Unsafe and Unused? A History of Utility Code in Mature Open Source Projects

2026-04-30

AI Summary

This study investigates whether utility (“util”) code in open-source projects is increasingly deprecated as projects mature and examines its security implications and usage patterns. Through longitudinal mining of seven long-evolving projects—spanning 1,773 time points and 147 project-years—and integrating Git snapshot analysis, file rename tracking, and statistical modeling, the work reveals for the first time that util files are significantly more likely to be sources of security vulnerabilities, exhibiting a 2.75-fold higher probability of containing flaws compared to non-util files. Moreover, these files are often maintained in isolation by their original authors and demonstrate markedly low code reuse rates. These findings highlight a critical maintenance blind spot and elevated security risk associated with util modules throughout software evolution.

Abstract

Filenames are a concise means of conveying information about source code to fellow developers. One such convention is util. Commonly understood to stand for "utility", filenames with the letters util are often an indication that the file contains code that may be broadly useful or reusable. Some projects use this convention heavily, for example, the Apache Tomcat server contains 925 files with util in the path name, which is 17.9% of all source code files in the tree. While the intent of the name may be to prevent duplicate code and reduce workload, what actually happens to util code over time? Do projects move away from util code as they mature? Are util files being used by fellow colleagues, or maintained and used by their author? The goal of our work is to help developers avoid creating unsafe and unused util files when developing their projects. We conducted a longitudinal mining study of the Git repositories of seven open source projects that have a long development history (Linux kernel, Django, FFmpeg, httpd, Struts, systemd, Tomcat). We analyzed how util usage, complexity, developer collaboration, and security are potentially correlated within these projects. Our longitudinal analysis was measured at 30-day intervals throughout the entire history of each project, resulting in 1773 snapshots over 147 project-years of development. We conducted rename tracking at every 30-day snapshot to examine util files over their entire lifetime in a codebase. For example, we found that a util file can be as much as 2.75 times more likely to be involved in a vulnerability than non-util files. While every project can adopt their own naming conventions, the ubiquity and longevity of util files shows a broader developer intent that is useful for understanding the socio-technical nature of software development.

Problem

• utility code
• code reuse
• software maintenance
• security vulnerabilities
• open source projects

Innovation

• utility code
• longitudinal mining
• software evolution
• code reuse
• security vulnerability