Hello, I put an ugly kludge(on my laptop) in the unix.cabal file For the includes-dir "attribute" I explicited specified the path to the cygwin include directory. The Unix package build gets farther and then gets errors. At this point, it appears that the cygwin sys/types.h has a "bug" .. id_t is not defined but id_t is referenced by sys/resources.h/(getpriority/setpriority). Please see see http://www.opengroup.org/onlinepubs/000095399/functions/setpriority.html for getpriority function signature. In any case, I want compare the Linux sys/types.h include. To summarize: 1) I am just learning about the .cabal file format from the Cabal .pdf. In any case, it appears that for the case of cygwin that unix.cabal is deficient. 2) It also appears that the cygwin sys/types.h failed to defined id_t which is needed by sys/resources.h which in turn is needed by System/Posix/DynamicLinker/Module.hsc (error at line 57 where HsUnix.h is refd .. and in HsUnix.h at line # 38 sys/resource.h is referenced.) I can provide a stderr "log". Kind regards, Vasya