December 2017 - ghc-tickets

[GHC] #13450: Better parse error for empy character literal
by GHC 19 Apr '18

19 Apr '18

#13450: Better parse error for empy character literal -------------------------------------+------------------------------------- Reporter: parsonsmatt | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Empty character literals give an obscure error message. As an example, this code: {{{#!hs example = foo : bar where foo = '' bar = "asdf" }}} gives the following error when loaded in GHCi: {{{ err.hs:4:6: parse error (possibly incorrect indentation or mismatched brackets) }}} This has affected me once, as a beginner. I've seen it affect a few other beginners, and the error message isn't very helpful to figuring out what's wrong. It would be nice if a better error message could be reported. If there's a parse error on `''`, then GHC could report something like: {{{ err.hs:3:11: parse error on `''`. Note: Character literals may not be empty. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13450> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10037: Several profiling tests give different results optimised vs. unoptimised
by GHC 19 Apr '18

19 Apr '18

#10037: Several profiling tests give different results optimised vs. unoptimised -------------------------------------+------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Profiling | Version: 7.10.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Most of the differences are relatively harmless (mostly CAF attribution), but it would be nice to get this right. In the meantime I'll mark them expect_broken and point to this ticket. The following tests in `tests/profiling/should_run` are affected: {{{ scc001 T2552 ioprof callstack001 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10037> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12860: GeneralizedNewtypeDeriving + MultiParamTypeClasses sends typechecker into an infinite loop
by GHC 17 Apr '18

17 Apr '18

#12860: GeneralizedNewtypeDeriving + MultiParamTypeClasses sends typechecker into an infinite loop -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This worked in GHC 7.6.3, but ever since GHC 7.8, this code will cause the typechecker to loop infinitely: {{{#!hs {-# LANGUAGE FunctionalDependencies #-} {-# LANGUAGE GeneralizedNewtypeDeriving #-} {-# LANGUAGE MultiParamTypeClasses #-} module Bug where class C a b | a -> b where c :: a -> Int newtype Foo a = Foo a deriving (C b) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12860> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9074: GHC 7.8.2's ghci does not track missing symbols when loading non-Haskell object files
by GHC 17 Apr '18

17 Apr '18

#9074: GHC 7.8.2's ghci does not track missing symbols when loading non-Haskell object files ------------------------------------+------------------------------------- Reporter: massysett | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- I have a package that bundles in C library sources. I never had a problem with this when using GHC 7.6. In GHC 7.8, the order of the c-sources in the cabal file now matters. Sources must be listed earlier if they have symbols that subsequently loaded object files will need. If the c-sources are in the wrong order, when running "cabal repl" I get Loading object (static) dist/build/decnumber/src/decQuad.o ... ghc: panic! (the 'impossible' happened) (GHC version 7.8.2 for x86_64-unknown-linux): Loading temp shared object failed: /tmp/ghc14294_0/ghc14294_1.so: undefined symbol: DECSTICKYTAB Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug When using the same code and cabal file with GHC 7.6, "cabal repl" works fine: GHCi loads each static object (regardless of ordering in the cabal file), links up the necessary symbols, and launches successfully. Haskell Cafe discussion here: http://www.haskell.org/pipermail/haskell-cafe/2014-May/114041.html -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9074> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11045: Loading temp shared object failed - undefined symbol
by GHC 17 Apr '18

17 Apr '18

#11045: Loading temp shared object failed - undefined symbol -------------------------------------+------------------------------------- Reporter: sjakobi | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While re-compiling [https://github.com/commercialhaskell/stack stack]: {{{ $ stack install --ghc-options -O2 stack-0.1.7.0: configure Configuring stack-0.1.7.0... stack-0.1.7.0: build Preprocessing library stack-0.1.7.0... [30 of 74] Compiling Stack.Types.Docker ( src/Stack/Types/Docker.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types/Docker.o ) [31 of 74] Compiling Options.Applicative.Complicated ( src/Options/Applicative/Complicated.hs, .stack- work/dist/x86_64-linux/Cabal-1.22.4.0/build/Options/Applicative/Complicated.o ) [32 of 74] Compiling Stack.Types.Config ( src/Stack/Types/Config.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types/Config.o ) [33 of 74] Compiling Stack.Constants ( src/Stack/Constants.hs, .stack- work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Constants.o ) [Stack.Types.Config changed] [34 of 74] Compiling Stack.Types.Internal ( src/Stack/Types/Internal.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types/Internal.o ) [Stack.Types.Config changed] [35 of 74] Compiling Stack.Types.StackT ( src/Stack/Types/StackT.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types/StackT.o ) [36 of 74] Compiling Stack.Docker.GlobalDB ( src/Stack/Docker/GlobalDB.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Docker/GlobalDB.o ) [Stack.Types.Config changed] [37 of 74] Compiling Stack.Types.Package ( src/Stack/Types/Package.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types/Package.o ) [Stack.Types.Config changed] [38 of 74] Compiling Stack.Types.Build ( src/Stack/Types/Build.hs, .stack- work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types/Build.o ) [39 of 74] Compiling Stack.Types ( src/Stack/Types.hs, .stack- work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/Types.o ) [Stack.Types.Build changed] [40 of 74] Compiling Stack.GhcPkg ( src/Stack/GhcPkg.hs, .stack- work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/GhcPkg.o ) [Stack.Constants changed] [41 of 74] Compiling Stack.PackageIndex ( src/Stack/PackageIndex.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/Stack/PackageIndex.o ) [Data.Binary.VersionTagged changed] ghc: panic! (the 'impossible' happened) (GHC version 7.10.2 for x86_64-unknown-linux): Loading temp shared object failed: /tmp/ghc22553_0/libghc_96.so: undefined symbol: stackzuFHzzONQT9HI3ATX2xQH198L_StackziTypesziCompiler_zdfBinaryCompilerVersionzuzdszdfGSumM2_closure Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -- While building package stack-0.1.7.0 using: /home/simon/.stack/setup-exe-cache/setup-Simple- Cabal-1.22.4.0-x86_64-linux-ghc-7.10.2 --builddir=.stack- work/dist/x86_64-linux/Cabal-1.22.4.0/ build lib:stack exe:stack --ghc- options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 $ git show commit 2fb2d11fffddde3c44920f7ea93e34b9d3195dad Author: Emanuel Borsboom <manny(a)fpcomplete.com> Date: Sun Nov 1 05:21:16 2015 -0800 <snip> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11045> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11499: Loading temp shared object failed in GHCi
by GHC 17 Apr '18

17 Apr '18

#11499: Loading temp shared object failed in GHCi --------------------------------------+------------------------------- Reporter: alfa07 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.10.3 Keywords: | Operating System: MacOS X Architecture: x86_64 (amd64) | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+------------------------------- While trying to launch ghci got the following error: ❯ stack ghci The following GHC options are incompatible with GHCi and have not been passed to it: -threaded -Odph Using main module: 1. Package `line-segment-intersection' component exe:demo with main-is file: /Users/maxim/Dev/ComputationGeometry/LineSegmentIntersection/app/Main.hs Configuring GHCi with the following packages: line-segment-intersection, GLUT, GLUtil, boundingboxes, freetype-simple, freetype2 GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-apple-darwin): Loading temp shared object failed: dlopen(/var/folders/dz/lm9jncs90nq0vn_5j7xhpg2xqyfj66/T/ghc23900_0/libghc_25.dylib, 5): Symbol not found: _bdf_driver_class Referenced from: /var/folders/dz/lm9jncs90nq0vn_5j7xhpg2xqyfj66/T/ghc23900_0/libghc_25.dylib Expected in: flat namespace in /var/folders/dz/lm9jncs90nq0vn_5j7xhpg2xqyfj66/T/ghc23900_0/libghc_25.dylib Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11499> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12982: Missed constant folding oportunities
by GHC 17 Apr '18

17 Apr '18

#12982: Missed constant folding oportunities -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.4.1 Component: | Version: 8.0.1 libraries/hoopl | 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: -------------------------------------+------------------------------------- A work colleague of mine found that some expressions were not being constant folded as expected. For example: {{#!hs module Test where import Data.Int number :: Int64 number = 2 ^ 10 - 3 }}} compiled using: {{{ ghc -O2 -keep-s-file -c test.hs }}} should result in an assembler file containing the constant `1021` but doesn't. However, if I change the above expression to: {{{ number = 1024 -3 }}} then the output assembler files does contain the value `1021`. I did a bit of a search and found some constant folding code in the `hoopl` library, but that doesn't seem to be what GHC actually uses. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12982> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11117: mdo blocks in error messages are shown modified
by GHC 17 Apr '18

17 Apr '18

#11117: mdo blocks in error messages are shown modified -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.8.3 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: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE RecursiveDo #-} main = mdo Just x <- return (Right x) return () }}} gives {{{ MdoTypeError.hs:3:3: Couldn't match expected type ‘Either a0 b0’ with actual type ‘Maybe b0’ Relevant bindings include x :: b0 (bound at MdoTypeError.hs:3:8) In the pattern: Just x In a stmt of an 'mdo' block: Just x <- return (Right x) In a stmt of an 'mdo' block: rec { Just x <- return (Right x) } }}} Note that the error message mentions `rec` even though that is not what the user entered. In other instances, we are careful to show the code more similar to the original (e.g. `do`-notation instead of `>>=`). This should also be done here. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11117> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13360: Add a flag to enable inferring HasCallStack constraints
by GHC 16 Apr '18

16 Apr '18

#13360: Add a flag to enable inferring HasCallStack constraints -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- GHC is careful to not infer a HasCallStack constraint for a function, because the user didn't ask for one, it would complicate the type, and because it would incur some runtime overhead. I think this is the right default, but it can make debugging exceptions tedious as you have to manually add HasCallStack constraints to the entire chain of functions in the stack. I sometimes use CPP to give myself a flag to toggle the constraints, but I'd rather not have to resort to CPP. Instead, it would be nice if GHC supported a `-finfer-hascallstack` flag (off by default) that would simply generalize over the HasCallStack constraints rather than defaulting them. Then, if my program blows up I can simply recompile with `-finfer-hascallstack` and get a more informative trace. No manual editing, no preparation with CPP, easy! Furthermore, if we had such a flag, it might be nice to '''enable''' it by default in ghci. The two prime concerns are 1. Complicating type signatures. But `:t` solves the HasCallStack constraint before printing the type, so this is only a concern if you use `:i`. 2. Runtime overhead. I don't think this is a valid concern in ghci. I think this would be a nice and simple improvement to the debugging experience. The downside is that even with `-finfer-hascallstack` you would not get full call-stacks for functions in an imported module that was compiled normally. So this would not help with e.g. partial functions in `base`. (It would be really nice to find a solution to this that doesn't involve building modules in multiple ways..) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13360> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10920: ghci can't load local Prelude module
by GHC 14 Apr '18

14 Apr '18

#10920: ghci can't load local Prelude module -------------------------------------+------------------------------------- Reporter: Yuras | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | -------------------------------------+------------------------------------- I have a `Prelude.hs` file which contains {{{#!hs module Prelude where }}} If I invoke `ghci` from the same directory, I get {{{ Top level: attempting to use module ‘Prelude’ (./Prelude.hs) which is not loaded }}} Note: `ghc --make` correctly compiles modules that use the local `Prelude.hs`, so I expect `ghci` to handle that case too. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10920> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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