YenTheFirst/ruby-prof — comment on commit bed57d10e680f115b0f212bfab47d6efdc422651
File:  line 0
By YenTheFirst:

I'm not 100% positive, but I think it's based on the most significant bit, after the multiplication. for tv_sec such that tv_sec * 1e9 < 2^31, it DOES drop in 0s (on my machine, at least), which is why it only failed some of the time. once tv_sec is >= 3, tv_sec * 1e9 is > 2^31, and everything is 0xFF.