January 2015 - ghc-tickets

[GHC] #10050: template haskell Ppr missing parentheses for SigT
by GHC 09 Feb '15

09 Feb '15

#10050: template haskell Ppr missing parentheses for SigT -------------------------------------+------------------------------------- Reporter: aavogt | 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: | -------------------------------------+------------------------------------- {{{#!hs ppr (SigE (VarE (mkName "a")) (SigT (VarT (mkName "x")) (VarT (mkName "k")))) }}} prints as "a :: x :: k". Ghc can't parse that, so I think it should be printed as "a :: (x :: k)" -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10050> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10004: rec {} causes "head:empty list" exception
by GHC 09 Feb '15

09 Feb '15

#10004: rec {} causes "head:empty list" exception -------------------------------------+------------------------------------- Reporter: alanz | 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 | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Using GHC HEAD 7.11.20150116 (and before) Trying to load the following into ghci {{{#!hs {-# LANGUAGE RecursiveDo #-} bar :: IO () bar = do rec {} return () }}} results in {{{ > :load "/home/alanz/mysrc/github/alanz/ghc- exactprint/tests/examples/Foo.hs" [1 of 1] Compiling Main ( /home/alanz/mysrc/github/alanz/ghc- exactprint/tests/examples/Foo.hs, interpreted ) *** Exception: Prelude.head: empty list > }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10004> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9337: Add `sortOn` function to Data.List
by GHC 09 Feb '15

09 Feb '15

#9337: Add `sortOn` function to Data.List -------------------------------------+------------------------------------- Reporter: JohnWiegley | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries/base | Version: 7.8.3 Keywords: | Differential Revisions: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: | Difficulty: Easy (less Blocking: | than 1 hour) | Blocked By: | Related Tickets: -------------------------------------+------------------------------------- This passed the vote on the libraries list a while ago, but I forget to add a ticket. The request was to add `sortOn` to `Data.List`: {{{ -- | Sort a list using a key on each element. This implements the -- decorate-sort-undecorate paradigm, also called a Schwarzian transform. sortOn :: Ord b => (a -> b) -> [a] -> [a] sortOn f = map snd . sortBy (comparing fst) . map (\x -> (f x, x)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9337> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9806: malloc and mallocArray ignore Storable alignment requirements
by GHC 08 Feb '15

08 Feb '15

#9806: malloc and mallocArray ignore Storable alignment requirements -------------------------------------+------------------------------------- Reporter: ekmett | Owner: ekmett Type: bug | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: 8627 | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Not sure if this is a bug or a feature request: `allocaBytesAligned` exists and allocates a new pinned byte array with a given alignment. It is used for both `alloca` and `allocaArray`. However, we don't currently have such a facility with `malloc`. `malloc` and `mallocArray` currently just invoke `mallocBytes`, and `mallocBytes` requests memory without alignment guarantees, so the resulting memory might well violate required `Storable` `alignment` for the result. We don't currently pad things out or get properly aligned memory. It strikes me that we should in theory add `mallocBytesAligned`, and switch `malloc` and `mallocArray` to invoke it instead of `mallocBytes`. `Foreign.Marshal.Alloc.mallocBytes` just invokes system `malloc`, so it seems that `memalign` or `posix_memalign` would be suitable. In theory `_malloc` on the system is probably aligning to a pretty common unit size, but if you start doing SIMD stuff you'll start seeing 16 byte alignment requirements, folks who care about cache architecture for example can have 128 byte alignments to pad things to separate cache lines. We probably haven't noticed since you likely get back bytes with slot- sized alignment just by construction, so if your alignment requirements stay in the <= 8 range you'll be okay, but for larger alignments it appears you'd just get wrong answers. If something more subtle is going on here (e.g. an `alignment` bigger than some threshold wont be respected or that users should explicitly expect `mallocArray` to silently allocate an array with the wrong alignment) that I missed then we definitely need better documentation to address the issue. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9806> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10041: Instance signatures (InstanceSigs) don't accept '[] :: [ĸ]
by GHC 06 Feb '15

06 Feb '15

#10041: Instance signatures (InstanceSigs) don't accept '[] :: [ĸ] -------------------------------------+------------------------------------- Reporter: | Owner: Iceland_jack | Status: new Type: bug | Milestone: Priority: low | Version: 7.8.3 Component: Compiler | Operating System: Linux (Type checker) | Type of failure: GHC rejects Keywords: | valid program Architecture: x86 | Blocked By: Test Case: | Related Tickets: #9582 #9833 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The following doesn't compile with 7.8.3: {{{#!hs {-# LANGUAGE PolyKinds, TypeFamilies, DataKinds #-} {-# LANGUAGE TypeOperators, GADTs, InstanceSigs #-} data family Sing (a :: ĸ) data instance Sing (xs :: [k]) where SNil :: Sing '[] class SingI (a :: ĸ) where sing :: Sing a instance SingI '[] where sing :: Sing '[] sing = SNil }}} and the error message suggests the very type provided (`Sing '[]`): {{{#!hs /tmp/Error.hs:11:11: Method signature does not match class; it should be sing :: Sing '[] In the instance declaration for ‘SingI '[]’ Failed, modules loaded: none. }}} Creating a local variable with the same type signature works fine: {{{#!hs instance SingI '[] where sing = tmp where tmp :: Sing '[] tmp = SNil }}} This is '''not''' a problem for other data kinds such as `Bool` though: {{{#!hs data instance Sing (xs :: Bool) where STrue :: Sing True SFalse :: Sing False instance SingI True where sing :: Sing True sing = STrue instance SingI False where sing :: Sing False sing = SFalse }}} This resembles #9582 but I don't believe it is the same error, it has possibly been fixed i 7.10 but unfortunately I don't have a more recent version of GHC to check. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10041> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9099: Add strict fmap
by GHC 06 Feb '15

06 Feb '15

#9099: Add strict fmap -------------------------------------------+------------------------------- Reporter: quchen | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: None | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 hour) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- Add a strict version of fmap to the standard libraries. {{{ infixl 4 <$!> (<$!>) :: Monad m => (a -> b) -> m a -> m b f <$!> m = do x <- m return $! f x {-# INLINE (<$!>) #-} }}} Libraries discussions: Take 1: http://www.haskell.org/pipermail/libraries/2013-November/021728.html Take 3: http://www.haskell.org/pipermail/libraries/2014-April/022864.html -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9099> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8796: -ddump-splices prints to error stream
by GHC 05 Feb '15

05 Feb '15

#8796: -ddump-splices prints to error stream -------------------------------------------+------------------------------- Reporter: jstolarek | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 hour) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- I just noticed that unlike other dump flags, `-ddump-splices` dumps to the error stream. I don't think this difference in behaviour is intended. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8796> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9004: Add sortOn function to Data.List
by GHC 05 Feb '15

05 Feb '15

#9004: Add sortOn function to Data.List -------------------------------------------+------------------------------- Reporter: JohnWiegley | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries/base | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 hour) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- The following passed for two weeks on the libraries mailing list without any dissenting votes. The request is to add the following function to Data.List: {{{ -- | Sort a list by comparing the results of a key function applied to each -- element. @sortOn f@ is equivalent to @sortBy . comparing f@, but has the -- performance advantage of only evaluating @f@ once for each element in the -- input list. This is called the decorate-sort-undecorate paradigm, or -- Schwartzian transform. sortOn :: Ord b => (a -> b) -> [a] -> [a] sortOn f = map snd . sortBy (comparing fst) . map (\x -> let y = f x in y `seq` (y, x)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9004> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9767: Add isSubsequenceOf to Data.List
by GHC 05 Feb '15

05 Feb '15

#9767: Add isSubsequenceOf to Data.List -------------------------------------+------------------------------------- Reporter: bernalex | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries/base | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Niklas Hambüchen suggested that we add the dual of subsequences, isSubsequenceOf (like isPrefixOf to inits & isSuffixOf to tails)[1]. It was a simple and noncontroversial proposal which received unanimous +1s. [1] https://www.haskell.org/pipermail/libraries/2014-November/024063.html -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9767> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8266: Dynamic linking on Mac
by GHC 04 Feb '15

04 Feb '15

#8266: Dynamic linking on Mac ------------------------------+-------------------------------------------- Reporter: kazu- | Owner: yamamoto | Status: new Type: bug | Milestone: Priority: highest | Version: 7.7 Component: Build | Operating System: MacOS X System | Type of failure: GHC doesn't work at all Keywords: | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: Unknown | Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- Many dynamic libraries refer to the build tree. (1) Every ".dylib" installed with GHC head refers to itself in its build directory. E.g. {{{ % otool -L libHSbase-4.7.0.0-ghc7.7.20130909.dylib | grep base libHSbase-4.7.0.0-ghc7.7.20130909.dylib: /Users/kazu/work/ghc/libraries/base/dist- install/build/libHSbase-4.7.0.0-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) }}} (2) Some ".dylib" installed with GHC head refers to other libraries in their build directories. E.g. {{{ % otool -L libHSvector-0.9.1-ghc7.7.20130909.dylib | grep /Users /Users/kazu/work/ghc/libraries/vector/dist- install/build/libHSvector-0.9.1-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) /Users/kazu/work/ghc/libraries/primitive/dist- install/build/libHSprimitive-0.4.0.1-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) }}} (3) All user installed libraries by cabal-install refer to other libraries in their build directories. E.g. {{{ % otool -L libHSghc-paths-0.1.0.9-ghc7.7.20130909.dylib| grep Users /Users/kazu/Library/Haskell/ghc-7.7.20130909/lib/ghc- paths-0.1.0.9/lib/libHSghc-paths-0.1.0.9-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) /Users/kazu/work/ghc/libraries/base/dist- install/build/libHSbase-4.7.0.0-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) /Users/kazu/work/ghc/libraries/integer-gmp/dist-install/build /libHSinteger-gmp-0.5.1.0-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) /Users/kazu/work/ghc/libraries/ghc-prim/dist-install/build /libHSghc-prim-0.3.1.0-ghc7.7.20130909.dylib (compatibility version 0.0.0, current version 0.0.0) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8266> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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