Installation question: cpphs, unix, and HEAD

[Kathleen Fisher]

I am trying to install the cpphs package with the current HEAD version of Haskell.  When I ask cabal to do the installation, I get the following error:

> Babylon:/Users/kfisher/sw/ghc-head-libraries/cpphs-1.11> ~/.cabal/bin/cabal install cpphs  -w ~/ghc-head/bin/ghc --with-haddock=/Users/kfisher/ghc-head/bin/haddock --package-db=/Users/kfisher/ghc-head/lib/ghc-6.13.20100831/package.conf.d
> Resolving dependencies...
> cabal: cannot configure unix-2.4.0.1. It requires base ==4.2.*
> For the dependency on base ==4.2.* there are these packages: base-4.2.0.0,
> base-4.2.0.1 and base-4.2.0.2. However none of them are available.
> base-4.2.0.0 was excluded because base-4.3.0.0 was selected instead
> base-4.2.0.0 was excluded because of the top level dependency base -any
> base-4.2.0.1 was excluded because base-4.3.0.0 was selected instead
> base-4.2.0.1 was excluded because of the top level dependency base -any
> base-4.2.0.2 was excluded because base-4.3.0.0 was selected instead
> base-4.2.0.2 was excluded because of the top level dependency base -any
> Babylon:/Users/kfisher/sw/ghc-head-libraries/cpphs-1.11>

This seems odd for multiple reasons:

1. I already have unix-2.4.0.1 installed (it was a boot library).  
   So why is cabal trying to install it again?
2. Given that I already have unix-2.4.0.1 installed and my base is 4.3.0.0, 
   why does unix-2.4.0.1 report that it needs base==4.2.*?
3. Given that the cabal file for cpphs says it needs base < 6 and haskell98 and
   my package database satisfies both of those constraints, why is cabal
   trying to install anything else?

I include the listing of my installed packages below.

What is going on is probably obvious to someone who knows more about the library installation process.  
Any ideas?  

Kathleen

> Babylon:/Users/kfisher/sw/ghc-head-libraries/cpphs-1.11>~/ghc-head/bin/ghc-pkg list
> /Users/kfisher/ghc-head/lib/ghc-6.13.20100831/package.conf.d:
>     Cabal-1.9.2
>     HUnit-1.2.2.1
>     array-0.3.0.0
>     base-4.3.0.0
>     bin-package-db-0.0.0.0
>     (binary-0.5.0.2)
>     bytestring-0.9.1.7
>     containers-0.3.0.0
>     directory-1.0.1.2
>     dph-base-0.4.0
>     (dph-par-0.4.0)
>     (dph-prim-interface-0.4.0)
>     (dph-prim-par-0.4.0)
>     (dph-prim-seq-0.4.0)
>     (dph-seq-0.4.0)
>     extensible-exceptions-0.1.1.2
>     ffi-1.0
>     filepath-1.2.0.0
>     (ghc-6.13.20100831)
>     ghc-prim-0.2.0.0
>     (haskell2010-1.0.0.0)
>     haskell98-1.0.1.1
>     hpc-0.5.0.5
>     integer-gmp-0.2.0.0
>     mtl-1.1.0.2
>     old-locale-1.0.0.2
>     old-time-1.0.0.5
>     pretty-1.0.1.1
>     process-1.0.1.3
>     random-1.0.0.2
>     regex-base-0.93.2
>     regex-posix-0.94.4
>     rts-1.0
>     syb-0.2.1
>     template-haskell-2.4.0.0
>     time-1.2.0.3
>     unix-2.4.0.1