July 2018 - ghc-tickets

[GHC] #15374: Testsuite: compile_timeout_multiplier is fragile
by GHC 15 Jul '18

15 Jul '18

#15374: Testsuite: compile_timeout_multiplier is fragile -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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: -------------------------------------+------------------------------------- I'm taking a sweep through the testsuite, trying to eliminate failures in a `DEBUG` compiler. But two tests are stymieing me: `pmcheck/should_compile/T11{276,374}`. Both of these use the `compile_timout_multiplier` option in their `all.T` entries. This option means that, instead of the normal 300s allotted to the test, these tests get only 3s. In my setup, with a `DEBUG` (read: unoptimized) stage2 compiler, these tests fail when I'm running the testsuite in parallel. Then, when I run the tests individually, they succeed. This poses two problems: 1. I can only see the failure when my machine is stressed, and it's disconcerting to have a failure appear and disappear depending on how I look. 2. There is (sometimes) a failure in `DEBUG` mode. What is the goal of `compile_timeout_multiplier`? If we're really testing performance (which #11276 and #11374 indicate), then these tests should be in `perf/compiler` and be "stat" tests, where some wibbling in the numbers is expected (and where `DEBUG` compilers are exempted). I would imagine that `compile_timeout_multiplier` should only ever get values greater than 1, when a non-performance test is so expensive to run that it takes more than 300s. As a local solution here, I think these two tests should move to `perf/compiler`. Other pattern-match tests also have `compile_timeout_multiplier`, too, and I can move these as well. Any objections? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15374> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14525: Backpack doesn't work with CPP
by GHC 15 Jul '18

15 Jul '18

#14525: Backpack doesn't work with CPP -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Steps to repro: 1. Create a package with a signature and a module which imports it 2. Add `{-# LANGUAGE CPP #-}` to the module Expected result: it works Actual result: {{{ <command line>: unknown package: hole }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14525> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15378: Use TcLevels to decide about floating out of implications
by GHC 15 Jul '18

15 Jul '18

#15378: Use TcLevels to decide about floating out of implications -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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: -------------------------------------+------------------------------------- If we have an implication constraint `forall[3] sk[3]. [W] alpha[2] ~ Maybe b[2]`, GHC ''floats'' the constraint out of the implication. This is necessary to solve this particular wanted, because the implication is at level 3, while the unification variable `alpha` is at level 2; the variable is thus untouchable in the implication. Right now, computing which constraints can float out is done by looking at the free variables of the constraint and comparing against the set of skolem variables bound in the implication, like `sk[3]`, above (among a few other places). However, there is a much easier way: just use the levels. We can look at the Wanted and determine that it can float out because the maximum level in the wanted is a 2, and the implication is level 3. Thus, this ticket is to track that refactoring: use levels, not free variables, in determining what to float out of an implication. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15378> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15142: GHC HEAD regression: tcTyVarDetails
by GHC 15 Jul '18

15 Jul '18

#15142: GHC HEAD regression: tcTyVarDetails -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.5 (Type checker) | Keywords: TypeInType, | Operating System: Unknown/Multiple TypeFamilies | Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This regression prevents the `generic-lens` library from building. Here is a minimized test case: {{{#!hs {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} module Bug where import Data.Kind class ListTuple (tuple :: Type) (as :: [(k, Type)]) where type ListToTuple as :: Type }}} On GHC 8.4.2, this compiles, but on GHC HEAD, it panics: {{{ $ ~/Software/ghc/inplace/bin/ghc-stage2 Bug.hs[1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.5.20180511 for x86_64-unknown-linux): tcTyVarDetails co_aWx :: (k_aWt[tau:2] :: *) ~# (* :: *) Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1162:37 in ghc:Outputable pprPanic, called at compiler/basicTypes/Var.hs:497:22 in ghc:Var }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15142> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15376: GHC determine illegal kind for standalone deriving with Deriving via
by GHC 14 Jul '18

14 Jul '18

#15376: GHC determine illegal kind for standalone deriving with Deriving via -------------------------------------+------------------------------------- Reporter: | Owner: (none) mizunashi_mana | Type: bug | Status: new Priority: normal | Milestone: 8.6.1 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: -------------------------------------+------------------------------------- Happy to release GHC 8.6.1-alpha1! I used it to test new extensions, and then I met below errors: {{{ $ ghci-8.6.0.20180627 GHCi, version 8.6.0.20180627: http://www.haskell.org/ghc/ :? for help Prelude> :set -XDerivingVia -XStandaloneDeriving Prelude> newtype FunctorWrapped f a = FunctorWrapped (f a) Prelude> deriving via f instance Functor f => Functor (FunctorWrapped f) <interactive>:3:33: error: • Expected kind ‘* -> *’, but ‘f’ has kind ‘*’ • In the first argument of ‘Functor’, namely ‘f’ In the stand-alone deriving instance for ‘Functor f => Functor (FunctorWrapped f)’ <interactive>:3:62: error: • Expected kind ‘* -> *’, but ‘f’ has kind ‘*’ • In the first argument of ‘FunctorWrapped’, namely ‘f’ In the first argument of ‘Functor’, namely ‘(FunctorWrapped f)’ In the stand-alone deriving instance for ‘Functor f => Functor (FunctorWrapped f)’ }}} However, {{{ newtype FunctorWrapped f a = FunctorWrapped (f a) deriving Functor via f }}} is passed through on GHC 8.6.1-alpha1. Is this a bug or my misunderstand? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15376> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15377: Cut an STM release
by GHC 14 Jul '18

14 Jul '18

#15377: Cut an STM release -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: libraries/stm | Version: 8.4.3 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: -------------------------------------+------------------------------------- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15377> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15375: GHC.Exts.Heap.getClosureData doesn't return the payload for AP_STACK
by GHC 13 Jul '18

13 Jul '18

#15375: GHC.Exts.Heap.getClosureData doesn't return the payload for AP_STACK -------------------------------------+------------------------------------- Reporter: simonmar | Owner: (none) Type: bug | Status: new Priority: low | Milestone: 8.6.1 Component: Runtime | Version: 8.4.3 System | 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: -------------------------------------+------------------------------------- See Phab:D4955 We used to return the payload, but a stack is a mixture of pointers and non-pointers, so this was bogus. In Phab:D4955 I changed it to ignore the payload, so now at least it doesn't crash, but we don't have any payload info. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15375> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7836: "Invalid object in processHeapClosureForDead" when profiling with -hb
by GHC 13 Jul '18

13 Jul '18

#7836: "Invalid object in processHeapClosureForDead" when profiling with -hb -------------------------------------+------------------------------------- Reporter: hyperthunk | Owner: (none) Type: bug | Status: merge Priority: normal | Milestone: Component: Profiling | Version: 8.5 Resolution: | Keywords: profiling Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #15063, #15087, | Differential Rev(s): Phab:D4928 #15165 | Wiki Page: | -------------------------------------+------------------------------------- Changes (by osa1): * status: patch => merge -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7836#comment:31> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7836: "Invalid object in processHeapClosureForDead" when profiling with -hb
by GHC 13 Jul '18

13 Jul '18

#7836: "Invalid object in processHeapClosureForDead" when profiling with -hb -------------------------------------+------------------------------------- Reporter: hyperthunk | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Profiling | Version: 8.5 Resolution: | Keywords: profiling Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #15063, #15087, | Differential Rev(s): Phab:D4928 #15165 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ömer Sinan Ağacan <omeragacan@…>): In [changeset:"2625f1310edeff62eb3876cc6efbe105a80fe4ad/ghc" 2625f131/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="2625f1310edeff62eb3876cc6efbe105a80fe4ad" Fix processHeapClosureForDead CONSTR_NOCAF case CONSTR_NOCAF was introduced with 55d535da10d as a replacement for CONSTR_STATIC and CONSTR_NOCAF_STATIC, however, as explained in Note [static constructors], we copy CONSTR_NOCAFs (which can also be seen in evacuate) during GC, and they can become dead, like other CONSTR_X_Ys. processHeapClosureForDead is updated to reflect this. Test Plan: Validates on x86_64. Existing failures on i386. Reviewers: simonmar, bgamari, erikd Reviewed By: simonmar, bgamari Subscribers: rwbarton, thomie, carter GHC Trac Issues: #7836, #15063, #15087, #15165 Differential Revision: https://phabricator.haskell.org/D4928 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7836#comment:30> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15355: Functional dependencies can get GHC to print "UnkSkol"
by GHC 13 Jul '18

13 Jul '18

#15355: Functional dependencies can get GHC to print "UnkSkol" -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple FunctionalDependencies | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When I say {{{#!hs class C a b | a -> b where foo :: a -> b instance C Int Bool where foo = (>0) blah :: C Int Double => Int -> _a blah = foo }}} I get {{{ • Couldn't match type ‘Double’ with ‘Bool’ arising from a functional dependency between constraints: ‘C Int Bool’ arising from a use of ‘foo’ at Scratch.hs:51:8-10 ‘C Int Double’ arising from UnkSkol at Scratch.hs:51:1-10 • In the expression: foo In an equation for ‘blah’: blah = foo }}} There are actually two problems: 1. If we replace `_a` with `Double`, GHC accepts the program. I'm not sure it should. But that's a larger problem than... 2. ... when it prints the error, it says `UnkSkol`. It probably shouldn't. This ticket is about the second problem, because the first one require more fundep love than is usually on offer around here. Erroring here is reasonable enoug -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15355> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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