August 2013 - ghc-tickets

Re: [GHC] #7953: Segfault on x86 with -O2
by GHC 13 Aug '13

13 Aug '13

#7953: Segfault on x86 with -O2 -------------------------------------+---------------------------- Reporter: igloo | Owner: simonmar Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86 Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+---------------------------- Comment (by kazu-yamamoto): Oh, it's magical. I cannot reproduce this on Linux. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7953#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5902: Cannot tell from an exception handler whether the exception was asynchronous
by GHC 13 Aug '13

13 Aug '13

#5902: Cannot tell from an exception handler whether the exception was asynchronous -------------------------------------+------------------------------------ Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by simonmar): Just never catch `SomeException` unless you intend to re-throw it. If you're handling an exception, you always know which exception(s) you're handling, so you can use type-specific handlers. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5902#comment:21> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3693: Show stack traces
by GHC 13 Aug '13

13 Aug '13

#3693: Show stack traces -------------------------------------+------------------------------------ Reporter: jpet | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.6.2 Component: Runtime System | Version: 6.10.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by scpmw): Great, thanks! I will start with splitting things up then. Unless there's other preferences I will submit the patches into a [https://github.com/scpmw/ghc/commits/profiling-import GitHub branch]. That way, we don't have to spam this ticket with individual patches - and can document all interesting design choices in the commit message along the way. Would be good to get feedback on the initial [https://github.com/scpmw/ghc/commit/d9df7b8b0fc46b344b6060800955e8f50110dbbb source notes patch], as that's probably the piece of code with the highest chance of screwing things up in subtle ways. I am currently trying again to hunt down any further Core optimization behaviour changes due to source notes, but this version already works very well in my experience. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3693#comment:46> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5902: Cannot tell from an exception handler whether the exception was asynchronous
by GHC 13 Aug '13

13 Aug '13

#5902: Cannot tell from an exception handler whether the exception was asynchronous -------------------------------------+------------------------------------ Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by exbb2): Replying to [comment:19 simonmar]: > > Every innocuous catch or try anywhere at any time in any library can make a thread unintentionally uncancelable > I'm not sure what you mean here. The issue in this ticket only arises when using `unsafePerformIO`. {{{ tryNTimes n | n <= 0 = return () | otherwise = forever (return ()) `catch` \(_::SomeException) -> tryNTimes (n - 1) }}} or {{{ try something :: IO (Either SomeException x) }}} Catching SomeException is sometimes reasonable, but it's unreasonable not to provide ability to discriminate against irrelevant asynchronous exceptions which do not directly follow from handled code. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5902#comment:20> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7953: Segfault on x86 with -O2
by GHC 13 Aug '13

13 Aug '13

#7953: Segfault on x86 with -O2 -------------------------------------+---------------------------- Reporter: igloo | Owner: simonmar Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86 Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+---------------------------- Comment (by simonmar): I tried and failed to reproduce this today, with a freshly built GHC on a 32-bit x86 Amazon EC2 instance running Ubuntu 12.04. {{{ ubuntu@ip-10-245-94-31:~/scratch$ uname -a Linux ip-10-245-94-31 3.2.0-40-virtual #64-Ubuntu SMP Mon Mar 25 22:07:32 UTC 2013 i686 i686 i386 GNU/Linux ubuntu@ip-10-245-94-31:~/scratch$ ~/ghc/inplace/bin/ghc-stage2 --version The Glorious Glasgow Haskell Compilation System, version 7.7.20130813 ubuntu@ip-10-245-94-31:~/scratch$ ~/ghc/inplace/bin/ghc-stage2 -O2 7.hs -fforce-recomp [1 of 1] Compiling Main ( 7.hs, 7.o ) Linking 7 ... ubuntu@ip-10-245-94-31:~/scratch$ ./7 Winner (E {_key = 1, prio = 0.7169761920394114} ... After atMost }}} Can anyone else still reproduce it on x86/Linux? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7953#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5144: Pattern synonyms
by GHC 13 Aug '13

13 Aug '13

#5144: Pattern synonyms -------------------------------------+------------------------------------ Reporter: simonpj | Owner: cactus Type: feature request | Status: new Priority: normal | Milestone: _|_ Component: Compiler | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by cactus): I've implemented infix notation as well, so now you can write this: {{{ {-# LANGUAGE ViewPatterns, PatternSynonyms #-} import qualified Data.Sequence as Seq pattern Empty = (Seq.viewl -> Seq.EmptyL) pattern x :< xs = (Seq.viewl -> x Seq.:< xs) pattern xs :> x = (Seq.viewr -> xs Seq.:> x) zipZag :: Seq.Seq a -> Seq.Seq b -> Seq.Seq (a, b) zipZag (x :< xs) (ys :> y) = (x, y) Seq.<| zipZag xs ys zipZag _ _ = Seq.empty }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5144#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7978: Profiling broken
by GHC 13 Aug '13

13 Aug '13

#7978: Profiling broken --------------------------------------------+------------------------------ Reporter: gmainland | Owner: Type: bug | Status: closed Priority: highest | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC doesn't work at all | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Changes (by simonmar): * status: new => closed * resolution: => fixed Comment: Fixed, thanks to everyone who helped narrow this down, it took me 2 minutes to find and fix the problem. a27895b359db20197d9ec72b03c4e304a20585d8 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7978#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5902: Cannot tell from an exception handler whether the exception was asynchronous
by GHC 13 Aug '13

13 Aug '13

#5902: Cannot tell from an exception handler whether the exception was asynchronous -------------------------------------+------------------------------------ Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by simonmar): @exbb2: we already have `SomeAsyncException`, and the asynchronous exceptions are children of this in the exception hierarchy. The exception hierarchy needs a single root, so `SomeException` remains. > Every innocuous catch or try anywhere at any time in any library can make a thread unintentionally uncancelable I'm not sure what you mean here. The issue in this ticket only arises when using `unsafePerformIO`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5902#comment:19> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5539: GHC panic - Simplifier ticks exhausted
by GHC 13 Aug '13

13 Aug '13

#5539: GHC panic - Simplifier ticks exhausted ---------------------------------------+---------------------------------- Reporter: hvr | Owner: simonpj Type: bug | Status: new Priority: high | Milestone: 7.6.2 Component: Compiler | Version: 7.3 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Compile-time crash | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: ---------------------------------------+---------------------------------- Changes (by ekmett): * cc: ekmett@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5539#comment:50> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5059: Pragma to SPECIALISE on value arguments
by GHC 13 Aug '13

13 Aug '13

#5059: Pragma to SPECIALISE on value arguments -------------------------------------+------------------------------------ Reporter: batterseapower | Owner: Type: feature request | Status: new Priority: low | Milestone: 7.6.2 Component: Compiler | Version: 7.0.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by ekmett): * cc: ekmett@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5059#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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