December 2013 - ghc-tickets

[GHC] #8594: sysctl name "hw.ncpu" (HW_NCPU) is deprecated in Mac OS X
by GHC 07 Apr '16

07 Apr '16

#8594: sysctl name "hw.ncpu" (HW_NCPU) is deprecated in Mac OS X ------------------------------------+--------------------------------- Reporter: kseo | Owner: simonmar Type: task | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.6.3 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+--------------------------------- According to the OS X man page for sysctl(https://developer.apple.com/library/mac/documentation/Darwin/Referen…, HW_NCPU used by the current implementation of getNumberOfProcessors() is deprecated. Instead, Mac OS X provides the following 4 options: * hw.physicalcpu: The number of physical processors available in the current power management mode. * hw.physicalcpu_max: The maximum number of physical processors that could be available this boot. * hw.logicalcpu: The number of logical processors available in the current power management mode. * hw.logicalcpu_max: The maximum number of logical processors that could be available this boot. I am not sure which one fits best to GHC runtime. Any idea? sysconf implementation of getNumberOfProcessors() seems to prefer _SC_NPROCESSORS_ONLN to _SC_NPROCESSORS_CONF when both are defined. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8594> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8132: Warning for Typeable instances misplaced
by GHC 16 Mar '16

16 Mar '16

#8132: Warning for Typeable instances misplaced -------------------------+------------------------------------------------- Reporter: | Owner: scottgw | Status: new Type: bug | Milestone: Priority: | Version: 7.7 normal | Operating System: Unknown/Multiple Component: | Type of failure: Incorrect warning at Compiler | compile-time Keywords: | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- There is currently a warning for hand-rolled instances of Typeable. However, this leads to some pretty surprising error messages: because the instance is ignored any code that relies on that instance in the same module just fails, which appears pretty weird to the user. {{{ #!haskell import Data.Typeable data K = K instance Typeable K where typeRep _ = undefined ex :: TypeRep ex = typeRep (undefined :: Proxy K) }}} Gives as an error: {{{ No instance for (Typeable * K) arising from a use of ‛typeRep’ In the expression: typeRep (undefined :: Proxy K) In an equation for ‛ex’: ex = typeRep (undefined :: Proxy K) }}} Which is of course surprising because the user just defined the instance. After commenting out the code that uses the instance, one gets: {{{ TypEx.hs:1:1: Warning: Typeable instances can only be derived; ignoring the following instance: instance Typeable * K -- Defined at TypEx.hs:5:10 }}} This information should clearly be somehow presented before or with the previous error if the user is to have any way to figure out what is going on. I suppose this could be fixed by: 1. Turning the Typeable instance warning into an error 2. Checking the missing instance in the existing error for Typeable and suggest that the user should look for hand written instances as a source of the problem. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8132> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8176: Language extensions not registered
by GHC 20 Feb '16

20 Feb '16

#8176: Language extensions not registered --------------------------------+------------------------------------------ Reporter: duncan | Owner: thoughtpolice Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: tests/driver/T4437.hs Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | --------------------------------+------------------------------------------ tests/driver/T4437.hs does not seem to be being used properly. That test is there to make sure that ghc developers do not forget to register their new extensions with Cabal. But it looks like it's just being silenced and they are being forgotten again. Recall, the protocol is that all Haskell implementations can register their extensions in the central location (which is Language.Haskell.Extensions in the Cabal package) when they are happy that they are ready for public consumption. This matters to users because extensions that are not ready for public consumption (ie not registered) cannot be used in packages uploaded to hackage. Currently `tests/driver/T4437.hs` contains: {{{ expectedGhcOnlyExtensions = [ "AllowAmbiguousTypes", "RelaxedLayout", "AlternativeLayoutRule", "AlternativeLayoutRuleTransitional", "ExplicitNamespaces", "TypeHoles", "OverloadedLists", "EmptyCase", "AutoDeriveTypeable", "NegativeLiterals", "NullaryTypeClasses"] }}} This looks like a much bigger list than it should be. Surely not all of these extensions are private to ghc or are still under development and not to be used? But if they are listed here, then the test doesn't complain about them. And the whole point of this test is to stop ghc devs from forgetting to register them. I think we need to change the test so that we distinguish between extensions that are really not ready, and ones that are on-track to be public. It should be a release blocker for the "on-track to be public" ones to still not be registered. The test should have comments giving this guidance for ghc contributors. I'm not quite sure how we adjust the test to make that happen (ie different behaviour for RC-build vs normal hacking validate). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8176> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8278: Improve error message when the same type is imported from two different library versions
by GHC 14 Feb '16

14 Feb '16

#8278: Improve error message when the same type is imported from two different library versions ------------------------------------+------------------------------------- Reporter: Yuras | Owner: Type: bug | 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: | ------------------------------------+------------------------------------- When a package indirectly depends on different versions of the same library, ghc reports cryptic error: {{{ Couldn't match expected type `ByteString' with actual type `bytestring-0.9.2.1:Data.ByteString.Internal.ByteString' }}} Error contains fully qualified type with package name and version only when the type is imported from different versions on the library, so looks like ghc knows what is wrong. Is it possible to add something like the next: {{{ Note: ByteString is imported from different package versions: bytestring-0.9.2.1 and bytestring-0.10.0.1 }}} It is inspired by a number of StackOverflow questions (e.g. http://stackoverflow.com/questions/12576817/couldnt-match-expected-type- with-actual-type-error-when-using-codec-bmp/12577025#12577025, http://stackoverflow.com/questions/18767086/bytestring-to-lazy-text-and- vice-versa/18769431?noredirect=1#comment27676563_18769431) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8278> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8136: arr020 test fails randomly with ghci way
by GHC 07 Feb '16

07 Feb '16

#8136: arr020 test fails randomly with ghci way -----------------------------+---------------------------------- Reporter: jstolarek | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.7 Keywords: | Operating System: Linux Architecture: x86 | Type of failure: Runtime crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -----------------------------+---------------------------------- I noticed that when I run arr020 (`make TEST=arr020`) it randomly segfaults when running `ghci` way. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8136> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8265: getTokenStream fails for source using cpp
by GHC 07 Feb '16

07 Feb '16

#8265: getTokenStream fails for source using cpp -----------------------------------+--------------------------------------- Reporter: alanz | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.6.3 Keywords: | Operating System: Linux Architecture: | Type of failure: Compile-time crash Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -----------------------------------+--------------------------------------- Calling getTokenStream (or getRichTokenStream) on a module that has CPP directives fails as the lexer is given un-preprocessed source -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8265> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8287: exploring calling convention changes and related engineering for 7.10
by GHC 25 Jan '16

25 Jan '16

#8287: exploring calling convention changes and related engineering for 7.10 ------------------------------------+------------------------------------- Reporter: carter | Owner: Type: task | Status: new Priority: high | Milestone: 7.10.1 Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Rocket Science | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- I'm creating this as a master ticket for systematically exploring and benchmarking (possibly breaking) changes to the GHC calling convention. This work will initially focus on x86/x86_64, but may have larger scope. Goals: 1. if possible, improve performance systematically for code run on recent CPU micro architecture generations (eg sandybridge, haswell, and future extensions like Knights Landing and Skylake), ideally without pessimizing code on other or older x86_64 micro-architectures 2. Try to bring native and llvm codegens closer to feature parity (or at the very least, do not widen their capability gap) 3. a few other pieces too, will amend this ticket as ideas / plans clarify -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8287> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8325: Pattern guards in anonymous functions
by GHC 25 Jan '16

25 Jan '16

#8325: Pattern guards in anonymous functions ------------------------------------+------------------------------------- Reporter: mcollis | 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: | ------------------------------------+------------------------------------- In the course of a project, I had an idea that would allow less cumbersome use of cases in anonymous functions. Here's a simple example of what I'm proposing: {{{ (\x y | x > y -> x | otherwise -> something else) }}} Currently, the only way to accomplish this is with if() then ... else syntax or the use of the MultiWayIf and LambdaCase extensions. The syntax I've proposed here matches with existing anonymous function syntax and doesn't conflict with any other GHC syntax. This would greatly improve the readability of complex anonymous functions. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8325> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8572: Building an empty module with profiling requires profiling libraries for integer-gmp
by GHC 24 Jan '16

24 Jan '16

#8572: Building an empty module with profiling requires profiling libraries for integer-gmp -------------------------------------------+------------------------------- Reporter: parcs | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.7 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- {{{ #!haskell {-# LANGUAGE NoImplicitPrelude #-} module A where }}} {{{ $ ghc-stage2 -prof -c A.hs Top level: Failed to load interface for ‛GHC.Integer.Type’ Perhaps you haven't installed the profiling libraries for package ‛integer-gmp’? Use -v to see a list of the files searched for. }}} I can't built module `A` without profiling libraries for `integer-gmp`, even though I don't use `integer-gmp` anywhere in the module. This happens because the `Tidy Core` pass attempts to look up the `mkInteger` name (in order to desugar integer literals) even when there are no integer literals in the module. The obvious fix is to lazily look up `mkInteger` in `Coreprep.lookupMkIntegerName`: {{{ #!diff diff --git a/compiler/coreSyn/CorePrep.lhs b/compiler/coreSyn/CorePrep.lhs index 5e0cd65..9836982 100644 --- a/compiler/coreSyn/CorePrep.lhs +++ b/compiler/coreSyn/CorePrep.lhs @@ -56,6 +56,7 @@ import Config import Data.Bits import Data.List ( mapAccumL ) import Control.Monad +import System.IO.Unsafe ( unsafeInterleaveIO ) \end{code} -- --------------------------------------------------------------------------- @@ -1119,6 +1120,7 @@ lookupMkIntegerName dflags hsc_env else if thisPackage dflags == integerPackageId then return $ panic "Can't use Integer in integer" else liftM tyThingId + $ unsafeInterleaveIO $ initTcForLookup hsc_env (tcLookupGlobal mkIntegerName) mkInitialCorePrepEnv :: DynFlags -> HscEnv -> IO CorePrepEnv }}} This way, we don't attempt to look up `mkInteger` until we actually need it, i.e. if there are integer literals that we must desugar. Relevant commits are 2ef5cd26db27543ac8664a3d18f45550d0109a8b and fdd552e0ecaa17300670a48562995040e1d6687e -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8572> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8285: unexpected behavior with encodeFloat on large inputs
by GHC 23 Jan '16

23 Jan '16

#8285: unexpected behavior with encodeFloat on large inputs --------------------------+------------------------------------------------ Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: | Version: 7.7 Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: Incorrect result at runtime Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: | Unknown | Blocked By: | Related Tickets: | --------------------------+------------------------------------------------ benjamin scarlet discovered some unexpected behavior in encodeFloat today {{{ <bscarlet> > map (\x -> encodeFloat 1 (shiftL 1 x)) [30,31] [23:47:47] <lambdabot> [Infinity,0.0] [23:49:09] <arkeet> > encodeFloat 1 60 [23:49:10] <lambdabot> 1.152921504606847e18 [23:49:09] <arkeet> > encodeFloat 1 60 [23:49:10] <lambdabot> 1.152921504606847e18 [23:49:18] <arkeet> er. [23:50:21] <bscarlet> down in the sane range I suspect it's just fine. [23:50:43] <bscarlet> > encodeFloat 1 1000 [23:50:44] <lambdabot> 1.0715086071862673e301 [23:50:52] <bscarlet> > encodeFloat 1 10000 [23:50:53] <lambdabot> Infinity [23:50:58] <bscarlet> That's sane. [23:51:03] <arkeet> > encodeFloat 1 (2^31) [23:51:04] <lambdabot> 0.0 [23:51:13] <bscarlet> That's what I think is weird. [23:51:19] <carter> bscarlet floats are weird [23:51:23] <arkeet> > encodeFloat 1 (2^31-1) [23:51:24] <lambdabot> Infinity }}} Benjamin did a wee bit of investigation, and the problem seems to lie in https://github.com/ghc/packages-integer- gmp/blob/master/cbits/float.c#L177 in integer-gmp, where it deliberately doesn't handle the edge cases (probably worth investigating) if integer-simple has similar behavior or not -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8285> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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