Predicting Null-Pointer Dereferences in Concurrent Programs ∗

We propose null-pointer dereferences as a target for finding bugs in concurrent programs using testing. A null-pointer dereference prediction engine observes an execution of a concurrent program under test and predicts alternate interleavings that are likely to cause null-pointer dereferences. Though accurate scalable prediction is intractable, we provide a carefully chosen novel set of techniques to achieve reasonably accurate and scalable prediction. We use an abstraction to the shared-communication level, take advantage of a static lock-set based pruning, and finally, employ precise and relaxed constraint solving techniques that use an SMT solver to predict schedules. We realize our techniques in a tool, ExceptioNULL, and evaluate it over 13 benchmark programs and find scores of nullpointer dereferences by using only a single test run as the prediction seed for each benchmark. D.2.4 [Software Engineer-D.2.5 [Software Engineer