December 2018 - ghc-tickets

[GHC] #15381: Write documentation for iserv-proxy
by GHC 19 Jan '19

19 Jan '19

#15381: Write documentation for iserv-proxy -------------------------------------+------------------------------------- Reporter: bgamari | 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: -------------------------------------+------------------------------------- We merged `iserv-proxy` but it doesn't yet have users guide documentation. We should fix this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15381> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 1

[GHC] #15916: GHC doesn't build on powerpc64 architecture on systems other than GNU / Linux
by GHC 18 Jan '19

18 Jan '19

#15916: GHC doesn't build on powerpc64 architecture on systems other than GNU / Linux ---------------------------------+---------------------------------------- Reporter: pkubaj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Research needed Component: Compiler | Version: 8.6.2 Keywords: | Operating System: Unknown/Multiple Architecture: powerpc64 | Type of failure: Building GHC failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ---------------------------------+---------------------------------------- I'd like to bootstrap GHC for FreeBSD/powerpc64, but GHC seems to be supported only on Linux for powerpc64 architecture. Relevant code: https://github.com/ghc/ghc/blob/1c2c2d3dfd4c36884b22163872feb87122b4528d/rt… https://github.com/ghc/ghc/blob/1c2c2d3dfd4c36884b22163872feb87122b4528d/rt… -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15916> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 46

[GHC] #16078: Hide -Weverything warnings for GHCi internals
by GHC 18 Jan '19

18 Jan '19

#16078: Hide -Weverything warnings for GHCi internals -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.6.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider Bar.hs {{{ module Bar where }}} Main.hs {{{ import Bar main :: IO () main = print "" }}} `stack ghci Main.hs --ghc-options -Weverything` produces {{{ ... GHCi, version 8.6.2: http://www.haskell.org/ghc/ :? for help <interactive>:1:1: warning: [-Wmissing-local-signatures] Polymorphic local binding with no type signature: _compileParsedExpr :: forall a. GHC.Types.IO a -> GHC.Types.IO a <interactive>:1:1: warning: [-Wmissing-import-lists] The module `Prelude' does not have an explicit import list Loaded GHCi configuration from C:\Users\ericcro\Desktop\VPC-Key- Distribution\src\.ghci <no location info>: warning: [-Wmissing-home-modules] Modules are not listed in command line but needed for compilation: Bar [1 of 2] Compiling Bar ( Bar.hs, interpreted ) ... }}} Those three errors have nothing to do with my code, and seem to be related to the internals of how GHCi works. It would be nice to hide all three. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16078> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 4

[GHC] #15717: Performance regression in for_ alternatives from GHC 8.2.2 to newer GHCs
by GHC 18 Jan '19

18 Jan '19

#15717: Performance regression in for_ alternatives from GHC 8.2.2 to newer GHCs -------------------------------------+------------------------------------- Reporter: nh2 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Keywords: | 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: -------------------------------------+------------------------------------- We are investigating various ways to make `for_` and `traverse_` not leak space by changing the type signature from `(a -> f b) -> t a -> f ()` to `(a -> f ()) -> t a -> f ()`. While doing so, we noticed a regression from GHC 8.2.2 to 8.4.3 and 8.6.1. The code: https://gist.github.com/nh2/b8f9f8e60443bdb30c1cd7e0acb8c8eb/bb1cc1a4987091… Run against 3 different GHC releases: {{{ # 8.2.2 stack --resolver lts-11.22 ghc -- --make -O2 -rtsopts ./TraverseMaybePerformance.hs && /usr/bin/time ./TraverseMaybePerformance 8 +RTS -sstderr 460,309,368 bytes allocated in the heap # 8.4.3 stack --resolver lts-12.11 ghc -- --make -O2 -rtsopts ./TraverseMaybePerformance.hs && /usr/bin/time ./TraverseMaybePerformance 8 +RTS -sstderr 860,301,736 bytes allocated in the heap # 8.6.1 stack --resolver nightly-2018-10-06 ghc -- --make -O2 -rtsopts ./TraverseMaybePerformance.hs && /usr/bin/time ./TraverseMaybePerformance 8 +RTS -sstderr 860,301,784 bytes allocated in the heap }}} Allocations doubled starting with 8.4. All was run on Ubuntu 16.04 64-bit. We haven't investigated in detail yet (also whether it's a GHC or libraries problem) since we're actually trying to do something else and this came out on the side, but it looks important enough to share already. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15717> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 7

[GHC] #16017: ghc-8.6.1 and ghc-8.6.2 use a log of memory
by GHC 18 Jan '19

18 Jan '19

#16017: ghc-8.6.1 and ghc-8.6.2 use a log of memory -------------------------------------+------------------------------------- Reporter: newhoggy | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.2 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: -------------------------------------+------------------------------------- Currently GHC uses a lot of memory to build a relatively small module and causes my CI to fail due to there being a 4G memory limit. The source code can be found here: https://github.com/haskell-works/hw- json/tree/73368cee21dc72eedd5291ba689f9abf10e7fcd2 The problem module is here: https://github.com/haskell-works/hw- json/blob/73368cee21dc72eedd5291ba689f9abf10e7fcd2/test/HaskellWorks/Data/Json/Backend/Standard/Succinct/CursorSpec.hs The build output follows: {{{ cabal new-build --enable-tests --enable-benchmarks --project- file="cabal.project" -j${CABAL_THREADS:-4} all Build profile: -w ghc-8.6.2 -O2 In order, the following will be built (use -v for more details): - hw-json-0.9.0.1 (lib) (first run) - hw-json-0.9.0.1 (test:hw-json-test) (first run) - hw-json-0.9.0.1 (exe:hw-json) (first run) - hw-json-0.9.0.1 (bench:bench) (first run) Configuring library for hw-json-0.9.0.1.. Preprocessing library for hw-json-0.9.0.1.. Building library for hw-json-0.9.0.1.. [ 1 of 32] Compiling HaskellWorks.Data.Json.DecodeError ( src/HaskellWorks/Data/Json/DecodeError.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/DecodeError.o ) [ 2 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.MakeIndex ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/MakeIndex.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/MakeIndex.o ) [ 3 of 32] Compiling HaskellWorks.Data.Json.Internal.Index ( src/HaskellWorks/Data/Json/Internal/Index.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Index.o ) [ 4 of 32] Compiling HaskellWorks.Data.Json.Internal.PartialIndex ( src/HaskellWorks/Data/Json/Internal/PartialIndex.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/PartialIndex.o ) [ 5 of 32] Compiling HaskellWorks.Data.Json.Internal.Token.Types ( src/HaskellWorks/Data/Json/Internal/Token/Types.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Token/Types.o ) [ 6 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.Token.Tokenize ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/Token/Tokenize.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/Token/Tokenize.o ) [ 7 of 32] Compiling HaskellWorks.Data.Json.Internal.Token ( src/HaskellWorks/Data/Json/Internal/Token.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Token.o ) [ 8 of 32] Compiling HaskellWorks.Data.Json.Internal.Value ( src/HaskellWorks/Data/Json/Internal/Value.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Value.o ) [ 9 of 32] Compiling HaskellWorks.Data.Json.Internal.Word8 ( src/HaskellWorks/Data/Json/Internal/Word8.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Word8.o ) [10 of 32] Compiling HaskellWorks.Data.Json.Internal.Word64 ( src/HaskellWorks/Data/Json/Internal/Word64.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Word64.o ) [11 of 32] Compiling HaskellWorks.Data.Json.Internal.CharLike ( src/HaskellWorks/Data/Json/Internal/CharLike.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/CharLike.o ) [12 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.Blank ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/Blank.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/Blank.o ) [13 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.BlankedJson ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/BlankedJson.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/BlankedJson.o ) [14 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.ToInterestBits64 ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/ToInterestBits64.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/ToInterestBits64.o ) [15 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.ToBalancedParens64 ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/ToBalancedParens64.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/ToBalancedParens64.o ) [16 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.IbBp ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/IbBp.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/IbBp.o ) [17 of 32] Compiling HaskellWorks.Data.Json.Backend.Standard.SemiIndex ( src/HaskellWorks/Data/Json/Backend/Standard/SemiIndex.hs, /root/project /dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Backend/Standard/SemiIndex.o ) [18 of 32] Compiling HaskellWorks.Data.Json.Backend.Simple.SemiIndex ( src/HaskellWorks/Data/Json/Backend/Simple/SemiIndex.hs, /root/project /dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Backend/Simple/SemiIndex.o ) [19 of 32] Compiling HaskellWorks.Data.Json.LightJson ( src/HaskellWorks/Data/Json/LightJson.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/LightJson.o ) [20 of 32] Compiling HaskellWorks.Data.Json.PartialValue ( src/HaskellWorks/Data/Json/PartialValue.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/PartialValue.o ) [21 of 32] Compiling HaskellWorks.Data.Json.Type ( src/HaskellWorks/Data/Json/Type.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Type.o ) [22 of 32] Compiling HaskellWorks.Data.Json.Backend.Standard.Cursor ( src/HaskellWorks/Data/Json/Backend/Standard/Cursor.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Backend/Standard/Cursor.o ) [23 of 32] Compiling HaskellWorks.Data.Json.Cursor ( src/HaskellWorks/Data/Json/Cursor.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Cursor.o ) [24 of 32] Compiling HaskellWorks.Data.Json.Internal.Backend.Standard.Cursor.Token ( src/HaskellWorks/Data/Json/Internal/Backend/Standard/Cursor/Token.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Internal/Backend/Standard/Cursor/Token.o ) [25 of 32] Compiling HaskellWorks.Data.Json.Value ( src/HaskellWorks/Data/Json/Value.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Value.o ) [26 of 32] Compiling HaskellWorks.Data.Json.FromValue ( src/HaskellWorks/Data/Json/FromValue.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/FromValue.o ) [27 of 32] Compiling HaskellWorks.Data.Json.Backend.Standard.LoadCursor ( src/HaskellWorks/Data/Json/Backend/Standard/LoadCursor.hs, /root/project /dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Backend/Standard/LoadCursor.o ) [28 of 32] Compiling HaskellWorks.Data.Json.LoadCursor ( src/HaskellWorks/Data/Json/LoadCursor.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/LoadCursor.o ) [29 of 32] Compiling HaskellWorks.Data.Json.Backend.Standard.Load ( src/HaskellWorks/Data/Json/Backend/Standard/Load.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Backend/Standard/Load.o ) [30 of 32] Compiling HaskellWorks.Data.Json.Load ( src/HaskellWorks/Data/Json/Load.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json/Load.o ) [31 of 32] Compiling HaskellWorks.Data.Json ( src/HaskellWorks/Data/Json.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/HaskellWorks/Data/Json.o ) [32 of 32] Compiling Paths_hw_json ( /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/autogen/Paths_hw_json.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/opt/build/Paths_hw_json.o ) Configuring test suite 'hw-json-test' for hw-json-0.9.0.1.. Configuring benchmark 'bench' for hw-json-0.9.0.1.. Configuring executable 'hw-json' for hw-json-0.9.0.1.. Preprocessing test suite 'hw-json-test' for hw-json-0.9.0.1.. Building test suite 'hw-json-test' for hw-json-0.9.0.1.. Preprocessing executable 'hw-json' for hw-json-0.9.0.1.. Preprocessing benchmark 'bench' for hw-json-0.9.0.1.. Building benchmark 'bench' for hw-json-0.9.0.1.. Building executable 'hw-json' for hw-json-0.9.0.1.. [ 1 of 11] Compiling HaskellWorks.Data.Json.Backend.Standard.Succinct.Cursor.InterestBitsSpec ( test/HaskellWorks/Data/Json/Backend/Standard/Succinct/Cursor/InterestBitsSpec.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/t /hw-json-test/opt/build/hw-json-test/hw-json-test- tmp/HaskellWorks/Data/Json/Backend/Standard/Succinct/Cursor/InterestBitsSpec.o ) [1 of 2] Compiling Main ( bench/Main.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/b/bench/opt/build/bench/bench-tmp/Main.o ) [1 of 7] Compiling App.Commands.Types ( app/App/Commands/Types.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x /hw-json/opt/build/hw-json/hw-json-tmp/App/Commands/Types.o ) [2 of 7] Compiling App.Lens ( app/App/Lens.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x/hw-json/opt/build /hw-json/hw-json-tmp/App/Lens.o ) [3 of 7] Compiling App.Commands.Demo ( app/App/Commands/Demo.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x /hw-json/opt/build/hw-json/hw-json-tmp/App/Commands/Demo.o ) [2 of 2] Compiling Paths_hw_json ( /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/b/bench/opt/build/bench/autogen/Paths_hw_json.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/b/bench/opt/build/bench/bench-tmp/Paths_hw_json.o ) Linking /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/b/bench/opt/build/bench/bench ... [4 of 7] Compiling App.Commands.CreateIndex ( app/App/Commands/CreateIndex.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x/hw-json/opt/build /hw-json/hw-json-tmp/App/Commands/CreateIndex.o ) [5 of 7] Compiling App.Commands ( app/App/Commands.hs, /root/project /dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x/hw- json/opt/build/hw-json/hw-json-tmp/App/Commands.o ) [ 2 of 11] Compiling HaskellWorks.Data.Json.Backend.Standard.Succinct.CursorSpec ( test/HaskellWorks/Data/Json/Backend/Standard/Succinct/CursorSpec.hs, /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/t /hw-json-test/opt/build/hw-json-test/hw-json-test- tmp/HaskellWorks/Data/Json/Backend/Standard/Succinct/CursorSpec.o ) [6 of 7] Compiling Main ( app/Main.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x/hw-json/opt/build /hw-json/hw-json-tmp/Main.o ) [7 of 7] Compiling Paths_hw_json ( /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x/hw-json/opt/build /hw-json/autogen/Paths_hw_json.hs, /root/project/dist- newstyle/build/x86_64-linux/ghc-8.6.2/hw-json-0.9.0.1/x/hw-json/opt/build /hw-json/hw-json-tmp/Paths_hw_json.o ) Linking /root/project/dist-newstyle/build/x86_64-linux/ghc-8.6.2/hw- json-0.9.0.1/x/hw-json/opt/build/hw-json/hw-json ... cabal: Failed to build test:hw-json-test from hw-json-0.9.0.1. The build process was killed (i.e. SIGKILL). The typical reason for this is that there is not enough memory available (e.g. the OS killed a process using lots of memory). Exited with code 1 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16017> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 3

[GHC] #15813: -Wredundant-constrains emits warning even if constraint is narrowing type
by GHC 18 Jan '19

18 Jan '19

#15813: -Wredundant-constrains emits warning even if constraint is narrowing type -------------------------------------+------------------------------------- Reporter: jvanbruegge | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Incorrect (amd64) | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I am not sure if this is the same as #12700 , but when having a constraint that uses type equality to narrow down a type, -Wredundant-constraints still emits the warning. My particular example is: {{{#!hs class RowCons (label :: Symbol) (ty :: k) (tail :: Row k) (row :: Row k) | label row -> ty tail, label ty tail -> row instance (RowDelete s r ~ tail, RowPrepend s ty tail ~ r) => RowCons s ty tail r get :: forall s ty t r. RowCons s ty t r => Record r -> Proxy s -> ty get _ _ = undefined test_rec = get (Proxy :: Record ('Cons "foo" '[String]) (Proxy :: Proxy "foo") }}} With the RowCons constraint, the inferred type of test_rec is String (or [Char]), but without it it is an ambiguous `ty`. If the implementation of the type classes is needed, they can be found here: https://github.com/jvanbruegge/Megarecord/blob/f65fa5f29dc393e32d42fc878724… I tested this with 8.6.1 and 8.4.3 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15813> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 3

[GHC] #9279: Optimisation bug
by GHC 18 Jan '19

18 Jan '19

#9279: Optimisation bug ------------------------------+-------------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime performance bug Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- I have a strange problem with a local function binding that is not being inlined. I've attached the repro code, build it like this: {{{ $ ghc -O2 Haxl/Core/Monad.hs }}} There are several modules, but the one with the problem is `Haxl/Core/Monad.hs`. In particular `Haxl.Core.Monad.$fApplicativeGenHaxl2`, which contains this fragment: {{{ let { $wa4_s6YQ $wa4_s6YQ = \ w_s6YF _ ww1_s6YM _ _ w1_s6YI -> case GHC.Prim.readMutVar# ipv7_X5Ne w1_s6YI of _ { (# ipv10_X5QO, ipv11_X5QQ #) -> case ipv11_X5QQ of _ { Haxl.Core.Monad.IVarFull a2_a3kK -> case lvl6_r7qi of wild3_00 { }; Haxl.Core.Monad.IVarEmpty dt2_d4Vs -> case GHC.Prim.writeMutVar# ipv7_X5Ne (Haxl.Core.Monad.IVarFull w_s6YF) ipv10_X5QO of s2#_a5OR { __DEFAULT -> case GHC.Prim.readMutVar# dt2_d4Vs s2#_a5OR of _ { (# ipv12_X5R0, ipv13_X5R2 #) -> case GHC.Prim.readMutVar# ww1_s6YM ipv12_X5R0 of _ { (# ipv14_X5SS, ipv15_X5SU #) -> letrec { go_a5ti go_a5ti = \ ds10_a5tj -> case ds10_a5tj of _ { [] -> ipv15_X5SU; : y_a5to ys_a5tp -> GHC.Types.: (y_a5to w_s6YF) (go_a5ti ys_a5tp) }; } in case go_a5ti ipv13_X5R2 of x'_a5P6 { __DEFAULT -> case GHC.Prim.writeMutVar# ww1_s6YM x'_a5P6 ipv14_X5SS of s2#1_a5P7 { __DEFAULT -> (# s2#1_a5P7, Haxl.Core.Monad.cacheRequest6 #) } } } } } } } } in let { a2_s6lH a2_s6lH = \ w_s6YF _ w2_s6YH w3_s6YI -> case w2_s6YH of _ { Haxl.Core.Monad.SchedState ww1_s6YL ww2_s6YM ww3_s6YN ww4_s6YO -> $wa4_s6YQ w_s6YF ww1_s6YL ww2_s6YM ww3_s6YN ww4_s6YO w3_s6YI } } in }}} I want `$wa4` to be inlined at its single occurrence in `a2`. I believe the reason it is not being inlined is that `a2` is a wrapper, but the situation seems silly because the wrapper isn't going away either, so we have a redundant closure being built (this is in my inner loop). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9279> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 26

[GHC] #15712: GHC panic with -XDerivingVia
by GHC 18 Jan '19

18 Jan '19

#15712: GHC panic with -XDerivingVia -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Keywords: DerivingVia | 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 slipped up and typed `Codensity GEndo` and now `Codensity (GEndo m)`, resulting in a GHC panic {{{#!hs {-# Language RankNTypes #-} {-# Language DerivingVia #-} import Control.Monad.Codensity import Data.Kind newtype GEndo m a = GEndo (m a -> m a) newtype LogicT m a = LogicT { runLogicT :: forall xx. (a -> (m xx -> m xx)) -> (m xx -> m xx) } deriving (Functor, Applicative, Monad) via (Codensity GEndo) }}} {{{ $ ghci -ignore-dot-ghci 476.hs GHCi, version 8.7.20180828: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 476.hs, interpreted ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20180828 for x86_64-unknown-linux): ASSERT failed! Type-correct unfilled coercion hole {co_a2aG} Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/utils/Outputable.hs:1219:5 in ghc:Outputable assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:1716:99 in ghc:TcHsSyn Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > }}} Deriving via `Codensity (GEndo m)` works as expected. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15712> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 3

[GHC] #15606: Don't float out lets in between lambdsa
by GHC 18 Jan '19

18 Jan '19

#15606: Don't float out lets in between lambdsa -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- Consider {{{ f = \x. let y = <blah> in \z. let v = h x y in <stuff> }}} The full laziness pass will float out that v-binding thus {{{ f = \x. let y = <blah> v = h x y in \z. <stuff> }}} And now (if `h` is, say, imported) it'll stay like that. But suppose `<blah>` simlifies to `Just x`. Then we allow ourselves to eta-expand thus {{{ f = \x z. let y = <blah> v = h x y in <stuff> }}} Now (an early design choice in the let-floater) we never float the v-binding in between the `\x` and `\z`. This is very non-confluent: a smal change in exactly how rapidly `<blah>` simplifies can have a big, irreversible effect on the code for `f`. IDEA: extend the let-floater's design choice to not float out between two lambdas, even if they are separated by lets/cases etc. One way to say this is to ask when a lambda gets a new level number compared to its immediately enclosing lambda. Examples where `y` gets the same level number as `x` * `\x.\y. blah` * `\x. let binds in \y` * `\x. case scrut of pi -> \y.blah` Examples where `y` gets the a level number one bigger than `x` * `\x. let v = \y.rhs in blah` * `\x. f (\y.rhs)` This probably won't make a lot of difference, but it'd be worth trying -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15606> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 1

[GHC] #13851: Change in specialisation(?) behaviour since 8.0.2 causes 6x slowdown
by GHC 18 Jan '19

18 Jan '19

#13851: Change in specialisation(?) behaviour since 8.0.2 causes 6x slowdown -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 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 was investigating some benchmarks and I noticed some odd results if I duplicated one of my tests. Reproduction: https://github.com/mpickering/probable-eureka Looking at the core, it seems that repeating the definition means that one of the key functions doesn't get specialised as expected which leads to a much slower program. Observe that in the first two benchmarks there is a worker function `go :: Int# -> Int -> ReaderT Int (StateT Int Identity Int` but in the third benchmark this is specialised to `$sgo :: Int# -> Int -> Int -> Int# -> Int# -> Identity (Int, Int)`. Removing the duplicate benchmark means that specialisation happens properly in the first case as well. The proper specialisation also happens in 8.0.2. This causes the first two cases to be 6x slower than the last case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13851> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

1 12