FD_ZERO is apparently defined as 32 bytes on an R/Pi 3:
uname -a
Linux ubuntu 4.4.0-1029-raspi2 #36-Ubuntu SMP Wed Oct 19 14:38:48 UTC 2016 armv7l armv7l armv7l GNU/Linux
I get the following compile error on an R/Pi 3 running latest version of ubuntu:
swift build
Cloning https://github.com/czechboy0/Redbird.git
HEAD is now at bb2ac0e Updated Swift to 08-15 (#38)
Resolved version: 0.10.0
Cloning https://github.com/czechboy0/Socks.git
HEAD is now at 460dc7f Merge pull request #73 from vapor/gm
Resolved version: 0.12.2
Compile Swift Module 'SocksCore' (14 sources)
/home/ubuntu/BlueCycles/linux/Packages/Socks-0.12.2/Sources/SocksCore/FDSet.swift:34:20: error: cannot assign value of type '(Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int)' to type '(__fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask, __fd_mask)' (aka '(Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int)')
set.__fds_bits = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<unknown>:0: error: build had 1 command failures
error: exit(1): /usr/bin/swift-build-tool -f /home/ubuntu/BlueCycles/linux/.build/debug.yaml