如何正确使用g ++与printf打印?

时间:2011-02-25 20:51:00

标签: g++

我正在用g ++编译这段代码:

#include <pthread.h>
#include <iostream>
#include <cstdlib>
#include <string>
#include <stdio.h>

using namespace std;

#define num_threads 3
#define car_limit 4

pthread_mutex_t mutex; // mutex lock
pthread_t cid;         // thread id
pthread_attr_t attr;   // thread attrubutes

void *OneCar(void *dir);
void ArriveBridge(int *direction);
void CrossBridge();
void ExitBridge(int *direction);


int main()
{

    int dir[3] = {0,1,1};
    pthread_mutex_init(&mutex, NULL);
    pthread_attr_init(&attr);

    //cout<< "Pthread Create" << endl;
    printf("Pthread Create\n");

    for(int i = 0; i < num_threads; i++)
    {
        pthread_create(&cid, &attr, OneCar, (void *)&dir[i]);
    }


return 0;
}


void ArriveBridge(int *direction)
{
    //cout<<"Arrive"<<*direction << endl;
    int dr;

    if(*direction == 0)
        dr=0;
    else
        dr=1;

    printf("Arrive%d", dr);
}

void CrossBridge(int *dir)
{   
    char d;

    if(*dir == 0)
        d = 'N';
    else
        d = 'S';

    //cout<<"Crossing Bridge going:"<<d<<endl;
    printf("Crossing Bridge going %c", d);
}

void ExitBridge(int *direction)
{
    //cout<<"Exit" <<*direction<<endl;
    int dr;

    if(*direction == 0)
        dr=0;
    else
        dr=1;

    printf("Exit%d\n", dr);
}

void *OneCar(void *dir)
{
    int *cardir;
    cardir = (int *) dir;

    //cout<<*cardir;

    ArriveBridge(cardir);
    CrossBridge(cardir);
    ExitBridge(cardir);

    return 0;
}

我期待这个结果打印到屏幕上:

> Pthread Create
> Arrive0Crossing Bridge going NExit0
> Arrive1Crossing Bridge going SExit1
> Arrive1Crossing Bridge going NExit1

但我得到了这个:

Pthread Create
Arrive0Crossing Bridge going NExit0

为什么不把它打印出去?

3 个答案:

答案 0 :(得分:3)

您是否尝试在main结束时加入主题?可能是程序在其他线程完全完成之前终止。

答案 1 :(得分:3)

您需要在main中使用“pthread_join”等待所有线程在程序终止之前退出。您还应该使用数组来保存您创建的每个线程的ID:

pthread_t cid[num_threads];  // thread id`

然后,您需要在您创建的每个线程上调用join:

for(int i = 0; i < num_threads; i++)
{
    pthread_create(&cid[i], &attr, OneCar, (void *)&dir[i]);
}


for(int i = 0; i < num_threads; ++i)
{
   pthread_join(cid[i], NULL);
};

现在运行修改后的代码:

Pthread Create
Arrive0Crossing Bridge going NExit0
Arrive1Crossing Bridge going SExit1
Arrive1Crossing Bridge going SExit1

答案 2 :(得分:1)

你错过了换行符(“\ n”):

printf("Arrive%d\n", dr);
printf("Crossing Bridge going %c\n", d);

因此,流可能不会被刷新。此外,如果您不等待线程(pthread_join),程序将在线程完成其工作之前退出。