POSIX线程

大多数线程函数以pthread_开头，.h为pthread.h,   用-lpthread来链接线程库。

编写多线程时，定义宏_REENTRANT告诉编译器需要可重入，此宏必须位于任何#include之前。#include <pthread.h>

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg);

//#define _REENTRANT
//#define _POSIX_C_SOURCE
#include <iostream>
#include <string>
#include <cstdio>
#include <assert.h>
#include <cstring>
#include <error.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <pthread.h>

using namespace std;

void *thread_fun(void *argument);

char message[] = "hello world";

int main(int argc, char* argv[])
{
    int res;
    pthread_t a_thread;
    void *thread_result;

res = pthread_create(&a_thread, NULL, thread_fun, (void *)message);
    if(res != 0)
    {
        perror("Thread creation failed");
        exit(EXIT_FAILURE);
    }

cout << "Waiting for thread to finish\n";
    res = pthread_join(a_thread, &thread_result);
    if(res != 0)
    {
        perror("Thread join failed");
        exit(EXIT_FAILURE);
    }

printf("Thread joined,it returned %s\n",(char *)thread_result);
    printf("Message is now %s\n",message);
    exit(EXIT_SUCCESS);
    return 0;
}

void *thread_fun(void *argument)
{
    printf("thread_fun is running. Arg was %s\n",(char *)argument);
    sleep(2);
    strcpy(message,"Bye!");
    pthread_exit(const_cast<char *>("Thank you for the CPU time"));
}