I've noticed a strange behaviour with ghc's -osuf flag: % cat >Test.hs {-# LANGUAGE ForeignFunctionInterface #-} module Test where import Foreign foreign import ccall "wrapper" c_callback :: Int -> IO (FunPtr Int) % ghc-7.0.3 -v -c -osuf .hs.o Test.hs % ls Tes_stub.hs.o Test.hs Test_stub.c Test.hi Test.hs.o Test_stub.h Notice that the .o for the _stub.c has acquired the .hs.o suffix, but the last 't' of 'Test' was chopped off. I tried the same test with the latest ghc-7.4, and it doesn't generate a Test_stub.c at all, though there is a Test_stub.h. But I guess it sidesteps the question of whether -osuf should apply to the _stub.c (I feel like it shouldn't, since it's a c file compiled by cc, not by ghc). I'm curious about why ghc no longer seems to need _stub.c files. I'd test in more details, but runghc ghci for 7.4 is segfaulting unpredictably so I think there are larger problems here.