Just wanted to report on the steps/hacks to a successful build of GHC HEAD on OS X 10.9 thanks to help from Carter Schonwald and Austin Seipp.

1) I installed LLVM 3.4

brew install llvm --with-clang --HEAD

2) I used this build.mk:

3) Austin let me know I needed to pass "-x assembler-with-cpp" to clang when in preprocessor mode, so I wrote a wrapper clang.hs, compiled it, put it in my path, and changed /usr/local/lib/ghc-7.6.2/settings to use it. (it also passes some flags Carter suggested, along with extra include flags, which were necessary as of a couple weeks ago but might have been fixed in the newer DPs)

4) I used 

./configure --with-gcc=clang 

(where clang is the wrapper script above)

5) "inplace/bin/mkdirhier" bootstrapping/. failed mysteriously, so I manually created bootstrapping/ in the ghc build dir.

6) DTrace failed with an "unsupported compiler" error during compilation, so I killed that section in configure.ac

7) I got the error:

I hacked through this by manually find-and-replacing WORD_SIZE_IN_BITS with 64 in Type.hs.

make && make install then ran to completion and some simple test programs seem to compile and run fine.

Cheers

Luke