-davenant:~/junk> cat t.hs main = error "bang!" -davenant:~/junk> ghc t.hs -davenant:~/junk> ./a.out Fail: bang! -davenant:~/junk> ghc -prof -auto -auto-all t.hs -davenant:~/junk> ./a.out Segmentation fault (core dumped) -davenant:~/junk> ghc --version The Glorious Glasgow Haskell Compilation System, version 4.06 -davenant:~/junk> This is with GHC 4.06, compiled by me for Linux/i386 using the Debianisation support files which came with Debian's GHC 4.05.19991206-1 and (IIRC) the use of cvs update. Ian.