October 2017 - ghc-tickets

[GHC] #14307: Nonexistent constructor name + NamedFieldPuns + DuplicateRecordFields can cause ambiguous occurrence message
by GHC 11 Oct '17

11 Oct '17

#14307: Nonexistent constructor name + NamedFieldPuns + DuplicateRecordFields can cause ambiguous occurrence message -------------------------------------+------------------------------------- Reporter: mgsloan | Owner: (none) Type: feature | Status: new request | Priority: low | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- This is a minor issue with error message clarity. I was confused for a few minutes because in a more complicated example I did not see the out of scope error, and was instead focused on the ambiguity error. {{{ {-# LANGUAGE DuplicateRecordFields #-} {-# LANGUAGE NamedFieldPuns #-} data A = A { field :: Int } data B = B { field :: Int } f :: A -> Int f C { field } = field }}} yields {{{ duplicate_records_bug.hs:8:3: error: Not in scope: data constructor ‘C’ | 8 | f C { field } = field | ^ duplicate_records_bug.hs:8:7: error: Ambiguous occurrence ‘field’ It could refer to either the field ‘field’, defined at duplicate_records_bug.hs:5:14 or the field ‘field’, defined at duplicate_records_bug.hs:4:14 | 8 | f C { field } = field | ^^^^^ }}} I actually think it would make sense to allow ambiguous identifiers in field puns even if DuplicateRecordFields is not enabled. This makes sense, because for an unambiguous constructor, a particular field name is always unambiguous. So, that might be another way to frame this issue: Should ambiguous field identifiers always be allowed in puns? In particular, this would make things more consistent with RecordWildCards, which does not care if the field names shadow anything that is in scope / other field names. I realize that broadening the code allowed by NamedFieldPuns could lead to issues where code written for newer GHC versions does not work with older GHC versions. This certainly will not change the meaning of older code. What's the policy on this? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14307> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14337: typeRepKind can perform substantial amounts of allocation
by GHC 11 Oct '17

11 Oct '17

#14337: typeRepKind can perform substantial amounts of allocation -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Core | Version: 8.2.1 Libraries | Keywords: Typeable | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I came up with a (rather contrived) test case to demonstrate that Phab:D4082 reduced big-O time complexity in pathological cases. But I expected it to increase space usage by a constant factor. What I found was very much the opposite: it dramatically reduced allocation. The reason for this is obvious in hindsight. Every time we call `typeRepKind`, we recalculate the kind entirely from scratch. That recalculation is only a potential ''time'' problem for `TrApp`, because we only need to walk down links, but it's also a ''space'' problem for `TrTyCon`, because we're building up a `TypeRep` from a `KindRep`. The solution, assuming we choose to keep `typeRepKind`, seems fairly clear: whether or not we choose to cache the kind in `TrApp`, we should almost certainly do so in `TrTyCon`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14337> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 10 Oct '17

10 Oct '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: nakaji_dayo Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4083 Wiki Page: | -------------------------------------+------------------------------------- Comment (by nakaji_dayo): Replying to [comment:22 mgsloan]: I agree. I think "-Wpartial-fields" is good name. I have submitted code review about `-Wpartial-fields`.\\ On the other hand, I don't have any commit about `-Wpartial-field-usages`. > I think it also makes sense to have an option to emit warnings for partial record fields. Perhaps call it -Wpartial-field-usages? The reason this is helpful is that some libraries may export partial fields. It's still helpful as a sanity check for users of a library to have this as an optional warning. I think that this is helpful in this case too. But as far as I know, GHC doesn't have warnings for usage of partial function.\\ In case of implement this, it seems that design considering the whole is necessary.\\ Is my understanding correct? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:25> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14334: Large static object : getLabelBc: Ran out of labels
by GHC 10 Oct '17

10 Oct '17

#14334: Large static object : getLabelBc: Ran out of labels -------------------------------------+------------------------------------- Reporter: h4ck3rm1k3 | Owner: (none) Type: bug | Status: new Priority: lowest | Milestone: Component: GHCi | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: GHCi crash (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- stack ghci The following GHC options are incompatible with GHCi and have not been passed to it: -threaded Configuring GHCi with the following packages: gcc-haskell Using main module: 1. Package `gcc-haskell' component exe:gcc-haskell-exe with main-is file: /home/mdupont/experiments/g\ cc-haskell/gcc-haskell/app/Main.hs GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help [1 of 3] Compiling LibData ( LibData.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): getLabelBc: Ran out of labels Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Compiling this project file here that is basically a large data object emitted from the rdf4h lib. I wanted to put the data into static space to improve load times and remove IO. https://github.com/h4ck3rm1k3/gcc-haskell/blob/master/src/LibData.hs -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14334> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 10 Oct '17

10 Oct '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: nakaji_dayo Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4083 Wiki Page: | -------------------------------------+------------------------------------- Changes (by nakaji_dayo): * differential: D4083 => Phab:D4083 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:24> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7169: Warning for incomplete record field label used as function
by GHC 10 Oct '17

10 Oct '17

#7169: Warning for incomplete record field label used as function -------------------------------------+------------------------------------- Reporter: goldfire | Owner: nakaji_dayo Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Warnings, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): D4083 Wiki Page: | -------------------------------------+------------------------------------- Changes (by nakaji_dayo): * differential: => D4083 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7169#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 10 Oct '17

10 Oct '17

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: 12262 Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by duog): It looks like trac:14092 could lead to nondeterministic interface files when using parallel --make. Single threaded --make does not seem to be nondetermistic, though I believe it is uncomfortably sensitve to the order in which modules are compiled, which can be determined by the order they are imported or passed to ghc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:237> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14115: GHC segfaults trying to use TH code when ghc is compiled as DYNAMIC_GHC_PROGRAMS=NO
by GHC 09 Oct '17

09 Oct '17

#14115: GHC segfaults trying to use TH code when ghc is compiled as DYNAMIC_GHC_PROGRAMS=NO -------------------------------------+------------------------------------- Reporter: pacak | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When ghc 8.2.1 compiled using DYNAMIC_GHC_PROGRAMS=NO attemps at using TH results in all sorts of exciting errors: source files: {{{ % cat A.hs {-# LANGUAGE TemplateHaskell #-} module Numeric.Sum where import B b }}} this file makes little sense, but it was segfaulting when it had more code as well {{{ % cat B.hs {-# LANGUAGE TemplateHaskellQuotes #-} module B where import Language.Haskell.TH b :: DecsQ b = return [ InstanceD Nothing [] (ConT ''Show `AppT` undefined) [] ] }}} Let's try running it a few times - note illegal hardware instruction {{{ % ghc -O2 A.hs [1 of 2] Compiling B ( B.hs, B.o ) [2 of 2] Compiling Numeric.Sum ( A.hs, A.o ) zsh: segmentation fault ghc -O2 A.hs % ghc -O2 A.hs [2 of 2] Compiling Numeric.Sum ( A.hs, A.o ) zsh: segmentation fault ghc -O2 A.hs % ghc -O2 A.hs [2 of 2] Compiling Numeric.Sum ( A.hs, A.o ) zsh: illegal hardware instruction ghc -O2 A.hs % ghc -O2 A.hs [2 of 2] Compiling Numeric.Sum ( A.hs, A.o ) zsh: segmentation fault ghc -O2 A.hs }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14115> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4017: Unhelpful error message in GHCi
by GHC 08 Oct '17

08 Oct '17

#4017: Unhelpful error message in GHCi -------------------------------------+------------------------------------- Reporter: simonpj | Owner: supersven Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by supersven): Looks like things (or symptoms) changed a bit over time - The problem seems to be the same. Starting a current version of GHC in interactive mode: {{{ [nix-shell:~/src/ghc]$ inplace/bin/ghc-stage2 --interactive GHCi, version 8.3.20170930: http://www.haskell.org/ghc/ :? for help }}} `:i GHC.Integer.Type.Integer` now responds with a "Not in scope" error. `:i Integer` still shows that `GHC.Integer.Type.Integer` is reachable: {{{ Prelude> :i GHC.Integer.Type.Integer <interactive>:1:1: error: Not in scope: ‘GHC.Integer.Type.Integer’ Prelude> :i Integer data Integer = integer-gmp-1.0.1.0:GHC.Integer.Type.S# GHC.Prim.Int# | integer-gmp-1.0.1.0:GHC.Integer.Type.Jp# {-# UNPACK #-}integer- gmp-1.0.1.0:GHC.Integer.Type.BigNat | integer-gmp-1.0.1.0:GHC.Integer.Type.Jn# {-# UNPACK #-}integer- gmp-1.0.1.0:GHC.Integer.Type.BigNat -- Defined in ‘integer-gmp-1.0.1.0:GHC.Integer.Type’ instance Eq Integer -- Defined in ‘integer-gmp-1.0.1.0:GHC.Integer.Type’ instance Ord Integer -- Defined in ‘integer-gmp-1.0.1.0:GHC.Integer.Type’ instance Show Integer -- Defined in ‘GHC.Show’ instance Read Integer -- Defined in ‘GHC.Read’ instance Enum Integer -- Defined in ‘GHC.Enum’ instance Num Integer -- Defined in ‘GHC.Num’ instance Real Integer -- Defined in ‘GHC.Real’ instance Integral Integer -- Defined in ‘GHC.Real’ }}} Setting the "integer-gmp" package doesn't change the situation: {{{ Prelude> :set -package integer-gmp package flags have changed, resetting and loading new packages... Prelude> :i Integer data Integer = integer-gmp-1.0.1.0:GHC.Integer.Type.S# GHC.Prim.Int# | integer-gmp-1.0.1.0:GHC.Integer.Type.Jp# {-# UNPACK #-}integer- gmp-1.0.1.0:GHC.Integer.Type.BigNat | integer-gmp-1.0.1.0:GHC.Integer.Type.Jn# {-# UNPACK #-}integer- gmp-1.0.1.0:GHC.Integer.Type.BigNat -- Defined in ‘integer-gmp-1.0.1.0:GHC.Integer.Type’ instance Eq Integer -- Defined in ‘integer-gmp-1.0.1.0:GHC.Integer.Type’ instance Ord Integer -- Defined in ‘integer-gmp-1.0.1.0:GHC.Integer.Type’ instance Show Integer -- Defined in ‘GHC.Show’ instance Read Integer -- Defined in ‘GHC.Read’ instance Enum Integer -- Defined in ‘GHC.Enum’ instance Num Integer -- Defined in ‘GHC.Num’ instance Real Integer -- Defined in ‘GHC.Real’ instance Integral Integer -- Defined in ‘GHC.Real’ Prelude> :i GHC.Integer.Type.Integer <interactive>:1:1: error: Not in scope: ‘GHC.Integer.Type.Integer’ }}} `GHC.Integer.Type` is still a hidden module: {{{ Prelude> import GHC.Integer.Type <no location info>: error: Could not find module ‘GHC.Integer.Type’ it is a hidden module in the package ‘integer-gmp-1.0.1.0’ }}} === Summary === The error message of `:i GHC.Integer.Type.Integer` changed to "Not in scope". But `:i Integer` still shows that the requested information would be available. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4017#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4017: Unhelpful error message in GHCi
by GHC 08 Oct '17

08 Oct '17

#4017: Unhelpful error message in GHCi -------------------------------------+------------------------------------- Reporter: simonpj | Owner: supersven Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by supersven): * owner: (none) => supersven -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4017#comment:14> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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