(resent after being indefinitely held in fedora-haskell validation queue) Hi, 1) I have installed FC5 on 2 different machines. On my Athlon1800+ everything works perfectly. My other machine is a Pentium IV with hyperthreading, considered by Linux as SMP (x86 32). This is where problems occur 2) I have installed GHC-6.4.1 from Fedora Extras When I compile 'Omega' with it, Omega (which has a read-eval system) produces a 'mallocBytesRWX: failed to protect 0x' message I have compiled ghc-6.5... from the head. Compiled with GHC-6.4.1, I get the 'mallocBytesRWX...' message when I run 'ghci' 3) I have then patched 'RtsUtils.c' to suppress the 'barf("mallocBytesRWX...', and rerun- the compilation of ghc-6.5... 'Omega' compiled with the resulting ghc-6.5 works OK. ghci still produces the 'malloc...' error 4) When I compile ghc-6.5... with my patched ghc-6.5..., ghci does not produce the 'mallocBytesRWX' error (which is logical), but in some cases creates a 'segfault' So obviously the ghc-6.4.1 rpm is incorrect, as is the source ghc HEAD version. Probably an incorrect #ifdef here : #elif defined(openbsd_HOST_OS) || defined(linux_HOST_OS) || defined(darwin_HOST_OS) on a Pentium IV machine. And there is probably something else somewhere. Alain