November 2016 - ghc-tickets

[GHC] #11575: Program crashes only when compiled via LLVM
by GHC 23 Nov '16

23 Nov '16

#11575: Program crashes only when compiled via LLVM --------------------------------------+---------------------------------- Reporter: Guest00000 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: None | Version: 7.10.3 Keywords: llvm | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- `llvm-test.hs`: {{{#!hs import System.IO import Foreign.Storable import Foreign.Marshal.Alloc import Data.Word main = do hSetBuffering stdout NoBuffering test 1000 test 5000 where test n = do allocaBytes (n * 4) $ \p -> do sequence_ [ pokeByteOff p (i * 4) (0x12345678 :: Word32) | i <- [ 0 .. n - 1 ] ] putStrLn $ show n ++ " fine" }}} ---- Cygwin shell: {{{ user@pc ~ $ ghc llvm-test.hs && ./llvm-test.exe [1 of 1] Compiling Main ( llvm-test.hs, llvm-test.o ) Linking llvm-test.exe ... 1000 fine 5000 fine user@pc ~ $ touch llvm-test.hs user@pc ~ $ ghc llvm-test.hs -fllvm && ./llvm-test.exe [1 of 1] Compiling Main ( llvm-test.hs, llvm-test.o ) Linking llvm-test.exe ... 1000 fine Segmentation fault }}} ---- {{{ <erikd> `Guest00000: try adding -O2 to the compiler command line. <`Guest00000> erikd: it now segfaults even before printing "1000 fine" <`Guest00000> wait, one time it printed one character "1" before crashing }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11575> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12872: Pattern synonyms allow multiple type signatures but only use the first
by GHC 23 Nov '16

23 Nov '16

#12872: Pattern synonyms allow multiple type signatures but only use the first -------------------------------------+------------------------------------- Reporter: jophish | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | 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: -------------------------------------+------------------------------------- GHC seems to only be using the first signature for pattern synonyms GHC 8.0.2 allows this to compile: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Pattern where pattern Foo :: () pattern Foo :: Bool pattern Foo = () }}} but not this: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Pattern where pattern Foo :: Bool pattern Foo :: () pattern Foo = () }}} This compiles and ghci tells me the type of `Foo` is `()`: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Pattern where pattern Foo :: () pattern Foo :: Bool pattern Foo <- _ where Foo = undefined }}} This doesn't compile (as expected): {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Pattern where pattern Foo :: () pattern Foo :: Bool Bool pattern Foo = () }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12872> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12868: Add groupOn function to Data.List
by GHC 23 Nov '16

23 Nov '16

#12868: Add groupOn function to Data.List -------------------------------------+------------------------------------- Reporter: wizzup | Owner: Type: feature | Status: new request | Priority: low | Milestone: Component: | Version: 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: -------------------------------------+------------------------------------- sortOn was already add in #9004 but what about groupOn ? According to https://wiki.haskell.org/List_function_suggestions#groupOn_and_sortOn both functions are "so common". Although rejected in #2659, this might be a good time to reconsider. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12868> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12852: threadWaitReadSTM does not provide a way to unregister action.
by GHC 22 Nov '16

22 Nov '16

#12852: threadWaitReadSTM does not provide a way to unregister action. -------------------------------------+------------------------------------- Reporter: qnikst | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Core | Version: 8.0.1 Libraries | 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: -------------------------------------+------------------------------------- In non-threaded RTS or on windows RTS does not return meaningful unregister action: {{{#!hs threadWaitWriteSTM :: Fd -> IO (Sync.STM (), IO ()) threadWaitWriteSTM fd #ifndef mingw32_HOST_OS | threaded = Event.threadWaitWriteSTM fd #endif | otherwise = do m <- Sync.newTVarIO False _ <- Sync.forkIO $ do threadWaitWrite fd Sync.atomically $ Sync.writeTVar m True let waitAction = do b <- Sync.readTVar m if b then return () else retry let killAction = return () return (waitAction, killAction) }}} As a result in case if data will never arrive, helper thread will never be deallocated. This may lead to a memory leaks in some cases, see https://github.com/lpeterse/haskell-socket/issues/27 for details. Minimal testcase is: {{{#!hs import GHC.Conc import GHC.IO import GHC.IO.FD as FD import System.Posix.IO import System.Posix.Types main = do (rfd,wfd) <- createPipe (waitread, unregister) <- threadWaitReadSTM rfd unregister result0 <- atomically $ (fmap (const False) waitread) `orElse` return True print result0 fdWrite wfd "test" threadDelay 20000 result1 <- atomically $ (fmap (const False) waitread) `orElse` return True print result1 (waitread1, _) <- threadWaitReadSTM rfd threadDelay 20000 result2 <- atomically $ (fmap (const True) waitread1) `orElse` return False print result2 }}} Expected output will be True, True, True, but non-threaded runtime gives True, False, True -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12852> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8300: split-objs doesn't split on LLVM
by GHC 22 Nov '16

22 Nov '16

#8300: split-objs doesn't split on LLVM ------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- `-split-objs` is allowed with `-fllvm`, but it doesn't really do anything. E.g. in my perf-llvm build I have a `libHSbase-4.7.0.0.a` with `Applicative__1.o`, `Arrow__1.o` etc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8300> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7637: split-objs not supported for ARM
by GHC 22 Nov '16

22 Nov '16

#7637: split-objs not supported for ARM -------------------------------------+------------------------------------- Reporter: singpolyma | Owner: Type: feature request | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: duplicate | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Compile-time | Test Case: performance bug | Blocked By: | Blocking: Related Tickets: #8300 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => duplicate * related: => #8300 Comment: Given that ARM is essentially solely supported by LLVM at this point, I think it's fair to call this a duplicate of #8300. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7637#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12857: associate pattern synonyms with a type synonym
by GHC 22 Nov '16

22 Nov '16

#12857: associate pattern synonyms with a type synonym -------------------------------------+------------------------------------- Reporter: int-e | 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: -------------------------------------+------------------------------------- I believe it would be useful to bundle pattern synonyms with type synonyms, which is currently not supported. For example, the `State` type synonym from monad transformers could profit from such bundling, as it would allow users to use `State (..)` in an import list: {{{#!hs {-# LANGUAGE ViewPatterns #-} {-# LANGUAGE PatternSynonyms #-} {-# LANGUAGE ScopedTypeVariables #-} module State ( State (State, runState) ) where import Control.Monad newtype Identity a = Identity { runIdentity :: a } newtype StateT s m a = StateT { runStateT :: s -> m (s, a) } type State s a = StateT s Identity a pattern State { runState } <- ((runIdentity .) . runStateT -> runState) where State runState = StateT (Identity . runState) }}} (I would have a use for this in `haskell-src-exts-simple` package, which, similar to the above example, uses type synonyms to instantiate a type parameter a few datatypes to a fixed type.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12857> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12859: ghc/packages/Cabal is not a valid repository name
by GHC 22 Nov '16

22 Nov '16

#12859: ghc/packages/Cabal is not a valid repository name --------------------------------------+--------------------------------- Reporter: philderbeast | Owner: hvr Type: bug | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: 8.0.1 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- On 2016-11-05 I was able to follow the newcomer build instructions [https://ghc.haskell.org/trac/ghc/wiki/Newcomers] for and built ghc on Windows with MSYS2 x64. I am now repeating those steps and see that doing a clean recursive clone of ghc fails for the Cabal submodule and many others ... {{{ $ git clone --recursive git://github.com/ghc/ghc Cloning into '/d/Dev/Src/ghc/libraries/Cabal'... fatal: remote error: ghc/packages/Cabal is not a valid repository name }}} I tried the exact same recursive clone on OSX and it completed without error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12859> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2893: Implement "Quantified contexts" proposal
by GHC 21 Nov '16

21 Nov '16

#2893: Implement "Quantified contexts" proposal -------------------------------------+------------------------------------- Reporter: porges | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.10.1 Resolution: | Keywords: proposal Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): I want to mention an example from 1997: [https://www.microsoft.com/en- us/research/wp-content/uploads/1997/01/multi.pdf Type classes: an exploration of the design space] > What we really want is universal quantification: > > {{{#!hs > class (forall s. Monad (m s)) > => StateMonad m where > get :: m s s > set :: s -> m s () > }}} which can be defined as {{{#!hs class ForallF Monad m => StateMonad m where get :: m s s set :: s -> m s () }}} How does it compare to `MonadState`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2893#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2893: Implement "Quantified contexts" proposal
by GHC 21 Nov '16

21 Nov '16

#2893: Implement "Quantified contexts" proposal -------------------------------------+------------------------------------- Reporter: porges | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.10.1 Resolution: | Keywords: proposal Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I have no specific, concrete plans to work on implication constraints, but I have a few enterprising students who may be looking for a project next semester. Implementation implication constraints is on the shortlist of projects to consider. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2893#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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