February 2016 - Glasgow-haskell-users

GHC 8.0.1 status
by Ben Gamari 01 Mar '16

01 Mar '16

tl;dr. Stabilizing the ghc-8.0 is taking a bit longer than was anticipated. The release schedule is being pushed back a bit. Hello everyone, As you likely know we are currently in the depths of the 8.0 release. In fact, under more ideal circumstances I would probably be cutting another release candidate right now instead of writing this email, in preparation for a final release next week or so. However, our world is far from ideal as evidenced by the number [1] of significant bugs present on the 8.0 branch. This isn't altogether unexpected; we knew we were taking a bit of a risk in merging so many high-impact patches in one release. However, we thought that given a longer-than-usual period between first-candidate and the final release, we'd have enough time to smooth out the wrinkles. Sadly, this has taken a bit longer than we anticipated. Of course, the last thing we want is to push a known buggy release out the door. Consequently, we won't be delivering the 8.0.1 release next week as originally planned. Instead, we'll be pushing the release back by about three weeks. This will give developers a bit more breathing room in which to work out the remaining issues. Hopefully in a few weeks the tree will be in such a state that we can push out yet another candidate which, with luck, will be the last before the release. If you'd like to expedite the process (and have fun in the process), you could do worse than to having a look at Trac [1], choosing a bug of your liking, and trying your hand at solving it. Thanks to everyone who has contributed to this effort thusfar. If you have any questions about the release process or how you can help, don't hesistate to ask. Cheers, - Ben [1] https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.0.1

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[Feedback requested]: -fhelpful-import-errors
by Tom Sydney Kerckhove 16 Feb '16

16 Feb '16

Hi, I raised a ticket to request a new feature: -fhelpful-import-errors. This flag should enable helpful errors if there are typo's in the internal imports of your projects. As suggested by `thomie`, I created a design proposal at https://ghc.haskell.org/trac/ghc/wiki/Proposal/HelpfulImportError and am now looking for feedback. Thank you for your time. -- Tom Sydney Kerckhove

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Reconsidering -Wall and -Wcompat
by Ben Gamari 15 Feb '16

15 Feb '16

tl;dr. GHC has a new set of warnings, -Wcompat, intended to give users advance notice of coming library changes. We want to know whether you think this set should be included in -Wall. See the Wiki [4] and voice your opinion via the linked poll. Hello everyone, GHC 8.0.1 will include a new warning group, -Wcompat, which arose out of the MonadFail proposal discussion [1] late last year. This warning set is intended to provide a means of informing users of coming changes in GHC's core libraries. We would like to solicit the community's feedback on whether this new flag set should be implied by -Wall. This proposal is motivated by concern expressed by some that -Wcompat would see little usage unless it is placed in one of the warning sets typically used during development. One such set is -Wall, which enables a generous fraction of GHC's warning collectionand is is intended [2] for use during development. Unfortunately, despite the (albeit only recently stated) intent of flag, -Wall is widely used outside of development [3], often with the expectation that the result be warning-clean across multiple GHC versions. While we hope that -Wall will see less use in this context in the future, given its current role we wouldn't want to add options to it that would cause undue burden for users. So, we are asking for your opinion: should -Wcompat be implied by -Wall? You can find a more thorough description of the precise proposal on the GHC Wiki [4]. It would be very much appreciated if you could take a few minutes familiarize yourself with the options and provide your thoughts via this quick poll, https://docs.google.com/forms/d/1BmIQvhHcnDB79LgBvaWl_xXpS1q0dMHe3Gq9JeU9od… Feel free to discuss the issue further in this thread. Thank you for sharing, - Ben [1] https://mail.haskell.org/pipermail/ghc-devs/2015-October/010101.html [2] https://mail.haskell.org/pipermail/ghc-devs/2016-January/010955.html [3] In a rather unscientific study, nearly half of packages on Hackage include it in ghc-options, $ tar -xf ~/.cabal/packages/00-INDEX.tar $ (for pkg in $(ls); do ls $pkg/*/*.cabal | sort -r | head -n1; done) | xargs grep -L '\-Wall' | wc -l 4352 $ ls | wc -l 9347 [4] https://ghc.haskell.org/trac/ghc/wiki/Design/Warnings/Wcompat

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LANGUAGE ConstraintKinds not needed to use ConstraintKinds?
by Evan Laforge 15 Feb '16

15 Feb '16

I recently upgraded to ghc 8 and started using stacks via ImplicitParams. For that I wind up using 'type Stack = (?stack :: CallStack)' and so ContraintKinds (I see that in the future GHC will do this by default). So now I can have a file like: module T where import qualified Log as Log f :: Log.Stack => IO () f = Log.warn "blah blah" I noticed that now haskell-src-exts refuses to parse this file, saying 'MultiParamTypeClasses language extension is not enabled.'. I assume it's a bug with haskell-src-exts in that it should require LANGUAGE ConstraintKinds instead, but then GHC itself doesn't want ConstraintKinds. Instead, it wants FlexibleContexts. From the docs, FlexibleContexts seems to be about the contexts in instance heads. Is this intentional? I'll go ahead and make a bug for haskell-src-exts, but the ghc behaviour here seems odd as well. What extension should haskell-src-exts require to parse this?

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[ANNOUNCE] GHC 8.0.1 release candidate 2
by Ben Gamari 08 Feb '16

08 Feb '16

Hello everyone, The GHC Team is very pleased to announce the second release candidate of the Glasgow Haskell Compiler 8.0.1 release. Source and binary distributions as well as the newly revised users guide and Haddock documentation can be found at http://downloads.haskell.org/~ghc/8.0.1-rc2/ This is the second in a series of release candidates leading up to the 8.0.1 release and fixes many of the issues reported in -rc1. These fixes include, * A re-rewrite of the pattern checker by George Karachalias. The new checker should have far more predictable performance characteristics while sacrificing minimal reasoning power. This should resolve a large number of the issues felt in -rc1. * Richard Eisenberg has been hammering out all manner of type-application- and TypeInType-related issues (#11335, #11416, #11405). There is still more work to do here, however (e.g. #11471). * Matthew Pickering has restored support for multi-clause pattern synonyms (#11367) * A latent bug in the constraint solver which popped up as a build failure in xmonad-contrib in -rc1 has been fixed (#11379) * Dimitrios Vytiniotis and Simon Peyton Jones has been squashing a variety of older type-checker bugs at a furious rate (#11458, #11248, #11330, #11408) * Simon Peyton Jones has taught demand analysis to more precisely handle exceptions (#11222) * Tamar Christina has added support for remote GHCi on Windows and resolved a long-standing linking issue (#11223) * Loading of compiled modules needing shared library symbols now works in GHCi thanks to Peter Trommler (#10458) * A variety of limitations in our implementation of Typeable implementation have been fixed (#11120) although there is still more to be done (#11334). * A terrible failure of type inference due to visible type application has been fixed (#11458) * InjectiveTypeFamilies has been renamed to TypeFamilyDependencies * Custom type errors are now more robust (#11391) although there is still more work to be done (#11541) * We now have a more conservative default warning set, as well as better mechanisms for managing warning changes in the future. (#11429, #11370) * Compatibility with earlier Cabal versions should be a bit more robust. * The user-facing interface of the (formerly "implicit") CallStack functionality has been reworked, hiding the implicit callstack parameter behind a constraint synonym. * Online haddock documentation has been restored (#11419) * We now offer xz archives exclusively * A variety of miscellaneous bug-fixes have also been merged. All of these changes add up to nearly 200 commits in total. Given the large amount of churn between this candidate and -rc1, as well as the fact that there is at least one more significant patch pending (D1891, to fix #11471 and others), we will be releasing a third release candidate in a few weeks which should address more of the issues listed on the release status page [1]. Assuming things go well, we should be able to cut a final release by early March at the latest. All of the builds above were produced from the ghc-8.0.1-rc2 tag (commit e2230228906a1c0fa1f86a0c1aa18d87de3cc49d) *with the exception of the Windows builds*. Unfortunately, it was realized only too late that the tagged commit is broken on Windows. Consequently, the Windows builds were produced from the ghc-8.0.1-rc2 tag with two additional patches (commit 5b35c5509adb1311856faa0bc9767aec9ad5e9b7). While this would of course be completely unacceptable for a proper release, time constraints have meant that this was unfortunately the only viable option for this release candidate. We apologize for any confusion this may cause. At this point we are working very hard to nail the remaining bugs labelled as "highest" priority on the 8.0.1 status page [1]. If you have an issue which you'd like to see addressed in the release that does not appear in this list, please bring it to our attention. As always, we look forward to hearing about any issues that you encounter with this candidate. Thanks to everyone who has contributed so far! Cheers, - Ben [1] https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.0.1

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problem compiling GHC 8.0.1 release candidate 2 src on Apple
by George Colpitts 07 Feb '16

07 Feb '16

"/usr/local/bin/ghc" -M -static -H32m -O -Wall -package-db libraries/bootstrapping.conf -this-unit-id terminfo-0.4.0.2 -hide-all-packages -i -ilibraries/terminfo/. -ilibraries/terminfo/dist-boot/build -ilibraries/terminfo/dist-boot/build/autogen -Ilibraries/terminfo/dist-boot/build -Ilibraries/terminfo/dist-boot/build/autogen -Ilibraries/terminfo/. -optP-include -optPlibraries/terminfo/dist-boot/build/autogen/cabal_macros.h -package-id base-4.9.0.0 -Wall -XHaskell2010 -no-user-package-db -rtsopts -fno-warn-unused-imports -fno-warn-deprecated-flags -odir libraries/terminfo/dist-boot/build -hidir libraries/terminfo/dist-boot/build -stubdir libraries/terminfo/dist-boot/build -dep-makefile libraries/terminfo/dist-boot/build/.depend-v.haskell.tmp -dep-suffix "" -include-pkg-deps libraries/terminfo/./System/Console/Terminfo.hs libraries/terminfo/./System/Console/Terminfo/Base.hs libraries/terminfo/./System/Console/Terminfo/Cursor.hs libraries/terminfo/./System/Console/Terminfo/Color.hs libraries/terminfo/./System/Console/Terminfo/Edit.hs libraries/terminfo/./System/Console/Terminfo/Effects.hs libraries/terminfo/./System/Console/Terminfo/Keys.hs ghc: unrecognised flag: -this-unit-id Usage: For basic information, try the `--help' option. make[1]: *** [libraries/terminfo/dist-boot/build/.depend-v.haskell] Error 1 make[1]: *** Waiting for unfinished jobs.... make: *** [all] Error 2 ghc --info [("Project name","The Glorious Glasgow Haskell Compilation System") ,("GCC extra via C opts"," -fwrapv -fno-builtin") ,("C compiler command","/usr/local/bin/gcc") ,("C compiler flags"," -m64 -fno-stack-protector") ,("C compiler link flags"," -m64") ,("Haskell CPP command","/usr/local/bin/gcc") ,("Haskell CPP flags","-E -undef -traditional") ,("ld command","/usr/bin/ld") ,("ld flags"," -arch x86_64") ,("ld supports compact unwind","YES") ,("ld supports build-id","NO") ,("ld supports filelist","YES") ,("ld is GNU ld","NO") ,("ar command","/usr/bin/ar") ,("ar flags","clqs") ,("ar supports at file","NO") ,("touch command","touch") ,("dllwrap command","/bin/false") ,("windres command","/bin/false") ,("libtool command","libtool") ,("perl command","/usr/bin/perl") ,("cross compiling","NO") ,("target os","OSDarwin") ,("target arch","ArchX86_64") ,("target word size","8") ,("target has GNU nonexec stack","False") ,("target has .ident directive","True") ,("target has subsections via symbols","True") ,("Unregisterised","NO") ,("LLVM llc command","llc") ,("LLVM opt command","opt") ,("Project version","8.0.0.20160111") ,("Project Git commit id","497454fc6610d67a2b2cd7902390c6497bddb483") ,("Booter version","7.10.2") ,("Stage","2") ,("Build platform","x86_64-apple-darwin") ,("Host platform","x86_64-apple-darwin") ,("Target platform","x86_64-apple-darwin") ,("Have interpreter","YES") ,("Object splitting supported","YES") ,("Have native code generator","YES") ,("Support SMP","YES") ,("Tables next to code","YES") ,("RTS ways","l debug thr thr_debug thr_l thr_p dyn debug_dyn thr_dyn thr_debug_dyn l_dyn thr_l_dyn") ,("RTS expects libdw","NO") ,("Support dynamic-too","YES") ,("Support parallel --make","YES") ,("Support reexported-modules","YES") ,("Support thinning and renaming package flags","YES") ,("Requires unified installed package IDs","YES") ,("Uses package keys","YES") ,("Dynamic by default","NO") ,("GHC Dynamic","YES") ,("GHC Profiled","NO") ,("Leading underscore","YES") ,("Debug on","False") ,("LibDir","/usr/local/lib/ghc-8.0.0.20160111") ,("Global Package DB","/usr/local/lib/ghc-8.0.0.20160111/package.conf.d") ] On Sun, Feb 7, 2016 at 2:13 PM, Ben Gamari <ben(a)well-typed.com> wrote: > > Hello everyone, > > The GHC Team is very pleased to announce the second release candidate of > the Glasgow Haskell Compiler 8.0.1 release. Source and binary > distributions as well as the newly revised users guide and Haddock > documentation can be found at > > http://downloads.haskell.org/~ghc/8.0.1-rc2/ > > This is the second in a series of release candidates leading up to the > 8.0.1 > release and fixes many of the issues reported in -rc1. These fixes > include, > > * A re-rewrite of the pattern checker by George Karachalias. The new > checker should have far more predictable performance characteristics > while sacrificing minimal reasoning power. This should resolve a > large number of the issues felt in -rc1. > > * Richard Eisenberg has been hammering out all manner of > type-application- and TypeInType-related issues (#11335, #11416, > #11405). There is still more work to do here, however (e.g. #11471). > > * Matthew Pickering has restored support for multi-clause pattern > synonyms (#11367) > > * A latent bug in the constraint solver which popped up as a build > failure in xmonad-contrib in -rc1 has been fixed (#11379) > > * Dimitrios Vytiniotis and Simon Peyton Jones has been squashing a > variety of older type-checker bugs at a furious rate (#11458, > #11248, #11330, #11408) > > * Simon Peyton Jones has taught demand analysis to more precisely > handle exceptions (#11222) > > * Tamar Christina has added support for remote GHCi on Windows > and resolved a long-standing linking issue (#11223) > > * Loading of compiled modules needing shared library symbols now works > in GHCi thanks to Peter Trommler (#10458) > > * A variety of limitations in our implementation of Typeable > implementation have been fixed (#11120) although there is still more > to be done (#11334). > > * A terrible failure of type inference due to visible type application > has > been fixed (#11458) > > * InjectiveTypeFamilies has been renamed to TypeFamilyDependencies > > * Custom type errors are now more robust (#11391) although there is > still more work to be done (#11541) > > * We now have a more conservative default warning set, as well as > better mechanisms for managing warning changes in the future. > (#11429, #11370) > > * Compatibility with earlier Cabal versions should be a bit more > robust. > > * The user-facing interface of the (formerly "implicit") CallStack > functionality has been reworked, hiding the implicit callstack > parameter behind a constraint synonym. > > * Online haddock documentation has been restored (#11419) > > * We now offer xz archives exclusively > > * A variety of miscellaneous bug-fixes have also been merged. > > All of these changes add up to nearly 200 commits in total. Given the > large amount of churn between this candidate and -rc1, as well as the > fact that there is at least one more significant patch pending (D1891, > to fix #11471 and others), we will be releasing a third release > candidate in a few weeks which should address more of the issues listed > on the release status page [1]. Assuming things go well, we should be > able to cut a final release by early March at the latest. > > All of the builds above were produced from the ghc-8.0.1-rc2 tag (commit > e2230228906a1c0fa1f86a0c1aa18d87de3cc49d) *with the exception of the > Windows builds*. Unfortunately, it was realized only too late that the > tagged commit is broken on Windows. Consequently, the Windows builds > were produced from the ghc-8.0.1-rc2 tag with two additional patches > (commit 5b35c5509adb1311856faa0bc9767aec9ad5e9b7). While this would of > course be completely unacceptable for a proper release, time constraints > have meant that this was unfortunately the only viable option for this > release candidate. We apologize for any confusion this may cause. > > At this point we are working very hard to nail the remaining bugs > labelled as "highest" priority on the 8.0.1 status page [1]. If you have > an issue which you'd like to see addressed in the release that does not > appear in this list, please bring it to our attention. > > As always, we look forward to hearing about any issues that you > encounter with this candidate. Thanks to everyone who has contributed so > far! > > Cheers, > > - Ben > > > [1] https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.0.1 > > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users > >

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Dropping bzip2 release tarballs?
by Ben Gamari 02 Feb '16

02 Feb '16

tl;dr do you rely on the .bz2 release tarballs on downloads.haskell.org? If so, let us know! Hello everyone, As you may have noticed, a few releases ago we started producing xz-compressed binary distributions in addition to the usual bzip2 tarballs. While preparing 8.0.1-rc1 it was suggested that we move to distributing xz tarballs exclusively. Not only would this move reduce storage and bandwidth demands on our infrastructure but it would also simplify the job of producing the distributions. Indeed there is plenty of precendent for projects who have moved exclusively to xz (the Linux kernel and git being two examples). Of course, these reasons alone aren't sufficient to abandon those who might rely on our bzip2 tarballs. If you feel strongly that we should continue to distribute bzip2 tarballs, please let us know. Thanks! - Your friendly GHC packaging gnomes

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