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Re: RFA: Recognize 'x' in response to 'p' packet
- From: Paul Schlie <schlie at comcast dot net>
- To: Steven Johnson <sjohnson at neurizon dot net>
- Cc: <gdb-patches at sources dot redhat dot com>
- Date: Thu, 02 Dec 2004 23:54:30 -0500
- Subject: Re: RFA: Recognize 'x' in response to 'p' packet
I would have thought that the BFD etc. description of the target machine
would have correctly identified the register set the machine supported.
(but the desire to support a value of x "un-defined/initialized" may
make sense if interfaced to a simulator, if the value of x were a
represent-able gdb value, and could propagate through expression
evaluations which it presently can't, but would be potentially useful
if it could to catch subtle bugs; but it's not clear that was the intent?)
> From: Steven Johnson <sjohnson@neurizon.net>
>
> The PowerPC is such an example, where the Register response usually
> includes floating point registers, but say the MPC860 family doesnt have
> them. I would imagine the reason to do it is so that, in future, GDB
> can remove from the users view registers that are non existent for a
> target, rather than show them as 0's.
>
> If so, then this would be a necessary first step (identifying such from
> the target.)
>
> Steven
>
> Paul Schlie wrote:
>
>>> Jim Blandy
>>> * remote.c (fetch_register_using_p): Recognize 'x's for the value
>>> of the register as indicating that the register's value is not
>>> available.
>>
>>
>> Out of curiosity, under what practical circumstances would the value of a
>> register not be accessible? (and if not, shouldn't an error be returned, as
>> opposed to an 'x' which is converted to a 0 anyway? Which I've noticed "g"
>> packets also assume?)