Debugging with Online Slicing and Dryrun

Efficient tools are indispensable in the battle against software bugs during both development and main-tenance. In this short paper, we introduce two tech-niques that target different phases of an interactive and iterative debugging session. To help fault diag-nosis, we split the costly computation of backward slicing into online and offline, and employ incre-mental updates after program edits. The result is a vast reduction of slicing cost. For the benchmarks we tested, slices can be computed in the range of seconds, which is 0.3%˜5 % of the unmodified slic-ing algorithm. The possibility of running slicing in situ and with instant response time gives rise to the possibility of editing-time validation, which we call dryrun. The idea is that a pair of slices, one forward from root cause and one backward from the bug site, defines the scope to validate a fix. This localization makes it possible to invoke symbolic execution and con-straint solving that are otherwise too expensive to use in an interactive debugging environment.