An improving approach to analyzing change impact of C programs

Abstract A seemingly small change in the software can usually have a big impact. Impact analysis is an assessment of multiple risks associated with the changes. Research over the past 20 years has shown that impact analysis can decrease the time and effort needed in the development and regression testing and reduce the negative effects of change on other parts of the software system. These researches used program slicing, control flow analysis, call graph to analyze intraprocedural and interprocedural impact. However, most of them only analyze the methods affected by changes of simple variables or statements, which have coarse granularity and can provide limited help. To solve these problems, we propose an improving approach that can analyze the finer granularity change impact of multiple types of variables. This approach first breaks code changes into a combination of basic operations on variables and adopts corresponding analysis mechanisms for different types of variables. The code is preprocessed before analysis to gather essential information such as global variables table, function summaries, and pointer information map. In the intraprocedural analysis, we first divide the variables into two types: definition point and use point. For the use point, a data flow graph is used to analyze its change impact. For the definition point, we first find the paths where it is and analyze the variables on these paths that are controlled by it. In addition, to deal with the change impact of complex variables in the C programs, we have proposed a corresponding analysis procedure and algorithm. In interprocedural analysis, the impacted methods are searched according to their relationship and the global variable information table. A prototype system is developed based on our approach. In our evaluation, we demonstrate that the prototype system can be used to support various software development and maintenance tasks.