This is the mail archive of the
gdb@sources.redhat.com
mailing list for the GDB project.
Re: REGISTER_BYTE() and pseudos
- From: Andrew Cagney <ac131313 at cygnus dot com>
- To: Richard dot Earnshaw at arm dot com
- Cc: Elena Zannoni <ezannoni at redhat dot com>, gdb at sources dot redhat dot com
- Date: Wed, 15 May 2002 16:01:40 -0400
- Subject: Re: REGISTER_BYTE() and pseudos
- References: <200205151807.TAA18580@cam-mail2.cambridge.arm.com>
> OK, I see what you are doing. Basically, if a pseudo maps onto a real
> register somewhere in the regcache, you return the address of that.
>
> However, what should be done if the pseudo doesn't exist as a single
> entry, or if it is a manipulation of a real register? For example, on the
> ARM, the CPSR may be just a few bits retrieved from the PC.
>
> Also, what would you do if you needed to address two non-adjacent
> registers?
Return ``not_lval''. I think that case can go in the too hard basket.
First, I don't know if GDB's ``struct value'' system is rich enough to
describe a value split across [disjoint] registers and memory. Second,
even if it was, the current get_saved_register() doesn't make that
knowledge available. An interface more like value_of_register() would
be better.
BTW, this code:
> OK, I'll have another look.
>
> The bit I'm worried about though is if we call something like
> generic_get_saved_register for a pseudo and we hit a call_dummy frame.
> The code in there goes:
>
> if (PC_IN_CALL_DUMMY (frame->pc, frame->frame, frame->frame))
> {
> if (lval) /* found it in a CALL_DUMMY frame */
> *lval = not_lval;
> if (raw_buffer)
> memcpy (raw_buffer,
> generic_find_dummy_frame (frame->pc, frame->frame) +
> REGISTER_BYTE (regnum),
> REGISTER_RAW_SIZE (regnum));
> return;
>
> Which will try to look up the pseudo in the buffer even if it isn't
there.
Reveals a problem with the patch:
http://sources.redhat.com/ml/gdb-patches/2002-05/msg00416.html
For the moment a custom get_saved_register will get around this.
Andrew