Not able to run C call from go

Question

I am trying to run a C call from go language code. Here is the program I am running:

package main

// #include<proxy.h>

import "C"
import "fmt"

func main(){
    fmt.Println(C.CMD_SET_ROUTE)
}

Here is the content of the file proxy.h:

#ifndef PROXY_H
#define PROXY_H

#include <netinet/in.h>

#ifdef CMD_DEFINE
#   define cmdexport
#else
#   define cmdexport static
#endif

cmdexport const int CMD_SET_ROUTE = 1;
cmdexport const int CMD_DEL_ROUTE = 2;
cmdexport const int CMD_STOP      = 3;

Now, here is the error I am getting when trying to run that program:

pensu@ubuntu:~$ go run test.go 
# command-line-arguments
could not determine kind of name for C.CMD_SET_ROUTE

I am using gccgo-5 and go version 1.4.2. Could you please help me figure out what exactly is the issue here? TIA.

Answer 1

Four things:

• You should be using double quotes when including proxy.h, as it resides in the same directory as your .go file.
• There cannot be a blank line before you "C" comment and the "C" import.
• You are missing an #endif at the end proxy.h.
• You need to define CMD_DEFINE before including proxy.h. Otherwise, Go cannot access the static variable.

Below is the corrected code:

package main

// #define CMD_DEFINE
// #include "proxy.h"
import "C"
import "fmt"

func main(){
    fmt.Println(C.CMD_SET_ROUTE)
}

#ifndef PROXY_H
#define PROXY_H

#include <netinet/in.h>

#ifdef CMD_DEFINE
#   define cmdexport
#else
#   define cmdexport static
#endif

cmdexport const int CMD_SET_ROUTE = 1;
cmdexport const int CMD_DEL_ROUTE = 2;
cmdexport const int CMD_STOP      = 3;

#endif