July 2017 - ghc-tickets

[GHC] #12670: Representation polymorphism validity check is too strict
by GHC 22 Dec '17

22 Dec '17

#12670: Representation polymorphism validity check is too strict -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: typeable | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- As of 465c6c5d15f8fb54afb78408f3a79e75e74d2cd4 GHC rejects this program, {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE RankNTypes #-} module Hi where import GHC.Exts data TypeRep (a :: k) where TrFun :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep) (a :: TYPE r1) (b :: TYPE r2). TypeRep a -> TypeRep b -> TypeRep (a -> b) }}} Claiming that it has inappropriate polymorphism over `RuntimeRep`, {{{ $ ghc hi2.hs [1 of 1] Compiling Hi ( hi2.hs, hi2.o ) hi2.hs:7:5: error: • A representation-polymorphic type is not allowed here: Type: a Kind: TYPE r1 • In the definition of data constructor ‘TrFun’ In the data type declaration for ‘TypeRep’ }}} I suspect this check is unnecessarily strict since we never need to store a value of type `a` to represent `TypeRep a` at runtime. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12670> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12512: UnboxedTupleRep-related panic involving typeclasses
by GHC 20 Dec '17

20 Dec '17

#12512: UnboxedTupleRep-related panic involving typeclasses -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: #11723 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- You can trigger a GHC panic by abusing `UnboxedTupleRep` in just the right way: {{{#!hs {-# LANGUAGE DataKinds #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE UnboxedTuples #-} import GHC.Exts class Wat (a :: TYPE 'UnboxedTupleRep) deriving instance Wat (# a, b #) }}} {{{ $ /opt/ghc/8.0.1/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): newTyConEtadArity (#,#) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} This is probably a leak that #11723 didn't plug, as it only considered datatypes, not typeclasses. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12512> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9244: Compiler could warn about type variable shadowing, and hint about ScopedTypeVariables
by GHC 18 Dec '17

18 Dec '17

#9244: Compiler could warn about type variable shadowing, and hint about ScopedTypeVariables -------------------------+------------------------------------------------- Reporter: | Owner: stusmith | Status: new Type: | Milestone: feature request | Version: 7.6.3 Priority: | Operating System: Unknown/Multiple normal | Type of failure: Incorrect warning at Component: | compile-time Compiler | Test Case: Keywords: | Blocking: Architecture: | Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- GHC already warns about variable shadowing: {{{ timesTwoPlusOne x = timesTwo x + 1 where timesTwo x = x * 2 Warning: This binding for `x' shadows the existing binding bound at <location> }}} However the similar warning doesn't happen for type variables. {{{ tryMaybe :: IO a -> IO (Maybe a) tryMaybe action = do result <- (try action) :: IO (Either SomeException a) return $ case result of Left _ -> Nothing Right v -> Just v Couldn't match type `a' with `a1' `a' is a rigid type variable bound by the type signature for tryMaybe :: IO a -> IO (Maybe a) at types.hs:<line>:13 `a1' is a rigid type variable bound by an expression type signature: IO (Either SomeException a1) at types.hs:<line>:15 Expected type: IO a1 Actual type: IO a ... }}} Here, I thought that the 'a' in the function's type declaration was the same 'a' in the expression type declaration. However in Haskell 98, they are completely different variables. Suggestion: if a type variable is renamed by the compiler due to a clash with another type variable, issue a warning that the second shadows the first, and give a hint about using -XScopedTypeVariables and forall. Alternative suggestion: if an error is displayed, where the error contains a renamed type variable, issue a hint that the second shadows the first, and give a hint about using -XScopedTypeVariables and forall. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9244> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13627: IndexError: pop from empty list
by GHC 16 Dec '17

16 Dec '17

#13627: IndexError: pop from empty list -------------------------------------+------------------------------------- Reporter: Lemming | Owner: (none) Type: bug | Status: new 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: -------------------------------------+------------------------------------- ==== How to Reproduce ==== While doing a GET operation on `/attachment/ticket/13626/`, Trac issued an internal error. ''(please provide additional details here)'' Request parameters: {{{ {u'action': u'new', 'path': u'13626/', 'realm': u'ticket'} }}} User agent: `#USER_AGENT#` ==== System Information ==== ''Systeminformation nicht verfügbar'' ==== Enabled Plugins ==== ''Plugininformation nicht verfügbar'' ==== Interface Customization ==== ''Interface customization information not available'' ==== Python Traceback ==== {{{ Traceback (most recent call last): File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 623, in _dispatch_request dispatcher.dispatch(req) File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 259, in dispatch iterable=chrome.use_chunked_encoding) File "build/bdist.linux-x86_64/egg/trac/web/chrome.py", line 1164, in render_template encoding='utf-8') File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 184, in render return encode(generator, method=method, encoding=encoding, out=out) File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 58, in encode for chunk in iterator: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 350, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 829, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 669, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 774, in __call__ for kind, data, pos in chain(stream, [(None, None, None)]): File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 594, in __call__ for ev in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "build/bdist.linux-x86_64/egg/trac/web/chrome.py", line 1431, in _strip_accesskeys for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "build/bdist.linux-x86_64/egg/trac/web/chrome.py", line 1420, in _generate for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 706, in _unmark for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 1101, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 118, in __iter__ event = self.stream.next() File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 734, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 702, in _mark for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 362, in _match content = list(content) File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 326, in _match for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 178, in _generate for event in msgbuf.translate(gettext(msgbuf.format())): File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 1051, in translate events = self.events[order].pop(0) IndexError: pop from empty list }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13627> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13418: IndexError: pop from empty list
by GHC 16 Dec '17

16 Dec '17

#13418: IndexError: pop from empty list -------------------------------------+------------------------------------- Reporter: ralf | Owner: (none) Type: bug | Status: new 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: -------------------------------------+------------------------------------- ==== How to Reproduce ==== While doing a GET operation on `/attachment/ticket/13417/`, Trac issued an internal error. ''(please provide additional details here)'' Request parameters: {{{ {u'action': u'new', 'path': u'13417/', 'realm': u'ticket'} }}} User agent: `Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.76 Safari/537.36` ==== System Information ==== ''Systeminformation nicht verfügbar'' ==== Enabled Plugins ==== ''Plugininformation nicht verfügbar'' ==== Interface Customization ==== ''Interface customization information not available'' ==== Python Traceback ==== {{{ Traceback (most recent call last): File "/usr/local/lib/python2.7/dist-packages/trac/web/main.py", line 613, in _dispatch_request dispatcher.dispatch(req) File "/usr/local/lib/python2.7/dist-packages/trac/web/main.py", line 273, in dispatch iterable=chrome.use_chunked_encoding) File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1159, in render_template encoding='utf-8') File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 184, in render return encode(generator, method=method, encoding=encoding, out=out) File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 58, in encode for chunk in iterator: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 350, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 829, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 669, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 774, in __call__ for kind, data, pos in chain(stream, [(None, None, None)]): File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 594, in __call__ for ev in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1426, in _strip_accesskeys for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1415, in _generate for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 706, in _unmark for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 1101, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 118, in __iter__ event = self.stream.next() File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 734, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 702, in _mark for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 362, in _match content = list(content) File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 326, in _match for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 178, in _generate for event in msgbuf.translate(gettext(msgbuf.format())): File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 1051, in translate events = self.events[order].pop(0) IndexError: pop from empty list }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13418> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8272: testing if SpLim=$rbp and Sp=$rsp changed performance at all
by GHC 15 Dec '17

15 Dec '17

#8272: testing if SpLim=$rbp and Sp=$rsp changed performance at all ----------------------------------------------+---------------------------- Reporter: carter | Owner: carter Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.7 Keywords: callingConvention | Operating System: Architecture: x86_64 (amd64) | Unknown/Multiple Difficulty: Project (more than a week) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- testing if SpLim=$rbp and Sp=$rsp changed performance at all would need a stack check but then push could be used to spill to the stack Idea via Nathan Howell. At the very least, the x86 PUSH instruction has a more succinct encoding than MOV. worth hacking out to see if this can measurable shift ghc perf on nofib or not. this would be part of a larger effort to explore ways to improve GHC's calling convention for modern hardware -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8272> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11203: Kind inference with SigTvs is wrong
by GHC 15 Dec '17

15 Dec '17

#11203: Kind inference with SigTvs is wrong -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 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: -------------------------------------+------------------------------------- Consider {{{#!hs data SameKind :: k -> k -> * data Q (a :: k1) (b :: k2) c = MkQ (SameKind a b) }}} This code should be rejected. Yet it is accepted. The problem is that, when kind-checking a datatype declaration without a CUSK, GHC uses `SigTv`s for user-written kind variables. `SigTv`s are allowed to unify with other `SigTv`s, leading to incorrect behavior here. The motivating scenario is this: {{{#!hs data T (a :: k1) x = MkT (S a ()) data S (b :: k2) y = MkS (T b ()) }}} This program should be accepted. Neither type has a CUSK and therefore is not generalized before kind-checking the group. GHC must then unify `k1` and `k2`. If they were skolems, this unification would fail and this pair of definitions would be rejected. This ticket is identical in spirit to #9201, but that example has a CUSK and thus works. The bug can happen only when there is no CUSK. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11203> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12372: bug: documentation for Control.Monad.guard not useful after AMP
by GHC 14 Dec '17

14 Dec '17

#12372: bug: documentation for Control.Monad.guard not useful after AMP -------------------------------------+------------------------------------- Reporter: ntc2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.0.1 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Since the AMP refactor, the documentation for `Control.Monad.guard` [1] is no longer useful for beginners. It simply gives the definition of `guard`, but in prose: {{{ guard b is pure () if b is True, and empty if b is False. }}} (and better to just use Haskell instead of prose here, no?) To use `guard` in a `MonadPlus`, you now need to know that `Alternative` is a super class of `MonadPlus`, and that `mzero = zero`. The documentation [2] for `MonadPlus` doens't mention `mzero = zero` in the default definition -- you must look at the source for that -- and the docs for `guard` don't mention `MonadPlus`. The documentation for `Control.Monad.guard` should suggest use with `MonadPlus`, and give an example (compare with the very helpful example for `Control.Monad.when`). A non-monadic example would also be useful. [1] https://hackage.haskell.org/package/base-4.9.0.0/docs/Control- Monad.html#v:guard [2] https://hackage.haskell.org/package/base-4.9.0.0/docs/Control- Monad.html#t:MonadPlus -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12372> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9364: GHCi (or haskeline?) confused by non-single-width characters
by GHC 13 Dec '17

13 Dec '17

#9364: GHCi (or haskeline?) confused by non-single-width characters -------------------------------------+------------------------------------- Reporter: cheater | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.8.3 Keywords: linux, terminal, | Operating System: colour, color, prompt | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Hi, there's an issue in the GHCi prompt. To reproduce: 1. Do everything in Linux (I don't have other operating systems); I'm using a version of the gnome 2 gnome-terminal. 2. Use the following to colourise the prompt in GHCi: echo -e :set prompt '"\033[32;1m%s\033[34;1m>\033[0m "' >> ~/.ghc/ghci.conf 3. Import quite a few modules (say, 5 to 10 should be enough) 4. Give the prompt enough text that it wraps around. It's best if you start the text with -- so that it's a comment and doesn't produce any output. For example, say I entered "-- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb", I now see the following: *Types Control.Monad.Writer Control.Monad Data.Functor Control.Applicative Data.Monoid> -- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb (do note that the first set of b's is located on the same line as the prompt, and the second is located under the prompt) 5. Press Enter. You should now see: *Types Control.Monad.Writer Control.Monad Data.Functor Control.Applicative Data.Monoid> -- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb *Types Control.Monad.Writer Control.Monad Data.Functor Control.Applicative Data.Monoid> 6. Press Ctrl-P or the up arrow key to select the previous history item. You will now see the following: *Types Control.Monad.Writer Control.Monad Data.Functor Control.Applicative Data.Monoid> -- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb *Types Control.Monad.Writer Control.Monad Data.Functor Control.Applicative Data.Monoid> -- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb 7. Press Ctrl-A or the Home cursor key to go to the beginning of the text entry, and then type X. You will now see the last prompt to be: *Types Control.Monad.Writer Control.Monad Data.Functor Control.Applicative Data.Monoid> -- bbbbbbbbbbbbX-- bbbbbbbbbbbbbbbbb bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb 8. If you press Enter, you will find out that prompt was actually (without line breaks): X-- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb I tried resizing the terminal window to 45 chars to make the lines above shorter; I imported Data.Monoid and Data.Functor in a new GHCi. The prompt contained garbage, most likely badly wrapped escape codes. See attachment. As both likely are a single bug in disguise, I include both reports in this ticket. Creating a test case for whether things actually work in a terminal might be difficult, but creating test for whether things get wrapped correctly (and not testing how things work out in a terminal) should be simple if annoying. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9364> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13210: Can't run terminfo code in GHCi on Windows
by GHC 12 Dec '17

12 Dec '17

#13210: Can't run terminfo code in GHCi on Windows -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 8.0.2 System (Linker) | Keywords: | Operating System: Windows Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It's possible this is a duplicate of another runtime linker on Windows issue out there, but I'll post this just in case this really is a unique case. I was attempting to compile the `terminfo` library on Windows, and I actually made it surprisingly far--but I quickly stumbled when I actually tried to run some code in GHCi. First, make sure you have a native Windows version of `ncurses` installed. On MSYS2: {{{ $ pacman -S mingw-w64-x86_64-ncurses }}} And here's a stripped-down version of `terminfo`, which I'll use to demonstrate the bug: {{{#!hs module Main where import Control.Exception import Foreign import Foreign.C.String import Foreign.C.Types data TERMINAL newtype Terminal = Terminal (ForeignPtr TERMINAL) -- Use "unsafe" to make set_curterm faster since it's called quite a bit. foreign import ccall unsafe set_curterm :: Ptr TERMINAL -> IO (Ptr TERMINAL) foreign import ccall "&" del_curterm :: FunPtr (Ptr TERMINAL -> IO ()) foreign import ccall setupterm :: CString -> CInt -> Ptr CInt -> IO () setupTerm :: String -> IO Terminal setupTerm term = withCString term $ \c_term -> with 0 $ \ret_ptr -> do -- NOTE: I believe that for the way we use terminfo -- (i.e. custom output function) -- this parameter does not affect anything. let stdOutput = 1 -- Save the previous terminal to be restored after calling setupterm. old_term <- set_curterm nullPtr -- Call setupterm and check the return value. setupterm c_term stdOutput ret_ptr ret <- peek ret_ptr if (ret /=1) then throwIO $ SetupTermError $ "Couldn't look up terminfo entry " ++ show term else do cterm <- set_curterm old_term fmap Terminal $ newForeignPtr del_curterm cterm data SetupTermError = SetupTermError String instance Show SetupTermError where show (SetupTermError str) = "setupTerm: " ++ str instance Exception SetupTermError where main :: IO () main = do Terminal t <- setupTerm "xterm" print t }}} If you compile this code, it "works" (in the sense that it'll actually call the C code): {{{ $ ghc -lncursesw Terminfo.hs [1 of 1] Compiling Main ( Terminfo.hs, Terminfo.o ) Linking Terminfo.exe ... $ ./Terminfo Terminfo.exe: setupTerm: Couldn't look up terminfo entry "xterm" }}} But attempting to run the same code in GHCi is a disaster: {{{ $ runghc -lncursesw Terminfo.hs ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `nanosleep' ghc.exe: Could not on-demand load symbol '_nc_cookie_init' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_cookie_init' ghc.exe: Could not on-demand load symbol '.refptr._nc_wacs' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `.refptr._nc_wacs' ghc.exe: Could not on-demand load symbol '_nc_WIN_DRIVER' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_WIN_DRIVER' ghc.exe: Could not on-demand load symbol '_nc_get_driver' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_get_driver' ghc.exe: Could not on-demand load symbol '_nc_setupterm_ex' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_setupterm_ex' ghc.exe: Could not on-demand load symbol 'newterm' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `newterm' ghc.exe: Could not on-demand load symbol '.refptr._nc_globals' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `.refptr._nc_globals' ghc.exe: Could not on-demand load symbol '_nc_err_abort' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_err_abort' ghc.exe: Could not on-demand load symbol 'tparm' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `tparm' ghc.exe: Could not on-demand load symbol '.refptr._nc_prescreen' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `.refptr._nc_prescreen' ghc.exe: Could not on-demand load symbol '_nc_outch_sp' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_outch_sp' ghc.exe: Could not on-demand load symbol '.refptr._nc_outch_sp' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `.refptr._nc_outch_sp' ghc.exe: Could not on-demand load symbol '_nc_scrolln_sp' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_scrolln_sp' ghc.exe: Could not on-demand load symbol '.refptr.SP' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `.refptr.SP' ghc.exe: Could not on-demand load symbol '.refptr.cur_term' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `.refptr.cur_term' ghc.exe: Could not on-demand load symbol '_nc_ospeed' ghc.exe: C:/msys64/mingw64/lib/../lib/libncursesw.a: unknown symbol `_nc_ospeed' ghc.exe: Could not on-demand load symbol 'set_curterm' Terminfo.hs: ByteCodeLink: can't find label During interactive linking, GHCi couldn't find the following symbol: set_curterm This may be due to you not asking GHCi to load extra object files, archives or DLLs needed by your current session. Restart GHCi, specifying the missing library using the -L/path/to/object/dir and -lmissinglibname flags, or simply by naming the relevant files on the GHCi command line. Alternatively, this link failure might indicate a bug in GHCi. If you suspect the latter, please send a bug report to: glasgow-haskell-bugs(a)haskell.org }}} Also reproducible on GHC HEAD. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13210> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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