- ghc-devs - Haskell.org

Status of ghcup?
by Dominick Samperi 22 Feb '23

22 Feb '23

I watched an interesting YouTube video explaining how to install and use the Haskell extension in VS code, but the information appears to be obsolete, because there is no mention of ghcup, and ghcup is now required, along with a new version of the Haskell extension (the old one is labeled "legacy"). Unfortunately, I could not install ghcup on Windows due to obscure PowerShell security issues, or missing libraries in MSYS. While wrestling with this problem I discovered that Unix tools from Rtools must not be in PATH while working with Stack, probably due to incompatible MSYS versions. But removing Rtools from PATH does not resolve the ghcup installation problems. Any tips on ghcup installation under Windows would be appreciated. Thanks, Dominick

2 3

Using GHC API with multiple targets
by Eternal Recursion 19 Feb '23

19 Feb '23

Hi Everyone! I'm new here, trying to learn the GHC API. using 944 with cabal 3.8.1.0. How do I correctly set a GHC Session's DynFlags (and/or other properties) to ensure local libraries imported by the main target are resolved properly at compile time? What flags need to be set so that GHC is able to load/analyze/compile all relevant Libraries in a package? This is my current code: withPath :: FilePath -> IO () withPath target = do let targetDir = takeDirectory target let targetFile = takeFileName target listing <- listDirectory targetDir let imports = filter (\f -> takeExtension f == ".hs") listing print imports let moduleName = mkModuleName targetFile g <- defaultErrorHandler defaultFatalMessager defaultFlushOut $ runGhc (Just libdir) $ do initGhcMonad (Just libdir) dynflags <- getSessionDynFlags setSessionDynFlags $ dynflags { ghcLink = LinkInMemory , ghcMode = CompManager , backend = Interpreter , mainModuleNameIs = moduleName , workingDirectory = Just targetDir , importPaths = [targetDir] ++ importPaths dynflags } targets <- mapM (\t -> guessTarget t Nothing Nothing) imports setTargets targets setContext [ IIDecl $ simpleImportDecl (mkModuleName "Prelude") ] load LoadAllTargets liftIO . print . ppr =<< getTargets getModuleGraph putStrLn "Here we go!" print $ ppr $ mgModSummaries g putStrLn "☝️ " However, when I run it (passing to example/app/Main.hs, in which directory are Lib.hs and Lib2.hs, the latter being imported into Main), I get: $ cabal run cli -- example/app/Main.hs Up to date ["Main.hs","Lib.hs","Lib2.hs"] [main:Main.hs, main:Lib.hs, main:Lib2.hs] Here we go! [ModSummary { ms_hs_hash = 23f9c4415bad851a1e36db9d813f34be ms_mod = Lib, unit = main ms_textual_imps = [(, Prelude)] ms_srcimps = [] }, ModSummary { ms_hs_hash = e1eccc23af49f3498a5a9566e63abefd ms_mod = Lib2, unit = main ms_textual_imps = [(, Prelude)] ms_srcimps = [] }, ModSummary { ms_hs_hash = 5f6751d7f0d5547a1bdf39af84f8c07f ms_mod = Main, unit = main ms_textual_imps = [(, Prelude), (, Lib2)] ms_srcimps = [] }] ☝ example/app/Main.hs:4:1: error: Could not find module ‘Lib2’ Use -v (or `:set -v` in ghci) to see a list of the files searched for. | 4 |import qualified Lib2 as L2 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ cli: example/app/Main.hs:4:1: error: Could not find module `Lib2' Use -v (or `:set -v` in ghci) to see a list of the files searched for. What do I need to do differently to make this work? I have a local Cabal file I could use, but to know what I need out of it, I need to understand the minimum required info to get this to work. TIA! Sincerely, Bob Sent with [Proton Mail](https://proton.me/) secure email.

3 8

[ANNOUNCE] GHC 9.6.1-alpha3 is now available
by Ben Gamari 17 Feb '23

17 Feb '23

The GHC team is very pleased to announce the availability of GHC 9.6.1-alpha3. As usual, binaries and source distributions are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.6.1-alpha3/ Beginning with GHC 9.6.1, GHC can be built as a cross-compiler to WebAssembly and JavaScript. This is an important step towards robust support for compiling Haskell to the Web, but there are a few caveats to be aware of in the 9.6 series: - Both the Javascript and WebAssembly backends are still at an early stage of development and are present in this release as a technology preview - Using GHC as a cross-compiler is not as easy as we would like it to be; in particular, there are challenges related to Template Haskell - GHC is not yet run-time retargetable; a given GHC binary targets exactly one platform, and both WebAssembly and JavaScript are considered platforms for this purpose. Cross-compilers must be built from source by their users We hope to lift all of these limitations in future releases. Additionally, 9.6.1 will include: - Significant latency improvements in the non-moving garbage collector - Efficient runtime support for delimited continuations - Improvements in compiler error messages - Numerous improvements in the compiler's memory usage See the [release notes] for a comprehensive accounting of changes in this release. As always, one can find a [migration guide] to aid in transitioning from older releases on the GHC Wiki. We have also recently started extending our release process to cover a wider set of Linux distributions. In particular, we now offer Rocky 8 and Ubuntu 20.04 binary distributions which cover RedHat-derivative and distributions using older `glibc` releases (namely 2.27), respectively. Please do give this release a try and open a [ticket] if you see anything amiss. Cheers, - Ben [ticket]: https://gitlab.haskell.org/ghc/ghc/issues/ [migration guide]: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.6 [release notes]: https://downloads.haskell.org/ghc/9.6.1-alpha3/docs/users_guide/9.6.1-notes…

2 5

`ideclImplicit` in compiler/GHC/Iface/Ext/Ast.hs?
by Brandon Allbery 14 Feb '23

14 Feb '23

I'm researching a potential GHC proposal to allow "Prelude-like" imports, which in practice means silencing warnings about implicit use of symbols from them (-Wmissing-import-lists and similar). So far, it looks like `ideclImplicit` does almost exactly what I want and all I need is syntax to set it on imports other than the implicit Prelude import. With one notable exception: around compiler/GHC/Iface/Ext/Ast.hs line 326 (HEAD as of Saturday) there is a use that appears to intend to exclude the implicit Prelude import, without conditionalizing on Prelude like e.g. compiler/GHC/Tc/Module.hs lines 1685--1687. I have several questions about it. 1. The implicit import, but not explicit imports, are excluded from the extended .hi file? This seems wrong-ish to me; I'm wondering if it's actually looking to do something else such as strip it down to only the symbols in use. But I don't really know what the code here is supposed to do. 2. Should other "implicit" imports also be excluded the same way? -- brandon s allbery kf8nh allbery.b(a)gmail.com

1 0

Getting Info Table Profiling to the finish line
by Hécate 14 Feb '23

14 Feb '23

Hello fellow devs, I am indexing the work necessary to bring Info Table Profiling to the finish line: Seamless for the user to employ. Some of the tickets refer to external ticket trackers, they have been marked as FOREIGN. Their counterpart tickets will be opened there when the situation unlocks on our side. The epic is at https://gitlab.haskell.org/groups/ghc/-/epics/3 Please feel free to link future tickets that are related to this newer, better way of doing space profiling. My thanks to Matthew Pickering, David Eichmann, and Ben Gamari. Cheers, Hécate (with a project manager hat on, apparently!) -- Hécate ✨ 🐦: @TechnoEmpress IRC: Hecate WWW: https://glitchbra.in RUN: BSD

1 0

[Haskell] [ANNOUNCE] GHC 9.2.6 released
by Zubin Duggal 11 Feb '23

11 Feb '23

The GHC developers are happy to announce the availability of GHC 9.2.6. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.2.6). Download Page: https://www.haskell.org/ghc/download_ghc_9_2_6.html Blog Post: https://www.haskell.org/ghc/blog/20230210-ghc-9.2.6-released.html This release is primarily a bugfix release addressing a few issues found in 9.2.5. These include: * Fixes for a number of simplifier issues typically resulting in compiler panics (#22491, #22482, #19824, #22718, #22662, #22039). * Fix for a simplifier regression in 9.2.5 that could impact runtime performance when compiling with optimisations due to duplication of expensive work (#22425). * Various stability improvments and bug fixes for the non moving and parallel GCs (#22528, #20221, #22264, #22327, #22929, #22927, #22929, #22930). * Allow certain keywords which can be used as variable names with `-XOverloadedRecordDot` (#20723). * Improvements to typechecker performance for modules with holes in type signatures (#14766) * Bump `gmp-tarballs` to a version which doesn't use the reserved `x18` register on AArch64/Darwin systems, and also has fixes for CVE-2021-43618 (#22497, #22789). * ... and a few more. See the [release notes] for a full accounting. As some of the fixed issues do affect correctness users are encouraged to upgrade promptly. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket][] if you see anything amiss. Happy compiling, - Zubin [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.2.6/docs/html/users_guide/9.2.6-notes.…

1 0

Registering account in gitlab.haskell.org
by ccycle 06 Feb '23

06 Feb '23

Hi, I'm new to ghc-devs(a)haskell.org and would like to report a bug in GHC that I have encountered. I tried to log in with an account registered in gitlab.haskell.org to create an issue and then I got the following error: > Your account is pending approval from your GitLab administrator and hence blocked. Please contact your GitLab administrator if you think this is an error. Could someone approve my account? My account pending approval is: Username: ccycle Email: ccycle713(a)gmail.com

2 4

Preventing inert caching in TC plugin?
by Sandy Maguire 05 Feb '23

05 Feb '23

Hi all, I'm working on a little TC plugin that solves the following class: ```haskell class KnownAnnotations where rawAnnotationsVal :: [Annotation] ``` Like `HasCallStack`, the result of `KnownAnnotations` is unique to each callsite. Thus, I am trying to prevent my TC plugin from adding the solved constraint to the inert set. As an example, the following program: ``` t2 :: ([Annotation], Int) t2 = (rawAnnotationsVal, test2) t3 :: ([Annotation], Int) t3 = (rawAnnotationsVal, test3) ``` dumps this output with `-ddump-cs-trace`: ``` Step 1[l:0,d:0] Kept as inert: [WD] $dKnownAnnotations_a18UB {0}:: KnownAnnotations Step 2[l:0,d:0] Dict equal (keep inert): [WD] $dKnownAnnotations_a18UD {0}:: KnownAnnotations ``` Is there some trick to prevent the inert caching for these solved wanteds? Cheers, Sandy

2 2

LLVM Support Range Bump (dropping LLVM 10 support)
by Matthew Pickering 02 Feb '23

02 Feb '23

Hi all, We are intending to bump the range of supported LLVM versions in the 9.6, release. For 9.4 the range is 10-14 (inclusive) For 9.6 we will support 11-15 (inclusive) If dropping support for LLVM 10 is a concern for anyone please let us know. Cheers, Matt

1 0

FFI changes?
by Dominick Samperi 02 Feb '23

02 Feb '23

Hello, I have been working with a program that uses FFI to communicate with R for several years, but today there is a segmentation fault while importing functions or data from R. Before giving up on this project, I'm posting a few detail here, in case anybody has ideas...perhaps something changed with FFI? I tried going back to the version of R and ghc where it worked using stack, but no luck. The Haskell code is a modification of the code in the package hR (by Dylan Simon), and here is a function that fails that worked before. It fails with a seg fault on the call to r_install. (s = "parse" when it fails)... foreign import ccall safe "Rf_install" r_Install :: CString -> IO R_EXP rInstall :: String -> IO REXP rInstall s = withCString s r_Install >>= extREXP The types are defined as follows... extREXP :: R_EXP -> IO REXP extREXP = newForeignPtr_ data REXPREC type R_EXP = Ptr REXPREC type REXP = ForeignPtr REXPREC newtype SEXP a = SEXP { unSEXP :: REXP } deriving (Eq, Show) Please let me know if you see anything obviously wrong and in need of improvement, perhaps because of changes to the FFI. Thanks, Dominick

3 3