Valgrind - invalid read and write

I have a mystery that I do not have an answer for. I have written a simple program in C++(and I should say that I'm not a professional C++ developer). Here it is: ``` #include <iostream> int main(){ const int SIZE = 1000; int pool1 [SIZE]; int pool2 [SIZE]; int result [SIZE*SIZE]; //Prepare data for(int i = 0; i < SIZE; i++){ pool1[i] = i + 1; pool2[i] = SIZE - i; } //Run test for(int i = 0; i < SIZE; i++){ for(int j = 0; j < SIZE; j++){ result[i*SIZE + j] = pool1[i]*pool2[j]; } } return 0; } ``` The program seems to work (I use it as a kind of benchmark for different languages) but then I ran it with valgrind and it started complaing: ``` ==25912== Invalid read of size 4 ==25912== at 0x804864B: main (in /home/renra/Dev/Benchmarks/array_iteration/array_iteration_cpp) ==25912== Address 0xbee79da0 is on thread 1's stack ==25912== Invalid write of size 4 ==25912== at 0x8048632: main (in /home/renra/Dev/Benchmarks/array_iteration/array_iteration_cpp) ==25912== Address 0xbeaa9498 is on thread 1's stack ==25912== More than 10000000 total errors detected. I'm not reporting any more. ==25912== Final error counts will be inaccurate. Go fix your program! ``` Hmm, does not look good. Size 4 probably refers to the size of int. As you can see at first I was using SIZE 1000 so the results array would be 1,000,000 ints long. So, I thought, it was just overflowing and I needed a larger value type(at least for the iterators and the array of results). I used unsigned long long (the max of unsigned long is 18,446,744,073,709,551,615 and all I needed was 1,000,000 - SIZE*SIZE ). But I'm still getting these error messages (and they still say the read and write size is 4 even though sizeof(long long) is 8). Also the messages are not there when I use a lower SIZE, but they seem to kick in exactly at SIZE 707 regardless of the used type. Anybody has a clue? I'm quite curious :-).