September 2016 - ghc-tickets

[GHC] #9588: Add `MonadPlus {IO, Either e}` and `Alternative (Either e)` instances
by GHC 29 Jun '17

29 Jun '17

#9588: Add `MonadPlus {IO,Either e}` and `Alternative (Either e)` instances -------------------------------------+------------------------------------- Reporter: hvr | Owner: hvr Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries/base | Version: Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The following 3 instances are currently Orphans in `transformers` but shall be defined in `base` instead: {{{#!hs instance MonadPlus IO instance MonadPlus (Either e) instance Alterantive (Either e) }}} This proposal by SPJ already passed the CLC back in April and only needs implementing. I'll submit a patch shortly to Phab -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9588> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11990: Custom Type Error not getting triggered in the nested Type function call
by GHC 27 Jun '17

27 Jun '17

#11990: Custom Type Error not getting triggered in the nested Type function call -------------------------------------+------------------------------------- Reporter: magesh.b | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc3 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 have partial type function which is invoked by another type function. When the inner type function fails with TypeError, outer type function is not been able to propagate that type error to its caller. As a result of it, I'm getting following error • No instance for (KnownSymbol (NestedPartialTF (TypeError ...))) instead of • Unexpected type @ NestedPartialTF: Char {{{#!hs {-# LANGUAGE DataKinds, TypeOperators, TypeFamilies, UndecidableInstances, ScopedTypeVariables, FlexibleContexts #-} -- | module CErrs where import GHC.TypeLits import Data.Proxy type family PartialTF t :: Symbol where PartialTF Int = "Int" PartialTF Bool = "Bool" PartialTF a = TypeError (Text "Unexpected type @ PartialTF: " :<>: ShowType a) type family NestedPartialTF (tsym :: Symbol) :: Symbol where NestedPartialTF "Int" = "int" NestedPartialTF "Bool" = "bool" NestedPartialTF a = TypeError (Text "Unexpected type @ NestedPartialTF: " :<>: ShowType a) testPartialTF :: forall a.(KnownSymbol (PartialTF a)) => a -> String testPartialTF t = symbolVal (Proxy :: Proxy (PartialTF a)) --t1 = testPartialTF 'a' {- Above code rightly fails with the following error: • Unexpected type: Char • In the expression: testPartialTF 'a' In an equation for ‘t1’: t1 = testPartialTF 'a' -} -- Bug? testNesPartialTF :: forall a.(KnownSymbol (NestedPartialTF (PartialTF a))) => a -> String testNesPartialTF t = symbolVal (Proxy :: Proxy (NestedPartialTF (PartialTF a))) t2 = testNesPartialTF 'a' {- Above code fails with the following error: • No instance for (KnownSymbol (NestedPartialTF (TypeError ...))) arising from a use of ‘testNesPartialTF’ • In the expression: testNesPartialTF 'a' In an equation for ‘t2’: t2 = testNesPartialTF 'a' -} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11990> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12412: SIMD things introduce a metric ton of known key things
by GHC 26 Jun '17

26 Jun '17

#12412: SIMD things introduce a metric ton of known key things -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In #12357 we were looking at reducing the number of entries in the `knownKeyNames`. This has the potential to improve compiler performance since this set of things is always present in the original name cache, which is often referred to. #12357 reduced the number of elements in `knownKeyNames` from 2017 to 1834. Not a bad improvement. That being said, the SIMD operations introduce nearly four times that number. These include things like `readWord64OffAddrAsWord64X2#`, `indexInt16OffAddrAsInt16X16#`, and `remInt16X16#`. All in all these operations constitute nearly a third of the known key names. I'm not really sure what can be done about this, but I thought it should be noted. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12412> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10286: native code generator: GHC crash at GHC.Prim SIMD vector
by GHC 26 Jun '17

26 Jun '17

#10286: native code generator: GHC crash at GHC.Prim SIMD vector -------------------------------------+------------------------------------- Reporter: hkanai | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When compiling attached source file, GHC panics. The following is the error message. {{{ $ ghc -Wall Vec3.hs [1 of 1] Compiling Data.Vector.Vec3 ( Vec3.hs, Vec3.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.1 for x86_64-unknown-linux): Size.intSize W256 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Currently native code generator does not support SIMD operations, and my computer does not support AVX instructions. Therefore ghc cannot compile the source at any case. So I think this bug is not so important. My system environment. {{{ $ uname -a Linux think 3.19.2-1-ARCH #1 SMP PREEMPT Wed Mar 18 16:21:02 CET 2015 x86_64 GNU/Linux $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.1 $ cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Core(TM)2 Duo CPU L9300 @ 1.60GHz stepping : 6 microcode : 0x60c cpu MHz : 1601.000 cache size : 6144 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 2 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts nopl aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm ida dtherm tpr_shadow vnmi flexpriority bugs : bogomips : 3193.86 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Core(TM)2 Duo CPU L9300 @ 1.60GHz stepping : 6 microcode : 0x60c cpu MHz : 1601.000 cache size : 6144 KB physical id : 0 siblings : 2 core id : 1 cpu cores : 2 apicid : 1 initial apicid : 1 fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts nopl aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm ida dtherm tpr_shadow vnmi flexpriority bugs : bogomips : 3193.86 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10286> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11224: Program doesn't preserve semantics after pattern synonym inlining.
by GHC 23 Jun '17

23 Jun '17

#11224: Program doesn't preserve semantics after pattern synonym inlining. -------------------------------------+------------------------------------- Reporter: anton.dubovik | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Windows Architecture: x86_64 | Type of failure: Incorrect result (amd64) | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# language PatternSynonyms , ViewPatterns #-} import Text.Read -- pattern PRead :: () => Read a => a -> String pattern PRead a <- (readMaybe -> Just a) foo :: String -> Int foo (PRead x) = (x::Int) foo (PRead xs) = sum (xs::[Int]) foo _ = 666 bar :: String -> Int bar (readMaybe -> Just x) = (x::Int) bar (readMaybe -> Just xs) = sum (xs::[Int]) bar _ = 666 main :: IO () main = do print $ foo "1" -- 1 print $ foo "[1,2,3]" -- 666 -- ??? print $ foo "xxx" -- 666 print $ bar "1" -- 1 print $ bar "[1,2,3]" -- 6 print $ bar "xxx" -- 666 }}} I'm expecting that semantics of the function `foo` would not change if I inline pattern synonym. However it does. `bar` successfully matches string against list of ints, whereas `foo` apperently skips this pattern and fall back to the catch-all case. Reproducible both in GHCi and GHC. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11224> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12379: WARN pragma gives warning `warning: [-Wdeprecations]'
by GHC 22 Jun '17

22 Jun '17

#12379: WARN pragma gives warning `warning: [-Wdeprecations]' -------------------------------------+------------------------------------- Reporter: zilinc | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Incorrect (amd64) | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Example: {{{#!hs -- Warn.hs module Warn where __todo :: String -> a {-# WARNING __todo "TODO" #-} __todo msg = error $ "TODO: " ++ msg }}} {{{#!hs -- Main.hs {- OPTIONS_GHC -Wall #-} import Warn inc :: Int -> Int inc n | n >= 0 = n + 1 inc _ = __todo "what about negatives?" }}} When compile the files (or ghci), I get {{{ UseWarn.hs:9:9: warning: [-Wdeprecations] In the use of ‘__todo’ (imported from Warn): "TODO" }}} Should the flag be `-Wwarnings-deprecations`? And `-Wdeprecations` is not in the user guide, if it is a genuine flag. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12379> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11758: Drop x86_64 binutils <2.17 hack
by GHC 20 Jun '17

20 Jun '17

#11758: Drop x86_64 binutils <2.17 hack -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1-rc2 (NCG) | 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: -------------------------------------+------------------------------------- `X86.CodeGen.genSwitch` contains this comment, {{{ else -- HACK: On x86_64 binutils<2.17 is only able to generate -- PC32 relocations, hence we only get 32-bit offsets in -- the jump table. As these offsets are always negative -- we need to properly sign extend them to 64-bit. This -- hack should be removed in conjunction with the hack in -- PprMach.hs/pprDataItem once binutils 2.17 is standard. }}} binutils 2.17 is now quite standard; even CentOS 5 shipped with 2.17. I think it is likely safe to remove this hack at this point. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11758> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8697: Type rationals
by GHC 16 Jun '17

16 Jun '17

#8697: Type rationals ------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- I've used GHC's Type Nats to implement my own type level rationals (code below). This works fine, but the syntax is a little funky because you have to write out the number as a fraction. For example, you must write 13/10 instead of 1.3; or even worse, 13/1 instead of 13. It would be nice to just write the decimal notation. I only see one potential problem with this feature: the dot in the decimal notation could interfere with the dot in forall statements. I guess this can be parsed unambiguously, but maybe not. {{{ data Frac = Frac Nat Nat data instance Sing (n::Frac) = SFrac Integer Integer instance (SingI a, SingI b) => SingI ('Frac a b) where sing = SFrac (fromSing (sing :: Sing a)) (fromSing (sing :: Sing b)) instance Fractional r => SingE (Kind :: Frac) r where fromSing (SFrac a b) = fromIntegral a/fromIntegral b type (/) a b = 'Frac a b }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8697> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12056: Too aggressive `-w` option
by GHC 12 Jun '17

12 Jun '17

#12056: Too aggressive `-w` option -------------------------------------+------------------------------------- Reporter: asr | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- By running {{{ ghc -w -Wunrecognised-warning-flags -Wfoo Main.hs }}} I would expect the warning {{{ on the commandline: warning: unrecognised warning flag: -Wfoo }}} however this warning isn't reported. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12056> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12545: Compilation time/space regression in GHC 8.0/8.1 (search in type-level lists and -O)
by GHC 12 Jun '17

12 Jun '17

#12545: Compilation time/space regression in GHC 8.0/8.1 (search in type-level lists and -O) -------------------------------------+------------------------------------- Reporter: | Owner: mikhail.vorozhtsov | 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 | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- After upgrading to GHC 8.0.1 I've noticed that compilation time of one of my libraries got unacceptably long. Please find the attached test case. Here are some numbers from my machine: {{{ $ time ~/Prefixes/ghc-7.10.3/bin/ghc -O -c -Rghc-timing TypeList.hs Regression.hs <<ghc: 19103924976 bytes, 1441 GCs, 73048470/256579104 avg/max bytes residency (18 samples), 542M in use, 0.000 INIT (0.002 elapsed), 14.163 MUT (14.257 elapsed), 5.707 GC (5.830 elapsed) :ghc>> real 0m20.160s user 0m19.937s sys 0m0.197s $ time ~/Prefixes/ghc-8.0.1/bin/ghc -O -c -Rghc-timing TypeList.hs Regression.hs <<ghc: 147662211104 bytes, 9635 GCs, 190336418/433097448 avg/max bytes residency (38 samples), 1210M in use, 0.000 INIT (0.001 elapsed), 101.707 MUT (101.840 elapsed), 27.907 GC (28.259 elapsed) :ghc>> real 2m10.195s user 2m9.773s sys 0m0.400s }}} Both versions are the official Debian 8 x86_64 binaries from haskell.org. I also compiled the git master and unfortunately it is affected as well. It is worth mentioning that turning off optimization makes the problem disappear: {{{ $ time ~/Prefixes/ghc-8.0.1/bin/ghc -O0 -c -Rghc-timing TypeList.hs Regression.hs <<ghc: 3779057184 bytes, 225 GCs, 17923355/81566792 avg/max bytes residency (8 samples), 164M in use, 0.000 INIT (0.001 elapsed), 2.847 MUT (2.941 elapsed), 0.553 GC (0.572 elapsed) :ghc>> real 0m3.593s user 0m3.507s sys 0m0.073s }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12545> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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