Re: new gdb arch routine FRAME_UNCHANGED

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Fri, 10 May 2002 21:04:47 -0400, Andrew Cagney <ac131313@cygnus.com> said:

  Andrew> Is the patch available somewhere?

Not online, but if you want me to, I'm happy to send the complete
patch to gdb-patches so you can see where I'm going (or thought I was
going... ;-).

  Andrew> When you say unwind library support do you mean dwarf2cfi or
  Andrew> something else?  From memory CFI identifies a frame using
  Andrew> CFA and PC, I'm wondering how things work here.

The ia64 conventions come with their own unwind info.  The conventions
do not define a unique address/identifier for each frame.

  Andrew> cf:
  Andrew> http://sources.redhat.com/ml/gdb-patches/2002-04/msg00749.html
  Andrew> There is code through out GDB that relies on being able to
  Andrew> re-find a frame in the frame chain.  The code typically
  Andrew> relies on just the frame address (oops).  The referenced
  Andrew> patch changes it to use frame/pc.  If I understand what
  Andrew> you're saying correctly, still more information will need to
  Andrew> be saved?

Yes, this is an issue I was wondering about, too.  My goal was fairly
limited though: I just wanted to change gdb/ia64 to an unwind-info
based implementation that works at least as well as the old version of
gdb/ia64.  I didn't look into this specific issue.

It sounds like for ia64 we would need to add a another field to struct
frame_id to track the register stack address of a frame.  Otherwise, a
recursive function that only uses the register stack would lead to a
series of indistinguishable frames (a simple recursive factorial would
do that).

Is the idea to treat frame_id as an opaque structure?  If so, I could
add a routine to the unwind library API to obtain a unique frame-id
for a given frame.  That way, the ia64 issue could be hidden behind
the API.

	--david