June 2015 - ghc-tickets

[GHC] #8947: Depending on hint/ghc API fixes the binary version I can use
by GHC 21 Jan '16

21 Jan '16

#8947: Depending on hint/ghc API fixes the binary version I can use ----------------------------+---------------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects valid program Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ----------------------------+---------------------------------------------- When I `build-depend` on hint-0.4.0.0 with GHC 7.6.3, I get {{{ % cabal configure Resolving dependencies... cabal: Could not resolve dependencies: trying: pointcloudviewer-0.1.0 (user goal) trying: hint-0.4.0.0/installed-cf3... (dependency of pointcloudviewer-0.1.0) trying: ghc-7.6.3/installed-494... (dependency of hint-0.4.0.0/installed-cf3...) trying: bin-package-db-0.0.0.0/installed-608... (dependency of ghc-7.6.3/installed-494...) trying: GLUtil-0.7.4/installed-223... (dependency of pointcloudviewer-0.1.0) next goal: linear (dependency of GLUtil-0.7.4/installed-223...) rejecting: linear-1.6/installed-300... (conflict: bin-package-db => binary==0.5.1.1/installed-72e..., linear => binary==0.7.1.0/installed-a33...) }}} This fails because `linear` uses a `binary > 0.5.1.1`, but through my use of `hint` which depends on `ghc` (`hint` does not directly depend on `binary`), I pull in a constraint `binary == 0.5.1.1`. I believe this is bad, because depending on the GHC API in any way fixes the binary version I can use, which immediately makes a range of newer libraries unavailable to my program. Probably GHC should somehow hide the fact that binary is used inside, and let the rest of my program use whatever binary it likes. ---- I am aware that this might not be immediately easy, since the GHC API might expose some `binary` types to my program that I could try use with my newer binary version, which of course would be illegal. Maybe it is possible to implement such a check into actual typechecking, and let it pass if I don't actually use types from the old version with functions from the new library. I actually believe I have seen compiler errors in the past where two identical types where not unified because one was from a different version, so maybe infrastructure for this is already in place? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8947> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8992: Instructions for using gdb with GHC on Windows
by GHC 21 Jan '16

21 Jan '16

#8992: Instructions for using gdb with GHC on Windows ------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Documentation | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- gdb remains a useful tool for debugging executables on Windows, but getting it setup can be tricky, since modern gdb requires Python, which means you will end up installing MSYS Python alongside native Python. Unfortunately, MSYS Python doesn't work with the test suite, so one is in the delicate situation where you want your path to have MSYS Python if you're running gdb, but Windows Python if you're running the test suite. While one can work around this with modest annoyance (the easiest thing I've found is to just uninstall gdb/python when I'm not using it), it would be better if we removed this friction in some way. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8992> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9037: Add option to make selected warnings errors
by GHC 21 Jan '16

21 Jan '16

#9037: Add option to make selected warnings errors ------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- It would be great if GHC offered a `-ferror-*` flag for every `-fwarn-*` flag, that turns the given type of warning into an error. For example, I would like to always error on uninitialized record fields, but don't want to go full `-Werror`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9037> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10137: Rewrite switch code generation
by GHC 21 Jan '16

21 Jan '16

#10137: Rewrite switch code generation -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 (CodeGen) | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Inspired by #10124 I looked at the code generation for enumeration and integer types, and I think this can be improved in a few ways. My goals are: * Fancier code for integer types. Currently, the code for enumeration types will emit jump tables for dense choices; there is no reason to treat integer types differently. * The ability to behave differently if some of the cases are equal, and, as an extension of that, * The possibility to create branchless code if multiple checks would go to the same jump. The current scheme is roughly: * When we generate Cmm code for a STG case expression, we handle enumeration types and literals separately. * At this point, the decisions about what code to generate are made (jump tables (but only for enumeration types) or if-then-else trees). * The Common Block Optimization on Cmm happens later in the pipeline, making it non-trivial to detect branches that do the same thing. My plan is the following: * In the STG→Cmm transformation, floats will be handled separately. Matching against literals literals is fishy anyways, so my suggestion is to simply generate a linear list of equality checks here – turning the intended operation (equality test) into something else (comparisons in a if-then-else tree) feels wrong to me for floats. And the rest would not work well for floats, so I’d like to have them out of the way. * The case of enumeration types will be reduced to word literals, and treated the same from now on. * For integer types, no code generation decisions is made at this point. Instead, always a `CmmSwitch` statement is generated. * In a separate Cmm transformation pass, which will run /after/ the common block optimization, we visit all `CmmSwitches` and create proper code for them. I’d like to separate the algorithm that plans the code generation into a function (possibly even module) of its own, so that the decisions can easily by analyized and modified. The algorithm has a few choices to make: * If multiple values point to the same code, we can generate branchless code (`y := x == 1 || x == 5 || x = 7; if (y==0) then goto l1 else goto l2`). * If there are whole ranges pointing to the same code, the above can also use comparisons. * If there are dense ranges (i.e. a range with more than half of the possible values mapped to something), we want to generate jump tables from them (still `CmmSwitch` values). * Unless all options are handled by one of these possibilities, they need to be combined using `if-then-else` trees. The `CmmSwitch` constructor needs to change for that. It currently takes a `[Maybe Label]` argument, which is not suitable for before that pass, when its table may be sparse. I think an `IntMap Label` would work nicely. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10137> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9357: Kind-polymorphic type family accepts unlifted type arguments
by GHC 21 Jan '16

21 Jan '16

#9357: Kind-polymorphic type family accepts unlifted type arguments -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: GHC Difficulty: Unknown | accepts invalid program Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The following code is accepted by ghc-7.8.2 and ghc-7.6.3: {{{#!hs {-# LANGUAGE TypeFamilies, MagicHash, PolyKinds #-} import GHC.Exts type family F (a :: k) :: * type instance F Int# = () }}} In nearly all other places, it seems that unlifted types are explicitly forbidden. I'm also not allowed to actually apply `F` to `Int#` after defining the type family like this. So I think the compiler should probably reject the `type instance`. (BTW, is it actually clear that using `#` as an argument kind to a type family or as an index kind for a GADT is in any way harmful?) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9357> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9215: GHC 7.8.2 mingw-w64: symbol not found in link
by GHC 21 Jan '16

21 Jan '16

#9215: GHC 7.8.2 mingw-w64: symbol not found in link ------------------------------------+------------------------------------- Reporter: stuartallenmills | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- This includes calls such as strdup, stat, , and snprintf. These calls are not available in the 64 bit libraries (though 64 bit versions are such as _strdup, _snprintf) These problems have occurred in building yaml and unix-compat. They also occurred in system-fileio but jmilikin generated a patch for that library -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9215> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9182: Empty case analysis for function clauses
by GHC 20 Jan '16

20 Jan '16

#9182: Empty case analysis for function clauses ------------------------------------+------------------------------------- Reporter: dfranke | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- Thanks to `-XEmptyCase`, the following is legal: {{{ module Empty where data Empty empty :: Empty -> a empty x = case x of { } }}} However, if I leave off the last line, GHC will complain that `The type signature for ‘empty’ lacks an accompanying binding`. I think this program should be accepted. It isn't that I'm not giving a definition for `empty`; it's that I'm defining it to be a function with no accompanying equations, as could be represented in Template Haskell by $(return [FunD (mkName "empty") []]) Currently, this too is rejected, with GHC complaining `Function binding for ‘empty’ has no equations`. I think this should be legal, with an empty list of clauses in a function definition being treated the same way as an empty list of matches in a case expression. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9182> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9202: Strange Closure Type
by GHC 20 Jan '16

20 Jan '16

#9202: Strange Closure Type -------------------------------------+------------------------------------- Reporter: athanclark | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: strange-closure- | Operating System: Linux type | Type of failure: Compile-time Architecture: x86_64 (amd64) | crash Difficulty: Project (more | Test Case: than a week) | Blocking: Blocked By: | Related Tickets: | -------------------------------------+------------------------------------- Hello masters of the universe, I am here with a plea. I have recently installed GHC 7.8.2 and cabal-install 1.20.0.0 (following [https://gist.github.com/wting/8498731 this] guide), and have ran into a fun road block on the way to installing yesod-platform. I have had a few incidents of the 'strange closure type ###' error on this machine before, on the 7.6.x version available in Ubuntu's repository. I believe this failure is occuring when installing text, because that was the error that I got when installing attoparsec alone, but without a sandbox. I know (barely) better now, so when I went to install yesod-platform, I did a {{{cabal unpack $1 && cd $1* && cabal sandbox init && cabal install --only-dependencies && cabal build}}}, but I failed at preventing the error, still :( I've attached the output as output.txt, and I've also included my `lspci` and `lshw` outputs just for giggles :) I hope someone can direct me in the right direction, I would appreciate it tremendously. Thank you! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9202> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10581: Recommend ScopedTypeVariables
by GHC 19 Jan '16

19 Jan '16

#10581: Recommend ScopedTypeVariables -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.10.1 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The !ScopedTypeVariables extension is one of the few that doesn't recommend itself when it should be used. I recognize that this may be hard to do, but here is a strawman proposal: Always behave as if !ScopedTypeVariables is on at binding sites for type variables (in an annotation with `forall`). Then, at ''occurrences'' of type variables, check if the extension is on. If a type variable is in scope but the extension is off, remember that the user probably wants the extension, but then rename the type variable occurrence away from the in- scope one. If a type error ensues, we've remembered that the lack of !ScopedTypeVariables may be to blame, and we recommend turning it on. There may be better approaches, too. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10581> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8114: GHC panic when building `thyme`
by GHC 16 Jan '16

16 Jan '16

#8114: GHC panic when building `thyme` -----------------------------------+--------------------------------------- Reporter: Ptharien's | Owner: Flame | Status: new Type: bug | Milestone: Priority: normal | Version: 7.6.3 Component: Compiler | Operating System: MacOS X Keywords: | Type of failure: Compile-time crash Architecture: x86_64 (amd64) | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -----------------------------------+--------------------------------------- While attempting to build `thyme` from Hackage with core, stg, and cmm linting and -O2 enabled, GHC crashed with an internal panic. See attached terminal log. {{{ rrdhcp-10-32-234-247:thyme-0.2.4.1 Alexander$ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.6.3 rrdhcp-10-32-234-247:thyme-0.2.4.1 Alexander$ cabal --version cabal-install version 1.16.0.2 using version 1.16.0 of the Cabal library rrdhcp-10-32-234-247:thyme-0.2.4.1 Alexander$ which ghc /usr/local/bin/ghc rrdhcp-10-32-234-247:thyme-0.2.4.1 Alexander$ which cabal /Users/Alexander/Library/Haskell/bin/cabal }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8114> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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