即使我包含正确的头文件,为什么会出现"未定义的引用"错误？

Question

当我尝试编译这个程序时,它失败了:

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

void *WriteNumbers(void *threadArg)
{
    int start, stop;

    start = atoi((char *)threadArg);
    stop = start + 10;

    while (start < stop)
    {
         printf("%d\n", start++);
         sleep(1);
    }
    return 0;
}

int main(int argc, char **argv)
{
        pthread_t thread1, thread2;

        // create the threads and start the printing
        pthread_create(&thread1, NULL, WriteNumbers, (void *)argv[1] );
        pthread_create(&thread2, NULL, WriteNumbers, (void *)argv[2]);

        pthread_join(thread1, NULL);
        pthread_join(thread2, NULL);

        return 0;
}

它给了我以下错误:

tmp/ccrW21s7.o: In function `main':
pthread.c:(.text+0x83): undefined reference to `pthread_create'
pthread.c:(.text+0xaa): undefined reference to `pthread_create'
pthread.c:(.text+0xbd): undefined reference to `pthread_join'
pthread.c:(.text+0xd0): undefined reference to `pthread_join'
collect2: ld returned 1 exit status

为什么它给了我这些未定义的引用错误,即使我已经包含pthread.h,它声明了这些函数？

Answer 1

您可能忘记链接Pthreads库(-lpthread在命令行上使用).

Answer 2

其他人提到你没有使用-lpthread标志链接到pthread库.现代海湾合作委员会(不确定现代,我的是4.3.3)允许你使用-pthread.从手册页:

-pthread
使用pthreads库添加对多线程的支持.此选项为预处理器和链接器设置标志.