Why isn't sizeof for a struct equal to the sum of sizeof of each member?

// SPDX-License-Identifier: GPL-2.0 /* * linux/ipc/shm.c * Copyright (C) 1992, 1993 Krishna Balasubramanian * Many improvements/fixes by Bruno Haible. * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994. * Fixed the shm swap deallocati

ping是基于ICMP(Internet Control Message Protocol)协议实现的,而ICMP协议是在IP层实现的. ping实际上是发起者发送一个Echo Request(type = 8)的,远程主机回应一个Echo Reply(type = 0)的过程. 为什么用ping不能测试某一个端口 刚开始接触网络的时候,可能很多人都有疑问,怎么用ping来测试远程主机的某个特定端口? 其实如果看下ICMP协议,就可以发现ICMP里根本没有端口这个概念,也就根本无法实现测试某一个

1.What does the following program print ? #include<iostream> using namespace std; int  main() { int x = 2 , y , z ; x  *=  (y=z=5) ;  //先 z = 5 ; y = z;  x = x * y = 2 * 5 = 10 cout<< x << endl ;   //  输出 10 z = 3; x == (y = z) ;  cout&l

超时检测的必要性:避免进程在没有数据时无限制地阻塞,当设定的时间到时,进程从原操作返回继续运行. 方法(1):使用setsockopt函数 时间结构体 struct timeval  tv; 可设定 tv.tv_sec = 5; // 设置5秒时间 tv.tv_usec = 0; 然后设置超时选项 setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)); 注意:将进程中和sockfd相关的阻塞,变为非阻塞. 实例代码: serve

套接字机制提供两个套接字选项来控制套接字行为.一个接口用来控制选项,另一个接口允许查询一个选项的状态. 1 #include <sys/types.h> 2 #include <sys/socket.h> 3 4 int getsockopt(int sockfd, int level, int optname, void *optval, socklen_t *optlen); 5 int setsockopt(int sockfd, int level, int optname

Maze Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65768/65768 K (Java/Others)Total Submission(s): 2012    Accepted Submission(s): 802Special Judge Problem Description When wake up, lxhgww find himself in a huge maze. The maze consisted by

原理很简单,SPFA可以多次入队,那么如果一个点入队的次数比点的总数还要多,或是起点入队两次,那么这个图肯定存在负环 例题 Luogu P3385 [模板]负环 #include<iostream> #include<cstring> #include<cstdio> #include<queue> #include<algorithm> using namespace std; struct zzz{ int f, t, len, nex; }

C - Linear Approximation 找出\(A_i - i\)的中位数作为\(b\)即可 题解 #include <iostream> #include <cstring> #include <cstdio> #include <algorithm> #define enter putchar('\n') #define space putchar(' ') #define fi first #define se second #define

1.创建udp的socket句柄 // 当host_port为0时,则表示让操作系统自动分配 bool createUdpSocket(string host_ip,unsigned short host_port, int& sock_fd) { sock_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); if(sock_fd <= 0) { return false; } struct sockaddr_in client_addr= {0};