April 2018 - ghc-tickets

[GHC] #11389: Print a message when loading a .ghci file
by GHC 13 May '18

13 May '18

#11389: Print a message when loading a .ghci file -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: GHCi | Version: 7.8.4 Keywords: newcomer | 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'd be nice to have a notice displayed when ghci loads a .ghci file, something like {{{ rwbarton@morphism:~$ ghci-7.10.1 GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rwbarton/.ghci Prelude> }}} I want this mostly so that we can tell whether people filing ghci bugs might have anything relevant in their `.ghci` files. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11389> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12721: Implement sigINT handler for Window's timeout.exe
by GHC 12 May '18

12 May '18

#12721: Implement sigINT handler for Window's timeout.exe ----------------------------------------+---------------------------- Reporter: Phyx- | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Test Suite | Version: 8.0.1 Keywords: | Operating System: Windows Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+---------------------------- On linux we current register a sigINT handler and kill the child processed. On Windows we don't. This sometimes leaves dangling processes when the testsuite is interrupted. Causing future failures until the dangling processes are killed. We already specifically create a job group and assign the processors to those jobs. All we have to do is register the handler and kill the process if the handler is called. See https://msdn.microsoft.com/en- us/library/windows/desktop/ms686016(v=vs.85).aspx -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12721> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15101: $tooldir not expanded for NoFib
by GHC 12 May '18

12 May '18

#15101: $tooldir not expanded for NoFib -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: NoFib | Version: benchmark suite | Keywords: | Operating System: Windows Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The nofib suite looks for gcc under $tooldir which doesn't seem to be expanded/set. {{{ > ~/ghc_head/nofib/shootout/fasta $ make boot $tooldir/mingw/bin/gcc.exe -std=gnu99 -O3 -fomit-frame-pointer fasta-c.c -o fasta-c /bin/sh: /mingw/bin/gcc.exe: No such file or directory make: *** [Makefile:22: fasta-c] Error 127 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15101> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14684: combineIdenticalAlts is only partially implemented
by GHC 09 May '18

09 May '18

#14684: combineIdenticalAlts is only partially implemented -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- combineIdenticalAlts commons up branches of case expressions which have the same RHS. However, it is not fully implemented so opportunities to common up branches are missed. For very big case expressions in might impact compilation time but it could be something which is enabled by `-O2`. For example, the `C` and `D` case for `foo` are not commened up but the `A` and `B` case in `foo2` are. {{{ module Foo where data T = A | B | C | D foo x = case x of A -> 0 B -> 1 C -> 2 D -> 2 foo2 x = case x of A -> 2 B -> 2 C -> 0 D -> 1 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14684> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14547: Wrong warning by -Wincomplete-patterns
by GHC 08 May '18

08 May '18

#14547: Wrong warning by -Wincomplete-patterns -------------------------------------+------------------------------------- Reporter: YoshikuniJujo | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.2.1 Keywords: incomplete- | Operating System: Linux patterns OverloadedLists | TypeFamilies | Type of failure: Incorrect Architecture: x86 | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Wrong warning occur where I use -Wincomplete-patterns with OverloadedLists and TypeFamilies. {{{#!hs {-# LANGUAGE OverloadedLists #-} {-# LANGUAGE TypeFamilies #-} {-# OPTIONS_GHC -Wall -fno-warn-tabs #-} class Foo f where type It f foo :: [It f] -> f data List a = Empty | a :! List a deriving Show instance Foo (List a) where type It (List a) = a foo [] = Empty foo (x : xs) = x :! foo xs }}} Pattern match(es) are non-exhaustive In an equation for `foo': Patterns not matched: [] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14547> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13958: Ghc linking failure for 8.2.1 rc3 on Alpine Linux
by GHC 08 May '18

08 May '18

#13958: Ghc linking failure for 8.2.1 rc3 on Alpine Linux -------------------------------------+------------------------------------- Reporter: mitchty | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc3 (Linking) | 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: -------------------------------------+------------------------------------- Bisected this down to commit 2785ef0e31a123400da950ffafebe6cb1ce3f4eb between rc2 and rc3. rc2 builds fine. This is on Alpine Linux which uses musl libc primarily and gcc/binutils patched for it as well (mostly PIE related), if wanted I can provide a Dockerfile to reproduce the issue more easily. Note that the switch provided by that commit, --disable-ld-override allows rc3 to link stage 2 properly again. But the error encountered with no override and when specifying the ld to use via configure, in this case ld.gold is this: {{{ "inplace/bin/ghc-stage2" -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/haddock-api/src -iutils/haddock/haddock- library/vendor/attoparsec-0.13.1.0 -iutils/haddock/haddock-library/sr c -iutils/haddock/dist/build -Iutils/haddock/dist/build -iutils/haddock/dist/build/haddock/autogen -Iutils/haddock/dist/build/haddock/autogen -optP-DIN_GHC_TREE -optP- include -optPutils/haddock/dist/build/haddock/autogen/cabal_macros.h -package-id base-4.10.0.0 -packag e-id filepath-1.4.1.2 -package-id directory-1.3.0.2 -package-id containers-0.5.10.2 -package-id deepseq-1.4.3.0 -package-id array-0.5.2.0 -package-id xhtml-3000.2.2 -package-id Cabal-2.0.0.0 -package-id ghc- boot-8.2.0.20170704 -package-id ghc-8.2.0.20170704 -package-id bytestring-0.10.8.2 -package-id transformers-0.5.2.0 -funbox-strict-fields -Wall -fwarn-tabs -O2 -threaded -XHaskell2010 -no-user-package-db -rtsopts -Wno-unused-imports -Wno-deprecations -Wnoncanonical-monad- instances -odir utils/haddock/dist/build -hidir utils/haddo ck/dist/build -stubdir utils/haddock/dist/build -c utils/haddock/driver/ResponseFile.hs -o utils/haddock/dist/build/ResponseFile.dyn_o "inplace/bin/ghc-stage2" -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/haddock-api/src -iutils/haddock/haddock- library/vendor/attoparsec-0.13.1.0 -iutils/haddock/haddock-library/sr c -iutils/haddock/dist/build -Iutils/haddock/dist/build -iutils/haddock/dist/build/haddock/autogen -Iutils/haddock/dist/build/haddock/autogen -optP-DIN_GHC_TREE -optP- include -optPutils/haddock/dist/build/haddock/autogen/cabal_macros.h -package-id base-4.10.0.0 -packag e-id filepath-1.4.1.2 -package-id directory-1.3.0.2 -package-id containers-0.5.10.2 -package-id deepseq-1.4.3.0 -package-id array-0.5.2.0 -package-id xhtml-3000.2.2 -package-id Cabal-2.0.0.0 -package-id ghc- boot-8.2.0.20170704 -package-id ghc-8.2.0.20170704 -package-id by testring-0.10.8.2 -package-id transformers-0.5.2.0 -funbox-strict-fields -Wall -fwarn-tabs -O2 -threaded -XHaskell2010 -no-user-package-db -rtsopts -Wno-unused-imports -Wno-deprecations -Wnoncanonical-monad- instances -odir utils/haddock/dist/build -hidir utils/haddock/dist/build -stubdir utils/haddock/dist/build -c utils/haddock/haddock- api/src/Haddock/GhcUtils.hs -o utils/haddock/dist/build/Haddock/GhcUtils.dyn_o "inplace/bin/ghc-stage2" -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/haddock-api/src -iutils/haddock/haddock- library/vendor/attoparsec-0.13.1.0 -iutils/haddock/haddock-library/sr c -iutils/haddock/dist/build -Iutils/haddock/dist/build -iutils/haddock/dist/build/haddock/autogen -Iutils/haddock/dist/build/haddock/autogen -optP-DIN_GHC_TREE -optP- include -optPutils/haddock/dist/build/haddock/autogen/cabal_macros.h -package-id base-4.10.0.0 -package-id filepath-1.4.1.2 -package-id directory-1.3.0.2 -package-id containers-0.5.10.2 -package-id deepseq-1.4.3.0 -package-id array-0.5.2.0 -package-id xhtml-3000.2.2 -package-id Cabal-2.0.0.0 -package-id ghc-boot-8.2.0.20170704 -package-id ghc-8.2.0.20170704 -package-id by testring-0.10.8.2 -package-id transformers-0.5.2.0 -funbox-strict-fields -Wall -fwarn-tabs -O2 -threaded -XHaskell2010 -no-user-package-db -rtsopts -Wno-unused-imports -Wno-deprecations -Wnoncanonical-monad- instances -odir utils/haddock/dist/build -hidir utils/haddo ck/dist/build -stubdir utils/haddock/dist/build -c utils/haddock /haddock-api/src/Haddock/Backends/Hyperlinker/Types.hs -o utils/haddock/dist/build/Haddock/Backends/Hyperlinker/Types.dyn_o "inplace/bin/ghc-stage2" -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/haddock-api/src -iutils/haddock/haddock- library/vendor/attoparsec-0.13.1.0 -iutils/haddock/haddock-library/sr c -iutils/haddock/dist/build -Iutils/haddock/dist/build -iutils/haddock/dist/build/haddock/autogen -Iutils/haddock/dist/build/haddock/autogen -optP-DIN_GHC_TREE -optP- include -optPutils/haddock/dist/build/haddock/autogen/cabal_macros.h -package-id base-4.10.0.0 -packag e-id filepath-1.4.1.2 -package-id directory-1.3.0.2 -package-id containers-0.5.10.2 -package-id deepseq-1.4.3.0 -package-id array-0.5.2.0 -package-id xhtml-3000.2.2 -package-id Cabal-2.0.0.0 -package-id ghc- boot-8.2.0.20170704 -package-id ghc-8.2.0.20170704 -package-id by testring-0.10.8.2 -package-id transformers-0.5.2.0 -funbox-strict-fields -Wall -fwarn-tabs -O2 -threaded -XHaskell2010 -no-user-package-db -rtsopts -Wno-unused-imports -Wno-deprecations -Wnoncanonical-monad- instances -odir utils/haddock/dist/build -hidir utils/haddo ck/dist/build -stubdir utils/haddock/dist/build -c utils/haddock /haddock-library/src/Documentation/Haddock/Types.hs -o utils/haddock/dist/build/Documentation/Haddock/Types.dyn_o "inplace/bin/ghc-stage2" -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/haddock-api/src -iutils/haddock/haddock- library/vendor/attoparsec-0.13.1.0 -iutils/haddock/haddock-library/sr c -iutils/haddock/dist/build -Iutils/haddock/dist/build -iutils/haddock/dist/build/haddock/autogen -Iutils/haddock/dist/build/haddock/autogen -optP-DIN_GHC_TREE -optP- include -optPutils/haddock/dist/build/haddock/autogen/cabal_macros.h -package-id base-4.10.0.0 -packag e-id filepath-1.4.1.2 -package-id directory-1.3.0.2 -package-id containers-0.5.10.2 -package-id deepseq-1.4.3.0 -package-id array-0.5.2.0 -package-id xhtml-3000.2.2 -package-id Cabal-2.0.0.0 -package-id ghc- boot-8.2.0.20170704 -package-id ghc-8.2.0.20170704 -package-id by testring-0.10.8.2 -package-id transformers-0.5.2.0 -funbox-strict-fields -Wall -fwarn-tabs -O2 -threaded -XHaskell2010 -no-user-package-db -rtsopts -Wno-unused-imports -Wno-deprecations -Wnoncanonical-monad- instances -odir utils/haddock/dist/build -hidir utils/haddo ck/dist/build -stubdir utils/haddock/dist/build -c utils/haddock/dist/build/haddock/autogen/Paths_haddock.hs -o utils/haddock/dist/build/Paths_haddock.dyn_o "inplace/bin/ghc-stage2" -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/haddock/driver -iutils/haddock/haddock-api/src -iutils/haddock/haddock- library/vendor/attoparsec-0.13.1.0 -iutils/haddock/haddock-library/sr c -iutils/haddock/dist/build -Iutils/haddock/dist/build -iutils/haddock/dist/build/haddock/autogen -Iutils/haddock/dist/build/haddock/autogen -optP-DIN_GHC_TREE -optP- include -optPutils/haddock/dist/build/haddock/autogen/cabal_macros.h -package-id base-4.10.0.0 -packag e-id filepath-1.4.1.2 -package-id directory-1.3.0.2 -package-id containers-0.5.10.2 -package-id deepseq-1.4.3.0 -package-id array-0.5.2.0 -package-id xhtml-3000.2.2 -package-id Cabal-2.0.0.0 -package-id ghc- boot-8.2.0.20170704 -package-id ghc-8.2.0.20170704 -package-id by testring-0.10.8.2 -package-id transformers-0.5.2.0 -funbox-strict-fields -Wall -fwarn-tabs -O2 -threaded -XHaskell2010 -no-user-package-db -rtsopts -Wno-unused-imports -Wno-deprecations -Wnoncanonical-monad- instances -odir utils/haddock/dist/build -hidir utils/haddo ck/dist/build -stubdir utils/haddock/dist/build -c utils/haddock /haddock-library/src/Documentation/Haddock/Utf8.hs -o utils/haddock/dist/build/Documentation/Haddock/Utf8.dyn_o Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.soError relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.soError relocating /home/build/aport s/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build/libHSrts_thr- ghc8.2.0.20170704.soError relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found: my_task: symbol not found : my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found: my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not foundError relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so : my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found Error relocating /home/build/aports/testing/ghc/src/ghc-8.2.0.20170704/rts/dist/build /libHSrts_thr-ghc8.2.0.20170704.so: my_task: symbol not found make[1]: *** [utils/haddock/ghc.mk:21: utils/haddock/dist/build/Haddock/GhcUtils.dyn_o] Error 127 make[1]: *** Waiting for unfinished jobs.... make[1]: *** [utils/haddock/ghc.mk:21: utils/haddock/dist/build/ResponseFile.dyn_o] Error 127 make[1]: *** [utils/haddock/ghc.mk:21: utils/haddock/dist/build/Haddock/Backends/Hyperlinker/Types.dyn_o] Error 127 make[1]: *** [utils/haddock/ghc.mk:21: utils/haddock/dist/build/Documentation/Haddock/Utf8.dyn_o] Error 127 make[1]: *** [utils/haddock/ghc.mk:21: utils/haddock/dist/build/Documentation/Haddock/Types.dyn_o] Error 127 make[1]: *** [utils/haddock/ghc.mk:21: utils/haddock/dist/build/Paths_haddock.dyn_o] Error 127 make: *** [Makefile:127: all] Error 2 >>> ERROR: ghc: all failed >>> ghc: Uninstalling dependencies... }}} I can attach the log file that comes from or just give a Dockerfile one can use to replicate things and debug directly. But there is a workaround so probably not a super critical bug from my perspective. I'm not sure how well this relates to the issues listed in that commit: #13541, #13810, #13883 so I'm just leaving those out of this issue for now. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13958> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10832: Generalize injective type families
by GHC 07 May '18

07 May '18

#10832: Generalize injective type families -------------------------------------+------------------------------------- Reporter: jstolarek | Owner: jstolarek Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 7.11 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- With injective type families we can now declare that type family result determines the arguments. But ITFs are not yet as expressive as functional dependencies. For example with FDs I can say: {{{#!hs data Nat = Zero | Succ a class Add a b r | a b -> r, r a -> b instance Add Zero b b instance (Add a b r) => Add (Succ a) b (Succ r) }}} Here we declare that the result and the first argument taken together uniquely determine the second argument. This is not currently possible with ITFs: {{{#!hs type family AddTF a b = r | r a -> b where AddTF Zero b = b AddTF (Succ a) b = Succ (AddTF a b) }}} But we want to be able to say that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10832> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11080: Open data kinds
by GHC 07 May '18

07 May '18

#11080: Open data kinds -------------------------------------+------------------------------------- Reporter: dmcclean | Owner: Type: feature | Status: new request | Priority: low | Milestone: Component: Compiler | Version: 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: -------------------------------------+------------------------------------- When we need type level symbols, we used to only have one option, `EmptyDataDecls`. The symbolic type parameters would be given kind `*`, but the convention would be to use types that are (mostly) uninhabited and that were made for the purpose of serving as symbols. For an example of this see http://hackage.haskell.org/package/servant-0.4.4.5/docs/Servant- API-ContentTypes.html. Now we also have the `Symbol` kind which can serve a similar purpose. Neither of these options is fully satisfactory for examples like servant's type-level encoding of content types, or the `units` libraries type-level encoding of physical dimensions, for the following reasons: We would prefer to give these types a kind other than `*` both because they are uninhabited and because we wish to provide documentation of what types are acceptable in these parameter positions. But the only facility we have for creating new kinds is `DataKinds`, and the kinds it creates are all closed. This is problematic because we wish to allow client modules to declare new content types or new physical dimensions. We could provide "newkind" wrappers around `Symbol` using `DataKinds`, but that runs in to name collision issues. The `EmptyDataDecls` solution is superior here because types with the same name declared in different modules remain distinct. Instead I propose the addition of a new feature where data kinds can be open. In a discussion at https://github.com/bjornbm/dimensional-dk/issues/96 in which @goldfire participated, we arrived at the following proposal for concrete syntax, but certainly there are many possible variations one could imagine which might have equal or greater merit: {{{#!hs -- declares a new kind which initially has no inhabitants data open ContentType -- declares a new type of kind ContentType, which is distinct -- from any others that may have been declared elsewhere, -- even if they have the same non-module-qualified name data constructor JSON :: ContentType }}} (@goldfire raised the possibility of one day interpreting the same `data constructor ...` syntax at the type level to declare inhabited types for which some constructors are defined in one module but which are open to extension with new constructors by other modules, but that is a distinct issue in all other ways apart from possibly wishing to share syntax.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11080> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11953: Export Word32#, Word64# on all architectures
by GHC 06 May '18

06 May '18

#11953: Export Word32#, Word64# on all architectures -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Currently we have no always-available fixed-width primitive types. For instance, if you want a 64-bit unsigned integer you need to use `Word#` on 64-bit targets and `Word32#` otherwise. This adds a fair bit of complexity in places which really should be simple (e.g. `Data.Word`). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11953> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14927: Hyperbolic area sine is unstable for (even moderately) big negative arguments.
by GHC 06 May '18

06 May '18

#14927: Hyperbolic area sine is unstable for (even moderately) big negative arguments. -------------------------------------+------------------------------------- Reporter: | Owner: (none) leftaroundabout | Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.2.1 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `asinh` is supposed to be the inverse of `sinh`, and this works pretty reliable for positive arguments. However, for negative arguments, the [http://hackage.haskell.org/package/base-4.10.1.0/docs/src/GHC.Float.html#li… currently used formula] {{{ asinh x = log (x + sqrt (1.0+x*x)) }}} gets unstable much earlier than necessary, namely when the summands in the logarithm cancel almost to zero, dominated by the numerical error of the square root. This is particularly troubling because mathematically **a)** `asinh` is a very “inert” function (i.e. you can carelessly put in huge numbers and – as long as they're not outright `Infinity` – always get a somewhat sane result), pseudo-sigmoidal as it were **b)** it is an ''odd function'', fulfilling `asinh (-x) = -asinh x`. Both is reflected in other implementations, e.g. Python, but not in GHC Haskell: {{{ GHCi, version 8.2.1 Python 3.5.2 (default, Nov 23 2017, 16:37:01) In [1]: from math import * Prelude> asinh 1e6 In [2]: asinh(1e6) 14.50865773852447 Out[2]: 14.50865773852447 Prelude> asinh (-1e6) In [3]: asinh(-1e6) -14.50865012405984 Out[3]: -14.50865773852447 Prelude> asinh 1e9 In [4]: asinh(1e9) 21.416413017506358 Out[4]: 21.416413017506354 Prelude> asinh (-1e9) In [5]: asinh(-1e9) -Infinity Out[5]: -21.416413017506354 Prelude> asinh 1e76 In [6]: asinh(1e76) 175.6896142481074 Out[6]: 175.68961424810743 Prelude> asinh (-1e76) In [7]: asinh(-1e76) -Infinity Out[7]: -175.68961424810743 }}} Demo of non-inverse property: {{{ Prelude> [(x, asinh $ sinh x) | x <- [-25..25]] [(-25.0,-Infinity) ,(-24.0,-Infinity) ,(-23.0,-Infinity) ,(-22.0,-Infinity) ,(-21.0,-Infinity) ,(-20.0,-Infinity) ,(-19.0,-18.021826694558577) ,(-18.0,-18.021826694558577) ,(-17.0,-17.0102257828801) ,(-16.0,-15.998624871201619) ,(-15.0,-14.999878578873695) ,(-14.0,-13.999968823323222) ,(-13.0,-12.999991335176079) ,(-12.0,-12.000000137072186) ,(-11.0,-10.999999903206444) ,(-10.0,-10.000000013503529) ,(-9.0,-9.000000000551713) ,(-8.0,-8.00000000017109) ,(-7.0,-7.000000000036329) ,(-6.0,-5.999999999998066) ,(-5.0,-5.000000000000641) ,(-4.0,-4.000000000000046) ,(-3.0,-2.999999999999989) ,(-2.0,-1.9999999999999991) ,(-1.0,-1.0) ,(0.0,0.0) ,(1.0,1.0) ,(2.0,2.0) ,(3.0,3.0) ,(4.0,4.0) ,(5.0,5.0) ,(6.0,6.0) ,(7.0,7.0) ,(8.0,8.0) ,(9.0,9.0) ,(10.0,10.0) ,(11.0,11.0) ,(12.0,12.0) ,(13.0,13.0) ,(14.0,14.0) ,(15.0,15.0) ,(16.0,16.0) ,(17.0,17.0) ,(18.0,18.0) ,(19.0,19.0) ,(20.0,20.0) ,(21.0,21.0) ,(22.0,22.0) ,(23.0,23.0) ,(24.0,24.0) ,(25.0,25.0)] }}} Those results are less than satisfying, even for inputs that aren't astronomically big at all. A simple fix would be to “copy” the sane positive-number behaviour to the negative side: {{{ asinh x | x < 0 = -asinh (-x) | otherwise = log (x + sqrt (1.0+x*x)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14927> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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