Compiling separate modules in GHC

Question

I am really struggling to do what must be a very simple thing in GHC: I have a program that works and compiles fine, but when I split it so that part of the code is in a separate module I can't get it to work. The separate module is called FICutilities

ghc -o FICutilities FICutilities.hs C:\\ghc\\ghc-6.10.1/libHSrts.a(Main.o):Main.c:(.text+0x7): undefined reference to __stginit_ZCMain' C:\\ghc\\ghc-6.10.1/libHSrts.a(Main.o):Main.c:(.text+0x36): undefined reference to ZCMain_main_closure' collect2: ld returned 1 exit status

As far as I can see this is because there is no main function, but I don't want one in this module. I am using version 6.10.1 because I can't get more recent ones to work.

Please can someone help?! Thanks, Clare.

Answer 1

Just add -c switch.

However, you shouldn't build modules yourself: the recommended way of building is by using Cabal.

Other ways are:

1. ghc --make Main.hs builds main and its dependencies recompiling as necessary.
2. ghc -M Main.hs parses the imports recursively and generates a makefile with dependencies so you can use this information in your build system.

Neither http://www.haskell.org/ghc/docs/latest/html/users_guide/modes.html nor http://www.haskell.org/ghc/docs/latest/html/users_guide/modes.html#make-mode say --make is deprecated. It's not recommended if Cabal is a viable option. A big project is a pain to maintain without Cabal. Some tools in Haskell toolchain have plugins for Cabal (eg UUAGC attribute grammar preprocessor and others).