Go language defer

/** * @Author: wyd * @Description:defer * @File:  function  * @Version: 1.0.0 * @Date: 2022/6/28 16:59 * @Blog: https://wuyandao.blog.csdn.net/ */

package main

import "fmt"

//func sum(x, y int) (ret int) {
    
// return x + y
//}
//func main() {
    
// //r := sum(4, 2)
// //fmt.Println(r)
// deferdemo()
//}
//Go In language defer Statement will delay the statement that follows it . stay defer When the belonging function is about to return , Press the deferred statement to defer The definition is executed in reverse order , in other words , Be first defer The statement of is finally executed , Finally being defer The sentence of , First executed .
//defer sentence 
//defer Mostly used for resource release before the end of a function （ File handle , Database connection ,socket Connect ）
//func deferdemo() {
    
// fmt.Println("heiheihei")
// defer fmt.Println(" Water... Water ")
// fmt.Println(" Jijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijijiji ")
//}

stay Go In the function of language return Statements are not atomic at the bottom , It is divided into assignment of return value and RET Command two steps . and defer The execution time of the statement is just after the return value assignment operation ,RET Before the command is executed . The details are shown in the following figure ：

//defer Interview questions 
func f1() int {
    
	x := 5
	defer func() {
    
		x++
	}()
	return x
}

func f2() (x int) {
    
	defer func() {
    
		x++
	}()
	return 5
}

func f3() (y int) {
    
	x := 5
	defer func() {
    
		x++
	}()
	return x
}
func f4() (x int) {
    
	defer func(x int) {
    
		x++
	}(x)
	return 5
}
func main() {
    
	fmt.Println(f1())
	fmt.Println(f2())
	fmt.Println(f3())
	fmt.Println(f4())
}