February 2018 - ghc-tickets

[GHC] #14291: Tests tend to fail in the ext-interp when testing a tree built with a source distribution
by GHC 25 Feb '18

25 Feb '18

#14291: Tests tend to fail in the ext-interp when testing a tree built with a source distribution -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- One issue I've noticed while working on #13716 is that most (if not all) of the tests runs in the `ext-interp` way fail when run inside a tree derived from a source distribution tarball. For instance, {{{ $ git clone git://git.haskell.org/ghc $ cd ghc $ git submodule update --init $ mk/get-win32-tarballs.sh download all $ ./boot $ ./configure $ make sdist $ mkdir tmp; cd tmp $ ls ../sdistprep/ghc-*-src.tar.xz | xargs -n1 tar -xf $ cd ghc-* $ ./boot $ ./configure $ make -j9 $ make test TEST=T10638 ... =====> T10638(normal) 1 of 1 [0, 0, 0] cd "./th/T10638.run" && "/mnt/work/ghc/ghc- testing/temp/ghc-8.3.20170927/inplace/bin/ghc-stage2" -c T10638.hs -dcore- lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed- specialisations -fshow-warning-groups -fdiagnostics-color=never -fno- diagnostics-show-caret -dno-debug-output -XTemplateHaskell -package template-haskell -v0 =====> T10638(ext-interp) 1 of 1 [0, 0, 0] cd "./th/T10638.run" && "/mnt/work/ghc/ghc- testing/temp/ghc-8.3.20170927/inplace/bin/ghc-stage2" -c T10638.hs -dcore- lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed- specialisations -fshow-warning-groups -fdiagnostics-color=never -fno- diagnostics-show-caret -dno-debug-output -XTemplateHaskell -package template-haskell -fexternal-interpreter -v0 Actual stderr output differs from expected: diff -uw "./th/T10638.run/T10638.stderr.normalised" "./th/T10638.run/T10638.comp.stderr.normalised" --- ./th/T10638.run/T10638.stderr.normalised 2017-09-27 12:18:45.737974039 -0400 +++ ./th/T10638.run/T10638.comp.stderr.normalised 2017-09-27 12:18:45.737974039 -0400 @@ -1,5 +1,18 @@ +ghc-iserv.bin: internal evacuate(static): strange closure type 16476 + (GHC version 8.3.20170927 for x86_64_unknown_linux) + Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -T10638.hs:26:11: - ‘static test2’ is not a valid C identifier - When checking declaration: - foreign import prim safe "static test2" cmm_test2 :: Int# -> Int# +T10638.hs:26:9: + Exception when trying to run compile-time code: + {handle: <file descriptor: 11>}: GHCi.Message.remoteCall: end of file + Code: do t <- [t| Int# -> Int# |] + cmm_test2 <- newName "cmm_test2" + addTopDecls + [ForeignD (ImportF Prim Safe "static test2" cmm_test2 t)] + .... + In the untyped splice: + $(do t <- [t| Int# -> Int# |] + cmm_test2 <- newName "cmm_test2" + addTopDecls + [ForeignD (ImportF Prim Safe "static test2" cmm_test2 t)] + [| test1 |]) *** unexpected failure for T10638(ext-interp) Unexpected results from: TEST="T10638" ... }}} The crashes are generally RTS panics or segmentation faults. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14291> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13011: Simplifier ticks exhausted: a 10-line case
by GHC 25 Feb '18

25 Feb '18

#13011: Simplifier ticks exhausted: a 10-line case -------------------------------------+------------------------------------- Reporter: L.K.Rebellion | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 Keywords: Simplifier | Operating System: Linux ticks exhausted | Type of failure: Compile-time Architecture: x86 | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: #8319 #12776 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I was trying to define a function that could take itself as an argument. {{{#!hs newtype MobiusFn a = MobiusFn { func :: MobiusFn a -> a } spin :: MobiusFn a -> a spin mf = func mf mf }}} Use it to find suffixes of a `String` {{{#!hs suffixes :: String -> [String] suffixes = spin $ MobiusFn suffixesMF where suffixesMF _ [] = [] suffixesMF mf s@(_:xs) = s : spin mf xs }}} Add `main` and compile {{{#!hs main = readLn >>= (print . suffixes) }}} The compiler panicked with {{{ [1 of 1] Compiling Main ( test.hs, test.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for i386-unknown-linux): Simplifier ticks exhausted When trying UnfoldingDone mf_s1UD }}} But if we ignore the empty string case, it works well with non-empty strings. {{{#!hs suffixes :: String -> [String] suffixes = spin $ MobiusFn suffixesMF where suffixesMF _ s@[_] = [s] suffixesMF mf s@(_:xs) = s : spin mf xs }}} Two versions tested. {{{ GHC version 8.0.1 for i386-unknown-linux GHC version 7.10.3 for i386-unknown-linux }}} Thank you for reading. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13011> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14841: Inconsistent allocation stats
by GHC 24 Feb '18

24 Feb '18

#14841: Inconsistent allocation stats -------------------------------------+------------------------------------- Reporter: patrickdoc | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: System | Keywords: GCStats, | Operating System: Unknown/Multiple RTSStats | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'm looking at Criterion internals, and seeing an inconsistency in the allocations reported by `GCStats` and `RTSStats`. Here is a small reproduction: {{{#!hs {-# LANGUAGE CPP #-} module Main where import GHC.Stats import System.Mem (performGC) main :: IO () main = do runOldThing 1000 #if __GLASGOW_HASKELL__ >= 802 putStrLn "Running new:" runThing 1000 #endif runOldThing :: Int -> IO () runOldThing n = loop n 0 >> return () where loop 0 _ = return 0 loop count x = do performGC stats <- getGCStats putStrLn $ show (count `mod` 15) ++ ": " ++ show (bytesAllocated stats - x) ++ " num: " ++ show (numGcs stats) loop (count-1) (bytesAllocated stats) #if __GLASGOW_HASKELL__ >= 802 runThing :: Int -> IO () runThing = loop where loop 0 = return () loop n = do performGC stats <- getRTSStats putStrLn $ show (n `mod` 15) ++ ": " ++ show (gcdetails_allocated_bytes (gc stats)) ++ " num: " ++ show (gcs stats) loop (n-1) #endif }}} This code just performs a garbage collection and then prints the stats in a loop. Here is a snippet of the output. {{{ ... 4: 8840 num: 1967 3: 4880 num: 1968 2: 4880 num: 1969 1: 4880 num: 1970 0: 4880 num: 1971 14: 4880 num: 1972 13: 4976 num: 1973 12: 4976 num: 1974 11: 4976 num: 1975 10: 4976 num: 1976 9: 4976 num: 1977 8: 4880 num: 1978 7: 4880 num: 1979 6: 4880 num: 1980 5: 4880 num: 1981 4: 8840 num: 1982 3: 4880 num: 1983 2: 4880 num: 1984 1: 4880 num: 1985 0: 4880 num: 1986 14: 4880 num: 1987 13: 4976 num: 1988 12: 4976 num: 1989 11: 4976 num: 1990 10: 4976 num: 1991 9: 4976 num: 1992 8: 4880 num: 1993 7: 4880 num: 1994 6: 4880 num: 1995 5: 4880 num: 1996 4: 8840 num: 1997 3: 4880 num: 1998 2: 4880 num: 1999 1: 4880 num: 2000 }}} On the left, I've included the gc number `mod` 15 to show that exactly every 15 gcs, there is an extra 4k bytes reported. This output was made with 8.2.1. On 7.8.4, 7.10.3, and 8.0.2 it's every 23. And on 8.4.0.20180204 it's every 9. I've played around with extra allocations between garbage collections, but the interval remained constant. I tried poking around the rts, but I've been unable to determine if this is a bug or just unavoidable noise. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14841> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8597: Git Hook script to prevent large binary blobs being checked in
by GHC 23 Feb '18

23 Feb '18

#8597: Git Hook script to prevent large binary blobs being checked in ------------------------------------+------------------------------------- Reporter: hvr | Owner: hvr Type: task | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- It has already occurred in the past in `testsuite.git` repo, that executables were checked in by accident, and caused the Git history to get bloated. In order to avoid such accidents in the future a Git hook script in the style of [http://stackoverflow.com/questions/20226132/is-there-a-git-hook- which-can-prevent-binary-check-ins this] might be useful, but taking also into account the size, and/or possibly with a magic safeword to be put in the commit message, to override the check for a single commit, if the author really knows what (s)he's doing. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8597> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1974: length "foo" doesn't work with -XOverloadedStrings
by GHC 23 Feb '18

23 Feb '18

#1974: length "foo" doesn't work with -XOverloadedStrings -------------------------------------+------------------------------------- Reporter: ganesh | Owner: (none) Type: feature request | Status: closed Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.8.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by sjakobi): * status: new => closed * resolution: => fixed Comment: Replying to [comment:9 parcs]: > Have you considered changing the instance declaration from > > {{{ > instance IsString String where > }}} > > to > > {{{ > instance (a ~ Char) => IsString [a] where > }}} > > This new instance will make `length "foo"` happily typecheck, but it will also overlap with other `IsString` instances of the form `[T]`. (Though I don't think such instances are common in practice.) That change with in GHC-8.0 / base-4.9: {{{#!hs GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help > length "foo" 3 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1974#comment:10> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14542: Renamer / typechecker hang (UndecidableSuperClasses)
by GHC 23 Feb '18

23 Feb '18

#14542: Renamer / typechecker hang (UndecidableSuperClasses) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Keywords: | Operating System: Unknown/Multiple UndecidableSuperClasses | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Adapted from [https://gist.github.com/ekmett/b26363fc0f38777a637d hask], this does not look like a normal superclass loop. Loop is avoided by removing `instance (Category p, Category q) => Category (Nat p q)`. {{{#!hs {-# language KindSignatures #-} {-# language PolyKinds #-} {-# language DataKinds #-} {-# language TypeFamilies #-} {-# language RankNTypes #-} {-# language NoImplicitPrelude #-} {-# language FlexibleContexts #-} {-# language MultiParamTypeClasses #-} {-# language GADTs #-} {-# language ConstraintKinds #-} {-# language FlexibleInstances #-} {-# language TypeOperators #-} {-# language ScopedTypeVariables #-} {-# language DefaultSignatures #-} {-# language FunctionalDependencies #-} {-# language UndecidableSuperClasses #-} {-# language UndecidableInstances #-} {-# language TypeInType #-} import GHC.Types (Constraint, Type) type Cat i = i -> i -> Type newtype Y p a b = Y { getY :: p b a } class (Functor p, Dom p ~ Op p, Cod p ~ Nat p (->), Ob (Op p) ~ Ob p) => Category (p :: Cat i) where type Op p :: Cat i type Op p = Y p type Ob p :: i -> Constraint class (Category (Dom f), Category (Cod f)) => Functor (f :: i -> j) where type Dom f :: Cat i type Cod f :: Cat j data Nat :: Cat i -> Cat j -> Cat (i -> j) instance (Category p, Category q) => Category (Nat p q) }}} I get {{{ $ ghci2 -ignore-dot-ghci -v /tmp/Hangs.hs GHCi, version 8.3.20171122: http://www.haskell.org/ghc/ :? for help Glasgow Haskell Compiler, Version 8.3.20171122, stage 2 booted by GHC version 8.2.1 ... Loading package integer-gmp-1.0.1.0 ... linking ... done. Loading package base-4.11.0.0 ... linking ... done. *** Parser [source]: !!! Parser [source]: finished in 0.66 milliseconds, allocated 0.136 megabytes *** Desugar: *** Simplify [expr]: !!! Simplify [expr]: finished in 0.43 milliseconds, allocated 0.233 megabytes *** CorePrep [expr]: !!! CorePrep [expr]: finished in 0.23 milliseconds, allocated 0.167 megabytes *** ByteCodeGen [Ghci1]: !!! ByteCodeGen [Ghci1]: finished in 0.35 milliseconds, allocated 0.284 megabytes *** Parser [source]: !!! Parser [source]: finished in 0.21 milliseconds, allocated 0.197 megabytes *** Desugar: *** Simplify [expr]: !!! Simplify [expr]: finished in 0.52 milliseconds, allocated 0.268 megabytes *** CorePrep [expr]: !!! CorePrep [expr]: finished in 0.23 milliseconds, allocated 0.113 megabytes *** ByteCodeGen [Ghci1]: !!! ByteCodeGen [Ghci1]: finished in 0.46 milliseconds, allocated 0.334 megabytes *** Chasing dependencies: Chasing modules from: !!! Chasing dependencies: finished in 0.14 milliseconds, allocated 0.047 megabytes Stable obj: [] Stable BCO: [] unload: retaining objs [] unload: retaining bcos [] Ready for upsweep [] Upsweep completely successful. *** Deleting temp files: Deleting: *** Chasing dependencies: Chasing modules from: */tmp/Hangs.hs !!! Chasing dependencies: finished in 6.10 milliseconds, allocated 10.504 megabytes Stable obj: [] Stable BCO: [] unload: retaining objs [] unload: retaining bcos [] Ready for upsweep [NONREC ModSummary { ms_hs_date = 2017-11-28 22:14:57.810561584 UTC ms_mod = Main, ms_textual_imps = [(Nothing, GHC.Types)] ms_srcimps = [] }] *** Deleting temp files: Deleting: compile: input file /tmp/Hangs.hs *** Checking old interface for Main (use -ddump-hi-diffs for more details): [1 of 1] Compiling Main ( /tmp/Hangs.hs, interpreted ) *** Parser [Main]: !!! Parser [Main]: finished in 2.63 milliseconds, allocated 4.821 megabytes *** Renamer/typechecker [Main]: }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14542> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13153: Several Traversable instances have an extra fmap
by GHC 23 Feb '18

23 Feb '18

#13153: Several Traversable instances have an extra fmap -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Core | Version: 8.1 Libraries | 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: -------------------------------------+------------------------------------- For example, we define {{{#!hs instance Traversable ZipList where traverse f (ZipList xs) = ZipList <$> traverse f xs }}} If the list is very short, the extra `fmap` could be bad. We can fix this by inlining the inner `traverse`. However, I suspect a better approach would be to add a method to `Traversable`: {{{#!hs mapTraverse :: Applicative f => (t b -> r) -> (a -> f b) -> t a -> f r mapTraverse p f xs = p <$> traverse f xs }}} but I need to work through whether this is enough power to solve enough problems. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13153> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11826: unsafe causes bug, news @ 11
by GHC 23 Feb '18

23 Feb '18

#11826: unsafe causes bug, news @ 11 -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: 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: -------------------------------------+------------------------------------- I know there has been plenty of levity here lately but here goes :) I didn't expect ‘isUndefined’ to be safe but this may be interesting to the devs (I am obedient and report it thusly and hereby-ly per GHC's request) {{{#!haskell % ghci -ignore-dot-ghci GHCi, version 8.1.20160117: http://www.haskell.org/ghc/ :? for help Prelude> import Control.Exception Prelude Control.Exception> import System.IO.Unsafe Prelude Control.Exception System.IO.Unsafe> import Unsafe.Coerce Prelude Control.Exception System.IO.Unsafe Unsafe.Coerce> isUndefined x = unsafePerformIO $ catch ((unsafeCoerce x :: IO ()) >> return False) (const $ return True :: SomeException -> IO Bool) Prelude Control.Exception System.IO.Unsafe Unsafe.Coerce> isUndefined (succ True) True Prelude Control.Exception System.IO.Unsafe Unsafe.Coerce> isUndefined (succ False) <interactive>: internal error: stg_ap_v_ret (GHC version 8.1.20160117 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Aborted (core dumped) % }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11826> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14799: QuantifiedConstraints: Problems with Typeable
by GHC 23 Feb '18

23 Feb '18

#14799: QuantifiedConstraints: Problems with Typeable -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 Keywords: | Operating System: Unknown/Multiple QuantifiedConstraints, wipT2893 | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This compiles {{{#!hs {-# Language GADTs, ConstraintKinds, ScopedTypeVariables, QuantifiedConstraints #-} import Data.Typeable data Ex cls where MkEx :: cls xx => xx -> Ex cls a :: Ex Typeable -> TypeRep a (MkEx (_::xx)) = typeRep @_ @xx Proxy -- b :: (forall xx. cls xx => Typeable xx) => Ex cls -> TypeRep -- b (MkEx (_::xx)) = typeRep @_ @xx Proxy c :: (forall xx. cls xx => Show xx) => Ex cls -> String c (MkEx xx) = show xx }}} but uncommenting `b` is too much: {{{ $ qc hs/189-bug.hs GHCi, version 8.5.20180128: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( hs/189-bug.hs, interpreted ) hs/189-bug.hs:12:20: error: • Could not deduce (Typeable xx) arising from a use of ‘typeRep’ from the context: forall xx. cls xx => Typeable xx bound by the type signature for: b :: forall (cls :: * -> Constraint). (forall xx. cls xx => Typeable xx) => Ex cls -> TypeRep at hs/189-bug.hs:11:1-60 or from: cls xx bound by a pattern with constructor: MkEx :: forall xx (cls :: * -> Constraint). cls xx => xx -> Ex cls, in an equation for ‘b’ at hs/189-bug.hs:12:4-15 • In the expression: typeRep @_ @xx Proxy In an equation for ‘b’: b (MkEx (_ :: xx)) = typeRep @_ @xx Proxy | 12 | b (MkEx (_::xx)) = typeRep @_ @xx Proxy | ^^^^^^^^^^^^^^^^^^^^ Failed, no modules loaded. Prelude> }}} This is maybe because of the `Typeable` solver. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14799> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12524: RFC: Allow prefixing result evaluated at GHCi prompt
by GHC 23 Feb '18

23 Feb '18

#12524: RFC: Allow prefixing result evaluated at GHCi prompt -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: lowest | Milestone: Component: GHCi | 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: -------------------------------------+------------------------------------- Similar to `prompt`, `prompt-cont` (previously `prompt2`): allowing users to supply a prefix to evaluation results with `result` has two use cases I can think of {{{ :set prompt " ghci> " :set prompt-cont " ghci| " :set result " " }}} the desired outcome would be `↓` as indented code for IRC, also reddit code format: {{{ ghci> 1 + 2 + 3 6 ghci> reverse "hello" "olleh" }}} ---- The other case came from [https://twitter.com/rightfold/status/767301255140179968 this tweet] {{{ :set prompt "" :set result "-- " }}} {{{ 1 + 2 + 3 -- 6 reverse "hello" -- "olleh" }}} This can be copied/pasted back to a separate GHCi session where the result is ignored. ---- I haven't seen this feature in any other repl, I'm not sure if this would see much use. This wouldn't work with IO actions without some magic. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12524> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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