How does reverse debugging work?

Question

GDB has a new version out that supports reverse debug (see http://www.gnu.org/software/gdb/news/reversible.html). I got to wondering how that works.

To get reverse

Answer 1

Although this question is old, most of the answers are too, and as reverse-debugging remains an interesting topic, I'm posting a 2015 answer. Chapters 1 and 2 of my MSc thesis, Combining reverse debugging and live programming towards visual thinking in computer programming, covers some of the historical approaches to reverse debugging (especially focused on the snapshot-(or checkpoint)-and-replay approach), and explains the difference between it and omniscient debugging:

The computer, having forward-executed the program up to some point, should really be able to provide us with information about it. Such an improvement is possible, and is found in what are called omniscient debuggers. They are usually classified as reverse debuggers, although they might more accurately be described as "history logging" debuggers, as they merely record information during execution to view or query later, rather than allow the programmer to actually step backwards in time in an executing program. "Omniscient" comes from the fact that the entire state history of the program, having been recorded, is available to the debugger after execution. There is then no need to rerun the program, and no need for manual code instrumentation.

Software-based omniscient debugging started with the 1969 EXDAMS system where it was called "debug-time history-playback". The GNU debugger, GDB, has supported omniscient debugging since 2009, with its 'process record and replay' feature. TotalView, UndoDB and Chronon appear to be the best omniscient debuggers currently available, but are commercial systems. TOD, for Java, appears to be the best open-source alternative, which makes use of partial deterministic replay, as well as partial trace capturing and a distributed database to enable the recording of the large volumes of information involved.

Debuggers that do not merely allow navigation of a recording, but are actually able to step backwards in execution time, also exist. They can more accurately be described as back-in-time, time-travel, bidirectional or reverse debuggers.

The first such system was the 1981 COPE prototype ...