[GHC] #7215: miscompilation due to broken interface hash

[GHC]

#7215: miscompilation due to broken interface hash
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 Reporter:  akio                         |          Owner:                
     Type:  bug                          |         Status:  new           
 Priority:  normal                       |      Component:  Compiler      
  Version:  7.4.2                        |       Keywords:                
       Os:  Linux                        |   Architecture:  x86_64 (amd64)
  Failure:  Incorrect result at runtime  |       Testcase:                
Blockedby:                               |       Blocking:                
  Related:                               |  
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 The following script should print '!MyFalse !MyTrue' but it prints
 '!MyFalse !MyFalse'. (warning: it removes files in the current directory)

 {{{
 rm -f main main.o main.hi MyBool.hi MyBool.o Foo.hi Foo.o

 ghc=ghc
 echo 'module MyBool where data MyBool = MyFalse | MyTrue deriving Show' >
 MyBool.hs
 echo 'module Foo where import MyBool; foo = MyFalse' > Foo.hs
 echo 'import Foo; main = print foo' > main.hs
 $ghc -c -O2 MyBool.hs
 $ghc -c -O2 Foo.hs
 $ghc -O2 main.hs
 ./main
 echo 'module Foo where import MyBool; foo = MyTrue' > Foo.hs
 $ghc -c -O2 Foo.hs
 $ghc -O2 main.hs
 ./main
 }}}

 The issue seems to be that the second version of Foo.hs gets the same
 interface hash as the old one. This stops GHC from updating Foo.hi, which
 contains an outdated unfolding.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7215>
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