May 2014 - ghc-devs - Haskell.org

old-time.git/tests/time004.hs is DST-sensitive :-/
by Herbert Valerio Riedel 26 Oct '14

26 Oct '14

Hi *, if anyone wonders, why TEST=time004 suddenly fails: it's sensitive to DST (and depends on your system's TZ-config): http://git.haskell.org/packages/old-time.git/blob/HEAD:/tests/time004.hs For me, the comparison this unit-test checks now suddenly fails, because the DST-switch occurs on different days in 2012 and 2013 in my TZ, i.e. length "Sun Oct 27 10:56:42 CET 2013" /= length "Sat Oct 27 11:56:42 CEST 2012" Does anyone happen to know what the rationale behind this 'time004' unit test was? Cheers, hvr

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FFI: c/c++ struct on stack as an argument or return value
by Yuras Shumovich 07 Oct '14

07 Oct '14

Hi, Right now ghc's FFI doesn't support c/c++ structures. Whenever we have foreign function that accepts or returns struct by value, we have to create wrapper that accepts or returns pointer to struct. It is inconvenient, but actually not a big deal. But there is no easy workaround when you want to export haskell function to use it with c/c++ API that requires structures to be passed by value (Usually it is a callback in c/c++ API. You can't change it's signature, and if it doesn't provide some kind of "void* userdata", then you are stuck.) I'm interested in fixing that. I'm going to start with 'foreign import "wrapper" ...' stuff. Calling conventions for passing c/c++ structures by value are pretty tricky and platform/compiler specific. So initially I'll use libffi for that (it will work when USE_LIBFFI_FOR_ADJUSTORS is defined, see rts/Adjustor.c). It will allow me to explore design space without bothering about low level implementation details. Later it could be implemented for native (non-libffi) adjustors. Is anybody interested it that? I appreciate any comments/ideas. Right now I don't have clear design. It would be nice to support plain haskell data types that are 1) not recursive, 2) has one constructor and 3) contains only c/c++ types. But it doesn't work with c/c++ unions. Any ideas are welcome. An example how to use libffi with structures: http://www.atmark-techno.com/~yashi/libffi.html#Structures Thanks, Yuras

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Extending fold/build fusion
by Akio Takano 05 Sep '14

05 Sep '14

Hi, I have been thinking about how foldl' can be turned into a good consumer, and I came up with something that I thought would work. So I'd like to ask for opinions from the ghc devs: if this idea looks good, if it is a known bad idea, if there is a better way to do it, etc. The main idea is to have an extended version of foldr: -- | A mapping between @a@ and @b@. data Wrap a b = Wrap (a -> b) (b -> a) foldrW :: (forall e. Wrap (f e) (e -> b -> b)) -> (a -> b -> b) -> b -> [a] -> b foldrW (Wrap wrap unwrap) f z0 list0 = wrap go list0 z0 where go = unwrap $ \list z' -> case list of [] -> z' x:xs -> f x $ wrap go xs z' This allows the user to apply an arbitrary "worker-wrapper" transformation to the loop. Using this, foldl' can be defined as newtype Simple b e = Simple { runSimple :: e -> b -> b } foldl' :: (b -> a -> b) -> b -> [a] -> b foldl' f initial xs = foldrW (Wrap wrap unwrap) g id xs initial where wrap (Simple s) e k a = k $ s e a unwrap u = Simple $ \e -> u e id g x next acc = next $! f acc x The wrap and unwrap functions here ensure that foldl' gets compiled into a loop that returns a value of 'b', rather than a function 'b -> b', effectively un-CPS-transforming the loop. I put preliminary code and some more explanation on Github: https://github.com/takano-akio/ww-fusion Thank you, Takano Akio

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Proposal: run GHC API tests on fast
by Edward Z. Yang 02 Sep '14

02 Sep '14

Currently, most GHC API tests are not run on 'make fast', ostensibly because linking against the GHC API can take a while. I propose that change this, and run GHC API tests by default. Reasons: 1. The GHC API is closely tied a lot of internal structure of GHC, so it's very easy to make a change, track it through the rest of the compiler, but forget to update the tests/documentation. 2. We can boost this into poor man's testable documentation. The idea is to duplicate all GHC API examples in the manual in the test suite, and have a comment on all of the examples asking the developer to update the manual. (Or we could automatically extract the snippets from the manual, but that's work and this I could do in a few minutes.) 3. I don't think running these tests will add that much extra run time to the test suite; certainly interactively the time spent linking is unnoticeable. Let's set a one week discussion period for this proposal. Thanks, Edward

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Can't install 32-bit ghc-7.8.1 on 64-bit xubuntu 14.04
by kyra 30 Aug '14

30 Aug '14

Hi, I have unpacked ghc-7.8.1-i386-unknown-linux-deb7.tar.xz to ~/data/Work/ghc-7.8.1-i386. Now I have the following: awson@awsonvirt:~/data/Work/ghc-7.8.1-i386$ ./configure --prefix=/home/awson/data/ghc-7.8.1-i386 checking for path to top of build tree... utils/ghc-pwd/dist-install/build/tmp/ghc-pwd-bindist: line 3: /home/awson/data/Work/ghc-7.8.1-i386/utils/ghc-pwd/dist-install/build/tmp/ghc-pwd: No such file or directory configure: error: cannot determine current directory ghc-pwd is definitely there but it does not start it seems. Perhaps, the system lacks some shared libs or something. There absolutely no problems with 64-bit ghc. Regards, Kyra

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7.8.1 plan
by Austin Seipp 16 Jul '14

16 Jul '14

Hello all, As I'm sure you're all aware, it's the final countdown. The (final) source distribution will be up within a few hours, and then we'll continue on from there. Yay! I will post an update when that is, so Gabor/Luke/Karel can make binaries from the sources as I do so. Second, there are just two things I want to note: - For people following the Windows debacle in #8834, there has been a bug fixed, but one may still remain. The TL;DR of this is that we currently have a committed workaround in place we'll keep using, but Simon has made some good steps towards finding the bug. - Lots of people, I'm sure, are wondering what's going on with Safe Haskell and the GND story. The TL;DR of this one is that "everything will be the same as in 7.6" - GND is considered an Unsafe feature, and Data.Coerce is behind Unsafe bars. From a safety point of view, nothing should change for library authors I cherry picked these changes into 7.8 last night. In the mean time, the 7.8 branch is effectively closed. If you have something to commit, and I *really* mean something, you can let me know. But your deadline is hours, not days! I'm doing a final review of all the trees before pushing the library tags, and after that I'll begin rolling the sdist. Anyway, the time is finally here, so let's get it over with! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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GHC 7.8.3 release
by Austin Seipp 03 Jul '14

03 Jul '14

Hello all, After a long week, I've finally gotten a little time to reply to emails, and I mainly have one question I'd like to ask. First, please direct your attention to this: https://ghc.haskell.org/trac/ghc/query?status=closed&status=merge&status=pa… This is the 7.8.3 milestone, but it only considers things that are: - 1) Fixed - 2) Going to be merged - 3) Are a patch to be still merged. That is, it is a solid representation of the difference between 7.8.2 and the 7.8 branch tip. The question is: when should we do the release? There are several bugs there that seem quite problematic for users - #9045, #7097, #9001, #8768 and #9078 in particular. If these bugs are really problematic (and I sort of feel they are) then the release can happen soon. I can do it within a week from now, and we could punt more to a 7.8.4 release. I ask this because my time to dedicate to GHC is a bit thin right now, so you must help me decide what's important! So please let me know - just a general vote in favor of doing it within some X timeframe (even 'real soon' or 'a week would be great') would be nice. PS: I apologize for the lack of status updates and brief email - my time for GHC has been in very short order the past two weeks in particular, and I've finally just returned to a computer (not mine) for right now to ask this. PPS: This might also impact the 7.10 schedule, but last Simon and I talked, we thought perhaps shooting for ICFP this time (and actually hitting it) was a good plan. So I'd estimate on that a 7.8.4 might happen a few months from now, after summer. -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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clang warnings
by Kazu Yamamoto 23 Jun '14

23 Jun '14

Hi, To test the coming GHC 7.8.3, I started to use the latest ghc-7.8 branch. Unfortunately, on my Mac, I saw many warnings which are not displayed with GHC 7.8.2: clang: warning: argument unused during compilation: '-fno-stack-protector' clang: warning: argument unused during compilation: '-D TABLES_NEXT_TO_CODE' clang: warning: argument unused during compilation: '-I test' clang: warning: argument unused during compilation: '-I dist/build/spec/spec-tmp' clang: warning: argument unused during compilation: '-I dist/build/spec/spec-tmp' clang: warning: argument unused during compilation: '-I dist/build/autogen' clang: warning: argument unused during compilation: '-I dist/build/spec/spec-tmp' Is this a known issue? --Kazu

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Proposal: Partial Type Signatures
by Thomas Winant 19 Jun '14

19 Jun '14

Dear GHC developers, Together with Tom Schrijvers, Frank Piessens and Dominique Devriese, I have been working on a proposal for adding *Partial Type Signatures* to GHC. In a partial type signature, annotated types can be mixed with inferred types. A type signature is written like before, but can now contain wildcards, written as underscores. The types of these wildcards or unknown types will be inferred by the type checker, e.g. foo :: _ -> Bool foo x = not x -- Inferred: Bool -> Boo The proposal also includes a form of generalisation which aligns with the existing generalisation that GHC does. We have written down a motivation (when and how might you use this) and details about the design and implementation on the following wiki page: https://ghc.haskell.org/trac/ghc/wiki/PartialTypeSignatures We have a (work in progress) implementation [1] of the feature based on GHC. It currently implements most of what we propose, but there are some remaining important bugs mostly concerning the generalisation. We also described our design and presented a formalisation based on the OutsideIn(X) formalism in a paper [2] presented at PADL'14. What we are hoping to get from the people on this list is any of the below: * Read the design, play with the implementation and tell us any comments you may have about the feature, its design and implementation. * Opinions on whether this feature might be acceptable in GHC upstream at some point (if not, we do not think it's worth developing the implementation much further). * Perhaps a code review or a discussion with someone more knowledgeable about the internals of GHC's type checker about how we might fix the remaining problems in our implementation (specifically, we could use some help with implementing the generalisation of partial type signatures). * Feedback on the `Questions and issues' section on the wiki page. Kind regards, Thomas Winant [1]: https://github.com/mrBliss/ghc-head/ [2]: https://lirias.kuleuven.be/bitstream/123456789/423475/3/paper.pdf Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

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Offering GHC builder build slaves
by Alain O'Dea 18 Jun '14

18 Jun '14

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi folks: I have successfully built Ian Lynagh's GHC builder on Ubuntu and SmartOS and I would like to offer build slaves based on Carter's mirroring of the code to https://github.com/cartazio/ghc-builder. I can offer several build slaves, but I'm not sure what the process is. How do I run multiple build slaves? Do I need a separate username for each? Is there a username convention? The suggestion at https://ghc.haskell.org/trac/ghc/wiki/Builder is that I post a username and password to ghc@. There are two issues with this: 1. ghc@ does not exist as far as I can tell 2. Posting a password to a mailing list will make it publicly accessible and allow others to impersonate my build slaves I am happy to send this information if the admins of the GHC builder infrastructure are comfortable with the risks. Alternatively, I am able to send this via GPG encrypted email given the public key and email of an admin. Feel free to contact me on or off list about this. Best, Alain -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTQ0uTAAoJEP0rIXJNjNSA+fMH/2p9yeWgpfDeaTHilur5qoZ6 6DZiktJgvMpVeqFwHyaFMk+ubEp8/xU/VUrOEztr01jmzNLS2UoqDVH/7EZPZPtV 0ONh/bcYYA8EBa9SCqaVXVb9I8EdDE6w2cQGDqnwHqaFerAUqv8OiQEWyJCuJSdr 7EL/vcacNfr5Ix4oG2pkESvEJBHHEN4ZTXoKeJnyQT93o2RaC1fgImm6F6tgpdQE Jh+QInIX1dRuSl+pDlHg6kbLZqFG8Mnyz0bcWuUL2ekGQBp3HtT0MwonM9HUTmmG 0baRYUaK/moO5Q6lUXhI2eRT/UFl4qnzwJw/sIVuaL7h1Ikj0ZMOuPs0GjfRbY8= =/Rwk -----END PGP SIGNATURE-----

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