I've hit a build failure when trying to build HEAD on Mavericks. I've logged a bug here with a lot of detail: https://ghc.haskell.org/trac/ghc/ticket/8528.

When using alex 3.1.2, some of the generated files have spaces preceding preprocessor statements, while alex 3.1.0 doesn't do this. I guess this is possibly an alex bug, but this is my first time building GHC so I'm not really sure how the ecosystem works :)

Huge shout-out to Carter S. for giving me a ton of help in nailing down this issue!

- Nick