Re: [RFC/RFA] gdbreplay V2.0

[Michael Snyder <msnyder at specifix dot com>]

On Tue, 2008-07-01 at 21:49 -0700, Michael Snyder wrote:
> Here's a new contribution -- I call it gdb-freeplay, an 
> improved and less restrictive version of gdbreplay.  Its
> something I've been playing around with for some time now.

Oops, and here it is with copyright assignments and
header comments.  Sorry about the oversight...

> 
> This is a remote protocol logger/replayer, that works in
> principal just like gdbreplay -- it even uses the same
> logfiles, with no changes or enhancements.
> 
> However, where gdbreplay constrains you in the replay session
> to giving *exactly* the same commands, in *exactly* the same
> sequence, as were used in the recorded session, gdb-freeplay
> frees you of that constraint -- you can change the order of
> the commands, or skip them entirely, even skip ahead past an
> arbitrary number of execution events to get to the "interesting"
> ones.  
> 
> You use step and next just like you did in the recorded
> session, but now you can set a breakpoint and continue on
> ahead to a later part of the session, even if you did not
> do so in the original session.  You can even next over a
> function call that you originally stepped into -- so long
> as you also stepped out of it.  Or you can skip out with
> "finish", even if you continued to debug the function 
> interminably in the original session.
> 
> You can print any variable(s) or registers that you 
> examined before, in any order, even combine them into
> expressions that were not used in the recorded session
> (so long as all the values of the expression were evaluated).
> In many ways, it's a lot like tracepoint debugging.
> 
> I picture it being useful for gdb testing -- we might 
> even create hand-crafted "sessions" and use it to play
> them back to explicitly test parts of the remote protocol.
> 
> I can also picture a user sending you a binary and a
> recorded log in which a bug happened -- you could debug
> it even with a cross-debugger, lacking the appopriate
> hardware (or simulator or what have you) -- and even if
> the recorded log was 50 megabytes long, you could skip
> ahead to the interesting bits.
> 
> But frankly, I just wrote it because it was fascinating to do...
> 
> Michael
> 
> PS I've already written back-ends for x86, MIPS64, and x86-64.
> Most other target architectures should be fairly easy to add, 
> and it will work with anything that uses the remote protocol.
>

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