April 2016 - ghc-tickets

[GHC] #11795: Performance issues with replicateM_
by GHC 11 Apr '16

11 Apr '16

#11795: Performance issues with replicateM_ -------------------------------------+------------------------------------- Reporter: snoyberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.10.3 libraries/base | Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When working on optimizing a program by minimizing allocations, I can into an issue with `replicateM_`. Consider the following code {{{#!hs import Control.Monad (replicateM_) import Foreign.C.String (withCString) import Foreign.Storable (peek) main :: IO () main = withCString "foo" $ replicateM_ 10000000 . peek }}} When I run this program, I get: 160,042,656 bytes allocated in the heap The result is the same whether I compile with `-O0`, `-O`, or `-O2`. And as expected, the total allocation increases or decreases based on the numbers of times I replicate the action. On the other hand, replacing `replicateM_` with a hand-written version makes the total allocations for the program only 42KB, and does not increase with the numbers of replications. {{{#!hs replicateM_ :: Monad m => Int -> m a -> m () replicateM_ cnt0 f = loop cnt0 where loop cnt | cnt <= 0 = return () | otherwise = f >> loop (cnt - 1) }}} By contrast, `Control.Monad.replicateM_` looks like: {{{#!hs replicateM_ :: (Monad m) => Int -> m a -> m () {-# INLINEABLE replicateM_ #-} {-# SPECIALISE replicateM_ :: Int -> IO a -> IO () #-} {-# SPECIALISE replicateM_ :: Int -> Maybe a -> Maybe () #-} replicateM_ n x = sequence_ (replicate n x) }}} I can't see an advantage to this implementation over the more direct implementation I've provided above. Unless there are objections, I'll send a patch to switch the implementation. (Since master already uses `Applicative`, I'll make the relevant updates to generalize the function signature too.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11795> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4275: add tests for and fix "-dynload wrapper", or remove it
by GHC 10 Apr '16

10 Apr '16

#4275: add tests for and fix "-dynload wrapper", or remove it -------------------------------------+--------------------------------- Reporter: igloo | Owner: Type: bug | Status: closed Priority: high | Milestone: 7.0.1 Component: Compiler | Version: 6.13 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: -------------------------------------+--------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"f3beed35309e4e8b60aa3f11372d1e00324eb046/ghc" f3beed35/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="f3beed35309e4e8b60aa3f11372d1e00324eb046" Remove left-over shell-tools.c The last user of this file was the "-dynload wrapper" which was removed in 169f5972d5398e75c4cf7f831b6ce703288ec73c for addressing #4275 Reviewers: austin, erikd, bgamari Reviewed By: bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2098 GHC Trac Issues: #4275 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4275#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5939: Standalone deriving Generic on type with instantiated arguments
by GHC 10 Apr '16

10 Apr '16

#5939: Standalone deriving Generic on type with instantiated arguments -------------------------------------+------------------------------------- Reporter: dreixel | Owner: dreixel Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.5 Resolution: fixed | Keywords: Generics Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | GenCannotDoRep0 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"7443e5c8dae24b83f5f4975c7accce02b819029c/ghc" 7443e5c8/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="7443e5c8dae24b83f5f4975c7accce02b819029c" Remove the instantiation check when deriving Generic(1) Previously, deriving `Generic(1)` bailed out when attempting to instantiate visible type parameters (#5939), but this instantiation check was quite fragile and doesn't interact well with `-XTypeInType`. It has been decided that `Generic(1)` shouldn't be subjected to this check anyway, so it has been removed, and `gen_Generic_binds`'s machinery has been updated to substitute the type variables in a generated `Rep`/`Rep1` instance with the user-supplied type arguments. In addition, this also refactors `Condition` in `TcDeriv` a bit. Namely, since we no longer need `tc_args` to check any conditions, the `[Type]` component of `Condition` has been removed. Fixes #11732. Test Plan: ./validate Reviewers: goldfire, kosmikus, simonpj, bgamari, austin Reviewed By: simonpj, bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2061 GHC Trac Issues: #5939, #11732 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5939#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11803: Users guide's `_static` directory isn't installed to correct location
by GHC 10 Apr '16

10 Apr '16

#11803: Users guide's `_static` directory isn't installed to correct location -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-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: -------------------------------------+------------------------------------- In the binary distributions the `_static` directory which contains CSS and other static resources gets installed to `share/doc/ghc-$VER/html/_static` whereas it is expected to live in `share/doc/ghc-$VER/html/users_guide/_static`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11803> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4114: Add a flag to remove/delete intermediate files generated by GHC
by GHC 10 Apr '16

10 Apr '16

#4114: Add a flag to remove/delete intermediate files generated by GHC -------------------------------------+------------------------------------- Reporter: guest | Owner: kaiha Type: feature request | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 6.10.4 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #2258 | Differential Rev(s): Phab:D2021 Wiki Page: | Phab:D2050 -------------------------------------+------------------------------------- Comment (by kaiha): Is there a reason why this ticket is still open? Must I reassign it to someone? Is it me who should set this ticket to close? Or is there still something missing? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4114#comment:30> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11806: GHC does not warn for mistakenly empty case
by GHC 09 Apr '16

09 Apr '16

#11806: GHC does not warn for mistakenly empty case -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE EmptyCase #-} {-# OPTIONS_GHC -Wall -fwarn-incomplete-uni-patterns #-} oops :: Int -> a oops x = case x of {} }}} Since `Int` is inhabited, I would expect a warning, but I get none. Since empty case is typically used in situations where programmers want GHC to see an absurdity, this seems most unfortunate. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11806> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11546: Compiler warning: cast from pointer to integer of different size
by GHC 09 Apr '16

09 Apr '16

#11546: Compiler warning: cast from pointer to integer of different size -------------------------------------+------------------------------------- Reporter: wereHamster | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 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: -------------------------------------+------------------------------------- While building the stage1 compiler: {{{ In file included from rts/Capability.h:25:0, from includes/dist-derivedconstants/header/tmp.c:15: rts/Task.h: In function 'serialiseTaskId': rts/Task.h:318:12: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] return (TaskId) taskID; ^ }}} I'm building a cross-compiler with build/host=x86_64-linux-gnu and target =mips-unknown-linux-musl -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11546> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7669: Empty case causes warning
by GHC 09 Apr '16

09 Apr '16

#7669: Empty case causes warning -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: closed Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.7 Resolution: duplicate | Keywords: EmptyCase, | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Incorrect | Test Case: warning at compile-time | deSugar/should_compile/T7669 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by gkaracha): * keywords: EmptyCase => EmptyCase, PatternMatchWarnings -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7669#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11801: RFC: Make browse command display everything unqualified
by GHC 08 Apr '16

08 Apr '16

#11801: RFC: Make browse command display everything unqualified -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: lowest | Milestone: Component: GHCi | Version: 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: -------------------------------------+------------------------------------- What the title says, sometimes the output of `:browse` (`:bro`) is highly verbose. If you want unqualified names you need to (as far as I know) import the modules in question, even then names may still be qualified if they clash with names from other modules in scope. {{{ ghci> :browse Control.Applicative.Free data Control.Applicative.Free.Ap (f :: * -> *) a where Control.Applicative.Free.Pure :: a -> Control.Applicative.Free.Ap f a Control.Applicative.Free.Ap :: (f a1) -> (Control.Applicative.Free.Ap f (a1 -> a)) -> Control.Applicative.Free.Ap f a Control.Applicative.Free.hoistAp :: (forall a. f a -> g a) -> Control.Applicative.Free.Ap f b -> Control.Applicative.Free.Ap g b }}} versus {{{ ghci> :newbrowse Control.Applicative.Free data Ap (f :: * -> *) a where Pure :: a -> Ap f a Ap :: (f a1) -> (Ap f (a1 -> a)) -> Ap f a hoistAp :: (forall a. f a -> g a) -> Ap f b -> Ap g b ... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11801> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11529: Show instance of Char should print literals for non-ascii printable charcters
by GHC 08 Apr '16

08 Apr '16

#11529: Show instance of Char should print literals for non-ascii printable charcters -------------------------------------+------------------------------------- Reporter: nushio | 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: -------------------------------------+------------------------------------- Show instance for non-ascii characters prints their character codes. This is sad for Haskell users that speaks language other than English. {{{#!hs > 'A' 'A' > 'Ä' '\196' > '漢' '\28450' > print $ [(++"'s dad"), (++"'s mom")] <*> ["Simon", "John"] ["Simon's dad","John's dad","Simon's mom","John's mom"] > print $ [(++"の父"), (++"の母")] <*> ["田中", "山田"] ["\30000\20013\12398\29238","\23665\30000\12398\29238","\30000\20013\12398\27597","\23665\30000\12398\27597"] }}} The function that needs improvement is showLitChar in GHC.Show, which currently prints any character larger than ASCII code 127 by its character code: http://haddock.stackage.org/lts-5.1/base-4.8.2.0/src/GHC-Show.html {{{#!hs showLitChar :: Char -> ShowS showLitChar c s | c > '\DEL' = showChar '\\' (protectEsc isDec (shows (ord c)) s) }}} On the other hand, there is GHC.Unicode.isPrint, the predicate for printable Unicode characters, that is calling on a foreign function u_iswprint for the knowledge. https://hackage.haskell.org/package/base-4.8.2.0/docs/src/GHC.Unicode.html#… I think one of the solution is to import and call u_iswprint from GHC.Show, too, but I don't know it's against any design choices. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11529> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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