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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