May 2016 - ghc-tickets

[GHC] #12066: Symbol not found: _stg_ap_0_upd_info
by GHC 05 Sep '16

05 Sep '16

#12066: Symbol not found: _stg_ap_0_upd_info -------------------------------------+------------------------------------- Reporter: pikajude | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When compiling project for which `double-conversion` is a dependency: {{{ [ 1 of 12] Compiling Models.TH ( src/Models/TH.hs, dist/build/Models/TH.o ) <command line>: can't load .so/.DLL for: /nix/store /m8whp07czawywfis99bfqpjmfy3vj1bf-double-conversion-2.0.1.0/lib/ghc-8.0.1 /double-conversion-2.0.1.0/libHSdouble-conversion-2.0.1.0 -CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib (dlopen(/nix/store /m8whp07czawywfis99bfqpjmfy3vj1bf-double-conversion-2.0.1.0/lib/ghc-8.0.1 /double-conversion-2.0.1.0/libHSdouble-conversion-2.0.1.0 -CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib, 5): Symbol not found: _stg_ap_0_upd_info Referenced from: /nix/store/m8whp07czawywfis99bfqpjmfy3vj1bf-double- conversion-2.0.1.0/lib/ghc-8.0.1/double-conversion-2.0.1.0/libHSdouble- conversion-2.0.1.0-CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib Expected in: flat namespace in /nix/store/m8whp07czawywfis99bfqpjmfy3vj1bf-double- conversion-2.0.1.0/lib/ghc-8.0.1/double-conversion-2.0.1.0/libHSdouble- conversion-2.0.1.0-CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12066> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12076: "lazy" leads to undefined reference to `stg_ap_0_upd_info'
by GHC 05 Sep '16

05 Sep '16

#12076: "lazy" leads to undefined reference to `stg_ap_0_upd_info' -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc2 (CodeGen) | 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 basically the same thing as #11155 but triggered differently. {{{ -- M.hs {-# OPTIONS_GHC -O0 #-} module M(f) where import GHC.Exts {-# NOINLINE z #-} z = () f :: () -> () f _ = let x = lazy z in g x x {-# NOINLINE g #-} g :: () -> () -> () g _ _ = () -- MM.hs import M main = f `seq` return () }}} On GHC 8.0, I get: {{{ ezyang@sabre:~$ ghc-8.0 --make MM.hs -fforce-recomp [1 of 2] Compiling M ( M.hs, M.o ) [2 of 2] Compiling Main ( MM.hs, MM.o ) Linking MM ... ./M.o: In function `r2aD_info': (.text+0x4a): undefined reference to `stg_ap_0_upd_info' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) }}} Error goes away when you turn on optimization. My understanding is that removing `lazy` in `CorePrep` is too late, because there's no pass afterwards that eliminates the trivial thunk assignment. This is blocking Phab:D2211, where the insertion of a `noinline` (which is optimized out similarly to `lazy`) triggers a stage 2 linker failure when you don't compile with optimization (unfortunately, this is NOT caught validate since we build GHC with optimization... but with this test it will be!) Perhaps there should be an ASSERT in the codegen so it doesn't create this symbol? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12076> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10858: Smaller generated instances
by GHC 05 Sep '16

05 Sep '16

#10858: Smaller generated instances -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- With very large modules with lots of deriving code, GHC spends quite some time compiling. I believe that we can improve things by reducing the size of the generated code. (More in the comments) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10858> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10161: GHC does not relink if a library's code changed
by GHC 03 Sep '16

03 Sep '16

#10161: GHC does not relink if a library's code changed -------------------------------------+------------------------------------- Reporter: nh2 | 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: | -------------------------------------+------------------------------------- Test case for reproducing: https://github.com/nh2/ghc-relinking-avoidance- bug/ ---- {{{myexe}}} is an executable that depends on {{{mylib}}}, whose {{{myfun = putStrLn "output 1"}}}. If we install {{{mylib}}}, compile {{{myexe}}}, then change mylib's code to {{{myfun = putStrLn "output 2"}}}, re-install it, and then compile {{{myexe}}}, then GHC does not notice that the library code changed. It avoids re-linking myexe, with the result that the program prints {{{output 1}}} when you told it to compile against code that prints {{{output 2}}}. ---- Note that I had to use {{{NOINLINE myfun}}} to trigger the bug, since otherwise {{{myfun}}}'s code would have ended up in the interface file, thus changing the package ID, which naturally forces GHC to relink (even re-compile). With the {{{NOINLINE}}}, the package IDs of the two different versions of {{{myfun}}} are completely identical. I think that is correct, since the package ID only hashes the API and ABI, not the actual implementation, right? How does GHC decide when to relink? I think in the present case, it doesn't notice that the object/archive file of the library changed. Does it check that somehow? Just looking at API and API can't be enough to make a decision for linking. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10161> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11565: Restore code to handle '-fmax-worker-args' flag
by GHC 02 Sep '16

02 Sep '16

#11565: Restore code to handle '-fmax-worker-args' flag -------------------------------------+------------------------------------- Reporter: slyfox | 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: -------------------------------------+------------------------------------- When i had a pass through DynFlags I've noticed dead code: https://phabricator.haskell.org/D1727 It was accidentally lost 3 years ago in major update changeset:0831a12ea2fc73c33652eeec1adc79fa19700578 The consensus is to try to put option handling back. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11565> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10923: GHC should recompile if flags change
by GHC 02 Sep '16

02 Sep '16

#10923: GHC should recompile if flags change -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | -------------------------------------+------------------------------------- Example: {{{ ezyang@sabre:~$ rm B.hi ezyang@sabre:~$ Dev/ghc-7.10.2/usr/bin/ghc -c B.hs ezyang@sabre:~$ Dev/ghc-7.10.2/usr/bin/ghc -c B.hs -O compilation IS NOT required }}} Pretty minor, but would be nice to have fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10923> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11740: RFC kind synonyms
by GHC 02 Sep '16

02 Sep '16

#11740: RFC kind synonyms -------------------------------------+------------------------------------- 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: -------------------------------------+------------------------------------- Are any of these useful now that we have kind synonyms: {{{#!hs -- Control.Category type Cat k = k -> k -> Type -- Data.Kind type Kind = Type type Types = [Type] type TypeClass = Type -> Constraint }}} `Cat` is not limited to `Control.Category` but applies in all [https://github.com/ekmett/hask/blob/master/src/Hask/Category.hs#L68 hask], [https://github.com/mikeizbicki/subhask/blob/b5433b959914d8214bcc4f130ff1b3d… subhask] and is defined by [https://github.com/ttuegel/recategorize/blob/master/src/Category/Category.h… recategorize]. It lets you rewrite: {{{#!hs -- newtype Yoneda (p :: i -> i -> *) (a :: i) (b :: i) = Op { getOp :: p b a } newtype Yoneda :: Cat i -> Cat i where Op :: { getOp :: p b a } -> Yoneda p a b -- type family Op (p :: i -> i -> *) :: i -> i -> * where type family Op (p :: Cat i) :: Cat i where Op (Yoneda p) = p Op p = Yoneda p -- data CatT (cat :: * -> * -> *) (a :: k) (b :: k) (cat1 :: k -> k -> *) (cat2 :: k -> k -> *) data CatT (cat :: Cat Type) (a :: k) (b :: k) (cat1 :: Cat k) (cat2 :: Cat k) -- class (Category' (Dom f), Category' (Cod f)) => Functor (f :: i -> j) where -- type Dom f :: i -> i -> * -- type Cod f :: j -> j -> * class (Category' (Dom f), Category' (Cod f)) => Functor (f :: i -> j) where type Dom f :: Cat i type Cod f :: Cat j -- data Nat (p :: i -> i -> *) (q :: j -> j -> *) (f :: i -> j) (g :: i -> j) where data Nat (p :: Cat i) (q :: Cat j) (f :: i -> j) (g :: i -> j) where -- instance Cartesian ((->) :: * -> * -> *) where instance Cartesian ((->) :: Cat Type) where }}} and {{{#!hs -- class (f x, g x) => And (f :: * -> Constraint) (g :: * -> Constraint) (x :: *) -- instance (f x, g x) => And (f :: * -> Constraint) (g :: * -> Constraint) (x :: *) class (f x, g x) => And (f :: TypeClass) (g :: TypeClass) (x :: *) instance (f x, g x) => And (f :: TypeClass) (g :: TypeClass) (x :: *) -- ToContext (fs :: [TypeClass]) :: TypeClass where type family ToContext (fs :: [* -> Constraint]) :: * -> Constraint where ToContext (f:g:fs) = And f (ToContext (g:fs)) ToContext '[f] = f }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11740> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12040: Code that builds on 7.8.4 and 7.10.3 but fails with requiring UndecidableInstances on 8.0.1-rc4
by GHC 31 Aug '16

31 Aug '16

#12040: Code that builds on 7.8.4 and 7.10.3 but fails with requiring UndecidableInstances on 8.0.1-rc4 -------------------------------------+------------------------------------- Reporter: dmcclean | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- (I am not sure if this is an issue with the release candidate or with my code. I'm sorry, I've tried hard to investigate that but not come to a firm conclusion. I'm reporting it on the chance that it might be an issue with the release candidate.) The code at https://github.com/bjornbm/dimensional/tree/c5b41bbcecb710d566f8af6e561dcaf… builds and passes tests on 7.8.4 and 7.10.3. The same code fails under 8.0.1-rc4 with the following message: {{{ src/Numeric/Units/Dimensional/Dynamic.hs:79:10: error: • The constraint ‘KnownDimension d’ is no smaller than the instance head (Use UndecidableInstances to permit this) • In the instance declaration for ‘Demotable (Quantity d)’ }}} I'm not sure if the relationship here between `Demotable`, `KnownDimension`, `HasDimension`, and `HasDynamicDimension` in fact requires undecidable instances (in which case 7.8.4 and 7.10.3 are either allowing it in error? or helpfully allowing it even though they aren't obligated to?) or if it does not in fact require undecidable instances (in which case 8.0.1-rc4 is disallowing it in error). Making things even more interesting, a new feature branch of the same project doesn't appear to change any of the things that should be relevant to this error message, but compiles and tests without the error on 8.0.1-rc4 as well as the earlier compiler versions. That one's at https://github.com/dmcclean/dimensional/tree/9f3b0a207258851964defd90ce497e…. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12040> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10963: Beginner-targeted language extension
by GHC 29 Aug '16

29 Aug '16

#10963: Beginner-targeted language extension -------------------------------------+------------------------------------- Reporter: kanetw | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 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: -------------------------------------+------------------------------------- FMP significantly complicated type signatures such as `length :: Foldable t => t a -> Int`, which makes teaching Haskell more difficult. I propose a language extension `-XBeginner` which instructs GHC(i) to specialize `Foldable` and `Traversable` to `[]` when possible and in case of an ambiguous instance, default those to `[]`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10963> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12029: Notify user to import * from Data.Kind with TypeInType on
by GHC 28 Aug '16

28 Aug '16

#12029: Notify user to import * from Data.Kind with TypeInType on -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: lowest | Milestone: Component: GHCi | Version: 8.1 Keywords: TypeInType | 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 `TypeInType` asking for the kind of `*` gives the user a warning to import it {{{ ghci> :set -XTypeInType ghci> :k * <interactive>:1:1: error: Not in scope: type constructor or class ‘*’ NB: With TypeInType, you must import * from Data.Kind <interactive>:1:1: error: Illegal operator ‘*’ in type ‘*’ Use TypeOperators to allow operators in types <interactive>:1:1: error: Operator applied to too few arguments: * }}} Should a similar warning be issued when she asks for information on it {{{ ghci> :i * class Num a where ... (*) :: a -> a -> a ... -- Defined in ‘GHC.Num’ infixl 7 * }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12029> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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