How to make unwind info always present?

[Ulrich Weigand]

Hello,

we are thinking of changing the debug setup for s390 to always use
DWARF-2 frame data for stack unwinding (e.g. backtraces).

This has two main advantages:

- we are currently maintaining an explicit stack frame back-chain
  pointer, which causes (measurable) run-time overhead for no other
  purpose but to enable debugging.  With DWARF-2 info, there would
  be no run-time overhead.

- with the introduction of prolog scheduling, our gdb backend has
  serious problems trying to figure out where the prolog ends and
  all variables are set up; this makes debugging with current gdb
  and gcc quite awkward.  DWARF-2 frame info would solve this.

My question is now how to best set up gcc so as to always generate
this info.  Are there other platforms that use a similar approach?

Is it possible to avoid duplication of this data if DWARF-2 frame
info is also needed for exception handling?


Mit freundlichen Gruessen / Best Regards

Ulrich Weigand

--
  Dr. Ulrich Weigand
  Linux for S/390 Design & Development
  IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen
  Phone: +49-7031/16-3727   ---   Email: Ulrich.Weigand@de.ibm.com