Problem setting registers if stack point or frame pointer is 0

[Antony KING]

Thanks for the information. Is the hack you mention the suggestion (you 
gave to my colleague) in the following response?

    http://www.cygwin.com/ml/gdb-patches/2006-05/msg00018.html

We did have this patch applied at some point in earlier versions of our 
GDB but we seem to have lost it along the way :-(.

Anyway it looks to be a better solution than the one I suggested (as 
every user of frame_find_by_id() will benefit), so I will reapply it to 
our version of GDB (unless you have a better version).

Cheers,

Antony.

Daniel Jacobowitz wrote:
> On Thu, Apr 03, 2008 at 10:35:41PM +0100, Antony KING wrote:
>> Hi,
>>
>> I have a problem trying to set a CPU register (using the GDB convenience  
>> variable mechanism) if the stack pointer (SP) or frame pointer (FP) CPU  
>> registers are 0. For example on an SH-4 device, where the FP register is  
>> R14 and the SP register is R15, I see the following error from GDB 
>> (6.7.1):
> 
> This is an unfortunate design problem in GDB.  You've found the right
> comment, but in fact the comment lies.
> 
>   /* ZERO denotes the null frame, let the caller decide what to do
>      about it.  Should it instead return get_current_frame()?  */
> 
> It doesn't denote just the null frame (nothing running).  It also
> denotes the last frame (can not unwind past here, outermost).  We've
> really got to get rid of that ambiguity.
> 
> I use a terrible hack in find_frame_by_id in our tools, since I
> still haven't found time to return to this problem :-(