Every once in a while I need to build demo setups to show debugging in action. As I have blogged before, finding a good bug when you need one isn’t always easy. The solution is to try to invent artificial bugs, and I was very happy when I managed to stage a buffer overrun in a VxWorks program.
It is pretty very nice demo in which you first start a period program A, which prints the value of an incrementing counter every target second. You then run a supposedly unrelated program B, resulting in the values that program A prints to become corrupted. Perfect to show off reverse execution and data breakpoints in reverse as you go from the point where the corrupted value is printed to the piece of code that overwrote the variable.
But then I ported the demo to a new platform… and the bug didn’t work anymore. My bug had caught a bug and was now not working, or at least not they way I expected it to. What had happened?
Continue reading “My Bug Doesn’t Work!”