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GHC Weekly News - 2015/09/17
by Austin Seipp 17 Sep '15

17 Sep '15

(This post is available online at https://ghc.haskell.org/trac/ghc/blog/weekly20150917) Hi *, Welcome for the latest entry in the GHC Weekly News. It's been a little while, but here we are! And your author has finally returned from his 8 week sabbatical, too! So without any futher ado, lets get going... == 8.0.1 release roadmap == So `HEAD` has been steaming along pretty smoothly for the past few months now. After talking with Simon last week, we decided that the best course of action would be to release 8.0.1 (a super-major release) sometime around late February, which were the plans for 7.10 (modulo a few weeks due to the FTP debates). The current schedule is roughly: - November: Fork the new `ghc-8.0` STABLE branch - At this point, `master` development will probably slow as we fix bugs. - This gives us 2 months or so until branch, from Today. - This is nice as the branch is close to the first RC. - December: First release candidate - Mid/late February: Final release. "'''Why call it 8.0.1?'''", you ask? Because we have a lot of excellent features planned! I'm particularly partial to Richard's work for merging types and kinds (Phab:D808). But there's a lot of other stuff. For all the nitty gritty details, be sure to check [wiki:Status/GHC-8.0.1 8.0.1 status page] to keep track of everything - it will be our prime source of information and coordination. And be sure to [https://mail.haskell.org/pipermail/ghc-devs/2015-September/009952.html read my email to `ghc-devs`] for more info. === ... and a 7.10.3 release perhaps? === On top of this, we've been wondering if another release in the 7.10 branch should be done. Ben did the release shortly after I left, and for the most part looked pretty great. But there have been some snags, as usual. So we're asking: [https://mail.haskell.org/pipermail/ghc-devs/2015-September/009953.html who needs GHC 7.10.3?] We'd really like to know of any major showstoppers you've found with 7.10 that are preventing you from using it. Especially if you're stuck or there's no clear workaround. Currently, we're still not 100% committed to this course of action (since the release will take time away from other things). However, we'll keep the polls open for a while - so ''please'' get in touch with us if you need it! (Be sure to read my email for specific information.) == List chatter == (Over the past two weeks) - Bartosz Nitka writes to `ghc-devs` about the ongoing work to try and fix deterministic compilation in GHC (the dreaded ticket #4012). There's a very detailed breakdown of the current problems and issues in play, with responses from others - https://mail.haskell.org/pipermail/ghc-devs/2015-September/009964.html - Richard Eisenberg wants to know - how can I download all of `Hackage` to play with it? GHC developers are surely interested in this, so they can find regressions quickly - https://mail.haskell.org/pipermail/ghc-devs/2015-September/009956.html - I wrote to the list about the upcoming tentative 7.10.3 plans, as I mentioned above. https://mail.haskell.org/pipermail/ghc-devs/2015-September/009953.html - I ''also'' wrote to the list about the tentative 8.0.1 plans, too. https://mail.haskell.org/pipermail/ghc-devs/2015-September/009952.html - Johan Tibell asks about his ongoing work for implementing unboxed sum types - in particular, converting unboxed sum types in `StgCmm`. https://mail.haskell.org/pipermail/ghc-devs/2015-September/009926.html - Ryan Scott wrote a proposal for the automatic derivation of `Lift` through GHC's deriving mechanism, specifically for `template-hasekll` users. The response was positive and the code is going through review now (Phab:D1168). https://mail.haskell.org/pipermail/ghc-devs/2015-September/009838.html - Andrew Gibiansky writes in with his own proposal for a new "Argument Do" syntax - a change which would allow `do` to appear in positions without `($)` or parenthesis, essentially changing the parser to insert parens as needed. The code is up at Phabricator for brave souls (Phab:D1219). https://mail.haskell.org/pipermail/ghc-devs/2015-September/009821.html - Edward Yang started a monstrous thread after some discussions at ICFP about a future for ''unlifted'' data types in GHC. These currently exist as special magic, but the proposals included would allow users to declare their own types as unlifted, and make unlifted values more flexible (allowing `newtype` for example). See wiki:UnliftedDataTypes and Edward's thread for more. https://mail.haskell.org/pipermail/ghc-devs/2015-September/009799.html == Noteworthy commits == (Over the past several weeks) - Commit 374457809de343f409fbeea0a885877947a133a2 - '''Injective Type Families''' - Commit 8ecf6d8f7dfee9e5b1844cd196f83f00f3b6b879 - '''Applicative Do notation''' - Commit 6740d70d95cb81cea3859ff847afc61ec439db4f - Use IP-based CallStack in `error` and `undefined` - Commit 43eb1dc52a4d3cbba9617f5a26177b8251d84b6a - Show `MINIMAL` complete definition in GHCi's `:info` - Commit 296bc70b5ff6c853f2782e9ec5aa47a52110345e - Use a response file for linker command line arguments - Commit 4356dacb4a2ae29dfbd7126b25b72d89bb9db1b0 - Forbid annotations when Safe Haskell is enabled - Commit 7b211b4e5a38efca437d76ea442495370da7cc9a - Upgrade GCC/binutils to 5.2.0 release for Windows (i386/amd64) == Closed tickets == (Over the past two weeks) #10834, #10830, #10047, #9943, #1851, #1477, #8229, #8926, #8614, #10777, #8596, #10788, #9500, #9087, #10157, #10866, #10806, #10836, #10849, #10869, #10682, #10863, #10880, #10883, #10787, #8552, #10884, #7305, #5757, #9389, #8689, #10105, #8168, #9925, #10305, #4438, #9710, #10889, #10885, #10825, #10821, #10790, #10781, #9855, #9912, #10033, #9782, #10035, #9976, #10847, and #10865. -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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HEADS UP: Need 7.10.3?
by Austin Seipp 17 Sep '15

17 Sep '15

Hi *, (This is an email primarily aimed at users reading this list and developers who have any interest). As some of you may know, there's currently a 7.10.3 milestone and status page on our wiki: https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-7.10.3 The basic summary is best captured on the above page: "We have not yet decided when, or even whether, to release GHC 7.10.3. We will do so if (but only if!) we have documented cases of "show-stoppers" in 7.10.2. Namely, cases from users where - You are unable to use 7.10.2 because of some bug - There is no reasonable workaround, so you are truly stuck - We know how to fix it - The fix is not too disruptive; i.e. does not risk introducing a raft of new bugs" That is, we're currently not fully sold on the need for a release. However, the milestone and issue page serve as a useful guide, and also make it easier to keep track of smaller, point-release worthy issues. So in the wake of the 8.0 roadmap I just sent: If you *need* 7.10.3 because the 7.10.x series has a major regression or problem you can't work around, let us know! - Find or file a bug in Trac - Make sure it's highest priority - Assign it to the 7.10.3 milestone - Follow up on this email if possible, or edit it on the status page text above - it would be nice to get some public feedback in one place about what everyone needs. Currently we have two bugs on the listed page in the 'show stopper category', possibly the same bug, which is a deal-breaker for HERMIT I believe. Knowing of anything else would be very useful. Thanks all! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Is it possible to build ghc with static linkage to its dependencies?
by Hengchu Zhang 17 Sep '15

17 Sep '15

Hi GHC Devs, I'd like to build ghc for an environment (linux x86_64) that I don't fully control, and most importantly libgmp.so on that environment is severely outdated. I was wondering if I can build ghc on another linux x86_64 machine but link in all the dependencies as static libraries instead finding them as dynamic libraries? Thank you! Best, Hengchu

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utils/hp2ps/Main.c:88: possible missing break ?
by David Binderman 15 Sep '15

15 Sep '15

Hello there, [utils/hp2ps/Main.c:88] -> [utils/hp2ps/Main.c:91]: (warning) Variable 'iflag' is reassigned a value before the old one has been used. 'break;' missing? Source code is switch( *(*argv + 1) ) { case '-': iflag = -1; case '+': default: iflag = 1; } Suggest add missing break. Regards David Binderman

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download all of Hackage?
by Richard Eisenberg 15 Sep '15

15 Sep '15

Hi devs, Is there an easy way to download (but not compile) all of Hackage? I know of the hackager package, but that's about compiling. I just want a whole big load of Haskell code to play with. I thought I could find a link on Hackage to do this, but failed. Thanks! Richard

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Using GHC API to compile Haskell file
by Neil Mitchell 15 Sep '15

15 Sep '15

Hi, Is this the right place for GHC API queries? If not, is there anywhere better? I want to compile a Haskell module, much like `ghc --make` or `ghc -c` does. The sample code on the Haskell wiki (https://wiki.haskell.org/GHC/As_a_library#A_Simple_Example) StackOverflow (http://stackoverflow.com/a/5631338/160673) and in GHC API slides (http://sneezy.cs.nott.ac.uk/fplunch/weblog/wp-content/uploads/2008/12/ghc-a…) says: import GHC import GHC.Paths ( libdir ) import DynFlags main = defaultErrorHandler defaultFatalMessager defaultFlushOut $ do runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags dflags target <- guessTarget "Test.hs" Nothing setTargets [target] load LoadAllTargets However, given a `Test.hs` file with the contents `main = print 1`, I get the error: C:/Program Files (x86)/MinGHC-7.8.3/ghc-7.8.3/mingw/bin/ld.exe: cannot find -lHSbase-4.7.0.1-ghc7.8.3 C:/Program Files (x86)/MinGHC-7.8.3/ghc-7.8.3/mingw/bin/ld.exe: cannot find -lHSinteger-gmp-0.5.1.0-ghc7.8.3 C:/Program Files (x86)/MinGHC-7.8.3/ghc-7.8.3/mingw/bin/ld.exe: cannot find -lHSghc-prim-0.3.1.0-ghc7.8.3 C:/Program Files (x86)/MinGHC-7.8.3/ghc-7.8.3/mingw/bin/ld.exe: cannot find -lHSrts-ghc7.8.3 C:/Program Files (x86)/MinGHC-7.8.3/ghc-7.8.3/mingw/bin/ld.exe: cannot find -lffi-6 collect2: ld returned 1 exit status Has the recipe changed? By turning up the verbosity, I was able to compare the command line passed to the linker. The failing GHC API call contains: "-lHSbase-4.7.0.1-ghc7.8.3" "-lHSinteger-gmp-0.5.1.0-ghc7.8.3" "-lHSghc-prim-0.3.1.0-ghc7.8.3" "-lHSrts-ghc7.8.3" "-lffi-6" While the succeeding ghc --make contains: "-lHSbase-4.7.0.1" "-lHSinteger-gmp-0.5.1.0" "-lHSghc-prim-0.3.1.0" "-lHSrts" "-lCffi-6" Should I be getting DynFlags differently to influence those link variables? Thanks, Neil

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Re: Cannot have GHC in ARMv6 architecture
by jmcf125＠openmailbox.org 14 Sep '15

14 Sep '15

Hi, sorry for not sending a CC to the mailing list, works differently from others I've used > > $ ls -R /home/jmcf125/ghc-raspberry-pi/sysroot/* > >/home/jmcf125/ghc-raspberry-pi/sysroot/lib: > >libcursesw.so libncurses.so libncurses++.so libncurses.so.5@ libncurses.so.5.9* libncursesw.so@ libncursesw.so.5@ libncursesw.so.5.9* > > > >/home/jmcf125/ghc-raspberry-pi/sysroot/usr: > >include/ > > > >/home/jmcf125/ghc-raspberry-pi/sysroot/usr/include: > >cursesapp.h cursesf.h curses.h cursesm.h cursesp.h cursesw.h cursslk.h ncurses_dll.h ncurses.h@ slcurses.h > > > This is misunderstadning, you need whole sysroot package for ARMv6. That > means basically copy whole / or just google for it. > > The reason is simple curses headers include another headers and those will > not be available in your way. Ditto for libs which depends at least on libc. That was actually just the 1st thing I tried, then as I said: > >I also tried extracting the ncurses official package for ARMv6 itself to > >sysroot, and got another error message, where the compiler did work. I > >begun to wonder whether I need a full ARMv6 system in sysroot to make > >this work, and as my Raspberry Pi is on an external hard drive, I > >mounted it on /mnt/jrpi, and changed the --sysroot option to it. > >Finally, configure worked! So, when doing that, configure works (the logs were for the previous attempts). But why is that when I try to make, with a working configure, and a real sysroot, that I get the following error? > > $ make -j5 > >(...) > >"inplace/bin/mkdirhier" compiler/stage2/doc/html/ghc//. > ><<ghc: 13398192 bytes, 14 GCs, 190152/210488 avg/max bytes residency (2 samples), 26M in use, 0.000 INIT (0.000 elapsed), 0.016 MUT (0.257 elapsed), 0.015 GC (0.020 elapsed) :ghc>> > >"inplace/bin/mkdirhier" utils/hsc2hs/dist-install/build/tmp//. > >"inplace/bin/mkdirhier" utils/ghc-pkg/dist-install/build/tmp//. > >"inplace/bin/mkdirhier" utils/ghctags/dist-install/build/tmp//. > ><<ghc: 13396968 bytes, 14 GCs, 190128/210440 avg/max bytes residency (2 samples), 26M in use, 0.000 INIT (0.000 elapsed), 0.015 MUT (0.213 elapsed), 0.014 GC (0.017 elapsed) :ghc>> > >"inplace/bin/mkdirhier" utils/ghc-pwd/dist-install/build/tmp//. > >"inplace/bin/mkdirhier" utils/ghc-cabal/dist-install/build/tmp//. > >"inplace/bin/mkdirhier" utils/hpc/dist-install/build/tmp//. > >"inplace/bin/mkdirhier" utils/runghc/dist-install/build/tmp//. > >docs/users_guide/users_guide.xml > >make[1]: docs/users_guide/users_guide.xml: Command not found > >docs/users_guide/what_glasgow_exts_does.gen.xml > >docs/users_guide/ghc.mk:24: recipe for target 'docs/users_guide/users_guide.xml' failed > >make[1]: *** [docs/users_guide/users_guide.xml] Error 127 > >make[1]: *** Waiting for unfinished jobs.... > >make[1]: docs/users_guide/what_glasgow_exts_does.gen.xml: Command not found > >docs/users_guide/ghc.mk:24: recipe for target 'docs/users_guide/what_glasgow_exts_does.gen.xml' failed > >make[1]: *** [docs/users_guide/what_glasgow_exts_does.gen.xml] Error 127 > >Writing utils/haddock/doc/haddock/license.html for section(license) > >Writing utils/haddock/doc/haddock/ch01s03.html for section > >Writing utils/haddock/doc/haddock/ch01s04.html for section > >Writing utils/haddock/doc/haddock/introduction.html for chapter(introduction) > >Writing utils/haddock/doc/haddock/invoking.html for chapter(invoking) > >Writing utils/haddock/doc/haddock/ch03s02.html for section > >Writing utils/haddock/doc/haddock/ch03s03.html for section > >Writing utils/haddock/doc/haddock/ch03s04.html for section > >Writing utils/haddock/doc/haddock/ch03s05.html for section > >Writing utils/haddock/doc/haddock/hyperlinking.html for section(hyperlinking) > >Writing utils/haddock/doc/haddock/module-attributes.html for section(module-attributes) > >Writing utils/haddock/doc/haddock/ch03s08.html for section > >Writing utils/haddock/doc/haddock/markup.html for chapter(markup) > >Writing utils/haddock/doc/haddock/ix01.html for index > >Writing utils/haddock/doc/haddock/index.html for book(haddock) > >cp mk/fptools.css utils/haddock/doc/haddock/ > >Makefile:71: recipe for target 'all' failed > >make: *** [all] Error 2 ghc-stage1 logically does not work, although it is created. I hope this is clearer. Cheers, João Miguel

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HEADS UP (devs, users): 8.0.1 Roadmap
by Austin Seipp 14 Sep '15

14 Sep '15

Hi *, I've returned from vacation, and last week Simon, Simon and I met up again after a long break, and talked a bit about the upcoming release. The good news is that it is going to be an exciting one! The flip side is, there's a lot of work to be done! The current plan we'd roughly like to follow is... - November: Fork the new `ghc-8.0` STABLE branch - At this point, `master` development will probably slow as we fix bugs. - This gives us 2 months or so until branch, from Today. - This is nice as the branch is close to the first RC. - December: First release candidate - Mid/late February: Final release. Here's our current feature roadmap (in basically the same place as all our previous pages): https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.0.1 As time goes on, this page will be updated to reflect Reality™ and track it as closely as possible. So keep an eye on it! It's got the roadmap (near top) and large bug list (bottom). Now, there are some things we need, so depending on who you are, please... - *Users*: please look over the bug list! If there's a bug you need fixed that isn't there, set it to the 8.0.1 milestone (updated in Trac). If this bug is critical to you, please let us know! You can bump the priority (if we disagree, or it's workaround-able, it might get bumped down). We just need a way to see what you need, so please let us know somehow! As a reminder, our regular policy is this: if a bug is NOT marked highest or high priority, it is essentially 100% the case we will not look at it. So please make sure this is accurate. Or if you can, write a patch yourself! - *Developers*: double check the roadmap list, _and if you're responsible for something, make sure it is accurate!_ There are some great things planned to land in HEAD, but we'll have to work for it. Onward! - A better LLVM backend for Tier-1 platforms - Types are kinds and kind equality - Overloaded record fields! - Enhancements to DWARF debugging - ApplicativeDo - ... and many more... Thanks everyone! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Proposal: Include GHC version target in libraries' description
by Alexander Berntsen 14 Sep '15

14 Sep '15

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Problem: A frequent usecase for especially base is browsing the haddocks online on hackage (I do this myself sometimes). A frequent associated pain with this is remembering which base version corresponds to which GHC version (I feel this myself sometimes). Current solution: Consult the boot library version chart[0]. An additional step -- where there needn't be one -- may annoy the user. Furthermore, if they don't know about the chart then they're essentially lost; which usually leads to them consulting another user - -- and now we've wasted a little time for *two* of our users for no real good reason. I conjecture that this happens quite often. Which means our culmination of GHC-related time waste eventually adds up quite a bit, detracting from the overall experience. Proposed improvement: Add "[library]-[library version] is bundled with ghc-[GHC version]." in the description string of [library].cabal. This immediately clears up the confusion when looking at [library]'s hackage page. [0] <https://ghc.haskell.org/trac/ghc/wiki/Commentary/Libraries/VersionHisto ry> - -- Alexander alexander(a)plaimi.net https://secure.plaimi.net/~alexander -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCgAGBQJVwezFAAoJENQqWdRUGk8B8jEQAMuAYjn25VB/aG5VWr8IdPoZ OSoUu+26XdJhmbOcYzHWje7gUs8FSfqxHyflasiO22uWOHHO3kfyzwOEZX0Nqc0b WboMRuNZ5dEPGAGFqxi/DWzPoaQ9shA+EUmCl8r2Qn9W7ZximaP3b1ORO0UvvgBo YK3T0f4TCoYKOYS2Txl5gjO3FKK6STdNxcELs3p6g0+paf5crEf3hcw2WZCcsdSc 0yU3dl5iFin4ofaByDmx7tj1ACYn7MusEH4zF+jjGYb4XbIV+WCy78Nsmlqt3AF9 P++HD4DMmh+rXW9tkqAbTgxn3LAgrkB0F3vYAEfiH4xFmWlQyzANtjILN6WYDOt0 5Gnpz/Meg6aGJY0U5y/XAPxzpar7oc/HPbdjS747iOTLj4dsOHeswmw++goG8ugw j/Yq00T17/3RJlZ03OdaRyl+HrXiNCq0J48LUUJu9jY9LCjr57hKZa3fFFM++fIU UaIMllxCiOdGDaTJCCZ/HEvZBtvxaeWWEc/Zi2XrtMI4PcAS/QACxlJJsHfnb/1B mCi5fIWjzX0UPo6YeRI2MeUlasKp8fLPm8AGKHQJGx2XHNHToNFR5X75VpCWWlp3 oboVm1qN46qpwnkrxWrIvlK40fLjmiZZMb0HS4cm+4ofNFc+CQMBqQ5fZxrwAO7e CTzw91s+6tbcp43Y+lgI =rmBv -----END PGP SIGNATURE-----

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Deriving Contravariant and Profunctor
by David Feuer 11 Sep '15

11 Sep '15

Would it be possible to add mechanisms to derive Contravariant and Profunctor instances? As with Functor, each algebraic datatype can only have one sensible instance of each of these. David Feuer

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