c语言，free总是提示触发了断点，求指导。

Question

引入了自定义的头文件BiTree.h

 typedef struct BiTNode
{
    int data;
    struct BiTNode *lchild, *rchild;

}BiTNode, *BiTree;

下面是cpp文件：

 #include "BiTree.h"
#include "stdlib.h"
#include "stdio.h"


bool Delete(BiTree &p)
{
    BiTree q = (BiTree)malloc(sizeof(BiTree));
    q = p;
    p = p->lchild;
    free(q);
    return true;
}



bool DeleteBST(BiTree &T, int key)
{
    if (!T)return false;
    else if (key==T->data)
    {
        return Delete(T);
    }
    else if (key < T->data)
    {
        return DeleteBST(T->lchild, key);
    }
}

int main()
{
    BiTree t1 = (BiTree)malloc(sizeof(BiTree));
    BiTree t2 = (BiTree)malloc(sizeof(BiTree));
    BiTree t3 = (BiTree)malloc(sizeof(BiTree));
    t1->data = 3;
    t2->data = 2;
    t3->data = 1;
    t1->lchild = t2;
    t1->rchild = NULL;
    t2->lchild = t3;
    t2->rchild = NULL;
    DeleteBST(t1, 2);

    printf("%d\n", t1->lchild->data);

    system("PAUSE");


    return 0;

}

运行时报错

求指教。另外像多问一句，这里的函数，我这里形参前加了取地址符，我觉得其逻辑上是有问题的（我是认为书上的有问题于是仿照其写出来的这样一个程序），按这样的程序运行free后第一个结点的lchild应该就会空了。请大神指教指教

Answer 1

错误在于Delete里的free(q);这句引起的，之所以释放出错，是由于你越界写入了，导致堆被破坏
根本原因在于malloc的时候申请的空间太小，(BiTree)malloc(sizeof(BiTree));中的BiTree是个指针，所以你只申请了4个字节的空间
应该改成(BiTree)malloc(sizeof(BiTNode));

  #include "BiTree.h"
#include "stdlib.h"
#include "stdio.h"


bool Delete(BiTree &p)
{
    BiTree q = (BiTree)malloc(sizeof(BiTNode));
    q = p;
    p = p->lchild;
    free(q);
    return true;
}



bool DeleteBST(BiTree &T, int key)
{
    if (!T)return false;
    else if (key==T->data)
    {
        return Delete(T);
    }
    else if (key < T->data)
    {
        return DeleteBST(T->lchild, key);
    }
}

int main()
{
    BiTree t1 = (BiTree)malloc(sizeof(BiTNode));
    BiTree t2 = (BiTree)malloc(sizeof(BiTNode));
    BiTree t3 = (BiTree)malloc(sizeof(BiTNode));
    t1->data = 3;
    t2->data = 2;
    t3->data = 1;
    t1->lchild = t2;
    t1->rchild = NULL;
    t2->lchild = t3;
    t2->rchild = NULL;
    DeleteBST(t1, 2);

    printf("%d\n", t1->lchild->data);

    system("PAUSE");


    return 0;

}