November 2013 - ghc-devs

tcfail174, T2494 and Simple14 failing
by Joachim Breitner 18 Nov '13

18 Nov '13

Hi, thanks to Duncan for fixing topHandler03. Three new tests are however failing: =====> T2494(normal) 805 of 3821 [0, 0, 0] Actual stderr output differs from expected: --- ./typecheck/should_compile/T2494.stderr 2013-11-15 19:07:53.298771915 +0000 +++ ./typecheck/should_compile/T2494.comp.stderr 2013-11-15 19:41:46.626713597 +0000 @@ -1,10 +1,10 @@ T2494.hs:15:14: - Couldn't match type ‛a’ with ‛b’ - ‛a’ is a rigid type variable bound by - the RULE "foo/foo" at T2494.hs:13:16 + Couldn't match type ‛b’ with ‛a’ ‛b’ is a rigid type variable bound by the RULE "foo/foo" at T2494.hs:14:16 + ‛a’ is a rigid type variable bound by + the RULE "foo/foo" at T2494.hs:13:16 Expected type: Maybe (m a) -> Maybe (m a) Actual type: Maybe (m b) -> Maybe (m b) Relevant bindings include @@ -17,11 +17,11 @@ In the second argument of ‛foo’, namely ‛(foo g x)’ T2494.hs:15:30: - Couldn't match type ‛a’ with ‛b’ - ‛a’ is a rigid type variable bound by - the RULE "foo/foo" at T2494.hs:13:16 + Couldn't match type ‛b’ with ‛a’ ‛b’ is a rigid type variable bound by the RULE "foo/foo" at T2494.hs:14:16 + ‛a’ is a rigid type variable bound by + the RULE "foo/foo" at T2494.hs:13:16 Expected type: Maybe (m a) -> Maybe (m a) Actual type: Maybe (m b) -> Maybe (m b) Relevant bindings include *** unexpected failure for T2494(normal) =====> tcfail174(normal) 1068 of 3821 [0, 1, 0] Actual stderr output differs from expected: --- ./typecheck/should_fail/tcfail174.stderr 2013-11-15 19:07:53.462762490 +0000 +++ ./typecheck/should_fail/tcfail174.comp.stderr 2013-11-15 19:42:10.823320120 +0000 @@ -6,11 +6,11 @@ In the expression: Base id tcfail174.hs:13:14: - Couldn't match type ‛a’ with ‛a1’ - because type variable ‛a1’ would escape its scope - This (rigid, skolem) type variable is bound by - the type forall a2. a2 -> a2 - at tcfail174.hs:13:14 + Couldn't match type ‛a1’ with ‛a’ + ‛a1’ is a rigid type variable bound by + the type forall a2. a2 -> a2 at tcfail174.hs:13:14 + ‛a’ is a rigid type variable bound by + the inferred type of h1 :: Capture a at tcfail174.hs:13:1 Expected type: Capture (forall x. x -> a) Actual type: Capture (forall a. a -> a) Relevant bindings include *** unexpected failure for tcfail174(normal) =====> Simple14(normal) 3306 of 3821 [0, 2, 0] Actual stderr output differs from expected: --- ./indexed-types/should_compile/Simple14.stderr 2013-11-15 19:07:52.465819783 +0000 +++ ./indexed-types/should_compile/Simple14.comp.stderr 2013-11-15 19:48:37.218070046 +0000 @@ -1,8 +1,7 @@ Simple14.hs:17:19: - Couldn't match type ‛z0’ with ‛n’ - ‛z0’ is untouchable - inside the constraints (Maybe m ~ Maybe n) + Could not deduce (n ~ z0) + from the context (Maybe m ~ Maybe n) bound by a type expected by the context: Maybe m ~ Maybe n => EQ_ z0 z0 at Simple14.hs:17:12-33 *** unexpected failure for Simple14(normal) I guess these have been introduced by SPJ’s most recent changes (https://github.com/nomeata/ghc-complete/commit/a8030acfc591f4069c27c9df86a8…) Greetings, Joachim -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0x4743206C Debian Developer: nomeata(a)debian.org

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GHC 7.8 release status
by Simon Peyton-Jones 15 Nov '13

15 Nov '13

Friends The 7.8 release is imminent. This email is to ask abou the status of your contributions. In each case could you update the wiki with the current state of play, and your intentions, including dates. That is, don't put your reply in email: it on the status page below; though by all means send email too! Summary here: http://ghc.haskell.org/trac/ghc/wiki/Status/GHC-7.8 Also : What is missing from the list that should be done? · Patrick Palka: status of ghc -make -j? · Nick: status of your three items? · Pedro/Richard: is all the Typeable stuff, and gcast and friends, finished? · Geoff: what about the new Template Haskell story? · Iavor: when do you think you can merge? · Austin: what about ARMv7? · Edsko/Thomas/Luite: if you want anything for 7.8 it'll have to be jolly soon. At the moment I don't even know the motivation or design, let alone implementation. Could you make a wiki page explaining the proposed design? Is it really important to do this for 7.8? · Dynamic GHCi. I have no idea who is driving this, or how important it is. · Ryan: atomic stuff. All merged? · AMP warnings: David Luposchainsky is driving this. Thanks! Simon Microsoft Research Limited (company number 03369488) is registered in England and Wales Registered office is at 21 Station Road, Cambridge, CB1 2FB

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bundle panic
by Simon Peyton-Jones 15 Nov '13

15 Nov '13

Windows build is failing again in a new way. It was fine a couple of days ago. Does this ring any bells? ghc-stage1.exe: panic! (the 'impossible' happened) (GHC version 7.7.20131107 for i386-unknown-mingw32): bundle Simon "inplace/bin/ghc-stage1.exe" -static -H32m -O -Werror -Wall -H64m -O0 -package-name integer-gmp-0.5.1.0 -hide-all-packages -i -ilibraries/integer-gmp/. -ilibraries/integer-gmp/dist-install/build -ilibraries/integer-gmp/dist-install/build/autogen -Ilibraries/integer-gmp/dist-install/build -Ilibraries/integer-gmp/dist-install/build/autogen -Ilibraries/integer-gmp/. -optP-include -optPlibraries/integer-gmp/dist-install/build/autogen/cabal_macros.h -package ghc-prim-0.3.1.0 -Wall -package-name integer-gmp -XHaskell2010 -dcore-lint -no-user-package-db -rtsopts -Ilibraries/integer-gmp/mkGmpDerivedConstants/dist -c libraries/integer-gmp/cbits/gmp-wrappers.cmm -o libraries/integer-gmp/dist-install/build/cbits/gmp-wrappers.o ghc-stage1.exe: panic! (the 'impossible' happened) (GHC version 7.7.20131107 for i386-unknown-mingw32): bundle c8 integer_cmm_importIntegerFromByteArrayzh [(c8, label: block{v c8}_info rep:StackRep [False, True, True, True]), (cg, label: block{v cg}_info rep:StackRep [False, True, True, True])] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug HEAD (master)$

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Re: Fwd: Any GHC plans to adopt tf-random?
by Michał Pałka 15 Nov '13

15 Nov '13

Hello Ryan and Nicolas, I'm happy to see some interest in the tf-random package. The package has not been extensively tested. I ran it on x86-64 and x86 Linux, and on x86 Windows. It would be good to check if it gives the same results on a big-endian architecture, such as ARM, however I don't have access to such a machine. When it comes to the performance, it is good on x86-64, but significantly slower on x86, and probably on other 32-bit architectures, because the cipher's code is optimised for 64-bit arithmetic. It may be possible to use a 32-bit optimised version for the 32-bit architectures to mitigate that, but that would mean even more C code to review. Another issue is whether to change the RandomGen/Random API, which might be considered at the same time. The current Random instances are slow, suffer from the modulo bias, and work only when the range of numbers returned by the generator is (0, 2147483562). However, I am aware that the disturbance would potentially be much larger if the API is changed, so doing it may need some planning. Ideally, it would be nice if people started using the package and see how it performs in practice before any decisions are made. Best regards, Michał > Begin forwarded message: > > From: Ryan Newton <rrnewton(a)gmail.com> > > Subject: Re: Any GHC plans to adopt tf-random? > > Date: 6 november 2013 22:51:02 CET > > To: Nicolas Frisby <nicolas.frisby(a)gmail.com> > > Cc: "ghc-devs(a)haskell.org" <ghc-devs(a)haskell.org> > > Reply-To: rrnewton(a)gmail.com > > Hi all, > > It looks like since the paper has come out the code has been > > released to Hackage. I personally would love to replace > > System.Random with something like this. > > I think the question of whether it's time comes down to some > > due-diligence issues outside the scope of the paper. This library > > has C code, have people tested it extensively on Mac/Linux/Windows? > > Does it have any performance divots we should know about? (Though > > the performance of the legacy implementation was bad in many > > respects -- it > > is a low bar.) > > -Ryan > > > > > > On Wed, Nov 6, 2013 at 3:12 PM, Nicolas Frisby > > <nicolas.frisby(a)gmail.com> wrote: > > Adding Ryan Newton to the TO field, as the maintainer of > > random. > > > > > > On Wed, Nov 6, 2013 at 2:02 PM, Nicolas Frisby > > <nicolas.frisby(a)gmail.com> wrote: > > Bugs #3575 #3620 have to do with splitting StdGens > > yielding dependent generators. > > > > The Haskell 2013 paper Splittable Pseudorandom > > Number Generators Using Cryptographic Hashing by > > Claessen and Pałka yielded the tf-random package on > > Hackage. > > > > Are there any plans to integrate these corrections > > into System.Random? > > Thanks. > > > > > > _______________________________________________ > > ghc-devs mailing list > > ghc-devs(a)haskell.org > > http://www.haskell.org/mailman/listinfo/ghc-devs > > > >

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topHandler03 failing
by Joachim Breitner 15 Nov '13

15 Nov '13

Hi, I don’t trust the travis setup enough to automatically relay failures, so I do it manually. Since these patches: Changes to ghc: commit 12cdd6d Author: Duncan Coutts <duncan(a)well-typed.com> Date: Thu Nov 14 16:02:03 2013 +0000 Don translate UserInterrupt into ExitFailure 1, let it propagate It is important that if a program recieved ^C from the user, and the program terminates as a result, that it exit with SIGINT so that the parent process knows that was the case. For example cabal calling ghc will then be able to tell the difference between it failing and the user interrupting with ^C and report (or not) appropriately. So we should just let the UserInterrupt exception propagate to the top level error handler which will do the right thing. See http://www.cons.org/cracauer/sigint.html commit a987b80 Author: Duncan Coutts <duncan(a)well-typed.com> Date: Thu Nov 14 15:54:13 2013 +0000 Improve the shutdownHaskellAndSignal and add fast exit This is the RTS part of a patch to base's topHandler to handle exiting by a signal. The intended behaviour is that on Unix, throwing ExitFailure (-sig) results in the process terminating with that signal. Previously shutdownHaskellAndSignal was only used for exiting with SIGINT due to the UserInterrupt exception. Improve shutdownHaskellAndSignal to do the signal part more carefully. In particular, it (should) now reliably terminates the process one way or another. Previusly if the signal was blocked, ignored or handled then shutdownHaskellAndSignal would actually return! Also, the topHandler code has two paths a careful shutdown and a "fast exit" where it does not give finalisers a chance to run. We want to support that mode also when we want to exit by signal. So rather than the base code directly calling stg_exit as it did before, we have a fastExit bool paramater for both shutdownHaskellAnd{Exit,Signal}. Changes to base: commit dd00004 Author: Duncan Coutts <duncan(a)well-typed.com> Date: Thu Nov 14 15:16:30 2013 +0000 Add tests for the top level exception handler The top level exception handler is wrapped around main, and FFI exports. It handles exceptions that are not otherwise caught in user code. For most exception is just prints them, but handles a few specially, including ExitCode and UserInterrupt. On Unix it installs a signal handler for SIGINT to translate it into a UserInterrupt async exception. So we test that: 1. receiving SIGINT does trigger a UserInterrupt async exception 2. an unhandled UserInterrupt makes us kill ourselves with SIGINT 3. an unhandled ExitFailure (-sig) makes us kill ourselves with sig commit 6b22a6e Author: Duncan Coutts <duncan(a)well-typed.com> Date: Thu Nov 14 15:15:31 2013 +0000 Handle ExitFailure (-sig) by killing process with signal On Unix we now use negative exit codes in ExitFailure to indicate that a process exited due to a signal. This patch implements the case for when a ExitFailure exception propagates out of the top of main (and is handled by the topHandler). For a negative ExitFailure code, we try to kill the process using that signal (the details of that are handled by shutdownHaskellAndSignal from the RTS). For an exit code outside the valid ranges, we use 0xff. Changes to process: commit 3ebbe13 Author: Duncan Coutts <duncan(a)well-typed.com> Date: Thu Nov 14 13:59:57 2013 +0000 Change the unix ExitCode encoding again! Now simply -signum So rather than a bitfield encoding, covering normal exit codes, signals and core dumps, we now simply use negative numbers for signal exit codes. We thus do not report core dumps by this mechanism. This encoding is a lot simpler to explain and use. It also happens to be the same encoding as Python's subprocess package uses. Anyone who cares about core dumps can still use the unix package. I get this failure on travis: =====> topHandler03(normal) 3622 of 3821 [0, 0, 0] Actual stderr output differs from expected: --- /dev/null 2013-11-14 17:46:34.724312327 +0000 +++ ../../libraries/base/tests/topHandler03.run.stderr 2013-11-14 18:24:52.367542630 +0000 @@ -0,0 +1 @@ +Terminated *** unexpected failure for topHandler03(normal) (Full log at https://s3.amazonaws.com/archive.travis-ci.org/jobs/13982142/log.txt) Does anyone feel responsible? Greetings, Joachim -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0x4743206C Debian Developer: nomeata(a)debian.org

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Trac formatting
by Simon Peyton-Jones 15 Nov '13

15 Nov '13

When Trac formats commit messages it is doing a terrible job. See for example: https://ghc.haskell.org/trac/ghc/ticket/5996 The commit message is nigh illegible until typeset without makup (see comment 10). Could this be done automatically? Simon Microsoft Research Limited (company number 03369488) is registered in England and Wales Registered office is at 21 Station Road, Cambridge, CB1 2FB

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Out with the new, in with the old for the vector library WAS: [commit: packages/vector] ghc-head: Snapshot of the real 0.10.0.1 release (a3a65b5)
by Geoffrey Mainland 14 Nov '13

14 Nov '13

Hi Bryan, I apologize for not bringing this issue up in a more timely fashion. I'm curious why the Bundle support that Roman added to the vector library was removed. I understand that the change in representation made it difficult for, e.g., dph to use the new vector library, but this change in representation was vital to our work on exploiting SIMD instructions. FWIW, I have been maintaining (and rebasing) a set of patches to DPH that allowed it to use Roman's new version of the vector library. If this is the path forward for the vector library, then I'm afraid anyone who wants to get any real use out of the new SIMD primops in GHC will be still stuck building their own version of the compiler using my patched primitive, vector, and dph libraries. That also requires me to maintain patched versions of these three libraries. Perhaps the roll-back in functionality was just done to get 7.8 out the door? Thanks, Geoff On 09/26/2013 05:54 AM, git(a)git.haskell.org wrote: > Repository : ssh://git@git.haskell.org/vector > > On branch : ghc-head > Link : http://git.haskell.org/packages/vector.git/commitdiff/a3a65b56a7d09e5166655… > >> --------------------------------------------------------------- > > commit a3a65b56a7d09e5166655c3877c389b7b71fb8af > Author: Bryan O'Sullivan <bos(a)serpentine.com> > Date: Wed Sep 25 10:39:32 2013 -0700 > > Snapshot of the real 0.10.0.1 release > > >> --------------------------------------------------------------- > > a3a65b56a7d09e5166655c3877c389b7b71fb8af > Data/Vector.hs | 16 +- > Data/Vector/Fusion/Bundle/Monadic.hs | 1098 ------------------------- > Data/Vector/Fusion/{Bundle.hs => Stream.hs} | 361 ++++---- > Data/Vector/Fusion/Stream/Monadic.hs | 517 +++++------- > Data/Vector/Fusion/{Bundle => Stream}/Size.hs | 4 +- > Data/Vector/Generic.hs | 463 ++++++----- > Data/Vector/Generic/Base.hs | 4 +- > Data/Vector/Generic/Mutable.hs | 273 +++--- > Data/Vector/Generic/Mutable/Base.hs | 135 --- > Data/Vector/Generic/New.hs | 103 ++- > Data/Vector/Primitive.hs | 16 +- > Data/Vector/Storable.hs | 16 +- > Data/Vector/Unboxed.hs | 16 +- > benchmarks/vector-benchmarks.cabal | 4 +- > include/vector.h | 10 +- > internal/GenUnboxTuple.hs | 4 +- > internal/unbox-tuple-instances | 30 +- > old-testsuite/Main.hs | 13 - > old-testsuite/Testsuite/Stream/AsList.hs | 134 --- > old-testsuite/Testsuite/Stream/Errors.hs | 41 - > old-testsuite/Testsuite/Utils/Generator.hs | 22 - > old-testsuite/Testsuite/Utils/List.hs | 25 - > old-testsuite/Testsuite/Utils/Property.hs | 155 ---- > old-testsuite/Testsuite/Utils/Test.hs | 123 --- > old-testsuite/Testsuite/Vector/AsList.hs | 174 ---- > old-testsuite/Testsuite/Vector/Errors.hs | 47 -- > old-testsuite/microsuite/README | 8 - > old-testsuite/microsuite/Test.hs | 200 ----- > old-testsuite/microsuite/and.hs | 3 - > old-testsuite/microsuite/append.hs | 5 - > old-testsuite/microsuite/cons.hs | 3 - > old-testsuite/microsuite/drop.hs | 4 - > old-testsuite/microsuite/elem.hs | 4 - > old-testsuite/microsuite/empty.hs | 3 - > old-testsuite/microsuite/eq.hs | 6 - > old-testsuite/microsuite/filter.hs | 4 - > old-testsuite/microsuite/find.hs | 4 - > old-testsuite/microsuite/findIndex.hs | 4 - > old-testsuite/microsuite/foldl1.hs | 4 - > old-testsuite/microsuite/from-to.hs | 2 - > old-testsuite/microsuite/head.hs | 4 - > old-testsuite/microsuite/index.hs | 3 - > old-testsuite/microsuite/init.hs | 4 - > old-testsuite/microsuite/last.hs | 4 - > old-testsuite/microsuite/length-bool.hs | 3 - > old-testsuite/microsuite/length-char.hs | 3 - > old-testsuite/microsuite/length-double.hs | 3 - > old-testsuite/microsuite/length-float.hs | 3 - > old-testsuite/microsuite/length-int16.hs | 4 - > old-testsuite/microsuite/length-int32.hs | 4 - > old-testsuite/microsuite/length-int64.hs | 4 - > old-testsuite/microsuite/length-int8.hs | 4 - > old-testsuite/microsuite/length-unit.hs | 3 - > old-testsuite/microsuite/length-word.hs | 4 - > old-testsuite/microsuite/length-word16.hs | 4 - > old-testsuite/microsuite/length-word32.hs | 4 - > old-testsuite/microsuite/length-word64.hs | 4 - > old-testsuite/microsuite/length-word8.hs | 4 - > old-testsuite/microsuite/length.hs | 3 - > old-testsuite/microsuite/lookup.hs | 5 - > old-testsuite/microsuite/map.hs | 4 - > old-testsuite/microsuite/maximum.hs | 4 - > old-testsuite/microsuite/maximumBy.hs | 4 - > old-testsuite/microsuite/minimum.hs | 4 - > old-testsuite/microsuite/minimumBy.hs | 4 - > old-testsuite/microsuite/null-ndp.hs | 3 - > old-testsuite/microsuite/null.hs | 3 - > old-testsuite/microsuite/or.hs | 3 - > old-testsuite/microsuite/product.hs | 4 - > old-testsuite/microsuite/repeat.hs | 4 - > old-testsuite/microsuite/replicate.hs | 3 - > old-testsuite/microsuite/singleton.hs | 3 - > old-testsuite/microsuite/snoc.hs | 3 - > old-testsuite/microsuite/sum-complex.hs | 5 - > old-testsuite/microsuite/sum-ratio.hs | 5 - > old-testsuite/microsuite/sum.hs | 8 - > old-testsuite/microsuite/tail.hs | 4 - > old-testsuite/microsuite/take.hs | 4 - > old-testsuite/microsuite/takeWhile.hs | 7 - > old-testsuite/microsuite/unfold.hs | 5 - > old-testsuite/microsuite/zip.hs | 6 - > old-testsuite/microsuite/zipwith.hs | 6 - > old-testsuite/microsuite/zipwith3.hs | 7 - > tests/Main.hs | 4 +- > tests/Tests/Bundle.hs | 163 ---- > tests/Tests/Stream.hs | 163 ++++ > tests/Tests/Vector.hs | 4 +- > tests/Utilities.hs | 16 +- > tests/vector-tests.cabal | 6 +- > vector.cabal | 10 +- > 90 files changed, 991 insertions(+), 3610 deletions(-) > > Diff suppressed because of size. To see it, use: > > git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc a3a65b56a7d09e5166655c3877c389b7b71fb8af > _______________________________________________ > ghc-commits mailing list > ghc-commits(a)haskell.org > http://www.haskell.org/mailman/listinfo/ghc-commits >

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RE: [commit: ghc] master: Make type-level evaluation work with :kind! (b2fa2d4)
by Simon Peyton-Jones 14 Nov '13

14 Nov '13

That is indeed revolting. Why not make sfMatchFam :: [Type] -> Maybe (CoAxiomRule, [Type], Type) thus getting rid of the TcCoercion, and baking in the flaky assumption by construction. Then I think you can put the whole definition of TcBuiltInSynFamily (with a non-Tc name) into CoAxiom. Would that work? Simon | -----Original Message----- | From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf Of | git(a)git.haskell.org | Sent: 13 November 2013 00:37 | To: ghc-commits(a)haskell.org | Subject: [commit: ghc] master: Make type-level evaluation work with | :kind! (b2fa2d4) | | Repository : ssh://git@git.haskell.org/ghc | | On branch : master | Link : | http://ghc.haskell.org/trac/ghc/changeset/b2fa2d41032882d3cf67be083489c | bcbf9e4ec07/ghc | | >--------------------------------------------------------------- | | commit b2fa2d41032882d3cf67be083489cbcbf9e4ec07 | Author: Iavor S. Diatchki <diatchki(a)galois.com> | Date: Tue Nov 12 16:36:23 2013 -0800 | | Make type-level evaluation work with :kind! | | The main change is to add a case to `reduceTyFamApp_maybe` to | evaluate | built-in type constructors (e.g., (+), (*), and friends). | | To avoid problems with recursive modules, I moved the definition of | TcBuiltInSynFamily from `FamInst` to `FamInstEnv`. I am still not | sure if | this is the right place. | | There is also a wibble that it'd be nice to fix: | | when we evaluate a built-in type function, using`sfMatchFam`, we | get | a `TcCoercion`. However, `reduceTyFamApp_maybe` needs a | `Corecion`. | I couldn't find a nice way to convert between the two, so I | resorted to | a bit of hack (marked with `XXX`). | | The hack is that we happen to know that the built-in constructors | for | the type-nat functions always return coercions of shape | `TcAxiomRuleCo`, | with no assumptions, so it easy to convert `TcCoercion` to | `Coercion` | in this one case. This is enough to make things work, but it is | clearly | a cludge. | | | >--------------------------------------------------------------- | | b2fa2d41032882d3cf67be083489cbcbf9e4ec07 | compiler/ghc.mk | 2 +- | compiler/typecheck/FamInst.lhs | 27 +----------- | compiler/typecheck/TcInteract.lhs | 2 +- | compiler/typecheck/TcTypeNats.hs | 2 +- | compiler/types/FamInstEnv.lhs | 43 | +++++++++++++++++++- | .../FamInst.lhs-boot => types/FamInstEnv.lhs-boot} | 2 +- | compiler/types/TyCon.lhs | 2 +- | 7 files changed, 47 insertions(+), 33 deletions(-) | | Diff suppressed because of size. To see it, use: | | git diff-tree --root --patch-with-stat --no-color --find-copies- | harder --ignore-space-at-eol --cc | b2fa2d41032882d3cf67be083489cbcbf9e4ec07 | _______________________________________________ | ghc-commits mailing list | ghc-commits(a)haskell.org | http://www.haskell.org/mailman/listinfo/ghc-commits

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Problems building HEAD on Mac OS X Mavericks/Xcode 5
by Nick Partridge 13 Nov '13

13 Nov '13

Hi, I've hit a build failure when trying to build HEAD on Mavericks. I've logged a bug here with a lot of detail: https://ghc.haskell.org/trac/ghc/ticket/8528. When using alex 3.1.2, some of the generated files have spaces preceding preprocessor statements, while alex 3.1.0 doesn't do this. I guess this is possibly an alex bug, but this is my first time building GHC so I'm not really sure how the ecosystem works :) Huge shout-out to Carter S. for giving me a ton of help in nailing down this issue! - Nick

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restrictions on Coercible
by Richard Eisenberg 13 Nov '13

13 Nov '13

Hi Simon, Joachim, and others, I'm in the midst of reimplementing GeneralizedNewtypeDeriving in terms of coerce. See #8503 for why I'm doing this. But, I've run up against a limitation of Coercible I'd like to know more about. Currently, the stage2 compiler fails to build because of the problem. In Module.lhs, there is this line: > newtype PackageId = PId FastString deriving( Eq, Typeable ) The deriving mechanism sensibly prefers to use the GND mechanism when it can, and it can (seemingly) for Eq here. But, I get this error: > compiler/basicTypes/Module.lhs:297:46: > No instance for (ghc-prim:GHC.Types.Coercible FastString PackageId) > because ‛PackageId’ is a recursive type constuctor This is curious, because PackageId is manifestly *not* recursive. A little poking around tells me that any datatype mentioned in a .hs-boot file is considered recursive. There is sense to this, but the error message sure is confusing. In any case, this opens up a broader issue: we want GND to work with recursive newtypes. For example: > class C a where > meth :: a > > instance C (Either a String) where > meth = Right "" > > newtype RecNT = MkRecNT (Either RecNT String) > deriving C The above code works just fine in 7.6.3. But, if Coercible isn't allowed over recursive newtypes, then this wouldn't work if GND is implemented in terms of coerce. So, my question is: why have this restriction? And, if there is a good reason for it, it should probably be documented somewhere. I couldn't find mention of it in the user's guide or in the haddock docs. If we do keep this restriction, what to do about GND? Seems like this may kill the idea of implementing GND in terms of coerce, but that makes me sad. Thanks, Richard

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