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Re: Does DW_OP_deref work?
On Wed, Jul 30, 2003 at 08:27:53PM -0400, Daniel Jacobowitz wrote:
> On Wed, Jul 30, 2003 at 05:23:06PM -0700, H. J. Lu wrote:
> > On Wed, Jul 30, 2003 at 05:56:12PM -0400, Daniel Jacobowitz wrote:
> > > On Wed, Jul 30, 2003 at 02:54:21PM -0700, H. J. Lu wrote:
> > > > Does DW_OP_deref work correctly with gdb?
> > >
> > > That depends on the context. Things that use decode_locdesc, probably
> > > not. As we find time, things are being converted to the full
> > > expression evaluator. Location descriptions and frame bases should
> > > work.
> >
> > I don't think it does. Intel Fortran compiler generartes DW_OP_deref.
> > I got
>
> Location descriptions for parameters may not work fully. Feel free to
> fix it, or to investigate the reasons why more thoroughly - search for
> LOC_COMPUTED_ARG, but I don't even think we generate those yet.
>
The problem is gdb has a different idea about DW_OP_deref than Intel
compiler. From what I can tell in DWARF 3 draft, DW_OP_deref specifies
an address. But dwarf2read.c and gdb doesn't support it at all. There
is LOC_REF_ARG, which is an offset from the frame base register.
new_symbol in dwarf2read.c has
else if (offreg)
{
if (isderef)
{
if (basereg != frame_base_reg)
dwarf2_complex_location_expr_complaint ();
SYMBOL_CLASS (sym) = LOC_REF_ARG;
}
else
{
SYMBOL_CLASS (sym) = LOC_BASEREG_ARG;
SYMBOL_BASEREG (sym) = DWARF2_REG_TO_REGNUM (basereg);
}
}
else
{
SYMBOL_CLASS (sym) = LOC_ARG;
}
Since DW_OP_deref doesn't use basereg nor frame_base_reg, SYMBOL_CLASS
is set to LOC_ARG. DW_OP_deref needs something like LOC_DEREF_ARG,
which works on address instead of offset from a base register.
H.J.