CODEWITHSUNDEEP
carrayspointersmultidimensional-array
verrochio
verrochio

Reputation: 1662

C multidimensional array heap assignment

I have a bunch of multidimensional arrays in C.

They look like this: (they are chars because ints in c take 4 bytes of memory instead of 1 byte for chars they are not used as strings)

char booting[96][25] = {{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},{0x00,0x18,0x18,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},{0x06,0x7e,0x7c,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00} ... .. ..

They are 2400 chars long and I have many of them. If I do this with a couple of them it works ok and i can acces them with:

char current_pixel = booting[34][2];

But after 9 or 10 arrays defined like this although it compiles ok, at runtime I get a StackOverflow error.

Question is: What is a better way to assign them on heap and to still keep accessing them like they are normal arrays on stack?

ps. I have looked around but still did not find exactly what I was looking for. Thanks for bearing with me!

Upvotes: 1

Views: 472

Answers (2)

Neil Kirk
Neil Kirk

Reputation: 21773

vector< vector< char > > booting(y_size, vector< char >(x_size, starting_value));

Access this way (x and y may be opposite to what you expect)

for (int y = 0; y < y_size; y++)
{
    for (int x = 0; x < x_size; x++)
    {
        cout << booting[y][x];
    }
}

Upvotes: 1

user529758
user529758

Reputation:

Either declare them as a global variable or as static so that they don't take up stack space:

static char booting[96][25] = { { 0x00, ... }, ... };

Or use malloc() for dynamic memory allocation:

char (*booting)[25] = malloc(96 * sizeof(*booting));

Upvotes: 5

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