July 2016 - ghc-tickets

[GHC] #9885: ghc-pkg parser eats too much memory
by GHC 21 Jan '18

21 Jan '18

#9885: ghc-pkg parser eats too much memory -------------------------------------+------------------------------------- Reporter: gnezdo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: ghc-pkg | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Runtime Difficulty: Moderate (less | performance bug than a day) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Parsing of spec files in ghc-pkg scales very poorly. The following script demonstrates memory consumption growth as a function of the number of tokens in ld-options (16K leads to ~6G) #!/bin/bash # Demonstrates memory consumption behavior of ghc-pkg as a function of # the number of ld-options arguments. for i in {10..14}; do size=$((1 << $i)) echo $size rm -fr a.packages /usr/bin/ghc-pkg init a.packages cat > a.spec <<EOF name: project id: project license: AllRightsReserved version: 1.0 EOF echo -n ld-options: >> a.spec for i in $(seq 1 $size); do echo -n "x "; done >> a.spec /usr/bin/time /usr/bin/ghc-pkg --global-package-db a.packages register --force a.spec done exit 0 # This was collected with ghc-7.6.3. 7.8.3 fares as badly. % bash a.sh 1024 Reading package info from "a.spec" ... done. 0.03user 0.00system 0:00.03elapsed 97%CPU (0avgtext+0avgdata 17848maxresident)k 0inputs+32outputs (0major+4973minor)pagefaults 0swaps 2048 Reading package info from "a.spec" ... done. 0.09user 0.01system 0:00.10elapsed 99%CPU (0avgtext+0avgdata 60872maxresident)k 0inputs+56outputs (0major+15723minor)pagefaults 0swaps 4096 Reading package info from "a.spec" ... done. 0.41user 0.07system 0:00.49elapsed 99%CPU (0avgtext+0avgdata 294340maxresident)k 0inputs+104outputs (0major+74090minor)pagefaults 0swaps 8192 Reading package info from "a.spec" ... done. 1.72user 0.30system 0:02.04elapsed 99%CPU (0avgtext+0avgdata 1168836maxresident)k 0inputs+192outputs (0major+292716minor)pagefaults 0swaps 16384 Reading package info from "a.spec" ... done. 9.11user 1.38system 0:10.51elapsed 99%CPU (0avgtext+0avgdata 5396932maxresident)k 0inputs+376outputs (0major+1349736minor)pagefaults 0swaps -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9885> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11645: Heap profiling - hp2ps: samples out of sequence
by GHC 21 Jan '18

21 Jan '18

#11645: Heap profiling - hp2ps: samples out of sequence -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Profiling | Version: 8.0.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #664 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `make TEST=hpc_fork WAY=prof` is failing, but it has nothing to do with `hpc`. {{{ hp2ps: hpc_fork.hp, line 9, samples out of sequence hp2ps error when processing heap profile for hpc_fork }}} hpc_fork.hs: {{{ module main where import system.posix.process import control.concurrent main = do pid1 <- forkprocess $ do threaddelay 100000 pid2 <- forkprocess $ do threaddelay 100000 print () }}} To reproduce: {{{ $ ghc-8.0.1 hpc_fork.hs -fforce-recomp -prof $ ./hpc_fork +RTS -hc $ hp2ps hpc_fork.hp }}} Example hpc_fork.hp: {{{ JOB "hpc_fork +RTS -hc" DATE "Thu Feb 25 22:37 2016" SAMPLE_UNIT "seconds" VALUE_UNIT "bytes" BEGIN_SAMPLE 0.000000 END_SAMPLE 0.000000 BEGIN_SAMPLE 0.005672 END_SAMPLE 0.005672 BEGIN_SAMPLE 0.003167 END_SAMPLE 0.003167 BEGIN_SAMPLE 0.003311 END_SAMPLE 0.003311 }}} This is a regression from 7.10.3. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11645> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11359: Consider removing RelaxedLayout and friends
by GHC 21 Jan '18

21 Jan '18

#11359: Consider removing RelaxedLayout and friends -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.10.3 (Parser) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- These three parsing-related language extensions were [[https://ghc.haskell.org/trac/ghc/wiki/LanguagePragmaHistory|introduced]] some time ago yet are likely not used in the wild as they still are not registered in Cabal's language extension list (which Hackage uploads are checked against, see #8176), * `RelaxedLayout` (introduced in 7.2, prompted by #1060) * `AlternativeLayoutRule` (introduced in 7.0, reason unknown) * `AlternativeLayoutRuleTransitional` (introduced in 7.0, reason unknown) As far as [[https://mail.haskell.org/pipermail/ghc- devs/2013-September/002267.html|I can]] [[https://ghc.haskell.org/trac/ghc/ticket/8176#comment:10|tell]] no one knows the status of these, nor are they listed in the users guide. We should ask the community whether they would mind seeing these extensions vanish and remove them if not. If so then we should see to it that they are registered properly with Cabal so they can be used on Hackage. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11359> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11091: Fix MonadFail warnings
by GHC 21 Jan '18

21 Jan '18

#11091: Fix MonadFail warnings -------------------------------------+------------------------------------- Reporter: quchen | Owner: Type: task | Status: new Priority: low | Milestone: 8.2.1 Component: Compiler | Version: 7.11 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: -------------------------------------+------------------------------------- #10751 implements the MonadFail warning mechanism. Using `-fwarn-missing-monadfail-instance`, GHC's internal warnings created by the patch can be shown and fixed. A second pass with `-XMonadFailDesugaring` then provides a hard check on whether any issues remain, by switching on the new desugaring mechanism properly. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11091> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10972: Add a :binfo (beginner info) GHCi command
by GHC 15 Jan '18

15 Jan '18

#10972: Add a :binfo (beginner info) GHCi command -------------------------------------+------------------------------------- Reporter: kanetw | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #10963 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- From goldfire: > Add a new command to GHCi, :binfo (for "beginner info") (please suggest a better name) that is like :info but presents different information. It suppresses in-scope instances, but attempts to specialize a function's type and presents specializations, using heuristics. So when we say :binfo find, we'll see Foldable t => (a -> Bool) -> t a -> Maybe a but also (a -> Bool) -> [a] -> Maybe a. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10972> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9285: IO manager startup procedure somewhat odd
by GHC 15 Jan '18

15 Jan '18

#9285: IO manager startup procedure somewhat odd ------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: bug | Status: new Priority: low | 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: | ------------------------------------+------------------------------------- Currently the RTS startup procedure for the threaded runtime with a single capability looks something like this: '''1. Capability gets initialized''' {{{ hs_main real_main hs_init_ghc initScheduler initCapabilities }}} '''2. IO Manager is started''' {{{ hs_main real_main hs_init_ghc ioManagerStart }}} '''3. ensureIOManagerIsRunning''' The IO manager of course is mostly written in Haskell, so `ioManagerStart` does {{{ cap = rts_lock(); rts_evalIO(&cap,&base_GHCziConcziIO_ensureIOManagerIsRunning_closure,NULL); rts_unlock(cap); }}} '''4. Bound task is created and we start running Haskell code''' Since this is the first call to `rts_lock`, it creates a bound task to correspond to the current OS thread. '''5. Haskell code does a safe FFI call: create worker task 1''' The first safe FFI call that the IO manager makes (ignoring `labelThread`) is to `c_setIOManagerControlFd`. At this point, the bound task gets suspended and we create a worker task. '''6. Worker task 1 starts executing `GHC.Event.Manager.loop`''' The worker tasks gets suspended due to an explicit call to `yield` in `GHC.Event.Manager.step`, at which point the bound task continues execution. It continues and finishes (`ensureIOManagerRunning` completes). The worker task takes over. '''7. Worker task 1 does a safe FFI call to `I.poll`, create new worker task 2''' (This safe call is from `GHC.Event.Manager.step`) '''8. Worker task 2 executes `GHC.Event.TimerManager.loop`, and does safe FFI call to `I.poll`; create worker task 3''' This worker task will remain spare for now. '''9. Start executing the actual main function''' The IO manager calls `rts_unlock`, which verifies if there are any spare workers available; it finds that there are and doesn't start a new one. Then when we start `main` itself of course we go through this `rts_lock, rts_evalIO, rts_unlock` sequence ''again''. This is somewhat confusing, and makes tracing the startup of the code more difficult to interpret. It seems that this could be simpler: only a single `rts_lock` should be necessary, in which we first call `ensureIOManagerIsRunning` and then `main`, followed by a single `rts_unlock`. A similar simplification should be possible in `forkProcess`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9285> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10634: Type class with bijective type functions
by GHC 14 Jan '18

14 Jan '18

#10634: Type class with bijective type functions -------------------------------------+------------------------------------- Reporter: Lemming | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- See the attached module. {{{ $ cat TypeFunctionBijection.hs {-# LANGUAGE TypeFamilies #-} module TypeFunctionBijection where import Data.Int (Int8, Int16, Int32) type family Up a type instance Up Int8 = Int16 type instance Up Int16 = Int32 class (Up (Down a) ~ a) => Convert a where type Down a down :: a -> Down a instance Convert Int16 where type Down Int16 = Int8 down = fromIntegral instance Convert Int32 where type Down Int32 = Int16 down = fromIntegral x :: Int8 x = down 8 }}} {{{ $ ghci-7.8.4 -Wall TypeFunctionBijection.hs GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling TypeFunctionBijection ( TypeFunctionBijection.hs, interpreted ) Ok, modules loaded: TypeFunctionBijection. *TypeFunctionBijection> :q Leaving GHCi. }}} {{{ $ ghci-7.10.1 -Wall TypeFunctionBijection.hs GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling TypeFunctionBijection ( TypeFunctionBijection.hs, interpreted ) TypeFunctionBijection.hs:24:5: Couldn't match expected type ‘Int8’ with actual type ‘Down a0’ The type variable ‘a0’ is ambiguous In the expression: down 8 In an equation for ‘x’: x = down 8 Failed, modules loaded: none. Prelude> :q Leaving GHCi. }}} Up to GHC-7.8.4 I could make a type function like `Down` a bijection by adding equality constraints to the `Convert` class. In GHC-7.10.1 this fails. Is this a bug or a feature? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10634> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10245: panic in new integer switch logic with "out-of-range" literals
by GHC 07 Jan '18

07 Jan '18

#10245: panic in new integer switch logic with "out-of-range" literals -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.11 (CodeGen) | Operating System: Unknown/Multiple Keywords: | Type of failure: Compile-time Architecture: x86_64 | crash (amd64) | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Compiling this module {{{ module D (f) where f :: Int -> String f n = case n of 0x8000000000000000 -> "yes" _ -> "no" }}} crashes with the error {{{ [1 of 1] Compiling D ( /tmp/D.hs, /tmp/D.o ) ghc-stage1: panic! (the 'impossible' happened) (GHC version 7.11.20150403 for x86_64-unknown-linux): Map.findMin: empty map has no minimal element }}} The constant does not have to be exactly `0x8000000000000000`, everything I tested from there up to `0xffffffffffffffff` yields the same crash. Also occurs with `Word` and negative literals. The bug seems to be tied to the target's word size somehow, though: a 64-bit compiler does not panic on `Int32` and `0x80000000`, but a 32-bit compiler does. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10245> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10731: System.IO.openTempFile is not thread safe on Windows
by GHC 04 Jan '18

04 Jan '18

#10731: System.IO.openTempFile is not thread safe on Windows -------------------------------------+------------------------------------- Reporter: | Owner: NeilMitchell | Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.10.1 libraries/base | Keywords: | Operating System: Windows Architecture: | Type of failure: Runtime crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Given the test program: {{{#!hs import Control.Concurrent import System.IO import Control.Monad import System.Directory main = do putStrLn "Starting" var <- newEmptyMVar tdir <- getTemporaryDirectory xs <- replicateM 10 $ do var <- newEmptyMVar flip forkFinally (\s -> do print s; putMVar var ()) $ do replicateM_ 100000 $ do (file, h) <- openTempFile tdir "test.txt" hClose h removeFile file return var mapM_ takeMVar xs }}} If I compile and run that with {{{ghc --make TmpFile.hs -threaded && tmpfile +RTS -N5}}} I get: {{{ Starting Left C:\Users\NDMIT_~1\AppData\Local\Temp\: openTempFile: permission denied (Permission denied) Left C:\Users\NDMIT_~1\AppData\Local\Temp\: openTempFile: permission denied (Permission denied) ... }}} I've reproduced this on GHC 7.8 and 7.10.1. We hit this in production about twice a day. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10731> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12022: unsafeShiftL and unsafeShiftR are not marked as INLINE
by GHC 02 Jan '18

02 Jan '18

#12022: unsafeShiftL and unsafeShiftR are not marked as INLINE -------------------------------------+------------------------------------- Reporter: Rufflewind | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 7.10.3 libraries/base | Keywords: performance, | Operating System: Unknown/Multiple inline, bits | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Given that they are fairly essential operations in core libraries such as containers, I think it would be useful to have them marked as INLINE (or INLINABLE at the very least). See also: https://github.com/haskell/containers/pull/216 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12022> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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