Question

我正在研究的程序的目的是通过模拟动态指针数组来创建一个“改进”默认整数数组数据类型的类。尝试删除指针和指针数组时，我一直遇到错误，其中“Windows已触发project4.exe中的断点。”

这可能是由于堆的损坏，这表示project4.exe或它已加载的任何DLL中存在错误。

这也可能是由于用户在project4.exe具有焦点时按下F12。

输出窗口可能包含更多诊断信息。“

class Array
{
private:
    int length;
int* data;
public:
    Array();
    Array(const Array &cpy);
    ~Array();
    bool addint(int toadd);
    bool deletelast();
    int getlength();
    friend ostream& operator<<(ostream &out, const Array &n);
};

ostream& operator<<(ostream &out, const Array &n);

Array::Array()
{
    length = -1;    
    data = NULL;
}

Array::Array(const Array &cpy)
{  
    length = cpy.length;                //value of length is copied

    if (length < 0)
        data = NULL;
    else
    {
        data = new int [length];

        for (int i=0; i<=length; i++)
            data[i] = cpy.data[i];
    }

}    

Array::~Array()
{
    if (length != 0)
        delete [] data;
    else
        delete data;

    data = NULL;
}  

bool Array::addint(int toadd)
{   
    length ++;
    int* point = new int[length];

    for (int i=0; i < length; i++)
        point[i] = data[i];             

    point[length] = toadd;

    if (length != 0)    
        delete [] data; 

    data = point;

    point = NULL;

    return true;
}    

bool Array::deletelast()
{
    int* temppoint;
    if (length > 0)
        temppoint = new int [length-1]; 
    else
        temppoint = new int[0];

    for (int i=0; i<length; i++)        
        temppoint[i] = data[i];

    if (length == 0)
        temppoint[0] = 0;

    length --;
    delete [] data; 
    data = temppoint;
    temppoint = NULL;

    return true;
}  

void menu(Array var)
{
    int selection=0,
        input;
    bool success;
    Array* arrcpy;
    while (selection != 3)
    {
        if (var.getlength() == -1)
        {
            cout << "What would you like to demonstrate?" << endl << "1) Add an integer " << endl
            << "2) Exit" << endl << "Enter your selection: ";
            cin >> selection;
            if (selection == 2)
                selection = 4;
        }
        else
        {
            cout << endl << "Now what would you like to demonstrate?" << endl << "1) Add an integer " << endl
            << "2) Delete the last entered integer" << endl << "3) Copy constructor" << endl << "4) Exit" << endl << "Enter your selection: ";
            cin >> selection;
        }

        if (selection==1)
        {
            cout << endl << "The length of the array before adding a new value is: " << var.getlength() + 1 << endl;
            cout << "Please enter the integer that you wish to add: ";
            cin >> input; 
            success = var.addint(input);
            if (success)
                cout << endl << "The data input was a success!" << endl << "The length of the array is now: " 
                << var.getlength() + 1 << endl << "The new value of the array is: " << var << endl;
            else
                cout << endl << "The input failed" << endl;
        }       
        if (selection == 2)
        {
            cout << endl << "The lenght of the array before the deletion is: " << var.getlength() + 1 << endl 
                << "and the value held in the array is: " << var << endl;
            success = var.deletelast();
            if (success)
                cout << endl << "The data deletion was a success!" << endl << "The length of the array is now: "
                << var.getlength() + 1 << endl << "The new value of the array is: " << var << endl;
            else
                cout << endl << "The deletion failed" << endl;
        }       
        if (selection == 3)
        {
                cout << endl << "The lenght of the array being copied is: " << var.getlength() + 1 << endl 
                << "and the value held in the array is: " << var << endl;
                arrcpy=new Array(var);
                cout << endl << "The length of the copied array is: " << arrcpy->getlength() +1 << endl
                << "and the value contained in the array is: " << *arrcpy;
                delete arrcpy;
        }
    }
}

这就是我所遇到的所有相关源代码。接下来，delete运算符和delete []运算符的每个实例都导致了这个断点错误，我不确定我做错了什么。

编辑：重写代码使得length的值默认为0而不是-1，现在一切正常！

Answer 1

我相信复制构造函数中的for (int i=0; i<=length; i++)应该包含i<length（小于，不小于或等于）。这是一个明显的问题。

此外，您正在传递addint()方法中的边界。数组中的最后一个元素是索引[length-1]。

Answer 2

int* point = new int[length];

由于您的长度从-1开始，因此该行的第一次调用将是new int[0]。可能是问题..如果你坚持不修复length的语义，你想在这里length+1

无关联，你应该看看std::vector是如何做到的，而不是重新分配每一个添加，你应该尝试进行全面定位，只有在空间被填满时才重新分配。

Answer 3

我了解这是一个老话题，我承认我没有阅读所有评论，但是关于为什么当长度更改为0时它似乎起作用的话题，我相信这可能是由于提供了nullptr到由无效大小组成的数组，然后再尝试删除此类指针将导致断点。

尝试删除指针会触发断点

3 个答案: