- ghc-devs - Haskell.org

Kind equalities
by Simon Peyton Jones 07 Dec '15

07 Dec '15

Richard What’s your ETA on the kind-equality stuff? We wondered in today’s call. We want to make an RC next week. Simon

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[ANNOUNCE] 7.10.3 release candidate 2
by Ben Gamari 07 Dec '15

07 Dec '15

Hello everyone, We are pleased to announce the second release candidate for GHC 7.10.3: https://downloads.haskell.org/~ghc/7.10.3-rc2/ This release differs from -rc1 by only two commits, * Disable the newly-introduced readelf configure check on non-ELF platforms. * Remove some tracing output from the typechecker that was causing some testsuites to fail. At the moment you should find the source tarball as well as 32- and 64-bit modern Linux (built on Debian 8) binary distributions available at the above URL. Windows and CentOS binaries will be made available shortly. As usual, you may need to work around our content delivery network's update latency by adding redundant forward-slashes to the URL. As far as OS X support goes, we are still looking for contributors to help us to support their platform by offering access to hardware, testing, or builds. Please let us know if you would be willing to provide any of the above. Happy testing! Cheers, - Ben

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How do I use CallStack?
by Richard Eisenberg 07 Dec '15

07 Dec '15

Hi devs, I wish to use the new CallStack feature to track call sites of a function. I want my function to print out where it was called from. I do not want to call `error`. How do I do this? I looked in the release notes. They describe the CallStack feature at an overview, and the docs suggest that it has a Show instance. But the notes don't say where to import CallStack from. I found it in GHC.Stack, but I'm unsure this is the right place to take it from. The GHC release notes also refer me to the ghc-prim release notes. These (which I assume are ghc-prim/changelog.md) don't discuss CallStack. In any case, when I try to `show ?callstack`, I learn that CallStack is not an instance of Show, or I somehow haven't imported the instance. Help? Thanks! Richard

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Haddock for GHC 8.0
by Ben Gamari 07 Dec '15

07 Dec '15

tl;dr: Help needed to bring Haddock up-to-date for the GHC 8.0 release. Hello everyone, As you likely know, the GHC 8.0 release cycle is quickly drawing to a close. One of the tasks that remains outstanding is porting the patches on Haddock's `ghc-head` branch to `master`. This task is bound to require a bit more work than usual this time around as both GHC and Haddock have evolved significantly (which is a good thing!). Sadly, Austin and I are quite busy at the moment and would be hard-pressed to undertake such a task ourselves. Consequently, we need a volunteer to pick up this work. At the moment the GHC release schedule is largely determined by progress on the no-kinds branch but we expect to have a release candidate out within the next two weeks. If we aren't able to find someone to bring haddock up-to-date by mid-January I'm afraid we'll have to release GHC 8.0 with the current state of the `ghc-head` branch. Considering the significant effort that went into this summer's GSoC projects, this would be a shame. If you think you might be able to contribute to this effort, please say so in this thread. Thanks for all of your effort, - Ben

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Phab out of memory
by Richard Eisenberg 07 Dec '15

07 Dec '15

I just tried to update D808, but the following happened. Any ideas? Thanks, Richard rae:22:44:22 ~/Documents/ghc> arc diff origin/master --update D808 --allow-untracked --head HEAD --trace libphutil loaded from '/Users/rae/local/share/libphutil/src'. arcanist loaded from '/Users/rae/local/share/arcanist/src'. Config: Reading user configuration file "/Users/rae/.arcrc"... Config: Did not find system configuration at "/etc/arcconfig". Working Copy: Reading .arcconfig from "/Users/rae/Documents/ghc/.arcconfig". Working Copy: Path "/Users/rae/Documents/ghc" is part of `git` working copy "/Users/rae/Documents/ghc". Working Copy: Project root is at "/Users/rae/Documents/ghc". Config: Did not find local configuration at "/Users/rae/Documents/ghc/.git/arc/config". Loading phutil library from '/Users/rae/Documents/ghc/.arc-linters/arcanist-external-json-linter'... >>> [0] <conduit> conduit.connect() <bytes = 545> >>> [1] <http> https://phabricator.haskell.org/api/conduit.connect <<< [1] <http> 172,210 us <<< [0] <conduit> 1,237,507 us >>> [2] <event> diff.didCollectChanges <listeners = 0> <<< [2] <event> 138 us >>> [3] <conduit> differential.query() <bytes = 189> >>> [4] <http> https://phabricator.haskell.org/api/differential.query <<< [4] <http> 134,230 us <<< [3] <conduit> 134,659 us >>> [5] <conduit> differential.getcommitmessage() <bytes = 212> >>> [6] <http> https://phabricator.haskell.org/api/differential.getcommitmessage <<< [6] <http> 109,179 us <<< [5] <conduit> 109,721 us >>> [7] <conduit> differential.parsecommitmessage() <bytes = 1,358> >>> [8] <http> https://phabricator.haskell.org/api/differential.parsecommitmessage <<< [8] <http> 106,739 us <<< [7] <conduit> 107,306 us >>> [9] <event> diff.didBuildMessage <listeners = 0> <<< [9] <event> 168 us >>> [10] <exec> $ git rev-parse --git-dir <<< [10] <exec> 8,502 us >>> [11] <exec> $ git rev-parse 'HEAD' <<< [11] <exec> 5,632 us >>> [12] <exec> $ git merge-base 'origin/master' '9eb7237750f9409a4e1b00c509f2519983d97130' <<< [12] <exec> 119,778 us >>> [13] <exec> $ git log --first-parent --format=medium 'c865c425a37b0bc52f4dead9d70eb0ee2bc287d6'..'9eb7237750f9409a4e1b00c509f2519983d97130' <<< [13] <exec> 117,008 us >>> [14] <conduit> differential.querydiffs() <bytes = 191> >>> [15] <http> https://phabricator.haskell.org/api/differential.querydiffs <<< [15] <http> 3,462,000 us <<< [14] <conduit> 3,462,526 us [2015-12-05 03:44:31] EXCEPTION: (HTTPFutureHTTPResponseStatus) [HTTP/500] Internal Server Error >>> UNRECOVERABLE FATAL ERROR <<< Out of memory (allocated 501743616) (tried to allocate 70083487 bytes) /opt/phabricator/src/aphront/response/AphrontResponse.php:167 ┻━┻ ︵ ¯\_(ツ)_/¯ ︵ ┻━┻ at [<phutil>/src/future/http/BaseHTTPFuture.php:339] arcanist(head=master, ref.master=87306cfe1453), external-json-linter(), phutil(head=master, ref.master=e65ffd33db02) #0 BaseHTTPFuture::parseRawHTTPResponse(string) called at [<phutil>/src/future/http/HTTPSFuture.php:415] #1 HTTPSFuture::isReady() called at [<phutil>/src/future/Future.php:37] #2 Future::resolve(NULL) called at [<phutil>/src/future/FutureProxy.php:34] #3 FutureProxy::resolve() called at [<phutil>/src/conduit/ConduitClient.php:58] #4 ConduitClient::callMethodSynchronous(string, array) called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:2231] #5 ArcanistDiffWorkflow::loadActiveLocalCommitInfo() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:2129] #6 ArcanistDiffWorkflow::getGitUpdateMessage() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:2095] #7 ArcanistDiffWorkflow::getDefaultUpdateMessage() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:1882] #8 ArcanistDiffWorkflow::getUpdateMessage(array, NULL) called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:763] #9 ArcanistDiffWorkflow::buildRevisionFromCommitMessage(ArcanistDifferentialCommitMessage) called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:469] #10 ArcanistDiffWorkflow::run() called at [<arcanist>/scripts/arcanist.php:382]

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Re: ambiguous type stuff
by David Feuer 06 Dec '15

06 Dec '15

I think I didn't explain myself well enough. I'm not talking about expanded defaulting, although that may be tied up with the same mechanisms. Perhaps the best thing is just to work on the error message text for certain ambiguous type situations. Notably, situations where adding a proxy argument or similar is needed to avoid the error tend to be pretty mysterious until you realize that the system is not complaining because it can't determine a type, but rather because there is no way to pinpoint that type at the use site. If F is a type family then f :: Foo x => F x has a perfectly sensible translation, namely f :: forall x . Foo x -> F x The problem is purely one of inference on the Haskell side: there is no way to add a signature *at the call site* that determines what value of x to pass to f. The error message about x being ambiguous because F is a type family has to be read a bit backwards. At a *use site*, it'll be pretty clear-cut what's ambiguous, and it will soon become clear why it can't be pinned down. Perhaps it would pay to change the error message to explain why the type signature renders the term unusable.

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Plugins: How to determine ghc vs ghci
by Levent Erkok 05 Dec '15

05 Dec '15

I'm working on a plugin, and would like to be able to tell if it's GHC or GHCi that's running. I tried: df <- getDynFlags let isGHCi = ghcMode df == CompManager Alas, while that correctly tells apart "ghci" from "ghc -c", it also returns True when ghc is called without the "-c" argument. Is there a better/more robust way of figuring out whether we're in an interactive session? -Levent.

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warnings in stage1
by Richard Eisenberg 04 Dec '15

04 Dec '15

Hi devs, I'm getting pattern-match warnings in my stage1 compiler. I assume that this is due to enhanced pattern-match checking. This is good! But I like to build (even stage1) with -Werror. Is this expected? Is someone working on this? Thanks! Richard

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RE: [GHC] #11160: New exhaustiveness checker breaks ghcirun004
by Simon Peyton Jones 04 Dec '15

04 Dec '15

No let’s not revert. But: · Please put a list of the tickets (there are several) on the wiki page (where is the wiki page?) o perf/compiler/T783 o #11163: perf/compiler/T5642 o · Let’s have a flag to skip overlap testing so that there is always a workaround · Are you happy to continue to work on these perf issues? Simon From: George Karachalias [mailto:george.karachalias@gmail.com] Sent: 04 December 2015 09:41 To: Simon Peyton Jones <simonpj(a)microsoft.com> Subject: Re: [GHC] #11160: New exhaustiveness checker breaks ghcirun004 Simon, On Fri, Dec 4, 2015 at 10:34 AM, GHC <ghc-devs(a)haskell.org<mailto:ghc-devs@haskell.org>> wrote: Comment (by simonpj): Very fast response thank you. Your commit message is very informative. Did you include the same information in a `Note` in the code, so that we don't lose the information here? I haven't yet but I can. Actually, I wanted to ask you something. At the moment I pass all the normal tests but I fail some performance tests. They do compile but there is a deviation from the expected and HEAD is broken. For the additional expressive power I expected some more memory and time. For example, for perf/compiler/T783.hs which has 500 guards in a single function definition I take ~5 sec to compile but the deviation in allocated bytes is 753%, compared to what the "expected" is. I feel terrible since we are really close to the freeze and I think I am stalling everyone. I know of no good way to reduce memory consumption without losing substantial expressivity. Do you think I shall revert? George -- things you own end up owning you

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The GHC 8.0 feature freeze is coming
by Ben Gamari 04 Dec '15

04 Dec '15

tl;dr: feature freeze is imminent; get any remaining patches in ASAP. Hello all, The GHC 8.0 release cycle is quickly approaching its conclusion. While there are a few patches still outstanding (most notably the no-kinds branch to which we owe the major version number bump), most everything else has at this point been merged. If you are still sitting on a patch then please post it for review as soon as possible. We will enter a formal feature freeze within the next week. If things go according to plan we will have be able to fork the 8.0 branch shortly thereafter and have a release candidate within two weeks. Thanks to everyone who has contributed to this release! Cheers, - Ben

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