- ghc-devs - Haskell.org

pattern signatures
by Richard Eisenberg 10 Jan '18

10 Jan '18

Hi devs, Is a pattern signature a) something you put after `pattern P ::` ? b) something you put after `::` in a pattern, as in `foo (Proxy :: Proxy a)` ? I've seen the term "pattern signature" apply to both, and I've been tripped up by this. Does anyone have terminology that unambiguously separates these two constructs that we can all adopt? Thanks! Richard

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Backing up and downloading Trac contents?
by Niklas Hambüchen 07 Jan '18

07 Jan '18

Working on something today, it came to my mind how much useful information is stored in Trac and how much time would get lost if it went down, corrupted or missing. With the source code there's no such issue as with git being a DVCS, everybody has the full history. But not so with Trac. Are there backups of Trac? Are there some publicly available ones that one could download and thus conveniently use offline? Thanks!

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Spectre mitigation
by Demi Obenour 06 Jan '18

06 Jan '18

The recent “Spectre” bug requires that speculative execution of indirect branches be disabled. For GHC, this will require passing a flag to LLVM and fixing the NCG to emit suitable calling sequences. This will be a disaster for the STG execution model, because it disables CPU branch prediction for indirect calls and jumps. This is a big argument in favor of doing a CPS→SSA conversion in the backend.

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Can't push to staging area?
by Bartosz Nitka 05 Jan '18

05 Jan '18

I'm trying to update a diff and I run into this: $ arc diff Linting... LINT OKAY No lint problems. Running unit tests... No unit test engine is configured for this project. PUSH STAGING Pushing changes to staging area... sudo: a password is required fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists. STAGING FAILED Unable to push changes to the staging area. Usage Exception: Failed to push changes to staging area. Correct the issue, or use --skip-staging to skip this step. I believe that it worked for me before with my setup, and I seem to be in compliance with https://ghc.haskell.org/trac/ghc/wiki/Phabricator#Startingoff:Fixingabugsub… Any ideas? Thanks, Bartosz

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Re: [ANNOUNCE] GHC 8.4.1-alpha1 available
by Ben Gamari 31 Dec '17

31 Dec '17

Emanuel Borsboom <manny(a)fpcomplete.com> writes: > Hi Ben, > > Are there any plans to start releasing Linux bindists linked with > libncurses.so.6? A number of Linux distributions have upgraded from 5, > including Fedora, Arch and Gentoo, and the currently available > official bindists don't work out of the box on those anymore. > Indeed I can add an ncurses.so.6 platform to the build matrix. I'll start with the next alpha. Thanks for mentioning this! Cheers, - Ben

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Naming of HEq_sc
by Matthew Pickering 29 Dec '17

29 Dec '17

Hi all, Does anyone know why the *record selector* `HEq_sc` started with a capital letter? Would it be sensible to rename it to start with a lower case letter and perhaps mention that it is a selector in the name? git grep "HEq_sc" doesn't yield any explanation, I could only work this out from reading the source doe. I propose "heq_sel" could be more self-explanatory. Cheers, Matt

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validate failure on Mac OSX for ghc head (validate fails with clang)
by Carter Schonwald 29 Dec '17

29 Dec '17

hey All, the current settings for warnings etc for ghc validate do not work on mac, this is because some gcc flag isn't in clang, or vice versa, or some version of gcc related matter the relevant error is: error: unknown warning option '-Werror=unused-but-set-variable'; did you mean '-Werror=unused-const-variable'? [-Werror,-Wunknown-warning-option] the culprit seems to be apple clang, at least if my reading of the config output by validate is correct Configure completed successfully. Building GHC version : 8.5.20171223 Git commit id : d7d0aa316f9d23d73ae617e0cc1b147907667ef4 Build platform : x86_64-apple-darwin Host platform : x86_64-apple-darwin Target platform : x86_64-apple-darwin Bootstrapping using : /Users/carter/.install-ghc/ghc-8.2.2-hq/bin/ghc which is version : 8.2.2 Using (for bootstrapping) : /usr/bin/clang Using gcc : /usr/local/bin/gcc-7 which is version : 7.2.0 Building a cross compiler : NO Unregisterised : NO hs-cpp : /usr/local/bin/gcc-7 hs-cpp-flags : -E -undef -traditional there seem to be several take aways: 1) clang doesn't support unused-but-set-variable 1.5) no one has run validate on OSX in the past few months with a vanilla checkout / env? 2) how do i change the compiler selected for boot strapping, whether via env variables or other twiddles thanks! -Carter

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RE: Haskell Platform 8.2.2 - virus?
by Gershom B 28 Dec '17

28 Dec '17

Note that HitmanPro has caused plenty of problems with GHC in the past, and should be avoided by Haskell devs: https://www.reddit.com/r/haskell/comments/77from/gettting_segmentation_faul… https://github.com/commercialhaskell/intero/issues/436

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Haskell Platform 8.2.2 - virus?
by Matthew Lamari 28 Dec '17

28 Dec '17

New Haskell install was tripping my Bitdefender like crazy and in weird ways - not new as that's how bitdefender rolls. However, I retested in a clean test, with (free) Hitman Pro I started from a base case with 2 clean windows 8 VMs. New 8.2.2 install - has virus Old 8.0.2 Jan 2017 - no virus According to Hitman Pro, touchy.exe, haddock-8.2.2, ghc-8.2.2.exe, and unlit.exe have some problem post-install. I went no further on the VMs. "Detection Names Kaspersky Trojan-Downloader.Win32.Paph.fsv " Bitdefender didn't get it on install but would lock the whole thing down on the first run of "Cabal".

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How do I build basic GHC packages with -fPIC?
by Viacheslav Lotsmanov 28 Dec '17

28 Dec '17

Hi there. My actual main goal is to build my own shared library written in Haskell that would be compatible with application written in C even without knowing that is is written in Haskell. So for now I compiled my shared library but I only could dynamically link it to Haskell dependencies such as "base" and "ghc-prim" packages. But I want to statically link Haskell dependencies but I realized it isn't simple and straightforward task. On Freenode's #haskell I was advised I should build GHC from scratch with -fPIC, on the Linux (I'm using Fedora Workstation 25 on x86_64) I couldn't go forward without this step. So I wrote some Dockerfile based on Debian 9, skipping first part which is containing 'apt-get update' and installing 'build-essential' here is what I have: COPY my-build.mk /my-build.mk RUN mkdir /compile && cd /compile \ && wget https://downloads.haskell.org/~ghc/8.2.2/ghc-8.2.2-src.tar.xz \ && tar -xvf ghc-8.2.2-src.tar.xz \ && rm ghc-8.2.2-src.tar.xz \ && cd ghc-8.2.2/ \ && ./configure --prefix=/ghc-8.2.2-fpic --disable-library-profiling --enable-shared \ && cp /my-build.mk mk/build.mk \ && make install \ && cd /usr/local/bin \ && ls /ghc-8.2.2-fpic/bin/ | xargs -I{} ln -s /ghc-8.2.2-fpic/bin/{} And as you can see I just use my own prepared /my-build.mk/ file which is: SRC_HC_OPTS = -H64m -O EXTRA_HC_OPTS = -fPIC SRC_CC_OPTS = -fPIC -O GhcStage1HcOpts = -fasm -O0 GhcStage2HcOpts = -fasm -O0 GhcLibHcOpts = -fasm -O2 GhcLibWays = v dyn DYNAMIC_GHC_PROGRAMS = YES DYNAMIC_BY_DEFAULT = NO SplitObjs = NO HADDOCK_DOCS = NO BUILD_DOCBOOK_HTML = NO BUILD_DOCBOOK_PS = NO BUILD_DOCBOOK_PDF = NO V = 1 LATEX_DOCS = NO HSCOLOUR_SRCS = NO BeConservative = YES I just combined it from parts I found in the internet during searching answers to my questions. So I built this container, I also installed dependencies by this commands: cd /mnt cabal update cabal sandbox init cabal install --enable-shared --ghc-option=-fPIC happy alex cabal install --enable-shared --ghc-option=-fPIC base-unicode-symbols filepath process directory lens containers qm-interpolated-string And when I tried to build my app by following commands (first command compiles some C-code to automatically initialize Haskell runtime, see link posted below, not sure if /-static/, /-shared/ or /-fPIC/ means something here but it's work in progress): ghc -static -shared -fPIC -optc-DMODULE=Foo src/lib-autoinit.c -outputdir builddir ghc -package-db=SOME_CABALS_SANDBOX_PKGDB_DIR --make-static-shared-fPIC src/Foo.hs builddir/src/lib-autoinit.o -o builddir/libfoo.o -isrc -outputdir builddir -Wall -O2 I failed with a lot of similar errors like this one: /usr/bin/ld.gold: error: /ghc-8.2.2-fpic/lib/ghc-8.2.2/ghc-prim-0.5.1.1/libHSghc-prim-0.5.1.1.a(Classes.o): requires dynamic R_X86_64_PC32 reloc against 'stg_ap_0_fast' which may overflow at runtime; recompile with -fPIC What have I missed? What should I do to make this happen? Any progress could be found here (Dockerfile, sources of modules, build-scripts): https://github.com/unclechu/haskell-experiment-shared-library-for-c-applica… Related stack overflow issue: https://stackoverflow.com/questions/47978884/how-do-i-recompile-ghc-with-fp…

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