I know it's going a long way back, but did you ever find a resolution to this? http://www.haskell.org/pipermail/cabal-devel/2009-June/005396.html Context: In my project the compilation of the C++ takes a long time (I'm working on wxHaskell) and I'm trying to avoid having to rebuild everything each time I make a change to the library. I've already written some code which will filter my "c-sources" of files which haven't changed since the last build (it uses gcc -M [1] for dependency tracking and stores the modified times in a file; I know, gcc dependant, I'm sorry). So now it doesn't recompile .cpps unless it has to, and all the .o files are sat waiting to be linked in "/dist/build/src/cpp/", but, of course they are not linked in to the library because they aren't in "c-sources". Dave, [1] http://gcc.gnu.org/onlinedocs/cpp/Invocation.html