "cracker.exe" ] }, { "outbound": "direct", "process_name": [ "xray.exe", "cracker.exe" ] }, { "outbound": "proxy", "network": "tcp,udp" } ] } }

Wrapper package that calls from main

import (
	"context"
	"fmt"
	"os"
	"os/user"
	"strconv"

	"github.com/sagernet/sing-box/experimental/deprecated"
	"github.com/sagernet/sing-box/include"
	"github.com/sagernet/sing-box/log"
	"github.com/sagernet/sing-box/option"
	"github.com/sagernet/sing/common/json"
	"github.com/sagernet/sing/service"
	"github.com/sagernet/sing/service/filemanager"

	box "github.com/sagernet/sing-box"
)

var (
	globalCtx context.Context
)

type SingBox struct {
	tun *box.Box
}

func New(configJson string) (*SingBox, error) {
	configBytes := []byte(configJson)
	options, err := json.UnmarshalExtendedContext[option.Options](globalCtx, configBytes)
	if err != nil {
		return nil, fmt.Errorf("Error while parse options from config json : ", err.Error())
	}
	ctx, cancel := context.WithCancel(globalCtx)
	instance, err := box.New(box.Options{
		Context: ctx,
		Options: options,
	})
	if err != nil {
		cancel()
		return nil, fmt.Errorf("Error while creating sing box instance : ", err.Error())
	}
	return &SingBox{
		tun: instance,
	}, nil
}

func (s *SingBox) Run() error {
	err := s.tun.Start()
	if err != nil {
		return fmt.Errorf("Error while starting sing box : ", err)
	}
	return nil
}

func (s *SingBox) Stop() error {
	err := s.tun.Close()
	if err != nil {
		return fmt.Errorf("Error while stoping sing box : ", err)
	}
	return nil
}

func init() {
	globalCtx = context.Background()
	sudoUser := os.Getenv("SUDO_USER")
	sudoUID, _ := strconv.Atoi(os.Getenv("SUDO_UID"))
	sudoGID, _ := strconv.Atoi(os.Getenv("SUDO_GID"))
	if sudoUID == 0 && sudoGID == 0 && sudoUser != "" {
		sudoUserObject, _ := user.Lookup(sudoUser)
		if sudoUserObject != nil {
			sudoUID, _ = strconv.Atoi(sudoUserObject.Uid)
			sudoGID, _ = strconv.Atoi(sudoUserObject.Gid)
		}
	}
	if sudoUID > 0 && sudoGID > 0 {
		globalCtx = filemanager.WithDefault(globalCtx, "", "", sudoUID, sudoGID)
	}

	globalCtx = service.ContextWith(globalCtx, deprecated.NewStderrManager(log.StdLogger()))
	globalCtx = box.Context(globalCtx, include.InboundRegistry(), include.OutboundRegistry(), include.EndpointRegistry())
}```

i need to use it as library for KMM project, i'm not expirenced in go and cgo. thanks for answer in advance

[Restia-Ashbell]

@palindrom228
I encountered a similar issue when compiling sing-box as a dynamic library on Windows—enabling TUN caused the program to crash. I switched to cross-compiling the Windows dynamic library on Linux using mingw-w64, and the TUN functionality worked fine. You can try this approach, and I hope it helps.

Further testing revealed that my issue seems to be caused by the mingw-w64 package from apt being linked to MSVCRT, while mine is linked to UCRT.