After some discussions at the S4D conference last week, I have some additional updates to the history and technologies of reverse execution. I have found one new commercial product at a much earlier point in time, and an interesting note on memory consistency.
Tag Archives: Reverse Execution
In this final part of my series on the history of reverse debugging I will look at the products that launched around the mid-2000s and that finally made reverse debugging available in a commercially packaged product and not just research prototypes. Part one of this series provided a background on the technology and part two discussed various research papers on the topic going back to the early 1970s. The first commercial product featuring reverse debugging was launched in 2003, and then there have been a steady trickle of new products up until today.
Post updated 2012-09-28 with a revised history.
This is the second post in my series on the history of reverse execution, covering various early research papers. It is clear that reverse debugging has been considered a good idea for a very long time. Sadly though, not a practical one (at the time). The idea is too obvious to be considered new. Here are some papers that I have found dating from the time before “practical” reverse debug which for me starts in 2003 (as well as a couple of later entrants).
For some reason, when I think of reverse execution and debugging, the sound track that goes through my head is a UK novelty hit from 1987, “Star Trekkin” by the Firm. It contains the memorable line “we’re only going forward ’cause we can’t find reverse“. To me, that sums up the history of reverse debugging nicely. The only reason we are not all using it every day is that practical reverse debugging has not been available until quite recently. However, in the past ten years, I think we can say that software development has indeed found reverse. It took a while to get there, however. This is the first of a series of blog posts that will try to cover some of the history of reverse debugging. The text turned out to be so long that I had to break it up to make each post usefully short. Part two is about research, and part three about products.
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I have a new post at my Wind River blog, about variability and determinism and how these two concepts interact. In short, even a deterministic simulator can expose great variability in a software workload and target system behavior.
Last week, I finally got the last “OK” from the maintainers of GDB, the Gnu Debugger, indicating that my contribution to the GDB project was accepted. This is my first contribution to an open-source project, and the piece of code that has my name on it is positively puny. It is actually not really code at all, it is just a piece of documentation, for the extensions to the GDB-MI command set needed to support reversible debugging. The actual code doing the work was contributed by a colleague of mine, Tomas Holmberg, credit where credit is due.
In my series (well, I have one previous post about checkpointing) about misunderstood simulation technology items, the turn has come to the most difficult of all it seems: determinism. Determinism is often misunderstood as meaning “unchanging” or “constant” behavior of the simulation. People tend to assume that a deterministic simulation will not reveal errors due to nondeterministic behavior or races in the modeled system, which is a complete misunderstanding. Determinism is a necessary feature of any simulation system that wants to be really helpful to its users, not an evil that hides errors.