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Heap allocation in the RTS
by David Feuer 20 Sep '18

20 Sep '18

I'm working on re-implementing the stable name system. For the new design, it seems much cleaner to allocate stable names in lookupStableName (in rts/StableName.c) rather than in the C-- code that calls it. But I haven't seen RTS code that does heap allocation. Is it possible? If so, how do I do it?

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touch# primitive
by Daniel Cartwright 19 Sep '18

19 Sep '18

in GHC.Prim, there is a primitive 'touch#'. It seems that it is used to keep pointers alive, and takes something of any runtime representation, and a State# RealWorld, but there's really no documentation on it, so my idea of what it does is just a guess. Can anyone explain what exactly it does?

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Redundant import warnings
by Simon Peyton Jones 17 Sep '18

17 Sep '18

Edward Can you perhaps bring the core libraries committee to consensus on this (I think minor) issue, and we can then get on with implementing it? Many thanks -- hope to se you at ICFP. Simon | -----Original Message----- | From: haskell-core-libraries(a)googlegroups.com <haskell-core- | libraries(a)googlegroups.com> On Behalf Of GHC | Sent: 17 September 2018 01:49 | Subject: [core libraries] Re: [GHC] #13064: Incorrect redudant imports | warning | | #13064: Incorrect redudant imports warning | -------------------------------------+---------------------------------- | --- | Reporter: phadej | Owner: (none) | Type: bug | Status: new | Priority: low | Milestone: 8.8.1 | Component: Compiler | Version: 8.0.1 | Resolution: | Keywords: | Operating System: Unknown/Multiple | Architecture: | Type of failure: Incorrect | Unknown/Multiple | error/warning at compile-time | Test Case: | Blocked By: | Blocking: | Related Tickets: #15393 | Differential Rev(s): | Wiki Page: | | -------------------------------------+---------------------------------- | --- | | Comment (by RyanGlScott): | | To follow up on my proposed experiment (in comment:29), I built about | 143 | commonly used Hackage libraries using the `wip/T13064` GHC branch. Of | those 143, I noticed new warnings being emitted in 31 of them (~22%): | | {{{ | - adjunctions-4.4 | - aeson-1.4.0.0 | - ansi-wl-pprint-0.6.8.2 | - asn1-encoding-0.9.5 | - async-2.2.1 | - attoparsec-0.13.2.2 | - blaze-builder-0.4.1.0 | - cassava-0.5.1.0 | - conduit-1.3.0.3 | - cookie-0.4.4 | - foundation-0.0.21 | - Glob-0.9.2 | - haskell-src-exts-1.20.2 | - hspec-core-2.5.6 | - lens-4.17 | - math-functions-0.3.0.2 | - memory-0.14.16 | - microstache-1.0.1.1 | - mono-traversable-1.0.9.0 | - network-2.8.0.0 | - primitive-0.6.4.0 | - resourcet-1.2.1 | - scientific-0.3.6.2 | - tasty-1.1.0.3 | - th-orphans-0.13.6 | - unordered-containers-0.2.9.0 | - uuid-types-1.0.3 | - x509-1.7.4 | - x509-store-1.6.6 | - x509-system-1.6.6 | - yaml-0.10.1.1 | }}} | | I still advocate adopting this change, but it is worth noting that a | non- | trivial number of existing libraries will need to be updated in order | to | accommodate the new warnings. | | -- | Ticket URL: | <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fghc.has | kell.org%2Ftrac%2Fghc%2Fticket%2F13064%23comment%3A36&data=02%7C01%7 | Csimonpj%40microsoft.com%7C24e789bc20ae453ead6408d61c374eb2%7C72f988bf86 | f141af91ab2d7cd011db47%7C1%7C0%7C636727421200703644&sdata=bN0jeTbzDk | GwItLs7gfnlmNsbfvpx2LQ7VU5g7JeSwg%3D&reserved=0> | GHC | <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.has | kell.org%2Fghc%2F&data=02%7C01%7Csimonpj%40microsoft.com%7C24e789bc2 | 0ae453ead6408d61c374eb2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636 | 727421200703644&sdata=tOARXvDO6s7m4WDjdmcNPfh2qvgusCc3qKrrUPRag9I%3D | &reserved=0> | The Glasgow Haskell Compiler | | -- | You received this message because you are subscribed to the Google | Groups "haskell-core-libraries" group. | To unsubscribe from this group and stop receiving emails from it, send | an email to haskell-core-libraries+unsubscribe(a)googlegroups.com. | For more options, visit | https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgroups. | google.com%2Fd%2Foptout&data=02%7C01%7Csimonpj%40microsoft.com%7C24e | 789bc20ae453ead6408d61c374eb2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0 | %7C636727421200703644&sdata=mvmddMlq2QoOaxTDZTcwv8wiMlv8VtKOYyggrrAD | 2gA%3D&reserved=0.

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GHC state of play at HIW, in 10 days time
by Simon Peyton Jones 14 Sep '18

14 Sep '18

GHC devs I'm going to give the traditional "state of play in GHC" at the Haskell Implementors Meeting. If you have an opinion, can you say what you'd like to see in it? My current list of topics is below. Please say what else should be there, and who else should be credited. Most of the work is done by people other than me!! Simon * A Backpack segment (given by Edward) * A DevOps segment (given by Ben) * TypeInType * Zillions of fixes * Substantial internal changes: e.g. * making flattening homogeneous; * making equality homogeneous, coercion quantification (thanks Ningning) * what else? * Small but significant language proposals: * Visible dependent quantification * Top-level kind signatures * Visible kind application * what else? * New and ongoing developments in GHC * Better exhaustiveness checking (thank you Ryan) * Quantified constraints * Linear types * Trees That Grow * Deriving via * Performance, performance, performance * Hadrian... soon, soon, soon!

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RE: [commit: ghc] master: Fix build (9912cdf)
by Simon Peyton Jones 14 Sep '18

14 Sep '18

Sorry about this, my fault. I had -Wwarn in my build.mk. I'll remove it! Thanks for fixing Krzysztof Simon | -----Original Message----- | From: ghc-commits <ghc-commits-bounces(a)haskell.org> On Behalf Of | git(a)git.haskell.org | Sent: 13 September 2018 22:04 | To: ghc-commits(a)haskell.org | Subject: [commit: ghc] master: Fix build (9912cdf) | | Repository : ssh://git@git.haskell.org/ghc | | On branch : master | Link : | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fghc.haske | ll.org%2Ftrac%2Fghc%2Fchangeset%2F9912cdf6dbb24a9d0188edc722ed6d9d8a3e0a1 | b%2Fghc&data=02%7C01%7Csimonpj%40microsoft.com%7C9952204b82734765e23d | 08d619bc6940%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636724694337978 | 889&sdata=867WGIQemLsbDnnOOy2jbFTidWY1opz26386sZLDSas%3D&reserved | =0 | | >--------------------------------------------------------------- | | commit 9912cdf6dbb24a9d0188edc722ed6d9d8a3e0a1b | Author: Krzysztof Gogolewski <krz.gogolewski(a)gmail.com> | Date: Thu Sep 13 22:52:05 2018 +0200 | | Fix build | | | >--------------------------------------------------------------- | | 9912cdf6dbb24a9d0188edc722ed6d9d8a3e0a1b | compiler/typecheck/TcValidity.hs | 1 - | 1 file changed, 1 deletion(-) | | diff --git a/compiler/typecheck/TcValidity.hs | b/compiler/typecheck/TcValidity.hs | index 351d0e1..df54dc2 100644 | --- a/compiler/typecheck/TcValidity.hs | +++ b/compiler/typecheck/TcValidity.hs | @@ -57,7 +57,6 @@ import Util | import ListSetOps | import SrcLoc | import Outputable | -import Module | import Bag ( emptyBag ) | import Unique ( mkAlphaTyVarUnique ) | import qualified GHC.LanguageExtensions as LangExt | | _______________________________________________ | ghc-commits mailing list | ghc-commits(a)haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.hask | ell.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc- | commits&data=02%7C01%7Csimonpj%40microsoft.com%7C9952204b82734765e23d | 08d619bc6940%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636724694337978 | 889&sdata=57N0FGleYkiz03HRAKYxf5VVU1lqpJIreaAqcRdIvSs%3D&reserved | =0

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[ANNOUNCE] GHC 8.6.1-beta1 available
by Ben Gamari 11 Sep '18

11 Sep '18

Hello everyone, The GHC development team is very pleased to announce the first beta leading up to GHC 8.6.1 release. The usual release artifacts are available from https://downloads.haskell.org/~ghc/8.6.1-beta1 This beta fixes most of the bugs reported in the first two alphas and brings all of the core libraries up to their final release versions. The 8.6 release fixes over 300 bugs from the 8.4 series and introduces a number of exciting features. These most notably include: * Significantly better handling of macOS linker command size limits, avoiding linker errors while linking large projects * A new deriving mechanism, `deriving via`, providing a convenient way for users to extend Haskell's typeclass deriving mechanism * Quantified constraints, allowing forall quantification in contexts * An early version of the GHCi `:doc` command * The `ghc-heap-view` package, allowing introspection into the structure of GHC's heap * Valid hole fit hints, helping the user to find terms to fill typed holes in their programs * The BlockArguments extension, allowing the `$` operator to be omitted in some unambiguous contexts * The next phase of the MonadFail proposal, enabling -XMonadFailDesugaring by default A full list of the changes in this release can be found in the release notes: https://downloads.haskell.org/~ghc/8.6.1-beta1/docs/html/users_guide/8.6.1-… This will very likely be the last release before the final 8.6.1 so do give it a thorough testing and, as always, report any issues you encounter. Thanks for your help! Cheers, - Ben

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ForeignPtr representation
by David Feuer 06 Sep '18

06 Sep '18

I'm trying, and failing, to understand why ForeignPtr is defined the way it is. It all seems rather complicated and redundant. I was thinking we might want to switch to something simpler and more explicit, like this: data ForeignPtr a = ForeignPtr { fptr :: !(Ptr a) -- What we point to froot :: MutableByteArray# RealWorld fwk :: MutVar# RealWorld Any -- The finalizers } froot represents the object the ForeignPtr points into. When created by one of the malloc variants, this will actually be the allocated byte array. Otherwise, it will be a 0-length array. fwk should be seen as having type fwk :: MutVar# RealWorld (Weak# (MutableByteArray# RealWorld)) but we can't express that directly right now. fwk is keyed on froot, and in the malloc case also points to it, to prevent it from being freed prematurely. It seems that this representation requires a couple extra primitive features from Weak#. I think that's okay: Weak# already has some primitive features designed to support ForeignPtr. 1. An operation to add a Haskell finalizer to a Weak#, similar to the one that adds a C finalizer. 2. A way to deal with mixed finalizers: either make the finalizer-adding primops report distinguishable failure on mixing or arrange to run the C finalizers after any Haskell finalizers (since C finalizers are much more likely to actually invalidate the pointer). 3. A documented guarantee about the order in which the finalizers attached to a particular Weak# run, compatible with the ForeignPtr documentation.

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Re: Unpacking coercions
by Ryan Scott 05 Sep '18

05 Sep '18

These aren't mutually exclusive ideas. While I'm sure there's many ways we could solve this problem, David's idea has the distinct advantage of being dead simple. I'd rather not block his vision on some other large refactor that may never materialize. (And if it _does_ materialize, we could revert any wiring-in of Coercible quite easily.) Ryan S.

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Running GHC 7.10.2 on Ubuntu 18.04 ?
by Ömer Sinan Ağacan 05 Sep '18

05 Sep '18

Hi, I'm trying to use GHC 7.10.2 (the Debian 8 bindist from haskell.org) on Ubuntu 18.04. It's currently failing with linker errors when I compile `main = return ()`: /usr/bin/x86_64-linux-gnu-ld: /home/omer/ghc_bins/ghc-7.10.3-bin/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM.a(Base__5.o): relocation R_X86_64_32S against `.text' can not be used when making a PIE object; recompile with -fPIC /usr/bin/x86_64-linux-gnu-ld: /home/omer/ghc_bins/ghc-7.10.3-bin/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM.a(Base__125.o): relocation R_X86_64_32S against `.text' can not be used when making a PIE object; recompile with -fPIC /usr/bin/x86_64-linux-gnu-ld: /home/omer/ghc_bins/ghc-7.10.3-bin/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM.a(Signal__13.o): relocation R_X86_64_32S against `.text' can not be used when making a PIE object; recompile with -fPIC /usr/bin/x86_64-linux-gnu-ld: /home/omer/ghc_bins/ghc-7.10.3-bin/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM.a(Sync__199.o): relocation R_X86_64_32S against `.text' can not be used when making a PIE object; recompile with -fPIC /usr/bin/x86_64-linux-gnu-ld: /home/omer/ghc_bins/ghc-7.10.3-bin/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM.a(Exception__170.o): relocation R_X86_64_32S against symbol `stg_bh_upd_frame_info' can not be used when making a PIE object; recompile with -fPIC I'm getting about 700 of these. Does anyone know a way to make GHC 7.10.2 work on Ubuntu 18.04? Not sure if related but the ld version is ~ $ /usr/bin/x86_64-linux-gnu-ld --version GNU ld (GNU Binutils for Ubuntu) 2.30 Copyright (C) 2018 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or (at your option) a later version. This program has absolutely no warranty. Thanks, Ömer

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Re: Running GHC 7.10.2 on Ubuntu 18.04 ?
by Ryan Scott 05 Sep '18

05 Sep '18

This is likely caused by an old GHC bug that interacts poorly with newer version of binutils (I can't remember the exact bug, unfortunately). I personally use hvr's Ubuntu PPA [1] whenever installing GHC on Ubuntu. This PPA backports patches to old versions of GHC to keep them working with newer versions of binutils, and I can confirm that the version of GHC 7.10.2 offered from here works well with Ubuntu 18.04. Ryan S. ----- [1] https://launchpad.net/~hvr/+archive/ubuntu/ghc

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