linux c/c++多线程程序的编写

#include[stdio.h]
#include[unistd.h]
#include[stdlib.h]
#include[pthread.h]
#include[string.h]
void *thread_function(void* arg);
char message[] = "Hello world!";
 
int main() {
    int res;
    pthread_t a_thread;
    void *thread_result;
 
    res = pthread_create(&a_thread, NULL, thread_function, (void*)message);
    if (0 != res) {
        perror("Thread creation faied");
        exit(EXIT_FAILURE);
    }
 
    printf("Waiting for thread to finish...\n");
    res = pthread_join(a_thread, &thread_result);
    if (0 != res) {
        perror("Thread join failed");
        exit(EXIT_FAILURE);
    }
    printf("Thread joined, it returned %s\n", (char*)thread_result);
    printf("Message is now %s\n",message);
    exit(EXIT_FAILURE);
}
void *thread_function(void* arg) {
    printf("thread_function is running. argument was %s\n",(char*)arg);
    sleep(3);
    strcpy(message,"bye!");
    pthread_exit("Thank you for the cpu time");
}

hqlong@ubuntu:~/code/c$ gcc test.c -o test -lpthread

hqlong@ubuntu:~/code/c$ ./test

thread_function is running. argument was Hello world!
Waiting for thread to finish...
Thread joined, it returned Thank you for the cpu time
Message is now bye!

int pthread_create
(
	pthread_t *restrict tidp,
	const pthread_attr_t *restrict attr,
	void *(*start_rtn)(void),
	void *restrict arg
);

int pthread_join
(
	pthread_t thread,
	void **value_ptr
);

  res = pthread_join(a_thread, &thread_result);
    if (0 != res) {
        perror("Thread join failed");
        exit(EXIT_FAILURE);
    }
    printf("Thread joined, it returned %s\n", (char*)thread_result);

tmp/ccnPVTWo.o: In function `main':
mthread.c:(.text+0x30): undefined reference to `pthread_create'
mthread.c:(.text+0x6f): undefined reference to `pthread_join'
collect2: ld returned 1 exit status