在百度知道里面得到了正确的答案

http://zhidao.baidu.com/question/198940026560129285.html?quesup2&oldq=1

#include<iostream>
#include <string>//出问题时，使用的是cstring,但换成string一样出问题
using namespace std;
struct stringy{
	char *str;
	int ct;
};
void set(stringy &beany,const char t[]);
void show(const stringy &beany,int count=0);
void show(const char t[],int count=0);
void main84()
{
	stringy beany;
	char testing[]="Reality isn't what it used to be.";
	//char testing[]="Reality";//what it used to be.";
	set(beany,testing);
	show(beany);
	show(beany,2);
	testing[0]='D';
	testing[1]='u';
	show(testing);
	show(testing,3);
	show("Done!");
	cout<<beany.str<<endl;
	cout<<"here is in"<<endl;
	
	if(beany.str!=NULL)	//总会引起中断，说是堆损坏
	{
		delete []beany.str;
		cout<<"no null"<<endl;
	}
	else 
		cout<<"str is null";

	system("pause");
	


}

void set(stringy &beany,const char t[])
{
	//delete beany.str;
	int size=strlen(t);//在这里，t已经退化成了一个指针，不能用sizeof获取长度！！！
	int size=sizeof(t);//这里出了问题，长度测试错误,当长度超过八个字符是，直接出错！
	cout<<"size="<<size<<endl;
	beany.str=new char[size+1];
	strcpy(beany.str,t);
	int sizeofStr=strlen(beany.str);
	cout<<"Sizeofstr="<<sizeofStr<<endl;
	beany.ct=size;


}

void show(const stringy &beany,int count)
{
	cout<<"Stringy show"<<endl;
	if(count!=0)
	{
		for(int j=0;j<count;j++)
		{
			//cout<<"in stringy here!"<<j<<endl;
			//cout<<"Stringy show"<<j<<endl;
			cout<<"str="<<beany.str<<endl;
		};
	}
	else
		cout<<"str="<<beany.str<<endl;
	
}
void show(const char t[],int count)
{
	cout<<"Testing show:"<<endl;
	if(count==0)
		cout<<"str="<<t<<endl;
	else
		for(int i=0;i<count;i++)
		{
			cout<<"Testing show:"<<i<<endl;
			cout<<"str="<<t<<endl;
		}

}