Re: Checkpoint-restart with different code

[Greg Bronevetsky <greg@bronevetsky.com>]

Thanks for your help! I've looked around some more and it looks like a 
number of debuggers provide some form of this functionality. However, 
they all seem to be binary rewriters. Does anybody know of work at the 
compiler level? I can imagine that it would be possible to allow for 
more flexible editing of the code if it could be recompiled from the source.

-- 
                             Greg Bronevetsky

Daniel Jacobowitz wrote:

>On Fri, Dec 09, 2005 at 04:57:57PM -0500, Greg Bronevetsky wrote:
>  
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>>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.
>
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