#12433: GHCi produces incorrect results when evaluating with compiled code -------------------------------------+------------------------------------- Reporter: diatchki | Owner: Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: ghci, dynamic | linking, compiled code Operating System: Linux | Architecture: x86_64 Type of failure: Incorrect result | (amd64) at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): I think it's `genSwitch` that is at fault here. It calculates the operand adjusted for the start of the jump table with `getSomeReg`, but that doesn't mean it is entitled to clobber the returned `reg` later, after `-- HACK: On x86_64 binutils<2.17 is only able to generate...`. Here is a single-module reproducer that does not involve the GC. It should be compiled with `-dynamic` (or `-fPIC`) and `-O`. {{{#!hs f :: Int -> IO () f p = case p of 0 -> return () 1 -> return () 2 -> return () 3 -> return () 4 -> return () 10 -> return () 11 -> return () _ -> print p {-# NOINLINE f #-} main = f 8 }}} I had to use a value that falls into the default case, as GHC creates an unfolding for a scrutinee that has been successfully matched against a numeric literal and then I couldn't find any way to get the generated code to refer to the original scrutinee. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12433#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler