September 2007 - Glasgow-haskell-users

FFI program seg faulting
by Ben Gaster 21 Sep '07

21 Sep '07

Hi, I am trying to build a very simple Haskell function (foo) which I can then call from C, using an example I got from the GHC FFI Wiki. The problem is that the resulting program fails to run with a seg fault. Here is the code: ---Haskell Module start (Foo.hs) module Foo where foreign export ccall foo :: Int -> IO Int foo :: Int -> IO Int foo n = return (length (f n)) f :: Int -> [Int] f 0 = [] f n = n:(f (n-1)) ---Haskell Module end /*- C module start foo.c*/ #include <stdio.h> #include "Foo_stub.h" int main(void) { int x = foo(100); //printf("x = %d\n", x); return 0; } /*- C module end */ The I build the a.out with the commands: ghc -fglasgow-exts -fffi -c Foo.hs ghc -fglasgow-exts -fffi Foo.o Foo_stub.o foo.c Now if I run the resulting a.out then I get: Segmentation fault Quickly putting this through GDB I get: gdb ./a.out GNU gdb Red Hat Linux (6.5-16.el5rh) Copyright (C) 2006 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-redhat-linux-gnu"... (no debugging symbols found) Using host libthread_db library "/lib/libthread_db.so.1". run Starting program: /home/brg/dev/haskell/ffi/a.out (no debugging symbols found) (no debugging symbols found) (no debugging symbols found) [Thread debugging using libthread_db enabled] [New Thread 7870144 (LWP 22448)] Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 7870144 (LWP 22448)] 0x0805c313 in allocateLocal () (gdb) where #0 0x0805c313 in allocateLocal () #1 0x0000005c in ?? () #2 0x08075c97 in base_DataziTypeable_zdLr42klvl4_srt () #3 0x4ee1dca0 in _dl_argv_internal () from /lib/ld-linux.so.2 #4 0x0807c920 in last_free_capability () #5 0x4ee1dca0 in _dl_argv_internal () from /lib/ld-linux.so.2 #6 0x00000000 in ?? () I am using GHC 6.6.1 built from sources on RHE5. Many regards, Ben Benedict R. Gaster S/W Architecture Team Lead ClearSpeed Technology Plc 3110 Great Western Court Hunts Ground Road Stoke Gifford Bristol BS34 8HP Phone: <blocked::mailto:karen@clearspeed.com> + 44 117 3172016 Fax: + 44 117 3172002 brg(a)clearspeed.com <mailto:brg@clearspeed.com> www.clearspeed.com <blocked::blocked::blocked::http://www.clearspeed.com> -- The contents of this email and any attachments are confidential and may be legally privileged. If you have received this email in error please notify the sender immediately and refrain from copying or disclosing the contents of the email to any third party. ClearSpeed accepts no liability for any viruses which may be transmitted by this email or its attachments. ClearSpeed Technology PLC is a company registered in England under company number 05159262 whose registered office is at 3110 Great Western Court, Hunts Ground Road, Bristol BS34 8HP, UK. ClearSpeed Technology INC is a wholly owned subsidiary of ClearSpeed Technology PLC and is incorporated in the United States of America, with its principle place of business at 3031 Tisch Way, Suite 200, San Jose, CA 95128, US. Additional Company information can be found at the following: http://www.clearspeed.com/aboutus/company/index.html

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Re: STG to JavaScript translation
by Victor Nazarov 21 Sep '07

21 Sep '07

I still have some questions regarding the GHC internals. There is a description of STG language in the "Making a Fast Curry: Push/Enter vs. Eval/Apply for Higher-oder Languages" (2004) by Simon Marlow and Simon Peyton Jones paper. In this description the constructor application (CONS closure) can only appear on the right hand side of the bindings. This is totally reasonable if "let" is the only construct that allocates objects. But in the GHC's StgSyn.hs any expression can be constructor application. How does constructor applications are compiled? Are they implicitly transformed to let? For example: f = let g = (THUNK h x) in (CONS g y) Is this exactly the same as (right variant following the paper) f = let g = (THUNK h x) in let freshvar = (CONS g y) in freshvar ? And the second question is how does constructor tag is passed to case when non-vector return is used? In register? In constructor closure? Are there any cases when closure is not build for constructor application? What the case binder is bound to if there is no closure for constructor application? -- vir http://vir.comtv.ru/

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GHC 6.8.1 RC debugger only breaking on first evaluation of a function
by Olivier Boudry 21 Sep '07

21 Sep '07

Hi all, I just tried the new GHCi debugger. A great new feature of GHCi 6.8.1. When debugging a function, as for example the qsort function given as an example in the "3.5 The GHCi Debugger" documentation page, the debugger will only break on first function evaluation. As haskell is pure and lazy it's probably a normal behavior (reuse last result instead of recompute) but it's not very practical in a debugger. I tried to reload (:r) but it doesn't seems to help. Is there a way to force the function to be re-evalutated without quitting, starting, loading prog and setting breakpoints again, other than making the function part of the IO monad. ;-) Thanks, Olivier.

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combination not supported: Threaded/Profiling when building NDP library
by Ben Gaster 20 Sep '07

20 Sep '07

Hello Having read the papers on Nested Data Parallelism in the Haskell I wanted to play around with the de-sugared implementation in the GHC library NDP. I have built GHC from source, on RHE5, and then installed the NDP library from the tar ball. Following the build instructions in the README I got to building the library which resulted in the following error being reported: ghc-6-6.1: combination not supported: Threaded/Profiling This seems to be down to the fact that -prof and -threaded have been specified on a particular build line, although I emit not to be completely sure about this. Looking through the GHC page on its SMP support it seems to imply that the option -threaded is not needed when building code, rather when linking a parallel program, but it is unclear if this is the case when building a library such as NDP. Having scanned through the GHC source tree it seems that -prof is referenced in numerous places such that it would be a bit of a pain to have to remove these over removing the single reference to -threaded in the ndp.mk file. Thanks for any help that you can provide on this. Many Regards, Ben Benedict R. Gaster S/W Architecture Team Lead ClearSpeed Technology Plc 3110 Great Western Court Hunts Ground Road Stoke Gifford Bristol BS34 8HP -- The contents of this email and any attachments are confidential and may be legally privileged. If you have received this email in error please notify the sender immediately and refrain from copying or disclosing the contents of the email to any third party. ClearSpeed accepts no liability for any viruses which may be transmitted by this email or its attachments. ClearSpeed Technology PLC is a company registered in England under company number 05159262 whose registered office is at 3110 Great Western Court, Hunts Ground Road, Bristol BS34 8HP, UK. ClearSpeed Technology INC is a wholly owned subsidiary of ClearSpeed Technology PLC and is incorporated in the United States of America, with its principle place of business at 3031 Tisch Way, Suite 200, San Jose, CA 95128, US. Additional Company information can be found at the following: http://www.clearspeed.com/aboutus/company/index.html

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Unknown option -XPatternSig used in warning
by Bas van Dijk 20 Sep '07

20 Sep '07

Hello, $ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.7.20070915 When loading the following incorrect program in ghci: foo (x :: a) = x ghci rightly complains: Illegal signature in pattern: a Use -XPatternSigs to permit it OK so I follow the advice and load: {-# OPTIONS_GHC -XPatternSigs #-} foo (x :: a) = x Now ghci complains: unknown flags in {-# OPTIONS #-} pragma: -XPatternSigs ??? The following works though: {-# OPTIONS_GHC -fglasgow-exts #-} foo (x :: a) = x results in: A pattern type signature cannot bind scoped type variables `a' unless the pattern has a rigid type context In the pattern: x :: a In the definition of `foo': foo (x :: a) = x Which I expect. Should I file a bug report, or is there an easy fix? regards, Bas van Dijk

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unique id for data types
by Barney Hilken 19 Sep '07

19 Sep '07

In order to make my records system practically useable, I need a type family > type family NameCmp n m which totally orders datatypes. More precisely, it should return one of the following types: > data NameLT = NameLT > data NameEQ = NameEQ > data NameGT = NameGT for each pair of datatypes n & m, according to whether n < m, n = m, or n > m in some global ordering. This ordering needs to be independent of the context, so it can't be affected by whatever imports there are in the current module. What I want to know is: does GHC give datatypes any global id I could use to generate such an ordering? Would fully qualified names work? Secondly (assuming it's possible) how easy would it be for me to write a patch to add NameCmp to GHC? Where in the source should I start looking? Thanks, Barney.

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6.8.1 from CVS
by Serge D. Mechveliani 18 Sep '07

18 Sep '07

People, please, how to download from CVS the ghc-6.8 branch ? (I need the last version of 6.8.1, the "nightly built") I do the following. set $CVSROOT to :pserver:anoncvs@glass.cse.ogi.edu:/cvs cd $HOME/ghc/cvs cvs login Logging in to :pserver:anoncvs@glass.cse.ogi.edu:2401/cvs -- its reply CVS password: -- password: cvs -- entered password Unknown host glass.cse.ogi.edu. Thank you in advance for your help, ----------------- Serge Mechveliani mechvel(a)botik.ru

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About PORT? GHC
by L.Guo 18 Sep '07

18 Sep '07

Hi glasgow-haskell-users: I have a linux PC (Host) which already have a GHC and a embed mini-linux system (Target) which I want to build a usable GHC for it. Currently, for the target system, the only way to build a program which can run on it, is compile on host using toolchain, and then copy the product of compiling to the target to execute. I want to build a GHC which can run on the target system. As a result, I may compile, GHCi or runHaskell any .hs file. I have read Building/Porting for GHC[1]. Bcuz of ./configure command cannot run on target system, I couldn't follow the tips. How can I get a GHC like that ? Regards [1] http://hackage.haskell.org/trac/ghc/wiki/Building/Porting -------------- L.Guo 2007-09-18

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STG to JavaScript translation
by Victor Nazarov 17 Sep '07

17 Sep '07

Hello. I'm working on the translation of GHC's STG language to JavaScript. I've started my implementation, but I've got stuck with the STG case statements. The problem is the binder in case expression. StgCase expr livevars liverhsvars bndr srt alttype alts Operationally, I need to save continuation and evaluate expr expression, but I have no idea what to do with the bndr. It seems to me that I need to build a closure binded by bndr with the body of expr evaluate it, update it, and use it in RHSs of alternatives. But It seems that this behavior isn't intended by GHC. Can you explain briefly how GHC implements this binder and what this binder points to. Here are some notes about Dmitries last year activity and my activity: http://haskell.org/haskellwiki/STG_in_Javascript -- vir http://vir.comtv.ru/

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compiling on solaris 9
by Robert Andersson 17 Sep '07

17 Sep '07

Hello! When compiling ghc-6.6.1 on SunOS 5.9 I get the following error message > posix/OSMem.c:20:20: error: stdint.h: No such file or directory > gmake[1]: *** [posix/OSMem.o] Error 1 > gmake[1]: *** Waiting for unfinished jobs.... > > GC.c:1870:0: warning: 'regparm' attribute directive ignored > gmake: *** [stage1] Error 1 stdint.h seems to be unavailable on solaris 9. Looking at the rts/posix/OSMem.c file we find /* no C99 header stdint.h on OpenBSD? */ #if defined(openbsd_HOST_OS) typedef unsigned long my_uintptr_t; #else #include <stdint.h> typedef uintptr_t my_uintptr_t; #endif so how would one go about not including the stdint.h for solaris? What would the typedef line look like, if one would e.g. do a check for defined(solaris2_HOST_OS)? yours, /robert PS. Fyi, I compiled with gcc 4.0.2 with CLFAGS="-O3 -mcpu=ultrasparc3 -m64" PPS. The binary distributed ghc-6.6.1 needs libm.so.2 which is not available prior to solaris 10. I also read ticket 1291 and no -- libm.so.2 is not available via Blastwave. -- Systems Administrator & IT-Coordinator Swedish National Graduate School of Language Technology Nordic Graduate School of Language Technology

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