Michael Bond on tracking null pointers via piggybacking

Eric | October 25, 2007

Michael Bond presented an interesting approach to tracking the origin of unusable values such as null today at OOPSLA. His team uses a piggybacking approach, which makes this task very efficient. Instead of storing null when null is assigned, they store some special data structure encoding the location at which this assignment occurs. If then a nullpointer exception happens later on, they are able to report that location. Runtime overheads for their java-based approach (based on modifications to the Jikes RVM) was about 4% in average only.