- ghc-devs - Haskell.org

Find the ghc binary path from libdir
by Fendor 10 Feb '21

10 Feb '21

Hello everyone! I want to find out the location of the `ghc` (and `ghc-pkg`) executable given the `$libdir` (obtained by `ghc --print-libdir`). Is there a platform independent way of doing that, which we can rely on? E.g. on windows, we found that the ghc executable's location is: * `$libdir/../bin/ghc` For NixOs (or when using ghcup), it works with: * `$libdir/../../bin/ghc` but I worry that this is a just an accident that is not guaranteed by the installation process. I also noticed there seems to be a binary in * `$libdir/bin/ghc` Is one of these ways documented to be guaranteed by the ghc installation process? (P. S. first time using a mailing list, hope I am doing it correctly) Best regards, Fendor

3 4

[ANNOUNCE] GHC 8.10.4 released
by Ben Gamari 10 Feb '21

10 Feb '21

The GHC team is very pleased to announce the availability of GHC 8.10.4. Source and binary distributions are available at the usual place: https://downloads.haskell.org/ghc/8.10.4/ This is a small bug-fix release, fixing two bugs present in 8.10.3: * Fix a linker hang triggered by dynamic code loading on Windows (#19155) * Fix a crash caused by inappropriate garbage of heap-allocated data reachable from foreign exports (#19149) As always, feel free to report any issues you encounter via [gitlab.haskell.org](https://gitlab.haskell.org/ghc/ghc/-/issues/new). Cheers, - Ben

2 1

Re: Plan for GHC 9.2
by Andrzej Rybczak 09 Feb '21

09 Feb '21

Hey Ben, It would be excellent to get NoFieldSelectors extension (https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4743) in. IIUC it's almost ready to be merged.

1 0

Has ghc-9.0 for windows changed to require installation?
by Takenobu Tani 09 Feb '21

09 Feb '21

Hi devs, The ghc-binary for windows needs to `make install` since ghc-9.0 [1]. Is this an intended change? Previously, ghc-8.10.4 binary for windows [2] doesn't need to `make install`. We only expand the tar-file and then we can execute `bin/ghcii.sh`. [1]: https://downloads.haskell.org/ghc/9.0.1/ghc-9.0.1-x86_64-unknown-mingw32.ta… [2]: https://downloads.haskell.org/ghc/8.10.4/ghc-8.10.4-x86_64-unknown-mingw32.… Regards, Takenobu

3 3

[ANNOUNCE] GHC 9.0.1 released
by Ben Gamari 09 Feb '21

09 Feb '21

The GHC team is very pleased to announce the availability of GHC 9.0.1. Source and binary distributions are available at the usual place: https://downloads.haskell.org/ghc/9.0.1/ In addition to numerous bug fixes, GHC 9.0.1 will bring a number of new features: * A first cut of the new LinearTypes language extension [2], allowing use of linear function syntax and linear record fields. * A new bignum library, ghc-bignum, improving portability and allowing GHC to be more easily used with integer libraries other than GMP. * Improvements in code generation, resulting in considerable runtime performance improvements in some programs. * Improvements in pattern-match checking, allowing more precise detection of redundant cases and reduced compilation time. * Implementation of the "simplified subsumption" proposal [3] simplifying the type system and paving the way for QuickLook impredicativity in GHC 9.2. * Implementation of the QualifiedDo extension [4], allowing more convenient overloading of `do` syntax. * An experimental new IO manager implementation for Windows platforms, both improving performance and fixing many of the quirks with the old manager built on POSIX-emulation. * Improvements in compilation time. And many more. See the release notes [5] for a full accounting of the changes in this release. As always, feel free to report any issues you encounter via gitlab.haskell.org. Cheers, - Ben [1]: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.0#ghc-prim-07 [2]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0111-l… [3]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0287-s… [4]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0216-q… [5]: https://downloads.haskell.org/ghc/9.0.1/docs/html/users_guide/9.0.1-notes.h…

3 4

Reduction in Windows CI capacity
by Ben Gamari 09 Feb '21

09 Feb '21

tl;dr. GHC's CI capacity will be a reduced due to a loss of sponsorship, particularly in Windows runner capacity. Help wanted in finding additional capacity. Hi all, For many years Google X has generously donated Google Compute Engine resources to GHC's CI infrastructure. We all owe a debt of gratitude to Google X for providing us with what has undoubtedly amounted to tens of thousands of dollars of computational capacity over the years. I would especially like to thank Greg Steuck, whose advocacy made this donation possible. Of course, organizational priorities understandably change and Google X will be unable to continue their sponsorship in the future. This puts us in a bit of a tricky situation; Google Compute Engine is currently the home of nearly 100 cores worth of CI capacity, including: * roughly 20% of our x86-64/Linux capacity * our only x86-64/FreeBSD runner * all five of our x86-64 Windows runners While the Linux runners are fairly easy to replace, the Windows capacity is a bit harder since Windows cloud capacity is quite expensive (IIRC nearly half of the cost of our Windows GCE instances is put towards the license). In the short term I can cover for some of this lost capacity by bringing up a Windows runner using our generous donation from Packet [1]. However, I am extrmely wary of outspending our welcome on Packet's infrastructure and therefore we will need to accept a small reduction in capacity for a bit while we work out a more sustainable path forward. We will have to see how things go but it may be necessary to disable the Windows jobs on (non-Marge) merge request validation pipelines. I am looking into various options for again reaching our previous capacity, but this is an area where you might be able to help: * Familiarity with Windows licensing. Unfortunately the details of Windows licensing for virtualization purposes are a bit tricky. I suspect that the cheapest way forward is a single Windows Server license on a large machine but if you are familiar with Windows licensing in this setting, please do be in touch. * Providing Windows licenses. If you know of an organization that may be able to donate Windows licenses either in-kind or via financial support, please do be in touch. * Providing Windows cloud instances. If you know of an organization that may be able to donate Windows cloud instances, do holler. As always, we welcome any hardware or cloud instance contributions. Do be in touch if you may be in an position to help out. Cheers, - Ben [1] https://www.packet.com/

1 0

remAddr# primop inconsistency
by Csaba Hruska 06 Feb '21

06 Feb '21

Hello, I've discovered that the remAddr# primop documentation is inconsistent with the implementation. According to the docs (primops.txt.pp) the remAddr# should be the same as remInt#. > primop AddrRemOp "remAddr#" GenPrimOp Addr# -> Int# -> Int# {Return the remainder when the {\tt Addr\#} arg, treated like an {\tt Int\#}, is divided by the {\tt Int\#} arg.} > > But it is implemented with the mo_wordURem instruction, just like the WordRemOp primop. > GHC/StgToCmm/Prim.hs: > AddrRemOp -> \args -> opTranslate args (mo_wordURem platform) > WordRemOp -> \args -> opTranslate args (mo_wordURem platform) > IntRemOp -> \args -> opTranslate args (mo_wordSRem platform) > Which one is correct, the docs or the implementation? Regards, Csaba Hruska

2 2

GHC Reading Guide
by Takenobu Tani 06 Feb '21

06 Feb '21

Dear devs, I've written a simple document about "GHC source reading" for myself and potential newcomers: * https://takenobu-hs.github.io/downloads/haskell_ghc_reading_guide.pdf (https://github.com/takenobu-hs/haskell-ghc-reading-guide) Please teach me if something's wrong. I'll learn and correct them. Happy Haskelling :) Regards, Takenobu

3 3

Happy version downgrade
by Simon Peyton Jones 04 Feb '21

04 Feb '21

Friends I can't build ghc-9.0 because of this: checking for ghc-pkg matching /opt/ghc/bin/ghc... /opt/ghc/bin/ghc-pkg checking for happy... /home/simonpj/.cabal/bin/happy checking for version of happy... 1.20.0 configure: error: Happy version 1.19 is required to compile GHC. What is the easiest way to fix? I have happy 1.19.8, but it's not called plain "happy" bash$ happy-1.19.8 --version Happy Version 1.19.8 Copyright (c) 1993-1996 Andy Gill, Simon Marlow (c) 1997-2005 Simon Marlow Happy is a Yacc for Haskell, and comes with ABSOLUTELY NO WARRANTY. This program is free software; you can redistribute it and/or modify it under the terms given in the file 'LICENSE' distributed with the Happy sources. Thanks Simon

2 1

Inspecting function arguments in GHCi
by Andrew Kvapil 02 Feb '21

02 Feb '21

Hello, I'm interested in inspecting the strictness of functions at runtime and the depth of thunks "in the wild." For this reason I'm modifying GHC 8.10.2, essentially to add additional information to breakpoints. I'd like to reuse the logic behind GHCi's :print command (pprintClosureCommand, obtainTermFromId, ...) for which I suppose I need Id's. Those however don't exist for destructuring patterns, such as those in the following equations: last [x] = x last (_:xs) = last xs So I'm wondering where would be a good place in the pipeline to transform patterns like these into at-patterns, to give them Id's. However, the breakpoint logic only looks at the free variables of the right-hand sides and not transitively, which means that e.g. in the following example neither ':print arg1' nor ':print as' works when the interpreter hits a breakpoint in the top level expression on the RHS: qsort arg1@(a:as) = qsort left ++ [a] ++ qsort right where (left, right) = (filter (<=a) as, filter (>a) as) Thus I'd also like to know how to extend the free var logic for Tickish that eventually leads to CgBreakInfo and :print's ability to inspect these bindings at runtime. My goal would be to determine to what extent was a thunk evaluated during function application. Any advice would be greatly appreciated! Regards, Andrew Kvapil

4 5