On Tue, Apr 26, 2011 at 4:56 PM, Andy Stewart wrote:

Ivan Lazar Miljenovic writes:

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On 26 April 2011 04:57, Michael Snoyman wrote:

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Hi all,

I'm experimenting with using the plugins package for yesod devel server. The basic approach is to use cabal for building the object files, and then load them with plugins. I can get everything to work when I compile with "ghc --make", but I believe name mangling is getting in the way with the "cabal build" route. Can someone give some guidance on how to properly mangle the function names so that plugins can load them?

I'm not sure if he reads this list, but Andy Stewart might know (and I've CC'd him to this). Hi Ivan, sorry for late, too busy on Linux job.

Yes, i have got hot-swap code work for Manatee (http://hackage.haskell.org/package/manatee)

I used to use plugins, but i found it's buggy. So i use GHC-API wrote my own code at: https://patch-tag.com/r/AndyStewart/manatee-core/snapshot/current/content/pr...

Michael, from your need, you just need read function `dynload`, other functions is write for Manatee framework.

Let me explain function `dynload`:

   dynload :: (String, String, [(String, HValue -> IO ())]) -> IO ()    dynload (filepath, moduleName, loadList) = ...

First argument is FilePath that contain module. Second argument is moduleName you need scan. Third argument is tuple list that contain symbol you need load and callback function for symbol's HValue.

Once function `dynload` find symbol in target module, it will use below code dynamic load new value:

   (do        hValue <- compileExpr (moduleName ++ "." ++ symbolName)        liftIO $ loadFun hValue)

function `compileExpr` will get the HValue of symbol, then use loadFun update HVaule in running program.

The key is `HValue -> IO ()`, you need build TVar/IORef in your running program, once you got new HValue, you should write writeTVar/writeIORef in function `HValue -> IO ()` to update the value of TVar/IORef, then you can dynamic loading new value and don't need reboot.

I have draw some picture to explain above framework: http://www.flickr.com/photos/48809572@N02/5304662424/in/photostream/lightbox...

Michael, hope above will help you, good luck! :)

 -- Andy

Hi Andy, Thanks you for your very helpful reply. I still have your previous advice on this subject in my "things to study" list. Looks like taking the easy way out didn't work after all. Thanks for the great example to work from, hopefully it will work out properly. Michael