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[GHC] #14762: Foreign.Marshal.Pool functions use inefficient O(n) operations
by GHC 26 Feb '18

26 Feb '18

#14762: Foreign.Marshal.Pool functions use inefficient O(n) operations -------------------------------------+------------------------------------- Reporter: nh2 | 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: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `Foreign.Marshal.Pool` uses `Data.List.delete` and `Data.List.elem` to determine whether a pointer is already in the pool and to delete them, as a result of `newtype Pool = Pool (IORef [Ptr ()])`. Thus repeated operations on pools with many entries can become very slow. If possible, we might consider using `Ord` on the `Ptr` and an O(log n) data structure instead of a `[Ptr]` list. Alternatively, we should warn in the docs that this is the case, but it seems better to just fix the implementation. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14762> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14853: Implement the "Semigroup and Monoid instances in Data.Functor.Product and friends" proposal
by GHC 25 Feb '18

25 Feb '18

#14853: Implement the "Semigroup and Monoid instances in Data.Functor.Product and friends" proposal -------------------------------------+------------------------------------- Reporter: lyxia | Owner: (none) Type: task | 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: -------------------------------------+------------------------------------- https://mail.haskell.org/pipermail/libraries/2018-February/028570.html -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14853> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14852: Implement the "Eq1, Ord1, Read1, Show1 instances in GHC.Generics" proposal
by GHC 25 Feb '18

25 Feb '18

#14852: Implement the "Eq1, Ord1, Read1, Show1 instances in GHC.Generics" proposal -------------------------------------+------------------------------------- Reporter: lyxia | Owner: (none) Type: task | 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: -------------------------------------+------------------------------------- https://mail.haskell.org/pipermail/libraries/2018-February/028570.html -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14852> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11777: RTS source code issues
by GHC 25 Feb '18

25 Feb '18

#11777: RTS source code issues -------------------------------------+------------------------------------- Reporter: simonpj | 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: -------------------------------------+------------------------------------- Tiago Silva <tiagosilva(a)hush.com> writes: Last night I started looking at the C files used in GHC and noticed these issues: {{{ /driver/utils/cwrapper.c : int main(int, char **); }}} `void *p` is apparently unused, even if the compiler optimizes it away.. you should check if something went missing. {{{ /rts/RetainerProfile.c : static nat sanityCheckHeapClosure(StgClosure *) }}} `StgInfoTable *info` has the same issue as above {{{ /rts/RetainerSet.c #elif defined(RETAINER_SCHEME_CC) // Retainer scheme 3: retainer = cost centre void printRetainerSetShort(FILE *f, RetainerSet *rs, nat max_length) { char tmp[max_length + 1]; int size; nat j; } }}} Unlike the other functions around it, this function does nothing. Its variables are also not unused? {{{ /rts/sm/MarkWeak.c : void markWeakPtrList (void); if (w->header.info == &stg_DEAD_WEAK_info) { last_w = &(w->link); } else { last_w = &(w->link); } }}} Not sure what's going on here. Regardless of the test the two branches do the same thing. {{{ /rts/win32/IOManager.c : AddIORequest, AddDelayRequest, AddProcRequest functions }}} If `(!ioMan || !wItem)` the functions either return 0 or FALSE, but they don't free `wItem` before. Is this optimized by the compiler? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11777> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14851: "Pattern match has inaccessible right hand side" with TypeRep
by GHC 25 Feb '18

25 Feb '18

#14851: "Pattern match has inaccessible right hand side" with TypeRep -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 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: -------------------------------------+------------------------------------- When I say {{{#!hs {-# LANGUAGE PatternSynonyms, ViewPatterns #-} module Bug where import Type.Reflection pattern X arg <- (checkFun -> arg) checkFun :: TypeRep fun -> a checkFun = undefined f x = case (x, True) of (X _, _) -> 5 _ -> 6 g x = case x of (X _) -> 5 _ -> 6 }}} I get {{{ Bug.hs:13:11: warning: [-Woverlapping-patterns] Pattern match has inaccessible right hand side In a case alternative: (X _, _) -> ... | 13 | (X _, _) -> 5 | ^^^^^^^^^^^^^ }}} I'm troubled by two things: 1. There's nothing inaccessible about my right-hand side. 2. This happens only for `f`, not `g`. If there's no tuple, there's no problem. Note that this problems requires `TypeRep`. Even another polykinded tycon (like `Proxy`) didn't trigger the problem. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14851> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14291: Tests tend to fail in the ext-interp when testing a tree built with a source distribution
by GHC 25 Feb '18

25 Feb '18

#14291: Tests tend to fail in the ext-interp when testing a tree built with a source distribution -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- One issue I've noticed while working on #13716 is that most (if not all) of the tests runs in the `ext-interp` way fail when run inside a tree derived from a source distribution tarball. For instance, {{{ $ git clone git://git.haskell.org/ghc $ cd ghc $ git submodule update --init $ mk/get-win32-tarballs.sh download all $ ./boot $ ./configure $ make sdist $ mkdir tmp; cd tmp $ ls ../sdistprep/ghc-*-src.tar.xz | xargs -n1 tar -xf $ cd ghc-* $ ./boot $ ./configure $ make -j9 $ make test TEST=T10638 ... =====> T10638(normal) 1 of 1 [0, 0, 0] cd "./th/T10638.run" && "/mnt/work/ghc/ghc- testing/temp/ghc-8.3.20170927/inplace/bin/ghc-stage2" -c T10638.hs -dcore- lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed- specialisations -fshow-warning-groups -fdiagnostics-color=never -fno- diagnostics-show-caret -dno-debug-output -XTemplateHaskell -package template-haskell -v0 =====> T10638(ext-interp) 1 of 1 [0, 0, 0] cd "./th/T10638.run" && "/mnt/work/ghc/ghc- testing/temp/ghc-8.3.20170927/inplace/bin/ghc-stage2" -c T10638.hs -dcore- lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed- specialisations -fshow-warning-groups -fdiagnostics-color=never -fno- diagnostics-show-caret -dno-debug-output -XTemplateHaskell -package template-haskell -fexternal-interpreter -v0 Actual stderr output differs from expected: diff -uw "./th/T10638.run/T10638.stderr.normalised" "./th/T10638.run/T10638.comp.stderr.normalised" --- ./th/T10638.run/T10638.stderr.normalised 2017-09-27 12:18:45.737974039 -0400 +++ ./th/T10638.run/T10638.comp.stderr.normalised 2017-09-27 12:18:45.737974039 -0400 @@ -1,5 +1,18 @@ +ghc-iserv.bin: internal evacuate(static): strange closure type 16476 + (GHC version 8.3.20170927 for x86_64_unknown_linux) + Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -T10638.hs:26:11: - ‘static test2’ is not a valid C identifier - When checking declaration: - foreign import prim safe "static test2" cmm_test2 :: Int# -> Int# +T10638.hs:26:9: + Exception when trying to run compile-time code: + {handle: <file descriptor: 11>}: GHCi.Message.remoteCall: end of file + Code: do t <- [t| Int# -> Int# |] + cmm_test2 <- newName "cmm_test2" + addTopDecls + [ForeignD (ImportF Prim Safe "static test2" cmm_test2 t)] + .... + In the untyped splice: + $(do t <- [t| Int# -> Int# |] + cmm_test2 <- newName "cmm_test2" + addTopDecls + [ForeignD (ImportF Prim Safe "static test2" cmm_test2 t)] + [| test1 |]) *** unexpected failure for T10638(ext-interp) Unexpected results from: TEST="T10638" ... }}} The crashes are generally RTS panics or segmentation faults. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14291> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13011: Simplifier ticks exhausted: a 10-line case
by GHC 25 Feb '18

25 Feb '18

#13011: Simplifier ticks exhausted: a 10-line case -------------------------------------+------------------------------------- Reporter: L.K.Rebellion | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 Keywords: Simplifier | Operating System: Linux ticks exhausted | Type of failure: Compile-time Architecture: x86 | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: #8319 #12776 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I was trying to define a function that could take itself as an argument. {{{#!hs newtype MobiusFn a = MobiusFn { func :: MobiusFn a -> a } spin :: MobiusFn a -> a spin mf = func mf mf }}} Use it to find suffixes of a `String` {{{#!hs suffixes :: String -> [String] suffixes = spin $ MobiusFn suffixesMF where suffixesMF _ [] = [] suffixesMF mf s@(_:xs) = s : spin mf xs }}} Add `main` and compile {{{#!hs main = readLn >>= (print . suffixes) }}} The compiler panicked with {{{ [1 of 1] Compiling Main ( test.hs, test.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for i386-unknown-linux): Simplifier ticks exhausted When trying UnfoldingDone mf_s1UD }}} But if we ignore the empty string case, it works well with non-empty strings. {{{#!hs suffixes :: String -> [String] suffixes = spin $ MobiusFn suffixesMF where suffixesMF _ s@[_] = [s] suffixesMF mf s@(_:xs) = s : spin mf xs }}} Two versions tested. {{{ GHC version 8.0.1 for i386-unknown-linux GHC version 7.10.3 for i386-unknown-linux }}} Thank you for reading. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13011> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14841: Inconsistent allocation stats
by GHC 25 Feb '18

25 Feb '18

#14841: Inconsistent allocation stats -------------------------------------+------------------------------------- Reporter: patrickdoc | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: System | Keywords: GCStats, | Operating System: Unknown/Multiple RTSStats | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'm looking at Criterion internals, and seeing an inconsistency in the allocations reported by `GCStats` and `RTSStats`. Here is a small reproduction: {{{#!hs {-# LANGUAGE CPP #-} module Main where import GHC.Stats import System.Mem (performGC) main :: IO () main = do runOldThing 1000 #if __GLASGOW_HASKELL__ >= 802 putStrLn "Running new:" runThing 1000 #endif runOldThing :: Int -> IO () runOldThing n = loop n 0 >> return () where loop 0 _ = return 0 loop count x = do performGC stats <- getGCStats putStrLn $ show (count `mod` 15) ++ ": " ++ show (bytesAllocated stats - x) ++ " num: " ++ show (numGcs stats) loop (count-1) (bytesAllocated stats) #if __GLASGOW_HASKELL__ >= 802 runThing :: Int -> IO () runThing = loop where loop 0 = return () loop n = do performGC stats <- getRTSStats putStrLn $ show (n `mod` 15) ++ ": " ++ show (gcdetails_allocated_bytes (gc stats)) ++ " num: " ++ show (gcs stats) loop (n-1) #endif }}} This code just performs a garbage collection and then prints the stats in a loop. Here is a snippet of the output. {{{ ... 4: 8840 num: 1967 3: 4880 num: 1968 2: 4880 num: 1969 1: 4880 num: 1970 0: 4880 num: 1971 14: 4880 num: 1972 13: 4976 num: 1973 12: 4976 num: 1974 11: 4976 num: 1975 10: 4976 num: 1976 9: 4976 num: 1977 8: 4880 num: 1978 7: 4880 num: 1979 6: 4880 num: 1980 5: 4880 num: 1981 4: 8840 num: 1982 3: 4880 num: 1983 2: 4880 num: 1984 1: 4880 num: 1985 0: 4880 num: 1986 14: 4880 num: 1987 13: 4976 num: 1988 12: 4976 num: 1989 11: 4976 num: 1990 10: 4976 num: 1991 9: 4976 num: 1992 8: 4880 num: 1993 7: 4880 num: 1994 6: 4880 num: 1995 5: 4880 num: 1996 4: 8840 num: 1997 3: 4880 num: 1998 2: 4880 num: 1999 1: 4880 num: 2000 }}} On the left, I've included the gc number `mod` 15 to show that exactly every 15 gcs, there is an extra 4k bytes reported. This output was made with 8.2.1. On 7.8.4, 7.10.3, and 8.0.2 it's every 23. And on 8.4.0.20180204 it's every 9. I've played around with extra allocations between garbage collections, but the interval remained constant. I tried poking around the rts, but I've been unable to determine if this is a bug or just unavoidable noise. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14841> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8597: Git Hook script to prevent large binary blobs being checked in
by GHC 24 Feb '18

24 Feb '18

#8597: Git Hook script to prevent large binary blobs being checked in ------------------------------------+------------------------------------- Reporter: hvr | Owner: hvr Type: task | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- It has already occurred in the past in `testsuite.git` repo, that executables were checked in by accident, and caused the Git history to get bloated. In order to avoid such accidents in the future a Git hook script in the style of [http://stackoverflow.com/questions/20226132/is-there-a-git-hook- which-can-prevent-binary-check-ins this] might be useful, but taking also into account the size, and/or possibly with a magic safeword to be put in the commit message, to override the check for a single commit, if the author really knows what (s)he's doing. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8597> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1974: length "foo" doesn't work with -XOverloadedStrings
by GHC 24 Feb '18

24 Feb '18

#1974: length "foo" doesn't work with -XOverloadedStrings -------------------------------------+------------------------------------- Reporter: ganesh | Owner: (none) Type: feature request | Status: closed Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.8.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by sjakobi): * status: new => closed * resolution: => fixed Comment: Replying to [comment:9 parcs]: > Have you considered changing the instance declaration from > > {{{ > instance IsString String where > }}} > > to > > {{{ > instance (a ~ Char) => IsString [a] where > }}} > > This new instance will make `length "foo"` happily typecheck, but it will also overlap with other `IsString` instances of the form `[T]`. (Though I don't think such instances are common in practice.) That change with in GHC-8.0 / base-4.9: {{{#!hs GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help > length "foo" 3 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1974#comment:10> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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