October 2016 - ghc-tickets

[GHC] #12755: Build from source fails on Ubuntu 16.10: ld: -r and -pie may not be used together
by GHC 11 Nov '16

11 Nov '16

#12755: Build from source fails on Ubuntu 16.10: ld: -r and -pie may not be used together -------------------------------------+------------------------------------- Reporter: SamuelMarks | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Build System | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Building GHC (amd64) | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ "inplace/bin/ghc-stage1" -hisuf hi -osuf o -hcsuf hc -static -H32m -O -Wall -this-unit-id ghc-prim-0.5.0.0 -hide-all-packages -i -ilibraries/ghc-prim/. -ilibraries/ghc-prim/dist-install/build -ilibraries /ghc-prim/dist-install/build/autogen -Ilibraries/ghc-prim/dist- install/build -Ilibraries/ghc-prim/dist-install/build/autogen -Ilibraries /ghc-prim/. -optP-include -optPlibraries/ghc-prim/dist- install/build/autogen/cabal_macros.h -package-id rts -this-unit-id ghc- prim -XHaskell2010 -O2 -no-user-package-db -rtsopts -Wno-trustworthy-safe -Wno-deprecated-flags -Wnoncanonical-monad-instances -odir libraries /ghc-prim/dist-install/build -hidir libraries/ghc-prim/dist-install/build -stubdir libraries/ghc-prim/dist-install/build -split-objs -dynamic-too -c libraries/ghc-prim/./GHC/Types.hs -o libraries/ghc-prim/dist- install/build/GHC/Types.o -dyno libraries/ghc-prim/dist- install/build/GHC/Types.dyn_o /usr/bin/ld: -r and -pie may not be used together collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) libraries/ghc-prim/ghc.mk:4: recipe for target 'libraries/ghc-prim/dist- install/build/GHC/Types.o' failed make[1]: *** [libraries/ghc-prim/dist-install/build/GHC/Types.o] Error 1 Makefile:129: recipe for target 'all' failed make: *** [all] Error 2 }}} Googling showed other builds with similar errors, for a bug report [which is now resolved]: - https://wiki.ubuntu.com/SteveBeattie/PIENotes - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518483 Running with `ld` GNU ld (GNU Binutils for Ubuntu) 2.27. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12755> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12748: BFD linker issue with GHCi
by GHC 09 Nov '16

09 Nov '16

#12748: BFD linker issue with GHCi ------------------------------------------+------------------------------- Reporter: hsyl20 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Linking) | Version: 8.0.1 Keywords: bfd,linker,ghci | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ------------------------------------------+------------------------------- On my project, GHCi seems to hang waiting for the BFD linker to complete the link of `libghc_1.so`. The hanging command has the form: `/usr/bin/ld @/tmp/ccHQ8Uzc` Using gdb, it seems the BFD linker `ld` is looping (infinitely?) into `bfd_elf_link_add_symbols`. I have tried to use the GOLD linker `ld.gold` instead on the `ccHQ8Uzc` file (removing the unsupported parameters `--hash-size=31` and `--reduce- memory-overhead`) and it links instantly. Could it be that GHC 8.0.1 generates too many symbols for the BFD linker or something like this? The BFD linker worked with GHC 7.10.3. I build the project with stack, the hanging happens with `stack repl` (GHCi's prompt never shows): {{{ @(Stack/Exec.hs:76:10) 2016-10-21 12:57:53.747332: [debug] Creating process: /usr/bin/ghc --interactive -i -odir=/home/hsyl20/travail/code/ViperVM/.stack-work/odir -hidir=/home/hsyl20/travail/code/ViperVM/.stack-work/odir -hide-all- packages -i/home/hsyl20/travail/code/ViperVM/src/lib -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/autogen -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build -stubdir=/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build /home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/src/lib/ViperVM/Arch/X86_64/Linux/syscall.o /home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/src/lib/ViperVM/Arch/X86_64/cpuid.o -package-id=base-4.9.0.0 -package-id=containers-0.5.7.1 -package- id=list-t-1-z6InD0gw7C2QDNkG2mqUf -package- id=stm-2.4.4.1-9HlGYelGmT69YkepeDjuRg -package-id=stm- containers-0.2.15-JTVESCf1d8uCXyJbMCLfQJ -package-id=stm- linkedlist-0.1.0.0-GCpyrfjLFyWFZy8qotX7VW -package- id=hashable-1.2.4.0-GnltDttmBjG9qGzcjuPOH4 -package- id=cereal-0.5.3.0-JHJQkHEuvBGFx8XwIB7eX0 -package-id=bytestring-0.10.8.1 -package-id=system-fileio-0.3.16.3-EDef2a4Ximk1z04PLLp95q -package-id =system-filepath-0.4.13.4-24DUGoIUqZu3MxGDhYLfCN -package- id=pureMD5-2.1.3-HBUMOqRjfoe6ZpLefZBT34 -package- id=text-1.2.2.1-FgcR4Xf0VlEHD9HLxzq9WJ -package-id=filepath-1.4.1.0 -package-id=either-4.4.1.1-H4kagIugHGeIf0psi4Z0to -package- id=vector-0.11.0.0-BEDZb5o2QOhGbIm6ky7rl6 -package-id=directory-1.2.6.2 -package-id=megaparsec-5.0.1-25EMPYC0AB61WKE0MffPOR -package- id=transformers-0.5.2.0 -package-id=unix-2.7.2.0 -package- id=criterion-1.1.1.0-Hq6Gg6oBMXcJvBdkiC2CBq -package-id=c-storable- deriving-0.1.3-DIL5UpBe3Em7XwOYU01lXH -package- id=pqueue-1.3.1.1-A3EjwMk8dUf7l1Swzqrred -package- id=mtl-2.2.1-6qsR1PHUy5lL47Hpoa4jCM -package-id=template-haskell-2.11.0.0 -package-id=text-format-0.3.1.1-IMczxQgUdKA8it9OEumLMx -package- id=diagrams-1.3.0.1-9gEbAUMmu7DEIEOtgBTN65 -package-id=diagrams- lib-1.3.1.4-EWFz1jRqz29KScpInBNJM4 -package-id=diagrams- core-1.3.0.8-GGXo5v7JBpPFzOrVLJC9nc -package-id=diagrams- rasterific-1.3.1.8-2NQiYfE0qFP7UFNV120Viv -package- id=JuicyPixels-3.2.8-GcqBxM3ZIJ83rYx9ygJ0bm -package- id=loop-0.3.0-98VH1UqsOHy2KxBxA55ICY -package- id=Rasterific-0.6.1.1-3xSOfexAru5AQFIj4yXZ8f -package- id=colour-2.3.3-1clKnMqHWhQAElTFd8Ydyp -package-id=file- embed-0.0.10-IXfudWSq57y1Athysk5ifZ -i/home/hsyl20/travail/code/ViperVM/src/apps -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/Disass/Disass-tmp -i/home/hsyl20/travail/code/ViperVM/src/apps/Elf -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/ElfWeb/ElfWeb-tmp -package-id =happstack-server-7.4.6.2-8UX7Pc8fxznJjPPJjgBwca -package- id=lucid-2.9.6-FZpI2dlNE9n8QXjEeTfhJW -package-id=optparse- applicative-0.12.1.0-4FckWvtE7Gp1EYdm7OVbJw -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/MemoryTest/MemoryTest-tmp -i/home/hsyl20/travail/code/ViperVM/src/apps/PlatformWeb -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/PlatformWeb/PlatformWeb-tmp -package-id=blaze-html-0.8.1.2-2ceCZ3Fm7x67ZwaaR7uQ3C -package-id=blaze- markup-0.7.1.0-BKRb0wHFpEyDJWTsyjQqnp -package- id=network-2.6.3.1-G4Up1CPKbp7DeFsnywOnGG -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/TestSyscalls/TestSyscalls-tmp -i/home/hsyl20/travail/code/ViperVM/src/apps/X86Web -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/X86Web/X86Web-tmp -package- id=HTTP-4000.3.3-Fl4VtSZsPE4A3kSlCM2M0U -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/gunzip/gunzip-tmp -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/huffman/huffman-tmp -i/home/hsyl20/travail/code/ViperVM/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/udev/udev-tmp -i/home/hsyl20/travail/code/dynamic-linker-template -i/home/hsyl20/travail/code/dynamic-linker-template/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build/autogen -i/home/hsyl20/travail/code/dynamic-linker-template/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build -stubdir=/home/hsyl20/travail/code/dynamic-linker-template/.stack- work/dist/x86_64-linux/Cabal-1.24.0.0/build -Wall -Wall -Wall -Wall -Wall -Wall -Wall -Wall -Wall -Wall -Wall -optP-include -optP/tmp/ghci13379/cabal_macros.h -ghci-script=/tmp/ghci13379/ghci-script @(System/Process/Run.hs:103:5) GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help }}} This is on ArchLinux, binutils-2.27, stack 1.2.0, GHC 8.0.1. Steps to reproduce (I don't have a smaller reproducing example for now): {{{ git clone https://github.com/hsyl20/ViperVM cd ViperVM stack repl # wait... the compilation is quite long # press enter when stack asks for the main module to load }}} `stack build` doesn't trigger this linker issue. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12748> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12630: Assertion failed with BuildFlavour = devel2
by GHC 08 Nov '16

08 Nov '16

#12630: Assertion failed with BuildFlavour = devel2 -------------------------------------+------------------------------------- Reporter: pacak | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- I tried to reproduce random ghc panic we have in our codebase with ghc8 so I decided to compile ghc with debug enabled. Source file: ghc-8.0.1-src.tar.xz build.mk changes: {{{ BuildFlavour = devel2 GhcStage1HcOpts = -DDEBUG GhcStage2HcOpts = -DDEBUG }}} source: {{{#!hs {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE PolyKinds #-} module A where import GHC.Generics class B f where b :: [f a] toEnumDefault :: (B (Rep a)) => Int -> a toEnumDefault i = let l = b in to }}} result: {{{ [1 of 1] Compiling A ( a.hs, a.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): ASSERT failed! CallStack (from HasCallStack): assertPprPanic, called at compiler/types/TyCoRep.hs:1974:56 in ghc:TyCoRep checkValidSubst, called at compiler/types/TyCoRep.hs:2010:17 in ghc:TyCoRep substTy, called at compiler/types/TyCoRep.hs:1952:3 in ghc:TyCoRep in_scope InScope [a1BD :-> a_a1BD[sk], a1BI :-> k_a1BI[tau:3], a1BJ :-> f_a1BJ[tau:3], a1BL :-> a_a1BL[sk]] tenv [a1BD :-> a_a1BL[sk]] tenvFVs [a1Bz :-> k_a1Bz[tau:5], a1BL :-> a_a1BL[sk]] cenv [] cenvFVs [] tys [[f_a1BJ[tau:3] a_a1BD[sk]]] cos [] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12630> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12728: setnumcapabilities001 sometimes fails on Windows
by GHC 08 Nov '16

08 Nov '16

#12728: setnumcapabilities001 sometimes fails on Windows --------------------------------------+---------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Runtime System | Version: 8.0.1 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- I have seen the `setnumcapabilities001` test fail at least once on Windows ([[https://phabricator.haskell.org/harbormaster/build/14178/?l=0]] It seems that the assertion `ASSERT(n_idle == 0);` in `Schedule.scheduleDoGC` is to blame in this particular case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12728> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12746: Assertion failed with BuildFlavour = devel2 (one more)
by GHC 08 Nov '16

08 Nov '16

#12746: Assertion failed with BuildFlavour = devel2 (one more) -------------------------------------+------------------------------------- Reporter: pacak | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Affected versions: ghc 8.0.1 and ghc git master as of 21 Oct 2016 (c23dc61) It compiles fine on first time but fails to compile on second attempt. Using -fforce-recomp recompiles both files and bug is not triggered. {{{ % ls A.hs B.hs % cat A.hs }}} {{{#!hs module A where import B foo a = case a of Foo -> True _ -> False }}} {{{ % cat B.hs }}} {{{#!hs {-# LANGUAGE PatternSynonyms, ScopedTypeVariables #-} module B where pattern Foo = 0x00000001 :: Int }}} {{{ % ghc -O2 A.hs ; touch A.hs ; ghc -O2 A.hs [1 of 2] Compiling B ( B.hs, B.o ) [2 of 2] Compiling A ( A.hs, A.o ) [2 of 2] Compiling A ( A.hs, A.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): ASSERT failed! CallStack (from HasCallStack): assertPprPanic, called at compiler/iface/BuildTyCl.hs:195:404 in ghc:BuildTyCl [] ~ [] [] ~ [] Int ~ Int [] ~ [] [] ~ [] [] ~ [Void#] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12746> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12738: GHC drops -optl flags
by GHC 08 Nov '16

08 Nov '16

#12738: GHC drops -optl flags -------------------------------------+------------------------------------- Reporter: niteria | Owner: Type: bug | Status: new Priority: high | 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: -------------------------------------+------------------------------------- This is a regression between GHC 7.10 and GHC 8.0. Repro script: {{{ GHC_ROOT=$HOME/local/ghc-8.0.1-facebook # built 8.0.1 branch, fails with recent HEAD as well GHC=$GHC_ROOT/inplace/bin/ghc-stage2 GPP=g++ touch build_info.o # irrelevant "$GHC" -no-auto-link-packages -pgml"$GPP" -o a.out build_info.o -optl- Xlinker -optl$GHC_ROOT/libraries/ghc-prim/dist-install/build/libHSghc- prim-0.5.0.0.a -optl-Xlinker -optl-u -optl-Xlinker -optlghczmprim_GHCziTypes_Izh_static_info -v }}} Output from GHC 7.10 (expected): {{{ Glasgow Haskell Compiler, Version 7.10.2, stage 2 booted by GHC version 7.8.4 Using binary package database: /usr/local/haskell/ghc-7.10.2-x86_64/lib/ghc-7.10.2/package.conf.d/package.cache Using binary package database: /home/bnitka/.ghc/x86_64-linux-7.10.2/package.conf.d/package.cache wired-in package ghc-prim mapped to ghc- prim-0.4.0.0-af16264bc80979d06e37ac63e3ba9a21 wired-in package integer-gmp mapped to integer- gmp-1.0.0.0-8e0f14d0262184533b417ca1f8b44482 wired-in package base mapped to base-4.8.1.0-4f7206fd964c629946bb89db72c80011 wired-in package rts mapped to builtin_rts wired-in package template-haskell mapped to template- haskell-2.10.0.0-90e8393d65f4ae44cb2026177a257f28 wired-in package ghc mapped to ghc-7.10.2-787f1a784665fb3ac2a1be1d9d85245b wired-in package dph-seq not found. wired-in package dph-par not found. Hsc static flags: Created temporary directory: /tmp/ghc2775839_0 *** C Compiler: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -c /tmp/ghc2775839_0/ghc_1.c -o /tmp/ghc2775839_0/ghc_2.o -I/usr/local/haskell/ghc-7.10.2-x86_64/lib/ghc-7.10.2/include *** C Compiler: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -c /tmp/ghc2775839_0/ghc_3.s -o /tmp/ghc2775839_0/ghc_4.o -I/usr/local/haskell/ghc-7.10.2-x86_64/lib/ghc-7.10.2/include *** Linker: 'g++' '-Wl,--hash-size=31' -Wl,--reduce-memory-overheads -Wl,--no-as- needed -Xlinker /home/bnitka/local/ghc-8.0.1-facebook/libraries/ghc-prim /dist-install/build/libHSghc-prim-0.5.0.0.a -Xlinker -u -Xlinker ghczmprim_GHCziTypes_Izh_static_info -o a.out build_info.o /tmp/ghc2775839_0/ghc_2.o /tmp/ghc2775839_0/ghc_4.o build_info.o: file not recognized: File truncated collect2: ld returned 1 exit status *** Deleting temp files: Deleting: /tmp/ghc2775839_0/ghc_4.o /tmp/ghc2775839_0/ghc_3.s /tmp/ghc2775839_0/ghc_2.o /tmp/ghc2775839_0/ghc_1.c *** Deleting temp dirs: Deleting: /tmp/ghc2775839_0 }}} Output from GHC 8.0: {{{ Glasgow Haskell Compiler, Version 8.0.1.20160729, stage 2 booted by GHC version 7.10.2 Using binary package database: /data/users/bnitka/ghc-8.0.1-facebook/inplace/lib/package.conf.d/package.cache loading package database /data/users/bnitka/ghc-8.0.1-facebook/inplace/lib/package.conf.d wired-in package ghc-prim mapped to ghc-prim-0.5.0.0 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1 wired-in package base mapped to base-4.9.0.0 wired-in package rts mapped to rts wired-in package template-haskell mapped to template-haskell-2.11.0.0 wired-in package ghc mapped to ghc-8.0.1.20160729 wired-in package dph-seq not found. wired-in package dph-par not found. Hsc static flags: Created temporary directory: /tmp/ghc2778573_0 *** C Compiler: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -c /tmp/ghc2778573_0/ghc_1.c -o /tmp/ghc2778573_0/ghc_2.o -I/data/users/bnitka/ghc-8.0.1-facebook/rts/dist/build -I/data/users/bnitka/ghc-8.0.1-facebook/includes -I/data/users/bnitka/ghc-8.0.1-facebook/includes/dist- derivedconstants/header *** C Compiler: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -c /tmp/ghc2778573_0/ghc_4.s -o /tmp/ghc2778573_0/ghc_5.o *** Linker: 'g++' '-Wl,--hash-size=31' -Wl,--reduce-memory-overheads -Wl,--no-as- needed -Xlinker -Xlinker -u -Xlinker ghczmprim_GHCziTypes_Izh_static_info -o a.out -Wl,--gc-sections build_info.o /tmp/ghc2778573_0/ghc_2.o /tmp/ghc2778573_0/ghc_5.o /home/bnitka/local/ghc-8.0.1-facebook/libraries /ghc-prim/dist-install/build/libHSghc-prim-0.5.0.0.a g++: ghczmprim_GHCziTypes_Izh_static_info: No such file or directory *** Deleting temp files: Deleting: /tmp/ghc2778573_0/ghc_7.rsp /tmp/ghc2778573_0/ghc_6.rsp /tmp/ghc2778573_0/ghc_5.o /tmp/ghc2778573_0/ghc_4.s /tmp/ghc2778573_0/ghc_3.rsp /tmp/ghc2778573_0/ghc_2.o /tmp/ghc2778573_0/ghc_1.c *** Deleting temp dirs: Deleting: /tmp/ghc2778573_0 `g++' failed in phase `Linker'. (Exit code: 1) }}} The relevant difference is in the flags passed to `g++`. {{{ 'g++' '-Wl,--hash-size=31' -Wl,--reduce-memory-overheads -Wl,--no-as- needed -Xlinker /home/bnitka/local/ghc-8.0.1-facebook/libraries/ghc-prim /dist-install/build/libHSghc-prim-0.5.0.0.a -Xlinker -u -Xlinker ghczmprim_GHCziTypes_Izh_static_info -o a.out build_info.o /tmp/ghc2775839_0/ghc_2.o /tmp/ghc2775839_0/ghc_4.o }}} vs {{{ 'g++' '-Wl,--hash-size=31' -Wl,--reduce-memory-overheads -Wl,--no-as- needed -Xlinker -Xlinker -u -Xlinker ghczmprim_GHCziTypes_Izh_static_info -o a.out -Wl,--gc-sections build_info.o /tmp/ghc2778573_0/ghc_2.o /tmp/ghc2778573_0/ghc_5.o /home/bnitka/local/ghc-8.0.1-facebook/libraries /ghc-prim/dist-install/build/libHSghc-prim-0.5.0.0.a }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12738> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11369: Suppress redundant-constraint warnings in case of empty classes
by GHC 07 Nov '16

07 Nov '16

#11369: Suppress redundant-constraint warnings in case of empty classes -------------------------------------+------------------------------------- Reporter: hvr | Owner: simonpj Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 8.1 (Type checker) | 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: -------------------------------------+------------------------------------- The technique described in http://www.well-typed.com/blog/2015/07/checked-exceptions/ makes use of a class without any methods, i.e. {{{#!hs class Throws e }}} However, this by definition results in redundant constraints, e.g. {{{#!hs readFoo :: Throws IOError => FilePath -> IO Foo readFoo fn = {- ... -} }}} which GHC 8.0 warns about. I propose to suppress warnings in case a class which has no methods is used as seemingly redundant constraint. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11369> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12220: TypeApplications and DefaultSignatures - problems deducing type variables.
by GHC 07 Nov '16

07 Nov '16

#12220: TypeApplications and DefaultSignatures - problems deducing type variables. -------------------------------------+------------------------------------- Reporter: mkloczko | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux DefaultSignatures, | TypeApplications | Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following example code throws an error. The example code: {{{#!hs {-#LANGUAGE TypeApplications#-} {-#LANGUAGE MultiParamTypeClasses #-} {-#LANGUAGE AllowAmbiguousTypes #-} {-#LANGUAGE FlexibleInstances #-} {-#LANGUAGE ScopedTypeVariables #-} {-#LANGUAGE DefaultSignatures #-} module Test1 where -- | Type a is only used for -- type application. class ToUse a where toUse :: Int -> Int -- | The type used for -- type application data Default -- | The instance using Default as type application. -- To call use: -- > toUse @Default instance ToUse Default where toUse a = 3*a -- | Typeclass whose methods work -- only with type application. class (ToUse a) => Uses a b where uses :: b -> [b] -- | Default Signature, which generates the problem. -- It is the same as the normal one -- Comment it to 'fix' the bug. default uses :: b -> [b] uses v = [v] -- | Normal instances, nothing special instance Uses Default Int where uses v = take (toUse @Default 3) $ repeat v -- | Another normal one instance Uses Default String where uses v = take (toUse @Default 2) $ repeat v -- | This one works nicely instance (ToUse t, Uses t a, Uses t b) => Uses t (a,b) where uses (vl,vr) = zip ls rs where ls = uses @t vl rs = uses @t vr -- | But this one doesn't. -- Unless you comment the default signature. instance (ToUse t, Uses t a, Uses t b, Uses t c) => Uses t (a,b,c) }}} The error: {{{ • Could not deduce (Uses a0 a) arising from a use of ‘Test1.$dmuses’ from the context: (ToUse t, Uses t a, Uses t b, Uses t c) bound by the instance declaration at Test1.hs:47:10-66 The type variable ‘a0’ is ambiguous Relevant bindings include uses :: (a, b, c) -> [(a, b, c)] (bound at Test1.hs:47:10) • In the expression: Test1.$dmuses In an equation for ‘uses’: uses = Test1.$dmuses In the instance declaration for ‘Uses t (a, b, c)’ }}} Commenting out the default signature fixes the problem. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12220> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12691: Refine the behaviour of -dno-debug-output and -dtrace-level
by GHC 06 Nov '16

06 Nov '16

#12691: Refine the behaviour of -dno-debug-output and -dtrace-level -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: task | Status: new Priority: low | 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: -------------------------------------+------------------------------------- It wasn't clear to me what these flags should do and what they should turn off. From the user guide. `-dno-debug-output`:: Suppress any unsolicited debugging output. When GHC has been built with the DEBUG option it occasionally emits debug output of interest to developers. The extra output can confuse the testing framework and cause bogus test failures, so this flag is provided to turn it off. `-dtrace-level`:: Not present `-dno-debug-output` currently suppresses the output of `-ddump-tc-trace` which is certainly not "unsolicited". It should be used, and is, in `Outputable` to suppress the output of `pprTrace`. `dtrace-level` is used in a few places but always as if was a boolean flag. I don't really see what the point of it is. The only commit which mentions it is "8cdb98b9909561671ab4e61c90ebb12504478e4d" and I can't find the origin of the flag. I think we should just remove it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12691> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12692: Can't find interface-file decl with Typeable
by GHC 06 Nov '16

06 Nov '16

#12692: Can't find interface-file decl with Typeable -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The attached code produces the following error: {{{ GHC error in desugarer lookup in Main: Can't find interface-file declaration for variable $tc'(,) Probable cause: bug in .hi-boot file, or inconsistent .hi file Use -ddump-if-trace to get an idea of which file caused the error ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): initDs IOEnv failure }}} when I run `stack bench lol`. The issue seems to be related to `Typeable` instances for types created with singletons. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12692> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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