February 2016 - ghc-tickets

[GHC] #11348: Local open type families instances ignored during type checking
by GHC 20 Jul '16

20 Jul '16

#11348: Local open type families instances ignored during type checking -------------------------------------+------------------------------------- Reporter: alexvieth | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE TypeInType #-} import Data.Kind import Data.Proxy type family TrivialFamily t :: Type type instance TrivialFamily (t :: Type) = Bool data R where R :: Proxy Bool -> R type ProblemType t = 'R ('Proxy :: Proxy (TrivialFamily t)) }}} Compiling this program as-is, GHC rejects it! {{{#!sh error: • Expected kind ‘Proxy Bool’, but ‘'Proxy’ has kind ‘Proxy (TrivialFamily t)’ • In the first argument of ‘R’, namely ‘(Proxy :: Proxy (TrivialFamily t))’ In the type ‘R (Proxy :: Proxy (TrivialFamily t))’ In the type declaration for ‘ProblemType’ }}} But if we move `TrivialFamily` to another module and import it, GHC discovers that `TrivialFamily t = Bool` and the program is accepted. When compiling the rejected program (with the local family instance) I observe that the instance environments given by `FamInst.tcGetFamInstEnvs` contain no instances! The renamer processes the local instance, but no `FamInst` is created for it, and nothing enters the `TcGblEnv`'s family instance record. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11348> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8732: Global big object heap allocator lock causes contention
by GHC 16 Jul '16

16 Jul '16

#8732: Global big object heap allocator lock causes contention ------------------------------------+------------------------------------- Reporter: tibbe | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- The lock allocate() takes when allocating big objects hurts scalability of I/O bound application. Network.Socket.ByteString.recv is typically called with a buffer size of 4096, which causes a ByteString of that size to be allocate. The size of this ByteString causes it to be allocated from the big object space, which causes contention of the global lock that guards that space. See http://www.yesodweb.com/blog/2014/02/new-warp for a real world example. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8732> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10647: Notice about lack of SIMD support.
by GHC 12 Jul '16

12 Jul '16

#10647: Notice about lack of SIMD support. -------------------------------------+------------------------------------- Reporter: mniip | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- In some cases, when SIMD primitives are used without the `-fllvm` flag, instead of giving the friendly `SIMD vector instructions require the LLVM back-end.`, GHC crashes with varying messages. The simplest example is {{{#!hs {-# LANGUAGE MagicHash #-} module Foo where import GHC.Prim data V = V Int8X16# }}} In 7.8.4 this crashes with {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.8.4 for x86_64-unknown-linux): Size.intSize W128 }}} According to osa1, in HEAD this still crashes, but with {{{ ghc-stage2: panic! (the 'impossible' happened) (GHC version 7.11.20150717 for x86_64-unknown-linux): Format.intFormat W128 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10647> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8308: Resurrect ticky code for counting constructor arity
by GHC 12 Jul '16

12 Jul '16

#8308: Resurrect ticky code for counting constructor arity ----------------------------------------------+---------------------------- Reporter: jstolarek | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Profiling | Version: 7.7 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less than a day) | Type of failure: Other Blocked By: | Test Case: Related Tickets: | Blocking: ----------------------------------------------+---------------------------- There is a dead piece of ticky profiling code that computes histograms of data constructor arities (including tuples) and size of vector returns. The function responsible is `bumpHistogram` in [[GhcFile(compiler/codeGen/StgCmmTicky.hs)]], which masks the commented out function `bumpHistogramE`. We can improve ticky profiling by resurrecting this dead code. There are following things that need to be done: 1. Replace current no-op `bumpHistogram` with `bumpHistogramE`. Note that current implementation of `bumpHistogramE` computes constructor arity at runtime. This is unnecessary because we know arity at compile time so we can avoid runtime check by doing sth like this: {{{ bumpHistogram lbl n = do let offset = n `min` 8 emit (addToMem cLong (cmmIndexExpr cLongWidth (CmmLit (CmmLabel (mkRtsDataLabel lbl))) (CmmReg (CmmInt (fromIntegral offset) cLongWidth))) 1) }}} Note that `mkRtsDataLabel` function does not exist anymore but we should be able to replace that call with `mkCmmDataLabel rtsPackageId lbl` (speculation). 2. We need to declare arrays that will store histogram values. Declarations of variables used for storing ticky statistics are in [[GhcFile(includes/stg/Ticky.h)]]. We also need to initialize the declared array to contain only zeros. 3. Having declared the arrays we need to fix printing of computed arities. This is done in [[GhcFile(rts/Ticky.c)]]. Note that there is a lot of code that is commented out (`/* krc: comment out some of this stuff temporarily */`) or disabled with `#if FALSE` pragma. We need to resurect *some* of it. There is a `PR_HST` macro for printing one histogram entry. This seems bad. We should probably rework the part of code responsible for printing out results of historgams. 4. Current code counts arities from 0 to 8. Everything above 8 is put into the same bin as 8. This magical 8 is spread all over the code. We should declare a constant that is visible both in Haskell sources (see `bumpHistogram` in 1.) and RTS files and have all code behave properly depending on that constant - we should have loops instead of statically printing 9 elements of histogram array. 5. Some ticky functions that count arity histograms are not used. For example `tickyReturnNewCon` should probably be called by `cgConApp` like this: {{{ ; emit =<< fcode_init ; tickyReturnNewCon ; emitReturn [idInfoToAmode idinfo] } }}} The above is a an outline, which should be fairly accurate, but unexpected things may show up along the way. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8308> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11554: Self quantification in GADT data declarations
by GHC 12 Jul '16

12 Jul '16

#11554: Self quantification in GADT data declarations -------------------------------------+------------------------------------- Reporter: Rafbill | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc2 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: -------------------------------------+------------------------------------- GHC hangs on this (it was panicking on the same code before : [https://github.com/goldfirere/ghc/issues/56](https://github.com/goldfirere/… : {{{#!hs {-# LANGUAGE GADTs, TypeInType #-} import Data.Kind data A :: Type where B :: forall (a :: A). A }}} I guess the typechecker tries to infer the kind of A from the type of the constructors and hangs. Maybe recursive occurrences of a type as a kind in its constructors should only be allowed when its kind signature is specified and can be used to typecheck the constructors. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11554> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10886: Remove the magic from `Any`
by GHC 11 Jul '16

11 Jul '16

#10886: Remove the magic from `Any` -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: task | Status: new Priority: normal | Milestone: 8.0.1 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: | -------------------------------------+------------------------------------- The `Any` type used to be very highly magical: a poly-kinded type in a mono-kinded world. Then it became only normally magical: a datatype with a return kind of `k` (instead of `*`). Then it became only a bit magical: a closed type family with no equations. Now that we have non-magical empty closed type families, I believe that we can remove the last bit of magic and just define {{{ type family Any :: k where { } }}} somewhere (`GHC.Types`?), wire it in (like, e.g., `Bool`), and be done with it. Objections? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10886> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10311: package name returned from tyConPackage is garbled
by GHC 08 Jul '16

08 Jul '16

#10311: package name returned from tyConPackage is garbled -------------------------------------+------------------------------------- Reporter: j.waldmann | 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 am using tyConPackage (etc.) to programmatically generate links to haddock documentation (e.g., from a typed edit widget). This is now broken: {{{ import Data.Map import Data.Typeable tyConPackage $ typeRepTyCon $ typeOf $ fromList [(1,2)] in ghc-7.8.4: "containers-0.5.5.1" in ghc-7.10.1: "conta_47ajk3tbda43DFWyeF3oHQ" }}} and I don't see how to get the actual package name. Cf. http://stackoverflow.com/questions/29638177/tyconpackage-changed-from- ghc-7-8-to-ghc-7-10 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10311> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9625: ghc: panic using --enable-executable-dynamic
by GHC 08 Jul '16

08 Jul '16

#9625: ghc: panic using --enable-executable-dynamic -------------------------------------+------------------------------------- Reporter: CoreyOConnor | 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: Compile- Blocked By: | time crash Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- (from: https://github.com/haskell/cabal/issues/2039) Using --enable-executable-dynamic leads to a ghc panic. Reproduction steps: 1. clone https://github.com/coreyoconnor/executable-dynamic-issue 2. cabal configure --enable-tests --enable-executable-dynamic 3. cabal test Expected results: Test executes and passes. Actual results: {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.8.2 for x86_64 -unknown-linux): Don't understand library name verify-foo }}} Actual results varies based on the name of "verify-foo" test suite. Other names tried: "verifyFoo", "VerifyFoo". All of which also fail. Removing "--enable-executable-dynamic" results in a pass regardless of test suite name. Reproduced on GHC 7.8.2, GHC 7.8.3, Cabal 1.18, Cabal 1.20. Ubuntu. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9625> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11617: DYLD_LIBRARY_PATH ignored on Mac OS X 10.11.x
by GHC 07 Jul '16

07 Jul '16

#11617: DYLD_LIBRARY_PATH ignored on Mac OS X 10.11.x --------------------------------------+--------------------------------- Reporter: borsboom | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: hsc2hs | Version: 7.10.3 Keywords: | Operating System: MacOS X Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- This was first reported on the Stack issue tracker at https://github.com/commercialhaskell/stack/issues/1161, but I've traced it to the fact that GHC uses shell script wrappers for many common commands, including `ghc`, `ghci`, and `hsc2hs`. Background: Mac OS X 10.11 introduced System Integrity Protection, which treats parts of the filesystem specially to prevent tampering with the system. Among those protections is that executables in `/bin`, such as `/bin/sh`, have the DYLD_LIBRARY_PATH variable stripped from the environment before being invoked. Since `ghc`, `hsc2hs`, and others are shell scripts that use `#!/bin/sh`, it means DYLD_LIBRARY_PATH is stripped from the environment when invoking them. I was able to work around this issue by copying `/bin/sh` to my home directory and then modifying the `#!` path in the `hsc2hs` to use the copy. I'm not sure what the best way to move forward is. Some possibilities I can think of: * Have installer tools for OS X (such as Stack, ghcformacosx, and Homebrew) apply the workaround themselves, although that leaves out anyone who installs directly from an official bindist or builds from source, and is a duplication of effort. * Have `make install` on OS X copy `/bin/sh` and "fix" the wrappers itself. * Replace the shell script wrappers with something written in Haskell that reads the paths from a configuration file. Note: I set the component to `hsc2hs` since that's where I encountered the problem, but I wouldn't be surprised if it also effected other cases (like `ghci`, and `ghc` with Template Haskell). I also hesitated to categorize this a "bug" since it's OS X's weird behaviour, and not actually something I feel GHC is doing wrong, causing this problem. But I doubt OS X is going to change, although it is possible (but not recommended) to disable SIP by booting into recovery mode and running `csrutil disable`, after which these protections are no longer in place. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11617> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11165: Testsuite framework failures are too easy to ignore and too hard to find
by GHC 01 Jul '16

01 Jul '16

#11165: Testsuite framework failures are too easy to ignore and too hard to find -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Test Suite | 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: -------------------------------------+------------------------------------- The testsuite driver really should do a better job of drawing the user's attention to framework failures. The only evidence in the testsuite summary that something went wrong is a non-zero "framework failures" count. If you notice that this count is non-zero then you need to sift manually through the initial log output produced by the driver and find the culprit. It's just generally terrible. Testsuite failures are failures, we should at least treat them as such and include them in the `TEST=...` message in the testsuite summary so they can be easily reproduced. Ideally we would also save the exception that caused the failure and show it in the summary as well. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11165> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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