December 2014 - ghc-tickets

[GHC] #9946: Expose the source location of template-haskell Names
by GHC 07 Jan '15

07 Jan '15

#9946: Expose the source location of template-haskell Names -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: Type: feature | Status: new request | Milestone: Priority: low | Version: 7.11 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I've often wanted to know where a particular `Name` is defined (specifically the filepath), but as far as I can tell, template-haskell doesn't currently support this. It'd be really nice to have a function {{{#!hs nameLoc :: Name -> Loc }}} to expose the definition site of the `Name`. I think this should be fairly straightforward to add since GHC carries the definition site around with its `Name`s, but I've never looked at the TH internals. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9946> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9872: Runing type functions is too slow
by GHC 06 Jan '15

06 Jan '15

#9872: Runing type functions is too slow -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Gergo reports, prompted by [http://stackoverflow.com/questions/26538595/more-efficient-type-level- computations-using-type-families this question on Stack Overflow]. I wrote some code today using closed type families and datakinds. Also, as a baseline, I typechecked the code using open type families from the original question. The two files are attached as slow1.hs and slow2.hs below. On GHC 7.8.3, typechecking took about 45 seconds for each. However, on a 'perf' build of GHC 7.9 d8c437b3, with ghc-stage2, the first one took 1m3s and the second one 1m12s. A 40% and 60% increase in typechecking time, respectively! Is this some known regression, something surprising, or is 'perf' simply not the right build flavour for this kind of comparison? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9872> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9939: Warn for duplicate superclass constraints
by GHC 06 Jan '15

06 Jan '15

#9939: Warn for duplicate superclass constraints -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.3 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- With the following code, GHC warns that there are duplicate constraints: {{{#!hs {-# LANGUAGE FlexibleInstances, UndecidableInstances #-} module Foo where class Foo a where foo :: Int -> a instance (Integral a, Integral a) => Foo a where foo x = (fromIntegral x) `div` 2 }}} However, when writing the code, I might start with: {{{#!hs {-# LANGUAGE FlexibleInstances, UndecidableInstances #-} module Foo where class Foo a where foo :: Int -> a instance Foo a where foo x = (fromIntegral x) `div` 2 }}} without any constraints on the instance. GHC complains that it needs `Num a` and `Integral a`, but of course `Num` is implied by `Integral`. I'm ''not'' asking that GHC figure this out on its own and only request the strongest constraint necessary. Rather, I'm suggesting that ''if'' I followed GHC's suggestion and wrote {{{#!hs {-# LANGUAGE FlexibleInstances, UndecidableInstances #-} module Foo where class Foo a where foo :: Int -> a instance (Num a, Integral a) => Foo a where foo x = (fromIntegral x) `div` 2 }}} then GHC should warn {{{ Duplicate constraint(s): Num a In the context: (Num a, Integral a) (Num a) is implied by (Integral a) }}} or something similar. The motivation for this feature request is that in large instances/programs, it is difficult for a human to keep track of superclasses. In large instances, GHC tends to request "weak" constraints first (say `Num`), then ask for progressively stronger constraints (say `Integral`). Again, I'm not suggesting that behavior should change. However, it tends to lead to instances that look like `(Num a, Real a, RealFrac a, RealFloat a) => ...` if by chance I happened to use methods from each class. It seems fairly simple for GHC to look at each constraint for an instance (or function), trace back up the class hierarchy to get a set of all implied constraints, and then warn if one set is a subset of another. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9939> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9508: Rename package key
by GHC 04 Jan '15

04 Jan '15

#9508: Rename package key -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Keywords: backpack | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- We were planning on renaming package key to something different. The two proposals on the table are "package instance" (which I don't like) and "library ID". -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9508> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9891: Fixity declarations for pattern synonyms not persisted
by GHC 03 Jan '15

03 Jan '15

#9891: Fixity declarations for pattern synonyms not persisted -------------------------------------+------------------------------------- Reporter: klkblake | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Incorrect Blocked By: | result at runtime Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- It appears fixity declarations for pattern synonyms only affect modules being compiled in the same run as the module the definition is in. For example, take the following files: Foo.hs: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Foo where data Type = Type Int RawType data RawType = Product Type Type | Num pattern a :*: b <- Type _ (Product a b) infixr 7 :*: }}} Bar.hs: {{{#!hs {-# LANGUAGE PatternSynonyms #-} module Main where import Foo value = Type 0 $ Product (Type 1 Num) $ Type 2 $ Product (Type 3 Num) $ Type 4 Num somethingElse = 23 main = case value of _ :*: _ :*: _ -> putStrLn "Success" _ -> putStrLn "Fail" }}} On the first compile, the executable will print "Success". Modifying Bar and recompiling will result in it printing "Fail". Modifying both and recompiling results in "Success" again. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9891> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9495: Do What I Mean RULES for foldr2 look shady
by GHC 02 Jan '15

02 Jan '15

#9495: Do What I Mean RULES for foldr2 look shady -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | crash Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- There's a comment in the source: {{{ The foldr2/right rule isn't exactly right, because it changes the strictness of foldr2 (and thereby zip) E.g. main = print (null (zip nonobviousNil (build undefined))) where nonobviousNil = f 3 f n = if n == 0 then [] else f (n-1) I'm going to leave it though. }}} This rule is intended to allow `foldr2` to fuse with ''either'' argument list. There are thus two problems, one already documented and the other not: 1. The rule can turn working code into non-working code, although this seems to be ''relatively'' unlikely. (The problem the above example is showing is that if the left list ends at the same time the right list bottoms out, the world goes boom. So `foldr2 f [1,2,3,4] (1:2:3:4:undefined)` appears to be a problem. You could argue this is not a big deal, I suppose. 2. The `foldr2/left` and `foldr2/right` rules are not confluent. They are both active in all phases, but if both list arguments are good producers, they will each want to rewrite the expression differently. So if you actually care about which one fuses, you need to explicitly block fusion with one argument using `NOINLINE`, which of course could easily muck up some other optimization. My uninformed opinion: nix the `foldr2/right` rule, and change the documentation to indicate that `foldr2` fuses with its ''left'' argument. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9495> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9852: Add missing export lists
by GHC 31 Dec '14

31 Dec '14

#9852: Add missing export lists -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: task | Status: new Priority: low | Milestone: Component: Core Libraries | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Moderate (less | Type of failure: than a day) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Some large modules, including `GHC.Base`, lack export lists, implicitly exporting all top-level identifiers. This is bad for various reasons, all of them obvious. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9852> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9944: Performance issue
by GHC 31 Dec '14

31 Dec '14

#9944: Performance issue -------------------------------------+------------------------------------- Reporter: clinton | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- The runtime of the following code actually decreases if the number 2147483647 (2^31-1) is increased to 2147483648 (2^31). {{{#!hs f n = go 1 0 where go i c = if i == n then c + i else go (i+1) (c+i) main = print $ f (2147483647 :: Int) }}} I've attached two dumps from ghc-core, core7 is the 2147483647 case and core8 is the 2147483648 case, however the main differences are below: '''2147483647 case:''' {{{ _c3Qg: cmpq $2147483647,%r14 jne _c3Q9 _c3Qa: leaq 2147483647(%rsi),%rbx jmp *(%rbp) _c3Q9: addq %r14,%rsi incq %r14 jmp _c3Qg }}} '''2147483648 case:''' {{{ _c3Qg: movl $2147483648,%eax cmpq %rax,%r14 jne _c3Q9 _c3Qa: movl $2147483648,%eax movq %rsi,%rbx addq %rax,%rbx jmp *(%rbp) _c3Q9: addq %r14,%rsi incq %r14 jmp _c3Qg }}} Despite the extra instructions, the latter approach seems faster for my PC. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9944> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9942: install GHC 7.8.1 at Ubuntu 13.10
by GHC 31 Dec '14

31 Dec '14

#9942: install GHC 7.8.1 at Ubuntu 13.10 -------------------------------------+------------------------------------- Reporter: | Owner: derekbarnes361 | Status: new Type: feature | Milestone: request | Version: 7.8.4 Priority: lowest | Operating System: Unknown/Multiple Component: Compiler | Type of failure: None/Unknown Keywords: | Blocked By: Architecture: | Related Tickets: Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Because you are on a unix-like system (Ubuntu) you can do the following: Choose a folder you like for installing ghc (e.g. in a subfolder of your home directory like $HOME/ghc7.8.1 or in a subfolder of /opt like /opt/ghc7.8.1 – I would prefer the later one if you are the only user of your computer and the first one if this isn't the case). See this wikipedia article for explanations about the unix directory structure. Download the source code into that folder and follow the installation instructions: See also https://ghc.haskell.org/trac/ghc/wiki/Building/Using#Runtheconfigurescript In configure setp its important, that you set the --prefix to the folder you have chosen above (if you don't do this, ghc will be installed in /usr/local/ which you do not want)! For example: ./configure --prefix=/opt/ghc7.8.1 After the installations look for the folder with the created binaries (it will be called bin if you did not use another name for bindir). Lets imagine this folder is /opt/ghc7.8.1/bin. Now you have two possibilities: Solution with creating symlinks: Create symlinks in a folder which is in your $PATH pointing to the created binaries (for example /usr/local/bin or $HOME/bin – I would use the first one, if you are the only user on your computer and the second if, if you are not). Therefore you have to use the command line tool ln. For example: sudo ln -s -T /opt/ghc7.8.1/bin/runghc /usr/local/bin/runghc7.8.1 After this command there is a file /usr/local/bin/runghc7.8.1 pointing to the binary /opt/ghc7.8.1/bin/runghc. Executing /usr/local/bin/runghc7.8.1 via typing runghc7.8.1 will now execute the runghc binary created in /opt (Note: sudo is not necessary if you create your symlink in $HOME/bin – it is just needed because root can create files under /usr) Solution with bash aliases: Write in your $HOME/.bash_aliases (@Others: you can alternatively choose $HOME/.bashrc or $HOME/.profile depending of your system/preference) the following line: alias runghc7.8.1='/opt/ghc7.8.1/bin/runghc' Now typing runghc7.8.1 in your terminal is an shortcut (alias) for typing /opt/ghc7.8.1/bin/runghc and will execute this binary. Note, that with this solution typing runghc7.8.1 will just work, when you typed it into your terminal. There are cases, when it does not work (for example calling runghc7.8.1 in a script). Send From: [http://www.vigrxtrial.net/] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9942> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9941: How do I install GHC 7.8.1 and assign it a different command?
by GHC 31 Dec '14

31 Dec '14

#9941: How do I install GHC 7.8.1 and assign it a different command? -------------------------------------+------------------------------------- Reporter: | Owner: derekbarnes361 | Status: new Type: bug | Milestone: Priority: lowest | Version: 7.8.4 Component: Compiler | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I would like to install GHC 7.8.1, but would like to assign it different commands, so as not to clash with 7.6.3. For example: runghc with runghc7.8.1 ghci with ghci7.8.1 etc... Or similar. (ghci would be most important, for typed holes.) Basically, I want to be able to use GHC 7.8 and 7.6, so if there is a more direct way to do this tell me (A-B problem.) Note: Ubuntu 13.10 Send From : https://www.smore.com/v6vm-penomet-hydro-pump -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9941> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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