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[GHC] #13411: GCC driver fails on Windows 10 15019+
by GHC 20 Apr '17

20 Apr '17

#13411: GCC driver fails on Windows 10 15019+ -------------------------------------+------------------------------------- Reporter: Phyx- | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Driver | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Our GCC driver seems to be failing with a compatibility error on Windows 10 Insider builds 15019+. Leaving error code 0xc0000142. This driver has been unchanged since Windows XP and may just need some old APIs replaced. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13411> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4092: Floating point manipulation : ulp and coerce IEEE-754 Double# into Word64#
by GHC 20 Apr '17

20 Apr '17

#4092: Floating point manipulation : ulp and coerce IEEE-754 Double# into Word64# -------------------------------------+------------------------------------- Reporter: malosh | Owner: (none) Type: feature request | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 6.12.2 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): phab:D3358 Wiki Page: | -------------------------------------+------------------------------------- Changes (by erikd): * status: new => closed * resolution: => fixed Comment: This was implemented in: {{{ commit aa206346e6f12c9f88fdf051185741761ea88fbb Author: Erik de Castro Lopo <erikd(a)mega-nerd.com> Date: Wed Apr 12 14:09:49 2017 -0400 base: Implement bit casts between word and float types Test Plan: Test on x86 and x86_64 Reviewers: duncan, trofi, simonmar, tibbe, hvr, austin, rwbarton, bgamari Reviewed By: duncan Subscribers: Phyx, DemiMarie, rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3358 }}} Unfortunately too late for the ghc-8.2 release, but it will make the ghc-8.4 release. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4092#comment:30> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13501: TH segmentation fault on Linux when calling function from another package
by GHC 20 Apr '17

20 Apr '17

#13501: TH segmentation fault on Linux when calling function from another package -------------------------------------+------------------------------------- Reporter: jmaki | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The bug was hit when using Buck (buckbuild.com) to build. I had two packages, A containing a single module with a TH function of type `TH.Q [TH.Dec]` and module B importing A it and calling that function at top-level. I've attached a tarball that reproduces the problem. I've verified that the problem occurs with 7.10.3, 8.0.2 and a semi-recent GHC HEAD from @bitonic. The issue doesn't occur on macOS and does not occur when the modules are in a single package or if the package is compiled as a shared library. The problem also does not occur when using stack, so this is likely related to how buck creates packages. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13501> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13458: Panic with unsafeCoerce and -dcore-lint
by GHC 20 Apr '17

20 Apr '17

#13458: Panic with unsafeCoerce and -dcore-lint -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE MagicHash, TypeInType, ScopedTypeVariables #-} module UIOST where import GHC.Exts import Data.Kind import Unsafe.Coerce unsafeCoerce' :: forall (r :: RuntimeRep) (a :: TYPE r) (b :: TYPE r). a -> b unsafeCoerce' = unsafeCoerce unsafeCoerce }}} Compiling this with optimization and `-dcore-lint` produces a panic: {{{ ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.1.20170308 for x86_64-unknown-linux): runtimeRepPrimRep typePrimRep (a_aW7 :: TYPE r_aW6) r_aW6 Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1191:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1195:37 in ghc:Outputable pprPanic, called at compiler/simplStg/RepType.hs:360:5 in ghc:RepType }}} Using `unsafeCoerce# unsafeCoerce` produces the panic without optimization. I have not been able to reproduce the problem without `-dcore-lint`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13458> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2648: Report out of date interface files robustly
by GHC 19 Apr '17

19 Apr '17

#2648: Report out of date interface files robustly -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: feature request | Status: new Priority: lowest | Milestone: Component: GHCi | Version: 7.6.3 Resolution: | Keywords: | TypeErrorMessages Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHCi crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => TypeErrorMessages -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2648#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2648: Report out of date interface files robustly
by GHC 19 Apr '17

19 Apr '17

#2648: Report out of date interface files robustly -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: feature request | Status: new Priority: lowest | Milestone: Component: GHCi | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHCi crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2648#comment:21> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1928: Confusing type error message
by GHC 19 Apr '17

19 Apr '17

#1928: Confusing type error message -------------------------------------+------------------------------------- Reporter: josef | Owner: (none) Type: bug | Status: new Priority: low | Milestone: ⊥ Component: Compiler (Type | Version: 6.8.1 checker) | Keywords: Resolution: | TypeErrorMessages Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => TypeErrorMessages * failure: => None/Unknown -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1928#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1330: Impredicativity bug: Church2 test gives a rather confusing error with the HEAD
by GHC 19 Apr '17

19 Apr '17

#1330: Impredicativity bug: Church2 test gives a rather confusing error with the HEAD -------------------------------------+------------------------------------- Reporter: igloo | Owner: simonpj Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler (Type | Version: 6.7 checker) | Keywords: Resolution: | TypeErrorMessages Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Church2 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => TypeErrorMessages * failure: => None/Unknown -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1330#comment:21> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9456: Weird behavior with polymorphic function involving existential quantification and GADTs
by GHC 19 Apr '17

19 Apr '17

#9456: Weird behavior with polymorphic function involving existential quantification and GADTs -------------------------------------+------------------------------------- Reporter: haasn | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: GHC Difficulty: Unknown | rejects valid program Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- This program is rejected by GHC 7.8.2: {{{ {-# LANGUAGE GADTs, ExistentialQuantification #-} module Foo where data Box = forall a. Box a foo :: Monad m => m () foo = do box <- return (Box ()) let f x = let _ = Box x `asTypeOf` box in x g :: a -> a g = f return () }}} With the following type error: {{{ foo.hs:15:11: Couldn't match type ‘a0’ with ‘a’ because type variable ‘a’ would escape its scope This (rigid, skolem) type variable is bound by the type signature for g :: a -> a at foo.hs:14:12-17 Expected type: a -> a Actual type: a0 -> a0 Relevant bindings include g :: a -> a (bound at foo.hs:15:7) f :: a0 -> a0 (bound at foo.hs:10:7) In the expression: f In an equation for ‘g’: g = f }}} Perplexingly, however, you can get it to compile either by adding a type signature to f: {{{ {-# LANGUAGE GADTs, ExistentialQuantification #-} module Foo where data Box = forall a. Box a foo :: Monad m => m () foo = do box <- return (Box ()) let f :: x -> x f x = let _ = Box x `asTypeOf` box in x g :: a -> a g = f return () }}} Or by disabling the GADTs extension: {{{ {-# LANGUAGE ExistentialQuantification #-} module Foo where data Box = forall a. Box a foo :: Monad m => m () foo = do box <- return (Box ()) let f x = let _ = Box x `asTypeOf` box in x g :: a -> a g = f return () }}} Or by getting rid of the asTypeOf: {{{ {-# LANGUAGE GADTs, ExistentialQuantification #-} module Foo where data Box = forall a. Box a foo :: Monad m => m () foo = do box <- return (Box ()) let f x = let _ = Box x in x g :: a -> a g = f return () }}} Or by defining ‘box’ differently: {{{ {-# LANGUAGE GADTs, ExistentialQuantification #-} module Foo where data Box = forall a. Box a foo :: Monad m => m () foo = do let box = Box () let f x = let _ = Box x `asTypeOf` box in x g :: a -> a g = f return () }}} And perhaps some other factors that I haven't tested yet. It appears to me that all of these should be valid programs. Real world source: https://github.com/andygill/io- reactive/blob/master/Control/Concurrent/Reactive.hs It happens here due to the usage of (putMVar box ret), which makes the function requestit in line 77 not as polymorphic as it should be, unless you add a type signature. The putMVar serves the same role as the `asTypeOf` in my smaller example. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9456> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9605: Misleading error message with forgotten "do"
by GHC 19 Apr '17

19 Apr '17

#9605: Misleading error message with forgotten "do" -------------------------------------+------------------------------------- Reporter: owst | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- In the following (simplified) code, I forgot to add the do keyword, when doing some refactoring. This caused GHC to give a strange error message that said approximately "The function F is applied to two arguments, but its type T has only two"... which is odd! {{{#!hs import Control.Monad.RWS ( evalRWS, RWS ) import Control.Monad.Writer.Class ( tell ) main = print $ evalRWS (go 1) () () go :: Int -> RWS () [String] () () go i = --Oops, forgot a do here return (show i) >>= (\l -> tell [l]) -- go $ i + 1 go i }}} Strangely, replacing the "go i" line with the commented-out line above it gives a sensible error message, the "Possible cause: `\l -> tell [l]' is applied to too many arguments" message, which is correct, and would've pointed me straight to the problem. The invalid error message, which appears to be the same using GHC 7.6.3 and 7.8.3, is: {{{ NFA.hs:8:25: Couldn't match type ‘String -> Control.Monad.Trans.RWS.Lazy.RWST () [String] () Data.Functor.Identity.Identity ()’ with ‘()’ Expected type: Int -> String -> Control.Monad.Trans.RWS.Lazy.RWST () [String] () Data.Functor.Identity.Identity () Actual type: Int -> () The function ‘\ l -> tell [l]’ is applied to two arguments, but its type ‘(Int -> RWS () [String] () ()) -> Int -> ()’ has only two In the second argument of ‘(>>=)’, namely ‘(\ l -> tell [l]) go i’ In the expression: return (show i) >>= (\ l -> tell [l]) go i }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9605> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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