April 2016 - ghc-tickets

[GHC] #11471: Note [The kind invariant] in TyCoRep needs to be updated
by GHC 28 Jun '16

28 Jun '16

#11471: Note [The kind invariant] in TyCoRep needs to be updated -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 (Type checker) | 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: -------------------------------------+------------------------------------- This Note, found in TyCoRep, needs to be updated to reflect `TypeInType`. It should not reference `OpenKind`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11471> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9078: Segfault with makeStableName
by GHC 28 Jun '16

28 Jun '16

#9078: Segfault with makeStableName ------------------------------------+------------------------------------- Reporter: robertce | 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: | ------------------------------------+------------------------------------- Calling `makeStableName` on the same object many times causes a segfault. The following triggers this behaviour on both OSX and Linux-x86_64, provided it is compiled (it doesn't seem to occur if the call to `makeStableName` is interpreted). {{{ module Main where import Control.Monad import System.Mem.StableName main :: IO () main = replicateM_ 100000 (makeStableName foo) foo :: Int foo = 1 }}} It seems to happen largely at random. The 100000 calls to `makeStableName` in the above example essentially guarantee its occurrence, but I have observed it happen with far fewer. The reason this bug was discovered is it is causing frequent failures in Accelerate on 7.8.2. See [https://github.com/AccelerateHS/accelerate/issues/162] In that case it seems to be causing more `strange closure type` errors than segfaults, but I assume it is the same root cause. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9078> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11948: GHC forgets constraints
by GHC 23 Jun '16

23 Jun '16

#11948: GHC forgets constraints -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Possibly related: #10338 The following program should compile, but fails with the error: {{{ Could not deduce (Bar (F zq) zq) arising from a use of ‘bar’ from the context (Bar (Foo (F zq)) (Foo zq)) bound by the type signature for bug :: Bar (Foo (F zq)) (Foo zq) => Foo (F zq) -> Foo zq }}} This is definitely incorrect: I am providing a `Bar` constraint in the context of `bug`, but GHC is asking for constraints so that it can resolve to the instance declared in Bar.hs. A few workarounds I've found so far, which may or may not help find the bug: 1. Adding `-XTypeFamilies` to Main.hs makes the program compile. 2. ''Removing'' the type signature from `x` in `bug` makes the program compile. 3. Defining `bug` without a `let` as `bug sk = bar sk :: Foo zq` or `bug sk = bar sk` makes the program compile. Main.hs: {{{ {-# LANGUAGE FlexibleContexts, ScopedTypeVariables #-} import Bar bug :: forall zq . (Bar (Foo (F zq)) (Foo zq)) => Foo (F zq) -> Foo zq bug sk = let x = bar sk :: Foo zq in x }}} Bar.hs {{{ {-# LANGUAGE MultiParamTypeClasses, TypeFamilies #-} module Bar where type family F b newtype Foo r = Foo r type instance F (Foo r) = Foo (F r) class Bar a b where bar :: a -> b instance (Bar a b) => Bar (Foo a) (Foo b) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11948> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10686: Process stops responding to sigINT
by GHC 22 Jun '16

22 Jun '16

#10686: Process stops responding to sigINT -------------------------------------+------------------------------------- Reporter: hamish | 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 | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Every now and then the leksah-server process has required a kill -9 it to get rid of it. Now Leksah is using the threaded RTS it seems to be happening in Leksah too. It is worse in Leksah because child processes inherit the behaviour and do not terminate when sent Leksah sends them sigINT (which Leksah does very frequently). Once the problem arrises it continues until the Leksah is restarted. Both leksah-server and Leksah start child processes using the process package. I think process package and the GHC GC both call blockUserSignals and it only has one place to store savedSignals. My guess is that two calls go into blockUserSignals from different threads before unblockUserSignals is called on either. The result is that when unblockUserSignals is called it does nothing (because savedSignals was overwritten). Perhaps savedSignals could use some kind of thread local storage? Also docs seem to indicate sigprocmask should not be used at all in multithreaded processes. Perhaps the GHC RTS should use pthread_sigprocmask instead? If the calling process delegates Ctrl+C the problem might be largely hidden. The sigINT signal is enabled again in the child fork and the parent will get an exception if the child is terminated with a sigINT. However I believe the parent is still left in a state where it will no longer respond to sigINT if the child process terminates normally (assuming two calls in a row were made to blockUserSignals at some point). The work around for now in Leksah is to reenable sigINT before each createProcess call. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10686> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11081: Implement Introspective Template Haskell
by GHC 22 Jun '16

22 Jun '16

#11081: Implement Introspective Template Haskell -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: feature | Status: new request | Priority: normal | Milestone: ⊥ Component: Template | Version: 7.10.2 Haskell | 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: | TemplateHaskell/Introspective -------------------------------------+------------------------------------- This ticket is to track commentary and reactions to TemplateHaskell/Introspective, and to help the proposal not get lost. Contrary to the title of this ticket, it is not yet resolved that Introspective Template Haskell should ever be implemented. But with some of the support that it's gotten, it seemed appropriate to make a ticket. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11081> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8713: libdl, libpthread may be unwanted too
by GHC 22 Jun '16

22 Jun '16

#8713: libdl, libpthread may be unwanted too -------------------------------------+------------------------------------- Reporter: ip1981 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/unix | Version: 7.6.3 Keywords: | Operating System: Other Architecture: x86_64 (amd64) | Type of failure: GHC doesn't work Difficulty: Moderate (less | at all than a day) | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- I have GHC on an unusual system [1] libdl.so.1, librt.so.1 and some others are "filter libraries": they do not provide real functions (almost all is in libc.so.1), but to make thing work libFOO.so are GNU ld linker scripts: thus linking is successful, libFOO.so.1 is not linked in :-) Unfortunately, runtime linker (ld.so.1) does not understand GNU ld linker scripts. And I get errors like this: {{{ # ghci -package unix GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package array-0.4.0.1 ... linking ... done. Loading package deepseq-1.3.0.1 ... linking ... done. Loading package bytestring-0.10.0.2 ... linking ... done. Loading package old-locale-1.0.0.5 ... linking ... done. Loading package time-1.4.0.1 ... linking ... done. Loading package unix-2.7.0.0 ... <command line>: can't load .so/.DLL for: /usr/lib/gcc/x86_64-pc-solaris2.11/4.7/../../../x86_64-illumos/libdl.so (ld.so.1: ghc: fatal: /usr/lib/gcc/x86_64-pc- solaris2.11/4.7/../../../x86_64-illumos/libdl.so: unknown file type) }}} The unix package v2.6 had the same issue with librt.so too, in version 2.7 libdl.so remains. I use the attached patch for GHC 7.6.3 to fix this issue. In general I suggest to use AC_SEARCH_LIBS instead of AC_CHECK_LIB [1] http://osdyson.org -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8713> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11980: Testsuite: run each test in its own /tmp directory, after copying required files
by GHC 20 Jun '16

20 Jun '16

#11980: Testsuite: run each test in its own /tmp directory, after copying required files -------------------------------------+------------------------------------- Reporter: thomie | Owner: thomie Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: Test Suite | Version: 8.0.1 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: -------------------------------------+------------------------------------- == Plan == For each TEST: * create a directory `<testdir>` inside `/tmp` * link/copy all source files that the test needs into `<testdir>` * run the test inside `<testdir>` * delete `<testdir>` == Benefits == * running tests in parallel always works, even when two tests write to the same file (for example .hi/.o files, from sharing a .hs file). This should reduce the number of unsuspected and annoying validate failures. There is no longer any need to specify `-outputdir` explicitly. * there is no longer any need to add entries to the perpetually out-of- date `testsuite/.gitignore`. * there is no longer any need to specify `extra_clean` or `clean_cmd` setup functions for tests. Sometimes you //will// have to specify which extra files a test needs, using the (new) `extra_files` setup function, but it will be immediately clear when to do so (i.e. the test won't run if you don't). By default only files with the name `<testname>*` are copied to `<testdir>`. * it could become possible to run //ways// for a single test in parallel (i.e. `make TEST=<testname> slow` would become faster) * `clean`ing the testsuite won't be necessary (except for a few files in `testsuite/mk` perhaps) Currently the only way to clean the testsuite is via `make CLEANUP=1 CLEAN_ONLY=1`, which requires a call to the testsuite, which requires building mk/ghc-config first. There are 2 problems with this: * you don't expect a call to `make clean` to start building stuff. Even less so in a pristine source distribution. * most of the time it doesn't clean all files, because lots of tests are missing are have incomplete `extra_clean`s. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11980> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9646: Strange performance bug
by GHC 20 Jun '16

20 Jun '16

#9646: Strange performance bug -------------------------------------+------------------------------------- Reporter: erikd | 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: Runtime Blocked By: | performance bug Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I've been chasing a weird performance bug for about a week now. I've reduced the testcase to the following git repo: https://github.com/erikd/ghc-perfbug-test The Readme.md file in that repo contains an explanation of how to reproduce the issue. The benchmark program in the repo uses Criterion to test the performance of one particular function. Running the program in a particular way results into two significanlty different results. The commands are: {{{ make clean bench-integer.html cp -f bench-integer.html bench-integer-slow.html touch New3/GHC/Integer/Natural.hs && make bench-integer.html }}} The results for one function in the file `New3/GHC/Integer/Natural.hs` is 8 times slower in the first test that the second while the other test function always executes at about the speed. I haven't been able to test this with ghc-7.6.3 because the code uses `isTrue#` which isn't available in 7.6.3. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9646> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9682: Implement "Add bifunctor related classes to base"-Proposal
by GHC 19 Jun '16

19 Jun '16

#9682: Implement "Add bifunctor related classes to base"-Proposal -------------------------------------+------------------------------------- Reporter: hvr | Owner: ekmett Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Core Libraries | Version: Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less | Type of failure: than a day) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- See [http://www.haskell.org/pipermail/libraries/2014-April/022844.html original libraries@ proposal] for more details -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9682> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10448: Implement rest of "Add bifunctor related classes to base"-Proposal
by GHC 19 Jun '16

19 Jun '16

#10448: Implement rest of "Add bifunctor related classes to base"-Proposal -------------------------------------+------------------------------------- Reporter: hvr | Owner: ekmett Type: task | Status: new Priority: normal | Milestone: 7.12.1 Component: | Version: libraries/base | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: #9682 Test Case: | Blocking: | Differential Revisions: Phab:D336 | -------------------------------------+------------------------------------- Cloned from #9682: ---- See [http://www.haskell.org/pipermail/libraries/2014-April/022844.html original libraries@ proposal] for more details -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10448> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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