protected 成员的 C++ 运行时错误

Question

我正在尝试做一个家庭作业，我们使用链接堆栈将字符串插入到字符串中的指定点，因此是 struct 和 typedef。无论如何，当我尝试在 InsertAfter 方法内的 StringModifier 类中访问 stringLength 时，出现运行时错误，我无法弄清楚问题出在哪里。我应该能够访问和修改该变量，因为它受到保护并且派生类是公开继承的。

struct StringRec
{
    char theCh;
    StringRec* nextCh;
};

typedef StringRec* StringPointer;

class String
{
    public:
        String();
        ~String();
        void SetString();
        void OutputString();
        int GetLength() const;
    protected:
        StringPointer head;
        int stringLength;
};

class StringModifier : public String
{
    public:
        StringModifier();
        ~StringModifier();
        void InsertAfter( StringModifier& subString, int insertAt );
};

void StringModifier::InsertAfter( StringModifier& subString, int insertAt )
{
// RUN TIME ERROR HERE
    stringLength += subString.stringLength;
}

在主要

StringModifier test;
StringModifier test2;

cout << "First string" << endl;
test.SetString();
test.OutputString();
cout << endl << test.GetLength();
cout << endl << "Second string" << endl;
test2.SetString();
test2.OutputString();
cout << endl << test2.GetLength();
cout << endl << "Add Second to First" << endl;
test.InsertAfter( test2, 2 );
test.OutputString();
cout << endl << test.GetLength();

//String Class

String::String()
{
    head = NULL;
    stringLength = 0;
}

String::~String()
{
// Add this later
}

void String::SetString()
{
    StringPointer p;
    char tempCh;

    int i = 0;
    cout << "Enter a string: ";
    cin.get( tempCh );
// Gets input and sets it to a stack
    while( tempCh != '\n' )
    {
        i++;
        p = new StringRec;
        p->theCh = tempCh;
        p->nextCh = head;
        head = p;
        cin.get( tempCh );
    }

    stringLength = i;
}

void String::OutputString()
{
    int i = stringLength;
    int chCounter;
    StringPointer temp;
// Outputs the string bottom to top, instead of top to bottom so it makes sense when read
    while( head != NULL && i > 0 )
    {
        temp = head;
        chCounter = 0;
        while( temp != NULL && chCounter < (i-1) )
        {
            temp = temp->nextCh;
            chCounter++;
        }
        cout << temp->theCh;
        i--;
    }
}

int String::GetLength() const
{
    return stringLength;
}

StringModifier 类具有空的构造函数和析构函数。

Answer 1

只是一个提示:C++ 中的运行时错误与公共(public)/ protected /私有(private)访问完全无关。编译器在编译您的代码时，已经检查是否遵循了所有类成员访问规则。

运行时错误意味着您的程序中存在错误，很可能是某种内存损坏。