January 2017 - ghc-tickets

[GHC] #12790: GHC 8.0.1 uses copious amounts of RAM and time when trying to compile lambdabot-haskell-plugins
by GHC 02 Mar '18

02 Mar '18

#12790: GHC 8.0.1 uses copious amounts of RAM and time when trying to compile lambdabot-haskell-plugins -------------------------------------+------------------------------------- Reporter: clint | Owner: 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: -------------------------------------+------------------------------------- When building lambdabot-haskell-plugins, Lambdabot.Plugin.Haskell.Pl.Parser compiles without incident on the non- profiling run, but cripples the build machine on the profiling run. An excerpt of -v3 output is below to show the number of terms skyrocketing. *** Common sub-expression [Lambdabot.Plugin.Haskell.Pl.Parser]: Result size of Common sub-expression = {terms: 39,049, types: 30,851, coercions: 990} !!! Common sub-expression [Lambdabot.Plugin.Haskell.Pl.Parser]: finished in 72.00 milliseconds, allocated 44.536 megabytes *** Float inwards [Lambdabot.Plugin.Haskell.Pl.Parser]: Result size of Float inwards = {terms: 39,049, types: 30,851, coercions: 990} !!! Float inwards [Lambdabot.Plugin.Haskell.Pl.Parser]: finished in 68.00 milliseconds, allocated 60.337 megabytes *** Simplifier [Lambdabot.Plugin.Haskell.Pl.Parser]: Result size of Simplifier iteration=1 = {terms: 977,045, types: 299,334, coercions: 1,058} Result size of Simplifier iteration=2 = {terms: 926,036, types: 263,306, coercions: 932} Result size of Simplifier = {terms: 922,724, types: 262,202, coercions: 932} !!! Simplifier [Lambdabot.Plugin.Haskell.Pl.Parser]: finished in 15480.00 milliseconds, allocated 9384.823 megabytes *** CoreTidy [Lambdabot.Plugin.Haskell.Pl.Parser]: Result size of Tidy Core = {terms: 922,623, types: 261,789, coercions: 865} !!! CoreTidy [Lambdabot.Plugin.Haskell.Pl.Parser]: finished in 2060.00 milliseconds, allocated 613.585 megabytes writeBinIface: 95 Names writeBinIface: 259 dict entries *** CorePrep [Lambdabot.Plugin.Haskell.Pl.Parser]: Result size of CorePrep = {terms: 1,128,145, types: 347,063, coercions: 865} !!! CorePrep [Lambdabot.Plugin.Haskell.Pl.Parser]: finished in 3468.00 milliseconds, allocated 1718.453 megabytes *** Stg2Stg: *** CodeGen [Lambdabot.Plugin.Haskell.Pl.Parser]: -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12790> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13075: Top-level bang pattern accepted
by GHC 27 Feb '18

27 Feb '18

#13075: Top-level bang pattern accepted -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: -------------------------------------+------------------------------------- When I compile/link {{{#!hs {-# LANGUAGE BangPatterns #-} module Main where !(Just x) = Nothing main = putStrLn "hi there!" }}} I get {{{ rae:09:50:49 ~/temp> ghc Bug.hs [1 of 1] Compiling Main ( Bug.hs, Bug.o ) Linking Bug ... ld: can't open output file for writing: Bug, errno=21 for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) `gcc' failed in phase `Linker'. (Exit code: 1) }}} This bogus code should be rejected more gracefully (and earlier). It actually also loads into GHCi, but shouldn't. Will fix while I'm in the area. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13075> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11107: Can't use type wildcard infix
by GHC 26 Feb '18

26 Feb '18

#11107: Can't use type wildcard infix -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 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: -------------------------------------+------------------------------------- This fails: {{{ foo :: Int `_a` Bool foo = Right True }}} But moving `_a` to be prefix works. I observe the same behavior with an unnamed type wildcard. This was discovered while poking around in the renamer, not in real code! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11107> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13088: Type operator holes don't work infix
by GHC 26 Feb '18

26 Feb '18

#13088: Type operator holes don't work infix -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Parser) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: #13050 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Originally noted in https://phabricator.haskell.org/D2910 (which fixed #13050). Currently, you can do this: Does this also work with TypeOperators? That is, you can do this: {{{#!hs {-# LANGUAGE TypeOperators #-} foo :: a `_over` b -> _over a b foo = id }}} But not this: {{{#!hs {-# LANGUAGE TypeOperators #-} foo :: a `_` b -> over a b foo = id }}} osa1 made an attempt at fixing this, and recorded his progress [https://phabricator.haskell.org/D2910#85423 here]: > I played with alternative implementations and attempted at implementing type-level version of this patch as suggested by @RyanGlScott. > > Since `_` needs special treatment by the renamer I think we have to have some kind of special treatment for `_` in the parser too, so this implementation may not be too bad. > > (alternatively I guess we could remove special treatment for `_` in the parser but that'd just move special cases to the renamer, so I'm not sure that's any better than the current approach) > > About the type-level named infix holes: Type renamer is quite different than term renamer (`RnTypes.hs`) and I don't understand type-checker parts of the compiler -- but I was able to made an attempt at implementing this > > {{{#!diff > diff --git a/compiler/hsSyn/HsTypes.hs b/compiler/hsSyn/HsTypes.hs > index 53f200f..877c243 100644 > --- a/compiler/hsSyn/HsTypes.hs > +++ b/compiler/hsSyn/HsTypes.hs > @@ -608,6 +608,7 @@ type LHsAppType name = Located (HsAppType name) > data HsAppType name > = HsAppInfix (Located name) -- either a symbol or an id in backticks > | HsAppPrefix (LHsType name) -- anything else, including things like (+) > + | HsAppWild (Located (HsWildCardInfo name)) > deriving instance (DataId name) => Data (HsAppType name) > > instance (OutputableBndrId name) => Outputable (HsAppType name) where > @@ -987,11 +988,18 @@ getAppsTyHead_maybe tys = case splitHsAppsTy tys of > splitHsAppsTy :: [LHsAppType name] -> ([[LHsType name]], [Located name]) > splitHsAppsTy = go [] [] [] > where > + go :: [LHsType name] > + -> [[LHsType name]] > + -> [Located name] > + -> [LHsAppType name] > + -> ([[LHsType name]], [Located name]) > go acc acc_non acc_sym [] = (reverse (reverse acc : acc_non), reverse acc_sym) > go acc acc_non acc_sym (L _ (HsAppPrefix ty) : rest) > = go (ty : acc) acc_non acc_sym rest > go acc acc_non acc_sym (L _ (HsAppInfix op) : rest) > = go [] (reverse acc : acc_non) (op : acc_sym) rest > + go acc acc_non acc_sym (L l (HsAppWild (L _ wc)) : rest) > + = go (L l (HsWildCardTy wc) : acc) acc_non acc_sym rest > > -- Retrieve the name of the "head" of a nested type application > -- somewhat like splitHsAppTys, but a little more thorough > @@ -1334,14 +1342,18 @@ ppr_fun_ty ctxt_prec ty1 ty2 > > -------------------------- > ppr_app_ty :: (OutputableBndrId name) => TyPrec -> HsAppType name -> SDoc > -ppr_app_ty _ (HsAppInfix (L _ n)) = pprInfixOcc n > +ppr_app_ty _ (HsAppInfix (L _ n)) > + = pprInfixOcc n > ppr_app_ty _ (HsAppPrefix (L _ (HsTyVar NotPromoted (L _ n)))) > = pprPrefixOcc n > ppr_app_ty _ (HsAppPrefix (L _ (HsTyVar Promoted (L _ n)))) > = space <> quote (pprPrefixOcc n) -- We need a space before the ' above, so > -- the parser does not attach it to the > -- previous symbol > -ppr_app_ty ctxt (HsAppPrefix ty) = ppr_mono_lty ctxt ty > +ppr_app_ty ctxt (HsAppPrefix ty) > + = ppr_mono_lty ctxt ty > +ppr_app_ty ctxt (HsAppWild (L _ (AnonWildCard _))) > + = empty -- FIXME > > -------------------------- > ppr_tylit :: HsTyLit -> SDoc > diff --git a/compiler/parser/Parser.y b/compiler/parser/Parser.y > index dfb6755..da4696a 100644 > --- a/compiler/parser/Parser.y > +++ b/compiler/parser/Parser.y > @@ -1833,6 +1833,7 @@ tyapp :: { LHsAppType RdrName } > [mj AnnSimpleQuote $1] } > | SIMPLEQUOTE varop {% ams (sLL $1 $> $ HsAppInfix $2) > [mj AnnSimpleQuote $1] } > + | '`' '_' '`' { sL1 $1 (HsAppWild (sL1 $1 (AnonWildCard PlaceHolder))) } > > atype :: { LHsType RdrName } > : ntgtycon { sL1 $1 (HsTyVar NotPromoted $1) } -- Not including unit tuples > diff --git a/compiler/rename/RnTypes.hs b/compiler/rename/RnTypes.hs > index f3fcf88..9298020 100644 > --- a/compiler/rename/RnTypes.hs > +++ b/compiler/rename/RnTypes.hs > @@ -1050,8 +1050,11 @@ collectAnonWildCards lty = go lty > > gos = mconcat . map go > > + prefix_types_only :: HsAppType Name -> Maybe (LHsType Name) > prefix_types_only (HsAppPrefix ty) = Just ty > prefix_types_only (HsAppInfix _) = Nothing > + prefix_types_only (HsAppWild (L l (AnonWildCard wc_name))) = > + Just (L l (HsWildCardTy (AnonWildCard wc_name))) > > collectAnonWildCardsBndrs :: [LHsTyVarBndr Name] -> [Name] > collectAnonWildCardsBndrs ltvs = concatMap (go . unLoc) ltvs > @@ -1646,8 +1649,9 @@ extract_apps t_or_k tys acc = foldrM (extract_app t_or_k) acc tys > > extract_app :: TypeOrKind -> LHsAppType RdrName -> FreeKiTyVars > -> RnM FreeKiTyVars > -extract_app t_or_k (L _ (HsAppInfix tv)) acc = extract_tv t_or_k tv acc > -extract_app t_or_k (L _ (HsAppPrefix ty)) acc = extract_lty t_or_k ty acc > +extract_app t_or_k (L _ (HsAppInfix tv)) acc = extract_tv t_or_k tv acc > +extract_app t_or_k (L _ (HsAppPrefix ty)) acc = extract_lty t_or_k ty acc > +extract_app t_or_k (L _ (HsAppWild (L l wc))) acc = extract_lty t_or_k (L l (HsWildCardTy wc)) acc > > extract_hs_tv_bndrs :: [LHsTyVarBndr RdrName] -> FreeKiTyVars > -> FreeKiTyVars -> RnM FreeKiTyVars > }}} > > Once I figure out how to do the `FIXME` part this patch may just work. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13088> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11777: RTS source code issues
by GHC 25 Feb '18

25 Feb '18

#11777: RTS source code issues -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- Tiago Silva <tiagosilva(a)hush.com> writes: Last night I started looking at the C files used in GHC and noticed these issues: {{{ /driver/utils/cwrapper.c : int main(int, char **); }}} `void *p` is apparently unused, even if the compiler optimizes it away.. you should check if something went missing. {{{ /rts/RetainerProfile.c : static nat sanityCheckHeapClosure(StgClosure *) }}} `StgInfoTable *info` has the same issue as above {{{ /rts/RetainerSet.c #elif defined(RETAINER_SCHEME_CC) // Retainer scheme 3: retainer = cost centre void printRetainerSetShort(FILE *f, RetainerSet *rs, nat max_length) { char tmp[max_length + 1]; int size; nat j; } }}} Unlike the other functions around it, this function does nothing. Its variables are also not unused? {{{ /rts/sm/MarkWeak.c : void markWeakPtrList (void); if (w->header.info == &stg_DEAD_WEAK_info) { last_w = &(w->link); } else { last_w = &(w->link); } }}} Not sure what's going on here. Regardless of the test the two branches do the same thing. {{{ /rts/win32/IOManager.c : AddIORequest, AddDelayRequest, AddProcRequest functions }}} If `(!ioMan || !wItem)` the functions either return 0 or FALSE, but they don't free `wItem` before. Is this optimized by the compiler? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11777> 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] #8597: Git Hook script to prevent large binary blobs being checked in
by GHC 24 Feb '18

24 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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[GHC] #13153: Several Traversable instances have an extra fmap
by GHC 24 Feb '18

24 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 24 Feb '18

24 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] #12524: RFC: Allow prefixing result evaluated at GHCi prompt
by GHC 24 Feb '18

24 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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