Dwarf is also the default in clang on i686, but libunwind currently has an issue relating to unwinding dwarf exceptions on i686 on windows (and less easily reproducible on other platforms), see https://reviews.llvm.org/D38680. This enables exceptions on aarch64, where they previously were avoided/disabled. When linking to a statically linked libunwind with support for dwarf, one (currently) has to link in -lpsapi.