December 2015 - ghc-tickets

Re: [GHC] #4945: Another SpecConstr infelicity
by GHC 16 Dec '15

16 Dec '15

#4945: Another SpecConstr infelicity -------------------------------------+------------------------------------- Reporter: batterseapower | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime | Test Case: performance bug | simplCore/should_compile/T4945 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by thomie): * priority: high => normal Comment: To summarise: test T4945 is failing. Lowering priority, because it is just some (-O2) runtime performance issue. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4945#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #781: GHCi on x86_64, cannot link to static data in shared libs
by GHC 16 Dec '15

16 Dec '15

#781: GHCi on x86_64, cannot link to static data in shared libs -------------------------------------+------------------------------------- Reporter: guest | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Runtime System | Version: 6.5 (Linker) | Keywords: Resolution: | getEnvironment Operating System: Linux | Architecture: x86_64 | (amd64) Type of failure: GHCi crash | Test Case: | getEnvironment01 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by thomie): * priority: high => normal Comment: Lowering priority, because this is only a problem when GHC is built with `DYNAMIC_GHC_PROGRAMS=NO` (the default is `YES`). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/781#comment:34> 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] #11218: Provide `-W(no-)` aliases for `-f(no-)warn` warning flags
by GHC 16 Dec '15

16 Dec '15

#11218: Provide `-W(no-)` aliases for `-f(no-)warn` warning flags -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 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: Design/Warnings -------------------------------------+------------------------------------- TODO: description -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11218> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11164: No way to import a data instance
by GHC 16 Dec '15

16 Dec '15

#11164: No way to import a data instance -------------------------------------+------------------------------------- Reporter: Feuerbach | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 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: -------------------------------------+------------------------------------- {{{#!hs import Foreign.R.Type as R (SComplex) }}} results in {{{ In module ‘Foreign.R.Type’: ‘SComplex’ is a data constructor of ‘Sing’ To import it use ‘import’ Foreign.R.Type( Sing( SComplex ) ) or ‘import’ Foreign.R.Type( Sing(..) ) }}} But if I try the suggested {{{#!hs import Foreign.R.Type as R (Sing(SComplex)) }}} I get {{{ Module ‘Foreign.R.Type’ does not export ‘Sing(SComplex)’ }}} So, when a module defines a data instance but does not export the family, there appears to be no way to bring that instance in scope (short of importing the whole module). Here's the module itself http://haddock.stackage.org/nightly-2015-10-19/inline-r-0.7.1.2/Foreign-R-T…. It doesn't have an explicit export list; that's how it manages to export instances without the family itself. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11164> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11102: `ghc --supported-extension` shall not list `TemplateHaskell` when unsupported
by GHC 16 Dec '15

16 Dec '15

#11102: `ghc --supported-extension` shall not list `TemplateHaskell` when unsupported -------------------------------------+------------------------------------- Reporter: hvr | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): phab:D1484 | Wiki Page: -------------------------------------+------------------------------------- Currently GHC advertises `TemplateHaskell` even though it's statically known to fail: {{{ $ ghc --supported-extensions | grep Template TemplateHaskell NoTemplateHaskell # `NoTemplateHaskell` works: $ ghc -XNoTemplateHaskell -c hello.hs # `TemplateHaskell` however fails even though advertised: $ ghc -XTemplateHaskell -c hello.hs ghc: on the commandline: Template Haskell requires GHC with interpreter support Perhaps you are using a stage-1 compiler? Usage: For basic information, try the `--help' option. }}} Having properly advertised extensions is particularly useful in combination with [[https://github.com/haskell/cabal/issues/2644|Cabal#2644]] allowing the solver to toggle flags depending on the availability of `-XTemplateHaskell`. For instance, cross-compilers and/or unregisterised GHC builds often don't have TemplateHaskell support. Having support for toggling flags based on availability of `-XTemplateHaskell` allows `cabal` to support such environments with less manual intervention. (See also https://github.com/haskell/cabal/pull/2930 for pre-GHC8 emulation of this feature) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11102> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11083: Documentation clarification for Data.List.isSubsequenceOf
by GHC 16 Dec '15

16 Dec '15

#11083: Documentation clarification for Data.List.isSubsequenceOf -------------------------------------+------------------------------------- Reporter: jura | Owner: Type: bug | Status: new Priority: lowest | Milestone: Component: Documentation | Version: 7.10.2 Keywords: Data.List, | Operating System: Unknown/Multiple isSubsequenceOf | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In order to clarify the difference between isInfixOf and isSubsequenceOf, I submit a patch which changes the wording from "The 'isSubsequenceOf' function takes two lists and returns 'True' if the first list is a subsequence of the second list." to "The 'isSubsequenceOf' function takes two lists and returns 'True' if all the elements of the first list occur, in order, in the second. The elements do not have to occur consecutively." -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11083> 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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