October 2015 - ghc-tickets

[GHC] #8228: GHC built under Windows does not generate dyn_hi files
by GHC 04 Feb '18

04 Feb '18

#8228: GHC built under Windows does not generate dyn_hi files ------------------------------+-------------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Keywords: | Operating System: Windows Architecture: | Type of failure: GHC doesn't work at all Unknown/Multiple | Test Case: cabal01 Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- I found cabal01 failing with: {{{ =====> cabal01(normal) 1 of 1 [0, 0, 0] cd . && $MAKE -s --no-print-directory cabal01 VANILLA=--enable-library- vanilla PROF=--disable-l ibrary-profiling DYN=--enable-shared </dev/null >cabal01.run.stdout 2>cabal01.run.stderr Wrong exit code (expected 0 , actual 2 ) Stdout: Stderr: Creating library file: dist\build\libHStest-1.0-ghc7.7.20130904.dll.a setup.exe: Error: Could not find module: A with any suffix: ["dyn_hi"] in the search path: ["dist\\build"] make[2]: *** [cabal01] Error 1 }}} but I bet some of the other failures are due to this. Indeed, in dist/build, there are no dyn_hi files When I look more closely at the commands being run, I see: {{{ bash.exe-3.1$ c:/Users/ezyang/Dev/ghc-validate/inplace/bin/ghc-stage2.exe --make -fbuilding-ca bal-package -O -static -dynamic-too -dynosuf dyn_o -dynhisuf dyn_hi -outputdir dist/build -odi r dist/build -hidir dist/build -stubdir dist/build -i -idist/build -i. -idist/build/autogen -I dist/build/autogen -Idist/build -optP-include -optPdist/build/autogen/cabal_macros.h -package- name test-1.0 -hide-all- packages -no-user-package-db -package-db local.db -package-db dist/pac kage.conf.inplace -package-id base-4.7.0.0-inplace -XHaskell98 -XForeignFunctionInterface A B. A -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db [1 of 2] Compiling B.A ( B\A.hs, dist\build\B\A.o ) [2 of 2] Compiling A ( A.hs, dist\build\A.o ) }}} which should result in dyn_hi files but does not. I haven't traced it any further yet. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8228> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10855: GHC rejects code that Haskell 2010 report accepts
by GHC 01 Feb '18

01 Feb '18

#10855: GHC rejects code that Haskell 2010 report accepts -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 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: Differential Revisions: | -------------------------------------+------------------------------------- According to [https://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-220003 The Haskell 2010 Report], the following two modules should compile. But they don't, failing with parse errors: {{{ {-# LANGUAGE Haskell2010 #-} module Bug where bool = - case b of False -> 0; True -> (-1) }}} {{{ {-# LANGUAGE Haskell2010 #-} instance Num (IO a) where negate = id main = - do putStrLn "hi!" }}} Note the unary `-` signs. I'm not sure whether we should complicate the parser to fix these, but we should document the compliance-failure in the manual. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10855> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10074: Implement the 'Improved LLVM Backend' proposal
by GHC 01 Feb '18

01 Feb '18

#10074: Implement the 'Improved LLVM Backend' proposal -------------------------------------+------------------------------------- Reporter: | Owner: thoughtpolice thoughtpolice | Status: new Type: task | Milestone: 7.12.1 Priority: high | Version: Component: Compiler | Operating System: Unknown/Multiple (LLVM) | Type of failure: None/Unknown Keywords: llvm, | Blocked By: codegen | Related Tickets: Architecture: | Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: Phab:D530 | -------------------------------------+------------------------------------- This is a meta ticket designed to reflect the current implementation status of the 'Improved LLVM Backend' proposal, documented here: https://ghc.haskell.org/trac/ghc/wiki/ImprovedLLVMBackend -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10074> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10754: truncate /= double2Int
by GHC 28 Jan '18

28 Jan '18

#10754: truncate /= double2Int -------------------------------------+------------------------------------- Reporter: cblp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.10.2 libraries/base | Keywords: truncate, | Operating System: Unknown/Multiple double2Int, rewrite, rule | Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- There is a rule in libraries/base/GHC/Float.hs: {{{#!hs "truncate/Double->Int" truncate = double2Int }}} But it is not true for some values. Particularly, {{{#!hs let infinity = 1/0 :: Double truncate infinity :: Int == 0 double2Int infinity == -9223372036854775808 -- minBound }}} As a result, the value of {{{truncate (1/0 :: Double) :: Int}}} depends on optimization level. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10754> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9885: ghc-pkg parser eats too much memory
by GHC 22 Jan '18

22 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] #10972: Add a :binfo (beginner info) GHCi command
by GHC 16 Jan '18

16 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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