TR-Fuzz: A syntax valid tool for fuzzing C compilers

Compilers play a critical role in current software construction. However, the vulnerabilities or bugs within the compiler can pose significant challenges to ensuring the security of the resultant software. In recent years, many compilers have made use of testing techniques to address and mitigate such concerns. Fuzzing is widely used among these techniques to detect software bugs. However, when fuzzing compilers, there are still shortcomings in terms of the diversity and validity of test cases. This paper introduces TR-Fuzz, a fuzzing tool specifically designed for C compilers based on Transformer. Leveraging position embedding and multi-head attention mechanisms, TR-Fuzz establishes relationships among data, facilitating the generation of well-formed C programs for compiler testing. In addition, we use different generation strategies in the process of program generation to improve the performance of TR-Fuzz. We validate the effectiveness of TR-Fuzz through the comparison with existing fuzzing tools for C compilers. The experimental results show that TR-Fuzz increases the pass rate of the generated C programs by an average of about 12% and improves the coverage of programs under test compared with the existing tools. Benefiting from the improved pass rate and coverage, we found five bugs in GCC-9.