Retrieve the ghc lib dir at build time

Makefile

@@ -6,7 +6,7 @@ gtk:
 	cd gtk && @runhaskell Setup.hs build
 
 build:
-	@runhaskell Setup.hs build
+	@runhaskell Setup.hs --with-ghc=ghc build
 
 config:
 	@runhaskell Setup.hs configure

Setup.hs

@@ -1,3 +1,33 @@
 #!/usr/bin/env runhaskell
+module Main where
+
 import Distribution.Simple
+import Distribution.PackageDescription
+import System.Info
+import System.Process
+import Data.List
+import System.IO
+--import Config
+
+main :: IO ()
 main = defaultMainWithHooks defaultUserHooks
+       { preBuild = setConfigInfo }
+
+setConfigInfo args _
+    = getLibDir args >>= \libdir ->
+      return
+      (Nothing,
+       [("yi", emptyBuildInfo
+       { options = [(GHC,[mkOpt ("GHC_LIBDIR",show libdir)])] })])
+    where mkOpt (name,def) = "-D"++name++"="++def
+
+getLibDir [arg]
+    | "--with-ghc" `isPrefixOf` arg
+        = do (_, out, _, pid) <- runInteractiveProcess ghcPath ["--print-libdir"]
+                                                       Nothing Nothing
+             libDir <- hGetLine out
+             waitForProcess pid
+             return libDir
+    where ghcPath = drop 1 (dropWhile (/='=') arg)
+
+getLibDir _ = error "failed to extract ghc path from command line"