- Glasgow-haskell-users

-xc giving very little information
by Stefan Reich 05 Jan '04

05 Jan '04

A complex program of mine fails with this message: Fail: Maybe.fromJust: Nothing I tried to extract more information about the error by compiling with -prof -auto-all and running the program with +RTS -xc, as advised on http://www.haskell.org/hawiki/TipsAndTricks . This yielded exactly one additional line: <Data.Maybe.CAF>. Fail: Maybe.fromJust: Nothing (Same result for GHC 6.0.1 and 6.2.) Is there another option I have to use to get a full stack trace? Or is my longing for stack traces a side-effect of writing too much Java code that I have to overcome? :) -Stefan

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RE: GHC 6.2 breaks multiline string literals
by Simon Marlow 05 Jan '04

05 Jan '04

> This worked in GHC 6.0.1: > > multilineLiteral = " > line1 > line2" > > But doesn't work in GHC 6.2. Is this a bug or rather a bugfix? > > Anyway, I found it very convenient to embed verbatim string > blocks this > way. Is there maybe another way to achieve the same thing? Just to clarify, this is actually illegal syntax according to Haskell 98, so it is now disallowed. Use string gaps and explicit \n characters in string literals. Cheers, Simon

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RE: -keep-hc-files with --make?
by Simon Marlow 05 Jan '04

05 Jan '04

> It seems that with GHC 6.2, -keep-hc-files and --make conflict: GHC > deletes the HC files it makes. I found an old bug report about this, > with a note from one of the developers claiming to have fixed > this, but > at least here the bug is reproduceable (a regression, perhaps?). > > This is on up-to-date Debian unstable. Looks like a bug; thanks for the report. It'll be fixed in the next release. Cheers, Simon

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RE: -xc giving very little information
by Simon Marlow 05 Jan '04

05 Jan '04

> A complex program of mine fails with this message: > > Fail: Maybe.fromJust: Nothing > > I tried to extract more information about the error by compiling with > -prof -auto-all and running the program with +RTS -xc, as advised on > http://www.haskell.org/hawiki/TipsAndTricks . This yielded > exactly one > additional line: > > <Data.Maybe.CAF>. > Fail: Maybe.fromJust: Nothing > > (Same result for GHC 6.0.1 and 6.2.) That is rather unfortunate, but it's the "correct" behaviour. fromJust is defined like this: fromJust Nothing = error "Maybe.fromJust: Nothing" fromJust (Just a) = a and GHC has compiled it like this: _lift = error "Maybe.fromJust: Nothing" fromJust Nothing = _lift fromJust (Just a) = a so that it can inline fromJust without creating too much code explosion. Unfortunately, this means that _lift is a CAF, and all CAF evaluation appears at the top level in the cost-centre-stack semantics (see the section on profiling in the User's Guide for details). There's no obvious way to work around this, I'm afraid. Cheers, Simon

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RE: classes and template haskell (bug?)
by Simon Peyton-Jones 05 Jan '04

05 Jan '04

Indeed, this is a bug. Well, two bugs actually. I've just fixed them. Thanks for the report. (You probably want to send TH-related mail to template-haskell(a)haskell.org, and other GHC bugs to Glasgow-haskell-bugs(a)haskell.org.) Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Jeremy Shaw | Sent: 02 January 2004 04:35 | To: glasgow-haskell-users(a)haskell.org | Subject: Re: classes and template haskell (bug?) | | Hello, | | No dice. Using cvs head from 12/31, I get the same behavior, (plus a | new bug). Using the same test as before (after updating the import | line): | | *Main> runQ [d| instance Test (a,b) |] >>= putStrLn . show | ghc-6.3: panic! (the `impossible' happened, GHC version 6.3): | Failed binder lookup: a{tv} {- tv a2jx -} | | Please report it as a compiler bug to glasgow-haskell-bugs(a)haskell.org, | or http://sourceforge.net/projects/ghc/. | | Also, a new bug has appeared (then again, it is cvs head) -- If I | start ghci, and then do this: | | Prelude> let n = 1 | Prelude> n | *** Exception: basicTypes/Var.lhs:226:32-58: Non-exhaustive patterns in record update | | Prelude> b | *** Exception: basicTypes/Var.lhs:226:32-58: Non-exhaustive patterns in record update | | Prelude> a | *** Exception: basicTypes/Var.lhs:226:32-58: Non-exhaustive patterns in record update | | Prelude> 3 + 4 | *** Exception: basicTypes/Var.lhs:226:32-58: Non-exhaustive patterns in record update | | | Or similarily: | | *Main> runQ [d| instance Test (Int,Int) |] >>= putStrLn . show | Loading package haskell98 ... linking ... done. | Loading package haskell-src ... linking ... done. | [InstanceD [] (AppT (ConT Main.Test) (AppT (AppT (TupleT 2) (ConT GHC.Base.Int)) (ConT | GHC.Base.Int))) []] | *Main> runQ [d| instance Test (a,b) |] >>= putStrLn . show | *** Exception: basicTypes/Var.lhs:226:32-58: Non-exhaustive patterns in record update | | Jeremy Shaw. | | | At Wed, 31 Dec 2003 08:11:47 -0000, | Simon Peyton-Jones wrote: | > | > In GHC 6.2, Template Haskell has various bugs. I think they are all | > fixed in the HEAD, so you can either build from source or grab a | > development snapshot from the GHC site. | > | > The HEAD version of TH has a slightly different programming interface | > too -- see | > http://research.microsoft.com/~simonpj/tmp/notes2.ps | > | > Simon | > | > | -----Original Message----- | > | From: glasgow-haskell-users-bounces(a)haskell.org | > [mailto:glasgow-haskell-users- | > | bounces(a)haskell.org] On Behalf Of Jeremy Shaw | > | Sent: 31 December 2003 02:19 | > | To: glasgow-haskell-users(a)haskell.org | > | Subject: classes and template haskell (bug?) | > | | > | Hello, | > | | > | I have loaded the following from a file into ghci 6.2: | > | | > | module Main where | > | | > | import Language.Haskell.THSyntax | > | | > | class Test a where | > | test :: a -> a | > | | > | instance Test (a,b,c) where | > | test x = x | > | | > | main = putStrLn "Hello, World!" | > | | > | This works for me: | > | | > | *Main> runQ [d| instance Test (Int,Int) |] >>= putStrLn . show | > | [InstanceD [] (AppT (ConT "Main:Test") (AppT (AppT (TupleT 2) (ConT | > "GHC.Base:Int")) (ConT | > | "GHC.Base:Int"))) []] | > | | > | But this doesn't: | > | | > | *Main> runQ [d| instance Test (a,b) |] >>= putStrLn . show | > | ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): | > | Failed binder lookup: a {- tv a20x -} | > | | > | Please report it as a compiler bug to | > glasgow-haskell-bugs(a)haskell.org, | > | or http://sourceforge.net/projects/ghc/. | > | | > | | > | Am I doing something wrong, or is this a bug? | > | | > | Thanks! | > | Jeremy Shaw. | > | _______________________________________________ | > | Glasgow-haskell-users mailing list | > | Glasgow-haskell-users(a)haskell.org | > | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users | > | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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RE: classes and template haskell (bug?)
by Simon Peyton-Jones 02 Jan '04

02 Jan '04

In GHC 6.2, Template Haskell has various bugs. I think they are all fixed in the HEAD, so you can either build from source or grab a development snapshot from the GHC site. The HEAD version of TH has a slightly different programming interface too -- see http://research.microsoft.com/~simonpj/tmp/notes2.ps Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Jeremy Shaw | Sent: 31 December 2003 02:19 | To: glasgow-haskell-users(a)haskell.org | Subject: classes and template haskell (bug?) | | Hello, | | I have loaded the following from a file into ghci 6.2: | | module Main where | | import Language.Haskell.THSyntax | | class Test a where | test :: a -> a | | instance Test (a,b,c) where | test x = x | | main = putStrLn "Hello, World!" | | This works for me: | | *Main> runQ [d| instance Test (Int,Int) |] >>= putStrLn . show | [InstanceD [] (AppT (ConT "Main:Test") (AppT (AppT (TupleT 2) (ConT "GHC.Base:Int")) (ConT | "GHC.Base:Int"))) []] | | But this doesn't: | | *Main> runQ [d| instance Test (a,b) |] >>= putStrLn . show | ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): | Failed binder lookup: a {- tv a20x -} | | Please report it as a compiler bug to glasgow-haskell-bugs(a)haskell.org, | or http://sourceforge.net/projects/ghc/. | | | Am I doing something wrong, or is this a bug? | | Thanks! | Jeremy Shaw. | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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RE: Running a "final" finaliser
by Simon Marlow 01 Jan '04

01 Jan '04

> Assuming the weak pointers solution is the way to go, I've been > re-aquainting myself with System.Mem.Weak and now I'm now wondering > what is an appropriate key for each ForeignPtr. Before we go down that route, I want to be sure that it's actually necessary to use weak pointers. It sounds like your application has the following properties: - there is a library that can allocate some resources, where each resource is represented by a ForeignPtr - a resource needs to be released when it is no longer referenced - at some point, we would like to free *all* outstanding resources (either at the end of the program, or when the library is no longer required). If this is the case, I'd do it something like this: - keep a global list of the pointers still to be released, probably a doubly-linked list. Lock the whole thing with an MVar. Elements are Ptrs, not ForeignPtrs. - the finaliser on each ForeignPtr removes the corresponding Ptr from the list. - the final cleanup routine explicitly releases all the remaining Ptrs in the list, holding the MVar lock as it does so to avoid race conditions with finalisers. Weak pointers aren't required, AFAICT. Cheers, Simon

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classes and template haskell (bug?)
by Jeremy Shaw 31 Dec '03

31 Dec '03

Hello, I have loaded the following from a file into ghci 6.2: module Main where import Language.Haskell.THSyntax class Test a where test :: a -> a instance Test (a,b,c) where test x = x main = putStrLn "Hello, World!" This works for me: *Main> runQ [d| instance Test (Int,Int) |] >>= putStrLn . show [InstanceD [] (AppT (ConT "Main:Test") (AppT (AppT (TupleT 2) (ConT "GHC.Base:Int")) (ConT "GHC.Base:Int"))) []] But this doesn't: *Main> runQ [d| instance Test (a,b) |] >>= putStrLn . show ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): Failed binder lookup: a {- tv a20x -} Please report it as a compiler bug to glasgow-haskell-bugs(a)haskell.org, or http://sourceforge.net/projects/ghc/. Am I doing something wrong, or is this a bug? Thanks! Jeremy Shaw.

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-keep-hc-files with --make?
by Antti-Juhani Kaijanaho 30 Dec '03

30 Dec '03

Hi, It seems that with GHC 6.2, -keep-hc-files and --make conflict: GHC deletes the HC files it makes. I found an old bug report about this, with a note from one of the developers claiming to have fixed this, but at least here the bug is reproduceable (a regression, perhaps?). This is on up-to-date Debian unstable. -- Antti-Juhani Kaijanaho, FM (MSc), http://www.mit.jyu.fi/antkaij/ ohjelmistotekniikan assistentti * assistant in software engineering Jyväskylän yliopisto * University of Jyväskylä Tietotekniikan laitos * Dept. of Mathematical Inf. Tech.

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RE: GHC Warning Request
by Simon Peyton-Jones 29 Dec '03

29 Dec '03

Good idea. Already done in the HEAD (which will become 6.4). I doubt we'll retrofit this to 6.2 though. Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Ashley Yakeley | Sent: 28 December 2003 12:10 | To: glasgow-haskell-users(a)haskell.org | Subject: GHC Warning Request | | When -fwarn-unused-imports is switched on, "import M()" should not issue | a warning. In 6.2, it does. | | The idea is that I only wish to import instance declarations here, and | that's the obvious way of making that explicit. I'm using -Werror (new | in 6.2, thanks), and most of the time I'm interested in knowing about | superfluous imports. | | -- | Ashley Yakeley, Seattle WA | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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