Re: [RFA] Debug info detection.

[Andrew Cagney <ac131313@redhat.com>]

> Hi all,
> The attached patch adds new function cfi_have_unwind_info() that I'll use for detection, whether a given function has a dwarf2 unwind info (from .eh_frame or .debug_frame) or not. I'll use it in the upcomming x86_64_frame_p() to detect which set of unwind functions should be returned for a given frame.

Your comment about x86_64_frame_p() makes me wonder if you're going in 
the right direction.

Looking at the d10v, you'll see:

   frame_unwind_append_predicate (gdbarch, d10v_frame_p);

For the x86-64, since it wants to also use dwarf2cfi and dwarf2eh, I'd 
expect to see something like:

   /* Try for a true CFI frame first.  If that fails, fall back to
      a .eh_frame info.  */
   frame_unwind_append_predicate (gdbarch, dwarf2cfi_frame_p);
   frame_unwind_append_predicate (gdbarch, dwarf2eh_frame_p);

   /* Finally, and as a last resort, use a prologue based unwinder.  */
   frame_unwind_append_predicate (gdbarch, x86_64_frame_p);

While I'm sure that splitting dwarf2cfi and dwarf2eh is logical, having 
separate x86_64_frame_p() that only implements traditional prologe based 
unwind is correct.

Can I suggest starting from the other end - a new file 
dwarf2cfi-frame.[hc] and then moving in from there?  The dwarf2expr.[hc] 
code was recently added and that was ment to superseed much of dwarf2cfi.c.

I'd also have a copy of cagney_offbyone-20030303-branch handy (you could 
even prototype the changes on it or a successor).  That contains a key 
fix that hasn't yet been committed to the mainline.

Andrew