Re: frame->unwind->this_base()

[Daniel Jacobowitz <drow at mvista dot com>]

On Sun, Mar 16, 2003 at 05:04:36PM -0500, Andrew Cagney wrote:
> At present there is a per-frame ID method since different frames 
> determine their ID using different techniques.  The ID (which identifies 
> a given frame instance) includes a base and pc/func value.
> 
> GDB's frame code also makes available the get_frame_base() method. 
> While the default implementation returns get_frame_id().base, I think 
> there is going to need to be a per-frame frame->unwind->this_base method.
> 
> For dwarf2 frames, it would return, DW_AT_frame_base.  For prologue 
> frames, it would return an attempt at an equivalent value.  Hopefully it 
> wouldn't be called for other frame types :-).
> 
> It might even be reasonable for a prologue based unwinder to error out 
> when asked for the frame's base before the stack frame has been created.
> 
> Thoughts?
> 
> I should note that dwarf2expr.c contains code that tries to 
> locally/directly evaluate the frame base.  I think that should instead 
> do a get_frame_base() call.

There's no guarantee right now that the DW_AT_frame_base agrees with
the frame's base.  I don't even think it's necessary that they be the
same.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer