[danfuzz]

You can blame me for those wasted four bytes (or, perhaps, that wasted terabyte in the aggregate).

The original idea was that on big-endian machines, the resulting .odex would be endian-swapped compared to the original .dex, and this field would provide a reasonably-blatant indication. This would probably help with debugging more than anything else (maybe help with security, but not much), because there's no reason anyone would drop a little-endian .odex file on a big-endian machine (or a big-endian one on a little-endian machine).

We wrote (most of?) the code to get the vm working on big-endian systems, but within Google we never shipped any big-endian hardware AFAIK. I have my doubts that anyone ever did.