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[GHC] #13660: Tail after and including `NUL` character in `FilePath`s silently truncated
by GHC 07 May '17

07 May '17

#13660: Tail after and including `NUL` character in `FilePath`s silently truncated -------------------------------------+------------------------------------- Reporter: hvr | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.0.2 libraries/base | 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: -------------------------------------+------------------------------------- The current behaviour is imho not ideal as it masks invalid input arguments; consider e.g. {{{#!hs Prelude> readFile "foo" *** Exception: foo: openFile: does not exist (No such file or directory) Prelude> readFile "foo\NULbar" *** Exception: foobar: openFile: does not exist (No such file or directory) Prelude> writeFile "foo\NULbar" "contents" Prelude> readFile "foo\NULbar" "contents" Prelude> readFile "foo" "contents" }}} The reason for the surprising behaviour above is most likely (I haven't yet looked at the code), that `"foo\NULbar"` gets converted into a zero- terminated `CString` which is then passed to C functions such as `fopen(3)`, but to those C function, the C strings `"foo\0bar"` and `"foo"` are equivalent, as both are interpreted as `"foo"`. What I'd expect to happen on POSIX systems is that operations taking a `FilePath` such as `writeFile` or `readFile` should throw an exception when the `FilePath` gets encoded in such a way into a zero-terminated CString in such a way that a zero octet occurs (except for the intended zero-termination zero octet at the end). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13660> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13656: Consider implementing atomicModifyMutVar# in Haskell
by GHC 07 May '17

07 May '17

#13656: Consider implementing atomicModifyMutVar# in Haskell -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: task | Status: new Priority: low | Milestone: 8.4.1 Component: Runtime | Version: 8.2.1-rc2 System | 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 believe we could implement `atomicModifyMutVar#` in Haskell, rather than making it a primop. This seems like a simpler/cleaner approach (among other things, it gets a perfectly legitimate type signature!), but we'd have to see how it affects performance. I think something like this should work: {{{#!hs atomicModifyMutVar# :: MutVar# s a -> (a -> (a,b)) -> State# s -> (# State# s, b #) atomicModifyMutVar# mv f s = case readMutVar# mv s of { (# s', old #) -> let f_old = f old in case casMutVar# mv old (fst $ f_old) s of { (# s', unchanged, new #) -> case unchanged of 0# -> (# s', snd f_old #) _ -> atomicModifyMutVar# mv f s' }} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13656> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10431: EqualityConstraints extension?
by GHC 06 May '17

06 May '17

#10431: EqualityConstraints extension? -------------------------------------+------------------------------------- Reporter: adamgundry | Owner: Type: feature | Status: new request | Milestone: 7.12.1 Priority: normal | Version: 7.11 Component: Compiler | Operating System: Unknown/Multiple (Type checker) | Type of failure: None/Unknown Keywords: | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- At the moment, writing an equality constraint in a type requires at least one of the `GADTs` or `TypeFamilies` extensions. However, each of these has other effects. Could we have an `EqualityConstraints` extension to permit equality constraints in types, but neither GADTs nor type families? Presumably this extension should imply `MonoLocalBinds`. The `GADTs` extension could then become precisely the conjunction of `GADTSyntax`, `EqualityConstraints` and `ExistentialQuantification`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10431> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12947: Core lint error
by GHC 06 May '17

06 May '17

#12947: Core lint error -------------------------------------+------------------------------------- Reporter: Iceland_jack | 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: -------------------------------------+------------------------------------- {{{#!hs import qualified Control.Monad.Fail as Fail newtype P m a = P { unP :: (a -> IO (m ())) -> IO (m ()) } instance Functor (P m) where instance Applicative (P m) where instance Monad (P m) where instance (Fail.MonadFail m) => Fail.MonadFail (P m) where fail msg = ContT $ \ _ -> Fail.fail msg }}} fails when run with `$ ghci -ignore-dot-ghci -fdefer-typed-holes -dcore- lint /tmp/tQZR.hs`, log is attached -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12947> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13640: Core lint error with deferred type holes
by GHC 06 May '17

06 May '17

#13640: Core lint error with deferred type holes -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) 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: -------------------------------------+------------------------------------- {{{#!hs {-# Options_GHC -dcore-lint -fdefer-typed-holes #-} import Prelude hiding ((.)) class Functor' f where map' :: (a -> b) -> f a -> f b class Bifunctor' f where map2' :: (a -> b) -> f a c -> f b c bimap' :: Bifunctor' f => (a -> b) -> (c -> d) -> (f a c -> f b d) bimap' f g = map2' f . map' }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13640> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13651: Invalid redundant pattern matches with -XTypeFamilyDependencies
by GHC 06 May '17

06 May '17

#13651: Invalid redundant pattern matches with -XTypeFamilyDependencies -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple InjectiveFamilies | Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following code triggers a warning about a redundant pattern match for `foo`: {{{ {-# LANGUAGE TypeFamilies, TypeFamilyDependencies #-} type family F r s = f | f -> r s type instance F (Bar h (Foo r)) (Bar h (Foo s)) = Bar h (Bar r s) data Bar s b data Foo a foo :: (F cr cu ~ Bar h (Bar r u), F cu cs ~ Bar (Foo h) (Bar u s)) => Bar h (Bar r u) -> Bar (Foo h) (Bar u s) -> Foo (cr -> cs) foo = undefined }}} {{{ warning: [-Woverlapping-patterns] Pattern match is redundant In an equation for ‘foo’: foo = .. }}} This warning seems invalid to me: I'm not sure how a single definition could constitute a redundant pattern match. Moreover, if I try to address the warning by removing the "redundant" pattern, the code (of course) fails to compile because there is no accompanying binding for the signature of `foo`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13651> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12156: -fdefer-typed-holes causes panic on unbound variable
by GHC 06 May '17

06 May '17

#12156: -fdefer-typed-holes causes panic on unbound variable -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: new Priority: high | 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: -------------------------------------+------------------------------------- {{{#!haskell module Main where main = do print v return () }}} Compile it without {{{-fdefer-typed-holes}}} and it fails as expected: {{{ ➜ hole_bug ghc --make Main.hs -fforce-recomp [1 of 1] Compiling Main ( Main.hs, Main.o ) Main.hs:4:11: error: Variable not in scope: v }}} Adding {{{-fdefer-typed-holes}}} is causing a panic instead of runtime error: {{{ ➜ hole_bug ghc --make Main.hs -fforce-recomp -fdefer-typed-holes [1 of 1] Compiling Main ( Main.hs, Main.o ) Main.hs:4:11: warning: [-Wtyped-holes] Variable not in scope: v ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): StgCmmEnv: variable not found $dShow_aKo local binds for: $trModule $trModule1_r16k $trModule2_r16s sat_s16x sat_s16z Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Tried with: 8.0.1, HEAD as of today. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12156> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9557: Deriving instances is slow
by GHC 06 May '17

06 May '17

#9557: Deriving instances is slow -------------------------------------+------------------------------------- Reporter: Feuerbach | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Let's take [https://raw.githubusercontent.com/haskell-suite/haskell-src- exts/8e0153d33b66add96fd5606614ce7938d2029510/src/Language/Haskell/Exts/Annotated/Syntax.hs this file] (from haskell-src-exts) and build it with -O0. On my machine it takes 55s. If we remove deriving of all classes except Functor (which is the only one used by the module itself), the time will drop down to 4s. Different classes vary in their compile-time cost, but there's no single culprit. Among the costly ones are Generic, Data, Show, Ord. haskell-src-exts users are very annoyed by its long compile time, about 10 minutes, especially because we don't compile with -O0 by default. It would be nice to get this fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9557> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13622: Regression: can't export constructor when conflicting, qualified constructor is also in scope
by GHC 06 May '17

06 May '17

#13622: Regression: can't export constructor when conflicting, qualified constructor is also in scope -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.2.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I ran into this regression when trying to compile the `ersatz` library with GHC 8.2.1-rc1. Here is a minimized example: {{{#!hs module Bug (Bits(Bits)) where import qualified Data.Bits as Bits newtype Bits = Bits Int }}} Compiling this with GHC 8.0.2 works fine, but with 8.2.1-rc1, you get this error: {{{ l$ /opt/ghc/8.2.1/bin/ghci Bug.hs GHCi, version 8.2.0.20170422: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:1:13: error: • Ambiguous occurrence ‘Bits’ It could refer to either ‘Bits.Bits’, imported qualified from ‘Data.Bits’ at Bug.hs:3:1-34 or ‘Bits’, defined at Bug.hs:5:1 • In the export: Bits(Bits) | 1 | module Bug (Bits(Bits)) where | ^^^^^^^^^^ }}} Despite the fact that `Bits` isn't actually ambiguous, since the `Bits` from `Data.Bits` is qualified. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13622> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13653: Re-allocate byteArray lead internal error: evacuate: strange closure type 241
by GHC 06 May '17

06 May '17

#13653: Re-allocate byteArray lead internal error: evacuate: strange closure type 241 -------------------------------------+------------------------------------- Reporter: winter | Owner: (none) Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Compile and run following code lead to {{{evacuate: strange closure type XXX}}} on GHC 7.10.3/8.0.2/head, which is unreasonable. But running in GHCi is fine. {{{ {-# LANGUAGE BangPatterns #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE UnboxedTuples #-} import qualified Data.List as List import GHC.Prim import Data.Primitive.ByteArray import GHC.Types import GHC.ST data Bytes = Bytes {-# UNPACK #-} !ByteArray -- payload {-# UNPACK #-} !Int -- s {-# UNPACK #-} !Int -- length packN :: Int -> [Word8] -> Bytes packN n0 ws0 = runST (newByteArray n0 >>= go 0 n0 ws0) where go :: Int -> Int -> [Word8] -> MutableByteArray s -> ST s Bytes go !i !n [] !mba = do ba <- unsafeFreezeByteArray mba return (Bytes ba 0 i) go !i !n (w:ws) !mba | i <= n = do writeByteArray mba i w go (i+1) n ws mba | otherwise = do let n' = (n + 1) `shiftL` 1 -- mba' <- newByteArray n' -- these dosen't work either -- copyMutableByteArray mba' 0 mba 0 i mba' <- resizeMutableByteArray mba n' writeByteArray mba' i w go (i+1) n' ws mba' resizeMutableByteArray :: MutableByteArray s -> Int -> ST s (MutableByteArray s) resizeMutableByteArray (MutableByteArray mba#) (I# i#) = ST (\ s# -> let (# s'#, mba'# #) = resizeMutableByteArray# mba# i# s# in (# s'#, MutableByteArray mba'# #) ) main = print $ packN 64 (List.replicate 8192 128) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13653> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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