类似于_beginthread的问题 ：

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); }