Re: [RFA/RFC] Add dump and load command to process record and replay

[Michael Snyder <msnyder@vmware.com>]

Eli Zaretskii wrote:
>> From: Hui Zhu <teawater@gmail.com>
>> Date: Fri, 7 Aug 2009 11:34:20 +0800
>> Cc: Eli Zaretskii <eliz@gnu.org>, "gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
>>
>> I think a warning is clear to most of people.
>>
>> And when he get this warning.  He can delete the record list and load
>> again.  He will lost nothing.
>>
>> If we delete the old record list, maybe he still need old record.  He
>> will lost something.
> 
> Instead of a warning, how about asking the user whether to discard the
> old records or keep them?

My concern is, in most cases keeping them will be the wrong thing to do.
It will be very easy to create an internally inconsistent state, and
rather unlikely to create one that is *not* internally inconsistant.

Think about it -- we will be concatenating two independent sets of
state changes, with no way of knowing that the actual machine state
at the end of one is the same as the machine state at the beginning
of the other.  When these are then replayed, their effect may have
little or nothing to do with what the real machine would actually do.

To actually get this right, you would have to be *sure* that your
target machine is in the exact same state "now" (ie. when you do
the load command) as it was at the *beginning* of the previous
recording/debugging session.

I would rather either make this a separate, "expert mode"
command, or better still, leave it for a future patch to extend
the basic (and safe) patch that we first accept.