Hongmin Fan <hongmin.fan.li...@gmail.com> writes: > Thanks Andy! Yes, I do need the second approach you listed here. I think the > plugin package actually > uses GHC API to load > too. > > My problem here is more technical than theoretical. The type safety isn't the > primary issue for me, > because I'm trying to > implement a certain genetic programming system (there is some papers like > this one: > http://citeseerx.ist.psu.edu/viewdoc/ > summary?doi=10.1.1.98.7686), which generates functions that I'm going to > dynamically evaluate. I'm > hoping to use GHC API to > avoid writing my own evaluator. The func generation component actually is > designed to generate > functions of the specific > type, so no worries about type safty. > > I'm looking for a clean/correct way to use GHC API to reload the module, > maybe there is some option > I should set but I > didn't? Being new to Haskell, the source code for GHCi isn't so accessible... > Thanks! If you want dynamic evaluation, you can try hint : Runtime Haskell interpreter (GHC API wrapper)
At http://hackage.haskell.org/package/hint Cheers, -- Andy > > On Tue, Jul 20, 2010 at 1:01 AM, Andy Stewart <lazycat.mana...@gmail.com> > wrote: > > Hi Hongmin, > > I think you're looking for how to hot-swap Haskell program. > > There are two approach to reach target: > > 1) Source-Code level: > Recompile source code to build new execute cache file, if re-compile > successful, use executeFile to switch new entry. You perhaps need use > Binary instance to save/restore state between re-launch new execute > file. > > 2) Dynamic Linking object code. > Compile plugins code to object file, the use .o and .hi file to > dynamic linking object code to running Haskell application. > Because .hi file have type/depend information, we can do type-check > when dynamic linking .o file. > > First way is simpler, but you perhaps will lost state after reboot, > because you can't serialize state (such as FFI) sometimes. > > Second way is more complicated, but you can present all state when > hot-swapping. > > Looks you need second way, from your code, that's wrong, you can't > dynamic link object file without type-check, and expect everything will > be fine. > If you don't type-check when linking code, it's very dangerous, it willl > *crash* your > program once type mismatch or runtime error occur. > > Infact, Don Stewart has implement a complete solution to dynamic > linking in Haskell program, at > http://hackage.haskell.org/package/plugins-1.4.1 > Unfortunately, it's broken with ghc-6.12.x > > Before Don fix plugins package, i recommend you read Don's new paper > (http://www.cse.unsw.edu.au/~dons/papers/dons-phd-thesis.pdf) > You will know every detail that how to dynamic extension Haskell > program. > > Hope above will help you. :) > > -- Andy > > Hongmin Fan <hongmin.fan.li...@gmail.com> writes: > > > Hi, > > > > I'm using GHC API to dynamically load some module, and evaluate it; and > later change the > content of > > the module, and > > re-evaluate it. But I found unless I delete the object file created by > previous compilation, > the > > module seems not reloaded. > > I have set ghcLink = LinkInMemory as an older post suggested > > > > To illustrate what I'm saying, here is a piece of code (sorry for any > naivety in the code, new > to > > Haskell too) > > > > import System.IO (IOMode(..),hClose,hPutStr,openFile) > > import Directory (removeFile) > > import GHC > > import GHC.Paths > > import DynFlags > > import Unsafe.Coerce > > > > src_file = "Target.hs" > > obj_file = "Target.o" > > > > main = do > > writeTarget "arg" > > func0 <- compileTarget > > putStrLn $ show $ func0 2 > > > > writeTarget "arg*2" > > func1 <- compileTarget > > putStrLn $ show $ func1 2 > > > > writeTarget input = do > > -- removeFile obj_file `catch` (const $ return ()) -- uncomment this > line to have correct > results > > h <- openFile src_file WriteMode > > hPutStr h "module Target (Target.target) where\n" > > hPutStr h "target::Double -> Double\n" > > hPutStr h "target arg = \n " > > hPutStr h input > > hClose h > > > > compileTarget = > > defaultErrorHandler defaultDynFlags $ do > > func <- runGhc (Just libdir) $ do > > -- setup dynflags > > dflags <- getSessionDynFlags > > setSessionDynFlags dflags { ghcLink = LinkInMemory } > > > > -- load target module > > target <- guessTarget src_file Nothing > > setTargets [target] > > r <- load LoadAllTargets > > case r of > > Failed -> error "Compilation failed" > > Succeeded -> do > > m <- findModule (mkModuleName "Target") Nothing > > -- set context and compile > > setContext [] [m] > > value <- compileExpr ("Target.target") > > do > > let value' = (unsafeCoerce value) :: Double -> > Double > > return value' > > return func > > > > The code basically write to a Haskell source file twice with different > content, and hoping to > get > > different results, but > > unless I uncomment the line with removeFile, the output of 2 runs are > the same; using 'touch' > to > > touch the source file being > > written between 2 runs also gives the correct results. So maybe caused > by some caching > mechanism? > > > > I'm using GHC 6.12.1 in Ubuntu 10.04. I have this workaround of > deleting the obj file, but I'm > > wondering the "correct" way > > of doing it. Did some search on GHC API, but never got something > relevant. > > > > Thanks, > > Hongmin > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe@haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
