CODEWITHSUNDEEP
c++arrayspointers
Syneri
Syneri

Reputation: 43

Cannot access global array in main after initializing in another function

I'm having a hard time understanding why I cannot access my global 2D array in my main function after I have initialized it already in another function. EDIT: Forgot to specify that d is a known int variable declared before all of this, usually 3 or 4.

void init();

int **board;

int main(){
    init();
    cout << board[0][0];
}

void init(){
    int **board = new int*[d];
        for (int i = 0; i < d; i++){
        board[i] = new int[d];
        }

    int n=d*d;
    for (int i = 0; i < d; i++){
        for (int j = 0; j < d; j++){
            board[i][j] = n;
            n--;
        }
    }

So the moment I try to access board[0][0] in main() I get an "Access violation at 0x00000000".
I enter debugging and see that board[0][0] points to 0x000000 when being called in main() but if I try to call it in the init() function, at the end for example, it works perfectly and I can access any variable.

Upvotes: 0

Views: 476

Answers (2)

yizzlez
yizzlez

Reputation: 8805

You're creating a new temporary variable:

int **board = new int*[d];

This is a memory leak and you cannot access the memory after the function. You can just do this:

board = new int*[d]; //remember to delete []!

I see you have tagged your question [c++]. If this is the case, you should be using the standard library instead of dealing with raw pointers. std::vector and std::array come to mind.

Upvotes: 2

Yu Hao
Yu Hao

Reputation: 122383

void init(){
    int **board = new int*[d];

Here, you are defining a local variable board in the function which blocks the global variable board.

Instead, assign the value directly, don't define another variable:

void init(){
    board = new int*[d];

Upvotes: 0

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