May 2018 - ghc-devs - Haskell.org

GHC's module hierarchy
by Simon Peyton Jones 02 Oct '19

02 Oct '19

Dear ghc-devs hsyl20 proposes a radical overhaul of the module structure of GHC itself. He or she suggested it six months ago in https://ghc.haskell.org/trac/ghc/ticket/13009 and has now offered a monster patch https://phabricator.haskell.org/D3647 It's clearly the result of a lot of work, but I was the only one who responded on the original ticket, and it'll affect all of your lives in a very immediate way. So, would you like to * consider the idea * look at the actual re-mapping of modules hsyl20 proposals * express an opinion about whether to go ahead Probably the ticket, rather than Phab, is the best place to comment on the general idea. I'd like to thank hsyl20. GHC's rather flat module structure has grown incrementally over years. But still, there are pros and cons. Simon

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Default options for -threaded
by lonetiger＠gmail.com 04 Jan '19

04 Jan '19

Hi All, A user on https://ghc.haskell.org/trac/ghc/ticket/11054 has asked why -N -qa isn’t the default for -threaded. I’m afraid I don’t know a good reason why it’s not. Can anyone help shed some light on this? If there is no good reason, Would anyone object to making it the default? Thanks, Tamar

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perf.haskell.org functional again
by Joachim Breitner 30 Nov '18

30 Nov '18

Hi, after a system upgrade to avoid weird linker errors, and after some fixes in the nofib submodule, http://perf.haskell.org/ghc is running again. I am collecting instruction counts instead of runtime, because the latter was just too often varying too wildly. I hope this will yield less false alarms. I am also running nofib with mode=fast. This way, building GHC, running the testsuite and nofib takes a bit over one hour. I hope this can keep up with y'all's commits (when it took 2h it couldn't). Now nothing of the setup requires a quiet dedicated machine, so if there is a need, we could move these builds into the cloud or into some CI infrastructure - but no changes are immediately planned. Enjoy, Joachim

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Steps to propose a new primop in GHC
by Mitsutoshi Aoe 25 Jul '18

25 Jul '18

Hi devs, I'm thinking to add a primop in GHC but not sure how I should proceed. The primop I have in mind is something like: traceEventBinary# :: Addr# -> Int# -> State# s -> State# s This function is similar to the existing traceEvent# but it takes a chunk of bytes rather than a null-terminated string. It is useful to trace custom user events (e.g. network packet arrival timestamps in an network application) in eventlogs. At library level, it is supposed to be used like the tracing functions in Debug.Trace but with ByteString argument: traceEventBinary :: ByteString -> a -> a traceEventBinaryIO :: ByteString -> IO () Note that this can't live in base because of the dependency on bytestring. So how should I proceed from here? Am I supposed to submit a GHC proposal or should I ask on the libraries list? This is not a prominently visible change in GHC. It rather affects only ghc-prim and no effects in base. Thanks, Mitsutoshi

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Loading GHC into GHCi (and ghcid)
by Matthew Pickering 04 Jul '18

04 Jul '18

Hi all, Csongor has informed me that he has worked out how to load GHC into GHCi which can then be used with ghcid for a more interactive development experience. 1. Put this .ghci file in compiler/ https://gist.github.com/mpickering/73749e7783f40cc762fec171b879704c 2. Run "../inplace/bin/ghc-stage2 --interactive -odir tmp -hidir tmp" from inside compiler/ It may take a while and require a little bit of memory but in the end all 500 or so modules will be loaded. It can also be used with ghcid. ghcid -c "../inplace/bin/ghc-stage2 --interactive -odir tmp -hidir tmp" Hopefully someone who has more RAM than I. Can anyone suggest the suitable place on the wiki for this information? Cheers, Matt

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Scavenging SRTs in scavenge_one
by Ben Gamari 26 Jun '18

26 Jun '18

Hi Simon, I'm a bit confused by scavenge_one; namely it doesn't scavenge SRTs. It appears that it is primarily used for remembered set entries but it's not at all clear why this means that we can safely ignore SRTs (e.g. in the FUN and THUNK cases). Can you shed some light on this? Cheers, - Ben

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Plan for GHC 8.6.1
by Ben Gamari 22 Jun '18

22 Jun '18

Hello fellow lazy purists, With GHC 8.4.2 out the door, it is time to begin looking forward to 8.6.1. In keeping with our six-month release schedule, this release will be targetted for early-September, with the stable branch being cut in mid-to-late June. Remarkably, this is only 6 weeks away. If you have patches that you would like to see in 8.6.1, please do put them up on Phabricator and the 8.6.1 status page [1] in the coming weeks to ensure that there is sufficient time for review. If you have a patch which you are concerned won't make the cut-off, do say something. Cheers, - Ben [1] https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.6.1

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Why do we prevent static archives from being loaded when DYNAMIC_GHC_PROGRAMS=YES?
by Moritz Angermann 13 Jun '18

13 Jun '18

Dear friends, when we build GHC with DYNAMIC_GHC_PROGRAMS=YES, we essentially prevent ghc/ghci from using archives (.a). Is there a technical reason behind this? The only only reasoning so far I've came across was: insist on using dynamic/shared objects, because the user said so when building GHC. In that case, we don't however prevent GHC from building archive (static) only libraries. And as a consequence when we later try to build another archive of a different library, that depends via TH on the former library, GHC will bail and complain that we don't have the relevant dynamic/shared object. Of course we don't we explicitly didn't build it. But the linker code we have in GHC is perfectly capable of loading archives. So why don't we want to fall back to archives? Similarly, as @deech asked on twitter[1], why we prevent GHCi from loading static libraries? I'd like to understand the technical reason/rational for this behavior. Can someone help me out here? If there is no fundamental reason for this behavior, I'd like to go ahead and try to lift it. Thank you! Cheers, Moritz --- [1]: https://twitter.com/deech/status/1001182709555908608

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ZuriHac 2018 GHC DevOps track - Request for Contributions
by Niklas Hambüchen 05 Jun '18

05 Jun '18

Hi GHC devs, The ZuriHac 2018 conference will feature a GHC DevOps track (which Andreas and I are coordinating), that will be all about fostering contributions to GHC and learning to hack it. There will be a room or two allocated at Zurihac for this purpose. We hope to focus on roughly these topics: * How to build GHC from source * How to iterate on changes quickly * What's the development workflow, how do I get my patch merged? * How do specific parts of GHC work * Extending GHC's test suite * Improving automation, processes and release quality * Documenting the undocumented If we are successful, we will have more GHC contributers after ZuriHac than before. But we need your contributions to add content to the track! Specifically, we're looking for ZuriHac attendees who could (help) run a session in this track. Such as: * Giving a talk about one of the above or related topics * Hosting a hack session where participants of the track work together on the GHC code base towards a specific goal * Being around as a "GHC mentor" during open hack sessions, helping new GHC contributors out To give some examples, I could offer to give a talk on a recent effort to improve Ctrl+C and signal handling in the RTS, and I would like to run a hack session where we add performance regression tests based on CPU instruction counters. Please contact Andreas or me (on this list or privately) if you think you could help in any of these directions! If you're not sure, contact us anyway and tell us your idea! Best, Niklas and Andreas ZuriHac 2018 GHC DevOps track coordinators

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Trac email
by Simon Peyton Jones 01 Jun '18

01 Jun '18

Devs Trac has entirely stopped sending me email, so I have no idea what's happening on the GHC front. Could someone unglue it? Thanks! Simon

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