March 2016 - ghc-tickets

[GHC] #11697: rts/posix/Itimer.c: ignoring return value of ‘read’
by GHC 11 Mar '16

11 Mar '16

#11697: rts/posix/Itimer.c: ignoring return value of ‘read’ -------------------------------------+------------------------------------- Reporter: erikd | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 8.1 System | 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: -------------------------------------+------------------------------------- Builds currently failing in travis. Eg : https://travis- ci.org/ghc/ghc/jobs/115023819 {{{ rts/posix/Itimer.c: In function ‘itimer_thread_func’: rts/posix/Itimer.c:205:17: error: error: ignoring return value of ‘read’, declared with attribute warn_unused_result [-Werror=unused-result] }}} The code being complained about is: {{{ if (USE_TIMERFD_FOR_ITIMER) { read(timerfd, &nticks, sizeof(nticks)); } else { }}} The value of `nticks` is never used, so a solution to this may be: {{{ if (USE_TIMERFD_FOR_ITIMER) { if (read(timerfd, &nticks, sizeof(nticks)) != sizeof(nticks)) nticks = 0; } else { }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11697> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10691: certain operations in new integer-gmp are too lazy
by GHC 11 Mar '16

11 Mar '16

#10691: certain operations in new integer-gmp are too lazy -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries | Version: 7.10.1 (other) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- This came up in #ghc the other day. {{{ rwbarton@morphism:~$ ghci-7.10.1 GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help Prelude> undefined * 0 0 }}} For consistency not just with Int, but also other integer-* implementations, this should be undefined. Also affected is for example `andInteger`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10691> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11678: runhaskell (and ghc, ghci) fail to run if HOME is not set
by GHC 11 Mar '16

11 Mar '16

#11678: runhaskell (and ghc, ghci) fail to run if HOME is not set -------------------------------------+------------------------------------- Reporter: crosser | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Steps to reproduce: {{{ $ env -i ghc HOME: getAppUserDataDirectory: does not exist (no environment variable) $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.3 }}} This may be not a big deal for the compiler and repl, but there are use cases to run `runhaskell` without HOME, e.g. I encountered this when running a cgi script under Apache. I think that the problem was introduced after 7.8. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11678> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11679: Quasi-quoting syntax is ambiguous with list comprehensions
by GHC 11 Mar '16

11 Mar '16

#11679: Quasi-quoting syntax is ambiguous with list comprehensions -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.3 (Parser) | 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: -------------------------------------+------------------------------------- There is an unfortunate ambiguity between list comprehension syntax and quasi-quotation. Consider the following with and without `-XQuasiQuotes` (noted [[https://github.com/haskell/haskell- mode/issues/1185#issuecomment-192624592|here]], {{{#!hs let x = [ v | v <- [1,2,3]] let x = [v| v <- [1,2,3]] }}} While the former is always a list comprehension, the latter is a quasi- quote when `-XQuasiQuotes` is enabled. The original quasi-quoting syntax required a dollar sign before the quoter, although this was dropped in 26f164e5759e9eca73deb0531ddec422d36a6924. 9ba922ee06b048774d7a82964867ff768a78126e suggests that the old dollar sign syntax is slated for eventual removal. Unfortunately, given it has been five years since the requirement for a dollar sign was dropped I suspect it's a bit late to revert to the previous syntax. This ticket is simply meant to document the fact that this ambiguity exists. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11679> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11696: Windows Install Makes Unnecessary/Incorrect PATH Changes
by GHC 11 Mar '16

11 Mar '16

#11696: Windows Install Makes Unnecessary/Incorrect PATH Changes -------------------------------------+------------------------------------- Reporter: AlexAndrews | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Package | Version: 7.10.3 system | Keywords: path | Operating System: Windows environment variable install | Architecture: x86 | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I installed haskell 7.10.3 (32-bit) under Windows XP SP3 into a folder on my L: drive. However, the installation process added a number of non- existent directories to my PATH variables: User environment variable PATH: C:\Documents and Settings\<username>\Application Data\cabal\bin System environment variable PATH: C:\Program Files\Haskell\bin If these directories need to be in the PATH variables, they should be created by the installer and, if so, since I installed haskell to my L: drive, surely these should be created on my L: drive (or the user should be prompted for their location)? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11696> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11354: Install script installs docs without -version suffix
by GHC 11 Mar '16

11 Mar '16

#11354: Install script installs docs without -version suffix -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.1 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: -------------------------------------+------------------------------------- This is potentially bad when multiple GHC versions are installed - last installed one overwrites all the docs. It seems like docs are installed under {{{$PACKAGE_TARNAME}}}, and tarname is initialized as {{{"ghc"}}} in the {{{ac}}} file. I guess one solution would be to add version suffix to tarname (it seems like tarname is only used when installing docs) or alternatively use {{{${PACKAGE_TARNAME}-${PACKAGE_VERSION}}}} to install docs. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11354> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1168: Optimisation sometimes decreases sharing in IO code
by GHC 10 Mar '16

10 Mar '16

#1168: Optimisation sometimes decreases sharing in IO code -------------------------------------+------------------------------------- Reporter: simonmar | Owner: Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.6 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime | Test Case: performance bug | nofib/spectral/calendar Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): See #11677 for another example -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1168#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11677: Dramatic de-optimization with "-O", "-O1", "-O2" options
by GHC 10 Mar '16

10 Mar '16

#11677: Dramatic de-optimization with "-O", "-O1", "-O2" options -------------------------------------+------------------------------------- Reporter: malphunction | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: optimization | Operating System: Linux deoptimization | Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Look for this simple program: {{{#!hs: import Control.Monad import Data.Maybe -- import qualified Data.HashMap.Strict as M -- import qualified Data.Map.Lazy as M import qualified Data.Map.Strict as M -- import Control.DeepSeq -- import Control.Exception main :: IO () main = do putStrLn "Start" n <- read <$> getLine q <- read <$> getLine dict' <- M.fromList <$> replicateM n ((\(k:v:_) -> (k,v)) <$> words <$> getLine) -- dict <- evaluate $ force dict' let dict = dict' count <- length <$> catMaybes <$> replicateM q (flip M.lookup dict <$> getLine) print count }}} When compiled __without__ "-O2" it runs about 0.07 sec on my computer. But when compiled __with__ "-O2" it runs about 77 sec (1100 times slowly!). Look: compile and run without "-O2": {{{ % rm -rf ./mime_type mime_type.{o,hi} && ghc mime_type.hs -o mime_type && cat my_data.txt | time ./mime_type [1 of 1] Compiling Main ( mime_type.hs, mime_type.o ) Linking mime_type ... Start 4738 ./mime_type 0,06s user 0,01s system 97% cpu 0,069 total }}} And with "-O2": {{{ % rm -rf ./mime_type mime_type.{o,hi} && ghc -O2 mime_type.hs -o mime_type && cat my_data.txt | time ./mime_type [1 of 1] Compiling Main ( mime_type.hs, mime_type.o ) Linking mime_type ... Start 4738 ./mime_type 76,73s user 0,10s system 99% cpu 1:17,12 total }}} But when force `dict` variable (`dict <- evaluate $ force dict'`), it runs fast in both cases (with and without "-O2"). Also this bug is reproductable with "-O", "-O1" options. Also this bug is reproductable with GHC 7.10.2 and GHC 8.0.1-rc2 (The Glorious Glasgow Haskell Compilation System, version 8.0.0.20160204). Data file my_data.txt is attached. It has simple structure: * N, number of key-value pairs * K, number of keys for searching * N key-value pairs * K kes You can generate it with this Ruby script: {{{ #!/usr/bin/env ruyb lst = ('a'..'z').to_a N = 10000 K = 10000 File.open('my_data.txt', 'w') do |f| f.puts(N) f.puts(K) N.times do f.puts("#{lst.sample(3).join} #{lst.sample(5).join}") # f.puts("(\"#{lst.sample(3).join}\",\"#{lst.sample(5).join}\")") end K.times do f.puts("#{lst.sample(3).join}") end end }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11677> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11693: Add `When` type family
by GHC 10 Mar '16

10 Mar '16

#11693: Add `When` type family -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Core | Version: 8.1 Libraries | 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: -------------------------------------+------------------------------------- Does a type family like `When` from [https://github.com/mikeizbicki/subhask/blob/master/src/SubHask/SubType.hs#L… here] belong somewhere in `Data.Types.*` {{{#!hs type family When (a :: Bool) (b :: Constraint) :: Constraint where When True b = b When False b = () }}} like [https://hackage.haskell.org/package/base/docs/Control- Monad.html#v:when when]. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11693> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1365: -fbyte-code is ignored in a OPTIONS_GHC pragma
by GHC 10 Mar '16

10 Mar '16

#1365: -fbyte-code is ignored in a OPTIONS_GHC pragma -------------------------------------+------------------------------------- Reporter: mnislaih | Owner: Type: feature request | Status: new Priority: lowest | Milestone: Component: GHCi | Version: 6.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * failure: => None/Unknown Comment: This came up on [[https://mail.haskell.org/pipermail/ghc- devs/2016-March/011566.html|ghc-devs]] recently in a thread discussing loading GHC itself into GHCi. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1365#comment:26> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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