On Wed, 2012-07-18 at 18:22 +0200, Simon Peter Nicholls wrote:
Some "sending" code:
Foreign.C.String.withCWString "frustrator" $ \s -> do let wParam = System.Win32.Types.castPtrToUINT s :: System.Win32.Types.WPARAM Graphics.Win32.sendMessage wnd Graphics.Win32.wM_APP wParam 0
wndProc "receiving" code:
| wmsg == Graphics.Win32.wM_APP = do s <- peekCWString $ System.Win32.Types.castUINTToPtr wParam putStrLn s return 0
From the docs ( http://hackage.haskell.org/packages/archive/base/4.5.1.0/doc/html/Foreign-C-... ):
the memory is freed when the subcomputation terminates (either normally or via an exception), so the pointer to the temporary storage must not be used after this
I'm noy a windows guru, but I assume that `sendMessage` just puts the message into a queue and exits. So, you receive a pointer to already deallocated memory.