Subject: bug#2790: emacs 22.1.1 cannot open 5GB file on
64GB 64-bit GNU/Linux box

>> Personally, I would change INT_MAX/4 to LONG_MAX/4,
> This is wrong, see also make_gap_larger. The range for buffer positions
> is still limited by the range of int.

Every place where that is the case is a bug (and yes, there are many
still). We should remove the check in make_gap_larger, BTW.