Re: [PATCH/i386newframe/RFC] DWARF CFI frame unwinder

[Mark Kettenis <kettenis@chello.nl>]

   Date: Sun, 4 May 2003 23:42:42 -0400
   From: Daniel Jacobowitz <drow@mvista.com>

   > >+static CORE_ADDR
   > >+dwarf_frame_base_address (struct frame_info *next_frame, void 
   > >**this_cache)
   > >+{
   > >+  struct dwarf_frame_cache *cache = dwarf_frame_cache (next_frame, 
   > >this_cache);
   > >+
   > >+  return cache->cfa;
   > >+}
   > 
   > This isn't right.

Probably yes.  I think I added this stuff when I was confused about
what exectly was the value printed by "info frame".

   > It should return DW_AT_frame_base.

I don't think that it is the job of the DWARF CFI module to provide
that.  I probably should simply remove the frame base code from the
DWARF CFI code, and trust the default frame base methods to do
something sane.

   > However, since 
   > dwarf2expr.c doesn't yet use these methods it doesn't [?] really matter. 
   >  Only affects ``info frame''.

   I don't think it should.

You mean return DW_AT_frame_base.

   The frame's CFA is the basis for identifying the frame and locating
   saved registers in the CFI.  It is always present when you have CFI.

   DW_AT_frame_base is the basis for locating saved variables and locals. 
   It is generally present when you have DWARF-2 debug info.

   The two are not necessarily related.

Indeed, there is no way of referencing the CFA from outside the DWARF
CFI info.

Mark