Fix free calls

src/Database/LevelDB/Base.hs

@@ -59,14 +59,14 @@
     )
 where
 
 import           Control.Applicative      ((<$>))
 import           Control.Monad            (liftM, void)
 import           Control.Monad.Catch
 import           Control.Monad.IO.Class   (MonadIO (liftIO))
 import           Data.ByteString          (ByteString)
 import           Data.ByteString.Internal (ByteString (..))
 import           Data.IORef
-import           Foreign                  hiding (void)
+import           Foreign                  hiding (free, void)
 import           Foreign.C.String         (withCString)
 
 import           Database.LevelDB.C
@@ -135,7 +135,7 @@
         if val_ptr == nullPtr
             then return Nothing
             else do res <- Just <$> BS.packCString val_ptr
-                    free val_ptr
+                    c_leveldb_free val_ptr
                     return res
   where
     prop (NumFilesAtLevel i) = "leveldb.num-files-at-level" ++ show i
@@ -178,7 +178,7 @@
                                     from_ptrs flen_ptrs
                                     to_ptrs tlen_ptrs
                                     size_ptrs
         liftM head $ peekArray 1 size_ptrs >>= mapM toInt64
 
   where
     toInt64 = return . fromIntegral
@@ -214,7 +214,7 @@
             then return Nothing
             else do
                 res' <- Just <$> BS.packCStringLen (val_ptr, cSizeToInt vlen)
-                free val_ptr
+                c_leveldb_free val_ptr
                 return res'
 
 -- | Delete a key/value pair.

src/Database/LevelDB/C.hsc

@@ -14,8 +14,8 @@
 module Database.LevelDB.C where
 
 import Foreign
-import Foreign.C.Types
 import Foreign.C.String
+import Foreign.C.Types
 
 #include <leveldb/c.h>
 
@@ -354,11 +354,18 @@ foreign import ccall safe "leveldb/c.h leveldb_cache_create_lru"
 foreign import ccall safe "leveldb/c.h leveldb_cache_destroy"
   c_leveldb_cache_destroy :: CachePtr -> IO ()
 
-
 --
--- Version
+-- Utility
 --
 
+-- Calls free(ptr).
+-- REQUIRES: ptr was malloc()-ed and returned by one of the routines
+-- in this file.  Note that in certain cases (typically on Windows), you
+-- may need to call this routine instead of free(ptr) to dispose of
+-- malloc()-ed memory returned by this library. */
+foreign import ccall safe "leveldb/c.h leveldb_free"
+  c_leveldb_free :: Ptr a -> IO ()
+
 foreign import ccall unsafe "leveldb/c.h leveldb_major_version"
   c_leveldb_major_version :: IO CInt