Towards Better Tool Support for Code Comprehension.

In software development, bug fixing and feature development requires a thorough understanding of all details and consequences of the planned changes. For long-existing large software systems, the code-base has been developed and maintained for decades by fluctuating teams, thus original intentions are lost, the documentation is untrustworthy or missing. Most times, the only reliable information is the code itself. Source code comprehension of such large software is an essential, but usually very challenging task. The comprehension process and approach of existing systems is fundamentally different from writing new software, and the usual development tools provide poor support in this area. Throughout the years, different tools have been developed with various complexity and feature set for code comprehension but none of them fulfilled all specific requirements yet. In this paper we discuss the most accepted models for code comprehension, the required feature set for tools supporting the comprehension process and the various approaches of existing solutions. We present CodeCompass – an open source LLVM/Clang based tool to help understanding large legacy software systems – in detail to analyse the required interface, possible design choices and implementation considerations. Based on the LLVM/Clang compiler infrastructure, CodeCompass gives exact information on complex C/C++ language elements such as inheritance, overloading, variable usage, possible function pointer and virtual function calls etc. These are all features for which various existing tools provide only partial support. Although CodeCompass supports mainly the C and C++ programming languages, it has a restricted support for Java and Python languages as well, therefore our investigation is language-independent.