Challenges of refactoring C programs

ABSTRACT

Refactoring has become a well-known technique for transforming code in a way that preserves behavior. Refactorings may be applied manually, although manual code manipulation is error prone and cumbersome, so maintainers need tools to make automatic refactorings. There is currently extensive literature on refactoring object-oriented programs and some very good tools for refactoring Smalltalk and Java code. Although there is more code written in C or C++ than in any other language, refactoring tools for C with full support for preprocessor directives have not yet appeared.The C programming language, especially the preprocessor directives that coexist with it, complicates refactorings in different ways as directives are not legal C code and may violate otherwise correct refactorings.Refactoring C poses two major research challenges. On the one hand, as preprocessor directives may violate correctness, new precondition and execution rules must be defined for existing refactorings to preserve behavior. On the other hand, the automated execution of refactorings requires specialized program analysis tools to represent and manipulate preprocessor directives. After studying the area we have found some results to overcome these challenges and make a correct tool for the C language attainable.This paper first discusses the difficulties in refactoring C code with preprocessor directives. It then defines preconditions and execution rules to maintain correctness of refactoring in the presence of macros and conditional directives. Moreover, new refactorings are proposed for macro definitions and conditionals. Lastly, the paper suggests enhancements to program analysis and program representation tools to correctly manipulate preprocessor directives.

REFERENCES

• 1: Robert W. Bowdidge , William G. Griswold, Supporting the restructuring of data abstractions through manipulation of a program visualization, ACM Transactions on Software Engineering and Methodology (TOSEM), v.7 n.2, p.109-157, April 1998 [doi>10.1145/279310.279312]
• 2: DMS Software Reengineering Toolkit. http://www.semdesigns.com/Products/DMS/DMSToolkit.html
• 3: Ernst, M., Badros, G. and Notkin, D. An Empirical Analysis of C Preprocessor Use. Revision of Technical Report UW-CSE-97-04-06. Dept. of Computer Science and Engineering. Univ. of Washington, Seattle, 1999.
• 4: Brian Foote , William F. Opdyke, Lifecycle and refactoring patterns that support evolution and reuse, Pattern languages of program design, ACM Press/Addison-Wesley Publishing Co., New York, NY, 1995
• 5: Refactoring: improving the design of existing code, Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1999
• 6: Fowler, M. Crossing Refactoring's Rubicon. http://www.martinfowler.com/articles/refactoringRubicon.html
• 7: Garrido, A. Software Refactoring Applied to C Programming Language. MS Thesis. University of Illinois at Urbana-Champaign, 2000.
• 8: William G. Griswold , Morison I. Chen , Robert W. Bowdidge , J. David Morgenthaler, Tool support for planning the restructuring of data abstractions in large systems, Proceedings of the 4th ACM SIGSOFT symposium on Foundations of software engineering, p.33-45, October 16-18, 1996, San Francisco, California, United States
• 9: IntelliJ IDEA: Java IDE with refactoring support. http://www.intellij.com/idea/
• 10: jFactor home page. http://www.instantiations.com/jfactor/
• 11: Brian W. Kernighan , Dennis M. Ritchie, The C programming language, Prentice Hall Press, Upper Saddle River, NJ, 1989
• 12: Moose Refactoring Engine. http://scgwiki.iam.unibe.ch:8080/SCG/19
• 13: Ó Cinnéide, M. Automated Application of Design Patterns: a Refactoring Approach. PhD thesis, University of Dublin, Trinity College, 2001.
• 14: William F. Opdyke, Refactoring object-oriented frameworks, University of Illinois at Urbana-Champaign, Champaign, IL, 1992
• 15: Roberts, D. Eliminating Analysis in Refactoring. PhD Thesis, University of Illinois at Urbana-Champaign, 1999.
• 16: Don Roberts , John Brant , Ralph Johnson, A refactoring tool for Smalltalk, Theory and Practice of Object Systems, v.3 n.4, p.253-263, 1997 [doi>10.1002/(SICI)1096-9942(1997)3:4<253::AID-TAPO3>3.3.CO;2-I]
• 17: Bjarne Stroustrup, The design and evolution of C++, ACM Press/Addison-Wesley Publishing Co., New York, NY, 1995
• 18: Lance Tokuda , Don Batory, Evolving Object-Oriented Designs with Refactorings, Proceedings of the 14th IEEE international conference on Automated software engineering, p.174, October 12-15, 1999
• 19: Xref- Technologies - refactoring development tools. http://xref-tech.com/xrefactory/

INDEX TERMS

Primary Classification:
  D. Software
  D.2 SOFTWARE ENGINEERING
      D.2.3 Coding Tools and Techniques
          Subjects: Program editors

Additional Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.2 Language Classifications
      D.3.3 Language Constructs and Features

General Terms:
Design, Languages

Keywords:
C programming, preprocessor directives, refactoring