To me, Marc's title and penultimate sentence imply that he thinks that mmap should not accept such files. (But he should speak for himself.) As I said, not accepting such files could break working code.

As for the alternative of 'fixing' methods: Is it only slicing or other methods, even *every* method that 'misbehaves' when attempting to read (or write) beyond the 1 gig limit? I am guessing the last. If so, just about every method (inherited from bytearray, like slicing, or mmap specific) would need a fix conditional on the build and access location (and OS or hardware?).

Even for slices, what change would you (or anyone) make? Keep in mind that is it a *feature* of slices that they generally always work, and that this is specifically true of bytearrays. ("Memory-mapped file objects behave like both bytearray and like file objects.") 

I am actually a bit surprised that the limit is 1 gb rather than 2, 3, or 4 gb. Is it the same on *nix? What is the limit for a bytearray on Win 7?