Re: Assertions in principle
On Mar 5, 1:50 pm, Ian Collins <ian-n...@hotmail.com> wrote:
Kirit S=E6lensminde wrote:
On Mar 4, 6:36 pm, "Gavin Deane" <deane_ga...@hotmail.com> wrote:
On 4 Mar, 10:29, rpbg...@yahoo.com (Roland Pibinger) wrote:
On Sun, 04 Mar 2007 23:14:14 +1300, Ian Collins rote:
I am describing using asserts to enforce the contract between the
application and its operating environment. If a device or library
specification specifies a valid set of output values, assert is a good
sanity check.
Is a contract violation a bug or an expected runtime scenario? IMO,
the latter.
How do you engineer a reliable product if you expect third party
components (software or hardware) not to adhere to their interface
specifications? If you expect them to do that you need to change
supplier.
Isn't the ability to do just that what we strive to do? To write
reliable software even in the face of the unexpected?
You can't defend against all possible invalid input form third party
components. You should be able to defend against all possible invalid
input from users.
Can't we? In the sense of analysing whether we have defended against
them all I suspect this is probably the same as solving the halting
problems. That doesn't mean we can't do it in specific circumstances
though. To turn the original question around:
"How do you engineer a reliable product if you expect third party
components (software or hardware) to always adhere to their interface
specifications?"
We should be defending against as many of these errors as we possibly
can in third party components and we shouldn't forget to do so for
those in our own as well.
I always looked at everything that I've done to try to engineer better
software as being able to cope with every more error cases and faulty
systems (and users) with the minimum of problems.
I'm sure we all do, but the are situations where the only safe thing to
do is bail out as soon as possible.
I completely agree, but this is a measure of last resort and should
really only be undertaken as a response when to not do so would cause
an even worse eventuality.
K