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[GHC] #13391: PolyKinds is more permissive in GHC 8
by GHC 29 Sep '17

29 Sep '17

#13391: PolyKinds is more permissive in GHC 8 -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The docs claim that the definition in section 9.11.10 {{{ data G (a :: k) where GInt :: G Int GMaybe :: G Maybe }}} "requires that `-XTypeInType` be in effect", but this isn't the case. The following compiles with GHC-8.0.2: {{{ {-# LANGUAGE PolyKinds, GADTs #-} data G (a :: k) where GInt :: G Int GMaybe :: G Maybe }}} The example does *not* compile with 7.10.3, so this seems to be a case where `-XPolyKinds` has become more permissive in GHC 8 (as outlined in section 9.11.1). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13391> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7401: Can't derive instance for Eq when datatype has no constructor, while it is trivial do do so.
by GHC 29 Sep '17

29 Sep '17

#7401: Can't derive instance for Eq when datatype has no constructor, while it is trivial do do so. -------------------------------------+------------------------------------- Reporter: jpbernardy | Owner: (none) Type: feature request | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: deriving, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #10577, #13117 | Differential Rev(s): Phab:D4047 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => patch * differential: Phab:D978 => Phab:D4047 Comment: Phab:D4047 implements the aforementioned proposal. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7401#comment:52> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14290: Strictness bug with existential contexts on data constructors
by GHC 28 Sep '17

28 Sep '17

#14290: Strictness bug with existential contexts on data constructors -------------------------------------+------------------------------------- Reporter: simonmar | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following: {{{ {-# LANGUAGE ExistentialQuantification #-} module Main (main) where main :: IO () main = r `seq` return () r :: Rec r = Rec{ a = error "xxx", b = 3, c = True } class C t instance C Bool data Rec = forall t. C t => Rec { a :: () , b :: !Int , c :: t } }}} Fails with `error "xxx"`, when it should succeed. The problem is that the strictness signature for the data con wrapper doesn't take into account the dictionary fields. I have a patch which I'll upload to Phabricator shortly... -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14290> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14017: "make install" with non-standard umask causes bad permission on package.cache
by GHC 28 Sep '17

28 Sep '17

#14017: "make install" with non-standard umask causes bad permission on package.cache -------------------------------------+------------------------------------- Reporter: djf | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: None | Version: 8.2.1-rc3 Keywords: | Operating System: Linux Architecture: | Type of failure: Installing GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Using Debian 8 binary package ghc-8.2.1-x86_64-deb8-linux.tar.xz to install with `configure` and then `su` and `make install`. If your umask is 0027 rather than the default 0022, a file doesn't get made world-readable. (Other files in this directory do though.) {{{ $ ls -l /usr/local/lib/ghc-8.2.1/package.conf.d/package.cache -rw-r----- 1 root staff 161490 Jul 23 10:02 /usr/local/lib/ghc-8.2.1/package.conf.d/package.cache }}} It results in this message when trying to use ghc or ghci: {{{ $ ghci GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help /usr/local/lib/ghc-8.2.1/package.conf.d/package.cache: openBinaryFile: permission denied (Permission denied) }}} (n.b. I have set the version field in this bug to 8.2.1-rc3 for now because 8.2.1 isn't in the list yet.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14017> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13497: GHC does not use select()/poll() correctly on non-Linux platforms
by GHC 28 Sep '17

28 Sep '17

#13497: GHC does not use select()/poll() correctly on non-Linux platforms -------------------------------------+------------------------------------- Reporter: nh2 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 8.0.1 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #8684, #12912 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- From my discovery at https://phabricator.haskell.org/D42#30542: {{{ Why does the existing code work on platforms that are not Linux? In my select man page it says: On Linux, select() modifies timeout to reflect the amount of time not slept; most other implementations do not do this. (POSIX.1-2001 per‐ mits either behavior.) This causes problems both when Linux code which reads timeout is ported to other operating systems, and when code is ported to Linux that reuses a struct timeval for multiple select()s in a loop without reinitializing it. Consider timeout to be undefined after select() returns. The existing select loop seems to rely on the fact that &tv is updated as described here. }}} Same for `man 2 poll`. E.g. `man 2 select` on FreeBSD 11 says explicitly: {{{ BUGS Version 2 of the Single UNIX Specification (``SUSv2'') allows systems to modify the original timeout in place. Thus, it is unwise to assume that the timeout value will be unmodified by the select() system call. FreeBSD does not modify the return value, which can cause problems for applications ported from other systems. }}} I have tested this now on FreeBSD, and indeed it doesn't work as expected. With GHC 7.10.2: {{{ import System.IO main = hWaitForInput stdin (1 * 1000) }}} `ghc --make test.hs -rtsopts` {{{ [root@ ~]# time ./test real 0m1.386s user 0m0.004s sys 0m0.000s [root@ ~]# time ./test +RTS -V0.01 real 0m1.386s user 0m0.001s sys 0m0.000s [root@ ~]# time ./test +RTS -V0.001 real 0m1.678s user 0m0.003s sys 0m0.002s [root@ ~]# time ./test +RTS -V0.0001 real 0m11.311s user 0m0.032s sys 0m0.139s }}} See how when we increase the timer signal, the sleep suddenly takes 10x longer than it should. That's because it triggers the case where EINTR is received in https://github.com/ghc/ghc/blob/f46369b8a1bf90a3bdc30f2b566c3a7e03672518%5E…, letting us use the same unmodified 1-second `struct timeval *timeout` again and again. This demo of the bug works for GHC 7.10 and 8.0.1; in 8.0.2 `hWaitForInput` is broken (https://ghc.haskell.org/trac/ghc/ticket/12912#comment:4) so the demo doesn't work there. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13497> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13966: Missed optimization - loop fusion
by GHC 28 Sep '17

28 Sep '17

#13966: Missed optimization - loop fusion -------------------------------------+------------------------------------- Reporter: jmspiewak | Owner: (none) Type: feature | Status: new request | Priority: low | Milestone: Component: Compiler | Version: 8.2.1-rc3 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: -------------------------------------+------------------------------------- I think GHC should be able to optimize func1 into func2, but currently it doesn't. {{{#!hs data Step s a = Done | Yield s a func1 high = loop1 0# 1# where loop1 acc i = case loop2 i of Done -> acc Yield (I# i') (I# x) -> loop1 (acc +# x) i' loop2 i = case tagToEnum# (i ># high) :: Bool of False -> case remInt# i 2# of 0# -> Yield (I# (i +# 1#)) (I# i) _ -> loop2 (i +# 1#) True -> Done func2 high = loop1 0# 1# where loop1 acc i = case tagToEnum# (i ># high) :: Bool of False -> case remInt# i 2# of 0# -> loop1 (acc +# i) (i +# 1#) _ -> loop1 acc (i +# 1#) True -> acc }}} When using the LLVM backend func2 is almost 4x faster than func1. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13966> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11342: Character kind
by GHC 28 Sep '17

28 Sep '17

#11342: Character kind -------------------------------------+------------------------------------- Reporter: alexvieth | Owner: alexvieth Type: feature | Status: new request | 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: -------------------------------------+------------------------------------- We know and love the Symbol kind, but as far as I know it's not possible to analyse a Symbol type, as we would a String term. It would be nice to have a Character kind and some related type families: {{{#!hs data Character -- Pattern match a Symbol. 'Nothing when empty, 'Just '(head, tail) -- otherwise. type family UnconsSymbol (s :: Symbol) :: Maybe (Character, Symbol) -- Put a Character at the head of a Symbol. type family ConsSymbol (c :: Character) (s :: Symbol) :: Symbol -- Work with Characters. Ideally we'd have counterparts for every -- function on Data.Char. type family ToUpper (c :: Character) :: Character type family IsAlpha (c :: Character) :: Bool }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11342> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14280: Aarch64 build is broken
by GHC 28 Sep '17

28 Sep '17

#14280: Aarch64 build is broken -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: aarch64 | Type of failure: Compile-time | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Trying to bootstrap 7446c7f68bd5addd2f2db0d8d5910fb963869c47 on an aarch64 (Debian 8, LLVM 5) box results in a reproducibly segfaulting `ghc-stage2`, {{{ (gdb) run Starting program: /mnt/ext/arm/ghc/inplace/lib/bin/ghc-stage2 -B/mnt/ext/arm/ghc/inplace/lib -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -H32m -O -Wall -hide-all-packages -i -iutils/check-ppr/. -iutils/check-ppr/dist-install/build -Iutils/check-ppr/dist-install/build -iutils/check-ppr/dist-install/build/check-ppr/autogen -Iutils/check-ppr /dist-install/build/check-ppr/autogen -optP-include -optPutils/check-ppr /dist-install/build/check-ppr/autogen/cabal_macros.h -package-id base-4.11.0.0 -package-id bytestring-0.10.8.2 -package-id containers-0.5.10.2 -package-id Cabal-2.0.0.2 -package-id directory-1.3.1.2 -package-id filepath-1.4.1.2 -package-id ghc-8.3 -Wall -XHaskell2010 -no-user-package- db -rtsopts -Wnoncanonical-monad-instances -odir utils/check-ppr/dist- install/build -hidir utils/check-ppr/dist-install/build -stubdir utils /check-ppr/dist-install/build -c utils/check-ppr/./Main.hs -o utils/check- ppr/dist-install/build/Main.dyn_o [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/aarch64-linux- gnu/libthread_db.so.1". [New Thread 0x3fafaff200 (LWP 29429)] Thread 1 "ghc-stage2" received signal SIGSEGV, Segmentation fault. 0x00000000005aa360 in stg_IND_STATIC_info () (gdb) bt #0 0x00000000005aa360 in stg_IND_STATIC_info () #1 0x0000007fb11b3450 in ccib_info$def () from /mnt/ext/arm/ghc/libraries/base/dist- install/build/libHSbase-4.11.0.0-ghc8.3.20170926.so Backtrace stopped: previous frame identical to this frame (corrupt stack?) (gdb) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14280> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14233: Remove old GetTickCount() code path for Windows
by GHC 27 Sep '17

27 Sep '17

#14233: Remove old GetTickCount() code path for Windows ----------------------------------------+--------------------------------- Reporter: nh2 | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.3 Keywords: | Operating System: Windows Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- Windows XP support was dropped since GHC 8.0 as per https://ghc.haskell.org/trac/ghc/wiki/WindowsGhc In `HsWord64 getMonotonicNSec()` on Windows we still fall back to the 32-bit `GetTickCount()` if `QueryPerformanceFrequency()` is not supported: [https://github.com/ghc/ghc/blob/ghc-8.2.1-release/rts/win32/GetTime.c#L69 Code] But [https://msdn.microsoft.com/en- us/library/windows/desktop/ms644905(v=vs.85).aspx Microsoft's documentation] says that `QueryPerformanceFrequency()` is guaranteed to be supported on Windows >= XP: > On systems that run Windows XP or later, the function will always succeed and will thus never return zero. Thus we can remove the `if (!qpc_supported)` check and all `if (!qpc_frequency.QuadPart)` code paths, and replace it with an assertion or a `./configure` check. We can also add a comment that `getMonotonicNSec()` will indeed always make use of the whole 64-bit domain. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14233> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12376: Allow function definitions in record syntax
by GHC 27 Sep '17

27 Sep '17

#12376: Allow function definitions in record syntax -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | 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: -------------------------------------+------------------------------------- Would it be possible to write {{{#!hs propertyMap :: (Monad m, Ord k) => v -> PropertyMap m k v propertyMap v0 = go v0 Map.empty where go v m = PropertyMap { getP = \k -> return $ maybe v id (Map.lookup k m) , putP = \k v' -> return $ go v (Map.insert k v' m) } }}} as {{{#!hs propertyMap :: (Monad m, Ord k) => v -> PropertyMap m k v propertyMap v0 = go v0 Map.empty where go v m = PropertyMap { getP k = return $ maybe v id (Map.lookup k m) , putP k v' = return $ go v (Map.insert k v' m) } }}} Simpler example `MkFoo { id = \x -> x }` as {{{#!hs MkFoo { id x = x } }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12376> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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