When Code Smells Twice as Much: Metric-Based Detection of Variability-Aware Code Smells

Code smells are established, widely used characterizations of shortcomings in design and implementation of software systems. As such, they have been subject to intensive research regarding their detection and impact on understandability and changeability of source code. However, current methods do not support highly configurable software systems, that is, systems that can be customized to fit a wide range of requirements or platforms. Such systems commonly owe their configurability to conditional compilation based on C preprocessor annotations (a. k. a. #ifdefs). Since annotations directly interact with the host language (e.g., C), they may have adverse effects on understandability and changeability of source code, referred to as variability-aware code smells. In this paper, we propose a metric-based method that integrates source code and C preprocessor annotations to detect such smells. We evaluate our method for one specific smell on five open-source systems of medium size, thus, demonstrating its general applicability. Moreover, we manually reviewed 100 instances of the smell and provide a qualitative analysis of its potential impact as well as common causes for the occurrence.