Understanding and Characterizing Type System-Related Bugs in Compilers of JVM Programming Languages

Presenter: Thodoris Sotiropoulos
Date: 05 March 2021


Over the past decade, there was a huge interest in compiler testing that led to the disclosure of thousands of bugs in well-established and widely-used compilers. Despite this tremendous success, current research endeavors have mainly focused on detecting frustrating compiler crashes, and subtle miscompilations caused by bugs in the implementation of compiler optimizations. However, in statically-typed languages, the frontend part of a compiler is equally important, as it is the component that decides whether the input program is correct or not. In modern programming languages with sophisticated type system features the implementation of frontend is much complex, and therefore, type system-related bugs are quite often. Bugs in the implementation of frontend can break the soundness of type system, lead to rejection of correct programs, or make the compiler produce misleading reports and warnings.

We present a study of bugs found in compiler frontends. Specifically, we examine frontend bugs reported in the top JVM programming languages, namely, Java, Scala, Kotlin, and Groovy. We evaluate each bug in terms of several criteria, including their symptom, root cause, characteristics of the test case that triggers the bug, and finally we propose a categorization. We believe that this work opens up a new direction in compiler testing, which is currently overlooked.