December 2016 - ghc-tickets

[GHC] #8772: ghci should safe history more often
by GHC 05 Mar '18

05 Mar '18

#8772: ghci should safe history more often ----------------------------------------------+---------------------------- Reporter: nomeata | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.6.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less than a day) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- It is very annoying if `ghci` crashes (due to using a foreign library wrongly, for example), and then the history is lost. It should be simple to save each line to history before it is being executed. Maybe a good task for new contributors? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8772> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12935: Object code produced by GHC is non-deterministic
by GHC 05 Mar '18

05 Mar '18

#12935: Object code produced by GHC is non-deterministic -------------------------------------+------------------------------------- Reporter: bgamari | Owner: 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: -------------------------------------+------------------------------------- This is a continuation of #4012, which made interface files deterministic. Now someone needs to make object code deterministic. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12935> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11984: Pattern match incompleteness / inaccessibility discrepancy
by GHC 03 Mar '18

03 Mar '18

#11984: Pattern match incompleteness / inaccessibility discrepancy -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- Consider this module: {{{ {-# LANGUAGE PolyKinds, TypeOperators, DataKinds, TypeFamilies, GADTs #-} module Bug where data family Sing (a :: k) data Schema = Sch [Bool] data instance Sing (x :: Schema) where SSch :: Sing x -> Sing ('Sch x) data instance Sing (x :: [k]) where SNil :: Sing '[] SCons :: Sing a -> Sing b -> Sing (a ': b) data G a where GCons :: G ('Sch (a ': b)) eval :: G s -> Sing s -> () eval GCons s = case s of -- SSch SNil -> undefined SSch (SCons _ _) -> undefined }}} Upon seeing this, GHC says {{{ Bug.hs:21:9: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: (SSch SNil) }}} So I uncomment the second-to-last line, inducing GHC to say {{{ Bug.hs:22:16: error: • Couldn't match type ‘a : b’ with ‘'[]’ Inaccessible code in a pattern with constructor: SNil :: forall k. Sing '[], in a case alternative • In the pattern: SNil In the pattern: SSch SNil In a case alternative: SSch SNil -> undefined }}} Thankfully, this pattern is much rarer than it once was, but it's a bit sad that it's still possible. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11984> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12706: Collecting type info is slow
by GHC 03 Mar '18

03 Mar '18

#12706: Collecting type info is slow -------------------------------------+------------------------------------- Reporter: vshabanov | Owner: Type: bug | Status: new Priority: normal | 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: -------------------------------------+------------------------------------- With `:set +c` option in GHCi, I'm waiting for 10-15 seconds for {{{ Collecting type info for 34 module(s) ... }}} after both first load and subsequent reloads, even if only top-level module was modified. And GHCi uses about 1.5-2x more memory than it uses without `:set +c`. My app has about 30k lines of code. Is it expected behavior and some performance improvements are planned or it's a bug? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12706> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12790: GHC 8.0.1 uses copious amounts of RAM and time when trying to compile lambdabot-haskell-plugins
by GHC 03 Mar '18

03 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] #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] #11777: RTS source code issues
by GHC 26 Feb '18

26 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] #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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