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Re: S/390: Default to -fasynchronous-unwind-tables
- From: Ulrich Weigand <weigand at immd1 dot informatik dot uni-erlangen dot de>
- To: jakub at redhat dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 15 Nov 2002 21:27:00 +0100 (MET)
- Subject: Re: S/390: Default to -fasynchronous-unwind-tables
Jakub Jelinek wrote:
>Is debugging the only reason for this change?
>If yes, shouldn't only .debug_frame section be emitted (and not .eh_frame
>section) if -fexceptions is not requested?
Well, we really want this data to be present for all libraries
at any time; if you crash somewhere in a library, you need to
be able to generate a stack backtrace even in production code.
(Note that the goal of this change is to remove the stack
back-chain at some point in the future. Once this is done,
there will be *no* way to even generate a stack backtrace
without the DWARF-2 data. The back-chain is currently
maintained at run-time, which implies a measurable overhead
of about 1-2% SPECint2000 for example.)
.debug_frame has the problem that it is stripped, so that it
won't be in libraries installed via RPM usually; also even -g1
appears to generate more stuff than just .debug_frame; and
finally if we need -fexceptions as well the info would be
duplicated ...
Bye,
Ulrich
--
Dr. Ulrich Weigand
weigand@informatik.uni-erlangen.de