Re: RFC: Make PowerPC backtraces more robust

[Kevin Buettner <kevinb@redhat.com>]

On Fri, 23 Sep 2005 15:34:03 -0400
Daniel Jacobowitz <drow@false.org> wrote:

> Index: rs6000-tdep.c
> ===================================================================
> RCS file: /big/fsf/rsync/src/src/gdb/rs6000-tdep.c,v
> retrieving revision 1.243
> diff -u -p -r1.243 rs6000-tdep.c
> --- rs6000-tdep.c	19 Sep 2005 17:38:03 -0000	1.243
> +++ rs6000-tdep.c	23 Sep 2005 18:26:39 -0000
> @@ -2852,6 +2852,7 @@ rs6000_frame_cache (struct frame_info *n
>    struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
>    struct rs6000_framedata fdata;
>    int wordsize = tdep->wordsize;
> +  CORE_ADDR func, pc;
>  
>    if ((*this_cache) != NULL)
>      return (*this_cache);
> @@ -2859,35 +2860,56 @@ rs6000_frame_cache (struct frame_info *n
>    (*this_cache) = cache;
>    cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
>  
> -  skip_prologue (frame_func_unwind (next_frame), frame_pc_unwind (next_frame),
> -		 &fdata);
> +  func = frame_func_unwind (next_frame);
> +  pc = frame_pc_unwind (next_frame);
> +  skip_prologue (func, pc, &fdata);
> +
> +  /* Figure out the parent's stack pointer.  */
> +
> +  /* NOTE: cagney/2002-04-14: The ->frame points to the inner-most
> +     address of the current frame.  Things might be easier if the
> +     ->frame pointed to the outer-most address of the frame.  In
> +     the mean time, the address of the prev frame is used as the
> +     base address of this frame.  */
> +  cache->base = frame_unwind_register_unsigned (next_frame, SP_REGNUM);
> +
> +  /* If the function appears to be frameless, check a couple of likely
> +     indicators that we have simply failed to find the frame setup.
> +     Two common cases of this are missing symbols (i.e.
> +     frame_func_unwind returns the wrong address or 0), and assembly
> +     stubs which have a fast exit path but set up a frame on the slow
> +     path.
> +
> +     If the LR appears to return to this function, then presume that
> +     we have an ABI compliant frame that we failed to find.  */
> +  if (fdata.frameless && fdata.lr_offset == 0)
> +    {
> +      CORE_ADDR saved_lr;
> +      int make_frame = 0;
> +
> +      func = frame_func_unwind (next_frame);

It appears to me that func has already been computed earlier in this
function and that the value should be the same.

The rest looks okay to me.

Kevin