proper CFI and dwarf engine to use it

223a16f
Opened by Graydon Hoare at 2011-01-27 00:49:40

Currently we're using a sort of 'shadow stack' approach wherein each frame self-identifies its metadata in a location easily found from ebp. This is not optimal, long term: to keep the metadata tractable, it means we're doing expensive stuff like zeroing frames and slots all the time, and never reusing lexical scopes. Painful. We need to get to the point of emitting Dwarf CFI (or at worst, something similarly instruction-accurate) so we can determine liveness and layout of everything in a frame, given an (sp,pc) pair.

Of course, the runtime also needs to learn how to reflect on this information well enough to provide it to the unwinder. So this part is a long, slow process. Possibly this needs to be a tracking bug for several sub-bugs.

  1. WONTFIX (not required for bootstrapping)

    Graydon Hoare at 2011-01-27 00:49:40