The Haskell toolchain has its share of weaknesses (e.g. the impurity of package builds has been painful recently), but I also feel the need to point out that GH

The Haskell toolchain has its share of weaknesses (e.g. the impurity of package builds has been painful recently), but I also feel the need to point out that GHC learned lesson 1 a long time ago: http://www.haskell.org/ghc/docs/latest/html/users_guide/separate-compilation.html#makefile-dependencies http://www.haskell.org/ghc/docs/latest/html/users_guide/sepa... Edit: I should also add that, as an expected corollary, if you use ghc -M to generate your Makefile dependencies parallel make works fine. I used ghc that way for years. I think there was a corner-case if you interrupted a parallel build, but it was easy to deal with.