nothrow by default

Walter Bright newshound2 at
Fri Jan 10 01:40:00 UTC 2020

On 1/9/2020 12:39 PM, H. S. Teoh wrote:
> It's not really the exceptions themselves
> that people object to, but the associated implementation issues.

Yes. They're very costly, even in code that never throws.

An approach I've been using with modest success is to design errors entirely out 
of the code. For example, in dmd a lot of errors are handled by making a special 
AST node for "Error". Subsequent code does nothing with Error nodes.

(Analogously to how floating point code deals with errors, it just sets a NaN 
value, which is sticky.)

Another technique is to check for errors in the data first, then the processing 
code does not have to check, and cannot fail.

I enjoy trying to set up an API so it cannot fail, then no special code is 
needed for errors. Of course, this isn't always possible, and isn't a general 
solution. But it's nice when one can make it work.

P.S. I hate throwing constructors, and would force them to be nothrow in D if I 
weren't faced with a tsunami of objection to it :-)

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