Having build ghc-6.8.1 from sources revealed the following problem after installation:
> ghci -package ghc
GHCi, version 6.8.1: http://www.haskell.org/ghc/ :? for help
Loading package base ... linking ... done.
Loading package old-locale-1.0.0.0 ... linking ... done.
Loading package old-time-1.0.0.0 ... linking ... done.
Loading package filepath-1.1.0.0 ... linking ... done.
Loading package directory-1.0.0.0 ... linking ... done.
Loading package array-0.1.0.0 ... linking ... done.
Loading package containers-0.1.0.0 ... linking ... done.
Loading package hpc-0.5.0.0 ... linking ... done.
Loading package bytestring-0.9.0.1 ... linking ... done.
Loading package pretty-1.0.0.0 ... linking ... done.
Loading package packedstring-0.1.0.0 ... linking ... done.
Loading package template-haskell ... linking ... done.
Loading package unix-2.2.0.0 ... linking ... done.
Loading package process-1.0.0.0 ... linking ... done.
Loading package readline-1.0.1.0 ... linking ... done.
Loading package Cabal-1.2.2.0 ... linking ... done.
Loading package random-1.0.0.0 ... linking ... done.
Loading package haskell98 ... linking ... done.
ghc-6.8.1: internal error: unconditional relative branch out of range: jump island out of range
(GHC version 6.8.1 for powerpc_apple_darwin)
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
Abort trap