Tolerating C Integer Error via Precision Elevation

In C programs, integer error is a common yet important kind of defect due to arithmetic operations that produce unrepresentable values in certain types. Integer errors are harbored in a wide range of applications and possibly lead to serious software failures and exploitable vulnerabilities. Due to the complicated semantics of C, manually preventing integer errors is challenging even for experienced developers. In this paper we propose a novel approach to automate C integer error repair by elevating the precision of arithmetic operations according to a set of code transformation rules. A large portion of integer errors can be repaired by recovering expected results (i.e., tolerance) instead of removing program functionality. Our approach is fully automatic without requiring code specifications. Furthermore, the transformed code is ensured to be well-typed and has conservativeness property with respect to the original code. Our approach is implemented as a prototype CIntFix which succeeds in repairing all the integer errors from 7 categories in NIST's Juliet Test Suite. Furthermore, CIntFix is evaluated on large code bases in SPEC CINT2000, scaling to 366 KLOC within 126 seconds while the transformed code has 10.5 percent slowdown on average. The evaluation results substantiate the potential of our approach in real-world scenarios.