A Fully Capable Bidirectional Debugger

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9619456 Traditional debuggers allow stepping along the forward execution path of a computer program and monitoring the program's state as it executes. They are a crucial tool in the process of program development, however they also can be frustrating in many situations when the user wishes to see not what the program is going to do in the future, but rather what happened in the past to bring it to where it currently is. This research will investigate and develop algorithms and mechanisms that can be used in constructing a bidirectional program debugger. Efficient backwards movement algorithms will be investigated for all traditional forward movement operations: step, next, finish, and location breakpoints. The underlying techniques expected to be utilized and developed in this research are code augmentation, transparent re-execution, I/O replay, and checkpointing. In addition, this research will investigate efficient bidirectional algorithms for conditional breakpoints and data breakpoints, which are currently often inefficient operations or unavailable even in the forward direction. Debuggers are widely used from introductory programming students trying to understand why their program has gone astray, to professional programmers trying to find bugs in large and complicated systems. Development of better debugging tools will benefit all who are involved in program development and maintenance. ***