c语言malloc之后再realloc的有关问题

c语言malloc之后再realloc的问题
不才学习严蔚敏的数据结构C语言版堆栈一课时,参考书上的内容自己编写的一个堆栈的程序,遇到了下面的怪问题.
程序如下(用vc++6.0环境)
stack.cpp:

C/C++ code

#include <stdio.h>
#include <stdlib.h>

#include "../Status.h"

#define STACK_INIT_SIZE 5    //堆栈初始大小
#define STACKINCREMENT 5     //堆栈满之后再增加的大小

typedef char *stackelem;

typedef struct
{
    stackelem *base,*top;
    int stacksize;
}sqstack;

/*------堆栈基本操作-------*/

Status initstack(sqstack *s)
{
    s->base=(stackelem *)malloc(STACK_INIT_SIZE*sizeof(stackelem));
    if(!s->base) exit(OVERFLOW);
    s->top=s->base;
    s->stacksize=STACK_INIT_SIZE;
    return OK;
}

Status stackempty(sqstack *s)
{
    if(s->base==s->top) return TRUE;
    return FALSE;
}

Status gettop(sqstack *s,stackelem *e)
{
    if(stackempty(s))
    {
        e=NULL;
        printf("取栈顶失败:堆栈为空!\n");
        return ERROR;
    }
    e=s->top-sizeof(stackelem);
    return OK;
}

int stacklength(sqstack *s)
{
    if(stackempty(s))
        return 0;
    else
        return (s->top-s->base)/sizeof(stackelem);
}

Status push(sqstack *s,stackelem e)
{
    if(stacklength(s)>=s->stacksize)
    {
        printf("堆栈已满,增加空间\n"); 
        s->base=(stackelem *)realloc(s->base,(s->stacksize+STACKINCREMENT)*sizeof(stackelem));
        if(!s->base)
        {
            printf("增加空间失败,压栈失败,程序退出!\n");
            exit(OVERFLOW);
        }
        s->top=s->base+s->stacksize*sizeof(stackelem);
        s->stacksize+=STACKINCREMENT;
    }
    *(s->top)=e;
    s->top+=sizeof(stackelem);
    printf("元素 %s 压栈成功!\n",e);
    return OK;
}

Status pop(sqstack *s,stackelem e)
{
    if(stackempty(s))
    {
        printf("出栈失败:栈为空!\n");
        return ERROR;
    }
    s->top-=sizeof(stackelem);
    e=*(s->top);
    /*    *(s->top)=NULL ;*/
    printf("元素 %s 出栈成功!\n",e);
    return OK;
}

Status clearstack(sqstack *s)
{
    stackelem e;
    while(!stackempty(s)) pop(s,e);
    printf("堆栈已经清空\n");
    return OK;
}

Status destroystack(sqstack *s)
{
    clearstack(s);
    free(s->base);
    printf("堆栈已经销毁\n");
    return OK;
}

Status printstack(sqstack *s)
{
    printf("开始打印堆栈...\n\n");
    if(stackempty(s))
    {
        printf("打印错误:没有可以打印的内容!\n");
        printf("\n打印堆栈结束.\n");
        return ERROR;
    }
    stackelem *p=s->top;
    while((p>s->base))
    {
        p-=sizeof(stackelem); //我认为malloc之后不管realloc多少次,如果没有失败,得到的空间应该是连续的,所以这样写
        printf("\t%s\n",*p);
    }
    
    printf("\n打印堆栈结束.\n");
    return OK;
}

void main()
{
    sqstack s;
    stackelem e;
    initstack(&s);
/*    push(&s,"2");
    printstack(&s);
    clearstack(&s);
    printstack(&s);*/
    push(&s,"1");
    push(&s,"2");
    push(&s,"3");
    push(&s,"4");
    push(&s,"5");
    push(&s,"6");
    push(&s,"7");
    push(&s,"8");
    push(&s,"9");
    push(&s,"10");
    push(&s,"11this is just for test");
    push(&s,"12this is just for test");
    push(&s,"13");
    push(&s,"14 this for test");
    push(&s,"15");
    push(&s,"16");
    push(&s,"17");
    push(&s,"18");
    printstack(&s);
    pop(&s,e);
    pop(&s,e);
    pop(&s,e);
    pop(&s,e);
    pop(&s,e);
    printstack(&s);
    destroystack(&s);
    
}

Status.h的内容如下:

C/C++ code


#define TRUE 1
#define FALSE 0
#define OK 1
#define ERROR 0
#define INFEASIBLE -1
#define OVERFLOW -2

typedef int Status;

c语言malloc之后再realloc的有关问题

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