December 2015 - ghc-tickets

[GHC] #11049: Allow CallStacks to be hidden or cut
by GHC 07 Jan '16

07 Jan '16

#11049: Allow CallStacks to be hidden or cut -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: feature | Status: new request | 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: #11035 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is a spin off of #11035. I’d like to see a way for a function `foo` * use another function `bar` with a `(?_::CallStack)` constraint so that `bar` will _not_ print a call stack, and * use another function `bar` with a `(?_::CallStack)` constraint so that if `bar` prints a call stack, it will stop at the call to `foo`. This might be possible to implement with a special `rootCallStack :: CallStack` which is a value such that {{{ x `pushCallStack` rootCallStack = rootCallStack }}} but {{{ rootCallStack `pushCallStack` x = rootCallStack “:” x }}} as before and a call stack that consists of only a rootCallStack causes no stack trace to be printed. The use case is to provide the user of a library less cluttered call stacks that do not expose unhelpful details and allow her to quickly spot the relevant information. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11049> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10464: ghc 7.8.4 on arm
by GHC 07 Jan '16

07 Jan '16

#10464: ghc 7.8.4 on arm -------------------------------------+------------------------------------- Reporter: | Owner: andrewufrank | Status: new Type: bug | Milestone: Priority: normal | Version: 7.8.4 Component: Compiler | Operating System: Linux Keywords: | Type of failure: Compile-time Architecture: arm | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- when compiling i get the warning /usr/bin/d.gold: warning: cannot scan executable section 1 of ..... transformers-04.3.0a... for Cortex-A8 erratum because it has no mapping symbols. there are some informations on the web on the cortex-a8 erratum, but i cannot see how i could apply them. should the compiler be recompiled? i installed from the debian distribution. the hardware is a cubietruck. i observe that compilation, especially the phase of preparing the configuration in cabal takes very long - perhaps this is related to this problem. the resulting code is ok and runs with expected speed. thank you for producing a full ghc for arm! andrew -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10464> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10625: Spurious unused quantified type variable warning with ExistentialQuantification
by GHC 07 Jan '16

07 Jan '16

#10625: Spurious unused quantified type variable warning with ExistentialQuantification -------------------------------------+------------------------------------- Reporter: | Owner: RyanGlScott | Status: new Type: bug | Milestone: Priority: normal | Version: 7.10.1 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: Incorrect Architecture: | warning at compile-time Unknown/Multiple | Blocked By: Test Case: | Related Tickets: #5331 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When using an existentially quantified type variable that shadows another variable in a data declaration, {{{-Wall}}} produces more warnings than necessary: {{{ $ ghci -XExistentialQuantification -Wall GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help λ> data Ex a = forall a. Ex a <interactive>:2:20: Warning: Unused quantified type variable ‘a’ In the definition of data constructor ‘Ex’ <interactive>:2:20: Warning: This binding for ‘a’ shadows the existing binding bound at <interactive>:2:9 }}} The unused quantified type variable warning seems wrong, since it ''is'' being used (as the shadowing warning indicates). Curiously, this warning doesn't seem to appear when doing something similar with {{{RankNTypes}}}: {{{ $ ghci -XRankNTypes -Wall GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help λ> data Ex a = Ex (forall a. a) <interactive>:2:24: Warning: This binding for ‘a’ shadows the existing binding bound at <interactive>:2:9 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10625> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10728: Add e.g. "-N<=4" in addition to the fixed "-N4" and variable "-N" RTS options
by GHC 05 Jan '16

05 Jan '16

#10728: Add e.g. "-N<=4" in addition to the fixed "-N4" and variable "-N" RTS options -------------------------------------+------------------------------------- Reporter: rrnewton | Owner: simonmar Type: feature | Status: new request | Priority: normal | Milestone: Component: Runtime | Version: 7.10.2 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- As discussed in this issue: https://github.com/commercialhaskell/stack/issues/680 stack is one example of a program that optimistically turned on "-N". Indeed, it feels like a reasonable and even safe option for a multithreaded program. Unfortunately, -N currently guarantees bad performance on large machines and especially on large machines with hyperthreading. Pretty much one should ship an executable with -N by default as of GHC 7.8 and 7.10 IMHO. Unfortunately, even if stack did get a speedup at, say, 4 or 8 cores, it would not be good to ship it with "-N8" either. This would be an unreasonable choice on small, one or two core machines. What we need is a way to say that the program can productively use parallelism up to a certain upper bound, but that fewer threads should be used if there are not enough cores available. I propose "-N<=8" as a potential syntax. Currently, this behavior can be achieved with `setNumCapabilities`/`getNumProcessors`, but I think it's worth a command line RTS option. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10728> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8560: undeducable Typeable error with data kinds when deriving Data for GADT in GHC version 7.7.20131122
by GHC 05 Jan '16

05 Jan '16

#8560: undeducable Typeable error with data kinds when deriving Data for GADT in GHC version 7.7.20131122 ------------------------------------+------------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- This may be an artifact of issue #8128 (see https://ghc.haskell.org/trac/ghc/ticket/8128#comment:5) but I'm seeing examples involving data kinds where Typeable isn't deducible. This could be an artifact of other problems, BUT since with 7.7 onwards, we have baked in polykinded Typeable, things should always "just work™" right? the error with current head is as follows (and i'm attaching the code + current finger print too) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8560> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9968: DeriveAnyClass fails on multi-parameter type classes
by GHC 05 Jan '16

05 Jan '16

#9968: DeriveAnyClass fails on multi-parameter type classes -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.10.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When I say {{{ {-# LANGUAGE DeriveAnyClass, MultiParamTypeClasses #-} module Bug where class C a b data X deriving (C Int) }}} and load that into GHCi, I see this: {{{ *Main> :load "/Users/rae/temp/DeriveAny.hs" [1 of 1] Compiling Bug ( /Users/rae/temp/DeriveAny.hs, interpreted ) Var/Type length mismatch: [b_a2YW] [] Var/Type length mismatch: [b_a2YW] [] Ok, modules loaded: Bug. *Bug> :info C class C a b -- Defined at /Users/rae/temp/DeriveAny.hs:5:1 instance C X -- Defined at /Users/rae/temp/DeriveAny.hs:7:13 }}} It seems my `Int` parameter to `C` is being dropped. I don't believe I have a debug build in this example, so that debugging output is shipping. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9968> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10487: Unhelpful error from instance Generic
by GHC 05 Jan '16

05 Jan '16

#10487: Unhelpful error from instance Generic -------------------------------------+------------------------------------- Reporter: | Owner: andreas.abel | Status: new Type: bug | Milestone: Priority: normal | Version: 7.10.1 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- That's the error you like too see, or rather not. ;( {{{ [180 of 289] Compiling Agda.TypeChecking.Serialise ( src/full/Agda/TypeChecking/Serialise.hs, dist-2.4.2.4/build/Agda/TypeChecking/Serialise.o ) src/full/Agda/TypeChecking/Serialise.hs:1:1: Duplicate instance declarations: instance GHC.Generics.Datatype Agda.TypeChecking.Serialise.D1Name -- Defined at src/full/Agda/TypeChecking/Serialise.hs:1:1 instance GHC.Generics.Datatype Agda.TypeChecking.Serialise.D1Name -- Defined at src/full/Agda/TypeChecking/Serialise.hs:1:1 src/full/Agda/TypeChecking/Serialise.hs:1:1: Duplicate instance declarations: instance GHC.Generics.Constructor Agda.TypeChecking.Serialise.C1_0Name -- Defined at src/full/Agda/TypeChecking/Serialise.hs:1:1 instance GHC.Generics.Constructor Agda.TypeChecking.Serialise.C1_0Name -- Defined at src/full/Agda/TypeChecking/Serialise.hs:1:1 }}} Problems: * no position in file * system generated names D1Name, C1_0Name * obvious bogus (same instance cannot be defined twice at same location) * leads me to suspect bug in Generics rather than in my code Reproduce: * git clone agda/agda from github, * checkout this commit https://github.com/agda/agda/commit/46823536559276807639488eae151a0e855fdb95 * and try to compile with {{{ make install-bin }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10487> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10716: Metadata in GHC.Generic should give access to strictness annotation
by GHC 05 Jan '16

05 Jan '16

#10716: Metadata in GHC.Generic should give access to strictness annotation -------------------------------------+------------------------------------- Reporter: StefanWehr | Owner: Type: feature | Status: new request | 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 Revisions: | -------------------------------------+------------------------------------- Currently, the metadata in the GHC.Generics module do not give access to the strictness annotations attached to a field of a datatype. It would be great if this piece of information could be added. Background: we are using a class FullyStrict for ensuring that a datatype is fully strict (in the sense that all fields have bang patterns and the types of all fields are also fully strict). Currently we are using TemplateHaskell to derive the instances automatically. The TemplateHaskell function also checks that all fields have bang patterns. To improve compilation speed, I would like to derive the instances with DeriveGeneric. But this is not possible because then I cannot implement the check whether all fields have bang patterns. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10716> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10579: full module names of names not in scope have gone missing in ghci
by GHC 05 Jan '16

05 Jan '16

#10579: full module names of names not in scope have gone missing in ghci -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | 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: | -------------------------------------+------------------------------------- Compare {{{ rwbarton@morphism:/tmp$ ghci-7.10.1 GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help Prelude> :t GHC.Read.readPrec GHC.Read.readPrec :: Read a => Text.ParserCombinators.ReadPrec.ReadPrec a }}} with {{{ rwbarton@morphism:/tmp$ ~/ghc/inplace/bin/ghc-stage2 --interactive GHCi, version 7.11.20150624: http://www.haskell.org/ghc/ :? for help Prelude> :t GHC.Read.readPrec GHC.Read.readPrec :: Read a => ReadPrec a }}} The `Text.ParserCombinators.ReadPrec.` bit can be quite helpful, was it suppressed intentionally? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10579> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11173: Infix declarations for record fields with DuplicateRecordFields are broken
by GHC 05 Jan '16

05 Jan '16

#11173: Infix declarations for record fields with DuplicateRecordFields are broken -------------------------------------+------------------------------------- Reporter: kanetw | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following program compiles fine {{{#!hs module Good where newtype A = A { foo :: Int } infixl 5 `foo` }}} but this one doesn't {{{#!hs {-# LANGUAGE DuplicateRecordFields #-} module Bad where newtype A = A { foo :: Int } infixl 5 `foo` }}} giving an error {{{ The fixity signature for ‘foo’ lacks an accompanying binding (The fixity signature must be given where ‘foo’ is declared) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11173> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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