Randolph Chung wrote:
>>I had the same analysis that it should never happen. If Andrew agrees,
>>I would recommend simply putting an assertion instead. Putting a dummy
>>value is not that satisfactory, as you don't know what this is going
>>to be used for.
> 
> 
> i've committed the following
> 
> 2004-12-05  Randolph Chung  <tausq@debian.org>
> 
> 	* hppa-tdep.c (hppa_stub_Frame_unwind_cache): Stop unwinding if 
> 	unwinding from a frame with pc == 0.
> 	(hppa_stub_frame_this_id): Likewise.
> 	(hppa_stub_frame_prev_register): Only provide real values if the frame
> 	cache is not NULL.

FYI,

> Index: hppa-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/hppa-tdep.c,v
> retrieving revision 1.185
> diff -u -p -r1.185 hppa-tdep.c
> --- hppa-tdep.c	6 Dec 2004 03:32:26 -0000	1.185
> +++ hppa-tdep.c	8 Dec 2004 01:41:08 -0000
> @@ -2111,17 +2124,21 @@ hppa_stub_frame_unwind_cache (struct fra
>    struct gdbarch *gdbarch = get_frame_arch (next_frame);
>    struct hppa_stub_unwind_cache *info;
>    struct unwind_table_entry *u;
>  
>    if (*this_cache)
>      return *this_cache;
>  
> +  if (frame_pc_unwind (next_frame) == 0)
> +    return NULL;
> +

I've checked in the attached.  This test is generic so might as well 
live in frame.c (you'll note that I've made the conditions on which it 
triggers more robust).

committed,
Andrew