在ConsoleApplication5.exe中的0x0F640E09(ucrtbased.dll)引发异常:0xC0000005:访问冲突写入位置0x014C3000? [英] Exception thrown at 0x0F640E09 (ucrtbased.dll) in ConsoleApplication5.exe: 0xC0000005: Access violation writing location 0x014C3000?

问题描述

我刚刚编译了这段代码，它向我显示了此错误:
在ConsoleApplication5.exe中的0x0F640E09(ucrtbased.dll)处引发了异常:0xC0000005:访问冲突写入位置0x014C3000.我真的不知道这个错误是什么意思，因为我刚刚使用C ++几个月了，我也曾尝试在任何其他网站上寻求帮助，但没有找到任何帮助.

I just compiled this code, and it showed me this error:
Exception thrown at 0x0F640E09 (ucrtbased.dll) in ConsoleApplication5.exe: 0xC0000005: Access violation writing location 0x014C3000. I literally have no idea what this error means as I've just been using C++ for a couple months, and I've also tried looking on any other websites to look for help, but I didn't find any.

对于此代码，只允许使用c字符串函数和<cstring>库.我不能使用字符串对象或包含库.我也可以使用辅助方法/功能.

For this code, I'm only allowed to use the c-string functions and the <cstring> library. I cannot use the string object or include the library. I can also use helper methods/functions.

#include <iostream>
#include <cstring>
#include <fstream>
using namespace std;

class MyString {
public:

    //default constructor
    MyString();

    MyString(char* chars);

    //copy constructor
    MyString(const MyString &);

    int length() const;

    //destructor
    ~MyString();

    //operator overloads
    char& operator[](int index);
    friend MyString operator+(const MyString& newWord, const MyString& newWord2);
    MyString& operator+=(const MyString& newWord);
    friend ostream& operator<<(ostream& newWord, const MyString& newWord2);
    friend istream& operator >> (istream& newWord, MyString& newWord2);
    friend bool operator==(const MyString& newWord, const MyString& newWord2);
    friend bool operator!=(const MyString& newWord, const MyString& newWord2);
    friend bool operator<(const MyString& newWord, const MyString& newWord2);
    friend bool operator<=(const MyString& newWord, const MyString& newWord2);
    friend bool operator>(const MyString& newWord, const MyString& newWord2);
    friend bool operator>=(const MyString& newWord, const MyString& newWord2);

private:
    char* value;
    int size;
};

//default constructor
MyString::MyString() {

    value = 0;
    size = 0;
}

//copy constructor
MyString::MyString(const MyString& newWord) {

    //perform a deep copy to copy each of the value to a new memory
    size = newWord.size;
    value = new char[size];

    for (int ii = 0; ii < size; ii++) {
        value[ii] = newWord.value[ii];
    }
}

//constructor with an argument
MyString::MyString(char* chars) {

    size = strlen(chars);
    value = new char[size];
    for (int i = 0; i < size; i++) {
        value[i] = chars[i];
    }

}

//find length
int MyString::length() const {

    return size;
}

//find the value of each index
char& MyString::operator[](int index) {

    return value[index];
}

//operator + (concatenate)
MyString operator+(const MyString& newWord, const MyString& newWord2) {

    MyString concatenated;
    concatenated = strcat(newWord.value, newWord.value);
    return concatenated;

}

//operator += (append)
MyString& MyString::operator+=(const MyString& newWord) {

    char * newMemory = value;
    value = new char[strlen(value) + newWord.length() + 1];
    strcpy(value, newMemory);
    strcat(value, newWord.value);
    if (size != 0)
    {
        delete[] newMemory;
    }
    size = strlen(value);
    return *this;
}

//ostream operator
ostream& operator<<(ostream& newWord, const MyString& newWord2) {

    newWord << newWord2.value;
    return newWord;
}


//istream operator
istream& operator >> (istream& newWord, MyString& newWord2) {

    const int MAX = 100;
    char* ptr = new char[MAX];
    newWord >> ptr;
    newWord2 = MyString(ptr);
    delete ptr;
    return newWord;
}

//all boolean operators
bool operator==(const MyString& newWord, const MyString& newWord2) {
    if (newWord.value == newWord2.value) {
        return true;
    }
    else {
        return false;
    }
}

bool operator!=(const MyString& newWord, const MyString& newWord2) {
    if (newWord.value != newWord2.value) {
        return true;
    }
    else {
        return false;
    }
}

bool operator<(const MyString& newWord, const MyString& newWord2) {
    if (newWord.value < newWord2.value) {
        return true;
    }
    else {
        return false;
    }
}

bool operator<=(const MyString& newWord, const MyString& newWord2) {
    if (newWord.value <= newWord2.value) {
        return true;
    }
    else {
        return false;
    }
}

bool operator>(const MyString& newWord, const MyString& newWord2) {
    if (newWord.value > newWord2.value) {
        return true;
    }
    else {
        return false;
    }
}

bool operator>=(const MyString& newWord, const MyString& newWord2) {
    if (newWord.value >= newWord2.value) {
        return true;
    }
    else {
        return false;
    }
}

//destructor to release memory
MyString::~MyString() {
    delete[] value;
}

void test_copy_and_destructor(MyString S) {
    cout << "test: copy constructor and destructor calls: " << endl;
    MyString temp = S;
    cout << "temp inside function test_copy_and_destructor: " << temp << endl;
}

int main() {

    MyString st1("abc abc");
    MyString st2("9fgth");

    cout << "Copy constructor , << operator" << endl;

    MyString  st3(st1);

    cout << "st3: " << st3 << endl;

    test_copy_and_destructor(st2);

    MyString  st4;

    cout << "operator + " << endl;

    st4 = st3 + st2;

    cout << "st4: " << st4 << endl;

    cout << "st1 + st2: " << (st1 + st2) << endl;

    cout << "operators  [ ] " << endl;

    for (int i = 0; i < st2.length(); i++)
        cout << st2[i] << " ";

    cout << endl;

    cout << "operators  += , ==, != " << endl;

    st2 += st1;

    if (st3 == st1)
        cout << "st3 and st1 are identical " << endl;
    else cout << "st3 and st1 are not identical " << endl;

    if (st2 != st1)
        cout << "st2 and st1 are not identical " << endl;
    else cout << "st2 and st1 are identical " << endl;

    cout << "operators  < , <=, >, >= " << endl;

    if (st2 < st1)
        cout << "st2 < st1 " << endl;
    else cout << "st2 is not less than st1 " << endl;

    if (st1 <= st2)
        cout << "st1 <= st2 " << endl;
    else cout << "st1 is not less than or equal to st2 " << endl;

    if (st1 > st2)
        cout << "st1 > st2 " << endl;
    else cout << "not (st1 >  st2) " << endl;

    if (st1 >= st2)
        cout << "st1 >= st2 " << endl;
    else cout << "not (st1 >=  st2) " << endl;

    cout << "operator >> " << endl;

    //Open the data file
    ifstream input("A9_input.txt");
    if (input.fail()) {
        cout << "unable to open input file A9_input.txt, Exiting..... ";
        system("pause");
        return 0;
    }
    MyString temp1;
    MyString temp2("aaa");
    input >> temp1;
    input >> temp2;
    cout << "first element of input file: " << temp1 << endl;
    cout << "second element of input file: " << temp2 << endl;
    input.close();

    cout << "MyString says farewell....." << endl;
    system("pause");
    return 0;
}

推荐答案

您的代码还有其他问题，其中大多数与比较运算符有关.

There are other issues with your code, most dealing with your comparison operators.

MyString的operator <和operator==不正确.要比较c样式的字符串，请使用strcmp，而不是==.相反，您的比较运算符正在比较指针值，而不是正在指向的数据.

Your operator < and operator== for MyString are incorrect. To compare c-style strings, you use strcmp, not ==. Your comparison operators instead is comparing pointer values, not the data that is being pointed to.

第二个问题是，您需要做的就是完全实现operator <和operator ==，因为所有其他比较运算符都可以根据这些功能实现.

The second issue is that all you need to do is fully implement operator < and operator ==, as all of the other comparison operators can be implemented in terms of these functions.

将所有内容放在一起，您的类的实现应如下所示:

Putting this all together, the implementation of your class should look something like this:

#include <cstring>
//...     
class MyString {
public:
    //...    
    friend bool operator==(const MyString& newWord, const MyString& newWord2);
    friend bool operator!=(const MyString& newWord, const MyString& newWord2);
    friend bool operator<(const MyString& newWord, const MyString& newWord2);
    friend bool operator<=(const MyString& newWord, const MyString& newWord2);
    friend bool operator>(const MyString& newWord, const MyString& newWord2);
    friend bool operator>=(const MyString& newWord, const MyString& newWord2);

private:
    char* value;
    int size;
};

bool operator==(const MyString& newWord, const MyString& newWord2) 
{ return strcmp(newWord.value, newWord2.value) == 0; } 

bool operator<(const MyString& newWord, const MyString& newWord2) 
{ return strcmp(newWord.value, newWord2.value) == -1; }

bool operator!=(const MyString& newWord, const MyString& newWord2)
{ return !(newWord == newWord2); }

bool operator<=(const MyString& newWord, const MyString& newWord2)
{ return !(newWord2 < newWord); }   

bool operator> (const MyString& newWord, const MyString& newWord2)
{ return newWord2 < newWord; }

bool operator>=(const MyString& newWord, const MyString& newWord2)
{ return !(newWord < newWord2); }

请注意，运算符使用<和==来实现其他运算符.

Note that the operators use the < and == to implement the other operators.

第三个问题是您缺少赋值运算符

The third issue is that you're missing an assignment operator

MyString& operator=(const MyString&)

如果没有此功能，则不能在不破坏内存的情况下相互分配MyString对象.

Without this function, you cannot assign MyString objects to each other without corrupting memory.

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