Question: gdb implemented support for [reverse debugging](http://en.wikipedia.org/wiki/Reverse_debugging) in 2009 (with gdb 7.0). I never heard about it until 2012. Now I find it extremely useful for certain types of debugging problems. I wished that I heard of it before.

Correct me if I'm wrong but my impression is that the technique is still rarely used and most people don't know that it exists. Why?

Do you know of any programming communities where the use of reverse debugging is common?

Background information:

* [Stackoverflow: How does reverse debugging work?](https://stackoverflow.com/questions/1470434/how-does-reverse-debugging-work)
* gdb uses the term "reverse debugging" but other vendors use other terms for identical or similar techniques:
	+ Microsoft calls it [IntelliTrace](http://msdn.microsoft.com/en-us/library/vstudio/dd264915.aspx) or "Historical Debugging"
	+ There's a Java reverse debugger called [Omniscient Debugger](http://www.lambdacs.com/debugger/), though it probably no longer works in Java 6
	+ There are other Java reverse debuggers
	+ OCaml's debugger (ocamldebug) calls it [time travel](http://caml.inria.fr/pub/docs/manual-ocaml-4.00/manual030.html)

Answer: 
For one, running in debug mode with recording on is **very** expensive compared to even normal debug mode; it also consumes a lot more memory. 

It is easier to decrease the granularity from line level to function call level. For example, the standard debugger in eclipse allows you to "drop to frame," which is essentially a jump back to the start of the function with a reset of all the parameters (nothing done on the heap is reverted, and `finally` blocks are not executed, so it is not a true reverse debugger; be careful about that). 

Note that this has been available for several years now and works hand in hand with hot-code replacement.
As mentioned already, performance is key e.g. with gdb's reversible debugging, running something like gzip sees a slowdown of 50,000x compared to running natively. There are commercial alternatives however: I work for Undo [undo.io](https://undo.io), and our UndoDB product does the same but with a slowdown of less than 2x. There are other commercial reversible debuggers available too.