wiki:Debugging/Compiler

Version 1 (modified by simonmar, 6 years ago) (diff)

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Debugging the compiler

Basic strategies

At compile time (see also the relevant User Manual section):

  • Use -v3 or -v4 to get an idea about what GHC is doing when the problem occurs.
  • Add -dcore-lint the GHC command line when compiling each Haskell module. This makes GHC type-check the intermediate program after every optimisation pass, which often nails a fault.
  • Add -ddump-simpl to see the optimised Core output. There are a number of other -ddump-x flags; see the user manual.
  • The flag -dppr-debug makes the -ddump-x flags print much more verbose output. Use this if you are getting desperate!