December 2004 - Glasgow-haskell-users

posting
by Kenny Chamber 16 Dec '04

16 Dec '04

How long after posting should it take for a message to appear on the list? ----------------------- Kenny Chamber http://gem-hs.org/contact.html

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RE: Stack overflow machine dependent?
by Simon Marlow 16 Dec '04

16 Dec '04

On 14 December 2004 12:42, Arjen van Weelden wrote: > Simon Marlow wrote: > >> On 14 December 2004 10:46, Arjen van Weelden wrote: >> >> Is the program completely self-contained and deterministic? i.e. >> does it read any files in the filesystem, check the time, or do >> anything that might give different results on the two machines? >> > This is exactly what makes the problem strange! Yes, it is completely > self-contained and deterministic. I forgot to mentions this, sorry. > The program looks like this: > main :: IO () > main = putStr (f 100 0). > Where f is a referential transparent function that doesn't do IO or > anything unsafe. Then I don't know... as far as I'm aware the same binary should perform identical operations as long as the program doesn't do any IO. Can you use profiling to track down the part of the code that is running out of stack space, and hence try to determine why? Cheers, Simon

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debian ghci on sparc64
by William Lee Irwin III 16 Dec '04

16 Dec '04

There seems to be some trouble with the debian ghci on sparc64. I can dredge up more information if given an idea of what to look for. $ ghci ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.2.2, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base ... linking ... done. zsh: 7796 segmentation fault ghci -- wli

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RE: -ddump-parsed and infix operators
by Simon Peyton-Jones 15 Dec '04

15 Dec '04

You're right: they are passed left-associatively, and fixed up later. That way the parser does not need to know about associativity and precedence. So it's not a bug. Just something you need to know about -ddump-parsed! Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Roberto Zunino | Sent: 14 December 2004 19:37 | To: Glasgow-haskell-users(a)haskell.org | Subject: -ddump-parsed and infix operators | | I noticed that GHC 6.2.2 always parse infix operators as they were | left-associative. For example: | | %%%%% | Prelude> :info : | -- : is a data constructor | infixr 5 : | (:) :: forall a. a -> [a] -> [a] | Prelude> 1:2:3:[] | | ==================== Parser ==================== | ((1 GHC.Base.: 2) GHC.Base.: 3) GHC.Base.: GHC.Base.[] | | | [1,2,3] | %%%%% | | I suppose that the parse tree is then "fixed" in a later stage. | | (Or maybe the parse tree is fine but it gets unparsed in the wrong way?) | | However, the output above is a bit puzzling to me. Should I report this | as a minor bug or is this the intended output? | | Thanks to your attention, | Zun.

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-ddump-parsed and infix operators
by Roberto Zunino 15 Dec '04

15 Dec '04

I noticed that GHC 6.2.2 always parse infix operators as they were left-associative. For example: %%%%% Prelude> :info : -- : is a data constructor infixr 5 : (:) :: forall a. a -> [a] -> [a] Prelude> 1:2:3:[] ==================== Parser ==================== ((1 GHC.Base.: 2) GHC.Base.: 3) GHC.Base.: GHC.Base.[] [1,2,3] %%%%% I suppose that the parse tree is then "fixed" in a later stage. (Or maybe the parse tree is fine but it gets unparsed in the wrong way?) However, the output above is a bit puzzling to me. Should I report this as a minor bug or is this the intended output? Thanks to your attention, Zun.

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RE: Stack overflow machine dependent?
by Simon Marlow 14 Dec '04

14 Dec '04

On 14 December 2004 10:46, Arjen van Weelden wrote: > I compiled a Haskell 98 program using ghc 6.2 -O and ran the > executable, using main +RTS -H256m -s, on two similar computers: > > PC 1: Athlon 1400, 512MB, Windows XP Prof SP2 (successful termination) > PC 2: Athlon XP 1800+, 512MB, Windows XP Prof SP2 (stack overflow) > > The program runs successful within 1MB of stack on PC 1, but it exits > with a stack overflow error on PC 2. > > Has anyone else observed such behaviour using the same binary, and > similar computers? I'm curious of what might trigger the stack > overflow. The program itself is partially generated and large, so > I'll omit it for the time being. Is the program completely self-contained and deterministic? i.e. does it read any files in the filesystem, check the time, or do anything that might give different results on the two machines? Cheers, Simon

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RE: Reading/Writing sockets concurrently
by Simon Marlow 14 Dec '04

14 Dec '04

On 10 December 2004 10:55, Mårten Dolk wrote: > Btw, you import GHC.IO and not System.IO. What is the diffrence > between those two? System.IO is guaranteed to be there in the next release :-) Cheers, Simon

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[ ghc-Feature Requests-1084122 ] RPM doesn't support --prefix
by SourceForge.net 14 Dec '04

14 Dec '04

Feature Requests item #1084122, was opened at 2004-12-13 01:54 Message generated for change (Comment added) made by simonmar You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=358032&aid=1084122&group_… >Category: None >Group: None >Status: Open Priority: 5 Submitted By: John Skaller (skaller) Assigned to: Nobody/Anonymous (nobody) >Summary: RPM doesn't support --prefix Initial Comment: After installing ghc for linux using rpm with --prefix=/usr/local, the ghc scriipt incorrectly thinks the libraries etc are in /usr: #!/bin/sh GHCBIN="/usr/lib/ghc-6.2.2/ghc-6.2.2"; TOPDIROPT="-B/usr/lib/ghc-6.2.2"; # Mini-driver for GHC exec $GHCBIN $TOPDIROPT ${1+"$@"} After editing, at least the compiler actually starts up :) ---------------------------------------------------------------------- >Comment By: Simon Marlow (simonmar) Date: 2004-12-13 16:26 Message: Logged In: YES user_id=48280 Re-opened. Any RPM gurus out there who could knock this one on the head? Note it's not just the ghc script, there's a couple of other scripts that need munging (ghci, ghc-pkg, hsc2hs maybe). ---------------------------------------------------------------------- Comment By: John Skaller (skaller) Date: 2004-12-13 14:54 Message: Logged In: YES user_id=5394 I can see it isn't supported :) However after the change to those two lines, the compiler works, links libraries, and the resultant binary executes correctly (as far as I can tell never having written any Haskell before .. :) So why not support it? I had no choice .. my root partition, containing /usr is 97% full.. :) ---------------------------------------------------------------------- Comment By: Simon Marlow (simonmar) Date: 2004-12-13 12:54 Message: Logged In: YES user_id=48280 You're trying to install the binary RPM using a different prefix? That's not supported, I'm afraid. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=358032&aid=1084122&group_…

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Reading/Writing sockets concurrently
by Mårten Dolk 13 Dec '04

13 Dec '04

Hi, I'm trying to create a client application that needs to read and write data from a socket. What I want to do is to have one thread reading the socket and another thread writing to the same socket, but I can't get it to work. I know that there is a problem with having two threads reading from the same Handle (as in the aaaa bbbb example), due to the locking. To avoid this blocking I open the socket with Network.Socket.socket and create two handles with socketToHandle, one in ReadMode and one in WriteMode. But the threads still seem to be blocking each other and the program runs very slowly. I am using channels to have the read and write threads communicate with other threads in the application and by removing a writeChan in one of these other threads the program crashes with a "Fail: thread blocked indefinitely". Are there any good examples of how to use sockets with Haskell. I have no way of knowing in which order I will need to read data from and write data to the socket. I am using ghc version 6.2.2 on Linux. Thanks in advance -Mårten-

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RE: Reading/Writing sockets concurrently
by Simon Marlow 10 Dec '04

10 Dec '04

On 09 December 2004 17:46, Mårten Dolk wrote: > I'm trying to create a client application that needs to read and write > data from a socket. What I want to do is to have one thread reading > the socket and another thread writing to the same socket, but I can't > get it to work. > > I know that there is a problem with having two threads reading from > the same Handle (as in the aaaa bbbb example), due to the locking. To > avoid this blocking I open the socket with Network.Socket.socket and > create two handles with socketToHandle, one in ReadMode and one in > WriteMode. Actually you don't need to create two Handles to a socket - the socket Handle is a "duplex" Handle with two locks, so the read and write sides don't interfere with each other. In fact, you shouldn't create two Handles to the same socket, because as soon as one of the finalizers runs it will close the socket. > But the threads still seem to be blocking each other and the program > runs very slowly. I am using channels to have the read and write > threads communicate with other threads in the application and by > removing a writeChan in one of these other threads the program > crashes with a "Fail: thread blocked indefinitely". Looks like a deadlock of some kind. Compiling with -debug and running with +RTS -Ds might give you some clues. Cheers, Simon

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