plink read_mes()
{
    plink P,H =(plink)malloc(Size);
    plink new_node;
    FILE *fp = NULL;
    if(NULL == H)
    {
        printf("ERROR:malloc error\n ");
        return NULL;
    }
    P = H;
    fp = fopen("stud.txt","rt+");
    if(NULL == fp)
    {
        printf("ERROR:cannot open file!\n ");
        return NULL;
    }
    while(!feof(fp))
    {
        new_node =(plink)malloc(Size);
        if(NULL == new_node)
        {
            printf("ERROR:malloc error\n ");
            return NULL;
        }
        P->next = new_node;
        new_node->next = NULL;
        P = new_node;
        fscanf(fp,"%d,%s,%d,%f",&P->id,P->name,&P->age,&P->score);Debug时 在这里出现错误No source available for "vfscanf() at 0x1c1083"
    }
    fclose(fp);
    return H;
}

我自己解决了 plink P,H =(plink)malloc(Size);
size我#define Size sizeof（plink）；plink是个结构体指针，然后在new_node =(plink)malloc(Size)时 内存分配就多了 然后 就发生上面的错误！