May 2015 - ghc-tickets

[GHC] #10226: Regression in constraint solver from 7.8 to 7.10
by GHC 13 Jul '15

13 Jul '15

#10226: Regression in constraint solver from 7.8 to 7.10 -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 (Type checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Best explained by example: {{{#!hs {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE AllowAmbiguousTypes #-} -- only necessary in 7.10 {-# LANGUAGE FlexibleContexts #-} -- necessary for showFromF' example type family F a type family FInv a -- This definition is accepted in 7.8 without anything extra, but requires -- AllowAmbiguousTypes in 7.10 (this, by itself, is not a problem): showFromF :: (Show a, FInv (F a) ~ a) => F a -> String showFromF fa = undefined -- Consider what happens when we attempt to call `showFromF` at some type b. -- In order to check that this is valid, we have to find an a such that -- -- > b ~ F a /\ Show a /\ FInv (F a) ~ a -- -- Introducing an intermeidate variable `x` for the result of `F a` gives us -- -- > b ~ F a /\ Show a /\ FInv x ~ a /\ F a ~ x -- -- Simplifying -- -- > b ~ x /\ Show a /\ FInv x ~ a /\ F a ~ x -- -- Set x := b -- -- > Show a /\ FInv b ~ a /\ F a ~ b -- -- Set a := FInv b -- -- > Show (FInv b) /\ FInv b ~ FInv b /\ F (FInv b) ~ b -- -- Simplifying -- -- > Show (FInv b) /\ F (FInv b) ~ b -- -- Indeed, we can give this definition in 7.8, but not in 7.10: showFromF' :: (Show (FInv b), F (FInv b) ~ b) => b -> String showFromF' = showFromF {------------------------------------------------------------------------------- In 7.10 the definition of showFromF' is not accepted, but it gets stranger. In 7.10 we cannot _call_ showFromF at all all, even at a concrete type. Below we try to call it at type b ~ Int. It would need to show > Show (FInv Int) /\ F (FInt Int) ~ Int all of which should easily get resolved, but somehow don't. -------------------------------------------------------------------------------} type instance F Int = Int type instance FInv Int = Int test :: String test = showFromF (0 :: Int) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10226> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10009: type inference regression when faking injective type families
by GHC 13 Jul '15

13 Jul '15

#10009: type inference regression when faking injective type families -------------------------------------+------------------------------------- Reporter: aavogt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- ghc-7.10.0.20141222 does not accept the program unless I uncomment the type signature (a :: a). ghc-7.8 accepts it as-is. {{{#!hs {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} class (UnF (F a) ~ a, Show a) => C a where type F a f :: F a -> a type family UnF a g :: forall a. C a => a -> String g _ = show a where a = f (undefined :: F a) -- :: a }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10009> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10463: Wrong warning with PartialTypeSignatures
by GHC 13 Jul '15

13 Jul '15

#10463: Wrong warning with PartialTypeSignatures -------------------------------------+------------------------------------- Reporter: augustss | 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: | -------------------------------------+------------------------------------- This program {{{#!hs {-# LANGUAGE ScopedTypeVariables, PartialTypeSignatures #-} f (x :: _) = x ++ "" }}} gives this warning {{{ Bug.hs:2:9: Warning: Found hole ‘_’ with type: [Char] Relevant bindings include f :: [Char] -> [Char] (bound at Bug.hs:2:1) In a pattern type signature: _ In the pattern: x :: _ In an equation for ‘f’: f (x :: _) = x ++ "" }}} But there is no hole, only an _ in a type. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10463> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8709: `make 1` does not work (well)
by GHC 11 Jul '15

11 Jul '15

#8709: `make 1` does not work (well) ------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Say I do a `sync-all pull` and then fix a bunch of merge errors. The changes mean that I need to recompile the stage-1 compiler. So, I dutifully `make distclean` and start rebuilding. I then find a bunch of compiler errors in my edited code. Now, I'd like to start the fix error/recompile loop. BUT, when I do `make 1` in the `compiler/` directory, I get errors: {{{ rae:13:49:29 ~/Documents/ghc/compiler> make 1 make -C .. stage=1 all_ghc_stage1 compiler_dist_NO_BUILD_DEPS=YES compiler_dist-boot_NO_BUILD_DEPS=YES compiler_dist- install_NO_BUILD_DEPS=YES NO_GENERATED_MAKEFILE_RULES=YES OMIT_PHASE_0=YES OMIT_PHASE_1=YES compiler_stage1_NO_BUILD_DEPS=YES compiler_stage2_NO_BUILD_DEPS=YES compiler_stage3_NO_BUILD_DEPS=YES ghc_stage1_NO_BUILD_DEPS=YES ghc_stage2_NO_BUILD_DEPS=YES ghc_stage3_NO_BUILD_DEPS=YES ONLY_DEPS_FOR="compiler_stage1 ghc_stage1" ===--- building final phase make -r --no-print-directory -f ghc.mk phase=final all_ghc_stage1 libraries/old-time/ghc.mk:5: libraries/old-time/dist-install/package- data.mk: No such file or directory libraries/haskell98/ghc.mk:5: libraries/haskell98/dist-install/package- data.mk: No such file or directory libraries/haskell2010/ghc.mk:5: libraries/haskell2010/dist-install /package-data.mk: No such file or directory libraries/random/ghc.mk:5: libraries/random/dist-install/package-data.mk: No such file or directory libraries/primitive/ghc.mk:5: libraries/primitive/dist-install/package- data.mk: No such file or directory libraries/vector/ghc.mk:5: libraries/vector/dist-install/package-data.mk: No such file or directory libraries/dph/dph-base/ghc.mk:5: libraries/dph/dph-base/dist-install /package-data.mk: No such file or directory libraries/dph/dph-prim-interface/ghc.mk:5: libraries/dph/dph-prim- interface/dist-install/package-data.mk: No such file or directory libraries/dph/dph-prim-seq/ghc.mk:5: libraries/dph/dph-prim-seq/dist- install/package-data.mk: No such file or directory libraries/dph/dph-prim-par/ghc.mk:5: libraries/dph/dph-prim-par/dist- install/package-data.mk: No such file or directory libraries/dph/dph-lifted-base/ghc.mk:5: libraries/dph/dph-lifted-base /dist-install/package-data.mk: No such file or directory libraries/dph/dph-lifted-boxed/ghc.mk:5: libraries/dph/dph-lifted-boxed /dist-install/package-data.mk: No such file or directory libraries/dph/dph-lifted-copy/ghc.mk:5: libraries/dph/dph-lifted-copy /dist-install/package-data.mk: No such file or directory libraries/dph/dph-lifted-vseg/ghc.mk:5: libraries/dph/dph-lifted-vseg /dist-install/package-data.mk: No such file or directory libraries/ghc-prim/ghc.mk:4: libraries/ghc-prim/dist-install/package- data.mk: No such file or directory libraries/integer-gmp/ghc.mk:4: libraries/integer-gmp/dist-install /package-data.mk: No such file or directory libraries/base/ghc.mk:4: libraries/base/dist-install/package-data.mk: No such file or directory libraries/filepath/ghc.mk:4: libraries/filepath/dist-install/package- data.mk: No such file or directory libraries/array/ghc.mk:4: libraries/array/dist-install/package-data.mk: No such file or directory libraries/deepseq/ghc.mk:4: libraries/deepseq/dist-install/package- data.mk: No such file or directory libraries/bytestring/ghc.mk:4: libraries/bytestring/dist-install/package- data.mk: No such file or directory libraries/containers/ghc.mk:4: libraries/containers/dist-install/package- data.mk: No such file or directory libraries/old-locale/ghc.mk:4: libraries/old-locale/dist-install/package- data.mk: No such file or directory libraries/time/ghc.mk:4: libraries/time/dist-install/package-data.mk: No such file or directory libraries/unix/ghc.mk:4: libraries/unix/dist-install/package-data.mk: No such file or directory libraries/directory/ghc.mk:4: libraries/directory/dist-install/package- data.mk: No such file or directory libraries/process/ghc.mk:4: libraries/process/dist-install/package- data.mk: No such file or directory libraries/hpc/ghc.mk:4: libraries/hpc/dist-install/package-data.mk: No such file or directory libraries/pretty/ghc.mk:4: libraries/pretty/dist-install/package-data.mk: No such file or directory libraries/template-haskell/ghc.mk:4: libraries/template-haskell/dist- install/package-data.mk: No such file or directory libraries/Cabal/Cabal/ghc.mk:4: libraries/Cabal/Cabal/dist-install /package-data.mk: No such file or directory libraries/binary/ghc.mk:4: libraries/binary/dist-install/package-data.mk: No such file or directory libraries/bin-package-db/ghc.mk:4: libraries/bin-package-db/dist-install /package-data.mk: No such file or directory libraries/hoopl/ghc.mk:4: libraries/hoopl/dist-install/package-data.mk: No such file or directory libraries/transformers/ghc.mk:4: libraries/transformers/dist-install /package-data.mk: No such file or directory libraries/xhtml/ghc.mk:4: libraries/xhtml/dist-install/package-data.mk: No such file or directory libraries/terminfo/ghc.mk:4: libraries/terminfo/dist-install/package- data.mk: No such file or directory libraries/haskeline/ghc.mk:4: libraries/haskeline/dist-install/package- data.mk: No such file or directory libraries/integer-gmp/gmp/ghc.mk:49: libraries/integer-gmp/gmp/config.mk: No such file or directory utils/hsc2hs/ghc.mk:16: utils/hsc2hs/dist-install/package-data.mk: No such file or directory utils/ghc-pkg/ghc.mk:66: utils/ghc-pkg/dist-install/package-data.mk: No such file or directory utils/dll-split/ghc.mk:18: utils/dll-split/dist-install/package-data.mk: No such file or directory utils/ghc-pwd/ghc.mk:8: utils/ghc-pwd/dist-install/package-data.mk: No such file or directory utils/ghc-cabal/ghc.mk:67: utils/ghc-cabal/dist-install/package-data.mk: No such file or directory utils/hpc/ghc.mk:18: utils/hpc/dist-install/package-data.mk: No such file or directory utils/runghc/ghc.mk:28: utils/runghc/dist-install/package-data.mk: No such file or directory utils/mkUserGuidePart/ghc.mk:18: utils/mkUserGuidePart/dist/package- data.mk: No such file or directory utils/compare_sizes/ghc.mk:8: utils/compare_sizes/dist-install/package- data.mk: No such file or directory make[2]: *** No rule to make target `libraries/integer-gmp/gmp/config.mk'. Stop. make[1]: *** [all_ghc_stage1] Error 2 make: *** [1] Error 2 }}} Using `make stage=1` works fine, but computing the dependencies each time is annoying. In past experience, I've seen that, once the stage-1 compiler builds to completion at least once, `make 1` works just fine -- it just fails after a `clean`. I don't recall having this problem with `make 2`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8709> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10298: Infinite loop when shared libraries are unavailable
by GHC 11 Jul '15

11 Jul '15

#10298: Infinite loop when shared libraries are unavailable -------------------------------------+------------------------------------- Reporter: snoyberg | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 7.10.1 System | Operating System: Linux Keywords: | Type of failure: Runtime crash Architecture: x86_64 | Blocked By: (amd64) | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Originally discussed at: https://groups.google.com/d/msg/haskell- cafe/5ZTv5mCG_HI/hBJ-VkdpxdoJ. Note that this was originally discussed as a static linking and Docker issue, but in fact affects dynamically linked executables without any containerization. I've put together the following script that reproduces my problem: {{{ cat > hello.hs <<EOF main :: IO () main = putStrLn "Hello World" EOF ghc hello.hs rm -rf tmp mkdir tmp cp hello tmp mkdir -p tmp/usr/lib/x86_64-linux-gnu cp /usr/lib/x86_64-linux-gnu/libgmp.so.10 tmp/usr/lib/x86_64-linux-gnu mkdir -p tmp/lib/x86_64-linux-gnu cp \ /lib/x86_64-linux-gnu/libm.so.6 \ /lib/x86_64-linux-gnu/librt.so.1 \ /lib/x86_64-linux-gnu/libdl.so.2 \ /lib/x86_64-linux-gnu/libc.so.6 \ /lib/x86_64-linux-gnu/libpthread.so.0 \ tmp/lib/x86_64-linux-gnu mkdir -p tmp/lib64 cp /lib64/ld-linux-x86-64.so.2 tmp/lib64 #mkdir -p tmp/usr/lib/x86_64-linux-gnu/gconv/ #cp \ # /usr/lib/x86_64-linux-gnu/gconv/UTF-32.so \ # /usr/lib/x86_64-linux-gnu/gconv/gconv-modules \ # tmp/usr/lib/x86_64-linux-gnu/gconv sudo chroot tmp /hello }}} If I uncomment the block that copies the gconv files, the program runs as expected. However, without those files copied, the program burns CPU and consumes memory until killed by the OS. I ran strace on a similar executable, and got the results at: https://gist.github.com/snoyberg/095efb17e36acc1d6360 Note that this problem also occurs with statically linked executables when some of the other dynamically linked libraries are not available in the chroot environment. Expected behavior: ideal would be not to require the gconv files and other shared libraries be present, especially when statically linked. Barring that, it would be much better if the RTS could produce a meaningful error message about the missing file. Note that strace does demonstrate that a open system call is failing, e.g.: open("/usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache", O_RDONLY) = -1 ENOENT (No such file or directory) Reproduced on GHC 7.8.4 and 7.10.1, on Ubuntu 14.04 64-bit. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10298> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10351: Inferred type is rejected
by GHC 09 Jul '15

09 Jul '15

#10351: Inferred type is rejected -------------------------------------+------------------------------------- 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: | -------------------------------------+------------------------------------- Consider {{{ class C a where op :: a -> () f x = op [x] }}} we get {{{ Foo.hs:14:1: error: Non type-variable argument in the constraint: C [t] (Use FlexibleContexts to permit this) When checking that ‘f’ has the inferred type f :: forall t. C [t] => t -> () }}} Arguably, if `FlexibleContexts` is not on, we should not infer a type that will immediately be rejected. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10351> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9665: Add "since" information to LANGUAGE extensions in GHC user guide
by GHC 08 Jul '15

08 Jul '15

#9665: Add "since" information to LANGUAGE extensions in GHC user guide -------------------------------------+------------------------------------- Reporter: andreas.abel | Owner: Type: task | Status: new Priority: high | Milestone: Component: Documentation | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- If one wants to support older versions of GHC, it is hard to find out whether one can use a certain LANGUAGE extension. One has to go to older versions of the GHC manual to find out whether the corresponding documentation was already there, or browse release notes. Requests: 1. Document for new LANGUAGE extensions that they are available since version 7.10. For example, by adding "(Since GHC 7.10)" to the heading of the new feature. 2. Do this also for the previous LANGUAGE extensions, by adding e.g., "(Since GHC 7.6)" etc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9665> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10023: Relax Monad constraint in traceM and traceShowM to Applicative
by GHC 08 Jul '15

08 Jul '15

#10023: Relax Monad constraint in traceM and traceShowM to Applicative -------------------------------------+------------------------------------- Reporter: | Owner: RyanGlScott | Status: new Type: feature | Milestone: request | Version: 7.10.1-rc1 Priority: normal | Operating System: Unknown/Multiple Component: | Type of failure: Other libraries/base | Blocked By: Keywords: | Related Tickets: Architecture: | Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Now that {{{Applicative}}} is a superclass of {{{Monad}}} in GHC 7.10, the current type signatures of {{{traceM}}} and {{{traceShowM}}} from {{{Debug.Trace}}} are too constricted: {{{#!hs traceM :: Monad m => String -> m () traceM string = trace string $ return () traceShowM :: (Show a, Monad m) => a -> m () traceShowM = traceM . show }}} These can be equivalently defined with {{{Applicative}}}: {{{#!hs traceM :: Applicative m => String -> m () traceM string = trace string $ pure () traceShowM :: (Show a, Applicative m) => a -> m () traceShowM = traceM . show }}} However, the {{{M}}} suffixes probably won't make sense after changing the type signatures, so it might be wise to create new {{{traceA}}} and {{{traceShowA}}} functions and deprecate {{{traceM}}} and {{{traceShowM}}}. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10023> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10439: Opt_ImplicitImportQualified doesn't work for constructor field name
by GHC 08 Jul '15

08 Jul '15

#10439: Opt_ImplicitImportQualified doesn't work for constructor field name -------------------------------------+------------------------------------- Reporter: watashi | Owner: watashi Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: x86 | Type of failure: GHC rejects Test Case: | valid program Blocking: | Blocked By: Differential Revisions: | Related Tickets: -------------------------------------+------------------------------------- {{{#!hs -- ghci -fimplicit-import-qualified Prelude> let tree = Data.Tree.Node 0 [] Prelude> Data.Tree.rootLabel tree 0 Prelude> let f i j = i { Data.Tree.rootLabel = j } <interactive>:4:17: ‘Data.Tree.rootLabel’ is not a (visible) constructor field name Prelude> import qualified Data.Tree Prelude Data.Tree> let f i j = i { Data.Tree.rootLabel = j } Prelude Data.Tree> f tree 1 Node {rootLabel = 1, subForest = []} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10439> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9863: Provide PowerPC 64 bit native code generator
by GHC 08 Jul '15

08 Jul '15

#9863: Provide PowerPC 64 bit native code generator -------------------------------------+------------------------------------- Reporter: trommler | Owner: trommler Type: feature request | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: powerpc64 | Type of failure: Difficulty: Project (more | None/Unknown than a week) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- I have started work on a native code generator for PowerPC 64 bit by extending the 32 bit code generator. The code is hosted on github: [https://github.com/trommler/ghc/tree/native] So far I plan to support the old ELF v1.9 ABI on big endian. I might look into little endian and ELF 2.0 later. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9863> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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