libunwind: make __{de,}register_frame compatible with libgcc API
The libgcc __register_frame and __deregister_frame functions take a
pointer to a set of FDE/CIEs, terminated by an entry where length is 0.
In Apple's libunwind implementation the pointer is taken to be to a
single FDE. I suspect this was just an Apple bug, compensated by Apple-
specific code in LLVM.
See lib/ExecutionEngine/RuntimeDyld/RTDyldMemoryManager.cpp and
http://lists.llvm.org/pipermail/llvm-dev/2013-April/061737.html
for more detail.
This change is based on the LLVM RTDyldMemoryManager.cpp. It should
later be changed to be alignment-safe.
Reported by: dim
Reviewed by: dim
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D8869
Reapply r351610:
Update libunwind custom frame register and deregister functions for
FreeBSD: use the new doubly underscored names for unw_add_dynamic_fde
and unw_remove_dynamic_fde.
NOTE: this should be upstreamed...
9f287522ce