February 2015 - ghc-tickets

[GHC] #9423: shutdownCapability sometimes loops indefinitely on OSX after hs_exit()
by GHC 02 Feb '15

02 Feb '15

#9423: shutdownCapability sometimes loops indefinitely on OSX after hs_exit() -------------------------------------+------------------------------------- Reporter: AndreasVoellmy | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.8.2 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: Incorrect Difficulty: Unknown | result at runtime Blocked By: | Test Case: Related Tickets: 9284 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Issue #9284 relates to `forkProcess`, which previously invoked the same code that is invoked by `hs_exit` and uncovered this problem. The resolution of #9284 is to not invoke the equivalent of `hs_exit` (for reasons that you can see in #9284). However, `hs_exit` can be called by programs that explicitly create and teardown a Haskell runtime, so the problem displayed by #9284 can still occur for those programs. The problem has only been observed on OS X, though it probably could occur on Linux OSes as well. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9423> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10027: Importing constructor of associated data type fails
by GHC 02 Feb '15

02 Feb '15

#10027: Importing constructor of associated data type fails -------------------------------------+------------------------------------- Reporter: lspitzner | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple constructor import associated | Type of failure: None/Unknown data type | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I will base my description on the code you find when searching for "instance PersistEntity" on http://www.yesodweb.com/book/persistent. In summary, the code looks like {{{#!hs instance PersistEntity Person where ... data EntityField Person typ where PersonId :: EntityField Person PersonId PersonName :: EntityField Person String PersonAge :: EntityField Person Int ... }}} This code is generated from TH (see above). I have not tested if it matters that it is generated. A first step could be to test if manually replacing the TH part yields different results. The problem is: When i add this code in one module, do ''not'' create an export list for that module, and try to import the constructors explicitly (i.e. with a list) in a different module, it does not work. I read and tried to follow the description on https://wiki.haskell.org/GHC/Type_families, chapter 4.3. == Testcase 1 == (not really expected to work; still intersting error message) {{{#!hs import MyModuleContainingInstancePerson ( PersonId ) }}} ghc says {{{ ‘PersonId’ is a data constructor of ‘EntityField’ To import it use ‘import’ MyModuleContainingInstancePerson( EntityField( VersionVersion ) ) or ‘import’ MyModuleContainingInstancePerson( EntityField(..) ) }}} == Testcase 2 == (no export list in {{{MyModuleContainingInstancePerson}}}) {{{#!hs import MyModuleContainingInstancePerson ( EntityField(..) ) }}} ghc says {{{ Module ‘MyModuleContainingInstancePerson’ does not export ‘EntityField(..)’ }}} == Testcase 3 == But ''when i do provide'' an export list in {{{MyModuleContainingInstancePerson}}}, like {{{#!hs module MyModuleContainingInstancePerson ( Person(..), EntityField(..) ) where .. }}} Testcase 2 suddenly works. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10027> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5654: Profiling semantics bug
by GHC 02 Feb '15

02 Feb '15

#5654: Profiling semantics bug -------------------------------------+------------------------------------- Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: low | Milestone: 7.12.1 Component: Profiling | Version: 7.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | profiling/should_run/scc004 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by simonmar): * cc: scpmw (added) * status: infoneeded => new Comment: `-fprof-auto` is needed to get the `main` SCC too. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5654#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10048: {-# UNPACK #-} support for size-indexed types
by GHC 02 Feb '15

02 Feb '15

#10048: {-# UNPACK #-} support for size-indexed types -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.11 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I don't know too much of the theory, but it seems to me that `{-# UNPACK #-}` should be able to work for something like this: {{{#!hs data Tup (l::[*]) where Nil :: HList '[] Cons :: e -> {-# UNPACK #-} !(HList l) -> HList (e ': l) }}} This is essentially just `HList` from the `HList` package but strict in the second `Cons` argument. What I would want is for `Tup '[a,b,c]` to be represented in just the same way as `(a,b,c)`. When possible, I'd want the getters/setters/lenses to be optimized to index into the unpacked structure rather than walking along it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10048> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10060: The Traversable instance for Array looks unlikely to be good
by GHC 02 Feb '15

02 Feb '15

#10060: The Traversable instance for Array looks unlikely to be good -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Core | Version: 7.11 Libraries | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime Architecture: | performance bug Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Currently, {{{#!hs instance Ix i => Traversable (Array i) where traverse f arr = listArray (bounds arr) `fmap` traverse f (elems arr) }}} Since `traverse` is (inherently) not a good producer for list fusion, this looks suspicious. I think we almost certainly want to walk the array by hand instead. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10060> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7103: Compiler panic, when loading wxc in GHCi
by GHC 01 Feb '15

01 Feb '15

#7103: Compiler panic, when loading wxc in GHCi -------------------------------------+------------------------------------- Reporter: Henk-Jan | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: GHCi | Version: 7.4.2 Resolution: | Keywords: Operating System: Windows | Architecture: Type of failure: GHCi crash | Unknown/Multiple Blocked By: 3658 | Test Case: Related Tickets: #9907, #10051 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by rwbarton): * related: => #9907, #10051 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7103#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7152: Add flag to configure that skips overwriting of symlinks on install
by GHC 01 Feb '15

01 Feb '15

#7152: Add flag to configure that skips overwriting of symlinks on install -------------------------------------+------------------------------------- Reporter: tibbe | Owner: Type: feature request | thoughtpolice Priority: normal | Status: new Component: Build System | Milestone: 7.12.1 Resolution: | Version: 7.4.2 Operating System: Unknown/Multiple | Keywords: Type of failure: None/Unknown | Architecture: Blocked By: | Unknown/Multiple Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by rwbarton): * cc: rwbarton (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7152#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10054: Misleading error message from unsaturated type family application
by GHC 01 Feb '15

01 Feb '15

#10054: Misleading error message from unsaturated type family application -------------------------------------+------------------------------------- Reporter: sherman | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 (Type checker) | Operating System: MacOS X Keywords: type | Type of failure: Incorrect families, constraint kinds | warning at compile-time Architecture: x86_64 | Blocked By: (amd64) | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- This program {{{#!hs {-# LANGUAGE GADTs, ConstraintKinds, KindSignatures #-} {-# LANGUAGE TypeFamilies #-} import GHC.Exts (Constraint) data Foo :: (* -> Constraint) -> * -> * where MkFoo :: c a => Foo c a type family Ap (f :: * -> Constraint) (x :: *) :: Constraint where Ap f x = f x test :: Ap Show a => Foo (Ap Show) a test = MkFoo }}} yields the following error message: {{{ [1 of 1] Compiling Main ( Test.hs, interpreted ) Test.hs:13:8: Could not deduce (Ap Show a) arising from a use of ‘MkFoo’ from the context (Ap Show a) bound by the type signature for test :: (Ap Show a) => Foo (Ap Show) a at Test.hs:12:9-36 Relevant bindings include test :: Foo (Ap Show) a (bound at Test.hs:13:1) In the expression: MkFoo In an equation for ‘test’: test = MkFoo Failed, modules loaded: none. }}} I have a hypothesis as to why this error occurs. Because the application of {{{Ap}}} in {{{Ap Show a}}} is fully applied in the context, it reduces to the constraint {{{Show a}}}. However, when error messages describe the typeclass context, they don't reduce type synonyms or type families. However, the {{{Ap Show a}}} that cannot be deduced, despite appearing like a saturated application of {{{Ap}}}, must not be due to the fact that the {{{Ap Show}}} in the argument to the {{{Foo}}} type constructor is partially applied. If the definition of {{{Ap}}} is eta-reduced, the program in fact successfully typechecks. Or, if the result type of {{{test}}} is instead specified as {{{Foo Show a}}}, the program successfully typechecks. If the type variable {{{a}}} is specialized to a concrete type with a {{{Show}}} instance such as {{{Int}}}, the misleading error message still occurs, with {{{Int}}} substituted for {{{a}}}. I am wondering if there might be some way to report the error in a way that brings attention to the fact that the compiler cannot figure out what {{{Ap Show a}}} ''is'' as the constraint that cannot be deduced. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10054> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10057: Ghc panic with syntax error in data declaration.
by GHC 01 Feb '15

01 Feb '15

#10057: Ghc panic with syntax error in data declaration. -------------------------------------+------------------------------------- Reporter: jfs | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Given a spurious "type" after an empty data declaration member list causes my GHC (Debian) to crash. -- test file -- module Test where data X = X {} X -- end test file -- $ ghc Test [1 of 1] Compiling Test ( Test.hs, Test.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.6.3 for x86_64-unknown-linux): tc_hs_type: record Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10057> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10055: Offer PolyKinded instances Data.Fixed.HasResolution
by GHC 01 Feb '15

01 Feb '15

#10055: Offer PolyKinded instances Data.Fixed.HasResolution -------------------------------------+------------------------------------- Reporter: redneb | Owner: Type: feature | Status: new request | Milestone: Priority: low | Version: 7.8.4 Component: | Operating System: Unknown/Multiple libraries/base | Type of failure: None/Unknown Keywords: | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Now that we have `DataKinds` and `PolyKinds`, how about offering an instance of `Data.Fixed.HasResolution` for type level natural numbers. For example {{{#!hs instance KnownNat n => HasResolution (n :: Nat) where resolution proxy = 10 ^ natVal proxy }}} or even {{{#!hs instance KnownNat n => HasResolution (n :: Nat) where resolution = natVal }}} This will make it very easy to create fixed-point types on the fly. The following extensions are required for that to work: `DataKinds`, `PolyKinds`, `FlexibleInstances`, and `UndecidableInstances`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10055> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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