指针数组的C ++错误:: EXC_BAD_ACCESS

Question

I keep getting the error message, exc_bad_access code=1 for my line

asize = *(***(y) + **(y + 1));

in the summation function. I dont quite understand what to do with this error, but i know that it is not a memory leak. I am trying to get the values stored in the y pointer array, add them, and store it in the variable asize.

void allocArr (int **&x, int ***&y, int **&q, int ****&z)
{
    x = new int *[2];
    y = new int **(&*x);
    q = &*x;
    z = new int ***(&q);
}


void putArr(int **&x, int &size1, int &size2)
{
    *(x) = *new int* [size1];

    *(x + 1) = *new int* [size2];

}

void Input (int **&x, int *&arr, int &size1,int &size2, int a, int b)
{

    cout << "Please enter 2 non-negative integer values: "<< endl;

    checkVal(size1, a);
    checkVal(size2, b);
    putArr(x, size1, size2);

    arr[0] = size1;
    arr[1] = size2;

    cout << x[0];
}


void summation(int ***&y, int *&arr)
{
    int asize = 0;
    asize = *(***(y) + **(y + 1));
    **y[2] = *new int [asize];

    *(arr + 2) = asize;

}

int main()
{
    int size1, size2;
    int a = 1, b = 2;

    int** x;
    int*** y;
    int** q;
    int**** z;

    int *arr = new int [2];

    allocArr(x, y, q, z);
    Input(x, arr, size1, size2, a, b);
    summation(y, arr);
    display(z);


}

Thank you for the help. Im really struggling here...

Answer 1

Not sure how you got started with the code. The code can be simplified quite a bit to help you, and readers of your code, understand what's going on.

Function allocArr

The lines

y = new int **(&*x);
q = &*x;

can be

y = new int **(x);  // &*x == x
q = x;

Function putArr

You have the function declaration as:

void putArr(int **&x, int &size1, int &size2)

It can be changed to:

void putArr(int **x, int size1, int size2)

without changing how you are using the variables.

Your code in the function seems strange. Did you mean for x[0] and x[1] to point to an array of size1 and size2 int s, respectively? If you did, the code would be:

x[0] = new int[size1];
x[1] = new int[size2];

If you don't mean the above, it's hard to figure out what you are trying to do with your code.

Function Input

You have the function declaration as:

void Input (int **&x, int *&arr, int &size1,int &size2, int a, int b)

It can be changed to:

void Input (int **x, int *arr, int &size1,int &size2, int a, int b)

without changing how you are using the variables.

You are calling a function checkVal , but your posted code doesn't have that function. It's not clear what that function is doing. You have the line

cout << "Please enter 2 non-negative integer values: "<< endl;

just before the calls to checkVal . Presumably, checkVal reads the input and stores them in size1 in the first call and size2 in the second call. It's not clear how the second argument to checkVal is used.

And then, you have the line:

cout << x[0];

It's not clear what you wish to accomplish from printing an int* to cout . Perhaps it was part of your debugging code. The line doesn't change anything else in the program. It's just strange to see it there.

Function summation

You have the function declaration as:

void summation(int ***&y, int *&arr)

It can be changed to:

void summation(int ***y, int *arr)

without changing how you are using the variables.

In this function, you have the expression:

asize = *(***(y) + **(y + 1));

What do you get when you evaluate ***(y) ?

***(y) = **(*y) = **(x) = *(*x) = *(x[0]) = uninitialized value from the line:

x[0] = new int[size1];

You will get unpredictable behavior when you use an uninitialized value.

The second term of the line, **(y + 1) is the worse culprit.

You allocated memory for y as:

y = new int **(&*x);

It's a pointer to a single object of type int** , not an array. y+1 is not a valid pointer. Dereferencing (y+1) leads to undefined behavior. In your case, you are seeing exc_bad_access , which makes sense now since you are accessing memory that is out of bounds.

Since I don't know what you are trying to compute in that expression, it's hard for me to suggest something useful. I hope you have enough to take it from here.