How to use C++ in Go

Using C++ in Go is a bit tricky. It’s because C++ can’t be used directly in Go. Instead, C++ must be wrapped into C or integrated through another tool, e.g., Simplified Wrapper and Image Generator (SWIG) acts as a bridge between C++ and Go and generates a wrapper for C++. SWIGSimplified Wrapper and Interface Generator, to be used in Go. This answer will show how SWIG helps us use C++ in Go.

canvasAnimation-image

Prerequisite

To integrate C++ and Go, we must have SWIG installed. Here’s how it can be done:

  • For MacBook:

brew install swig

  • For Linux/Ubuntu:

sudo apt install swig

Steps

To understand how to use C++ in Go, we will write a simple code that takes the product of two non-zero numbers. Let’s look at the steps below:

  1. Create a directory named swig that has one folder multiplier and a file main.go in it. We will begin with creating the primary files inside the multiplier folder.

  2. Create a C++ header file, multiplier.hpp. Inside it, create a class Multiplier. The public section of the class will have a constructor Multiplier() that initializes a private member variable _v with the value 1. A public method Multiply will be declared, which takes an integer v as an argument. This function will be responsible for performing multiplication with the private variable _v. Another method Get() will be created to return the final result. 

#ifndef _MULTIPLIER_H_
#define _MULTIPLIER_H_
class Multiplier{
public:
    Multiplier() : _v(1) {} // Initialize _v with 1 for multiplication
    void Multiply(int v); // New method for multiplication
    int Get();
private:
    int _v;
};
#endif //_MULTIPLIER_H_

  1. Create a C++ file multiplier.cpp. Inside it, include the previously created header file multiplier.hpp. Implement the Multiply() and Get() method of class Multipler created in the header file. 

#include "multiplier.hpp"
void Multiplier::Multiply(int v) {_v *= v;} // Implementation of the Multiply method
int Multiplier::Get() {return _v;}

  1. Create a SWIG file and name it multiplier.swigcxx. This file will be responsible for wrapping the C++ code so it can be used in Go. We will create a directive that will specify the name of the SWIG module that will be generated. In this code example, we will name it multiplier. Now, we will include our header file directly in the wrapper file generated by SWIG. For this, we use %{}% code blocks. At the end of the file, we will include multiplier.hpp separately to ensure that the C++ class and functions declared in multiplier.hpp are properly accessible from the Go code.

%module multiplier
%{
    #include "multiplier.hpp"
%}
%include "multiplier.hpp"

  1. Create a file package.go. 

package multiplier
import "C"

  1. Now we write our main file, i.e., main.go, inside the swig directory. In this file, we will pass two numbers we want to multiply to our Multiply() function. To fulfill the initial constraints of the problem, i.e., both the numbers should be non-zero, we will implement a check using if else. Get() will be called to display the final product. 

package main
import (
	"fmt"
	"tutorial/swig/multiplier"
)
func main() {
	a := multiplier.NewMultiplier()
	defer multiplier.DeleteMultiplier(a)
	num1 := 4 // First number for multiplication
	num2 := 2 // Second number for multiplication
	// Check if both numbers are non-zero
	if num1 != 0 && num2 != 0 {
		// Multiply the numbers 
		
		a.Multiply(num1)
		a.Multiply(num2)
		fmt.Printf("The product of two numbers is: %d\n", a.Get())
	} else {
		fmt.Println("Both numbers must be non-zero for multiplication.")
	}
}

  1. Lastly, we create the go.mod file. To create this file, we run the following command on the terminal inside the swig directory: 

go mod init tutorial/swig
go mod tidy

Note: The tutorial/swig is the user’s directory path.

After running these commands, go.mod is created inside the swig folder:

module tutorial/swig
go 1.21.0

  1. Inside the swig folder, run the go run . command on the terminal.

Code

package multiplier
import "C"
Code to use C++ in Go

Output

The expected output of the following code is: 

The product of two numbers is: 8
Expected output of the code

Conclusion

Using C++ in Go is more complex than using C in Go. Golang doesn’t support C++ functions directly. However, the solution is using wrappers for C++ code. For this, we use SWIG. SWIG is a tool that generates a wrapper to allow a language to access declarations from other languages. Hence, it can allow Go to use C++ functions in code efficiently.

Free Resources

Copyright ©2025 Educative, Inc. All rights reserved