Hi Matthew,

On Thu, Oct 15, 2009 at 7:46 AM, Matthew D. Swank akopa@charter.net wrote:

I am playing with a lisp dialect (at least in my head) that I am thinking about implementing on the CLR.  Like Java the CLR requires jumps across method call boundaries to be done using the exception handling mechanism.

If I have code like the following in abcl:

(block foo  (flet ((callback () (return-from foo t)))    (something-that-calls-into-java #'callback)    ... stuff that won't happen if the callback is invoked))

And the plain old Java I'm calling into is pathological and catches the exception raised by calling the callback without re-throwing it, the non-local return never happens.  Is that correct?

That's correct.

If so, is there no way around it?

Well, given that the work around would have a performance impact, I wouldn't like to make it a generic one, but you could do this:

(block foo (let (boo) (flet ((callback () (setf boo t) (return-from foo t))) (something that calls into java #'callback) (when boo (return-from foo t)) ...))

I.O.W.: You can set a variable to be checked after you return from Java.

Hope that helps,

Erik.