August 2016 - ghc-tickets

[GHC] #12010: Incorrect return types for recv() and send() on Windows
by GHC 05 Sep '16

05 Sep '16

#12010: Incorrect return types for recv() and send() on Windows --------------------------------------+---------------------------------- Reporter: enolan | Owner: enolan Type: bug | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- They return signed 32 bit ints on Windows, even on a 64 bit OS, rather than Linux's 64 bit ssize_t. This means when recv() returned -1 to signal an error we thought it was 4294967295. It was converted to an int, -1 and the buffer was memcpy'd which caused a segfault. Other bad stuff happened with send()s. The problem is in `blockingReadRawBufferPtr` and `blockingWriteRawBufferPtr` in `GHC.IO.FD` which are only called in the threaded RTS. See also note CSsize in System.Posix.Internals. I have a patch and a test incoming. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12010> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12133: ConstraintKinds inference failure (regression from 7.10)
by GHC 05 Sep '16

05 Sep '16

#12133: ConstraintKinds inference failure (regression from 7.10) -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Posting for a friend who was believed to be spam: {{{#!hs {-# LANGUAGE CPP #-} {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeOperators #-} module T where #if __GLASGOW_HASKELL__ >= 800 import GHC.Classes (IP(..)) #else import GHC.IP (IP(..)) #endif import GHC.Exts (Constraint) -- | From "Data.Constraint": data Dict :: Constraint -> * where Dict :: a => Dict a newtype a :- b = Sub (a => Dict b) infixl 1 \\ -- required comment (\\) :: a => (b => r) -> (a :- b) -> r r \\ Sub Dict = r -- | GHC 7.10.2 type checks this function but GHC 8.0.1 does not unless -- you modify this example in one of the following ways: -- -- * uncomments the type signature for 'Sub' -- -- * flatten the nested pairs of constraints into a triple of constraints -- -- * replace 'IP sym ty' with 'c9', where 'c9' is a new constraint variable. -- -- The error message is listed below. foo :: forall c1 c2 c3 sym ty . (c1, c2) :- c3 -> (c1, (IP sym ty, c2)) :- (IP sym ty, c3) foo sp = ( Sub -- :: ((c1, (IP sym ty, c2)) => Dict (IP sym ty, c3)) -- -> (c1, ((IP sym ty), c2)) :- (IP sym ty, c3) ) ( (Dict \\ sp) :: Dict (IP sym ty, c3) ) {- Compiler error message: GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling T ( t.hs, interpreted ) t.hs:44:13: error: • Could not deduce: IP sym ty arising from a use of ‘Dict’ from the context: (c1, (IP sym ty, c2)) bound by a type expected by the context: (c1, (IP sym ty, c2)) => Dict (IP sym ty, c3) at t.hs:(40,10)-(44,49) or from: c3 bound by a type expected by the context: c3 => Dict (IP sym ty, c3) at t.hs:44:13-22 • In the first argument of ‘(\\)’, namely ‘Dict’ In the first argument of ‘Sub’, namely ‘((Dict \\ sp) :: Dict (IP sym ty, c3))’ In the expression: (Sub) ((Dict \\ sp) :: Dict (IP sym ty, c3)) • Relevant bindings include foo :: (c1, c2) :- c3 -> (c1, (IP sym ty, c2)) :- (IP sym ty, c3) (bound at t.hs:40:1) Failed, modules loaded: none. -} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12133> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12055: Typechecker panic instead of proper error
by GHC 05 Sep '16

05 Sep '16

#12055: Typechecker panic instead of proper error -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider this modification of the testcase from #12021, {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE NoImplicitPrelude #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE TypeInType #-} import GHC.Base ( Constraint, Type ) import GHC.Exts ( type (~~) ) type Cat k = k -> k -> Type class Category (p :: Cat k) where type Ob p :: k -> Constraint class (Category (Dom f), Category (Cod f)) => Functor (f :: j -> k) where type Dom f :: Cat j type Cod f :: Cat k functor :: forall a b. Iso Constraint (:-) (:-) (Ob (Dom f) a) (Ob (Dom f) b) (Ob (Cod f) (f a)) (Ob (Cod f) (f b)) class (Functor f , Dom f ~ p, Cod f ~ q) => Fun (p :: Cat j) (q :: Cat k) (f :: j -> k) | f -> p q instance (Functor f , Dom f ~ p, Cod f ~ q) => Fun (p :: Cat j) (q :: Cat k) (f :: j -> k) data Nat (p :: Cat j) (q :: Cat k) (f :: j -> k) (g :: j -> k) type Iso k (c :: Cat k) (d :: Cat k) s t a b = forall p. (Cod p ~~ Nat d (->)) => p a b -> p s t data (p :: Constraint) :- (q :: Constraint) }}} With GHC 8.0.1 it fails with a compiler panic, {{{ $ ghc Hi.hs -fprint-explicit-kinds [1 of 1] Compiling Main ( Hi.hs, Hi.o ) Hi.hs:21:1: error: • Non type-variable argument in the constraint: Category j (Dom k j f) (Use FlexibleContexts to permit this) • In the context: (Category j (Dom k j f), Category k (Cod k j f)) While checking the super-classes of class ‘Functor’ In the class declaration for ‘Functor’ Hi.hs:29:20: error: • GHC internal error: ‘Dom’ is not in scope during type checking, but it passed the renamer tcl_env of environment: [a2yi :-> Type variable ‘j’ = j, a2yj :-> Type variable ‘p’ = p, a2yk :-> Type variable ‘k’ = k, a2yl :-> Type variable ‘q’ = q, a2ym :-> Type variable ‘f’ = f, r2xT :-> ATcTyCon Fun] • In the first argument of ‘~’, namely ‘Dom f’ In the class declaration for ‘Fun’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12055> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12555: bindist configure checks involving the compiler are broken
by GHC 05 Sep '16

05 Sep '16

#12555: bindist configure checks involving the compiler are broken -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- Commit 6554dc60304bbd4b2edb93be7e1658bff237e067 added this code to `distrib/configure.ac.in`: {{{ BinDistNeedsLibdw=@HaveLibdw@ if test "x$BinDistNeedsLibdw" = "xyes" ; then AC_CHECK_LIB(dw, dwfl_attach_state, [HaveLibdw=YES], [AC_MSG_ERROR([Binary distribution was built with libdw support but target system doesn't have supported libdw version (needs at least 0.158)])] )]; fi }}} It occurs before any other autoconf command involving the compiler. So apparently the expansion of `AC_CHECK_LIB` includes the code responsible for checking how to invoke the compiler, checking the object file suffix, etc. (Yes, this is a crazy way to do it.) Since the official bindist has `BinDistNeedsLibdw=NO`, none of that code ever actually runs. Later (in `FPTOOLS_SET_HASKELL_PLATFORM_VARS`) the configure script uses ` AC_COMPILE_IFELSE` to check for features of the compiler like non- executable stack support, but these checks are broken because autoconf never actually determined basic information about the compiler. So the 8.0.1 bindist produces binaries with executable stacks, which is a problem on some systems. It would be better anyways to move this `AC_CHECK_LIB` later in `distrib/configure.ac.in`, to after where we select flags to be used when invoking the compiler. There are also some other bugs in this code: there is an extra `];` and the correct value of `BinDistNeedsLibdw` is `YES` (not `yes`) so the code currently can never run anyways. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12555> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12546: GeneralizedNewtypeDeriving produces error messages with incorrect kind signatures
by GHC 05 Sep '16

05 Sep '16

#12546: GeneralizedNewtypeDeriving produces error messages with incorrect kind signatures -------------------------------------+------------------------------------- Reporter: lexi.lambda | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Given the following program: {{{ {-# LANGUAGE GeneralizedNewtypeDeriving #-} {-# LANGUAGE FlexibleInstances #-} import Control.Monad.Reader newtype AppM a = AppM (ReaderT Int IO a) deriving (Functor, Applicative, Monad, MonadReader) }}} The `MonadReader` deriving declaration should be `MonadReader Int`. GHC produces the following error message: {{{ • Expecting one more argument to ‘MonadReader’ Expected kind ‘* -> Constraint’, but ‘MonadReader’ has kind ‘* -> (* -> *) -> Constraint’ • In the newtype declaration for ‘AppM’ }}} This error message is confusing to me. The kind of `MonadReader` is `* -> (* -> *) -> Constraint`, as the error message states, which makes sense. However, the error message states that it expects kind `* -> Constraint`, despite the fact that `MonadReader Int` is actually of kind `(* -> *) -> Constraint`. ,,(This description is adapted from [http://stackoverflow.com/q/39172590/465378 this Stack Overflow question].),, -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12546> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12497: Make runtime linker be able to find POSIX functions under their deprecated name.
by GHC 05 Sep '16

05 Sep '16

#12497: Make runtime linker be able to find POSIX functions under their deprecated name. -------------------------------------+------------------------------------- Reporter: Phyx- | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.0.2 Component: Runtime | Version: 8.0.1 System (Linker) | Keywords: newcomer | Operating System: Windows Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- With GHC 8.0.1 the new runtime linker stopped re-exporting posix symbols under their deprecated names and instead follows the names on MSDN. Unfortunately there seems to be far more libraries than expected using these deprecated names. (Rather, far more libraries using posix functions and it happening to work on Windows). These are all broken now, and while we're doing the right thing, for the sake of compatibility with mingw-w64's behavior and allowing all these packages to work then we should re-export these symbols. e.g. rexport `strdup` as a forward from `_strdup`. We don't have to actually re-export them. just forward them in `RtsSymbol.c`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12497> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12066: Symbol not found: _stg_ap_0_upd_info
by GHC 05 Sep '16

05 Sep '16

#12066: Symbol not found: _stg_ap_0_upd_info -------------------------------------+------------------------------------- Reporter: pikajude | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When compiling project for which `double-conversion` is a dependency: {{{ [ 1 of 12] Compiling Models.TH ( src/Models/TH.hs, dist/build/Models/TH.o ) <command line>: can't load .so/.DLL for: /nix/store /m8whp07czawywfis99bfqpjmfy3vj1bf-double-conversion-2.0.1.0/lib/ghc-8.0.1 /double-conversion-2.0.1.0/libHSdouble-conversion-2.0.1.0 -CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib (dlopen(/nix/store /m8whp07czawywfis99bfqpjmfy3vj1bf-double-conversion-2.0.1.0/lib/ghc-8.0.1 /double-conversion-2.0.1.0/libHSdouble-conversion-2.0.1.0 -CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib, 5): Symbol not found: _stg_ap_0_upd_info Referenced from: /nix/store/m8whp07czawywfis99bfqpjmfy3vj1bf-double- conversion-2.0.1.0/lib/ghc-8.0.1/double-conversion-2.0.1.0/libHSdouble- conversion-2.0.1.0-CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib Expected in: flat namespace in /nix/store/m8whp07czawywfis99bfqpjmfy3vj1bf-double- conversion-2.0.1.0/lib/ghc-8.0.1/double-conversion-2.0.1.0/libHSdouble- conversion-2.0.1.0-CatAMVNq05S8lUOKX28ozh-ghc8.0.1.dylib) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12066> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12216: GHC 8.0.1 panics when compiling JuicyPixels-repa 0.7.1
by GHC 05 Sep '16

05 Sep '16

#12216: GHC 8.0.1 panics when compiling JuicyPixels-repa 0.7.1 -------------------------------------+------------------------------------- Reporter: cgo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This just happened on macOS 10.11.5: Configuring JuicyPixels-repa-0.7.1.0... Building JuicyPixels-repa-0.7.1.0... Preprocessing library JuicyPixels-repa-0.7.1.0... [1 of 1] Compiling Codec.Picture.Repa ( Codec/Picture/Repa.hs, dist/dist- sandbox-94652cd7/build/Codec/Picture/Repa.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-apple-darwin): filterImports/combine (Array, Array{Array, AByteString, ACursored, ADelayed, AForeignPtr, AInterleave, ASmall, APart, AUnboxed, AUndefined, AVector, cursoredExtent, loadCursor, makeCursor, shiftCursor}, Nothing) (Array, Source{Source, Array, deepSeqArray, extent, index, linearIndex, unsafeIndex, unsafeLinearIndex}, Nothing) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug cabal: Leaving directory '/var/folders/lj/5d92khf937120qgs9xccbn400000gn/T /cabal-tmp-24887/JuicyPixels-repa-0.7.1.0' Updating documentation index -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12216> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12076: "lazy" leads to undefined reference to `stg_ap_0_upd_info'
by GHC 05 Sep '16

05 Sep '16

#12076: "lazy" leads to undefined reference to `stg_ap_0_upd_info' -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc2 (CodeGen) | 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: -------------------------------------+------------------------------------- This is basically the same thing as #11155 but triggered differently. {{{ -- M.hs {-# OPTIONS_GHC -O0 #-} module M(f) where import GHC.Exts {-# NOINLINE z #-} z = () f :: () -> () f _ = let x = lazy z in g x x {-# NOINLINE g #-} g :: () -> () -> () g _ _ = () -- MM.hs import M main = f `seq` return () }}} On GHC 8.0, I get: {{{ ezyang@sabre:~$ ghc-8.0 --make MM.hs -fforce-recomp [1 of 2] Compiling M ( M.hs, M.o ) [2 of 2] Compiling Main ( MM.hs, MM.o ) Linking MM ... ./M.o: In function `r2aD_info': (.text+0x4a): undefined reference to `stg_ap_0_upd_info' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) }}} Error goes away when you turn on optimization. My understanding is that removing `lazy` in `CorePrep` is too late, because there's no pass afterwards that eliminates the trivial thunk assignment. This is blocking Phab:D2211, where the insertion of a `noinline` (which is optimized out similarly to `lazy`) triggers a stage 2 linker failure when you don't compile with optimization (unfortunately, this is NOT caught validate since we build GHC with optimization... but with this test it will be!) Perhaps there should be an ASSERT in the codegen so it doesn't create this symbol? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12076> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12472: "lazy" is not optimized away
by GHC 05 Sep '16

05 Sep '16

#12472: "lazy" is not optimized away -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 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: -------------------------------------+------------------------------------- Consider: {{{ import GHC.Magic {-# INLINE f #-} f x = True g = lazy f False }}} Two things should happen: (1) f should not be inlined, but (2) lazy should not be present in final STG (having been eliminated in core prep). I thought this was briefly working on HEAD, but apparently it never worked at all: {{{ ezyang@sabre:~$ ghc-8.0 -c test.hs -ddump-stg -fforce-recomp -O2 ==================== STG syntax: ==================== Test.f [InlPrag=INLINE (sat-args=1)] :: forall t_axB. t_axB -> GHC.Types.Bool [GblId, Arity=1, Caf=NoCafRefs, Str=DmdType <L,A>, Unf=OtherCon []] = \r srt:SRT:[] [eta_sHD] GHC.Types.True []; Test.g :: GHC.Types.Bool [GblId, Str=DmdType] = \u srt:SRT:[] [] GHC.Magic.lazy Test.f GHC.Types.False; }}} Clearly it has not been eliminated. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12472> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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