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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 ...


  Dr. Ulrich Weigand

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