I'm aware of arithmetic overflow, thanks. It was the subject of my research (which will eventually be open source, watch www.peripetylabs.com/publications/ if you're interested). See my sizeop library in the meantime: https://bitbucket.org/eliteraspberries/sizeop

I am not dismissive of the problem. I just know from experience that the chances of code like that being fixed at all, let alone correctly, is near zero.