Hi, I tried profiling a program with the GHC 6.12 release candidate. I got this: $ ghc -O1 -prof -auto-all --make CommsTime.hs [1 of 1] Compiling Main ( CommsTime.hs, CommsTime.o ) Linking CommsTime ... /usr/bin/ld: cannot find -lHSffi_p collect2: ld returned 1 exit status Googling turned up this link, which suggests this problem was fixed earlier this year: http://www.mail-archive.com/cvs-ghc@haskell.org/msg13546.html However: $ find ~ -iname "libHSffi*" /home/nccb2/lib/ghc-6.12.0.20091010/libHSffi.a /home/nccb2/lib/ghc-6.12.0.20091010/libHSffi-ghc6.12.0.20091010.so /home/nccb2/ghc-6.11.20090915/libffi/libHSffi.a /home/nccb2/ghc-6.11.20090915/libffi/libHSffi-ghc6.11.20090915.so /home/nccb2/ghc-6.12.0.20091010/libffi/libHSffi-ghc6.12.0.20091010.so /home/nccb2/ghc-6.12.0.20091010/libffi/libHSffi.a /home/nccb2/ghc-6.12.0.20091010/libffi/libHSffi_p.a This seems to indicate that the library is built (/home/nccb2/ghc-6.12.0.20091010 is where I built GHC) but not installed on my system. This is a Debian 32-bit system, and I don't remember passing any options to the GHC configure command besides --prefix. Neil.