[GHC] #12696: Exception gives not enough information to be useful
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: exception | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I was told in #haskell @freenode to report this as a bug. I have a program that throws exceptions and tried debugging the problem within ghci and also outside of ghci with these commands: {{{ stack build --ghc-options '-rtsopts -fprof-auto -fprof-auto-calls' --executable-profiling stack exec -- vhdl +RTS -xc }}} {{{#!hs tfComment :: Data from => from -> from tfComment = transformBi tf where tf (Comment ((pos_c, c), (pos_s, s))) = Comment $ ((pos_c, T.concat ["--", c]), (pos_s, s)) tf a = a zeroPos :: Data from => from -> from zeroPos = transformBi zp where zp sp@(M.SourcePos _ _ _) = sp { M.sourceName="", M.sourceLine=unsafePos 1, M.sourceColumn=unsafePos 1} zp x = x -- (a)dd (e)xtended(i)dentifier (s)laches aeis :: Data from => from -> from aeis = transformBi x where x (IExtended a) = let updated_text :: Text updated_text = T.concat ["\\", snd $ t_text a, "\\"] in IExtended $ a {t_text = (fst $ t_text a, updated_text)} x a = a bla = something.. where parser_prop :: ContextClause -> Bool parser_prop = \x -> (transformIn <$> Right x) == (transformOut <$> parseSource parser $ T.toStrict . printSource $ transformIn x) transformIn ast = zeroPos ast transformOut ast = tfComment $ aeis $ zeroPos ast }}} ghci trace {{{ λ> :trace main Stopped in <exception thrown>, <unknown> _exception :: e = _ λ> :back Logged breakpoint at Main.hs:95:13-26 _result :: from -> from tf :: Comment -> Comment λ> :list 94 tfComment :: Data from => from -> from 95 tfComment = transformBi tf -- transformBi tf highlighted here 96 where tf (Comment ((pos_c, c), (pos_s, s))) = Comment $ ((pos_c, T.concat ["--", c]), (pos_s, s)) λ> :back Logged breakpoint at Main.hs:242:28-57 _result :: from ast :: from λ> :list 241 transformIn ast = zeroPos ast 242 transformOut ast = tfComment $ aeis $ zeroPos ast -- tfComment $ aeis $ zeroPos ast highlighted here 243 λ> :force ast ast = Right [] λ> transformIn (Right []) Right [] λ> transformOut (Right []) Right [] λ> zeroPos (Right []) Right [] λ> aeis (Right []) Right [] λ> tfComment (Right []) Right [] }}} run with profiling options (this was aborted at some point) {{{ » stack exec -- vhdl +RTS -xc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Data.CAF --> evaluated by: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 *** Exception (reporting due to +RTS -xc): (THUNK_STATIC), stack trace: Data.Generics.Uniplate.Internal.Data.uniplateVerbose, called from Data.Generics.Uniplate.Internal.Data.CAF:uniplateVerbose --> evaluated by: Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 --> evaluated by: Data.Generics.Uniplate.Internal.Data.fromOracle, called from Data.Generics.Uniplate.Internal.Data.biplateData, called from Data.Generics.Uniplate.Data.biplate, called from Main.tfComment, called from Main.qcrp.transformOut, called from Main.qcrp.parser_prop, called from Main.qcrp.parser_prop, called from Main.qc2.logInput, called from Main.qc2.logInput, called from Main.qc2.logInput, called from Main.qc2, called from Test.QuickCheck.Property.forAllShrink.\.\, called from Test.QuickCheck.Property.property, called from Test.QuickCheck.Test.quickCheckWithResult.property', called from Test.QuickCheck.Test.quickCheckWithResult.\, called from Test.QuickCheck.Text.withNullTerminal, called from Test.QuickCheck.Test.quickCheckWithResult, called from Main.qc2, called from Main.qcrp, called from Main.ntc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2025_r3oe3 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2025_r3oe3 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2022_r3oe0 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2022_r3oe0 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl1945_r3oc9 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer6_r3ocg --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer6_r3ocg *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer7_r3ocp --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer7_r3ocp *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer8_r3ocy --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer8_r3ocy ^C^C^C^C }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): What is the bug? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by flip101): it's a bug that ghc is not reporting something useful -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): Reporting something useful about what? Please be specific. We are not mind readers. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by flip101: @@ -10,0 +10,5 @@ + + The bug is that it's a bug that ghc is not reporting something useful on + the exception. So i don't get sufficient information from the debug + facilities. When i have sufficient information i can go ahead and debug my + program. This ticket is not about solving a possible bug in my code. New description: I was told in #haskell @freenode to report this as a bug. I have a program that throws exceptions and tried debugging the problem within ghci and also outside of ghci with these commands: {{{ stack build --ghc-options '-rtsopts -fprof-auto -fprof-auto-calls' --executable-profiling stack exec -- vhdl +RTS -xc }}} The bug is that it's a bug that ghc is not reporting something useful on the exception. So i don't get sufficient information from the debug facilities. When i have sufficient information i can go ahead and debug my program. This ticket is not about solving a possible bug in my code. {{{#!hs tfComment :: Data from => from -> from tfComment = transformBi tf where tf (Comment ((pos_c, c), (pos_s, s))) = Comment $ ((pos_c, T.concat ["--", c]), (pos_s, s)) tf a = a zeroPos :: Data from => from -> from zeroPos = transformBi zp where zp sp@(M.SourcePos _ _ _) = sp { M.sourceName="", M.sourceLine=unsafePos 1, M.sourceColumn=unsafePos 1} zp x = x -- (a)dd (e)xtended(i)dentifier (s)laches aeis :: Data from => from -> from aeis = transformBi x where x (IExtended a) = let updated_text :: Text updated_text = T.concat ["\\", snd $ t_text a, "\\"] in IExtended $ a {t_text = (fst $ t_text a, updated_text)} x a = a bla = something.. where parser_prop :: ContextClause -> Bool parser_prop = \x -> (transformIn <$> Right x) == (transformOut <$> parseSource parser $ T.toStrict . printSource $ transformIn x) transformIn ast = zeroPos ast transformOut ast = tfComment $ aeis $ zeroPos ast }}} ghci trace {{{ λ> :trace main Stopped in <exception thrown>, <unknown> _exception :: e = _ λ> :back Logged breakpoint at Main.hs:95:13-26 _result :: from -> from tf :: Comment -> Comment λ> :list 94 tfComment :: Data from => from -> from 95 tfComment = transformBi tf -- transformBi tf highlighted here 96 where tf (Comment ((pos_c, c), (pos_s, s))) = Comment $ ((pos_c, T.concat ["--", c]), (pos_s, s)) λ> :back Logged breakpoint at Main.hs:242:28-57 _result :: from ast :: from λ> :list 241 transformIn ast = zeroPos ast 242 transformOut ast = tfComment $ aeis $ zeroPos ast -- tfComment $ aeis $ zeroPos ast highlighted here 243 λ> :force ast ast = Right [] λ> transformIn (Right []) Right [] λ> transformOut (Right []) Right [] λ> zeroPos (Right []) Right [] λ> aeis (Right []) Right [] λ> tfComment (Right []) Right [] }}} run with profiling options (this was aborted at some point) {{{ » stack exec -- vhdl +RTS -xc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Data.CAF --> evaluated by: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 *** Exception (reporting due to +RTS -xc): (THUNK_STATIC), stack trace: Data.Generics.Uniplate.Internal.Data.uniplateVerbose, called from Data.Generics.Uniplate.Internal.Data.CAF:uniplateVerbose --> evaluated by: Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 --> evaluated by: Data.Generics.Uniplate.Internal.Data.fromOracle, called from Data.Generics.Uniplate.Internal.Data.biplateData, called from Data.Generics.Uniplate.Data.biplate, called from Main.tfComment, called from Main.qcrp.transformOut, called from Main.qcrp.parser_prop, called from Main.qcrp.parser_prop, called from Main.qc2.logInput, called from Main.qc2.logInput, called from Main.qc2.logInput, called from Main.qc2, called from Test.QuickCheck.Property.forAllShrink.\.\, called from Test.QuickCheck.Property.property, called from Test.QuickCheck.Test.quickCheckWithResult.property', called from Test.QuickCheck.Test.quickCheckWithResult.\, called from Test.QuickCheck.Text.withNullTerminal, called from Test.QuickCheck.Test.quickCheckWithResult, called from Main.qc2, called from Main.qcrp, called from Main.ntc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2025_r3oe3 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2025_r3oe3 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2022_r3oe0 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2022_r3oe0 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl1945_r3oc9 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer6_r3ocg --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer6_r3ocg *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer7_r3ocp --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer7_r3ocp *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer8_r3ocy --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer8_r3ocy ^C^C^C^C }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mpickering): It still isn't clear to me what the code is which causes the exception. Could you please provide a test case which you can invoke with one invocation of the 'ghc' executable which shows the error you think is bad? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by flip101: @@ -11,0 +11,2 @@ + Paraphrased my own words and others from irc: + @@ -16,0 +18,15 @@ + The specific issue is that it's producing what ghci calls an undefined + exception, and -xc is producing *** Exception (reporting due to +RTS -xc): + (THUNK_2_0). + "(THUNK_2_0)" doesn't tell anyone anything. I'd expect to see that it + reentered something it wasn't supposed to, or something like that. + THUNK_2_0 sounds like an internal GHC thing, which i why i'm filing a bug. + + The +RTS -xc includes names of info tables, which would help identify + *what* it's throwing on. but unless the Core is generated at the same time + during compilation, it's not possible to find out what. If i generate core + now i will get different names. The exception could even be in the + standard library. +RTS -xc definitely has a lot of room for improvement + + When the program runs normally it doesn't terminate. The GHCI run + terminate because -fbreak-on-exception was set. @@ -53,0 +70,22 @@ + λ> _exception + + <interactive>:2:1: error: + • No instance for (Show e) arising from a use of ‘print’ + Cannot resolve unknown runtime type ‘e’ + Use :print or :force to determine these types + Relevant bindings include it :: e (bound at <interactive>:2:1) + These potential instances exist: + instance [safe] Show Args -- Defined in ‘Test.QuickCheck.Test’ + instance [safe] Show Result -- Defined in ‘Test.QuickCheck.Test’ + instance Show a => Show (ZipList a) + -- Defined in ‘Control.Applicative’ + ...plus 297 others + ...plus 133 instances involving out-of-scope types + (use -fprint-potential-instances to see them all) + • In a stmt of an interactive GHCi command: print it + λ> :print e + + <interactive>:1:1: error: Not in scope: ‘e’ + λ> :force e + + <interactive>:1:1: error: Not in scope: ‘e’ New description: I was told in #haskell @freenode to report this as a bug. I have a program that throws exceptions and tried debugging the problem within ghci and also outside of ghci with these commands: {{{ stack build --ghc-options '-rtsopts -fprof-auto -fprof-auto-calls' --executable-profiling stack exec -- vhdl +RTS -xc }}} Paraphrased my own words and others from irc: The bug is that it's a bug that ghc is not reporting something useful on the exception. So i don't get sufficient information from the debug facilities. When i have sufficient information i can go ahead and debug my program. This ticket is not about solving a possible bug in my code. The specific issue is that it's producing what ghci calls an undefined exception, and -xc is producing *** Exception (reporting due to +RTS -xc): (THUNK_2_0). "(THUNK_2_0)" doesn't tell anyone anything. I'd expect to see that it reentered something it wasn't supposed to, or something like that. THUNK_2_0 sounds like an internal GHC thing, which i why i'm filing a bug. The +RTS -xc includes names of info tables, which would help identify *what* it's throwing on. but unless the Core is generated at the same time during compilation, it's not possible to find out what. If i generate core now i will get different names. The exception could even be in the standard library. +RTS -xc definitely has a lot of room for improvement When the program runs normally it doesn't terminate. The GHCI run terminate because -fbreak-on-exception was set. {{{#!hs tfComment :: Data from => from -> from tfComment = transformBi tf where tf (Comment ((pos_c, c), (pos_s, s))) = Comment $ ((pos_c, T.concat ["--", c]), (pos_s, s)) tf a = a zeroPos :: Data from => from -> from zeroPos = transformBi zp where zp sp@(M.SourcePos _ _ _) = sp { M.sourceName="", M.sourceLine=unsafePos 1, M.sourceColumn=unsafePos 1} zp x = x -- (a)dd (e)xtended(i)dentifier (s)laches aeis :: Data from => from -> from aeis = transformBi x where x (IExtended a) = let updated_text :: Text updated_text = T.concat ["\\", snd $ t_text a, "\\"] in IExtended $ a {t_text = (fst $ t_text a, updated_text)} x a = a bla = something.. where parser_prop :: ContextClause -> Bool parser_prop = \x -> (transformIn <$> Right x) == (transformOut <$> parseSource parser $ T.toStrict . printSource $ transformIn x) transformIn ast = zeroPos ast transformOut ast = tfComment $ aeis $ zeroPos ast }}} ghci trace {{{ λ> :trace main Stopped in <exception thrown>, <unknown> _exception :: e = _ λ> _exception <interactive>:2:1: error: • No instance for (Show e) arising from a use of ‘print’ Cannot resolve unknown runtime type ‘e’ Use :print or :force to determine these types Relevant bindings include it :: e (bound at <interactive>:2:1) These potential instances exist: instance [safe] Show Args -- Defined in ‘Test.QuickCheck.Test’ instance [safe] Show Result -- Defined in ‘Test.QuickCheck.Test’ instance Show a => Show (ZipList a) -- Defined in ‘Control.Applicative’ ...plus 297 others ...plus 133 instances involving out-of-scope types (use -fprint-potential-instances to see them all) • In a stmt of an interactive GHCi command: print it λ> :print e <interactive>:1:1: error: Not in scope: ‘e’ λ> :force e <interactive>:1:1: error: Not in scope: ‘e’ λ> :back Logged breakpoint at Main.hs:95:13-26 _result :: from -> from tf :: Comment -> Comment λ> :list 94 tfComment :: Data from => from -> from 95 tfComment = transformBi tf -- transformBi tf highlighted here 96 where tf (Comment ((pos_c, c), (pos_s, s))) = Comment $ ((pos_c, T.concat ["--", c]), (pos_s, s)) λ> :back Logged breakpoint at Main.hs:242:28-57 _result :: from ast :: from λ> :list 241 transformIn ast = zeroPos ast 242 transformOut ast = tfComment $ aeis $ zeroPos ast -- tfComment $ aeis $ zeroPos ast highlighted here 243 λ> :force ast ast = Right [] λ> transformIn (Right []) Right [] λ> transformOut (Right []) Right [] λ> zeroPos (Right []) Right [] λ> aeis (Right []) Right [] λ> tfComment (Right []) Right [] }}} run with profiling options (this was aborted at some point) {{{ » stack exec -- vhdl +RTS -xc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Data.CAF --> evaluated by: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 *** Exception (reporting due to +RTS -xc): (THUNK_STATIC), stack trace: Data.Generics.Uniplate.Internal.Data.uniplateVerbose, called from Data.Generics.Uniplate.Internal.Data.CAF:uniplateVerbose --> evaluated by: Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2028_r3oe6 --> evaluated by: Data.Generics.Uniplate.Internal.Data.fromOracle, called from Data.Generics.Uniplate.Internal.Data.biplateData, called from Data.Generics.Uniplate.Data.biplate, called from Main.tfComment, called from Main.qcrp.transformOut, called from Main.qcrp.parser_prop, called from Main.qcrp.parser_prop, called from Main.qc2.logInput, called from Main.qc2.logInput, called from Main.qc2.logInput, called from Main.qc2, called from Test.QuickCheck.Property.forAllShrink.\.\, called from Test.QuickCheck.Property.property, called from Test.QuickCheck.Test.quickCheckWithResult.property', called from Test.QuickCheck.Test.quickCheckWithResult.\, called from Test.QuickCheck.Text.withNullTerminal, called from Test.QuickCheck.Test.quickCheckWithResult, called from Main.qc2, called from Main.qcrp, called from Main.ntc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2025_r3oe3 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2025_r3oe3 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2022_r3oe0 --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl2022_r3oe0 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.biplate.answer, called from Data.Generics.Uniplate.Data.biplate, called from Main.CAF:lvl1945_r3oc9 *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer6_r3ocg --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer6_r3ocg *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer7_r3ocp --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer7_r3ocp *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: Data.Generics.Uniplate.Internal.Data.sybChildren.f, called from Data.Generics.Uniplate.Internal.Data.sybChildren, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f.cs, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate.f, called from Data.Generics.Uniplate.Internal.Data.insertHitMap.populate, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer8_r3ocy --> evaluated by: Data.HashMap.Base.toList', called from Data.HashMap.Base.equal, called from Data.HashMap.Base.==, called from Data.Generics.Uniplate.Internal.Data.fixEq, called from Data.Generics.Uniplate.Internal.Data.insertHitMap, called from Data.Generics.Uniplate.Internal.Data.readCacheFollower, called from Data.Generics.Uniplate.Data.descend.answer, called from Data.Generics.Uniplate.Data.descend, called from Data.Generics.Uniplate.Operations.transform.g, called from Data.Generics.Uniplate.Operations.transform, called from Main.CAF:answer8_r3ocy ^C^C^C^C }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by flip101): mpickering i can attempt to. However this is my first haskell project and the original file is over 2000 lines with a lot of tangled code which i assume you would like have reduced to just a few lines without any dependencies. To be honest i'm not sure if i will be able to pull that off. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by flip101): Maybe a test case is not needed to help the issue along .. i discovered some more things {{{ λ> :trace main Stopped in <exception thrown>, <unknown> _exception :: e = _ λ> :print _exception _exception = (_t1::e) λ> seq _exception () () λ> :p _exception _exception = GHC.Exception.SomeException (GHC.Exception.ErrorCallWithLocation (_t9::String) (_t10::String)) λ> _t9 "Data.Data.fromConstr" λ> _t10 "" }}} https://hackage.haskell.org/package/base-4.9.0.0/docs/src/Data.Data.html#fro... I would say this pretty much points to the origin of the exception. I found out about the seq-trick after another read of the debugging wiki. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12696: Exception gives not enough information to be useful -------------------------------------+------------------------------------- Reporter: flip101 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: exception Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by flip101): The scope of this ticket is just the issue of poorly reported exceptions. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12696#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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