Duh. The debugger simulation of returns doesn't handle any of the
exception stuff from the look of it. I suppose we need to implement
analogues of all the scan/unwind VM code.

In the test case the debugger step _steps over_ the block return that
would normally trigger the ensure behaviour.  If you add '.3+4' after
the 'sema wait' in the critical block, all behaves as expected because
the debugger step code only does the 3+4 and not the return.

tim

-- 
Tim Rowledge, tim at sumeru.stanford.edu, http://sumeru.stanford.edu/tim
'Calm down -- it's only ones and zeros.'