Hi,
I post this to the list because I think it may be a good idea for
documentation reasons.
In the past days I've been thinking about how the whole stack-
unwinding code can be tested, like -[NSObject release]ing objects when
exceptions or non-local returns fly by over the stack locations of
their references. The more I think about it, the more I come to the
conclusion that a formal model of it may be a good idea.
An interesting thing I noticed was: Exception handling mechanisms can
be implemented using non-local returns. Non-local returns can be
implemented using an existing exception handling mechanism.
Because of that observation, I started to wonder how well the LK non-
local returns play together with the stack unwinding done in Objective-
C exception handling, particularly in cases like these:
test [
[
self mayThrowException
] onException: 'NSSurpriseException' do: [
^ false "Non-local return!"
]
^ true
]
The point here is this: Objective-C exception handling requires you to
use NS_VALUERETURN inside of Try- and/or Catch-Blocks. The
onException:do: implementation does exactly that with the handler
block's return value. However, by using non-local returns, this can be
circumvented.
I'd like to write a test to check that, but I currently really don't
know how to check for incorrect stack unwinding. Does anyone of you
know this?
Best regards,
Günther
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