February 2017 - ghc-tickets

[GHC] #13265: perf-llvm build fails with "Too many sections: 123418 (>= 65280)"
by GHC 10 Mar '17

10 Mar '17

#13265: perf-llvm build fails with "Too many sections: 123418 (>= 65280)" -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Building current git head in the "BuildFlavour = perf-llvm", the build fails with: {{{ "inplace/bin/ghc-stage1" -o iserv/stage2_p/build/tmp/ghc-iserv-prof -hisuf \ p_hi -osuf p_o -hcsuf p_hc -static -prof -eventlog -O -H64m -fllvm -Wall \ -Werror -hide-all-packages -i -iiserv/src -iiserv/stage2_p/build \ -Iiserv/stage2_p/build -iiserv/stage2_p/build/iserv/autogen \ -Iiserv/stage2_p/build/iserv/autogen \ -optP-include -optPiserv/stage2_p/build/iserv/autogen/cabal_macros.h \ -package-id array-0.5.1.2 -package-id base-4.10.0.0 \ -package-id binary-0.8.4.1 -package-id bytestring-0.10.8.2 \ -package-id containers-0.5.7.1 -package-id deepseq-1.4.3.0 \ -package-id ghci-8.1 -package-id unix-2.7.2.1 -XHaskell2010 \ -threaded -optl-Wl,--export-dynamic -no-hs-main -no-user-package-db \ -rtsopts -Wnoncanonical-monad-instances -odir iserv/stage2_p/build \ -hidir iserv/stage2_p/build -stubdir iserv/stage2_p/build \ -static -prof -eventlog -O -H64m -fllvm -Wall -Werror -hide-all- packages \ -i -iiserv/src -iiserv/stage2_p/build \ -Iiserv/stage2_p/build -iiserv/stage2_p/build/iserv/autogen \ -Iiserv/stage2_p/build/iserv/autogen -optP-include \ -optPiserv/stage2_p/build/iserv/autogen/cabal_macros.h -package-id \ array-0.5.1.2 -package-id base-4.10.0.0 -package-id binary-0.8.4.1 \ -package-id bytestring-0.10.8.2 -package-id containers-0.5.7.1 \ -package-id deepseq-1.4.3.0 -package-id ghci-8.1 -package-id unix-2.7.2.1 \ -XHaskell2010 -threaded -optl-Wl,--export-dynamic -no-hs-main \ -no-user-package-db -rtsopts -Wnoncanonical-monad-instances \ iserv/stage2_p/build/Main.p_o iserv/stage2_p/build/GHCi/Utils.p_o \ iserv/stage2_p/build/cbits/iservmain.p_o Warning: -rtsopts and -with-rtsopts have no effect with -no-hs-main. Call hs_init_ghc() from your main() function to set these options. /usr/bin/ld: iserv/stage2_p/build/tmp/ghc-iserv-prof: Too many sections: 123418 (>= 65280) /usr/bin/ld: final link failed: Nonrepresentable section on output collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13265> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12910: Mirror mingw signature files
by GHC 10 Mar '17

10 Mar '17

#12910: Mirror mingw signature files ----------------------------------------+--------------------------------- Reporter: bgamari | Owner: bgamari Type: task | Status: new Priority: high | Milestone: 8.2.1 Component: None | Version: 8.0.1 Keywords: | Operating System: POSIX Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- We should really provide signatures alongside the mingw binaries and sources on `ghc.haskell.org`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12910> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13068: GHC should not allow modules to define instances of abstract type classes
by GHC 10 Mar '17

10 Mar '17

#13068: GHC should not allow modules to define instances of abstract type classes -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- hs-boot files permit a type class to be given "abstractly", in which case any implementation of the type class is permissible. But it does not reject instances defined for such a class. {{{ -- A.hs-boot module A where class C a -- B.hs module B where import {-# SOURCE #-} A instance C Int where -- A.hs module A where import B class C a where f :: a -- Main.hs import A main = print (f :: Int) }}} I get this when I build with `--make`: {{{ ezyang@sabre:~$ ghc-head --make C.hs -fforce-recomp [1 of 4] Compiling A[boot] ( A.hs-boot, A.o-boot ) [2 of 4] Compiling B ( B.hs, B.o ) [3 of 4] Compiling A ( A.hs, A.o ) [4 of 4] Compiling Main ( C.hs, C.o ) Linking C ... ./B.o:(.data+0x0): undefined reference to `A_CZCC_con_info' collect2: error: ld returned 1 exit status }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13068> 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] #13348: Consider making throw and throwIO strict
by GHC 10 Mar '17

10 Mar '17

#13348: Consider making throw and throwIO strict -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: 8.4.1 Component: Core | Version: 8.1 Libraries | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It's possible for code to throw an exception that itself throws an imprecise exception. Such an exception is tricky to catch. For example: {{{#!hs import Control.Exception strange = throwIO (undefined :: SomeException) `catch` \ex -> case () of _ | Just _ <- (fromException ex :: Maybe IOError) -> print "IOError" | otherwise -> print "Something else" }}} You might think that this would catch the exception and print "Something else", but in fact it does not. If others think this is as surprising as I do, perhaps we should make `throwIO` and `throw` strict, so an exception will never itself be bottom. Using {{{#!hs throwIO' !e = throwIO e }}} in the code above instead of `throwIO` allows the exception to be caught. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13348> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13177: Give Data.Functor.* its lifted unit and void
by GHC 08 Mar '17

08 Mar '17

#13177: Give Data.Functor.* its lifted unit and void -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.0.1 libraries/base | 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: -------------------------------------+------------------------------------- `GHC.Generics` has {{{#!hs data U1 a = U1 data V1 a }}} They are simple but why are they not present in the `Data.Functor` hierarchy along with functions like (from [https://hackage.haskell.org/package/one-liner-0.7/docs/src/Generics- OneLiner-Internal.html one-liner]) {{{#!hs absurd :: V1 a -> b absurd = \case }}} Packages like [https://hackage.haskell.org/package/linear linear] provide basically the same lifted functors {{{#!hs data V0 a = V0 newtype V1 a = V1 a }}} if they or those from `GHC.Generics` should be preferred it could be added to the documentation. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13177> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13341: Lift constraint products
by GHC 08 Mar '17

08 Mar '17

#13341: Lift constraint products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- I want to get a discussion going, could we lift constraint products automatically. Although not partially applicable, we can consider `(,)` as having kind {{{#!hs (,) :: Constraint -> Constraint -> Constraint }}} I propose also giving it kinds {{{#!hs (,) :: (k -> Constraint) -> (k -> Constraint) -> (k -> Constraint) (,) :: (k -> k' -> Constraint) -> (k -> k' -> Constraint) -> (k -> k' -> Constraint) -- etc. }}} == Translation {{{#!hs (Eq, Num, Show) (Monad, Foldable) (Category, Profunctor) }}} gets turned into something like {{{#!hs class (c a, d a) => (c :&: d) a instance (c a, d a) => (c :&: d) a infixl 7 :&: Eq:&:Num:&:Show Monad:&:Foldable Category:&:Profunctor }}} == Uses Very often I need to be able to combine constraints. A small modification of [https://hackage.haskell.org/package/free- functors-0.7.2/docs/Data-Constraint-Class1.html SuperClasses] {{{#!hs type c :~ d = forall xx. c x :- d xx class HasSuperClasses (c :: k -> Constraint) where type SuperClasses c :: k -> Constraint type SuperClasses c = c superClasses :: c :~ SuperClasses c containsSelf :: SuperClasses c :~ c instance HasSuperClasses Functor where superClasses :: Functor :~ Functor superClasses = Sub Dict containsSelf :: Functor :~ Functor containsSelf = Sub Dict instance HasSuperClasses Foldable where superClasses :: Foldable :~ Foldable superClasses = Sub Dict containsSelf :: Foldable :~ Foldable containsSelf = Sub Dict }}} I want to be able to write {{{#!hs instance HasSuperClasses Traversable where type Traversable = (Traversable, Functor, Foldable) superClasses :: Traversable :~ (Traversable, Functor, Foldable) superClasses = Sub Dict containsSelf :: (Traversable, Functor, Foldable) :~ Traversable containsSelf = Sub Dict }}} If this doesn't pose any difficulties I'll open a GHC proposal. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13341> 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] #13212: Support abs as a primitive operation on floating point numbers.
by GHC 07 Mar '17

07 Mar '17

#13212: Support abs as a primitive operation on floating point numbers. -------------------------------------+------------------------------------- Reporter: dominic | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Haskell differs from C and FORTRAN on the manner in which it computes the absolute value of floating point numbers. Both FORTRAN and C support a `fabs` primitive function that is compiled directly to the underlying `fabs` machine instruction on either AMD64 or Intel x86 processors (with a small amount of stack manipulation). Haskell, however, does not support `abs` as a primitive operation on floating point numbers. Instead, Haskell desugars `abs` to the following: abs x | x == 0 = 0 -- handles (-0.0) | x > 0 = x | otherwise = negateFloat x Rather than calling the utilizing the `fabs` mnemonic or twiddling the sign bit, both of which can be executed in a single instruction, this implementation results in ~15 machine instructions and requires ~4-5 times the number of clock cycles to execute. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13212> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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