Re: [discuss] Re: [patches] Re: x86_64 frame unwind info

[Geert Bosch <bosch at gnat dot com>]

On Wed, 17 Oct 2001, Jan Hubicka wrote:
  
  There is demand to allow standard way of stack unwinding of the code.
  To my understanding this is mostly to allow Java runtimes garbage collect
  non-conservativly in the JITs (they needs to see trought the C code to the
  JIT compiled stack frames to track down the references).

This should be possible using the EH frame.
  
  If we will keep the current scheme of eh_frame emitted sometimes and
  only for exception handling in internal gcc format and debug_frame
  emit for debugging and strip by "strip", we still need some third frame
  unwinding that can be used by the GC code.

The eh_frame should be emitted always using the standard DWARF format.
Any extensions absolutely needed for this format should be standardized
as well, and made part of the x86-64 EH ABI.
  
  Such info must be present, at least, in the all shared libraries so it
  looks like good idea to me to commonize all those tasks to single section.

The whole idea of the ABI is to always have this unwinding information
present, to be able to do all of the things you mention with all code,
and without requiring frame-pointers being present, which is desirable
for optimization purposes.

  -Geert