I sent this message to cabal-devel. After reading the cabal website more carefully I noticed I should sent questions here. Apologies for the noise in cabal-devel. Hello, I have cabal file which specifies some c-sources to compile together with the usual Haskell stuff. I noticed that cabal automatically passes -optc-O2 to GHC when compiling C files. If I specify some additional cc-options in my cabal file they just get prepended to the list of options passed to ghc. How do I get rid of the -optc-O2? With my current cc-options "-D_OPENMP -O3 -funroll-loops" GHC is invoked like this during a "cabal build": /usr/bin/ghc -Ilevmar-2.4 -package base-3.0.3.1 -optc-D_OPENMP -optc-O3 -optc-funroll-loops -optc-O2 -odir dist/build -c levmar-2.4/lm.c I don't know which -optc-O? will be picked by the C compiler. Normally -O2 is ok, but in this case I really want -O3. Thanks in advance, Roel van Dijk