Question

c编程中main函数中使用了库文件中定义的函数，编译时却提示该函数未定义，这是什么问题，坐等高手解答

c源码如下
#include<pthread.h>
#include<stdio.h>
#include<stdlib.h>
#define REPEAT_NUM 5
#define DELAY_TIME_LEVELS 10.0
#define THREAD_NUM 3

void * phrd_func(void *arg)
{
void * thrd_ret;
int count=0;
int delay_time=0;
int thread_num=(int)arg;
printf("thread %d is starting\n");
for(count=0;count<REPEAT_NUM;++count)
{
delay_time=(int)(rand()*DELAY_TIME_LEVELS/(RAND_MAX))+1;
sleep(delay_time);
printf("thread %d :iob %d : delay %ds\n",thread_num,count,delay_time);
}
printf("thread %d finishde\n",thread_num);
pthread_exit(NULL);
}
int main()
{
void * thrd_ret;
pthread_t thread[THREAD_NUM];
int no,ret;
srand(time(NULL));
for(no=0;no<THREAD_NUM;++no)
{
ret=pthread_create(&thread[no],NULL,phrd_func,(void *)no);
if(ret!=0)
{
printf("error pthresd\n");
exit(ret);
}
}
printf("creat threads sucess : waiting threads finished\n");
for(no=0;no<THREAD_NUM;no++)
{
ret=pthread_join(thread[no],&thrd_ret);
if(!ret)
{
printf("thread %d joined\n",no);
}
else
{
printf("thread %d joined failed\n",no);
}
}
return 0;
}
编译报告如下
[lyc@localhost lyc]$ gcc a.c
/tmp/cco2MhOv.o(.text+0x108): In function `main':
: undefined reference to `pthread_create'
/tmp/cco2MhOv.o(.text+0x168): In function `main':
: undefined reference to `pthread_join'
collect2: ld returned 1 exit status
pthread.h如下：
/* Function for handling threads. */

/* Create a thread with given attributes ATTR (or default attributes
if ATTR is NULL), and call function START_ROUTINE with given
arguments ARG. */
extern int pthread_create (pthread_t *__restrict __threadp,
__const pthread_attr_t *__restrict __attr,
void *(*__start_routine) (void *),
void *__restrict __arg) __THROW;
/* Terminate calling thread. */
extern void pthread_exit (void *__retval)
__THROW __attribute__ ((__noreturn__));

/* Make calling thread wait for termination of the thread TH. The
exit status of the thread is stored in *THREAD_RETURN, if THREAD_RETURN
is not NULL. */
extern int pthread_join (pthread_t __th, void **__thread_return) __THROW;
求高手解答

Answer 1

原因：
头文件 pthread.h 没有包含到源文件中
解决方法：
1）将 pthread.h 复制到源文件相同的文件夹中
2）修改为：#include "pthread.h"

追问

我这样尝试了，但还是不行

追答

也许pthread.h 文件本身有问题了

Answer 2

添加编译选项-lpthread，因为pthread不是标准的编译链接的库，需要自己添加

Answer 3

你编译 a.c 怎么涉及到 cco2MhOv.o 或 cco2MhOv.c ?

头文件除了 #include <pthread.h>
是否还要 #include <sys/types.h>