March 2015 - ghc-tickets

[GHC] #9975: RecordWildCards and PatternSynonyms cause impossible bug
by GHC 24 Dec '15

24 Dec '15

#9975: RecordWildCards and PatternSynonyms cause impossible bug -------------------------------------+------------------------------------- Reporter: gamegoblin | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: MacOS X RecordWildCards PatternSynonyms | Type of failure: Compile-time Architecture: x86_64 | crash (amd64) | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When using RecordWildCards with PatternSynonyms, I have found a way to cause this bug: $ /usr/local/bin/ghc-7.10.0.20141222 test.hs [1 of 1] Compiling Main ( test.hs, test.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.0.20141222 for x86_64-apple-darwin): find_tycon Test [Test defined at test.hs:6:9, Test parent:Test defined at test.hs:4:13] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Here is the full code that causes it: {{{#!hs {-# LANGUAGE RecordWildCards #-} {-# LANGUAGE PatternSynonyms #-} data Test = Test { x :: Int } pattern Test wat = Test { x = wat } }}} If you remove RecordWildCards, the bug does not happen. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9975> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9739: GHC 7.8 chokes on recursive classes
by GHC 23 Dec '15

23 Dec '15

#9739: GHC 7.8 chokes on recursive classes -------------------------------------+------------------------------------- Reporter: bitonic | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.3 checker) | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Difficulty: Unknown | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Type checking this makes GHC 7.8.3 loop: {{{#!hs {-# LANGUAGE MultiParamTypeClasses #-} module Foo where class Class3 a => Class1 a where class Class2 t a where class2 :: (Class3 t) => a -> m class (Class1 t, Class2 t t) => Class3 t where }}} Does not happen in 7.6.3. I think it's something to do with the `Class3` constraint appearing in `class2`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9739> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10039: Make Const (Control.Applicative) kind polymorphic in its second argument
by GHC 21 Dec '15

21 Dec '15

#10039: Make Const (Control.Applicative) kind polymorphic in its second argument -------------------------------------+------------------------------------- Reporter: | Owner: Iceland_jack | Status: new Type: feature | Milestone: request | Version: 7.8.4 Priority: normal | Operating System: Unknown/Multiple Component: | Type of failure: None/Unknown libraries/base | Blocked By: Keywords: | Related Tickets: Architecture: | Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Is there any reason why `Const` isn't kind polymorphic? {{{#!hs newtype Const a (b :: k) = Const { getConst :: a } deriving (Generic, Generic1) }}} An example where I need it is for [[http://wiki.ocharles.org.uk/Name%20Binding%20in%20EDSLs|interpreting typed PHOAS]], the following fails to compile complaining that `The first argument of ‘PTerm’ should have kind ‘Ty -> *’, but ‘Const Char’ has kind ‘* -> *’`: {{{#!hs {-# LANGUAGE DataKinds, KindSignatures, GADTs, RankNTypes, PolyKinds #-} import Control.Applicative data Ty = TyBool | TyArr Ty Ty data PTerm :: (Ty -> *) -> Ty -> * where Var :: v t -> PTerm v t Tru :: PTerm v 'TyBool Fals :: PTerm v 'TyBool App :: PTerm v ('TyArr t1 t2) -> PTerm v t1 -> PTerm v t2 Abs :: (v t1 -> PTerm v t2) -> PTerm v ('TyArr t1 t2) newtype Term t = Term (forall v. PTerm v t) showT :: Term t -> String showT (Term pterm) = show' 'a' pterm where show' :: Char -> PTerm (Const Char) t -> String show' _ (Var (Const c)) = [c] show' _ Tru = "True" show' _ Fals = "False" show' s (App x y) = "(" ++ show' s x ++ ") " ++ show' s y show' s (Abs f) = [s] ++ ". " ++ show' (succ s) (f (Const s)) }}} but it compiles if one defines a bespoke form of `Const` with kind `* -> Ty -> *` (or the more general suggestion at the beginning of the ticket), I implemented all the related instances from `Control.Applicative` and the compiled without a hitch. Relevant discussion: a [[http://stackoverflow.com/questions/2023052/haskell-specifying-kind-in- data-declaration|question on StackOverflow]] that predates the `PolyKinds` extension effectively wants to define `type Const' (a :: * -> *) = Const Integer a` which would be possible if it were kind polymorphic. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10039> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9394: Show data/type family instances with ghci's :info command
by GHC 18 Dec '15

18 Dec '15

#9394: Show data/type family instances with ghci's :info command -------------------------------------+------------------------------------- Reporter: s9gf4ult | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.6.3 Keywords: ghci | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Current version of ghci (7.6.3) does not show data instances. For example, I have some Yesod application and I want to see all data constructors of (Route App) data family instance: {{{#!hs *Application> :info Route App class Eq (Route a) => yesod-routes-1.2.0.6:Yesod.Routes.Class.RenderRoute a where data family Route a1 ... -- Defined in `yesod-routes-1.2.0.6:Yesod.Routes.Class' instance Eq (Route App) -- Defined at Foundation.hs:48:1 instance Read (Route App) -- Defined at Foundation.hs:48:1 ................. }}} It just shows info about `Route`, then info about `App` separately. When I try this: {{{#!hs *Application> :info (Route App) <interactive>:1:2: parse error on input `Route' }}} I am getting parse error. I offer to use this syntax (with parentheses) to show info about instance of data/type family, namely, data constructors and such stuff, just like for ordinal `data`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9394> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10034: Regression in mapM_ performance
by GHC 16 Dec '15

16 Dec '15

#10034: Regression in mapM_ performance -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: ekmett Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Core | Version: 7.10.1-rc2 Libraries | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime Architecture: | performance bug Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: Phab:D632 | -------------------------------------+------------------------------------- The current `mapM_` is sometimes worse than the version in 7.8.3. This can be fixed easily by eta-expansion, matching `mapM`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10034> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9276: audit ghc floating point support for IEEE (non)compliance
by GHC 16 Dec '15

16 Dec '15

#9276: audit ghc floating point support for IEEE (non)compliance ------------------------------------+------------------------------------- Reporter: carter | Owner: carter Type: task | Status: new Priority: high | Milestone: 7.10.1 Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- As best I can determine, ghc has never been closely audited for conformance to IEEE-754 (floating point) standard and currently is a bit far from providing a compliant implementation. This impacts both a number of other tasks i wish to do for ghc **and** much of my own use of haskell is in a floating point heavy workloads, I will do a bit of leg work to: a) improve test suite support for checking for compliance b) write some patches to provide portable compliant primops for the operations which need compiler support c) try to determine how to allow ghc optimizer to be a bit more aggressive in a sound way in the presence of floating point. (this may grow into a few subtickets, we'll see) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9276> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9304: Floating point woes; Different behavior on Mac vs Linux
by GHC 16 Dec '15

16 Dec '15

#9304: Floating point woes; Different behavior on Mac vs Linux ------------------------------------+------------------------------------- Reporter: lerkok | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.8.3 Keywords: floating point | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- I've the following snippet: {{{ x, y, r :: Double x = -4.4 y = 2.4999999999999956 r = x * y }}} Using GHC 7.8.3, on a Mac, I get the following response from ghci: {{{ *Main> decodeFloat r (-6192449487634421,-49) }}} Using GHC 7.8.3, on a Linux machine, I get the following response: {{{ *Main> decodeFloat r (-6192449487634422,-49) }}} Note that off-by-one difference in the first component of the output. I'm not 100% sure as to which one is actually correct; but the point is that these are IEEE floating point numbers running on the same architecture (Intel X86), and thus should decode in precisely the same way. While I observed this with 7.8.3; I don't think this is a new regression; I suspect it'll show up in older versions as well. Also, for full disclosure: I ran the Mac version naively; but the Linux version on top of a VirtualBox image. I'd very much doubt that would make a difference, but there might be 32/64-bit concerns. So, if someone can validate the Linux output on a true 64-bit Linux machine, that would really help track down the issue further. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9304> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9306: Crash when shifting Integers too much
by GHC 16 Dec '15

16 Dec '15

#9306: Crash when shifting Integers too much ------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Runtime crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- When shifting an Integer by `fromIntegral (maxBound::Int) + 2` or more, the RTS crashes. The attached program gives the following output (on x86_64, at least): [dfeuer@lemur src]$ ./shiftcrash Okay 0 gmp: overflow in mpz type Aborted I found the bug in 7.6.3, but it's been verified to be present also in 7.8.3. The crash also occurs when running similar code in GHCi. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9306> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8347: Add a Strict LANGUAGE pragma
by GHC 16 Dec '15

16 Dec '15

#8347: Add a Strict LANGUAGE pragma ------------------------------------+------------------------------------- Reporter: tibbe | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- A `Strict` `LANGUAGE` pragma would allow us to experiment with writing in a strict sub-language. Since this pragma works on a per module basis, it needs to be modular. I propose the following semantics: * Patterns are strict at the top-level, as if they had a top-level bang, unless an explicit ~ is used to make the pattern lazy. * Functions evaluate their parameters to WHNF. * Data type fields are strict (as if they had a bang-pattern). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8347> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8424: quasi-quotes have carriage returns on Windows
by GHC 16 Dec '15

16 Dec '15

#8424: quasi-quotes have carriage returns on Windows ------------------------------------+------------------------------------- Reporter: GregWeber | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- A Windows user rerported using Data.Text.IO.writeFile to write out quasi- quoted text. writeFile automatically translates '\r' to "\r\n", so the user ended up writing out "\r\r\n" to a file. Haskell seems to be adopting the policy or removing '\r' from Haskell land. Is there any reason why quasi-quotes should not automatically strip carriage returns? I asked this question on ghc-users and there was no response. I am willing to make this fix if it is deemed appropriate. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8424> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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