2010/7/10 Günther Schmidt <gue.schmidt@web.de>
Hi,

does anyone here have experience what it takes to build ghc-6.12.3 from source on Open Solaris, with binary ghc-6.12.1 installed?

This isn't specific to Open Solaris, but it's where I would start:
http://hackage.haskell.org/trac/ghc/wiki/Building/Solaris

See also:
http://hackage.haskell.org/trac/ghc/wiki/Platforms#Tier2platforms

Jason