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Re: [RFA/mips(commit?)] Unwinding from noreturn function
- From: Daniel Jacobowitz <drow at false dot org>
- To: Joel Brobecker <brobecker at adacore dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Wed, 7 Mar 2007 07:20:32 -0500
- Subject: Re: [RFA/mips(commit?)] Unwinding from noreturn function
- References: <20070307041643.GJ25742@adacore.com>
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