July 2015 - ghc-tickets

[GHC] #10716: Metadata in GHC.Generic should give access to strictness annotation
by GHC 05 Jan '16

05 Jan '16

#10716: Metadata in GHC.Generic should give access to strictness annotation -------------------------------------+------------------------------------- Reporter: StefanWehr | Owner: Type: feature | Status: new request | 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: | -------------------------------------+------------------------------------- Currently, the metadata in the GHC.Generics module do not give access to the strictness annotations attached to a field of a datatype. It would be great if this piece of information could be added. Background: we are using a class FullyStrict for ensuring that a datatype is fully strict (in the sense that all fields have bang patterns and the types of all fields are also fully strict). Currently we are using TemplateHaskell to derive the instances automatically. The TemplateHaskell function also checks that all fields have bang patterns. To improve compilation speed, I would like to derive the instances with DeriveGeneric. But this is not possible because then I cannot implement the check whether all fields have bang patterns. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10716> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10579: full module names of names not in scope have gone missing in ghci
by GHC 05 Jan '16

05 Jan '16

#10579: full module names of names not in scope have gone missing in ghci -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Compare {{{ rwbarton@morphism:/tmp$ ghci-7.10.1 GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help Prelude> :t GHC.Read.readPrec GHC.Read.readPrec :: Read a => Text.ParserCombinators.ReadPrec.ReadPrec a }}} with {{{ rwbarton@morphism:/tmp$ ~/ghc/inplace/bin/ghc-stage2 --interactive GHCi, version 7.11.20150624: http://www.haskell.org/ghc/ :? for help Prelude> :t GHC.Read.readPrec GHC.Read.readPrec :: Read a => ReadPrec a }}} The `Text.ParserCombinators.ReadPrec.` bit can be quite helpful, was it suppressed intentionally? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10579> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10643: GHC cannot import submodules when run from subfolder
by GHC 05 Jan '16

05 Jan '16

#10643: GHC cannot import submodules when run from subfolder -------------------------------------+------------------------------------- Reporter: FPtje | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: subfolder | Operating System: Unknown/Multiple import submodule cd | Type of failure: GHC rejects Architecture: | valid program Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I'm taking a huge risk in looking like an idiot, but it's worth trying to attack the elephant in the room. The first response I expect is ''"This is expected behaviour!"''. This is what intuition says, but I disagree. It's a simple problem and the fix should be easy, unless there's some advanced import mechanism that would conflict with the solution that I don't know about. That is exactly where I'm taking the risk in reporting this issue. The problem is simple: 1. Create a folder called "Yes". 2. Create Yes/A.hs with the following code: {{{#!hs module Yes.A where import Yes.B }}} 3. Create Yes/B.hs with the following code: {{{#!hs module Yes.B where }}} 4. Open a terminal in the folder that contains "Yes" and run: {{{ $ ghc Yes/A.hs }}} '''This works fine'''. Now try the following: {{{ $ cd Yes Yes/ $ ghc A.hs }}} You'll be greeted with the beautiful error: {{{ A.hs:3:8: Could not find module ‘Yes.B’ Use -v to see a list of the files searched for. }}} A screenshot is worth the above thousand words: http://i.imgur.com/8AxRa0K.png '''This is silly'''. Running with the -v option shows that ghc is not looking for Yes/B.hs, but Yes/Yes/B.hs. I can understand ''why'' it looks there, but not why ghc isn't just this ''tiny'' bit more intelligent in knowing where to look. After all, the module name tells ghc ''exactly'' in which subfolder it is located: {{{#!hs module Yes.A where -- This module is very likely to be in Yes/, because otherwise a name inconsistency error is thrown. }}} '''Proposed solution:''' The module name tells ghc exactly where it is located. If Yes.A imports Yes.B, then you know that they're in the same subfolder. Simple as that. Instead of ignoring that information and looking for Yes/Yes/B.hs, it should simply look for Yes/B.hs. Relative to ghc (which is run from Yes/) this would be ./B.hs. This solution is scalable. Imagine a module Ding.Dong.Biddly.Bong that imports Ding.Dong.Doodle.Bell. Running "ghc Bong.hs" from Ding/Dong/Biddly/ should '''not''' make it look for "Ding/Dong/Biddly/Ding/Dong/Doodle/Bell.hs", but for Ding/Dong/Doodle/Bell.hs. Relative to ghc (run from Ding/Dong/Biddly/), this would be ../Doodle/Bell.hs. So yeah, right now ghc is arbitrarily restricted to run from the root of the source directory. This '''looks''' like intended behaviour until you realise that the silly bug mentioned here is probably the only thing that prevents ghc from running from ''any'' subfolder. Of course there are the -i and :set options for ghc that allows one to work around this, but one should not be expected to jump through all the -iFile hoops to be allowed to run ghc from any arbitrary subdirectory of the source folder. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10643> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10045: type holes related ghc panic
by GHC 04 Jan '16

04 Jan '16

#10045: type holes related ghc panic -------------------------------------+------------------------------------- Reporter: pacak | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- {{{ sample.hs:9:13: Couldn't match expected type ‘t’ with actual type ‘()’ ‘t’ is untouchable inside the constraints () bound by the inferred type of foo :: Meta -> t1 at sample.hs:(6,1)-(9,17)ghc: panic! (the 'impossible' happened) (GHC version 7.10.0.0 for x86_64-unknown-linux): No skolem info: t_avJ[sk] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug sample.hs: module Blah where newtype Meta = Meta () foo (Meta ws1) = let copy :: _ copy w from = copy w 1 in copy ws1 1 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10045> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10531: modules that can be linked successfully when compiled with optimizations, fail to link with: multiple definition of `__stginit_ZCMain'
by GHC 04 Jan '16

04 Jan '16

#10531: modules that can be linked successfully when compiled with optimizations, fail to link with: multiple definition of `__stginit_ZCMain' -------------------------------------+------------------------------------- Reporter: imz | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: GHC rejects (amd64) | valid program Test Case: attached | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When compiling a set of 3 modules (in a certain order), linking of the final executable fails because there conflicting symbols in some of the `.o`. When doing the compilation in the same order, but with optimizations, it succeeds. The simple test case: A.hs: {{{#!hs module A where main :: IO () main = putStrLn "A" }}} B.hs: {{{#!hs module B where import A() main :: IO () main = putStrLn "B" }}} C.hs: {{{#!hs import B() main :: IO () main = putStrLn "hi" }}} When I compile it with in the order specified by the attached `./bug- reproduce.sh` and `Makefile`, the following happens: {{{ ./bug-reproduce.sh rm -fv a A.o A.hi removed 'a' removed 'A.o' removed 'A.hi' rm -fv b B.o B.hi removed 'b' removed 'B.o' removed 'B.hi' rm -fv c C.o C.hi removed 'c' removed 'C.o' removed 'C.hi' ghc -Wall A.hs -main-is A.main -o a [1 of 1] Compiling A ( A.hs, A.o ) Linking a ... ghc -Wall B.hs -main-is B.main -o b [1 of 2] Compiling A ( A.hs, A.o ) [flags changed] [2 of 2] Compiling B ( B.hs, B.o ) Linking b ... ghc -Wall C.hs -o c [2 of 3] Compiling B ( B.hs, B.o ) [flags changed] [3 of 3] Compiling Main ( C.hs, C.o ) Linking c ... removed 'A.o' ghc -Wall A.hs -main-is A.main -o a [1 of 1] Compiling A ( A.hs, A.o ) Linking a ... ghc -Wall B.hs -main-is B.main -o b [2 of 2] Compiling B ( B.hs, B.o ) [flags changed] Linking b ... ./A.o: In function `siv_closure': (.data+0x0): multiple definition of `__stginit_ZCMain' B.o:(.data+0x0): first defined here ./A.o: In function `ZCMain_main_srt': (.data+0x70): multiple definition of `ZCMain_main_closure' B.o:(.data+0x70): first defined here ./A.o:(.text+0xb8): multiple definition of `ZCMain_main_info' B.o:(.text+0xb8): first defined here collect2: error: ld returned 1 exit status make: *** [B.o] Error 1 }}} But it succeeds if done as `./bug-reproduce.sh GHC_OPTS=-O1` (probably, the optimizations remove the conflicting symbols): {{{ ./bug-reproduce.sh GHC_OPTS=-O1 rm -fv a A.o A.hi removed 'a' removed 'A.o' removed 'A.hi' rm -fv b B.o B.hi removed 'b' removed 'B.o' removed 'B.hi' rm -fv c C.o C.hi removed 'c' removed 'C.o' removed 'C.hi' ghc -Wall -O1 A.hs -main-is A.main -o a [1 of 1] Compiling A ( A.hs, A.o ) Linking a ... ghc -Wall -O1 B.hs -main-is B.main -o b [1 of 2] Compiling A ( A.hs, A.o ) [flags changed] [2 of 2] Compiling B ( B.hs, B.o ) Linking b ... ghc -Wall -O1 C.hs -o c [2 of 3] Compiling B ( B.hs, B.o ) [flags changed] [3 of 3] Compiling Main ( C.hs, C.o ) Linking c ... removed 'A.o' ghc -Wall -O1 A.hs -main-is A.main -o a [1 of 1] Compiling A ( A.hs, A.o ) Linking a ... ghc -Wall -O1 B.hs -main-is B.main -o b [1 of 2] Compiling A ( A.hs, A.o ) [flags changed] [2 of 2] Compiling B ( B.hs, B.o ) [flags changed] Linking b ... ghc -Wall -O1 C.hs -o c [2 of 3] Compiling B ( B.hs, B.o ) [flags changed] Linking c ... }}} Couldn't the compiler detect and handle such cases? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10531> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10379: Prefix syntax for promoted list kind isn't parsed properly
by GHC 04 Jan '16

04 Jan '16

#10379: Prefix syntax for promoted list kind isn't parsed properly -------------------------------------+------------------------------------- Reporter: cactus | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.1 (Parser) | Operating System: Unknown/Multiple Keywords: | Type of failure: GHC rejects Architecture: | valid program Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- (Originally from https://stackoverflow.com/questions/27673578/) Given the following input file: {{{ {-# LANGUAGE KindSignatures, GADTs, DataKinds, TypeOperators #-} data Foo1 :: [*] -> * where data Foo2 :: ([] *) -> * where }}} it fails on the definition of `Foo2`: {{{ list-promote2.hs:4:16: parse error on input `]' }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10379> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10554: Replacing existing attachment with the same name doesn't work
by GHC 03 Jan '16

03 Jan '16

#10554: Replacing existing attachment with the same name doesn't work -------------------------------------+------------------------------------- Reporter: thomie | Owner: hvr Type: bug | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10554> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10592: Allow cycles in class declarations
by GHC 03 Jan '16

03 Jan '16

#10592: Allow cycles in class declarations -------------------------------------+------------------------------------- Reporter: | Owner: MikeIzbicki | Status: new Type: feature | Milestone: request | Version: 7.10.1 Priority: normal | Operating System: Unknown/Multiple Component: Compiler | Type of failure: None/Unknown (Type checker) | Blocked By: Keywords: | Related Tickets: Architecture: | Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- In particular, I would like to have a class hierarchy that looks like: {{{ {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleContexts #-} type family Scalar x class Field (Scalar x) => Vector x class Vector x => Field x }}} It is the case that every field is a vector, and the scalar associated with every vector is a field. But we can't currently enforce that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10592> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9590: AMP breaks `haskell2010` package
by GHC 02 Jan '16

02 Jan '16

#9590: AMP breaks `haskell2010` package -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: high | Milestone: 7.10.1 Component: | Version: 7.9 libraries/haskell2010 | Operating System: Keywords: AMP | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: GHC Difficulty: Unknown | rejects valid program Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- (and probably also `haskell98`) I hate to be the one pointing this out, but the AMP has one ugly side- effect. Consider the following session: ``` $ inplace/bin/ghc-stage2 --interactive -XHaskell2010 -hide-all-packages -package haskell2010 GHCi, version 7.9.20140914: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim-0.3.1.0 ... linking ... done. Loading package integer-gmp-0.5.1.0 ... linking ... done. Loading package base-4.8.0.0 ... linking ... done. Loading package array-0.5.0.1 ... linking ... done. Loading package haskell2010-1.1.2.1 ... linking ... done. λ:2> data Identity a = Identity a data Identity a = Identity a λ:3> instance Monad Identity <interactive>:3:10: No instance for (base-4.8.0.0:GHC.Base.Applicative Identity) arising from the superclasses of an instance declaration In the instance declaration for ‘Monad Identity’ λ:4> :info Monad class base-4.8.0.0:GHC.Base.Applicative m => Monad (m :: * -> *) where (>>=) :: m a -> (a -> m b) -> m b (>>) :: m a -> m b -> m b return :: a -> m a fail :: String -> m a -- Defined in ‘base-4.8.0.0:GHC.Base’ instance Monad (Either e) -- Defined in ‘base-4.8.0.0:Data.Either’ instance Monad Maybe -- Defined in ‘base-4.8.0.0:Data.Maybe’ instance Monad [] -- Defined in ‘base-4.8.0.0:GHC.Base’ instance Monad IO -- Defined in ‘base-4.8.0.0:GHC.Base’ instance Monad ((->) r) -- Defined in ‘base-4.8.0.0:GHC.Base’ λ:5> ``` -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9590> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8182: Parser.y.pp needs special treatment with -fcmm-sink
by GHC 31 Dec '15

31 Dec '15

#8182: Parser.y.pp needs special treatment with -fcmm-sink ------------------------------------+------------------------------------- Reporter: thoughtpolice | Owner: thoughtpolice Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: Build System | 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: | ------------------------------------+------------------------------------- This bug is really more of a reminder, but it's critical for the 7.8.1 release. Right now, `Parser.y.pp` uses a very weird hack to pass `-fcmm-sink` to the compiler. Here's the relevant comment: {{{ -- CPP tricks because we want the directives in the output of the -- first CPP pass. -- -- Clang note, 6/17/2013 by aseipp: It is *extremely* important (for -- some reason) that there be a line of whitespace between the two -- definitions here, and the subsequent use of __IF_GHC_77__ - this -- seems to be a bug in clang or something, where having the line of -- whitespace will make the preprocessor correctly format the rendered -- lines in the 'two step' CPP pass. No, this is not a joke. #define __IF_GHC_77__ #if __GLASGOW_HASKELL__ >= 707 #define __ENDIF__ #endif __IF_GHC_77__ -- Required on x86 to avoid the register allocator running out of -- stack slots when compiling this module with -fPIC -dynamic. {-# OPTIONS_GHC -fcmm-sink #-} __ENDIF__ }}} This is because the parser is first preprocessed before being run with GHC (which again preprocesses,) so we want the resulting `#ifdef` in the final `.hs` file. Things to note: * We really shouldn't be doing this, it's amazingly fragile. I think the correct thing to do is to ensure the build system correctly passes `-fcmm- sink` during the stage[2,3] build. * `./configure.ac` needs to check to see if the bootstrapping compiler is `ghc >= 7.7` (or `7.8`) and if it is, ''also'' pass `-fcmm-sink` during the stage1 build. * This hack needs to be removed once we can rely on >= 7.8 for bootstrap. Probably something like the hypothetical 7.12-7.14 timeframe. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8182> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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