If you ever pick this up again, I'd recommend starting with llvm's libunwind library, which is an import of Apple's libunwind + support for other operating systems. As far as I can tell it's the only fully functional unwind library that's actually maintained at the moment. We discussed porting whatever functionality it is missing (probably linux support and the basic assembly profiling heuristics we added to our fork of Apple's libunwind) and just using it for julia on all platforms.