线程函数unsigned int __stdcall Fun(void *pPM) 中pPM指针是什么时候给赋值的？

转载自https://blog.csdn.net/mengyafei43/article/details/17532397?utm_medium=distribute.pc_relevant.none-task-blog-title-7&spm=1001.2101.3001.4242 教程的代码，想问一下线程函数

unsigned int __stdcall Fun(void *pPM) 

中pPM指针是什么时候给赋值的？是在系统内部吗？

//经典线程同步互斥问题
#include <stdio.h>
#include <process.h>
#include <windows.h>

long g_nNum; //全局资源
unsigned int __stdcall Fun(void *pPM); //线程函数
const int THREAD_NUM = 10; //子线程个数

int main()
{
    g_nNum = 0;
    HANDLE  handle[THREAD_NUM];

    int i = 0;
    while (i < THREAD_NUM) 
    {
        handle[i] = (HANDLE)_beginthreadex(NULL, 0, Fun, &i, 0, NULL);
        i++;//等子线程接收到参数时主线程可能改变了这个i的值
    }
    //保证子线程已全部运行结束
    WaitForMultipleObjects(THREAD_NUM, handle, TRUE, INFINITE);  
    return 0;
}

unsigned int __stdcall Fun(void *pPM)
{
//由于创建线程是要一定的开销的，所以新线程并不能第一时间执行到这来
    int nThreadNum = *(int *)pPM; //子线程获取参数
    Sleep(50);//some work should to do
    g_nNum++;  //处理全局资源
    Sleep(0);//some work should to do
    printf("线程编号为%d  全局资源值为%d\n", nThreadNum, g_nNum);
    return 0;
}