I am using Ubuntu 14.04 64-bit. Here is my C++ code to see how memory is used.
int main() {
int **ptr;
ptr = new int* [2];
cout << &ptr << " -> " << ptr << endl;
for (int r = 1; r <= 2; r++) {
ptr[r-1] = new int [2 * r];
cout << &ptr[r-1] << " -> " << ptr[r-1] << endl;
for (int c = 0; c < 2 * r; c++) {
ptr[r-1][c] = r * c;
cout << &ptr[r-1][c] << " -> " << ptr[r-1][c] << endl;
}
}
return 0;
}
Here is my output:
0x7fff09faf018 -> 0x1195010
0x1195010 -> 0x1195030
0x1195030 -> 0
0x1195034 -> 1
0x1195018 -> 0x1195050
0x1195050 -> 0
0x1195054 -> 2
0x1195058 -> 4
0x119505c -> 6
I expected the OS would allocate memory contiguously. So ptr[0][0] would be at 0x1195020 instead of 0x1195030!? What does OS use at 0x1195020 - 0x119502F, 0x1195038 - 0x0x119504F for?
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