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haskell / hoopl

Higher-order optimization library
http://hackage.haskell.org/package/hoopl
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Runtime error caused by fromJust in module Dataflow #32

Open anakreontas opened 8 years ago

anakreontas commented 8 years ago

In line 274 of DataFlow, function arfx uses fromJust assuming that looking up a fact always produces a result. Would you please change the implementation into:

    arfx arf thing fb =
      case lookupFact (entryLabel thing) (joinInFacts lattice fb) of
        Nothing -> error $
                   "Dataflow.hs: arfx => Clueless on label:"
                   ++ (show . entryLabel) thing
        Just x -> arf thing x

It was hard to spot where the error was raised. Including clues in the error message should help.

Regards

mlite commented 8 years ago

Is this check in arfx too late? Will adding an invariant check "all entry labels should have a fact" to analyzeAndRewriteFwd be better? A similar invariant check can be added to analyazeAndRewriteBwd.

anakreontas commented 8 years ago

I don't know where it would be best to check runtime invariants. However if an invariant doesn't hold because of a programming error, like in my case, an informative error message would help.

Regards

On 12:11, Fri, 27 May 2016 Ning Wang, notifications@github.com wrote:

Is this check in arfx too late? Will adding an invariant check "all entry labels should have a fact" to analyzeAndRewriteFwd be better? A similar invariant check can be added to analyazeAndRewriteBwd.

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