I believe variables are usually allocated onto the stack in reverse order. So first a 4-byte allocation for the pointer to k, then maybe a word padding (for optimization with 64-bit platforms), then ... in the first example, a 16-byte boundry for j. Then another 4- or 8-byte boundary for i. But when I say reverse-order, I mean they are "pushed" "down" the stack. But they are read "up" the stack. So that j[0] is very close to i.

This might help explain going on, as you can imagine uninitialized parts of the stack having different values depending on where in the stack they are located. Try adding a function that has an "interesting" stack and calling this new function just before your function is called. You might experience different results each time.