C++ 读取访问冲突错误

Question

I am currently getting an "0xC0000005: Access violation reading location 0xcccccce0." error and I have tried diagnose the problem...I think the problem comes in when my rule of 3 that I have defined comes in play and points me to here.

size_type size() const
    {   // return length of sequence
    return (this->_Mysize); <---------------------this line
    }

I'm actually not sure if there is any problem at all, I have been dwelling on this for days on end.

Below is my rule of three

ArrayStorage::ArrayStorage(){
     myArray = new string[7079];
}

ArrayStorage::~ArrayStorage(){
    delete[] _data;
    delete[] myArray;
}

ArrayStorage::ArrayStorage(const ArrayStorage &A) {
    _size = A.size();
    _data = new string [size()];
    for (int i = 0; i < size(); ++i)
        _data[i] = A[i];
}

ArrayStorage& ArrayStorage::operator=(const ArrayStorage &A){
    if (this != &A) {
        delete [] _data;
        _size = A.size();
        _data = new string [A.size()];
        for (int i = 0; i < size(); ++i) {
             _data[i] = A[i];
        }
    }
    return *this;
}

const string& ArrayStorage::operator[](int i) const{
    assert((i >= 0) && (i < size()));
    return _data[i];
}

string& ArrayStorage::operator[](int i){
    assert((i >= 0) && (i < size()));
    return _data[i];
}

Answer 1

When uninitialized, stack variables are filled with 0xCC bytes if compiled with msvc. So 0xcccccce0 is probably the result of "this" being an uninitialized pointer variable on the stack plus _MySize offset in the object structure.

Answer 2

There are a number of obvious problems with your code: your destructor, for example, does a delete [] _data and a delete [] myArray , but _data is never initialized in your default constructor, and myArray is never initialized in the copy constructor. And you're assignment operator can leave the object in an invalid state, if eg the new fails. (In general, if you have to test for self assignment, it's almost certain that your assignment operator is broken.) Either of these problems result in undefined behavior which could corrupt the free space arena, causing who knows what problem later.

Still, it would be interesting to see where size was called. The error message suggests an invalid this ; that you've called the function with an invalid address.

Answer 3

在这篇小文章中，您可能会遇到其他类型的内存模式： http ： //www.docsultant.com/site2/articles/debug_codes.html

Answer 4

Breakpoints/watchlist. I'm guessing that this is null.

Answer 5

I'd guess it's a pointer problem but it's impossible to tell without a stacktrace/backtrack. Somewhere you are calling size() at an adress where you think there's an ArrayStorage but there isn't. Since it's 0xccccce0 I'd go with an unitialized pointer.

For example, do you have something like this

ArrayStorage storage1;
ArrayStorage* storage2;
*storage2 = storage1;

That would result in this or a similar error, invalid this pointer.

And why are you writing your own std::vector?