November 2016 - ghc-tickets

[GHC] #11958: Improved testing of cross-compiler
by GHC 21 Jun '18

21 Jun '18

#11958: Improved testing of cross-compiler -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: task | Status: new Priority: low | Milestone: 8.2.1 Component: Test Suite | Version: 7.10.3 Keywords: cross-compile | 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 is already possible to build cross compiler eg from x86_64/linux to armhf/linux or arm64/linux, but there is currently no way to run the test suite. However, at least for the host and targets above, it should be possible to run the test executables under the Qemu user space emulation. I know this works, because in my own personal jenkins build instance, I test exactly this by doing (for x86_64/linux to amr64/linux cross): {{{ echo -e 'main :: IO ()\nmain = putStrLn "Hello World"\n' > hello-world.hs inplace/bin/ghc-stage1 hello-world.hs -o hello-world test $(file hello-world | grep -c 'ARM aarch64, version 1') -eq 1 ./hello-world }}} The linux machine I run the above test on is x86_64/linux but has Qemu and `binfmt` stuff set up so that it can run some foreign binaries. For instance, if GHC worked as a Linux to Windows cross-compiler the resulting windows binaries should work under Wine. To get this working, I suspect that just about all the required work is in the build system. Not sure if it might not be better to wait until the Shake based build system is in better shape. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11958> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10059: :i doesn't work for ~
by GHC 21 Jun '18

21 Jun '18

#10059: :i doesn't work for ~ -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- {{{#!hs Prelude> :set -XTypeOperators Prelude> :i (~) <interactive>:1:2: parse error on input ‘~’ Prelude> :k (~) (~) :: k -> k -> Constraint }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10059> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9106: GHC Panic related to functional dependencies - kindFunResult
by GHC 18 Jun '18

18 Jun '18

#9106: GHC Panic related to functional dependencies - kindFunResult ----------------------------+--------------------------------------- Reporter: yuriy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Windows Architecture: x86 | Type of failure: Compile-time crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ----------------------------+--------------------------------------- Minimal example: {{{ {-# LANGUAGE MultiParamTypeClasses, DataKinds, FunctionalDependencies, TypeOperators, KindSignatures, PolyKinds, FlexibleInstances, FlexibleContexts, UndecidableInstances #-} import GHC.TypeLits data Proxy (a :: k) = Proxy class FunctorN n f a fa | n f a -> fa where fmapn :: Proxy n -> Proxy f -> (a -> a) -> fa -> fa instance FunctorN 0 f a a where fmapn _ _ a = a instance (Functor f, FunctorN (n - 1) f a fa) => FunctorN n f a (f fa) where fmapn _ pf f = fmap (fmapn (Proxy :: Proxy (n-1)) pf f) }}} Crashes with ghc and ghci: {{{ >ghc test [1 of 1] Compiling Main ( test.hs, test.o ) ghc.exe: panic! (the 'impossible' happened) (GHC version 7.8.20140130 for x86_64-unknown-mingw32): kindFunResult k{tv azb} [sk] >ghci test GHCi, version 7.8.20140130: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( test.hs, interpreted ) ghc.exe: panic! (the 'impossible' happened) (GHC version 7.8.20140130 for x86_64-unknown-mingw32): kindFunResult k{tv aPm} [sk] }}} Removing the functional dependency makes the code compile. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9106> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8619: Support anonymous string literals in C-- (OR) give better ASSERT failure messages in C--
by GHC 17 Jun '18

17 Jun '18

#8619: Support anonymous string literals in C-- (OR) give better ASSERT failure messages in C-- ------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- So if I say "foobar" in C--, it turns into: {{{ section "rodata" { fresh_name : bits8[] "foobar\0"; } }}} This would let us fix the ASSERT macro in Cmm.h to also get the filename. Requires parser changes. Alternatively, we can redefine the ASSERT macro per C-- file to have a hardcoded filename with some preprocessor trickery. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8619> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11259: Use system runtime linker in GHCi on PowerPC 64 bit
by GHC 14 Jun '18

14 Jun '18

#11259: Use system runtime linker in GHCi on PowerPC 64 bit -------------------------------------+------------------------------------- Reporter: trommler | Owner: trommler Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: GHCi | Version: 7.11 Keywords: | Operating System: Linux Architecture: powerpc64 | Type of failure: GHCi crash Test Case: ghcilink004, | Blocked By: prog001, and 11 more | Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Teach GHCi to use the system runtime linker to load Haskell libraries on powerpc64. See the following test failures. ghcilink004: {{{ ghc-stage2: dir004/libfoo.a: unknown architecture (e_machine == 21) ghc-stage2: panic! (the 'impossible' happened) (GHC version 7.11.20151219 for powerpc64-unknown-linux): loadArchive "dir004/libfoo.a": failed CallStack (from ImplicitParams): error, called at libraries/ghci/GHCi/ObjLink.hs:91:21 in ghci-0.0:GHCi.ObjLink Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} prog001: {{{ ghc-iserv.bin: /home/peter/ghc/libraries/ghc-prim/dist-install/build /libHSghc-prim-0.5.0.0.a: unknown architecture (e_machine == 21) ghc-iserv.bin: loadArchive "/home/peter/ghc/libraries/ghc-prim/dist- install/build/libHSghc-prim-0.5.0.0.a": failed CallStack (from ImplicitParams): error, called at libraries/ghci/GHCi/ObjLink.hs:91:21 in ghci-0.0:GHCi.ObjLink ghc-stage2: ghc-iserv terminated (1) }}} Using the system runtime linker fixes 13 failing tests. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11259> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12903: SIGINT is not handled in forked process
by GHC 14 Jun '18

14 Jun '18

#12903: SIGINT is not handled in forked process -------------------------------------+------------------------------------- Reporter: qnikst | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 8.0.1 System | 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: -------------------------------------+------------------------------------- If haskell program is forked in a toplevel hander that sends UserInterrupt in the main thread doesn't work, because Thread 1 doesn't exists in forked program, so that action is noop. Minimal example: {{{#!hs import Control.Concurrent import Control.Exception import System.Posix main = do pid <- forkProcess $ do handle (\UserInterrupt{} -> putStrLn "caught") $ threadDelay 2000000 signalProcess sigINT pid threadDelay 2000000 }}} Expected result: "caught" printed to stdout. Actual result: nothing is printed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12903> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9539: TQueue can lead to thread starvation
by GHC 12 Jun '18

12 Jun '18

#9539: TQueue can lead to thread starvation -------------------------------------+------------------------------------- Reporter: jwlato | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries (other) | Version: 7.8.2 Keywords: stm | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- For background, please see [http://stackoverflow.com/questions/25536604 /huge-memory-consumption-for-simple-multithreaded- haskell/25560047#25560047 this SO question] When using TQueue, a sufficiently fast/persistent writer can result in the reader never getting scheduled, causing the queue to continually grow and lost concurrency. I believe the issue is caused by the definition of readTQueue: {{{ readTQueue :: TQueue a -> STM a readTQueue (TQueue read write) = do xs <- readTVar read case xs of (x:xs') -> do writeTVar read xs' return x [] -> do ys <- readTVar write case ys of [] -> retry _ -> case reverse ys of [] -> error "readTQueue" (z:zs) -> do writeTVar write [] writeTVar read zs return z }}} Note that the last `case` needs to traverse the write-end of the queue within the STM transaction. If the list is sufficiently large, a writer can commit a new transaction much more quickly, invalidating the read transaction. If threads continue to write to the queue, the reader will never get an opportunity to commit (and the list will grow, exacerbating the problem). This alternative definition seems to fix the problem, but I don't know if there are other drawbacks to using it. {{{ readTQueue' :: TQueue a -> STM a readTQueue' (TQueue read write) = do xs <- readTVar read case xs of (x:xs') -> do writeTVar read xs' return x [] -> do ys <- readTVar write case ys of [] -> retry _ -> do writeTVar write [] let (z:zs) = reverse ys writeTVar read zs return z }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9539> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11798: Recompiling with -fhpc flag added does nothing
by GHC 10 Jun '18

10 Jun '18

#11798: Recompiling with -fhpc flag added does nothing -------------------------------------+------------------------------------- Reporter: drathier | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When you recompile without modifiying any source code, nothing happens, as expected. The file is already compiled, after all. If you then add the -fhpc flag, it still doesn't recompile, even though it now should generate .tix files. These files are now unexpectedly missing, until the source files are modified or the .o and .hi files are deleted, and the code is recompiled again with the -fhpc flag. reproduce: 1. compile program 2. compile program with -fhpc note: missing .tix file 3. delete .hi and .o files 4. compile program with -fhpc 5. success; .tix file is generated -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11798> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11376: Inconsistent specified type variables among functions and datatypes/classes when using -XTypeApplications
by GHC 08 Jun '18

08 Jun '18

#11376: Inconsistent specified type variables among functions and datatypes/classes when using -XTypeApplications -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Originally reported [https://mail.haskell.org/pipermail/ghc- devs/2016-January/010915.html here]. When applying types via `-XTypeApplications`, the type/kind that gets instantiated seems to be different depending on whether you're using functions, datatypes, or typeclasses. Here's an example contrasting functions and datatypes: {{{ $ /opt/ghc/head/bin/ghci GHCi, version 8.1.20160106: http://www.haskell.org/ghc/ :? for help λ> :set -fprint-explicit-kinds -XTypeApplications -XTypeInType λ> data Prox a = Prox λ> prox :: Prox a; prox = Prox λ> :t prox prox :: forall k (a :: k). Prox k a λ> :t prox @Int prox @Int :: Prox * Int λ> :t Prox Prox :: forall k (a :: k). Prox k a λ> :t Prox @Int Prox @Int :: Prox Int a }}} This is the core of the problem: with a function, `Int` seems to be applied to type variable `a`, whereas with data types, `Int` appears to be applied to the kind variable `k`. This confuses me, since `k` wasn't specified anywhere in the definition of `Prox`. Andres Löh also [https://mail.haskell.org/pipermail/ghc- devs/2016-January/010916.html observed] a similar discrepancy between functions and typeclasses: {{{ λ> :set -XScopedTypeVariables λ> class C a where c :: () λ> d :: forall a. C a => (); d = c @_ @a λ> :t d d :: forall k (a :: k). C k a => () λ> :t d @Int d @Int :: C * Int => () λ> :t c c :: forall k (a :: k). C k a => () λ> :t c @Int c @Int :: C Int a => () λ> :t c @_ @Int c @_ @Int :: C * Int => () }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11376> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12023: Problems getting information and kind from GHC.Prim ~#, ~R#, ...
by GHC 07 Jun '18

07 Jun '18

#12023: Problems getting information and kind from GHC.Prim ~#, ~R#, ... -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | 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: -------------------------------------+------------------------------------- {{{ >>> import GHC.Prim >>> :bro GHC.Prim [...] type role (~#) nominal nominal data (~#) (t3 :: a) (t4 :: b) type role ~P# phantom phantom data ~P# (t3 :: a) (t4 :: b) type role (~R#) representational representational data (~R#) (t3 :: a) (t4 :: b) }}} getting the kind of `~`, `~#`, `~~` works fine: {{{ >>> import GHC.Prim >>> import GHC.Types >>> :kind (~) (~) :: k -> k -> Constraint >>> :kind (~#) (~#) :: a -> b -> TYPE 'VoidRep >>> :kind (~~) (~~) :: j -> k -> Constraint }}} but `#` gets incorrectly treated as an operator in `~R#` and `~P#`: {{{ >>> :kind (~R#) <interactive>:1:3: error: Illegal operator ‘#’ in type ‘~R #’ Use TypeOperators to allow operators in types <interactive>:1:3: error: Operator applied to too few arguments: ~R # <interactive>:1:4: error: Not in scope: type constructor or class ‘R’ }}} Furthermore while running `:info` on `~~` and `~#` works fine {{{ >>> :info (~~) class a ~# b => (~~) (a :: j) (b :: k) -- Defined in ‘GHC.Types’ >>> :info (~#) type role (~#) nominal nominal data (~#) (t3 :: a) (t4 :: b) -- Defined in ‘GHC.Prim’ }}} the others don't parse {{{ >>> :info (~) <interactive>:1:2: error: parse error on input ‘~’ >>> :info (~R#) <interactive>:1:2: error: parse error on input ‘~’ >>> :info (~P#) <interactive>:1:2: error: parse error on input ‘~’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12023> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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