[Haskell-cafe] Compiling Setup.hs with -threaded

I found a weird bug at, https://bugs.gentoo.org/show_bug.cgi?id=537500 There is an awesome tool called shellcheck: git clone https://github.com/koalaman/shellcheck.git and we want to run its test suite. Basically: * If you run the test suite using runghc, then it works fine. * If you compile Setup.hs to setup, then the test suite hangs. * But if you compile Setup.hs to setup using -threaded, it works? Normally I would blabber on about what I think the problem could be, but the WTF factor here is just too high. Should we (always?) be compiling Setup.hs with -threaded? Or is this a bug in the runtime or a library or REALITY ITSELF?