Setup doesn't know Cabal's version

Good morning, I'm currently migrating Gtk2hs to use Cabal to build. There is one issue that makes it really difficult to build Setup.hs files that work with several Cabal versions, namely that the version of Cabal itself is not passed to Setup.hs via CPP #defines. Thus, even though I can portably pre-process my Setup.hs scripts, I cannot reliably write code that works with Cabal 1.6 and 1.8. Am I missing something? Furthermore, I cannot build an executable that depends on the library being built in the same Cabal file. Is that intentional? Cheers, Axel.