Writing logging messages is a well-established conventional programming practice, and it is of vital importance for a wide variety of software development activities. The logging mechanism in Solidity programming is enabled by the high-level event feature, but up to now there lacks study for understanding Solidity event logging practices in the wild. To fill this gap, we in this paper provide the first quantitative characteristic study of the current Solidity event logging practices using 2,915 popular Solidity projects hosted on GitHub. The study methodically explores the pervasiveness of event logging, the goodness of current event logging practices, and in particular the reasons for event logging code evolution, and delivers 8 original and important findings. The findings notably include the existence of a large percentage of independent event logging code modifications, and the underlying reasons for different categories of independent event logging code modifications are diverse (for instance, bug fixing and gas saving). We additionally give the implications of our findings, and these implications can enlighten developers, researchers, tool builders, and language designers to improve the event logging practices. To illustrate the potential benefits of our study, we develop a proof-of-concept checker on top of one of our findings and the checker effectively detects problematic event logging code that consumes extra gas in 35 popular GitHub projects and 9 project owners have already confirmed the detected issues.

翻译：编写日志消息是一种成熟的常规编程实践，对于各种软件开发活动至关重要。Solidity编程语言中的日志记录机制通过高级事件特性实现，但迄今为止，尚缺乏对野外Solidity事件日志记录实践的系统性研究。为填补这一空白，本文利用GitHub上托管的2,915个热门Solidity项目，首次对当前Solidity事件日志记录实践进行了定量特征研究。该研究系统性地探讨了事件日志记录的普遍性、当前事件日志记录实践的优势，特别是事件日志记录代码演化的原因，并提出了8项原创且重要的发现。这些发现尤其包括：存在大量独立的事件日志记录代码修改，且不同类别的独立事件日志记录代码修改背后的原因各不相同（例如，修复漏洞和节省Gas费用）。此外，我们给出了研究发现的启示，这些启示可启发开发者、研究人员、工具构建者和语言设计者改进事件日志记录实践。为展示本研究的潜在价值，我们基于一项发现开发了一个概念验证检查器，该检查器有效检测了35个热门GitHub项目中消耗额外Gas的有问题的事件日志记录代码，其中9个项目的所有者已确认检测到的问题。