September 2014 - ghc-tickets

[GHC] #8974: 64 bit windows executable built with ghc-7.9.20140405+LLVM segfaults
by GHC 30 Nov '16

30 Nov '16

#8974: 64 bit windows executable built with ghc-7.9.20140405+LLVM segfaults -----------------------------------+---------------------------------- Reporter: awson | Owner: Type: bug | Status: new Priority: high | Milestone: 7.8.2 Component: Compiler (LLVM) | Version: 7.9 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -----------------------------------+---------------------------------- {{{ -- test.hs import System.Mem (performMajorGC) main = performMajorGC >> putStrLn "Done" }}} built with `ghc -pgmlo opt -pgmlc llc -fllvm --make test.hs` segfaults both for LLVM 3.4 and 3.5svn (taken from http://sourceforge.net/projects/msys2/files/REPOS/MINGW/x86_64) 32-bit ghc-7.9.20140404+llvm produces good executable. Adding `ArchX86_64` `OSMinGW32` case to `moduleLayout` in `compiler/llvmGen/LlvmCodeGen/Ppr.hs` improves things slightly (some code segfaulting without it starts to work) but still does not cure the code above. Also I've found the Cmm produced for LLVM CG differs from that produced for NCG. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8974> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9007: relocation R_X86_64_32 against `stg_CHARLIKE_closure' can not be used when making a shared object
by GHC 29 Nov '16

29 Nov '16

#9007: relocation R_X86_64_32 against `stg_CHARLIKE_closure' can not be used when making a shared object ----------------------------------+---------------------------------------- Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Building GHC failed Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ----------------------------------+---------------------------------------- Building HEAD on Debian wheezy with the Debian packaging setup fails: {{{ configure: Building in-tree ghc-pwd /usr/bin/ld: utils/ghc-pwd/dist-boot/Main.o: relocation R_X86_64_32 against `stg_CHARLIKE_closure' can not be used when making a shared object; recompile with -fPIC utils/ghc-pwd/dist-boot/Main.o: could not read symbols: Bad value collect2: error: ld returned 1 exit status configure: error: Building ghc-pwd failed }}} http://deb.haskell.org/dailies/2014-04-16/ghc_7.9.20140416-0.daily_amd64.bu… This is possibly related to the Hardening flags added by Debian: {{{ ~ $ dpkg-buildflags --get LDFLAGS -Wl,-z,relro ~ $ dpkg-buildflags --get CFLAGS -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror =format-security }}} Other related bug might be #3668 and https://bugs.debian.org/712228 I’ll disable the hardening flags and see if it helps. The error first occurred 2014-03-27. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9007> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8300: split-objs doesn't split on LLVM
by GHC 22 Nov '16

22 Nov '16

#8300: split-objs doesn't split on LLVM ------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- `-split-objs` is allowed with `-fllvm`, but it doesn't really do anything. E.g. in my perf-llvm build I have a `libHSbase-4.7.0.0.a` with `Applicative__1.o`, `Arrow__1.o` etc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8300> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8321: improve basic block layout on LLVM backend by predicting stack/heap checks
by GHC 17 Nov '16

17 Nov '16

#8321: improve basic block layout on LLVM backend by predicting stack/heap checks ------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler (LLVM) | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Currently we don't give the LLVM optimizer any information about which branch of an `if` is likely to be taken. As a result, the optimizer is likely to produce a basic block layout which is not optimal. Improving the layout can improve performance through better instruction cache usage and better branch prediction by the hardware. We can control LLVM's idea of what is likely with the `llvm.expect` intrinsic function. Some obvious branches which we can predict accurately are the stack and heap checks that appear near the entry of many functions. Here's a small example of some Cmm code and the output of the LLVM optimizer/compiler. {{{ block_c2Lc_entry() // [R1, R2] { info_tbl: [(c2Lc, label: block_c2Lc_info rep:StackRep [])] stack_info: arg_space: 0 updfr_space: Nothing } {offset c2Lc: Hp = Hp + 24; if (Hp > HpLim) goto c2Lm; else goto c2Ll; c2Lm: HpAlloc = 24; R2 = R2; R1 = R1; call stg_gc_pp(R2, R1) args: 8, res: 8, upd: 24; c2Ll: I64[Hp - 16] = :_con_info; P64[Hp - 8] = R1; P64[Hp] = R2; R1 = Hp - 14; Sp = Sp + 8; call (P64[Sp])(R1) args: 24, res: 0, upd: 24; } }] }}} {{{ 00000000000002b8 <c2Lc_info>: 2b8: 4c 89 e0 mov %r12,%rax 2bb: 4c 8d 60 18 lea 0x18(%rax),%r12 2bf: 4d 3b a5 18 01 00 00 cmp 0x118(%r13),%r12 2c6: 76 10 jbe 2d8 <c2Lc_info+0x20> 2c8: 49 c7 85 48 01 00 00 movq $0x18,0x148(%r13) 2cf: 18 00 00 00 2d3: e9 00 00 00 00 jmpq 2d8 <c2Lc_info+0x20> 2d4: R_X86_64_PC32 stg_gc_pp+0xfffffffffffffffc 2d8: 48 c7 40 08 00 00 00 movq $0x0,0x8(%rax) 2df: 00 2dc: R_X86_64_32S ghczmprim_GHCziTypes_ZC_con_info 2e0: 48 89 58 10 mov %rbx,0x10(%rax) 2e4: 4c 89 70 18 mov %r14,0x18(%rax) 2e8: 48 8b 45 08 mov 0x8(%rbp),%rax 2ec: 48 83 c5 08 add $0x8,%rbp 2f0: 49 8d 5c 24 f2 lea -0xe(%r12),%rbx 2f5: ff e0 jmpq *%rax 2f7: 90 nop }}} It would likely be better to invert the branch at `2c6` to a `ja`, so that the common case is adjacent to the function entry, and when `llvm.expect` is used on the condition in the branch, the LLVM optimizer does produce this alternate layout. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8321> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9010: TemplateHaskell leads to an "unknown symbol" error
by GHC 04 Nov '16

04 Nov '16

#9010: TemplateHaskell leads to an "unknown symbol" error ------------------------------------+------------------------------------- Reporter: Feuerbach | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | 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: | ------------------------------------+------------------------------------- Code: {{{ {-# LANGUAGE TemplateHaskell #-} module M where import System.Console.Editline import Data.Lens.Template data S = S { _a :: EditLine } makeLens ''S }}} When compiled with `ghc link.hs`, everything is fine; {{{ [1 of 1] Compiling M ( link.hs, link.o ) Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package array-0.4.0.1 ... linking ... done. Loading package deepseq-1.3.0.1 ... linking ... done. Loading package containers-0.5.0.0 ... linking ... done. Loading package bytestring-0.10.0.2 ... linking ... done. Loading package tagged-0.7.1 ... linking ... done. Loading package transformers-0.3.0.0 ... linking ... done. Loading package transformers-compat-0.1.1.1 ... linking ... done. Loading package contravariant-0.4.4 ... linking ... done. Loading package distributive-0.4.3.1 ... linking ... done. Loading package mtl-2.1.3.1 ... linking ... done. Loading package text-1.1.0.1 ... linking ... done. Loading package hashable-1.2.1.0 ... linking ... done. Loading package nats-0.1.2 ... linking ... done. Loading package unordered-containers-0.2.3.3 ... linking ... done. Loading package semigroups-0.12.2 ... linking ... done. Loading package comonad-4.0.1 ... linking ... done. Loading package semigroupoids-4.0.1 ... linking ... done. Loading package data-lens-2.10.4 ... linking ... done. Loading package pretty-1.1.1.0 ... linking ... done. Loading package template-haskell ... linking ... done. Loading package data-lens-template-2.1.8 ... linking ... done. }}} However, when compiling with `ghc -package-id editline-0.2.1.1-ef91ae78e7ea1b9142c2fb0b84e85c11 link.hs`, I get {{{ [1 of 1] Compiling M ( link.hs, link.o ) Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package editline-0.2.1.1 ... linking ... ghc: /home/feuerbach/work /.cabal-sandbox/lib/i386-linux- ghc-7.6.3/editline-0.2.1.1/HSeditline-0.2.1.1.o: unknown symbol `el_reset' ghc: unable to load package `editline-0.2.1.1' }}} This is a problem because that's how cabal invokes ghc. This looks similar to #4899, except there's nothing "non-standard" here (no profiling or dynamic linking). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9010> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9494: Probable data corruption with GHCi 7.8.* and Zlib
by GHC 15 Oct '16

15 Oct '16

#9494: Probable data corruption with GHCi 7.8.* and Zlib -------------------------------------+------------------------------------- Reporter: nominolo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Incorrect Blocked By: | result at runtime Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The following program causes Zlib data corruption errors when run from inside GHCi. It launches two threads which then concurrently read a file, compress it, and immediately decompress it. You need libraries `zlib`, `SHA`, and `async`. {{{ module Main where import qualified Codec.Compression.Zlib as Zlib import qualified Data.ByteString.Lazy as BL import qualified Data.ByteString.Internal as BI import Control.Exception (bracket) import Control.Concurrent import Control.Monad import Control.Exception ( evaluate) import Data.Digest.Pure.SHA ( sha1) -- from the 'SHA' package import Control.Concurrent.Async ( mapConcurrently) import System.Mem ( performGC ) import Debug.Trace test :: Int -> IO String test _ = do tid <- myThreadId -- testdata is: dd if=/dev/urandom of=/tmp/testdata bs=100k count=100 -- Could also be replaced by: (BL.take (10^7) "/dev/urandom") dat <- BL.readFile "/tmp/testdata" let cbuf = Zlib.compress $ traceChunks tid $ dat s <- evaluate $ sha1 $ Zlib.decompress $ cbuf return $ show s where -- We used this to check whether buffers were reused by different threads, but that -- doesn't seem to be the case. Removing the call to traceChunks, however, makes it -- harder to reproduce possibly because of scheduler effects. In a much larger program -- it could be reproduced more easily without the trace, but in this small example -- tracing seems to cause the right amount of nondeterminism. traceChunks tid bs = BL.fromChunks $ zipWith (\n x -> trace (show tid ++ ":" ++ showBS x) x) [1..] $ BL.toChunks bs showBS (BI.PS ptr off len) = show ptr main = do r <- withGCThread $ mapConcurrently (test) ([1..2] :: [Int]) putStrLn $ show $ r where -- Regularly forcing the GC makes the test-case more reproducible. withGCThread io = bracket (forkIO $ forever $ performGC >> threadDelay 1000) killThread (const io) }}} The output should be something like: {{{ ... ThreadId 51:0x00000001091ee010 ThreadId 49:0x00000001091a7010 ... ThreadId 49:0x000000010986f010 zlib-test-case.hs: user error (Codec.Compression.Zlib: incorrect data check) }}} You'll get different Zlib errors, depending on where it detects the inconsistency. Sometimes Zlib doesn't throw an error, but the checksums are different. So far we've only been able to reproduce this using GHCi 7.8.3 on both Linux (NixOS) and Mac. We haven't been able to trigger it with a compiled executable, nor with GHCi 7.6.3. It '''was''' reproducable with HEAD from Jan 30 (I had that lying around somewhere). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9494> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9547: Empty constraint tuples are mis-kinded
by GHC 06 Oct '16

06 Oct '16

#9547: Empty constraint tuples are mis-kinded -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Consider {{{ -- If :: forall k. 'Bool -> k -> k -> k type family If cond tru fls where If True tru fls = tru If False tru fls = fls foo :: If True () (Eq a) => a -> a foo = error "urk" }}} This should work fine. But we get {{{ Foo.hs:8:21: The third argument of `If' should have kind `*', but `Eq a' has kind `Constraint' In the type signature for `foo': foo :: If True () (Eq a) => a -> a }}} Reason: GHC is treating the `()` unit tuple as of kind `*`. Reason is that in the `HsTupleTy` case of `tc_hs_type` in `TcHsType`, we see {{{ -- In the [] case, it's not clear what the kind is, so guess * }}} And that guess is plain wrong in this case. Unfortunately I don't see an easy fix, but it's plain wrong as-is. Simon -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9547> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8870: GHC 7.8.0 RC2 fails when compiling a hello world program on Windows 7 32bits
by GHC 01 Oct '16

01 Oct '16

#8870: GHC 7.8.0 RC2 fails when compiling a hello world program on Windows 7 32bits ----------------------------+--------------------------------------- Reporter: facundoq | Owner: Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 7.8.1-rc2 Keywords: | Operating System: Windows Architecture: x86 | Type of failure: Compile-time crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ----------------------------+--------------------------------------- Windows shows a window that says "GHC has stopped working" when compiling a simple hello world. Steps to reproduce 1) Download GHC 7.8 RC2 (http://www.haskell.org/ghc/dist/7.8.1-rc2/ghc-7.8.0.20140228-i386 -unknown-mingw32.tar.bz2) 2) Extract the contents of the tar to folder $GHC$ 3) Add $GHC$\bin and $GHC$\mingw\bin folder to the PATH, add env var "LANG=C". 4) Create file test.hs with contents: main = putStrLn "Hello, World!" 5) run "ghc test.hs". Interestingly, the error is not deterministic, ie, after running the command several times the program gets compiled. When that happens, and ff the file test.o is not deleted, further attempts to compile run succesfully. GHCi appears to work normally (when doing simple tests). More details: http://stackoverflow.com/questions/22291739/cant-install-packages-with- cabal-using-ghc-7-8rc2-and-windows-7 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8870> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9520: Running an action twice uses much more memory than running it once
by GHC 29 Sep '16

29 Sep '16

#9520: Running an action twice uses much more memory than running it once -------------------------------------+------------------------------------- Reporter: snoyberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: Runtime Difficulty: Unknown | performance bug Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- This started as a [http://www.haskell.org/pipermail/haskell- cafe/2014-August/115751.html Haskell cafe discussion] about conduit. This may be related to #7206, but I can't be certain. It's possible that GHC is not doing anything wrong here, but I can't see a way that the code in question is misbehaving to trigger this memory usage. Consider the following code, which depends on conduit-1.1.7 and conduit- extra: {{{#!hs import Data.Conduit ( Sink, (=$), ($$), await ) import qualified Data.Conduit.Binary as CB import System.IO (withBinaryFile, IOMode (ReadMode)) main :: IO () main = do action "random.gz" --action "random.gz" action :: FilePath -> IO () action filePath = withBinaryFile filePath ReadMode $ \h -> do _ <- CB.sourceHandle h $$ CB.lines =$ sink2 1 return () sink2 :: (Monad m) => Int -> Sink a m Int sink2 state = do maybeToken <- await case maybeToken of Nothing -> return state Just _ -> sink2 $! state + 1 }}} The code should open up the file "random.gz" (I simply `gzip`ed about 10MB of data from /dev/urandom), break it into chunks at each newline character, and then count the number of lines. When I run it as-is, it uses 53KB of memory, which seems reasonable. However, if I uncomment the second call to `action` in `main`, maximum residency shoots up to 45MB (this seems to be linear in the size of the input file. I additionally tried copying `random.gz` into two files, `random1.gz` and `random2.gz`, and changed the two calls to `action` to use different file names. It still resulted in large memory usage. I'm going to continue working to make this a smaller reproducing test case, but I wanted to start with what I had so far. I'll also attach the core generated by both the low-memory and high-memory versions. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9520> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9349: excessive inlining with -fpre-inlining
by GHC 29 Sep '16

29 Sep '16

#9349: excessive inlining with -fpre-inlining --------------------------------------------+------------------------------ Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Differential: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime performance bug | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ The program at https://gist.github.com/jorendorff/a3005968adc8f054baf7 runs very slowly when compiled with `-O` or higher. It seems that `arr` and/or `rangeMap` is being inlined into the do block on lines 89-91 and recomputed for each iteration of the loop. The program runs nearly instantly when compiled with `-O0` or with `-O -fno-pre-inlining`. (Of course, this does not mean `-fpre-inlining` is necessary the culprit; it could be enabling some subsequent misoptimization.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9349> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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