C++相对于ubuntu的意外行为

Question

我正在通过Ubuntu编写一个简单的C++应用程序.

int main()
{
    printf("Just a test line"); 
    Server();
    cout << "2"; 
return 1;
}

尽管服务器功能是什么,但应用程序在控制台上写入任何内容之前都会开始执行它(即Just a test line)

---

我的详细问题:

---

请查看整个应用程序,其中server()负责监听端口4444上的连接.

#include <stdio.h>
#include <sys/types.h>
#include <cstdlib>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>
#include <strings.h>
#include <cstring>
#include <pthread.h>
#include <algorithm>
#include <iostream>
#include "message.h"
using namespace std;

#define iPort 4444

void Server(){
    cout << "3"; 
    int sockfd, newsockfd, n;
    socklen_t clilen;
    message m; // predefined class
    char *buffer = (char *) malloc (sizeof (m));
    struct sockaddr_in serv_addr, cli_addr;
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
        cerr << "ERROR opening socket";
    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(iPort);
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    if (bind(sockfd, (struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
        cerr << "ERROR on binding"<< endl;
    listen(sockfd,5);
    clilen = sizeof(cli_addr);
    int pid =0;
    while (1)
    {
        newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
        if (newsockfd < 0)
            cerr << "ERROR on accept" << endl;
        pid = fork();
        if (pid < 0)
            cerr << "ERROR on fork"<< endl;
        if (pid == 0)
        {
            close(sockfd);
            bzero(buffer,sizeof(m));
            buffer= (char*)&m;
            n = read(newsockfd,buffer,sizeof(m));
            if (n < 0) cerr << "ERROR reading from socket"<< endl;
            exit(0);
        }
        else close(newsockfd);
    }
}

int main()
{
    printf("Just a test line"); 
    Server();
    cout << "2"; 
return 1;
}

我通过终端执行命令如下:

pc@pc-SM40P:~/Desktop/LCR$ g++ -Wall -W -Werror main.cpp -o prog
pc@pc-SM40P:~/Desktop/LCR$ sudo ./prog

我期待着进入Just a test line屏幕,而没有任何东西出现.如果您有任何帮助,请提前致谢

Answer 1

默认情况下,到终端的stdout输出是行缓冲的,因此在换行之前不会打印输出.改成:

printf("Just a test line\n"); 

或者在线fflush(stdout)后打电话printf().