A Soundness and Precision Benchmark for Java Debloating Tools

TL;DR

This paper introduces Deblometer, a benchmark for evaluating Java debloating tools' ability to balance removing unnecessary code with preserving program correctness, revealing significant soundness issues in existing tools.

Contribution

We created Deblometer, a comprehensive benchmark with ground truth for systematically assessing Java debloating tools' support for language features and their soundness and precision.

Findings

All evaluated tools remove required constructs, causing semantic changes or crashes.

Dynamic class loading causes unsoundness in all tools.

ProGuard often removes more required constructs than others.

Abstract

Modern software development reuses code by importing libraries as dependencies. Software projects typically include an average of 36 dependencies, with 80% being transitive, meaning they are dependencies of dependencies. Recent research indicates that only 24.9% of these dependencies are required at runtime, and even within those, many program constructs remain unused, adding unnecessary code to the project. This has led to the development of debloating tools that remove unnecessary dependencies and program constructs while balancing precision by eliminating unused constructs and soundness by preserving all required constructs. To systematically evaluate this trade-off, we developed Deblometer, a micro-benchmark consisting of 59 test cases designed to assess support for various Java language features in debloating tools. Each test case includes a manually curated ground truth specifying necessary and bloated classes, methods, and fields, enabling precise measurement of soundness and precision. Using Deblometer, we evaluated three popular Java debloating tools: Deptrim, JShrink, and ProGuard. Our evaluation reveals that all tools remove required program constructs, which results in changed semantics or execution crashes. In particular, the dynamic class loading feature introduces unsoundness in all evaluated tools. Our comparison shows that Deptrim retains more bloated constructs, while ProGuard removes more required constructs. JShrink's soundness is significantly affected by limited support for annotations, which leads to corrupted debloated artifacts. These soundness issues highlight the need to improve debloating tools to ensure stable and reliable debloated software.