- Glasgow-haskell-users

the impossible happened, large static list.
by Philip Weaver 30 Jan '09

30 Jan '09

Hello. I think I've seen other people encounter this problem before, but I wasn't able to find the solution, if there is one. I have a very large static list of type [[Int]]. It is 128 lists of 128 integers each. When I try to load the module that defines this list, I get an error: ghc: panic! (the 'impossible' happened) (GHC version 6.10.1 for i386-apple-darwin): linkBCO: >= 64k insns in BCO Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug This happens on both linux and mac os, both ghc-6.8.3 and ghc-6.10.1, and both GHC and GHCi. Is there anything I can do to avoid this? Thanks! - Philip

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Haskell runtime in shared library?
by Patrick LeBoutillier 30 Jan '09

30 Jan '09

Hi, I'm trying to make a shared library containing the Haskell runtime, but no Haskell code per se. This shared library would then dynamically load other shared libraries containing conpiled Haskell code. Here is some pseudo code: In my_program: dlopen('my_haskell_runtime.so', RT_GLOBAL) ; hs_init(...) ; then later, in my_haskell_runtime.so: dlopen('my_haskell_module.so') ; __stginit_MyModule(); I've found some great information about FFI stuff here: http://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html#using-… and here: http://blog.haskell.cz/pivnik/building-a-shared-library-in-haskell/ but I can't seem to find examples where the runtime is in a different shared object from the Haskell code/module. Is this possible to do something like this using GHC? If so, where can I find more information of how exactly to link my_haskell_runtime.so and my_haskell_module.so? Note: I'm fairy new to FFI (and Haskell in general), so it is possible that my terminology is lacking. Thanks a lot, Patrick -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada

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a new impossible happened in ghci?
by Peter Hercek 30 Jan '09

30 Jan '09

Hi, My preliminary search indicated this is new, but still, should I add this to GHC Trac? Maybe I just cannot formulate my query well. See the ghci session log at the end. Peter. status:0 peter@dwarf [715] ~ % ghci GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> :def err (\_->return$concat$replicate(read "\"1\"") "a") Prelude> :err ghc: panic! (the 'impossible' happened) (GHC version 6.10.1 for i386-unknown-linux): Prelude.read: no parse Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug status:0 peter@dwarf [715] ~ %

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RE: [Haskell] type inference & instance extensions
by Simon Peyton-Jones 28 Jan '09

28 Jan '09

[Redirecting to GHC users] The <<loop>> is a bug. Thank you! I'll Trac it. Simon | -----Original Message----- | From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] | On Behalf Of Sittampalam, Ganesh | Sent: Monday, January 19, 2009 2:05 PM | To: haskell(a)haskell.org | Subject: RE: [Haskell] type inference & instance extensions | | Doug McIlroy wrote: | > A fragment of an attempt to make pairs serve as complex numbers, | using | > ghc/hugs extensions: | > | > instance Num a => Num (a,a) where | > (x,y) * (u,v) = (x*u-y*v, x*v+y*u) | > | > Unfortunately, type inference isn't strong enough to cope with | > | > (1,1)*(1,1) | > | > Why shouldn't it be strengthened to do so? | | The problem is that type classes are an "open" system. Although it's | obvious that your instance is the only one in this code that can be | used to type-check (1,1), that doesn't preclude new code adding an | instance that could make it behave differently. | | I had hoped that the code below (GHC 6.10+) would work, but it just | sends GHC into a loop when you actually try to typecheck (1,1). I don't | know if that's a bug in GHC or a misunderstanding on my part of how the | typechecking should work. | | {-# LANGUAGE FlexibleInstances, TypeFamilies #-} | | instance (a~b, Num a) => Num (a, b) where | fromInteger k = (fromInteger k, fromInteger 0) | (x,y) * (u,v) = (x*u-y*v, x*v+y*u) | | PS: Sorry, I didn't mean to say "typecheck (1,1)". I meant to say | "evaluate (1,1)*(1,1)" - I had a suspicion that some kind of infinite | polymorphic recursion through the Num instance is happening and | accidentally turned that thought into a completely different statement. | | | Ganesh | | ======================================================================= | ======= | Please access the attached hyperlink for an important electronic | communications disclaimer: | | http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html | ======================================================================= | ======= | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell

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new build system build fails on Solaris/x86
by Karel Gardas 28 Jan '09

28 Jan '09

Hello, I attempt to test new build system on solaris/x86 platform and after applying patch from here: http://hackage.haskell.org/trac/ghc/ticket/2951 I've been able to boot and configure the tree. On the other hand build alone fails with: checking for unistd.h... yes checking editline/readline.h usability... no checking editline/readline.h presence... no checking for editline/readline.h... no checking editline/editline.h usability... no checking editline/editline.h presence... no checking for editline/editline.h... no checking readline/readline.h usability... no checking readline/readline.h presence... no checking for readline/readline.h... no checking for sign of read_history result on error... negative checking for rl_completion_matches... no checking for completion_matches... no configure: error: editline not found, so this package cannot be built See `config.log' for more details. gmake[1]: *** [libraries/editline/dist-install/package-data.mk] Error 1 gmake: *** [all] Error 2 karel@silence:/tmp/ghc-new-build-system$ Do you have any idea how to proceed or what exactly to install? Thanks, Karel

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how can I run ghci monad actions from ghci command line
by Peter Hercek 28 Jan '09

28 Jan '09

Is it possible to run ghci monad actions from ghci command line somehow? For example: I would like to check whether "it" variable is of type Bool and whether it is True using normal Haskell code (i.e. not using ghci commands starting with colon like :type :print). Peter.

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permissions api in directory package is useless (and possibly harmful)
by Duncan Coutts 28 Jan '09

28 Jan '09

All, We need to think about a new better permissions api for the System.Directory module. The current api and also the implementation are at best useless and possibly harmful. I've been trying to debug various permission problems related to installing files with Cabal on Unix and Windows. Half the problems seem to stem from the permissions api and the copying of permissions in copyFile. data Permissions = Permissions { readable :: Bool, writable :: Bool, executable :: Bool, searchable :: Bool } getPermissions :: FilePath -> IO Permissions setPermissions :: FilePath -> Permissions -> IO () These are clearly designed for the unix permissions model, however they do not map onto it very usefully. get/setPermissions only get the user permissions, not the group or other. So for example if I have a file: -rw-rw-rw- 1 duncan users 0 2009-01-28 12:34 foo then setPermissions "foo" (Permissions True False False False) only removes write permissions from me, not from everyone else: -r--rw-rw- 1 duncan users 0 2009-01-28 12:34 foo which cannot be what we wanted. It's also pretty useless for installing files globally. For that we want to say that a file is readable by everyone and only writable by the owner (usually root). It might even be ok to say only readable by everyone and writable by nobody, but we cannot even do that. Combine that with copyFile copying permissions and we can easily lock people out or install world-writable files depending on the umask of the user building the software. On windows getPermissions tells us almost nothing. In particular if it says the file is readable or writable, this is no guarantee that we can read or write the file. getPermissions does not look at permissions. It only consults the old DOS read-only attribute (and the file extension to tell us if a file is executable). Similarly, on windows setPermissions also only sets the read-only attribute. The read-only attribute should really be avoided. It has rather unhelpful semantics. For example moving a file over a read-only file fails, where as if windows permissions (ACLs) are used then it works as expected (same as on POSIX). The read-only attribute is only there for compatibility with heritage software, we should really never set it. There is also an implementation of copyPermissions, it's not actually exposed in System.Directory but it is used by copyFile. It calls stat to get the permissions and chmod to set them. The implementation is the same between unix and windows, on windows it uses the stat and chmod from the msvcrt library. On Unix copyPermissions does work and is probably the right thing for copyFile to do. It's the default behaviour of /bin/cp for example. However it does mean there is no easy efficient way to make a copy of a file where the destination file gets the default permissions, given the umask of the current user. This means that copyFile is not appropriate for installing files, since the user building a package is not necessarily the same as the one installing it and their umasks can and often are different. The unix install program does not copy permissions, instead it sets them explicitly. We have no portable way of doing the same. But we can at least use the System.Posix.Files.setFileMode to do it. One nice thing about copyFile is that it replaces the destination file atomically. However if we have to set the permissions in a second step then we loose this nice property. Ideally we would create the temporary file in the destination directory (exclusively and with permissions such that no other user could write to our file), we'd copy the data over, set the new destination permissions and atomically replace the destination file. The copyPermissions function on windows is useless. It does not copy permissions. The way that msvcrt implements stat and chmod means that the only "permissions" that are copied is the old DOS read-only attribute. Perhaps copying the read-only attribute is the right thing for copyFile to do, it's what the Win32 CopyFile function does, however it's never what I want to do for installing software package files. So, can we craft a useful api for permissions? We should consider what the defaults for copyfile etc should be with respect to permissions. Where those defaults are not helpful can we think of a way to let us do what we want (eg get default or specific permissions instead of copying permissions). Or is it impossible and we just have to use system-specific functions whenever we need something non-standard. In which case we need to make those functions better, they appear to be mostly lacking for the Win32 case. In either case I'm sure the existing permissions api needs to be deprecated with big flashing warnings. Duncan Oh, and while I'm thinking about it: it's not currently possible to open new/exclusive files with specific permissions and the open temp file functions on windows do not ensure the file is writable only by the current user.

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seg-fault
by Serge D. Mechveliani 24 Jan '09

24 Jan '09

Yesterday, I promised to provide a bug report with Segmentation fault on missing some method implementation. I saved this source copy. Hm ... today I still failed to reproduce this seg-fault situation! I am sorry. Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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seg-fault in 6.10.1
by Serge D. Mechveliani 24 Jan '09

24 Jan '09

Dear GHC team, I `make' my (large) project in ghc-6.10.1, Linux Debian, i386-unknown, run the executable, and obtain Segmentation fault. Then, I noted that in a few places the compiler warned about skipping some class member implementations in some instances. I added these implementations, and now it works correct. Are you interested in the bug report on the above part of Segmentation fault ? ----------------- Serge Mechveliani mechvel(a)botik.ru

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Changes in scoped type variable behavior?
by Austin Seipp 24 Jan '09

24 Jan '09

Hi, I've been reading Oleg Kiselyov's "Implicit Configurations" paper and while getting the modulus math code to work I've hit a bit of a problem. The code is attached to this message; the problem is in the normalize function: > normalize :: (Modular s a, Integral a) => a -> M s a > normalize a = M (mod a (modulus (u :: s))) Trying this code gives: > $ ghci implicit-config.hs > GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help > Loading package ghc-prim ... linking ... done. > Loading package integer ... linking ... done. > Loading package base ... linking ... done. > [1 of 1] Compiling Main ( implicit-config.hs, interpreted > ) > > implicit-config.hs:34:24: > Could not deduce (Modular s a) > from the context (Modular s1 a, Integral a) > arising from a use of `modulus' at implicit-config.hs:34:24-38 > Possible fix: > add (Modular s a) to the context of > the type signature for `normalize' > In the second argument of `mod', namely `(modulus (u :: s))' > In the first argument of `M', namely `(mod a (modulus (u :: s)))' > In the expression: M (mod a (modulus (u :: s))) > Failed, modules loaded: none. > Prelude> The paper uses the following code, which annotates the return of normalize while at the same time binding the 's' type variable for use on the right hand side: > normalize :: (Modular s a, Integral a) ⇒ a → M s a > normalize a :: M s a = M (mod a (modulus (u :: s))) This code fails with: > $ ghci implicit-config.hs > GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help > Loading package ghc-prim ... linking ... done. > Loading package integer ... linking ... done. > Loading package base ... linking ... done. > [1 of 1] Compiling Main ( implicit-config.hs, interpreted > ) > > implicit-config.hs:34:0: Parse error in pattern > Failed, modules loaded: none. > Prelude> Even with the ScopedTypeVariables extension - am I missing something? I've also tried the actual literate haskell code from the technical report and it fails with the same error (parse error in pattern.) I'm using Mac OS X 10.6 and GHC 6.10.1. Austin

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