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Re: [rfc/rfa] Use ARM exception tables as GDB unwinder
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: matthew dot gretton-dann at arm dot com (Matthew Gretton-Dann)
- Cc: gdb-patches at sourceware dot org, rearnsha at arm dot com, dan at codesourcery dot com
- Date: Thu, 21 Oct 2010 17:38:58 +0200 (CEST)
- Subject: Re: [rfc/rfa] Use ARM exception tables as GDB unwinder
Matthew Gretton-Dann wrote:
> Firstly an apology - I'm not going to be able to look at this in detail
> for a while, and Richard Earnshaw is away as well for a couple of weeks.
No problem, thanks for looking at this patch!
> One of the 'optimisations' that can be applied to the exception unwind
> table is that if two contiguous functions have the same unwind tables
> they can be merged.
> Can the change you detail above handle this?
That depends on whether there is symbol information for those functions.
If there *is* a symbol for the second function, my patch would detect
that the symbol is closer than the unwind start address, in which case
it would refuse to use unwind data, and fall back to prologue parsing.
If there is no symbol, the patch would use the function start address
from the unwind information as part of the frame ID, which isn't really
correct. On the other hand, since there is no symbol, we don't *know*
the real start address either ... Using the address from unwind data
seems as good as anything else that we could possibly do here.
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE