February 2019 - ghc-tickets

[GHC] #16292: Wildcards in visible kind application
by GHC 06 Feb '19

06 Feb '19

#16292: Wildcards in visible kind application -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- `TcHsType.tcInferApps` contains this terrible code {{{ ; ki_arg <- addErrCtxt (funAppCtxt orig_hs_ty hs_ki_arg n) $ unsetWOptM Opt_WarnPartialTypeSignatures $ setXOptM LangExt.PartialTypeSignatures $ -- Urgh! see Note [Wildcards in visible kind application] -- ToDo: must kill this ridiculous messing with DynFlags }}} It's a knock-on from the Visible Kind Application patch -- see the Note referred to above. But it's ghastly and we must fix it. There's a [https://github.com/ghc- proposals/ghc-proposals/pull/194 GHC Proposal about this], but it's relatively ambitious. Maybe there is a shorter term thing we can do here. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16292> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14730: Missing predicate for "ResourceVanished" IOException/IOErrorType
by GHC 06 Feb '19

06 Feb '19

#14730: Missing predicate for "ResourceVanished" IOException/IOErrorType -------------------------------------+------------------------------------- Reporter: bit | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.2.2 libraries/base | 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: -------------------------------------+------------------------------------- `IOErrorType` has a "`ResourceVanished`" constructor: https://hackage.haskell.org/package/base-4.10.1.0/docs/src/GHC.IO.Exception… But there is no way to detect this for an `IOException` or `IOErrorType`. Here is some real-world code I found, where the author wants to catch "`ResourceVanished`", but resorts to catching all `IOException`: https://hackage.haskell.org/package/http-client-tls-0.3.5.1/docs/src /Network-HTTP-Client-TLS.html#convertConnection Docs for `hPutBuf` also mention the public existence of "`ResourceVanished`": https://hackage.haskell.org/package/base-4.10.1.0/docs/GHC-IO- Handle.html#v:hPutBuf Suggestion: We need to add functions: {{{#!haskell isResourceVanished :: IOError -> Bool resourceVanishedErrorType :: IOErrorType isResourceVanishedErrorType :: IOErrorType -> Bool }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14730> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16264: Install reqlib'd libraries during CI
by GHC 06 Feb '19

06 Feb '19

#16264: Install reqlib'd libraries during CI -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: Component: Continuous | Version: 8.6.3 Integration | 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: -------------------------------------+------------------------------------- Currently tests requiring external libraries are hardly ever run. We likely don't want to run them in every job but we should have at least one job that makes a point of doing so. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16264> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16294: Code generation corrupts writes to Addr#
by GHC 06 Feb '19

06 Feb '19

#16294: Code generation corrupts writes to Addr# -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- This issue affects at least GHC 8.4.4 and GHC 8.6.3. Here is a somewhat minimal example: {{{#!hs {-# language BangPatterns #-} {-# language MagicHash #-} {-# language UnboxedTuples #-} {-# options_ghc -Wall -Werror -O2 #-} import Data.Primitive import Data.Void import Data.Word import Data.Monoid import GHC.IO (IO(..)) import Foreign.Storable import Numeric (showHex) import qualified GHC.Exts as E import qualified Data.Primitive as PM main :: IO () main = do arr <- compute 0xABCD 0x79 putStrLn (showString "raw packet: " . appEndo (foldMap (Endo . showHex) (E.toList arr)) $ "") compute :: Word16 -> Word8 -> IO ByteArray compute totlen prot = do buf <- PM.newPinnedByteArray 28 PM.setByteArray buf 0 28 (0 :: Word8) let !(Addr addr) = PM.mutableByteArrayContents buf !ptr = E.Ptr addr :: E.Ptr Void pokeByteOff ptr 0 (0x45 :: Word8) pokeByteOff ptr 1 (0 :: Word8) pokeByteOff ptr 2 (totlen :: Word16) pokeByteOff ptr 4 (0 :: Word16) pokeByteOff ptr 6 (0 :: Word16) pokeByteOff ptr 8 (0x40 :: Word8) pokeByteOff ptr 9 (prot :: Word8) touchMutableByteArray buf PM.unsafeFreezeByteArray buf touchMutableByteArray :: MutableByteArray E.RealWorld -> IO () touchMutableByteArray (MutableByteArray x) = touchMutableByteArray# x touchMutableByteArray# :: E.MutableByteArray# E.RealWorld -> IO () touchMutableByteArray# x = IO $ \s -> case E.touch# x s of s' -> (# s', () #) }}} For those curious about the particular interleaving of 8-bit and 16-bit writes, this was adapted from code that fills out an `iphdr` for use with raw sockets. The output will be dependent on your platform's endianness. On my little-endian architecture, I get: {{{ raw packet: 450cdab00004079000000000000000000 }}} As we expect, the `abcd` from the source gets flipped to `cdab` because of the little endian architecture this ran on. However, it starts in an unusual place. It's not even byte-aligned. Something, possible a cmm optimization or a codegen optimization, makes the `writeWord16OffAddr#` end up straddling three bytes. Someone will probably want to write a more minimal example that eliminates the use of the `primitive` library. Sorry to be the bearer of bad news :( -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16294> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16106: Remove PowerPC OS X (Darwin) support
by GHC 06 Feb '19

06 Feb '19

#16106: Remove PowerPC OS X (Darwin) support --------------------------------+--------------------------------- Reporter: trommler | Owner: (none) Type: task | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 8.6.3 Keywords: | Operating System: MacOS X Architecture: powerpc | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------+--------------------------------- OS X for PowerPC is not supported by Apple anymore. GHC's support has most likely bit-rotted and we have no test machine. Let's go ahead and remove support for PowerPC Darwin. The following components contain PowerPC Darwin specific code: * native code generator * RTS * driver * build system -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16106> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15897: Negative MUT time in +RTS -s -RTS when heap profiling is enabled
by GHC 06 Feb '19

06 Feb '19

#15897: Negative MUT time in +RTS -s -RTS when heap profiling is enabled -------------------------------------+------------------------------------- Reporter: maoe | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.3 Component: Profiling | Version: 8.6.2 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Debugging (amd64) | information is incorrect Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Mutator run time in +RTS -s -RTS can go negative in GHC 8.6.x when retainer profiling is enabled. Here is an example taken from https://ghc.haskell.org/trac/ghc/ticket/881#comment:9 {{{ {-# OPTIONS_GHC -fprof-auto #-} import Control.Monad import Data.IORef import System.Environment main = do [n] <- getArgs replicateM (read n) (newIORef [1,2,3]) }}} {{{ % ghc-8.6.2 -prof -rtsopts -fforce-recomp repro.hs [1 of 1] Compiling Main ( repro.hs, repro.o ) Linking repro ... % ./repro 10000000 +RTS -s -h 3,053,080,472 bytes allocated in the heap 5,538,404,848 bytes copied during GC 1,013,615,328 bytes maximum residency (16 sample(s)) 36,422,944 bytes maximum slop 966 MB total memory in use (0 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 2600 colls, 0 par 1.375s 1.376s 0.0005s 0.0019s Gen 1 16 colls, 0 par 4.355s 4.355s 0.2722s 1.0136s INIT time 0.000s ( 0.000s elapsed) MUT time 0.000s ( -0.833s elapsed) GC time 4.016s ( 4.016s elapsed) RP time 0.000s ( 0.000s elapsed) PROF time 1.715s ( 1.715s elapsed) EXIT time 1.715s ( 1.715s elapsed) Total time 6.612s ( 6.612s elapsed) %GC time 0.0% (0.0% elapsed) Alloc rate 0 bytes per MUT second Productivity -12.6% of total user, -12.6% of total elapsed }}} Here is what I found so far: * GHC 8.6.1, 8.6.2, and yesterday's HEAD have the same issue. GHC 8.4.4 doesn't have this issue. * `-hr` has the same issue. `-hT` is fine. * Without heap profiling the numbers this doesn't happen -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15897> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16146: Trivial partial type signature kills type inference in the presence of GADTs
by GHC 05 Feb '19

05 Feb '19

#16146: Trivial partial type signature kills type inference in the presence of GADTs -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- Suppose we have {{{#!hs data G a where G1 :: G Char G2 :: G Bool }}} If I now write {{{#!hs foo x = case x of G1 -> 'z' G2 -> True }}} I rightly get an error around untouchable variables. If I add the type signature {{{#!hs foo :: G a -> a }}} all is well again. So far, so good. Now, I write {{{#!hs foo :: forall a. G a -> a foo x = ((case x of G1 -> 'z' G2 -> True) :: _) }}} and I get those untouchable errors again. Untouchable-variable errors usually arise when there are multiple possible answers to the type inference problem. Yet, that isn't the case here: `_` must stand for `a`. Solution: mumble mumble bidirectional type inference mumble mumble. Part of the problem comes from Note [Partial expression signatures] in TcExpr, which states {{{ here is a guiding principile e :: ty should behave like let x :: ty x = e in x }}} Indeed, if we behave like that, the untouchable-variable errors are to be expected. But I also think that it would be a nice principle to say that `:: _` is always a no-op. This is not an idle nice-to-have: if we fix this, `singletons` will continue to work with GHC. Right now, it doesn't: https://github.com/goldfirere/singletons/issues/357 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16146> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16290: Export `noinline` function from `GHC.Exts`
by GHC 05 Feb '19

05 Feb '19

#16290: Export `noinline` function from `GHC.Exts` -------------------------------------+------------------------------------- Reporter: Ptharien's | Owner: (none) Flame | Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.6.3 libraries/base | Keywords: noinline | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The other `id`s-with-special-behavior `inline`, `lazy`, and `oneShot` that are declared in `GHC.Magic` are re-exported from `GHC.Exts` (and thus made user-accessible), but `noinline` isn’t. This seems like an oversight. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16290> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16134: Continuous integration on FreeBSD
by GHC 05 Feb '19

05 Feb '19

#16134: Continuous integration on FreeBSD -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- Arrowd has been looking at introducing CI for FreeBSD/amd64. He has a build script using poudriere [[http://arrowd.name/ghc-ci|here]] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16134> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #16269: Postfix operator precedence
by GHC 05 Feb '19

05 Feb '19

#16269: Postfix operator precedence -------------------------------------+------------------------------------- Reporter: anuyts | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 (Parser) | Keywords: fixity | Operating System: Unknown/Multiple PostfixOperators | Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I want to define a postfix operator $- that feeds a default argument (obtained from a typeclass) to a given function. However, I would like to be able to write things like (f $ g $ h $-) for (f (g (h (defaultArg)))). This is not allowed, as $ has precedence 0 and $- is required to have lower precedence, which is impossible. I think it would be sensible if $- was required to have precedence at most infixr 0 (which is the precedence of $). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16269> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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