Linux下undefined reference to ‘pthread_create’问题解决

Linux下undefined reference to ‘pthread_create’问题解决

在试用Linux 线程模块时，试用pthread_create 函数。
编译命令为 gcc main.c -o test时，会出现如下错误

/usr/bin/ld: /tmp/ccAusWl8.o: in function `main':
05_concurrent_server_thread.c:(.text+0x44c): undefined reference to `pthread_create'
/usr/bin/ld: 05_concurrent_server_thread.c:(.text+0x468): undefined reference to `pthread_detach'
collect2: error: ld returned 1 exit status

  问题的原因：pthread不是linux下的默认的库，也就是在链接的时候，无法找到phread库中该函数的入口地址，于是链接会失败。

解决：在gcc编译的时候，附加要加 -lpthread参数即可解决。

试用如下命令即可编译通过

gcc main.c -o test -lpthread

如下编译通过 

#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <pthread.h>
  
#define N 128

void handler(int sig){
	wait(NULL);
}

typedef struct{
	struct sockaddr_in addr;
	int acceptfd;
}MSG;

void *pthread_fun(void *arg){
	int count = 0;
	ssize_t bytes;
    MSG msg =  *(MSG *)arg;	
	char buf[N] = "666";
	char text[N] = "";
	
	while(1){
		// 打印客户端信息
		printf("ip:%s, port:%d\n", inet_ntoa(msg.addr.sin_addr), ntohs(msg.addr.sin_port));
		
		// 接收数据
		if((count = recv(msg.acceptfd,text,N,0))==-1){
			perror("fail to recv");
			exit(1);
	}else if(count == 0){
		printf("The client quited\n");
		pthread_exit(NULL);
	}
		
		printf("from client: ");
		for(int j=0;j<count;j++){
			printf("%c",text[j]);
		}
		printf("\n");
		
		//发送buf数据
		if(send(msg.acceptfd,buf,sizeof(buf),0)==-1){
			perror("fail to send");
			exit(1);
		}
	}
}

int main(int argc, char const * argv[]){
	
	if(argc < 3){
		fprintf(stderr, "server Usage:%s ip port\n",argv[0]);
		exit(1);
	}
	
	int sockfd;
	
	// 创建tcp套接字
	if((sockfd=socket(AF_INET,SOCK_STREAM,0)) == -1){
		perror("fail to socket");
		exit(1);
	}
	
	struct sockaddr_in serveraddr;
	socklen_t addrlen = sizeof(serveraddr);  
	
	serveraddr.sin_family = AF_INET; // 协议族 AF_INET:ipv4网络协议
	// inet_addr: 将点分十进制字符串ip地址转为整形数据
	serveraddr.sin_addr.s_addr = inet_addr(argv[1]); // ip地址
	// atoi 将数字型字符串转换为整形数据
	// htons 将主机字节序转化为网络字节序
	serveraddr.sin_port = htons(atoi(argv[2]));
	
	// 将套接字和网络信息绑定
	if(bind(sockfd,(struct sockaddr*)&serveraddr, addrlen) == -1){
		perror("fail to connect");
		exit(1);
	};
	
    // 将套接字设置为监听状态
	if(listen(sockfd,5) == -1){
		perror("fail to listen");
		exit(1);
	}
	
	struct sockaddr_in clientsock;
	addrlen = sizeof(clientsock);
	
	
	
	printf("准备阻塞...\n");
	
	// 使用信号，异步的方式处理僵尸进程
	signal(SIGCHLD,handler);
	
	while(1){	
		// 阻塞等待客户端的链接
		int clisock = accept(sockfd,(struct sockaddr*)&clientsock, &addrlen);
		
		// 创建子线程与客户端通信
		MSG msg;
		msg.addr = clientsock;
		msg.acceptfd = clisock;
		pthread_t thread;
		
		if(pthread_create(&thread,NULL,pthread_fun,&msg)!=0){
			perror("fail to pthread_create");
		}
		
		pthread_detach(thread);
		
	}
	
	// 关闭套接字描述符
	//close(clisock);
	//close(sockfd);
	return 0;
}