Who defines __GLASGOW_HASKELL__, __HADDOCK__, etc?

So far, I had assumed that every tool defined its own macro, but it seems that __GLASGOW_HASKELL__ is defined by ghc and by cabal, while __HADDOCK__ is defined only by the latter. Is that right? Context is http://trac.haskell.org/haddock/ticket/48 , ie, how to adapt sources that had to bypass or help along haddock1 for haddock2 (which should need fewer workarounds). Claus