January 2016 - ghc-tickets

[GHC] #9418: Warnings about "INLINE binder is (non-rule) loop breaker"
by GHC 27 Mar '17

27 Mar '17

#9418: Warnings about "INLINE binder is (non-rule) loop breaker" -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Gabor rightly complains: I see literally ''thousands'' of these warnings (in yesterday's and) today's bootstraps: {{{ HC [stage 1] libraries/base/dist-install/build/GHC/Base.o *** Core Lint warnings : in result of Desugar (after optimization) *** {-# LINE 261 "libraries/base/GHC/Base.lhs #-}: Warning: [RHS of $c>>_arr :: forall r_agf a_adQ b_adR. (r_agf -> a_adQ) -> (r_agf -> b_adR) -> r_agf -> b_adR] INLINE binder is (non-rule) loop breaker: $c>>_arr {-# LINE 632 "libraries/base/GHC/Base.lhs #-}: Warning: [RHS of $c>>_apH :: forall a_adQ b_adR. GHC.Types.IO a_adQ -> GHC.Types.IO b_adR -> GHC.Types.IO b_adR] INLINE binder is (non-rule) loop breaker: $c>>_apH }}} }}} This is clearly unsatisfactory, because it is unsettling, and perhaps conceals more important warnings. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9418> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9701: GADTs not specialized properly
by GHC 21 Mar '17

21 Mar '17

#9701: GADTs not specialized properly -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | performance bug Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- This has probably been raised before, but I can't find a ticket. If I write {{{#!hs data Silly a where Silly :: Ord a => a -> Silly a isItSilly :: a -> Silly a -> Bool isItSilly a (Silly x) = a < x isItSillyInt :: Int -> Silly Int -> Bool isItSillyInt = isItSilly }}} then I get {{{ isItSilly isItSilly = \ @ a_aBq eta_B2 eta1_B1 -> case eta1_B1 of _ { Silly $dOrd_aBs x_aAy -> < $dOrd_aBs eta_B2 x_aAy } isItSillyInt isItSillyInt = isItSilly }}} Although GHC knows that `eta_B2` is an `Int`, and `x_aAy` therefore must be one as well, it looks up the `<` method in the `eta1_B1` dictionary instead of just using `ltInt`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9701> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8751: Show parenthesised output of expressions in ghci
by GHC 21 Mar '17

21 Mar '17

#8751: Show parenthesised output of expressions in ghci ------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Iceland_jack Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | 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: | ------------------------------------+------------------------------------- Operator fixity can be a source of bugs (even for experienced users!),[#point1 (1)] precedence levels may vary between languages and then there are user-defined operators. Attached is a patch for a ghci command allowing users to quickly parenthesise expressions as a sanity check (and as an alternative to using :info and parsing the result yourself). The command itself is activated with `:paren`: {{{ ghci> :paren 2 + 10 * 4 / 3 2 + ((10 * 4) / 3) ghci> :paren \a b → a == b || b && a == (b == a) || b \ a b -> (a == b) || ((b && (a == (b == a))) || b) ghci> :paren 5 + 1 `mod` 2 5 + (1 `mod` 2) ghci> :paren 5 * 1 `mod` 2 (5 * 1) `mod` 2 }}} A friend of mine also pointed out that this could eventually be integrated into `haskell-mode` where the user could temporarily replace an expression with a parenthesised version or have different colours indicate different levels of logical nesting. [=#point1 (1)] [http://www.knosof.co.uk/cbook/accu06.html Developer beliefs about binary operator precedence] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8751> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10143: Separate PprFlags (used by Outputable) from DynFlags
by GHC 18 Mar '17

18 Mar '17

#10143: Separate PprFlags (used by Outputable) from DynFlags -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- At the moment, SDoc computations have full access to the entirety of DynFlags, despite only a minusculely small amount of the data structure being relevant to them. This proposal is to split out a `PprFlags` structure which will be contained in a `DynFlags`, and contain dynamic flags JUST for pretty-printing. There will be a function `pprFlags :: DynFlags -> PprFlags`. This also helps eliminate the circular dependency between `DynFlags` and `Outputable`. This structure is not complete, but it should give a sense for some of the things that need to be put in here: {{{ data PprFlags = PprFlags { pprUserLength :: Int, pprCols :: Int, useUnicode :: Bool, useUnicodeSyntax :: Bool, targetPlatform :: Platform, suppressUniques :: Bool, errorSpans :: Bool, suppressModulePrefixes :: Bool } }}} I have a patch in-progress which factors this out, but I want to get some sign-offs that this is a good refactoring before I finish it. Thanks! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10143> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11431: GHC instantiates levity-polymorphic type variables with foralls
by GHC 16 Mar '17

16 Mar '17

#11431: GHC instantiates levity-polymorphic type variables with foralls -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- Consider the following use of `error`. {{{ ghci> :t error error :: forall (v :: GHC.Types.Levity) (a :: TYPE v). (?callStack::GHC.Stack.Types.CallStack) => [Char] -> a ghci> :t error "bad" :: (forall a. a -> a) -> a error "bad" :: (forall a. a -> a) -> a :: (?callStack::GHC.Stack.Types.CallStack) => (forall a1. a1 -> a1) -> a }}} GHC is instantiating the type variable `a` in the output with `(forall a. a -> a) -> a`, which requires impredicative polymorphism. So this example should actually be rejected by the type checker. Note that GHC also does this with open-kinded type variables, so the behavior with `error` and `undefined` has been around for a while. There are tests that depend on it, and a Note that describes the decision to accept these programs. Still, Simon PJ says perhaps we should really just reject these programs. So here's a ticket to discuss the matter. For more information, see the discussion starting at https://phabricator.haskell.org/D1739#51408. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11431> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11450: Associated types at wrong type in instance
by GHC 14 Mar '17

14 Mar '17

#11450: Associated types at wrong type in instance -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Consider {{{ class C x where type T x instance C (Either a b) where type T (Either b a) = b -> a }}} This is bogus, because the equation for `T` has the parameters to `Either` reversed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11450> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8255: GC Less Operation
by GHC 08 Mar '17

08 Mar '17

#8255: GC Less Operation ------------------------------+-------------------------------------------- Reporter: sirinath | Owner: Type: feature | Status: new request | Milestone: Priority: highest | Version: 7.6.3 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime performance bug Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: Unknown | Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- Hi, Is it possible to eliminated GC through Automatic Reference Counting (ARC) like in Objective C / Clang. S -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8255> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10712: Regression: make TEST=exceptionsrun001 WAY=optasm is failing
by GHC 07 Mar '17

07 Mar '17

#10712: Regression: make TEST=exceptionsrun001 WAY=optasm is failing -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: high | Milestone: 7.12.1 Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: base/tests/exceptionsrun001 | Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- The following program, extracted from the test exceptionsrun001, should exit with exitcode 100. Instead, when compiled with `-O1`, it never gets past the ioTest and somehow manages to exit with exitcode 0. {{{ {-# LANGUAGE ScopedTypeVariables #-} module Main where import Control.Exception import System.IO.Error import System.Exit main = do ioTest exitWith (ExitFailure 100) ioTest :: IO () ioTest = (catch (ioError (userError "wibble")) (\(e::IOException) -> return ()) }}} I think this will require a git bisect: * last known good commit: 34bb4605d4ec5b131df57ca4c91d6840b7539194 * first known bad commit: f83aab95f59ae9b29f22fc7924e050512229cb9c. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10712> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11006: Warning: Glomming in Main
by GHC 07 Mar '17

07 Mar '17

#11006: Warning: Glomming in Main -------------------------------------+------------------------------------- Reporter: ezyang | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 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: -------------------------------------+------------------------------------- The Travis build bot is reporting a test failure with debugging on, relating to glomming: {{{ Actual stderr output differs from expected: --- /dev/null 2015-01-28 16:31:58.000000000 +0000 +++ ./lib/integer/integerConstantFolding.run.stderr.normalised 2015-10-22 20:31:03.287376925 +0000 @@ -0,0 +1,2 @@ +WARNING: file compiler/simplCore/OccurAnal.hs, line 66 + Glomming in Main: [s3k0 :->, s3kc :->, s3kq :->, s3kr :->] \ No newline at end of file *** unexpected failure for integerConstantFolding(normal) }}} Full log https://s3.amazonaws.com/archive.travis- ci.org/jobs/86899099/log.txt -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11006> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11076: Demand information of foreign calls is wrong
by GHC 06 Mar '17

06 Mar '17

#11076: Demand information of foreign calls is wrong -------------------------------------+------------------------------------- Reporter: luite | 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: -------------------------------------+------------------------------------- Foreign calls of all types (including prim calls) use `mkFCallId` to create a fresh `Id` for each one. This Id claims to be strict in all arguments, which is not correct for foreign calls that allow lifted types to be passed. This also causes some trouble for GHCJS. I hope to get a fix in 7.10.3. Can we leave the strictness sig out entirely perhaps? Most arguments would be trivially strict since they're unboxed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11076> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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