April 2026 - Haskell-Cafe

Conduit missing closing file handles
by Henning Thielemann 14 May '26

14 May '26

I have a pretty simple program for converting ZIP to TAR archives using the 'zip' and 'tar-conduit' packages, both using Conduit for streaming data. In principle the program works, but if the ZIP archive contains a non-trivial number of files, the program breaks because of exceeded limit of open file handles: $ zip2tar /usr/share/libreoffice/share/config/images_colibre.zip >/tmp/images_colibre.tar zip2tar: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException: /usr/share/libreoffice/share/config/images_colibre.zip: openFile: resource exhausted (Too many open files) While handling /usr/share/libreoffice/share/config/images_colibre.zip: openFile: resource exhausted (Too many open files) HasCallStack backtrace: throwIO, called at ./Control/Monad/Trans/Resource.hs:195:13 in resourcet-1.3.0-8b355f9483371034fb75ff40adb2e07157502721c941fbf8a6f607df6dd81546:Control.Monad.Trans.Resource The main function is essentially this one: [1] convertZipToTar :: (Zip.EntrySelector -> Zip.EntryDescription -> CTar.FileInfo) -> Sort -> FilePath -> IO () convertZipToTar fileInfoFromZipEntry_ sortMode zipPath = Zip.withArchive zipPath $ do entries <- Map.toList <$> Zip.getEntries files <- for entries $ \(selector, descr) -> flip fmap (Zip.getEntrySource selector) $ \src -> src .| (C.yield (Left $ fileInfoFromZipEntry_ selector descr) >> C.mapC Right) C.liftIO $ runConduitRes $ sequence_ files .| void CTar.tar .| C.stdoutC 'Zip.getEntrySource selector' generates a conduit for reading a file from the ZIP archive. It opens the archive anew for every accessed file, but it calls Conduit.Binary.sourceIOHandle, which promises to close a file promptly after reading. [2] It seems that files are not immediately closed after reading, but I cannot spot the cause. I suspected that "sequence_ files" might concatenate the Conduits while accumulating open file handles, but I think it should not and I did not find a matching alternative to sequence_. [1] https://hackage-content.haskell.org/package/zip2tar-0.0/src/src/Main.hs [2] https://hackage-content.haskell.org/package/zip-2.2.1/docs/src/Codec.Archiv…

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Third CfP: Festschrift and Workshop in Honor of David Basin (Deadline extended to 11 June 2026)
by Achim D. Brucker 27 Apr '26

27 Apr '26

Dear Fellow Researchers! Our dear colleague and friend David Basin is turning 65 in December 2026 and this has to be celebrated! We therefore organize a Festschrift and a Fest to celebrate his birthday and his extensive research contributions! The Fest/celebration itself will be held as a one-day event on the 15th of January 2027 at ETH Zürich. We have already checked that David is available. You do not have to keep it a secret - on the contrary, it is great if you share this message with anybody who might like to contribute! We hereby cordially invite you to contribute an article to the Festschrift and present it at the Fest. We welcome contributions in all areas close to David's research and interests, including but not limited to security, privacy, formal methods, logic, automated reasoning, model checking, theorem proving, software engineering, bridge, juggling, biking and more. The articles will be lightly reviewed by the Festschrift committee, and the proceedings will be **published by Springer Heidelberg in the LNCS series**. David will of course love to receive a research article from you, but also short personal articles that celebrate the history and friendship with David will be very much appreciated. We would like to set a deadline for submissions at the 21st of May 2026 via our submission site <https://easychair.org/conferences/?conf=feschi2027>. Articles should be formatted in Springer’s LNCS style and not exceed 5 pages for personal articles and 16 pages for scientific articles. If you have a work that you would like to contribute that does not fit into this page limit, it might be possible, but please reach out to us first. There will be no participation fee for the Fest and coffee breaks, lunch, and dinner will be included. Travel and accommodation costs are at the expense of the participants. We are happy to provide hotel suggestions for Zürich. Submission Information: * Format: 16 pages in LNCS format, templates available at: <https://www.springer.com/gp/computer-science/lncs/conference-proceedings-gu…> * Submission: <https://easychair.org/conferences/?conf=feschi2027> * Website (under construction) with updates and further information: <https://feschi2027.github.io/> * Timeline: * Submission: 11 June 2026 (extended) * Notification: end of June 2026 (to be confirmed) * Camera Ready Copy: early September 2026 (to be confirmed) Please let us know if you have any questions! Best wishes Achim D. Brucker (University of Exeter) Sebastian Mödersheim (Danmarks Tekniske Universitet) Christoph Sprenger (ETH Zürich) Luca Viganò (King’s College London) -- Prof. Achim Brucker | Chair in Cybersecurity & Head of Group | University of Exeter https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Storing a Haskellwiki-page fails
by X Y 24 Apr '26

24 Apr '26

L.S., After editing a page at wiki.haskell.org, I tried to store the page and got the following error message: Database error A database query error has occurred. This may indicate a bug in the software. [274dd5bf9e736eea1c9a5c34] 2026-04-23 13:41:25: Fatal exception of type "Wikimedia\Rdbms\DBQueryError" Can someone solve this please? Regards, ಹೆಂಕ್-ಜಾನ್ ವ್ಯಾನ್ ಟುಯ್ಲ್ Henk-Jan van Tuyl

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Wiki account creation
by Vanessa McHale 06 Apr '26

06 Apr '26

Would it be possible for me to get a Wiki account? I sent something to wiki-account-request(a)haskell.org but that has been quiet. Preferred username would be vem or vmchale Cheers, Vanessa McHale

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Aeson
by Ivan Perez 03 Apr '26

03 Apr '26

Hi Café The aeson (https://github.com/haskell/aeson) package hasn't seen updates in a while. The last one I see is from Oct 2025. It's getting out of date wrt new versions of dependencies available on Hackage, such as QuickCheck. It's also heavily depended on. What's the best course of action here? What can be done to get this updated? Thanks, Ivan

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Enriching errors in the "network" library
by Kazu Yamamoto 02 Apr '26

02 Apr '26

Hi all, For many years, users of the "network" library have been suffered from poor error handling. For example, the "bind" function displays an error message like the following, but it doesn't tell you which port you were trying to bind to. Network.Socket.bind: resource busy (Address already in use) I am working to improve this situation. The error message becomes as follows: Network.Socket.bind: resource busy (Address already in use [EADDRINUSE] <socket: 13> [::1]:53) If you're interested, please join the discussion: https://github.com/haskell/network/pull/610 P.S. In my opinion, Show IOException should display errno. Why doesn't it display? instance Show IOException where showsPrec p (IOError hdl iot loc s _errno fn) = (case fn of Nothing -> case hdl of Nothing -> id Just h -> showsPrec p h . showString ": " Just name -> showString name . showString ": ") . (case loc of "" -> id _ -> showString loc . showString ": ") . showsPrec p iot . (case s of "" -> id _ -> showString " (" . showString s . showString ")") --Kazu

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