我不得不把这个程序用于作业，它已经被评分，得到了80分。我要回去清理一些代码了。在我的代码的底部是重载= operator的函数。出于某种原因，我注释掉的cout语句会导致我的程序崩溃，但是，当我删除// s程序运行正常时...
任何人都有任何想法，为什么会这样？
#include <iostream>
using namespace std;
class Poly
{
private:
int order; //order of the polynomial
int * coeff;//pointer to array of coeff on the heap
public:
Poly();
Poly(int Order);
Poly(int Order, int * Coeff);
~Poly(){/*cout << "Deconstructor\n";*/};
Poly(const Poly &rhs);
//accessors & mutators
void set();
void set(int * Coeff, int Order);
void Print2();
void PtrReset();
int getorder(){return order;};
int * get()const{return coeff;};
//Overloaded Operators
Poly operator+(const Poly &rhs);
Poly operator-(const Poly &rhs);
Poly operator*(const int scale);
Poly operator=(const Poly &rhs);
Poly operator*(const Poly &rhs);
const int& operator[](int I)const;
int& operator[](int I);
bool operator==(const Poly &rhs);
int operator( )(int X);
friend ostream & operator<<(ostream & Out, const Poly &rhs);
friend istream & operator >>(istream & In, Poly &rhs);
};
int main()
{
int coeff1[ ] = {-19,1,-12,3,1};
int coeff2[ ] = {-19,1,-6,0,0,7,0,-1};
bool flag;
Poly P1(4, coeff1);
Poly P2(7, coeff2);
Poly P3;
P3 = P1 + P2;
cout << "P1 + P2: " << P3;
P3 = P2 - P1;
cout << "P2 - P1: " << P3;
P3 = P1 * 10;
cout << "P1 * 10: " << P3;
P3 = P1 * P2;
cout << "P1 * P2: " << P3;
flag = (P2 == P2);
cout << "P2 and P2 are ";
if (flag)
cout << "Equal\n";
else
cout << "Not Equal\n";
flag = (P1 == P2);
cout << "P1 and P2 are ";
if (flag)
cout << "Equal\n";
else
cout << "Not Equal\n";
cout << "P1(4) = " << P1(4) << endl;
cout << "P1: ";
cout << P1;
cout << "P2: ";
cout << P2;
P1[3] = P2[5];
cout << "P1(after P1[3] = P2[5]): " << P1;
P1[3] = P2[4];
cout << "P1(after P1[3] = P2[4]): " << P1;
return 0;
}
Poly::Poly()
{
coeff = (int *) malloc(sizeof(int));
order = 0;
*coeff = 0;
//cout << "Default Constructor\n";
}
Poly::Poly(int Order)
{
order = Order;
coeff = new int[order+1];
for(int i(0); i <= order; i++)
coeff[i] = 0;
}
Poly::Poly(int Order, int * Coeff)
{
order = Order;
coeff = Coeff;
}
Poly::Poly(const Poly &rhs)
{
order = rhs.order;
int *temp;
temp = (int *) malloc((rhs.order + 1) * sizeof(int));
coeff = (int *) malloc((order + 1) * sizeof(int));
temp = rhs.coeff;
for(int i(0); i <= order; i++)
{
*coeff = *temp;
coeff++;
temp++;
}
PtrReset();
}
void Poly::set()
{
coeff = (int *) malloc((order + 1) * sizeof(int));
if(coeff == NULL)
{
cout << "Error allocating memory!\n";
exit(1);
}
cout << "Begin entering with the non x value, then x^1 coefficient, x^2, etc:\n";
for(int i(0); i <= order; i++)
{
cout << (i+1) << ". ";
cin >> * coeff;
coeff++;
}
PtrReset();
}
void Poly::set(int * Coeff, int Order)
{
order = Order;
for(int i(0); i <= order; i++)
{
*coeff = *Coeff;
coeff++;
Coeff++;
}
PtrReset();
}
void Poly::Print2()
{
for(int i(0); i <= order; i++)
{
cout << * coeff << " ";
coeff++;
}
cout << endl;
PtrReset();
}
void Poly::PtrReset()
{
for(int i(0); i <= order; i++)
coeff--;
}
Poly Poly::operator+(const Poly &rhs)
{
int neworder;
int * newpointer;
int * temp;
temp = rhs.coeff;
if(order >= rhs.order)
{
neworder = order;
newpointer = (int *) malloc((neworder+1) * sizeof(int));
for(int i(0); i <= rhs.order; i++)
{
*newpointer = *coeff + *temp;
newpointer++;
coeff++;
temp++;
}
for(int i(0); i < (order - rhs.order); i++)
{
*newpointer = *coeff;
newpointer++;
coeff++;
}
}
else
{
neworder = rhs.order;
newpointer = (int *) malloc((neworder+1) * sizeof(int));
for(int i(0); i <= order; i++)
{
*newpointer = *coeff + *temp;
newpointer++;
coeff++;
temp++;
}
for(int i(0); i < (rhs.order - order); i++)
{
*newpointer = *temp;
newpointer++;
temp++;
}
}
PtrReset();
for(int i(0); i <= neworder; i++)
newpointer--;
return Poly(neworder, newpointer);
}
Poly Poly::operator-(const Poly &rhs)
{
int neworder;
int * newpointer;
int * temp;
temp = rhs.coeff;
if(order >= rhs.order)
{
neworder = order;
newpointer = (int *) malloc((neworder+1) * sizeof(int));
for(int i(0); i <= rhs.order; i++)
{
*newpointer = *coeff - *temp;
newpointer++;
coeff++;
temp++;
}
for(int i(0); i < (order - rhs.order); i++)
{
*newpointer = *coeff;
newpointer++;
coeff++;
}
}
else
{
neworder = rhs.order;
newpointer = (int *) malloc((neworder+1) * sizeof(int));
for(int i(0); i <= order; i++)
{
*newpointer = *coeff - *temp;
newpointer++;
coeff++;
temp++;
}
for(int i(0); i < (rhs.order - order); i++)
{
*newpointer = 0 - *temp;
newpointer++;
temp++;
}
}
PtrReset();
for(int i(0); i <= neworder; i++)
newpointer--;
return Poly(neworder, newpointer);
}
Poly Poly::operator*(const int scale)
{
int neworder = order;
int * temp = new int[order+1];
for(int i(0); i <= order; i++)
temp[i] = scale * coeff[i];
return Poly(neworder, temp);
}
Poly Poly::operator*(const Poly &rhs)
{
int neworder = order + rhs.order;
int * newcoeff;
int * temp;
temp = rhs.coeff;
newcoeff = (int *) malloc((neworder + 1) * sizeof(int));
for(int i(0); i <= neworder; i++)
{
*newcoeff = 0;
newcoeff++;
}
for(int i(0); i <= neworder; i++)
newcoeff--;
for(int i(0); i <= order; i++)
{
for(int j(0); j <= rhs.order; j++)
{
*newcoeff += (*coeff * *temp);
newcoeff++;
temp++;
}
coeff++;
for(int j(0); j < rhs.order; j++)
newcoeff--;
for(int j(0); j <= rhs.order; j++)
temp--;
}
for(int i(0); i <= (neworder - rhs.order); i++)
newcoeff--;
PtrReset();
return Poly(neworder, newcoeff);
}
bool Poly::operator==(const Poly &rhs)
{
bool test = true;
int count = 0;
while(test && (count <= order))
{
if(order != rhs.order)
test = false;
else if(coeff[count] != rhs.coeff[count])
test = false;
count++;
}
return test;
}
int Poly::operator()(int X)
{
int * temp;
int * temp2;
temp = (int *) malloc((order + 1) * sizeof(int));
temp2 = temp;
for(int i(0); i < order; i++)
coeff++;
for(int i(0); i <= order; i++)
{
*temp = *coeff;
temp++;
coeff--;
}
coeff++;
for(int i(0); i < order; i++)
temp--;
for(int i(0); i < order; i++)
{
*temp += (X * *temp2);
temp++;
*temp2++;
}
return *temp2;
}
ostream &operator <<(ostream& out, const Poly &source)
{
for(int i(source.order); i >= 0; i--)
{
if(i == 1)
{
if(i == source.order)
if(source.coeff[i] == 1)
out << "X";
else if(source.coeff[i] == -1)
out << "-X";
else
out << source.coeff[i] << "X";
else if(source.coeff[i] == 1)
out << " + " << "X";
else if(source.coeff[i] == -1)
out << " - " << "X";
else if(source.coeff[i] > 0)
out << " + " << source.coeff[i] << "X";
else if(source.coeff[i] < 0)
out << " - " << abs(source.coeff[i]) << "X";
}
else if(i > 1)
{
if(i == source.order)
if(source.coeff[i] == 1)
out << "X^" << i;
else if(source.coeff[i] == -1)
out << "-X^" << i;
else
out << source.coeff[i] << "X^" << i;
else if(source.coeff[i] == 1)
out << " + " << "X^" << i;
else if(source.coeff[i] == -1)
out << " - " << "X^" << i;
else if(source.coeff[i] > 1)
out << " + " << source.coeff[i] << "X^" << i;
else if(source.coeff[i] < -1)
out << " - " << abs(source.coeff[i]) << "X^" << i;
}
else
{
if(source.coeff[i] > 0)
out << " + " << source.coeff[i];
else if(source.coeff[i] < 0)
out << " - " << abs(source.coeff[i]);
}
}
out << endl;
return out;
}
int& Poly::operator[](int I)
{
if(I > (order + 1) || I < 0)
{
cout << "Request to access outside Poly boundaries!" << endl;
exit(1);
}
return coeff[I];
}
const int& Poly::operator[](int I) const
{
if(I > (order + 1) || I < 0)
{
cout << "Request to access outside Poly boundaries!" << endl;
exit(1);
}
return coeff[I];
}
Poly Poly::operator=(const Poly &rhs)
{
order = rhs.order;
//cout << "new order = " << rhs.order << endl; ******HERE*******
for(int i(0); i <= rhs.order; i++)
coeff[i] = rhs.coeff[i];
return Poly(order, coeff);
}
答案 0 :(得分：2)
Assignment operator作为会员应返回对this的引用
如果不这样做，那么您可能不应该使用assignment operator。
除了注释外，您的赋值运算符的另一个直接问题是，当您手动构建新的coeff数组时，您正在泄漏更多内存。您还将返回第三个对象，这不是任何使用assignment operator的人所期望的，这是彻头彻尾的危险
Poly& Poly::operator=(const Poly &rhs)
{
order = rhs.order;
// you should probably initialize coeff here
//cout << "new order = " << rhs.order << endl; ******HERE*******
for(int i(0); i <= rhs.order; i++)
coeff[i] = rhs.coeff[i];
//This is wrong return this. see signature fix above
//return Poly(order, coeff);
return *this;
}
其次，不要手动纠正你在代数运算符中所做的任何事情，复制构造FIRST然后修改THAT对象。
例如乘法：
//member multiplication which still sucks because we are going to copy construct again to return..
Poly Poly::operator*(const int scale)
{
Poly result(*this);
// now manipulate your new object and leave THIS this alone
for(int i(0); i <= result.order; i++)
result.coeff[i] *= scale;
return result;
}
如果你把它变成一个非成员函数，然后创建一个成员函数*=operator，然后你可以像Ben和我想象的那样做
Poly operator*(Poly result, int scale)
{
return (result *= scale);
}
我看到的主要问题是你正在疯狂地泄露记忆，并且从未对它有任何限制。
答案 1 :(得分：0)
当我看到这个时，它背后的常见问题是双重免费/删除。你可能会在相同的指针上自由地调用两次（或者一个无效的指针），这会导致一切变得奇怪，并且崩溃几乎可以在任何时候发生。
当你混合malloc和new时也会发生这种情况。将所有内容切换为新内容，看看你是否仍然遇到了崩溃。