Re: GHCi bug - the impossible happened loading FranTk with ghc-6.0 on Win32

I tidied up this aspect of TclHaskell / FranTk as part of a Galois
project a while ago. Attached are the as-is changes needed to
avoid being dependent on RTS internals & stop doing a busy wait.
In addition to these diffs, you also want to comment out the defn of
isOnlyProcess in  TclCompatibilityGhcSupportsConcurrency.hs

hth
--sigbjorn

----- Original Message ----- 
From: "Simon Peyton-Jones" <simonpj@xxxxxxxxxxxxx>
To: "GHC bugs" <glasgow-haskell-bugs@xxxxxxxxxxx>; <simon.guest@xxxxxxxxxx>
Cc: "Meurig Sage" <msage@xxxxxxxxxxxxxxxxx>
Sent: Monday, June 23, 2003 02:32
Subject: RE: GHCi bug - the impossible happened loading FranTk with ghc-6.0
on Win32


> Simon
>
> The underlying problem is that no one is maintaining FranTk at the
> moment.  Perhaps you'd like to?
>
> Anyway, FranTk seems to use an un-documented (and therefore unreliable)
> hook into GHC's RTS.  When you use GHCi to load systems that link to RTS
> hooks, the dynamic linker's symbol table must be initialised to include
> those symbols.  So the 'solution' here is to add 'run_queue_hd' to the
> RTS_SYMBOLS in ghc/rts/Linker.c.  You'll need to build GHC from source
> do to this.
>
> Longer term, it'd be a good plan to see just what FranTk wants to know
> here, and what API the RTS should expose to support it.
>
> Admittedly, ghci dies with a rather unhelpful message
>
> Simon
>
>
> | -----Original Message-----
> | From: Meurig Sage [mailto:msage@xxxxxxxxxxxxxxxxx]
> | Sent: 12 June 2003 16:26
> | To: Simon Peyton-Jones
> | Cc: Meurig Sage
> | Subject: Re: GHCi bug - the impossible happened loading FranTk with
> ghc-6.0 on Win32
> |
> | Hi Simon
> |
> ...
> |
> | That being said as far as I remember:
> | FranTk contains the following function which attempts to check whether
> there
> | are any other threads waiting to be scheduled. If there are none then
> it
> | blocks waiting for more user input events, if there are any then it
> simply
> | queries the user input event queue and returns immediately. This makes
> use
> | of a variable run_queue_hd exported by Schedule.h (I think) in the ghc
> | run-time system. When I was working on this in ghc-5.0x ghc compiled
> ghc
> | code provided access to this variable but ghc-i did not. Not sure what
> Simon
> | Marlow has done to this since.
> |
> | Hope this helps
> |
> | The function that does the check is the following one in
> | FranTk/TclHaskellSrc/TclCompatibilityGhcSupportsConcurrency.hs.
> |
> |
> | isOnlyProcess :: IO Bool
> | isOnlyProcess = fmap toBool $ _casm_ ``%r = run_queue_hd ==
> END_TSO_QUEUE;''
> |  where
> |   toBool :: Int -> Bool
> |   toBool 0 = False
> |   toBool _ = True
> |
> | Meurig
> |
> | ----- Original Message -----
> | From: "Simon Peyton-Jones" <simonpj@xxxxxxxxxxxxx>
> | To: "Meurig Sage" <meurig@xxxxxxxxxxxxx>
> | Sent: Thursday, June 12, 2003 2:13 PM
> | Subject: FW: GHCi bug - the impossible happened loading FranTk with
> ghc-6.0
> | on Win32
> |
> |
> | Hi Meurig
> |
> | Are you still around?  Do you remember what the issue is here?  We
> | havn't the foggiest idea
> |
> | Simon
> |
> | -----Original Message-----
> | From: glasgow-haskell-bugs-admin@xxxxxxxxxxx
> | [mailto:glasgow-haskell-bugs-admin@xxxxxxxxxxx] On Behalf Of Guest,
> | Simon
> | Sent: 12 June 2003 09:12
> | To: glasgow-haskell-bugs@xxxxxxxxxxx
> | Subject: GHCi bug - the impossible happened loading FranTk with
> ghc-6.0
> | on Win32
> |
> | I can use FranTk with GHC-6.0 on Windows XP just fine in some
> | configurations.
> | It's OK when compiling with GHC.  It's also OK with GHCi when using
> | FranTk with no concurrency.
> |
> | However, when trying to load a concurrency enabled FranTk into GHCi, I
> | get "the impossible happened".
> |
> | I tried the workaround for the other GHCi bug, but this apparently
> | different, as shown below.
> |
> | Full disclosure requires me to highlight the following text from the
> | FranTk makefile:
> |
> | # Ununcomment this line to support concurrency.
> | # This support does NOT work with ghci. It does not currently export
> | # the special run_head_queue variable. Will allegedly
> | # be fixed in a future version of ghc.
> |
> | # this version supports concurrency
> | SUPPORTCONCURRENCY = TclCompatibilityGhcSupportsConcurrency.hs
> |
> | Is it simply that this hasn't been fixed yet?  (I'm not sure what
> | symptoms are "expected".)
> | I'd very much like to be able to use FranTk with concurrency.  Any
> | chance of a fix?
> |
> | cheers,
> | Simon
> |
> | ------------
> | sjg-pc$ ghci
> |    ___         ___ _
> |   / _ \ /\  /\/ __(_)
> |  / /_\// /_/ / /  | |      GHC Interactive, version 6.0, for Haskell
> 98.
> | / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
> | \____/\/ /_/\____/|_|      Type :? for help.
> |
> | Loading package base ... linking ... done.
> | Loading package lang ... linking ... done.
> | Loading package text ... linking ... done.
> | Prelude> :t GHC.Err.error
> | GHC.Err.error :: forall a. [Char] -> a
> | Prelude> :set -package FranTk
> | Loading package concurrent ... linking ... done.
> | Loading package haskell98 ... linking ... done.
> | Loading package util ... linking ... done.
> | Loading package data ... linking ... done.
> | Loading package FranTk ... linking ...
> | \\pinkgin\redrum_disk2\sjg\software\I686-~$5\ghc\latest\bin\ghc.exe:
> | panic! (the `impossible' happened, GHC version 6.0):
> |         can't load package `FranTk'
> |
> | Please report it as a compiler bug to
> glasgow-haskell-bugs@xxxxxxxxxxx,
> | or http://sourceforge.net/projects/ghc/.
> |
> | --
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> | Bracknell,
> | Berkshire. RG12 8FZ
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