CrossLangFuzzer: Differential Testing of Cross-Language JVM Compilers

2026-06-26

AI Summary

This work addresses the challenge of detecting cross-language compilation bugs in multi-language JVM applications, which arise from semantic discrepancies between languages and are largely overlooked by existing compiler testing approaches focused on single-language settings. To bridge this gap, the authors propose the first differential testing framework tailored for cross-language JVM compilation. The approach leverages Kotlin’s unified intermediate representation (IR) to synthesize cross-language test programs and introduces seven custom mutation operators to enhance test diversity. This methodology enables the first systematic differential testing of multi-language JVM compilation scenarios, uncovering 32 confirmed bugs across five major compilers—Kotlin, Groovy, Scala 2/3, and Java. The findings demonstrate that the framework effectively exposes and mitigates semantic inconsistencies at language boundaries, significantly improving compiler reliability.

Abstract

Modern JVM software increasingly integrates multiple programming languages, such as Java, Kotlin, Groovy, and Scala, within a single application. Supporting such interoperability requires JVM compilers to perform cross-language compilation while reconciling subtle semantic differences across language boundaries. Errors in this process can lead to critical miscompilations, yet existing compiler testing techniques focus exclusively on isolated, singlelanguage compilation. To address this gap, we present CrossLangFuzzer, the first differential testing framework for cross-language JVM compilation. CrossLangFuzzer leverages the Kotlin compiler's unified intermediate representation (IR) to synthesize cross-language test programs. It further applies seven mutation operators to diversify generated test programs and improve bug-finding capability. Evaluated on the latest versions of five major JVM compilers, CrossLangFuzzer uncovered 32 confirmed bugs, including 15 in Kotlin, 4 in Groovy, 7 in Scala 3, 2 in Scala 2, and 4 in Java. CrossLangFuzzer is open-source at https://github.com/XYZboom/CrossLangFuzzer

Problem

• cross-language compilation
• JVM compilers
• compiler testing
• semantic differences
• multi-language interoperability

Innovation

• Cross-language compilation
• Differential testing
• JVM compilers
• Intermediate representation (IR)
• Mutation operators