Re: [hppa] FYI: confusion in unwind descriptor field meaning

[Randolph Chung <randolph@tausq.org>]

Joel,

> This is really for anybody's FYI, and maybe Randolph if he'd like to
> dig in some of the issues with me.
> 
> This is something I'm still working on, so I haven't verified my theory
> just yet. But I think there is a confusion in the meaning of Save_SP
> in the unwind descriptor. The document I have says:
> 
>     18. Save_SP (bit 27): One if the entry value of SP is saved by this
>         regions entry sequence in the current frame marker (current_SP - 4);
>         zero otherwise.
> 
> It doesn't say that the frame has a frame base register. For this, we
> have another field:

Be careful here, some of this is to work around gcc's interpretation of 
these fields, which does not always correspond to the documentation. gcc 
only uses a few of the bits in the unwind record.

Dave Anglin (pa gcc maintainer) is the expert on these issues.

I only have a few minutes now, will respond in more detail to your two 
messages later this evening.

thanks and I do hope to have a little more time to start looking at gdb 
again.

randolph