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[ANNOUNCE] GHC 8.8.1 release candidate 1 is now available
by Ben Gamari 26 Jul '19

26 Jul '19

Hello everyone, The GHC team is pleased to announce the release candidate for GHC 8.8.1. The source distribution, binary distributions, and documentation are available at https://downloads.haskell.org/ghc/8.8.1-rc1 This release is the culmination of over 3000 commits by over one hundred contributors and has several new features and numerous bug fixes relative to GHC 8.6: * Profiling now works correctly on 64-bit Windows (although still may be problematic on 32-bit Windows due to platform limitations; see #15934) * A new code layout algorithm for amd64's native code generator * The introduction of a late lambda-lifting pass which may reduce allocations significantly for some programs. * Further work on Trees That Grow, enabling improved code re-use of the Haskell AST in tooling * More locations where users can write `forall` (GHC Proposal #0007) * A comprehensive audit of GHC's memory ordering barriers has been performed, resulting in a number of fixes that should significantly improve the reliability of programs on architectures with weakly-ordered memory models (e.g. PowerPC, many ARM and AArch64 implementations). * A long-standing linker limitation rendering GHCi unusable with projects with cyclic symbol dependencies has been fixed (#13786) * Further work on the Hadrian build system * Numerous bug-fixes As always, if anything looks amiss do let us know. Happy compiling! Cheers, - Ben [1] https://downloads.haskell.org/ghc/8.8.1-rc1/docs/html/users_guide/8.8.1-not…

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Typing rules for Haskell
by Richard Eisenberg 25 Jul '19

25 Jul '19

Hi devs, Simon and I were wondering about a tight specification for the recent action in proposal #253 (https://github.com/ghc-proposals/ghc-proposals/pull/253 <https://github.com/ghc-proposals/ghc-proposals/pull/253>). We needed to see the typing rules. So I made a repo (https://gitlab.haskell.org/rae/haskell <https://gitlab.haskell.org/rae/haskell>) to collect typing rules for source Haskell. I managed to convince the CI infrastructure to produce a PDF at every upload; it is linked from the README. The current version contains the proposed result signatures; it should probably be in a branch, but life is short. Contributions very welcome! Richard

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Any ways to test a GHC build against large set of packages (including test suites)?
by Ömer Sinan Ağacan 25 Jul '19

25 Jul '19

Hi, I'd like to test some GHC builds + some compile and runtime flag combinations against a large set of packages by building them and running test suites. For this I need - A set of packages that are known to work with latest GHC - A way to build them and run their test suites (if I could specify compile and runtime flags that'd be even better) I think stackage can serve as (1) but I don't know how to do (2). Can anyone point me to the right direction? I vaguely remember some nix-based solution for this that was being discussed on the IRC channel, but can't recall any details. Thanks, Ömer

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HIE files?
by Richard Eisenberg 24 Jul '19

24 Jul '19

Hi devs, I recently learned about the code for HIE files. This is quite a substantial new development in GHC, judging from the amount of code. I understand broadly why it's here, but I'd like to learn more specifics. For example, if I'm adding a new bit of syntax, how should I update HIE generation? What if I'm changing a bit of syntax? Is there a primer to all this? Thanks! Richard

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Tracking issues for GHC proposals?
by Ömer Sinan Ağacan 24 Jul '19

24 Jul '19

Hi all, It's currently quite hard to see progress of proposals. For example, I'm looking at the "small primitives" proposal [1]. After some digging I can see that it's mostly (if not completely) implemented [2, 3], but finding all this takes time. I think it'd make sense to create a tracking issue when a proposal is accepted, on GHC's Gitlab, and link to it from the proposal. All related MRs and issues would then be linked from the tracking issue, making seeing progress easier. How does that sound? Ömer [1]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0014-s… [2]: https://phabricator.haskell.org/D5006 [3]: https://phabricator.haskell.org/D4475

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gitlab subject lines
by Richard Eisenberg 23 Jul '19

23 Jul '19

Hi Ben, Since the recent GitLab upgrade, all GitLab emails have "GHC | Glasgow Haskell Compiler | " prefixed to their subject lines. This reduces the bandwidth of information in my mail reader. Is there a way of going back to just "GHC |"? Thanks! :) Richard

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How do Coercions work
by Jan van Brügge 22 Jul '19

22 Jul '19

Hi, currently I have some problems understanding how the coercions are threaded through the compiler. In particular the function `normalise_type`. With guessing and looking at the other cases, I came to this solution, but I have no idea if I am on the right track: normalise_type ty = go ty where go (RowTy k v flds) = do { (co_k, nty_k) <- go k ; (co_v, nty_v) <- go v ; let (a, b) = unzip flds ; (co_a, ntys_a) <- foldM foldCo (co_k, []) a ; (co_b, ntys_b) <- foldM foldCo (co_v, []) b ; return (co_a `mkTransCo` co_b, mkRowTy nty_k nty_v $ zip ntys_a ntys_b) } where foldCo (co, tys) t = go t >>= \(c, nt) -> return (co `mkTransCo` c, nt:tys) RowTy has type Type -> Type -> [(Type, Type)] What I am not sure at all is how to treat the coecions. From looking at the go_app_tys code I guessed that I can just combine them like that, but what does that mean from a semantic standpoint? The core spec was not that helpful either in that regard. Thanks in advance Jan

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GHC native bootstrap
by Igor Chudov 22 Jul '19

22 Jul '19

Hello! I want to bootstrap GHC on an exotic architecture and I have GCC-compatible compiler but miss cross-compiling toolchain. I was able to bootstrap Hugs98 (with manual fixes) and guys on IRC channel pointed me to GHC bootstrap articles: - https://elephly.net/posts/2017-01-09-bootstrapping-haskell-part-1.html - http://www.joachim-breitner.de/blog/748-Thoughts_on_bootstrapping_GHC which I read and plan to give it a try. I also read articles about cross-compiling GHC on Haskell wiki but the problem is complex so I don't know where to start. Are there anyone who has experience with GHC compiling (cross-compiling?) and bootstrap on new architectures who could possibly help me to solve the problem or describe the steps needed? -- With best regards, Igor Chudov

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head.hackage upstream
by Ben Gamari 22 Jul '19

22 Jul '19

Hi everyone, As I noted just a moment ago in another thread on this list, head.hackage's upstream repository will be moving to GitLab. I'll but publishing a blog post soon describing some of the infrastructure we have built around head.hackage. Otherwise, if you want to submit a patch to head.hackage please open a merge request against the GitLab repository [1]. Cheers, - Ben [1] https://gitlab.haskell.org/ghc/head.hackage

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Moving head.hackage upstream
by Ben Gamari 22 Jul '19

22 Jul '19

Hi Herbert, Last week I did some work to clean up and document GHC's head.hackage infrastructure. At this point we have a full CI pipeline, including automatic deployment of a Hackage repository. I asked on #ghc and there was quite some appetite to use gitlab.haskell.org:ghc/head.hackage as the head.hackage upstream repository to eliminate confusion and enjoy the benefits of having merge requests checked via CI. Moreover, this would significantly simplify the process of testing GHC against head.hackage as it would eliminate the need to pull from a separate upstream repository. Would you be okay with moving head.hackage's upstream? Thanks again for everything you have done in the head.hackage area. Cheers, - Ben

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