Question

我收到＆＃34;调试错误＆＃34; CRT检测到应用程序在堆结束后写入内存。但我不明白为什么，也找不到类似的例子。

完整的代码是...... 虽然我认为这可能只是主要问题。

#include <iostream>
#include <cmath>
#include <array>

using namespace std;
// Declare global consts
const double pi = 3.1415926583;


// Base class Shape
class Shape{
protected:
    double *sides;
public:
    Shape(const int n){ //parameterized for n dimensional shape
    sides = new double[n];
}
// need virtual destructor
virtual ~Shape(){
    delete[] sides;
}
virtual double area() const = 0; // pure virtual function for area
virtual double volume() const = 0; // pure virtual function for volume
};

//////////////////////////////////////////////////////////
//Derived classes for 2D and 3D Shapes
class Shape2D : public Shape{ // inherit shape
protected:
    int n = 2; //n denotes the number of dimensions
public:
    // default constructor
    Shape2D() :Shape(n){}
    // param constructor
    Shape2D(const double side1, const double side2) :Shape(n){
        sides[0] = side1; sides[1] = side2;
    }
    virtual ~Shape2D(){} //virtual destructor
    double volume() const { cout << "trying to calculate volume of 2d   shape..." << endl; return 0; };
};

/////////////////////////////////////////////////////////////////////
//2D shapes
class Rectangle : public Shape2D{
public:
    // constructors
    Rectangle() :Shape2D() {}
    Rectangle(const double side1, const double side2) :Shape2D(side1, side2){}
    ~Rectangle(){}
    double area() const { return (sides[0] * sides[1]); }
};

int main(){
    Shape **ShapePointer = new Shape*[2];
    ShapePointer[0] = new Rectangle(2, 5);
    ShapePointer[1] = new Rectangle(1, 3);
    // clean up 
    delete ShapePointer[0];
    delete ShapePointer[1];
    delete[] ShapePointer;
    system("pause");
    return 0;
}

Answer 1

危险!!!

protected:
    int n = 2; //n denotes the number of dimensions
public:
    // default constructor
    Shape2D() :Shape(n){}

初始化n

时，

Shape(n)未定义

与

相同的问题

Shape2D(const double side1, const double side2) :Shape(n)

如果可以，请将n定义为static const（或static constexpr，因为您标记了C ++ 11）

 protected:
    static constexpr int n = 2; //n denotes the number of dimensions

否则，您应该定义一个静态const / constexpr变量（比如nDef），其值为2，并初始化n和{{1这个常数。

无论如何，请记住，现在Shape()（Shape的基类）在 Shape2D之前初始化，这是该成员类。

Answer 2

问题是以下两行代码： int n = 2; //n denotes the number of dimensions Shape2D(const double side1, const double side2) :Shape(n){ ... }

问题是Shape()在初始化n之前执行。有关详细信息，请参阅constructors-called-before-initializing-variables。

要解决此问题，请在Shape类

中创建以下方法

protected: 
void InitializeBuffer(const int n)
{
sides = new double[n]
}

而不是在父构造函数中初始化sides，而是在InitializeBuffer类的构造函数中调用此Shape2D

Shape2D(const double side1, const double side2) :Shape()
{
    InitializeBuffer (n);
    sides[0] = side1; sides[1] = side2;
}

CRT检测到应用程序在堆缓冲区（新/删除）类结束后写入内存

2 个答案: