Hi, when I try to use System.Posix.Semaphore.semUnlink on Ubuntu 13.04 I get the following liker error: /usr/bin/ld: /home/sol/.install/haskell/ghc-7.0.4/lib/ghc-7.0.4/unix-2.4.2.0/libHSunix-2.4.2.0.a(Semaphore__3.o): undefined reference to symbol 'sem_unlink@@GLIBC_2.2.5' /usr/bin/ld: note: 'sem_unlink@@GLIBC_2.2.5' is defined in DSO /lib/x86_64-linux-gnu/libpthread.so.0 so try adding it to the linker command line /lib/x86_64-linux-gnu/libpthread.so.0: could not read symbols: Invalid operation collect2: error: ld returned 1 exit status The issue can be reproduced by compiling -- Main.hs import System.Posix.Semaphore main :: IO () main = do semUnlink "pwsafe" with `ghc --make Main.hs`. Probably related to those changes to DSO liking: https://fedoraproject.org/wiki/UnderstandingDSOLinkChange Any chances that we fix this for previous releases, too (I'm interested in ghc-6.12.1 to ghc-7.6.3)? Cheers, Simon