generate random float in for loop

I have a very simple for loop to generate some random float numbers:

int dim = 6;
int n = 100000;

int size = n * dim;

float data[size],r;
for(int i = 0; i < size; i++)
{
    r = static_cast <float> (rand()) / static_cast <float> (RAND_MAX);
    data[i] = r;
}

It works fine until i increase the size of the n from 100000 to 1000000. Here is the full code on ideone: http://ift.tt/14dwdKv

Actually on my computer it works only with n=10000. Any bigger number causes a crash. No error message.