August 2015 - ghc-tickets

Re: [GHC] #7102: Type family instance overlap accepted in ghci
by GHC 07 Aug '15

07 Aug '15

#7102: Type family instance overlap accepted in ghci -------------------------------------+------------------------------------- Reporter: exbb2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by oerjan): I suspect the purging in (2) can already be achieved by just redeclaring the type family, after which new instances would refer to the new entity. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7102#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7669: Empty case causes warning
by GHC 07 Aug '15

07 Aug '15

#7669: Empty case causes warning -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.7 Resolution: duplicate | Keywords: EmptyCase Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Incorrect | Test Case: warning at compile-time | deSugar/should_compile/T7669 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by bgamari): The issue of no warnings being produced despite non-exhaustive pattern matches (described in comment:3) has been reported separately as #10746. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7669#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9953: Pattern synonyms don't work with GADTs
by GHC 06 Aug '15

06 Aug '15

#9953: Pattern synonyms don't work with GADTs -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Consider this variant of test `T8968-1`: {{{ {-# LANGUAGE GADTs, KindSignatures, PatternSynonyms #-} module ShouldCompile where data X :: * -> * where Y :: a -> X (Maybe a) pattern C :: a -> X (Maybe a) pattern C x = Y x foo :: X t -> t foo (C x) = Just x }}} * If we had `(Y x)` instead of `(C x)` in the LHS of `foo`, then this is an ordinary GADT program and typechecks fine. * If we omit the pattern signature, it typechecks fine, and `:info C` says {{{ pattern C :: t ~ Maybe a => a -> X t -- Defined in ‘ShouldCompile’ }}} * But as written, it fails with {{{ Foo.hs:11:6: Couldn't match type ‘t’ with ‘Maybe a0’ ‘t’ is a rigid type variable bound by the type signature for: foo :: X t -> t at Foo.hs:10:8 Expected type: X t Actual type: X (Maybe a0) Relevant bindings include foo :: X t -> t (bound at Foo.hs:11:1) In the pattern: C x In an equation for ‘foo’: foo (C x) = Just x }}} Moreover, `:info C` says {{{ pattern C :: a -> X (Maybe a) -- Defined at Foo.hs:8:9 }}} Do you see the difference? In the former, the "prov_theta" equality constraint is explicit, but in the latter it's implicit. The exact thing happens for `DataCons`. It's handled via the `dcEqSpec` field. Essentially `PatSyn` should have a new field for the implicit equality constraints. And, just as for data consructors, we need to generate the equality constraints, and the existentials that are needed, when we process the signature. Use the code in `TcTyClsDecls.rejigConRes` (perhaps needs a better name). This is all pretty serious. Without fixing it, GADT-style pattern signatures are all but useless. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9953> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7102: Type family instance overlap accepted in ghci
by GHC 06 Aug '15

06 Aug '15

#7102: Type family instance overlap accepted in ghci -------------------------------------+------------------------------------- Reporter: exbb2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): That is indeed very very bad. Never mind Safe Haskell -- it's just unsound. You didn't get a seg fault, but you very well might have. (For class instances it wouldn't be unsound, just possibly a bit incoherent.) I'm not sure what to do: 1. Prohibit `type instance` declarations in GHCi that overlap/override earlier ones? 2. Do (1) but also provide a way to purge the GHCi environment, so you can get back to a clean slate without restarting GHCi 3. Try to be clever: purge only functions (or whatever) whose types mention `T`. But it's tricky: what about data types mentioning `T`, and functions whose types use those data types... I incline to (2). Any other opinions? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7102#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10720: New GHC fails to specialize imported function
by GHC 06 Aug '15

06 Aug '15

#10720: New GHC fails to specialize imported function -------------------------------------+------------------------------------- Reporter: wyager | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: MacOS X performance, inline, specialize | Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- I just installed the new Haskell platform for OS X. It seems to have caused a major performance regression for a program I'm working on, making it well over 25x slower. The culprit appears to be that the new GHC (7.10.2) fails to specialize an imported function. If I manually add a SPECIALIZE pragma, performance goes back to around what it used to be. The code in question is located at https://github.com/wyager/HNet . As it stands, the code takes about 30 seconds to run on my machine. With the previous haskell-platform, it only took about .9 seconds. If I modify Operations.hs and uncomment the SPECIALIZE pragma, runtime goes down to about 1.1 seconds (still slower for some reason, but not awful). To test, compile with -O2 (as the program makes heavy use of Data.Vector, which requires -fspec-constr for performance). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10720> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10743: Data declaration order matters to compiler.
by GHC 06 Aug '15

06 Aug '15

#10743: Data declaration order matters to compiler. -------------------------------------+------------------------------------- Reporter: | Owner: thomaseding | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Windows Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- {{{ {-# LANGUAGE GADTs #-} {-# LANGUAGE TemplateHaskell #-} import Control.Lens.TH (makeLenses) data Handle h where PlayerHandle :: Int -> Handle Player -- GHC 7.8.3 complains that NonPlayer is not in scope NonPlayerHandle :: Int -> Handle NonPlayer data Player = Player -- Deferring this until after NonPlayer is defined, resolves the compile error. -- Commenting this out also works. makeLenses ''Player data NonPlayer }}} (The exact version of 'lens' I have tried this with is 'lens-4.7' if that matters.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10743> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7102: Type family instance overlap accepted in ghci
by GHC 06 Aug '15

06 Aug '15

#7102: Type family instance overlap accepted in ghci -------------------------------------+------------------------------------- Reporter: exbb2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by oerjan): * cc: oerjan (added) * status: closed => new * resolution: wontfix => Comment: I think this behavior should be reconsidered when Safe Haskell is enabled. {{{ Prelude> :set -XSafe Prelude> :seti -XSafe Prelude> :set -XTypeFamilies Prelude> type family T a b Prelude> type instance T a b = a Prelude> let fro :: a -> T a b; fro = id Prelude> type instance T a b = b Prelude> let uc :: a -> b; uc = fro Prelude> uc 'a' :: Int 97 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7102#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #427: Random.StdGen slowness
by GHC 06 Aug '15

06 Aug '15

#427: Random.StdGen slowness -------------------------------------+------------------------------------- Reporter: remit | Owner: ekmett Type: bug | Status: closed Priority: normal | Milestone: ⊥ Component: Core Libraries | Version: Resolution: duplicate | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * status: new => closed * resolution: None => duplicate Comment: This bug is now being tracked in the `random` bug tracker on Github: [https://github.com/haskell/random/issues/28 Random.StdGen slowness]. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/427#comment:25> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2280: randomR too slow
by GHC 06 Aug '15

06 Aug '15

#2280: randomR too slow -------------------------------------+------------------------------------- Reporter: guest | Owner: ekmett Type: bug | Status: closed Priority: normal | Milestone: ⊥ Component: Core Libraries | Version: 6.8.2 Resolution: duplicate | Keywords: randomR Operating System: Linux | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | Blocked By: | Blocking: Related Tickets: #427 | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * status: new => closed * resolution: => duplicate Comment: This bug is now being tracked in the `random` bug tracker on Github: [https://github.com/haskell/random/issues/29 randomR too slow]. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2280#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9848: List.all does not fuse
by GHC 06 Aug '15

06 Aug '15

#9848: List.all does not fuse -------------------------------------+------------------------------------- Reporter: klapaucius | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.9 Keywords: | Operating System: Windows Architecture: x86 | Type of failure: Runtime Difficulty: Easy (less than 1 | performance bug hour) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- {{{ primes = 2:3:filter isPrime [5,7..] :: [Int] isPrime x = all (/= 0) . map (x `rem`) . takeWhile ((<= x) . (^2)) $ primes main = print . length . takeWhile (<= 2^24) $ primes }}} {{{ 12,133,812,164 bytes allocated in the heap 53,433,372 bytes copied during GC 14,235,488 bytes maximum residency (7 sample(s)) 1,110,916 bytes maximum slop 30 MB total memory in use (0 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 56357 colls, 0 par 0.094s 0.125s 0.0000s 0.0001s Gen 1 7 colls, 0 par 0.031s 0.034s 0.0049s 0.0154s INIT time 0.000s ( 0.000s elapsed) MUT time 8.094s ( 8.069s elapsed) GC time 0.125s ( 0.159s elapsed) EXIT time 0.000s ( 0.003s elapsed) Total time 8.219s ( 8.231s elapsed) %GC time 1.5% (1.9% elapsed) Alloc rate 1,499,158,259 bytes per MUT second Productivity 98.5% of total user, 98.3% of total elapsed }}} {{{ Rec { $sgo1_r2RE :: GHC.Prim.Int# -> [Int] -> Data.Monoid.All [GblId, Arity=2, Caf=NoCafRefs, Str=DmdType <L,U><L,U>] $sgo1_r2RE = \ (sc_s2PS :: GHC.Prim.Int#) (sc1_s2PT :: [Int]) -> case sc_s2PS of _ [Occ=Dead] { __DEFAULT -> go_r2RF sc1_s2PT; 0 -> GHC.Types.False `cast` (Sym Data.Monoid.NTCo:All[0] :: Bool ~R# Data.Monoid.All) } go_r2RF :: [Int] -> Data.Monoid.All [GblId, Arity=1, Caf=NoCafRefs, Str=DmdType <S,1*U>] go_r2RF = \ (ds_a1YK :: [Int]) -> case ds_a1YK of _ [Occ=Dead] { [] -> GHC.Types.True `cast` (Sym Data.Monoid.NTCo:All[0] :: Bool ~R# Data.Monoid.All); : y_a1YP ys_a1YQ -> case y_a1YP of _ [Occ=Dead] { GHC.Types.I# x_a1Tk -> case x_a1Tk of _ [Occ=Dead] { __DEFAULT -> go_r2RF ys_a1YQ; 0 -> GHC.Types.False `cast` (Sym Data.Monoid.NTCo:All[0] :: Bool ~R# Data.Monoid.All) } } } end Rec } lvl4_r2RG :: Int -> Data.Monoid.All [GblId, Arity=1, Str=DmdType] lvl4_r2RG = \ (x_aqY [OS=ProbOneShot] :: Int) -> case x_aqY of _ [Occ=Dead] { GHC.Types.I# y_a1Uc -> case GHC.Prim.tagToEnum# @ Bool (GHC.Prim.<=# 4 y_a1Uc) of _ [Occ=Dead] { False -> GHC.Types.True `cast` (Sym Data.Monoid.NTCo:All[0] :: Bool ~R# Data.Monoid.All); True -> $sgo1_r2RE (GHC.Prim.remInt# y_a1Uc 2) (letrec { go1_a1S5 [Occ=LoopBreaker] :: [Int] -> [Int] [LclId, Arity=1, Str=DmdType <S,1*U>] go1_a1S5 = \ (ds_a1S6 :: [Int]) -> case ds_a1S6 of _ [Occ=Dead] { [] -> GHC.Types.[] @ Int; : y1_X1T4 ys_X1T6 -> case y1_X1T4 of _ [Occ=Dead] { GHC.Types.I# x1_X1VM -> case GHC.Prim.tagToEnum# @ Bool (GHC.Prim.<=# (GHC.Prim.*# x1_X1VM x1_X1VM) y_a1Uc) of _ [Occ=Dead] { False -> GHC.Types.[] @ Int; True -> GHC.Types.: @ Int (case x1_X1VM of wild5_a1TE { __DEFAULT -> case GHC.Prim.remInt# y_a1Uc wild5_a1TE of wild6_a1TJ { __DEFAULT -> GHC.Types.I# wild6_a1TJ }; (-1) -> GHC.Real.$fIntegralInt1; 0 -> GHC.Real.divZeroError @ Int }) (go1_a1S5 ys_X1T6) } } }; } in go1_a1S5 Main.main3) } } }}} foldr, however, fuse just fine: {{{ primes = 2:3:filter isPrime [5,7..] :: [Int] isPrime x = foldr (&&) True . map (/= 0) . map (x `rem`) . takeWhile ((<= x) . (^2)) $ primes main = print . length . takeWhile (<= 2^24) $ primes }}} {{{ 365,770,752 bytes allocated in the heap 48,197,488 bytes copied during GC 13,031,232 bytes maximum residency (7 sample(s)) 1,570,524 bytes maximum slop 28 MB total memory in use (0 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 694 colls, 0 par 0.016s 0.029s 0.0000s 0.0005s Gen 1 7 colls, 0 par 0.031s 0.032s 0.0046s 0.0146s INIT time 0.000s ( 0.000s elapsed) MUT time 3.438s ( 3.439s elapsed) GC time 0.047s ( 0.062s elapsed) EXIT time 0.000s ( 0.003s elapsed) Total time 3.484s ( 3.504s elapsed) %GC time 1.3% (1.8% elapsed) Alloc rate 106,406,036 bytes per MUT second Productivity 98.7% of total user, 98.1% of total elapsed }}} {{{ lvl4_r2qr :: Int -> Bool [GblId, Arity=1, Str=DmdType] lvl4_r2qr = \ (x_aqW [OS=ProbOneShot] :: Int) -> case x_aqW of _ [Occ=Dead] { GHC.Types.I# y_a1tq -> case GHC.Prim.tagToEnum# @ Bool (GHC.Prim.<=# 4 y_a1tq) of _ [Occ=Dead] { False -> GHC.Types.True; True -> case GHC.Prim.remInt# y_a1tq 2 of _ [Occ=Dead] { __DEFAULT -> letrec { go_a1ud [Occ=LoopBreaker] :: [Int] -> Bool [LclId, Arity=1, Str=DmdType <S,1*U>] go_a1ud = \ (ds_a1ue :: [Int]) -> case ds_a1ue of _ [Occ=Dead] { [] -> GHC.Types.True; : y1_X1vf ys_X1vh -> case y1_X1vf of _ [Occ=Dead] { GHC.Types.I# x1_X1x9 -> case GHC.Prim.tagToEnum# @ Bool (GHC.Prim.<=# (GHC.Prim.*# x1_X1x9 x1_X1x9) y_a1tq) of _ [Occ=Dead] { False -> GHC.Types.True; True -> case x1_X1x9 of wild6_X1x3 { __DEFAULT -> case GHC.Prim.remInt# y_a1tq wild6_X1x3 of _ [Occ=Dead] { __DEFAULT -> go_a1ud ys_X1vh; 0 -> GHC.Types.False }; (-1) -> GHC.Types.False; 0 -> case GHC.Real.divZeroError of wild7_00 { } } } } }; } in go_a1ud Main.main3; 0 -> GHC.Types.False } } } }}} And List.all from ghc 7.8 base library does fuse, so this is regression. Windows 8.1 x64, ghc --info: {{{ [("Project name","The Glorious Glasgow Haskell Compilation System") ,("GCC extra via C opts"," -fwrapv") ,("C compiler command","$topdir/../mingw/bin/gcc.exe") ,("C compiler flags"," -U__i686 -march=i686 -fno-stack-protector") ,("C compiler link flags","") ,("Haskell CPP command","$topdir/../mingw/bin/gcc.exe") ,("Haskell CPP flags","-E -undef -traditional ") ,("ld command","$topdir/../mingw/bin/ld.exe") ,("ld flags","") ,("ld supports compact unwind","YES") ,("ld supports build-id","NO") ,("ld supports filelist","NO") ,("ld is GNU ld","YES") ,("ar command","$topdir/../mingw/bin/ar.exe") ,("ar flags","q") ,("ar supports at file","YES") ,("touch command","$topdir/touchy.exe") ,("dllwrap command","$topdir/../mingw/bin/dllwrap.exe") ,("windres command","$topdir/../mingw/bin/windres.exe") ,("libtool command","") ,("perl command","$topdir/../perl/perl.exe") ,("target os","OSMinGW32") ,("target arch","ArchX86") ,("target word size","4") ,("target has GNU nonexec stack","False") ,("target has .ident directive","True") ,("target has subsections via symbols","False") ,("Unregisterised","NO") ,("LLVM llc command","llc") ,("LLVM opt command","opt") ,("Project version","7.9.20141129") ,("Project Git commit id","447f592697fef04d1e19a2045ec707cfcd1eb59f") ,("Booter version","7.8.3") ,("Stage","2") ,("Build platform","i386-unknown-mingw32") ,("Host platform","i386-unknown-mingw32") ,("Target platform","i386-unknown-mingw32") ,("Have interpreter","YES") ,("Object splitting supported","YES") ,("Have native code generator","YES") ,("Support SMP","YES") ,("Tables next to code","YES") ,("RTS ways","l debug thr thr_debug thr_l thr_p ") ,("Support dynamic-too","NO") ,("Support parallel --make","YES") ,("Support reexported-modules","YES") ,("Support thinning and renaming package flags","YES") ,("Uses package keys","YES") ,("Dynamic by default","NO") ,("GHC Dynamic","NO") ,("Leading underscore","YES") ,("Debug on","False") ,("LibDir","D:\\msys32\\usr\\local\\lib") ,("Global Package DB","D:\\msys32\\usr\\local\\lib\\package.conf.d") ] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9848> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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