August 2006 - Glasgow-haskell-users

Holidays
by Simon Peyton-Jones 14 Aug '06

14 Aug '06

GHC enthusiasts, Simon M is on holiday this week (14 Aug), and I'm on holiday next week (21 Aug), so GHC HQ may seem less responsive than usual. For example, thanks for Johan and Esa for recent patches -- but I'll leave them for Simon to review and commit. keep hacking, though! Simon

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Re: OpenSSL License (was Replacement for GMP: Update)
by Peter Tanski 12 Aug '06

12 Aug '06

John, > Have you carefully investigated the OpenSSL license? We in Debian > have > had repeated problems since the OpenSSL license is, as written, > incompatible with the GPL (even linking to OpenSSL is incompatible > with > the GPL). I would hate to have a situation where all GHC-compiled > programs can't be under the GPL. I have been discussing this very issue with several people in this list. At first I thought it was a peripheral issue because I had not carefully reviewed the GPL license until Florian Weimer pointed out what the problem was. By that time I had already decided to work with another replacement library--I have not yet decided which because I am still testing things out--based on good arguments other people gave for not subjecting users to OpenSSL's advertising clause. The libraries I am working with are either public domain or BSD licenses. Sorry to scare you. Best regards, Peter

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GHC Error in linker "undeined reference"
by Johan Grönqvist 12 Aug '06

12 Aug '06

Hello, I am using ghc on ubuntu 6.06, and it has worked well for my first few attempts (one example pasted below), but I now have a file that works well in ghci, but not in ghc. When loading the file (pasted below) into ghci, it works fine.and the program runs as expected. Compilation (linking, actually) with ghc gives error messages (pasted below), but when I again start ghci adn load the program, I can see that it now uses the compiled ".o"-file instead of interpreting the program. I assume that some files that should be installed by default are not installed. I apologize if I am violating any policy about pasting in messages. Thanks in advance for any help / johan ---------------------------------------------------- -- Working example: sort [] = [] sort (x:xs) = insert x (sort xs) where insert x [] = [x] insert x (y:ys) | x <= y = (x:y:ys) | otherwise = y : (insert x ys) main = print $ sort [1,4,53,45,1,435,45,45,1,435,45,145,45345,3,345] ---------------------------------------------------------- ------------------------------------------------------ -- Non-linkable example {-# OPTIONS_GHC -fglasgow-exts #-} import Control.Monad.State import Control.Monad.ST import Data.Array.ST import Data.List class Stack s a where emptyStack :: (s a) isEmpty :: State (s a) Bool pop :: State (s a) a push :: a -> State (s a) () nTh :: Int -> State (s a) a depth :: State (s a) Int instance Stack [] a where emptyStack = [] :: [a] isEmpty = get >>= \lst -> return (length lst == 0) pop = get >>= \(x:xs) -> put xs >> return x push x = get >>= \xs -> put (x:xs) >> return () nTh n = get >>= \lst -> return $ lst !! n depth = get >>= (return . length) class Mem m a where emptyMem :: Int -> a -> ST s (m s Int a) fetch :: (m s Int a) -> Int -> ST s a store :: (m s Int a) -> Int -> a -> ST s () instance Mem STArray a where emptyMem n val = newArray (0,n) val :: ST s (STArray s Int a) fetch m ix = readArray m ix store m ix val = writeArray m ix val stackTest = evalState doStackTest (emptyStack :: [Int]) where doStackTest = (push 4 >> push 2 >> pop >>= \a -> pop >>= \b -> return (a,b)) memTest = runST doMemTest where doMemTest :: ST s (Int,Int) doMemTest = ((emptyMem 2 0 :: ST s (STArray s Int Int)) >>= \mem -> store mem 0 2 >> store mem 1 4 >> fetch mem 0 >>= \a -> fetch mem 1 >>= \b -> return (a,b)) main = (print stackTest >> print memTest >> return ()) -------------------------------------------------------------------- Error messages frm ghc: ---------------------------------------------------- ubuntu@ubuntu:~/haskell/Forth$ ghc forth.lhs forth.o: In function `s2Q0_info': undefined reference to `ControlziMonadziState_zdfMonadStates_closure' forth.o: In function `s2Q6_info': undefined reference to `ControlziMonadziState_zdfMonadStates_closure' forth.o: In function `s2Qp_info': undefined reference to `ControlziMonadziState_zdfMonadStates_closure' forth.o: In function `s2QA_info': undefined reference to `ControlziMonadziState_zdfMonadStates_closure' forth.o: In function `s2R5_info': undefined reference to `ControlziMonadziState_zdfMonadStates_closure' forth.o: more undefined references to `ControlziMonadziState_zdfMonadStates_closure' follow forth.o: In function `s2TI_info': undefined reference to `ControlziMonadziState_zdfMonadState_closure' forth.o: In function `s2TL_info': undefined reference to `ControlziMonadziState_zdfMonadState_closure' forth.o: In function `s2Tm_info': undefined reference to `ControlziMonadziState_zdfMonadState_closure' forth.o: In function `s2Tp_info': undefined reference to `ControlziMonadziState_zdfMonadState_closure' forth.o: In function `s2TO_info': undefined reference to `ControlziMonadziState_zdfMonadState_closure' forth.o: In function `r2Pv_info': undefined reference to `ControlziMonadziState_evalState_closure' forth.o: In function `__stginit_Main_': undefined reference to `__stginit_ControlziMonadziState_' forth.o: In function `Main_zdfStackZMZN_srt': undefined reference to `ControlziMonadziState_zdfMonadStates_closure' forth.o: In function `s2TO_srt': undefined reference to `ControlziMonadziState_zdfMonadState_closure' forth.o: In function `r2Pv_srt': undefined reference to `ControlziMonadziState_evalState_closure' collect2: ld returned 1 exit status ---------------------------------------------------

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Re: Replacement for GMP: Update
by Peter Tanski 12 Aug '06

12 Aug '06

Einar, >> Summary: I finally settled on modifying OpenSSL, since that would be >> the easiest to work with under GHC's hood (plain C code, not C++). I >> have to: > > Does this cause license problems? > > I think OpenSSL license had the advertising clause which means > problems if Haskell programs want to link against GPLed > libraries too. The relevant portion of the OpenSSL license (reproduced in all source code and documentation) is: * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] (NOTE: this section is actually from the original SSLeay (1995-1998) license, but applies because OpenSSL is distributed under a dual license.) Otherwise the OpenSSL license is a BSD-style license that gives the authors credit (BSD2 and BSD3 do not require names in all the source code and documentation, only the distribution). The copying restriction means that I cannot simply take the BN library out of the OpenSSL distribution and put that code under the GHC license; it does not mean that I cannot distribute the OpenSSL code (still under the OpenSSL license) along with GHC code. For developers (commercial or open source), the OpenSSL license only mentions redistribution of the OpenSSL code in binary form (paragraph 2). In this context "binary form" means the complete program binary, not partial binary as with statically linking to a library, so developers of GHC programs would *not* have to include the whole OpenSSL&SSLeay license in their source code. Paragraph 6 of the OpenSSL (1998-2005) license states that: * 6. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit (http://www.openssl.org/)". All developers would have to do is include the acknowledgment stated above. On the other hand, the OpenSSL FAQ at <http://www.openssl.org/support/ faq.html#LEGAL2> mentions that some "GPL" programs do not allow binary combination (static linking) or interoperation (dynamic linking) with OpenSSL. Honestly I have not seen any "GPL" licenses like this. The GNU GPL version 2, at <http://www.gnu.org/licenses/ gpl.html>, does not mention OpenSSL, nor does version 1, nor does the GNU LGPL, at <http://www.gnu.org/licenses/lgpl.html>. In any case, I think it would be more of a restriction to someone *using* the OpenSSL program, not a developer. Best regards, Peter P.S. On a related note, OpenSSL's BN library does not contain any patented algorithms.

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recursive import problems
by Serge D. Mechveliani 12 Aug '06

12 Aug '06

Dear GHC team, Can you, please help me with recursive import? I have a certain large project which compiles under ghc-6.4.1. Then I add a certain import declaration to the module Dumatel.Reduce, which leads to import loop, and `make' (under Cabal) reports --------------- Module imports form a cycle for modules: Bool0 imports: Dumatel.Reduce Parse2 Parse1 Prelude4 Prelude3_1 Prelude3 Prelude2_0 Prelude2 Prelude1 Prelude00 Prelude0 List Maybe Data.Map Data.Set Dumatel.Reduce imports: Prelude5 Debug.Trace NewUnify Parse1 Prelude4 Prelude3_0 Prelude3 Prelude2 Prelude1 Prelude00 Prelude0 List Maybe Data.Map Data.Set Prelude5 imports: Bool0 Dumatel.Reduce Parse1 Prelude4 Prelude3_1 Prelude3_0 Prelude3 Prelude2_0 Prelude2 Prelude1 Prelude00 Prelude0 List Char Maybe Data.Map Data.Set -------------------- I am trying the .hs-boot modules and {-# SOURCE #-} import for each of the above 3 modules. And fail, because the situation is much more complex than in the GHC guide examples. Does GHC provide a tool for automating producing a .hs-boot module from .hs module? Because this is tedious to convert from a large .hs module by hand. It tried short variants for .hs-boot with exporting a single type instead of many items in .hs. But this was not sufficient. If I send you the source project, could you show me the simplest .hs-boot modules and import pragmas that enable to `make' it ? ----------------- Serge Mechveliani mechvel(a)botik.ru

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ANN: TextRegexLazy 0.70 (stable)
by Chris Kuklewicz 11 Aug '06

11 Aug '06

What: "TextRegexLazy" version 0.70 Where: darcs get --partial http://evenmere.org/~chrisk/trl/stable/ (and darcs get --partial http://evenmere.org/~chrisk/trl/head/ ) The conversion to separate regex-* packages seems stable now. More changes will be done as part of interfacing with GHC. What should I do to advance the plan of changing GHC's regex support? Note that the new Posix library backend is much higher performance than the old one when searching for all the (non-overlapping) matches. The regex-compat package provides Text.Regex.New that uses this better wrapping. The low level API from the Wrap modules always handles errors with Either types. The (Byte)String modules provide a medium level API that handles errors with Either types (compile/execute/regexec). By comparison, the "match" or "=~" high level API still calls error or fail. The build environment will have to be slightly edited when installing. Details are in the README file (and you can and should email me questions). I would appreciate someone with ghc on windows to build as many of the packages as possible and tell me how to do it or how to fix it. GHC includes a copy of the Posix regex library to compile on windows, but regex-posix does not do this (yet). regex-parsec may undergo some small changes to give it a more posix-compatible mode. Right now QuickCheck has found some sub-expression captures that are different for pcre and posix, and parsec agrees with pcre in its left-most strategy but does not always agree with posix in its longest strategy. -- Chris

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dependingOn in 6.6
by John Meacham 11 Aug '06

11 Aug '06

I was wondering if we could be sure to get dependingOn :: a -> b -> a dependingOn = .... in ghc 6.6? this has been discussed before, it is implemented in jhc and I have found all sorts of use for it as it can be used to control let floating and inlining in a nice general way and is trivial to implement. (one for ghc was posted before based on primitives it already implements) we just need to decide on a module to export it. the meaning is that x = ... `dependingOn` y returns x with an artificial dependency on y. so things using x cannot be floated out above where y is defined. John -- John Meacham - ⑆repetae.net⑆john⑈

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getMBlocks
by Rich Fought 11 Aug '06

11 Aug '06

Hello, I'm still chasing down a memory leak in my server application written in Haskell using GHC 6.4.x under MinGW/MSYS. In the scenario described below, I am repeating the same server request once per second continuously. After utilizing some memory monitoring tools I've discovered that memory usage fluctuates within in a range of approximately 850 KB (I assume as garbage is collected), but at regular intervals the range gets bumped up by ~ 1 MB. So in effect I get a stair-stepping of memory usage that keeps repeating until memory runs out. WinDbg has revealed that this stepping coincides with the GHC runtime function getMBlocks(). My question is: what conditions affect when the runtime determines that it needs more memory? Is it a pure "no more room" trigger or is there some sort of algorithm behind it? I assume that this behavior means I still have a space leak somewhere in my Haskell code, though none of leak check tools I utilize indicate such. Thanks, Rich

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GHC 6.4.3 on FreeBSD
by Simon Marlow 11 Aug '06

11 Aug '06

An update on the GHC/FreeBSD front: I didn't manage to reproduce the reported threading bugs on a UP, will be trying on a MP shortly. However, I did discover one odd case that libpthread doesn't appear to handle properly, but libthr does. This arose from a test in GHC's test suite, but I've transliterated the code from Haskell to C: $ cat thr1.c #include <unistd.h> #include <signal.h> #include <pthread.h> int main(int argc, char *argv[]) { sigset_t s; sigemptyset (&s); sigaddset(&s, SIGUSR1); sigprocmask(SIG_BLOCK, &s, NULL); pthread_kill(pthread_self(), SIGUSR1); sigpending(&s); printf("%x\n", s); exit(0); } $ gcc -pthread thr1.c $ ./a.out 0 $ gcc -lthr thr1.c $ ./a.out 20000000 $ This might (or might not) be related to the other threading issues with GHC on FreeBSD. Do you think we should link with -lthr by default on FreeBSD? This would be a trivial change to make, and given that GHC has its own lightweight threading runtime, we probably aren't getting much from having the KSE-based threading implementation anyway. Cheers, Simon

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Re: Replacement for GMP: Update
by Peter Tanski 10 Aug '06

10 Aug '06

Reilly, > ... this shouldn't prohibit linking > GMP in dynamically, should it? It's just a C library and GCC should > happily generate relocatable code. As a dynamically linked library, > there should be no tainting issues to worry about even if the > dynamically linked code is shipped with the executable. > > Am I missing something? Not at all. GHC builds the GMP library only if it is not already available on the system. On my Mac OS X computer it uses a dynamic library. I have not tried using gmp.dll on Windows since I have not built GHC on my Windows computer (it is a bit slow--a 600MHz P3). But the dynamic library form of GMP only solves the licensing problem (admittedly, for my purposes the worst of the bunch). It should be easy to change GMP's build settings so GHC is distributed with a dynamic GMP library. The other problem is that GMP has a mechanism to let the user determine its memory allocator, with the caveat that only one allocator can be used by a single program. GHC configures GMP to use GHC's RTS-GC for allocation so GHC-compiled programs can't interface with GHC separately. (This would not be such a big problem for general programs but C-Haskell cryptographic or scientific programs that might benefit from GMP's additional functionality would suffer.) On a side note, if you have been reading this user-list recently it seems that programmers (including myself, I guess) do not want to have to package a dynamic library (GMP) with programs compiled with GHC--a particularly irksome task if your Haskell program doesn't even *use* Integer. Not only do users have to package the separate dll, they also have to package a notice of the GMP copyright along with the binary. Just today Einar Karttunen mentioned that: >> * "This product includes software developed by the OpenSSL Project >> * for use in the OpenSSL Toolkit (http://www.openssl.org/)". >> >> All developers would have to do is include the acknowledgment stated >> above. > ... > ps. personally I don't think the advertising clause is bad, but > I think it is bad to force it on other users. Einar does have a good point, here. Personally speaking, such packaging and licensing stuff is o.k. for free software but for a clean commercial distribution it would be a bad thing; a reason to choose not to use GHC (or nhc98, for that matter). Best regards, Peter

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