又是段错误!!请高手指导下一般段错误该怎么解决
程序如下,就是创建一个动态链表..自己写了库函数叫list.h 主函数list.c 在gcc下编译通过,运行是段错误.
我将2个程序放一起写在下面了,顺便打包..

#ifndef _LIST_H_
#define _LIST_H_
#include<stdio.h>
#include<stdlib.h>
#define OFFSIDE(TYPE,ELEMENT) (&(((TYPE*)0)->ELEMENT))
#define BASE_ADD(TYPE,ELEMENT,ADDR) (ADDR - OFFSIDE(TYPE,ELEMENT))

typedef struct node node_t;
struct node
{
    int date;
    node_t *next;
};
typedef struct stu stu_t;
struct stu
{
    int id;
    char name[20];
    int age;
    char sex;
    node_t tag;
};
typedef struct tch tch_t;
struct tch
{
    int id;
    char name[20];
    char lesson[20];
    int age;
    char sex;
    node_t tag;
};
typedef struct list list_t;
struct list
{
    int size;
    node_t *head;
};
void init(list_t *lt)
{
    lt->head = NULL;
    lt->size = 0;
}
void add(list_t *lt,node_t *nd)
{
    node_t *index = lt->head;
    if(lt->head == NULL)
        lt->head = nd;
    else{
        while(index->next){
            index = index->next;}
        index->next = nd;
    }
}

void ergod(list_t *lt,void (*f)(node_t *nd))
{
    node_t *index = lt->head;
    while(index){
        f(index);
        index = index->next;
    }
}
void print_stu(node_t *nd)
{
  stu_t *stp = (stu_t *)BASE_ADD(stu_t,tag,nd);
  printf("stu:%6d %10s %6d %c\n",stp->id,stp->name,stp->age,stp->sex);
}
void print_tch(node_t *nd)
{
  tch_t *tp = (tch_t *)BASE_ADD(tch_t,tag,nd);
  printf("stu:%6d %10s %10s %6d %c\n",tp->id,tp->name,tp->lesson,tp->age,tp->sex);
}
#endif

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include"list.h"

int main()
{
    list_t lt,lt_tch;
    init(&lt);
    init(&lt_tch);
    int i;
    for(i=0;i<20;i++)
    {
        stu_t *stp = (stu_t*)malloc(sizeof(stu_t));
        stp->id = i + 1;
        sprintf(stp->name,"NB%d",i+1);
        stp->age = i*10;
        stp->sex = 'm';
        stp->tag.date = i;
        stp->tag.next = NULL;
        add(&lt,&(stp->tag));
        tch_t *tp = (tch_t*)malloc(sizeof(tch_t));
        tp->id = i + 1;
        sprintf(tp->name,"NB %d",i+1);
        sprintf(tp->lesson,"work %d",i);
        tp->age = i*10;
        tp->sex = 'm';
        tp->tag.date = i;
        tp->tag.next = NULL;
        add(&lt_tch,&(tp->tag));
    ergod(&lt,print_stu);
    printf("*************************");
    printf("*************************");
    printf("*************************");
    printf("*************************");
    ergod(&lt_tch,print_tch);   
    }
  return 0;

}