Sporadic GHCJS crashes and panics

[johannesgerer]

Hello,

ghcjs-8.6.0.1 -O2 obtained through Reflex Platform on x86_64 GNU/Linux crashes sporadically on my codebase and usually runs through on retry.

Unable to identify a pattern, I would not know where to start debugging this and am aware that the information in this (initial) post is not enough to investigate the root cause.

This issue is started to keep track of these crashes, also for reference for other people experiencing similar crashes.

Retrying a compilation here and there is not a big issue, my real concern is that GHCJS might produce incorrect or corrupt code(?).

Some of the error messages mention: Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug, but I guess given this is GHCJS this does not apply here?

These are four examples:

(cabal is compiling modules in parallel so I am not sure whether the Linking Template Haskell actually came from the crashed compilation.)

<no location info>: error:
    expectJust cpeBody:collect_args
CallStack (from HasCallStack):
  error, called at compiler/utils/Maybes.hs:55:27 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:Maybes
  expectJust, called at compiler/coreSyn/CorePrep.hs:930:32 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:CorePrep

Linking Template Haskell ([...])

<no location info>: error:                                                                                
    ghcjs: panic! (the 'impossible' happened)
  (GHC version 8.6.5 for x86_64-unknown-linux):
        tcIfaceExtId                                                                                                                                                                                                
  $fPersistEntityColumnA_$ckeyToValues                                                                                                                                                                            
  Coercion axiom ‘D:R:EntityFieldIndexProdtyp0’                                                                                                                                                                     
  Call stack:                                                                                                                                                                                                       
      CallStack (from HasCallStack):                                                                      
        callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:Outputable
        pprPanic, called at compiler/iface/TcIface.hs:1695:38 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:TcIface

Linking Template Haskell ([...])

<no location info>: error:
    ghcjs: panic! (the 'impossible' happened)
  (GHC version 8.6.5 for x86_64-unknown-linux):
        getClassPredTys
  forall a b.
  WhenMatched f_a1iYU x_a1iYV y_a1iYW a
  -> (a -> WhenMatched f_a1iYU x_a1iYV y_a1iYW b)
  -> WhenMatched f_a1iYU x_a1iYV y_a1iYW b
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:Outputable
        pprPanic, called at compiler/types/Type.hs:1848:29 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:Type

<no location info>: error:                                                                                                                                                                                              ghcjs: panic! (the 'impossible' happened)                                                                                                                                                                       
  (GHC version 8.6.5 for x86_64-unknown-linux):                                                                                                                                                                             getClassPredTys                                                                                                                                                                                             
  Put ()                                                                                                                                                                                                            
  Call stack:                                                                                                                                                                                                             CallStack (from HasCallStack):                                                                                                                                                                                
        callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:Outputable                                                                                               pprPanic, called at compiler/types/Type.hs:1848:29 in ghc-api-ghcjs-8.6.5-6FVyIFYUYrGAjZejsOfZHE:Type                                                                                                                                                                                                                     

Thanks,
Johannes

[cdsmith]

One thing you might try is telling cabal not to build in parallel. This fixed my random GHCJS panics with the same version of GHCJS. If you disable parallel builds and it fixes the problem, that is a huge step toward identifying the cause.

[3noch]

Possibly related: #654

[ddssff]

We had these problems until we switched from cabal to cabal-v2. Mysterious, I know.

[ilyakooo0]

I get a reproducible error: https://github.com/typeable/octopod/pull/83/checks?check_run_id=3408759131

rerunning the job yields the same result

for history: this is the commit typeable/octopod@8091758