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Date: Wed, 05 Mar 2003 18:25:00 -0000
From: Andrew Cagney <ac131313@redhat.com>
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To: Michal Ludvig <mludvig@suse.cz>
Cc: GDB Patches <gdb-patches@sources.redhat.com>
Subject: Re: [patch/rfc] Add a sentinel frame
References: <3E305670.3020700@redhat.com> <3E48378E.6090007@suse.cz> <3E492953.8010001@redhat.com> <3E52173B.1030800@suse.cz> <3E538770.6070209@redhat.com> <3E5B98D8.3030002@suse.cz> <3E5BAB7D.8090801@redhat.com> <3E5BD957.9010605@suse.cz> <3E5BDCBD.2030205@redhat.com> <3E5C7512.2080207@suse.cz> <3E5E58FC.3080704@redhat.com> <3E5F5DEE.3030505@suse.cz> <3E5F8559.1020708@redhat.com> <3E663605.6030105@suse.cz>
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> +struct frame_id
> +generic_unwind_dummy_id (struct gdbarch *gdbarch, struct frame_info *frame)
> +{
> +  static struct frame_id id;
> +
> +  id.base = dummy_frame_stack->top;
> +  id.pc = frame->pc;
> +
> +  return id;
> +}
> +

No.  That would make unwind dummy id's implementation circular.  The 
ID's value is needed to find the correct dummy frame in the 
dummy_frame_stack.

This method needs to unwind register value's from the NEXT_FRAME and 
then use that to determine the dummy frame's ID.  The d10v's 
implementation (not yet committed) looks like:

/* Assuming NEXT_FRAME->prev is a dummy, return the frame ID of that
    dummy frame.  The frame ID's base needs to match the TOS value
    saved by save_dummy_frame_tos(), and the PC match the dummy frame's
    breakpoint.  */

static struct frame_id
d10v_unwind_dummy_id (struct gdbarch *gdbarch, struct frame_info 
*next_frame)
{
   ULONGEST base;
   struct frame_id id;
   id.pc = frame_pc_unwind (next_frame);
   frame_unwind_unsigned_register (next_frame, SP_REGNUM, &base);
   id.base = d10v_make_daddr (base);
   return id;
}

Andrew