Heterogeneous Testing for Coverage Profilers Empowered with Debugging Support

Ensuring the correctness of code coverage profilers is crucial, given the widespread adoption of code coverage for various software engineering tasks. Existing validation techniques, such as differential testing and metamorphic testing, have shown effectiveness in uncovering bugs in coverage profilers. However, these techniques have limitations as they primarily rely on homogeneous sources, i.e., different coverage profilers or the profilers themselves, for validation. In this paper, we propose Decov, a novel heterogeneous testing technique, to validate coverage profilers using the information provided by debuggers as a heterogeneous source. Coverage profilers record execution counts for each source line in the program, while debuggers monitor hit counts for each source line when running the program in debug mode. Our key insight is that the execution counts obtained from coverage profilers should align with the hit counts monitored by debuggers, without conflicts. Decov constructs multiple heterogeneous relations and utilizes them to uncover bugs in coverage profilers. Through experiments on Gcov and LLVM-cov, two widely used code coverage profilers, we discovered 21 new bug reports, with 19 of them directly confirmed by developers. Notably, developers have resolved 5 bugs in the latest trunk version. Decov serves as a simple yet effective coverage profiler validator and offers a complementary approach to existing techniques.