The who_points_at thing prints out something like Searching for pointers to 0xnotdead *0xalsonot points at 0xnotdead Address 0xalsonot is 168 bytes inside a block of size 232 alloc'd but when I need to chain backwards from that block I need to compute 0xalsonot - 168 which is hex minus decimal, which means I need to do it 3 times to sure I subtracted the right thing from the right other thing and converted the right thing from decimal to hex. Which is more than my poor little brain can handle reliably :-) THanks