January 2018 - ghc-tickets

[GHC] #14669: Executable finishing via unhandled exception results in segmentation fault on 32 bit Windows
by GHC 27 Jan '18

27 Jan '18

#14669: Executable finishing via unhandled exception results in segmentation fault on 32 bit Windows --------------------------------------+---------------------------------- Reporter: sergv | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 8.2.1 Keywords: | Operating System: Windows Architecture: x86 | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- It seems that 32 bit Windows GHC version 8.2.1 onwards (I can reproduce it with 8.2.1, 8.2.2 and 8.4.1-alpha, but not with 8.0.2) has some issues in Runtime System related to exception handling. The symptom is that executable exiting via unhandled exception ends with a segmentation fault and non-zero exit code. It would be okay-ish if not for the fact that this bug causes tools like `ghc-pkg` or `hsc2hs` to exit with non-zero exit code when asked for their `--version`. In turn, this breaks cabal-the- executable which interprets non-zero exit code of the `--version` call as a failure and refuses to `configure` further. Why do those executables segfault when invoked with `--version`? It's because they call `exitSuccess` after printing a version, which throws an `ExitSuccess` exception. Thus executables exit with unhandled exception and this bit seems to be faulty. Please see minimalistic example below: {{{ $ cat HW.hs import System.Exit main :: IO () main = do putStrLn "Situation normal" exitWith ExitSuccess $ ghc HW.hs [1 of 1] Compiling Main ( HW.hs, HW.o ) Linking HW.exe ... ./HW.exe Situation normal Segmentation fault $ echo $? 139 }}} If exception is caught then everything's ok. But then it's hard to signal non-zero exit code: {{{ $ cat HWCatch.hs {-# LANGUAGE ScopedTypeVariables #-} import Control.Exception import System.Exit main :: IO () main = do (res :: Either SomeException ()) <- try $ do putStrLn "Situation normal" exitWith ExitSuccess print res $ ghc HWCatch.hs [1 of 1] Compiling Main ( HWCatch.hs, HWCatch.o ) Linking HWCatch.exe ... $ ./HWCatch.exe Situation normal Left ExitSuccess $ echo $? 0 }}} System info: {{{ $ uname -a MINGW64_NT-6.1 box 2.9.0(0.318/5/3) 2017-09-13 23:16 x86_64 Msys $ ghc --version The Glorious Glasgow Haskell Compilation System, version 8.2.2 $ ghc --info [("Project name","The Glorious Glasgow Haskell Compilation System") ,("GCC extra via C opts"," -fwrapv -fno-builtin") ,("C compiler command","$topdir/../mingw/bin/gcc.exe") ,("C compiler flags"," -U__i686 -march=i686 -fno-stack-protector") ,("C compiler link flags"," ") ,("C compiler supports -no-pie","YES") ,("Haskell CPP command","$topdir/../mingw/bin/gcc.exe") ,("Haskell CPP flags","-E -undef -traditional") ,("ld command","$topdir/../mingw/bin/ld.exe") ,("ld flags","") ,("ld supports compact unwind","YES") ,("ld supports build-id","YES") ,("ld supports filelist","NO") ,("ld is GNU ld","YES") ,("ar command","$topdir/../mingw/bin/ar.exe") ,("ar flags","q") ,("ar supports at file","YES") ,("touch command","$topdir/bin/touchy.exe") ,("dllwrap command","$topdir/../mingw/bin/dllwrap.exe") ,("windres command","$topdir/../mingw/bin/windres.exe") ,("libtool command","") ,("perl command","$topdir/../perl/perl.exe") ,("cross compiling","NO") ,("target os","OSMinGW32") ,("target arch","ArchX86") ,("target word size","4") ,("target has GNU nonexec stack","False") ,("target has .ident directive","True") ,("target has subsections via symbols","False") ,("target has RTS linker","YES") ,("Unregisterised","NO") ,("LLVM llc command","llc") ,("LLVM opt command","opt") ,("Project version","8.2.2") ,("Project Git commit id","0156a3d815b784510a980621fdcb9c5b23826f1e") ,("Booter version","8.2.1") ,("Stage","2") ,("Build platform","i386-unknown-mingw32") ,("Host platform","i386-unknown-mingw32") ,("Target platform","i386-unknown-mingw32") ,("Have interpreter","YES") ,("Object splitting supported","YES") ,("Have native code generator","YES") ,("Support SMP","YES") ,("Tables next to code","YES") ,("RTS ways","l debug thr thr_debug thr_l thr_p ") ,("RTS expects libdw","NO") ,("Support dynamic-too","NO") ,("Support parallel --make","YES") ,("Support reexported-modules","YES") ,("Support thinning and renaming package flags","YES") ,("Support Backpack","YES") ,("Requires unified installed package IDs","YES") ,("Uses package keys","YES") ,("Uses unit IDs","YES") ,("Dynamic by default","NO") ,("GHC Dynamic","NO") ,("GHC Profiled","NO") ,("Leading underscore","YES") ,("Debug on","False") ,("LibDir","C:\\home\\ghc\\ghc-8.2.2-x32\\lib") ,("Global Package DB","C:\\home\\ghc\\ghc-8.2.2-x32\\lib\\package.conf.d") ] $ ghc-pkg --version # This is a sign of the problem GHC package manager version 8.2.2 Segmentation fault $ echo $? 139 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14669> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14644: Improve cmm/assembly for pattern matches with two constants.
by GHC 27 Jan '18

27 Jan '18

#14644: Improve cmm/assembly for pattern matches with two constants. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 (CodeGen) | Keywords: Codegen, CMM, | Operating System: Unknown/Multiple Patterns, Pattern Matching | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- For a pattern like: {{{ f_test :: Int#->Int# f_test a = case a of 1# -> 33# 7# -> 34# _ -> -1# }}} GHC currently generates code that works best if the default branch is taken most often. Pseudo-Code {{{ if (a >= 8) return -1; else { if (a < 7) { if(a != 1) return -1; else return 33; } else return 34; } }}} CMM: {{{ c1cr: // global if (%MO_S_Ge_W64(R2, 8)) goto c1co; else goto u1cu; u1cu: // global if (%MO_S_Lt_W64(R2, 7)) goto u1cv; else goto c1cq; u1cv: // global if (R2 != 1) goto c1co; else goto c1cp; c1co: // global R1 = (-1); call (P64[Sp])(R1) args: 8, res: 0, upd: 8; c1cp: // global R1 = 33; call (P64[Sp])(R1) args: 8, res: 0, upd: 8; c1cq: // global R1 = 34; call (P64[Sp])(R1) args: 8, res: 0, upd: 8; } }}} Wouldn't the following be better? {{{ if(a == 1) return 33 else if(a == 7) return 34 else return -1 }}} I would expect that to * Improve the cases: * a = 1 * a < 7 * Be the same for: * a = 7 * Be worse for * a > 8 This would be especially nice for the cases where the default branch is raising a pattern match exception. Which is a code path I wouldn't expect to be taken often nor be very performance sensitive. Even if we keep the current logic there is room for improvement. GHC currently creates the following assembly: {{{ _c1cr: cmpq $8,%r14 jge _c1co _u1cu: cmpq $7,%r14 jl _u1cv _c1cq: movl $34,%ebx jmp *(%rbp) _u1cv: cmpq $1,%r14 jne _c1co _c1cp: movl $33,%ebx jmp *(%rbp) _c1co: movq $-1,%rbx jmp *(%rbp) }}} It would be nice if we could remove one comparison at least. {{{ _c1cr: cmpq $7,%r14 jg _c1co _u1cu: ;No longer neccesary cmpq $7,%r14 jl _u1cv _c1cq: movl $34,%ebx jmp *(%rbp) _u1cv: cmpq $1,%r14 jne _c1co _c1cp: movl $33,%ebx jmp *(%rbp) _c1co: movq $-1,%rbx jmp *(%rbp) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14644> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14634: Add print stacktrace to exception handler in runtime system
by GHC 27 Jan '18

27 Jan '18

#14634: Add print stacktrace to exception handler in runtime system -------------------------------------+------------------------------------- Reporter: flip101 | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- {{{#!hs main :: IO () main = do someIO putStrLn "hello world" someIO :: IO () someIO = ioError $ IOError Nothing IllegalOperation "a" "b" Nothing Nothing }}} This code prints the following {{{ exception: a: illegal operation (b) }}} I think there is something in the runtime system which takes this exception and prints this text to the terminal. I will call this the "runtime exception handler" (for i don't know any better). {{{#!hs main :: IO () main = do ex <- try someIO :: IO (Either IOException ()) case ex of Left e -> error (show e) Right _ -> putStrLn "hello world" someIO :: IO () someIO = ioError $ IOError Nothing IllegalOperation "a" "b" Nothing Nothing }}} output: {{{ exception: a: illegal operation (b) CallStack (from HasCallStack): error, called at src/Main.hs:10:15 in main:Main }}} Now i use an explicit handler in my code and show the stacktrace with `error`. Could this handler be moved into the RTS so that i can stacktraces with exceptions just like with error? I think this issue is related to, but not the same as https://ghc.haskell.org/trac/ghc/ticket/12096 Because "Attach stacktrace information to SomeException" -- whatever there is being attached right now (with lts-10.2 ghc 8.2.2) is good enough to provide the information, it's just the print option in the handler that seems to be missing. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14634> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14694: Can't coerce given assumptions
by GHC 26 Jan '18

26 Jan '18

#14694: Can't coerce given assumptions -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- {{{ $ ghci -ignore-dot-ghci GHCi, version 8.5.20180105: http://www.haskell.org/ghc/ :? for help Prelude> newtype WF f a = WF (f a) Prelude> import Data.Coerce Prelude Data.Coerce> :set -XFlexibleContexts Prelude Data.Coerce> :t coerce :: Coercible (cat a b) (a -> f b) => cat a b -> (a -> WF f b) <interactive>:1:1: error: • Couldn't match representation of type ‘cat1 a1 b1’ with that of ‘a1 -> WF f1 b1’ arising from a use of ‘coerce’ • In the expression: coerce :: Coercible (cat a b) (a -> f b) => cat a b -> (a -> WF f b) }}} I'm not sure if I've filed this before or if it's even a bug. But we know that `Coercible (a -> f b) (a -> WF f b)` so why doesn't this work? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14694> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7414: plugins always trigger recompilation
by GHC 26 Jan '18

26 Jan '18

#7414: plugins always trigger recompilation -------------------------------------+------------------------------------- Reporter: jwlato | Owner: (none) Type: feature request | Status: new Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: plugin, | RecompilationCheck Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): > Is there anything blocking this ticket or does someone just need to implement it? There's nothing particularly blocking. The plan that I wrote about may or may not be the right way to go about this. It's also quite unclear what the right way forward would be if it turned out that implementation hashes are expensive to compute. Regardless, osa1 may be looking into this for Well-Typed client at some point in the next few months. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7414#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14526: GHC fails to configure on MacOS if Cuda is installed
by GHC 26 Jan '18

26 Jan '18

#14526: GHC fails to configure on MacOS if Cuda is installed -------------------------------------+------------------------------------- Reporter: nehal | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.0.2 Keywords: Cuda | Operating System: MacOS X Architecture: x86_64 | Type of failure: Building GHC (amd64) | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Hello, I had the following issue trying to build ghc (indirectly via stack) {{{ [error] Running /usr/bin/make install in directory /Users/nehal/.stack/programs/x86_64-osx/ghc-8.0.2.temp/ghc-8.0.2/ exited with ExitFailure 2 mk/config.mk:521: *** missing separator. Stop. @(Stack/Setup.hs:991:21) 2017-10-16 07:16:01.831719: [error] Error: Error encountered while installing GHC with make install run in /Users/nehal/.stack/programs/x86_64-osx/ghc-8.0.2.temp/ghc-8.0.2/ }}} Here is the line from `mk/config.mk:521`: {{{ 519 WhatGccIsCalled = /usr/bin/gcc 520 GccVersion = 9.0.0 521 8.0 522 ifeq "$(phase)" "0" ... }}} output from gcc: {{{ nehal$ gcc -v Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 9.0.0 (clang-900.0.37) Target: x86_64-apple-darwin16.7.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin Found CUDA installation: /usr/local/cuda, version 8.0 }}} It looks like the version detection is getting confused by the cuda installation (and so is thinking the version is something like `"9.0.0\n8.0"`) This could be something for further upstream (e.g. autotools mainainters), but I'm just rebooting my "try to grok Haskell" efforts, so I am going to take the lazy approach and report it here.... Thanks for ghc! (downstream bug report is here: https://github.com/commercialhaskell/stack/issues/1582#issuecomment-3469174… -- two others have hit this in the past month or so) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14526> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14726: Add AnnTypeAt to distinguish between '@' for type application
by GHC 26 Jan '18

26 Jan '18

#14726: Add AnnTypeAt to distinguish between '@' for type application -------------------------------------+------------------------------------- Reporter: alanz | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 (Parser) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect API Unknown/Multiple | annotation Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- At the moment all uses of '@' have the same annotation. It simplifies tools to provide a different one for the `@` in visible type application. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14726> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14712: After git pull make can't work with make clean
by GHC 26 Jan '18

26 Jan '18

#14712: After git pull make can't work with make clean -------------------------------------+------------------------------------- Reporter: jiamo | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Build System | Version: 8.5 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Building GHC (amd64) | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In the clean master repo: configure make can work. But after git pull. Just run make. It always failed. After make clean. it can success. But it will take long time as in the clean repo. (It is not bug I can find other type to desc) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14712> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13352: Strange requirement for re-exported duplicate record fields
by GHC 26 Jan '18

26 Jan '18

#13352: Strange requirement for re-exported duplicate record fields -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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: -------------------------------------+------------------------------------- In the following example, {{{ module A(A(..)) where data A = A {x::Int} module B(B(..)) where data B = B {x::Bool} {-# LANGUAGE DuplicateRecordFields #-} module C(A(..),B(..)) where import A(A(..)) import B(B(..)) }}} I get an error about `conflicting exports for 'x'`. This doesn't seem right to me: I've got `-XDuplicateRecordFields` exactly where the duplicate occurs. However, I noticed that the if I move the pragma to A.hs, C.hs compiles without error: {{{ {-# LANGUAGE DuplicateRecordFields #-} module A(A(..)) where data A = A {x::Int} module B(B(..)) where data B = B {x::Bool} module C(A(..),B(..)) where import A(A(..)) import B(B(..)) }}} This is bizarre because it is asymmetric (I arbitrarily put the pragma in A.hs, but it need not occur in B.hs), and because no duplicate records exist in module A, but they ''do'' exist in module C, where the pragma isn't needed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13352> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14721: internal error: stg_ap_v_ret
by GHC 25 Jan '18

25 Jan '18

#14721: internal error: stg_ap_v_ret --------------------------------------+--------------------------------- Reporter: jdm12 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- I got the following message when trying to inspect an unboxed vector: <interactive>: internal error: stg_ap_v_ret (GHC version 8.0.2 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Aborted (core dumped) ... so here I am, following instructions :) I'm running Kubuntu Zesty (4.13.0-25-generic) in a VirtualBox vm on a Win10 host. I don't know what other info will help, but I'll save the code as it stands and provide details on request. If the core dump will be useful, I'm happy to provide, but will need help finding it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14721> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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