May 2016 - ghc-tickets

[GHC] #12028: Large let bindings are 6x slower (since 6.12.x to 7.10.x)
by GHC 14 Jun '16

14 Jun '16

#12028: Large let bindings are 6x slower (since 6.12.x to 7.10.x) -------------------------------------+------------------------------------- Reporter: tommd | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- See the attached somewhat reduced version of the main (manually unrolled) portion of an MD5 implementation taken from PureMD5. It used to compile in about 200ms, which is already bad enough, but now takes 1200 ms (ghc 6.12.3 to ghc 7.10.3 using -O2). I'd like to note that in my light testing the UNPACK pragma accounts for 400ms of this delta. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12028> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12032: Performance regression with large numbers of equation-style decls
by GHC 14 Jun '16

14 Jun '16

#12032: Performance regression with large numbers of equation-style decls -------------------------------------+------------------------------------- Reporter: tommd | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- See the attached for a slice of code taken from Crypto-API that demonstrates a 2x regression in GHC compile times using -O2 (from 6.12.x to 7.10.x). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12032> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11700: pattern match bug
by GHC 13 Jun '16

13 Jun '16

#11700: pattern match bug -------------------------------------+------------------------------------- Reporter: TobyGoodwin | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: https://github.com/TobyGoodwin | /odd-ghc-pattern-bug | Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- With some types built by persistent-template, I'm running into very odd behaviour. Attempting to pull apart a tuple in one go... {{{#!hs let (Entity museKey muse, Entity msgKey msg, Entity fldrKey fldr) = cluster }}} fails (or rather, attempting to use msg or fldr fails) with errors like {{{ Couldn't match expected type ‘Folder’ with actual type ‘Folder’ }}} But splitting the pattern up: {{{#!hs let (a, b, c) = cluster Entity museKey muse = a Entity msgKey msg = b Entity fldrKey fldr = c }}} everything works normally Complete test case here: https://github.com/TobyGoodwin/odd-ghc-pattern- bug -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11700> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11788: Enable Thin Library support for the Runtime linker on Windows.
by GHC 13 Jun '16

13 Jun '16

#11788: Enable Thin Library support for the Runtime linker on Windows. -------------------------------------+------------------------------------- Reporter: Phyx- | Owner: Phyx- Type: feature | Status: new request | Priority: normal | Milestone: 8.2.1 Component: Runtime | Version: 7.10.3 System (Linker) | Keywords: | Operating System: Windows Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The runtime linker currently has an `#ifdef` that removes support for AR's thin archives for Windows. This because all the code is based on `char*` and Windows would require `wchar_t`. Using the abstraction of `pathchar` this can be enabled for Windows and remove another `#ifdef` from the RTS. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11788> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12069: Possible type inference regression: "Expected a type, but 'a' has kind 'k0'"
by GHC 13 Jun '16

13 Jun '16

#12069: Possible type inference regression: "Expected a type, but 'a' has kind 'k0'" -------------------------------------+------------------------------------- Reporter: akio | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | 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: -------------------------------------+------------------------------------- The following program causes GHC HEAD to give an error: {{{#!hs {-# LANGUAGE ScopedTypeVariables #-} module Foo where foo (_ :: p a) = [] :: [a] }}} {{{ [1 of 1] Compiling Foo ( kind.hs, kind.o ) kind.hs:4:25: error: • Expected a type, but ‘a’ has kind ‘k0’ • In an expression type signature: [a] In the expression: [] :: [a] In an equation for ‘foo’: foo (_ :: p a) = [] :: [a] }}} GHC 7.10.1 compiles it fine, and infers the type `foo :: p a -> [a]`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12069> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12033: [TypeApplications] GHC internal error
by GHC 13 Jun '16

13 Jun '16

#12033: [TypeApplications] GHC internal error -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple TypeApplications | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Toying around, got {{{ GHCi, version 8.1.20160503: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/CatFail.hs, interpreted ) /tmp/CatFail.hs:55:26: error: • GHC internal error: ‘a’ is not in scope during type checking, but it passed the renamer tcl_env of environment: [a1Ej :-> Type variable ‘i’ = i, a1Ek :-> Type variable ‘p’ = p, a1Et :-> Type variable ‘a’ = a, a1Eu :-> Type variable ‘b’ = b] • In the first argument of ‘Vacuous’, namely ‘a’ In the type ‘Vacuous a’ In the expression: Dict @(Vacuous a) /tmp/CatFail.hs:66:10: error: • Couldn't match type ‘Fun p q’ with ‘Vacuous’ arising from a use of ‘Main.$dmsrc’ • In the expression: Main.$dmsrc In an equation for ‘src’: src = Main.$dmsrc In the instance declaration for ‘Category (Nat p q)’ • Relevant bindings include src :: Nat p q a b -> Dict (Ob (Nat p q) a) (bound at /tmp/CatFail.hs:66:10) Failed, modules loaded: none. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12033> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11670: Can't infer type
by GHC 13 Jun '16

13 Jun '16

#11670: Can't infer type -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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 {-# LANGUAGE InstanceSigs, PartialTypeSignatures #-} import Foreign.C.Types import Foreign.Storable import Foreign.Ptr data CTimeval = MkCTimeval CLong CLong peek :: Ptr CTimeval -> IO CTimeval peek ptr = do s <- peekElemOff (castPtr ptr) 0 :: _ _ mus <- peekElemOff (castPtr ptr) 1 return (MkCTimeval s mus) }}} Fails with {{{ baldur@Loki:~$ ghci -ignore-dot-ghci /tmp/tLcV.hs GHCi, version 8.1.20160117: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( /tmp/tLcV.hs, interpreted ) /tmp/tLcV.hs:11:10: error: • No instance for (Storable t) Possible fix: add (Storable t) to the context of an expression type signature: IO t • In a stmt of a 'do' block: s <- peekElemOff (castPtr ptr) 0 :: _ _ In the expression: do { s <- peekElemOff (castPtr ptr) 0 :: _ _; mus <- peekElemOff (castPtr ptr) 1; return (MkCTimeval s mus) } In an equation for ‘peek’: peek ptr = do { s <- peekElemOff (castPtr ptr) 0 :: _ _; mus <- peekElemOff (castPtr ptr) 1; return (MkCTimeval s mus) } Failed, modules loaded: none. }}} while {{{#!hs {-# LANGUAGE InstanceSigs, PartialTypeSignatures #-} import Foreign.C.Types import Foreign.Storable import Foreign.Ptr data CTimeval = MkCTimeval CLong CLong peek :: Ptr CTimeval -> IO CTimeval peek ptr = do s <- peekElemOff (castPtr ptr) 0 :: _ CLong mus <- peekElemOff (castPtr ptr) 1 return (MkCTimeval s mus) }}} succeeds. Is this expected? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11670> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11638: referring to the existential type from a GADT pattern match with a type application
by GHC 12 Jun '16

12 Jun '16

#11638: referring to the existential type from a GADT pattern match with a type application -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple TypeApplications | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #11387 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Currently I can define a GADT like {{{ data T where MkT :: forall a. (Num a, Show a) => T }}} but it's useless on two counts: * At a use of the constructor `MkT`, I can't specify what type `a` I want to pack dictionaries for. (In fact the declaration is an error unless either the constraints are defaultable (as in the case above) or AllowAmbiguousTypes is enabled.) * At a pattern match against `MkT`, I have no way to refer to the type for which dictionaries were packed. The solution is to add a field of type `Proxy a` (possibly strict/unpacked) or `Proxy# a` to `MkT`. But these options are all a bit verbose and each have minor drawbacks. I had hoped that TypeApplications would address the two points above directly. * At a use of the constructor `MkT`, specify the type with a type application `MkT @a`. This part works as of 90f35612f16ff9cb2466cc936f12e748402abb85. * At a pattern match against `MkT`, I would like to be able to match the type directly like this: {{{ f :: T -> String f t = case t of MkT @a -> show (0 :: a) }}} This is the feature request. Note that, while this may be stressful for the parser due to as-patterns, I don't think there is any actual ambiguity as long as (1) type applications only appear on constructors, not variables, and (2) all type applications appear before any value-level fields of the constructor. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11638> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11204: Recompilation checking stochastically broken on Darwin
by GHC 12 Jun '16

12 Jun '16

#11204: Recompilation checking stochastically broken on Darwin ----------------------------------------+---------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.11 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+---------------------------- The `retc001` test usually fails on Darwin. Unfortunately, it also sometimes passes. Failures look like this, {{{ =====> retc001(normal) 1 of 1 [0, 0, 0] cd . && $MAKE -s --no-print-directory retc001 </dev/null > retc001.run.stdout 2> retc001.run.stderr Actual stderr output differs from expected: --- ./retc001.stderr.normalised 2015-12-11 23:02:23.000000000 +0200 +++ ./retc001.run.stderr.normalised 2015-12-11 23:02:23.000000000 +0200 @@ -1,2 +0,0 @@ - -C.hs:3:11: Module ‘B’ does not export ‘foo’ \ No newline at end of file Actual stdout output differs from expected: --- ./retc001.stdout.normalised 2015-12-11 23:02:23.000000000 +0200 +++ ./retc001.run.stdout.normalised 2015-12-11 23:02:23.000000000 +0200 @@ -3,5 +3,3 @@ [3 of 3] Compiling Main ( C.hs, nothing ) Middle End -[2 of 3] Compiling B ( B.hs, nothing ) -[3 of 3] Compiling Main ( C.hs, nothing ) [B changed] \ No newline at end of file *** unexpected failure for retc001(normal) }}} I suspect the problem is mtime resolution as if I apply the following patch it almost always passes, {{{ diff --git a/testsuite/tests/driver/retc001/Makefile b/testsuite/tests/driver/retc001/Makefile index a3cf6eb..bb1eca8 100644 --- a/testsuite/tests/driver/retc001/Makefile +++ b/testsuite/tests/driver/retc001/Makefile @@ -20,5 +20,6 @@ retc001: clean echo 'Middle' '$(TEST_HC)' $(TEST_HC_OPTS_NO_RECOMP) -fno-code -fwrite-interface --make C.hs echo 'End' + sleep 1 cp B2.hs B.hs -'$(TEST_HC)' $(TEST_HC_OPTS_NO_RECOMP) -fno-code -fwrite- interface --make C.hs }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11204> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12099: ghc --show-options lists invalid flags
by GHC 10 Jun '16

10 Jun '16

#12099: ghc --show-options lists invalid flags -------------------------------------+------------------------------------- Reporter: DanielG | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While porting ghc-mod to GHC 8 I noticed that all `-fwarn` flags are missing from `flagsForCompletion` instead only `-fwarn-` and `-fno-warn-` appear. This also shows up in the front-end when running `ghc --show- options`. Looking at the code this turned out to be because the old `-fwarn` flags were marked as hidden using `hideFlag` and hidden flags are explicitly filtered out in `flagsForCompletion` but for some reason the `-fwarn-` and `-fno-warn-` prefixes still show up in the list. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12099> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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