【发布时间】：2016-11-12 04:19:35
【问题描述】：
我刚刚编译了这段代码，它显示了这个错误：
在 ConsoleApplication5.exe 中的 0x0F640E09 (ucrtbased.dll) 处引发异常：0xC0000005：访问冲突写入位置 0x014C3000。我真的不知道这个错误意味着什么，因为我已经使用 C++ 几个月了，我也尝试在任何其他网站上寻找帮助，但我没有找到任何帮助。
对于这段代码，我只能使用 c-string 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/函数。
#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;
}
【问题讨论】：
-
strlen(chars)的长度不足以容纳整个 c 字符串。 -
此代码优于it was when you last asked about it。您仍在比较指针而不是值，并且您的 operator+ 仍然滥用 strcat。
-
您的
MyString赋值运算符（operator=）在哪里？您的main程序没有进行彻底的测试，因为它不会在任何地方测试temp1 = temp2;。 -
另外，你只需要写
operator <和operator==完整的实现。所有其他比较运算符都可以根据这两个运算符编写——无需从头开始编写其他运算符。例如operator !=就是return !(newWord == newWord2); -
让我们回到基础。您不允许使用 C++ 字符串，但您可以使用现有的所有其他 C++ 功能吗？这是为什么呢？
标签： c++ arrays pointers dynamic-memory-allocation c-strings