- ghc-devs - Haskell.org

Re: [ANNOUNCE] GHC 8.4.1 released
by Ben Gamari 08 Mar '18

08 Mar '18

Apostolos Syropoulos via Glasgow-haskell-users <glasgow-haskell-users(a)haskell.org> writes: > Hello, > > I tried to compile the latest bits on OpenIndiana (the open version of Solaris) and > compilation never starts because: > Can you try applying the attached patch? Cheers, - Ben

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[ANNOUNCE] GHC 8.4.1-rc1 available
by Ben Gamari 08 Mar '18

08 Mar '18

The GHC development team is pleased to announce the first (and likely final) release candidate of GHC 8.4.1. The usual release artifacts are available from https://downloads.haskell.org/~ghc/8.4.1-rc1 This release will likely be the last release before the final 8.4.1 release, which, if things go well, will be released one week from today. Due to user demand we now offer a binary distribution for 64-bit Fedora 27, which links against ncurses6. This is in contrast to the Debian 8 distribution, which links against ncurses5. Users of newer distributions (Fedora 27, Debian Sid) should use this new Fedora 27 distribution. Also due to user demand we have reintroduced compatibility with GCC 4.4, which earlier alphas had dropped due to #14244. Note that this release candidate is still affected by #14705, although this will certainly be resolved before the final release is made. === Notes on release scheduling === The 8.4.1 release marks the first release where GHC will be adhering to its new, higher-cadence release schedule [1]. Under this new scheme, major releases will be made in 6-month intervals with interstitial minor releases as necessary. In order to minimize the likelihood of schedule slippage and to ensure adequate testing, each major release will be preceded by a number of regular alpha releases. We will begin issuing these releases roughly three months before the final date of the major release and will issue roughly one every two weeks during this period. This high release cadence will allow us to quickly get fixes into users' hands and more quickly identify potential issues. As always, do let us know if you encounter any trouble in the course of testing. Thanks for your help! Cheers, - Ben [1] https://ghc.haskell.org/trac/ghc/blog/2017-release-schedule

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ghc, OpenBSD and stack pointer checking
by Matthias Kilian 06 Mar '18

06 Mar '18

Hi, while working on an ghc update for OpenBSD (to ghc-8.2.2), I tested a diff for OpenBSD which enforces a special mmap(2) option, MAP_STACK for the system stack and, if the check fails, just aborts the process.[1] (Please note that this differs from the meaning of MAP_STACK on some other operating systems) At first, everything looked fine, but later during the build, *sometimes* ghc (to be specific, inplace/lib/bin/ghc-stage2) got aborted after *many* succesfull runs of it (for example, while compiling the bundled haddock and after already a couple of haddock sources had been successfully compiled). So, if the stack pointer checking diff to OpenBSD is correct, and if I'm not running into a completely unrelated problem: does ghc and/or the runtime library sometimes move the system stack pointer to newly allocated/mapped memory? If so, where in the code? Please note: the check happens on traps and system calls, so the doesn't happen when the stack pointer is changed to newly allocated/mapped memory, but after the next trap or system call. Unfurtunately, I was stupid enough to drop my recent build logs and back traces, but they weren't very enlightening, anyway ;-) I may to get some more information tomorrow or on thursday. I'd appreciate any help on this. After all it's probably just a matter of changing one call to mmap(2), shielded by an #ifdef. Ciao and thanks in advance for any help, Kili [1]: https://marc.info/?l=openbsd-tech&m=151572838911297&w=2

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FFI-free NaN checks? (isDoubleNan and friends)
by Mateusz Kowalczyk 06 Mar '18

06 Mar '18

Hi, Recently at a client I was profiling some code and isDoubleNaN lit up. We were checking a lot of doubles for NaN as that's what customer would send in. I went to investigate and I found that FFI is used to achieve this. I was always under the impression that FFI costs a little. I had at the time replaced the code with a hack with great results: ``` isNaN' :: Double -> Bool isNaN' d = d /= d ``` While this worked and provided good speedup in my case, this fails catastrophically if the program is compiled with -ffast-math. This is expected. I have since reverted it. Seeking an alternative solution I have thought about re-implementing the C code with a native Haskell version: after all it just checks a few bits. Apparently unsafeCoerce# and friends were a big no-no but I found https://phabricator.haskell.org/D3358 . I have implemented the code at the bottom of this post. Obviously it's missing endianness (compile-time switch). This seems to be faster for smaller `mkInput` list than Prelude.isNaN but slower slightly on the one below. The `/=` version is the fastest but very fragile. My question to you all is whether implementing a version of this function in Haskell makes sense and if not, why not? The stgDoubleToWord64 is implemented in CMM and I don't know anything about the costs of that. * Is there a cheaper alternative to FFI way? * If yes, does anyone know how to write it such that it compiles to same code but without the call overhead? I must have failed below as it's slower on some inputs. Basically if a faster way exists for isNaN, something I have to do a lot, I'd love to hear about it. I leave you with basic code I managed to come up with. 8.4.x only. ``` {-# LANGUAGE MagicHash #-} {-# OPTIONS_GHC -O2 -ddump-simpl -ddump-stg -ddump-to-file -ddump-asm #-} module Main (main) where import GHC.Float import GHC.Prim isNaN' :: Double -> Bool isNaN' d = d /= d isNaNBits :: Double -> Bool isNaNBits (D# d) = case (bits `and#` expMask) `eqWord#` expMask of 1# -> case bits `and#` mantissaMask of 0## -> False _ -> True _ -> False where bits :: Word# bits = stgDoubleToWord64 d expMask, mantissaMask :: Word# expMask = 0x7FF0000000000000## mantissaMask = 0x000FFFFFFFFFFFFF## main :: IO () main = sumFilter isNaN {-isNaN'-} {-isNaNBits-} (mkInput 100000000) `seq` pure () where nan :: Double nan = log (-1) mkInput :: Int -> [Double] mkInput n = take n $ cycle [1, nan] sumFilter :: (Double -> Bool) -> [Double] -> Double sumFilter p = Prelude.sum . Prelude.filter (not . p) ``` -- Mateusz K.

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RE: Type checking expressions
by Simon Peyton Jones 05 Mar '18

05 Mar '18

Always cc ghc-devs! Bottle-necking on me may well yield a slow response! Or even Haskell-café. What is the type of (\x -> [x,y])? Where y is in scope with type y::a. Presumably something like a -> [a]? Or is it forall a. a -> [a]? And would your answer change if you had just (\x -> [x,x])? Generalisation is tricky, and for terms with non-closed types it is hard to know what you need in your use-case. A type like ‘a’ might be a very fine answer! A lot depends on precisely what you are trying to do. Simon From: Peter Podlovics [mailto:peter.d.podlovics@gmail.com] Sent: 05 March 2018 14:54 To: Simon Peyton Jones <simonpj(a)microsoft.com> Subject: Re: Type checking expressions My main concern with that approach is that it might not give the correct type. For example the hsPatType function only gives unconstrained types, so it is incorrect for any numeric literal, since it gives "a" instead of "Num a => a". So the question is whether it is possible to retrieve the context of the type variables as well. Also this problem may arise in the case of expressions as well, that is why I scrapped that approach and tried to type check the AST with the TcM monad directly, but without any success. Could you give me any leads on how to solve this problem? Thanks in advance, Peter On Mon, Mar 5, 2018 at 9:44 AM, Simon Peyton Jones <simonpj(a)microsoft.com<mailto:simonpj@microsoft.com>> wrote: Peter My goal is to determine the type of every expression, pattern etc. in the syntax tree After type checking is complete, the syntax tree is liberally annotated with types. We do not yet have a function hsExprType :: HsExpr Id -> Type but we do have TcHsTyn.hsPatType :: Pat GhcTc -> Type and you or someone could readily make an equivalent for HsExpr. Most type errors are reported by adding an error constraint, but still returning an annotated tree. Some, I’m afraid, are still done in the old way, by throwing an exception – so you don’t get back an annotated tree in that case. But they are relatively rare. Others must have wanted something like this… Simon From: ghc-devs [mailto:ghc-devs-bounces@haskell.org<mailto:ghc-devs-bounces@haskell.org>] On Behalf Of Peter Podlovics Sent: 02 March 2018 12:05 To: ghc-devs(a)haskell.org<mailto:ghc-devs@haskell.org> Subject: Fwd: Type checking expressions Hello everyone, I would like to ask for some advice regarding the type checker part of GHC. My goal is to determine the type of every expression, pattern etc. in the syntax tree. Currently the compiler doesn't store this information, so I have to type check manually. One important aspect is that the program may be ill-typed, but I still want to extract as much information as possible. I tried using local type checking functions (eg.: tcInferSigma), but whenever I used it on an expression that had some "out-of-scope" names in it, it failed. > f xs = length xs The reason was that xs was not in the local environment. My question is: how could I provide the necessary local environment for these type checking functions? Also in the general case, is it possible to somehow annotate each expression with its type during the type checking? The motivation for this is that I want to implement a tool that automatically corrects ill-typed programs based heuristics. For that I need to know the types of certain AST nodes. Peter Podlovics

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Perf for T5837
by Simon Peyton Jones 05 Mar '18

05 Mar '18

Ben Why did you revert this? commit 2756117bd26c2cb70d3f51954a88b7d7bdf3d3f2 Author: Ben Gamari <ben(a)smart-cactus.org> Date: Thu Mar 1 14:06:04 2018 -0500 Revert "Better stats for T5837" This reverts commit d675a354e8db67d87d1f257c3d1d2bf2d58c2b3f. - (wordsize(64), 55813608, 7)]) + (wordsize(64), 51294232, 7)]) It's consistently 8% better for me, but I guess not for you. Does anyone else find this? Simon

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ghcpkg05
by Simon Peyton Jones 05 Mar '18

05 Mar '18

ghcpkg05 is failing on my Linux box. Any ideas? This is a clean build. Simon =====> ghcpkg05(normal) 1 of 1 [0, 0, 0] cd "./ghcpkg05.run" && $MAKE -s --no-print-directory ghcpkg05 Actual stderr output differs from expected: diff -uw "./ghcpkg05.run/ghcpkg05.stderr.normalised" "./ghcpkg05.run/ghcpkg05.run.stderr.normalised" --- ./ghcpkg05.run/ghcpkg05.stderr.normalised 2018-03-05 12:02:14.828489599 +0000 +++ ./ghcpkg05.run/ghcpkg05.run.stderr.normalised 2018-03-05 12:02:14.828489599 +0000 @@ -10,6 +10,13 @@ cannot find any of ["C/D.hi","C/D.p_hi","C/D.dyn_hi"] cannot find any of ["C/E.hi","C/E.p_hi","C/E.dyn_hi"] cannot find any of ["libtestpkg-2.0-XXX.a","libtestpkg-2.0-XXX.p_a","libtestpkg-2.0-XXX-ghc<VERSION>.so","libtestpkg-2.0-XXX-ghc<VERSION>.dylib","testpkg-2.0-XXX-ghc<VERSION>.dll"] on library path +Warning: include-dirs: /5playpen/simonpj/HEAD-1/compiler/stage2/build/utils doesn't exist or isn't a directory +Warning: include-dirs: /5playpen/simonpj/HEAD-1/compiler/stage2/build/../rts/dist/build doesn't exist or isn't a directory +Warning: include-dirs: /5playpen/simonpj/HEAD-1/compiler/stage2/build/stage2 doesn't exist or isn't a directory +Warning: include-dirs: /5playpen/simonpj/HEAD-1/libraries/haskeline/dist-install/build/includes doesn't exist or isn't a directory +Warning: include-dirs: /5playpen/simonpj/HEAD-1/libraries/text/dist-install/build/include doesn't exist or isn't a directory +Warning: include-dirs: /5playpen/simonpj/HEAD-1/libraries/containers/dist-install/build/include doesn't exist or isn't a directory +Warning: include-dirs: /5playpen/simonpj/HEAD-1/libraries/bytestring/dist-install/build/include doesn't exist or isn't a directory The following packages are broken, either because they have a problem listed above, or because they depend on a broken package. *** unexpected failure for ghcpkg05(normal) Unexpected results from: TEST="ghcpkg05" SUMMARY for test run started at Mon Mar 5 12:02:14 2018 GMT 0:00:01 spent to go through 1 total tests, which gave rise to 1 test cases, of which 0 were skipped 0 had missing libraries 0 expected passes 0 expected failures 0 caused framework failures 0 caused framework warnings 0 unexpected passes 1 unexpected failures 0 unexpected stat failures Unexpected failures: ghcpkg05.run ghcpkg05 [bad stderr] (normal)

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RE: tigetnum etc -- help!
by Simon Peyton Jones 05 Mar '18

05 Mar '18

| just to check the obvious, have you made sure to `git submodule | update` everything? have you properly cleaned your build-tree? Thanks. I did clean; and I usually obsessively do git submodule update, but I may have forgotten this time. I think for cabal and hsc2hs. Trying again now... Simon | -----Original Message----- | From: Herbert Valerio Riedel [mailto:hvriedel@gmail.com] | Sent: 05 March 2018 10:55 | To: Simon Peyton Jones <simonpj(a)microsoft.com> | Subject: Re: tigetnum etc -- help! | | Hi Simon, | | just to check the obvious, have you made sure to `git submodule | update` everything? have you properly cleaned your build-tree? | | -- hvr

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tigetnum etc -- help!
by Simon Peyton Jones 05 Mar '18

05 Mar '18

My stage-1 build (from clean) has started failing thus (on Linux). Any ideas? It's pretty disabling because I can't build GHC any more. Simon make ===--- building phase 0 make --no-print-directory -f ghc.mk phase=0 phase_0_builds make[1]: Nothing to be done for 'phase_0_builds'. ===--- building phase 1 make --no-print-directory -f ghc.mk phase=1 phase_1_builds "/usr/local/bin/ghc" -o utils/ghc-pkg/dist/build/tmp/ghc-pkg -hisuf hi -osuf o -hcsuf hc -static -O0 -H64m -Wall -package-db libraries/bootstrapping.conf -hide-all-packages -i -iutils/ghc-pkg/. -iutils/ghc-pkg/dist/build -Iutils/ghc-pkg/dist/build -iutils/ghc-pkg/dist/build/ghc-pkg/autogen -Iutils/ghc-pkg/dist/build/ghc-pkg/autogen -optP-DWITH_TERMINFO -optP-include -optPutils/ghc-pkg/dist/build/ghc-pkg/autogen/cabal_macros.h -package-id Cabal-2.1.0.0 -package-id base-4.10.0.0 -package-id binary-0.8.5.1 -package-id bytestring-0.10.8.2 -package-id containers-0.5.10.2 -package-id directory-1.3.0.2 -package-id filepath-1.4.1.2 -package-id ghc-boot-8.5 -package-id process-1.6.1.0 -package-id terminfo-0.4.1.1 -package-id unix-2.7.2.2 -XHaskell2010 -no-user-package-db -rtsopts -odir utils/ghc-pkg/dist/build -hidir utils/ghc-pkg/dist/build -stubdir utils/ghc-pkg/dist/build -static -O0 -H64m -Wall -package-db libraries/bootstrapping.conf -hide-all-packages -i -iutils/ghc-pkg/. -iutils/ghc-pkg/dist/build -Iutils/ghc-pkg/dist/build -iutils/ghc-pkg/dist/build/ghc-pkg/autogen -Iutils/ghc-pkg/dist/build/ghc-pkg/autogen -optP-DWITH_TERMINFO -optP-include -optPutils/ghc-pkg/dist/build/ghc-pkg/autogen/cabal_macros.h -package-id Cabal-2.1.0.0 -package-id base-4.10.0.0 -package-id binary-0.8.5.1 -package-id bytestring-0.10.8.2 -package-id containers-0.5.10.2 -package-id directory-1.3.0.2 -package-id filepath-1.4.1.2 -package-id ghc-boot-8.5 -package-id process-1.6.1.0 -package-id terminfo-0.4.1.1 -package-id unix-2.7.2.2 -XHaskell2010 -no-user-package-db -rtsopts utils/ghc-pkg/dist/build/Main.o utils/ghc-pkg/dist/build/Version.o /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):r6De_info: error: undefined reference to 'tigetnum' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):r6Df_info: error: undefined reference to 'tigetflag' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):r6Dg_info: error: undefined reference to 'tigetstr' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6Gn_info: error: undefined reference to 'set_curterm' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6Gb_info: error: undefined reference to 'set_curterm' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6I7_info: error: undefined reference to 'tparm' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6JP_info: error: undefined reference to 'set_curterm' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6JA_info: error: undefined reference to 'setupterm' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6Jn_info: error: undefined reference to 'set_curterm' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o):s6KR_info: error: undefined reference to 'tputs' /5playpen/simonpj/HEAD-1/libraries/terminfo/dist-boot/build/libHSterminfo-0.4.1.1.a(Base.o)(.data+0xdc8): error: undefined reference to 'del_curterm' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) utils/ghc-pkg/ghc.mk:70: recipe for target 'utils/ghc-pkg/dist/build/tmp/ghc-pkg' failed make[1]: *** [utils/ghc-pkg/dist/build/tmp/ghc-pkg] Error 1 Makefile:122: recipe for target 'all' failed make: *** [all] Error 2 simonpj@cam-05-unx:~/5builds/HEAD-1$

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Fwd: Type checking expressions
by Peter Podlovics 05 Mar '18

05 Mar '18

Hello everyone, I would like to ask for some advice regarding the type checker part of GHC. My goal is to determine the type of every expression, pattern etc. in the syntax tree. Currently the compiler doesn't store this information, so I have to type check manually. One important aspect is that the program may be ill-typed, but I still want to extract as much information as possible. I tried using local type checking functions (eg.: tcInferSigma), but whenever I used it on an expression that had some "out-of-scope" names in it, it failed. > f xs = length xs The reason was that xs was not in the local environment. My question is: how could I provide the necessary local environment for these type checking functions? Also in the general case, is it possible to somehow annotate each expression with its type during the type checking? The motivation for this is that I want to implement a tool that automatically corrects ill-typed programs based heuristics. For that I need to know the types of certain AST nodes. Peter Podlovics

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