Re: Checkpoint-restart with different code

[Daniel Jacobowitz <drow@false.org>]

On Fri, Dec 09, 2005 at 04:57:57PM -0500, Greg Bronevetsky wrote:
> I see that there's been some discussion on this list on checkpointing 
> techniques that may be included in gdb. My research group at Cornell is 
> working on a number of such checkpointers for both sequential and 
> parallel programs and we recently decided to try a more challenging 
> variant of checkpointing where the user can take a checkpoint of their 
> program, modify their source code a bit (add remove stack variables, 
> move function calls around a bit and a few other things) and then resume 
> computation using the modified code. This seems to be very useful for 
> debugging long-running applications since the user would be able to work 
> around the bug without losing a week's or month's worth of results. (can 
> happen in high-performance computing) Similarly, its useful for 
> situations where your execution is in some particularly buggy corner 
> case and you want to keep making modifications and trying them out 
> without having to guide the program's execution back into that corner 
> case after every code change.
> 
> My question is, has anybody heard of anything that can do this? 
> Obviously, this kind of checkpointing would require compiler support, so 
> gdb wouldn't have done this, but have you heard of any systems/research 
> that has addressed this question? Thanks.

Better: I know at least one production debug environment which supports
this - Apple's Xcode.  The option is called fix-and-continue.  I don't
think they combine it with checkpointing, though, only as an action on
a running process.  It's partly compiler-based and partly in their
debug environment.

Merging that with Michael's fork-based code would be fairly
straightforward, I expect.

-- 
Daniel Jacobowitz
CodeSourcery, LLC