didiffff: A Viewer for Comparing Changes in both Code and Execution Traces

One of the important purposes of code review is to find potential defects caused by other developers' code changes. When reviewing bug fixes, it is important to check the program behavior is properly changed to remove the bug. On the other hand, it is also impor-tant to check the program behavior that is not related to the bug is not changed. To investigate the program behavior, omniscient debugging which records all the runtime events is proposed. With omniscient debugging techniques, existing tools visualize multiple execution paths and the states of local variables of a method, but they are not focusing on code changes. In this paper, we imple-mented a prototype tool that compares and visualizes the difference between two execution traces caused by code changes. Each vari-able has a maximum of two lists of values, before and after the code changes, so we proposed their categorization based on their difference of length and contents. We also developed a viewer to show both code changes and the difference of execution traces at a glance by extending our previous viewer for omniscient debugging.