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Prototype of a fuzzer for Julia based on concolic execution
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Prototype of a fuzzer using concolic execution. This project is based on Cassette and Julia 0.7-dev and since the former is experimental and the latter in development no gurantees what so ever are given.


  • Julia 1.0


  • Able to generate a trace of an arbitrary Julia program. A trace is an execution of a whole program, with linearised control-flow
  • We are able to "taint" input variables to generate traces that are concolic in nature
  • Can manually assert conditions
  • automatically insert assert statements before branches
  • verification of traces, so that concolic values are propagated
  • reasoning about intrinsics/built-in functions is limited
  • Experimental support for loops
  • No support for functions that return tuples
  • Very limited translation of traces to Z3 (only for programs using <:Integer )
  • Support for tainting values generated by rand
  • Allow for seeding of rand values to have deterministic execution Currently disabled
  • Use values generated by rand function within program as a source of exploration.
  • Use Z3 to generate input values that explore branches
  • Iterate through all controlable or random controlled branches


  • Currently functions need to be manually annotated as leaf-functions for the taint analysis (see src/taint.jl). I would like to support generic taint of functions with the only leaf functions being Julia runtime intrinsics and built-ins. This requires recursive trace generation.
  • Currently doesn't handle floats.
  • No memory-model/No support for Arrays.
  • Bool in Julia is a subtype of Integer, therefore arithmetic and comparision operations are defined. It is not clear to me how to translate that into SMT2. One possibility is translate all Bool to (_ BitVec 1), but than we can no longer use them as output for comparision operations. This will require reasoning over Julia's type system in the solver...
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