这个析构函数哪里错了？

[austinlui2]

调试了下，错误定位在析构函数，大家帮忙看下..........为了方便，代码全附上，应付作业..用动态数组求多项式...写得很烂，别见笑
头文件：

#ifndef POLY_H
#define POLY_H
#include<iostream>
using namespace std;
struct term
{
	double coef;
	int exp;
};
class poly
{
public:
	poly(const int n);
	poly(const poly& p);
	poly();
	~poly();
	friend poly operator +(const poly p1, const poly p2);
	friend poly operator -(const poly p1, const poly p2);
	friend poly operator *(const poly p1, const poly p2);
	void  operator = (const poly p);
	double  result(double x);
	void getCoef();
	void setCoef();
private:
	int max;
	term* expression;
};
	
#endif

实现文件

#include<iostream>
#include<cmath>
#include"poly.h"
using namespace std;
poly::poly(const int n)
{
	max = n;
	expression = new term [max];

}

poly::poly()
{
	max = 1;
	expression = new term [max];
	expression[0].coef=expression[0].exp =0;

}

void poly::operator =(const poly p)
{
	int i = 0;
	max = p.max;
	while(i<max)
	{
		expression[i].coef = p.expression[i].coef;
		expression[i].exp = p.expression[i].exp;
		i++;
	}
}

poly::poly(const poly &p)
{
	max = p.max;
	expression = new term [max];
	int i = 0;
	while(i < max)
	{
		expression[i].coef = p.expression[i].coef;
		expression[i].exp = p.expression[i].exp;
		i++;
	}

}

poly::~poly()
{
	delete [] expression;
}


poly operator +(const poly p1, const poly p2)
{
	int n;
	if(p1.max>p2.max)
		n = p1.max;
	else
		n = p2.max;
	poly temp(n);
	int i = 0,j = 0,t =0;
	while(t <temp.max)
	{
		if(p1.expression[i].exp < p2.expression[j].exp)
		{
			temp.expression[t].coef = p2.expression[j].coef;
			temp.expression[t].coef = p2.expression[j].coef;
			t++;
			j++;

		}
		else if(p1.expression[i].exp> p2.expression[j].exp)
		{
			temp.expression[t].coef = p1.expression[i].coef;
			temp.expression[t].exp = p1.expression[i].exp;
			t++;
			i++;
		}
		else
		{
			temp.expression[t].coef = p1.expression[i].coef+p2.expression[j].coef;
			temp.expression[t].exp = p1.expression[i].exp+p2.expression[j].exp;
			t++;
			i++;
			j++;
		}
	}
	while(i <p1.max)
	{
		temp.expression[t].coef = p1.expression[i].coef;
		temp.expression[t].exp = p1.expression[i].exp;
		t++;
		i++;
	}
	while(j<p2.max)
	{
		temp.expression[t].coef = p2.expression[j].coef;
		temp.expression[t].exp = p2.expression[j].exp;
		t++;
		j++;
	}
	return temp;
}



poly operator -(const poly p1, const poly p2)
{
	int n;
	if(p1.max>p2.max)
		n = p1.max;
	else
		n = p2.max;
	poly temp(n);
	int i = 0,j = 0,t =0;
	while(t <temp.max)
	{
		if(p1.expression[i].exp < p2.expression[j].exp)
		{
			temp.expression[t].coef = -p2.expression[j].coef;
			temp.expression[t].exp = -p2.expression[j].exp;
			t++;
			j++;

		}
		else if(p1.expression[i].exp> p2.expression[j].exp)
		{
			temp.expression[t].coef = p1.expression[i].coef;
			temp.expression[t].exp = p1.expression[i].exp;
			t++;
			i++;
		}
		else
		{
			temp.expression[t].coef = p1.expression[i].coef-p2.expression[j].coef;
			temp.expression[t].exp = p1.expression[i].exp-p2.expression[j].exp;
			t++;
			i++;
			j++;
		}
	}
	while(i <p1.max)
	{
		temp.expression[t].coef = p1.expression[i].coef;
		temp.expression[t].exp = p1.expression[i].exp;
		t++;
		i++;
	}
	while(j<p2.max)
	{
		temp.expression[t].coef = -p2.expression[j].coef;
		temp.expression[t].exp = -p2.expression[j].exp;
		t++;
		j++;
	}
	return temp;
}
/*poly operator *(const poly p1, const poly p2);*/

double  poly::result(double x)
{
	double sum = 0;
	int i = 0;
	while(i<max)
	{
		sum += pow(x, expression[i++].exp);
	}
	return sum;
}
void poly::getCoef()
{
	int i = 0;
	while(i<max)
	{
		cout<<expression[i++].coef<< " ";
	}
	cout<<endl;
}
void poly::setCoef()
{
	int i = 0;
	while(i<max)
	{
		cin>>expression[i++].coef;
	}
}

主文件

#include<iostream>
#include"poly.h"

using namespace std;

int main()
{
	poly p1(5);
	p1.setCoef();
	poly p2(p1);
	p1.getCoef();
	p2.getCoef();
	poly p3;
	p3 = p1+p2;
	p3.getCoef();
	return 0;

}

[forster]

头文件呢 其他都没用

[mmilmf]

poly::~poly()
{
    //delete [] expression;注释掉
}

[deng1243]

poly::poly()
{
    max = 1;//这里才一个空间
    expression = new term [max];
    expression[0].coef=expression[0].exp =0;

}

int main()
{
    poly p1(5);
    p1.setCoef();
    poly p2(p1);
    p1.getCoef();
    p2.getCoef();
    poly p3;//调用构造函数poly（），或改为poly p3（5），或修改无参构造函数poly（）
    p3 = p1+p2;//相加后空间越界了
    p3.getCoef();
    return 0;

}

[austinlui2]

[Quote=引用 2 楼 mmilmf 的回复:]
C/C++ code
poly::~poly()
{//delete [] expression;注释掉}
[/Quote] 这个我知道，但是规定得手动写个析构函数...

[austinlui2]

[Quote=引用 3 楼 deng1243 的回复:]
C/C++ code
poly::poly()
{
max=1;//这里才一个空间 expression=new term [max];
expression[0].coef=expression[0].exp=0;

}
C/C++ codeint main()
{
poly p1(5);
p1.setCoef();
poly p2(p1);
p1.getCoef();
p2.getCoef();
poly p3;//调用构造函数poly（），或改为poly p3（5），或修改无参构造函数poly（） p3= p1+p2;//相加后空间越界了 p3.getCoef();return0;

}
[/Quote]

我重载了 + = 这些东西 ， 里面会动态分配空间的。。。难道不对么？

[wyzhao0102]

可能是野指针问题
看看有没有把一个对象赋给另外一个
我猜测的

[huahenyueying]

这个问题是这样造成的：
poly p3;//你的无参数构造函数分配了1个空间
delete [] expression 就会出错
正确的应该是 delete expression,如果想办法在析构函数函数里加上这句delete expression就不会出错.

不过建议你这么改：
void poly::operator =(const poly p)
{
if (expression != NULL)
{
if (max >1 )
{
delete [] expression;
}
else
{
delete expression;
}
expression = NULL;
}
max = p.max;
expression = new term [max];
int i = 0;
while(i<max)
{
expression[i].coef = p.expression[i].coef;
expression[i].exp = p.expression[i].exp;
i++;
}
}


poly::~poly()
{
if (expression !=NULL )
{
delete [] expression;
}
expression =NULL;
}


删除一个指针后，一定要将指针置为空，不然会成野指针