this paper is structured in the following way: a thorough description of the structure of a decompiler, followed by the description of our implementation of an # An idiom is a sequence of instruction that forms a logical entity and has a meaning that cannot be derived by considering the primary meanings of the individual instructions # # # # HLL program (language dependent) Back-end (analysis) UDM (machine dependent) Front-end binary program Figure 1. Decompiler modules automatic decompiling system, and conclusions. The paper is followed by the definitions of graph theoretical concepts used throughout the paper (Appendix I), and sample output from different phases of the decompilation of a program (Appendix II)

While a compiler produces object code from source code, a decompiler produces source code from object code, and has applications in the testing and validation of safety-critical software. Decompiling an object code provides an independent demonstration of correctness that is hard to better for industrial purposes (the alternative is to prove the compiler correct). But although compiler compilers are in common use in the software industry, a decompiler compiler is much more unusual. It turns out that a data type specification representing a programming language grammar can be remolded into a functional program that enumerates all the abstract syntax trees. This observation is the springboard for a general method for compiling decompilers from the specifications of (non-optimizing) compilers. This paper deals with methods and theory, together with an application of the technique. The correctness of a decompiler generated from the specification for a simple occam-like compiler is demonstrated.

Compiler compilers are in widespread use, but decompiler compilers are a more novel concept.