Re: assertions: does it matter that they are disabled in production?
on Sat Aug 16 2008, Tony Delroy <tony_in_da_uk-AT-yahoo.co.uk> wrote:
On Aug 5, 2:13 pm, marlow.and...@googlemail.com wrote:
Assertions via assert.h (or cassert) are disabled in production and
have to be enabled via the NDEBUG macro. This is one reason I don't
use the assert macro. I always throw an exception that means a fatal
programming error has occurred. [snip]
For the purposes of this post, please consider:
- An "assertion" is a stated condition which is only false if some
manner of "critical error" has occurred, with an associated (implicit
or explicit) programmatic action. (If you're already replying to
argue, read on first).
- A "critical error" is a relative term, necessarily only understood
in the context of the test. For example, list where pointer to head
is NULL when size() > 0.
Assertions can then be divided into two types:
- NECESSARY assertions
- helping provide behaviours defined in the usage specification of a
software (sub)system
- OPTIONAL assertions
- situations where:
- behaviour is undefined (i.e. unsupporting inputs), or
- defined behaviour can not be (or perhaps can not
necessarily continue to be) reliably provided
These definitions are deliberately kept inclusive
i.e. vague. What you're talking about is inclusive enough to mean
little more than "if statement" does. The power of terminology comes
from its ability to make distinctions. Thus, my definition is crisp:
An assertion is a runtime check for a condition that would indicate a
programming error.
In general, such a condition can not be (reliably) recovered from and
indicates an arbitrary and unknowable amount of brokenness in the
program state. Unrecoverable conditions should be handled with minimal
emergency measures -- the details of which may depend on the application
-- and not by using the same code paths as recoverable errors, which can
be written to execute in an environment of full confidence in the
program state. That's why it's important to distinguish assertions from
other kinds of "error" checks.
--
Dave Abrahams
BoostPro Computing
http://www.boostpro.com
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