[GHC] #12696: Exception gives not enough information to be useful

[GHC]

#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>
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