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Re: [GHC] #481: Recompilation check fails for TH
by GHC 06 Feb '18

06 Feb '18

#481: Recompilation check fails for TH -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: 7.2.1 Component: Template Haskell | Version: 6.4.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: TH_recompile Blocked By: | Blocking: Related Tickets: #14769 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by nh2): * related: => #14769 Comment: I believe I have found a bug with the current implementation of the `[TH]`/`RecompBecause "TH"` check: It doesn't work when the build is interrupted. See #14769 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/481#comment:21> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12685: getNumProcessors semantics dont match documentation
by GHC 06 Feb '18

06 Feb '18

#12685: getNumProcessors semantics dont match documentation ----------------------------------------+--------------------------------- Reporter: Llgn | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- Hi, The documentation of getNumProcessors says : "Returns the number of CPUs that the machine has", but it is true only for program compiled with -threaded option. https://hackage.haskell.org/package/base-4.9.0.0/docs/GHC-Conc- Sync.html#v:getNumProcessors I guess the documentation is just misleading. Or is it a bug ? Regards -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12685> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14717: Hidden package hints no longer display
by GHC 06 Feb '18

06 Feb '18

#14717: Hidden package hints no longer display -------------------------------------+------------------------------------- Reporter: snoyberg | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This started as a mailing list thread: https://mail.haskell.org/pipermail /haskell-cafe/2018-January/128485.html. Dan Burton demonstrated a reproduction without any build tool. With GHC 8.0.2, when you try to use a module from a hidden package, you get an error message with a helpful hint to add the package to the build- depends. With GHC 8.2.2 (and I believe 8.2.1), it appears that this hint is no longer displayed. To demonstrate, I'll copy Dan's repro: {{{ $ cat Main.hs module Main where import Data.Map main = putStrLn "It compiles" $ ghc-pkg list containers /usr/local/Cellar/ghc/8.2.2/lib/ghc-8.2.2/package.conf.d containers-0.5.10.2 $ ghc --make -hide-all-packages -package base Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Main.hs:2:1: error: Could not find module ‘Data.Map’ Use -v to see a list of the files searched for. | 2 | import Data.Map | ^^^^^^^^^^^^^^^ $ ghc --make -hide-all-packages -package base -package containers Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Linking Main ... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14717> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14693: Computing imp_finst can take up significant amount of time
by GHC 06 Feb '18

06 Feb '18

#14693: Computing imp_finst can take up significant amount of time -------------------------------------+------------------------------------- Reporter: niteria | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I profiled a build of a production code base with thousands of modules and merging `imp_finsts` [1] from different imports came up on top taking up 9% of total compile time. I made a synthetic test case to reproduce the issue (see attached `generateModules`). The test case is basically multiple layers of modules where each module defines a type family instance through deriving Generic. The problem is quite obvious, `unionLists` is quadratic and `imp_finsts` just keeps growing with the size of the code base. [1] https://phabricator.haskell.org/diffusion/GHC/browse/master/compiler/typech… -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14693> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14637: Simplifier Ticks Exhausted when compiling with profiling
by GHC 06 Feb '18

06 Feb '18

#14637: Simplifier Ticks Exhausted when compiling with profiling -------------------------------------+------------------------------------- Reporter: cfhammill | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Hi GHC devs, I've run into a problem with the Frames library, I can compile a simple example using stack without executable profiling enabled, but when I enable profiling I get the simplifier ticks exhausted error. I've tried using -fsimpl-tick-factor=1000 to no avail. I've attached the stack config, cabal file, haskell code, two csv files, and the simplifier dump. Any help would be appreciated. Chris -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14637> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14683: Hole-y partial type signatures lead to slow compile times
by GHC 06 Feb '18

06 Feb '18

#14683: Hole-y partial type signatures lead to slow compile times -------------------------------------+------------------------------------- Reporter: harpocrates | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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 came up while investigating the compile times of Happy grammars: https://github.com/simonmar/happy/issues/109. GHC 8 and later take a lot longer to compile grammars with types that rely on `PartialTypeSignatures` and have lots of wildcards. Example: {{{#!hs happyReduce_6 :: () => Happy_GHC_Exts.Int# -> L Token -> Happy_GHC_Exts.Int# -> Happy_IntList -> HappyStk (HappyAbsSyn _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) -> ParserMonad (HappyAbsSyn _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) }}} There is an example repo (https://github.com/wiz/too-happy) in that thread containing a grammar whose generated code has lots of wildcards. On my laptop, the project takes about 25 seconds to compile on 7.10.3. With 8.0.2, 8.2.2, and HEAD it takes on the order of 4 minutes. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14683> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14396: Hs-boot woes during family instance consistency checks
by GHC 05 Feb '18

05 Feb '18

#14396: Hs-boot woes during family instance consistency checks -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 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: -------------------------------------+------------------------------------- Consider this set of modules (related to #13981 but not the same) {{{ {-# LANGUAGE TypeFamilies #-} module Fam where type family XListPat a {-# LANGUAGE TypeFamilies #-} module T1 where import Fam import {-# SOURCE #-} T( SyntaxExpr ) type instance XListPat Int = SyntaxExpr {-# LANGUAGE TypeFamilies #-} module T2 where import Fam type instance XListPat Bool = Int -- T.hs-boot module T where data SyntaxExpr = S -- T.hs module T where import T1 import T2 data SyntaxExpr = S }}} Compiled with GHC 8.0, 8.2, and HEAD we get {{{ ghc.exe: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-mingw32): tcIfaceGlobal (local): not found You are in a maze of twisty little passages, all alike. While forcing the thunk for TyThing SyntaxExpr which was lazily initialized by initIfaceTcRn, I tried to tie the knot, but I couldn't find SyntaxExpr in the current type environment. If you are developing GHC, please read Note [Tying the knot] and Note [Type-checking inside the knot]. Consider rebuilding GHC with profiling for a better stack trace. Contents of current type environment: [] }}} Reason: * After renaming, but before type checking, we try to do family-instance consistency checking in `FamInst.checkFamInstConsistency` * To do so we have to pull in the axioms from `T1` and `T2`. * Then we poke on those axioms, to check consistency, we pull in both LHS and RHS of the type instances. * Alas that pulls on `SyntaxExpr`, which we have not yet typechecked. I don't think it's enough to make lazier the loading of the RHS of the axiom, because I think `checkFamInstConsistency` ends up looking at the RHS too. See the call to `compatibleBranches` in `lookupFamInstEnvConflicts`. This setup is actually used in Alan's `wip/ttg-2017-10-13` branch for Trees That Grow. Here module `T` is `HsExpr`, `T1` is `HsPat`. And indeed GHC 8.0 crashes when compiling this branch. SO it's becoming a real problem. Generally I'm concerned that #13981 may also become more pressing; and #14080 is still open -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14396> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #481: Recompilation check fails for TH
by GHC 05 Feb '18

05 Feb '18

#481: Recompilation check fails for TH -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonmar Type: bug | Status: closed Priority: normal | Milestone: 7.2.1 Component: Template Haskell | Version: 6.4.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: TH_recompile Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by nh2): * cc: nh2 (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/481#comment:20> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6087: Join points need strictness analysis
by GHC 05 Feb '18

05 Feb '18

#6087: Join points need strictness analysis -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: infoneeded Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: JoinPoints 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: | -------------------------------------+------------------------------------- Comment (by simonpj): We agreed that Omer would invest a small amount of effort to see if any of the other benchmarks that have increased are easier to understand -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6087#comment:24> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8684: hWaitForInput cannot be interrupted by async exceptions on unix
by GHC 05 Feb '18

05 Feb '18

#8684: hWaitForInput cannot be interrupted by async exceptions on unix ------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- http://hackage.haskell.org/package/base-4.6.0.1/docs/System-Timeout.html claims that {{{timeout}}} can interrupt {{{hWaitForInput}}}, but in fact that's false (e.g. mentioned in https://ghc.haskell.org/trac/ghc/ticket/7353#comment:4) {{{ -- import Control.Concurrent import System.IO import System.Timeout main = timeout (1 * 1000000) $ hWaitForInput stdin (5 * 1000) }}} will not be killed after 1 second, but instead wait for the full 5 seconds timeout passed to {{{hWaitForInput}}}. The implementation is {{{ready}}} at http://www.haskell.org/ghc/docs/latest/html/libraries/base/src/GHC-IO- FD.html, where we have two foreign calls: {{{safe fdReady}}} and {{{unsafe unsafe_fdReady}}}. The actual C implementation is at https://github.com/haskell- suite/base/blob/master/cbits/inputReady.c#L16. It uses {{{select}}} on Unix, and does check for {{{EINTR}}}, so I believe that according to http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/ffi.html#ffi- interruptible both foreign calls can be replaced by a single {{{interruptible}}} one. Is that true? If not, it's a documentation bug in {{{timeout}}} at least. Also, does {{{interruptible}}}, apart from allowing the function to be interrupted, behave more like {{{safe}}} or {{{unsafe}}}? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8684> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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