April 2023 - ghc-devs

Build of GHC 9.6 fails when the build directory is not a child of the source directory
by Viktor Dukhovni 30 Apr '23

30 Apr '23

For some time now I'd been unable to build GHC 9.6 from source. The reason turned out to be that my hadrian command-line selected an explicit build directory that was not an immediate child of the source directory (default it seems is "_build"). With the source tree under "$HOME/dev/ghc/", the hardrian command $ hadrian/build -V -V -o"$HOME/dev/buildghc" --docs=no-sphinx binary-dist-dir after building stage0, and running "configure" in libraries/base, reports an error finding HsFFI.h: Reading parameters from $HOME/dev/buildghc/stage1/libraries/base/build/base.buildinfo /usr/bin/cc '-fuse-ld=gold' /tmp/2303653-4.c -o /tmp/2303653-5 '-D__GLASGOW_HASKELL__=906' \ '-Dlinux_BUILD_OS=1' \ '-Dx86_64_BUILD_ARCH=1' \ '-Dlinux_HOST_OS=1' \ '-Dx86_64_HOST_ARCH=1' \ -I$HOME/dev/buildghc/stage1/libraries/base/build/autogen \ -I$HOME/dev/buildghc/stage1/libraries/base/build/include \ -Ilibraries/base/include \ -Ilibraries/base \ -I/usr/include \ -I$HOME/dev/buildghc/stage1/inplace/../../..//libraries/ghc-bignum/include/ \ -I$HOME/dev/buildghc/stage1/libraries/ghc-bignum/build/include/ \ -I$HOME/dev/buildghc/stage1/inplace/../../..//libraries/ghc-bignum/include \ -I$HOME/dev/buildghc/stage1/libraries/ghc-bignum/build/include \ -I$HOME/dev/buildghc/stage1/inplace/../../..//rts/include \ -I$HOME/dev/buildghc/stage1/rts/build/include \ '-I$HOME/dev/buildghc/stage1/inplace/../../..//rts/@FFIIncludeDir@' \ '-I$HOME/dev/buildghc/stage1/rts/build/@FFIIncludeDir@' \ '-I$HOME/dev/buildghc/stage1/inplace/../../..//rts/@LibdwIncludeDir@' \ '-I$HOME/dev/buildghc/stage1/rts/build/@LibdwIncludeDir@' \ -L$HOME/dev/buildghc/stage1/inplace/../libraries/ghc-bignum/build \ -L$HOME/dev/buildghc/stage1/inplace/../libraries/ghc-prim/build \ -L$HOME/dev/buildghc/stage1/inplace/../rts/build -iquote \ $HOME/dev/ghc/libraries/base \ '-fuse-ld=gold' There are two issues to note here: - "hadrian" fails to substitute @FFIIncludeDir@ and @LibdwIncludeDir@. This used to be handled by "configure", but the job of turning "rts.cabal.in" into "rts.cabal" seems to have been reassigned to "hadrian". - With the build output directory a sibling rather than a child of the source tree, the path to "rts/include" is not constructed correctly. The path: -I$HOME/dev/buildghc/stage1/inplace/../../..//rts/include should have been: -I$HOME/dev/buildghc/stage1/inplace/../../../ghc/rts/include Switching to the default path proved to be a viable work-around, but perhaps other choices should also work. -- Viktor.

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does llvm 16 work with ghc 9.6.1 ?
by George Colpitts 25 Apr '23

25 Apr '23

Hi Does anybody know if llvm 16 works with ghc 9.6.1 ? Thanks George

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GHC 9.6.1 rejects previously working code
by Harendra Kumar 25 Apr '23

25 Apr '23

The following code compiles with older compilers but does not compile with GHC 9.6.1: {-# LANGUAGE KindSignatures #-} module A () where import Control.Monad.IO.Class import Control.Monad.Trans.Class data T (m :: * -> *) a = T instance Functor (T m) where fmap f T = undefined instance Applicative (T m) where pure = undefined (<*>) = undefined instance MonadIO m => Monad (T m) where return = pure (>>=) = undefined instance MonadTrans T where lift = undefined It fails with the following error: xx.hs:20:10: error: [GHC-39999] • Could not deduce ‘MonadIO m’ arising from the head of a quantified constraint arising from the superclasses of an instance declaration from the context: Monad m bound by a quantified context at xx.hs:20:10-21 Possible fix: add (MonadIO m) to the context of a quantified context • In the instance declaration for ‘MonadTrans T’ | 20 | instance MonadTrans T where | ^^^^^^^^^^^^ What is the correct resolution for this? -harendra

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[Haskell] [ANNOUNCE] GHC 9.4.5 released
by Zubin Duggal 18 Apr '23

18 Apr '23

The GHC developers are happy to announce the availability of GHC 9.4.5. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.4.5). Download Page: https://www.haskell.org/ghc/download_ghc_9.4.5.html Blog Post: https://www.haskell.org/ghc/blog/20230418-ghc-9.4.5-released.html This release is primarily a bugfix release addressing a few issues found in 9.4.4. These include: * Fixes for a number of bug fixes in the simplifier (#22623, #22718, #22913, 22695, #23184, #22998, #22662, #22725). * Many bug fixes to the non-moving and parallel GCs (#22264, #22327, #22926, #22927, #22929, #22930, #17574, #21840, #22528) * A fix a bug with the alignment of RTS data structures that could result in segfaults when compiled with high optimisation settings on certain platforms (#22975 , #22965). * Bumping `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). * A number of improvements to recompilation avoidance with multiple home units (#22675, #22677, #22669, #22678, #22679, #22680) * Fixes for regressions in the typechecker and constraint solver (#22647, #23134, #22516, #22743) * Easier installation of binary distribution on MacOS platforms by changing the installation Makefile to remove the quarantine attribute when installing. * ... and many 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/9.4.5/docs/html/users_guide/9.4.5-notes.…

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Performance of small allocations via prim ops
by Harendra Kumar 12 Apr '23

12 Apr '23

I was looking at the RTS code for allocating small objects via prim ops e.g. newByteArray# . The code looks like: stg_newByteArrayzh ( W_ n ) { MAYBE_GC_N(stg_newByteArrayzh, n); payload_words = ROUNDUP_BYTES_TO_WDS(n); words = BYTES_TO_WDS(SIZEOF_StgArrBytes) + payload_words; ("ptr" p) = ccall allocateMightFail(MyCapability() "ptr", words); We are making a foreign call here (ccall). I am wondering how much overhead a ccall adds? I guess it may have to save and restore registers. Would it be better to do the fast path case of allocating small objects from the nursery using cmm code like in stg_gc_noregs? -harendra

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[ANNOUNCE] GHC 9.6.1 is now available
by Ben Gamari 02 Apr '23

02 Apr '23

The GHC team is very pleased to announce the availability of GHC 9.6.1. As usual, binaries and source distributions are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.6.1/ 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 includes: - 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][migration-guide]. 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. Thanks to everyone who has contributed code, documentation, testing, and tickets to this release process. As this release represents upstream GHC's first step towards supporting web targets, we are very excited to have this release out the door! 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/docs/users_guide/9.6.1-notes.html

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