Duncan Coutts wrote:

Chris Parrott found that ghc-6.4.1 doesn't work with gcc 4.1 on amd64, although it does work on x86.

The error manifests itself as link errors due to undefined symbols:

/var/tmp/portage/ghc-6.4.1-r2/work/ghc-6.4.1/ghc/rts/libHSrts.a(Linker.o):(.data+0x48): undefined reference to `StgReturn' /var/tmp/portage/ghc-6.4.1-r2/work/ghc-6.4.1/ghc/rts/libHSrts.a(RtsStartup.o): In function `hs_add_root': RtsStartup.c:(.text+0x1a8): undefined reference to `StgRun'

Coincidentally, I just upgraded our x86_64 box to FC5, and the nightly build fell over with exactly these errors. It turns out that the HEAD already had fixes in some arch's for this, but it was fixed by making StgRunIsImplementedInAssembler() non-static. The attribute fix is better, so I've applied it consistently and merged to 6.4.2. Cheers, Simon