- Glasgow-haskell-users

Segmentation fault/access violation in generated code
by Bas van Dijk 24 Jun '12

24 Jun '12

Hello, I'm trying to solve #5254 (http://hackage.haskell.org/trac/ghc/ticket/5254) The issue can be isolated to the following short program which only uses bindings-libusb (http://hackage.haskell.org/packages/archive/bindings-libusb/1.4.4.1/doc/htm…) -------------------------------------------------- module Main where import Foreign import qualified Foreign.Concurrent as FC import Control.Concurrent import Bindings.Libusb.InitializationDeinitialization main :: IO () main = do ctxPtr <- alloca $ \ctxPtrPtr -> do _ <- c'libusb_init ctxPtrPtr peek ctxPtrPtr fp <- newForeignPtr p'libusb_exit ctxPtr -- fp <- FC.newForeignPtr ctxPtr $ c'libusb_exit ctxPtr threadDelay 3000000 print $ fp == fp -------------------------------------------------- When I run this program on Windows I get the following error after 3 seconds: >example.exe True Segmentation fault/access violation in generated code The error disappears when I change the newForeignPtr line to the commented FC.newForeignPtr line. Any idea why this is happening? I don't know if it has anything to do with it but note that the libusb FFI functions are using the stdcall calling convention on Windows. I'm using GHC-7.4.2 but this error also occurs in previous versions. To reproduce this just download libusb (I recommend http://libusbx.org/) and when cabal installing bindings-libusb tell it the path to the include and library files, as in: cabal install bindings-libusb --extra-include-dirs="...\libusb\include\libusb-1.0" --extra-lib-dirs="...\libusb\MinGW32\dll" and make sure the libusb-1.0.dll is in your working directory when running the example program. Regards, Bas

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Windows 64bit GHC port: First alpha release
by Ian Lynagh 19 Jun '12

19 Jun '12

Dear GHC users, Windows 64bit GHC port: First alpha release ------------------------------------------- The Industrial Haskell Group has recently funded work by Well-Typed to make a Windows 64bit port of GHC. The port will officially be released as part of the upcoming GHC 7.6.1 release, but in the mean-time we are pleased to announce that an alpha release is available. You can download the installer for the alpha release from http://www.haskell.org/ghc/dist/win64_alpha1/ If you encounter any problems with the alpha, please report them as GHC bugs in the normal way: http://hackage.haskell.org/trac/ghc/wiki/ReportABug If any significant issues are found, then the platform page at http://hackage.haskell.org/trac/ghc/wiki/WindowsGhc will also be updated. About the IHG ------------- The Industrial Haskell Group (IHG) is an organisation to support the needs of commercial users of the Haskell programming language. The IHG funds work to improve the Haskell ecosystem for industrial Haskell users. http://industry.haskell.org/ About Well-Typed ---------------- Well-Typed LLP is a Haskell services company, providing Haskell consultancy services and writing bespoke Haskell applications. http://www.well-typed.com/

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JustHub 'Sherkin' Release
by Chris Dornan 13 Jun '12

13 Jun '12

I am pleased to announce the Sherkin release of the JustHub distribution of Haskell for Enterprise Linux and the release of the Hub source code on which the distribution is based to Hackage and GitHub. The JustHub distribution is distinctive in providing a comprehensive back-catalogue of GHC tool chains (back to 6.10.4) and major Haskell Platform releases (currently back to 2011.2.0.1) as well as the timely appearance of leading edge GHC releases (such as GHC 7.4.2) in addition to the Haskell Platform de jour (2012.2.0.0), all of which can be deployed simultaneously on the same system. Previous releases of the distribution have been confined to Red Hat Enterprise Linux versions 5 and 6 (and of course CentOS and Scientific Linux); this release expands this coverage to Fedora Linux 16 and 17, which can deployed along side or integrated into Fedora Linux's excellent native Haskell distribution. The JustHub distribution is based on the Hub system for sandbox development that allows each work tree to work in its own sandboxed environment with a specific tool chain and a private user-package database. All of the standard Haskell tools inter-operate cleanly and transparently with the sandboxes and operate in the normal way outside of them. Sandboxed environments (hubs) can be shared between work trees as well as being (re)named, annotated, replicated, swapped, archived, locked and removed. Proper package deletion with the option of garbage collecting orphaned code and documentation is also supported. If anyone would like to incorporate the hub system into a Haskell distribution or port it to a non-Posix system then they are very welcome to contact me (though be warned: time is tight just now). Note that while the distro has had plenty of serious usage (funnily enough it is popular with build-bot admins) it has also been recently extended and revised the software remains in beta testing for now. For news, documentation, articles, download and installation instructions, links to the repositories and trackers etc., see http://justhub.org. Chris Dornan

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Is stderr flushed automatically after exceptions are printed
by Johan Tibell 13 Jun '12

13 Jun '12

Hi, If a program throws an exception that will cause it to be terminated (i.e. the exception isn't caught), will the code that prints out the error message to stderr make sure to flush stderr before terminating the process? -- Johan

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Kindness of strangers (or strangeness of Kinds)
by AntC 12 Jun '12

12 Jun '12

I'm confused about something with promoted Kinds (using an example with Kind- promoted Nats). This is in GHC 7.4.1. (Apologies if this is a known bug/limitation/already explained somewhere -- I know 7.4.1 is relatively experimental. I have searched the bug tracs and discussions I could find.) Starting with nats at type level, this works fine: {-# OPTIONS_GHC -XTypeFamilies -XFlexibleInstances -XUndecidableInstances -XScopedTypeVariables #-} data ZeT; data SuT n class NatToIntT n where natToIntT :: n -> Int instance NatToIntT ZeT where natToIntT _ = 0 instance (NatToIntT n) => NatToIntT (SuT n) where natToIntT _ = 1 + natToIntT (undefined :: n) I converted naively to promoted Kinds: {-# OPTIONS_GHC -XDataKinds -XPolyKinds -XKindSignatures #-} data MyNat = Z | S Nat class NatToIntN (n :: MyNat) where natToIntN :: (n :: MyNat) -> Int instance NatToIntN Z where natToIntN _ = 0 instance (NatToIntN n) => NatToIntN (S n) where natToIntN _ = 1 + natToInt (undefined :: n) But GHC rejects the class declaration (method's type): "Kind mis-match Expected kind `ArgKind', but `n' has kind `MyNat'" (Taking the Kind signature out of the method's type gives same message.) Eh? MyNat is what I want the argument's Kind to be. A PolyKinded version (cribbed from 'Giving Haskell a Promotion' on multi- kinded TypeRep) also works fine: data Proxy a = Proxy class NatToInt (n :: MyNat) where natToInt :: Proxy (n :: MyNat) -> Int instance NatToInt Z where natToInt _ = 0 instance (NatToInt n) => NatToInt (S n) where natToInt _ = 1 + natToInt (Proxy :: Proxy n) But this seems too Kind. I only ever want to supply Nats as arguments. What does the `ArgKind' message mean? (I've also seen messages with `AnyKind' -- what that?) There's a discussion in SPJ's Records proposal last year http://hackage.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields#Sho… ethaveaproxyargument Is that related? Do I need explicit Type/Kind application for this to work? AntC

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Re: [Haskell] ANNOUNCE: GHC version 7.4.2
by Brent Yorgey 11 Jun '12

11 Jun '12

Thanks for the release! One quick question -- the release notes say "A bug in dependency analysis of type declarations in the presence of type families (#5826) has been fixed." However, #5826 seems to be about something entirely different (something about the user guide). Does anyone know the actual ticket being referred to? I'd like to read it in more detail but haven't been able to find it. thanks, -Brent On Sun, Jun 10, 2012 at 08:20:18PM +0100, Paolo Capriotti wrote: > ============================================================= > The (Interactive) Glasgow Haskell Compiler -- version 7.4.2 > ============================================================= > > The GHC Team is pleased to announce a new patchlevel release of GHC. > This release contains a number of bugfixes relative to 7.4.1, so we > recommend upgrading. > > The release notes are here: > > http://www.haskell.org/ghc/docs/7.4.2/html/users_guide/release-7-4-2.html > > How to get it > ~~~~~~~~~~~~~ > > The easy way is to go to the web page, which should be self-explanatory: > > http://www.haskell.org/ghc/ > > We supply binary builds in the native package format for many > platforms, and the source distribution is available from the same > place. > > Packages will appear as they are built - if the package for your > system isn't available yet, please try again later. > > > Background > ~~~~~~~~~~ > > Haskell is a standard lazy functional programming language. > > GHC is a state-of-the-art programming suite for Haskell. Included is > an optimising compiler generating good code for a variety of > platforms, together with an interactive system for convenient, quick > development. The distribution includes space and time profiling > facilities, a large collection of libraries, and support for various > language extensions, including concurrency, exceptions, and foreign > language interfaces (C, whatever). GHC is distributed under a > BSD-style open source license. > > A wide variety of Haskell related resources (tutorials, libraries, > specifications, documentation, compilers, interpreters, references, > contact information, links to research groups) are available from the > Haskell home page (see below). > > > On-line GHC-related resources > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Relevant URLs on the World-Wide Web: > > GHC home page http://www.haskell.org/ghc/ > GHC developers' home page http://hackage.haskell.org/trac/ghc/ > Haskell home page http://www.haskell.org/ > > > Supported Platforms > ~~~~~~~~~~~~~~~~~~~ > > The list of platforms we support, and the people responsible for them, > is here: > > http://hackage.haskell.org/trac/ghc/wiki/Contributors > > Ports to other platforms are possible with varying degrees of > difficulty. The Building Guide describes how to go about porting to a > new platform: > > http://hackage.haskell.org/trac/ghc/wiki/Building > > > Developers > ~~~~~~~~~~ > > We welcome new contributors. Instructions on accessing our source > code repository, and getting started with hacking on GHC, are > available from the GHC's developer's site run by Trac: > > http://hackage.haskell.org/trac/ghc/ > > > Mailing lists > ~~~~~~~~~~~~~ > > We run mailing lists for GHC users and bug reports; to subscribe, use > the web interfaces at > > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users > http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs > > There are several other haskell and ghc-related mailing lists on > www.haskell.org; for the full list, see > > http://www.haskell.org/mailman/listinfo/ > > Some GHC developers hang out on #haskell on IRC, too: > > http://www.haskell.org/haskellwiki/IRC_channel > > Please report bugs using our bug tracking system. Instructions on > reporting bugs can be found here: > > http://www.haskell.org/ghc/reportabug > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell

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Haddock problems with Haskell-Platform2012.2.0.0
by Katsutoshi Itoh 11 Jun '12

11 Jun '12

Hi all. I installed ghc-7.4.1 and haskell-platform-2.12.2.0.0 on debian linux. I'm getting lots of complaints from 'ghc-pkg check', of the following form: ---- Warning: haddock-interfaces: /usr/pkg/share/doc/haskell- platform-2012.2.0.0/html/haskell-platform.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/pkg/share/doc/haskell-platform-2012.2.0.0/ html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/pkg/share/doc/zlib-0.5.3.3/html/ zlib.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/pkg/share/doc/zlib-0.5.3.3/html doesn't exist or isn't a directory ... ---- Any advice? -- ---- いとうかつとし cutsea110(a)gmail.com

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ANNOUNCE: GHC version 7.4.2
by Paolo Capriotti 10 Jun '12

10 Jun '12

============================================================= The (Interactive) Glasgow Haskell Compiler -- version 7.4.2 ============================================================= The GHC Team is pleased to announce a new patchlevel release of GHC. This release contains a number of bugfixes relative to 7.4.1, so we recommend upgrading. The release notes are here: http://www.haskell.org/ghc/docs/7.4.2/html/users_guide/release-7-4-2.html How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: http://www.haskell.org/ghc/ We supply binary builds in the native package format for many platforms, and the source distribution is available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ GHC developers' home page http://hackage.haskell.org/trac/ghc/ Haskell home page http://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, is here: http://hackage.haskell.org/trac/ghc/wiki/Contributors Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://hackage.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC's developer's site run by Trac: http://hackage.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see http://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug

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problem with FFI and libsane
by Ganesh Sittampalam 07 Jun '12

07 Jun '12

Hi, I'm having some trouble making Haskell bindings to libsane (a scanner access library: http://www.sane-project.org/) When I build the cut down sample of my code (below) with GHC 7.4.1 with the non-threaded runtime, it hangs at runtime in the call to c'sane_get_devices (after printing "go"). Pressing ^C causes it to continue and print "done" before exiting. If I compile with GHC 7.2.2 non-threaded, it doesn't hang, printing first "go" then "done" after a few seconds. That pause is expected, as it's also seen in the equivalent C version (also below). If I switch to the threaded runtime, then things go wrong differently. Most of the time there's a hang after "go" and after pressing ^C they just exit immediately, without printing "done". This doesn't change between 7.2.2 and 7.4.1. Occasionally, things do work and I get "go" then "done". All these symptoms seem to point to some kind of threading problem, and I believe that libsane is using pthreads, although ldd doesn't report it and strace only shows it loading the library. The platform is Linux x86, and I've reproduced the behaviour on two different machines (Debian and Ubuntu). I've also tried with GHC 7.4.1.20120508, the most recent i386 snapshot I could fine. Is there anything obvious I'm doing wrong, or something I could try next? Cheers, Ganesh Haskell code: {-# LANGUAGE ForeignFunctionInterface #-} import Foreign.Marshal.Alloc import Foreign.Ptr import System.IO import Foreign.C.Types foreign import ccall "sane_init" c'sane_init :: Ptr CInt -> Callback -> IO CUInt type Callback = FunPtr (Ptr CChar -> Ptr CChar -> Ptr CChar -> IO ()) foreign import ccall "sane_exit" c'sane_exit :: IO () -- the () in the ptr type is incorrect, but in -- this cut-down example we never try to dereference it foreign import ccall "sane_get_devices" c'sane_get_devices :: Ptr (Ptr (Ptr ())) -> CInt -> IO CUInt main :: IO () main = do hSetBuffering stdout NoBuffering _ <- c'sane_init nullPtr nullFunPtr putStrLn "go" ptr <- malloc _ <- c'sane_get_devices ptr 0 putStrLn "done" c'sane_exit C code: #include <sane/sane.h> #include <stdlib.h> int main() { sane_init(NULL, NULL); puts("go"); const SANE_Device **ptr; sane_get_devices(&ptr, 0); puts("done"); sane_exit(); }

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Known problems with promoted tuples and lists in GHC 7.4.1?
by David Menendez 07 Jun '12

07 Jun '12

Are there any known issues involving type-level pairs and lists? I've hit a few baffling type errors that went away when I refactored my code to use locally-defined pairs and lists instead of those provided by the prelude. More worryingly, I had one function that would stop passing the type checker if I replaced '[n] with (n ': '[]) in its signature. -- Dave Menendez <dave(a)zednenem.com> <http://www.eyrie.org/~zednenem/>

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