New type signatures for legacy Fortran subroutines

ABSTRACT

We are currently developing a methodological framework for reverse engineering Fortran77 programs used by Electricité de France, in which the first step is the construction of an algebraic specification which faithfully represents the Fortran code. To construct this specification, we must decide on a coherent set of "profiles" (type signatures) for the specifications of the Fortran sub-programs. We propose an analysis of the dynamic aliases between formal and actual sub-program arguments in order to derive these profiles. In many examples of real Fortran code this analysis does not give satisfactory results if arrays are treated as indivisible. Instead, we must take into account which fragment of the array may really be accessed by the sub-program. We have therefore implemented our analysis as an extension of the PIPS code parallelisation tool, which provides us with a precise analysis of inter-procedural array data-flow.

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INDEX TERMS

Primary Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.2 Language Classifications

          Nouns: FORTRAN

Additional Classification:
  D. Software
  D.2 SOFTWARE ENGINEERING
      D.2.7 Distribution, Maintenance, and Enhancement
          Subjects: Restructuring, reverse engineering, and reengineering

General Terms:
Design, Languages, Measurement, Performance, Theory

Keywords:
Fortran, alias analysis, array region, dynamic alias, reverse engineering