Re: [RFA/RFC] dwarf2-frame read_reg

[Daniel Jacobowitz <drow@false.org>]

On Wed, Apr 12, 2006 at 08:17:07PM +0200, Mark Kettenis wrote:
> > Date: Tue, 11 Apr 2006 21:42:01 -0700
> > From: "Jim Blandy" <jimb@red-bean.com>
> > 
> > On 4/11/06, Michael Snyder <msnyder@redhat.com> wrote:
> > > I want you guys to vett this change.  I was getting wrong results
> > > on a target where sizeof (SP) != sizeof (void *).  The local func
> > > read_reg was calling extract_unsigned_integer with the wrong size.
> > 
> > Well, extract_typed_address requires the type of the register to be
> > some sort of pointer.  read_reg is given as a callback to the Dwarf
> > expression evaluator in dwarf2expr.c, so it could be handed any
> > register at all.
> > 
> > How about unpack_long (buf, register_type (gdbarch, regnum))? 
> > Definitely regression-test this on several platforms...
> 
> This is likely to be wrong for platforms where addresses are signed.

It shouldn't be.

unpack_long (struct type *type, const gdb_byte *valaddr)
{
...
    case TYPE_CODE_PTR:
    case TYPE_CODE_REF:
      /* Assume a CORE_ADDR can fit in a LONGEST (for now).  Not sure
         whether we want this to be true eventually.  */
      return extract_typed_address (valaddr, type);

which calls POINTER_TO_ADDRESS.  And that will be the signed unpack for
MIPS, and the unsigned unpack for other targets.

So I think unpack_long is a good choice.

(I didn't realize that before.  I think I have another pending patch
that this would be useful for - maybe the psaddr_t one?)

-- 
Daniel Jacobowitz
CodeSourcery