Linux下"undefined reference to ‘pthread_create’"问题解决

实验环境

Centos 7.0, gcc 4.8.5

问题

在运行一个多线程的c文件时候报了错：

#include <stdio.h>#include <stdlib.h>#include <pthread.h>#include <semaphore.h>pthread_mutex_t mutex=PTHREAD_MUTEX_INITIALIZER;pthread_cond_t cond=PTHREAD_COND_INITIALIZER;void* thread1(void*);void* thread2(void*);void* thread3(void*);int i=1;int buffer1[1];//char buffer1[4];int buffer2[1];sem_t sample_sem;int main(void){    pthread_t t1;    pthread_t t2;    pthread_t t3;    pthread_create(&t1,NULL,(void*)thread1,NULL);    pthread_create(&t2,NULL,(void*)thread2,NULL);    pthread_create(&t3,NULL,(void*)thread3,NULL);    pthread_join(t1,NULL);    pthread_join(t2,NULL);    pthread_join(t3,NULL);    pthread_mutex_destroy(&mutex);    pthread_cond_destroy(&cond);    exit(0);}void* thread1(void* arg){    FILE *f1;    if((f1=(fopen("1.dat","r"))) == NULL){        printf("Open 1.dat failed.");    }    for(i=1;i<=27;i++)    {        pthread_mutex_lock(&mutex);        if ((i%2==0) || (i%3==0)){            pthread_cond_signal(&cond);        }        else{            printf("thread1's i : %d\n",i);            fscanf(f1,"%d",buffer1);//fread(buffer1,2,1,f1);            printf("thread1 write: %d\n", buffer1[0]);        }        pthread_mutex_unlock(&mutex);        sleep(1);    }    fclose(f1);}void* thread2(void* arg){    FILE *f2;    if((f2=(fopen("2.dat","r"))) == NULL){        printf("Open 2.dat failed.");    }    while(i<=27){        sem_post(&sample_sem);         pthread_mutex_lock(&mutex);        if (i%2!=0){            pthread_cond_wait(&cond,&mutex);        }        printf("thread2's i : %d\n",i);        fscanf(f2,"%d",buffer2);//fread(buffer1,2,1,f1);        printf("thread2 write: %d\n", buffer2[0]);        pthread_mutex_unlock(&mutex);        sleep(1);    }    fclose(f2);}void* thread3(void* arg){    while(i<=27)    {        sem_wait(&sample_sem);         pthread_mutex_lock(&mutex);        if (i%3!=0){            pthread_cond_wait(&cond,&mutex);        }        printf("thread3's i:%d\n",i);        printf("PLUS: %d + %d = %d\n",buffer1[0],buffer2[0],buffer1[0]+buffer2[0]);        printf("MULTIPLY: %d * %d = %d\n",buffer1[0],buffer2[0],buffer1[0]*buffer2[0]);        //printf("get B1: %d,",buffer1[0]);        //printf("get B2: %d\n",buffer2[0]);        pthread_mutex_unlock(&mutex);        sleep(1);    }}

PS:这个代码有问题- -运行完了退不出来。。。好迷啊

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原因

pthread不是Linux下的默认的库，也就是在链接的时候，无法找到phread库中函数的入口地址，于是链接会失败。

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解决

在gcc编译的时候，附加要加 -lpthread参数即可解决。