January 2001 - Glasgow-haskell-users

"Illegal class assertion"
by George Russell 04 Jan '01

04 Jan '01

is not a very helpful message, especially as GHC can't be bothered to pinpoint exactly where the error occurred. In this particular case, "Missing type variable in instance context" might be more helpful.

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Happy InstallShield update
by Reuben Thomas 04 Jan '01

04 Jan '01

I just noticed that the Happy 1.9 InstallShield contained a dynamically linked executable for Happy. This was a Bad Idea, so I've replaced it with a statically linked executable. This should work for more people. -- http://sc3d.org/rrt/ | maxim, n. wisdom for fools

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RULES and -fglasgow-exts
by Manuel M. T. Chakravarty 03 Jan '01

03 Jan '01

It seems that in order to use RULES pragmas in a module, the module has to be compiled with -fglasgow-exts (at least, this is so with 4.08.1). This is a little surprising as pragmas usually don't require this flag. Indeed, it seems as if the keyword `forall' within a RULES pragma is what irritates GHC without -fglasgow-exts - maybe because forall is an extension in "normal" code? Cheers, Manuel

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My program is crashing - help!
by Marcin 'Qrczak' Kowalczyk 02 Jan '01

02 Jan '01

I don't know if this is a bug in my code, in ghc, or in the python interpreter. I could not find it for a long time. Would somebody please help me? In <http://qrczak.ids.net.pl/HsPython-bug.tar.gz> there is a simplest fragment I could ake which exposes the bug. It requires ghc-4.11 and python-2.0. It should be tweakable for older versions of both: - For older ghc versions, either replace Ptr/FunPtr with Addr and ForeignPtr with ForeignObj, or use QForeign instead of Foreign. In any case you must install hsc2hs from ghc >= 4.09 or QForeign. QForeign is at <http://download.sourceforge.net/qforeign/qforeign-0.63.tar.gz>. - For older Python versions, fix paths in the Makefile. The program should do an equivalent of main = putStr (repeat '9') but in a very indirect way, calling Python which calls back Haskell for each digit. On my machine it crashes after several lines of output (inside malloc). It is very sensitive to small changes. When compiled with -O, it works fine. When the PyObject module is merged with Main, it works fine. When nullFunPtr is passed in Main.hsFunctionNew instead of freeMethodDefPtr, it still crashes, but if nullFunPtr is replaced with 0 and the corresponding type in a foreign import is changed to Int, it works fine (well, this applied to a version before removing unnecessary junk, now it may be different). When freeMethodDef is written in C and foreign imported instead of being written in Haskell and foreign exported, it works fine. Et caetera. I tried to run it under ghc-4.08.1 and python-1.5 (after necessary tweaking), but it's very different: it crashes very soon and ltrace shows that a message about passing a non-tuple as arguments is strcpy'ed just before the crash. Perhaps the crash is expected, since I don't catch Python exceptions in the simplified version, but the message is not: I am passing the result of PyTuple_New(0) (after wrapping in a ForeignPtr). Anyway, it is very sensitive to small changes of compilers or the source itself. Maybe I am using the Python interface in a wrong way, or I am doing some stupid mistake, or there is a bug in ghc - I really don't know what is going on. Help! -- Marcin 'Qrczak' Kowalczyk

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RE: Realtime-GC
by Simon Peyton-Jones 02 Jan '01

02 Jan '01

Yes -- Andy Cheadle and Tony Field (whose paper is in ICFP00) are planning to bring their incremental GC fully into GHC, so it'll become part of the distribution. I think Andy will be delighted to have a Real Customer! So far, GC is sufficiently unobtrusive that no one notices, so it'll be fun to have someone who does. Are there any other GHC users who notice GC pauses? Simon | -----Original Message----- | From: Sven Panne [mailto:Sven.Panne@informatik.uni-muenchen.de] | Sent: 30 December 2000 22:09 | To: GHC Users | Cc: Armin Sander | Subject: Realtime-GC | | | IIRC there was some activity in the realtime GC area | for GHC (something like experimental support for 4.0x, | but I can't remember exactly). Any progress yet? It | would be quite cool to fly through Quake levels without | those small hiccups. And I'm quite sure there are more | serious applications which would profit from that, too... :-) | | Cheers, | Sven | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users |

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