http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55844
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-02 21:07:21 UTC --- Could you please do an extra merge soon, even before switching the default? You've raised some cases where on ubuntu _Unwind_* based backtrace wasn't accurrate, it would be nice to check it out on other distros and find out the reason. BTW, glibc backtrace(3) on i?86 (32-bit only) uses a combination of _Unwind_* based backtrace for as long as unwind info is provided, and then grabs ebp from the unwind info at the outermost frame before unwind info isn't provided, and from there attempts to use the fast backtrace method (for cases where older i?86 code when gcc still didn't default to asynchronous unwind tables on i?86 calls newer code where gcc defaults to it). On x86_64 this isn't done, as asynchronous unwind tables have been the default basically for the whole support of the architecture.
