non-exhaustive pattern in getSRTInfo

Here is the code I am attempting to execute:

res :: CoreBind
defaultCodeGen :: [StgBinding] -> IO [Cmm]

coreToStg mainPackageId [res] >>= defaultCodeGen >>= mapM_ (GHC.printDump . GHC.ppr)

defaultCodeGen makes a call to GHC's codeGen.

When I try to run coreToStg, I get the following error:

*** Exception: codeGen/CgUtils.hs:(993,2)-(1009,60): Non-exhaustive patterns in case

Looking at getSRTInfo and the SRT data type, it looks like the SRTEntries data constructor for SRT is never matched. From the comment in the SRT data type, it sounds like this entry is generated precisely by the coreToStg function.

getSRTInfo :: FCode C_SRT
getSRTInfo = do
  srt_lbl <- getSRTLabel
  srt <- getSRT
  case srt of
    -- TODO: Should we panic in this case?
    -- Someone obviously thinks there should be an SRT
    NoSRT -> return NoC_SRT
    SRT off len bmp
      | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
      -> do id <- newUnique
            let srt_desc_lbl = mkLargeSRTLabel id
	    emitRODataLits srt_desc_lbl
             ( cmmLabelOffW srt_lbl off
	       : mkWordCLit (fromIntegral len)
	       : map mkWordCLit bmp)
	    return (C_SRT srt_desc_lbl 0 srt_escape)

    SRT off len bmp
      | otherwise 
      -> return (C_SRT srt_lbl off (fromIntegral (head bmp)))
		-- The fromIntegral converts to StgHalfWord

data SRT = NoSRT
	 | SRTEntries IdSet
		-- generated by CoreToStg
         | SRT !Int{-offset-} !Int{-length-} !Bitmap{-bitmap-}
		-- generated by computeSRTs

If necessary I can package up some code that can be run to reproduce this bug, but perhaps there is a simpler answer first. Maybe I'm doing something in the wrong order in the code generation stuff.

Trac metadata

Trac field	Value
Version	6.8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
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Blocking
CC
Operating system
Architecture	Unknown