April 2015 - ghc-tickets

[GHC] #10194: Shouldn't this require ImpredicativeTypes?
by GHC 18 Jun '15

18 Jun '15

#10194: Shouldn't this require ImpredicativeTypes? -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 (Type checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC accepts Architecture: | invalid program Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The following program compiles: {{{ {-# LANGUAGE RankNTypes #-} module TestRN1 where type X = forall a . a comp :: (X -> c) -> (a -> X) -> (a -> c) comp = (.) }}} But this one fails: {{{ {-# LANGUAGE RankNTypes #-} module TestRN2 where comp :: ((forall a . a) -> c) -> (a -> (forall a . a)) -> (a -> c) comp = (.) }}} Error: {{{ Cannot instantiate unification variable ‘b0’ with a type involving foralls: forall a1. a1 Perhaps you want ImpredicativeTypes In the expression: (.) In an equation for ‘comp’: comp = (.) }}} I would expect both to fail. Both seem to rely on impredicative types. I wouldn't expect expansion of a type synonym to make a difference between a type-checking program and one that does not typecheck. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10194> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10131: improve error message for build on noexec-mounted device
by GHC 17 Jun '15

17 Jun '15

#10131: improve error message for build on noexec-mounted device -------------------------------------+------------------------------------- Reporter: lspitzner | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.4 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: Other Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- i was building (in a sandbox) on a ramdisk that was accidentally mounted with the noexec flag. for example during the install of `vector`, you get an error like Loading package primitive-0.5.4.0 ... <command line>: can't load .so/.DLL for: somepath/.cabal-sandbox/lib/x86_64-linux- ghc-7.8.4/primitive-0.5.4.0/libHSprimitive-0.5.4.0-ghc7.8.4.so (somepath /.cabal-sandbox/lib/x86_64-linux- ghc-7.8.4/primitive-0.5.4.0/libHSprimitive-0.5.4.0-ghc7.8.4.so: failed to map segment from shared object) relevant output of `mount`: none on somepath type tmpfs (rw,nosuid,nodev,noexec,relatime,gid=103,user=lspitzner) this is by far no minimal test-case, but i hope my description of the problem is sufficient. if not, i can provide verbose output for my or other test-cases. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10131> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8785: Replace hooks API in the RTS with something better
by GHC 16 Jun '15

16 Jun '15

#8785: Replace hooks API in the RTS with something better ------------------------------------+------------------------------------- Reporter: simonmar | Owner: simonmar Type: task | Status: new Priority: high | Milestone: 7.10.1 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: | ------------------------------------+------------------------------------- Hooks rely on static linking behaviour which doesn't always work: we have to disable -Bsymbolic for the RTS on Linux (see `compiler/main/SysTools.lhs`) and it apparently doesn't work at all on Mac (#8754). So instead of hooks we should be passing in information when we initialize the RTS, like we already do for some other things (`-rtsopts` etc.). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8785> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9991: runghc shows the value produced by main when its type is a non-() Show instance
by GHC 14 Jun '15

14 Jun '15

#9991: runghc shows the value produced by main when its type is a non-() Show instance -------------------------------------+------------------------------------- Reporter: shachaf | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When running a program like this: {{{#!hs main :: IO Int main = return 5 }}} With `runghc`, it'll print a value, which is contrary to expected behavior and to compiled program behavior: {{{ $ runghc Main.hs 5 $ ghc Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Linking Main ... $ ./Main $ }}} This is the same as `ghci`'s behavior with an IO action, so presumably `runghc` is taking a shortcut here. But a program should behave the same way in both cases. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9991> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9769: ghc-7.8.3-x86_64-unknown-mingw32.tar.xz missing User's Guide
by GHC 14 Jun '15

14 Jun '15

#9769: ghc-7.8.3-x86_64-unknown-mingw32.tar.xz missing User's Guide -------------------------------------+------------------------------------- Reporter: Dangthrimble | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | Version: 7.8.3 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Difficulty: Unknown | Documentation bug Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Context: I am relatively new to Haskell and am trying to build a Haskell IDE around `Sublime Text`. I have been using `Haskell Platform` but have encountered a number of problems using `cabal`. Consequently I have been advised to uninstall `Haskell Platform` and download `ghc`. I have just downloaded and extracted `ghc-7.8.3-x86_64-unknown- mingw32.tar.xz`. Hoping for advice on setting up `ghc`, I have opened `ghc-7.8.3\doc\html\index.html` in Firefox and clicked on "The User's Guide". Unfortunately the `ghc-7.8.3/doc/html/users_guide` folder is missing. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9769> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8591: Concurrent executions of ghc-pkg can cause inconstant package.cache files
by GHC 14 Jun '15

14 Jun '15

#8591: Concurrent executions of ghc-pkg can cause inconstant package.cache files ------------------------------------+---------------------------- Reporter: janm | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Package system | Version: 7.6.3 Keywords: ghc-pkg race | Operating System: FreeBSD Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+---------------------------- I am doing 24 way parallel builds of system images, including all packages on a system. This includes ghc and multiple ghc packages. I am seeing intermittent dependency failure from the ghc packaging system. From examining Main.hs in ghc-pkg, I see the function withFileAtomic write to a temporary file in package.conf.d and then atomically rename on top of a target file, package.cache in the case. With parallel execution the last rename would win, leading to lost entries in package.cache. In my case, the following things happened: ("Building" indicates a start, "Built" indicates completion, "Installing" is setup in a separate chroot'd environment and is isolated) The FreeBSD ports system is used to drive the Haskell build system. The process works single threaded and fails intermittently when done in parallel. Building: devel/hs-data-default-instances-base Building: devel/hs-data-default-instances-containers Building: devel/hs-data-default-instances-old-locale Built: devel/hs-dlist Building: devel/hs-data-default-instances-dlist Built: devel/hs-temporary Built: jail-image-full Installing: system-image__jail-image-full Built: devel/hs-base64-bytestring Built: archivers/hs-zlib Building: security/hs-digest Built: devel/hs-syb Building: textproc/hs-hs-bibutils Building: textproc/hs-pandoc-types Built: devel/hs-utf8-string Built: devel/hs-data-default-instances-old-locale Built: devel/hs-data-default-instances-containers Built: devel/hs-data-default-instances-base Built: devel/hs-data-default-instances-dlist Building: devel/hs-data-default Built: devel/hs-random Installed: system-image__lang/ghc Installing: system-image__archivers/hs-zlib Installing: system-image__devel/hs-utf8-string Installing: system-image__devel/hs-syb Installing: system-image__devel/hs-base64-bytestring Installing: system-image__devel/hs-data-default-class Installing: system-image__devel/hs-dlist Installing: system-image__devel/hs-random Installing: system-image__devel/hs-temporary Installing: system-image__devel/hs-extensible-exceptions Built: devel/hs-data-default FAILED The error from the Haskell data-default build was: setup: At least the following dependencies are missing: data-default-instances-base -any Looking in the in the package.conf.d directory shows that the data- default-instances-base-0.0.1-7bdf8678f0d8637e096e397e7910f82a.conf file was present, but running "ghc-pkg list" did not show data-default- instances-base Running /usr/local/lib/cabal/ghc-7.6.3/data-default-instances- base-0.0.1/register.sh (which was also present) caused ghc-pkg to now show data-default-instances-base. To me this looks like a race condition between multiple instances of ghc- pkg causing the cache to become inconsistent. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8591> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9511: Remove deprecated -fglasgow-exts from NoFib suite
by GHC 14 Jun '15

14 Jun '15

#9511: Remove deprecated -fglasgow-exts from NoFib suite -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: task | Status: new Priority: low | Milestone: Component: NoFib benchmark | Version: 7.8.3 suite | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Someone on #ghc noted that replacing -fglasgow-exts with only the necessary options in each case may change compile times, which may be undesirable. I think a reasonable workaround would be to just put all the options on the command line, whether necessary or not. This will increase the time needed to parse the command lines, but presumably by a trivial amount. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9511> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10152: Testsuite diffs can be misleading when normalisers are in use
by GHC 12 Jun '15

12 Jun '15

#10152: Testsuite diffs can be misleading when normalisers are in use -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: task | Status: new Priority: low | Milestone: Component: Test Suite | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When output fails to match, GHC will output the diff based on the original outputs. However, this is misleading: some "differences" will actually have been normalised by the whitespace and more substantive normalisers we apply. So you really have to compare the normalised output to see what the /real/ difference is. Unfortunately, the real normalised output is missing newlines, so it's not really suitable for diffing. So it's not really clear what an improved algorithm would be. This seems to not actually be a problem in practice, since SOP for messages which need heavy normalizing is that when the new message looks good, it's just 'make accept'ed. Can be a little confusing when you're developing normalisers. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10152> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8435: Do not copy stack after stack overflow
by GHC 12 Jun '15

12 Jun '15

#8435: Do not copy stack after stack overflow ------------------------------+-------------------------------------------- Reporter: ezyang | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 7.7 System | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime performance bug Architecture: | Test Case: Unknown/Multiple | Blocking: Difficulty: Unknown | Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- I am not sure, but I was doing a close reading of `threadStackOverflow` and noticed that after we throw a stack overflow exception, we fall through to the code responsible for allocating a new stack and copying the code over. An old iteration of the stack overflow code (removed in the commit cited below) did return after throwing the exception, and I did not see anything in the commit message suggesting the change was intentional. It seems sound to copy the stack; it will just become dead immediately. The relevant commit: {{{ commit f30d527344db528618f64a25250a3be557d9f287 Author: Simon Marlow <marlowsd(a)gmail.com> Date: Wed Dec 15 12:08:43 2010 +0000 Implement stack chunks and separate TSO/STACK objects }}} Suggested (untested) patch: {{{ diff --git a/rts/Threads.c b/rts/Threads.c index 742119d..ccd6b17 100644 --- a/rts/Threads.c +++ b/rts/Threads.c @@ -533,6 +533,7 @@ threadStackOverflow (Capability *cap, StgTSO *tso) // Send this thread the StackOverflow exception throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure); + return; } }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8435> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10175: User's Guide 7.4.4 ExplicitTypeOperators typo
by GHC 12 Jun '15

12 Jun '15

#10175: User's Guide 7.4.4 ExplicitTypeOperators typo -------------------------------------+------------------------------------- Reporter: Shou | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.8.4 Documentation | Operating System: Unknown/Multiple Keywords: typo | Type of failure: None/Unknown extension | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- > There is now some potential ambiguity in import and export lists; for example if you write import M( (+) ) do you mean the function (+) or the type constructor (+)? The default is the former, but with -XExplicitNamespaces (which is implied by -XExplicitTypeOperators) GHC allows you to specify the latter by preceding it with the keyword type, thus: [...] GHC lists no extension `-XExplicitTypeOperators`, so it is assumed to be a mistake intended to be `-XTypeOperators`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10175> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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