RE: [boost] Re: Programming by contract & Re: Passing parametersthroughfunctions

From: Noah Stein (Noah_at_[hidden])
Date: 2002-10-31 09:40:19

> Martin Bosticky:

> I wanted to deal with exceptions. ie when exceptions are thrown,
> i wanted to
> execute code to test for invariants conditions. This is because exceptions
> could be cought later as part of normal programming flow but the object
> invariants could have been broken.
>
> The other reason is that if there is more than one "return" from
> the body of
> the function [run()] then this is always handled correctly. ie. next
> programmer after you managing the code can not awoid the postconditions
> checking easily by putting extra return somewhere in the middle
> of the body.

That seems like it will be pretty tough to handle both cases in C++.  If
you're using the RAII idiom to handle post-conditions for multiple returns,
won't you end up checking your post-condition on an exception?  Since you'll
violate that post-condition - by definition you haven't finished the
operation if you've thrown an assertion from it - you'll end up throwing out
a post-condition assertion exception instead of the original exception.
Unless of course there's some means to determine that your condition object
is being destroyed due to an exception.  As far as I know, the language
won't help you there, you'd be forced to rely upon some solution you have to
manually create and keep updated properly.  I'm not an exception expert, so
I could be wrong.

DBC is just an acronym to mean Design By Contract without having to type in
the whole phrase every time.

-- Noah