When Does My Program Fail?

Oops! My program fails. Which are the circumstances under which this failure occurs? Answering this question is one of the first steps in debugging -- and a crucial one, as it helps characterizing, understanding, and classifying the problem. In this paper, we propose a technique to identify failure circumstances automatically. Given a concrete failure, we first compute the path condition leading to the failure and then use a constraint solver to identify, from the constraints in the path condition, the general failure conditions: "The program fails whenever the credit card number begins with 6, 5, and a non-zero digit." A preliminary evaluation of the approach on real programs demonstrates its potential usefulness.