Creating an 2-dimensional array of a struct results in crash

Question

I am trying to generate a two-dimensional array of a struct, but this results in the program not launching. The window freezes and the program quits after a few

Answer 1

You are allocating 801 * 401 (=321201) elements of struct absCell on the stack. Assuming you have a 32bit machine it is 2569608 Byte (~2.45 MB). According to this it is blowing up your stack.

Move the elements to heap like:

class Field {
public:
    static const int minX = -400;
    static const int maxX = 400;
    static const int minY = 0;
    static const int maxY = 400;

    Field() {
        cells = new absCell*[maxX - minX + 1];
        for(int i=0; i<maxX - minX + 1; i++)
            cells[i] = new absCell[maxY - minY + 1];
    }

    ~Field() {
        for(int i=0; i<maxX - minX + 1; i++)
            delete[] cells[i];

        delete[] cells;
    }

private:
    struct absCell {
        unsigned char material;
        unsigned char health;
    }**cells;
};

Update

Material and health can be saved in a char. Accessing health you have to recalculate it:

put -> x*100
get -> x/100

Update 2

Except you have some reasons, using a vector is most likely the better option, as Mark B 's answer describes.

Answer 2

My guess is you're hitting the stack limit. When you make that array like it is its trying to put 801*401*8 bytes on your stack. I did a quick compile and was having crashes until I lowered the numbers for your various mins and maxes.

Answer 3

Based on update note:

The first thing you can do is easily optimize your struct for space by using unsigned char for each attribute, using a fixed-point representation for your existing float (for example 0.23 would be stored as the integer 23).

Then store the structs on the heap with vector instead of an array:

    struct absCell {
        unsigned char material;
        unsigned char health;
    };
    std::vector<std::vector<absCell> > cells_;

Then set up the constructor:

Field() : cells_(maxX - minX + 1, std::vector<absCell>(maxY - minY + 1)) {}

Answer 4

If I got your snippet right way, you're trying to create an array. Allocation of the array is stack-based, with more than 2 Mb size required. There may be a chance that your stack has less than that 2Mb available, thus the code crashes right at the moment you're entering the function.

Try to allocate the same array dinamically.