c - 为什么我们需要 "-pthread"标志来编译 c 文件

Question

这个问题已经有答案了:

Significance of -pthread flag when compiling (2 个回答)

Difference between -pthread and -lpthread while compiling (3 个回答)

已关闭 5 年前。

我尝试编译一个包含线程的c 文件。但我尝试像这样正常编译

gcc -o thread thread.c -Wall

但它给出了一个错误。但我尝试这样编译

gcc -pthread -o thread thread.c -Wall

它成功了。这是什么原因，-pthread 标志会做什么？下面是我的 C 代码

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

void *thread_function(void *arg)
{
    int a;
    for(a=0;a<10; a++)
    {
    printf("Thread says hi!\n");
    sleep(2);
    }
    return NULL;
}

int main(void)
{
    pthread_t mythread;
    if ( pthread_create( &mythread, NULL, thread_function, NULL) )
    {
        printf("error creating thread.");
        abort();
    }
    if ( pthread_join ( mythread, NULL ) )
    {
    printf("error joining thread.");
    abort();
    }
    printf("Main thread says hi!\n");
    exit(0);
}

Answer 1

根据gcc引用:

-pthreads

Add support for multithreading using the POSIX threads library. This option sets flags for both the preprocessor and linker. This option does not affect the thread safety of object code produced by the compiler or that of libraries supplied with it.