linux 下多线程错误 undefined reference to `sem_init'

原文地址::http://www.cnblogs.com/stli/archive/2010/03/11/1683823.html

undefined reference to `sem_init'

undefined reference to `sem_post'

undefined reference to `sem_wait'

编译选项需要加入一个多线程

gcc -pthread -o outfile.out filename.c

[source code]

#include "sched.h"

#include "pthread.h"

#include "stdio.h"

#include "stdlib.h"

#include "semaphore.h"

int producer(void * args);

int consumer(void * args);

pthread_mutex_t mutex;

sem_t product;

sem_t warehouse;

char buffer[8][4];

int bp=0;

int main(int argc,char * * argv)

{

pthread_mutex_init(& mutex,NULL);

sem_init(& product,0,0);

    sem_init(& warehouse,0,8);

int clone_flag,arg,retval;

    char * stack;

    clone_flag=CLONE_VM | CLONE_SIGHAND | CLONE_FS | CLONE_FILES;

    int i;

for(i=0;i<2;i++)

{ //创建四个线程

        arg=i;

        stack=(char *)malloc(4096); 

        retval=clone((void *)producer,& (stack[4095]),clone_flag,(void *) & arg);

   stack=(char *)malloc(4096); 

        retval=clone((void *)consumer,& (stack[4095]),clone_flag,(void *) & arg);

    }

    exit(1);

return 0;

}

int producer(void * args)

{

    int id = *((int *)args);

    int i;

    for(i=0;i<10;i++)

    {

   sleep(i+1); //表现线程速度差别

        sem_wait(&warehouse);

        pthread_mutex_lock(&mutex);

        if(id==0)

            strcpy(buffer[bp],"aaa\0");

        else

            strcpy(buffer[bp],"bbb\0");

        bp++;

        printf("producer%d produce %s in %d\n",id,buffer[bp],bp-1);

        pthread_mutex_unlock(&mutex);

        sem_post(&product);

    }

    printf("producer%d is over!\n",id);

}

int consumer(void * args)

{

    int id = * ((int *)args);

    int i;

    for(i=0;i<10;i++)

    {

        sleep(10-i); //表现线程速度差别

        sem_wait(&product);

        pthread_mutex_lock(&mutex);

        bp--;

        printf("consumer%d get %s in%d\n",id,buffer[bp],bp+1);

        strcpy(buffer[bp],"zzz\0");

        pthread_mutex_unlock(&mutex);

        sem_post(&warehouse);

    }

    printf("consumer%d is over!\n",id);

}本文转自：http://hi.baidu.com/luosiyong/blog/item/e5e1980fffd1b6e5ab6457e5.html