June 2018 - ghc-tickets

[GHC] #11394: Base should use native Win32 IO on Windows
by GHC 20 Aug '18

20 Aug '18

#11394: Base should use native Win32 IO on Windows -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Core | Version: 7.10.3 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: -------------------------------------+------------------------------------- There are a variety of issues caused by the impedance mismatch between GHC's use of Posix I/O interfaces on Windows (particularly with respect to console I/O), * #10542: Incorrect Unicode input on Windows Console * #7593: Unable to print exceptions of unicode identifiers * #4471: Incorrect Unicode output on Windows Console * #2189: hSetBuffering stdin NoBuffering doesn't work on Windows As pointed on in ticket:2189#comment:12 the ultimate solution to this would be to move all of GHC's IO to use the respective Win32 interfaces. = Also relevant = * #7353: Windows lacks support in the I/O manager * #806: hGetBufNonBlocking doesn't work on Windows * #3081: Double output after Ctrl+C on Windows -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11394> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14530: hWaitForInput causes the program to abort on Windows
by GHC 20 Aug '18

20 Aug '18

#14530: hWaitForInput causes the program to abort on Windows --------------------------------------+---------------------------------- Reporter: dnadales | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- When running the following program on Windows (10): {{{#!hs readWithinNSecs :: IO () readWithinNSecs = withSocketsDo $ do h <- connectTo "localhost" (PortNumber 9090) hSetBuffering h NoBuffering readerTid <- forkIO $ politeReader h threadDelay (2 * 10^6) killThread readerTid where politeReader h = do info <- hShow h putStrLn info line <- ifM (hWaitForInput h (10^6)) (hGetLine h) (return "Nothing!") putStrLn $ "Got " ++ line }}} The program aborts with the following error: {{{#!text {loc=<socket: 380>,type=duplex (read-write),buffering=none} fdReady: fd is too big This application has requested the Runtime to terminate it in an unusual way. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14530> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12873: hWaitForInput with socket as handle excepts on windows
by GHC 20 Aug '18

20 Aug '18

#12873: hWaitForInput with socket as handle excepts on windows --------------------------------------+---------------------------------- Reporter: bwurk | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- If I create a socket wrapped in a Handle (either by directly creating a handle with connectTo, or by creating a socket and wrapping it), hWaitForInput and hReady always give an exception with that handle. It excepts directly when calling, it does not wait until the given timeout of hWaitForInput has expired. The following code exposes the bug (requiring that a server-socket is listening on port 7892): {{{#!hs module SockDebug where import System.IO import Network main = do sock <- connectTo "localhost" (Service $ show 7892) hWaitForInput sock 5000 }}} Excepts with "hWaitForInput: invalid argument (Invalid argument)" Happens both on windows 10 and windows 7. This is the same error as in ticket 1198 so I'd guess that the bug is in cbits/inputReady.c as well, but I'm not an expert. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12873> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10542: Incorrect Unicode input on Windows Console
by GHC 20 Aug '18

20 Aug '18

#10542: Incorrect Unicode input on Windows Console -------------------------------------+------------------------------------- Reporter: ptroev | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.8.3 Keywords: windows | Operating System: Windows stdin utf-8 cmd chcp 65001 | Type of failure: Incorrect result getLine | at runtime Architecture: | Blocked By: Unknown/Multiple | Related Tickets: 4471 Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- To reproduce: - start a windows console - change the console's font to a ttf unicode font, like "Lucida Console". - type "chcp 65001" to set it to the UTF-8 code page. - start ghci (same error appears when running compiled executable) - > import System.IO (or GHC.IO.Handle) - > enc <- mkTextEncoding "UTF8" - > hSetEncoding stdin enc - > getLine - > Фывфыв (or any international unicode sequence) *** Exception: <stdin>: hGetLine: end of file -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10542> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9441: Merge identical top-level expressions following simplification when it is safe to do so
by GHC 18 Aug '18

18 Aug '18

#9441: Merge identical top-level expressions following simplification when it is safe to do so -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- If I redefine {{{#!hs {-# INLINE reverse #-} reverse :: [a] -> [a] reverse xs = build $ \c n -> foldl (\a x -> x `c` a) n xs }}} and then write a couple test cases: {{{#!hs appRev xs ys = xs ++ reverse ys revAppRev xs ys = reverse xs ++ reverse ys }}} I end up getting some rather annoying code duplication (lots of stuff omitted from the following): {{{#!hs Rec { poly_go_r2v3 poly_go_r2v3 = \ @ a_a2nF ds_a2zc eta_Xl -> case ds_a2zc of _ { [] -> eta_Xl; : y_a2zh ys_a2zi -> poly_go_r2v3 ys_a2zi (: y_a2zh eta_Xl) } end Rec } reverse reverse = \ @ a_a2nF eta_B1 -> poly_go_r2v3 eta_B1 ([]) Rec { revAppRev2 revAppRev2 = \ @ a_a2y7 ds_a2zc eta_B1 -> case ds_a2zc of _ { [] -> eta_B1; : y_a2zh ys_a2zi -> revAppRev2 ys_a2zi (: y_a2zh eta_B1) } end Rec } Rec { revAppRev1 revAppRev1 = \ @ a_a2y7 ds_a2zc eta_B1 -> case ds_a2zc of _ { [] -> eta_B1; : y_a2zh ys_a2zi -> revAppRev1 ys_a2zi (: y_a2zh eta_B1) } end Rec } Rec { appRev1 appRev1 = \ @ a_a2xE ds_a2zc eta_B1 -> case ds_a2zc of _ { [] -> eta_B1; : y_a2zh ys_a2zi -> appRev1 ys_a2zi (: y_a2zh eta_B1) } end Rec } }}} The `reverse` function was inlined three times. In each case, there was no fusion, so `build` was inlined and the resulting copy of the `reverse` worker lifted to the top level. It would seem to me that once simplification is complete, it should be safe to merge all these copies into one. They are all `Rec {\ ... -> ...}` forms, so I don't think this has any potential to introduce undesirable sharing. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9441> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15050: ScopedTypeVariables could allow more programs
by GHC 18 Aug '18

18 Aug '18

#15050: ScopedTypeVariables could allow more programs -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.1 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 {{{ data P a = P data T1 a where MkT1 :: forall a. P a -> T1 a MkT2 :: forall a. P a -> T1 (a,a) MkT3 :: forall a b. b ~ Int => P a -> P b -> T1 a MkT4 :: forall a b. P a -> P b -> T1 a MkT5 :: forall a b c. b ~ c => P a -> P b -> P c -> T1 a }}} I can write this function {{{ foo :: T1 (Int, Int) -> () foo (MkT1 (P::P (Int,Int))) = () foo (MkT2 (P::P x)) = (() :: x ~ Int => ()) foo (MkT3 P (P::P Int)) = () foo (MkT4 P (P::P b)) = () foo (MkT5 P (P::P b) (P::P b)) = () }}} but this these two equations fail {{{ foo (MkT1 (P::P (Int,x))) = (() :: x ~ Int => ()) foo (MkT1 (P::P x)) = (() :: x ~ (Int,Int) => ()) }}} I am especially surprised by the second one, given that the very similar equation with `MkT2` works. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15050> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8944: Warn instead of stopping on misplaced Haddock comments
by GHC 16 Aug '18

16 Aug '18

#8944: Warn instead of stopping on misplaced Haddock comments -------------------------------------+------------------------------------- Reporter: Fuuzetsu | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Parser) | Version: 7.9 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- Given a simple module like {{{ module H where data F = F () -- ^ Comment for first type argument () }}} and trying to run Haddock on it, we'll get back {{{ /tmp/H.hs:4:12: parse error on input ‘(’ }}} The error message is rather sub-par in this scenario. It'd be great if we could instead print a warning saying that a Haddock comment is unexpected in that position and then continue on parsing. Best case scenario would be a more informative message such as “Documenting each constructor argument is not supported” but that might be quite a bit harder. Filing on GHC Trac as it's the parser that needs changing I believe. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8944> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15149: Identical distinct type family fields miscompiled
by GHC 16 Aug '18

16 Aug '18

#15149: Identical distinct type family fields miscompiled -------------------------------------+------------------------------------- Reporter: NeilMitchell | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Given the code: {{{#!hs -- An.hs {-# LANGUAGE TypeFamilies #-} module An where data family An c :: * -- AnInt.hs {-# LANGUAGE TypeFamilies #-} module AnInt where import An data instance An Int = AnInt {an :: Int} deriving Show -- AnDouble.hs {-# LANGUAGE TypeFamilies #-} module AnDouble where import An data instance An Double = AnDouble {an :: Double} deriving Show -- Main.hs {-# LANGUAGE DisambiguateRecordFields #-} module Main where import AnInt import AnDouble main = print (AnDouble{an=1}, AnInt{an=1}) }}} I would expect this code to work. In reality it fails at runtime with GHC 8.2.2: {{{ Main.hs:4:15-28: warning: [-Wmissing-fields] * Fields of `AnDouble' not initialised: an * In the expression: AnDouble {an = 1} In the first argument of `print', namely `(AnDouble {an = 1}, AnInt {an = 1})' In the expression: print (AnDouble {an = 1}, AnInt {an = 1}) | 6 | main = print (AnDouble{an=1}, AnInt{an=1}) | ^^^^^^^^^^^^^^ *** Exception: Main.hs:4:15-28: Missing field in record construction an }}} And fails at compile time in GHC 8.4.2: {{{ Main.hs:4:31-41: error: * Constructor `AnInt' does not have field `an' * In the expression: AnInt {an = 1} In the first argument of `print', namely `(AnDouble {an = 1}, AnInt {an = 1})' In the expression: print (AnDouble {an = 1}, AnInt {an = 1}) | 6 | main = print (AnDouble{an=1}, AnInt{an=1}) | ^^^^^^^^^^^ }}} This code was extracted from a real example, where this bug is pretty fatal, as I haven't been able to find any workarounds (without just avoiding clashing record fields). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15149> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12980: Unlifted class method rejected
by GHC 13 Aug '18

13 Aug '18

#12980: Unlifted class method rejected -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire 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: -------------------------------------+------------------------------------- If I say {{{#!hs class C a where meth :: Array# a }}} I get {{{ • Expecting a lifted type, but ‘Array# a’ is unlifted • In the type signature: meth :: Array# a In the class declaration for ‘C’ }}} This definition looks OK to me. I don't see why we can't have an unlifted member of a class. (As @oerjan points out in comment:25:ticket:12708, we can't have a ''levity-polymorphic'' class member, but this is solidly levity- monomorphic.) I'm happy to lift this restriction in ongoing work in this area, but I wanted to double-check before doing so. For the record, the same error occurs even when the class has more than one member, so it's not the no-unlifted-newtypes restriction. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12980> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14373: Introduce PTR-tagging for big constructor families
by GHC 11 Aug '18

11 Aug '18

#14373: Introduce PTR-tagging for big constructor families -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- Currently only ''small'' constructor families come into the benefit of pointer tagging. In big fams, 1 is the tag that says "I am evaluated". I suggest to do best-effort pointer tagging on big families too by this scheme: Ptr-tag 1..6 for the first 6 constructors, 7 would signify "look into the info table and branch on that tag". In the info table the tags will then be 6..(familySize - 1). I have an implementation which I'll submit to fabricator soon. TODOs: update wiki pages. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14373> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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