[Haskell-cafe] segfault when using ghc api

[Edward Amsden]

Thanks, that fixed it. Why was it segfaulting on "Nothing" though?

Secondly,

I'd like to get to a GHC session that just has, say, Prelude in scope
so I can use dynCompileExpr with "show" etc, but I cannot figure out
how to bring it into scope. The closest I got was to get GHC
complaining that it was a package module.

On Sun, Feb 27, 2011 at 9:24 AM, Anthonin Bonnefoy
<anthonin.bonnefoy at gmail.com> wrote:
> Hi,
>
> The first argument of runGhc takes the directory where GHC's library
> are. You can use the ghc-paths module
> (http://hackage.haskell.org/package/ghc-paths ) for this.
>
> Just install ghc-paths with cabal, import Ghc.Paths and call runGhc
> with (Just libdir), it should get past the segfault.
>
> On Sun, Feb 27, 2011 at 10:51 AM, Edward Amsden <eca7215 at cs.rit.edu> wrote:
>> I'm trying to run the following code. I'm not at all sure it's
>> correct, it's based off of a bit of poking around in the ghc api.
>> Running it with a command line argument like "show (5 + 2)" gives me a
>> segmentation fault. Poking around with gdb and following the steps at
>> http://hackage.haskell.org/trac/ghc/wiki/Debugging/CompiledCode yields
>> precisely nothing, as even the "disassemble" command complains "No
>> function contains program counter for selected frame."
>>
>> Any ideas?
>>
>> == code ==
>> module Main where
>>
>> import GHC
>> import DynFlags
>> import Data.Dynamic
>> import System
>>
>> evalString :: Typeable a => String -> IO (Maybe a)
>> evalString s = defaultErrorHandler defaultDynFlags $ runGhc Nothing $ do
>>  dynflags <- getSessionDynFlags
>>  setSessionDynFlags $ dynflags
>>  target <- guessTarget "Prelude" Nothing
>>  setTargets [target]
>>  load LoadAllTargets
>>
>>  dyn <- dynCompileExpr s
>>  return $ fromDynamic dyn
>>
>> main = do
>>  (s:_) <- getArgs
>>  e <- evalString s
>>  putStrLn $ maybe "oops" id e
>>
>> --
>> Edward Amsden
>> Undergraduate
>> Computer Science
>> Rochester Institute of Technology
>> www.edwardamsden.com
>>
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>
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-- 
Edward Amsden
Undergraduate
Computer Science
Rochester Institute of Technology
www.edwardamsden.com