Re: [RFA/mips(commit?)] Unwinding from noreturn function

[Daniel Jacobowitz <drow@false.org>]

On Tue, Mar 06, 2007 at 08:16:43PM -0800, Joel Brobecker wrote:
>      However, this doesn't work very well in our case, especially
>      in this situation:
> 
>         static const struct frame_unwind *
>         mips_insn16_frame_sniffer (struct frame_info *next_frame)
>         {
>           CORE_ADDR pc = frame_unwind_address_in_block (next_frame, NORMAL_FRAME);
>           if (mips_pc_is_mips16 (pc))
>             return &mips_insn16_frame_unwind;
>           return NULL;
>         }

I Am Dumb.  Check CVS history, but I think I changed that just a
couple of weeks ago; I audited all the sniffers looking for what ought
to use the unwound PC and what ought to use the unwound block address.
Here, I'm pretty sure I made the wrong choice.

I would recommend you revert my changes to this function and
mips_insn32_frame_sniffer instead.

>      It seems to me that the above check is only an optimization,
>      and I've spotted at least one instance where I cannot see an
>      obvious guaranty that the address has not been decremented
>      by one of the _in_block functions... So the decision I made
>      was to remove that check.

No, it's not just an optimization.  Especially with limited debug
info, it's important.

> 
>   2. One minor: There was a confusion in the unwinder between
>      the return address and the address of the instruction calling us.
>      So I replaced frame_pc_unwind calls by their associated
>      frame_unwind_address_in_block.

This half looks right.

-- 
Daniel Jacobowitz
CodeSourcery