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[GHC] #7809: Silly error message suggesting LiberalTypeSynonyms
by GHC 13 Apr '13

13 Apr '13

#7809: Silly error message suggesting LiberalTypeSynonyms -----------------------------+---------------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- The following code (rightly) does not compile: {{{ {-# LANGUAGE RankNTypes, TypeFamilies, LiberalTypeSynonyms #-} type PolyId = (forall a. a -> a) type family F a foo :: F PolyId foo = undefined }}} The error message is {{{ Illegal polymorphic or qualified type: PolyId Perhaps you intended to use -XLiberalTypeSynonyms In the type signature for `foo': foo :: F PolyId }}} The code doesn't compile because we can't apply a type family to a polytype. The first line of the error message says this well enough, though more information might be helpful here. However, the second line of the error message is silly: I've turned on {{{LiberalTypeSynonyms}}}! -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7809> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7808: data families and TH names do not mix well (e.g. cannot use TH deriving)
by GHC 13 Apr '13

13 Apr '13

#7808: data families and TH names do not mix well (e.g. cannot use TH deriving) -----------------------------+---------------------------------------------- Reporter: duncan | Owner: Type: feature request | Status: new Priority: normal | Component: Template Haskell Version: 7.6.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- lots of Haskell libraries have TH functions like: {{{ deriveJSON :: Name -> Q [Dec] }}} (e.g. aeson package for deriving JSON conversion) They're used like {{{ data Foo = Foo This That $(deriveJSON ''Foo) }}} the `deriveJSON` reifies the Name and expects to find that the name refers to a data type, from which it finds the data constructors and generates the appropriate code. Now, this doesn't work when the data type we want to derive an instance for is defined using a data family: {{{ class FooClass a where data Foo a ... instance FooClass Bar where data Foo Bar = Bar This That $(deriveJSON ''Foo Bar) -- ??? }}} We'd like to make the type Foo Bar an instance of the class (e.g. To/FromJSON) but `deriveJSON` expects a Name, and there is no name for this data type, its "name" is `Foo Bar` but obviously that's not a `TH.Name`. Of course in general a name for a type application doesn't make sense, but for data family instances what other way do we have to refer to them? -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7808> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7807: Parse error with "where" and file-ending comment
by GHC 13 Apr '13

13 Apr '13

#7807: Parse error with "where" and file-ending comment -----------------------------+---------------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Parser) Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- Consider the following file: {{{ {-# LANGUAGE TypeFamilies #-} type family F a type instance where F Int = Bool {- -} }}} If there is a file-ending newline, after the comment, the file parses. If there is not a file-ending newline, I get a parse error. I wrote the code dealing with {{{type instance where}}} notation, but this seems more related to parsing issues (which I know little about) than {{{type instance where}}}. Please correct me if I'm wrong. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7807> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7806: Dynamic linking and libffi
by GHC 13 Apr '13

13 Apr '13

#7806: Dynamic linking and libffi ----------------------------------+----------------------------------------- Reporter: kazu-yamamoto | Owner: Type: bug | Status: new Priority: normal | Component: Build System Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Installing GHC failed | Blockedby: Blocking: | Related: ----------------------------------+----------------------------------------- After dynamic linking became the default, building/installing GHC on FreeBSD and Mac fails due to libffi. I don't see any problems on Linux. = FreeBSD without system libffi = GHC can be build: {{{ % make maintainer-clean % perl boot % ./configure --prefix=/ghc-head \ --with-iconv-includes=/usr/local/include \ --with-iconv-libraries=/usr/local/lib \ --with-gmp-includes=/usr/local/include \ --with-gmp-libraries=/usr/local/lib \ --with-gcc=/usr/local/bin/gcc47 \ --with-gcc-4.2=/usr/local/bin/gcc47 % gmake -j10 }}} But installation fails: {{{ % gmake install Installing library in /ghc-head/lib/ghc-7.7.20130323/haskell2010-1.1.1.0 "/ghc-head/lib/ghc-7.7.20130323/bin/ghc-pkg" --force --global-package-db "/ghc-head/lib/ghc-7.7.20130323/package.conf.d" update rts/package.conf.install Shared object "libffi.so.6" not found, required by "libHSrts- ghc7.7.20130323.so" gmake[1]: *** [install_packages] Error 1 gmake: *** [install] Error 2 }}} = FreeBSD with system libffi = The following procedure has no problems: {{{ % make maintainer-clean % perl boot % ./configure --prefix=/ghc-head \ --with-iconv-includes=/usr/local/include \ --with-iconv-libraries=/usr/local/lib \ --with-gmp-includes=/usr/local/include \ --with-gmp-libraries=/usr/local/lib \ --with-gcc=/usr/local/bin/gcc47 \ --with-gcc-4.2=/usr/local/bin/gcc47 --with-system-libffi \ --with-ffi-includes=/usr/local/include \ --with-ffi-libraries=/usr/local/lib % gmake -j10 % gmake install }}} = Mac without system libffi = GHC can be build: {{{ % make maintainer-clean % perl boot % ./configure --prefix=/ghc-head % make -j6 }}} But installation fails: {{{ % make install Installing library in /ghc-head/lib/ghc-7.7.20130323/haskell2010-1.1.1.0 "/ghc-head/lib/ghc-7.7.20130323/bin/ghc-pkg" --force --global-package-db "/ghc-head/lib/ghc-7.7.20130323/package.conf.d" update rts/package.conf.install dyld: Library not loaded: @loader_path/../terminfo-0.3.2.5/libHSterminfo-0.3.2.5-ghc7.7.20130323.dylib Referenced from: /ghc-head/lib/ghc-7.7.20130323/bin/ghc-pkg Reason: image not found make[1]: *** [install_packages] Trace/BPT trap: 5 make: *** [install] Error 2 }}} = Mac with system libffi = If I do: {{{ % make maintainer-clean % perl boot % ./configure --prefix=/ghc-head \ --with-system-libffi \ --with-ffi-includes=/usr/include/ffi \ --with-ffi-libraries=/usr/lib % make -j6 }}} hsc2hs cannot find necessary .h files. {{{ "inplace/bin/hsc2hs" '--cc=/usr/bin/gcc' '--ld=/usr/bin/gcc' --cross-safe --cflag=-m64 --cflag=-fno-stack-protector --cflag=-m64 --lflag=-m64 --cflag=-D__GLASGOW_HASKELL__=707 --cflag=-Dx86_64_HOST_ARCH=1 --cflag=-Ddarwin_HOST_OS=1 '--cflag=-m64' '--cflag=-fno-stack-protector' ' --cflag=-Icompiler/../rts/dist/build' '--cflag=-Icompiler/stage2' '-- cflag=-Icompiler/.' '--cflag=-Icompiler/parser' '--cflag=-Icompiler/utils' '--cflag=-DGHCI' '-- cflag=-I/Users/kazu/work/ghc/libraries/process/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/directory/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/unix/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/time/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/containers/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/bytestring/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/array/include' '-- cflag=-I/Users/kazu/work/ghc/libraries/base/include' '-- cflag=-I/Users/kazu/work/ghc/rts/dist/build' '-- cflag=-I/Users/kazu/work/ghc/includes' '-- cflag=-I/Users/kazu/work/ghc/includes/dist-derivedconstants/header' '-- lflag=-m64' '--lflag=-L/Users/kazu/work/ghc/libraries/transformers/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/template-haskell /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/hpc/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/hoopl/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/bin-package-db /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/binary /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/Cabal/Cabal /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/process /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/pretty /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/directory /dist-install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/unix/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/time/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/old-locale/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/filepath/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/containers/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/bytestring/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/deepseq/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/array/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/base/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/integer-gmp/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/libraries/ghc-prim/dist- install/build' '--lflag=-L/Users/kazu/work/ghc/rts/dist/build' '-- lflag=-ldl' '--lflag=-liconv' '--lflag=-lm' '--lflag=-ldl' '--lflag=-lffi' --cflag=-Icompiler/stage2/build/autogen --cflag=-include --cflag=compiler/stage2/build/autogen/cabal_macros.h compiler/ghci/LibFFI.hsc -o compiler/stage2/build/LibFFI.hs LibFFI.hsc:9:17: error: ffi.h: No such file or directory LibFFI.hsc: In function ‘main’: LibFFI.hsc:42: error: ‘ffi_cif’ undeclared (first use in this function) LibFFI.hsc:42: error: (Each undeclared identifier is reported only once LibFFI.hsc:42: error: for each function it appears in.) LibFFI.hsc:82: error: ‘ffi_status’ undeclared (first use in this function) LibFFI.hsc:82: error: expected expression before ‘int’ LibFFI.hsc:82: error: expected ‘)’ before numeric constant LibFFI.hsc:82: error: expected ‘)’ before numeric constant LibFFI.hsc:83: error: ‘ffi_abi’ undeclared (first use in this function) LibFFI.hsc:83: error: expected expression before ‘int’ LibFFI.hsc:83: error: expected ‘)’ before numeric constant LibFFI.hsc:83: error: expected ‘)’ before numeric constant LibFFI.hsc:99: error: ‘FFI_OK’ undeclared (first use in this function) LibFFI.hsc:106: error: ‘FFI_DEFAULT_ABI’ undeclared (first use in this function) compiling compiler/stage2/build/LibFFI_hsc_make.c failed (exit code 1) command was: /usr/bin/gcc -c compiler/stage2/build/LibFFI_hsc_make.c -o compiler/stage2/build/LibFFI_hsc_make.o -m64 -fno-stack-protector -I/Users/kazu/work/ghc/includes -m64 -fno-stack-protector -m64 -D__GLASGOW_HASKELL__=707 -Dx86_64_HOST_ARCH=1 -Ddarwin_HOST_OS=1 -m64 -fno-stack-protector -Icompiler/../rts/dist/build -Icompiler/stage2 -Icompiler/. -Icompiler/parser -Icompiler/utils -DGHCI -I/Users/kazu/work/ghc/libraries/process/include -I/Users/kazu/work/ghc/libraries/directory/include -I/Users/kazu/work/ghc/libraries/unix/include -I/Users/kazu/work/ghc/libraries/time/include -I/Users/kazu/work/ghc/libraries/containers/include -I/Users/kazu/work/ghc/libraries/bytestring/include -I/Users/kazu/work/ghc/libraries/array/include -I/Users/kazu/work/ghc/libraries/base/include -I/Users/kazu/work/ghc/rts/dist/build -I/Users/kazu/work/ghc/includes -I/Users/kazu/work/ghc/includes/dist-derivedconstants/header -Icompiler/stage2/build/autogen -include compiler/stage2/build/autogen/cabal_macros.h -I/Users/kazu/work/ghc/inplace/lib/include/ make[1]: *** [compiler/stage2/build/LibFFI.hs] Error 1 make: *** [all] Error 2 }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7806> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7800: Error message when deriving Typeable without PolyKinds
by GHC 13 Apr '13

13 Apr '13

#7800: Error message when deriving Typeable without PolyKinds ----------------------------------------------+----------------------------- Reporter: monoidal | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect warning at compile-time | Blockedby: Blocking: | Related: ----------------------------------------------+----------------------------- Module M: {{{ {-# LANGUAGE PolyKinds #-} module M where data A a }}} Module N: {{{ {-# LANGUAGE StandaloneDeriving, DeriveDataTypeable #-} module N where import M import Data.Typeable deriving instance Typeable A }}} We get a confusing error message: {{{ N.hs:7:1: Derived typeable instance must be of form (Typeable A) In the stand-alone deriving instance for ‛Typeable A’ }}} The error disappears when N is compiled with -XPolyKinds. The reason is: without -XPolyKinds, A defaults to A *. I think it's simplest to suggest the flag in the error message. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7800> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7797: re-enable the defun RULE from a SPECIALISE instance pragma
by GHC 13 Apr '13

13 Apr '13

#7797: re-enable the defun RULE from a SPECIALISE instance pragma -----------------------------+---------------------------------------------- Reporter: nfrisby | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.6.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- As of commit [https://github.com/ghc/ghc/commit/51d89a55c3 51d89a55c3], `SPECIALISE instance` pragmas do not result in a RULE for the dictionary function. For example, consider this `Eq` instance for `List`. {{{ module M where data List a = Nil | Cons a (List a) instance (Eq a) => Eq (List a) where {-# SPECIALISE instance Eq (List Char) #-} Nil == Nil = True (Cons x xs) == (Cons y ys) = x == y && xs == ys _xs == _ys = False }}} With ghc-7.4.2, we get: {{{ ==================== Tidy Core rules ==================== "SPEC $c/=" [ALWAYS] forall ($dEq :: GHC.Classes.Eq GHC.Types.Char). M.$fEqList_$c/=1 @ GHC.Types.Char $dEq = M.$fEqList_$c/= "SPEC $c==" [ALWAYS] forall ($dEq :: GHC.Classes.Eq GHC.Types.Char). M.$fEqList_$c==1 @ GHC.Types.Char $dEq = M.$fEqList_$c== "SPEC M.$fEqList" [ALWAYS] forall ($dEq :: GHC.Classes.Eq GHC.Types.Char). M.$fEqList @ GHC.Types.Char $dEq = M.$fEqList_$fEqList }}} Note the last rule: it specializes the normal defun `M.$fEqList` when applied at type `Char`. With anything after 7.4.2 -- eg if you download the binary sources for 7.4.2 and make [https://github.com/ghc/ghc/commit/51d89a55c3#L0L779 the change at line 779] from that commit --- you instead get this: {{{ ==================== Tidy Core rules ==================== "SPEC $c/=" [ALWAYS] forall ($dEq :: GHC.Classes.Eq GHC.Types.Char). M.$fEqList_$c/=1 @ GHC.Types.Char $dEq = M.$fEqList_$c/= "SPEC $c==" [ALWAYS] forall ($dEq :: GHC.Classes.Eq GHC.Types.Char). M.$fEqList_$c==1 @ GHC.Types.Char $dEq = M.$fEqList_$c== }}} (Actually, after some patch the /= RULE disappears too, but I don't know which/why.) If the dictionary is used at the relevant type in the same module, the specializer will automatically create the omitted rule. That will not, however, currently happen across module boundaries. In my contrived example, omitting this defun specialization increases runtime by a factor of 2 at -O1. {{{ {-# LANGUAGE ExistentialQuantification #-} module Main where import M data Box = forall a. Eq a => Box a a box = Box (go 10000000) (go 10000000) where go :: Int -> List Char go 0 = Nil go n = Cons 'c' $ go (n - 1) {-# NOINLINE box #-} main = print $ case box of Box l r -> l == r }}} (-O2 squashes the runtime difference; I haven't investigated in detail.) -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7797> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7794: GHCi "Prelude.undefined" exceptions on ARM; ByteCodeItbls.mkJumpToAddr unimplemented
by GHC 13 Apr '13

13 Apr '13

#7794: GHCi "Prelude.undefined" exceptions on ARM; ByteCodeItbls.mkJumpToAddr unimplemented -----------------------+---------------------------------------------------- Reporter: cjwatson | Owner: Type: bug | Status: new Priority: normal | Component: GHCi Version: 7.6.2 | Keywords: Os: Linux | Architecture: arm Failure: GHCi crash | Blockedby: Blocking: | Related: -----------------------+---------------------------------------------------- A number of non-trivial operations fail in ghci on ARM (specifically armhf on both Debian experimental and Ubuntu raring). I initially noticed this as conduit's doctests failing, but reduced this to: $ ghci GHCi, version 7.6.2: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude> data Type a = Nothing *** Exception: Prelude.undefined This is a singularly unhelpful exception, coming as it does without context, but I eventually tracked it down to ByteCodeItbls.mkJumpToAddr having no specific implementation for ARM and thus falling back to the default of "undefined". I've tried adding this: +#elif arm_TARGET_ARCH +type ItblCode = Word32 +mkJumpToAddr a + = [ 0xe51ff004 -- ldr pc, [pc, #-4] # pc reads as <current insn>+8 + , fromIntegral (ptrToInt a) ] This definitely changes the nature of the problem, so I think I'm on the right track, and I'm reasonably confident that that's the correct branch implementation; but when I actually try it in practice I get crashes (SIGSEGV/SIGILL/SIGBUS) with trashed stack traces, so I'm clearly not done yet. Friends of mine suggest that I may need to __clear_cache or equivalent, which sounds plausible, so my current line of attack is figuring out how to glue that in; but if any actual GHC hackers can spot something obviously missing in the meantime then that would be great. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7794> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7790: Add dummy undefined symbols to indicate ways
by GHC 13 Apr '13

13 Apr '13

#7790: Add dummy undefined symbols to indicate ways -----------------------------+---------------------------------------------- Reporter: ezyang | Owner: ezyang Type: task | Status: new Priority: normal | Component: Compiler Version: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- Currently, "way" information is not recorded into object files; it is only recorded into 'hi' files. This means if you are using, say, rts/Linker.c (say, if you're GHCi or a dynamic plugins package), if you mess up and load an object file compiled the wrong way, you will be very sad. I think a cute trick we could play is to define a bunch of dummy symbols per-way, and add them as undefined symbols to objects, to indicate what way they were compiled, e.g. with the `-u` linker flag. Various RTS's export the symbols of ways they support, and attempting to link an object with an incompatible RTS results in a link error. Are there any problems with this scheme? If not, I'll go ahead and implement it. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7790> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7789: GHCI core dumps when used with VTY
by GHC 13 Apr '13

13 Apr '13

#7789: GHCI core dumps when used with VTY -----------------------------+---------------------------------------------- Reporter: timthelion | Owner: Type: bug | Status: new Priority: normal | Component: GHCi Version: 7.4.2-rc1 | Keywords: core dump Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHCi crash | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- Load the attached script in ghci: {{{ $ghci ghci-coredumper.hs }}} (you need the vty-menu package from hackage) and type die {{{ >die }}} You may see a menu with a set of ten numbers. If you do press enter repeatedly. Eventually it will core dump(at least it does for me) Unfortunately I have been unable to collect this core dump, but here is the output at least: {{{ 7f7ad1fc4000-7f7ad1fc5000 rwxp 000fd000 00:10 2839271 /usr/lib/libm-2.17.so 7f7ad1fc5000-7f7ad2032000 r-xp 00000000 00:10 3028085 /usr/lib/libgmp.so.10.1.1 7f7ad2032000-7f7ad2231000 ---p 0006d000 00:10 3028085 /usr/lib/libgmp.so.10.1.1 7f7ad2231000-7f7ad2232000 r-xp 0006c000 00:10 3028085 /usr/lib/libgmp.so.10.1.1 7f7ad2232000-7f7ad223b000 rwxp 0006d000 00:10 3028085 /usr/lib/libgmp.so.10.1.1 7f7ad223b000-7f7ad2252000 r-xp 00000000 00:10 2839310 /usr/lib/libpthread-2.17.so 7f7ad2252000-7f7ad2451000 ---p 00017000 00:10 2839310 /usr/lib/libpthread-2.17.so 7f7ad2451000-7f7ad2452000 r-xp 00016000 00:10 2839310 /usr/lib/libpthread-2.17.so 7f7ad2452000-7f7ad2453000 rwxp 00017000 00:10 2839310 /usr/lib/libpthread-2.17.so 7f7ad2453000-7f7ad2457000 rwxp 00000000 00:00 0 7f7ad2457000-7f7ad245a000 r-xp 00000000 00:10 2839316 /usr/lib/libdl-2.17.so 7f7ad245a000-7f7ad2659000 ---p 00003000 00:10 2839316 /usr/lib/libdl-2.17.so 7f7ad2659000-7f7ad265a000 r-xp 00002000 00:10 2839316 /usr/lib/libdl-2.17.so 7f7ad265a000-7f7ad265b000 rwxp 00003000 00:10 2839316 /usr/lib/libdl-2.17.so 7f7ad265b000-7f7ad265d000 r-xp 00000000 00:10 2839280 /usr/lib/libutil-2.17.so 7f7ad265d000-7f7ad285c000 ---p 00002000 00:10 2839280 /usr/lib/libutil-2.17.so 7f7ad285c000-7f7ad285d000 r-xp 00001000 00:10 2839280 /usr/lib/libutil-2.17.so 7f7ad285d000-7f7ad285e000 rwxp 00002000 00:10 2839280 /usr/lib/libutil-2.17.so 7f7ad285e000-7f7ad2865000 r-xp 00000000 00:10 2839273 /usr/lib/librt-2.17.so 7f7ad2865000-7f7ad2a64000 ---p 00007000 00:10 2839273 /usr/lib/librt-2.17.so 7f7ad2a64000-7f7ad2a65000 r-xp 00006000 00:10 2839273 /usr/lib/librt-2.17.so 7f7ad2a65000-7f7ad2a66000 rwxp 00007000 00:10 2839273 /usr/lib/librt-2.17.so 7f7ad2a66000-7f7ad2ac0000 r-xp 00000000 00:10 3403181 /usr/lib/libncursesw.so.5.9 7f7ad2ac0000-7f7ad2cbf000 ---p 0005a000 00:10 3403181 /usr/lib/libncursesw.so.5.9 7f7ad2cbf000-7f7ad2cc3000 r-xp 00059000 00:10 3403181 /usr/lib/libncursesw.so.5.9 7f7ad2cc3000-7f7ad2cc5000 rwxp 0005d000 00:10 3403181 /usr/lib/libncursesw.so.5.9 7f7ad2cc5000-7f7ad2ce6000 r-xp 00000000 00:10 2839312 /usr/lib/ld-2.17.so 7f7ad2e39000-7f7ad2eba000 rwxp 00000000 00:00 0 7f7ad2ee4000-7f7ad2ee6000 rwxp 00000000 00:00 0 7f7ad2ee6000-7f7ad2ee7000 r-xp 00021000 00:10 2839312 /usr/lib/ld-2.17.so 7f7ad2ee7000-7f7ad2ee8000 rwxp 00022000 00:10 2839312 /usr/lib/ld-2.17.so 7f7ad2ee8000-7f7ad2ee9000 rwxp 00000000 00:00 0 7fff979b8000-7fff979d9000 rwxp 00000000 00:00 0 [stack] 7fff979fe000-7fff97a00000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall] Neúspěšně ukončen (SIGABRT) (core dumped [obraz paměti uložen]) }}} Sometimes it dumps immediately, sometimes it takes a while. Sometimes the errors are different: {{{ *** Exception: user error (Terminal does not define required capability "cup") *Main> }}} {{{ *** Exception: user error (Terminal does not define required capability "setab") *Main> <stdin>: hWaitForInput: end of file }}} But mostly it just core dumps. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7789> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7788: Recursive type family causes <<loop>>
by GHC 13 Apr '13

13 Apr '13

#7788: Recursive type family causes <<loop>> ----------------------------------------+----------------------------------- Reporter: shachaf | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.6.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Incorrect result at runtime | Blockedby: Blocking: | Related: ----------------------------------------+----------------------------------- This file: {{{ {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE UndecidableInstances #-} data Proxy a = Proxy foo :: Proxy (F (Fix Id)) -> () foo = undefined newtype Fix a = Fix (a (Fix a)) newtype Id a = Id a type family F a type instance F (Fix a) = F (a (Fix a)) type instance F (Id a) = F a main :: IO () main = print $ foo Proxy }}} Dies with `<<loop>>`. The type family is recursive, of course: {{{ *Main> :kind! F (Fix Id) F (Fix Id) :: *^CInterrupted. }}} But `<<loop>>` is still not the behavior I'd expect. The actual value is just `undefined`. In the file that this example came up, the situation was even worse -- there was a situation where {{{ moldMapOf l f = runAccessor . l (Accessor . f) main = print $ (flip appEndo [] . moldMapOf (ix 3) (Endo . (:)) $ testVal :: [Int]) -- <<loop>> main = print $ (flip appEndo [] . runAccessor . (ix 3) (Accessor . Endo . (:)) $ testVal :: [Int]) -- undefined }}} I.e. substitution can turn one program (which happens to be ⊥ here, admittedly, but that's not fundamental) into another (`<<loop>>`). This makes it very tricky to track down the recursive type family. If necessary I can hunt down a working test case and post it here -- it's a bit tricky to get working, though. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7788> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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