Fixing Haddock with OS X

gistfile1.txt

I have had problems getting Haddock to function properly on OSX.
See for example:
https://github.com/haskell/cabal/issues/1790

Apparently there is an issue with OS X because it uses Clang, and its
C preprocessor is doing something funny.  Previously people reported fixes
by having Haddock pass "-optP-P" to the C compiler, but this has not worked
for me.

Confusing the whole thing is that on OS X /usr/bin/gcc is actually Clang.

Currently the easiest fix is just to make GHC use GCC rather than the
Apple-provided Clang.  To do this, install gcc with Macports.  Be sure
to use "port select" to actually activate GCC; otherwise the usual
names such as "/opt/local/bin/gcc" will not be present.

Then, follow the directions left by Carter Schonwald here:

http://stackoverflow.com/a/20352421/1017252

but when editing the file, also change the value for "Haskell CPP command" to
"/opt/local/bin/gcc".

As of 2015-01-19 that fixed things.