I may be wrong but it seems to me that this primitives are just there  
to mark the method.
so that after the stack can is scanned for caller of 198 and 199  
(on:do:)

Have a look in the answer I got in squeak dev this summer about my  
questions about exceptions.

stef

On Nov 7, 2008, at 5:32 PM, Igor Stasenko wrote:

> I'm exploring the exception support in VM, and found two strange
> primitives used by BlockClosure, which simply fail and doing nothing.
>
> primitiveMarkUnwindMethod
> 	"Primitive. Mark the method for exception unwinding. The primitive
> must fail after marking the context so that the regular code is run."
> 	self inline: false.
> 	^self primitiveFail
>
> primitiveMarkHandlerMethod
> 	"Primitive. Mark the method for exception handling. The primitive
> must fail after marking the context so that the regular code is run."
> 	self inline: false.
> 	^self primitiveFail
>
> Any ideas, why they still in use? Can there be something in between,
> when interpreter enters the method? Or, if nothing, then why they
> still there? :)
>
> -- 
> Best regards,
> Igor Stasenko AKA sig.
>
>