I've just come across a subtle build issue (as haskell-platform just
got updated, I thought I might give it a try) The scenario is

* OSX 10.7 (everything is up to date with xcode etc... the usual)
* The 32bit version of Haskell Platform 2012.2

The issue is when libdiskfree.c is compiled and linked to git-annex, 
OSX defaults to a 64bit binary, thus...

        Linking git-annex ...
        ld: warning: ignoring file Utility/libdiskfree.o, file was built for unsupported file format which is not the architecture being linked (i386)
        Undefined symbols for architecture i386:
          "_diskfree", referenced from:
              _UtilityziDiskFree_zdwa_info in DiskFree.o
        ld: symbol(s) not found for architecture i386
        collect2: ld returned 1 exit status
        make: *** [git-annex] Error 1

You can either compile up the c library in a 32bit mode if you have the 32bit 
version of Haskell Platform installed as in the following example

        laplace:git-annex jtang$ cc  -m32  -c -o Utility/libdiskfree.o Utility/libdiskfree.c
        Utility/libdiskfree.c: In function ‘diskfree’:
        Utility/libdiskfree.c:61: warning: ‘statfs64’ is deprecated (declared at /usr/include/sys/mount.h:379)
        laplace:git-annex jtang$ make
        ghc -O2 -Wall -ignore-package monads-fd -outputdir tmp -IUtility -DWITH_S3 --make git-annex Utility/libdiskfree.o

        Utility/Touch.hs:1:12:
            Warning: -#include and INCLUDE pragmas are deprecated: They no longer have any effect

        Utility/Touch.hs:2:12:
            Warning: -#include and INCLUDE pragmas are deprecated: They no longer have any effect

        Utility/Touch.hs:3:12:
            Warning: -#include and INCLUDE pragmas are deprecated: They no longer have any effect

        Utility/Touch.hs:4:12:
            Warning: -#include and INCLUDE pragmas are deprecated: They no longer have any effect
        Linking git-annex ...

Or else just install the 64bit haskell platform. I'm not too sure where
you would but the intelligence to detect 32 or 64 outputs from the
different compilers. I suspect checking what ghc outputs then putting in
the appropriate -m32 or -m64 for the c compiler is the right thing to do. 
Or just telling users to use the 64bit version of the haskell platform?
It may also be possible to get osx's c compiler to output a universal binary 
to give you everything, but that be going down the _being too platform 
specific route_.

> [[done]], it'll detect this and force -m32. --[[Joey]]