🚀 go-pugleaf

In article 48n@netcom.com, smeyers@netcom.com (Scott Meyers) writes:
> There is a small performance penalty to be paid for each exception
> specification, because they have to be checked at runtime to be sure
> they're not violated.  This typically increases code size and decreases
> code speed, though the cost of the feature varies from compiler to
> compiler.

Well, not really.  If you can trust them (and you can now) a lot of them
can be eliminated at compile time.  Also, until the exception is thrown, the
cost can be reduced to an entry in a table that doesn't even need to be paged
in until the exception is thrown.  Of course, some archaic or otherwise
brain-damaged OS's don't support efficient exceptions, so they may have
problems. :-)

> In addition, it's probably not practical to get an exception specification
> for every function used in a program, because existing libraries typically
> don't have them.  That being the case, it will be close to impossible to
> guarantee they are never violated.

This is certainly true.  Also, how do you put them on template functions?
Then, what do you do about extern "C" functions?  You can put the exception
specification on them, but you pretty much have to just trust them.

-Mike Ball
SunSoft Developer Products.




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