July 2017 - ghc-devs - Haskell.org

Simon's (lack of) input
by Simon Peyton Jones 12 Jul '17

12 Jul '17

Friends My GHC inbox has grown to alarming proportions. I try to keep abreast of tickets where I think I have something substantial contribute, and generally succeed, but I've been failing badly in the last few weeks because of a storm of other commitments. I'll get back to it, but probably not before my summer holiday 3-17 August. Meanwhile if you are stalled awaiting input from me, please feel free to ping me about it. Simon

1 0

[ANNOUNCE] GHC 8.2.1 release candidate 3 available
by Ben Gamari 10 Jul '17

10 Jul '17

Hello everyone, I am pleased to at long last announce the third (and almost certainly last) release candidate of GHC 8.2.1. Binary and source distributions can be found at, https://downloads.haskell.org/~ghc/8.2.1-rc3/ This release candidate fixes a number of regressions from 8.0.2 found in -rc2, as well as a major correctness bug (#13615) present in several previous GHC major releases. Users taking advantage of parallelism in their programs will be strongly encouraged to upgrade to 8.2.1 once it is released. Among the other issues resolved in this candidate are, * Functionality allowing GHC to automatically use the ld.gold linker when available (see #13541). Not only has there recently been significant user demand for this feature, but this also serves to work around a performance bug in BFD ld affecting GHC 8.2 (#13739) * A regression resulting in the package cache file to be out-of-date after binary distribution installation (#13375) * Numerous type-checker bugs (#13625, #1370, #13782, #13871, #13594, #13879, #13881, #13875) * A bug wherein a thread blocked on a BLACKHOLE may not be woken up (#13751) * and many more... There are a few changes in release-engineering matters that should be mentioned, * Binary distributions for CentOS 6.7 have been dropped due to the release of CentOS 7.0 which can use Debian 8 binaries. If you would like us to continue to produce CentOS 6.7 bindists please let me know. * GHC HQ now also provides FreeBSD and OpenBSD distributions for amd64; this will allow us to more quickly ship distributions to users by eliminating the need for a long lag time between source release availability and having all binary distributions available. * There is a technology-preview of an AArch64 Linux binary distribution, as well as an ARM Linux build (although the latter won't be uploaded until a few hours from now). AArch64 support is quite preliminary but should be stable in 8.4 thanks to further linker fixes by Moritz Angerman. ARM should be stable. As always, let us know if you encounter problems. If all goes well we will hopefully have a final 8.2.1 release in the next two weeks. Finally, thanks for your patience during this admittedly quite drawn out release cycle. While it has been long, we are confident that the result will be worth the wait. Moreover, we have been steadily working on infrastructure which should shrink future release cycles and give us better testing between releases. More details on this coming soon. Happy testing, - Ben

3 3

can't validate on Linux
by Richard Eisenberg 10 Jul '17

10 Jul '17

Hi devs, When I try validating my patch, validation fails with > ... > Registering library for ghc-prim-0.5.0.0.. > ghc-cabal: '/home/rae/ghc/ghc-valid/bindisttest/install > dir/lib/ghc-8.3.20170312/bin/ghc-pkg' exited with an error: > ghc-pkg: Couldn't open database /home/rae/ghc/ghc-valid/bindisttest/install > dir/lib/ghc-8.3.20170312/package.conf.d for modification: {handle: > /home/rae/ghc/ghc-valid/bindisttest/install > dir/lib/ghc-8.3.20170312/package.conf.d/package.cache.lock}: hLock: invalid > argument (Bad file descriptor) > make[3]: *** [ghc.mk:990: install_packages] Error 1 > make[2]: *** [Makefile:51: install] Error 2 > make[1]: *** [bindisttest/ghc.mk:33: test_bindist] Error 2 > make: *** [Makefile:127: test_bindist] Error 2 Any advice? Thanks! Richard

5 7

Re: Compilation time
by Ryan Scott 08 Jul '17

08 Jul '17

Another things to note about 8.2 build times is that a bulk of the time is probably being spent during the linking phase. This is because GHC 8.2 has switched over to split-sections by default, but unfortunately, old versions of the BFD linker take a long time to link code that uses split-sections (see the discussion at [1]). There is ongoing work (which should hopefully land before the final 8.2 release) to use gold instead of BFD as the default linker when available, which will reduce linking times dramatically. Ryan S. ----- [1] https://ghc.haskell.org/trac/ghc/ticket/13739

5 6

Listing Trac keywords
by Ben Gamari 07 Jul '17

07 Jul '17

Hello everyone, Today I took a few minutes to write some SQL to generate a list of all of the keywords in Trac tickets. There are still a few quirks (e.g. no hyperlinking of ticket numbers, some mysterious duplicate ticket numbers). Nevertheless, it's better than nothing. The result can be found here [1]. Cheers, - Ben [1] https://ghc.haskell.org/trac/ghc/report/25?sort=n_tickets&asc=0&page=1

1 0

Updating Phabricator
by Ben Gamari 06 Jul '17

06 Jul '17

I'll be upgrading Phabricator in a few minutes. I expect this will only take 30 minutes or so and will let you know when it's done. Cheers, - Ben

1 1

Haskell Implementors' Workshop Call for Talks
by Richard Eisenberg 04 Jul '17

04 Jul '17

Call for Contributions ACM SIGPLAN Haskell Implementors' Workshop http://icfp17.sigplan.org/track/hiw-2017 Oxford, UK, 9 September, 2017 Co-located with ICFP 2017 http://www.icfpconference.org/icfp2017/ Important dates --------------- Proposal Deadline: Thursday, 6 July, 2017 Notification: Thursday, 20 July, 2017 Workshop: Saturday, 9 September, 2017 The 9th Haskell Implementors' Workshop is to be held alongside ICFP 2017 this year in Oxford. It is a forum for people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure, to share their work and discuss future directions and collaborations with others. Talks and/or demos are proposed by submitting an abstract, and selected by a small program committee. There will be no published proceedings. The workshop will be informal and interactive, with open spaces in the timetable and room for ad-hoc discussion, demos, and impromptu short talks. Scope and target audience ------------------------- It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2017. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides and presented data available with the consent of the speakers. The Implementors' Workshop is an ideal place to describe a Haskell extension, describe works-in-progress, demo a new Haskell-related tool, or even propose future lines of Haskell development. Members of the wider Haskell community encouraged to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. Students working with Haskell are specially encouraged to share their work. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- We invite proposals from potential speakers for talks and demonstrations. We are aiming for 20-minute talks with 5 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 300 words. Submissions should be made via HotCRP. The website is: https://icfp-hiw17.hotcrp.com/ We will also have a lightning talks session which will be organised on the day. These talks will be 5-10 minutes, depending on available time. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Program Committee ----------------- * Richard A. Eisenberg -- chair (Bryn Mawr College) * Adam Gundry (Well-Typed) * Bartosz Nitka (Facebook) * Wren Romano (X, formerly Google[x]) * Alejandro Serrano Mena (Utrecht University) * Jan Stolarek (University of Edinburgh) Contact ------- * Richard A. Eisenberg <rae(a)cs.brynmawr.edu>

1 1

Compilation time
by Deest, Gaël 04 Jul '17

04 Jul '17

Hi all, As you are probably well aware, GHC performance has been a growing concern over the last few years. Many Haskell programmers complain that build time has significantly increased over the last few releases. However, to our knowledge, there isn't much data available to substantiate this claim and the severity of these problems is not well known. That's why we would like to bring some anecdotal evidence to your attention that seems to indicate really major performance regressions. We stumbled upon the CI of the data-reify package, which is built against all GHC releases since 2010 : https://travis-ci.org/ku-fpg/data-reify tl;dr: Build time has gone from 1 min 32s for GHC 7.0 to 4 min 35s for GHC 8.2. The 8.2 release alone seems to have increased compilation time by almost 2 minutes, with the current development branch bringing only minor performance improvements. Of course, this single data point is not sufficient to establish how severe and widespread these problems are. More data could probably be gathered from other packages. However, it certainly matches our (subjective) experience and we felt important to report it to you. Regards, -- Gaël Deest Tweag I/O

4 3