December 2014 - ghc-tickets

Re: [GHC] #1168: Optimisation sometimes decreases sharing in IO code
by GHC 11 Dec '14

11 Dec '14

#1168: Optimisation sometimes decreases sharing in IO code -------------------------------------+------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.6 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: Test Case: | nofib/spectral/calendar | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): David, it's be very helpful if you could * Specify the exact steps to reproduce the performance changes you see, with and without `-fno-state-hack`. * Say which version of GHC you are using Thanks Simon -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1168#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3927: Incomplete/overlapped pattern warnings + GADTs = inadequate
by GHC 10 Dec '14

10 Dec '14

#3927: Incomplete/overlapped pattern warnings + GADTs = inadequate -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 6.12.1 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: #4139 Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by vlopez): Instead of fixing the exhaustiveness checker, we could have some way to tell the compiler that a particular branch in a case expression (or function definition) is inaccessible. A possible syntax for this would be an "empty guard" (a vertical bar immediately followed by a semicolon). {{{ data T a where T1 :: T Int T2 :: T Bool f1 :: T a -> T a -> Bool f1 T1 T1 = True f1 T2 T2 = False f1 T1 T2 |; -- absurd branch f1 T2 T1 |; -- another absurd branch f2 :: T a -> T a -> Bool f2 a b = case (a,b) of (T1, T1) -> True (T2, T2) -> False (T1, T2) |; (T2, T1) |; }}} * In GHC 7.8.3, it results in an immediate parser error at the `;`, so it shouldn't conflict with other features. * It works well with the indentation heuristics in emacs haskell-mode (and hopefully with other editors too). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3927#comment:38> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9874: Unhandled exception in Phab
by GHC 10 Dec '14

10 Dec '14

#9874: Unhandled exception in Phab -------------------------------------+------------------------------------- Reporter: goldfire | Owner: hvr Type: bug | Status: new Priority: normal | Milestone: Component: Trac & Git | 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: -------------------------------------+------------------------------------- Several times over the past few days, loading Phab:D546 has given me a window with Unhandled Exception ("InvalidArgumentException") Argument 2 passed to DifferentialTransactionComment::sortAndGroupInlines() must be of the type array, null given, called in /opt/phabricator/src/applications/differential/view/DifferentialTransactionView.php on line 118 and defined -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9874> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7015: Add support for 'static'
by GHC 10 Dec '14

10 Dec '14

#7015: Add support for 'static' -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: feature | Status: new request | Milestone: 7.12.1 Priority: normal | Version: 7.4.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D119, | Phab:D550 | -------------------------------------+------------------------------------- Comment (by goldfire): Quick note: there is nothing in the release notes about this significant feature. Please add. Thanks for doing all of this! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7015#comment:42> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7015: Add support for 'static'
by GHC 10 Dec '14

10 Dec '14

#7015: Add support for 'static' -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: feature | Status: new request | Milestone: 7.12.1 Priority: normal | Version: 7.4.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D119, | Phab:D550 | -------------------------------------+------------------------------------- Comment (by facundo.dominguez): > Alternatively, we can milestone this to 7.10.1 and close it, and track future improvements through separate tickets. What do you think, Facundo? I think this is best to give its own space to the discussions arising from further work. > (Note, adding the old Phab:D119 to the revision list still, mostly to keep track of historical attempts. ...) Quite appropriate. Thanks. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7015#comment:41> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7015: Add support for 'static'
by GHC 10 Dec '14

10 Dec '14

#7015: Add support for 'static' -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: feature | Status: new request | Milestone: 7.12.1 Priority: normal | Version: 7.4.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D119, | Phab:D550 | -------------------------------------+------------------------------------- Comment (by mboes): Thanks for landing this! As far as I know all features that were requested as part of the GHC 7.10 milestone according to [wiki:StaticPointers/ImplementationPlan] have been implemented and all issues raised by the reviewers addressed. Seeing as this has been merged by now, perhaps it would make sense to go for the latter option, namely track future improvements through separate tickets? The major future improvement I see is this: * Store (higher-order) `TypeRep`s in the SPT and check them upon pointer lookups, in order to reduce the size of trusted base that guarantees type safety. That improvement is not really possible without switching to a new API for `Data.Typeable`, as outlined by Simon PJ [wiki:Typeable here], which is a potentially high impact change to `base`. I think it means two separate new tickets to track: implement type indexed `Data.Typeable`, add type representation checking to the SPT. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7015#comment:40> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7015: Add support for 'static'
by GHC 10 Dec '14

10 Dec '14

#7015: Add support for 'static' -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: feature | Status: new request | Milestone: 7.12.1 Priority: normal | Version: 7.4.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D119, | Phab:D550 | -------------------------------------+------------------------------------- Changes (by thoughtpolice): * status: patch => new * differential: Phab:D550 => Phab:D119, Phab:D550 * milestone: 7.10.1 => 7.12.1 Comment: The first draft has landed, awesome! OK, I'm now punting the version on this to 7.12 since there's some future work to do. Alternatively, we can milestone this to 7.10.1 and close it, and track future improvements through separate tickets. What do you think, Facundo? (Note, adding the old Phab:D119 to the revision list still, mostly to keep track of historical attempts. Feel free to undo again.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7015#comment:39> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9870: Document deviation of Data.List.splitAt from Report semantics
by GHC 10 Dec '14

10 Dec '14

#9870: Document deviation of Data.List.splitAt from Report semantics -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Documentation | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | Documentation bug Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: Phab:D562 -------------------------------------+------------------------------------- `Data.List.splitAt` is strict in its first argument. The Report specifies that `splitAt n xs = (take n xs, drop n xs)`. This should be noted in the user's guide. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9870> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7015: Add support for 'static'
by GHC 10 Dec '14

10 Dec '14

#7015: Add support for 'static' -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: feature | Status: patch request | Milestone: 7.10.1 Priority: normal | Version: 7.4.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D550 | -------------------------------------+------------------------------------- Comment (by Austin Seipp <austin@…>): In [changeset:"fc45f32491313d2a44e72d8d59cdf95b1660189d/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="fc45f32491313d2a44e72d8d59cdf95b1660189d" Implement -XStaticValues Summary: As proposed in [1], this extension introduces a new syntactic form `static e`, where `e :: a` can be any closed expression. The static form produces a value of type `StaticPtr a`, which works as a reference that programs can "dereference" to get the value of `e` back. References are like `Ptr`s, except that they are stable across invocations of a program. The relevant wiki pages are [2, 3], which describe the motivation/ideas and implementation plan respectively. [1] Jeff Epstein, Andrew P. Black, and Simon Peyton-Jones. Towards Haskell in the cloud. SIGPLAN Not., 46(12):118–129, September 2011. ISSN 0362-1340. [2] https://ghc.haskell.org/trac/ghc/wiki/StaticPointers [3] https://ghc.haskell.org/trac/ghc/wiki/StaticPointers/ImplementationPlan Authored-by: Facundo Domínguez <facundo.dominguez(a)tweag.io> Authored-by: Mathieu Boespflug <m(a)tweag.io> Authored-by: Alexander Vershilov <alexander.vershilov(a)tweag.io> Test Plan: `./validate` Reviewers: hvr, simonmar, simonpj, austin Reviewed By: simonpj, austin Subscribers: qnikst, bgamari, mboes, carter, thomie, goldfire Differential Revision: https://phabricator.haskell.org/D550 GHC Trac Issues: #7015 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7015#comment:38> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3085: warn about language extensions that are not used
by GHC 09 Dec '14

09 Dec '14

#3085: warn about language extensions that are not used -------------------------------------+------------------------------------- Reporter: | Owner: PVerswyvelen | Status: new Type: feature | Milestone: 7.10.1 request | Version: 6.10.1 Priority: normal | Keywords: warnings Component: Compiler | extensions language Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: #9757 None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonmar): Replying to [comment:33 thomie]: > To cite rwbarton from #9757: > > I think the purpose of compiler warnings should be to warn about code that is probably bad, not code that is probably fine that could be written in a (potentially) better way. (After all, we don't warn about excess parentheses in code either.) That is the domain of hlint, as Richard notes. > > Anyone disagree with a `wontfix` here as well? This is an argument that the warning shouldn't be on by default, or perhaps that it shouldn't be in `-Wall`, but not an argument that we shouldn't implement it at all. We have several warnings that are not part of `-Wall` and fall into the category of "a matter of taste". (FWIW, HLint already does this for a subset of extensions). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3085#comment:37> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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