On Fri 15 Mar 2013 22:01, Brent Pinkney <b...@4dst.com> writes: > When I resume the continuation in another thread, all works perfectly > UNLESS the continued execution throws and exception. > Then guile exits with a core dump. > > By contrast if I resume the continuation in the same thread and then > throw and exception all works as expected.
I think I know what this is. So, a delimited continuation should capture that part of the dynamic environment made in its extent. (See Oleg Kiselyov and Chung-Chieh Shan's "Delimited Dynamic Binding" paper.) That is what Guile does, for fluids, prompts, and dynamic-wind blocks. Our implementation of exception handling uses a fluid, %exception-handler (boot-9.scm:86). However that fluid references a stack of exception handlers on the heap. There is the problem: an exception in a reinstated delimited continuation continuation will walk the captured exception handler stack from the heap, not from its own dynamic environment. Therefore it could abort to a continuation that is not present on the new thread. The solution is to have the exception handler find the next handler from the dynamic environment. This will need a new primitive to walk the dynamic stack, I think. I can't look at this atm as I broke my arm (!) and so typing is tough. For now as a workaround I suggest you put a catch #t in each of your delimited continuations. This way all throws will be handled by catches established by the continuation. Regards, Andy -- http://wingolog.org/
