Implementation and Optimization of exceptions ( static analysis possible? )

    The exception processing model I'm most familiar with ( from long
years on a VAX, and from similar implementations for various
languages ) is the stack based one, where every procedure or
protected block of code has some stack based structure that indicates
how ( and maybe what ) exceptions are handled. ( This is also the
only language independent way I can think of to implement exception
handling - although stack based doesn't have to imply the return
stack - it could mean separate stacks for handlers for various
signals. )


    A continuation model - whether visible in the language (as in
Scheme) or hidden in the implementation is the other common model I
know of. ( Any others? )


    Do any language implementations do static analysis and optimization
of exceptions within a procedure - in effect, translating them into
goto's and avoiding the overhead of handlers ?




    As exceptions are designed to handle dynamic or unpredictable
errors, clearly static analysis cannot always be done, but this
question was inspired by the recent assertion ( again ) in another
newsgroup that 'goto's are unnecessary' - I think they are certainly
*undesirable*, but unnecessary ? - I think Knuth is still the last
word on this. I often use exceptions as a way to break out of an
inner loop - in effect, as a "structured goto". Is this necessarily
less effecient, or are there cases where a compiler could produce the
equivalent code? I would think such cases would be a subset that
would be tractable to static analysis.




( I'ld like to add a special section on exception handling and some
    other more implementation oriented topics to my Programming Language
    Critiques Page at: <http://minsky.med.virginia.edu/sdm7g/LangCrit>,
    so if you've got any good tips, URL-links, or papers, please pass
    then on to me.)




---| Steven D. Majewski (804-982-0831) <sdm7g@Virginia.EDU> |---
---| Computer Systems Engineer University of Virginia |---
---| Department of Molecular Physiology and Biological Physics |---
---| Box 449 Health Science Center Charlottesville,VA 22908 |---
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