November 2016 - ghc-tickets

[GHC] #10143: Separate PprFlags (used by Outputable) from DynFlags
by GHC 18 Mar '17

18 Mar '17

#10143: Separate PprFlags (used by Outputable) from DynFlags -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- At the moment, SDoc computations have full access to the entirety of DynFlags, despite only a minusculely small amount of the data structure being relevant to them. This proposal is to split out a `PprFlags` structure which will be contained in a `DynFlags`, and contain dynamic flags JUST for pretty-printing. There will be a function `pprFlags :: DynFlags -> PprFlags`. This also helps eliminate the circular dependency between `DynFlags` and `Outputable`. This structure is not complete, but it should give a sense for some of the things that need to be put in here: {{{ data PprFlags = PprFlags { pprUserLength :: Int, pprCols :: Int, useUnicode :: Bool, useUnicodeSyntax :: Bool, targetPlatform :: Platform, suppressUniques :: Bool, errorSpans :: Bool, suppressModulePrefixes :: Bool } }}} I have a patch in-progress which factors this out, but I want to get some sign-offs that this is a good refactoring before I finish it. Thanks! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10143> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12718: Segmentation fault, runtime representation polymorphism
by GHC 15 Mar '17

15 Mar '17

#12718: Segmentation fault, runtime representation polymorphism -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHCi crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# Language RebindableSyntax, NoImplicitPrelude, MagicHash, RankNTypes, PolyKinds, ViewPatterns, TypeInType, FlexibleInstances #-} import Prelude hiding (Eq (..), Num(..)) import qualified Prelude as P import GHC.Prim import GHC.Types class Num (a :: TYPE rep) where (+) :: a -> a -> a fromInteger :: Integer -> a instance P.Num a => Num a where (+) = (P.+) fromInteger = P.fromInteger instance Num Int# where (+) = (+#); fromInteger (fromInteger -> I# n) = n u :: Bool u = isTrue# v_ where v_ :: forall rep (a :: TYPE rep). Num a => a v_ = fromInteger 10 }}} segfaults {{{#!hs $ ./bin/repo/ghc4/inplace/bin/ghc-stage2 --interactive -ignore-dot-ghci /tmp/tMjN.hs GHCi, version 8.1.20160930: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/tMjN.hs, interpreted ) Ok, modules loaded: Main. *Main> u True *Main> Segmentation fault (core dumped) $ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12718> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11431: GHC instantiates levity-polymorphic type variables with foralls
by GHC 15 Mar '17

15 Mar '17

#11431: GHC instantiates levity-polymorphic type variables with foralls -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider the following use of `error`. {{{ ghci> :t error error :: forall (v :: GHC.Types.Levity) (a :: TYPE v). (?callStack::GHC.Stack.Types.CallStack) => [Char] -> a ghci> :t error "bad" :: (forall a. a -> a) -> a error "bad" :: (forall a. a -> a) -> a :: (?callStack::GHC.Stack.Types.CallStack) => (forall a1. a1 -> a1) -> a }}} GHC is instantiating the type variable `a` in the output with `(forall a. a -> a) -> a`, which requires impredicative polymorphism. So this example should actually be rejected by the type checker. Note that GHC also does this with open-kinded type variables, so the behavior with `error` and `undefined` has been around for a while. There are tests that depend on it, and a Note that describes the decision to accept these programs. Still, Simon PJ says perhaps we should really just reject these programs. So here's a ticket to discuss the matter. For more information, see the discussion starting at https://phabricator.haskell.org/D1739#51408. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11431> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11450: Associated types at wrong type in instance
by GHC 14 Mar '17

14 Mar '17

#11450: Associated types at wrong type in instance -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider {{{ class C x where type T x instance C (Either a b) where type T (Either b a) = b -> a }}} This is bogus, because the equation for `T` has the parameters to `Either` reversed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11450> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11555: catch under unsafePerformIO breaks on -O1
by GHC 10 Mar '17

10 Mar '17

#11555: catch under unsafePerformIO breaks on -O1 -------------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Discovered on xmonad-0.12 test failure. Happens on today's -HEAD and ghc-8.0.1-rc1,-rc2 Short example is (needs only base): {{{#!hs -- cat F.hs module F where import qualified Control.Exception as C import System.IO.Unsafe import qualified Data.List as L abort :: String -> a abort x = error $ "xmonad: StackSet: " ++ x prop_abort x = unsafePerformIO $ C.catch (abort "fail") (\(C.SomeException e) -> return $ "xmonad: StackSet: fail" `L.isPrefixOf` show e ) where _ = x :: Int }}} Session 1 [ok]: {{{ $ ghci F.hs GHCi, version 8.0.0.20160204: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling F ( F.hs, interpreted ) Ok, modules loaded: F. *F> prop_abort 1 True }}} Session 2 [fails]: {{{ $ ghci -O1 -fobject-code F.hs GHCi, version 8.0.0.20160204: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling F ( F.hs, F.o ) Ok, modules loaded: F. Prelude F> prop_abort 1 *** Exception: xmonad: StackSet: fail CallStack (from HasCallStack): error, called at F.hs:9:11 in main:F }}} I would expect exception to be caught on both cases. Is it unreasonable expectation in light of unsafePerformIO? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11555> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8255: GC Less Operation
by GHC 07 Mar '17

07 Mar '17

#8255: GC Less Operation ------------------------------+-------------------------------------------- Reporter: sirinath | Owner: Type: feature | Status: new request | Milestone: Priority: highest | Version: 7.6.3 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime performance bug Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: Unknown | Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- Hi, Is it possible to eliminated GC through Automatic Reference Counting (ARC) like in Objective C / Clang. S -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8255> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10712: Regression: make TEST=exceptionsrun001 WAY=optasm is failing
by GHC 07 Mar '17

07 Mar '17

#10712: Regression: make TEST=exceptionsrun001 WAY=optasm is failing -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: high | Milestone: 7.12.1 Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: base/tests/exceptionsrun001 | Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- The following program, extracted from the test exceptionsrun001, should exit with exitcode 100. Instead, when compiled with `-O1`, it never gets past the ioTest and somehow manages to exit with exitcode 0. {{{ {-# LANGUAGE ScopedTypeVariables #-} module Main where import Control.Exception import System.IO.Error import System.Exit main = do ioTest exitWith (ExitFailure 100) ioTest :: IO () ioTest = (catch (ioError (userError "wibble")) (\(e::IOException) -> return ()) }}} I think this will require a git bisect: * last known good commit: 34bb4605d4ec5b131df57ca4c91d6840b7539194 * first known bad commit: f83aab95f59ae9b29f22fc7924e050512229cb9c. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10712> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11006: Warning: Glomming in Main
by GHC 07 Mar '17

07 Mar '17

#11006: Warning: Glomming in Main -------------------------------------+------------------------------------- Reporter: ezyang | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The Travis build bot is reporting a test failure with debugging on, relating to glomming: {{{ Actual stderr output differs from expected: --- /dev/null 2015-01-28 16:31:58.000000000 +0000 +++ ./lib/integer/integerConstantFolding.run.stderr.normalised 2015-10-22 20:31:03.287376925 +0000 @@ -0,0 +1,2 @@ +WARNING: file compiler/simplCore/OccurAnal.hs, line 66 + Glomming in Main: [s3k0 :->, s3kc :->, s3kq :->, s3kr :->] \ No newline at end of file *** unexpected failure for integerConstantFolding(normal) }}} Full log https://s3.amazonaws.com/archive.travis- ci.org/jobs/86899099/log.txt -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11006> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11076: Demand information of foreign calls is wrong
by GHC 06 Mar '17

06 Mar '17

#11076: Demand information of foreign calls is wrong -------------------------------------+------------------------------------- Reporter: luite | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Foreign calls of all types (including prim calls) use `mkFCallId` to create a fresh `Id` for each one. This Id claims to be strict in all arguments, which is not correct for foreign calls that allow lifted types to be passed. This also causes some trouble for GHCJS. I hope to get a fix in 7.10.3. Can we leave the strictness sig out entirely perhaps? Most arguments would be trivially strict since they're unboxed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11076> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10830: maximumBy has a space leak
by GHC 04 Mar '17

04 Mar '17

#10830: maximumBy has a space leak -------------------------------------+------------------------------------- Reporter: | Owner: NeilMitchell | Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.10.2 libraries/base | Keywords: | Operating System: Windows Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Given the program: {{{#!hs import Data.List main = print $ maximumBy compare [1..10000] }}} Compiling with {{{-O2}}}, on GHC 7.8.3 this runs in constant stack space (works fine with {{{+RTS -K1K}}}). With GHC 7.10.2 I get: {{{ $ ghc --make Test.hs -O2 -rtsopts [1 of 1] Compiling Main ( Test.hs, Test.o ) Linking Test.exe ... $ Test +RTS -K100K Stack space overflow: current size 33680 bytes. Use `+RTS -Ksize -RTS' to increase it. }}} Not sure why it's failing at 33K instead of 100K, but it's certainly taking more than 1K as GHC 7.8.3 did. See #3416 for previous discussion of this issue. My guess is that in older versions of GHC the strictness analysis managed to kick in and optimise things. With the burnt bridges that no longer works. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10830> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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