I tried to build the head of GHC and it works fine the first time around. Compiling it with itself fails to build GHCi due to the new library system:

/home/as49/local/bin/ghc-5.03 -DGHCI -cpp -fglasgow-exts -Rghc-timing -I. -IcodeGen -InativeGen -Iparser -iutils:basicTypes:types:hsSyn:prelude:rename:typecheck:deSuga r:coreSyn:specialise:simplCore:stranal:stgSyn:simplStg:codeGen :absCSyn:main:profiling:parser:usageSP:cprAnalysis:compMan:ndp Flatten:nativeGen:ghci -package concurrent -package posix -package util -recomp -Rghc-timing -H16M -O -fvia-C -monly-3-regs -c utils/PrimPacked.lhs -o utils/PrimPacked.o

utils/PrimPacked.lhs:55: Ambiguous occurrence `unsafePerformIO' It could refer to either `PrelIOBase.unsafePerformIO', imported from Foreign at utils/PrimPacked.lhs:40 or `GHC.IOBase.unsafePerformIO', imported from GlaExts at utils/PrimPacked.lhs:33

This is very odd - it looks like you've got the .hi files for two versions of GHC mixed up somehow. There shouldn't be a PrelIOBase at all in the latest GHC, and yet it seems to be picking one up from somewhere. When doing a 2-stage bootstrap you can run the first stage directly from the build tree without installing it - just point the second stage at ghc/compiler/ghc-inplace in the first stage (i.e. ./configure --with-ghc=/some/where/ghc/compiler/ghc-inplace). Cheers, Simon