Hi all
I am trying to build a GUI for GHCi using "GHC as a library". See
http://haskell.org/haskellwiki/GHC/As_a_library .
One requirement is that the GUI is still responsive when executing code
using GHC.runStmt. Therefore I do:
forkIO $ GHC.runStmt someStatement >> return()
While this works fine, it does give me one problem. How do I terminate a
call to runStmt prematurely? One would think that this would work:
threadId <-forkIO $ GHC.runStmt someStatement >> return()
...
killThread threadId
However, as runStmt also uses forkIO internally I am not killing the
thread that runs "someStatement" - actually nothing seems to happen when
executing the action "killThread threadId".
Anybody knows how to kill the thread running "someStatement"?
I have attached a more complete program which illustrates the problem
described above. I have only tested the program on Debian/Linux.
Greetings,
Mads Lindstrøm
module Main where
-- Compile with: ghc -package ghc-6.6 --make StopingRunStmt.hs
import qualified GHC
import qualified Outputable
import qualified Packages
import qualified PackageConfig
import DynFlags
import System.IO
import Control.Concurrent
path = "/usr/lib/ghc-6.6/"
main = do session <- initializeSession
threadId <- forkIO $ GHC.runStmt session "let foo = do threadDelay 100000; putStrLn \"a\"; foo in foo" >> return ()
threadDelay (10^6*1)
putStrLn "Killing thread"
killThread threadId -- the thread is not killed here. Only when the hole programs terminates, is the thresad killed.
threadDelay (10^6*5)
initializeSession =
do -- start a new interactive session using the path specified above
session <- GHC.newSession GHC.Interactive (Just path)
-- initialize the default packages
dflags1 <- GHC.getSessionDynFlags session
(dflags2, packageIds) <- Packages.initPackages dflags1
GHC.setSessionDynFlags session dflags2{GHC.hscTarget=GHC.HscInterpreted}
-- now the order of the statements is important:
-- 1) load our modified prelude functions
target <- GHC.guessTarget "MyPrelude.hs" Nothing
GHC.addTarget session target
-- this would unload the standard prelude if it had already been loaded
GHC.load session GHC.LoadAllTargets
-- 2) load the standard prelude
let preludeModule = GHC.mkModule (PackageConfig.stringToPackageId "base") (GHC.mkModuleName "Prelude")
controlConcurrentModule <- GHC.findModule session (GHC.mkModuleName "Control.Concurrent") Nothing
GHC.setContext session [] [preludeModule, controlConcurrentModule]
-- 3) replace "putStrLn" and "getLine" with our modified versions
-- replaceFunctions session
return session
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