0x00AE18F8 处有未经处理的异常: 0xC0000005: 读取位置 0x00000020 时发生访问冲突。

代码如下：

#include
#include
struct DON_STUD_STR
{
    long num;
    char name[20];
    float score;
    int mark;
    struct DON_STUD_STR * next;
};
这个函数为什么老是出错
struct DON_STUD_STR * DON_STUD_BRO(struct DON_STUD_STR *head)
{
    struct DON_STUD_STR * p1;
    p1 = (struct DON_STUD_STR *)malloc(sizeof(struct DON_STUD_STR));
    p1 = head->next;
    while (p1 != NULL)
    {
        printf("%-20s%-20s%-20s%-20s", "选好", /*"名字",*/ "成绩", "标记");
        printf("%-20d\n", p1->num);
        //printf("%-20d\n", p1->name);
        printf("%-20f\n", p1->score);
        printf("%-20d\n", p1->mark);
        p1 = p1->next;
    }
    return(head);
}