Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Mon, 23 May 2011 22:13:24 +0200

Am Montag, 23. Mai 2011, um 21:33:42 schrieb Jim Thomas:
> >>>>> "Dirk" == Dirk Zimoch <[email protected]> writes:
>  >> [...] One exception frequently cited is when starting an IOC its maybe
>  >> ok, but if this occurs in common library code then it's probably going
>  >> to be used inappropriately in other situations, and surely eventually
>  >> we will need to upgrade allowing online add and delete of records and
>  >> then it's less clear when iocInit starts and ends?
>
>  Dirk> This show why C++ exceptions are better than the good old C abort().
>
> Sorry, but an exception is only a fancy goto.  There is little new .....

It is not "new" in any way, considering what LISP and others offered decades
before C++, but it is still not a goto (however fancy) because where you throw
the exception you don't have to say where it should go to, the stack gets
unwound until a try with a matching handler is found. This is what makes
exceptions much more powerful than goto, the control flow is determined by the
caller as well as the callee. You could emulate this in C only by threading
through *every* procedure an extra parameter (a stack of handlers plus
environment), adding a new frame (handler+env) each time you would use a
try/catch. This is possible but only at the expense of a large overhead, at
run-time as well as in lines of code (which is why nobody uses this pattern in
C).

Cheers
Ben

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System