March 2016 - ghc-tickets

[GHC] #8901: (very) bad inline heuristics
by GHC 25 Jan '17

25 Jan '17

#8901: (very) bad inline heuristics ------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- I observe a bad case for inlining blowup for the time library. Observed for 7.7, just checked in 7.9. The problem is so bad that the PowerPC32 assembler cannot resolve cross- routine references. (I have no error message at hand, but could try to get one.) Instead here are the stats for x86, with inlining and certain inlining suppressed. The architecture seems irrelevant. {{{ $ file ./libraries/time/dist-install/build/Data/Time/Format.o ./libraries/time/dist-install/build/Data/Time/Format.o: Mach-O object i386 $ ls -l ./libraries/time/dist-install/build/Data/Time/Format.* -rw-r--r-- 1 ggreif staff 61875 Mar 15 16:48 ./libraries/time/dist- install/build/Data/Time/Format.dyn_hi -rw-r--r-- 1 ggreif staff 450864 Mar 15 16:48 ./libraries/time/dist- install/build/Data/Time/Format.dyn_o -rw-r--r-- 1 ggreif staff 61863 Mar 15 16:48 ./libraries/time/dist- install/build/Data/Time/Format.hi -rw-r--r-- 1 ggreif staff 332216 Mar 15 16:48 ./libraries/time/dist- install/build/Data/Time/Format.o }}} With following patch applied: <https://github.com/ggreif/packages- time/commit/83f08b8896b950707a910fed4e30bddb7ee7f52f> I get: {{{ $ ls -l ./libraries/time/dist-install/build/Data/Time/Format.* -rw-r--r-- 1 ggreif staff 10554 Mar 16 00:08 ./libraries/time/dist- install/build/Data/Time/Format.dyn_hi -rw-r--r-- 1 ggreif staff 106832 Mar 16 00:08 ./libraries/time/dist- install/build/Data/Time/Format.dyn_o -rw-r--r-- 1 ggreif staff 10542 Mar 16 00:08 ./libraries/time/dist- install/build/Data/Time/Format.hi -rw-r--r-- 1 ggreif staff 78864 Mar 16 00:08 ./libraries/time/dist- install/build/Data/Time/Format.o }}} The factor is 4.2 for Format.o, Format.dyn_o and 5.8 for the .hi files. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8901> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8156: amd64 + in-tree gmp build broken
by GHC 22 Jan '17

22 Jan '17

#8156: amd64 + in-tree gmp build broken -------------------------------------+------------------------------------- Reporter: errge | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Build System | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 (amd64) | Type of failure: Building GHC Difficulty: Easy (less than 1 | failed hour) | Test Case: Blocked By: | Blocking: Related Tickets: #4022 #4366 #4374 | -------------------------------------+------------------------------------- Currently, the GHC build system has an in-tree GMP. This GMP seems to be used only if there is no usable GMP found on the system and the user didn't provide one using configure flags. When we build GHC using an external shared version of GMP, the resulting GHC is dynamically linked against GMP and also the generated programs are linked dynamically against GMP. When the in-tree GMP is used, it is built statically, even if the GHC we are building is shared GHC on GNU/Linux. This feature is currently broken on amd64 (#4366, #4022), but is working currently very well on Linux i686. Apart from the breakage this setting is very flexible and I'd be very happy if it were possible to keep it, in spite of removeal requests like #4374. When there is a system GMP, nothing would change, this is the most typical usage, e.g. distributions are all building this way. On the other hand, if the user removes his GMP (maybe we should provide an option to explicity trigger this in ./configure, instead of having to remove GMP); she can build a GHC that is not linked dynamically against GMP and the resulting programs are not linked either. This makes it possible to generate binaries that link dynamically against libc (no -static) which is quite compatible amongst versions, but doesn't require a libgmp.so to run. For binary deployments this seems to be the best kind of setup nowadays. Now, if we were only able to fix this for amd64. See this: https://www.gentoo.org/proj/en/base/amd64/howtos/index.xml?part=1&chap=3 On amd64 we can continue to compile GMP statically and link into the binary library, we just have to compile GMP with the fPIC. I attached the patch to fix this. Previously a similar patch has been rejected in #4022 because "this shouldn't be platform specific", but this is clearly not the case, this is specific to amd64. Tadaaaam: {{{ errge@sid64:~/ghc/inplace/bin$ cat test.hs main = print (2^100) errge@sid64:~/ghc/inplace/bin$ ./ghc-stage2 test.hs [1 of 1] Compiling Main ( test.hs, test.o ) Linking test ... errge@sid64:~/ghc/inplace/bin$ ./test 1267650600228229401496703205376 errge@sid64:~/ghc/inplace/bin$ ldd ./test linux-vdso.so.1 (0x00007fff79962000) libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fe4b9a83000) librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fe4b987a000) libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fe4b9676000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe4b92c6000) libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fe4b90a6000) /lib64/ld-linux-x86-64.so.2 (0x00007fe4b9d83000) }}} No GMP! I attach the build file patch to the bugreport. So, can we please apply this patch and just keep the in-tree GMP? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8156> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9223: Type equality makes type variable untouchable
by GHC 21 Jan '17

21 Jan '17

#9223: Type equality makes type variable untouchable -------------------------------------------+------------------------------- Reporter: Feuerbach | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------+------------------------------- This doesn't look right: {{{ {-# LANGUAGE RankNTypes, TypeFamilies #-} type family TF (m :: * -> *) run1 :: (forall m . Monad m => m a) -> a run1 = undefined run2 :: (forall m . (Monad m, TF m ~ ()) => m a) -> a run2 = undefined -- this works x1 = run1 (return ()) -- this fails x2 = run2 (return ()) {- Couldn't match expected type ‘a’ with actual type ‘()’ ‘a’ is untouchable inside the constraints (Monad m, TF m ~ ()) bound by a type expected by the context: (Monad m, TF m ~ ()) => m a at untouchable.hs:15:6-21 ‘a’ is a rigid type variable bound by the inferred type of x2 :: a at untouchable.hs:15:1 Relevant bindings include x2 :: a (bound at untouchable.hs:15:1) In the first argument of ‘return’, namely ‘()’ In the first argument of ‘run2’, namely ‘(return ())’ -} }}} I would expect x2 to type check just like x1 does. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9223> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10515: ghc: panic: tyThingTyCon Identifier ‘$fStencil:.a(,,,,)7’
by GHC 20 Jan '17

20 Jan '17

#10515: ghc: panic: tyThingTyCon Identifier ‘$fStencil:.a(,,,,)7’ -------------------------------------+------------------------------------- Reporter: yongqli | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Has anyone seen something like this? {{{ <no location info>: ghc: panic! (the 'impossible' happened) (GHC version 7.10.1.20150519 for x86_64-unknown-linux): tyThingTyCon Identifier ‘$fStencil:.a(,,,,)7’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10515> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11736: Allow unsaturated uses of unlifted types in Core
by GHC 19 Jan '17

19 Jan '17

#11736: Allow unsaturated uses of unlifted types in Core -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Currently Core Lint checks for unsaturated uses of unlifted types in . These are easily produced in the new type-indexed `Typeable` scheme. For instance, consider solving for `Typeable # (Array# Int)`: * We decompose the application into wanteds `Typeable (* -> #) Array#` and `Typeable * Int` * We construct dictionaries for both, giving us a term `typeRepArray# :: TypeRep (* -> #) Array#` While nothing seems to blow up with this patch, {{{#!patch diff --git a/compiler/coreSyn/CoreLint.hs b/compiler/coreSyn/CoreLint.hs index 99625c9..2c401de 100644 --- a/compiler/coreSyn/CoreLint.hs +++ b/compiler/coreSyn/CoreLint.hs @@ -1040,7 +1040,7 @@ lintType ty@(TyConApp tc tys) = lintType ty' -- Expand type synonyms, so that we do not bogusly complain -- about un-saturated type synonyms - | isUnliftedTyCon tc || isTypeSynonymTyCon tc || isTypeFamilyTyCon tc + | isTypeSynonymTyCon tc || isTypeFamilyTyCon tc -- Also type synonyms and type families , length tys < tyConArity tc = failWithL (hang (text "Un-saturated type application") 2 (ppr ty)) }}} I otherwise have no reason to believe that this is safe. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11736> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9137: A way to match RULES only for literals
by GHC 16 Jan '17

16 Jan '17

#9137: A way to match RULES only for literals ------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- In `GHC/Enum` we have {{{ {-# RULES "enumDeltaToInteger1" [0] forall c n x . enumDeltaToIntegerFB c n x 1 = up_fb c n x 1 #-} -- This rule ensures that in the common case (delta = 1), we do not do the check here, -- and also that we have the chance to inline up_fb, which would allow the constructor to be -- inlined and good things to happen. -- We do not do it for Int this way because hand-tuned code already exists, and -- the special case varies more from the general case, due to the issue of overflows. }}} This rule would be useful for all literals, not just for `1`. I remember a discussion that such a rule would be more useful if we had a way to specify that, for example (random syntax). {-# RULES "enumDeltaToInteger1" [0] forall c n x d . isLiteral d => enumDeltaToIntegerFB c n x d = up_fb c n x d #-} I’m reporting this now to be able to link to it from #9136, where this feature might also help. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9137> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11140: add command-line option to GHC to dump raw parse trees of Haskell programs
by GHC 16 Jan '17

16 Jan '17

#11140: add command-line option to GHC to dump raw parse trees of Haskell programs -------------------------------------+------------------------------------- Reporter: bollu | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.2 Keywords: newcomer | 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 now, GHC has no option to dump the parse tree of a given Haskell source file. `-ddump-parsed` only displays the pretty-printed AST structure, and cannot be used to inspect parse trees. An existing implementation of such a feature is present in apply- refact(https://github.com/mpickering/apply-refact) by invoking the tool as `refactor --debug`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11140> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10073: Idris REPL is pretty and we can too
by GHC 14 Jan '17

14 Jan '17

#10073: Idris REPL is pretty and we can too -------------------------------------+------------------------------------- Reporter: bitemyapp | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.4 Component: GHCi | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Manual for configuring colors in the Idris REPL: https://github.com/idris- lang/Idris-dev/wiki/Manual#colours Screenshot: http://i.imgur.com/rYHCI4T.png Particularly, I'd like to make type errors and warnings more visually distinct. I think little touches like this can go a long way to making it nice to work with Haskell code. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10073> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11695: On GHCi prompt the arrow (movement) keys create strange character sequences
by GHC 12 Jan '17

12 Jan '17

#11695: On GHCi prompt the arrow (movement) keys create strange character sequences --------------------------------------+--------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.1 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- Fire up `GHCi` and sit on the arrow down (or left) keys. This is what I get after constantly pressing for some time: {{{ $ ghci GHCi, version 8.1.20160202: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/ggreif/.ghci Prelude> OBOBOBBOBOBOBOBOBOBOBCOCCOCOCCOCCOC <interactive>:1:1: error: Data constructor not in scope: OBOBOBBOBOBOBOBOBOBOBCOCCOCOCCOCCOC }}} When such a strange letter appears, there is also a blinking of the terminal. It is not happening on Windows. I have seen it on RHEL5 and RHEL6. Pretty annoying, especially when you want to quickly navigate in the repl. This is probably a `haskeline` bug, but I am coming here to see whether others suffer from it too, i.e. is it reproducible for elseone? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11695> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10083: ghc: panic! (the 'impossible' happened)
by GHC 12 Jan '17

12 Jan '17

#10083: ghc: panic! (the 'impossible' happened) -------------------------------------+------------------------------------- Reporter: hedayaty | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- I used hprotoc to generate some code for Google protocol buffers. The QueryValue.proto file is attached. You can install hprotoc tool using cabal. then use ''hprotoc QueryValue.proto'' to generate code. Then create a minimal cabal file. ''cabal init -m --is-library -n'' Then if you build it with '''optimization enabled''', the build will fail ghc: panic! (the 'impossible' happened) (GHC version 7.8.3 for x86_64-apple-darwin): Simplifier ticks exhausted When trying UnfoldingDone $j_sEMq{v} [lid] To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 59242 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10083> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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