September 2015 - ghc-tickets

[GHC] #10824: Let-bindings of kind # are processed backwards
by GHC 21 Nov '15

21 Nov '15

#10824: Let-bindings of kind # are processed backwards -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Consider this module: {{{ {-# LANGUAGE MagicHash #-} import GHC.Exts main = do let x = error "bar" :: Int# y = error "foo" :: Int# print (I# x + I# y) }}} When you run this, you will get the error "foo" and not the error "bar". This is backwards! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10824> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10666: Distinguish between semantic module / identity module in TcGblEnv, ModIface and ModGuts
by GHC 21 Nov '15

21 Nov '15

#10666: Distinguish between semantic module / identity module in TcGblEnv, ModIface and ModGuts -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: Package | Version: 7.10.1 system | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When we write a signature like {{{ package p where signature H where data T }}} and compile it to an interface file, there are two ways we might say what the `Module` of this interface is: 1. The **identity module** uniquely identifies an interface file, and is used for dependency analysis and tracking. In the example above, the identity module is `p(H -> HOLE:H):H`. 2. The **semantic module** tells us what the `Name`s of the entities defined in the module are supposed to be; e.g., it's used for generating new names when type-checking hs files or interfaces. In the example above, the semantic module is `hole:H`, since this signature exports one entity named `hole:H.T`. The semantic module can always be derived from the identity module. For normal Haskell modules, the semantic and identity module coincide. However, for signatures they differ: we may have many signatures for the same module; they all share their semantic module but have differing identity modules. By in large, when GHC manipulates `Module` directly it is interested in the identity module. However, when a `Module` is used with reference to a `Name` (primarily `nameIsLocalOrFrom`), we want to use the SEMANTIC module. (Another example: when we filter out the type environment before making a `ModIface`, need to filter against the semantic module.) I tried a few ways of factoring GHC's code so we'd be less likely to confuse these two `Module`s when typechecking signatures: the big problem is if you're adding a `getModule` call to `TcRn`, you're probably not going to think too hard whether or not you actually wanted the semantic module or the identity module. But if you pick the wrong thing that will break all sorts of things for signatures. Here are some things we could do: 1. My initial attempt was to change `tcg_mod`, `mg_module` and `mi_module` to record a new data type `TopModule` which recorded both the semantic and identity module, with `getModule` in `TcRn` continuing to return a semantic module, but `mi_module` returning an identity module. However, the resulting patch was pretty ugly and it's not altogether clear that `getModule` returning the semantic module is always correct. 2. My other idea is to say that these entries always are IDENTITY modules (this will result on fail fast behavior for signatures if you get it wrong), and then rewrite `nameIsLocalOrFrom`, `externaliseAndTidyId`, `initIfaceTcRn`, `newGlobalBinder` so that they always do the right thing (i.e. use the semantic module); thus, the only time you can get it wrong is if you're creating some new functionality that's not these functions that needs to use semantic modules. Pretty delicate. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10666> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10462: GHCi doesn't work Any and missing RealWorld foreign prim imports
by GHC 21 Nov '15

21 Nov '15

#10462: GHCi doesn't work Any and missing RealWorld foreign prim imports -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Here are two issues with our GHCi support for foreign prim imports: Here is a program that works: {{{ {-# LANGUAGE GHCForeignImportPrim, MagicHash, UnliftedFFITypes, UnboxedTuples #-} module Serum where import GHC.Exts foreign import prim "cheneycopy" cheneycopy :: Word# -> State# RealWorld -> (# State# RealWorld, Word# #) }}} If I remove the world token passing, as in here: {{{ {-# LANGUAGE GHCForeignImportPrim, MagicHash, UnliftedFFITypes, UnboxedTuples #-} module Serum where import GHC.Exts foreign import prim "cheneycopy" cheneycopy :: Word# -> Word# }}} I get: {{{ (GHC version 7.10.1 for x86_64-unknown-linux): ByteCodeGen.generateCCall: missing or invalid World token? }}} Another error is if I try to pass Any as an argument: {{{ {-# LANGUAGE GHCForeignImportPrim, MagicHash, UnliftedFFITypes, UnboxedTuples #-} module Serum where import GHC.Exts foreign import prim "cheneycopy" cheneycopy :: Any -> State# RealWorld -> (# State# RealWorld, Word# #) }}} Then I get: {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.10.1 for x86_64-unknown-linux): primRepToFFIType }}} Note to anyone who is running into this problem: an easy workaround is to use `-fobject-code` which bypasses bytecode generation. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10462> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9651: Increasing verbosity doesn't give useful information for why we couldn't load package
by GHC 21 Nov '15

21 Nov '15

#9651: Increasing verbosity doesn't give useful information for why we couldn't load package -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I don't time to fix this now, so recording so I remember. {{{ [ezyang@hs01 ghc-nocode]$ /home/hs01/ezyang/ghc-head/inplace/bin/ghc- stage2 -package-key ghc_GE0xPzNsQzT2p10hpwDwSW --interactive -package-db libraries/bootstrapping.conf -v GHCi, version 7.9.20140929: http://www.haskell.org/ghc/ :? for help Glasgow Haskell Compiler, Version 7.9.20140929, stage 2 booted by GHC version 7.8.3 Using binary package database: /home/hs01/ezyang/ghc- head/inplace/lib/package.conf.d/package.cache Using binary package database: libraries/bootstrapping.conf/package.cache *** Deleting temp files: Deleting: *** Deleting temp dirs: Deleting: <command line>: cannot satisfy -package-key ghc_GE0xPzNsQzT2p10hpwDwSW (use -v for more information) [ezyang@hs01 ghc-nocode]$ /home/hs01/ezyang/ghc-head/inplace/bin/ghc- stage2 -package-key ghc_GE0xPzNsQzT2p10hpwDwSW --interactive -package-db libraries/bootstrapping.conf GHCi, version 7.9.20140929: http://www.haskell.org/ghc/ :? for help <command line>: cannot satisfy -package-key ghc_GE0xPzNsQzT2p10hpwDwSW (use -v for more information) [ezyang@hs01 ghc-nocode]$ /home/hs01/ezyang/ghc-head/inplace/bin/ghc- stage2 -package-key ghc_GE0xPzNsQzT2p10hpwDwSW --interactive -package-db libraries/bootstrapping.conf -v GHCi, version 7.9.20140929: http://www.haskell.org/ghc/ :? for help Glasgow Haskell Compiler, Version 7.9.20140929, stage 2 booted by GHC version 7.8.3 Using binary package database: /home/hs01/ezyang/ghc- head/inplace/lib/package.conf.d/package.cache Using binary package database: libraries/bootstrapping.conf/package.cache *** Deleting temp files: Deleting: *** Deleting temp dirs: Deleting: <command line>: cannot satisfy -package-key ghc_GE0xPzNsQzT2p10hpwDwSW (use -v for more information) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9651> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8079: Redo T7919 with a cabal file
by GHC 21 Nov '15

21 Nov '15

#8079: Redo T7919 with a cabal file -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Test Suite | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Compile-time Difficulty: Easy (less than 1 | crash hour) | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- Right now T7919 fails because the new dynamic-by-default GHC means that Template Haskell must be built with dynamic; of course, GHC isn't clever enough to figure this out. If we Cabalize the test, the example should start building again (and if they don't, well, that's a bug!) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8079> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8199: Get rid of HEAP_ALLOCED
by GHC 21 Nov '15

21 Nov '15

#8199: Get rid of HEAP_ALLOCED ----------------------------------------------+---------------------------- Reporter: ezyang | Owner: ezyang Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.7 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Project (more than a week) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- This bug is to track progress of removing HEAP_ALLOCED from GHC, promising faster GC, as long as we can keep the cost of indirections down. The relevant wiki article: http://ghc.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/HeapAlloced ; we are implementing method 2. The attached patchset is *almost* able to support GHC itself; a ghc-stage2 built this way can compile most files, but is much slower in some cases, and probably has some correctness bugs. Improvements possible: * Don't pay for a double indirection when -fPIC is turned on. Probably the easiest way to do this is to *not* bake in the indirections into compiled code when it is -fPIC'd, and instead scribble over the GOT. However, I don't know how to go backwards from a symbol to a GOT entry, so we might need some heinous assembly hacks to get this working. * Closure tables should have their indirections short-circuited by the initialization code. * We are paying an indirection when a GC occurs when the closure is not in R1. According to the wiki page, technically this is not needed, but I don't know how to eliminate references to the closure itself from stg_gc_fun. * Properly handle the Windows DLL case (e.g. SRTs); this should be simpler now that everything is an indirection. * Bikeshed hs_main API changes (because closures are not valid prior to RTS initialization, so you have to pass in an indirection instead) * Improve static indirection and stable pointer registration, avoiding binary bloat from `__attribute(constructor)__` stubs. * Need to implement a new megablock tracking structure so we can free/check for lost blocks -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8199> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10900: Suggestions for improvement of the PatternSynonyms chapter in the User's Guide
by GHC 20 Nov '15

20 Nov '15

#10900: Suggestions for improvement of the PatternSynonyms chapter in the User's Guide -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.10.2 Documentation | Keywords: | Operating System: Unknown/Multiple PatternSynonms | Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- I read the chapter on PatternSynonyms recently. Seems like a very useful feature! Here are my notes, in the same spirit as #10140. == 7.3.9 == * This section starts with a nice example of how pattern synonyms can make some code much clearer. No problems sofar. > Note that in this example, the pattern synonyms Int and Arrow can also be > used as expressions (they are bidirectional). * How can a pattern (synonym) possibly be used as an expression. They seem such different concepts. You say "bidirectional", but what are the directions? You mentioned "constructor-like" before, maybe it's something like that? * This could use an example. * Is `Arrow Int Int` an example of using a pattern synonym as an expression? * What about `pattern Maybe t`, can it also be used as an expression? Why is this not mentioned? What is it doing there anyway, it's not used in either of the functions `collectArgs`, `isInt` and `isIntEndo`. > This is not necessarily the case: unidirectional pattern synonyms can also be > declared with the following syntax * Ok. > We can give an explicit inversion of a pattern synonym using the > following syntax * What does inverting a pattern synonym mean? * You mentioned unidirectional and bidirectional pattern synonyms. Can I invert both? {{{ pattern Head x <- x:xs where Head x = [x] }}} * Weird syntax. But what does it //do//? (I'm very confused now) == 7.3.9.1 == > Either prefix or infix syntax can be used. * I have no idea what this refers to. > For implicitly bidirectional pattern synonyms * This is the first time you mention the word "implicit". > For unidirectional and explicitly-bidirectional pattern synonyms * Ok, now it's getting clear. There seem to be 3 types of pattern synonyms. I wish you had said this earlier. (goes back to read from the beginning: ok I guess the first time you mentioned bidirectional patttern synonyms, they were the implicit ones, and the "explicit inversion" stuff with the weird syntax are the explicit ones.) == 7.3.9.2 == {{{ import Data.Maybe( pattern Just ) }}} * This doesn't compile. It turns out I need the PatternSynonyms extension in the importing module, even though you said in the beginning "it is required for defining them, but //not// for using them". * I later found #10653, so that explains it. Maybe mention that ticket. == 7.3.9.3 == > In the common case where CReq is empty, (), it can be omitted altogether. * Why is it more common for CReq to empty than for CProv to be empty? * What if CProv is empty, but CReq isn't? * What if both are empty, can they both be omitted? > so function f is rejected because the type signature is Maybe a * I tried this example, and f is not rejected at all. **Bug**? == 7.3.9.4 == > A pattern synonym occurrence in a pattern is evaluated by first matching > against the pattern synonym itself, and then on the argument patterns. * Should be "against the //rhs// of the pattern synonym" I think. * This is tricky stuff. Why is pattern synonym semantics not just defined as 'textual substitution'? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10900> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10168: generalize filterM, mapAndUnzipM, zipWithM, zipWithM_, replicateM, replicateM_
by GHC 18 Nov '15

18 Nov '15

#10168: generalize filterM, mapAndUnzipM, zipWithM, zipWithM_, replicateM, replicateM_ -------------------------------------+------------------------------------- Reporter: strake888 | Owner: ekmett Type: bug | Status: new Priority: normal | Milestone: Component: Core | Version: 7.10.1-rc1 Libraries | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- These need only an Applicative constaint. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10168> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10276: ApiAnnotations : ITopenExpQuote needs SourceText
by GHC 16 Nov '15

16 Nov '15

#10276: ApiAnnotations : ITopenExpQuote needs SourceText -------------------------------------+------------------------------------- Reporter: alanz | Owner: alanz Type: bug | Status: new Priority: normal | Milestone: 7.10.2 Component: Compiler | Version: 7.10.1 (Parser) | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- In the lexer, `ITopenExpQuote` can be recognised for '[e|' or '[|'. The token definition needs to capture the original `SourceText`, and pass it through to `ExpBr`, which also needs a `SrcText` field. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10276> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9579: Runtime suggests using +RTS when that's not possible
by GHC 15 Nov '15

15 Nov '15

#9579: Runtime suggests using +RTS when that's not possible -------------------------------------+------------------------------------- Reporter: gintas | Owner: simonmar Type: bug | Status: new Priority: low | Milestone: Component: Runtime System | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I just ran into a stack overflow in an application, and GHC told me: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it. I tried to specify +RTS and got an error saying "Most RTS options are disabled. Link with -rtsopts to enable them." The runtime should not suggest using +RTS when that is not possible. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9579> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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