For Windows get the default GF_LIB_PATH from the executable path

src/GF.hs

@@ -119,15 +119,13 @@ helpMsg = unlines [
   ]
 
 welcomeMsgLib = do
-  lib <- catch 
-    (getEnv "GF_LIB_PATH" >>= return . ("GF_LIB_PATH is set to" +++)) 
-    (const (return $ "GF_LIB_PATH is set to the default, " ++ libdir))
+  lib <- getLibraryPath
   return $ welcomeMsg lib
 
 welcomeMsg lib = 
   "Welcome to " ++ authorMsg ++++ 
   "If \228 and \246 (umlaut letters) look strange, see 'h -coding'." ++
-  "\n" ++ lib ++
+  "\nGF_LIB_PATH is set to " ++ lib ++
   "\n\nType 'h' for help, and 'h [Command] for more detailed help.\n"
 
 authorMsg = unlines [

src/GF/Devel/UseIO.hs

@@ -1,3 +1,4 @@
+{-# OPTIONS -cpp #-}
 ----------------------------------------------------------------------
 -- |
 -- Module      : UseIO
@@ -26,6 +27,12 @@ import System.Environment
 import System.CPUTime
 import Control.Monad
 
+#ifdef mingw32_HOST_OS
+import System.Win32.DLL
+import System.FilePath.Windows
+import Foreign.Ptr
+#endif
+
 putShow' :: Show a => (c -> a) -> c -> IO ()
 putShow' f = putStrLn . show . length . show . f
 
@@ -123,11 +130,23 @@ doesFileExistPath paths file = do
   mpfile <- ioeIO $ getFilePathMsg "" paths file
   return $ maybe False (const True) mpfile
 
+getLibraryPath :: IO FilePath
+getLibraryPath =
+  catch
+    (getEnv "GF_LIB_PATH")
+#ifdef mingw32_HOST_OS
+    (\_ -> do exepath <- getModuleFileName nullPtr
+              let (path,_) = splitFileName exepath
+              canonicalizePath (combine path "../lib"))
+#else
+    (const (return libdir))
+#endif
+
 -- | first var is lib prefix, second is like class path
 -- | path in environment variable has lower priority
 extendPathEnv :: String -> String -> [FilePath] -> IO [FilePath]
 extendPathEnv lib var ps = do
-  b <- catch (getEnv lib) (const (return libdir)) -- e.g. GF_LIB_PATH
+  b <- getLibraryPath                             -- e.g. GF_LIB_PATH
   s <- catch (getEnv var) (const (return ""))     -- e.g. GF_GRAMMAR_PATH
   let fs = pFilePaths s
   let ss = ps ++ fs

src/GF/Infra/UseIO.hs

@@ -1,3 +1,4 @@
+{-# OPTIONS -cpp #-}
 ----------------------------------------------------------------------
 -- |
 -- Module      : UseIO
@@ -25,6 +26,14 @@ import System.IO.Error
 import System.Environment
 import Control.Monad
 
+#ifdef mingw32_HOST_OS
+import System.Win32.DLL
+import System.FilePath.Windows
+import System.Directory
+import Foreign.Ptr
+#endif
+
+
 putShow' :: Show a => (c -> a) -> c -> IO ()
 putShow' f = putStrLn . show . length . show . f
 
@@ -122,11 +131,23 @@ doesFileExistPath paths file = do
   mpfile <- ioeIO $ getFilePathMsg "" paths file
   return $ maybe False (const True) mpfile
 
+getLibraryPath :: IO FilePath
+getLibraryPath =
+  catch
+    (getEnv "GF_LIB_PATH")
+#ifdef mingw32_HOST_OS
+    (\_ -> do exepath <- getModuleFileName nullPtr
+              let (path,_) = splitFileName exepath
+              canonicalizePath (combine path "../lib"))
+#else
+    (const (return libdir))
+#endif
+
 -- | first var is lib prefix, second is like class path
 -- | path in environment variable has lower priority
 extendPathEnv :: String -> String -> [FilePath] -> IO [FilePath]
 extendPathEnv lib var ps = do
-  b <- catch (getEnv lib) (const (return libdir)) -- e.g. GF_LIB_PATH
+  b <- getLibraryPath                             -- e.g. GF_LIB_PATH
   s <- catch (getEnv var) (const (return ""))     -- e.g. GF_GRAMMAR_PATH
   let fs = pFilePaths s
   let ss = ps ++ fs