Hello, Where is the documentation on how pinning works in the GHC garbage collector (from a GHC users point of view). I have copied the following code from array/IO.hs and am thinking that it is assuming that the array is pinned? What triggers the pinning? On a second note. Why is the type signiture so constricted. The code below works on any IOUArray (which is very usefull, not just on Int Word8). Naturally this assumes the particular in memory array layout that GHC uses on a particular platform, so would not be compatible (probably) with other Haskell compilers. Rene. hPutArray :: Handle -- ^ Handle to write to -> IOUArray Int Word8 -- ^ Array to write from -> Int -- ^ Number of 'Word8's to write -> IO () hPutArray handle (IOUArray (STUArray l u raw)) count | count == 0 = return () | count < 0 || count > rangeSize (l,u) = illegalBufferSize handle "hPutArray" count | otherwise = do wantWritableHandle "hPutArray" handle $ \ handle_@Handle__{ haFD=fd, haBuffer=ref, haIsStream=stream } -> do old_buf@Buffer{ bufBuf=old_raw, bufRPtr=r, bufWPtr=w, bufSize=size } <- readIORef ref -- enough room in handle buffer? if (size - w > count) -- There's enough room in the buffer: -- just copy the data in and update bufWPtr. then do memcpy_baoff_ba old_raw w raw (fromIntegral count) writeIORef ref old_buf{ bufWPtr = w + count } return () -- else, we have to flush else do flushed_buf <- flushWriteBuffer fd stream old_buf writeIORef ref flushed_buf let this_buf = Buffer{ bufBuf=raw, bufState=WriteBuffer, bufRPtr=0, bufWPtr=count, bufSize=count } flushWriteBuffer fd stream this_buf return ()