November 2015 - ghc-tickets

[GHC] #9887: No message when GCHI reusing compiled code
by GHC 12 Mar '16

12 Mar '16

#9887: No message when GCHI reusing compiled code -------------------------------------+------------------------------------- Reporter: jsrice | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: Other hour) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Running ":l Main.hs" at the GHCI prompt would load the compiled module. I am new to Haskell and this was a stumbling block that made it so that I could not interactively debug my code with GHCI. Deleting the object files was suggested to me on IRC and that allowed me to get the "*Main" prompt I was looking for. A message warning users "reusing compiled code" would likely save some future users some time. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9887> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10691: certain operations in new integer-gmp are too lazy
by GHC 11 Mar '16

11 Mar '16

#10691: certain operations in new integer-gmp are too lazy -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries | Version: 7.10.1 (other) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- This came up in #ghc the other day. {{{ rwbarton@morphism:~$ ghci-7.10.1 GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help Prelude> undefined * 0 0 }}} For consistency not just with Int, but also other integer-* implementations, this should be undefined. Also affected is for example `andInteger`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10691> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9699: TH function to list names in scope
by GHC 07 Mar '16

07 Mar '16

#9699: TH function to list names in scope -------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | 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: -------------------------------------+------------------------------------- I [asked about this on stackoverflow](http://stackoverflow.com/questions/26394199/using- templatehaskell-to-list-all-names-in-a-namespace), and apparently it doesn't exist yet. I want a TemplateHaskell function `variablesInScope :: Q [Name]` that returns a list of the `Name`'s of all the variables in scope. TemplateHaskell obviously has this information available in order to implement functions like `reify :: Name -> Q Info` and `lookupValueName :: String -> Q (Maybe Name)`. So it seems like this might be a pretty simple function to add. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9699> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10472: SigOf tests fail following renamer tidy-up
by GHC 01 Mar '16

01 Mar '16

#10472: SigOf tests fail following renamer tidy-up -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I'm about to commit a patch that fixes #7672. Sadly, though, it causes these failures {{{ driver/sigof02 sigof02dmt [bad stderr] (normal) driver/sigof02 sigof02dt [bad stderr] (normal) driver/sigof02 sigof02mt [bad exit code] (normal) driver/sigof02 sigof02t [bad exit code] (normal) }}} with errors like {{{ Main.hs:8:13: error: Can't find interface-file declaration for variable empty Probable cause: bug in .hi-boot file, or inconsistent .hi file Use -ddump-if-trace to get an idea of which file caused the error In the second argument of ‘($)’, namely ‘empty’ In the expression: insert 0 "foo" . delete 1 . insert 1 undefined . insert (6 :: Int) "foo" $ empty In an equation for ‘x’: x = insert 0 "foo" . delete 1 . insert 1 undefined . insert (6 :: Int) "foo" $ empty Main.hs:10:12: error: Can't find interface-file declaration for variable toList Probable cause: bug in .hi-boot file, or inconsistent .hi file Use -ddump-if-trace to get an idea of which file caused the error In the first argument of ‘print’, namely ‘(toList x)’ In a stmt of a 'do' block: print (toList x) In the expression: do { let x = insert 0 "foo" . delete 1 . insert 1 undefined . insert (6 :: Int) "foo" $ empty; print (member 1 x); print (toList x); print x } }}} Clearly there is only one bug here, and it's in the signature-handling code, which I do not fully understand. Happily, it's Edward's territory, and he is also involved in #7672. So I plan to mark these tests as broken on this ticket, and hope that Edward can adapt the signature stuff (which in any case is in-flight) to the new code. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10472> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10873: Bad error message for incorrect pattern synonym signature
by GHC 29 Feb '16

29 Feb '16

#10873: Bad error message for incorrect pattern synonym signature -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 (Type checker) | Keywords: newcomer | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Consider the following program {{{ {-# LANGUAGE PatternSynonyms #-} pattern Pat :: Show a => () => a -> Maybe a pattern Pat a = Just a }}} GHC complains that {{{ test.hs:4:9: No instance for (Show a) arising from a pattern }}} I think this is quite difficult to understand. The problem is that matching on `Just a` doesn't provide the show constraint (it provides no constraints). A better error message here would explain this fact and maybe a short explanation of the difference between prov/req in a pattern synonym signature. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10873> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11134: Limit frequency of idle GCs
by GHC 29 Feb '16

29 Feb '16

#11134: Limit frequency of idle GCs -------------------------------------+------------------------------------- Reporter: dcturner | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Runtime | Version: 7.10.2 System | 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: -------------------------------------+------------------------------------- In a server process with a relatively large heap (100s of MB) serving regular but relatively infrequent requests (~1 per sec) the idle GC runs after essentially every request which turns out to be extremely expensive: switching it off takes us from ~30% CPU to ~0.3% CPU. It is certainly useful have the GC run when idle but running it *every* time the process goes idle isn't necessary. It doesn't work to increase the delay (e.g. say -I2) as then the idle GC would never run, because the requests are rather regular. I'd quite like to be able to say something of the form "do a GC if idle for at least 0.3s as long as the idle GC has not run in the last 120s" - where 120s is another option passed to the RTS. Does this sound like a reasonable idea? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11134> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9043: Add missing type class instances for data types in GHC.Generics
by GHC 27 Feb '16

27 Feb '16

#9043: Add missing type class instances for data types in GHC.Generics ------------------------------------+------------------------------------- Reporter: ocharles | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- GHC.Generics offers a bunch of data types which have valid instances of various type classes in base, such as Functor. There's no good reason not to have these instances, so they should be added. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9043> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10316: Move Typeable type-rep generation from use site to definition site
by GHC 27 Feb '16

27 Feb '16

#10316: Move Typeable type-rep generation from use site to definition site -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- This ticket is a continuation of #9858. The interim solution for 7.10 was to generate `Typeable` data structures on the fly, as needed in client modules. This ticket is about moving the generation of the runtime representation of type constructors to their definition sites. (#9858 already has too much going on in it, so I started a fresh ticket for this refactoring.) The branch is `wip/T9858-typeable-spj`. In favour of (A) code at use site (as in 7.10): * Pay as you go. No code at all is generated unless you use `Typeable` In favour of (B) code at definition site: * More sharing. We make a `TyCon` (see `Data.Typeable.Internal`) for `T` (say) just once, in the module that defines `T`. * We may ultimately want the `TyCon` for `T` to include its source location, and perhaps more besides. If it is defined in `T` it becomes easier to do that. General observation: (B) is like `Typeable` was before, when it was an ordinary class. The difference now is that all types are `Typeable`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10316> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8710: Overlapping patterns warning misplaced
by GHC 27 Feb '16

27 Feb '16

#8710: Overlapping patterns warning misplaced -------------------------+------------------------------------------------- Reporter: | Owner: goldfire | Status: new Type: bug | Milestone: Priority: low | Version: 7.7 Component: | Operating System: Unknown/Multiple Compiler | Type of failure: Incorrect warning at Keywords: | compile-time Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- Consider {{{ {-# OPTIONS_GHC -fwarn-overlapping-patterns #-} len [] = 0 len (_:t) = 1 + len t len _ = error "urk" }}} GHC reports the problem with this definition at the first line of it. I think it would be more helpful to have it at the last line, which is the pattern that will never match. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8710> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9917: ddump-llvm runs opt/llc even when -fllvm isnt set
by GHC 27 Feb '16

27 Feb '16

#9917: ddump-llvm runs opt/llc even when -fllvm isnt set -------------------------------------+------------------------------------- Reporter: carter | 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: -------------------------------------+------------------------------------- to reproduce put {{{ main= putStrLn "hello world" }}} in hello.hs and then invoke `ghc hello.hs -O2 -v3 -fforce-recomp -ddump-llvm` then at some point you'll see something like {{{ *** LLVM Optimiser: opt-3.4 /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_2.ll -o /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_4.bc -O2 '--enable-tbaa=true' *** LLVM Compiler: llc-3.4 -O2 '-relocation-model=pic' /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_4.bc -o /var/folders/py/wgp_hj9d2rl3cx48yym_ynj00000gn/T/ghc88460_0/ghc88460_5.lm_s '--enable-tbaa=true' '-mattr=+sse2' *** LLVM Mangler: }}} in the output -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9917> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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