RE: Stopping reverse debugging behaves differently with btrace

["Metzger, Markus T" <markus dot t dot metzger at intel dot com>]

Hi Marc,

> I noticed a difference of behaviour when stopping reverse debugging
> with btrace vs record/replay (full mode).
> 
> If full mode, if I step to line 200 and then back to line 150 then give
> the record stop command, real execution will start from line 150 as
> I step my program. (This is really cool btw.)
> 
> In btrace mode (I tried bts), after I step back to line 150 and send
> the record stop command, GDB appears to still be at line 150 but on
> the next step, execution jumps to line 200 before doing the step
> operation.
> 
> I'm guessing this has to do with the fact that btrace does not store
> registers and memory, so cannot restart execution just anywhere.

That's correct.


> I find it strange though that when turning off record, every indication
> to the user is that we are still at line 150, when in reality, GDB is
> effectively back at line 200.  This is particularly noticeable in a
> frontends when execution jumps (unexpectedly) when the first step
> is requested.
> 
> Variables also remain unavailable until the next step (or strangely,
> until I send some register command).
> 
> I was wondering if GDB should reset its execution to the proper
> place upon a 'record stop' for btrace?  And notify the frontend of
> that change.

I agree.  I'll look into it.  Thanks for pointing it out.

Regards,
Markus.
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