> I think that the throw mechanism uses the error handler and
> any unwinding done to reach it in flat mode, like longjmp() 
> in C.

Which error handler are you talking about and what is 'flat mode'? ARe
you referring to a specific implementation of exception handling? If so,
remeber: the existence of a bad or broken implementation of a concept is
no proff against that conecpt!

> longjmp() is one of the things one is expressly warned 
> not to use in an interrupted environment. As you know, it 
> uses a static data structure (or several).

No, I don't know, because I never usef setjmp/longjmp. 

> There is no way to 
> know whether the time between when throw occurs and when the 
> handler is executed affords any protection to the variables 
> and to the stack involved.

Sorry, his makes no sense at all.

> If an interrupt occurs in the same 
> thread and the interrupt thread does anything related to the 
> throw context (such as, initializing the throw data block 
> upon entry into the try segment),

An interrupt executes on its own stack or on an extension of the
interrupted stack. the exception throwing/hndling/catching mechanism can
(and should) be implemented fully reentrant, so there will be no problem
at all.

> So unless throw is specifically thread safe in a 
> compiler I don't think that it can be used in an 
> interruptible environment.

Of course, anything that is not 'reentrant'-safe can not be used in both
main and interrupts. But throw/catch can and should be fully reentrant.

Wouter van Ooijen

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