Let’s talk about how to use the cgo tool in golang

Cgo is a very powerful feature in the Golang programming language, which allows programmers to easily interact between different programming languages. Let's introduce the basic use of Cgo.

What is Cgo?
Cgo is a tool that allows Golang programs to interact with the C compiler. Through Cgo, Golang programmers can mix and compile C and Golang codes together, so that Golang programs can use C language libraries and functions, and C language programs can also call Golang language functions and libraries.

Usage of Cgo
Cgo is a powerful tool. Using Cgo in Golang can greatly improve the scalability and usability of the program. Let's learn how to use Cgo.

1. Define C function
   Before using Cgo, we first need to define a C function, which will be called by the Golang program. The example below is a very simple C function that will return the sum of two numbers.

//file: sum.c
int sum(int a, int b) {
    return a + b;
}

2. Generate dynamic link library
   After writing the C function, we also need to compile it into a dynamic link library. Next we use the gcc command to compile the sum.c file into a dynamic link library.

gcc -o libsum.so -shared sum.c

After successful compilation, we will get a dynamic link library, its name is libsum.so.

3. Writing Golang files
   Now we have prepared the C function and dynamic link library. Next we need to write a Golang file, which will call our C function.

package main

/*
#include <stdlib.h>
#include <stdio.h>

int sum(int a, int b);

*/
import "C"

import (
    "fmt"
)

func main() {
    a := C.int(10)
    b := C.int(20)
    output := C.sum(a, b)
    fmt.Println(output)
}

It should be noted that in this Golang file, we use the form of comments to introduce C code. After the import "C" statement, we can use predefined types, such as C.int. The reason why C.int here is in this form is because it is a wrapper for the int type in the C language.

In the main function, we define two variables a and b, which are of type C.int respectively, and their values ​​are 10 and 20 respectively. Next we called the sum function and assigned the output to the output variable. Finally, we used the fmt.Println statement to print the value of the output.

4. Compile Golang files
   The last step is to compile our Golang program. Use the go build command to compile our program.

go build

After successful compilation, we can run our program. In this example, our program will output 30.

Summary
Cgo is a very useful tool for Golang programmers. Through Cgo, we can easily interact with different programming languages, thereby expanding the functionality and flexibility of our programs. I hope this article will be helpful to everyone learning Cgo.

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